JP4862728B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an electromagnetic induction heating type fixing device. This type of electromagnetic induction heating type fixing device is typically incorporated in an image forming apparatus such as a copying machine or a printer, and is used to fix toner on a sheet such as paper.

  The present invention also relates to an image forming apparatus provided with such a fixing device.

  Conventionally, as an electromagnetic induction heating type fixing device, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2001-43965), a fixing roller and a pressure roller that are pressed against each other so as to form a nip portion, And an exciting coil disposed along the fixing roller. The fixing roller is heated by electromagnetic induction by the exciting coil, and a sheet (recording paper) to which a toner image is attached is conveyed through the nip portion to fix the fixing roller. A toner image is melted and fixed on a sheet by heat generated by a roller. In this document, a degaussing coil is provided along an exciting coil in a region corresponding to the axial end of the fixing roller. When the maximum size sheet is passed, the degaussing coil is open. On the other hand, when a small-size sheet is passed, by closing the degaussing coil, the change in magnetic flux due to the exciting coil is canceled in the area where the degaussing coil is arranged, and the axial end of the fixing roller It is designed to prevent excessive temperature rise.

In the conventional example, an inverter circuit for supplying power to the exciting coil is provided. In the temperature control of the fixing roller, the surface temperature of the fixing roller is detected by a temperature sensor, and the output frequency of the inverter circuit is varied so that the surface temperature of the fixing roller becomes a predetermined target temperature. This is performed by increasing or decreasing the power supply (feedback control).
JP 2001-43965 A

However, with the opening and closing of the degaussing coil, as illustrated in FIG. 7, for example, the load viewed from the power supply side (inverter circuit) with respect to the exciting coil, that is, the exciting coil and the degaussing coil and the fixing electromagnetically coupled thereto. The impedance of the equivalent circuit created by the roller changes. Accordingly, the frequency characteristic when the degaussing coil is open (shown by a solid line. The resonance frequency is f ₀₁ ) is different from the frequency characteristic when the degaussing coil is closed (shown by a broken line. The resonance frequency is f ₀₂ ). Shift to high frequency side. For this reason, for example, when the demagnetizing coil is switched from open to closed when the power P to be supplied to the fixing roller is 1200 W, the output frequency f of the inverter circuit is sufficiently higher than the assumed output frequency (see FIG. 7 is set to f ₁ ) and gradually shifted to a lower output frequency (f _{2 in} FIG. 7). The reason for this is to prevent an excessive power of 1200 W or more from being input immediately after switching the opening and closing of the degaussing coil. Further, if the output frequency f coincides with the resonance frequency (resonance point), the inverter circuit may be destroyed. As a result, in such a control method, there is a problem that the response time until returning to the steady state becomes long and the fixing quality is impaired.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that can prevent an excessive increase in temperature at the end of a fixing member when passing through a small-size sheet and can solve the problem of fixing quality caused by response time.

  Another object of the present invention is to provide an image forming apparatus provided with such a fixing device.

In order to solve the above problems, the fixing device of the present invention is:
A fixing member in which the conveyed sheet is pressed against the outer peripheral surface;
An excitation coil disposed elongated along the outer circumferential surface of the fixing member in the width direction of the conveyed sheet;
A capacitor connected to the excitation coil and equivalently constituting a resonance circuit;
A demagnetizing coil disposed along the exciting coil in a region corresponding to the end of the fixing member in the width direction of the sheet on the opposite side of the fixing member with respect to the exciting coil;
A high-frequency power supply unit that induction-heats the fixing member via the excitation coil by applying an AC voltage to the resonance circuit;
A temperature detector for detecting the temperature of the fixing member;
The relationship between the output power value output from the high-frequency power supply unit to the resonance circuit and the output frequency of the high-frequency power supply unit corresponding to the output power value in each of the case where the degaussing coil is open and closed A characteristic acquisition unit to acquire;
Based on the correspondence between the output power value acquired by the characteristic acquisition unit and the output frequency, the high-frequency power source so that the temperature of the fixing member detected by the temperature detection unit matches a predetermined target temperature. A fixing control unit that performs control to vary and set the output frequency of the unit.

  In the fixing device according to the present invention, the characteristic acquisition unit corresponds to the output power value output from the high frequency power supply unit to the resonance circuit and the output power value in each of the case where the demagnetizing coil is open and the case where the demagnetizing coil is closed. The correspondence relationship with the output frequency of the high frequency power supply unit is acquired. Thereafter, the fixing control unit sets the temperature of the fixing member detected by the temperature detection unit to a predetermined target temperature based on the correspondence relationship between the output power value acquired by the characteristic acquisition unit and the output frequency. Control is performed to variably set the output frequency of the high frequency power supply unit so as to match.

  In this fixing device, thanks to the degaussing coil, it is possible to prevent an excessive temperature rise at the end of the fixing member when the small size sheet passes. The control by the fixing control unit is performed based on the correspondence relationship between the output frequency acquired by the characteristic acquisition unit and the output power value. Therefore, even if the degaussing coil is opened and closed, the output frequency of the high frequency power supply unit set immediately after switching the degaussing coil is not greatly deviated from the output frequency that gives a steady state. Therefore, according to this fixing device, the steady state can be reached immediately, and the fixing quality can be kept good. That is, the problem of fixing quality caused by the response time can be solved.

  The fixing device according to an embodiment includes a storage unit that stores a correspondence relationship between the output power value acquired by the characteristic acquisition unit and the output frequency.

  In the fixing device according to this embodiment, the correspondence relationship between the output power value acquired by the characteristic acquisition unit and the output frequency is stored in the storage unit. Therefore, the characteristic acquisition unit does not need to acquire the correspondence relationship between the output frequency and the output power value every time the job of the apparatus is started. For example, acquired only when there is a possibility that the correspondence between the output frequency and the output power value (that is, the frequency characteristics of the resonance circuit) may fluctuate, such as after a member is removed or replaced due to a jam. All you need is enough. Thereby, processing time can be shortened.

  In the fixing device according to an embodiment, when the characteristic acquisition unit acquires a correspondence relationship between the output power value and the output frequency, the storage unit uses the correspondence relationship acquired by the characteristic acquisition unit. The stored contents are updated.

  In the fixing device according to the embodiment, when the characteristic acquisition unit acquires the correspondence relationship between the output power value and the output frequency, the storage unit stores the correspondence relationship acquired by the characteristic acquisition unit. It is used to update the stored contents. Therefore, even if the correspondence relationship between the output power value and the output frequency is changed after a member is attached / detached or a part is replaced due to the occurrence of a jam, the fixing quality can be kept good. That is, the problem of fixing quality due to the response time does not occur.

  An image forming apparatus of the present invention is an image forming apparatus provided with the above-described fixing device.

  In the image forming apparatus according to the present invention, in the fixing device, it is possible to prevent an excessive temperature rise at the end of the fixing member when passing through the small size sheet, and to solve the problem of fixing quality caused by the response time. Therefore, the image quality can be improved.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 shows a block configuration of a fixing device according to an embodiment of the present invention. The fixing device includes a fixing unit 10, a demagnetizing unit 30 provided in the vicinity of the fixing unit 10, a power supply device 11 as a high frequency power supply unit, and a system control unit 20 that controls the operation of the entire fixing device. It has.

  The fixing unit 10 includes a fixing roller 1 as a fixing member, a pressure roller 2 as a pressure member, an excitation coil 3, and a temperature detection sensor 4 as a temperature detection unit, which are positioned and attached. Yes.

  The fixing roller 1 and the pressure roller 2 are pressed against each other by a biasing means such as a spring (not shown) so as to form a nip 5 through which a sheet 6 such as paper passes. However, when a jam occurs, the pressure roller 2 can be removed in the right direction (+ Y direction) in FIG. 1 while leaving the exciting coil 3 and the fixing roller 1. Further, when replacing the parts, the fixing roller 1 and the pressure roller 2 can be removed in the right direction in FIG. 1 while leaving the exciting coil 3.

  As shown in FIG. 1, with the components 1, 2, 3, and 4 attached to the fixing unit 10, the fixing roller 1 is moved in the direction of arrow a (counterclockwise in FIG. 1) by a drive source (such as a motor) not shown. The pressure roller 2 is rotated in the direction of arrow b (clockwise in FIG. 1). During the fixing operation, the sheet 6 having the toner 9 attached to one side 6a is conveyed from below to above through the nip 5 in FIG. As a result, the toner 9 is fixed to the sheet 6. A direction (X direction) perpendicular to the paper surface of FIG. 1 corresponds to the width direction of the sheet 6. Note that the fixing roller 1 may be driven to rotate and the pressure roller 2 may be driven to rotate. That is, the relationship between driving and driven may be reversed.

  The fixing roller 1 includes, for example, a 5 mm thick Si (silicon) sponge rubber layer, a 50 μm thick Ni (nickel) and Cr (chromium) alloy layer, and a 1 mm thick Si core on an iron core. A rubber layer and a surface layer made of PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) having a thickness of 20 μm are provided. Further, the pressure roller 2 is configured by providing a Si foam rubber layer having a thickness of 5 mm and a PFA surface layer having a thickness of 30 μm on an iron cored bar.

  For example, as shown in FIG. 4A, the exciting coil 3 is elongated above the fixing roller 1 in the axial direction of the fixing roller 1 (corresponding to the X direction in FIG. 1). Specifically, the exciting coil 3 is formed by winding an electric wire bundle into an oval shape a plurality of times so as to form a layer. The layer is supported by a holder (not shown) and is disposed close to the outer peripheral surface of the fixing roller 1. As a result, by passing an alternating current through the exciting coil 3, the NiCr alloy layer included in the fixing roller 1 is directly heated by electromagnetic induction. One conductive wire bundle is formed by bundling a few hundred dozens of strands (copper wires having a diameter of about 0.18 mm to 0.20 mm, which are insulated and coated with enamel) in order to increase the energization efficiency. It is a known stranded wire having a diameter of about several mm.

  As shown in FIG. 4A, the temperature detection sensor 4 as a temperature detection unit is disposed opposite to the central portion A in the axial direction on the outer peripheral surface of the fixing roller 1, and is fixed by a known infrared method. The surface temperature of this central portion A (referred to as temperature Ta) is detected. The temperature Ta detected by the temperature detection sensor 4 is sent to the system control unit 20 shown in FIG.

  In the demagnetizing unit 30 shown in FIG. 1, two demagnetizing coils 31A and 31B are positioned and attached. As shown in FIG. 4A, the degaussing coils 31A and 31B are arranged along the exciting coil 3 in areas corresponding to the end portions B and B on both sides in the axial direction of the fixing roller 1 above the exciting coil 3, respectively. ing. Each of the degaussing coils 31A and 31B is shorter than the exciting coil 3, but is formed by winding a wire bundle in an elliptical shape a plurality of times in the same manner as the exciting coil 3. These degaussing coils 31A and 31B are held at positions separated from the excitation coil 3 by a distance Z1 in the Z direction.

  The power supply device 11 shown in FIG. 1 converts commercial power into a high frequency having a frequency corresponding to the excitation control signal SigE from the system control unit 20 (hereinafter referred to as “output frequency”), The voltage (power) is output to the exciting coil 3. As a result, an alternating current is passed through the exciting coil 3 to inductively heat the NiCr alloy layer included in the fixing roller 1. At the same time, the power supply device 11 opens and closes the degaussing coils 31A and 31B by turning off and on a switch (not shown) according to the demagnetization control signal SigD from the system control unit 20. If the degaussing coil is in the “open” state, no induced current flows through the degaussing coil, so degaussing is not performed. If the degaussing coil is in the “closed” state, an induced current flows through the degaussing coil, and degaussing becomes possible.

  Specifically, as shown in FIG. 4B, when the degaussing coils 31A and 31B are “open”, the demagnetizing force of the degaussing coils 31A and 31B is not generated, and as a result, the electric power input at the end B of the fixing roller 1 Qb is substantially equal to the electric power Qa input to the central portion A. In this case, it is possible to satisfactorily fix a maximum size sheet that passes through substantially the entire axial direction of the fixing roller 1. On the other hand, as shown in FIG. 4A, when the degaussing coils 31A and 31B are “closed”, the demagnetizing force Qd of the degaussing coils 31A and 31B is generated. As a result, compared with the electric power Qa input to the central portion A of the fixing roller 1, the electric power input at the end B of the fixing roller 1 is small, for example, Qb (<Qa). Therefore, even if the sheet 6 shown in FIG. 1 is a small size sheet that passes only through the central portion A of the fixing roller 1, it is possible to prevent an excessive temperature rise at the end B of the fixing roller 1. This makes it possible to fix the small size sheet satisfactorily.

  FIG. 2 specifically shows the configuration of an inverter circuit included in the power supply device 11 in order to cause an alternating current to flow through the exciting coil 3. As a configuration of the inverter circuit, a parallel resonance circuit and a series resonance circuit are conceivable. FIG. 2 shows an example of a preferable series resonance circuit.

  In FIG. 2, the exciting coil 3 shown in FIG. 1 is represented by a series equivalent circuit 43 including an inductance Ls43 and an effective resistance Rs43. This series equivalent circuit 43 includes contributions of the fixing roller 1 and the demagnetizing coils 31A and 31B coupled to the exciting coil 3 by electromagnetic induction in addition to the exciting coil 3. The values of the inductance Ls43 and the effective resistance Rs43 are obtained by connecting an impedance measuring instrument generally called an LCR meter to both ends of the exciting coil 3 and measuring.

A resonance capacitor 44 as a capacitor is connected in series to the IH unit 43, actually the exciting coil 3, thereby forming a series resonance circuit 42. The resonance frequency f ₀ (unit: Hz) of the series resonance circuit 42 is given by the following equation (1).
f ₀ = 1 / (2π (LsC) ^1/2 ) (1)

    However, Ls is the value of inductance Ls43 (unit; H (henry)), and C is the capacity of resonance capacitor 44 (unit: F (farad)).

  The inverter circuit includes a diode bridge DB41 connected to a commercial power supply (AC power supply) 12, a rectifier circuit 41 including a smoothing coil Lf41 and a smoothing capacitor Cf41, a pair of switching elements 45A and 45B each including a power transistor, and It comprises flywheel diodes D45A and D45B for protecting the switching elements 45A and 45B from overvoltage.

  The pair of switching elements 45 </ b> A and 45 </ b> B are on / off controlled at an output frequency f corresponding to the excitation control signal SigE from the system control unit 20. As a result, power is supplied to the fixing roller 1 via the IH unit 43.

FIG. 3 shows a drive waveform of the series resonance circuit 42. I _Ls represents the current through the IH unit _{43, V CE} is the respective switching elements 45A, shows the collector-emitter voltage of 45B, also, T is shows a switching element on period.

  FIG. 5 illustrates the frequency characteristics of the series resonance circuit 42, that is, the relationship between the output frequency f of the inverter circuit and the power P input to the fixing roller 1. In the series resonance circuit 42, when the output frequency f coincides with the resonance frequency (frequency that gives the peak of the graph), the impedance Z is minimized and the current flows most. Accordingly, the power value P input to the fixing roller 1 is maximized. A plurality of graphs C1, C2, C3, C4, and C5 show modes in which the frequency characteristics change depending on opening / closing of the degaussing coils 31A and 31B, attachment / detachment of a member due to jam occurrence, assembly variation accompanying component replacement, and the like. In this example, a graph C5 shows a standard frequency characteristic when the degaussing coil is open, and a graph C2 shows a standard frequency characteristic when the degaussing coil is closed. In FIG. 5, five graphs C1, C2, C3, C4, and C5, that is, five frequency characteristics are shown. However, the series resonance circuit 42 can take various characteristics continuously or substantially continuously in multiple stages. .

  The system control unit 20 illustrated in FIG. 1 sets a power instruction value that represents a power value (output power value) to be output by the power supply device (particularly the inverter circuit) 11. Then, a control signal indicating the output frequency of the power supply device 11 is output according to the power instruction value, and the temperature of the outer peripheral surface of the fixing roller 1 becomes the target temperature based on the temperature Ta detected by the temperature detection sensor 4. As described above, the excitation control signal SigE is output to feedback control the power supply device 11 (details will be described later). In the control example described later, the degaussing coils 31A and 31B are switched between open and closed by a demagnetization control signal SigD. The system control unit 20 includes, for example, a CPU (Central Processing Unit) 21 and a storage unit 23 that stores processing programs and various data. The system control unit 20 may be a circuit that controls only the fixing device, or may be a part of a circuit that controls the entire upper apparatus, for example, the entire image forming apparatus in which the fixing device is incorporated. There may be.

  Further, the system control unit 20 detects the output power value and the output frequency output from the power supply device (particularly the inverter circuit) 11. This function includes, for example, a pickup coil wound around an output cable from the power supply device (particularly an inverter circuit) 11 to the electromagnetic induction coil 3, and detects power or current using a counter electromotive force induced in the pickup coil. This can be realized by a known technique.

  FIG. 6 shows a specific control flow by the system control unit 20.

First, in step S1 of FIG. 6, the system control unit 20 functions as a characteristic acquisition unit, and is output from the power supply device 11 to the series resonance circuit 42 in each of the cases where the demagnetizing coils 31A and 31B are open and closed. The correspondence relationship between the output power value and the output frequency of the power supply device 11 corresponding to the output power value is acquired. Specifically, for example, as shown in FIG. 5, assuming that the current frequency characteristic is C3 and the power P to be input to the fixing roller 1 is 1200 W (watts), the power supply according to them is as follows. Since the output frequency f of the device 11 is controlled to f ₃ = about 43 kHz, this frequency f ₃ is measured. In this way, the correspondence between the output power value P and the output frequency f is acquired in each of the cases where the degaussing coils 31A and 31B are open and closed (step S2). Next, the correspondence relationship between the acquired output power value P and the output frequency f is stored in the storage unit 23 (see FIG. 1) (step S3).

  Thereafter, the system control unit 20 works as a fixing control unit, and the fixing roller 1 detected by the temperature detection sensor 4 based on the correspondence between the output power value P stored in the storage unit 23 and the output frequency f. An excitation control signal SigE is output so that the power supply device 11 is feedback-controlled so that the temperature Ta of the outer peripheral surface becomes the target temperature Tt.

Specifically, the system control unit 20 sets the power value (output power value) to be output by the power supply device (particularly the inverter circuit) 11, and outputs the output power value P and the output frequency f stored in the storage unit 23. The output frequency f of the power supply device 11 is set based on the correspondence relationship between the two. For example, as shown in FIG. 5, assuming that the current frequency characteristic is C3 and the power P to be input to the fixing roller 1 is 1200 W (watts), the output frequency of the power supply device 11 according to them. f ₃ is set to about 43 kHz with f as an initial value.

  In step S <b> 4 of FIG. 6, the system control unit 20 detects the temperature Ta of the fixing roller 1 (the central portion A) by the temperature detection sensor 4. Next, in step S5, the temperature Ta is compared with the target temperature Tt corresponding to the output power value P to be output by the power supply device (particularly the inverter circuit) 11. Here, if Ta <Tt, the process proceeds to step S6, and the output frequency f of the power supply device 11 is decreased. As a result, the actual power supplied to the fixing roller 1 increases according to the slope of the frequency characteristic C3 in FIG. 5, and the temperature Ta of the fixing roller 1 rises. On the other hand, if Ta> Tt in step S5, the process proceeds to step S7 to increase the output frequency f of the power supply device 11. As a result, the actual power supplied to the fixing roller 1 increases according to the slope of the frequency characteristic C3 in FIG. 5, and the temperature Ta of the fixing roller 1 decreases. In this way, the system control unit 20 performs feedback control so that the temperature Ta of the fixing roller 1 matches the target temperature Tt (steps S4 to S7).

  If the temperature Ta of the fixing roller 1 coincides with the target temperature Tt in step S5 of FIG. 6, the fixing control (feedback control) has reached a steady state, and the process returns to another control.

  Thus, this fixing control is performed based on the correspondence between the output power value P and the output frequency f. Therefore, for example, even if the degaussing coils 31A and 31B are opened and closed outside the control flow of FIG. 6, the output frequency f of the power supply device 11 set immediately after switching of the degaussing coils 31A and 31B is an output frequency that gives a steady state. Will not deviate significantly from Therefore, according to this fixing device, the steady state can be reached immediately, and the fixing quality can be kept good. That is, the problem of fixing quality caused by the response time can be solved.

  In this fixing device, the storage unit 23 stores a correspondence relationship between the acquired output power value P and the output frequency f. Therefore, the system control unit 20 does not need to acquire the correspondence between the output power value P and the output frequency f every time the job of this apparatus is started. For example, only when there is a possibility that the correspondence between the output frequency and the output power value (that is, the frequency characteristic of the series resonant circuit 42) may fluctuate, such as after the attachment / detachment of a member due to the occurrence of a jam or after the replacement of a component. You only need to get it. Thereby, processing time can be shortened.

  If the correspondence between the output power value P and the output frequency f is acquired, the storage unit 23 desirably updates the stored content using the acquired correspondence. In such a case, even if the correspondence between the output power value P and the output frequency f is changed after a member is attached / detached or a part is replaced due to the occurrence of a jam, the fixing quality can be kept good. That is, the problem of fixing quality due to the response time does not occur.

  As described above, in this fixing device, it is possible to prevent the excessive temperature rise at the end B of the fixing roller 1 when passing through the small size sheet, and it is possible to solve the problem of fixing quality caused by the response time. Therefore, in the image forming apparatus provided with this fixing device, the image quality can be improved.

  In the above-described embodiment, the case where the fixing roller 1 as a fixing member is directly subjected to electromagnetic induction by the exciting coil 3 and is heated by eddy current (this is referred to as a direct heating method) has been described. It is not limited to. The present invention is also preferably applied to a case where the fixing member is indirectly heated via another heat generating member that receives electromagnetic induction from the electromagnetic induction coil and generates heat by eddy current (this is referred to as an indirect heating method). Is done.

  In the above-described embodiment, the exciting coil 3 and the resonant capacitor 44 are connected in series to form the series resonant circuit 42. However, the present invention is not limited to this. The present invention can also be applied to a case where a parallel resonance circuit is configured by an exciting coil and a capacitor.

  In the above-described embodiment, the temperature detection sensor 4 as the temperature detection unit is provided corresponding to only the central portion A of the fixing roller 1, but is not limited thereto. Another temperature detection sensor may be provided corresponding to the end B of the fixing roller 1 so that the temperature Ta at the central portion A of the fixing roller 1 and the temperature Tb at the end B coincide with each other.

1 is a block diagram of a fixing device according to an embodiment of the present invention. It is a figure which shows the structure of the inverter circuit contained in the power supply device in FIG. It is a figure which shows the drive waveform of the series resonance circuit by the inverter circuit in FIG. It is a figure explaining the temperature rising state of a fixing roller when a degaussing coil is closed. It is a figure explaining the temperature rising state of a fixing roller when a degaussing coil is open. It is a figure which illustrates the frequency characteristic of the series resonance circuit in FIG. 2 including the case where a degaussing coil is open and the case where it is closed. It is a figure which shows the flow of control by the system control part of the said fixing device. It is a figure explaining the control system used as the foundation of this application when a degaussing coil is opened and closed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3 Excitation coil 4 Temperature detection sensor 5 Nip 11 Power supply device 12 Commercial power supply 20 System control part 23 Memory | storage part 31A, 31B Demagnetizing coil

Claims (4)

A fixing member in which the conveyed sheet is pressed against the outer peripheral surface;
An excitation coil disposed elongated along the outer circumferential surface of the fixing member in the width direction of the conveyed sheet;
A capacitor connected to the excitation coil and equivalently constituting a resonance circuit;
A demagnetizing coil disposed along the exciting coil in a region corresponding to the end of the fixing member in the width direction of the sheet on the opposite side of the fixing member with respect to the exciting coil;
A high-frequency power supply unit that induction-heats the fixing member via the excitation coil by applying an AC voltage to the resonance circuit;
A temperature detector for detecting the temperature of the fixing member;
The relationship between the output power value output from the high-frequency power supply unit to the resonance circuit and the output frequency of the high-frequency power supply unit corresponding to the output power value in each of the case where the degaussing coil is open and closed A characteristic acquisition unit to acquire;
Based on the correspondence between the output power value acquired by the characteristic acquisition unit and the output frequency, the high-frequency power source so that the temperature of the fixing member detected by the temperature detection unit matches a predetermined target temperature. A fixing control unit that performs control to vary and set the output frequency of the unit. The fixing device according to claim 1,
A fixing device comprising: a storage unit that stores a correspondence relationship between the output power value acquired by the characteristic acquisition unit and the output frequency. The fixing device according to claim 2,
When the characteristic acquisition unit acquires the correspondence between the output power value and the output frequency, the storage unit updates the stored content using the correspondence acquired by the characteristic acquisition unit. A fixing device characterized in that   An image forming apparatus comprising the fixing device according to claim 1.

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