JPH0980951A - Induction heating fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the total inductance of a coil without lowering heating efficiency and to prevent oscillation in an audio frequency band by connecting plural coils for making a conductive body to be heated generate heat by causing an induced current to flow in the body to be heated in parallel. SOLUTION: In the fixing device where a toner image formed on a recording medium is fixed on the recording medium; plural coils are connected in parallel in order to make the body to be heated which is formed of the conductive member to generate the heat by causing the induced current to flow therein. To put it concretely, for example, plural coils 301, 302... are spirally wound round one columnar core 2 inside a conductive fixing roller 5 and connected in parallel. Wirings 50 connected to the respective coils are connected to a high frequency power source and a capacitor for resonance. Thus, necessary ampere-turn is secured, and oscillation frequency is made high and removed from the audio frequency band without lowering the heating efficiency. Then, the optimum frequency is selected and noise is prevented from being produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to a fixing device used in printers, facsimiles, and the like, and more specifically, to an induction heating fixing device that fixes a toner image on a recording medium by using dielectric heating.

[0002]

2. Description of the Related Art An electrophotographic copying machine or the like is provided with a fixing device for fixing a toner image transferred onto a sheet such as recording paper or a transfer material as a recording medium onto the sheet. This fixing device has, for example, a fixing roller that heat-melts the toner on the sheet, and a pressure roller that presses the fixing roller to sandwich the sheet. The fixing roller is formed in a cylindrical shape, and a heating element is held by a holding means on the central axis of the fixing roller. This heating element is located on the central axis of the fixing roller, the heat generated from the heating element is radiated to the inner wall of the fixing roller, and the temperature distribution on the outer wall of the fixing roller becomes uniform in the circumferential direction. The outer wall of the fixing roller has a temperature suitable for fixing (for example, 150 ° C.).
Up to 200 ° C). In this state, the fixing roller and the pressure roller rotate in mutually opposite directions while slidingly contacting each other, and sandwich the sheet to which the toner has adhered. At the sliding contact portion between the fixing roller and the pressure roller (hereinafter referred to as the nip portion), the toner on the sheet is melted by the heat of the fixing roller,
It is fixed on the sheet by the pressure applied from both rollers.
After the toner is fixed, the sheet is conveyed by a paper discharge roller and discharged onto a paper discharge tray as the fixing roller and the pressure roller rotate.

In such a fixing device, a halogen lamp is generally used as a heating element. Therefore, after the power is turned on, a comparison is made until the temperature of the fixing roller reaches a predetermined temperature suitable for fixing. It took a very long time. Meanwhile, the user cannot use the copier,
There was a problem of having to wait for a long time. On the other hand, when the heat capacity of the fixing roller is increased in order to reduce the waiting time and improve the operability for the user, the power consumption of the fixing device increases, which is a problem against energy saving.

Therefore, in order to increase the value of a product such as a copying machine, energy saving (low power consumption) of the fixing device is performed.
At the same time, it has become more important and more important to achieve both the improvement of user operability (quick print). Along with this, it has become necessary to improve not only the toner fixing temperature and the heat capacity of the fixing roller, which have been conventionally performed, but also the electric-heat conversion efficiency.

An induction heating type fixing device has been proposed as a device that satisfies the above requirements. This induction heating
It has the following advantages over other heating methods. First of all, the temperature rises faster than indirect heating such as near-infrared heating of a halogen lamp, and less heat is generated and transferred to parts other than the fixing roller. Further, there is no loss corresponding to the light leakage of the halogen lamp. Second, heat generation efficiency is higher due to the skin effect peculiar to electromagnetic induction than surface heating with a solid resistance heating element on the surface of the fixing roller, and the reliability of the fixing device is also high over a long period of time because there is no sliding contact. . Thirdly, compared to heating with a film belt and a solid resistance heating element, the heat transfer loss due to contact resistance is smaller and the temperature of the heating surface can be easily detected, so the temperature controllability is excellent. Therefore, from these points, energy saving of the fixing device (low power consumption)
It is expected that both the improvement of user operability (quick printing) and the improvement of operability will be achieved.

[0006] As a fixing device using this induction heating, for example, in Japanese Patent Laid-Open No. 59-33787, an open magnetic circuit iron core in which a coil is spirally wound is arranged inside a fixing roller made of a metal conductor. . Then, a high-frequency current is passed through the coil close to the inner surface of the fixing roller, an induced eddy current is generated in the fixing roller by the high-frequency magnetic field generated thereby, and the fixing roller itself causes Joule heat generation by the skin resistance of the fixing roller itself. Has become.

Further, Japanese Patent Laid-Open No. 58-178385 discloses that two sets of coils are used and the energization of the two sets of coils is switched according to the size of the paper, that is, one coil is used when the size of the paper is small. In the case where the paper size is large, the two coils are energized so that only the required heating area is induction-heated, thereby further saving energy.

[0008]

However, such an induction heating fixing device also has a problem. One of the problems is that the oscillation by the coil for generating the induced current and the resonance capacitor is in the audible frequency band ( About 15Hz-2
0 kHz) causes a noise problem of the fixing device itself.

The oscillation frequency f by the coil and the resonance capacitor is roughly calculated by the following equation (1) (details will be described later). f = 1 / (Ip × L / VI + 1.5π√ (LC)) (1) where Ip is the peak value of the coil current, L is the inductance of the coil, VI is the voltage applied to the coil, and C is
Is the capacitance of the resonance capacitor.

As can be seen from the equation (1), the oscillation frequency changes depending on the inductance of the coil.

Therefore, the oscillation frequency can be shifted outside the audible frequency band by lowering the inductance of the coil. However, as in the above-mentioned Japanese Patent Laid-Open No. 59-33787, an induction current is generated by one coil. in case of,
If the length of the coil is shortened in order to reduce the inductance of the coil, the ampere-turn required for induction heating cannot be obtained, and the gap with the fixing roller (heated body) becomes large, resulting in deterioration of heat generation efficiency. Therefore, the core may be thickened to reduce the gap, or the coil may be thickened. In that case, however, the core is upsized and work efficiency for winding a thick coil is reduced. Therefore, cost increase is unavoidable and it is not economically preferable.

Further, even when a plurality of coils are used as in JP-A-58-178385, the inductance of each coil becomes small, but when these are connected in series, As in the case of using one coil, the inductance becomes high, and the same problem as above occurs, and when controlling multiple coils separately, multiple control circuits are required for that, which increases cost. There is such a problem.

Therefore, it is an object of the present invention to provide an induction heating fixing device in which the total inductance of a coil is lowered and oscillation in an audible frequency band is prevented without securing a necessary ampere-turn and lowering heating efficiency. And

[0014]

The present invention for achieving the above object is a fixing device for fixing a toner image formed on a recording medium to the recording medium, which is formed of a conductive member. An induction heating fixing device comprising: a heating body; and at least two or more coils connected in parallel for generating an induced current in the heated body to generate heat.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiment of the present invention configured as described above, for example, a conductive fixing roller is used as a heated body, and at least two coils for inductively heating the fixing roller are used. A plurality of more than one coils are connected in parallel, and the plurality of coils connected in parallel are mounted inside the fixing roller.

More specifically, for example, as shown in FIG. 1, a plurality of coils 301, 302, ... Are spirally wound around one cylindrical core 2 inside a conductive fixing roller 5, and each coil is wound. In which 301, 302, ... Are connected in parallel, and FIG.
, A plurality of cores 2a, 2b, etc., in which coils 301, 302 ... Are respectively wound inside a conductive fixing roller 5, and the respective coils 301, 302 ... Are connected in parallel. As shown in FIG. 3, inside the conductive fixing roller 5, a plurality of coils 301 are attached to one prism-shaped core 2.
302 are wound in the longitudinal direction of the core 2, and each coil 30
, 302 connected in parallel, and further, as shown in FIG. 4, inside the conductive fixing roller 5, a plurality of prism-shaped cores 2a, 2b, ...
a, 301b ... And 302a, 302b ... Are wound in the longitudinal direction of the core 2, and coils 301a, 301b ... And 302a, 302b ... Are connected in series, respectively, and coils 301a, 301b. 302
a, 302b ... Are connected in parallel. In each figure, the wiring 50 connected to each coil is connected to a high frequency power source and a resonance capacitor.

Further, a circuit diagram of an embodiment of a fixing device in which the number of coils used is changed is shown in FIG. 5a, in which two coils 301 and 302 are connected in parallel, and in FIG. 5b. The coils 301a and 3
01b and coils 302a and 302b are connected in series, respectively, and are connected in parallel in two rows, FIG. 5c.
As shown in Fig. 4, four coils 301, 302, 303 and 304 are connected in parallel, and as shown in Fig. 6a, coils 301a, 301b, 301c and coils 302a, 302b, 302c are connected in series, respectively. Which are connected in parallel in two rows, as shown in FIG. 6b, coils 301a and 301b, coil 302a.
And 302b, and coils 303a and 303b are connected in series, respectively, and are connected in parallel in three rows. As shown in FIG. 6c, six coils 301, 302, 30 are provided.
Various forms are conceivable such as 3, 304, 305, and 306 connected in parallel. In each figure, reference numeral 24 is a resonance capacitor, and reference numeral 100 is a high frequency power supply.

Further, here, the fixing roller is used as the object to be heated and is directly heated by induction.
It may be provided inside a fixing roller made of heat-resistant resin, or instead of using the fixing roller, a metal plate or the like serving as a heated body may be provided via a film following a recording medium.

The change in the oscillation frequency due to such parallel connection will be described in detail below.

First, when a high frequency power source for inductively heating the fixing roller is turned on, oscillation occurs due to the coil and the resonance capacitor. Referring to the voltage-current chart shown in FIG. 7, when the power supply voltage VG (FIG. 7 (A)) is turned on, current flows through the coil and its current value ID (FIG. 7).
(B)) rises. The current value ID is the peak value I
When it reaches p, the power is turned off. Then, the energy stored in the coil is charged in the resonance capacitor and the capacitor voltage VD (Fig. 7 (C)) rises. When all the coil energy is charged in the capacitor, it is discharged from the capacitor this time. Becomes

Therefore, the oscillation cycle is such that the energy stored in the coil and the current flowing through the coil have a peak value Ip.
Time to reach the charge and discharge time T of the capacitor
This is the time when b is added.

Therefore, in order to obtain the oscillation frequency, first,
The time Ta until energy is stored in the coil and reaches the peak current Ip is obtained. Voltage V applied to the coil
The relationship between I and the inductance of the coil is represented by VI = L · di / dt. Therefore, the relation between current and time is di / dt = VI / L. Therefore, the time Ta until the current value reaches Ip is Ta = Ip · L / VI.

Next, the charge / discharge time Tb of the capacitor is obtained. This is divided into charging and discharging, and the charging time is Tb 'and the discharging time is Tb ".
b ″ is determined by the resonance period of the coil and the capacitor. The resonance period T0 is T0 = 2π√ (LC) from the formula f0 = 1 / (2π√ (LC)) for obtaining the resonance frequency f0. ″ Becomes Tb ″ = π√ (LC). Here, Tb is about 1.5 times Tb ″, so that when Tb is approximated, Tb = Tb ′ + Tb ″ ≈1.5Tb ″.

Therefore, the oscillation frequency f becomes f = 1 / (Ta + Tb) = 1 / (Ip.L / VI + 1.5.pi. (LC)) (1).

From this equation (1), the oscillation frequency when the coils are connected in parallel as shown in FIGS. 5b and 5c is obtained as an example of the oscillation frequency. For comparison, as shown in FIG. 8a, the case where a conventional ampere turn is obtained by one coil 300 is divided into four coils 300a, 300b, 300c as shown in FIG. 8b.
Then, the oscillation frequency is obtained by assuming that and 300d are connected in series.

Here, in obtaining the oscillation frequency, the voltage VI applied to the coil is 100 V and the peak current value Ip.
Is 7 A, the capacitance C of the resonance capacitor is 0.033 μF, and the inductance L of one coil is 400 μH.

Therefore, in the case where the four coils shown in FIG. 8b are connected in series, the inductance of all the coils is 400 × 4 = 1600 μH, and in the embodiment of the present invention constituted by four coils similarly. In the case of the one shown in FIG. 5b, 400 × 2 × 1/2 = 400 μ
H, and 400 × 1/4 for the one shown in FIG. 5c.
= 100 μH.

The oscillation frequency f calculated according to the equation (1) is 6 in the conventional case shown in FIG. 8b.
It can be seen that it becomes 8 kHz and oscillates in the audible band.
On the other hand, in the embodiment of the present invention shown in FIG. 5b, the frequency is 22.2 kHz, and similarly in the embodiment shown in FIG.
It becomes 1.4 kHz, and both are outside the audible frequency band. In addition, in the one to which the present invention is applied, when the coils having the same ampere-turn are used, the inductance of the coil is reduced by connecting them in parallel. It goes up and goes out of the audible range. When carrying out the present invention,
Depending on the capacity of the resonance capacitor and the required ampere-turn, it is advisable to appropriately combine the number of coils to be connected in parallel and the form of connection as described above to obtain the optimum oscillation frequency, preferably 20 kHz to 40 kHz.
It is better to set it to Hz.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an induction heating fixing device to which the present invention is applied will be described below with reference to the drawings. The members having the same function are designated by the same reference numerals as those in the above-mentioned drawings.

FIG. 9 is a schematic sectional view of an induction heating fixing device to which the present invention is applied, FIG. 10 is a schematic perspective view showing a fixing roller and a pressure roller used in this device, and FIG. FIG. 3 is a perspective view of a fixing roller used in this device.

As shown in FIG. 9, an induction heating fixing device incorporated in a printer or the like has a fixing roller 5 rotatably driven in the direction of arrow a and a fixing roller provided in pressure contact with the fixing roller 5. 5 and a pressure roller 6 that is driven to rotate with the rotation of the pressure roller 5. The fixing roller 5 is a cylindrical hollow pipe made of a conductor, and inside thereof, as shown in FIG. 11, the coils 301, 302, 30 of the coil assembly 31 for generating an induced current in the fixing roller 5.
Four of 3 and 304 are connected in parallel. The coil assembly 31 is housed in a holder unit 30 which is fixed to the fixing roller 5 with a slight gap so that the fixing roller 5 can rotate.

As shown in FIG. 12, the coil assembly 31 has a core 2 and a square-shaped through hole 1a.
A bobbin 1 is provided so as to surround the core by inserting into the through hole 1a, and a copper wire is wound around the bobbin 1 to form a coil 3 (this coil 3 is any one of the coils 301 to 304, Or, these are collectively referred to as
The same shall apply hereinafter).

This coil 3 is wound around the bobbin 1 in the direction along the rotation axis of the fixing roller 1 by using a single or litz copper wire having a fusion layer and an insulating layer on the surface and having a diameter of 0.8 mm. Has been done.

The core 2 is made of, for example, a ferrite core or a laminated core, and the bobbin 1 is made of, for example, ceramic or heat-resistant insulating engineering plastic, and plays a role of pressing the coil 3 and adjusting its shape.

As shown in FIG. 13, the holder unit 30 accommodating the coil assembly 31 constitutes a holder by a holder stay 4a and a holder cover 4b mounted on the holder stay 4a. Made of plastic. Recesses 41 for holding the coil assembly 31 are formed on the inner surfaces of the holder stay 4a and the holder cover 4b, and fitting portions 42 for fixing the holder unit 30 to the fixing unit frame of the apparatus body are formed at both ends.
Is provided. In this holder unit 30, the bobbin 1 wound with coils 301, 302, 303 and 304 connected in parallel to the recess 41 provided in the holder stay 4a is inserted, and the core 2 is inserted into the through hole 1a of the bobbin 1,
An insulating film 45 is arranged on the outer peripheral surfaces of the coils 301, 302, 303 and 304, and the holder cover 4b is attached to the holder stay 4a for assembly. The holder unit 30 is made of a heat-resistant insulating material such as PPS or liquid crystal polymer.

The fixing roller 5 is formed of a conductive member such as a carbon steel pipe, a stainless alloy pipe, or an aluminum alloy pipe. The outer peripheral surface of the fixing roller 5 is coated with fluororesin, and the heat-resistant release layer is formed on the surface. . The fixing roller 5 is more preferably formed of a conductive magnetic member. The pressure roller 6 has a silicon rubber layer 62, which is a surface releasable heat resistant rubber layer, formed around a shaft core 61.

The fixing roller 5 has sliding bearings 51 formed at both ends thereof and is rotatably attached to the fixing unit frame. Further, the fixing roller 5 has a drive gear (not shown) fixed to one end thereof, and is rotationally driven by a drive source (not shown) such as a motor connected to the drive gear. The holder 4 is housed inside the fixing roller 5 with a minimum gap of a predetermined dimension maintained between the holder 4 and the inner peripheral surface of the fixing roller 5, and is fixed to the fixing unit frame so as not to rotate. The sliding bearing 51 and the separating claw 7 are
Formed from heat resistant sliding engineering plastics.

Further, above the fixing roller 5, a temperature sensor for detecting the temperature of the fixing roller 5, for example, a thermistor 8 is provided. The thermistor 8 is in pressure contact with the surface of the fixing roller 5 so as to face the side surface of the coil 3 across the fixing roller 5. The thermistor 8 is composed of, for example, a thermistor. While the temperature of the fixing roller 5 is detected by the thermistor 8, the energization of the coil 3 is controlled so that the temperature of the fixing roller 5 becomes the optimum temperature. In addition to the thermistor 8, as a safety mechanism when the temperature rises abnormally, the coil 3 is used when an abnormally high temperature is detected.
A thermostat 9 is provided for cutting off the power supply to the.

Next, the control system of this fixing device will be described. FIG. 14 is a block diagram of a control system of this fixing device.

The high frequency current is generated by rectifying the alternating current of the commercial power source 10 by the rectifying circuit 11 and converting it into a high frequency by the self-excited inverter circuit 12. The current to the induction heating coil 3 is applied to the surface of the fixing roller 5 by the thermostat 9 which is pressed against the surface of the fixing roller 5.
When the surface temperature of the fixing roller 5 reaches a preset abnormal temperature, the thermostat 9 disconnects the current path.

The control circuit 13 is composed of a microprocessor, a memory, etc., and monitors the temperature of the fixing roller 5 based on the potential of the thermistor 8 while controlling the inverter circuit 1
An ON / OFF signal is output to the drive circuit 20 in 2 to control the temperature.

The inverter circuit 12 frequency-converts the direct current from the rectifier circuit 11 into a high frequency current and supplies it to the coil 3.

In the inverter circuit 12, when the control signal (heating signal) issued from the control circuit 13 is turned on, the drive circuit 20 first turns on the switching element 21 formed of, for example, a transistor, an FET, an IGBT, or the like. An electric current flows through the induction heating coil 3.
On the other hand, when the current detection circuit 22 detects that the current value Ip has been reached, it sends a signal to the drive circuit 20 to turn off the switching element 21. The waveform of the drain current ID flowing through the coil 3 detected by the current detection circuit 22 is as shown in FIG. 7 (B). Switching element 21
When is turned off, a resonance current flows between the induction heating coil 3 and the resonance capacitor 24. When the voltage detection circuit 23 detects that the drain voltage VD of the switching element 21 on the induction heating coil 3 side has dropped to around 0 V due to resonance, it sends a signal to the drive circuit 20 to turn the switching element 21 on again. . Hereinafter, by repeating this switching cycle, a high frequency current is passed to the induction heating coil 3. The waveform of the voltage VD detected by the voltage detection circuit 23 is shown in FIG. 7C, and the ON / OFF signal VG of the switching element 21 (for example, the gate ON / OFF signal in the case of FET) is shown in FIG. 7A. As shown in.

As a result, a high frequency (several kHz to several
When a current of several tens of kHz) is applied, the fixing roller 5 generates heat and the toner image is fixed on the sheet (recording medium) 14 according to the principle described later.

The induction heating fixing device configured as described above operates as follows. First, the sheet 14 on which the unfixed toner image is transferred is conveyed from the left side in FIG.
It is fed toward the nip portion between the fixing roller 5 and the pressure roller 6. The sheet 14 is conveyed through the nip portion while the heat of the fixing roller 5 heated by the principle described later and the pressure acting from both rollers 5 and 6 are applied. As a result, the unfixed toner is fixed, and a fixed toner image is formed on the sheet 14. The sheet 14 that has passed through the nip portion is naturally separated from the fixing roller 5, or as shown in FIG. 1, is fixed by a separation claw 7 or a separation guide that is provided so that the leading end of the sheet 14 is in sliding contact with the surface of the fixing roller 5. It is forcibly separated from the roller 5 and conveyed rightward in FIG. The sheet 14 is conveyed by a paper discharge roller (not shown) and discharged onto the paper discharge tray.

FIG. 15 is an explanatory view for explaining the heating principle of the fixing roller 5 in this induction heating fixing device. When a high-frequency (several kHz to several tens of kHz) current is applied to the coil 3, a magnetic flux 31a orthogonal to the longitudinal axis direction of the fixing roller 5 is drawn from the core 2 in accordance with "Ampere's right-hand screw law", as shown in the figure. Occurs. This magnetic flux 31a is also a high frequency magnetic flux.

Magnetic flux 31 reaching the fixing roller 5 made of a conductor
b is a magnetic flux 31 which bends along the fixing roller 5 and passes through the circumferential surface of the fixing roller 5 at a ratio depending on the relative magnetic permeability of the conductor.
c. Magnetic flux 31c concentrated on the peripheral surface of the fixing roller 5
Has the maximum density in the portion facing the coil 3.

In this structure, P of the fixing roller 5
The magnetic flux density in the circumferential surface becomes maximum at point R, and conversely, Q and S
It becomes the minimum at the point. Therefore, since the induced current density has the same tendency, the heat generation of the fixing roller 5 is not uniform in the circumferential surface, and the portions 32a and 32b surrounded by the two-dot chain line generate heat locally. This locally heated portion 32a, 3
2b corresponds to the upper region and the lower region of the fixing roller 5, as shown in FIG. Therefore, the nip portion and one heat generating portion (area) overlap at least in part. In addition, the thermistor 8
Are placed in contact with each other. The thermistor 8 may be attached to either the upper portion or the lower portion of the fixing roller 5, but in the illustrated embodiment, it is attached to the outside of the upper portion. If the thermistor 8 is small, it may be mounted inside the upper part or the lower part of the fixing roller 5.

Due to the action of the magnetic flux 31c thus concentrated, a vortex-shaped induced current is generated in the fixing roller 5 according to the "Lenz's law" so as to generate a magnetic flux in the opposite direction to the magnetic flux 31c which obstructs the magnetic flux 31c. It occurs inside the wall. This induced current is converted into Joule heat by the skin resistance of the fixing roller 5, so that the fixing roller 5 generates heat and
As described above, the toner image is fixed on the sheet 14. At this time, the oscillation frequency generated by the coil 3 and the resonance capacitor 24 is outside the audible frequency band by applying the present invention.

[0050]

As described above, according to the present invention, by connecting a plurality of coils in parallel, the oscillation frequency is increased to remove it from the audible frequency band, and the optimum frequency is selected to prevent noise. You can Therefore, the noise can be easily prevented without taking measures such as an increase in the size of the core and an increase in the thickness of the coil, which would increase the cost.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining an embodiment of an induction heating fixing device of the present invention.

FIG. 2 is a perspective view for explaining an embodiment of the induction heating fixing device of the present invention.

FIG. 3 is a perspective view for explaining an embodiment of the induction heating fixing device of the present invention.

FIG. 4 is a perspective view for explaining an embodiment of the induction heating fixing device of the present invention.

FIG. 5 is a circuit diagram for explaining an embodiment of the induction heating fixing device of the present invention.

FIG. 6 is a circuit diagram for explaining an embodiment of the induction heating fixing device of the present invention.

FIG. 7 is a diagram showing a current-voltage waveform when the fixing roller is heated.

FIG. 8 is a circuit diagram showing connection of a conventional coil.

FIG. 9 is a sectional view showing an induction heating fixing device according to an embodiment of the present invention.

FIG. 10 is a perspective view showing a fixing roller and a pressure roller shown in FIG.

FIG. 11 is a perspective view for explaining the fixing roller shown in FIG.

12 is a perspective view for explaining the coil assembly shown in FIG.

FIG. 13 is an exploded perspective view for explaining the holder unit shown in FIG.

FIG. 14 is a block diagram illustrating a control system of an induction heating fixing device according to an embodiment of the present invention.

FIG. 15 is a diagram for explaining the heating principle of the fixing roller.

[Explanation of symbols]

1 ... Bobbin, 2, 2a, 2b ... Core, 3, 301-306, 301a, 301b, 301c,
302a, 302b, 302c, 303a, 303b ...
Coil 4 ... Holder, 5 ... Fixing roller, 6 ... Pressure roller.

Claims (1)

[Claims] 1. A fixing device for fixing a toner image formed on a recording medium to the recording medium, comprising: a heated body formed of a conductive member; and an induced current generated in the heated body. An induction heating fixing device comprising: at least two coils connected in parallel to generate heat.