JP2009271304A - Image forming apparatus and heating control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, capable of further improving safety of an IH fixing system. <P>SOLUTION: The apparatus comprises a heating coil 125 which heats a heating member of a fixing device 100A for fixing a toner image transferred onto a recording medium according to power supply; a demagnetizing coil 129 which suppresses heating of the heating coil 125 according to power supply; a CPU 303 which controls the power supply to the heating coil 125 and the demagnetizing coil 129; a current detection circuit 133 which detects an operating state of the demagnetizing coil 129; and an AND circuit 301 which determines whether the heating coil 125 is abnormal or not based on the state of power supply to the demagnetizing coil 129 and the detection result by the current detection circuit 133. The CPU 303 interrupts the power supply to the heating coil 125 when abnormality is determined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a heating control method for safely heating a fixing system.

  In recent years, a scanner that reads a document image, a copier that prints a document image read by the scanner, a printer or facsimile machine that prints image data input from the outside, or a so-called MFP (Multi Function Peripheral) that combines these functions A multi-function machine called is used. Such a multifunction machine includes a scanner unit for reading an image, an engine unit for forming a toner image corresponding to the image read by the scanner unit on the transfer paper, and a toner image on the transfer paper formed by the engine unit. And a fixing device (fixing system) for fixing by a fixing roller and a pressure roller.

  As a safety circuit of the IH fixing system, which is a fixing method using IH (Induction Heating), a method for forcibly shutting off the power supply to the heating element by detecting a high temperature with a temperature sensor is known. Yes. Further, as a system for detecting normal operation of a heating coil and a heat reduction coil, a method of forcibly cutting off energization when an abnormal current is detected using a current detection circuit is also known (for example, Patent Document 1).

JP 2007-127866 A

  However, in the safety device that detects an abnormality by detecting an electric current as in Patent Document 1, when the disconnection or the abnormality of the current detection circuit occurs, the abnormality cannot be detected, and the heating coil is continuously heated. There was a problem that could be considered.

  The present invention has been made in view of the above, and an object thereof is to provide an image forming apparatus and a heating control method capable of further improving the safety of an IH fixing system.

  In order to solve the above-described problems and achieve the object, the invention according to claim 1 is a heating unit that heats a heating member of a fixing unit that fixes a toner image transferred to a recording medium according to power supply; Heat reduction means for suppressing heat generation of the heating means in response to power supply; heating control means for controlling power supply to the heating means; and heat reduction control means for controlling power supply to the heat reduction means; An operation detection unit that detects an operation state of the heat reduction unit, a state of power supply to the heat reduction unit by the heat reduction control unit, and a detection result of the operation state of the heat reduction unit by the operation detection unit. A first determination unit that determines whether there is an abnormality in the heating unit, and a blocking unit that blocks power supply to the heating unit when it is determined that there is an abnormality in the heating unit. It is characterized by that.

  According to a second aspect of the present invention, in the first aspect of the invention, the first determination means includes a state of power supply to the heating means by the heating control means and the heat reduction by the heat reduction control means. The presence or absence of abnormality of the heating unit is determined based on the state of power supply to the unit and the detection result of the operation state of the heat reduction unit by the operation detection unit.

  The invention according to claim 3 is the invention according to claim 1, further comprising temperature detection means for detecting the temperature of the heating means, wherein the first determination means is further predetermined as the detected temperature. The presence or absence of abnormality of the heating means is determined by comparing with a given threshold value.

  According to a fourth aspect of the present invention, there is provided the temperature detecting means for detecting the temperature of the heating means in the invention according to the first aspect, and the heating means when the detected temperature is larger than a predetermined threshold value. And a second determination means for determining that there is an abnormality.

  According to a fifth aspect of the present invention, in the first aspect of the invention, when the blocking means determines that the heating means is abnormal for a plurality of times consecutively by the first determination means, the heating means The power supply to the means is cut off.

  According to a sixth aspect of the present invention, in the first aspect of the invention, the operation detecting unit detects an operation state of the heat reducing unit based on a current supplied to the heat reducing unit. .

  The invention according to claim 7 is characterized in that, in the invention according to claim 1, the heating means generates a magnetic field by the current flowing through the exciting coil and generates heat by electromagnetic induction by the magnetic field.

  The invention according to claim 8 is the invention according to claim 1, wherein the heat reduction means generates a magnetic field that cancels a magnetic field generated by the excitation coil of the heating means. It is characterized by suppressing heating by.

  According to a ninth aspect of the present invention, there is provided a heating control method for controlling heating of a heating member of a fixing unit for fixing a toner image transferred to a recording medium, wherein the heating control means responds to supply of electric power to the heating member. A heating control step for controlling power supply to the heating means for heating the heating means, and a heat reduction control step for controlling the power supply to the heat reduction means for suppressing heat generation of the heating means according to the power supply by the heat reduction control means. A determination step for determining whether the heating means is abnormal based on a detection result of the operation state of the heat reduction means by an operation detection means for detecting an operation state of the heat reduction means; However, when it is determined that there is an abnormality in the heating means, there is provided a shut-off step for shutting off the power supply to the heating means.

  According to the present invention, there is an effect that the safety of the IH fixing system can be further improved.

  Exemplary embodiments of an image forming apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings.

(First embodiment)
The image forming apparatus according to the first embodiment includes a signal indicating ON / OFF of the heating coil of the IH fixing system, a signal indicating ON / OFF of the heat reduction coil (demagnetization coil), and detection from the current detection circuit. An abnormality in heat reduction control is detected from the signal.

  FIG. 1 is a schematic configuration diagram illustrating an example of a mechanism unit of the multifunction peripheral 100 according to the first embodiment. The multifunction peripheral 100 is an image forming apparatus including a digital copying machine. That is, the multifunction peripheral 100 has a copying function and other functions, for example, a printer function and a facsimile function. By operating an application switching key (not shown) of the operation unit, the copying function, the printer function, It is possible to select the facsimile function by switching sequentially. Thus, the copy mode is selected when the copy function is selected, the printer mode is selected when the printer function is selected, and the facsimile mode is selected when the facsimile function is selected.

  In this multifunction device 100, an image surface is placed on a document tray (also referred to as “document table”) 102 provided in an automatic paper feeder (also referred to as “automatic document feeder”; hereinafter referred to as “ADF”) 101. When the start key on the operation unit (not shown) is pressed in the copy mode, the contact glass 103 is sequentially fed by the feed roller and the feed belt one by one from the bottom document. It is fed to the predetermined position above and set. The ADF 101 has an increment function for incrementing the number of documents every time a document is fed. The document set on the contact glass 103 is read by an image reading device (also referred to as “scanner” or “reading unit”) 104, and after the reading is finished, the paper is discharged by a feeding belt and a discharge roller. It is discharged on the table.

  Each time an image of one original is read, an original set detector (also referred to as “original set detection sensor”) detects whether or not there is a next original on the original tray 102 and detects the original set. When it is detected that the next document is present on the document tray 102, the lowermost document on the document tray 102 is contacted with the contact roller and the feed belt in the same manner as the previous document. The sheet is fed to a predetermined position on 103, and thereafter the same operation as described above is performed. Further, the feeding roller, the feeding belt, and the discharging roller are driven by a conveyance motor (not shown).

  When the first paper feeding device 109a, the second paper feeding device 109b, and the third paper feeding device 109c are selected, the first paper feeding tray 108a, the second paper feeding tray 108b, and the third paper feeding tray 108c, respectively. The transfer paper (paper) loaded on the paper is fed, and the transfer paper is transported by the vertical transport unit 111 to a position where it contacts the photoconductor 106. For example, a photosensitive drum is used as the photosensitive member 106, and is rotated by a main motor (not shown).

  Image data (image information) input by reading an image of a document by the image reading device 104 is subjected to predetermined image processing by an image processing device (not shown) and is shown as it is or as an image storage unit. After being temporarily stored in the omitted image memory, it is sent to the writing unit 105 constituting the image printing means (printer), converted into optical information by the writing unit 105, and the surface of the photoreceptor 106 is not shown in the figure. After being uniformly charged by the device, it is exposed with optical information from the writing unit 105 to form an electrostatic latent image. The electrostatic latent image on the photosensitive member 106 is developed by a developing device (also referred to as “developing unit”) 107 to form a toner image.

  Image forming operation for forming an image on transfer paper by image data by electrophotographic method by the photosensitive member 106, the charger, the writing unit 105, the developing device 107, and other well-known devices around the photosensitive member 106 not shown. A printer engine which is an image forming means for performing the above is configured. The conveyance belt serves as both a sheet conveyance unit and a transfer unit, and a transfer bias is applied from a power source, and the toner image on the photoconductor 106 is transferred while conveying the transfer paper from the vertical conveyance unit 111 at a constant speed with the photoconductor 106. Transfer to paper. The transfer paper is fixed with a toner image by the fixing device 100 </ b> A, and is discharged to the paper discharge tray 113 by the paper discharge unit 114. The photosensitive member 106, the charger, the writing unit 105, the developing device 107, the transfer unit, and the image forming unit for forming an image on the transfer paper by the image data are configured.

  The above operation is an operation for copying an image on one side of the transfer paper in the normal mode. When copying an image on both sides of the transfer paper in the double-side mode, the first to third paper feed trays 108a are used. To 108c, the transfer sheet on which the image is formed on the surface as described above is switched by the paper discharge unit 114 to the double-sided paper feed path side instead of the paper discharge tray 113 side. Is switched back and the front and back are reversed and conveyed to the duplex conveying unit.

  The transfer paper transported to the double-sided transport unit is transported to the vertical transport unit 111 by the double-sided transport unit, transported to a position where it contacts the photoconductor 106 by the vertical transport unit 111, and formed on the photoconductor 106 in the same manner as described above. The toner image thus transferred is transferred to the back surface, and the toner image is fixed by the fixing device 100A, whereby double-sided copying is performed. This double-sided copy is discharged to the paper discharge tray 113 by the paper discharge unit 114. When the transfer sheet is reversed and discharged, the transfer sheet that is switched back by the reversing unit 112 and turned upside down is not conveyed to the duplex conveying unit but passes through the reversed discharge conveying path and is discharged from the discharging unit 114. As a result, the paper is discharged to the paper discharge tray 113.

  In the print mode, image data from the outside is input to the writing unit 105 instead of the image data from the image processing apparatus, and an image is formed on the transfer paper as described above. Further, in the facsimile mode, the image data from the image reading device 104 is transmitted to the other party by a facsimile transmission / reception unit (not shown), and the image data from the other party is received by the facsimile transmission / reception unit. By inputting the data to the writing unit 105 instead of the data, an image is formed on the transfer paper as described above.

  The multi-function device 100 includes a large-volume paper supply device (hereinafter referred to as “LCT”), a post-processing device that performs processing including sorting, punching, and stapling (not shown), and a document image. An operation unit having a display including a mode for reading, setting of a copying magnification, setting of a paper feed stage, setting of post-processing by a post-processing device, and various keys for displaying to an operator and an LCD.

  The image reading apparatus 104 includes a contact glass 103 on which an original is placed and an optical scanning system. The optical scanning system includes various parts including an exposure lamp, a first mirror, a lens, and a CCD image sensor. The exposure lamp and the first mirror are fixed on a first carriage (not shown), and the second mirror and the third mirror are fixed on a second carriage (not shown). When reading an image of a document, the first carriage and the second carriage are mechanically scanned at a relative speed of 2: 1 so that the optical path length does not change. The optical scanning system is driven by a drive unit including a scanner drive motor (not shown).

  The image reading device 104 optically reads an image of a document and converts it into an electrical signal (reads image data of the document). That is, the image surface of the original is illuminated by an exposure lamp of the optical scanning system, and the reflected light image from the image surface is connected to the light receiving surface of the CCD image sensor through the first mirror, the second mirror, the third mirror, and the lens. The image is converted into an electric signal by the CCD image sensor. At this time, the image reading magnification in the document feeding direction is changed by moving the lens and the CCD image sensor in the left-right direction in FIG. That is, the left and right positions of the lens and the CCD image sensor are set in accordance with a preset image reading magnification.

  The writing unit 105 includes various parts including a laser output unit, an imaging lens, and a mirror. Inside the laser output unit, a laser diode that is a laser light source and a polygon mirror (rotating polygon mirror) that is rotated at a constant speed by a motor. Is equipped. A laser beam (laser light) emitted from the laser output unit is deflected by a polygon mirror that rotates at a constant speed, passes through an imaging lens, is folded by a mirror, and is focused on a charged surface of the photosensitive member 106 to form an image. The

  That is, the laser beam deflected by the polygon mirror is exposed and scanned in a direction (main scanning direction) orthogonal to the direction in which the photosensitive member 106 rotates, and image data output from the image processing apparatus is written in units of lines. By repeating main scanning at a predetermined cycle corresponding to the rotational speed and scanning density (recording density) of the photoconductor 106, an electrostatic latent image is formed on the charged surface of the photoconductor 106.

  Next, the configuration of the fixing device 100A shown in FIG. 1 will be described. FIG. 2 is an explanatory diagram showing a configuration example of the fixing device 100A shown in FIG.

  As shown in the figure, the fixing device 100A heats and dissolves the toner on the transfer paper onto which the toner has been transferred and fixes it onto the transfer paper in the transfer path of the transfer paper in the same manner as in a normal halogen heater method. A fixing roller 121 and a pressure roller 123 disposed opposite to the fixing roller 121 to apply pressure to the transfer paper to fix the toner.

  A heating roller 122 is provided at a position spaced from the fixing roller 121, and a fixing belt 124 is stretched between the heating roller 122 and the fixing roller 121. The fixing belt 124 is a member to be heated that is induction-heated by an exciting coil (hereinafter also referred to as a heating coil as appropriate) 125, and has a multi-layer structure including a heated metal portion (metal conductor) and a non-thermally conductive portion. Consists of.

  The heating coil 125 is for inductively heating the fixing belt 124 with an eddy current. In the first embodiment, the heating coil 125 is an external heating system, and is a base that has a shape that covers the outer circumferential surface of the heating roller 122 by about a half circumference. The coil is wound in a spiral shape. Such a heating coil 125 is energized with an electric current having an arbitrary frequency characteristic by an inverter circuit, and an eddy current flows through the heating roller 122 by receiving a magnetic flux generated by the electric current to be heated. The heat of the heating roller 122 is transmitted to the rotating fixing belt 124, and the transfer paper advances in the rotation direction between the fixing roller 121 and the pressure roller 123 by the nip pressure between the heat and the fixing roller 121 and the pressure roller 123. The toner is fixed on the transfer paper.

  Further, the temperature of the fixing belt 124 is always monitored by a thermistor (temperature sensor) 126 close thereto, and current supply to the heating coil 125 is continued when the temperature is lower than the control temperature, and supply is stopped when the temperature is higher. Temperature control is performed by an engine control board, which will be described later, but a safety device that directly shuts off the power supply by a thermostat 127 is mounted when the temperature becomes too high due to control failure.

  The fixing roller 121 is rotationally driven by a power source such as a fixing motor (not shown), and the fixing belt 124 is moved and rotated by the power. The heating roller 122 is a driven roller that is driven and rotated by the movement of the fixing belt 124.

  In addition, an encoder 128 that functions as a sensor for detecting that the fixing belt 124 is rotating is provided on the shaft of the heating roller 122, and the heating is performed despite the rotation of the fixing roller 121. When the roller 122 does not rotate, it is determined that the belt has run out or the belt has slipped, and the operation of the inverter circuit is interrupted to prevent the heating coil 125 from burning due to an abnormal belt temperature rise.

  However, the induction heating type fixing device 100 </ b> A is not limited to the illustrated external heating method, and may be, for example, an internal heating method of a type in which an exciting coil is built in the fixing roller 121.

  FIG. 3 is a functional block diagram of the fixing device 100A according to the first embodiment and the engine control board 300 that controls the fixing device 100A.

  As shown in the figure, in addition to the heating coil 125, the fixing device 100A of the first embodiment includes a demagnetizing coil 129 that generates a magnetic field in a direction to cancel the magnetic field generated in the heating coil 125. ing. The fixing device 100 </ b> A includes a switch 131 that switches between ON / OFF of the power supply and energization of the heating coil 125, and a switch 132 that switches ON / OFF of the power supply and energization of the degaussing coil 129. The switches 131 and 132 can be switched ON / OFF by the CPU 303 of the engine control board 300.

  The fixing device 100 </ b> A further includes a current detection circuit 133 that detects a current flowing through the degaussing coil 129. The signal of the current detection circuit 133 is input to the AND circuit 301 of the engine control board 300. The AND circuit 301 also receives ON / OFF switching signals for the degaussing coil 129 and the heating coil 125.

  That is, the AND circuit 301 includes a relay ON / OFF signal for supplying power to the degaussing coil 129, an IH power enable signal for supplying power to the heating coil 125 that is a main coil, and a sub coil. A current detection signal for detecting a current flowing in a relay that supplies power to a certain degaussing coil 129 is input.

  A temperature sensor 126 is provided in the vicinity of the heating coil 125, and information from the temperature sensor 126 is input to the abnormality detection signal via the comparator 302.

  Next, a heating control process of the fixing device 100A by the multifunction peripheral 100 according to the first embodiment configured as described above will be described.

  The multi-function device 100 according to the first embodiment is configured such that a heating coil is generated by an AND circuit 301 shown in FIG. The presence / absence of 125 abnormality is determined. If there is an abnormality, the CPU 303 outputs a signal for forcibly turning off the relay of the heating coil 125 to avoid an unauthorized increase in temperature.

  FIG. 4 is a diagram illustrating an example of the determination result of the AND circuit 301. This figure shows the judgment results of the AND circuit 301 during normal operation and abnormal operation of the current detection circuit 133, respectively.

  As shown in the figure, during normal operation, the IH power enable signal is basically always at the H (High) level. When the temperature is lowered, the relay of the degaussing coil 129 is turned ON (H level), and in this case, the current detection signal becomes L (Low) level. Further, when it is better to keep the temperature raised, the relay of the degaussing coil 129 is turned off (L level), and in this case, the current detection signal becomes H level. Therefore, during normal operation, the operation abnormality determination circuit (AND circuit 301) always outputs L level.

  Only by detecting the current of the degaussing coil 129 as in the conventional method, when any abnormality such as a connector disconnection occurs in the current detection circuit 133, the abnormality cannot be detected. On the other hand, according to the method of the first embodiment, when the relay of the degaussing coil 129 is ON and the IH power supply enable signal is ON, the current detection signal also outputs an H signal (by pull-up). In this case, the output signal from the operation abnormality determination circuit is also H. For this reason, the CPU 303 can detect that an abnormality has occurred, and can immediately stop the power supply to the heating coil 125. Thereby, it becomes possible to prevent the temperature from rising abnormally, and the safety of the IH fixing system can be further improved.

  Further, as shown in FIG. 3, the high temperature detection signal output from the temperature sensor 126 via the comparator 302 is also output to the abnormality detection circuit of the CPU 303 as the same abnormality detection signal as the output signal from the AND circuit 301. Therefore, both high temperature abnormality and relay abnormality of the degaussing coil 129 can be detected simultaneously. Thereby, it is possible to provide an inexpensive and safer fixing device.

  As described above, in the image forming apparatus according to the first embodiment, in addition to the heating coil ON / OFF control signal and the heat reduction coil ON / OFF control signal, the current detection signal of the heat reduction coil is supplied to the AND circuit. By inputting, an abnormality of the current detection signal or the current detection circuit itself can be found. As a result, although the heat reduction control is executed by supplying a current to the degaussing coil, it is possible to detect an abnormal state when the current is not actually flowing and to prevent the fixing system from continuing to be heated. .

(Second Embodiment)
The image forming apparatus according to the second embodiment can input the abnormality detection signal from the AND circuit and the high temperature detection signal from the temperature sensor to different detection circuits in the CPU, and determine the cause of the abnormality. And

  FIG. 5 is a functional block diagram of the fixing device 100A and the engine control board 500 according to the second embodiment. As shown in the figure, in the second embodiment, the function of the engine control board 500 is different from that of the first embodiment.

  That is, the engine control board 500 according to the second embodiment receives a high temperature detection signal obtained by inputting the detection signal of the temperature sensor 126 to the comparator 302 and an abnormality detection signal for detecting an abnormality of the current detection circuit 133. To separate ports. As a result, the CPU 503 can determine which of the temperature sensor 126 and the current detection circuit 133 has failed.

(Third embodiment)
The image forming apparatus according to the third embodiment uses a fixing controller having a function of forcibly turning off the relay of the heating coil, and quickly stops heating when an abnormality is detected.

  FIG. 6 is a functional block diagram of the fixing device 100A and the engine control board 600 according to the third embodiment. As shown in the figure, in the second embodiment, the function of the engine control board 600 is different from that in the first embodiment.

  The engine control board 600 includes a fixing controller 604 that is a hardware circuit having a function of forcibly turning off the relay of the heating coil 125. As a result, when an abnormality occurs, the relay can be immediately turned off by hardware alone without using software executed by the CPU 603. Further, as shown in the figure, since the current detection signal and the high temperature detection signal are respectively input to the general-purpose ports of the CPU 603, the CPU 603 can identify the cause of the abnormality.

  Note that the fixing controller 604 may be configured to output a relay forced OFF signal when an abnormality detection signal is detected continuously a plurality of times. Thereby, it is possible to prevent the power supply from being stopped due to a malfunction due to noise or the like.

  The fixing high temperature detection circuit 602 is a circuit that detects that the fixing device 100A is in a high temperature state based on information from the temperature sensor, and may be configured by a comparator as in the first and second embodiments.

  The output from the fixing high temperature detection circuit 602 is input to the fixing controller 604 similarly to the abnormality detection signal from the AND circuit 301. Thereby, the heating of the heating coil 125 can be forcibly turned off when a temperature abnormality occurs.

1 is a schematic configuration diagram illustrating an example of a mechanism unit of a multifunction machine according to a first embodiment; FIG. 3 is an explanatory diagram illustrating a configuration example of a fixing device. 2 is a functional block diagram of a fixing device and an engine control board according to the first embodiment. FIG. It is a figure which shows an example of the judgment result of an AND circuit. FIG. 6 is a functional block diagram of a fixing device and an engine control board according to a second embodiment. FIG. 10 is a functional block diagram of a fixing device and an engine control board according to a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 MFP 100A Fixing device 101 Automatic paper feeder 102 Document tray 103 Contact glass 104 Image reading device 105 Writing unit 106 Photoconductor 107 Developing device 108a First paper feed tray 108b Second paper feed tray 108c Third paper feed tray 109a First 1 sheet feeding device 109 b second sheet feeding device 109 c third sheet feeding device 111 longitudinal conveyance unit 112 reversing unit 113 sheet ejection tray 114 sheet ejection unit 121 fixing roller 122 heating roller 123 pressure roller 124 fixing belt 125 heating coil 126 temperature sensor 127 Thermostat 128 Encoder 129 Degaussing coil 131, 132 Switch 133 Current detection circuit 300, 500, 600 Engine control board 301 AND circuit 302 Comparator 303, 50 , 603 CPU
602 Fixing high temperature detection circuit 604 Fixing controller

Claims (9)

Heating means for heating the heating member of the fixing unit for fixing the toner image transferred to the recording medium in response to power supply;
A heat reducing means for suppressing heat generation of the heating means in response to power supply;
Heating control means for controlling power supply to the heating means;
Heat reduction control means for controlling power supply to the heat reduction means;
An operation detecting means for detecting an operating state of the heat reducing means;
First determining whether there is an abnormality in the heating unit based on a state of power supply to the heat reduction unit by the heat reduction control unit and a detection result of an operation state of the heat reduction unit by the operation detection unit. Judgment means,
A shut-off means for shutting off the power supply to the heating means when it is determined that there is an abnormality in the heating means;
An image forming apparatus comprising: The first determination means includes a state of power supply to the heating means by the heating control means, a state of power supply to the heat reduction means by the heat reduction control means, and the heat reduction means by the operation detection means. Determining the presence or absence of abnormality of the heating means based on the detection result of the operating state of
The image forming apparatus according to claim 1. A temperature detecting means for detecting the temperature of the heating means;
The first determination means further determines the presence or absence of an abnormality of the heating means by comparing the detected temperature with a predetermined threshold;
The image forming apparatus according to claim 1. Temperature detecting means for detecting the temperature of the heating means;
A second determination means for determining that the heating means is abnormal when the detected temperature is greater than a predetermined threshold; and
The image forming apparatus according to claim 1. The shut-off means shuts off the power supply to the heating means when the first judging means determines that there is an abnormality in the heating means continuously several times;
The image forming apparatus according to claim 1. The operation detecting means detects an operating state of the heat reducing means by a current passed through the heat reducing means;
The image forming apparatus according to claim 1. The heating means generates a magnetic field by the current flowing through the exciting coil, and generates heat by electromagnetic induction by the magnetic field;
The image forming apparatus according to claim 1. The heat reduction means suppresses heating by the excitation coil of the heating means by generating a magnetic field that cancels the magnetic field generated by the excitation coil of the heating means;
The image forming apparatus according to claim 1. A heating control method for controlling heating of a heating member of a fixing unit for fixing a toner image transferred to a recording medium,
A heating control step, wherein the heating control means controls the power supply to the heating means for heating the heating member in response to the power supply;
A heat reduction control step, wherein the heat reduction control means controls power supply to the heat reduction means that suppresses heat generation of the heating means in response to power supply; and
A determination step of determining whether or not there is an abnormality in the heating unit based on a detection result of an operation state of the heat reduction unit by an operation detection unit that detects an operation state of the heat reduction unit;
A blocking step of blocking power supply to the heating unit when the blocking unit is determined to have an abnormality in the heating unit;
A heating control method comprising:

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