JP2002260837A - Induction heating device and image forming device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating device that has eliminated the interface of the magnetic field generating means and, especially, can eliminate temperature unevenness at the top end parts in the longitudinal direction of the heating roller. SOLUTION: This induction heating device in which the heating roller 42 of longitudinal shape that has a conductive layer that generates heat in the alternating field is made to generate heat by the action of magnetic field by the magnetic field generating means and that heat is conveyed to the recording paper that is transferred by the heating roller. The length of the heating roller in the longitudinal direction is made longer than the length of the core 43a of the magnetic field generating means, and the length of the transfer region (maximum paper width) of the heated material is made shorter than the length of the core of the magnetic field generating means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating system which is preferably used for a fixing device in a dry electrophotographic apparatus, a drying apparatus in a wet electrophotographic apparatus, a drying apparatus in an ink jet printer, and an erasing apparatus for rewritable media. The present invention relates to an induction heating device and an image forming apparatus provided with the same.

[0002]

2. Description of the Related Art In general, a fixing device used in a dry electrophotographic apparatus employs a configuration in which a halogen lamp is provided in a heating roller and the heating roller is heated by the halogen lamp. However, in such a configuration, there is a problem that the rise at the start of heating is slow.
Therefore, in recent years, a heating roller having a conductive layer is formed, and an eddy current is generated by applying an alternating magnetic field from a magnetic field generating means to the heating roller, and the heating roller itself is heated by Joule heat due to the eddy current. Attention has been paid to an induction heating type fixing device using such a configuration.

As such an induction heating device, for example, as disclosed in JP-A-8-16005,
In order to make the heat generation distribution uniform in the pressure contact nip portion (fixing nip portion) between the heating roller and the pressure roller, the following method is employed.

That is, the core material (core) is divided into a plurality of pieces, and the divided core materials are laminated in the longitudinal direction (axial direction) of the heating roller for conveying the paper so as to pass through the pressure nip portion.

[0005] When a ferrimagnetic material is used as the divided core material, the spontaneous magnetization of the divided core material decreases with an increase in temperature, and the magnetic flux generated from the core material decreases. Eddy currents induced in the layer are reduced,
The calorific value will be reduced. In addition, when a plurality of divided cores are stacked in the longitudinal direction of the heating roller, the interface between the divided cores has a heat insulating effect, so that a structure that is thermally separated can be obtained. However, if there is no interface,
The heat in the non-sheet passing area is easily transmitted to the sheet passing area of the small-size paper, which causes an increase in the temperature in the sheet passing area. As a result, the amount of generated heat is reduced, and a fixing failure occurs. Therefore, by forming this interface according to the paper size, the influence of the temperature rise in the non-sheet passing area due to the rise in the temperature of the non-sheet passing portion when the small size paper is passed due to the heat insulating effect at the interface. The amount of heat generated in the paper passing area of the small size paper can be made uniform without giving it to the paper passing area.

Further, of the plurality of divided core materials, the core material corresponding to the end of the nip portion where heat is radiated is made of a material that generates a large amount of magnetic flux (a material having a high relative magnetic permeability) or a material of the core material. The configuration is such that the cross-sectional area is increased or the distance between this portion and the conductive layer of the heating roller is reduced. With this configuration, the amount of magnetic flux at the end of the nip portion where much heat is dissipated is increased, thereby increasing the amount of heat generation and making the temperature in the nip portion longitudinal direction uniform.

[0007]

However, the above-described conventional induction heating apparatus has the following problems.

That is, the magnetic flux passing through the magnetic field generating means such as the split core material becomes discontinuous at the portion (interface) if the interface exists there. For this reason, at the portion where the interface of the magnetic field generating means exists, the magnetic flux links with the conductive layer of the heating member such as the heating roller as it is, causing heat generation unevenness. If the interface is positively formed in the magnetic field generating means in this way, when heating a large-sized sheet, the conductive layer of the heating member corresponding to the interface may become uneven in temperature.

Further, since the cross-sectional area of the magnetic field generating means at the interface (split core material connecting portion) is relatively large, heat transfer to the adjacent core material across the interface can be prevented even with a heat insulating structure. Impossible. Moreover, in order to obtain the expected effect, it is necessary to increase the thickness of the interface to increase the heat insulating effect, but this causes a further increase in temperature unevenness at the interface.

Further, when the material of the core material or the cross-sectional shape is changed at the longitudinal end of the heating member by utilizing the connection of the plurality of divided core materials, the magnetic flux distribution is continuously changed at the interface. It becomes difficult to carry out, and it causes temperature unevenness.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and has as its object to eliminate the interface of the magnetic field generating means, and to particularly eliminate temperature unevenness at the longitudinal end of the heating member. It is an object of the present invention to provide an induction heating device capable of performing the above-described steps.

[0012]

In order to achieve the above object, according to the present invention, a longitudinal heating member having a conductive layer that generates heat in an alternating magnetic field is heated by the action of a magnetic field by a magnetic field generating means. It is assumed that the induction heating device is configured to transmit the heat to the material to be heated conveyed by the heating member. The heating member is set so that its length in the longitudinal direction is substantially equal to or longer than the length of the magnetic field generating means, and the length of the transfer area of the heating member through which the material to be heated is transferred is determined by the magnetic field. It is set to be shorter than the length of the generating means.

According to this specific matter, if the longitudinal end of the heating member is made longer than the longitudinal end of the magnetic field generating means,
As the magnetic flux linked to the heating member approaches the end, it becomes radially and sparsely distributed, causing a decrease in the calorific value, making it impossible to make the temperature of the contact nip uniform, Although it may cause fixing failure, etc., by making the length of the magnetic field generating means longer than the length of the transport area of the heating member to which the material to be heated is transported, without changing the core shape of the magnetic field generating means In addition, it is possible to solve the shortage of heat generation at the end of the heating member.

On the other hand, when the length of the heating member is set to be shorter than the length of the magnetic field generating means, the length of the heating member is set to be smaller than the length of the magnetic field generating means. The magnetic flux concentrates on the portion, and the amount of heat generated at this end can be increased. In this way, by making the length of the heating member shorter than the length of the magnetic field generating means, it is possible to similarly solve the shortage of heat generation at the end of the heating member without changing the core shape of the magnetic field generating means. Becomes

In particular, when the length of the heating member in the longitudinal direction is set to be equal to or longer than the length of the magnetic field generating means, the following configuration is provided to increase the amount of heat generated at the longitudinal end of the heating member. Be raised.

That is, the magnetic field generating means is provided with a core material having surfaces facing each other via a gap, and a coil wound around the core material, and the gap between the gaps is set at the longitudinal end of the magnetic field generating means. The part is set to be narrower than the central part.

According to this specific matter, the interval between the surfaces of the core material via the gap is set so as to be smaller at the end, so that the magnetic flux linked to the heating member is made denser toward the end.
It is possible to increase the amount of heat generated at the end of the heating member.

On the other hand, when the length of the heating member in the longitudinal direction is set shorter than the length of the magnetic field generating means, the following configuration is provided as a means for lowering the temperature at the end of the heating member.

That is, the magnetic field generating means is provided with a core material having surfaces facing each other via a gap, and a coil wound around the core material, and the gap between the gaps is set at the longitudinal end of the magnetic field generating means. The part is set to be wider than the central part.

According to this specific matter, the interval between the surfaces of the core material via the gap is set so as to be larger at the end, so that the magnetic flux linked to the heating member is reduced at the end.
The amount of heat generated at the end of the heating member can be reduced.
In other words, when applied to a case where the temperature at the end of the heating member is too high, it is possible to lower the temperature at this end to facilitate adjustment of the temperature distribution.

In particular, the following configuration is provided for controlling the amount of heat generated at the end of the heating member.

That is, the magnetic field generating means is provided with a guide member capable of changing the space of the gap at the longitudinal end.

According to this specific matter, in the case where the length of the heating member in the longitudinal direction is set to be equal to or longer than the length of the magnetic field generating means, if the distance between the surfaces of the core material via the gap is reduced, the magnetic field generating means Is guided to the heating member through the guide member, and the magnetic flux density at the end of the heating member is more concentrated than at the center, so that the amount of heat generated at the end of the heating member can be increased. On the other hand, in the case where the length of the heating member in the longitudinal direction is set shorter than the length of the magnetic field generating means, if the distance between the surfaces through the gap of the core material is widened, the magnetic flux density becomes smaller than that of the central portion. This is effective for lowering the heat generation amount of a portion corresponding to this portion when it becomes too high. As described above, it is possible to control the amount of heat generated at the end of the heating member only by changing the distance between the surfaces of the core material via the gap.

In addition, since the longitudinal end of the core member (magnetic field generating means) is formed by a guide member which is a separate member, it is necessary to continuously change the cross-sectional shape of the magnetic field generating means in the axial direction. In addition, the control of the heat generation amount at the end of the heating member can be realized with a very simple configuration.

In particular, the following configuration is provided to eliminate a local difference in the amount of heat generated at the end of the heating member.

That is, the inclined portion is provided on the center side of the guide member of the magnetic field generating means.

According to this specific matter, the guide member, which is a member separate from the core member, is prevented from locally concentrating the magnetic flux interlinking with the heating member by the inclined portion on the central portion side, and the end portion of the heating member is prevented. It is possible to eliminate a local difference in the amount of heat generated at the time.

In particular, the following configuration is listed as one that controls the amount of heat generated at the end of the heating member according to the situation.

That is, a horizontal moving means for moving the guide member in the horizontal direction is provided in the magnetic field generating means, and the horizontal moving means adjusts the interval of the gap at the longitudinal end.

According to this specific matter, by moving the guide member in the horizontal direction, the distance between the surfaces of the guide member (core material) through the gap is changed, and the magnetic flux linked to the heating member is changed according to the situation. It can be adjusted. Thus, the amount of heat generated at the end of the heating member is controlled, and the temperature of the heating member can be stabilized regardless of the sheet size.

On the other hand, in the case where a vertical moving means for moving the guide member in the vertical direction is provided in the magnetic field generating means and the distance between the core member and the guide member is adjusted by the vertical moving means. By moving the guide member vertically, the connection gap of the magnetic field generating means can be changed to control the amount of magnetic flux passing through the guide member, and the magnetic flux linked to the heating member can be adjusted according to the situation. It becomes possible. Thus, the amount of heat generated by the heating member is also controlled according to the situation, and the temperature of the heating member can be stabilized without being affected by the sheet size.

Further, when the above-described induction heating device is provided in the image forming apparatus, temperature unevenness in the longitudinal direction including the end of the heating member can be eliminated, and the temperature can be made uniform, so that defective fixing can be suppressed. As a result, it is possible to provide an image forming apparatus capable of outputting a high-quality image.

[0033]

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

<First Embodiment> FIG. 1 is a schematic structural view of a color image forming apparatus to which an induction heating apparatus according to a first embodiment of the present invention is applied.

In FIG. 1, a color image forming apparatus X
Are four-color visible image forming units 1Y, 1M, 1C, 1B
Are arranged along the recording medium transport path, which is a so-called tandem type printer. Specifically, four sets of visible image forming units 1Y, 1M, 1C, and 1B are provided with recording paper P as a material to be heated.
The toner T of each color (indicated by ● in FIG. 1) is multiplexed on the recording paper P, which is disposed along the transport path of the recording paper P connecting the supply tray 2 and the fixing device 4 of FIG. After the transfer, the toner image is fixed by the fixing device 4 to form a full-color image.

The recording paper conveying means 3 is stretched by a pair of driving rollers 31 and an idling roller 32.
It has an endless transport belt 33 that rotates while being controlled at a predetermined peripheral speed (134 mm / s in this example). The recording paper P is electrostatically attracted onto the transport belt 33 and transported. Each of the visible image forming units 1Y, 1M, 1C and 1B includes a charging roller 12, a laser beam irradiating unit 1 around a photosensitive drum 11.
3, a developing device 14, a transfer roller 15, and a cleaner 16 are arranged. The developing device 14 of each visible image forming unit 10 includes yellow (Y), magenta (M), cyan (C),
Each toner T of black (B) is stored. Each of the visible image forming units 1Y, 1M, 1C and 1B forms a toner image on the recording paper P by the following steps.

That is, after the surface of the photosensitive drum 11 is uniformly charged by the charging roller 12, the surface of the photosensitive drum 11 is exposed to laser light by the laser beam irradiation means 13 in accordance with image information to form an electrostatic latent image. . Thereafter, a toner image is developed with respect to the electrostatic latent image on the photosensitive drum 11 by the developing device 14, and this visualized toner image is transferred by the transfer roller 15 to which a bias voltage having a polarity opposite to that of the toner T is applied. Are sequentially transferred onto the recording paper P conveyed by the conveying means 3.

Thereafter, the recording paper P is separated from the transport belt 33 by the curvature of the drive roller 31, and then transported to the fixing device 4. Therefore, an appropriate temperature and pressure are given by the heating roller 42 and the pressure roller 41 maintained at a predetermined temperature. Then, the toner T dissolves and is fixed to the recording paper P to form a robust image.

Next, a detailed configuration of the fixing device 4 will be described with reference to FIG. FIG. 2 shows the fixing device 4.
Is a cross-sectional view in the direction perpendicular to the axis.

The fixing device 4 includes an induction heating device 40 and a pressure roller 41. The induction heating device 40
Includes a heating roller 42 as a heating member, a magnetic field generating means 43, an excitation circuit 44, and a thermistor 45. The magnetic field generating means 43 includes a core 43a as a core having a substantially U-shaped cross section having surfaces facing each other via a gap,
Induction coil 43b (coil) wound around core 43a
And The heating roller 42 has a hollow structure and heats the recording paper P.

The pressure roller 41 is disposed opposite to the heating roller 42, and is formed by an elastic member (not shown).
Is pressed in the direction of pressing (upward in FIG. 2). The magnetic field generating means 43 is provided inside the heating roller 42 and is arranged so as to heat the contact nip N to which the pressure roller 41 is pressed.

The fixing device 4 as described above includes a heating roller 4
The sheet-shaped recording paper P is nipped and conveyed between the pressure roller 2 and the pressure roller 41, so that the toner transferred to the recording paper P is heated and melted and fixed. FIG. 2 shows how the toner T before fixing changes to the toner T after fixing.

Next, the heating roller 42, the pressing roller 41, and the magnetic field generating means 43 (core 43a) according to the present embodiment are described.
The configuration of the induction coil 43b) will be described in detail.

The heating roller 42 is configured to have at least one or more conductive layers 42a to generate heat by receiving a fluctuating magnetic field. The conductive layer 42a preferably has a large relative magnetic permeability. For example, it is desirable to be made of iron, magnetic stainless steel (SUS430 or the like), silicon steel sheet, electromagnetic steel sheet, nickel steel or the like. Even if the material has a low relative magnetic permeability, a material having a high resistivity (for example, non-magnetic stainless steel: SUS304 or the like) may be used because it generates a large amount of heat when an eddy current is generated. Alternatively, the configuration may be such that the material having a high relative magnetic permeability is disposed on a non-magnetic base member (for example, ceramic or the like) so as to have conductivity. In the present embodiment, as the heating roller 42, an iron roller (material: STKM) having a diameter of φ30 mm and a thickness of 0.4 mm is used.

In order to prevent the toner T from offsetting (adhering to the heating roller 42), a release layer 42b is provided on the surface of the heating roller 42 (conductive layer 42a). For the release layer 42b, a fluorine-based material such as PFA (copolymer of tetrafluoroethylene and perfluoroalkylvinyl ether) or PTFE (polytetrafluoroethylene), silicon rubber, or fluorine rubber is suitable. In the present embodiment, the release layer 42b is formed by coating PTFE with 20 μm.

Next, the induction coil 43 of the magnetic field generating means 43
b will be described. The purpose of the induction coil 43b is to
The eddy current is induced in the conductive layer 42a of the heating roller 42 to generate heat by Joule heat, thereby heating the heating roller 42.

In this embodiment, a single aluminum wire (a surface insulating layer (for example, with an oxide film)) is used as the wire in consideration of heat resistance, but it is a copper wire or a copper-based composite member wire. Alternatively, the wire may be a litz wire (a wire obtained by twisting an enamel wire or the like). Regardless of which wire is used, in order to suppress Joule loss in the induction coil,
The total resistance of the induction coil 43b should be 0.5Ω or less, preferably 0.1Ω or less.

The core 43a is desirably made of a material having a high relative magnetic permeability in order to concentrate more magnetic flux.
Materials that can be used include a silicon steel sheet, an electromagnetic steel sheet, and ferrite, but any material having a high relative magnetic permeability can be used. Further, in order to suppress the eddy current generated in the core 43a, it is desirable that the core 43a has a laminated structure. However, this does not apply when the material resistance value of ferrite or the like is high.

The pressure roller 41 is configured to have a heat-resistant elastic layer 41b made of silicon rubber or the like on a core metal 41a of iron, stainless steel or aluminum. Further, a release layer may be formed on the surface. The pressure roller 41 is pressed against the heating roller 2 with a force of 100 N by an elastic member. Thereby, a contact nip portion N having a width of about 3.5 mm is formed between the heating roller 42 and the heating roller 42.

Next, the fixing operation in the fixing device 4 will be described.

First, at the time of warm-up, the excitation circuit 44 connected to the induction coil 43b is turned on, the induction coil 43b is excited, and the conductive layer 4 of the heating roller 42 is heated.
An AC eddy current is induced in 2a and generates heat by Joule heat. The calorific value at this time is about 800 W. At the same time as the energization by the excitation circuit 44 starts, the heating roller 42
Is driven to rotate, the pressure roller 41 is driven to rotate.

The surface temperature of the heating roller 42 is controlled by the thermistor 4.
5, when the surface temperature of the heating roller 42 reaches a predetermined temperature (180 ° C. in this embodiment), the warm-up is completed, and the induction coil 4
The energization to 3b is switched to ON-OFF control, and the surface temperature of the heating roller 42 is maintained at a predetermined temperature. Then, the recording paper P on which the unfixed toner image has been transferred is transported to the contact nip N, where the heat of the heating roller 42 and the pressure roller 4
The toner image is fused and fixed by the pressure of 1, and is fixed on the recording paper P to be a robust image.

Next, the magnetic field generating means 43 which is a feature of the present invention will be described.

First, the heating roller 42 and the magnetic field generating means 43
The relationship between the length in the axial direction (the horizontal direction in FIG. 3) and the paper passing area of the recording paper P will be described with reference to FIG.

FIG. 3 shows a heating roller 42 and an induction coil 43.
3 shows a positional relationship between the pressure roller 41 and the core 43a. FIG. 3A is a diagram of the heating roller 42 and the induction coil 43b viewed from the pressure roller 41 side, and shows a state of a magnetic flux linking the core 43a to the heating roller 42 (indicated by an arrow in the figure). It is a thing. For convenience, the bearing of the heating roller 42 is not shown.

The magnetic flux linked to the heating roller 42 is shown in FIG.
As shown in (a), the distribution becomes radial and sparse as it approaches the end of the heating roller 42. This phenomenon occurs because the relative permeability of the conductive layer 42a of the heating roller 42 is lower than that of the core 43a.

Since the core 43a can effectively concentrate the magnetic flux generated by the coil 43b, a magnetic member (for example, ferrite) having a relative magnetic permeability of 1000 or more is generally used. For the same reason, the conductive layer 42a of the heating roller 42 is also desirably made of a material having a high relative permeability. However, many magnetic members having a high relative permeability have poor workability and cannot be processed into a roller shape. At present, materials that can be easily processed into a roller shape are limited to materials such as nickel having a relative magnetic permeability of 600, iron and stainless steel having a relative permeability of 100 or less. Therefore, the heating roller 42
All of the magnetic flux from the core 43a cannot be received and escaped as leakage magnetic flux, which causes uneven heat generation distribution. This phenomenon is caused by the core 43a where the magnetic flux distribution changes rapidly.
In the end portion, it appears particularly when the length of the heating roller 42 is longer than that of the core 43a.

For this reason, in the present embodiment, the recording paper P having the largest size is set so that the influence of the magnetic flux escape is reduced.
Is set to be shorter than the length of the end of the core 43a (the length of the core 43a is 320 mm with respect to the sheet width of 297 mm). , The length of the heating roller 42 is 330 mm
), And is used in a portion where the temperature distribution becomes constant. FIG. 3B shows the heating roller 4 at this time.
2 shows the temperature distribution and the maximum paper width.

As described above, the width of the core 43 is larger than the width of the recording paper P.
a so that the length of the heating roller 42 is
Has a length that is equal to or longer than the core 43a, so that the temperature unevenness can be improved without a complicated configuration such as adjusting the cross-sectional area of the core 43a and the gap between the heating roller 42 at the center and the end. Will be able to do that.

Further, by providing the induction heating device 40 in the color image forming apparatus X, temperature unevenness in the longitudinal direction including the end of the heating roller 42 can be eliminated, and the temperature can be made uniform. It is possible to provide a color image forming apparatus X that can suppress and output a high-quality image.

<Second Embodiment> Next, a second embodiment of the present invention will be described.
Will be described with reference to FIG.

In this embodiment, the relationship between the axial length of the heating roller 42 and the magnetic field generating means 43 and the area through which the recording paper P passes is changed. FIG. 4A shows the heating roller 4 when the length of the end of the heating roller 42 is shorter than the core 43a.
2 shows a view of the end position of No. 2 viewed from the pressure roller 41 side,
The state of the magnetic flux distribution linking from the core 43a to the heating roller 42 is shown.

That is, in the present embodiment, the heating roller 42
Is set shorter than the core 43a. With this configuration, the magnetic flux density is high at the edge (end) of the heating roller 42. This is heating roller 4
2, the length of the core 43a is longer than that of the heating roller 42.
This is because the magnetic flux from the core corresponding to the position where the heat roller 42 does not exist is linked to the end of the heating roller 42, thereby reducing the influence of the leakage magnetic flux at the end of the heating roller 42.
Therefore, the amount of heat generated at the end of the heating roller 42 can be increased.

FIG. 4B shows the distribution of the calorific value at this time. Although this figure shows a heat generation amount distribution for the sake of explanation, the temperature distribution becomes uniform since heat is actually taken by the bearing portion. In this embodiment, the maximum paper width of the recording paper P is 297 mm, and the length of the heating roller 42 is 310 m.
m, and the length of the core 43a was 320 mm.

As described above, by making the length of the heating roller 42 shorter than the core 43a, the magnetic flux can be concentrated on the end of the heating roller 42, and the heat generation distribution at the end of the heating roller 42 can be controlled. .

<Third Embodiment> Next, a third embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

In this embodiment, the shape of the end of the magnetic field generating means 43 is changed.

That is, as shown in FIG. 5B, the length of the heating roller 42 is formed longer than the core 51 a of the magnetic field generating means 43. As shown in FIG. 5 (a), the core 51a has one surface (front surface in the drawing) of the surfaces facing each other, and the other surface (rear surface in the drawing) approaches the end. Are formed so as to be closer to the center, and thereby the interval between the cores 51a is set to be narrower. FIG. 5B shows the positional relationship between the core 51a and the heating roller 42 from the same angle.

As described above, by narrowing the interval between the cores 51a toward the end, as shown in FIG. 5C, the state of the magnetic flux linked to the heating roller 42 becomes denser as approaching the end. As shown in FIG. 5D, the amount of heat generated at the end of the heating roller 42 can be increased.

Further, since the area where the magnetic flux links to the heating roller 42 is narrowed, the magnetic flux leaking in the axial direction of the heating roller 42 is also reduced, and the heating area can be limited.

In the third embodiment, the core 51a
Although only one surface of the core 52a is formed in a tapered shape, the opposite surfaces of the core 52a may be formed in a tapered shape as shown in FIG. In this case, the reason for continuously deforming the shape of the core 52a into a tapered shape is as follows.
This is because the magnetic flux linked to the heating roller 42 is continuously changed so that a portion where the temperature is locally increased is less likely to occur (if there is an acute edge in the portion that guides the magnetic flux from the core to the heating roller, there is no sharp edge there). The magnetic flux tends to concentrate, and that portion tends to be locally hot.) In short, the shape of the core may be changed stepwise as long as it can be adjusted so as to suppress local heat generation.

The amount of heat generated at the end of the heating roller 42 is
Although it can be increased by reducing the interval between the cores, as shown in FIG. 7, the value of the interval W between the cores 53a (the distance between the opposing surfaces of the cores 53a) is set to
When the air gap distance d is smaller than or equal to d, the magnetic flux short-circuits the air and does not link with the heating roller 42. Therefore, the value of the interval W between the cores 53a is set to the set gap d with the heating roller 42.
It is necessary to set above. By adopting the above configuration, the cross-sectional area of the core and the gap between the heating roller and the central portion and the end portion can be adjusted without a complicated configuration such as adjusting.
The magnetic flux linked to the end of the heating roller 42 can be concentrated.

On the other hand, when the length of the heating roller is shorter than the length of the core of the magnetic field generating means, the interval between the cores near the end of the heating roller may be set wider than the center. As described above, when the interval between the cores is increased at the end of the heating roller, the magnetic flux density linked to the heating roller is reduced at that portion, so that the amount of heat generated at the end of the heating roller can be reduced. If the magnetic flux concentrates too much on the end, the amount of heat generated can be reduced.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

In this embodiment, the configuration of the end of the magnetic field generating means 43 is changed.

That is, in the present embodiment, as shown in FIG.
It is formed longer.

Then, as shown in FIG.
Cores 54 whose surfaces of 4a protrude in a direction facing each other
A pair of guide members 55, 55 made of separate members are provided at the end of “a”, and the distance between the surfaces facing each other is smaller at the end than at the center (FIG. 8C) by the respective guide members 55. I am trying to become. Each of the guide members 55 protrudes in a direction in which the surfaces of the core 54a face each other. With this configuration, the magnetic flux generated by the coil 43b passes through the core 54a (the guide member 55) and is guided to the heating roller 42, thereby making the magnetic flux density at the end of the heating roller 42 denser than that at the center. Can heat roller 42
The amount of heat generated at the end can be increased.

Further, since the guide members 55, 55 made of separate members are provided at the ends of the core 54a, the core 54a
It is not necessary to continuously change the cross-sectional shape of the
It can be easily configured.

Further, the guide members 55, 55 are
Since this is a separate member, the value of the gap distance d between the guide members 55 and 55 and the heating roller 42 can be easily changed, and it is easy to cope with various forms such as bringing the tip closer to the heating roller 42. In addition, it can be easily manufactured.

In short, the very simple core 54a
With this configuration, the amount of heat generated at the end of the heating roller 42 can be increased.

On the other hand, when the length of the heating roller 42 is shorter than the length of the magnetic field generating means 43, the interval between the guide members 55 at the end of the heating roller 42 is set to be wider than the center. Good. That is, if the distance between the guide members 55 is increased, the magnetic flux density linked to the end of the heating roller 42 becomes low, and the heating roller 42
The shorter length allows for adjustment of the over-concentrated magnetic flux.

<Fifth Embodiment> Next, a fifth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

In this embodiment, the shape of the guide member is changed.

That is, in the present embodiment, as shown in FIG. 9, the sides 56a on the central portion side of the guide members 56, 56 in which the surfaces of the core 54a protrude in the directions facing each other.
Is formed in a tapered shape (inclined portion) so as to become wider toward the center.

With this configuration, since the magnetic flux linked to the heating roller 42, particularly, the magnetic flux continuously transmitted from the core 54a to the heating roller 42, the temperature unevenness on the heating roller 42 can be reduced.

In the present embodiment, each guide member 56 is projected in a direction in which the surfaces of the core 54a are opposed to each other. However, as shown in FIG.
Are provided to be inclined with respect to the core 54a, and each guide member 56 is made to approach the heating roller 42, so that more magnetic flux can be linked to the heating roller 42.

<Sixth Embodiment> Next, a sixth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

In this embodiment, the shape of the guide member is changed.

That is, in the present embodiment, as shown in FIG. 11, the magnetic field generating means 53 includes moving means for individually moving guide members 57, 57 whose surfaces of the core 54a protrude in directions facing each other. 58, 58 are provided. Each of the moving means 58 is adapted to adjust the distance between the gaps W between the opposing surfaces of the core 54a in the contact / separation direction (horizontal direction in FIG. 11) by moving the guide members 57. As the moving means, a general method, for example, a solenoid or the like is used.

Thus, in the present embodiment, when the temperature at the end of the heating roller 42 rises abnormally, for example, by increasing the interval of the gap W, the amount of heat generated at the end is reduced to suppress the temperature rise. Can be.

In the present embodiment, the gap W between the opposing surfaces of the core 54a is set by the movement of the guide member 57.
12, the guide members 57, 57 whose surfaces of the core 54a protrude in the direction facing each other are individually moved by the magnetic field generating means 53, as shown in FIG. Moving means 59 are provided to move the moving means 59 so that the space of the gap t in the direction orthogonal to the surfaces facing each other with respect to the core 54a in the approaching / separating direction (vertical direction in FIG. 12). It may be adjusted. In this case, usually, each guide member 59 and the core 5
4a, and when an abnormal temperature rise at the end of the heating roller 42 is detected, each guide member 59 is moved so as to provide a gap t between the core 54a. The magnetic flux linked to the guide member 59 can be reduced, and the calorific value can be reduced. In particular, as for the gap t between each guide member 59 and the core 54a, a sufficient effect can be obtained if the gap is 0.3 mm, so that the mechanical stroke can be reduced and it can be easily realized.

Further, the temperature distribution of the entire heating roller may be controlled by providing a guide member made of a separate member at the center and moving these members. At that time, by setting the size of the guide member to a size corresponding to the paper size, a greater effect can be obtained.

Further, in each of the above embodiments, the magnetic field generating means 53 is provided inside the heating roller 42, but the magnetic field generating means 53 may be provided outside the heating roller 42 as shown in FIG.

[0094]

As described above, the length of the heating member is set to be equal to or longer than the length of the magnetic field generating means, and the length of the transfer region of the heating member is set to be shorter than the length of the magnetic field generating means. Insufficient heat generation at the end of the heating member can be solved without changing the core shape of the generating means.

On the other hand, by setting the length of the heating member to be shorter than the length of the magnetic field generating means, the magnetic flux is concentrated on the end of the heating member from the magnetic field generating means located outside the heating member. The amount of heat generated at the end can be increased. In addition, the shortage of heat generation at the end of the heating roller can be similarly solved without changing the core shape of the magnetic field generating means.

In particular, when the length of the heating member in the longitudinal direction is set to be equal to or longer than the length of the magnetic field generating means, the distance between the surfaces of the core material via the gap is made smaller at the end. By setting, the magnetic flux linked to the heating member is made denser toward the end,
The amount of heat generated at the end of the heating roller can be increased.

On the other hand, when the length of the heating member in the longitudinal direction is set shorter than the length of the magnetic field generating means, the interval between the surfaces of the core material via the gap is made wider at the end. By setting, the magnetic flux linked to the heating member is made sparser toward the end, the amount of heat generated at the end of the heating member can be reduced, and the temperature at the end is reduced to facilitate the adjustment of the temperature distribution. be able to.

In particular, when the length of the heating member is set to be equal to or longer than the length of the magnetic field generating means by providing a guide member capable of changing the gap of the core material at the end of the magnetic field generating means. In addition, when the distance between the surfaces through the voids of the core material is reduced,
The magnetic flux is guided to the heating member through the guide member, and the magnetic flux density at the end of the heating member is more concentrated than at the center, so that the amount of heat generated at the end of the heating member can be increased. On the other hand, when the length of the heating member in the longitudinal direction is set shorter than the length of the magnetic field generating means, if the space between the surfaces of the core material via the gap is widened, the magnetic flux density will be smaller than that of the central portion. Thus, the amount of heat generated can be reduced, and the amount of heat generated at the end of the heating member can be controlled. In addition, since the end of the core member is constituted by a separate guide member, there is no need to continuously change the cross-sectional shape of the magnetic field generating means, and it is very easy to control the amount of heat generated at the end of the heating member. It can be realized with a simple configuration.

In particular, by providing an inclined portion on the central portion side of the guide member of the magnetic field generating means, local concentration of magnetic flux linked to the heating member is prevented by the inclined portion on the central portion side of the guide member. A local difference in the amount of heat generated at the end of the member can be eliminated.

Also, by moving the guide member in the direction in which the surfaces of the core member face each other and changing the distance between the surfaces through the gap of the guide member, the magnetic flux linked to the heating member can be changed according to the situation. The temperature of the heating member can be stabilized regardless of the sheet size by controlling the amount of heat generated at the end of the heating member.

On the other hand, by moving the guide member in a direction perpendicular to the direction in which the surfaces of the core members face each other and adjusting the distance between the core member and the guide members, the magnetic flux linked to the heating member is reduced. By adjusting according to the situation, the amount of heat generated by the heating member can be controlled according to the situation, and the temperature of the heating member can be stabilized regardless of the sheet size.

Further, by providing the above-described induction heating device in the image forming apparatus, it is possible to eliminate the temperature unevenness in the longitudinal direction including the end of the heating member, to make the temperature uniform, to suppress the fixing failure and the like, and to reduce the quality. An image forming apparatus capable of outputting a good image can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus in which an induction heating device of the present invention is applied to a fixing device.

FIG. 2 is a sectional view showing the structure of the fixing device.

FIG. 3A is an explanatory diagram illustrating a relationship between a heating roller, a magnetic field generating unit, and a region of a recording sheet to which the induction heating device according to the first embodiment of the present invention is applied; (B) is a characteristic diagram showing the temperature distribution of the heating roller in the axial direction.

FIG. 4A is an explanatory diagram showing a relationship between a heating roller, a magnetic field generating unit, and a recording paper area to which an induction heating device according to a second embodiment of the present invention is applied. (B) similarly shows the heat generation distribution in the axial direction of the heating roller.

FIG. 5 (a) is a perspective view of a core end to which an induction heating device according to a third embodiment of the present invention is applied. (B)
FIG. 3 is a perspective view of an end of the core with a heating roller added. (C) is an explanatory view showing the magnetic flux density at the core end. (D) is a characteristic diagram showing the temperature distribution in the axial direction of the heating roller.

FIG. 6 is a perspective view of a core end to which an induction heating device according to a modification of the third embodiment is applied.

FIG. 7 is a cross-sectional view illustrating a structure of a heating roller to which an induction heating device according to another modification of the third embodiment is applied.

FIG. 8A is a perspective view of a core end to which an induction heating device according to a fourth embodiment of the present invention is applied. (B)
FIG. 4 is an explanatory diagram showing the magnetic flux density at the core end.
(C) is an explanatory view showing the state of the magnetic flux density at the center of the core.

FIG. 9 is a perspective view of a core end to which an induction heating device according to a fifth embodiment of the present invention is applied.

FIG. 10 is a perspective view of a core end to which an induction heating device according to a modification of the fifth embodiment is applied.

FIG. 11 is a schematic explanatory view of a core end to which an induction heating device according to a sixth embodiment of the present invention is applied.

FIG. 12 is a schematic explanatory view of a core end to which an induction heating device according to a modification of the sixth embodiment is applied.

FIG. 13 is a cross-sectional view illustrating a structure of a fixing device to which an induction heating device according to a modification of each embodiment is applied.

[Explanation of symbols]

 Reference Signs List 40 induction heating device 42a conductive layer 42 heating roller (heating member) 43 magnetic field generating means 43a, 51a, 52a, 53a, 54a core (core material) 43b induction coil (coil) 55, 56, 57 guide member 56a side (inclined portion) ) 58,59 Moving means P Recording paper (material to be heated) W Air gap t Distance between core and guide member

Claims (9)

[Claims] An elongate heating member having a conductive layer that generates heat in an alternating magnetic field is heated by the action of a magnetic field generated by a magnetic field generating means, and the heat is transmitted to a material to be heated conveyed by the heating member. In the induction heating device, the length of the heating member is set to be substantially equal to or longer than the length of the magnetic field generating means, and the length of the heating member is set to be equal to or longer than the length of the magnetic field generating means. An induction heating apparatus characterized in that the length is set to be shorter than the length of the magnetic field generating means. 2. A heating method according to claim 1, wherein the heating member is provided with a conductive layer that generates heat in an alternating magnetic field. In the induction heating device described above, the heating member is set so that its length in the longitudinal direction is shorter than the length of the magnetic field generating means. 3. The induction heating device according to claim 1, wherein the magnetic field generating means includes a core having surfaces facing each other via a gap, and a coil wound around the core. The space | interval of the said space | gap is set so that the longitudinal direction edge part of the magnetic field generation means may become narrower than a center part, The induction heating apparatus characterized by the above-mentioned. 4. The induction heating apparatus according to claim 2, wherein the magnetic field generating means includes a core having surfaces facing each other via a gap, and a coil wound around the core. An induction heating device, wherein the gap is set such that the longitudinal end of the magnetic field generating means is wider than the center. 5. The induction heating device according to claim 3 or 4, wherein the magnetic field generating means includes a guide member capable of changing an interval of a gap at a longitudinal end thereof. And induction heating equipment. 6. The induction heating device according to claim 5, wherein the magnetic field generating means has an inclined portion on the center side of the guide member. 7. The induction heating device according to claim 3, wherein the magnetic field generating means includes a moving means for moving the guide member in a direction in which the surfaces of the core material face each other. An induction heating apparatus characterized in that a gap between the gaps at the longitudinal end is adjusted. 8. The induction heating device according to claim 3 or 4, wherein the magnetic field generating means includes a moving means for moving the guide member in a direction perpendicular to a direction in which the surfaces of the core members face each other. An induction heating apparatus characterized in that the distance between the core member and the guide member is adjusted by the moving means. 9. An image forming apparatus comprising the induction heating device according to any one of claims 1 to 8.