JPH1195591A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To homogenize and stabilize a fixed image by preventing defective transfer caused by temperature drop by a simple constitution. SOLUTION: The change of the temperature of a pressure roller 3 is detected by the change of the volume of gas with which the hollow part 10 of the pressure roller 3 is filled by specified pressure. The occurrence of the defective transfer caused by the temperature drop of a fixing roller 2 is prevented by maintaining specified fixing temperature by heating the fixing roller 2 by an external heating lamp 4 when the temperature of the pressure roller 3 is detected to be <=a fixed temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, or the like, which heats a heat-fusible developer image formed on a recording material surface such as recording paper to form a fixed image. The present invention relates to a fixing device, particularly to homogenization and stabilization of a fixed fixed image.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a toner image electrostatically transferred from a photoreceptor to a recording sheet or the like easily peels off. Therefore, the toner image transferred to the recording sheet or the like is heated and pressed. It is necessary to permanently fix the recording paper to recording paper or the like. This step is called a fixing process.
Various methods are employed in the fixing process, and the heat roller fixing method is most widely used because of its high thermal efficiency and safety. In the heat roller fixing method, two rollers are pressed against each other, at least one of the rollers is heated, and a recording paper or the like on which an unfixed toner image has been transferred passes through a nip portion which is a pressed portion of the two rollers. In this method, the toner image is heated and fixed on a recording paper or the like. In this heat roller fixing method, when one of the two rollers is heated, the roller to be heated is called a fixing roller, and the other roller is called a pressure roller. Inside the fixing roller, a heat source such as a halogen lamp or an electric heater is provided along the axial direction of the fixing roller. A temperature sensor is attached to the outer surface of the fixing roller, and the amount of power supply to the heat source is controlled so that the temperature of the nip is maintained at a temperature suitable for fixing.

In recent years, attempts have been made to reduce the heat capacity of the fixing roller and the pressure roller in the heat roller fixing type fixing device in order to save energy, thereby shortening the startup time until the temperature reaches a set temperature. . As a result, the ratio of the heat capacity of the fixing roller and the pressure roller to the heat capacity of the recording paper or the like having the toner image is reduced, and a sufficient amount of heat is applied to the fixing roller to fix the toner image on one recording paper or the like. There is a problem that the toner cannot be stored in the pressure roller, and a fixing failure due to a temperature drop occurs in the latter half of the recording paper or in continuous copying. If the set temperature of the fixing roller is increased to prevent this fixing failure, the temperature rises excessively in the first half of the recording paper or the like, and the toner is excessively melted and adheres to the fixing roller, so that the surface of the recording paper or the like becomes dirty. Will occur.

A fixing device for eliminating this problem is disclosed in, for example, JP-A-6-75504, JP-A-6-13084, and JP-A-5-281875. JP-A-6-75
According to the fixing device disclosed in Japanese Patent No. 504, when the low-temperature recording paper passes through the nip portion between the fixing roller and the pressure roller, the surface temperature of the fixing roller is high in the first half of the recording paper and decreases in the second half. In order to prevent this, the amount of heat generated by the heater of the fixing roller is increased when fixing the second half of the recording paper so that the amount of heat applied to the first half and the second half of the recording paper is substantially equal. In the fixing device disclosed in Japanese Patent Application Laid-Open No. Hei 6-130843, a heat conductive roller that rotates independently of the fixing roller is provided inside the fixing roller, and the outer peripheral surface of the heat conductive roller contacts the inner peripheral surface of the fixing roller. In this way, the amount of heat supplied to the nip is increased to prevent the temperature of the nip from dropping. Also,
The fixing device disclosed in Japanese Patent Application Laid-Open No. 5-281875 measures the temperature of the fixing roller when the leading end of the recording paper reaches the nip and the temperature of the fixing roller when the trailing end passes through the nip. Is changed to the set temperature of the fixing roller to prevent the temperature from dropping during continuous copying.

[0005]

In order to increase the calorific value of the heater of the fixing roller when fixing the latter half of the recording paper, as in the fixing device disclosed in Japanese Patent Application Laid-Open No. 6-75504, It is necessary to predict the amount of temperature decrease in advance and determine the amount of increase in the calorific value of the heater. However, the amount of temperature decrease depends on the type of recording paper, initial temperature, moisture content, and the like, and it is difficult to make a correct prediction. Further, as in the fixing device disclosed in Japanese Patent Application Laid-Open No. 6-130843, a method of increasing the amount of heat supplied to the nip portion by providing a heat conductive roller inside the fixing roller is disclosed.
Because there is thermal resistance between the fixing roller and the heat transfer roller,
There is a limit to the amount of heat supply that can be increased, and there is no problem with ordinary recording paper or the like. However, it is difficult to exhibit a sufficient effect when the recording paper is thick or when high-speed copying is performed. JP 5
As in the fixing device disclosed in JP-A-281875, the temperature of the fixing roller when the leading end of the recording paper reaches the nip and the temperature of the fixing roller when the trailing end passes through the nip are measured. The method of changing the set temperature of the fixing roller requires a means for detecting that the leading end of the recording paper has reached the nip portion and that the trailing end has passed through the nip portion, which complicates the structure of the fixing device. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device which can solve the above-mentioned disadvantages, prevent defective fixing due to a decrease in temperature with a simple structure, and can homogenize and stabilize a fixed image fixed. Things.

[0007]

SUMMARY OF THE INVENTION A fixing device according to the present invention includes a fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller, and rotating in cooperation with rotation of the fixing roller. , An auxiliary heating unit and an auxiliary heating power supply unit, and the pressure roller is formed of a surface layer made of a deformable elastic body coated with a thin metal layer on the inner surface, a metal core, and a surface layer and a shaft core. A hollow portion is filled with a gas of a constant pressure, the auxiliary heating portion is disposed opposite to the fixing roller, and a power supply portion for auxiliary heating is a temperature of the gas filled in the hollow portion of the pressure roller. And the auxiliary heating unit is heated when the surface thin metal layer and the shaft core come into contact with each other.

A second fixing device according to the present invention includes a fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller, and a heating unit. The pressure roller has a surface layer made of an easily deformable elastic body having an inner surface coated with a thin metal layer, a metal core, and a hollow part formed by the surface layer and the shaft core. Then, the hollow part is filled with gas at a constant pressure,
The heating unit is provided at the subsequent stage of the fixing roller, and the conveyance path switching unit is provided at the subsequent stage of the fixing roller when the temperature of the gas filled in the hollow portion of the pressure roller drops and the thin metal layer of the surface layer comes into contact with the shaft core. The heating material transport path is switched to the heating unit side.

A third fixing device according to the present invention includes a fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller, and a heating unit. The pressure roller has a surface layer made of an easily deformable elastic body coated with a thin metal layer on the inner surface, a metal core, and a hollow part formed by the surface layer and the shaft core. Then, the hollow part is filled with gas at a constant pressure,
The heating unit is provided at the subsequent stage of the fixing roller, and the heating power supply unit heats the heating unit when the temperature of the gas filled in the hollow portion of the pressure roller drops and the thin metal layer of the surface layer comes into contact with the shaft core. It is characterized by the following.

A fourth fixing device according to the present invention includes a fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller, and a fixing roller. The fixing roller, the pressing roller and the discharging roller have a forward / reverse rotation mechanism, and the inner surface of the pressing roller is coated with a thin metal layer. It has a surface layer made of an elastic body that is easily deformed, a metal core, and a hollow portion formed by the surface layer and the shaft core, the hollow portion is filled with gas at a constant pressure, and the rotation switching portion is a pressure roller. When the temperature of the gas filled in the hollow portion decreases and the surface metal thin layer comes into contact with the shaft core, when the material to be heated passes through the nip portion between the fixing roller and the pressure roller, the fixing roller, the pressure roller, and the discharge roller are discharged. Rotate the paper roller in reverse to transfer the heated material to the fixing roller and the pressure roller. Characterized in that it send again to the nip portion of the La.

A fifth fixing device according to the present invention includes a fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller, and rotating in cooperation with the rotation of the fixing roller, and a conveyance path switch. The pressure roller has a surface layer made of an easily deformable elastic body coated with a thin metal layer on the inner surface, a metal core, and a hollow part formed by the surface layer and the shaft core. When the temperature of the gas filled in the hollow portion of the pressure roller drops and the surface metal thin layer comes into contact with the shaft core, the fixing roller and the pressure roller The material to be heated sent out from the nip portion is sent again to the nip portion between the fixing roller and the pressure roller.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fixing device according to the present invention includes a fixing roller having a heat source such as a halogen lamp and a heater, a pressing roller pressed against the fixing roller by a pressing mechanism, and a heating unit serving as an auxiliary heating unit. It has a lamp and a heating lamp power supply circuit section. The pressure roller has a surface layer, a shaft core, and a hollow portion. The surface layer is formed of an elastic body that is easily deformed, for example, silicon rubber, and has a metal thin layer coated on its inner surface with a metal having good electric conductivity. The shaft core is formed of a metal material having good electric conductivity. The hollow portion is formed of a surface layer and a shaft core, and a plurality of soft and elastic cylindrical spacers are continuously or intermittently arranged over substantially the entire length of the pressure roller. This hollow portion is filled with gas at a constant pressure. The heating lamp has substantially the same length as the entire length of the fixing roller, and is arranged opposite to the fixing roller. The heating lamp power supply circuit unit heats the heating lamp when the temperature of the gas filled in the hollow portion of the pressure roller drops and the surface metal thin layer comes into contact with the shaft core.

When the toner image is fixed to the recording paper on which the toner image has been transferred by the fixing device, the fixing roller is heated to a predetermined fixing temperature by a heat source, and the heat of the fixing roller fills the hollow portion of the pressure roller. The expanded gas is the most expanded, and the surface layer of the pressure roller is in the highest tension state.
In this state, the recording paper on which the toner image has been transferred is heated and pressed through a nip portion, which is a contact position between the fixing roller and the pressure roller, to fix and fix the toner image transferred to the recording paper. When the recording paper is fixed by the fixing roller and the pressure roller, the heat of the fixing roller and the pressure roller is taken by the recording paper in the nip portion, and the temperature of the fixing roller and the pressure roller gradually decreases. When the gas filled in the hollow portion of the pressure roller gradually contracts and the thin metal layer on the inner surface of the pressure roller comes into contact with the shaft core and the thin metal layer and the shaft core are connected, the heating lamp power supply The circuit unit supplies electric power to the heating lamp and heats it to apply heat to the fixing roller, thereby increasing the temperature of the fixing roller to an appropriate fixing temperature. As described above, the temperature change of the pressure roller is detected by the change in the volume of the gas filled in the hollow portion of the pressure roller at a constant pressure, so that the temperature change between the pressure roller and the fixing roller can be accurately detected with a simple configuration. Can be detected. Further, when the temperature of the pressure roller falls below a certain temperature, heat is applied to the fixing roller from the outside to reach a predetermined fixing temperature, so that it is possible to prevent the occurrence of defective fixing due to a temperature drop of the fixing roller.

Further, a heating section is provided after the fixing roller and the pressure roller, so that the temperature of the fixing roller and the pressure roller gradually decreases, and the gas filled in the hollow portion of the pressure roller gradually contracts. When the thin metal layer on the inner surface of the pressure roller comes into contact with the shaft core and the thin metal layer and the shaft core are electrically connected to each other, the recording paper passing through the fixing roller and the pressure roller is heated and pressed again. Is also good.

Further, the temperature of the fixing roller and the pressure roller gradually decreases, and the gas filled in the hollow portion of the pressure roller gradually contracts, and the thin metal layer and the shaft on the inner surface of the surface of the pressure roller are contracted. When the core comes into contact and the metal thin layer and the shaft core are connected to each other, the recording paper that has passed through the fixing roller and the pressure roller is again subjected to the fixing roller and the pressure roller from the exit side or the entrance side of the fixing roller and the pressure roller. May be reheated.

[0016]

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention. As shown in the figure, a fixing device 1 used for an image forming apparatus such as a copying machine has a fixing roller 2, a pressure roller 3, a heating lamp 4 as an auxiliary heating unit, and a heating lamp power supply circuit unit 5. The fixing roller 2 is formed of a material having a high thermal conductivity such as aluminum, and the surface layer portion 6 is coated with a smooth material having good heat resistance, for example, a fluororesin in order to prevent toner as a developer from adhering. Inside, a heat source 7 such as a halogen lamp or a heater is provided along the axial direction at substantially the same length as the entire length of the fixing roller 2. The pressure roller 3 is disposed in pressure contact with the fixing roller 2 by a pressing mechanism (not shown), rotates in cooperation with the rotation of the fixing roller 2, and has a surface layer 8, a shaft core 9, and a hollow portion 10. . The surface layer 8 is formed of an elastic body that is easily deformed, for example, silicon rubber or the like, and has a thin metal layer 11 coated on its inner surface with a metal having good electric conductivity, such as copper or silver. The shaft core 9 is formed of a metal material having a good electric conductivity, or the surface of a reinforced plastic is coated with a metal having a good electric conductivity such as copper or silver. Hollow part 10 is surface layer 8
A plurality of cylindrical spacers 12 formed of a soft core and an elastic material such as a sponge are continuously or intermittently arranged over substantially the entire length of the pressure roller 3. The hollow portion 10 is filled with a gas such as an inert gas such as an argon gas at a constant pressure. The heating lamp 4 has substantially the same length as the entire length of the fixing roller 2, and is arranged to face the fixing roller 2. The heating lamp power supply circuit section 5 heats the heating lamp 4 when the temperature of the gas filled in the hollow portion 10 of the pressure roller 3 decreases and the thin metal layer 11 of the surface layer 8 comes into contact with the shaft core 9.

When the toner image is fixed on the recording paper 13 on which the toner image formed on the photosensitive member is transferred by the electrophotographic method in the fixing device 1 having the above-described configuration, the fixing roller 2 is heated by the heat source 7 to a predetermined temperature. Heated to fixing temperature. The heat of the fixing roller 2 is transmitted to the pressure roller 3, and the gas filled in the hollow portion 10 of the pressure roller 3 expands most, the surface layer 8 is stretched the most, and the cross section is as shown in FIG. It is almost a perfect circle. In this state, the recording paper 13 to which the toner image has been transferred is heated and pressed through a nip portion, which is a contact position between the fixing roller 2 and the pressure roller 3, so that the toner image transferred to the recording paper 13 is fixed and fixed. . When the recording paper 13 is fixed through the nip portion between the fixing roller 2 and the pressure roller 3, the heat of the fixing roller 2 and the pressure roller 3 is taken by the recording paper 13 at the nip portion, and the heat is applied to the fixing roller 2. Pressure roller 3
Temperature gradually decreases. Due to the temperature drop of the pressure roller 3, the gas filling the hollow portion 10 gradually contracts. The pressure roller 3 is pressed against the fixing roller 2 by a pressing mechanism, and the surface layer 8 is formed of an easily deformable elastic body such as silicon rubber. As shown in the figure, when the surface layer 8 becomes concave at the nip portion and the gas in the hollow portion 10 becomes lower than a certain temperature, the metal thin layer 11 on the inner surface of the surface layer 8 comes into contact with the shaft core 9 to make contact with the metal thin layer 11. Conduction is made between the shaft cores 9. When detecting the conduction between the thin metal layer 11 and the shaft core 9, the heating lamp power supply circuit section 5 supplies electric power to the heating lamp 4 to heat it. Heat is applied to the fixing roller 2 by the heating of the heating lamp 4 to raise the temperature of the fixing roller 2 to an appropriate fixing temperature.

As described above, the temperature change of the pressure roller 3 is detected by the change in the volume of the gas filling the hollow portion 10 of the pressure roller 3 at a constant pressure. The temperature change of the roller 2 can be accurately detected. Further, when the temperature of the pressure roller 3 becomes lower than a certain temperature, heat is applied to the fixing roller 2 from the outside to reach a predetermined fixing temperature. Can be. Here, even if the temperature of the gas in the hollow portion 10 becomes lower than a certain temperature, when the spacer 12 comes to the nip portion, the thin metal layer 1
1 and the shaft core 9 do not contact each other, but the heating lamp power supply circuit 5
If the thin metal layer 11 and the shaft core 9 do not come into contact with each other for a certain period of time or longer, the heating lamp 4 is heated assuming that the thin metal layer 11 and the shaft core 9 are in contact with each other.

In the above embodiment, the fixing roller 2 and the pressure roller 3
When the temperature of the fixing roller 2 and the pressure roller 3 gradually decreases due to the heat of the fixing roller 2 being taken by the recording paper 13 at the nip portion, heat is applied from the heating lamp 4 to the fixing roller 2 to set the temperature of the fixing roller 2 to a predetermined value. Although the case where the fixing roller 2 is maintained at the fixing temperature has been described, a heating section is provided at the subsequent stage of the fixing roller 2 and the pressing roller 3 so that when the temperature of the pressing roller 3 becomes lower than a certain temperature, the fixing roller 2 and the pressing roller 3 are pressed. The recording paper 13 that has passed through the nip portion of the roller 3 may be heated and pressed again.

FIG. 3 shows a second embodiment in which the recording paper 13 which has passed through the nip between the fixing roller 2 and the pressure roller 3 is heated and pressed again when the temperature of the pressure roller 3 falls below a certain temperature. Is shown. The fixing device 1a shown in FIG. 3 includes a heating roller 2 which is set at a constant temperature on a sheet discharge side, which is a stage subsequent to the fixing roller 2 and the pressure roller 3, which are exactly the same as in the first embodiment.
1 and a pressure roller 22, and two paper guides 23 and 24 on the exit side of the fixing roller 2 and the pressure roller 3.
The paper guide 23 has a paper discharge roller 25 at an intermediate portion, and directly discharges the recording paper 13 that has passed through the fixing roller 2 and the pressure roller 3. The paper guide 24 sends the recording paper 13 that has passed through the fixing roller 2 and the pressure roller 3 to the subsequent heating roller 21 and pressure roller 22. The paper guide 23 and the paper guide 24 are integrally connected, and are driven by a solenoid 27 and springs 28 and 29 driven by a solenoid operating circuit 26 connected to the thin metal layer 11 of the surface layer 8 of the pressure roller 3 and the shaft core 9. Can be switched.

When the recording paper 13 is fixed through the nip portion between the fixing roller 2 and the pressure roller 3 by the fixing device 1a configured as described above, the temperature of the fixing roller 2 and the pressure roller 3 is higher than a predetermined temperature. In this case, the recording paper 13 on which the toner image has been fixed passes through the fixing roller 2 and the pressure roller 3, and is discharged directly through the paper guide 23. In this state, the recording paper 13 is continuously fed, the heat of the fixing roller 2 and the pressure roller 3 is taken by the recording paper 13 at the nip portion, and the temperatures of the fixing roller 2 and the pressure roller 3 gradually decrease. Hollow part 1 of pressure roller 3
As shown in FIG. 4, the thin gas layer 11 on the inner surface of the surface layer 8 of the pressure roller 3 and the shaft core 9 come into contact with each other so that the gas When the connection is established, the solenoid operation circuit unit 26 drives the solenoid 27,
The conveyance path of the recording paper 13 at the subsequent stage of the fixing roller 2 and the pressure roller 3 is switched from the paper guide 23 to the paper guide 24.
By switching the paper guide 24, the recording paper 13 on which the toner image has been fixed passes through the fixing roller 2 and the pressure roller 3.
Is sent to a heating roller 21 and a pressure roller 22 at the subsequent stage, where it is heated and pressed again. The recording paper 13 is heated
Since the recording paper 13 is heated by the fixing roller 2 and the pressure roller 3 when the recording paper 13 is heated by the pressure roller 22, the recording paper 13 takes less heat from the heating roller 21 and the pressure roller 22, 21 and the pressure roller 22 are maintained at a substantially constant temperature. The heating roller 21 and the pressure roller 22
By heating and pressurizing the recording paper 13 again, it is possible to prevent the occurrence of defective fixing.

The fixing of the toner image transferred onto the recording paper 13 by the fixing roller 2 and the pressure roller 3 is not performed for a certain period of time.
When the temperature of the fixing roller 2 and the pressure roller 3 becomes higher than a predetermined temperature, and the thin metal layer 11 on the inner surface of the surface layer 8 of the pressure roller 3 is separated from the shaft core 9, the solenoid operation circuit 26 drives the solenoid 27 to drive the paper guide 24. To the paper guide 23.

In the second embodiment, two systems of paper guides 23 and 24 are provided at the subsequent stage of the fixing roller 2 and the pressure roller 3 so that the temperature of the fixing roller 2 and the pressure roller 3 becomes lower than a predetermined temperature. Recording paper 1 passed through fixing roller 2 and pressure roller 3
Although the case where the heating roller 21 is heated and pressed again by the heating roller 21 and the pressing roller 22 has been described, as shown in the configuration diagram of the third embodiment in FIG. A heating roller power supply circuit section 31 connected to the shaft 11 and the heating roller 11 is provided. When the temperature of the fixing roller 2 and the pressure roller 3 becomes lower than a predetermined temperature, the heating roller power supply circuit section 31 is provided after the fixing roller 2 and the pressure roller 3. The roller 21 may be heated.

When the temperature of the fixing roller 2 and the pressure roller 3 is equal to or higher than a predetermined temperature, the fixing device 1b of this embodiment does not heat the heating roller 21 provided at the subsequent stage of the fixing roller 2 and the pressure roller 3. The recording paper 13 that has passed through the fixing roller 2 and the pressure roller 3 is discharged from the paper guide 32 through the heating roller 21 and the pressure roller 22. When the temperature of the fixing roller 2 and the pressure roller 3 becomes lower than a certain temperature and the metal thin layer 11 on the inner surface of the surface layer 8 of the pressure roller 3 comes into contact with the shaft core 9 and the metal thin layer 11 and the shaft core 9 become conductive, Then, the heating roller 21 is heated by the heating roller power supply circuit section 31, and the recording paper 13 that has passed through the fixing roller 2 and the pressure roller 3 is heated and pressed again by the heating roller 21 and the pressure roller 22. As described above, when the temperature of the fixing roller 2 and the pressure roller 3 becomes lower than a predetermined temperature, the heating roller 21 is heated by the heating roller power supply circuit section 31 to heat and press the recording paper 13 again, so that a fixing defect occurs. In addition, power consumption of the heating roller 21 can be reduced.

In the second and third embodiments, the heating roller 21 and the pressure roller 22 are provided after the fixing roller 2 and the pressure roller 3.
Has been described, and the recording paper 13 that has passed through the fixing roller 2 and the pressure roller 3 is heated and pressed again, but the fixing roller 2 and the pressure roller 3 are The recording paper 13 that has passed through may be heated and pressed again.

FIG. 6 is a block diagram of a fourth embodiment in which the recording paper 13 is heated and pressed again by the fixing roller 2 and the pressure roller 3. In FIG. The fixing roller 2 and the pressure roller 3 of the fixing device 1c shown in FIG. 6 and the paper discharge roller 41 provided on the paper guide 32 at the subsequent stage of the fixing roller 2 and the pressure roller 3 have a forward / reverse rotation mechanism. The forward / reverse rotation mechanism includes a reverse rotation operation circuit unit 42 connected to the metal thin layer 11 on the inner surface 8 of the surface layer 8 of the pressure roller 3 and the shaft core 9.
Switches between forward rotation and reverse rotation.

When the temperature of the fixing roller 2 and the pressure roller 3 is equal to or higher than a predetermined temperature, the fixing device 1c discharges the recording paper 13 passing through the fixing roller 2 and the pressure roller 3 in a normal direction.
Discharge with 1. The recording paper 1 is fixed by the fixing roller 2 and the pressure roller 3.
When the toner image transferred to the fixing roller 3 and the toner image on the recording paper 13 are continuously fixed, the temperature of the fixing roller 2 and the pressure roller 3 becomes lower than a predetermined temperature. When the metal thin layer 11 on the inner surface of the surface layer 8 of the pressure roller 3 comes into contact with the shaft core 9 and the metal thin layer 11 and the shaft core 9 are electrically connected,
After the recording paper 13 passes through the fixing roller 2 and the pressure roller 3, the reverse rotation operation circuit section 42
Then, the recording paper 13 sent to the paper guide 32 is returned to the fixing roller 2 and the pressure roller 3 from the paper discharge side, and heated and heated again by the fixing roller 2 and the pressure roller 3. Press. The returned recording paper 13 is applied to the fixing roller 2.
After passing through the fixing roller 2 and the pressing roller 3, the reverse rotation operation circuit unit 42 switches the fixing roller 2, the pressing roller 3, and the discharging roller 41 to normal rotation, and again the fixing roller 2, the pressing roller 3, and the discharging roller 41. Then, the recording paper 13 is discharged. In this manner, when the temperature of the fixing roller 2 and the pressure roller 3 becomes lower than a certain temperature, the recording paper 13 is repeatedly heated and pressed, so that it is possible to prevent the occurrence of defective fixing.

In the fourth embodiment, the case where the recording paper 13 having passed through the fixing roller 2 and the pressure roller 3 is fed back and repeatedly heated and pressed by the fixing roller 2 and the pressure roller 3 has been described. As shown in FIG.
And a circulation path 5 for conveying the recording paper 13 to the pressure roller 3.
1 and a sheet guide 32 provided at a stage subsequent to the fixing roller 2 and the pressure roller 3 is attached to the thin metal layer 11 of the surface layer 8 of the pressure roller 3.
The recording paper 13 passed through the fixing roller 2 and the pressure roller 3 is switched by the fixing roller 2 and the pressure roller 3 by switching between a solenoid 27 driven by a solenoid operation circuit unit 26 connected to the shaft core 9 and springs 28 and 29. Heating and pressurization may be performed again.

In the fixing device 1d, when the temperature of the fixing roller 2 and the pressure roller 3 is equal to or higher than a predetermined temperature, the recording paper 13 passing through the fixing roller 2 and the pressure roller 3 is directly discharged from the paper guide 32. The recording paper 13 is fixed by the fixing roller 2 and the pressure roller 3.
When the toner image transferred to the recording paper 13 is fixed, or when the toner images of the plurality of recording papers 13 are continuously fixed,
As shown in FIG. 8, when the temperature of the fixing roller 2 and the pressure roller 3 becomes lower than a predetermined temperature, the metal thin layer 11 on the inner surface 8 of the surface layer 8 of the pressure roller 3 comes into contact with the shaft core 9 to contact the metal thin layer 11. When the conduction between the shaft cores 9 is established, the solenoid operation circuit unit 26 drives the solenoid 27 to switch the paper guide 32 to the circulation path 51. By the switching of the paper guide 32, the recording paper 13 on which the toner image has been fixed through the fixing roller 2 and the pressure roller 3 is sent again to the entry side of the fixing roller 2 and the pressure roller 3 through the circulation path 51. , Fixing roller 2 and pressure roller 3
Is heated and pressurized again. On the other hand, the solenoid operating circuit unit 26 drives the solenoid 27, and after a certain timing, or the thin metal layer 11 on the inner surface 8 of the surface layer 8 of the pressure roller 3 and the shaft core 9
When the contact is not made, the solenoid 27 is driven to switch the paper guide 32 from the circulation path 51 to the paper discharge side, and the heated and pressurized recording paper 13 is discharged again. By repeatedly heating the recording paper 13 with the fixing roller 2 and the pressure roller 3 in this manner, it is possible to prevent the occurrence of fixing failure with a simple configuration.

[0030]

As described above, according to the present invention, a change in the temperature of the pressure roller is detected by a change in the volume of gas filled in the hollow portion of the pressure roller at a constant pressure. Temperature changes between the pressure roller and the fixing roller can be accurately detected.

Further, when it is detected that the temperature of the pressure roller has fallen below a certain temperature due to a change in the volume of gas filled in the hollow portion of the pressure roller at a constant pressure, heat is externally applied to the fixing roller. In addition, since the fixing temperature is set to a predetermined value, it is possible to prevent occurrence of defective fixing due to a decrease in the temperature of the fixing roller, and it is possible to stably form an image with good quality.

Further, a heating section is provided after the fixing roller and the pressing roller, and when the temperature of the fixing roller and the pressing roller becomes lower than a predetermined temperature, the recording paper passing through the fixing roller and the pressing roller is heated again. By applying pressure, it is possible to prevent occurrence of fixing failure with a simple configuration. Further, the power consumption can be reduced by heating the heating unit when the temperature of the fixing roller and the pressure roller becomes equal to or lower than a certain temperature.

Further, when the temperature of the fixing roller and the pressure roller becomes lower than a predetermined temperature, the recording paper passing through the fixing roller and the pressure roller is fixed again from the exit side or the entrance side of the fixing roller and the pressure roller. By performing reheating through the roller and the pressure roller, it is possible to prevent the occurrence of fixing defects while further reducing power consumption.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a state in which the temperatures of a fixing roller and a pressure roller are reduced.

FIG. 3 is a configuration diagram of a second embodiment.

FIG. 4 is a configuration diagram illustrating a state where the temperatures of a fixing roller and a pressure roller according to a second embodiment are reduced.

FIG. 5 is a configuration diagram of a third embodiment.

FIG. 6 is a configuration diagram of a fourth embodiment.

FIG. 7 is a configuration diagram of a fifth embodiment.

FIG. 8 is a configuration diagram illustrating a state where the temperatures of a fixing roller and a pressure roller according to a fifth embodiment are reduced.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing apparatus 2 Fixing roller 3 Pressure roller 4 Heating lamp 5 Heating lamp power supply circuit part 7 Heat source 8 Surface layer 9 Shaft core 10 Hollow part 11 Thin metal layer 12 Spacer 21 Heating roller 22 Pressure roller 23 Paper guide 24 Paper guide 26 Solenoid Operation circuit 27 Solenoid 31 Heat roller power supply circuit section 42 Reverse rotation operation circuit section 51 Circulation path

Claims (5)

[Claims] A fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller, an auxiliary heating unit and an auxiliary heating power supply unit. The pressure roller has a surface layer made of an easily deformable elastic body coated with a thin metal layer on the inner surface, a metal shaft core, and a hollow portion formed by the surface layer and the shaft core. The gas under pressure is filled, the auxiliary heating unit is arranged opposite to the fixing roller, and the power supply unit for auxiliary heating reduces the temperature of the gas filled in the hollow part of the pressure roller and reduces the surface metal thin layer and the shaft core. A fixing device configured to heat the auxiliary heating unit when the fixing device contacts the fixing device. A fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller, and a heating unit and a conveyance path switching unit. The pressure roller has a surface layer made of an easily deformable elastic body coated with a thin metal layer on the inner surface, a metal core, and a hollow portion formed by the surface layer and the shaft core. Gas is filled, the heating unit is provided at the subsequent stage of the fixing roller,
The transport path switching unit switches the heated material transport path downstream of the fixing roller to the heating unit side when the temperature of the gas filled in the hollow portion of the pressure roller drops and the thin metal layer of the surface layer comes into contact with the shaft core. A fixing device characterized by the above-mentioned. 3. A fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller, a heating unit and a heating power supply unit. The pressure roller has a surface layer made of an easily deformable elastic body coated with a thin metal layer on the inner surface, a metal core, and a hollow portion formed by the surface layer and the shaft core. Gas is filled, the heating unit is provided at the subsequent stage of the fixing roller,
A fixing device characterized in that the heating power supply unit heats the heating unit when the temperature of the gas filled in the hollow portion of the pressure roller decreases and the surface metal thin layer contacts the shaft core. 4. A fixing roller having a heat source therein, a pressure roller disposed in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller, and a discharge roller provided at a subsequent stage of the fixing roller A fixing roller, a pressure roller, and a paper discharge roller. The pressure roller has a forward / reverse rotation mechanism. The pressure roller is a surface layer made of a deformable elastic body having an inner surface coated with a thin metal layer. And a hollow portion formed of a metal shaft core and a surface layer and a shaft core.The hollow portion is filled with a gas of a constant pressure, and the rotation switching portion controls the temperature of the gas filled in the hollow portion of the pressure roller. When the material to be heated passes through the nip portion between the fixing roller and the pressure roller when the metal thin layer of the surface layer and the shaft core come into contact with each other and the material to be heated passes through the nip portion between the fixing roller and the pressure roller, the fixing roller, the pressure roller, and the discharge roller are rotated in the reverse direction, and Again to the nip between the fixing roller and the pressure roller. A fixing device for the butterflies. 5. A fixing device comprising: a fixing roller having a heat source therein; a pressure roller disposed in pressure contact with the fixing roller and rotating in cooperation with rotation of the fixing roller; Has a surface layer made of an easily deformable elastic body coated with a thin metal layer on the inner surface, a metal shaft core, and a hollow portion formed by the surface layer and the shaft core, and the hollow portion is filled with a gas of a constant pressure. When the temperature of the gas filled in the hollow portion of the pressure roller decreases and the shaft core comes into contact with the surface metal thin layer, the transport path switching section is heated by the nip between the fixing roller and the pressure roller. A fixing device for feeding a material to a nip portion between a fixing roller and a pressure roller again.