JPH0962132A - Induction heating and fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating and fixing device where heating efficiency is high though it has a simple structure having high mass-productivity, and also heating quantity distribution can be arbitrarily set. SOLUTION: A core 23 is arranged in the orthogonal direction to a fixing roller 10, and a coil 22 where the coil is wound on the core 23 so as to generate a magnetic flux in the orthogonal direction to the fixing roller 10 is arranged. Then, an air gap L1 at the end part of the fixing roller 10 in the longitudinal direction is made smaller than the air gap L2 at the center part.

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 electrophotographic copying machines, printers, facsimiles and the like, and more particularly to a fixing device for fixing a toner image to 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. The heating element is composed of, for example, a halogen lamp or the like, and generates heat when a predetermined voltage is applied. Since this heating element is located on the central axis of the fixing roller, the heat generated from the heating element is radiated uniformly to the inner wall of the fixing roller, and the temperature distribution of the outer wall of the fixing roller becomes uniform in the circumferential direction. The outer wall of the fixing roller is heated until its temperature reaches a temperature suitable for fixing (for example, 150 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 (hereinafter referred to as a nip portion) between the fixing roller and the pressure roller, the toner on the sheet is melted by the heat of the fixing roller and 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 the above fixing device provided with a heating element composed of a halogen lamp or the like, after the power is turned on,
It took a relatively long time for the temperature of the fixing roller to reach a predetermined temperature suitable for fixing. During that time, the user cannot use the copying machine and is forced to wait for a long time. On the other hand, when the heat capacity of the fixing roller is increased in order to shorten the waiting time and improve the operability for the user, the power consumption of the fixing device increases, which causes a problem of 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 satisfying such a request (Japanese Patent Laid-Open No. 59-33).
788). This induction heating fixing device is shown in FIG.
As shown in (A) and (B), a spirally wound coil 2 is concentrically arranged inside a fixing roller 1 made of a metal conductor. Then, a high-frequency current is passed through the coil 2 close to the inner surface of the fixing roller 1, and an induced eddy current is generated in the fixing roller 1 by the high-frequency magnetic field generated thereby, and the fixing roller 1 itself is jouled by the skin resistance of the fixing roller itself. It is designed to generate heat.

This induction heating method 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. .

In recent years, development of low fixing temperature toner has progressed, and due to the spread and cost reduction of inverter circuit switching elements in high frequency power supplies for home appliances, it has become possible to realize an induction heating fixing device having the above characteristics. is there.

[0008]

In order to achieve uniform fixability along the rotational axis direction (longitudinal direction) of the fixing roller in the induction heating fixing device, the temperature distribution along the rotational axis direction of the fixing roller should be substantially equal. It is necessary to make it uniform, but since both ends of the fixing roller are affected by heat dissipation,
The temperature will be lower than in the center. For this reason, it is general that the heat generation amount at both ends of the fixing roller is made higher than that at the central part.

Even in the induction heating fixing device disclosed in the above-mentioned publication (Japanese Patent Laid-Open No. 59-33788), the temperature drop due to heat radiation at both ends of the roller is taken into consideration, and FIG.
As shown in (A) to (C), the coil 2 at both ends of the roller
Is set to be "closer" than the central portion, the heat generation amount at both ends of the roller is made larger than that in the central portion, and the temperature distribution along the rotation axis direction of the fixing roller 1 is made substantially uniform.

However, in such a configuration, the coil 2
Because the winding density of changes along the longitudinal direction,
There is a problem that the mass productivity of the coil 2 is not good and it is difficult to reduce the price of the coil 2.

Further, as shown in FIGS. 18A and 18B, the winding direction of the coil 2 is the same as the circumferential direction of the fixing roller 1, and the generated magnetic flux and the fixing roller 1 are parallel to each other. There is a problem that the leakage of magnetic flux from the part increases and the heat generation efficiency is poor.

The present invention has been made in order to solve the problems associated with the prior art described above, and its object is to adjust the distribution of the amount of heat generation without changing the winding density of the coil, or a roller or a metal plate. It is an object of the present invention to provide an induction heating fixing device which can make the temperature distribution along the longitudinal direction substantially uniform, has a good mass productivity of coils, and has a small magnetic flux leakage and a high heat generation efficiency.

[0013]

In order to achieve the above object, an induction heating fixing device of the present invention according to claim 1 comprises a metal hollow roller or a metal heating plate which is a metal body to be heated, and Induction having a core arranged in a direction orthogonal to a heated metal body, and a coil having a winding wound around the core so that a magnetic flux is generated in a direction orthogonal to the heated metal body. In the heat fixing device, the distribution of the calorific value is changed along the longitudinal direction of the heated metal body by changing the distance between the heated metal body and the core.

In the induction heating fixing device of the present invention, since the magnetic flux is generated in the direction orthogonal to the heated metal body, the leakage of the magnetic flux is small even at the longitudinal end portion of the heated metal body, and the heat generation efficiency is high. Be efficient.

When the distance between the core and the metal body to be heated is reduced, the magnetic coupling is strengthened and the amount of heat generated is increased.
If the distance is increased, the magnetic coupling becomes weaker and the amount of heat generation becomes smaller. Therefore, even if the winding density of the coil is not changed, by changing the distance between the metal body to be heated and the core, the distribution of the calorific value can be changed along the longitudinal direction of the metal body to be heated as desired. The coil can be adjusted by using the above method, and the mass productivity of the coil is excellent.

Here, since the end portion in the longitudinal direction of the metal body to be heated is easily affected by heat radiation and the temperature becomes lower than that in the central portion, the metal body to be heated as described in claim 2. The distance between the metal body to be heated and the core at the longitudinal end of is preferably smaller than the distance between the metal body to be heated and the core at the central portion.

With this configuration, the temperature distribution along the longitudinal direction of the metal body to be heated can be made substantially uniform in consideration of the effect of heat radiation, and thus the fixing property is uniform along the longitudinal direction of the metal body to be heated. Can be realized.

According to a third aspect of the present invention, there is provided an induction heating fixing device in which a metal hollow roller or a metal heating plate which is a metal body to be heated and a direction which is orthogonal to the metal body to be heated are arranged. In an induction heating fixing device having a plurality of cores and a coil in which a winding is wound around each core so that a magnetic flux is generated in a direction orthogonal to the metal body to be heated, By disposing different cores along the longitudinal direction of the heated metal body, the distribution of the amount of heat generation is changed along the longitudinal direction of the heated metal body.

In the induction heating fixing device of the present invention, since the magnetic flux is generated in the direction orthogonal to the heated metal body, the leakage of the magnetic flux is small even at the longitudinal end portion of the heated metal body, and the heat generation efficiency is high. Be efficient.

Further, the higher the magnetic permeability of the core is, the larger the generated magnetic flux is. Therefore, if the magnetic permeability of the core is increased, the magnetic flux intersecting the metal body to be heated is increased and the amount of heat generation is increased. If the magnetic susceptibility is reduced, the magnetic flux that intersects the metal body to be heated is reduced and the amount of heat generation is reduced. Therefore, even if the winding density of the coil is not changed, by changing the magnetic permeability of the individual cores arranged along the longitudinal direction of the metal body to be heated, the distribution of the heat generation amount can be changed as desired. It can be adjusted along the longitudinal direction of the body, and the mass productivity of the coil is also excellent.

Here, since the longitudinal end portion of the metal body to be heated is easily affected by heat radiation and the temperature becomes lower than that of the central portion, the metal body to be heated as described in claim 4. It is preferable that the magnetic permeability of the core at the end portion in the longitudinal direction is higher than the magnetic permeability of the core at the central portion.

With this arrangement, the temperature distribution along the longitudinal direction of the metal body to be heated can be made substantially uniform in consideration of the effect of heat radiation, and thus the fixing property is uniform along the longitudinal direction of the metal body to be heated. Can be realized.

[0023]

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

<First Embodiment> FIG. 1 is a sectional view showing an induction heating fixing device according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a fixing roller and a pressure roller shown in FIG. is there.

As shown in FIG. 1, an induction heating fixing device incorporated in a printer or the like is provided with a heat roller, that is, a fixing roller 10 rotatably driven in a direction of an arrow a, and a pressure roller that is in contact with the fixing roller 10. And a pressure roller 11 that is rotated by rotation of the fixing roller 10.
The fixing roller 10 is a hollow conductor pipe, and a plurality of coil assemblies 12 for generating an induced current (eddy current) in the fixing roller 10 are provided inside the fixing roller 10. Each coil assembly 12 has a holder 24
The holder unit 13 is held by the. It is the fixing roller 10 itself that generates heat due to the induced current,
The fixing roller 10 corresponds to the metal body to be heated.

The fixing roller 10 has sliding bearings formed at both ends thereof, and is rotatably attached to a fixing unit frame (not shown). Further, the fixing roller 10
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. Further, the holder unit 13 is housed inside the fixing roller 10 with a gap of a predetermined dimension maintained between the holder unit 13 and the inner peripheral surface of the fixing roller 10. The holder unit 13 is fixed to the fixing unit frame and is non-rotating.

The toner carrier, that is, the sheet 14 on which the unfixed toner image is transferred is conveyed from the left as shown by an arrow b in FIG. 1, and is fixed by the fixing roller 10 and the pressure roller 11.
It is fed toward the nip part between and. Sheet 14
Is conveyed through the nip portion while the heat of the fixing roller 10 heated by the principle described later and the pressure acting from both rollers 10 and 11 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 10 depending on the curvature of the fixing roller 10, or as shown in FIG. 1, the leading end portion is provided so as to be in sliding contact with the surface of the fixing roller 10. It is forcibly separated from the fixing roller 10 by the claw 15 or the separation guide and is conveyed rightward in FIG. This sheet 14
The sheet is conveyed by a sheet discharge roller (not shown) and discharged onto the sheet discharge tray.

A temperature sensor 16 for detecting the temperature of the fixing roller 10 is provided above the fixing roller 10. The temperature sensor 16 is in pressure contact with the surface of the fixing roller 10 so as to face the side surface of the coil 22 across the fixing roller 10. The temperature sensor 16 is composed of, for example, a thermistor. While the temperature of the fixing roller 10 is detected by the thermistor 16, the energization of the coil 22 is controlled so that the temperature of the fixing roller 10 becomes the optimum temperature.

A thermostat 17 is further provided above the fixing roller 10 as a safety mechanism when the temperature rises abnormally. This thermostat 17 is used for the fixing roller 1.
It is pressed against the surface of No. 0, and when the temperature reaches a preset temperature, the contact is opened and the coil 22 is de-energized. This prevents the fixing roller 10 from reaching a temperature higher than a predetermined temperature.

The fixing roller 10 is made of a conductive material such as iron, stainless alloy tube, nickel, carbon steel tube or aluminum alloy tube. The outer peripheral surface of the fixing roller 10 is coated with fluororesin, and a heat-resistant release layer is formed on the surface. Has been formed. The fixing roller 10 is more preferably formed of a conductive magnetic member. The pressure roller 11 includes a silicon rubber layer 1 which is a surface-releasing heat-resistant rubber layer around the shaft core 18.
9 is formed. In addition, sliding bearings and separation claws 15
Is made of heat resistant sliding engineering plastic and the like.

As shown in FIG. 3, the coil assembly 12 has a square-shaped bobbin 20 having a through hole 20a formed in the center thereof, and a copper wire 21 is unidirectionally arranged around the bobbin 20 in one direction. The coil 22 is formed by winding a plurality of times. Bobbin 2
A core 23 is inserted into the 0 through hole 20 a so as to be orthogonal to the copper wire 21 of the coil 22. The bobbin 20 may be formed of, for example, ceramic or heat-resistant insulating engineering plastic, and the coil 22 is preferably a single or litz copper wire having a fusion layer and an insulating layer on the surface. The core 23 is, for example, a ferrite core or a laminated core.

FIG. 4 is a perspective view showing the coil 22 and the core 23 in the fixing roller 10. Coil assembly 12
Means that the copper wire 21 wound around the bobbin 20 is along a plane parallel to the rotation axis of the fixing roller 10 so that magnetic flux is generated in a direction orthogonal to the rotation axis direction which is the longitudinal direction of the fixing roller 10. That is, that is, the core 23 is arranged in a direction orthogonal to the rotation axis.

Further, in the present embodiment, as shown in FIGS. 1 and 5, a plurality of (four in the illustrated example) coil assemblies 12 are arranged such that the cores 23 are parallel to the sheet 14 conveyance direction and the coils 22 are arranged in parallel. Are arranged side by side in the axial direction of the fixing roller 10 by using a holder 24 so as to face the pressure roller 11. This holder 24 is made of heat-resistant insulating engineering plastic, and has a shape in which a plurality of holes that penetrate vertically and horizontally are formed around a cylinder as shown in FIG. 5, and both ends are fixed to a fixing unit frame. A protrusion 25 for doing so is provided. coil·
In the assembly 12, for example, the bobbin 20 is inserted into the left and right holes provided in the holder 24, and then the core 23 is inserted into the upper and lower holes.
Is inserted into the holder 24 by inserting. The plurality of coils 22 are connected in series in a holder 24, and lead wires 26 for passing a current to these coils 22 are drawn out at both ends of the holder 24. The holder unit 13 has an outer diameter slightly smaller than the inner diameter of the fixing roller 10 so that a gap is formed between the holder unit 13 and the inner wall of the fixing roller 10.

FIG. 6 is an explanatory view for explaining the heating principle of the fixing roller 10 in the induction heating fixing device to which the present invention is applied. High frequency (several kHz to several tens of kHz) in the coil 22
When an electric current of 1 is applied, a magnetic flux perpendicular to the longitudinal axis direction of the fixing roller 10 is generated from the core 23, as shown in the figure, in accordance with "Ampere's right-hand screw law". This magnetic flux is also a high frequency magnetic flux.

The magnetic flux of the conductor, which has reached the fixing roller 10, bends along the fixing roller 10 and becomes a magnetic flux passing through the circumferential surface of the fixing roller 10 at a ratio depending on the relative permeability of the conductor. The magnetic flux concentrated on the peripheral surface of the fixing roller 10 has the maximum density in the portion facing the coil 22.

Due to the action of the concentrated magnetic flux, a vortex-shaped induced current that causes a magnetic flux in the opposite direction to the magnetic flux that obstructs the magnetic flux is generated in the wall surface of the fixing roller 10 according to the "Lenz's law". This induced current is converted into Joule heat by the skin resistance of the fixing roller 10, so that the fixing roller 10 generates heat.

In this construction, the magnetic flux density in the circumferential surface becomes maximum at points P and R of the fixing roller 10, and conversely becomes minimum at points Q and S. Therefore, since the induced current density has the same tendency, the heat generation of the fixing roller 10 is not uniform in the circumferential surface, and the portion surrounded by the two-dot chain line locally generates heat. The portions that locally generate heat correspond to the upper region and the lower region of the fixing roller 10 in FIG.
Therefore, the nip portion and one of the heat generating points (area) are
At least some overlap. Further, the thermistor 16 is in contact with the other heat generating portion (region), and the thermostat 17 is also arranged so as to be in contact with or close to it.
The fixing point of the thermistor 16 is the fixing roller 1.
It may be either the upper part or the lower part of 0, but in the illustrated embodiment, it is attached to the outside of the upper part. If the thermistor 16 is small, it may be mounted inside the upper part or the lower part of the fixing roller 10.

In the present embodiment, FIG. 7 (A)
As shown in (B), the core 23 of each coil assembly 12 is arranged in a direction orthogonal to the fixing roller 10,
Since the coil 22 is arranged so as to be wound around an axis orthogonal to the rotation axis of the fixing roller 10, the direction of the magnetic flux generated is orthogonal to the fixing roller 10 and the fixing roller 10 and the core. 23 and 23 form a closed magnetic circuit. Therefore, there is no or little leakage of magnetic flux at both ends of the fixing roller 10, and the heat generation efficiency is high.

FIG. 8 is a block diagram of a circuit for controlling the temperature of the fixing roller 10 by supplying a high frequency current to the induction heating coil 22.

In the induction heating fixing device, since it is necessary to pass a high frequency current in order to increase the heating efficiency, a means for temporarily rectifying and smoothing the alternating current of the commercial power source and inverting it to a high frequency is adopted.

That is, the high frequency current rectifies the alternating current of the commercial power source 35 by the rectifier circuit 36, and the inverter circuit 3
It is converted to a high frequency at 7 and generated. A thermostat 17 is provided between the commercial power source 35 and the circuit for safety protection during runaway.
Is included. The current to the induction heating coil 22 is supplied through the thermostat 17 pressed against the surface of the fixing roller 10, and when the surface temperature of the fixing roller 10 reaches a preset abnormal temperature, the thermostat 17 causes the current path to flow. It is supposed to be disconnected. Control circuit 38
Is composed of a microprocessor, a memory, etc., and controls the temperature while monitoring the temperature of the fixing roller 10 based on the potential of the thermistor 16. The control circuit 38 outputs an ON / OFF signal to the drive circuit 40 in the inverter circuit 37 to control the temperature. The inverter circuit 37 frequency-converts the direct current from the rectifier circuit 36 into a high frequency current and supplies the high frequency current to the coil 22.

In the inverter circuit 37, when the control signal issued from the control circuit 38 is turned on, the drive circuit 40 first turns on the switching element 41 to apply a voltage to the LC resonance circuit of the induction heating coil 22 and the resonance capacitor 44. . As a result, a current flows through the induction heating coil 22. The switch-on time is determined by the timer circuit 47, and the timer circuit 47 controls the switching element 41 for a certain time determined by the CR charge / discharge characteristics of the reference voltage 46.
Turn on to obtain a stable heating output. When the time is up, a signal is sent to the drive circuit 40 to turn off the switching element 41. When the switching element 41 is turned off, a resonance current flows between the induction heating coil 22 and the resonance capacitor 44. Then, the voltage detection circuit 43
Induction heating coil 22 of switching element 41 due to resonance
When it is detected that the drain voltage on the side has dropped to around 0 V, a signal is sent to the drive circuit 40 to turn on the switching element 41 again. That is, the switch-off time is determined by the voltage detection circuit 43. Hereinafter, by repeating this switching cycle, a high frequency current is passed to the induction heating coil 22.

The circuit DC power supply 45 is a simple stabilizing power supply for supplying a DC power supply to the timer circuit 47, the drive circuit 40, the voltage detection circuit 43, and the reference voltage 46.

As described above, since both ends of the fixing roller 10 are affected by the heat radiation and the temperature becomes lower than that of the central portion, the heat generation amount of both ends of the fixing roller 10 must be higher than that of the central portion. If this is the case, the temperature distribution in the longitudinal direction of the fixing roller 10 will not be substantially uniform, and it will be difficult to achieve uniform fixability along the longitudinal direction.

Therefore, in the present embodiment, FIG.
As shown in (B), the distribution of the heat generation amount is changed along the longitudinal direction of the fixing roller 10 by changing the distance between the fixing roller 10 and the core 23. Fixing roller 10 and core 2 at the end
The distance to 3 is smaller than the distance in the central portion. That is, the core 2 in the outer two coil assemblies 12 of the four coil assemblies 12
3 and the inner surface of the fixing roller 10 with an air gap L1
It is smaller than the air gap L2 in the inner two coil assemblies 12.

If the distance between the fixing roller 10 and the core 23 is made small, the magnetic coupling becomes strong and the amount of heat generation becomes large. On the other hand, if the distance is made large, the magnetic coupling becomes weak and the amount of heat generation becomes small. Therefore, even if the winding density of the coil 22 is not changed, only by changing the distance between the fixing roller 10 and the core 23, the distribution of the heat generation amount can be changed along the longitudinal direction of the fixing roller 10 as desired. Can be adjusted. Further, since the coil 22 can be manufactured with a uniform winding density, the mass productivity of the coil 22 is excellent and the coil 2
The price of 2 can be reduced.

Here, the outer two coil assemblies 1
Since the air gap L1 in No. 2 is smaller than the air gap L2 in the two inner coil assemblies 12, the distribution of the heat generation amount along the longitudinal direction of the fixing roller 10 is as shown in FIG. 9 (C). . With such a calorific value distribution, although the end portion in the longitudinal direction of the fixing roller 10 is easily affected by heat radiation, the temperature distribution along the longitudinal direction of the fixing roller 10 can be made substantially uniform. It is possible to realize uniform fixing properties along the direction.

<< Second Embodiment >> FIGS. 10A and 10B
FIG. 6C is a lateral perspective view of the fixing roller according to the second embodiment, a cross-sectional view taken along the line BB in FIG. 7A, and a heat generation distribution diagram, respectively.

The second embodiment is similar to the above-described first embodiment in that the fixing roller 10 and the plurality of coil assemblies 12 are used, and the heat generation amount is continuously changed. This is different from the first embodiment in which the calorific value is changed stepwise.

As shown in FIG. 10 (A), the upper and lower end surfaces of each core 23 in the drawing are inclined surfaces, and the air gap is gradually reduced from the central portion of the fixing roller 10 toward the end portion. By doing so, the distribution of the heat generation amount along the longitudinal direction of the fixing roller 10 becomes as shown in FIG. 6C, and the heat generation amount along the longitudinal direction of the fixing roller 10 continuously changes.

Also in the second embodiment, since the magnetic flux is generated in the direction orthogonal to the fixing roller 10, the leakage of the magnetic flux at both ends of the fixing roller 10 is small and the heat generation efficiency is high. Further, the temperature distribution along the longitudinal direction of the fixing roller 10 can be made substantially uniform, and therefore, it becomes possible to realize the uniform fixability along the longitudinal direction of the fixing roller 10.

<< Third Embodiment >> FIGS. 11A and 11B.
13C is a lateral perspective view of the fixing roller according to the third embodiment, a cross-sectional view taken along the line BB of FIG. 13A, and a heat generation distribution diagram, respectively.

The third embodiment is similar to the second embodiment in that the fixing roller 10 is used and the amount of heat generated is continuously changed, and one comparatively long coil assembly 12 is used. In terms of use, 4 relatively short coils
This is different from the second embodiment using the assembly 12.

As shown in FIG. 11 (A), the upper and lower end surfaces of one relatively long core 23 in the drawing are inclined surfaces, and the air gap is gradually increased from the central portion of the fixing roller 10 toward the end portion. It is made small. By doing so, the distribution of the heat generation amount along the longitudinal direction of the fixing roller 10 is shown in FIG.
It is as shown in.

Also in the third embodiment, the heat generation efficiency is high, and it becomes possible to realize a uniform fixing property along the longitudinal direction of the fixing roller 10.

<Embodiment 4> The induction heating fixing device includes:
In some cases, instead of the fixing roller 10, a fixing belt made of a conductive material such as metal that is transferred while contacting the recording paper is used. The fixing belt itself is adapted to generate Joule heat by an induction heating coil arranged so as to face the fixing belt, and the fixing belt corresponds to a metal heating plate.

In the induction heating fixing device using the fixing belt 30, as shown in FIGS. 12A and 12B, the core 33 of each coil assembly 34 is arranged in a direction orthogonal to the fixing belt 30, The coil 32 is arranged so as to be wound around an axis orthogonal to the fixing belt 30. Therefore, as in the first to third embodiments, the direction of the generated magnetic flux is orthogonal to the fixing belt 30, and the fixing belt 30 and the core 33 form a closed magnetic path. Therefore, there is no or little leakage of magnetic flux at both ends of the fixing belt 30 in the longitudinal direction (width direction), and the heat generation efficiency is high.

13A, 13B and 13C respectively show
A lateral perspective view showing the main part of the fourth embodiment, FIG.
3 is a cross-sectional view taken along the line BB of FIG.

The fourth embodiment is different from the first embodiment except that the fixing belt 30 is used instead of the fixing roller 10.
Is the same as

As shown in FIG. 13A, the air gap L1 in the two outer coil assemblies 34 is smaller than the air gap L2 in the two inner coil assemblies 34. By doing so, the distribution of the heat generation amount along the width direction of the fixing belt 30 becomes as shown in FIG.

Also in the fourth embodiment, since the magnetic flux is generated in the direction orthogonal to the fixing belt 30, the leakage of the magnetic flux at the widthwise both ends of the fixing belt 30 is small, and the heat generation efficiency is high. Further, the fixing belt 30
The temperature distribution along the width direction of the fixing belt 30 can be made substantially uniform, so that it is possible to realize uniform fixing property along the width direction of the fixing belt 30.

<< Fifth Embodiment >> FIGS. 14A and 14B
(C) is a horizontal perspective view showing a main part in the fifth embodiment, a cross-sectional view taken along the line BB of the same figure (A), and a heat generation distribution diagram, respectively.

The fifth embodiment is different from the second embodiment except that the fixing belt 30 is used instead of the fixing roller 10.
Is the same as

As shown in FIG. 14A, the lower end surface of each core 23 in the drawing is an inclined surface, and the air gap is gradually reduced from the central portion of the fixing belt 30 toward the width direction. By doing so, the distribution of the heat generation amount along the width direction of the fixing belt 30 becomes as shown in FIG.
The heat generation amount along the width direction of the fixing belt 30 continuously changes.

Also in the fifth embodiment, the heat generation efficiency is high, and it is possible to realize the uniform fixing property along the width direction of the fixing belt 30.

<< Sixth Embodiment >> FIGS. 15A and 15B
(C) is a lateral perspective view showing a main part in the sixth embodiment, a cross-sectional view taken along the line BB of the same figure (A), and a heat generation distribution diagram, respectively.

The sixth embodiment is different from the third embodiment except that the fixing belt 30 is used instead of the fixing roller 10.
Is the same as

As shown in FIG. 15A, the lower end surface of one relatively long core 33 in the figure is an inclined surface, and the air gap is gradually increased from the central portion of the fixing belt 30 toward the width direction. It is made small. By doing so, the distribution of the heat generation amount along the width direction of the fixing belt 30 becomes as shown in FIG.

Also in the sixth embodiment, the heat generation efficiency is high, and it is possible to realize the uniform fixing property along the width direction of the fixing belt 30.

<< Embodiment 7 >> FIGS. 16A and 16B.
(C) is a lateral perspective view showing a main part in the seventh embodiment, a cross-sectional view taken along the line BB of the same figure (A), and a heat generation distribution diagram, respectively.

This Embodiment 7 uses a coil assembly 34 having the same structure, but FIG. 16 (A)
As shown in, the air gap gradually decreases from the central portion of the fixing belt 30 toward the width direction,
Each coil assembly 34 is arranged to be inclined with respect to the fixing belt 30. By doing so, the distribution of the heat generation amount along the width direction of the fixing belt 30 becomes as shown in FIG. 7C, and the heat generation amount along the width direction of the fixing belt 30 continuously changes.

Also in the seventh embodiment, the heat generation efficiency is high, and it becomes possible to realize uniform fixing property along the width direction of the fixing belt 30.

<< Embodiment 8 >> FIGS. 17A and 17B.
13C is a lateral perspective view of the fixing roller according to the eighth embodiment, a cross-sectional view taken along the line BB of FIG. 16A, and a heat generation distribution diagram, respectively.

In the eighth embodiment, the distribution of the heat generation amount is changed along the longitudinal direction of the fixing roller 10 by changing the magnetic permeability of the core 23.
The magnetic permeability of the core 23 at the longitudinal end is larger than the magnetic permeability of the core 23 at the central portion. In the illustrated example, four coil assemblies 12 are arranged in parallel, and the core 2 in each coil assembly 12 is arranged.
3, the coil 22 has the same shape and the same winding method, and all the coils 22 are connected so that the same current flows. The magnetic permeability of the core 23 in the outer two coil assemblies 12 of the four coil assemblies 12 is made larger than the magnetic permeability of the core 23 in the two inner coil assemblies 12.

Since the generated magnetic flux increases as the magnetic permeability of the core 23 increases, increasing the magnetic permeability of the core 23 increases the magnetic flux intersecting the fixing roller 10 and increases the amount of heat generation. If the magnetic permeability is reduced, the magnetic flux intersecting the fixing roller 10 is reduced and the amount of heat generation is reduced. Therefore, even if the winding density of the coil is not changed, only by changing the magnetic permeability of the individual cores 23 arranged along the longitudinal direction of the fixing roller 10, the distribution of the heat generation amount can be changed as desired. Can be adjusted along the longitudinal direction. Further, since the coil 22 can be manufactured with a uniform winding density, mass productivity of the coil 22 is also excellent.

Here, the outer two coil assemblies 1
Since the magnetic permeability of the core in No. 2 is larger than the magnetic permeability of the core in the two inner coil assemblies 12, the distribution of the heat generation amount along the longitudinal direction of the fixing roller 10 is
As shown in FIG. 17C. With such a calorific value distribution, although the end portion in the longitudinal direction of the fixing roller 10 is easily affected by heat radiation, the temperature distribution along the longitudinal direction of the fixing roller 10 can be made substantially uniform. It is possible to realize uniform fixing properties along the direction.

A ferrite core can be used as the core 23. For ferrite, Zn ferrite as well as Mn can be used.
-Zn ferrite, Ni-Zn ferrite, Mn-Mg
There are ferrites. The strength of these spontaneous magnetizations is 4
00-500 G (0.5-0.6 Wb / m ² ),
The cores may be selectively used along the longitudinal direction of the fixing roller 10 depending on the characteristics of each ferrite, that is, the strength of spontaneous magnetization (difference in magnetic permeability).

Although not shown, by changing the magnetic permeability of the core 33, the distribution of the heat generation amount can be changed along the width direction of the fixing belt 30. Further, the distance between the heated metal body (fixing roller 10 or fixing belt 30) and the cores 23, 33 is changed, and the cores 23, 33
The distribution of the amount of heat generated may be changed along the longitudinal direction of the heated metal bodies 10 and 30 by changing the magnetic permeability of 33 as well.

[0079]

As described above, according to the induction heating fixing device of the first aspect, the magnetic flux is generated in the direction perpendicular to the metal body to be heated, and the magnetic flux between the metal body to be heated and the core is generated. With a simple structure of changing the distance, the heat generation efficiency is high, and the distribution of the heat generation amount along the longitudinal direction of the metal body to be heated can be set arbitrarily. Further, since the coil can be manufactured with a uniform winding density, the mass productivity of the coil also becomes excellent.

According to the induction heating fixing device of the second aspect, the temperature distribution along the longitudinal direction of the metal body to be heated can be made substantially uniform in consideration of the influence of heat radiation, and thus the metal body to be heated can be heated. It is possible to realize uniform fixing properties in the longitudinal direction.

Further, according to the induction heating fixing device of the third aspect, the magnetic flux is generated in the direction orthogonal to the metal body to be heated, and the magnetic permeability of the core is changed, so that the heat generation efficiency is high. Moreover, it is possible to arbitrarily set the distribution of the amount of heat generation along the longitudinal direction of the metal body to be heated. Also,
Since the coil can be manufactured with a uniform winding density, the mass productivity of the coil is also excellent.

Further, according to the induction heating fixing device of the fourth aspect, the temperature distribution along the longitudinal direction of the metal body to be heated can be made substantially uniform in consideration of the influence of heat radiation. It is possible to realize uniform fixing properties in the longitudinal direction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an induction heating fixing device to which the present invention is applied.

FIG. 2 is a perspective view showing a fixing roller and a pressure roller used in the induction heating fixing device shown in FIG.

FIG. 3 is a perspective view showing a coil assembly used in the induction heating fixing device shown in FIG.

FIG. 4 is a perspective view showing a coil and a core in a fixing roller.

5 is a perspective view showing a holder unit in which the coil assembly shown in FIG. 3 is held by a holder.

FIG. 6 is an explanatory diagram illustrating a heating principle of a fixing roller in the induction heating fixing device shown in FIG.

7 (A) is a horizontal perspective view showing the direction of magnetic flux generated in the induction heating fixing device shown in FIG. 1, and FIG. 7 (B).
FIG. 4B is a sectional view taken along the line BB of FIG.

FIG. 8 is a block diagram of a circuit that controls a temperature of a fixing roller by applying a high frequency current to an induction heating coil.

9A, 9B, and 9C are respectively a lateral perspective view of the fixing roller according to the first embodiment, a cross-sectional view taken along the line BB of FIG. 9A, and a heat generation distribution. It is a figure.

10A, 10B, and 10C are lateral perspective views of the fixing roller according to the second embodiment, respectively.
3 is a cross-sectional view taken along the line BB of FIG.

11A, 11B, and 11C are lateral perspective views of the fixing roller according to the third embodiment, respectively.
3 is a cross-sectional view taken along the line BB of FIG.

12A is a lateral perspective view showing the direction of magnetic flux generated in the induction heating fixing device in Embodiment 4, and FIG. 12B is a line BB in FIG. 12A. FIG.

13 (A), (B), and (C) are respectively a lateral perspective view showing a main part in the fourth embodiment, a cross-sectional view taken along the line BB of FIG. 13 (A), and heat generation. It is a distribution map.

14 (A), (B), and (C) are respectively a lateral perspective view showing a main part of the fifth embodiment, a cross-sectional view taken along the line BB of FIG. 14 (A), and heat generation. It is a distribution map.

15 (A), (B), and (C) are respectively a lateral perspective view showing a main part of the sixth embodiment, a cross-sectional view taken along the line BB of FIG. 15 (A), and heat generation. It is a distribution map.

16 (A), (B) and (C) are respectively a lateral perspective view showing a main part of the seventh embodiment, a cross-sectional view taken along the line BB of FIG. 16 (A), and heat generation. It is a distribution map.

17 (A), (B), and (C) are respectively a lateral perspective view showing a main part of the eighth embodiment, a cross-sectional view taken along the line BB of FIG. 17 (A), and heat generation. It is a distribution map.

FIG. 18 (A) is a lateral perspective view showing the direction of magnetic flux generated in a conventional induction heating fixing device, and FIG. 18 (B) is a sectional view taken along line BB in FIG. 18 (A). Is.

19A, 19B, and 19C are horizontal perspective views of a fixing roller in a conventional induction heating fixing device, respectively.
It is the sectional view which follows the BB line of the figure (A), and the heat generation distribution diagram.

[Explanation of symbols]

10 ... Fixing roller (Metal hollow roller (heated metal body)) 11 ... Pressure roller 12, 34 ... Coil assembly 14 ... Sheet (recording medium) 22, 32 ... Coil 23, 33 ... Core 30 ... Fixing belt ( Metal heating plate (metal to be heated))

Claims (4)

[Claims] 1. A metal hollow roller or a metal heating plate which is a metal to be heated, a core arranged in a direction orthogonal to the metal to be heated, and a core orthogonal to the metal to be heated. In an induction heating fixing device having a coil wound around the core so that magnetic flux is generated in a direction, by changing the distance between the heated metal body and the core, An induction heating fixing device characterized in that the distribution is changed along the longitudinal direction of the metal body to be heated. 2. The distance between the heated metal body and the core at the longitudinal end of the heated metal body is smaller than the distance between the heated metal body and the core at the central portion. The induction heating fixing device according to claim 1, wherein: 3. A metal hollow roller or a metal heating plate which is a metal body to be heated, a plurality of cores arranged in a direction orthogonal to the metal body to be heated, and a metal body to be heated. In an induction heating fixing device having a coil wound around each core so that magnetic flux is generated in a direction orthogonal to each other, cores having different magnetic permeability are arranged along the longitudinal direction of the heated metal body. The induction heating fixing device is characterized in that the distribution of the amount of heat generated is changed along the longitudinal direction of the heated metal body. 4. The induction heating fixing device according to claim 3, wherein the magnetic permeability of the core at the longitudinal end portion of the heated metal body is made larger than the magnetic permeability of the core at the central portion. .