JP2002252078A - Magnetizing coil and image heating device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetizing coil and an image heating device or the like wherein a nonuniformity of electromagnetic induction exotherm due to an influence of distribution of magnetic fluxes generated from the magnetizing coil by the application of alternating current to generate the magnetic fluxes for the electromagnetic induction exotherm can be reduced by a simple constitution. SOLUTION: This magnetizing coil 1 has electroconductive wire material 2 wound up in an oval state in a longitudinal direction, and at least one inflection part 3 is formed wound up in the state that the curvature has been changed at a site 1c except return bending parts 1a, 1b which become longitudinal both end parts. Further, the electroconductive wire material 2 is wound up in a spiral form, and is wound up in the state that both sides 2c, 2d of wire drawn out part respectively drawn out from the initial winding part 2a and from the final winding part 2b of this coil do not cross the winding part 2e.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exciting coil for electromagnetic induction heating and an image heating apparatus using the same.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exciting coil applicable to a case where an image formed of a developer in an image forming apparatus such as a printer, a copier, a facsimile, and a multifunction peripheral is heated by using heat generated by electromagnetic induction, and an image heating apparatus using the same. .

[0002]

2. Description of the Related Art In recent years, a technique has been proposed in which an electromagnetic induction heating method is applied to a heating device such as a fixing device in an image forming apparatus such as a printer.

As a fixing device using such an electromagnetic heating method, for example, a fixing belt (film) on which a conductive layer of iron, nickel or the like is formed is rotatably supported by a support roll or a pressing member (pad). And a pressure member such as a pressure roll for forming a nip portion between the fixing belt and the fixing belt supported by the support roll is provided so as to be in pressure contact with the fixing belt. Alternatively, there is an apparatus in which a magnetic flux generating means for generating a magnetic flux for electromagnetic induction heating is provided in the nip portion (in the pressing member). The magnetic flux generating means mainly includes a magnetic core such as ferrite disposed along a width direction of the fixing belt (a direction orthogonal to a rotation direction of the fixing belt), and a magnetic core for electromagnetic induction heating wound around the magnetic core. And an exciting coil made of a conductive wire that generates a magnetic flux of the type described above, and configured to apply an alternating current having a predetermined frequency such as a high frequency from an exciting circuit (feeding device) to the exciting coil.

In such a fixing device, when an alternating current is applied from an excitation circuit to an excitation coil of a magnetic flux generating means, the excitation coil (the conductive layer of the fixing belt) is supplied from the excitation coil.
Is generated in a state where the magnetic flux passes through the magnetic core, and an eddy current is generated in the conductive layer by the magnetic flux, and the conductive layer generates electromagnetic induction heat. Heated. Then, by the fixing belt heated by the electromagnetic induction heat, an unfixed image made of a developer carried on a recording material such as recording paper fed to the nip portion is heated and melted immediately before the nip portion or in the nip portion. To be fixed on the recording material.

[0005]

Incidentally, in an image heating apparatus such as a fixing apparatus utilizing such an electromagnetic induction heating system, a fixing belt which generates heat by electromagnetic induction has a relatively small heat capacity. In addition, since the fixing belt is heated in a short time, the uniformity of the temperature distribution at the time of electromagnetic induction heating of the fixing belt is easily affected by the distribution state of the magnetic flux generated from the exciting coil of the magnetic flux generating means. There are two issues.

First, one of the problems is that the exciting coil 100 in the magnetic flux generating means generally has a portion 1 in the longitudinal direction along the width direction of the fixing belt as illustrated in the upper part of FIG.
00a is wound in a substantially linear state, and is wound in a shape approximate to an ellipse such that it is wound in a state of being bent and folded at both ends 100b and 100c in the longitudinal direction. In particular, the folded part 1
In 00b and 100c, the magnetic flux (magnetic force) is concentrated in the longitudinal direction (linear portion) and the magnetic flux density increases,
The magnetic flux penetrating through the conductive layer of the fixing belt also becomes relatively large, and as a result, the folded portions 100b, 1
The amount of heat generated by electromagnetic induction heating in the portion corresponding to 00c also increases.

As a result, as shown by the graph in the lower part of FIG. 21, the temperature of the folded portions 100b and 100c of the exciting coil 100 becomes higher than that of the central portion 100a in the longitudinal direction when the fixing belt is heated by electromagnetic induction. In addition, the fixing belt cannot be heated uniformly in the width direction (the longitudinal direction of the exciting coil).

Conventionally, in order to make uniform the temperature distribution in the longitudinal direction of a conductive member (such as a dielectric heating film) which generates electromagnetic induction heat by a magnetic field (magnetic field) generated by a magnetic field generating means comprising an exciting coil and a core. ,
There has been proposed a heating device or the like in which a member having good thermal conductivity such as ceramic is disposed between the magnetic field generating means and the conductive member so that heat is diffused in the longitudinal direction by the member (Japanese Patent Application Laid-Open No. H8-208). -30126). However, in this case, the heat of the electromagnetic induction heating of the conductive member is deprived by the presence of the good thermal conductivity, so that the heating in a short time is hindered. It is difficult for the heat at both ends in the longitudinal direction to be sufficiently diffused toward the center via the good heat conductive member, and it is difficult to make the temperature distribution uniform.

Further, in order to make the temperature distribution uniform in the fixing nip portion subjected to electromagnetic induction heating, the core of the magnetic field generating means including the core and the exciting coil wound around the core is arranged in the longitudinal direction of the fixing nip portion. A heating device which is divided into a plurality of parts, and which enables local heating corresponding to the difference in the size of the object to be heated (paper carrying an unfixed image) to achieve uniform heat distribution. Has been proposed (JP-A-8-16005). However, in this case, the problem of non-uniformity of the temperature distribution due to a large amount of local heat generation at both ends (turned bent portions) of the exciting coil cannot be solved at all.

Further, a heating device using an electromagnetic induction heating fixing belt having a heating layer formed of a ferromagnetic material such as nickel or iron is used to obtain a uniform temperature distribution in a heating area (for example, a fixing nip). A heating device or the like configured to incline the magnetic core and the excitation coil, which are magnetic field generating means, by a predetermined angle toward the fixing nip with respect to the traveling direction of the fixing belt, thereby increasing the amount of heat generated at the end of the fixing belt (Japanese Patent Laid-Open No. 11-1)
No. 67982). This is to prevent a decrease in the temperature of the end portion of the fixing nip affected by the influence of the heat radiation amount in the longitudinal direction of the support roll that supports the fixing belt compared to the central portion thereof. is there.

However, in the heating device and the like of this proposal, as in the case of the above-mentioned prior art, the non-uniformity of the temperature distribution due to the large amount of local heat generation at both ends (turned bent portions) of the exciting coil. The problem cannot be solved at all.
In this heating device and the like, since the heat generation layer of the fixing belt is formed of a ferromagnetic material, the variation in the heat generation due to the relative increase in the magnetic flux density at both ends of the excitation coil causes the heat generation. There is a tendency that the layer does not easily appear as compared with the case where the layer is formed of the above-described nonmagnetic material. In addition, since this exciting coil has a portion that is inclined with its end bent, the magnetic flux density is locally too dense at that portion, and the amount of heat generated by electromagnetic induction heating locally increases, and on the contrary, There is a possibility that uniform heating in the longitudinal direction of the fixing nip may be impaired.

Another problem is that the exciting coil 100 in the magnetic flux generating means is, as exemplified in FIG.
The winding start portion 100d and the winding end portion 10 of the coil
0e, respectively, the lead wire portions 120, 1
At least one of the winding portions 100 is a region (magnetic field) in which a magnetic flux is generated while reaching an excitation circuit (power supply).
f, the magnetic field (the state of magnetic flux) of the winding portion 100f is disturbed, and as a result, the winding portion d crossed by the lead wire portion (130).
In this case, an original normal magnetic field (magnetic flux) cannot be obtained, and the fixing belt cannot be heated uniformly in the winding portion. This phenomenon is particularly noticeable in an exciting coil having a small number of turns, for example, 30 or less. The excitation coil 100 shown in FIG. 2A is two-dimensionally wound along a certain surface (a flat surface or a curved surface), and FIG. 2B is three-dimensionally wound like a spiral.

In this case, the lead wire portion 1 of the coil
The length of the two lead wire portions is different from each other as the lengths (lengths from the winding start portion and the winding end portion) are longer as shown in FIG.
In the case where the length of one of the lead wire portions is extremely long as exemplified in (1), the resistance component is excessively increased, so that the power required for electromagnetic induction heating also increases, which is uneconomical. This is because power is represented by I ² R (I: current, R: resistance).
This is because when a current of 30 A flows, power consumption is likely to increase significantly if the resistance R increases even a little. In addition, there is a problem that the radiation noise increases as the length of the lead line portion increases.

In any case, it is difficult to uniformly heat an image due to the non-uniformity of the electromagnetically induced heat (heating) in the width direction of the fixing belt due to the above-described factors. May be induced.

The present invention has been made in view of such circumstances, and a main object of the present invention is to reduce the non-uniformity of electromagnetic induction heat generated by the influence of the distribution of magnetic flux generated from an exciting coil. An object of the present invention is to provide an exciting coil that can be reduced by the configuration and an image heating device using the exciting coil.

[0016]

The exciting coil of the present invention (the first invention) capable of achieving the above object is obtained by winding a conductive wire in an elliptical shape having a longitudinal direction, and applying an electromagnetic wave by applying a high-frequency current. A coil for generating a magnetic flux for induction heating, wherein at least one or more inflection portions wound in a state where the curvature is changed are formed at portions other than the folded portions serving as both ends in the longitudinal direction thereof; It is characterized by having.

In the exciting coil according to the first aspect of the present invention, the magnetic flux density at the inflection portions formed at portions other than the folded portions, which are both end portions in the longitudinal direction, increases, and at the portions other than the folded portions. The electromagnetic induction heating performance is increased, and the difference from the electromagnetic induction heating performance at the folded portion is reduced. Thereby, the non-uniformity of the electromagnetic induction heating in the entire exciting coil is reduced. In addition, the above-mentioned elliptical shape usually refers to a shape in which a portion in the longitudinal direction is linear and both ends are curved, but the portion in the longitudinal direction is a uniform curve. It also includes a shape that is in a state (a general elliptical shape).

The exciting coil of the present invention (the second invention), which can achieve the above object, has a conductive wire wound spirally and generates a magnetic flux for electromagnetic induction heating by applying a high-frequency current. The coil is characterized in that both the lead wire portions respectively drawn from the winding start portion and the winding end portion of the coil are wound without crossing the winding portion.

In the exciting coil according to the second aspect of the present invention, since both the lead wire portions respectively drawn from the winding start portion and the winding end portion do not cross the winding portion, the magnetic field in the winding portion is not disturbed, and the magnetic field in the winding portion is not disturbed. The unevenness of the electromagnetically induced heat due to the disturbance is reduced. As a result, the non-uniformity of the electromagnetically induced heat in the lead wire portion of the exciting coil is eliminated. Note that a coil wound in a spiral shape includes a coil whose shape has a winding portion at the center portion and has substantially no space at the center portion as illustrated in FIG. Because the core is placed at the center of the coil for the purpose of increasing the magnetic flux density, the center (at least the space for installing the core)
It is preferable that the winding state is such that a space exists.

Further, according to the present invention (third aspect) which achieves the above object,
The excitation coil according to the invention) is a combination of the first invention and the second invention. That is, as in the second invention, the exciting coil of the first invention is wound so that both the lead wire portions respectively drawn from the winding start portion and the winding end portion of the coil do not cross the winding portion. It was done.

In the exciting coil according to the third aspect of the present invention, both the above-described effects of the first aspect and the effects of the second aspect can be obtained. Thereby, the non-uniformity of the electromagnetic induction heating in the entire exciting coil is further reduced.

Each of the exciting coils according to the first to third aspects of the present invention preferably has a winding part of 3 to 3 turns.
0. If the number of turns is less than three, it is necessary to generate more magnetic flux in order to obtain a required amount of heat generated by electromagnetic induction heating, so that a larger amount of alternating current must be applied. Conversely, if the number of turns exceeds 30, the length of the conductive wire constituting the coil becomes longer,
The resistance loss of the coil increases, and the entire coil tends to increase in size.

In each of the exciting coils according to the first to third aspects of the present invention, preferably, the conductive wire is a litz wire. When an exciting coil is manufactured using this litz wire, the skin effect when a high-frequency current is applied can be prevented, heat loss can be reduced, and due to its good formability, bending during coil manufacturing can be achieved. Processing and winding work are facilitated, and the manufacture of the exciting coil is facilitated.

The exciting coil according to the second or third aspect of the present invention, when the coil is a coil formed by winding a conductive wire in a two-dimensional spiral shape, preferably from the winding start portion of the coil. It is wound from the outer side of the winding part to the inner side (or from the inner side to the outer side) up to the halfway to the winding end, and is wound to the inner side (or the outer side). From the intermediate portion to the end of the winding, it is assumed that the winding is performed so as to return from the inner peripheral side to the outer peripheral side (from the outer peripheral side to the inner peripheral side). Here, the term "two-dimensional spirally wound" means that the conductive wire is wound from the inner circumferential side to the outer circumferential side (or the outer circumferential side) so that the winding direction of the conductive wire is substantially along a certain surface (a flat surface or a curved surface). From the side to the inner peripheral side) (referred to as a wound state in which the sheet is unfolded in the direction of the X and Y coordinate axes).

In the case where the exciting coil of the second or third aspect of the present invention is a coil formed by winding a conductive wire in a three-dimensional spiral shape, preferably, the exciting coil starts from the winding start portion of the coil. From the one end of the winding part to the other end, it is wound in a three-dimensional spiral shape up to the middle part toward the winding end, and from the halfway wound to the other end. It is assumed that the winding end portion is wound in a three-dimensional spiral shape so as to return from the other end to the one end. here,
The three-dimensional spiral winding means that the conductive wire is wound three-dimensionally like a spiral staircase (X,
A winding state in which it is three-dimensionally developed in the directions of the Y and Z coordinate axes. For example, spiral shape).

Each of the above-mentioned exciting coils including the exciting coil of the second or third invention is preferably wound so that the winding start portion and the winding end portion are close to each other. In this case, the lengths of a plurality (usually two) of the lead wires of the coil can be made substantially the same as each other, and furthermore, unnecessarily long lead wires are required for connection with an excitation circuit serving as a power supply unit. No portion is generated and the length can be reduced as much as possible. As a result, the occurrence of resistance loss and radiation noise due to the useless length of the lead wire portion is reduced. Reduce power consumption during electromagnetic induction heating,
An adverse effect on other components due to radiation noise can be avoided.

On the other hand, an image heating apparatus according to the present invention, which achieves the above object, has an exciting coil wound in an elliptical shape having a longitudinal direction, a magnetic flux generating means for generating a magnetic flux for electromagnetic induction heating, and a magnetic flux generating means. An induction heating element disposed in a state facing the generation means, and electromagnetically generating heat by magnetic flux generated from the magnetic flux generation means, and an image heating device for heating an image formed of a developer by the heat of the induction heating element. The exciting coil is any one of the exciting coils described above. This image heating device is configured as, for example, a transfer fixing device that transfers an image formed on an image carrier to a recording material and simultaneously heat-fixes the image, and as a fixing device that thermally fixes an image carried on the recording material. Configuration, but not limited to this.

In the image heating apparatus, when the exciting coil of the magnetic flux generating means is an exciting coil of the type having the inflection portion, preferably, the portion of the exciting coil where the inflection portion is formed is provided. Then, a magnetic core having at least a curved surface portion having a shape corresponding to the curvature of the inflection portion is disposed. In this case, the magnetic flux generated from the inflection portion of the exciting coil passes through the curved surface portion of the magnetic core, and is reliably generated in a dense state along the curvature of the inflection portion. As a result, the magnetic flux density at the inflection portion of the exciting coil increases, and the magnetic flux concentrated at the portion of the induction heating element corresponding to the inflection portion can be reliably penetrated without loss, and the location of the induction heating element can be accurately determined. Can be heated by electromagnetic induction.

Preferably, each of the image heating devices as described above has a position in the magnetic flux generating means opposite to the induction heating element side with respect to the excitation coil side and the excitation heating element side of the induction heating element. Places the magnetic core at the opposite side. In this case, a magnetic path is formed so that the magnetic flux generated from the exciting coil passes through the magnetic core without fail, so that the magnetic coupling is enhanced, the power factor is improved, and the magnetic flux is induced. It is possible to prevent a loss due to sneaking into a part different from the heating element.

[0030] In particular, in the image heating apparatus in which the magnetic cores are arranged at both of the above positions, the magnetic cores are arranged at a plurality of independent magnetic cores arranged at intervals in the longitudinal direction of the exciting coil. It is more preferable that the magnetic core blocks are composed of blocks and that the respective magnetic core blocks are alternately shifted so as not to face each other between the two positions. In this case, the magnetic flux generated from the exciting coil reaches the induction heating element evenly in the longitudinal direction.

In any of the above image heating apparatuses, at least a portion of the induction heating element that generates electromagnetic induction heat may be formed of a ferromagnetic material such as iron, cobalt, and nickel. However, preferably, it is formed of a non-magnetic material of copper, silver, or aluminum, or a metal or alloy having a resistivity equal to or less than these. Here, the resistivity equal to or less than that of the nonmagnetic material means, for example, 2.7 × 10 ⁻⁸ Ωm or less.

Further, the present invention comprises an image heating device for transferring and fixing or fixing an image formed of a developer on a recording material while heating the recording material, and using the image heating device as described above as the image heating device. It is.

[0033]

[First Embodiment] FIG. 1 is a schematic diagram showing an exciting coil 1A according to a first embodiment of the present invention.

The exciting coil 1A is formed by winding the conductive wire 2 in an elliptical shape having a longitudinal direction and changing the curvature to a portion 1c other than the folded portions 1a and 1b at both ends in the longitudinal direction. At least one or more inflection portions 3 are formed. In the illustrated example, three inflection portions 3a, 3b, 3c are formed on one side of a portion 1c other than the folded portions 1a, 1b.
A total of six inflection portions 3a to 3f are formed on both sides of c. In the illustrated excitation coil 1A, the conductive wire 2
Although drawn in a completed state for each winding, this is for convenience of explanation or illustration, and in fact, a series of wires is spirally wound (the same may be applied to drawings other than FIG. 1). ). Although not shown, the exciting coil 1A has a lead wire portion that is drawn out from the winding start portion and the winding end portion and is connected to an excitation circuit or the like.

The curvature R (R1) of the curvatures (af) of the inflection portion 3
To R6) are appropriately selected according to the degree of increase in the magnetic flux density in the portion 1c other than the folded portions 1a and 1b, and accordingly the degree of increase in the amount of heat generated by electromagnetic induction heating. The curvatures R (R1 to R6) are the curvature radii Ra and Rb (= R) of the folded portions 1a and 1b.
a) or the radius of curvature Ra,
It may be smaller than Rb or conversely larger.

The inflection portions 3 (a to f) may be curved (excluding bent portions) to either the outside or the inside of the portion 1c other than the folded portion. For example, when the inflection portion 3 is not formed in the portion 1c (a linear portion indicated by a two-dot chain line in the drawing), the portion 1c
Widths K1 and K2 protruding with respect to the coil width (winding width) J of
Should be set in a range of about 0.5 × J to 1.0 × J. In particular, when the projection width K1 of the inflection portion 3 projecting outside the coil is set within the above range, the coil 1
This is advantageous because the size of A is also avoided.

Further, as shown in FIGS. 2A and 2C, the inflection portion 3 may be formed only on one side of the portion 1c other than the coil folded portion. When an induction heating element that generates electromagnetic induction by magnetic flux for electromagnetic induction heating generated by application of an alternating current from the excitation coil 1A moves so as to pass through the excitation coil 1A in a certain direction (the direction of arrow A). As shown in FIG. 2A, a portion 1c on one side which is located on the upstream side in the moving direction B of the induction heating element may be provided.

In addition to this, the inflection portion 3 is formed so as to bend only outside (or inside, not shown) of the portion 1c other than the folded portion of the coil 1A as illustrated in FIG. From the viewpoint of efficiently increasing the magnetic flux density at the portion 1d of the coil and eventually increasing the amount of heat generated by electromagnetic induction heating, as shown in FIG. Those formed to bend in both directions are preferable.

Further, the inflection portion 3 may be formed under different conditions on both sides of the portion 1c other than the folded portion as illustrated in FIG. Excitation coil 1A illustrated in FIG. 2B has five inflection portions 3a to 3e formed on one side of portion 1c other than the folded portion, while the five inflection portions 3a are formed on the remaining side of portion 1c. In this embodiment, four inflection portions 3f to 3i are formed at positions corresponding to the switching portions (boundary portions) 3 to 3e. In this case, when the moving induction heating element is heated by electromagnetic induction heating, the five inflection portions 3a to 3e on one side and the four inflection portions 3f to 3i on the other side generate electromagnetic induction heat. The increase in the amount of generated heat can be complemented with each other in combination with the movement of the induction heating element, which is advantageous for making the distribution of generated heat uniform.

As the conductive wire 2 constituting the exciting coil 1A, a litz wire obtained by twisting a plurality of individually insulated (coated with an insulating material) conductive wires is used. For example, a litz wire (about 2 to 6 mm in diameter) formed by twisting 20 to 40 conductive wires each having a diameter of about 0.1 to 0.3 mm is used. By using such a litz wire, even the excitation coil 1A having the inflection portion 3 as described above can be easily manufactured. The production may be performed, for example, by preparing a winding member having the inflection portion 3 formed thereon and winding the winding member with an automatic winding machine. The number of turns of the winding portion of the exciting coil 1A is relatively small, about 5 to 30 turns.

The exciting coil 1A usually forms a magnetic flux generating means by appropriately combining with a magnetic core, and connects a lead wire portion of the exciting coil to an exciting circuit or the like to apply a predetermined alternating current. It is used to generate magnetic flux for electromagnetic induction heating. Further, depending on the application, the coil alone may be used as a so-called coreless magnetic flux generating means without being combined with the magnetic core.

[Embodiment 2] FIGS. 3A, 4A and 5
(a) is a schematic diagram showing an exciting coil 1B according to Embodiment 2 of the present invention.

In each of the illustrated exciting coils 1B, the conductive wire 2 is spirally wound, and both of the lead wire portions 2c and 2d drawn out from the winding start portion 2a and the winding end portion 2b of the coil, respectively. Is wound without crossing the winding portion 2e. this house,
Each of the excitation coils 1B shown in FIGS. 3A and 4A is formed by winding the conductive wire 2 in a two-dimensional spiral shape (in a winding state such that the conductive wire 2 is spread out in the direction of the X and Y coordinate axes). In the excitation coil shown in FIG.
c, 2d outside the winding part 2e (outside the outermost periphery)
In the excitation coil shown in FIG. 4A, the lead wire portions 2c and 2d are drawn inside the winding portion 2e (inner than the innermost peripheral portion) (in this case, the drawing direction is perpendicular to the paper surface). ). In addition, the excitation coil 1B shown in FIG. 5A turns the conductive wire 2 into a three-dimensional spiral (X,
It is wound (in a winding state such that it is three-dimensionally developed in the directions of the Y and Z coordinate axes). Regarding the exciting coil 1B of FIG. 5A, the portion that is folded and wound is shown by a dotted line.

In manufacturing the excitation coil 1B shown in FIG. 3A, as shown in FIG. 3B, for example, as shown in FIG. 3B, a halfway portion from the winding start portion 2a to the winding end portion 2b of the coil (conductive wire 2). Until 2f, winding is performed from the outer peripheral side to the inner peripheral side of the winding part 2e (the first part shown in the upper part of the drawing).
(Partitioned portion), and from the intermediate portion 2f wound to the inner peripheral side to the winding end portion 2b, is wound so as to return from the inner peripheral side to the outer peripheral side (the second part shown in the lower part of the figure).
Split part). In the winding portion 2 of the exciting coil 1B, a wire rod 2 serving as a first divided part wound from the outer peripheral side toward the inner peripheral side and a wire rod serving as a second divided part wound from the inner peripheral side toward the outer peripheral side 2 and some places (mainly folded part 1
Although they intersect at an acute angle at (a, 1b), the magnetic fields (magnetic fluxes) generated at these acute intersections are hardly disturbed (the same applies to other examples).

At this time, by arranging the winding start portion 2a and the winding end portion 2b at close positions (adjacent positions), the winding state as shown in FIG. An exciting coil 1B in a close state is obtained. Thereby, the lead line portions 2c,
Both 2d can be made not to traverse the winding portion 2e, and can have the shortest and almost the same length.

In producing the excitation coil 1B shown in FIG. 4A, for example, as shown in FIG.
The conductive wire 2 is wound from the inner peripheral side to the outer peripheral side of the winding part 2e from the winding start part 2a to the halfway part 2g toward the winding end part 2b (first divided part shown in the upper part of the figure). The intermediate portion 2g wound up to the outer peripheral side and the winding end portion 2b are wound so as to return from the outer peripheral side toward the inner peripheral side (a second divided portion shown in the lower part of the figure). At this time, by arranging the winding start portion 2a and the winding end portion 2b at positions close to each other (adjacent positions), the winding state as shown in FIG. Exciting coil 1
B is obtained. Thereby, the lead line portions 2c, 2
Both of d can be the same state and length as in the case of the exciting coil 1B of FIG. 3A described above.

Further, in manufacturing the excitation coil 1B shown in FIG. 5A, as shown in a schematic sectional view of FIG. 5B (a schematic sectional view taken along line BB in FIG. 5A), the conductive wire 2 is From the winding start 2a to the winding end 2
The three-dimensional spiral winding (in the figure) from one end side (the winding start position side) of the winding part to the other end side (the turning position side away from the winding start position) from the one end side (winding start position side) of the winding part up to the middle part 2h toward b. The winding end portion 2b wound from the halfway portion 2h wound up to the other end portion is wound in a three-dimensional spiral so as to return from the other end portion to the one end portion side. (The winding portion indicated by the dotted line in the figure). At this time, the winding start portion 2a and the winding end portion 2
b is arranged at a close position (adjacent position) so that it is in a wound state as shown in FIG.
Excitation coil 1B in which c and 2d are close to each other is obtained. Thereby, both the lead wire portions 2c and 2d can be set in the same state and length as in the case of the exciting coil 1B of FIG. 3A described above.

Each of these exciting coils 1B (FIGS. 3, 4a and 5a) uses a litz wire as the conductive wire 2 similarly to the exciting coil 1A according to the first embodiment. The number of turns is about 5 to 30. Furthermore, this exciting coil 1B
Usually, a magnetic flux generating means is formed by appropriately combining with a magnetic core, and a lead wire portion of the exciting coil is connected to an exciting circuit or the like to apply a predetermined alternating current to generate a magnetic flux for electromagnetic induction heating. Used as Also,
Depending on the application, as in the case of the first embodiment, the coil may be used alone as a so-called coreless magnetic flux generating means without being combined with the magnetic core.

[Third Embodiment] FIG. 6 is a schematic diagram showing an excitation coil 1C according to a third embodiment of the present invention. The exciting coil 1C is the same as the exciting coil 1A according to the first embodiment.
And a characteristic portion of the exciting coil 1B according to the second embodiment. The detailed configuration is the same as that of the first and second embodiments (the same reference numerals are used for the same components. Attached).

More specifically, this exciting coil 1C has a structure shown in FIG.
The base is based on the excitation coil 1A having the inflection portion 3 shown in FIG. 3A, and both the lead-out portions 2c and 2d are wound so as not to cross the winding portion 2e like the excitation coil 1B shown in FIGS. 3A and 3B. (FIG. 6b). Also in this exciting coil 1C, if necessary, the lead wire portions 2c,
2d may be configured to be drawn inside the winding portion as illustrated in FIGS. 4a and 4b.

[Fourth Embodiment] FIG. 7 is a schematic diagram showing an image heating apparatus 50 according to a fourth embodiment of the present invention. The image heating device 50 is configured as a transfer and fixing device 51 that transfers a toner image T composed of a developer formed by a predetermined image forming unit onto a recording material P such as recording paper and simultaneously thermally fixes the toner image.

This transfer fixing device 51 has an excitation coil 10 and a magnetic core 20 wound in an elliptical shape having a longitudinal direction, and a magnetic flux generator 3 for generating a magnetic flux for electromagnetic induction heating.
0, and a transfer belt 41 as an induction heating element which is disposed in a state facing the magnetic flux generating device 30 and generates electromagnetic induction by the magnetic flux generated from the magnetic flux generating device 30. An excitation coil 1A (FIG. 1a) according to the first embodiment is applied as the 30 excitation coils 10. In the figure, reference numerals 42 to 44 denote first to third support rolls (the third support roll 44 is a drive roll) for rotatably supporting the endless transfer belt 41 in the direction of arrow A, and reference numeral 45 denotes a drive roll. This is a rotatable pressure roll that presses the recording material P against the transfer belt 41 at a position facing the second support roll 52.

As shown in FIG. 8, the magnetic flux generator 30
A non-magnetic and long plate-shaped pedestal 31 provided on the inner peripheral surface side of the transfer belt 41 in a width direction of the belt (a width in a direction perpendicular to the rotation direction A), and a transfer belt of the pedestal 31 An elongated plate-shaped magnetic core 21 disposed on a surface facing 41 and a conductive wire 2 wound in a state of being wound around the magnetic core 21 (side surface portion). The main components of the exciting coil 10 (1A) and an exciting circuit (feeding device) 35 to which the lead wires 2c and 2d of the exciting coil 10 are connected to apply a high-frequency (for example, 20 to 40 kHz) alternating current to the coil are provided. Unit is configured. Further, the magnetic flux generator 30 in this embodiment further includes a plurality of short plate-like (rear side) magnetic core blocks on the rear side of the pedestal 31 (the surface opposite to the surface on which the magnetic core 21 is disposed). 22 and a plurality of short plate-like () attached to the pedestal 32 at a position facing the pedestal 31 with the transfer belt 41 interposed therebetween and in a positional relationship corresponding to the back magnetic core block 22. A magnetic core block 23 is provided.

Here, the exciting coil 10 (1A) corresponds to FIG.
As shown in FIG. 8A and FIG. 8C, portions other than the folded portions 1a and 1b, which are both ends of the coil wound in an elliptical shape, are upstream and downstream in the rotation direction A of the transfer belt 41. A total of six inflections 3 (3a
~ 3f) formed. These six inflection parts 3a-
Each of the curvature radii R1 to R6 of 3f is the same, and in the present embodiment, the folded portion 1
The curvature radii Ra and Rb of a and 1b are set to be the same. In this embodiment, the radius of curvature R of the inflection portion 3 (including the folded portion) is set within a range of 5 to 55 mm. The exciting coil 10 is connected to the conductive wire 2.
Is wound in a spiral so that the number of turns is about 5 to 30. And, this exciting coil 10
Has a length in the longitudinal direction of about 200 to 600 mm and a width in a direction orthogonal to the longitudinal direction of 20 to 60 mm.
It is of the order of magnitude.

The magnetic core 21 and the magnetic core block 2
Both 2 and 23 are formed using fillite or the like. In this embodiment, as shown in FIG. 8C and FIG. 11, the magnetic core 21 is used in a state where the magnetic cores 21a to 21c divided into three are integrated. The magnetic core blocks 22 and 23 are alternately shifted so as not to face each other as shown in FIGS. 8B and 8C. Pedestal 31, 3
2 is, for example, heat-resistant glass, liquid crystal polymer, PP
It is formed using a heat-resistant resin such as S (polyphenylene sulfide) and PC (polycarbonate).

On the other hand, as shown in FIG. 9, the transfer belt 41 has a sheet-like base layer 41a having excellent heat resistance, a conductive layer (electromagnetic induction heating layer) 41b laminated thereon, and an uppermost layer. This is an endless belt having a three-layer structure including a surface release layer 41c.

The base layer 41a has a thickness of 10 to 10
It is formed in a sheet shape of 0 μm.
In consideration of the electrostatic transfer, it is preferable to be formed of a semiconductive material. As the semiconductive material,
For example, a material obtained by dispersing a conductive material such as carbon black in a synthetic resin having high heat resistance represented by polyester, polyethylene terephthalate, polyether sulfone, polyether ketone, polysulfan, polyimide, polyimide amide, polyamide and the like is used. Is done. Conductive layer 41
b is a metal layer of, for example, copper, having a thickness of 0.05 to 50 μm. The laminate is formed by a method such as plating. The surface release layer 41c is formed of a synthetic resin or the like having a release property from the toner image. This surface release layer 41c
Is preferably an elastic layer having releasability in consideration of avoiding poor transfer fixing and uneven image gloss.
If necessary, the surface release layer 41c may have a two-layer structure in which a release layer made of a synthetic resin is formed on the upper layer side and an elastic layer is formed on the lower layer side to separate functions. Good. In the case of a single-layer structure having a surface release layer having elasticity, or in the case of the above-described two-layer structure, the thickness of the layer to be the elastic layer is 10 μm or more, preferably 2 μm or more.
It is good to be 0 μm or more.

The pressure roll 45 is supported by a contact / separation mechanism so as to contact and separate from the transfer belt 41 supported by the second support roll 52. In other words, the toner image T on the transfer belt 41 is in contact with the transfer material P when the toner image is transferred and fixed to the recording material P, and is separated at other times.

Next, the operation of the transfer fixing device 51 will be described.

First, the transfer belt 41 is rotated in the direction of arrow A by a third support roll 44 which is a driving roll, and a toner image is formed on the transfer belt 41 by a desired image forming device (means) (not shown). T is formed. When the timing at which the toner image T is transferred and fixed to the recording material P sent between the fixing belt 41 and the pressure roll 35 (nip portion) comes, the fixing belt 41 faces the magnetic flux generator 30. When the toner image passes through, the toner image is heated and melted by electromagnetic induction heating.

That is, in the magnetic flux generator 30, FIG.
As shown in (1), a high-frequency AC current is applied from the excitation circuit 35 to the excitation coil 10, and a magnetic flux (magnetic field line H) penetrating the conductive layer 41b of the transfer belt 41 in the thickness direction is generated from the excitation coil 10. By doing so, the conductive layer 41
b, an eddy current is generated to generate Joule heat, and the conductive layer 41b generates electromagnetically induced heat. As a result, the conductive layer 41b
Is transferred to the surface layer (surface release layer 41c) of the transfer belt 41 and the surface layer side of the fixing belt 41 is heated.
The toner image T on the fixing belt 41 is heated and melted.

Subsequently, the toner image fused on the transfer belt 41 is transferred to the fixing belt 4 in accordance with the conveyance of the recording material P.
Due to the pressure of the pressure roll 45 contacting the recording material 1, the recording material P is brought into close contact with the recording material P and is rapidly cooled by contact with the recording material P at about room temperature. Thus, while the recording material P passes through the nip between the intermediate transfer belt 41 and the pressure roll 45, the toner image on the transfer belt 41 is transferred to the recording material P and fixed. Thus, the transfer and fixing by the transfer and fixing device 51 is performed, and a toner image is formed on the recording material P.

When the magnetic flux generating device 30 heats the transfer belt 41 by electromagnetic induction, the portions other than the folded portions 1a and 1b of the exciting coil 10 are made up of a total of six inflection portions 3a to 3f formed at those portions. As a result, the magnetic flux density increases and the electromagnetic induction heating performance increases. For this reason, the difference between the electromagnetic induction heating performance of the portion of the excitation coil 10 and the electromagnetic induction heating performance of the folded portions 1a and 1b is reduced, and as shown in FIG. 11, (the conductive layer 41b of) the transfer belt 41. The electromagnetic induction heating region is also substantially uniformly heated (heated) in the width direction. Accordingly, the toner image T on the transfer belt 41 is heated and melted substantially uniformly in the width direction of the belt 41, and thus the recording material P
And transfer and fixation can be performed uniformly and satisfactorily.

Moreover, in the magnetic flux generator 30, since the magnetic core blocks 22, 23 are alternately arranged so as not to be opposed to each other, FIG.
As shown in the figure, the magnetic flux (lines of magnetic force H) generated from the exciting coil 10 is generated by the magnetic core block 22 in the longitudinal direction.
23 are formed in a zigzag manner without unevenness, so that (the conductive layer 41b of) the transfer belt 41 can be uniformly heated by electromagnetic induction in the width direction. As a result, the toner image T on the transfer belt 41 can be heated and melted more uniformly in the width direction of the belt 41, so that the toner image T can be transferred and fixed more uniformly and well on the recording material P. It is possible to be.

In the image heating device 51 according to the fourth embodiment, the exciting coil 1 of the magnetic flux generator 30 is used.
As 0, it is also possible to apply the exciting coil 1A of another mode illustrated in FIG. 2 and the like in the first embodiment. The exciting coil 10 is connected to the lead wire portions 2c, 2c.
It is also possible to apply the excitation coil 1C (FIG. 6) according to the third embodiment configured so that d does not cross the winding part.

In some cases, the magnetic flux generator 30 may not be provided with the magnetic core 22 on the back side or the magnetic core 23 on the opposite side as shown in FIG. . In addition, the magnetic flux generator 30 is provided with a magnetic core 24 having an E-shaped cross section as illustrated in FIG. 13 as the magnetic core 21 provided on the center side regardless of the presence or absence of the magnetic core 22 and the magnetic core 23. May be configured. When the exciting coil 10 is arranged in the concave portion by applying such a magnetic core 24, in addition to the inner core portion 24a located inside the winding portion of the exciting coil 10, the exciting coil 10 is located outside the winding portion. Outer core portion 24
Since b and c are present, the magnetic flux (lines of magnetic force H) generated from the exciting coil 10 forms a magnetic path surrounding the coil and is favorably generated.

Further, the magnetic flux generating device 30 has the structure shown in FIG.
As an example, a curved surface portion having a shape corresponding to the radius of curvature R (see FIG. 1A) of the inflection portion 3 is provided at the portion of the exciting coil 10 where the inflection portion 3 is formed as the magnetic core 21. May be arranged to arrange the magnetic core 25 having the following. In this case, the magnetic core 25 having the curved surface portion may be a single structure, but in consideration of the manufacturing convenience and the like, is constituted by a plurality of divided magnetic cores 25a to 25c, When used, it is in a state of being integrated. In the illustrated example, the divided magnetic core 25a has a curved surface portion corresponding to the radius of curvature (R1, R4) of the inflection portions 3a, 3d.
b, the radii of curvature of the inflection portions 3b and 3e (R2, R
5), and the radius of curvature (R) of the inflection portions 3c and 3f for the divided magnetic core 25c is assumed.
(3, R6). In the case of such a configuration, the magnetic flux in each inflection portion 3 of the exciting coil 10 can be more reliably concentrated, and the electromagnetic induction heating performance in the entire coil can be made uniform. The magnetic cores 21a and 21c disposed near the bent portions 1a and 1b of the exciting coil 10 are:
Since it is not necessary to increase the magnetic flux density at the portion, the core having the curved portion as described above is not used.

Further, the magnetic flux generator 30 includes an inflection portion 3 of the exciting coil 10 as exemplified by a two-dot chain line in FIG.
Is formed, and a magnetic core 26 having a curved surface portion having a shape corresponding to the radius of curvature R of the inflection portion 3 (see FIG. 1A) is arranged outside the winding portion. Good. When the magnetic core 26 having the curved surface portion is provided, the same effect as when the magnetic core 25 is provided can be obtained. Also, the magnetic core 26 has a split configuration (26) as in the case of the magnetic core 25 described above.
a to 26c). The magnetic core 26
Is not limited to being disposed on one side outside the coil winding portion (upstream in the rotation direction A of the transfer belt 41), and may be disposed both outside the winding portion. Further, the magnetic core 26 is not limited to the case where the magnetic core 25 is arranged together with the magnetic core 25 arranged inside the above-mentioned coil winding portion.
(However, the magnetic core 21 may be provided), but may be provided alone.

Further, the magnetic flux generating device 30 has the structure shown in FIG.
As shown in FIG. 2, the magnetic coil 22 on the back surface and the magnetic coil 23 on the opposing surface can be provided so as to face each other. However, when provided in such a state, a portion 41d of the transfer belt 41 corresponding to the portion 27 where both the magnetic coil 22 and the magnetic coil 23 do not exist is generated, and the magnetic flux (C) from the coil is generated in the portion 41d. The line of magnetic force H) may not penetrate sufficiently, and the amount of heat generated by electromagnetic induction may also be uneven due to such magnetic flux unevenness. In this regard, when the magnetic coils 22 and the magnetic coils 23 are arranged so as to be alternately shifted so as not to face each other as described above (FIGS. 8 and 12), there is no such fear.

[Fifth Embodiment] FIG. 16 shows an image forming apparatus according to a fifth embodiment of the present invention. This image forming apparatus is one to which the transfer fixing device 51 according to the fourth embodiment is applied.

In FIG. 16, reference numeral 61 denotes a photosensitive drum on the surface of which an electrostatic latent image is formed by a potential difference, 62 denotes a charging device for charging the surface of the photosensitive drum 61 almost uniformly, 63
Is an exposure device that irradiates a laser beam corresponding to image information of each color component on the surface of the charged photosensitive drum 61 to form an electrostatic latent image. 64 is yellow (Y), magenta (M), and Ian (C). , A black (K) toner, and a developing device for developing the electrostatic latent image on the photosensitive drum 61 with the toner of each color to form a toner image T. A primary transfer roll for transferring the toner image to the transfer belt 41 of the transfer fixing device 51; a cleaning device 65 for cleaning the surface of the photosensitive drum 61 after the transfer;
Reference numeral denotes a neutralization lamp for neutralizing the surface of the photosensitive drum 61.

In the same figure, reference numeral 51 denotes the fourth embodiment.
(See FIG. 7), in which the transfer belt 41 is used as an intermediate transfer belt and the first support roll 4 is used.
2 has the same configuration as that of the fourth embodiment except that the second transfer roll is a primary transfer roll, the second support roll 43 is a drive roll, and the third support roll 44 is a tension roll. (FIGS. 7 to
See FIG. 12). In particular, the exciting coil 10 having the inflection portion 3 is used as the exciting coil of the magnetic flux generator 30.

Further, in the same figure, reference numeral 67 denotes a sheet feeding unit for accommodating the recording material P, and 67a denotes a sheet feeding unit 67.
A sending mechanism for feeding the recording material P one by one from the inside, a registration roll 68a for feeding the recording material P between the intermediate transfer belt 41 and the pressure roll 45 (a nip portion) at a predetermined timing, and a recording material 68b for feeding the recording material P A discharge roll 69 that discharges and conveys the recording material P to the outside is a discharge tray that stores the discharged recording material P.

In this image forming apparatus, the photosensitive drum 6
Reference numeral 1 denotes an organic photosensitive material (OP) on the surface of a cylindrical conductive substrate.
C) or a photosensitive layer made of amorphous silicon or the like, and the conductive substrate is electrically grounded. The exposure device 63 includes a laser scanner 63a,
It is composed of an optical system 64b such as a reflection mirror. The developing device 64 includes four developing devices 64Y, 64M, 64C, and 64K that respectively store the four color toners. The developing devices 64 are disposed on a rotating support so that the developing devices 64 can face the photosensitive drum 61. ing. Each developing unit 64 includes:
A developing roll that carries and transports the toner is provided, and the developing roll has a developing bias in which a DC voltage is superimposed on an AC voltage (for example, a rectangular wave alternating voltage having an alternating voltage Vp-p of 2 kV and a frequency f of 2 kHz). (A superimposed voltage of 400 V) is applied. Each developing device 64 is supplied with a toner of a predetermined color from a developer supply device 64a. Further, the intermediate transfer belt 41
The transport speed of the recording material P and the nip width thereof are set so that the recording material P exists in the nip between the pressure roll 45 and the transfer belt 41 for a time of 10 to 50 msec.

Next, the operation of such an image forming apparatus will be described.

First, the photosensitive drum 61 is rotated in the direction of the arrow in FIG. 16 and the surface thereof is charged substantially uniformly by the charging device 62. Then, the pulse width is changed from the exposure device 63 in accordance with the yellow image signal of the image information. The modulated laser light is irradiated to form a yellow component electrostatic latent image on the photosensitive drum 61. Next, the electrostatic latent image is moved to a position opposed to the photosensitive drum 61 by the yellow developing device 6.
It is developed by 4Y to become a yellow toner image. Next, this yellow toner image is transferred to the intermediate transfer belt 41 by the operation of the primary transfer roll 42 at a primary transfer portion, which is a contact portion between the photosensitive drum 11 and the intermediate transfer belt 41. The intermediate transfer belt 41 rotates in synchronization with the photosensitive drum 61, and prepares for the primary transfer of a toner image of the next color with the yellow toner image carried on the belt surface.

On the other hand, after the surface of the photosensitive drum 61 is cleaned by the cleaning device 65, the photosensitive drum 61 is charged substantially uniformly again by the charging device 62, and thereafter, the exposure device 63 responds to the magenta image signal in response to the magenta image signal. An electrostatic latent image of the components is formed. This electrostatic latent image is developed by a magenta developing device 64M that rotates and moves to a position facing the photosensitive drum 61 to become a magenta toner image. Next, the yellow toner image is transferred to the intermediate transfer belt 41 by the action of the primary transfer roll 42 in the primary transfer section. Subsequently, the above-described process up to the primary transfer of each toner image is similarly repeated for cyan and black image signals. In this way, the four color toner images are transferred onto the intermediate transfer belt 41 in a state where the toner images are superimposed. At this time, during the primary transfer of the final color black toner image or the like, the recording material P is transferred from the paper feeding unit 67 to the nip portion between the intermediate transfer belt 41 and the pressure roll 45 via the paper conveyance path such as the registration roll 68a. The sheet is conveyed to a certain secondary transfer section.

The four color toner images transferred onto the intermediate transfer belt 41 are heated when passing through a heating area facing the magnetic flux generator 30 disposed on the upstream side of the secondary transfer portion. You. That is, in accordance with the passage of the toner image, the magnetic flux generator 30 applies a high-frequency alternating current from the excitation circuit 35 to the excitation coil 10 as described in the fourth embodiment, and The toner image is heated by causing 41b to generate heat by electromagnetic induction and heating the belt surface. As a result, the toner image is in a molten state before reaching the secondary transfer portion.

Particularly, at this time, since the exciting coil 10 of the magnetic flux generator 30 has the inflection portion 3 (see FIG. 8), the intermediate transfer belt 4 is formed as in the case of the fourth embodiment.
1 is heated substantially uniformly by electromagnetic induction heating over its width direction (see FIG. 11), so that the toner image is also heated substantially uniformly. Further, since the magnetic flux generator 30 is provided with the magnetic cores 21 to 23 (see FIG. 8), the intermediate transfer belt 4 is provided as in the case of the fourth embodiment.
1 is more uniformly heated in the width direction by electromagnetic induction heating (see FIG. 12), and thus the toner image is also heated substantially uniformly.

Next, the toner image melted on the intermediate transfer belt 41 is brought into close contact with the recording material P by the pressure of the pressure roll 45 which comes into contact with the conveyance of the recording material P at the secondary transfer portion. Further, the recording material P has a secondary transfer portion of 10 to 50 ms.
The molten toner image is rapidly cooled by the recording material P by passing through the time ec. Thus, the toner image on the intermediate transfer belt 41 is transferred and fixed to the recording material P as described in the fourth embodiment. Further, the recording material P at this time removes heat from the toner image and the intermediate transfer belt 41 and is sent out from the nip portion. At this time, the temperature of the toner image at the exit of the nip portion is lower than the softening point temperature because the nip width of the secondary transfer portion and the conveyance speed of the recording material P are appropriately set as described above. . Therefore, the cohesive force of the toner is increased, and the toner image is almost completely transferred to the recording material P with almost no offset (a phenomenon that the toner image remains on the intermediate transfer belt 41).

As described above, a full-color image is formed on the recording material P which has passed through the nip portion (of the secondary transfer portion) of the transfer fixing device 51, and is finally discharged onto the discharge tray 69 by the discharge roll 68b. . Thus, the basic operation of full-color image formation by this image forming apparatus is completed.

In this image forming apparatus, the respective components (the excitation coil 10, the magnetic cores 21 to 22, etc.) of the transfer fixing device 51 can be appropriately changed in the same manner as in the fourth embodiment. It is possible.

[Sixth Embodiment] FIG. 17 is a schematic diagram showing an image heating apparatus 50 according to a sixth embodiment of the present invention. The image heating device 50 is configured as a fixing device 52 that thermally fixes a toner image T composed of a developer formed by a predetermined image forming unit to a recording material P such as recording paper.

The fixing device 52 controls the toner image T
Roll 71 disposed in a direction perpendicular to the conveying direction of the recording material P carrying the recording material P, and an exciting coil 12 and a magnetic core 20 wound in an elliptical shape along the axial direction of the pressure roll 71 A magnetic flux generator 30 for generating a magnetic flux for electromagnetic induction heating, and an induction heating element disposed opposite to the magnetic flux generator 30 and generating electromagnetic induction by a magnetic flux generated from the magnetic flux generator 30 And a belt supporter 72 that rotatably supports the fixing belt 46 in a substantially cylindrical shape from the inner space side and presses against the pressure roll 71 to form a fixing nip portion. The excitation coil 1 </ b> A according to the first embodiment is provided as the excitation coil 12 of the magnetic flux generator 30.
(FIG. 1a) is applied.

The pressure roll 71 is made of a metal roll core 7.
A heat-resistant elastic layer 71b is formed on the outer peripheral surface of 1a, and is rotated in an arrow direction by an electric motor (not shown). Also, the belt support 7
Reference numeral 2 denotes a box-shaped support frame 73 disposed on the inner space side of the fixing belt 46, and one end of the support frame 73 on the side opposite to the pressure roll 71, and fixes the fixing belt 46 to the pressure roll 71. Pressure pad portion 74 to be brought into pressure contact with the support frame 7
A lubricating oil application pad portion 75 formed at the other end of the fixing belt 46 to apply lubricating oil to the inner peripheral surface of the fixing belt 46; and a curved belt-like belt running to support the fixing belt 46 in a cylindrical and slidable manner. It mainly comprises a guide 76.

The pressure pad 7 on the belt support 72
Reference numeral 4 denotes a wide elastic pad member 74a for forming the fixing belt 46 with a wide fixing nip, and a concave pad holder 74b for holding the elastic pad member 74a.
And formed. As for the elastic pad member 74a, the surface in contact with the inner peripheral surface of the fixing belt 46 has a curved surface depressed inward along the cylindrical outer peripheral surface of the pressure roll 71, and has a low frictional force. Is formed on the low friction layer. Regarding the pad holder 74b, the passage exit side of the recording material P in the fixing nip portion is formed as a rounded pressure contact portion so as to slightly press and deform the elastic layer 71b of the pressure roll 71. On the other hand, the lubricating oil application pad portion 75 of the belt support 72 is formed of a porous material impregnated with lubricating oil.
Further, the belt traveling guide 76 has a low friction property against the inner peripheral surface of the fixing belt 46 and
It is formed of a non-magnetic material having thermal conductivity such that heat is not easily removed from the material.

The magnetic flux generator 30 is spaced apart (for example, 1 to 3 mm) at a position opposite to the pressure roll 71 of the fixing belt 46 supported in a cylindrical shape and along the cylindrical outer peripheral surface of the belt 46. Non-magnetic, long curved plate-shaped pedestal 33 disposed in a shape forming a curved surface, and a long plate-shaped magnetic core disposed on a surface of the pedestal 33 facing the fixing belt 46. 27, an exciting coil 12 (1A) made of a conductive wire 2 wound in a state of being wound around the magnetic core 24 (side surface portion), and a lead wire portion (2c, 2c) of the exciting coil 12 2d) is connected, and its main part is constituted by an exciting circuit (not shown) for applying a high-frequency (for example, 20 to 40 kHz) alternating current to the coil. Further, the magnetic flux generator 30 according to this embodiment
Further, a plurality of short plate-like (rear side) magnetic core blocks 28 are disposed on the rear side of the pedestal 33 (the surface opposite to the surface on which the magnetic core 27 is disposed), and a fixing belt is provided. A plurality of short plate-shaped (opposite surface side) magnetic core blocks 28 attached to a position opposite to the pedestal 33 with a position corresponding to the rear magnetic core block 27 with the 46 interposed therebetween are connected to the belt travel guide. 76.

Here, the excitation coil 12 (1A) is, as in the excitation coil 10 of the fourth embodiment, both ends of a coil which is entirely elliptically wound as shown in FIGS. 1a and 8c. At a portion other than the folded portions 1a and 1b,
In addition, a total of six inflection portions 3 (3a to 3a) are provided on the upstream and downstream sides in the rotation direction A of the fixing belt 46.
f) formed. In particular, this exciting coil 12
The difference from the excitation coil 10 in the fourth embodiment is that
The only difference is that the shape is made three-dimensional in accordance with the curvature (cylindrical shape) of the fixing belt 46 as an induction heating element.

The magnetic core 27 and the magnetic core block 2
8 and 29 have substantially the same configuration as the magnetic coils 21 to 23 in the fourth embodiment. In particular, the magnetic core blocks 28 and 29 are alternately shifted so as not to face each other as shown in FIGS. 8B and 8C.

On the other hand, similarly to the transfer belt 41 (FIG. 9) in the fourth embodiment, the fixing belt 46 has a film-shaped base layer having excellent heat resistance and a conductive layer (electromagnetic layer) laminated thereon. This is an endless belt having a three-layer structure including an induction heating layer) and an uppermost surface release layer. In FIG. 17, reference numeral 77 denotes a peeling unit for assisting peeling of the fixed recording material P from the fixing belt 46. The peeling means 77 is provided on the support member 77a by a peeling guide sheet 77b.
Is mounted so as to face the fixing nip. Reference numeral 78 denotes a non-contact type temperature sensor for measuring the surface temperature of the fixing belt 46. The measurement result of the temperature sensor 78 is transmitted to the excitation circuit 3 of the magnetic flux generator 30.
5 is fed back to a control unit such as the fixing belt 46.
Is controlled so that the surface temperature at the time of electromagnetic induction heating is maintained at a predetermined temperature.

Next, the operation of the fixing device 52 will be described.

First, when the pressure roll 71 rotates in the direction of the arrow, the fixing belt 46 rotates in the direction of the arrow A. Then, a recording material P carrying a toner image formed and transferred in a predetermined image forming unit (not shown) is conveyed so as to pass through a fixing nip portion. Operates and the fixing belt 4
6 is heated by electromagnetic induction heating. That is, as described in the fourth embodiment, a high-frequency alternating current is applied from the excitation circuit 35 to the excitation coil 12 to cause the conductive layer of the fixing belt 46 to generate heat by electromagnetic induction, thereby heating the surface of the belt.

At this time, the exciting coil 1 of the magnetic flux generator 30
2 is formed with the inflection portion 3 (see FIG. 8),
As in the case of the fourth embodiment, the fixing belt 46 is substantially uniformly heated by electromagnetic induction heating in the width direction thereof (see FIG. 11), and the toner image is also substantially uniformly heated. In addition, the magnetic flux generator 30 is
7 to 29, the fixing belt 46 is more uniformly heated by electromagnetic induction heating in the width direction thereof (see FIG. 12), and the toner image is also substantially uniform, similarly to the fourth embodiment. Will be heated.

Thus, the toner image on the recording material P passing through the fixing nip is heat-fixed to the recording material P by the pressure acting on the fixing nip and the heat of the fixing belt 46 heated. After passing through the fixing nip portion, the recording material P is generally supplied to the pad holder 74a near the exit of the fixing nip portion.
Due to the deformation of the fixing belt 46, the peeling is performed without being wrapped around the fixing belt 46, but the peeling unit 77 is more reliably peeled.

In the fixing device 52, the respective components (the excitation coil 12, the magnetic cores 27 to 29, etc.) can be appropriately changed in the same manner as in the fourth embodiment. Further, this fixing device 52 is replaced with, for example, the transfer fixing device 51 in the image forming apparatus according to the fifth embodiment (the magnetic flux generating device 30 is removed and the intermediate transfer belt 41 is replaced with a general intermediate transfer belt having no conductive layer). After the toner image on the intermediate transfer belt 41 is secondarily transferred to the recording material P, it can be used as a fixing device for fixing the toner image on the recording material P.

[Seventh Embodiment] FIG. 18 is a schematic diagram showing an image heating apparatus 50 according to a seventh embodiment of the present invention. The image heating device 50 is configured as a fixing device 53 for thermally fixing a toner image T composed of a developer formed by a predetermined image forming means to a recording material P such as recording paper.

Then, the fixing device 53 controls the toner image T
Roll 81 arranged and rotated in a direction perpendicular to the conveying direction of the recording material P carrying the recording material P, and wound in an elliptical and two-dimensional spiral shape along the axial direction of the pressure roll 81. A magnetic flux generator 30 having an exciting coil 15 and a magnetic core 20 for generating magnetic flux for electromagnetic induction heating, and a magnetic flux generated from the magnetic flux generator 30 which is disposed in a state facing the magnetic flux generator 30 And a fixing belt 47 serving as an induction heating element that generates heat by electromagnetic induction. The exciting coil 15B of the magnetic flux generator 30 is similar to the exciting coil 1B according to the second embodiment (FIG. 3A). Is applied. In FIG.
Reference numerals 2 and 83 denote support rolls that rotatably support the fixing belt 47. The support roll 82 is a pressure roll 81
A drive roll and a support roll 83 are disposed in opposition to the above, and are tension rolls for applying tension to the fixing belt 47.

As shown in FIGS. 18 and 19, the magnetic flux generator 30 is moved along the belt width direction at a position inside the belt portion of the fixing belt 47 moving from the tension roll 83 to the drive roll 82. An exciting coil 15 composed of a long magnetic core 38 having an E-shaped cross section and spaced apart from each other, and a conductive wire 2 wound in a state of being wound in a concave portion of the magnetic core 38. (1B) and an exciting circuit 35 connected to the lead-out portions (2c, 2d) of the exciting coil 15 and applying a high-frequency (for example, 20 to 40 kHz) alternating current to the coil, constitutes a main part thereof. I have.

Here, the exciting coil 15 (1B) uses a litz wire as the conductive wire 2 and is entirely wound in an elliptical and two-dimensional spiral shape as shown in FIG. Lead wire portions 2c and 2d respectively drawn from the winding start portion 2a and the winding end portion 2b of the coil.
Are wound without crossing the winding portion 2e. The production of the exciting coil 15 in such a winding state can be performed as illustrated in FIG. 3A. The exciting coil 27 according to the fourth embodiment is used as the exciting coil 27.
The same as 1 etc. is used.

The fixing belt 47 is substantially the same as the transfer belt 41 (FIG. 9) in the fourth embodiment, and has a sheet-like base layer 47a having excellent heat resistance, and a conductive layer ( This is an endless belt having a four-layer structure including an electromagnetic induction heating layer) 47b, an elastic layer 47c formed on the conductive layer 47b, and a release layer 47d formed on the elastic layer 47c (see FIG. 19). ).

Next, the operation of the fixing device 53 will be described.

First, when the drive roll 82 rotates in the direction of arrow A, the fixing belt 47 also rotates in the direction of arrow A, while the pressure roll 81 rotates following the rotation. Then, a recording material P carrying a toner image formed and transferred in a predetermined image forming unit (not shown) is conveyed so as to pass through a fixing nip portion. Operates to heat the fixing belt 47 by electromagnetic induction heat generation. That is, as described in the fourth and sixth embodiments, the high-frequency alternating current is applied from the excitation circuit 35 to the
Is heated by electromagnetic induction to heat the belt surface.

At this time, the exciting coil 1 of the magnetic flux generator 30
5 is a state in which the lead wire portions 2c and 2d are wound without crossing the winding portion 2e (see FIG. 20).
As in the second embodiment, the disturbance of the magnetic induction (heat) due to the disturbance of the magnetic field is reduced without causing the disturbance of the magnetic flux (magnetic field) due to the lead lines 2c and 2d crossing the winding part 2e. As a result, the non-uniformity of the electromagnetic induction heat in the lead-out portions 2c and 2d of the excitation coil 15 is eliminated, so that the fixing belt 47 is heated almost uniformly by the electromagnetic induction heat in the width direction, and the toner is accordingly reduced. The image is also heated almost uniformly.

As a result, the toner image on the recording material P passing through the fixing nip is heat-fixed to the recording material P by the pressure acting on the fixing nip and the heat of the fixing belt 47 heated.

By the way, the lead line portion 2 as described above
In the case where the excitation coil 15 having the winding state of c and 2d is used (this embodiment), the conventional excitation coil 100 (see FIG. 21,
In the case of using (see FIG. 22a) (comparative example), the magnetic field uniformity near the lead wire portion, the resistance of the whole exciting coil including the lead wire portion, and the radiation noise of the whole exciting coil were measured and compared. Table 1 shows the results.

Regarding the uniformity of the magnetic field in the vicinity of the lead wire portion, the portion having the lead wire portion (the winding start portion and the winding ending portion) and the portion having no lead wire portion among the winding portions 2e of the respective exciting coils of the embodiment and the comparative example. Measuring device (manufactured by FW BELL: Gauss / Teslameter, Model 99)
50), and was expressed as the maximum degree of variation (percentage of the variation) of the magnetic flux density in the winding portion having the lead wire portion, based on the magnetic flux density of the winding portion having no lead wire portion. For the resistance of the entire exciting coil, the resistance value including the skin resistance was measured using an LCZ meter manufactured by NF Circuit Design Block Co., Ltd. at an application frequency of 20 kHz to 10 kHz.
The measurement was performed at 0 kHz, and the evaluation was made based on the criteria of “○” when the resistance ratio of the lead wire at that time was 1% or less and “X” when it was 1% or more. For the radiation noise of the entire excitation coil, EMI Test Receiver manufactured by BilongAnatenna / Chase and Rohde / Schwa
Using a Spectrum Analyzer made by rz, etc., the frequency 20k
The radiation noise at Hz to 100 kHz is measured, and when the measured value is 20 dbμV or less, “○”, 20 d
The evaluation was made based on the criteria of “Δ” when the value was larger than bμV and smaller than 30 dbμV, and “x” when the value was 30 dbμV or more. In Table 1, the result of the radiation noise of the comparative example is indicated by “x” in parentheses, showing the result when the measurement was performed with the position of the lead line changed. In each of the excitation coils of the example and the comparative example, the wire diameter of the coated wire with the heat-resistant insulating film for 20 to 40 coils was 0.3.
mm and was wound 10 times using a litz wire twisted so as to be mm.

[0107]

[Table 1]

From the results shown in Table 1, in the excitation coil of the comparative example in which the lead wire portion of the excitation coil crosses the winding portion, the magnetic flux density of the winding portion crossing the winding portion is 1 at the maximum.
While it was disturbed by about 0%, it was confirmed that in the excitation coil of the example, the degree of variation of the magnetic flux density in the winding portion near the lead wire portion was almost 1%, which is almost the same. Also, it was confirmed that the coil resistance and radiation noise can be suppressed to be lower than the excitation coil of the comparative example by winding the lead wire so as not to cross the winding part as in the excitation coil of the example. Was done.

In the fixing device 53, the respective components (the excitation coil 15, the magnetic core 28, etc.) can be appropriately changed in the same manner as in the fourth embodiment. Further, similarly to the case of the sixth embodiment, for example, instead of the transfer fixing device 51 in the image forming apparatus according to the fifth embodiment, the toner image on the intermediate transfer belt 41 is secondarily transferred to the recording material P. Later, it can be used as a fixing device for fixing the toner image on the recording material P. Further, the exciting coil 15 of the sixth embodiment is used as the exciting coil 15 of the magnetic flux generator 30.
In the same manner as in the above, the folded portion 1 which is both ends of the coil
a, three inflection portions 3 (3a to 3f) are formed at portions other than a and 1b and on the upstream and downstream sides in the rotation direction A of the fixing belt 47. Is also good. When such an inflection portion 3 is formed, the exciting coil conforms to the exciting coil 1C of the third embodiment (FIG. 6). When the inflection portion 3 is formed in the exciting coil 15, the magnetic field of the lead wire portion is not disturbed, and the fixing belt 47 extends in the width direction similarly to the fourth embodiment. Is also substantially uniformly heated by the electromagnetic induction heating (see FIG. 11), and thus the toner image is more uniformly heated.

[0110]

As described above, according to the present invention,
By forming an inflection portion as described above in the exciting coil, or by winding the lead wire portion so as not to cross the winding portion, the electromagnetic effect due to the distribution of magnetic flux generated from the exciting coil can be obtained. The non-uniformity of the induced heat can be easily reduced with a simple configuration. As a result, it becomes possible to perform more uniform electromagnetic induction heating over the entire region in the longitudinal direction of the exciting coil and, consequently, image heating.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an entire excitation coil and a main part according to a first embodiment;

FIG. 2 is a schematic diagram showing another example of the excitation coil according to the first embodiment;

FIGS. 3A and 3B are a schematic view and an exploded view showing the whole and wound state of an example of an exciting coil according to a second embodiment; FIGS.

FIG. 4 is a schematic diagram and an exploded view showing the whole and winding state of another example of the exciting coil according to the second embodiment.

FIG. 5 is a schematic diagram and an exploded view showing the whole and winding state of another embodiment of the exciting coil according to the second embodiment.

FIG. 6 is a schematic diagram showing an entire excitation coil according to a third embodiment.

FIG. 7 is a schematic diagram showing a main part of an image heating device (transfer fixing device) according to a fourth embodiment.

FIG. 8 is a schematic cross-sectional view and a partial schematic view showing the whole and a main part of a magnetic flux generator in the transfer fixing device.

FIG. 9 is a schematic sectional view showing a main part of an intermediate transfer belt in the transfer fixing device.

FIG. 10 is an explanatory diagram illustrating an operation state of the transfer fixing device (a state of the exciting coil in a width direction at the time of electromagnetic induction heating).

FIG. 11 is an explanatory diagram showing a relationship between an exciting coil used in a transfer fixing device and a temperature distribution state of an electromagnetic induction heating region thereof.

FIG. 12 is an explanatory diagram showing an operation state of the transfer fixing device (a state in a longitudinal direction of the exciting coil at the time of electromagnetic induction heating).

FIG. 13 is a schematic diagram showing another embodiment (magnetic core) of the magnetic flux generator according to the fourth embodiment.

FIG. 14 is a schematic diagram showing another embodiment (magnetic core) of the magnetic flux generator according to the fourth embodiment.

FIG. 15 is a schematic diagram showing another example of the magnetic flux generation device according to Embodiment 4 (the arrangement of the magnetic cores).

FIG. 16 is a schematic diagram illustrating a main part of an image forming apparatus according to a fifth embodiment.

FIG. 17 is a schematic diagram showing a main part of an image heating device (fixing device) according to a sixth embodiment.

FIG. 18 is a schematic diagram showing a main part of an image heating device (fixing device) according to a seventh embodiment.

FIG. 19 is a schematic sectional view showing a main part of a magnetic flux generator and a fixing belt in the fixing device.

FIG. 20 is a schematic plan view showing an excitation coil and an excitation circuit of a magnetic flux generator in the fixing device.

FIG. 21 is an explanatory diagram showing a relationship between an exciting coil and a temperature distribution state of an electromagnetic induction heating region in a conventional magnetic flux generator.

FIG. 22 is a schematic perspective view showing another example of the exciting coil in the conventional magnetic flux generator.

FIG. 23 is an explanatory view showing a coil wound in a spiral shape.

[Explanation of symbols]

1A, 1B, 1C, 10, 12, 15 ... exciting coil, 1
a, 1b: folded portion, 1c: portion other than folded portion, 2: conductive wire, 2a: winding start portion, 2b: winding end portion, 2c, 2d: lead wire portion, 2d: winding portion, 3 ... Inflection portion, 20, 21, 24, 27, 33: magnetic core, 22, 23, 28, 29: magnetic core block, 2
5, 26: magnetic core having a curved surface portion, 30: magnetic flux generator, 38: magnetic core, 41: transfer belt (induction heating element), 46, 47 ... fixing belt (induction heating element), Ra,
Rb, R1 to R6: radius of curvature, T: toner image (image composed of developer), P: recording material.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasutaka Naito 430 Green Tech Nakai, Nakai-cho, Ashigara-gun, Kanagawa Prefecture, Inside Fuji Xerox Co., Ltd. Inside Fuji Xerox Co., Ltd. (72) Inventor Motofumi Baba 430 Green Tech Nakai-cho, Nakai-machi, Ashigara-kami, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. F term (for reference) 2H033 AA03 BA25 BB18 BE06 3K059 AA08 AB19 AB28 AD05 CD52 CD77

Claims (14)

[Claims] 1. A coil in which a conductive wire is wound in an elliptical shape having a longitudinal direction and generates a magnetic flux for electromagnetic induction heating by application of a high-frequency current, and is folded at both ends in the longitudinal direction. An exciting coil characterized in that at least one or more inflection portions wound in a state of changing curvature are formed in a portion other than the portion. 2. The method according to claim 2, wherein the conductive wire is spirally wound,
A coil for generating a magnetic flux for electromagnetic induction heating by application of a high-frequency current, wherein both of a lead wire portion drawn from a winding start portion and a winding end portion of the coil are wound without crossing the winding portion. An exciting coil, characterized in that: 3. The exciting coil according to claim 1, wherein both of the lead wire portions respectively drawn from the winding start portion and the winding end portion of the coil are wound without crossing the winding portion. 4. The exciting coil according to claim 1, wherein the number of turns of the winding portion is 3 to 30. 5. The exciting coil according to claim 1, wherein the conductive wire is a litz wire. 6. The exciting coil according to claim 2, wherein the coil is a coil formed by winding a conductive wire in a two-dimensional spiral shape, and the coil is wound from a winding start portion to a winding end portion. Until the middle part of the winding is wound from the outer side to the inner side (or from the inner side to the outer side) of the winding part,
A state of being wound from the middle part wound to the inner peripheral side (or the outer peripheral side) to the end of the winding so as to return from the inner peripheral side to the outer peripheral side (the outer peripheral side to the inner peripheral side). An excitation coil characterized in that: 7. The exciting coil according to claim 2, wherein the coil is a coil formed by winding a conductive wire in a three-dimensional spiral shape, and the coil is wound from a winding start portion to a winding end portion. Until the middle part of the winding, it is wound in a three-dimensional spiral from one end of the winding part to the other end, and the winding ends from the halfway part wound to the other end. The exciting coil, wherein the portion is wound in a three-dimensional spiral so as to return from the other end to the one end. 8. The excitation coil according to claim 2, wherein the winding start portion and the winding end portion are wound so as to be close to each other. 9. A magnetic flux generating means having an excitation coil wound in an elliptical shape having a longitudinal direction and generating magnetic flux for electromagnetic induction heating, and disposed in a state facing the magnetic flux generating means, An induction heating element for generating electromagnetic induction by magnetic flux generated from a generation unit, wherein the heating coil heats an image formed of a developer by the heat of the induction heating element, wherein the excitation coil comprises: An image heating apparatus comprising the excitation coil according to any one of the above. 10. The image heating apparatus according to claim 9, wherein said excitation coil of said magnetic flux generating means is provided with an excitation coil.
Or a magnetic core having a curved surface portion having a shape corresponding to the curvature of the inflection portion is disposed in a portion of the excitation coil where the inflection portion is formed. Image heating device. 11. The image heating apparatus according to claim 9, wherein a position of the magnetic flux generating means opposite to the induction heating element with the excitation coil interposed therebetween and a position of the induction heating element closer to the excitation coil. Is an image heating device with a magnetic core located at the opposite side. 12. The image heating apparatus according to claim 11, wherein the magnetic core comprises a plurality of independent magnetic core blocks arranged at intervals in a longitudinal direction of the exciting coil, and An image heating apparatus in which the magnetic core blocks are alternately arranged so as not to face each other between the two positions. 13. The image heating apparatus according to claim 9, wherein at least a portion of the induction heating element that generates electromagnetic induction heats,
An image heating device formed of a non-magnetic material of copper, silver or aluminum, or a metal or alloy having a resistivity equal to or less than these. 14. An image forming apparatus comprising an image heating device for transferring and fixing or fixing an image formed of a developer onto a recording material while heating the recording material, wherein the image heating device is any one of claims 9 to 13. An image forming apparatus comprising: an image heating apparatus;