JP2002014566A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent temperature rising at an abnormal time by discriminating whether a toner heating medium is made in a rotating state or not by a temperature detecting means in the fixing device of an electromagnetic induction heating system. SOLUTION: This device possesses a heating roller 1 heated by the magnetic induction of an induction heating means 6, a fixing roller 2 arranged in parallel with the heating roller 1, a heat-resistant belt 3 laid and rotated between the heating roller 1 and the fixing roller 2, a pressure roller 4 coming into press- contact with the fixing roller 2 through the heat-resistant belt 3 and forming a fixing nip part N by rotating in a forward direction to the heat-resistant belt 3, the temperature detecting means 5a disposed in the vicinity of the entrance of the fixing nip part N so as to detect the temperature of the heat- resistant belt 3, a second temperature detecting means 5b arranged on the inner surface of the heating part of the heating roller 1 so as to detect the temperature of the heating roller 1 and a discriminating means to discriminate whether the heat-resistant belt 3 is made in the rotating state or not based on temperature information detected by the temperature detecting means 5a and 5b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. 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 fixing device of an electromagnetic induction heating system. .

[0002]

2. Description of the Related 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. And
In order to achieve these required performances, it is important to improve the thermal efficiency of the fixing device used in the image forming apparatus.

Here, the image is transferred (indirectly) by an appropriate image forming process means such as electrophotographic recording, electrostatic recording, or magnetic recording.
As a fixing device for fixing the unfixed toner image formed by the direct or direct method to recording materials such as recording material sheets, printing paper, photosensitive paper, electrostatic recording paper, etc., a heat roller method, a film heating method, electromagnetic induction A fixing device of a contact heating type such as a heating type is widely used.

A fixing device of a heat roller type has a rotating roller pair of a fixing roller having a heat source such as a halogen lamp therein and adjusted to a predetermined temperature, and a pressing roller pressed against the fixing roller. The recording material is introduced into a contact portion of the pair of rotating rollers, a so-called fixing nip portion, and nipped and conveyed, and the unfixed toner image is melted and fixed by heat and pressure from the fixing roller and the pressure roller. is there.

Further, a fixing device of a film heating system is disclosed in, for example, JP-A-63-313182 and
63679 and the like.

In this apparatus, a recording material is brought into close contact with a heating member fixed and supported by a supporting member via a thin fixing film having heat resistance, and the heating member is slidably moved with respect to the heating member. Is supplied to the recording material via the film material. In this fixing device, as a heating body, for example, a ceramic substrate such as alumina (Al ₂ O ₃ ) or aluminum nitride (AlN) having characteristics such as heat resistance, insulation, and good thermal conductivity, and heat is generated by energization. Since a ceramic heater based on a configuration having a resistance layer on this substrate can be used as a fixing film having a thin film and low heat capacity, the heat transfer efficiency is higher than that of a heat roller type fixing device, and the warm-up is achieved. Time can be reduced, and quick start and energy saving can be achieved.

[0007] As a fixing device of the electromagnetic induction heating type, Japanese Patent Publication No. Hei 8-22206 discloses an eddy current generated in a magnetic metal member by an alternating magnetic field to generate Joule heat. It has been proposed to generate magnetically induced heat.

Hereinafter, the configuration of a magnetic induction heating type fixing device will be described. FIG. 8 is a schematic diagram showing a conventional fixing device using an electromagnetic induction heating method.

As shown in FIG. 8, the fixing device is provided with a heating element 20 which is an electromagnetic induction heating structure comprising an exciting coil unit 18 in which a coil is wound and a magnetic metal member 19 as a heating section. A film inner guide 21 and a heat-resistant cylindrical film 17 surrounding the film inner guide 21 with the magnetic metal member 19 facing the inner wall.
And a pressure roller 2 that presses against the film 17 at the position of the magnetic metal member 19 to form a fixing nip N between the film 17 and the driven rotation of the film 17.
And 2.

The film 17 has a thickness of 100 μm.
m, preferably 50 μm or less, and a single-layer film of PTFE, PFA, FEP or the like having a heat resistance of 20 μm or more, or polyimide, polyamideimide, PEE
PTF on the outer surface of film such as K, PES, PPS
A composite layer film coated with E, PFA, FEP or the like is used.

Further, the film inner surface guide 21 has a rigidity made of a thermosetting resin such as PEEK or PPS.
The heating element 20 is made of a member having heat resistance, and is fitted into a substantially central portion of the lower surface of the film inner surface guide 21.

The pressure roller 22 is composed of a core metal 22a and a heat-resistant rubber layer 22b with good releasability such as silicon rubber provided around the core metal 22a. (Not shown) so that the film 17 is pressed against the magnetic metal member 19 of the heating element 20 with a predetermined pressing force. Then, it is rotationally driven counterclockwise by a driving means (not shown).

The rotation of the pressure roller 22 generates a frictional force between the pressure roller 22 and the film 17, and a rotational force acts on the film 17.
Slides and rotates while being in close contact with the magnetic metal member 19 of the heating element 20.

In a state where the heating body 20 has risen to a predetermined temperature, the film 17 in the fixing nip portion N formed by the heating body 20 and the pressure roller 22 via the film 17 is provided.
The recording material 11 having the unfixed toner image T formed by the image forming unit (not shown) is introduced between the recording material 11 and the pressure roller 22. Then, the recording material 11 is conveyed through the fixing nip N by being sandwiched between the pressure roller 22 and the film 17, so that heat held by the magnetic metal member 19 of the heating element 20 is transferred via the film 17 to the recording material 11. And recording material 1
1 is melted and fixed on the recording material 11. At the exit of the fixing nip N, the recording material 11 that has passed is separated from the surface of the film 17 and is conveyed to a paper discharge tray (not shown).

Japanese Patent Application Laid-Open No. 7-295414 discloses a structure in which an electromagnetic induction heating member is provided outside a cylindrical rotary heating member and a temperature sensor is provided outside a region heated by the electromagnetic induction heating member. ing.

Further, Japanese Patent Application Laid-Open No. 7-319312 discloses that an electromagnetic induction heating member is provided inside a cylindrical rotary heating member and a temperature detecting element is provided outside the cylindrical rotary heating member at a position facing the electromagnetic induction heating member. Is disclosed.

[0017]

SUMMARY OF THE INVENTION Here, JP-A-7-2
In the fixing device of the electromagnetic induction heating system disclosed in Japanese Patent No. 95414, a temperature sensor for detecting the surface temperature of the rotary heating member is provided outside the region heated by the electromagnetic induction heating member. When the member stops rotating for some reason, a problem occurs such that an abnormal rise in temperature in the heating unit cannot be detected, which may cause damage to the device.

In the fixing device of the electromagnetic induction heating type disclosed in Japanese Patent Application Laid-Open No. 7-31912,
A safety device such as a thermostat is provided at a position facing the electromagnetic induction heating member to prevent abnormal temperature rise in the heat generating portion due to runaway such as temperature control. However, a rubber layer and a release layer are generally formed on the outer peripheral surface of the electromagnetic induction heating member. Particularly, in a fixing device in a full-color image forming apparatus, a thick layer composed of toner particles laminated in four or more layers. Is sufficiently wrapped and uniformly heated and melted, a rubber layer of about 200 μm is provided on the surface of the film.

In such a configuration, the thermal responsiveness is deteriorated due to the low thermal conductivity of the rubber layer, and the inner surface of the rotary heating member heated by the electromagnetic induction heating member and the outer surface in contact with the toner are not provided. Then, the temperature difference becomes very large. For this reason, it becomes difficult to control the temperature of the surface of the film, which is the toner heating medium, which greatly affects the fixing performance of the toner. In addition, since the air layer and the rubber layer exist between the rotating heating member and the safety device, the response speed of the safety device is slower than the heating speed of the heating member, and the temperature of the rotating heating member rises rapidly. As a result, the rotary heating member itself may cause damage such as thermal deformation.

Accordingly, an object of the present invention is to provide an electromagnetic induction heating type fixing device which can prevent an abnormal temperature rise of a toner heating medium heated by electromagnetic induction of an induction heating means.

[0021]

In order to solve this problem, a fixing device according to the present invention comprises a heating roller which is made of a magnetic metal member and is heated by electromagnetic induction of an induction heating means; An endless belt-shaped toner heating medium that is stretched between the arranged fixing roller, the heating roller and the fixing roller, heated by the heating roller and rotated by these rollers, and pressed against the fixing roller via the toner heating medium. And a pressure roller that rotates in the forward direction with respect to the toner heating medium to form a fixing nip portion, and a first temperature detection device disposed near the entrance of the fixing nip portion for detecting the temperature of the toner heating medium. Means, second temperature detecting means for detecting the temperature of the heating roller, and whether or not the toner heating medium is in a rotating state based on temperature information detected by these temperature detecting means. And a determination unit configured to,
When the determination unit determines that the toner heating medium is in the stopped state, the induction heating unit stops heating by electromagnetic induction.

As described above, the first temperature detecting means for detecting the temperature of the toner heating medium and the first temperature detecting means for detecting the temperature of the heating roller are provided in the vicinity of the entrance of the fixing nip portion so as to detect the rotation and the stopped state of the toner heating medium. Since the determination is made by the second temperature detecting means, it is possible to prevent an abnormal temperature rise of the toner heating medium heated by the electromagnetic induction of the induction heating means.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention relates to a heating roller made of a magnetic metal member and heated by electromagnetic induction of an induction heating means, and a fixing roller arranged in parallel with the heating roller. And an endless belt-shaped toner heating medium that is stretched over a heating roller and a fixing roller, is heated by the heating roller and is rotated by these rollers, and is pressed against the fixing roller via the toner heating medium while heating the toner. A pressure roller configured to rotate in a forward direction with respect to the medium to form a fixing nip; a first temperature detecting unit disposed near an entrance of the fixing nip to detect a temperature of the toner heating medium; Second temperature detecting means for detecting the temperature of the toner, and determining means for determining whether or not the toner heating medium is in a rotating state based on the temperature information detected by these temperature detecting means. The first temperature detecting means and the second temperature detecting means determine the rotation and stop state of the toner heating medium, so that the toner heating medium is heated by electromagnetic induction of the induction heating means. It has an effect that abnormal temperature rise can be prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, when the determination unit determines that the toner heating medium is in the stopped state, the heating of the induction heating unit by the electromagnetic induction is stopped. The fixing device is capable of accurately detecting the temperature rise of the toner heating medium with a faster response speed, and thus has the effect of preventing damage due to thermal deformation of the toner heating medium. .

Hereinafter, the first 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 duplicate description is omitted.

FIG. 1 is an explanatory view showing a fixing device according to an embodiment of the present invention. FIG. 2A is a sectional view showing an exciting coil of induction heating means in the fixing device shown in FIG. 1, and FIG. 1 is a side view showing an exciting coil of induction heating means in the fixing device of FIG. 1, FIG. 3 is an explanatory view showing generation of an alternating magnetic field and an eddy current by the induction heating means in the fixing device of FIG. 1, and FIG. FIG. 5 is a flowchart showing the operation of the apparatus, and FIG.
FIG. 6 is a graph showing the relationship between the inner surface temperature of the heat resistant belt in the normal state and the inner surface temperature of the heating portion of the heating roller when subjected to electromagnetic induction heating in the fixing device of FIG. FIG. 7 is a graph showing the relationship between the inner surface temperature of the heat-resistant belt and the inner surface temperature of the heating portion of the heating roller when heated by electromagnetic induction in a state where the heat-resistant belt is not rotated from the initial stage. 4 is a graph showing the relationship between the inner surface temperature of a heat-resistant belt and the inner surface temperature of a heating portion of a heating roller when electromagnetic induction heating is performed in a state in which rotation stops after a predetermined time from the start of heating.

The fixing device shown in FIG. 1 is an electromagnetic induction heating type fixing device used in an image forming apparatus, and is arranged in parallel with the heating roller 1 heated by electromagnetic induction of the induction heating means 6 and the heating roller 1. Endless belt-shaped heat-resistant belt (toner heating medium) that is stretched between the fixing roller 2 and the heating roller 1 and the fixing roller 2, is heated by the heating roller 1, and rotates in the direction of arrow A by the rotation of the fixing roller 2. 3 and a pressure roller which is pressed against the fixing roller 2 via the heat-resistant belt 3 and rotates in the forward direction with respect to the heat-resistant belt 3.

As shown in the figure, the fixing device is provided with two temperature detecting means 5 such as thermistors, which are thermosensitive elements having high thermal response. That is, the temperature detecting means 5
A first temperature detecting means 5a which is disposed in contact with the inner surface side of the heat resistant belt 3 near the entrance side of the fixing nip N to detect the temperature of the heat resistant belt 3; The second temperature detecting means 5b is disposed in contact with the heating roller 1 and detects the temperature of the heating roller 1.

Here, the heating roller 1 is made of a hollow cylindrical magnetic metal member such as SUS and has an outer diameter of, for example, 20 mm, a wall thickness of, for example, 0.3 mm, a low heat capacity and a rapid temperature rise. Has become.

The fixing roller 2 includes a metal core 2a made of metal such as SUS, and an elastic member 2b formed by solidifying or foaming silicone rubber having heat resistance and covering the core 2a. In order to form a contact portion having a predetermined width with the pressing roller 4 by the pressing force from the pressing roller 4, the outer diameter is set to about 30 mm, which is larger than that of the heating roller 1. The thickness is about 3 to 8 mm, and the hardness is about 15 to 50 ° (Asker C).

With such a configuration, the heat capacity of the pressure roller 1 becomes smaller than the heat capacity of the fixing roller 2, so that the heating roller 1 is rapidly heated and the warm-up time is reduced.

The heat resistant belt 3 stretched between the heating roller 1 and the fixing roller 2 is heated at a contact portion W of the heating roller 1 heated by the induction heating means 6. Then, the inner surface of the heat resistant belt 3 is continuously heated by the rotation of the heat resistant belt 3 accompanying the rotation of the fixing roller 2 by the driving means (not shown), and as a result, the entire belt is heated.

Here, the heat-resistant belt 3 is made of Ni, Cu,
Heat generation layer 3a based on a metal member having magnetism such as Cr
And a release layer 3b made of an elastic member such as silicone rubber or fluorine rubber provided so as to cover the surface thereof.

According to this, even if for some reason, for example, a foreign matter is mixed between the heat-resistant belt 3 and the heating roller 1 to form a gap, the heat-generating layer 3a of the heat-resistant belt 3 is not affected by electromagnetic induction. Since the heat-resistant belt 3 itself generates heat due to the heat generation, the temperature non-uniformity is small and the reliability is improved.

The heating layer 3a has a thickness of 20 μm.
m to about 50 μm, and preferably about 30 μm.

If the thickness of the heat generating layer 3a is larger than 50 μm, the strain stress generated during the rotation of the belt increases, causing cracks due to shearing force and extremely lowering the mechanical strength. The thickness of the heat generating layer 3a is 20 μm.
If it is smaller, a thrust load on the belt end caused by meandering at the time of rotation of the belt causes breakage such as cracks and cracks.

On the other hand, the thickness of the release layer 3b is 100
It is desirable that the thickness is about μm to 300 μm, and particularly about 200 μm. By doing so, the surface layer of the heat-resistant belt 3 sufficiently wraps the toner image T formed on the recording material 11, so that the toner image T can be uniformly heated and melted.

When the thickness of the release layer 3b is smaller than 100 μm, the heat capacity of the heat-resistant belt 3 becomes small, and the belt surface temperature drops rapidly in the toner fixing step,
The fixing performance cannot be sufficiently secured. If the thickness of the release layer 3b is larger than 300 μm, the heat capacity of the heat-resistant belt 3 is increased and the time required for warm-up is prolonged. As a result, the effect of coagulating the melted toner at the exit of the fixing unit cannot be obtained, and the so-called hot offset, in which the releasability is reduced and the toner adheres to the belt, occurs.

The base material of the heat-resistant belt 3 is N
A heat-resistant resin layer such as a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, and a PPS resin is used instead of the heat generating layer 3a made of a metal member such as i, Cu, or Cr. You may.

If the base material is formed of a resin layer, which is a resin member having high heat resistance, the heat-resistant belt 3 can easily adhere to the heating roller 1 in accordance with the curvature of the heating roller 1. Is efficiently transmitted to

In this case, the thickness of the resin layer is 20 μm.
m to about 150 μm, particularly 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 heat shielding effect is increased and the heat transfer efficiency from the heating roller 1 to the release layer 3b of the heat resistant belt 3 is reduced, so that the fixing performance is reduced. appear.

The pressure roller 4 is a metal core 4 made of a cylindrical member made of metal having high heat conductivity such as SUS or aluminum.
a, and an elastic member 4b provided on the surface of the cored bar 4a and having high heat resistance and toner releasing property.

The pressure roller 4 is a heat-resistant belt 3
The fixing nip N is formed by pressing the fixing roller 2 through the fixing roller 2. However, in this embodiment, the outer diameter of the fixing nip N is increased so that the toner separating action at the exit of the fixing nip N is increased. Same as 2 but about 30mm, but the thickness is 2-5m
m, which is thinner than the fixing roller 2 and has a hardness of 20 to 60.
° (Asker C), which is harder than the fixing roller 2.

As shown in FIG. 2, the induction heating means 6 for heating the heating roller 1 by electromagnetic induction comprises an exciting coil 7 as a magnetic field generating means and a coil guide plate 8 around which the exciting coil 7 is wound. Have. Here, the coil guide plate 8 has a semi-circular shape arranged close to the outer peripheral surface of the heating roller 1, and the exciting coil 7 is configured by applying a single long exciting coil wire to the heating roller 1 along the coil guide plate 8. The winding length is the same as the area where the heat-resistant belt 3 and the heating roller 1 are in contact with each other.

According to this, the area of the heating roller 1 which is subjected to electromagnetic induction heating by the induction heating means 6 is maximized,
Since the time during which the surface of the heating roller 1 that is generating heat and the heat-resistant belt 3 are in contact with each other is maximized, the heat transfer efficiency is increased.

The excitation coil 7 is connected to a drive power supply (not shown) whose oscillation circuit has a variable frequency.

Further outside the excitation coil 7, an excitation coil core 9, which is a semi-circular member made of a ferromagnetic material such as ferrite, is fixed to the excitation coil core support member 10 and is arranged close to the excitation coil 7. . In the present embodiment, the excitation coil core 9 having a relative magnetic permeability of 2500 is used.

The excitation coil 7 has a frequency of 10 kHz from the driving power supply.
~ 1MHz high frequency alternating current, preferably 20kHz ~
A high frequency alternating current of 800 kHz is fed, thereby generating an alternating magnetic field. Then, in the contact area W between the heating roller 1 and the heat resistant belt 3 and in the vicinity thereof, the alternating magnetic field causes the heating layer 3 of the heating roller 1 and the heat resistant belt 3 to be heated.
a, and an eddy current I flows in these directions in the direction B which hinders the change of the magnetic field.

The eddy current I generates Joule heat according to the resistance of the heating roller 1 and the heat generating layer 3a, and mainly in the contact area between the heating roller 1 and the heat resistant belt 3 and in the vicinity thereof, The heat-resistant belt 3 having 3b is heated by electromagnetic induction.

The heat-resistant belt 3 thus heated
The temperature of the inner surface is detected by the first temperature detecting means 5a. Further, the heating roller 1 is controlled by the second temperature detecting means 5b.
The temperature of the inner surface of the heating section is detected. Then, the temperatures detected by these temperature detecting means 5a and 5b are sent to a judging means (not shown).
Based on the temperature information detected in a and 5b, it is determined whether or not the heat resistant belt 3 is in a rotating state.

Next, the operation of the fixing device of the electromagnetic induction heating system having such a configuration will be described with reference to FIGS. 4, 5, 6, and 7. FIG.

In FIG. 4, first, the fixing roller 2 is rotated by driving means (not shown) (step S1).
Heating by electromagnetic induction is started (step S2). When the electromagnetic induction heating is started, the inner surface temperature θa of the heat-resistant belt 3 near the entrance side of the fixing nip portion N detected by the first temperature detecting means 5a becomes a predetermined temperature, for example, 180 ° C. Control is performed (step S3). In the present embodiment, temperature control is performed by proportional integral control.

Here, when the temperature is controlled, the state of the inner surface temperature θa of the heat resistant belt 3 and the inner surface temperature θb of the heating portion of the heating roller 1 in the normal state are as shown in FIG. FIG.
, The inner surface temperature θb of the heating roller 1 and the inner surface temperature θa of the heat resistant belt 3 change while maintaining a predetermined temperature difference θba. This is because the inner surface temperature θa and the inner surface temperature θb are the same at the contact portion W with the heating roller 1, but since the heat resistant belt 3 is not heated after the contact portion W, the temperature is reduced by the amount of heat dissipation.

In step S3, temperature control is performed to calculate a difference between the inner surface temperature θb of the heating portion of the heating roller 1 and the inner surface temperature θa of the heat-resistant belt 3, and the difference is compared with a predetermined temperature difference θc (step S4). ). Here, the temperature difference θc is a value obtained by adding a variation due to the environment and the like to the temperature difference θb-a in the normal state, and is 30 ° C. here.

If the result of the comparison in step S4 is θb−θa <θc, it is determined that the state is the normal state, and the process proceeds to step S5. Also, the result of the comparison is θ
If b−θa ≧ θc, the heat-resistant belt 3 is determined to be in the stopped state as shown in FIGS. 6 and 7, and the process proceeds to step S6.

That is, if the result of the comparison in step S4 is θb−θa <θc, it is determined whether or not the printing is completed (step S5). If the printing is not completed, the process proceeds to step S3 to control the temperature. To continue.
If printing is completed, the electromagnetic induction heating is turned off (step S7), and the driving of the fixing drive roller is turned off (step S8), thereby completing the fixing operation.

If the result of the comparison in step S4 is θb−θa ≧ θc, an error message indicating that the heat-resistant belt 3 is in a stopped state is notified to the user by notification means (not shown) (step S4). S6) The electromagnetic induction heating is turned off (step S7), and the driving of the fixing drive roller is turned off (step S8), and the fixing operation is completed.

This makes it possible to prevent an abnormal rise in temperature at the contact portion with the heating roller 1 when the heat resistant belt 3 stops rotating for some reason.

As described above, according to the present embodiment, the rotation or stop state of the heat-resistant belt 3 is determined by the temperature information of the temperature detecting means 5 disposed near the entrance of the fixing nip N. In addition, the size of the fixing device can be reduced, and the cost of parts can be reduced. In addition, the temperature rise can be detected with a higher response speed and accuracy, so that damage due to thermal deformation of the toner heating medium can be prevented. Can be prevented.

As described above, according to the present embodiment, the rotation or stopped state of the heat-resistant belt 3 is controlled by the first temperature detecting means 5a and the heating roller 1 provided near the entrance of the fixing nip N. Second temperature detecting means 5b disposed on the inner surface of the unit
And the cost of parts can be reduced, and the temperature rise can be detected with a higher response speed and higher accuracy. Damage due to deformation or the like can be prevented beforehand.

[0061]

As described above, according to the present invention, the rotation or stop state of the toner heating medium is controlled by the first temperature detecting means disposed near the entrance of the fixing nip and the inner surface of the heating section of the heating roller. Since the determination is made based on the temperature information of the second temperature detecting means disposed, an effective effect that it is possible to prevent an abnormal temperature rise of the toner heating medium heated by the electromagnetic induction of the induction heating means. can get.

When the determining means determines that the toner heating medium is in a stopped state, the induction heating means stops heating by electromagnetic induction, thereby preventing the toner heating medium from being damaged due to thermal deformation or the like. An effective effect is obtained that is possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a fixing device according to an embodiment of the present invention;

2A is a sectional view showing an exciting coil of induction heating means in the fixing device shown in FIG. 1; FIG.

FIG. 3 is an explanatory diagram showing generation of an alternating magnetic field and an eddy current by the induction heating means in the fixing device of FIG. 1;

FIG. 4 is a flowchart showing the operation of the fixing device of FIG. 1;

5 is a graph showing the relationship between the inner surface temperature of a heat-resistant belt in a normal state and the inner surface temperature of a heating portion of a heating roller when electromagnetic induction heating is performed in the fixing device of FIG. 1;

FIG. 6 shows a relationship between the inner surface temperature of the heat resistant belt and the inner surface temperature of the heating section of the heating roller when the heat resistant belt is not rotated from the initial stage of heating and subjected to electromagnetic induction heating in the fixing device of FIG. Graph

FIG. 7 shows the relationship between the inner surface temperature of the heat-resistant belt and the inner surface temperature of the heating portion of the heating roller when the heat-resistant belt is not rotated after a predetermined time from the start of heating and heated by electromagnetic induction in the fixing device of FIG. Graph showing relationship

FIG. 8 is a schematic view showing a fixing device using a conventional electromagnetic induction heating method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating roller 2 Fixing roller 3 Heat resistant belt (toner heating medium) 4 Pressure roller 5 Temperature detecting means 5a First temperature detecting means 5b Second temperature detecting means 6 Induction heating means 7 Exciting coil 9 Exciting coil core 12 Induction heating Means 15 Excitation coil core N Fixing nip T Toner image

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunori Matsuo 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H033 AA42 BA11 BA12 BA25 BA32 BE06 CA07 CA34 CA48 3K059 AB20 AB28 AC33 AD10 AD17 AD34 BD24 CD10 CD64

Claims (2)

[Claims] A heating roller made of a magnetic metal member and heated by electromagnetic induction of an induction heating means; a fixing roller arranged in parallel with the heating roller; and a stretcher between the heating roller and the fixing roller. And an endless belt-shaped toner heating medium which is heated by the heating roller and rotated by these rollers. The toner heating medium is pressed against the fixing roller via the toner heating medium and is directed in a forward direction with respect to the toner heating medium. A pressure roller that rotates to form a fixing nip; a first temperature detecting unit that is disposed near an entrance of the fixing nip to detect a temperature of the toner heating medium; and detects a temperature of the heating roller. A second temperature detecting means for detecting the temperature of the toner heating medium based on temperature information detected by the first temperature detecting means and the second temperature detecting means. Fixing apparatus characterized by having a determining means for determining whether the rotational state. 2. The fixing device according to claim 1, wherein when the determination unit determines that the toner heating medium is in a stopped state, heating of the induction heating unit by electromagnetic induction is stopped.