JP2002278339A - Fixing device and fixing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device and a fixing method for detecting the practical temperature of a nip part even when the size of paper is random and preventing the generation of defective fixing by a temperature drop due to the transfer of heat to recording paper. SOLUTION: A material to be heated is press-contacted between a fixing roller 2 having a heat source in its inside and a pressurizing roller 3 arranged so as to be press-contacted with the roller 2 and allowed to be rotated in cooperation with the rotation of the roller 2 and passed while being heated. The roller 2 has double structure having a surface layer 4 and an axial core 7 and having a space 6 between the layer 4 and the core 7, the space 6 is filled with gas of fixed pressure and the layer 4 or the core 7 is provided with an ultrasonic transducer 5 having a transmitter for radiating ultrasonic waves to the air and a receiver for receiving ultrasonic waves flying in the air. The layer 4 has flexibility, a distance between the layer 4 and the core 7 is detected by the transducer 5 and such a specific operation that the heating means of the fixing roller 2 is driven by a change of the distance is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a facsimile, an electrophotographic printer, etc., which heats an image formed of a heat-fusible toner formed on a recording material surface such as paper and records it as a permanently fixed image. 1. Field of the Invention The present invention relates to a heat fixing device for fixing on a material surface and an electrophotographic apparatus including the fixing device.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, toner electrostatically transferred from a photoreceptor to a recording material such as paper is easily peeled off. Therefore, the toner is permanently applied to the recording material by heating or pressing. It is necessary to fix it. This step is called a fixing process. There are various methods for fixing, and the heat roller fixing method is most widely used because of its high thermal efficiency and safety. In this method, two rollers are pressed against each other, and at least one of the rollers is heated, and an unfixed toner image support (such as paper or an OHP sheet) is applied to a pressed portion (referred to as a “nip portion”) of the two rollers. (Recording material) to heat the unfixed toner to fix it on the support.

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. A heat source such as a halogen lamp or an electric heater is provided inside the fixing roller in 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.

[0004] 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. I have. As a result, the ratio of the heat capacity of the fixing roller and the pressure roller to the heat capacity of the support (hereinafter, referred to as “paper”), which is the heated body on which the toner image is placed, is reduced, and one sheet is fixed. In this case, a sufficient amount of heat cannot be stored in the fixing roller and the pressure roller, and a fixing failure due to a temperature drop occurs in the second half of the sheet or in a repeat copy. Therefore, if an attempt is made to prevent a fixing failure by increasing the set temperature of the fixing roller, this time,
The temperature is too high in the first half of the paper, the toner melts too much and adheres to the fixing roller, and the toner of the fixing roller adheres to the paper and stains the surface of the paper (hot offset).
Is generated.

Techniques for eliminating this problem are disclosed in JP-A-6-75504, JP-A-6-130843, and JP-A-5-281875. The invention described in JP-A-6-75504 is to detect the surface temperature of the fixing roller and to control the heating of the heater of the fixing roller so that the temperature becomes constant. When the low-temperature paper passes through the nip, the surface temperature of the fixing roller is high in the first half of the paper and decreases toward the second half. For this reason, the fixing temperature may change before and after the sheet passing through the nip portion, and the temperature may drop in the latter half to cause defective fixing. Therefore, when the second half of the sheet is fixed, the amount of heat generated by the heater is increased to prevent the temperature of the fixing roller from dropping.

In the invention described in Japanese Patent Application Laid-Open No. Hei 6-130844, a heat conductive roller is provided inside a fixing roller, an outer peripheral surface of the heat conductive roller is brought into contact with an inner peripheral surface of the fixing roller, and a heat supply amount to a nip portion is provided. The fixing device is intended to prevent the temperature of the nip from dropping by increasing the temperature. Japanese Patent Laid-Open No. 5-
Japanese Patent Publication No. 281875 relates to a temperature setting method for a case where a temperature drop occurs during repeat copying. The temperature when the leading edge of the paper reaches the nip and the temperature of the fixing roller when the trailing edge passes through the nip are measured, and the temperature difference is added to the standard control temperature. This is a method of changing the set temperature of.

[0007]

In the above-mentioned prior art, when the temperature of the fixing roller is changed, the type of paper, Since the amount of temperature decrease varies depending on the initial temperature, moisture content, and the like, it is difficult to make a correct prediction. A method of increasing the amount of heat supplied to the nip by providing a heat conductive roller inside the fixing roller has a limit on the amount of heat supply that can be increased due to the thermal resistance between the fixing roller and the heat conductive roller. It is doubtful whether a sufficient effect can be obtained for thick or high-speed copying.

A method for measuring the temperature when the leading end of the sheet reaches the nip and the temperature of the fixing roller when the trailing end of the sheet passes through the nip, and changing the set temperature of the fixing roller, The mechanism becomes complicated, for example, a means for detecting that the leading end or the trailing end of the member has reached the nip portion is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and detects the actual nip temperature even when the paper size is random.
It is an object of the present invention to provide a fixing device and a fixing method that can prevent a fixing defect from occurring due to a temperature drop due to heat being taken by a sheet.

[0010]

In order to achieve the above object, a fixing device of the present invention comprises a fixing roller having a heat source inside, and a fixing roller provided so as to be in pressure contact with the fixing roller. A fixing roller that has a pressure roller that rotates in cooperation with the fixing roller and presses the material to be heated between the fixing roller and the pressure roller while passing the material to be heated, wherein the pressure roller is , Having a double layer structure having a surface layer and a shaft core and having a space between them, the space is filled with a gas of a constant pressure, and the surface layer or the shaft core emits ultrasonic waves into the gas. An ultrasonic transducer having a wave receiver and a receiver for receiving the ultrasonic waves flying in the gas is provided, and the surface layer has flexibility, and the surface layer and the shaft core are flexible with the ultrasonic transducer. The distance is detected, and a change Characterized in that it starts operating.

According to a second aspect of the present invention, there is provided a fixing method comprising: a fixing roller having a heat source inside; and a pressure roller installed so as to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller. A fixing method in which a material to be heated is passed between the fixing roller and the pressure roller while being pressed and heated, and the pressure roller includes a surface layer and a shaft core and has a space between them. Double-layer structure, the hollow part is filled with gas at a constant pressure, and the surface layer or shaft has a transmitter that emits ultrasonic waves into the gas and a receiver that receives ultrasonic waves that have flown in the gas. Along with disposing an ultrasonic transducer, the surface layer is made flexible, and a change in the distance between the surface layer of the pressure roller and the axis is detected by the ultrasonic transducer,
A specific operation is started.

The invention according to claim 3 or 4 is characterized in that the ultrasonic transducer is provided on the axis of the pressure roller. The invention according to claim 5 or 6 is characterized in that when the distance between the surface layer and the axis becomes a specific distance, the heating means of the fixing roller is operated. The invention according to claim 7 or 8 is characterized in that when the distance between the surface layer and the axis becomes a specific distance, the rotation speed of the fixing roller and the pressure roller is reduced by the speed control means.

According to a ninth or tenth aspect of the present invention, when the distance between the surface layer and the axis becomes a specific distance, the pressing force between the fixing roller and the pressing roller is increased by the pressing force control means. I do. The invention according to claim 11 or 12 is characterized in that when the distance between the surface layer and the axis becomes a specific distance, the heating lamps around the fixing roller and the pressure roller are turned on by the heating lamp power supply control circuit. And The invention according to claim 13, 14, 23, or 24 is characterized in that the gas filling the space is an inert gas.

According to the present invention, when the distance between the surface layer and the axis becomes a specific distance, the temperature of the fixing roller is increased by the heating means, and the rotation of the fixing roller and the pressure roller is performed. It is characterized in that the speed is reduced. The invention according to claim 17 or 18, wherein when the distance between the surface layer and the axis becomes a specific distance, the temperature of the fixing roller is increased by the heating means, and the pressure contact force between the fixing roller and the pressure roller is increased. It is characterized by making it.

According to the present invention, when the distance between the surface layer and the axis becomes a specific distance, a heating lamp around the fixing roller and the pressure roller is turned on, and the rotation speed is reduced. It is characterized in that it is reduced. Claim 2
The invention described in 1 or 22 is characterized in that, when the distance between the surface layer and the axis becomes a specific distance, a heating lamp around the fixing roller and the pressure roller is turned on, and the pressure contact between the fixing roller and the pressure roller is performed. It is characterized by increasing force.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a fixing device and an image forming apparatus using the same according to the present invention will be described with reference to the drawings. FIG. 1 shows a main part of a normal fixing device viewed obliquely. In FIG. 1, reference numeral 1 denotes a heat source for heating the fixing roller, and 2 denotes a fixing roller. The heat source 1 is formed of a halogen lamp or the like, and is disposed in the axial direction of the fixing roller 2 so as to have a length substantially equal to the entire length of the fixing roller 2, so that the inner surface of the fixing roller 2 can be uniformly heated in the axial direction. I have. Reference numeral 3 indicates a pressure roller. The pressing roller 3 is pressed against the fixing roller 2 by a pressing mechanism (not shown). The surface layer of the fixing roller 2 is made of a smooth material such as a fluororesin (for example, trade name “Teflon”) so that the toner does not adhere thereto, and the other layer is made of aluminum, so that the heat from the heat source 1 is quickly supplied. Make it communicate. However, not limited to aluminum,
Other materials may be used as long as they have a high thermal conductivity and a hardness sufficient to prevent deformation in the axial direction.

FIG. 2B shows a main part of the fixing device in a cross section perpendicular to the axial direction near the center in the roller axial direction. FIG. 2A is an enlarged view of the surface layer 4 and the axis 7 of the pressure roller 3 constituting the fixing device. A space 6 is formed between the surface layer 4 and the shaft core 7, and the space 6 is filled with gas. An appropriate number of circular spacers 8 are interposed between the surface layer 4 and the shaft core 7, thereby maintaining the space 8. As a material of the spacer 8, a soft and elastic sponge or the like is desirable. An ultrasonic transducer 5 is disposed on the surface layer 4 so as to be embedded in the surface layer 4.

When there is no sheet, the temperature of the fixing roller 2 is the temperature at the time of fixing, and when the pressure roller 3 is pressed against the fixing roller 2, the above-mentioned gas as the filling material is inflated most. At that time, the surface of the pressure roller 3 is expanded most. In the example shown in FIG. 2, the ultrasonic transducer 5 having a transmitter and a receiver is arranged on the surface layer 4, but may be arranged on the shaft core 7. Ultrasonic waves emitted from the transmitter are reflected by the shaft core 7 and enter the receiver of the ultrasonic transducer 5 in the surface layer 4. The time from transmission to reception is measured, and the width of the space 6 is measured. Various operations start when the width of the space 6 changes.

When the sheet to be heated is inserted into the nip between the fixing roller 2 and the pressure roller 3, the temperature of the rollers 2 and 3 is reduced, and the shaft 4 of the pressure roller 3 The gas in the space 6 with the surface layer 4 made of an elastic material contracts. Since the pressure roller 3 is in pressure contact with the fixing roller 2 and the surface layer 4 of the pressure roller 3 is flexible, the width of the space 6 is reduced by the contraction of the gas. Therefore, if the width of the space 6 in the nip portion is monitored, various actions can be started or ended based on the actual temperature of the nip portion.

FIG. 3 is a flowchart showing the operation of the above embodiment. Each operation step is indicated as “S1” or “S2”. As described above and as shown in FIG. 3, when the temperature of the nip decreases due to the paper passing through the nip (S1), the space 6 of the pressure roller 3 contracts (S2). Is measured (S3), when the space 6 contracts, this can be detected, and thereby various actions such as an operation for raising the temperature of the nip portion can be started or ended. .

Since the ultrasonic transducer 5 rotates together with the pressure roller and only needs to measure the width of the space when it reaches the nip, the number of ultrasonic transducers 5 in the roller circumferential direction is at least one. Good, but as the number is increased, the interval between measurements becomes shorter, and more delicate control can be performed quickly. Since the speed of sound is about 340 m / s, in order to detect a change of several tens of μm, the transmitter must be set to 10 MHz.
It is necessary to oscillate at about z. Ultrasonic waves are technically capable of oscillating up to about 1000 MHz.

Since the shaft core 7 of the pressure roller 3 is arranged at a distance from the fixing roller 2 which becomes hot, the temperature of the shaft core 7 of the pressure roller 3 is less likely to rise than that of the surface layer 4.
Therefore, if the ultrasonic transducer 5 is used as the axis 7 of the pressure roller 3, the temperature compensation of the ultrasonic transducer 5 is simplified and the accuracy is improved. The operation in this case is shown in FIG.
Is the same as the flowchart shown in FIG.

Next, another embodiment of the present invention will be described. FIG. 4 is a sectional view of a main part thereof. In FIG. 4, reference numerals 1 to 8 indicate the same members as those given in the embodiment shown in FIGS. This embodiment is different from the above-described embodiment in that a temperature control circuit 9 is provided. As in the above-described embodiment, when the temperature of the fixing roller 2 is equal to the temperature at the time of fixing without a sheet and the pressing roller 3 is pressed against the fixing roller 3, the gas filling the space 6 is used. Is the most expanded, and at that time, the surface of the surface layer 4 made of the elastic body is the most expanded. At the time of copying, heat is deprived of the sheet, and the temperature of the pressure roller 3 gradually decreases. The gas filled in the space 6 gradually contracts, and the pressure roller 3 is in pressure contact with the fixing roller 2.
Width is reduced. The distance is detected by the ultrasonic transducer, and when the distance reaches a specific distance, the temperature control circuit 9 is operated to increase the temperature of the heating source of the fixing roller 2. As a result, the temperature of the pressure roller 3 rises, and defective fixing due to the temperature drop is prevented. Based on the actual measured temperature of the fixing unit, if the temperature drops below a specific temperature, it will be overheated, so even if the paper size is random and the temperature drop is random, correct temperature control will prevent fixing defects. It can be reliably prevented.

FIG. 5 is a flowchart of the above operation.
As shown in FIG. 5, the temperature of the nip is reduced (S4)-the space contraction of the pressure roller (S5)-the distance of the space is measured (S6).
When it is detected that the space of the pressure roller has become smaller than the predetermined width, the control operation of the temperature control circuit 9 starts the heating of the fixing roller.

Still another embodiment will be described with reference to FIGS. In FIG. 6, reference numerals 1 to 8
Indicates the same members and the same members as in the above embodiment. This embodiment is different from the above-described embodiment in that a rotation speed control circuit 10 is provided. As in the above-described embodiment, when the temperature of the fixing roller is equal to the temperature at the time of fixing when there is no paper and the pressing roller 3 is pressed against the fixing roller 2, the gas of the filling material in the space 6 is It expands most, and at that time, the surface of the surface layer 4 made of the elastic body is expanded most.

At the time of copying, the heat is deprived by the sheet, and the temperature of the pressure roller 3 gradually decreases. Accordingly, the gas filling the space 6 gradually contracts, and the pressure roller 3 is in pressure contact with the fixing roller 2, so that the width of the space 6 is reduced. The distance is detected by the ultrasonic transducer, and when the distance reaches a specific distance, the rotation speed control circuit 10 is operated to control the rotation speeds of the fixing roller 2 and the pressure roller 3 to decrease. As a result, the time required for the paper to pass through the nip is lengthened, the amount of heat applied to the paper is increased, and poor fixing due to a decrease in temperature is prevented. In this way, the temperature of the nip portion is actually measured, and based on the result, the fixing roller 2 and the pressure roller 3 are measured.
Since the rotation speed is controlled, when the temperature of the nip portion decreases, the rotation speed can be reduced to prevent defective fixing.

FIG. 7 is a flowchart of the above embodiment. As shown in FIG. 7, a decrease in the nip temperature (S7)-
Space contraction of pressure roller (S8)-Measure distance of space (S8)
7), if it is detected that the space of the pressure roller is smaller than a predetermined width, the rotation speed control circuit 10
The rotation speeds of the fixing roller 2 and the pressure roller 3 are reduced by the control operation described above.

Next, the embodiment shown in FIGS. 8 and 9 will be described. In FIG. 8, reference numerals 1 to 8 indicate the same members and the same members used in the above embodiment. This embodiment is different from the above-described embodiment in that a pressure contact force control circuit 11 is provided. As in the above-described embodiment, when the temperature of the fixing roller is equal to the temperature at the time of fixing when there is no paper and the pressing roller 3 is pressed against the fixing roller 2, the gas of the filling material in the space 6 is It is the most expanded, and at that time, the surface of the surface layer 4 made of the elastic body is the most expanded.

At the time of copying, the heat is deprived of the sheet and the temperature of the pressure roller 3 gradually decreases. Accordingly, the gas filling the space 6 gradually contracts, and the pressure roller 3 is in pressure contact with the fixing roller 2, so that the width of the space 6 is reduced. The distance is detected by the ultrasonic transducer, and when the distance reaches a specific distance, the pressure contact control circuit 11 is operated to increase the pressure contact force between the fixing roller 2 and the pressure roller 3. As a result, the nip pressure increases, the area of the nip portion increases, the amount of heat applied to the sheet increases, and it is possible to prevent defective fixing due to a decrease in temperature. As described above, the actual temperature of the nip portion is measured, whereby the nip pressure between the fixing roller 2 and the pressure roller 3 is increased, and the fixing failure can be prevented.

FIG. 9 is a flowchart showing the operation of the above embodiment. As shown in FIG. 9, the temperature of the nip is reduced (S10), the space of the pressure roller is contracted (S11), the distance of the space is measured (S12), and the space of the pressure roller becomes smaller than a predetermined width. When it is detected that the fixing roller 2 and the pressure roller 3 are in contact with each other, the pressing operation of the fixing roller 2 and the pressure roller 3 is increased by the control operation of the pressure control circuit 11.

Next, the embodiment shown in FIGS. 10 and 11 will be described. In FIG. 10, reference numerals 1 to 8 indicate the same members and the same members attached in the embodiment. This embodiment is different from the above-described embodiment in that it has a heating lamp power supply control circuit 12 and a heating lamp 21 which operates under the control of the heating lamp power supply control circuit 12. As in the above-described embodiment, when the temperature of the fixing roller is equal to the temperature at the time of fixing when there is no paper and the pressing roller 3 is pressed against the fixing roller 2, the gas of the filling material in the space 6 is It is the most expanded, and at that time, the surface of the surface layer 4 made of the elastic body is the most expanded.

At the time of copying, the heat is deprived of the paper and the temperature of the pressure roller 3 gradually decreases. Accordingly, the gas filling the space 6 gradually contracts, and the pressure roller 3 is in pressure contact with the fixing roller 2, so that the width of the space 6 is reduced. The distance is detected by the ultrasonic transducer, and when the distance reaches a specific distance, the heating lamp power supply control circuit 12 starts a control operation to turn off the power of the heating lamp 21 around the fixing roller 2 and the pressure roller 3. When turned on, the rollers 2 and 3 whose temperature has dropped are heated to prevent defective fixing. The heating lamp 21 is provided on the fixing roller 2 in this example, and is disposed in the axial direction of the fixing roller 2 so as to have a length substantially equal to the entire length of the fixing roller 2. The position of the heating lamp 21 is not limited to this, and may be anywhere around the fixing roller 2 and the pressure roller 3.

FIG. 11 is a flowchart showing the operation of the above embodiment. As shown in FIG. 11, the temperature of the nip is reduced (S13), the space of the pressure roller is contracted (S14), and the distance of the space is measured (S15), and the space of the pressure roller becomes smaller than a predetermined width. When it is detected that the heating lamp 21 is turned on, the heating lamp 21 is turned on by the control operation of the heating lamp power supply control circuit 12 to heat the fixing roller 2 and the pressure roller 3.

Next, another embodiment shown in FIGS. 12 and 13 will be described. In FIG. 12, reference numerals 1 to 8
Indicates the same members and the same members as in the above embodiment. This embodiment is different from the above-described embodiment in that a temperature control circuit 9 and a rotation speed control circuit 10 are provided. When the temperature of the rollers 2 and 3 decreases due to the insertion of the material to be heated, the pressure roller 3
The width of the space between the surface layer and the shaft core is reduced. When a specific distance between the surface layer and the shaft core is reached, the temperature control circuit 9 is operated to increase the temperature of the heating source 1 of the fixing roller 2 and the rotation speed control circuit 10 is operated to establish a connection with the fixing roller 2. The rotation speed of the pressure roller 3 is reduced.

When the temperature of the heat source 1 of the fixing roller 2 is increased, it is possible to prevent a fixing failure due to a decrease in temperature caused by paper passing. However, since the fixing roller 2 has a certain heat capacity, the temperature is immediately increased. Does not rise. On the other hand, roller 2,
The rotation speed of No. 3 can be reduced immediately, which can increase the time for the paper to come into contact with the nip portion, so that it has an immediate effect, but it is not always necessary to give a sufficient amount of heat to prevent poor fixing. Can not. Therefore, as in the above-described embodiment, when the temperature rise of the fixing roller 2 and the decrease in the rotation speed of the fixing roller 2 and the pressure roller 3 are combined, it is possible to more reliably prevent the fixing failure. Also,
Since control is performed while measuring the actual temperature of the nip portion, highly accurate control can be performed.

FIG. 13 is a flowchart showing the operation of the above embodiment. As shown in FIG. 13, the temperature of the nip is reduced (S16), the space of the pressure roller is contracted (S17), the distance of the space is measured (S18), and the space of the pressure roller is narrower than a predetermined width. When it is detected that the fixing roller 2 is heated, the heating of the fixing roller 2 and the reduction of the rotation speed of the fixing roller 2 and the pressure roller 3 are performed simultaneously.

Next, another embodiment shown in FIGS. 14 and 15 will be described. In FIG. 14, reference numerals 1 to 8
Indicates the same members and the same members as in the above embodiment. This embodiment is different from the above-described embodiment in that it has a temperature control circuit 9 and a pressing force control circuit 11. The roller 2 is inserted by inserting the material to be heated.
When the temperature of the pressure roller 3 decreases, the width of the space between the surface layer of the pressure roller 3 and the shaft core decreases as described above. When the specific distance between the surface layer and the shaft core is reached, the temperature control circuit 9 is operated to raise the temperature of the heating source 1 of the fixing roller 2, and the pressing force control circuit 11 is operated to make contact with the fixing roller 2. The pressing force of the pressure roller 3 is increased, and the nip pressure between the rollers 2 and 3 is increased.

As described above, raising the temperature of the heat source 1 of the fixing roller 2 prevents the fixing failure due to the temperature drop caused by the sheet passing, but the temperature of the fixing roller 2 does not rise immediately. On the other hand, the pressing force of the rollers 2 and 3 can be increased immediately, so that the nip pressure can be increased immediately, so that there is an immediate effect. On the other hand, in some cases, it is not always possible to obtain a sufficient amount of heat for preventing defective fixing. Therefore, in this embodiment, the fixing failure can be more reliably prevented by combining the rise in the temperature of the fixing roller 2 and the increase in the pressure contact force between the fixing roller 2 and the pressing roller 3. Further, since the actual temperature of the nip portion is measured and the heating and the nip pressure are increased based on the measured temperature, the control can be performed with high accuracy.

FIG. 15 is a flowchart showing the operation of the above embodiment. As shown in FIG. 15, the temperature of the nip is reduced (S19), the space of the pressure roller is contracted (S20), and the distance of the space is measured (S21). The space of the pressure roller is smaller than a predetermined width. When it is detected that the fixing roller 2 is pressed, the heating of the fixing roller 2 and the increase in the pressure contact force between the fixing roller 2 and the pressing roller 3 are performed simultaneously.

Next, another embodiment shown in FIGS. 16 and 17 will be described. In FIG. 16, reference numerals 1 to 8
Indicates the same members and the same members as in the above embodiment. This embodiment differs from the above-described embodiment in that a rotation speed control circuit 10 and a heating lamp control circuit 12 are provided. When the temperature of the rollers 2 and 3 decreases due to the insertion of the material to be heated, the width of the space between the surface layer of the pressure roller 3 and the shaft core decreases as described above. When a specific distance between the surface layer and the axis is reached, the heating lamp control circuit 12
To turn on the heating lamp 21 to increase the peripheral temperature of the fixing roller 2 and the pressure roller 3 and to operate the rotation speed control circuit 10 to reduce the rotation speed of the fixing roller 2 and the pressure roller 3. In this way, the time required for the paper to pass through the nip between the rollers 2 and 3 is lengthened to prevent the fixing failure. Reference numeral 16 denotes a guide, and 15 denotes a sheet as a material to be heated.

By energizing the heating lamp 21 and raising the temperature around the fixing roller 2 and the pressure roller 3, it is possible to prevent a fixing failure due to a temperature drop caused by paper passing. Temperature does not rise. On the other hand, the rotation speed of the rollers 2 and 3 can be immediately reduced, and the amount of heat applied to the sheet from the nip portion can be immediately increased. On the other hand, in some cases, it is not always possible to obtain a sufficient amount of heat for preventing defective fixing. Therefore, in this embodiment, the fixing failure can be more reliably prevented by combining the rise in the temperature of the fixing roller 2 and the decrease in the rotation speed of the fixing roller 2 and the pressure roller 3. Further, since the actual temperature of the nip portion is measured and the heating and the rotation speed of the rollers 2 and 3 are reduced based on the measured temperature, the control can be performed with high accuracy.

FIG. 17 is a flowchart showing the operation of the above embodiment. As shown in FIG. 17, the temperature of the nip is reduced (S22) -the space contraction of the pressure roller (S23) -the distance of the space is measured (S24), and the space of the pressure roller becomes smaller than a predetermined width. When it is detected that the fixing lamp 2 is turned on, the heating of the fixing roller 2 and the rotation speed reduction of the fixing roller 2 and the pressure roller 3 are simultaneously performed.

Next, another embodiment shown in FIGS. 18 and 19 will be described. In FIG. 18, reference numerals 1 to 8
Indicates the same members and the same members as in the above embodiment. This embodiment is different from the above-described embodiment in that a heating lamp control circuit 12 and a pressing force control circuit 11 are provided. When the temperature of the rollers 2 and 3 decreases due to the insertion of the material to be heated, the width of the space between the surface layer of the pressure roller 3 and the shaft core decreases as described above. When a specific distance between the surface layer and the axis is reached, the heating lamp control circuit 12
Is activated to energize the heating lamp 21 to increase the peripheral temperature of the fixing roller 2 and the pressing roller 3 and to operate the pressing force control circuit 11 to fix the fixing roller 2 and the pressing roller 3.
, The nip pressure between the rollers 2 and 3 is increased to prevent defective fixing.

By energizing the heating lamp 21 and raising the temperature around the fixing roller 2 and the pressure roller 3, it is possible to prevent defective fixing due to a decrease in temperature caused by paper passing. Temperature does not rise. On the other hand, the pressing force of the rollers 2 and 3 can be immediately increased, and the amount of heat applied to the sheet from the nip portion can be immediately increased. On the other hand, in some cases, it is not always possible to obtain a sufficient amount of heat for preventing defective fixing. Therefore, in this embodiment, the fixing failure can be more reliably prevented by combining the rise in the temperature of the fixing roller 2 and the increase in the pressing force between the fixing roller 2 and the pressing roller 3. Further, since the actual temperature of the nip portion is measured and the heating and the nip pressure are increased based on the measured temperature, the control can be performed with high accuracy.

FIG. 19 is a flowchart showing the operation of the above embodiment. As shown in FIG. 19, the process proceeds with the decrease of the nip temperature (S25), the space contraction of the pressure roller (S26), and the measurement of the distance of the space (S27), and the space of the pressure roller becomes narrower than a predetermined width. When it is detected that the fixing lamp 2 is turned on, the heating of the fixing roller 2 and the increase of the nip pressure between the fixing roller 2 and the pressure roller 3 are simultaneously performed.

[0046]

According to the first, second, third, and fourth aspects of the present invention, various operations can be started or ended at the actually measured temperature of the nip portion to perform high-precision control. Thus, it is possible to prevent defective fixing.

According to the fifth and sixth aspects of the present invention, the temperature drop of the roller due to the insertion of the paper is monitored at the nip, and when the temperature of the roller drops as a result, the heating means is operated to activate the fixing roller. Since the temperature is increased, it is possible to prevent the fixing failure due to the temperature decrease. In addition, based on the measured temperature of the fixing unit, if the temperature falls below a specific temperature, it is overheated, so even if the paper size is random and the temperature drop is also random, fixing is performed by accurate temperature control. Defects can be reliably prevented.

According to the seventh and eighth aspects of the present invention, the temperature decrease of the roller accompanying the insertion of the paper is monitored at the nip portion, and when the temperature of the roller is decreased as a result, the rotational speed of the fixing roller and the pressure roller is changed. Is reduced, the amount of heat applied to the sheet from the nip between the fixing roller and the pressure roller increases, and it is possible to prevent a fixing failure due to a temperature decrease.

According to the ninth and tenth aspects of the present invention, the temperature drop of the roller accompanying the insertion of the paper is monitored at the nip,
As a result, when the temperature of the roller decreases, the pressure contact force between the fixing roller and the pressure roller is increased, so that the amount of heat applied to the paper from the nip portion between the fixing roller and the pressure roller increases, and the fixing due to the temperature decrease is performed. Failure can be prevented.

According to the eleventh and twelfth aspects of the present invention, the temperature drop of the roller accompanying the insertion of the paper is monitored at the nip portion. As a result, when the temperature of the roller drops, the temperature around the fixing roller and the pressure roller is reduced. Since the heating lamp is turned on to increase the temperature of the roller, it is possible to prevent a fixing failure due to a decrease in temperature.

According to the thirteenth, fourteenth, twenty-third and twenty-fourth aspects of the present invention, the gas filling the space between the surface layer of the pressure roller and the shaft core is made into an inert gas, so that the medium as a sound wave The gas can be prevented from causing a chemical change.

According to the fifteenth and sixteenth aspects of the present invention, the fixing failure caused by the lowering of the temperature of the roller due to the insertion of the paper is prevented by increasing the temperature of the fixing roller and decreasing the rotation speed of the fixing roller and the pressure roller. This can be prevented by lengthening the time required for the paper to pass through the nip. Further, a fixing effect can be more effectively prevented by a complementary effect of the immediate effect of decreasing the rotation speed and the provision of a sufficient amount of heat by increasing the temperature of the fixing roller.

According to the seventeenth and eighteenth aspects of the present invention, the fixing failure caused by the temperature drop of the roller due to the insertion of the paper is prevented by increasing the temperature of the fixing roller and increasing the pressure contact force between the fixing roller and the pressure roller. Can be prevented. In addition, a fixing effect can be more effectively prevented by a complementary effect of the immediate effect of increasing the nip pressure and the provision of a sufficient amount of heat by increasing the temperature of the fixing roller.

According to the nineteenth and twentieth aspects of the present invention, the fixing failure caused by the lowering of the temperature of the roller due to the insertion of the paper is fixed by raising the temperature of the roller by turning on the heating lamp around the fixing roller and the pressure roller. This can be prevented by reducing the rotation speed of the roller and the pressure roller to increase the time required for the paper to pass through the nip. Further, a fixing effect can be more effectively prevented by a complementary effect of the immediate effect of decreasing the rotation speed and the provision of a sufficient amount of heat by increasing the temperature of the fixing roller.

According to the twenty-first and twenty-second aspects of the present invention, the fixing failure caused by the lowering of the temperature of the roller caused by the insertion of the paper is fixed by raising the temperature of the roller by turning on the heating lamp around the fixing roller and the pressure roller. This can be prevented by increasing the nip pressure by operating a mechanism that increases the pressure contact force between the roller and the pressure roller. In addition, a fixing effect can be more effectively prevented by a complementary effect of the immediate effect of increasing the nip pressure and the provision of a sufficient amount of heat by increasing the temperature of the fixing roller.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of the appearance of a fixing roller and a pressure roller that can be used in a fixing device according to the present invention.

FIGS. 2A and 2B show an embodiment of a fixing device and a fixing method according to the present invention, wherein FIG. 2A is an enlarged front view showing a part of a pressure roller, and FIG. .

FIG. 3 is a flowchart showing an operation of the embodiment.

FIG. 4 is a front view showing another embodiment of the fixing device and the fixing method according to the present invention.

FIG. 5 is a flowchart showing an operation of the embodiment.

FIG. 6 is a front view showing still another embodiment of the fixing device and the fixing method according to the present invention.

FIG. 7 is a flowchart showing an operation of the embodiment.

FIG. 8 is a front view showing still another embodiment of the fixing device and the fixing method according to the present invention.

FIG. 9 is a flowchart showing an operation of the embodiment.

FIG. 10 is a front view showing still another embodiment of the fixing device and the fixing method according to the present invention.

FIG. 11 is a flowchart showing the operation of the embodiment.

FIG. 12 is a front view showing still another embodiment of the fixing device and the fixing method according to the present invention.

FIG. 13 is a flowchart showing the operation of the embodiment.

FIG. 14 is a front view showing still another embodiment of the fixing device and the fixing method according to the present invention.

FIG. 15 is a flowchart showing the operation of the embodiment.

FIG. 16 is a front view showing still another embodiment of the fixing device and the fixing method according to the present invention.

FIG. 17 is a flowchart showing an operation of the embodiment.

FIG. 18 is a front view showing still another embodiment of the fixing device and the fixing method according to the present invention.

FIG. 19 is a flowchart showing an operation of the embodiment.

[Explanation of symbols]

 2 Fixing roller 3 Pressure roller 4 Surface layer 5 Ultrasonic transducer 6 Space 7 Shaft core

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 3/00 335 H05B 3/00 335 F term (Reference) 2H033 AA03 BA11 BA25 BA27 BA30 BA59 BB18 BB28 BB33 BB34 BB35 BB38 CA12 CA13 CA23 CA30 CA35 CA39 CA40 CA44 3K058 AA02 AA72 BA18 CA12 CA23 DA02 5J083 AA02 AC28 AD04 AE06

Claims (24)

[Claims] An image forming apparatus comprising: a fixing roller having a heat source inside; and a pressure roller installed to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller. In a fixing device that passes while heating while being pressed between the fixing roller and the pressure roller, the pressure roller has a surface layer and a shaft core, and has a double structure having a space therebetween. The space is filled with a gas of a constant pressure, and the surface layer or the axis has an ultrasonic transducer having a transmitter for emitting ultrasonic waves into the gas and a receiver for receiving ultrasonic waves flying in the gas. And the surface layer has flexibility, the ultrasonic transducer detects a distance between the surface layer and the axis, and a change in the distance starts a specific operation. Fixing device. 2. A heating device comprising: a fixing roller having a heat source inside; and a pressure roller installed to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller. And a fixing method in which the pressing roller is pressed and heated while passing through while being heated, wherein the pressing roller has a double structure having a surface layer and a shaft core and having a space between them, Filled with a gas of a constant pressure, and on the surface layer or shaft core, with an ultrasonic transducer having a transmitter that emits ultrasonic waves into the gas and a receiver that receives ultrasonic waves flying in the gas, A fixing method comprising: making the surface layer flexible; detecting a change in the distance between the surface layer of the pressure roller and the axis with the ultrasonic transducer; and starting a specific operation. 3. The fixing device according to claim 1, wherein the ultrasonic transducer is provided on a shaft of the pressure roller. 4. The fixing method according to claim 2, wherein the ultrasonic transducer is provided on the axis of the pressure roller. 5. The fixing device according to claim 1, wherein a distance between the surface layer and the shaft core is detected, and when the distance reaches a specific distance, a heating unit of the fixing roller is operated. 6. The fixing method according to claim 2, wherein a distance between the surface layer and the shaft core is detected, and when the distance reaches a specific distance, a heating unit of the fixing roller is operated. 7. A speed control means for detecting a distance between a surface layer and a shaft core, and reducing a rotation speed of a fixing roller and a pressure roller when a specific distance is reached.
Or the fixing device according to 3. 8. The fixing method according to claim 2, wherein the distance between the surface layer and the shaft core is detected, and when the distance reaches a specific distance, the rotational speeds of the fixing roller and the pressure roller are reduced. 9. The apparatus according to claim 1, wherein a distance between the surface layer and the shaft center is detected, and when a specific distance is reached, a pressing force control means for increasing a pressing force between the fixing roller and the pressing roller is operated. 3. The fixing device according to item 3. 10. The fixing method according to claim 2, wherein the distance between the surface layer and the shaft core is detected, and when the distance reaches a specific distance, the pressure contact force between the fixing roller and the pressure roller is increased. 11. A power supply control circuit for a heating lamp located around a fixing roller and a pressure roller when a distance between a surface layer and a shaft core is detected and a specific distance is reached. 3. The fixing device according to item 3. 12. The fixing device according to claim 2, wherein a distance between the surface layer and the shaft core is detected, and when a specific distance is reached, a heating lamp around the fixing roller and the pressure roller is turned on. Method. 13. The fixing device according to claim 1, wherein the gas filling the space is an inert gas. 14. The fixing method according to claim 2, wherein a pressure roller in which the gas filling the space is an inert gas is used. 15. A fixing roller comprising: a fixing roller having a heat source inside; and a pressing roller which is provided so as to be in pressure contact with the fixing roller and rotates in cooperation with the rotation of the fixing roller.
In a fixing device in which a material to be heated is passed between the fixing roller and the pressure roller while being pressed while being heated, the pressure roller has a surface layer and an axis, and has a space between them. The space is filled with a gas of constant pressure, and the surface layer or shaft has a transmitter that emits ultrasonic waves into the gas and a receiver that receives ultrasonic waves that have flown through the gas. And an ultrasonic transducer for detecting a distance between the surface layer and the axis, the surface layer having flexibility, and a fixing roller when the distance between the surface layer and the axis becomes a specific distance. A heating unit for increasing the temperature of the fixing roller, and a speed control unit for decreasing the rotation speed of the fixing roller and the pressure roller. 16. An image forming apparatus comprising: a fixing roller having a heat source inside; and a pressure roller installed to be in pressure contact with the fixing roller and rotating in cooperation with the rotation of the fixing roller. The fixing roller is pressed between the pressure roller and the pressure roller, and is passed while heating. The pressure roller has a double structure having a surface layer and a shaft core and having a space between them. Filled with a gas of constant pressure, and on the surface layer or shaft core, with an ultrasonic transducer having a transmitter that emits ultrasonic waves into the gas and a receiver that receives ultrasonic waves flying in the gas, The surface layer is made flexible, a change in the distance between the surface layer of the pressure roller and the axis is detected by the ultrasonic transducer, and when the distance between the surface layer and the axis becomes a specific distance, heating means To raise the fusing roller temperature. A fixing method characterized by raising the speed and operating a speed control means to reduce the rotation speeds of the fixing roller and the pressure roller. 17. The fixing device according to claim 15, further comprising a pressing force control unit that increases a pressing force between the fixing roller and the pressure roller, instead of the speed control unit. 18. The fixing method according to claim 16, wherein the pressing force control means is operated instead of the speed control means to increase the pressing force between the fixing roller and the pressure roller. 19. The fixing device according to claim 15, wherein the heating unit is a heating lamp around the fixing roller and the pressure roller. 20. A heating means for heating a periphery of a fixing roller and a pressure roller using a heating lamp.
The fixing method described in the above. 21. The heating means is a heating lamp around the fixing roller and the pressure roller, and has a pressure contact force control means for increasing the pressure contact force between the fixing roller and the pressure roller instead of the speed control means. The fixing device according to claim 15, wherein: 22. A heating lamp is used as a heating means to heat the periphery of the fixing roller and the pressure roller,
17. The fixing method according to claim 16, wherein the pressing force control means is operated instead of the speed control means to increase the pressing force between the fixing roller and the pressure roller. 23. The fixing device according to claim 15, wherein the gas filling the space is an inert gas. 24. A pressure roller wherein the gas filled in the hollow portion is an inert gas.
23. The fixing method according to 18, 20, or 22.