JPH11125988A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device having high reliability and excellent productivity, at a low cost by making the ripple of a control temp. small and further, making a stable highly-accurate temperature control not causing overshooting possible, in a fixing device with a magnetic induction heating system using a heat-resistant film. SOLUTION: An operating variable is decided with a proportional term gain, with respect to the deviation between a fixing control target voltage and a voltage divided by a temperature measuring means 6a, by an error amplifier 13. Further, the operating variable is decided with an integral term gain with respect to the integrated value of a deviation value up to now, by an error amplifier 11, based on the voltage of a temperature measuring means 6b, to use the sum of this operating variable and that with the above-mentioned proportional term as a controlled variable. Further, the operating variable is decided with a differential term gain with respect to the differential value of the temp. of a fixing unit by an error amplifier 12, based on the voltage of a temperature measuring means 6c, to use the sum of this operating variable and that with the above-mentioned PI control term as the control variable. Thus, the on-duty control of a switching element 5 is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a fixing device for fixing a developer (toner) image formed by an electrophotographic process by magnetic induction heating.

[0002]

2. Description of the Related Art Conventionally, copiers, laser beam printers, facsimile machines, microfilm reader printers,
As a fixing device applicable to an image forming apparatus such as an image display (display) device and a recording machine, a heat roller type fixing device is widely used.

As shown in FIG. 8, a heat roller type fixing device has a hollow metal core 20 made of aluminum or the like.
a fixing roller 20 having a rubber elastic layer 20b on the core roller 21a and a pressing roller 21 having a rubber elastic layer 21b on the core metal 21a.
Are pressed against each other, and a heating means H such as a halogen heater is disposed in the fixing roller 20. When the heating means H generates heat, the heat is transmitted to the core metal 20a of the fixing roller 20 by radiation and convection. Then, heat is applied to the recording material P and the toner conveyed by the conveying means 22 and nipped between the pressure contact portions of the fixing roller 20 and the pressure roller 21 to perform fixing.

However, the temperature control method in the heat roller type fixing device is based on a temperature measured by a temperature measuring means 23 such as a thermistor close to the fixing roller 20, and a heating means H is connected between the heating means H and the AC power supply. Since the switching element such as a triac provided is turned on / off, the overshoot due to the heat resistance from the heating unit H to the fixing roller 20 and the heat capacity of the fixing roller 20 may increase. Was. In addition, there is also a problem that the warm-up time is prolonged due to such heat resistance and heat capacity.

Therefore, in order to solve the problems in such a heat roller type fixing device, a magnetic induction heating type fixing device has been proposed. For example, Japanese Patent Publication 5-9027
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses a method in which an eddy current is generated in a fixing roller as a heating member by magnetic flux and heat is generated by Joule heat.

[0006] In the fixing device of the magnetic induction heating system, the heat generation position can be made closer to the toner by utilizing the generation of the eddy current, and the warm-up time can be reduced as compared with the heat roller system using a halogen lamp. It has the advantage that it can be achieved.

Further, the present inventors adhere a heat-resistant film such as a heat-resistant carbon member to a heating body composed of a magnetic material (induction magnetic material, magnetic metal member, magnetic field absorbing conductive material, conductive member) and an exciting coil. The high frequency magnetic field is magnetically coupled to the magnetic material by applying a high frequency switching current to the exciting coil, and the magnetic material is heated by eddy current loss caused by magnetism, and the heat is applied to the heat resistant film. A magnetic induction heating film-type fixing device that transfers heat to a material to be heated through the intermediary is proposed.

Further, the heat-resistant film itself is made of a magnetic material and is heated by magnetic induction heating so that the heat-resistant film does not become a thermal resistance, thereby improving the heat efficiency of the magnetic induction heating film type fixing device. Also came up with a proposal.

In this method, a high frequency is applied to an exciting coil, and a magnetic field is repeatedly generated and extinguished in a film as a magnetic material moving in the generated magnetic field, thereby generating an eddy current in a magnetic layer in the film. . Then, the eddy current is converted into heat (Joule heat) by the electric resistance of the magnetic layer, and as a result, only the film as the heating member that is in close contact with the material to be heated generates heat.

As described above, since heat is directly generated near the surface layer of the film as the heating member, there is an advantage that the film can be rapidly heated regardless of the thermal conductivity and heat capacity of the film base layer. Not only can this be achieved, but also overshoot during temperature control can be reduced.

On the other hand, as a control method for suppressing overshoot, a control amount is calculated by a well-known PID control method based on temperature information from a temperature measuring means, and the obtained result is obtained as a conduction time of a switching control element. In the above-described magnetic induction heating type fixing device using a fixing roller or a heat-resistant film, energy saving and quick start property are realized by using a temperature control method using the PID control. It is possible to provide a fixing device capable of performing stable temperature control with little overshoot without loss.

[0012]

However, the above-mentioned conventional PID control system requires a dedicated power supply for generating a reference voltage, which may increase the cost.

[0013] In the conventional PID control method as well, high-speed control is required to perform ideal control in accordance with the difference in temperature between paper passing and non-paper passing, the difference in paper quality, or the change in ambient temperature. Unless high-precision temperature measuring means is used, stable control may not be achieved.

Accordingly, the present invention provides a magnetic induction heating type fixing device using a heat-resistant film, in which the control temperature ripple is small, stable and accurate temperature control without overshoot is enabled, and high reliability is achieved. It is an object of the present invention to provide an image forming apparatus excellent in productivity and productivity at low cost.

[0015]

According to a first aspect of the present invention, the object is to develop an electrostatic latent image formed on an image carrier based on image information into a toner image, An image forming apparatus comprising: an image forming unit that transfers an image to a recording material; a fixing device that fixes an unfixed toner image on the recording material; and a unit that supplies a high-frequency current to the fixing device. The apparatus includes a fixing rotator, a pressure member rotatably disposed while being in pressure contact with the fixing rotator, and an excitation connected to a means for supplying the high-frequency current disposed inside the fixing rotator. A coil, a heat-generating metal body disposed so as to face the exciting coil, or a heat-generating metal body forming the fixing rotating body itself, and a temperature measuring means disposed around the pressure contact portion. Image formation by heating with eddy current generated in heat-generating metal body In the apparatus, the means for supplying the high-frequency current includes a temperature control means for controlling a temperature based on an output from the temperature measurement means, and power supply to the temperature control means is performed by a power supply device of the image forming apparatus main body. The reference voltage input to the temperature measuring unit and the temperature control unit is achieved by being supplied from a power supply device of the image forming apparatus main body.

According to the second aspect of the present invention,
The above object is achieved in the first aspect by the fact that the fixing rotator is a fixing roller or a heat-resistant film.

Further, according to a third aspect of the present invention, the above object is achieved in the first aspect or the second aspect, wherein the control means of the image forming apparatus controls the fixing permission signal and the reference of the temperature control means. This is achieved by setting a target temperature set value.

According to a fourth aspect of the present invention,
The object is, in any one of the first to third inventions, provided with a plurality of temperature measurement means, wherein the temperature control means performs proportional control, integral control, and temperature control based on temperature information from each temperature measurement means. This is achieved by performing temperature control by obtaining each parameter of the differential control.

Further, according to a fifth aspect of the present invention, the above object is achieved in any one of the first to fourth aspects of the invention by recording on the pressure contact portion between the fixing rotating body and the pressing member. A recording material passage detecting means for detecting the passage of the recording material; and a means for supplying a high-frequency current, when the recording material passage detecting means determines that the recording material has started to pass through the press-contact portion, the start is performed. During the delay time of the temperature measuring means from time to the time when the temperature measuring means becomes effective, the predetermined power is supplied according to the size and thickness of the recording material and the conveying speed, and from when the temperature measuring means becomes effective. By performing temperature control, during the delay time of the temperature measuring means from the time when the recording material has finished passing through the pressure contact portion to the time when the temperature measuring means becomes effective, the heating is interrupted or the predetermined power is supplied again. Achieved.

That is, in the first invention according to the present application, power is supplied to the temperature control means by the power supply device of the image forming apparatus main body, and the reference voltage inputted to the temperature measurement means and the temperature control means is changed to the image signal. Since the power is supplied from the power supply device of the forming apparatus main body, the temperature control is stably performed.

Further, in the second invention according to the present application, since the fixing rotator of the first invention is a fixing roller or a heat-resistant film, stable temperature control can be achieved without impairing energy saving and quick start performance. Good fixation under

Further, in the third invention according to the present application, the fixing permission signal required in the first invention or the second invention and the setting of the temperature target set value serving as a reference of the temperature control means are set. Since the control is performed by the control unit of the image forming apparatus, temperature control is performed based on an optimum target temperature according to the material and size of the recording material, the conveyance speed, and the like.

According to a fourth aspect of the present invention, there is provided a plurality of the temperature measuring means according to any one of the first to third aspects, wherein the temperature controlling means comprises a temperature measuring means for detecting the temperature from each temperature measuring means. Temperature control is performed by obtaining parameters of proportional control, integral control, and differential control based on the information, so that responsive and highly accurate temperature control can be performed without using high-speed and high-precision temperature measurement means. Will be

Further, in the fifth invention according to the present application, the passage of the recording material to the pressure contact portion of the fixing rotator and the pressing member according to any one of the first to fourth inventions is detected. The recording material passage detection means is provided, and the means for supplying a high-frequency current, when the recording material passage detection means determines that the recording material has started passing through the press-contact portion, the temperature measurement means from the start. During the delay time of the temperature measuring means until it becomes effective, power predetermined by the size and thickness of the recording material and the conveying speed is supplied, and when the temperature measuring means becomes effective, the temperature is controlled and recording is performed. During the delay time of the temperature measuring means from the time when the material has passed through the pressure contact portion to the time when the temperature measuring means becomes effective, the heating is interrupted or a predetermined power is supplied again, so that the temperature at the time of passing the recording material Minimize ripple.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a diagram illustrating a schematic configuration of the image forming apparatus of the present embodiment. In FIG. 2, reference numeral 71 denotes a photosensitive drum as an image carrier for forming an image of electrophotography, which is rotatably disposed in the direction of the arrow. When the photosensitive drum 71 is charged by the charger 72 and the laser beam L is irradiated by the laser beam scanner 73 in accordance with the image information, an electrostatic latent image is formed on the photosensitive drum 71, and the static latent image is formed. The electrostatic latent image is developed as a toner image by the toner carried on the developing roller 74a of the developing device 74.

On the other hand, the recording material P stored in the cassette 75
Are fed one by one by a feed roller 76,
7, the photosensitive drum 7 is conveyed by the conveying roller 78.
It is transported to one side. When the recording material P is guided by the guide 79 to the pressure contact portion 82 between the photosensitive drum 71 and the transfer roller 80, the toner image is transferred onto the recording material P by the transfer roller 80 to which a high voltage is applied from the power supply 81. Is transferred to the fixing device 85 via the transfer section 84.

The fixing device 85 is provided so that the film 9 as a fixing rotating body and the pressing roller 14 as a pressing member are pressed against each other. By passing through the film 16, the film 9 and the pressure roller 14 start rotating, and the heating means described later is raised to a predetermined temperature.

When the recording material P to which the unfixed toner image has been transferred is sandwiched between the nips, heat is transmitted to the toner image and the recording material P, and the recording is performed by applying pressure at the nip. The toner on the material P is melted, soaked into the fibers of the recording material P, and fixed.

Then, when the recording material P on which the fixing has been completed passes through the paper discharge sensor 17 which is a recording material passage detecting means, the rotation of the film 9 and the pressure roller 14 is stopped, and the recording material P is stopped.
Is discharged onto the discharge tray 86, thereby completing the image formation. Note that, at the time of transfer, the toner remaining on the photosensitive drum 71 without being transferred onto the recording material P is cleaned by a cleaning unit 83 to prepare for the next image formation.

Next, a temperature control section of the fixing device 85 in the image forming apparatus of the present embodiment as described above will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a DC power supply and a controller as a power supply device and a control unit in the main body, 2 denotes a switching regulator control circuit, 3 denotes a temperature control circuit as a temperature control unit, 4 denotes a temperature setting circuit, 5 denotes an FET or a bipolar element (transistor). IGBT), 6 is a temperature measuring means, 7 is an exciting coil, 8 is a resonance capacitor, and 9 is a film as a fixing rotating body made of a ferromagnetic metal material or the like.

In the image forming apparatus of this embodiment, when the controller 1 outputs a fixing permission signal after turning on the main body, the PWM circuit of the switching regulator control circuit 2 for turning on / off the switching element 5 of the fixing device is provided. Starting the oscillation, the on-duty is increased from 0 to a predetermined value for a predetermined time by the soft start circuit, and a steady output state is set. The temperature is measured by a temperature measuring means 6 such as a thermistor attached to the film 9.
Is controlled by changing the on-time width (on-duty) of the switching element by the temperature control circuit 3 based on the information.

That is, based on the temperature setting signal output from the controller 1, the temperature setting circuit 4 outputs a fixing control target voltage corresponding to the set temperature to the error amplifier 10,
In the error amplifier 10, the on-duty of the switching element 5 is adjusted by performing PID control in accordance with the deviation between the fixing control target voltage and the voltage obtained from the temperature measuring unit 6.

In the apparatus of this embodiment, the reference voltage of the temperature measuring means 6 and the power supply of the temperature control circuit are
The fixing control target voltage supplied by the internal DC power supply / controller 1 and output from the temperature setting circuit 4
Since the power is generated based on the power supplied by the C power supply / controller 1, stable control is possible.

Further, duplication of parts can be avoided, parts can be saved, and the circuit can be simplified and the cost can be reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, the fixing control target voltage output to the error amplifier 10 is directly
/ D converter. This allows
The fixing temperature target value can be easily changed.

Note that instead of the A / D converter, PW
Transmission means such as M may be used. Further, the reference voltage of the A / D converter may be used as the reference voltage of the temperature control circuit 3 and the temperature measuring means 6.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 3 is a block diagram of a temperature control unit in the image forming apparatus according to the present embodiment. In the present embodiment, a plurality of temperature measuring means 6a, 6
b, 6c, and the error amplifier is also an error amplifier 11 for integral term control and an error amplifier 1 for differential term control.
2. The difference from the first embodiment is that an error amplifier 13 for proportional term control is provided.

In this embodiment, when the temperature adjustment of the fixing unit is started, the error amplifier 13 outputs the fixing control target voltage output from the temperature setting circuit 4 based on the temperature setting signal from the controller 1 and the temperature measurement. An operation variable (on-duty) is determined by the proportional term gain K1 with respect to the deviation e of the voltage divided by the means 6a, so that the offset of the target temperature is reduced.

However, in actual operation, since the film 9 to be controlled is a heat storage system and has a characteristic that is difficult to control, it is impossible to set the offset to 0 only by proportional term control.

In order to make the offset close to 0, the error amplifier 11 determines the manipulated variable (on-duty) by the integral term gain K2 with respect to the integrated value of the deviation amount up to the present time. Is the control amount.

Further, when disturbance (input voltage fluctuation, passage of a recording medium, etc.) enters the controlled object, it is impossible to respond only by these PI operations. Therefore, in order to speed up the control response, the error amplifier 12 determines the manipulated variable by the differential term gain K3 with respect to the differential value of the fixing device temperature, and uses the sum with the PI control term as the control amount.

That is, in the present embodiment, the control is performed by calculating the coefficient of each term of the following equation based on information from the sensor.

[0046]

(Equation 1)

Further, in the present embodiment, in order to perform the above-described control, the temperature measuring means 6a for obtaining the proportional term K1 is used.
Is provided as close as possible to the part to be controlled using a highly accurate sensor. The temperature measuring means 6b for obtaining the differential term K2 uses a sensor having a fast response speed, and is also provided as close as possible to the control target. Further, a temperature measuring means 6c for obtaining the integral term K3
Uses a sensor with high accuracy, a sensor with high response speed, or a sensor having both characteristics, and is provided as close to the control target as possible.

FIGS. 4 and 5 show examples of the arrangement of the temperature measuring means. In any case, of the signals from the temperature measuring means, the temperature measuring means 6b having good responsiveness (but not good in accuracy)
From the temperature control means 6 as a differential control term.
The proportional term and the integral term are obtained from the signals a and 6c.

In order to obtain the above proportional constants of the P, I, and D terms, one value of the temperature measuring means is defined as a proportional term and the other value is defined as a differential term. The result of calculating the value of the means may be obtained as each term of proportional, integral and differential.

The deviation between the fixing control target voltage and the voltage obtained from the temperature measuring means is calculated by analog calculation or A
The / D-converted sampling value may be digitally calculated by a CPU or the like.

As described above, in the present embodiment, the detection of each parameter of the proportional control, the integral control, and the differential control is performed by distributing them to a plurality of temperature measuring means. Without using it, it is possible to perform temperature control with good responsiveness and high accuracy. In addition, temperature control can be performed in a portion where measurement cannot be performed directly due to mechanical arrangement.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first and second embodiments are denoted by the same reference numerals, and description thereof is omitted.

Normally, a thermistor temperature measuring element used as a temperature measuring means has a delay time td with respect to the temperature of an object to be measured, as shown in FIG. In addition, a delay time tm occurs depending on the mounting position of the thermistor temperature measuring element. Therefore, during this time, normal temperature measurement cannot be expected, and the film temperature when disturbance occurs is disturbed.

For example, assuming that the recording material enters the nip tl hours after the power supply to the fixing device is turned on, the film temperature decreases as shown in FIG. 7A, but the temperature information of the thermistor is shown in FIG. As shown in FIG. 7B, the output power changes after the delay time tm, and the supplied power is delayed correspondingly as shown in FIG. Accordingly, the film temperature greatly deviates from the fixing control target temperature as shown in FIG.

Therefore, in this embodiment, stable temperature control is performed by performing power correction in consideration of the delay time. That is, in the example of FIG. 7, a predetermined power is forcibly supplied tl time after the power is supplied to the fixing device without being based on the temperature information of the thermistor to prevent the temperature drop due to the entry of the recording material. It is.

Hereinafter, the temperature control method of the present embodiment before and after the fixing operation will be described. In the present embodiment, when the sensor detects that the recording material has begun to pass the predetermined position, the controller 1 operates a temperature setting signal to supply electric power corresponding to the fixing control target temperature. This fixing control target temperature is determined by the CPU in accordance with a predetermined table based on the size of the recording material, the conveying speed of the recording material, and the like.

When the leading edge of the recording material reaches the fixing portion (nip), the predetermined power is supplied by the table for the leading edge of the recording material, not by the table in the normal control mode, but by the predetermined time. (For a delay time tm + td from when the recording material enters the nip), the recording material is supplied to the excitation coil 7. Alternatively, the temperature information is supplied until the temperature information obtained from the temperature measuring means becomes valid. This control can be executed by software by setting a target temperature by a temperature setting signal. After the temperature control of the recording material tip,
Transition to the normal control state.

Next, when the sensor detects that the recording material has passed, the process shifts to the temperature control of the rear end of the recording material, and operates the temperature setting signal from the controller 1 so that the electric power corresponding to the fixing target temperature is obtained. Supply.

Further, when the trailing end of the recording material exits from the fixable portion (nip), not the table in the normal control mode but the table for the trailing edge of the recording material, a predetermined power is applied for a predetermined time. (For a delay time tm + td from when the recording material enters the nip), the recording material is supplied to the excitation coil 7. Alternatively, the temperature information is supplied until the temperature information obtained from the temperature measuring means becomes valid.

If there is no recording material to be fixed thereafter, the power supply is cut or stopped in the standby state. This control can be executed by software by setting a target temperature by a temperature setting signal.

By performing this correction, stable temperature control can be performed even when disturbance occurs.

In each of the embodiments described above, the case where the present invention is applied to a magnetic induction heating type fixing device having a heat resistant film as a magnetic material has been described, but the present invention is not limited to this. Instead, the present invention can be applied to a magnetic induction heating type fixing device in which a heat-resistant film is closely attached to a magnetic body and is movable, and a magnetic induction heating type fixing device using a fixing roller.

[0063]

As described above, the first embodiment according to the present application is described.
According to the invention, the power supply to the temperature control unit is performed by the power supply device of the image forming apparatus main body, and the reference voltage input to the temperature measuring unit and the temperature control unit is supplied from the power supply device of the image forming apparatus main body. In addition, the control temperature ripple is small, stable and high-precision temperature control without overshoot is enabled, and a device having high reliability and excellent productivity can be realized at low cost. Further, it is possible to avoid duplication of parts, to save parts, to simplify the circuit, and to reduce the cost.

According to the second invention of the present application,
Since the fixing rotator of the first aspect is a fixing roller or a heat-resistant film, good fixing can be performed under stable temperature control without impairing energy saving and quick start performance.

Further, according to the third aspect of the present invention, the fixing permission signal required in the first aspect or the second aspect and the setting of the temperature target set value serving as a reference of the temperature control means are set. Since the control is performed by the control unit of the image forming apparatus, it is possible to perform temperature control with an optimum target temperature according to the material and size of the recording material, the conveyance speed, and the like.

According to the fourth invention of the present application,
A plurality of temperature measuring means according to any one of the first to third inventions is provided, and the temperature controlling means is configured to control each parameter of proportional control, integral control, and differential control based on temperature information from each temperature measuring means. Therefore, the temperature control can be performed with good responsiveness and high accuracy without using a high-speed and high-precision temperature measuring means. In addition, temperature control can be performed in a portion where measurement cannot be performed directly due to mechanical arrangement.

Further, according to the fifth aspect of the present invention, the passage of the recording material to the pressure contact portion between the fixing rotary member and the pressing member according to any one of the first to fourth aspects is detected. Means for supplying a high-frequency current, the means for supplying a high-frequency current, when the means for detecting the passage of the recording material determines that the recording material has started to pass through the press-contact portion, the means for measuring the temperature from the start. During the delay time of the temperature measuring means until the effective, the power is determined in advance by the size and thickness of the recording material and the conveying speed, to perform the temperature control from the time the temperature measuring means is effective, During the delay time of the temperature measuring means from the time when the recording material has finished passing through the pressure contact portion to the time when the temperature measuring means becomes effective, heating is interrupted or a predetermined power is supplied again, so that when the recording material passes, Minimizing temperature ripple It can be.

[Brief description of the drawings]

FIG. 1 is a block diagram of a temperature control unit according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of an image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a temperature control unit according to a third embodiment of the present invention.

FIG. 4 is a diagram showing an arrangement example of a temperature measuring unit according to a third embodiment of the present invention.

FIG. 5 is a diagram showing another example of the arrangement of the temperature measuring means according to the third embodiment of the present invention.

FIG. 6 is a diagram illustrating a response example of a temperature measuring unit according to a fourth embodiment of the present invention.

FIG. 7A shows a change in film temperature due to temperature control in a fourth embodiment of the present invention, FIG. 7B shows a change in temperature information of a temperature measuring means in the temperature control, and FIG. It is a figure showing change of supply electric power.

FIG. 8 is a diagram illustrating a schematic configuration of a conventional fixing device.

[Explanation of symbols]

1 DC power supply / controller in the main body (power supply device of image forming apparatus main body, control means) 2 Switching regulator control circuit (means for supplying high-frequency current) 3 Temperature control circuit (means for supplying high-frequency current, temperature control means) 5 Switching Element (means for supplying high-frequency current) 6, 6a, 6b, 6c Temperature measuring means 7 Exciting coil 9 Film (fixing rotating body) 14 Pressure roller (pressing member) 16 Pre-fixing sensor (recording material passage detecting means) 17 Paper discharge sensor (recording material passage detection means) 71 Photoconductor drum (image carrier) 85 Fixing device P Recording material

Claims (5)

[Claims] An image forming section for developing an electrostatic latent image formed on an image carrier based on image information into a toner image and transferring the toner image to a recording material, and an unfixed toner image on the recording material An image forming apparatus comprising: a fixing device for fixing the fixing device; and a unit for supplying a high-frequency current to the fixing device.
A fixing rotator, a pressure member rotatably disposed while being in pressure contact with the fixing rotator, and an excitation coil disposed inside the fixing rotator and connected to the means for supplying the high-frequency current, A heat-generating metal body disposed so as to face the exciting coil or a heat-generating metal body forming the fixing rotating body itself; and a temperature measuring means disposed around the press-contact portion, wherein the heat-generating metal body is provided. In the image forming apparatus that performs heating by eddy current generated in the image forming apparatus, the means for supplying the high-frequency current includes a temperature control means for controlling a temperature based on an output from the temperature measuring means, and an electric power to the temperature control means. The supply is performed by a power supply unit of the image forming apparatus main body, and the reference voltage input to the temperature measuring unit and the temperature control unit is supplied from the power supply unit of the image forming apparatus main body. 2. The image forming apparatus according to claim 1, wherein the fixing rotator is a fixing roller or a heat-resistant film. 3. The image forming apparatus according to claim 1, wherein the control means of the image forming apparatus sets a fixing permission signal and a temperature target set value serving as a reference for the temperature control means. 4. A plurality of temperature measuring means, wherein the temperature controlling means performs temperature control by obtaining respective parameters of proportional control, integral control and differential control based on temperature information from each temperature measuring means. The image forming apparatus according to claim 1. 5. A recording material passage detecting means for detecting the passage of the recording material to and from the pressure contact portion between the fixing rotating body and the pressing member, wherein the means for supplying a high-frequency current includes the recording material passage. When the detecting means determines that the recording material has started passing through the pressure contact portion, the size and thickness of the recording material are determined during the delay time of the temperature measuring means from the start to the time when the temperature measuring means becomes effective. And a predetermined electric power is supplied according to the conveying speed, and the temperature is controlled from the time when the temperature measuring means becomes effective, and from when the recording material finishes passing through the pressure contact portion until the temperature measuring means becomes effective. The image forming apparatus according to any one of claims 1 to 4, wherein heating is interrupted or a predetermined power is supplied again during the delay time of the temperature measuring means.