JP2004102121A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent an abnormal rise in temperature at a heating roller heated by an introduction heater in a fixing device. <P>SOLUTION: The fixing device for holding and transporting a sheet material by a fixing nip part and for melting and pressing an unfixed toner on the sheet material to fix it on the sheet material comprises a heating roller 130 composed of a rotating body made of magnetic metal member; an introduction heating means 180 which is oppositely placed to an outer peripheral face of the heating roller 130 and has an exciting coil 190 to be fed electric power from a driving power source 191 and heat the heating roller 130 by electromagnetic induction; a rotator 230 for rotating in conjunction with rotation of the heating roller 130; a sensor 240 for detecting the rotation of the rotator 230; and a controller 250 for stopping or reducing electric power feeding from the driving power source 191 to the exciting coil 190 when it is detected that the rotator 230 is abnormally rotated by the sensor 240. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device used in an electrostatic recording type image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly, to a toner image fixing device using an electromagnetic induction heating system.
[0002]
[Prior art]
In recent years, market demands for energy saving and high speed have been increasing for image forming apparatuses such as printers, copiers, and facsimile machines. In order to achieve these required performances, it is important to improve the thermal efficiency of a fixing device used in an image forming apparatus.
[0003]
In an image forming apparatus, an unfixed toner image is recorded on a sheet material, printing paper, photosensitive paper, electrostatic recording paper, or the like by an image transfer method or a direct method by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording. Formed on the medium. As a fixing device for fixing an unfixed toner image, a contact heating type fixing device such as a heat roller system, a film heating system, and an electromagnetic induction heating system is widely used.
[0004]
Japanese Patent Application Laid-Open No. Hei 8-22206 discloses an electromagnetic induction heating type fixing device in which an eddy current generated in a heating member, which is a magnetic metal member, by an alternating magnetic field of an induction heating means including an excitation coil generates Joule heat. There is proposed a technique of causing the electromagnetic wave to generate heat by electromagnetic induction.
[0005]
Here, a heat-resistant belt is stretched between the heat-generating member and the fixing roller, or the heat-generating member and the fixing roller are arranged close to each other, and the heat of the heat-generating member generated by the induction heating means is The heat is transmitted by a fixing roller directly through a heat-resistant belt by the rotation of the heating member or by the rotating heating member. Then, the recording medium is nipped and conveyed by a fixing nip formed by a fixing roller and a pressure roller, and the unfixed toner on the recording medium is melted and pressed to fix the toner on the recording medium.
[0006]
Therefore, if the heating member is not rotating at an appropriate speed while the drive power supply for supplying power to the excitation coil is turned on, the heating member locally generates heat and the temperature thereof rises abnormally.
[0007]
In order to prevent such an abnormal rise in the temperature of the heat generating member, it is conceivable to provide a means for detecting a malfunction of a motor that rotationally drives a rotating system including the heat generating member.
[0008]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-236429
[Problems to be solved by the invention]
However, in the technology for detecting a malfunction of the motor, when a transmission mechanism such as a drive gear for transmitting the rotational force of the motor to the heat generating member is damaged, or when the heat generating member becomes heat resistant due to rotation of the fixing roller or the pressure roller. When the heat-resistant member slips between the heat-resistant belt and the heat-generating member due to a structure in which the heat-generating member is rotated by the driven belt, an abnormal increase in the temperature of the heat-generating member cannot be prevented.
[0010]
That is, the rotation of the heat generating member may be stopped due to a cause other than the malfunction of the motor, or may be slower than a normal rotation speed. This is because, in the case of "rotational abnormality" in the specification, the above-described abnormal increase in the temperature of the heat generating member occurs even though the motor is operating normally.
[0011]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device that can reliably prevent an abnormal rise in temperature of a heat generating member that generates heat by induction heating means.
[0012]
[Means for Solving the Problems]
In order to solve this problem, a fixing device according to the present invention is a fixing device that nips and conveys a recording medium at a fixing nip portion, melts and presses unfixed toner on the recording medium, and fixes the unfixed toner on the recording medium. A heating member comprising a rotating body of a magnetic metal member, an induction heating means provided with an exciting coil disposed opposite to the outer peripheral surface of the heating member and receiving heat from a driving power source to generate heat by electromagnetic induction; A rotating body that rotates in conjunction with the rotation of a member, a sensor that detects the rotation of the rotating body, and control that stops or reduces power supply from the driving power supply to the excitation coil if the rotating body is detected as abnormal rotation by the sensor. And a part.
[0013]
As described above, since the rotation of the rotating body that rotates in conjunction with the heat generating member is detected, it is also possible to detect a rotation abnormality of the heat generating member due to a cause other than a malfunction of the motor, and to generate heat generated by the induction heating means. An abnormal rise in temperature of the member can be reliably prevented.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
According to a first aspect of the present invention, there is provided a fixing device that nips and conveys a recording medium at a fixing nip portion, melts and presses unfixed toner on the recording medium, and fixes the unfixed toner on the recording medium. A heating member comprising a rotating body of members, an induction heating means provided with an excitation coil disposed opposite to the outer peripheral surface of the heating member and receiving power from a driving power supply to generate heat by electromagnetic induction, and rotation of the heating member. A rotating body that rotates in conjunction with the rotating body, a sensor that detects rotation of the rotating body, and a control unit that stops or reduces power supply from the driving power supply to the exciting coil if the rotating body is detected to be abnormally rotated by the sensor. Since it detects the rotation of the rotating body that rotates in conjunction with the heat-generating member, it can also detect abnormal rotation of the heat-generating member due to causes other than the malfunction of the motor, and generate heat by the induction heating means. Has the effect of an abnormal increase in temperature can be reliably prevented in the heat generating member that.
[0015]
According to a second aspect of the present invention, there is provided a fixing device according to the first aspect, wherein the rotating body is arranged coaxially with a rotation axis of the heat generating member, and rotates in conjunction with the heat generating member. Since the rotation of the rotating body is detected, it is possible to detect the stop of the rotation of the heating member due to a cause other than the malfunction of the motor, and it is possible to reliably prevent the temperature of the heating member heated by the induction heating means from abnormally rising. It has the effect of being able to.
[0016]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In these drawings, the same members are denoted by the same reference numerals, and redundant description is omitted.
[0017]
FIG. 1 is an explanatory view showing a configuration of an image forming apparatus provided with a fixing device according to an embodiment of the present invention, and FIG. 2 is a fixing device according to an embodiment of the present invention used in the image forming apparatus of FIG. FIG. 3 is an exploded view showing a configuration of a heating roller constituting the fixing device of FIG. 2 cut away, and FIG. 4 is an explanatory diagram showing a configuration of a heat resistant belt constituting the fixing device of FIG. 5, FIG. 5 is an explanatory view showing a part of the induction heating means constituting the fixing device of FIG. 2, FIG. 6 is an explanatory view showing an example of a main part of the fixing device of FIG. 2, and FIG. FIG. 8 is an explanatory diagram showing another example of a main part, and FIG. 8 is an explanatory diagram showing a configuration of a fixing device according to another embodiment of the present invention used in the image forming apparatus of FIG.
[0018]
First, an outline of an image forming apparatus according to the present invention will be described. The image forming apparatus described in the present embodiment is provided with a developing device for each of the four basic color toners that particularly contribute to the color development of a color image among the devices employing the electrophotographic method, and the transfer member has four color toners. This is a tandem method in which images are superimposed and collectively transferred to a sheet material. However, it is needless to say that the present invention is not limited to the tandem type image forming apparatus, and can be applied to any type of image forming apparatus regardless of the number of developing devices, the presence or absence of the intermediate transfer member, and the like. .
[0019]
In FIG. 1, charging means 20a, 20b, 20c, which uniformly charge the surface of each of the photosensitive drums 10a, 10b, 10c, 10d to a predetermined potential, are provided around the photosensitive drums 10a, 10b, 10c, 10d. Exposure means for forming an electrostatic latent image by irradiating the charged photosensitive drums 10a, 10b, 10c, and 10d with scanning lines 30K, 30C, 30M, and 30Y of laser beams corresponding to image data of a specific color. 30, developing means 40a, 40b, 40c, 40d for visualizing the electrostatic latent images formed on the photosensitive drums 10a, 10b, 10c, 10d, and visible images on the photosensitive drums 10a, 10b, 10c, 10d Transfer means 50a, 50b, 50c, 50d for transferring the converted toner image to an endless intermediate transfer belt (intermediate transfer body) 70, and photosensitive drums 10a, 10b, 0c, the photosensitive drum 10a after the toner image has been transferred to the intermediate transfer belt 70 from 10d, 10b, 10c, cleaning means 60a for removing residual toner remaining 10d, 60b, 60c, 60d are respectively disposed.
[0020]
Here, the exposing means 30 is arranged with a predetermined inclination with respect to the photosensitive drums 10a, 10b, 10c, 10d. The intermediate transfer belt 70 rotates in the direction of arrow A in the illustrated case. In the image forming stations Pa, Pb, Pc, and Pd, a black image, a cyan image, a magenta image, and a yellow image are formed, respectively. Then, the single-color images of the respective colors formed on the photosensitive drums 10a, 10b, 10c, and 10d are sequentially transferred onto the intermediate transfer belt 70 so as to form a full-color image.
[0021]
At the lower part of the apparatus, there is provided a paper feed cassette 100 in which a sheet material (recording medium) 90 such as printing paper is stored. Then, the sheet material 90 is sent out from the sheet feeding cassette 100 to the sheet conveying path one by one by the sheet feeding roller 80.
[0022]
On the sheet transport path, a sheet material transfer roller 110 that contacts the outer peripheral surface of the intermediate transfer belt 70 for a predetermined amount and transfers the color image formed on the intermediate transfer belt 70 to the sheet material 90, A fixing device 120 is provided for fixing the transferred color image to the sheet material 90 by the pressure and heat generated by the rotation of the rollers.
[0023]
In the image forming apparatus having such a configuration, first, the charging unit 20a and the exposing unit 30 of the image forming station Pa form the latent image of the black component color of the image information on the photosensitive drum 10a. This latent image is visualized as a black toner image by the developing unit 40a having black toner by the developing unit 40a, and is transferred as a black toner image onto the intermediate transfer belt 70 by the transfer unit 50a.
[0024]
On the other hand, while the black toner image is being transferred to the intermediate transfer belt 70, a latent image of a cyan component color is formed in the image forming station Pb, and then the cyan toner image of the cyan toner is visualized by the developing unit 40b. You. Then, the cyan toner image is transferred by the transfer means 50b of the image station Pb to the intermediate transfer belt 70 where the transfer of the black toner image has been completed at the previous image station Pa, and is superimposed on the black toner image.
[0025]
Hereinafter, image formation is performed for the magenta toner image and the yellow toner image in the same manner, and when the superposition of the four color toner images on the intermediate transfer belt 70 is completed, the paper is fed from the paper feed cassette 100 by the paper feed roller 80. The four color toner images are collectively transferred onto the sheet material 90 by the sheet material transfer roller 110. Then, the transferred toner image is heated and fixed to the sheet material 90 by the fixing device 120, and a full-color image is formed on the sheet material 90.
[0026]
Next, a fixing device used in such an image forming apparatus will be described.
[0027]
As shown in FIG. 2, the fixing device includes a heating roller (heating member) 130 heated by electromagnetic induction of induction heating means 180, a fixing roller 140 arranged in parallel with heating roller 130, An endless belt-shaped heat-resistant belt (toner heating medium) 150 stretched between rollers 140 and heated by the heating roller 130 and rotated in the direction of arrow B by rotation of at least one of these rollers; A pressure roller 160 is pressed into contact with the fixing roller 140 via 150 and rotates in the forward direction with respect to the heat resistant belt 150.
[0028]
The heating roller 130 is made of a rotating body of a hollow cylindrical magnetic metal member such as iron, cobalt, nickel, or an alloy of these metals. It has a fast configuration.
[0029]
As shown in FIG. 3, both ends of the heating roller 130 are rotatably supported by bearings 132 fixed to a supporting side plate 131 made of a galvanized steel plate. The heating roller 130 is rotationally driven by a driving unit (not shown) of the apparatus main body. The heating roller 130 is made of a magnetic material that is an alloy of iron, nickel, and chromium, and is adjusted so that its Curie point is 300 ° C. or higher. The heating roller 130 is formed in a pipe shape with a thickness of 0.3 mm.
[0030]
The surface of the heating roller 130 is coated with a release layer (not shown) made of a fluororesin having a thickness of 20 μm in order to impart release properties. As the release layer, a resin or rubber having good releasability such as PTFE, PFA, FEP, silicone rubber, and fluororubber may be used alone or in combination. When the heating roller 130 is used for fixing a monochrome image, only the releasability may be secured, but when the heating roller 130 is used for fixing a color image, it is desirable to impart elasticity. Need to form a thicker rubber layer.
[0031]
The fixing roller 140 includes a metal core 140a made of a metal such as stainless steel, for example, and an elastic member 140b in which heat-resistant silicone rubber is solid or foamed to cover the core metal 140a. Then, in order to form a fixing nip portion N having a predetermined width between the pressing roller 160 and the fixing roller 140 by the pressing force from the pressing roller 160, the outer diameter is set to about 30 mm and is made larger than that of the heating roller 130. . The elastic member 140b has a thickness of about 3 to 8 mm and a hardness of about 15 to 50 ° (Asker hardness: 6 to 25 ° in JIS A hardness). With this configuration, since the heat capacity of the heating roller 130 is smaller than the heat capacity of the fixing roller 140, the heating roller 130 is rapidly heated, and the warm-up time is reduced.
[0032]
The heat resistant belt 150 stretched between the heating roller 130 and the fixing roller 140 is heated at a contact portion W1 of the heating roller 130 heated by the induction heating means 180. Then, the inner surface of the heat resistant belt 150 is continuously heated by the rotation of the heating roller 130 and the fixing roller 140, and as a result, the entire belt is heated.
[0033]
Hereinafter, the configuration of the heat resistant belt used in the fixing device will be described.
[0034]
As shown in FIG. 4, the heat-resistant belt 150 covers a heat-generating layer 150 a made of a metal having magnetism such as iron, cobalt, nickel, or the like or an alloy based on them, and the surface thereof. And a release layer 150b made of an elastic member such as silicone rubber or fluorine rubber.
[0035]
The use of the composite belt makes it possible to directly heat the belt, improve the heat generation efficiency, and increase the response.
[0036]
Also, even if for some reason, for example, a foreign matter is mixed between the heat-resistant belt 150 and the heating roller 130 to form a gap, even if a heat-generating layer 150a of the heat-resistant belt 150 generates heat due to electromagnetic induction, the heat-resistant belt 150 is heated. Since the heat itself is generated, there is little temperature unevenness, and the reliability of fixing is increased.
[0037]
Note that the thickness of the heat generating layer 150a is desirably about 20 μm to 50 μm, and particularly desirably about 30 μm.
[0038]
As described above, when the heat generating layer 150a is made of a material based on a metal having magnetism such as iron, cobalt, nickel, or the like or an alloy based on them, if the thickness is larger than 50 μm, In addition, the strain stress generated when the belt rotates increases, causing cracks due to shearing force and extremely lowering the mechanical strength. If the thickness of the heat generating layer 150a is smaller than 20 μm, the composite layer belt may be damaged by cracks and cracks due to a thrust load on the belt end caused by meandering during belt rotation.
[0039]
On the other hand, the thickness of the release layer 150b is preferably about 100 μm to 300 μm, and more preferably about 200 μm. By doing so, the surface layer of the heat-resistant belt 150 sufficiently wraps the toner image T formed on the sheet material 90, so that the toner image T can be uniformly heated and melted.
[0040]
If the thickness of the release layer 150b is smaller than 100 μm, the heat capacity of the heat-resistant belt 150 becomes small, and the belt surface temperature drops rapidly in the toner fixing step, so that sufficient fixing performance cannot be secured. If the thickness of the release layer 150b is larger than 300 μm, the heat capacity of the heat-resistant belt 150 increases, and the time required for warm-up increases. In addition, in the toner fixing step, the surface temperature of the belt is hardly reduced, so that the aggregation effect of the melted toner at the fixing unit outlet is not obtained, and the releasability of the belt is reduced and the toner adheres to the belt. Hot offset occurs.
[0041]
The inner surface of the heat generating layer 150a may be coated with a resin for the purpose of preventing metal oxidation and improving contact with the heating roller 130.
[0042]
In addition, as a base material of the heat-resistant belt 150, instead of the heat-generating layer 150a made of the above-described metal, it has heat resistance such as a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, and a PPS resin. A resin layer may be used.
[0043]
If the base material is formed of a resin layer which is a resin member having high heat resistance, the heat resistant belt 150 can easily adhere to the heat roller 130 according to the curvature of the heat roller 130. 150 is transmitted efficiently. In addition, there is an effect that the resin is hardly cracked. However, the thermal conductivity is higher when a metal layer is used.
[0044]
In this case, the thickness of the resin layer is preferably from about 20 μm to 150 μm, and particularly preferably about 75 μm. If the thickness of the resin layer is smaller than 20 μm, mechanical strength against meandering during belt rotation cannot be obtained. When the thickness of the resin layer is larger than 150 μm, the thermal conductivity of the resin is small, so that the heat transfer efficiency from the heating roller 130 to the release layer 150b of the heat resistant belt 150 is reduced, and the fixing performance is reduced. Occurs.
[0045]
In FIG. 2, a pressure roller 160 includes a metal core 160a made of a cylindrical member made of a metal having high thermal conductivity such as copper or aluminum, and heat resistance and toner releasability provided on the surface of the metal core 160a. High elastic member 160b. SUS may be used for the metal core 160a in addition to the above metals.
[0046]
The pressing roller 160 forms a fixing nip portion N that presses the fixing roller 140 via the heat-resistant belt 150 to pinch and convey the sheet material 90. In the present embodiment, the hardness of the pressing roller 160 is By making the fixing roller 140 harder than the fixing roller 140, the pressure roller 160 bites into the fixing roller 140 (and the heat-resistant belt 150), so that the sheet material 90 follows the circumferential shape of the surface of the pressure roller 160. Therefore, the sheet member 90 has an effect of easily separating from the surface of the heat resistant belt 150. The outer diameter of the pressure roller 160 is about 30 mm, which is the same as that of the fixing roller 140, but the wall pressure is about 2 to 5 mm, which is thinner than the fixing roller 140, and the hardness is 20 to 60 ° (Asker hardness: JIS A hardness). As described above, the fixing roller 140 is harder than the fixing roller 140.
[0047]
Next, the configuration of the induction heating means 180 will be described.
[0048]
The induction heating means 180 for heating the heating roller 130 by electromagnetic induction is arranged to face the outer peripheral surface of the heating roller 130 as shown in FIG. As shown in FIG. 2 and FIG. 5, it has an exciting coil 190 as a magnetic field generating means, and a coil guide plate 200 around which the exciting coil 190 is wound. The coil guide plate 200 has a semi-cylindrical shape disposed close to the outer peripheral surface of the heating roller 130. Further, the excitation coil 190 is formed by winding a wire bundle obtained by bundling wires whose surfaces are insulated along the coil guide plate 200 so as to extend in the rotation axis direction of the heating roller 130. It is formed along the circumference. The excitation coil 190 has an oscillation circuit connected to a drive power supply 191 whose frequency is variable. The power supply from the drive power supply 191 causes the heating roller 130 to generate heat by electromagnetic induction. In the present embodiment, the number of twists of the exciting coil 190 is 40, and this is wound 9 times.
[0049]
Outside the excitation coil 190, a semi-cylindrical excitation coil core 210 made of a ferromagnetic material such as ferrite is fixed to the excitation coil core support member 220 and is arranged close to the excitation coil 190. In the present embodiment, the exciting coil core 210 having a relative magnetic permeability of 2500 is used.
[0050]
In the fixing device having such a configuration, in FIG. 4, a high-frequency AC current of 10 kHz to 1 MHz, preferably a high-frequency AC current of 20 kHz to 800 kHz is supplied to the excitation coil 190 from a driving power source, thereby generating an alternating magnetic field D. I do. Then, the alternating magnetic field acts on the heating layer 150a of the heating roller 130 and the heat resistant belt 150 in the contact area W1 between the heating roller 130 and the heat resistant belt 150 and in the vicinity thereof, and the change of the alternating magnetic field D is generated inside these. An eddy current I flows in the obstructing direction.
[0051]
The eddy current I generates Joule heat according to the resistance of the heating roller 130 and the heat generating layer 150a, and has the heating roller 130 and the heat generating layer 150a mainly in the contact area between the heat roller 130 and the heat resistant belt 150 and in the vicinity thereof. The heat resistant belt 150 is heated by electromagnetic induction.
[0052]
The heat-resistant belt 150 heated in this manner is a temperature-sensitive thermosensitive element such as a thermistor disposed in contact with the inner surface of the heat-resistant belt 150 near the entrance side of the fixing nip N shown in FIG. The temperature of the inner surface of the belt is detected by the temperature detecting means 170 including an element.
[0053]
Accordingly, the fixing performance is continuously ensured without the temperature detecting means 170 damaging the surface of the heat resistant belt 150, and the temperature immediately before entering the fixing nip portion N of the heat resistant belt 150 is detected. Then, by controlling the input power to the induction heating means 180 based on a signal output based on this temperature information, the temperature of the heat resistant belt 150 is stably maintained at, for example, 180 ° C.
[0054]
Here, as shown in FIG. 6, a rotating body 230 is connected to the heating roller 130 via a gear 260, and the disc-shaped rotating body 230 rotates in conjunction with the rotation of the heating roller 130. ing. In the rotating body 230, three slits 230a are formed at regular intervals in the circumferential direction.
[0055]
In the vicinity of the rotator 230, a sensor 240 such as a photosensor that detects the rotation of the rotator 230 when the rotator 230 rotates and the light from the light emitting unit to the light receiving unit is blocked and transmitted by the slit 230a. Is installed.
[0056]
The sensor 240 stops or reduces the power supply from the driving power supply 191 to the exciting coil 190 when the rotation of the rotating body 230 is detected to be abnormal by the sensor 240 (that is, the rotation of the rotating body 230 is stopped or the rotation speed is abnormally decreased). The control unit 250 is connected.
[0057]
Note that the control of stopping or decreasing the power supply to the excitation coil 190 in the control unit 250 may be either control by hardware or software control using a CPU.
[0058]
Here, in the present embodiment, one slit 230a is detected at 280 ms at a normal rotation speed, and when this slit 230a is not detected for 1.4 seconds continuously, a rotation abnormality is determined. Is to be detected. However, the present invention is not limited to such numerical values.
[0059]
In addition, the sensor 240 is not limited to a photosensor, and various sensors capable of performing detection by mechanical means, electrical means, magnetic means, and the like can be applied. Further, even when a photo sensor is used, various types of photo sensors can be used. Further, a member having optical transparency can be used instead of the slit 230a described above.
[0060]
In the above configuration, if the sensor 240 does not detect the slit 230a of the rotating body 230 that rotates in conjunction with the heating roller 130 for a predetermined time, the rotating body 230 stops rotating or the rotation speed is abnormally reduced. That is, since the rotation of the heating roller 130 is stopped or the rotation speed is abnormally reduced, this is detected as a rotation abnormality and a signal is issued to the control unit 250. Then, the control unit 250 that has received this signal controls the drive power supply 191 to stop or reduce the power supply to the excitation coil 190 of the induction heating unit 180. In addition, when the power supply is reduced, the temperature is set to such an extent that the temperature does not abnormally rise due to local heat generation of the heating roller 130 by the exciting coil 190.
[0061]
As described above, according to the present embodiment, since the rotation of the rotating body 230 that rotates in conjunction with the heating roller 130 is detected, abnormal rotation of the heating roller 130 due to a cause other than a malfunction of the motor can be detected. The temperature of the heating roller 130 which can be detected and is heated by the induction heating means 180 can be reliably prevented from abnormally rising.
[0062]
In the above description, the rotating body 230 is connected to the heating roller 130 via the gear 260, but may be arranged coaxially with the rotating shaft of the heating roller 130 as shown in FIG.
[0063]
Further, in the above description, the configuration is shown in which the fixing is performed by the fixing roller 140 heated from the heating roller 130 heated by the induction heating unit 180 via the heat-resistant belt 150, but the heat-resistant belt 150 is not used. A configuration in which fixing is performed directly by the heating roller 130 may be employed.
[0064]
That is, as shown in FIG. 8, the heating roller 130 heated by electromagnetic induction of the induction heating means 180 and the pressing roller 160 pressed against the heating roller 130 and rotating in the forward direction with respect to the heating roller 130. It may be configured.
[0065]
Further, in the present embodiment, the sensor 240 detects the rotation stop of the rotator 230 and the abnormal decrease in the rotation speed, but may detect only one of them.
[0066]
【The invention's effect】
As described above, according to the present invention, since the rotation of the rotating body that rotates in conjunction with the heat-generating member is detected, it is possible to detect the rotation abnormality of the heat-generating member due to a cause other than the malfunction of the motor, and to perform the induction. An advantageous effect is obtained that an abnormal rise in temperature of the heat generating member generated by the heating means can be reliably prevented.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus provided with a fixing device according to an embodiment of the present invention. FIG. 2 is a fixing device according to an embodiment of the present invention used in the image forming apparatus of FIG. FIG. 3 is an exploded view showing a configuration of a heating roller constituting the fixing device shown in FIG. 2; FIG. 4 is an explanatory diagram showing a configuration of a heat-resistant belt constituting the fixing device shown in FIG. 2; FIG. 5 is an explanatory view showing a part of the induction heating means constituting the fixing device of FIG. 2; FIG. 6 is an explanatory view showing an example of a main part of the fixing device of FIG. 2; FIG. 8 is an explanatory diagram showing another example of the main part of FIG. 8. FIG. 8 is an explanatory diagram showing a configuration of a fixing device according to another embodiment of the present invention used in the image forming apparatus of FIG.
90 sheet material (recording medium)
130 Heating roller (heating member)
180 Induction heating means 190 Excitation coil 191 Driving power supply 230 Rotating body 240 Sensor 250 Control section N Fixing nip section

Claims (2)

A fixing device that nips and conveys a recording medium at a fixing nip portion and melts and pressurizes unfixed toner on the recording medium to fix the recording medium on the recording medium,
A heat-generating member comprising a rotating body of a magnetic metal member;
An induction heating means provided with an exciting coil that is arranged to face the outer peripheral surface of the heat generating member and receives power from a driving power source to generate heat by heating the heat generating member by electromagnetic induction;
A rotating body that rotates in conjunction with the rotation of the heating member,
A sensor for detecting rotation of the rotating body,
A fixing unit that stops or reduces power supply from the driving power supply to the exciting coil when the rotation of the rotating body is detected as abnormal by the sensor. 2. The fixing device according to claim 1, wherein the rotating body is disposed coaxially with a rotation axis of the heat generating member.

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