JP2000039797A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the warm-up time from delaying caused by getting slow of the temperature rise of material to be heated by setting the Curie point of a magnetic conductor so that saturation temperature made stable under the self temperature control of the material to be heated is equal to or under hot offset start temperature and equal to or above fixing feasible temperature. SOLUTION: As for this fixing device 1; an energizing member 3 is arranged inside a heat roller 2 consisting of the hollow cylindrical magnetic conductor, and a pressure roller 4 is rotatably arranged to press-contact with the roller 2 under the roller 2. A nip 6 to hold and carry recording paper 5 is formed between the rollers 2 and 4. The magnetic alloy having the Curie point at or above the fixing feasible temperature of toner is used for the roller 2. Especially, iron-nickel alloy or iron-nickel-chromium alloy where the Curie point of the magnetic alloy is adjusted so that the stable temperature of the heat roller owing to self temperature control characteristic is equal to or above the fixing temperature and equal to or under the hot offset start temperature is used therefor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device of an electromagnetic induction heating type applicable to a recording device such as an electrophotographic device and a facsimile.

[0002]

2. Description of the Related Art In a heat fixing type recording apparatus, a fixing device is used to heat and fix a material to be fixed represented by a toner to a material to be recorded. As a heating method of the fixing device, there are a lamp method of heating with a lamp such as a halogen lamp and an induction heating method of heating by generating an eddy current by linking an alternating magnetic field to a magnetic conductor.

[0003] An induction heating type fixing device can directly heat a material to be heated such as a heat roller by utilizing Joule heat generated by eddy current, and thus achieves more efficient heating than a lamp type. There are advantages that can be done.

Japanese Patent Application Laid-Open No. 8-6413 discloses an example in which an induction heating type fixing device is applied to an image forming apparatus. The material to be heated in which the eddy current is generated has a Curie temperature necessary for fixing. When the magnetic conductor is heated and exceeds the Curie temperature, the spontaneous magnetization disappears. Therefore, the magnetic field generated in the material to be heated (conductor) decreases, eddy current decreases, and heat generation is suppressed. Therefore,
If the material to be heated has a Curie temperature necessary for fixing, the temperature of the material to be heated is self-controlled near the fixing temperature at which the Curie point is reached. By performing the self-temperature control near the fixing temperature, the heating temperature of the material to be heated can always be maintained near the fixing temperature without performing complicated temperature control.

As described above, when an electromagnetic induction type heat source is used and a magnetic conductor having a self-temperature control function is used for the heat roller, if the Curie point is set appropriately, the fixing temperature of the toner on the paper is improved. Self-control becomes possible.

By the way, as shown in FIG. 18, when the temperature of the magnetic conductor, which is a material of the heat roller or the like, is near the Curie point, the electric resistance is reduced even when a constant current is applied to the induction heating coil, so that the heat quantity is reduced. I do. For this reason, it is desirable to set the Curie point so that self-temperature control is performed near the fixing temperature.However, when heat is taken from the heat roller when paper is passed and a state in which the heat supply amount cannot keep up occurs, There is a possibility that the temperature of the heat roller will be lowered, resulting in defective fixing.

Further, when the temperature of the heat roller is raised from room temperature, the slope of the temperature rise becomes gentle near the Curie point. Therefore, if the Curie point is set so as to perform self-temperature control near the fixing temperature, the warm-up time is reduced. Lengthens and becomes an obstacle to quick start.

In order to shorten the warm-up time and realize a quick start, the heat capacity of the heat roller is reduced and the Curie point is set to a temperature higher than the fixing temperature to increase the amount of heat generated by the heater serving as a heat source. There is a need to.

However, if the heat capacity of the heat roller is reduced and the Curie point is higher than the fixing temperature, hot offset occurs when continuous printing of a small size recording material is performed and then wide paper is passed. May degrade the image. As shown in FIG. 19, the heat is removed from the paper passing portion, but the non-paper passing portion becomes higher than the fixing temperature without being deprived of heat, so that the non-paper passing portion becomes higher than the fixing temperature. When a wide paper is passed through the printer, excessive fixing occurs at a portion higher than the fixing temperature, and a hot offset occurs in which the toner once transferred to the paper adheres to the heat roller again.

[0010]

As described above, in the conventional induction heating type fixing device, when the Curie point is set so as to control the temperature in the vicinity of the fixing temperature, the heat supply amount cannot catch up with the fixing device. There is a possibility that. On the other hand, if the Curie point is set higher than the fixing temperature, hot offset may occur.

The present invention has been made in view of the above circumstances, and it is possible to prevent a delay in warm-up time due to a slow rise in temperature of a material to be heated near the Curie point, and to further reduce hot offset. It is an object of the present invention to provide a fixing device that does not cause the fixing device.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a magnetic material in which the saturation temperature which is stabilized under self-temperature control of the material to be heated is lower than the hot offset starting temperature and higher than the fixing temperature. The Curie point of the conductor was set.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first aspect of the present invention, a magnetic conductor having a Curie point set so that a saturation temperature based on a self-temperature control characteristic falls within a range of not less than a fixing temperature and not more than a hot offset starting temperature. Then, a configuration is adopted in which the material to be heated is fixed.

According to this configuration, the Curie point of the magnetic conductor is adjusted so that the saturation temperature based on the self-temperature control characteristic falls within the range of not less than the fixing temperature and not more than the hot offset start temperature. However, it is possible to prevent the warm-up time from being delayed due to the slowing of the temperature rise near the Curie point, and to prevent the occurrence of hot offset.

According to a second aspect of the present invention, the Curie point of the magnetic conductor is set to be equal to or higher than the hot offset start temperature.

According to this configuration, since the Curie point of the magnetic conductor is set to be equal to or higher than the hot offset start temperature, the saturation temperature based on the self-temperature control characteristic falls within the range between the fixing temperature and the hot offset start temperature. .

In a third aspect of the present invention, the Curie point is set such that the saturation temperature of the magnetic conductor approaches the hot offset start temperature from the fixing temperature.

According to this configuration, since the saturation temperature of the magnetic conductor is closer to the hot offset start temperature than the fixing temperature, it is possible to prevent a delay in the warm-up time due to a slower temperature rise near the fixing temperature.

A fourth aspect of the present invention is such that the temperature of the paper passing area on the surface of the magnetic conductor does not fall below the fixing temperature even during continuous paper passing, and the temperature of the non-paper passing area does not exceed the hot offset start temperature. Set Curie point.

With this configuration, even during continuous paper passing, the temperature of the paper passing area on the surface of the magnetic conductor does not fall below the fixing temperature, and the temperature of the non-paper passing area does not exceed the hot offset start temperature. Insufficient fixing due to insufficient temperature and hot offset in the non-sheet passing area can be prevented.

According to a fifth aspect of the present invention, there is provided a magnetic conductor having a Curie point set so that the saturation temperature based on the self-temperature control characteristic is in the range of not less than the fixing temperature and not more than the hot offset start temperature, and And a feeding means for supplying an alternating current to the exciting means, and a conveying means for conveying the material to be heated with the material being opposed to the magnetic conductor.

According to this configuration, the Curie point of the magnetic conductor is adjusted so that the saturation temperature based on the self-temperature control characteristic falls within the range of not less than the fixing temperature and not more than the hot offset start temperature. However, it is possible to prevent the warm-up time from being delayed due to the slowing of the temperature rise near the Curie point, and to prevent the occurrence of hot offset.

According to a sixth aspect of the present invention, in the fifth aspect, a temperature sensor for detecting a temperature in the vicinity of the magnetic conductor or the fixing region, and the temperature of the magnetic conductor is fixed based on a temperature detected by the temperature sensor. And a control unit for controlling the power supplied to the power supply unit so as to be close to the temperature.

According to this configuration, since the power supplied to the power supply means is controlled so that the temperature of the magnetic conductor becomes close to the fixing temperature, power saving can be achieved.

According to a seventh aspect of the present invention, in the sixth aspect, the control means reduces the power supplied to the power supply means when the detected temperature reaches a target temperature corresponding to the fixing temperature. In this case, the fixing temperature is maintained.

According to this configuration, after the detected temperature reaches the target temperature corresponding to the fixing temperature, the target temperature can be maintained even if the power supplied to the power supply means is reduced. Power saving can be achieved by reducing the supplied power.

According to an eighth aspect of the present invention, in the sixth aspect, when the detected temperature reaches a target temperature corresponding to the fixing temperature, the control means turns on and off the power supplied to the power supply means. In this case, the fixing temperature is maintained.

According to this configuration, after the detected temperature reaches the target temperature corresponding to the fixing temperature, the target temperature can be maintained even if the power supplied to the power supply means is reduced. Turning power on and off can save power.

According to a ninth aspect of the present invention, in the fifth to eighth aspects, a non-magnetic material having a lower resistance than the magnetic conductor is arranged in contact with the exciting means with the magnetic conductor interposed therebetween. Take.

According to this configuration, since the non-magnetic material having a lower resistance than the magnetic conductor is arranged in contact with the magnetic conductor, when the temperature of the magnetic conductor reaches the Curie point and becomes non-magnetic, the non-magnetic material has a lower resistance. Since the induction current flows, the heat generation is suppressed and the temperature drops rapidly, so that the self-temperature control characteristics are improved.

A tenth aspect of the present invention is the non-magnetic material according to the fifth to eighth aspects, wherein the non-magnetic material has a lower resistance than the magnetic conductor via a heat insulating layer at a position facing the exciting means with the magnetic conductor interposed therebetween. Is adopted.

According to this configuration, since the nonmagnetic material having a lower resistance than the magnetic conductor is disposed at the position facing the exciting means with the magnetic conductor interposed therebetween via the heat insulating layer, the temperature of the magnetic conductor reaches the Curie point. In addition, the heat generation of the magnetic conductor after demagnetization can be suppressed, and the heat of the nonmagnetic material can be prevented from being transmitted to the magnetic conductor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1) An example in which the induction heating type fixing device of the present invention is applied to a copying machine or a combined machine of a copying machine and a facsimile will be described.

FIG. 1 shows the overall configuration of the fixing device according to the first embodiment of the present invention.

The fixing device 1 includes an excitation member 3 disposed inside a heat roller 2 made of a hollow cylindrical magnetic conductor, and a pressure roller 4 that presses the heat roller 2 under the heat roller 2.
Are rotatably arranged. A nip 6 for nipping and conveying the recording paper 5 is formed between the heat roller 2 and the pressure roller 4.

The heat roller 2 uses a magnetic alloy (also referred to as a temperature-sensitive metal) having a Curie point higher than the temperature at which the toner can be fixed. In particular, an iron-nickel alloy or an iron-nickel-chromium alloy in which the Curie point of the magnetic alloy is adjusted so that the heat roller stabilization temperature based on the self-temperature control characteristic is equal to or higher than the fixing temperature and equal to or lower than the hot offset start temperature is used.
Since the fixable temperature and the hot offset depend on the toner, the composition of the magnetic alloy is changed so that the fixable temperature is suitable for the toner.

In this example, for a fixing temperature of 190 ° C.,
The Curie point is set at 250 ° C., which is 60 ° C. higher, and the heat roller stabilization temperature based on the self-temperature control characteristic is controlled near the fixing temperature of 210 ° C. It is assumed that the toner hot offset is from 220 ° C. to 250 ° C.

The outer peripheral surface of the heat roller 2 is coated with a fluororesin 7 having a thickness of about 15 μm in order to improve releasability from toner. The exciting member 3 includes a hollow cylindrical bobbin 8.
And an exciting coil 9 spirally wound on the peripheral surface of the bobbin 8, and a ferrite 10 inserted into the bobbin 8. The exciting coil 9 uses a litz wire that is formed by bundling thin conductive wires into a stranded wire.

The excitation coil 9 is connected to an inverter circuit 11 for supplying a high-frequency current.
1 is connected to a control circuit 12 for variably controlling the power supplied to the excitation member 3. As shown in FIG. 2, the control circuit 12 includes a CPU 21 that controls the power supplied to the exciting member 3 with a command value V0, and a voltage control circuit 22 that generates an output voltage V1 corresponding to the command value V0. .

Next, the operation of the present embodiment configured as described above will be described.

When a switch (not shown) is operated, a voltage application command is issued from the control circuit 12 to the inverter circuit 11. Inverter circuit 1 receiving a command from control circuit 12
When a high-frequency current flows from 1 to the exciting coil 9, an alternating magnetic field generated from the exciting coil 9 interlinks the heat roller 2 made of a magnetic conductor, and an eddy current flows through the heat roller 2. FIG.
As shown in (a), the eddy current flowing through the heat roller 2 at this time is reduced by a skin effect in a narrow area 31 on the surface of the heat roller 2.
(Shaded area), the heat generation efficiency by Joule heat increases. When the temperature of the heat roller 2 reaches the Curie point, as shown in FIG. 3B, the heat roller 2 is demagnetized, and the eddy current flows through the entire heat roller. As a result, the cross-sectional area of the passage through which the induced current flows increases, the Joule heat generation efficiency decreases significantly, and the heat roller temperature decreases.

Here, the relationship between the saturation temperature of the heat roller 2, the fixing temperature of the toner, and the hot offset will be described with reference to FIG.

In this embodiment, the Curie point of the magnetic alloy constituting the heat roller 2 is set to 25 for the fixing temperature of the toner of 190 ° C.
Since the temperature is set to 0 ° C., the saturation temperature (heat roller stable temperature) by the self-temperature control of the heat roller 2 becomes the fixing temperature 190
The temperature is around 210 ° C. which is higher than 0 ° C. and lower than the hot offset start temperature 220 ° C.

For this reason, when the heat roller 2 is induction-heated from room temperature, the temperature rise rate of the heat roller 2 becomes gentle before the saturation temperature of 220 ° C. as shown by the solid line a in FIG. The rate of temperature rise hardly decreases.

On the other hand, a broken line b shows a temperature rise curve of the heat roller in which the Curie point of the magnetic alloy is set to 230 ° C. and the self-temperature control is adjusted to 190 ° C. In this case, the temperature rise rate becomes gentle before reaching the fixing temperature of 190 ° C., so that the rising time, which is the time required to reach the fixing temperature, is delayed.

FIG. 5 is a schematic diagram of the heat distribution in the longitudinal direction of the heat roller 2 of the fixing device according to the present embodiment. The example shown in FIG. 5 is a case where small-sized recording paper is continuously fed. Heat roller 2 serving as a paper feed area for small-size recording paper
Of the central portion of the heat roller 2 is lowered because heat is taken away by the recording paper, but the saturation temperature of the heat roller 2 becomes lower than the fixing temperature 190.
Since the temperature is set to be higher than ° C, the temperature is maintained slightly higher than the fixing temperature. For this reason, the occurrence of a fixing defect due to a decrease in the temperature of the sheet feeding area is prevented.

On the other hand, since both ends of the heat roller 2 sandwiching the paper feed area are not deprived of heat by the recording paper, the temperature is higher than the fixing temperature. However, since the saturation temperature is suppressed to a value lower than the hot offset start temperature, self-temperature control is performed so as not to exceed the hot offset start temperature. Therefore, it is possible to prevent hot offset from occurring at both ends of the heat roller 2 even when a large-size recording paper is passed.

In this embodiment, the inverter circuit 1
The control circuit 12 controls a high-frequency current flowing from 1 to the exciting coil 9. The control circuit 12 controls the current value of the high-frequency current flowing through the exciting coil 9 according to each mode such as at the time of startup or standby.

FIG. 6 shows a command value V0 output from the CPU 21.
4 shows the relationship between the output voltage V1 output from the voltage generation circuit 22, the high-frequency current I0 output from the inverter circuit 11, and the roller temperature of the heat roller 2. The CPU 21
The voltage command V0 is output according to a predetermined time. According to the voltage command V0, the voltage generation circuit 22 outputs the voltage output V
Outputs 1. Further, according to the output voltage V1, the inverter circuit 11 supplies the high-frequency current I0 to the induction heating coil. As shown in the figure, when the voltage value VA shifts to VB and VC, the output current I0 of the inverter circuit 11 also decreases from the current value IA to IB and IC, and the power supplied to the exciting coil 9 decreases. The temperature of the temperature decreases. Therefore, by the CPU 21 detecting each mode and outputting a command value corresponding to the mode, appropriate power saving control can be performed.

FIG. 7 shows a modification of the control system of the fixing device.
Although the control system shown in FIG. 2 controls the current value of the inverter circuit 11 with the output voltage of the voltage generation circuit 22, the control system shown in FIG. 7 controls the current value with the duty ratio.

The control circuit 71 comprises a CPU 73 and a duty generation circuit 74. FIG. 8 shows a circuit configuration of the duty generation circuit 74. Duty generation circuit 74
Has an oscillation circuit 82 connected between both ends of a DC power supply 81,
Further, two transistors 83,
84 are connected in parallel.

In the circuit shown in FIG. 8, an ammeter 86 and a voltmeter 87 are provided between the inverter circuit 72 and the exciting member 3, so that the power supplied to the exciting member can be measured.

As shown in FIG. 9, CPU 73 outputs command value V0 according to a predetermined time. According to V0, the duty generation circuit 74 outputs an output S0 having a different ON-OFF ratio (duty). In the inverter circuit 72, the transistors 83 and 84 are alternately turned ON and OFF at a predetermined oscillation frequency corresponding to the output S0 from the oscillation circuit 22, and the high frequency current is
Supply to When the duty ratio of the output S0 decreases from SA to SB and SC, the high-frequency current I1 changes from ID to I
E, IF and supply power are reduced. The above operation lowers the temperature of the heat roller in the same manner as described above.

(Embodiment 2) FIG. 10 shows the overall configuration of a fixing device according to Embodiment 2 of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals.

The second embodiment is the same as the first embodiment except that the surface temperature of the heat roller is detected and the temperature is controlled near the fixing temperature. That is, also in the present embodiment, the fixing temperature of the toner is 1
It is assumed that the temperature is 90 ° C. and the hot offset start temperature is 220 ° C.

Thermistor 1 for detecting temperature of heat roller 2
00 is provided. The thermistor 100 is disposed within the width of the member to be heated such as paper.

Next, the operation of the present embodiment configured as described above will be described.

In this embodiment, the temperature of the heat roller is detected by the thermistor 100 and output to the control circuit 101. In the control circuit 101, the CPU 102 monitors the heat roller temperature input from the thermistor 100. Then, after detecting from the thermistor output that the heat roller 2 has reached the fixing temperature of 190 ° C., the power applied to the exciting coil 9 is reduced, and the heat roller 2 is maintained at 190 ° C. As a method for maintaining the heat roller 2 at 190 ° C., the power applied to the exciting coil 9 may be turned on and off.

FIG. 11 shows a temperature rise curve of the heat roller when the power applied to the exciting coil 9 is turned on and off. Further, the state of the temperature distribution in the longitudinal direction of the heat roller 2 when the small-size paper is continuously copied is the same as in the first embodiment.
As shown in FIG. The temperature of the heat roller 2 in the range where the sheet passes is substantially constant at 190 ° C. because the control by thermistor detection is performed. Although the temperature of the heat rollers 2 at both ends where the paper does not pass is higher than that of the central part, the temperature does not exceed 210 ° C. because the self-temperature control of the heat roller 2 is functioning.

In the first embodiment, the thermistor 100
, The temperature of the heat roller is constantly controlled at around 210 ° C. Therefore, in the first embodiment, compared to the second embodiment, there is a possibility that heat is released to the entire apparatus and the temperature of the entire apparatus increases. Also, since the heat roller needs to be maintained at a high temperature, the power consumption energy is naturally high.

Therefore, according to the second embodiment, by controlling the temperature near the fixing temperature based on the detection of the heat roller temperature by the thermistor 102, a more efficient fixing device can be obtained.

(Embodiment 3) In this embodiment, the self-temperature control function is enhanced by using two layers of heat rollers in the above-described fixing device. Only the heat roller will be described.

As shown in FIG. 12, the heat roller 120 is
A two-layer structure including an inner peripheral portion 121 made of a magnetic conductor and an outer peripheral portion 122 made of a nonmagnetic material and arranged in contact with the outer peripheral surface of the inner peripheral portion 122 may be used. Inner circumference 121
The Curie point is set to be equal to or higher than the hot offset start temperature so that the saturation temperature of the heat roller 120 is equal to or higher than the fixing temperature and equal to or lower than the hot offset. Outer part 12
2 is made of a non-magnetic conductor having a lower resistance than the inner peripheral portion 121. Aluminum or copper is suitable as the material of the non-magnetic conductor.

As described above, in the heat roller 120 having the two-layer structure in which the resistivity on the non-magnetic material side is lower than that on the magnetic conductor side, the temperature of the inner peripheral portion 121 on the magnetic conductor side is equal to or lower than the Curie temperature. As shown in FIG. 12A, an induced current flows only on the surface due to the skin effect and the temperature rises rapidly. When the temperature of the inner peripheral portion 121 rises and exceeds the Curie point and becomes a non-magnetic material, as shown in FIG. It flows on the 122 side. As a result, the calorific value of the inner peripheral portion 121 is greatly reduced, and the temperature of the entire heat roller is rapidly reduced.

Therefore, the heat roller 12 having the two-layer structure
Heat roller 1 reached Curie point by using 0
20 can be rapidly lowered, so that the performance of the self-temperature control characteristic can be improved. In order to keep the saturation temperature of the heat roller 120 below the fixing temperature and below the hot offset start temperature, high self-temperature control characteristics are required, so that the heat roller 120 having the two-layer structure is extremely effective.

In the above example, the roller-type fixing device is described in detail. Instead of the heat roller, a film made of a temperature-sensitive metal or a film having a heat-resistant film in contact with or close to a temperature-sensitive metal plate of a fixed heat source. A fixing device of the type can also be configured. At this time, if the laminated non-magnetic metal material is arranged on the opposite surface of the heating coil of each temperature-sensitive metal,
The self-temperature control characteristic can be improved as in the case of the heat roller fixing device.

(Embodiment 4) FIG. 13 is a perspective view showing an induction heating section of a fixing device according to Embodiment 4 of the present invention. In the fourth embodiment, a spirally wound excitation coil 132 is disposed outside the magnetic alloy 131 whose Curie temperature is set to an appropriate temperature so as not to contact the magnetic alloy 131 by an appropriate method. Also, inside the magnetic alloy 131,
Non-magnetic metal material 1 having a lower resistivity than magnetic alloy 131
33 is arranged with a space from the magnetic alloy 131.

With the above configuration, the object to be heated by the excitation coil 132 is only the magnetic alloy 131, and a heating means with high thermal efficiency can be realized. That is, according to the fourth embodiment, since the magnetic alloy 131 and the non-magnetic metal material 133 are arranged with a space therebetween, the excitation coil 132 is heated only by the magnetic alloy 131. The heating target has a very small heat capacity as compared with the case where the entire heat roller is heated. Further, even when the non-magnetic metal material 133 is not in contact with the magnetic alloy 131, the magnetically identical operation is performed. That is, when the temperature of the magnetic alloy 131 exceeds the Curie point, when the magnetic alloy 131 becomes non-magnetic and a magnetic flux passes through the magnetic alloy 131, an induced current flows through the non-magnetic metal material 133 inside.

As described above, according to the fourth embodiment, only the magnetic alloy 131 can be heated by the excitation coil 132, a fixing device with high thermal efficiency can be realized, and the time required to reach a predetermined temperature can be shortened. it can.

(Embodiment 5) FIG. 14 is a schematic diagram showing an induction heating section of a fixing device according to Embodiment 5 of the present invention. In the fifth embodiment, as shown in FIG. 14, the arrangement position of the exciting coil 141 is
31 or a position immediately before the magnetic alloy 131 contacts the object 142 to be heated. Also,
In the fifth embodiment, the nonmagnetic metal material 133 is arranged so as to form a circular arc facing a part of the magnetic alloy 131 with a space from the magnetic alloy 131. Arrow 14 in the figure
The direction indicated by 4 indicates the rotation direction of the magnetic alloy 131. In the fifth embodiment, the pressure roller 145 is also made of a low-resistance non-magnetic metal material.

With the above configuration, the exciting coil 141 is
A position where the magnetic alloy 131 is in contact with the object to be heated 142 or a position immediately before contacting the object to be heated 142 is heated.
As a result, the magnetic alloy 131 that has reached the predetermined temperature immediately heats the object to be heated 142, the time during which the magnetic alloy 131 is at a high temperature is shortened, the amount of heat radiation from the surface of the magnetic alloy 131 is reduced, and A low-power fixing device can be realized.

In the fifth embodiment, the magnetic alloy 131
The non-magnetic metal material 133 arranged in order to enhance the self-temperature controllability of the non-magnetic metal material is formed into an arc, and the action of the non-magnetic metal material 133 is performed by using the non-magnetic metal material.
45 to complement.

(Embodiment 6) FIG. 15 is a schematic diagram showing an induction heating section of a fixing device according to Embodiment 6 of the present invention. In the sixth embodiment, the excitation coil 151 is arranged at a position where the object to be heated 142 and the magnetic alloy 131 are separated from each other. Since the arrangement position of the excitation coil 151 is set to this position, it takes time until the magnetic alloy 131 rotates as indicated by an arrow 144 and contacts the object 142 to be heated next. Therefore, the temperature of the portion where the magnetic alloy 131 contacts the object to be heated is lower than the temperature of the portion that is heated by the exciting coil 151, but the temperature distribution becomes more uniform.

(Embodiment 7) FIG. 16 is a schematic diagram showing an induction heating section of a fixing device according to Embodiment 7 of the present invention. In the fixing device according to the seventh embodiment, the magnetic conductor film is induction-heated, and the induction current due to the magnetic flux transmitted through the magnetic conductor film that has become non-magnetic at the Curie temperature is converted into the electric resistivity embedded in the pressure roller. Of non-magnetic material having a low flow rate.

An exciting coil 162 in which a ferrite 161 is wound with a magnetic conductor film 160 having substantially the same thickness as the skin depth at a predetermined Curie temperature by adjusting the composition.
A high-frequency current is passed through to induce induction heating. The magnetic conductor film 160 rotates by sliding under a guide plate 163 made of resin or ceramic. And paper 16 with toner powder on it
4 is heated and fixed while being pressed between the magnetic conductive film 160 and the pressure roller 165.

The pressure roller 165 has an elastic surface,
It is made of silicone rubber 166 that plays the role of a heat insulator. A nonmagnetic material 167 having a low electric resistivity is embedded inside the pressure roller 165. Such a pressure roller 1
65 rotates about axis 168. With such a configuration, the magnetic conductor film 160 generates heat below the Curie temperature, and the current induced by the magnetic flux 169 transmitted through the non-magnetic magnetic conductor film 160 above the Curie temperature is embedded in the pressure roller 165. By flowing the non-magnetic material 167 having a low electric resistivity, the amount of heat generation is reduced, and the self-temperature control performance is exhibited.

The non-magnetic material 167 having a low electric resistivity
Is preferably aluminum or copper, but may be a nonmetal such as carbon if the electric resistivity is low. Also, the shaft 168 may be made of the same material and integrated.

(Eighth Embodiment) FIGS. 17 (a) and 17
(B) is a schematic diagram illustrating an induction heating unit of a fixing device according to Embodiment 8 of the present invention. In the eighth embodiment, the magnetic conductor pipe 170 is externally heated by the excitation coil 171. A non-magnetic material 172 having a lower electric resistivity than the magnetic conductor pipe 170 is arranged inside the magnetic conductor pipe 170 via a space. If a heat insulating material 173 is wound around the surface of the nonmagnetic material 172 so as not to be in contact with the magnetic conductor pipe 170, the air can also have a heat insulating effect and a small heat capacity, and at the same time, the nonmagnetic material 172 having a low electric resistivity can be used. 173 can be fixed to provide a structure in which only the magnetic conductor pipe 170 rotates.

On the other hand, as shown in FIG.
When the contact is made with the magnetic conductor pipe 170, the strength of the magnetic conductor pipe 170 can be reinforced by the nonmagnetic material 172 and the heat insulating material 173 having low electric resistivity.

[0081]

As described above in detail, according to the present invention, it is possible to prevent the warm-up time from being delayed due to the slowing of the temperature rise near the Curie point of the material to be heated, and furthermore, the fixing without causing hot offset. Equipment can be provided.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a control system provided in the fixing device according to the first embodiment.

FIG. 3 is a diagram showing a skin effect of a magnetic conductor and a state after the Curie temperature is reached.

FIG. 4 is a diagram illustrating a temperature rise curve of a heat roller in the fixing device according to the first embodiment.

FIG. 5 is a longitudinal temperature distribution diagram of a heat roller when small-size paper is continuously copied.

FIG. 6 is a diagram illustrating a relationship among a command value, a high-frequency current value, and a roller temperature;

FIG. 7 is a block diagram of a modification of the control system of the fixing device according to the first embodiment;

8 is a circuit diagram of the duty generation circuit and the excitation member shown in FIG.

FIG. 9 is a diagram illustrating a relationship among a command value, a high-frequency current value, and a roller temperature in a modified example.

FIG. 10 is a configuration diagram of a fixing device according to a second embodiment.

FIG. 11 is a diagram showing a temperature rise curve of a heat roller in the fixing device according to the second embodiment.

FIG. 12 is a configuration diagram of a heat roller provided in a fixing device according to a third embodiment;

FIG. 13 is a configuration diagram of a heat roller portion of the fixing device according to the fourth embodiment.

FIG. 14 is a configuration diagram of a heat roller portion of the fixing device according to the fifth embodiment.

FIG. 15 is a configuration diagram of a heat roller portion of the fixing device according to the sixth embodiment.

FIG. 16 is a configuration diagram of a heat roller portion of the fixing device according to the seventh embodiment.

FIG. 17 is a configuration diagram of a heat roller portion of the fixing device according to the eighth embodiment.

FIG. 18 is a diagram showing self-temperature control characteristics of a heat roller.

FIG. 19 is a temperature distribution diagram in the longitudinal direction of the heat roller when a small-sized recording material is continuously printed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing apparatus 2 Heat roller 3 Exciting member 4 Pressure roller 5 Recording paper 8 Bobbin 9 Exciting coil 10 Ferrite 11 Inverter circuit 12 Control circuit

Claims (10)

[Claims] 1. A method for fixing a material to be heated by induction heating a magnetic conductor having a Curie point set so that a saturation temperature based on a self-temperature control characteristic falls within a range of not less than a fixing temperature and not more than a hot offset start temperature. Fixing device. 2. The fixing device according to claim 1, wherein the Curie point of the magnetic conductor is set to a temperature equal to or higher than a hot offset start temperature. 3. The fixing device according to claim 1, wherein the Curie point is set such that the saturation temperature of the magnetic conductor approaches the hot offset start temperature from the fixing temperature. 4. The Curie point is set so that the temperature of the paper passing area on the surface of the magnetic conductor does not fall below the fixing temperature even during continuous paper passing, and the temperature of the non-paper passing area does not exceed the hot offset start temperature. The fixing device according to claim 1, wherein: 5. A magnetic conductor having a Curie point set so that a saturation temperature based on a self-temperature control characteristic falls within a range of not less than a fixing temperature and not more than a hot offset start temperature, and excitation for applying an alternating magnetic flux to the magnetic conductor. A fixing device comprising: a power supply unit that supplies an alternating current to the excitation unit; and a conveyance unit that conveys the material to be heated by opposing the magnetic conductor. 6. A temperature sensor for detecting a temperature in the vicinity of the magnetic conductor or the fixing region, and electric power supplied to the power supply unit based on a temperature detected by the temperature sensor so that the temperature of the magnetic conductor becomes close to a fixing temperature. The fixing device according to claim 5, further comprising a control unit configured to control the fixing device. 7. The control device according to claim 1, wherein when the detected temperature reaches a target temperature corresponding to the fixing temperature, the control unit decreases the power supplied to the power supply unit to maintain the fixing temperature. Item 7. A fixing device according to Item 6. 8. The control device according to claim 1, wherein when the detected temperature reaches a target temperature corresponding to the fixing temperature, the control unit turns on and off the power supplied to the power supply unit to maintain the fixing temperature. Item 7. A fixing device according to Item 6. 9. The fixing device according to claim 5, wherein a non-magnetic material having a lower resistance than the magnetic conductor is laminated so as to face the exciting means with a magnetic conductor interposed therebetween. 10. A non-magnetic material having a lower resistance than the magnetic conductor is disposed at a position facing the exciting means with a magnetic conductor interposed therebetween with a heat insulating layer interposed therebetween. Fixing device.