JP4609146B2 - Heating device, manufacturing method thereof, fixing device using the same, and image forming apparatus - Google Patents

Description

  The present invention relates to, for example, a heating device used in a fixing device for heating and pressure-fixing an unfixed toner image in an image recording apparatus such as a copying machine, a printer, or a facsimile employing an electrophotographic method, a manufacturing method thereof, and The present invention relates to a fixing device and an image forming apparatus using the same, and more particularly to a heating device for heating a thin belt-like member as a member to be heated, a manufacturing method thereof, and a fixing device and an image forming apparatus using the same.

  Conventionally, for example, in an image recording apparatus such as a copying machine, printer, or facsimile employing an electrophotographic system, at least a metal core is used as a fixing device used for heating and pressure-fixing an unfixed toner image. A heating source such as a halogen lamp is provided inside the heating roll, and the heating roll is heated from the inside, and a pressure roll is disposed so as to be in pressure contact with the heating roll. By passing the recording material onto which the unfixed toner image has been transferred between the nip portions formed by the above method, the unfixed toner image is fixed on the surface of the recording material with heat and pressure so as to obtain a fixed image. The composition is mainly used.

  Here, as a heating device for heating the fixing device, the heated member is instantaneously heated to a predetermined temperature from the viewpoint of energy saving or not allowing the user to wait when using the image recording apparatus, The thing which can make waiting time (warm-up time) zero is demanded, but it is achieved by the following reasons in the heating source (heating device) such as the halogen lamp arranged in the heating roll described above. Can not do it.

  That is, the heating roll that is a member to be heated is a member to which a pressure member such as a pressure roll is pressed, so that it must maintain a predetermined rigidity and has a metal core having a certain thickness or more. Yes. Therefore, the heating roll cannot reduce the heat capacity so much, and the halogen lamp as a heating source is provided inside the heating roll, and the heating roll is heated from the inside. It takes time to transfer heat to the surface of the. Therefore, the waiting time is inevitably long. Furthermore, since the halogen lamp for heating the heating roll normally has a glass tube, the halogen lamp itself has a certain heat capacity, and it takes time to warm the halogen lamp itself.

  For this reason, the conventional fixing device has a problem that it takes time to warm up and the waiting time becomes long. Further, when a halogen lamp is used as a heating source, there is a problem that a so-called “flicker” phenomenon occurs in which an energized current flows transiently when the halogen lamp is turned on and off.

  Therefore, in recent years, in such a fixing device, a heating means using an induction heating method instead of a halogen lamp has been studied. This is to heat a member to be heated by an electromagnetic induction effect by applying a magnetic field generated by a magnetic field generating means to a member to be heated (heating element) having a conductive layer (heat generating layer). This is a very effective heating means in order to provide a fixing device with a short waiting time.

  Also, the heating means such as the halogen lamp can be used only when the surroundings of 360 ° such as the inside of the heating roll are covered, because high heat leaks to the outside, whereas in the case of the induction heating method As long as a magnetic field can be applied to the member to be heated, not only the member to be heated but also a magnetic field generating means may be provided outside, and it can be placed at an arbitrary position depending on the configuration of the fixing device. Can be arranged. That is, in the case of a heating means adopting the induction heating method, by arranging it at an arbitrary position, a magnetic field is applied only to the part to be heated, and only that part can be selectively and instantaneously heated. It has the advantage of being able to.

  Thus, the magnetic field generating means in the induction heating method can be arranged at an arbitrary position with respect to the heating roll as the member to be heated, so that the degree of freedom in designing the apparatus can be expanded. Further, as compared with a fixing device using a halogen lamp or the like as a heating source, only the heating roll to be heated is selectively heated, so that the warm-up time can be shortened by about 10 to 30%.

  FIG. 36 illustrates a fixing device employing such an induction heating method. Here, FIG. 36 is a perspective view showing an example of a conventional fixing device adopting an induction heating method. In the fixing device, a coil 310 is disposed in a non-contact manner inside a rigid iron fixing roll 300 having a thickness of about 0.5 to 2 mm, which is in contact with the pressure roll 320 to form a nip portion. FIG. 37 shows a cross-sectional view of the fixing roll 300 in the fixing device.

As a modification of the fixing device, only the fixing roll and coil are extracted and shown in a sectional view in FIG. In the modification, a coil 310 ′ is arranged outside the iron fixing roll 300 ′.
Note that, depending on the shape of the coil, a heating device that heats the fixing roll in the circumferential direction as a whole or a heating device that locally heats a part in the circumferential direction is determined.

In addition, various other conventional techniques of the heating apparatus adopting the induction heating method are listed.
A heating device that induction-heats the roll as a whole in the circumferential direction depending on the shape of the coil for electromagnetic induction (see, for example, Patent Document 1).
A heating device in which a belt having nickel as a heat generating layer having a thickness of about 50 μm is induction-heated by a coil inserted inside the belt (see, for example, Patent Document 2).

  Heating means having conductivity, pressure-contacting means that press-contacts the heating means, a magnetic-field generating means that is formed in a coil shape from a conductive wire and that causes the generated magnetic field to act on the heating means, and generated by the magnetic-field generating means It comprises a magnetic field blocking means for blocking a magnetic field, and is arranged such that the magnetic field generating means is sandwiched between the heating means and the magnetic field blocking means (for example, see Patent Document 3).

A fixing device in which a magnetic field generating unit is arranged outside or inside a heating roll as a heating unit having conductivity (see, for example, Patent Document 4).
A fixing device using an endless film belt as a fixing member (see, for example, Patent Documents 5 to 7).
Various arrangements of coils and cores in such a fixing device have been proposed (see, for example, Patent Documents 8 to 10).

The heating layers of the heating devices used in these fixing devices are all made of a magnetic metal, and the thickness thereof is equal to or greater than the skin depth. In any fixing device, it is not possible to complete the warm-up time in 10 seconds or less.
Here, the “skin depth” refers to the depth at which the electromagnetic field can enter the conductor, and specifically refers to the distance at which the electromagnetic field incident on a certain material attenuates to 1 / e = 0.37.

  In general, a heating apparatus using an electromagnetic induction action has been known, and a magnetic metal such as iron or nickel is used for most of the heat generating layer that performs induction heating. The thickness of the conventional magnetic metal heating layer is about 50 μm to 2 mm. This thickness is approximately equal to or greater than the thickness for induction heating of the heat generating layer, that is, the skin depth. Thus, when the heat generation layer thickness is equal to or greater than the skin depth, the electromagnetic field due to electromagnetic induction converges inside the heat generation layer, and the magnetic flux hardly leaks from the side opposite to the coil of the heat generation layer. . The conventional heat generating layer in which “the magnetic flux hardly leaks” refers to a heat generating layer having a thickness equal to or greater than the skin depth.

  On the other hand, a heating device using electromagnetic induction emits a large electromagnetic field, so it is necessary to prevent human exposure. For example, even if heating design (for example, a design that increases the degree of electromagnetic coupling) and leakage magnetic field prevention are implemented by forming a magnetic path in the heating configuration, there is a concern that some leakage electromagnetic field may be generated by that alone. Yes, measures to reduce the final exposure to the human body are desired.

By the way, with recent energy savings, it is desirable that the heating device can heat the non-heated object with a minimum amount of heat. However, in a fixing device of an electrophotographic image recording apparatus, for example, since the heat capacity of the member to be heated is large, heating exceeding a necessary amount of heat is performed. For this reason, there is a problem that the time (warm-up time) until a state where predetermined heating can be performed becomes long, and the convenience in using the heating device is poor.
Therefore, in the induction heating method, it is conceivable to reduce the thickness of the heat generating layer of the member to be heated to reduce the heat capacity and further reduce the weight.

  In order to shorten the warm-up time, if the heat capacity is reduced, that is, if the heat generating layer (metal) is made thinner, the heat generating layer having a small specific resistance value is required. For example, a ferromagnetic metal such as iron or nickel has a high specific resistance value. Therefore, when the layer is thinned to about 10 μm, electromagnetic induction heating becomes difficult for a high-frequency power source having high versatility. Metals that can be heated by electromagnetic induction even with a thickness of about 10 μm are nonmagnetic metals typified by aluminum, copper, silver and the like. Then, since it is sufficiently thinner than the skin depth, the magnetic field leaks and spreads from the side opposite to the coil of the heat generating layer, and there is a concern that the efficiency may be reduced and adversely affected by electromagnetic induction to the surroundings.

  Further, the conventional fixing device has the following problems. That is, for example, in the case of the fixing devices disclosed in Patent Documents 1 to 4, since the induction heating method is employed, the warm-up time is faster than when a heating source such as a halogen lamp is used. However, since the heating roll itself has a metal core that is thicker than a certain thickness in order to maintain rigidity, it has a certain amount of heat capacity. It has been difficult to set the warm-up time for completing the preparation for fixing the toner image to 10 seconds or less.

  On the other hand, the fixing devices disclosed in Patent Documents 5 to 7 use a conductive film as a fixing member, and the heat capacity of the film itself is 1/2 to that of the fixing roll of an equivalent class fixing device. The film is reduced to about 1/10. Further, by directly heating the film by induction heating, the film as a fixing member can be raised to a desired temperature in about 20 to 30 seconds.

However, even when the image heating film having a small heat capacity including the magnetic metal heat generating layer is heated by the exciting coil as described above, the warm-up time has not been sufficiently shortened.
Similarly, in the fixing device adopting the arrangement of coils and cores disclosed in Patent Documents 8 to 10, the warm-up time has not been sufficiently shortened yet.

  Reducing the waiting time, particularly achieving a warm-up time of 10 seconds or less, means that when the fixing device or the image recording device is actually used, it is only necessary to turn on the power. An apparatus with high convenience in use can be provided. This is an important element from the viewpoint of energy saving, and does not require preheating when not in use, and a heating device that inputs energy only when used, a fixing device using the same, and an image recording apparatus (image forming apparatus) The significance of providing is great.

  Furthermore, it is necessary to provide a highly safe heating apparatus and an image recording apparatus using the same, which reduce exposure to the human body due to a leakage electromagnetic field. No matter how high the performance, it is meaningless unless sufficient safety is ensured. In addition, as long as an electromagnetic field is generated, the exposure cannot theoretically be reduced to zero if a person is present in the vicinity of the electromagnetic field. Therefore, a countermeasure for reducing the exposure as much as possible is desired.

  By the way, in the heating device using the induction heating method, when trying to heat the surface of a wide heating rotator such as a heat fixing belt or a fixing roll, particularly depending on the position in the width direction (rotation axis direction of the heating rotator), There may be a difference in heating efficiency between the central portion and the end portion, and it may be necessary to take some means to make this as uniform as possible.

JP 11-316509 A JP 2000-321895 A JP 2000-181258 A JP 2000-29332 A JP-A-7-295411 JP-A-8-69190 JP 11-38827 A Japanese Patent No. 3426229 JP 2001-343847 A Japanese Patent Laid-Open No. 2002-148983 JP 2000-29341 A JP 2000-56603 A JP 2000-181258 A JP 2003-338365 A

Therefore, in view of the above-described problems of the prior art, the first object of the present invention is to make heating efficiency substantially uniform and substantially constant in the width direction (rotating axis direction) of the heating rotating body as the member to be heated. It is providing the heating apparatus used as temperature distribution, and its manufacturing method.
In addition, the second object of the present invention is to ensure a stable induction heating state with extremely short warm-up time, less leakage electromagnetic field exposure to the human body, excellent safety and functionality, miniaturization possible. It is in providing the heating apparatus which can be manufactured, and its manufacturing method.
Furthermore, a third object of the present invention is to provide a fixing device and an image forming apparatus using a heating device having the above-mentioned excellent features.

The above object is achieved by the present invention described below. That is, the present invention
<1> A heating device for heating an endless heating rotator having at least a heat generating layer that generates heat by electromagnetic induction,
An exciting coil for inductively heating the heating rotator is arranged along a part of the outer peripheral surface or the inner peripheral surface of the heating rotator,
A leakage electromagnetic field shielding member made of a non-magnetic metal for shielding an electromagnetic field leaking from around the excitation coil is disposed so as to surround the electromagnetic field generated from the excitation coil,
In addition, in the temperature distribution in the rotation axis direction when the distance between the leakage electromagnetic field shielding member and the excitation coil is the same at any position in the rotation axis direction of the heating rotator, the leakage electromagnetic field shielding is applied to a portion that becomes high in the temperature distribution in the rotation axis direction. The temperature distribution in the rotation axis direction of the heating rotator is substantially reduced by reducing the distance between the member and the excitation coil and / or increasing the distance between the leakage electromagnetic field shielding member and the excitation coil at a low temperature part. The distance between the leakage electromagnetic field shielding member and the excitation coil is adjusted to be constant, and the shape of the leakage electromagnetic field shielding member depends on the position of the heating rotator in the rotation axis direction. A heating device, wherein the heating device is formed so as to have a different distance from the exciting coil.

< 2 > The heating apparatus according to <1 > , wherein a distance between the leakage electromagnetic field shielding member and the excitation coil is greater in a central portion than in an end portion of the excitation coil.

< 3 > The heating apparatus according to either <1> or < 2 >, wherein the leakage electromagnetic field shielding member is made of an aluminum plate or an aluminum alloy plate having a thickness of 500 μm to 2 mm.

< 4 > The thickness of the heat generating layer of the heating rotator is thinner than the skin depth,
The excitation coil is formed by winding a wire along the surface in a non-contact manner with the surface of the heating rotator so as to generate a variable magnetic field along the thickness direction of the heat generating layer,
A magnetic path of a variable magnetic field generated by the exciting coil is formed so as to face the opposite side of the exciting coil across the heating rotating body and not in contact with the surface of the heating rotating body, thereby shielding the magnetic field. The heating apparatus according to any one of <1> to < 3 >, wherein a magnetic path forming member (preferably formed in the following shape) is provided.
-Shape of the magnetic path forming member: a shape formed so that the surface of the magnetic path forming member facing the excitation coil follows the inner peripheral surface shape or outer peripheral surface shape of the heating rotator.

< 5 > The heating rotator has an endless belt shape, and rotates in a predetermined direction. Before and after the rotation direction, both end portions of the magnetic path forming member extend beyond both end portions of the opposing excitation coils. The heating apparatus according to < 4 >, wherein the heating apparatus extends.

< 6 > The heating device according to < 5 >, wherein the heating rotator is cylindrical.

< 7 > The heating device according to any one of < 4 > to < 6 >, wherein the magnetic path forming member is formed of soft ferrite.

< 8 > The heating layer of the heating rotator is mainly formed of copper having a thickness of 2 to 15 μm, and the frequency of the alternating current applied to the exciting coil is 20 to 100 kHz. < 4 >-< 7 > characterized by these. The heating apparatus in any one of < 7 >.

< 9 > A second magnet that forms a magnetic path of a variable magnetic field generated by the excitation coil and shields the magnetic field across the excitation coil and the heating rotator so as to face the magnetic path forming member. The heating apparatus according to any one of < 4 > to < 8 >, wherein a path forming member is disposed.

< 10 > At least one of the magnetic path forming member and the second magnetic path forming member is a small piece member group in which a plurality of small piece members are arranged with a predetermined gap therebetween in the rotation axis direction of the heating rotator. The heating apparatus according to < 9 >, wherein the heating apparatus is configured.

< 11 > Both the magnetic path forming member and the second magnetic path forming member are constituted by the small piece member group, and the small piece member group constituting the magnetic path forming member and the second magnetic path forming member. Each small piece member and each gap formed by two small piece members adjacent to each other in the small piece member group constituting the magnetic path forming member or the second magnetic path forming member facing each other so as to face each other. < 10 > The heating apparatus according to < 10 >, wherein

< 12 > Both the magnetic path forming member and the second magnetic path forming member are configured by the small piece member group, and the small piece member group of the magnetic path forming member and the second magnetic path forming member < 10 > The heating apparatus according to < 10 >, wherein the small piece member group is disposed so as to complement each gap between the opposing small piece member groups facing each other.

< 13 > Each small piece member in the small piece member group constituting the magnetic path forming member and the second magnetic path forming member is a pair of small piece member groups on the opposite side whose centers in the rotation axis direction of the heating rotator face each other. The heating apparatus according to < 11 > or < 12 >, wherein the gaps are arranged so as to substantially coincide with the centers of the gaps in the same direction.

< 14 > A heat-fixing belt having at least a heat-generating layer and an outermost release layer, and a nip portion that is in contact with the heat-fixing belt and into which a recording material carrying an unfixed toner image is inserted and heated and pressed to fix it. A fixing device comprising: a pressure member that forms a heating member; and a heating member that heats the heating and fixing belt,
The fixing device, wherein the heating member is the heating device according to any one of <1> to < 13 >, wherein the heating fixing belt is a heating rotator.

< 15 > At least the image forming means for forming an unfixed toner image on the surface of the recording material, the heat fixing belt and the pressure member are in contact with each other, and the recording material on which the unfixed toner image is formed is inserted. An image forming apparatus comprising: a fixing unit in which a nip portion is formed; and a heating member that heats the heating and fixing belt,
The heat-fixing belt has at least a heat generating layer and an outermost release layer, and
The image forming apparatus, wherein the heating member is the heating device according to any one of <1> to < 13 >, in which the heating fixing belt is a heating rotator.

< 16 > A method for manufacturing a heating device for heating an endless heating rotator having a heat generating layer that generates heat by at least electromagnetic induction,
An exciting coil for inductively heating the heating rotator is arranged along a part of the outer peripheral surface or inner peripheral surface of the heating rotator,
A leakage electromagnetic field shielding member (preferably formed in the following shape) made of a non-magnetic metal for shielding an electromagnetic field leaking from the periphery of the excitation coil is disposed so as to surround the electromagnetic field generated from the excitation coil. The manufacturing method of the heating apparatus characterized by these.
-Shape of the leakage electromagnetic field shielding member: The distance between the leakage electromagnetic field shielding member and the excitation coil is substantially constant in the temperature distribution in the rotation axis direction of the heating rotator depending on the position of the heating rotator in the rotation axis direction. Shape adjusted so that.

< 17 > The thickness of the heat generating layer of the heating rotator is thinner than the skin depth,
The excitation coil is formed by winding a wire along the surface in a non-contact manner with the surface of the heating rotator so as to generate a variable magnetic field along the thickness direction of the heat generating layer, And,
A magnetic path of a variable magnetic field generated by the exciting coil is formed so as to face the opposite side of the exciting coil across the heating rotating body and not in contact with the surface of the heating rotating body, thereby shielding the magnetic field. The method for manufacturing a heating device according to < 16 >, further comprising a step of disposing a magnetic path forming member formed in the following shape.
-Shape of the magnetic path forming member: a shape formed so that the surface of the magnetic path forming member facing the excitation coil follows the inner peripheral surface shape or outer peripheral surface shape of the heating rotator.

  According to the present invention, the shape of the leakage electromagnetic field shielding member is appropriately changed in the size of the gap between the leakage electromagnetic field shielding member and the exciting coil according to the position in the rotation axis direction of the heating rotating body as the member to be heated. As a result, it is possible to provide a heating apparatus having substantially uniform heating efficiency and a substantially constant temperature distribution, and a method for manufacturing the same. By simply adjusting and designing the shape of the leakage electromagnetic field shielding member that is often required to be installed, the heating temperature distribution in the direction of the rotation axis of the heated rotating body that is the object to be heated can be made substantially uniform. it can.

Further, according to the present invention, the leakage electromagnetic field shielding member having an appropriate shape as described above, the thickness of the heating layer of the heating rotator is made thinner than the skin depth, and the fluctuation generated by the exciting coil is changed. By arranging the magnetic path forming member that forms the magnetic path of the magnetic field and shields the magnetic field, the warm-up time is extremely shortened, the exposure to the human body of the leaked electromagnetic field is small, and it is excellent in safety and functionality. It is possible to provide a heating device that can be miniaturized and can ensure a stable induction heating state and a method for manufacturing the same.
Furthermore, according to the present invention, it is possible to provide a fixing device and an image forming apparatus using the heating device having the above-described excellent features.

Hereinafter, the present invention will be described in detail with reference to the drawings with preferred embodiments.
[Heating device and fixing device]
<First Embodiment>
FIG. 1 is a schematic cross-sectional view of a fixing device 10 according to a first embodiment, which is an exemplary aspect of the present invention. The fixing device of the present embodiment includes the heating device of the present invention, and a leakage electromagnetic field shielding member 6 is attached thereto as shown in FIG.

  The fixing device of this embodiment is intended to shorten the warm-up time and secure the separation performance of the recording material. As a fixing member for fixing a toner image, a flexible belt having a small heat capacity is used. These members are used, and the belt-shaped member is configured so that a member for removing heat is not disposed as much as possible. In other words, the endless belt member (heat fixing belt) is disposed without stretching members such as drive rolls on the inner side thereof, and is disposed so as to face the pressure member, and the fixing nip portion is provided. Only a pad member (pressing member) to be formed is basically provided. Further, a heating layer is provided inside the belt-like member so that the belt-like member to be heated can be directly heated, and this heating layer is induction-heated by a variable magnetic field generated by an exciting coil.

  Specifically, as shown in FIG. 1, a thin hollow cylindrical heat fixing belt 20 having a heat generating layer, and a pressure disposed so as to be in pressure contact with a lower outer peripheral surface of the heat fixing belt 20 in the figure. An elastic member 24 that is in contact with the inner peripheral surface of the heating and fixing belt 20 that is provided with a roll 23 and faces the pressure roll 23 is supported by the support member 22 and disposed. The inside of the heat-fixing belt 20 on the side opposite to the surface facing the pressure roll 23 (upper part in the drawing) is not in contact with the inner peripheral surface of the heat-fixing belt 20 and faces a part of this inner peripheral surface. An exciting coil 1A is provided as described above. Further, outside of the heat fixing belt 20 facing the exciting coil 1A, a magnetic path forming member 41 made of ferrite is provided so as to face a part of the outer peripheral surface without contacting the outer peripheral surface of the heat fixing belt 20. Is arranged.

  In the fixing device 10 configured as described above, the nip portion 1Y is formed by holding the heat fixing belt 20 with the pressure roll 23 and the elastic member 24, and unfixed toner is formed in the nip portion 1Y. By inserting the recording material 27 onto which the image 25 has been transferred, the unfixed toner image 25 is fixed on the recording material 27 by heat and pressure, and a fixed image is formed. The thin heating and fixing belt 20 having the heat generation layer is heated by electromagnetic induction heating with a fluctuating magnetic field generated by the exciting coil 1A, so that heating for fixing an unfixed toner image is performed. .

Next, details of constituent members of the fixing device 10 will be described below.
First, a heat fixing belt (heating rotator) 20 as a heat fixing member is formed as an endless belt having a heat generating layer. Specifically, as shown in FIG. 2, from the inner peripheral surface side, a base material layer 20a made of a sheet-like member having high heat resistance and a single layer laminated on the outer peripheral surface side of the base material layer 20a. The heat generating layer 20b, which is a heat generating layer, and the release layer 20c, which is the uppermost layer, are formed as an endless belt having a diameter of 30 mm.

  As shown in FIG. 3, an elastic layer 20d made of, for example, silicone rubber having a rubber hardness of 35 ° (JIS-A) may be further provided between the heat generating layer 20b and the release layer 20c. Further, in the present embodiment, although not shown, the end portions of the endless heat fixing belt 20 are abutted against the edge guides, whereby the meandering of the heat fixing belt 20 is regulated and used.

  The base material layer 20a of the heat fixing belt 20 is a sheet having a high heat resistance of, for example, a thickness of 10 to 100 μm, more preferably 50 to 100 μm (for example, 75 μm). For example, polyester, polyethylene terephthalate, polyether sal It can be formed from a synthetic resin having high heat resistance such as phon, polyether ketone, polysulfone, polyimide, polyimide amide, polyamide.

  The heat generating layer 20b is a conductive layer that generates heat by electromagnetic induction of a magnetic field generated by the exciting coil 1A, and is formed of copper with a thickness of about 2 to 15 μm. If a uniform layer is to be formed by plating, vapor deposition, or the like, if it is less than 2 μm, problems may occur in terms of poor manufacturing yield, ensuring film thickness accuracy, quality control, and cost. On the other hand, if it exceeds 15 μm, the heat capacity increases, which affects the achievement of warm-up for 10 seconds or less, and the flexibility of the heat generating layer is reduced. Therefore, it is difficult to bend to obtain the peeling performance of the fixing device. Therefore, it is desirable that the thickness is 15 μm or less.

  Further, when the thickness exceeds 15 μm, the induction heating performance at a frequency of 20 k to 100 kHz is lowered. This means that an eddy current flows through the entire metal layer with a thickness sufficiently thinner than the skin depth, but the resistance value decreases as the thickness increases, making it difficult to obtain Joule heat loss due to the eddy current. to cause. In other words, Joule heating is determined by multiplying the square value of the eddy current by the resistance value of the main path through which the eddy current flows. Therefore, if the resistance value is too low, no heat will be generated no matter how much eddy current flows. It is.

  In this embodiment, although not shown in FIGS. 2 and 3, heating is performed in which a nickel layer having a thickness of about 0.1 to 5 μm is provided on the surface release layer side of the heat generation layer 20 b that is a copper layer. It was also carried out with a fixing belt. The nickel layer is provided to improve the strength of the heat-fixing belt, and contributes to heat generation due to electromagnetic induction, but has a small effect on electromagnetic induction characteristics (changes in inductance and resistance in the induction state). Is approximately 10% or less). As an actual example, when comparing the electromagnetic induction characteristics of a heat-fixing belt having two layers contributing to heat generation in which a nickel layer of 5 μm is provided on a copper layer of 10 μm and a heat-fixing belt having a single copper layer of 10 μm, Changes in inductance and resistance in the electromagnetic induction state are 5% or less, and the difference from a single copper layer is very small. Even if such a layer is provided, the layer that generates heat mainly becomes the copper layer of the heat generating layer 20b, and therefore there is almost no problem in the implementation of the present invention.

  In general, in order to reduce the warm-up time as close as possible to 0 and to 10 seconds or less, it is most important to reduce the heat capacity of the heat generating layer (metal) that is heated by electromagnetic induction. For this purpose, it is possible to realize a metal layer that contributes to heat generation within a total range of 30 μm or less, preferably 2 to 20 μm. Further, when there is one layer that mainly generates heat, the layer is preferably about 10 μm in view of manufacturability (yield and uniformity of layer formation) and cost.

  For example, there may be a plurality of layers (metal layers) that contribute to heat generation for manufacturing reasons or strength reinforcement reasons. The number of layers that generate heat due to electromagnetic induction is preferably one from the viewpoint of cost. However, when there are a plurality of layers that contribute to heat generation due to the above reasons, the total thickness of each layer is preferably 30 μm or less. . In the present invention, even if there are a plurality of layers that contribute to heat generation, a layer that can generate an electromagnetic induction heat generation amount that is 50% or more of the total heat generation amount is simply referred to as a “heat generation layer” as a layer that generates heat. All the contributing layers are collectively referred to simply as “layers contributing to heat generation”.

  Inductive heating of a conductor having a heat generation layer as thin as about 10 μm, that is, a metal or a metal mixture, with a versatile and low-cost high-frequency power source (for example, a quasi-E class parallel resonant circuit power source used in an electromagnetic cooker) For this, it is necessary to use a nonmagnetic metal. Since magnetic metal has a high specific resistance value, when it is thinned, an induced eddy current hardly flows and heating becomes difficult. If it is attempted to inductively heat a heat generating layer in which an induced eddy current does not easily flow, it is necessary to apply a high voltage to the coil, which causes problems such as an increase in the voltage of the power source, making it difficult to actually adapt. Although an eddy current due to electromagnetic induction flows when an alternating electromagnetic field is applied to all metals, in order to design a heating device using Joule heat generation, it is important to give conditions that easily generate heat. In contrast, non-magnetic metals such as aluminum, copper, and silver have low specific resistance values, and are suitable for induction heating by being sufficiently thinner than the skin depth. Specifically, for example, about 10 μm. It becomes easy to heat by thinning.

For example, when the non-magnetic metal copper is taken as an example of a single heat generating layer, the skin depth δ at which the electromagnetic field penetrates into the copper layer in the frequency band of 20 to 100 kHz is expressed by the following (Equation 1): μ = 1, ρ = 1.67 × 10 ⁻⁸ Ωm, which is 200 to 500 μm, and the thickness of the heat generating layer is sufficiently smaller than the skin depth δ.

  However, non-magnetic metals having a low specific resistance value typified by aluminum, copper, silver, etc., are generated from an excitation coil that is an alternating magnetic field generating means when induction heating is performed on a metal whose heating layer is thinner than the skin depth δ. The reaction magnetic field due to the magnetic field and the induced eddy current leaks from the side opposite to the exciting coil across the heat generation layer. Table 1 shows the difference in magnetic flux density with and without the magnetic path forming member, but it can be seen that when there is no magnetic path forming member, a strong magnetic field is generated around the heat generating layer. This magnetic field is generated by the magnetic field generated by the coil and the magnetic field generated by the eddy current flowing in the heat generating layer, and leaks from the heat generating layer.

  Accordingly, the heating device of the present invention used in the fixing device of the present embodiment includes the heat-fixing belt 20 that includes the conductive heat-generating layer 20b and the heat-generating layer 20b is thinner than the skin depth thereof as a member to be heated. The heating fixing belt 20 having the exciting coil 1A for electromagnetically heating the heat generating layer 20b by generating a variable magnetic field along the thickness direction of the heat generating layer 20b of the member to be heated, including the heat generating layer 20b, The exciting coil 1 </ b> A and the magnetic path forming member 41 are opposed to each other. By setting it as the said structure, since a magnetic flux path can be formed with the exciting coil 1A-heating layer 20b-magnetic path formation member 41, the stable induction heating state is realizable. Accordingly, it is possible to provide a heating device that can obtain a safe and stable induction heating state even with a nonmagnetic metal that is sufficiently thinner than the skin depth.

Here, the relationship between the thickness of the copper layer (heat generation layer) and the applied frequency will be further described with reference to FIG. FIG. 4 is a diagram showing the change of the power factor equivalent amount with respect to the frequency, and is a characteristic diagram showing the ease of heat generation when the copper layer thickness is 2 μm to 15 μm.
In FIG. 4, stable heating is possible if the heat factor corresponding to the power factor reaches 0.5 over the frequency band of 20 k to 100 kHz, but the thickness is as shown in the figure. It can be seen that the frequency is about 60 kHz to 100 kHz in the case of 2 μm, and about 30 kHz or less in the case of 15 μm.

  Therefore, the frequency of the current applied to the coil is desirably 20 kHz to 100 kHz. If it is less than 20 kHz, the oscillation noise sound cannot be adopted because it falls within the human audible region, and if it exceeds 100 kHz, the switching loss of the induction heating power source that applies current to the coil increases, affecting peripheral devices. This is because the radiation noise increases and the skin resistance of the coil increases and the loss due to these increases.

  In the present embodiment, the heat fixing belt 20 needs to follow the shape of the nip portion inside the nip portion formed by the pad member and the pressure roll. For this reason, it is necessary to be a flexible belt, and the heat generating layer 20b is preferably as thin as possible. Therefore, in the present embodiment, copper having high conductivity is plated on the outer peripheral surface of the base material layer 20a made of polyimide with a very thin thickness of about 10 μm so as to increase the heat generation efficiency as the heat generation layer 20b. Things are used.

Further, since the release layer 20c is a layer in direct contact with the unfixed toner image 25 transferred to the surface of the recording material 27, it is desirable to use a material having good release properties. Examples of the material constituting the release layer 20c include tetrafluoroethylene perfluoroalkyl vinyl ether polymer (PFA), polytetrafluoroethylene (PTFE), silicone copolymer, or a composite layer thereof. The release layer 20c is a layer appropriately selected from these materials and provided as the uppermost layer of the belt with a thickness of 1 to 50 μm. On the other hand, if the thickness of the release layer 20c is too thin, the durability is poor in terms of wear resistance, and the life of the heat fixing belt 20 is shortened. Conversely, if the thickness is too large, the heat capacity of the belt is reduced. Increases the warm-up time.
In the present embodiment, a 20 μm thick tetrafluoroethylene perfluoroalkyl vinyl ether polymer (PFA) is used as the release layer 20 c of the heat-fixing belt 20 in consideration of the balance between wear resistance and the heat capacity of the belt. in use.

  An elastic member 24 as a pad (pressing member) made of, for example, silicone rubber is provided inside the heat fixing belt 20 configured as described above. In this embodiment, as the elastic member 24, a support member 22 having a rigidity made of a silicone rubber having a rubber hardness of 35 ° in JIS-A, a metal such as stainless steel (SUS) or iron, a synthetic resin having high heat resistance, or the like. Laminates are used.

  For example, the elastic member 24 made of silicone rubber has a uniform thickness. The support member 22 is arranged in a state of being fixed to a frame of a fixing device (not shown), but a spring or the like (not shown) is used so that the elastic member 24 is pressed against the surface of the pressure roll 23 with a predetermined pressing force. You may press toward the surface of the pressure roll 23 by a biasing means.

  In the present embodiment, the surface of a solid iron roll having a diameter of 26 mm as the pressure roll 23 is coated with a tetrafluoroethylene perfluoroalkyl vinyl ether polymer (PFA) having a thickness of 30 μm as the release layer. Things are used. The pressure roll 23 is rotationally driven by a driving unit (not shown) while being pressed against the elastic member 24 via the heat fixing belt 20 by a pressing unit (not shown).

  The pressure roll 23 may be provided with a metal roll (not shown) made of a metal such as aluminum or stainless steel having good thermal conductivity so as to be able to contact and separate. This metal roll stops at a position away from the pressure roll 23 when the temperature of the heat fixing belt 20 or the pressure roll 23 is cooled to the room temperature, for example, in the morning when the energization of the fixing device is started. Yes. In the fixing device, when the fixing device is used, for example, when a small-size sheet is continuously fixed, the temperature along the axial direction is applied to the heat fixing belt 20 and the pressure roll 23. When the difference occurs, the metal roll may be configured to contact the pressure roll 23.

  The heat fixing belt 20 as a member to be heated is circulated in a predetermined direction following the rotation of the pressure roll 23. Accordingly, in the present embodiment, a sheet material having high friction resistance and good slidability, for example, Teflon (registered trademark) resin, is provided between the heat-fixing belt 20 and the elastic member 24 to improve the slidability. By interposing a glass fiber sheet impregnated with (Nakako Kasei Kogyo: FGF400-4, etc.) and further applying a release agent such as silicon oil as a lubricant to the inner surface of the heat fixing belt 20, It is configured to improve. In this way, during actual heating, the driving torque during idling of the pressure roll 23 can be reduced from about 6 kg · cm to about 3 kg · cm. Accordingly, the heat fixing belt 20 is driven without sliding with the pressure roll 23 and is driven to rotate at a speed equal to the rotation speed of the pressure roll 23.

FIG. 5 is an explanatory diagram for explaining the heating principle of the heat fixing belt used in the fixing device of this embodiment. In FIG. 5, the inner peripheral surface of the heat fixing belt faces upward.
As shown in FIG. 5, the exciting coil 1 </ b> A is formed so as to follow the inner peripheral surface of the thin cylindrical heating and fixing belt 20 by winding a linear member having a core made of a ferromagnetic material. The fixing member 20 is supported by the coil support member 18 with the direction orthogonal to the rotation direction (circumferential direction) of the fixing belt 20 as a longitudinal direction. The heat fixing belt 20 that is a member to be heated is disposed so as to face the surface of the heat fixing belt 20 while maintaining a gap of about 0.5 mm to 3 mm.

  Here, as the exciting coil 1A, for example, one in which a predetermined number of litz wires obtained by bundling 90 copper wires having a diameter of 0.16 mm that are insulated from each other in a straight line are arranged in parallel is used. The method of winding the litz wire is not limited to a single winding method. For example, the litz wire may be wound in a spiral shape, and the variable magnetic field H generated by the alternating current flowing through the exciting coil 1A is illustrated with respect to the heating layer 20b. It should work as follows. Further, it is desirable to use a heat-resistant nonmagnetic material as the coil support member 18, and for example, a heat-resistant resin such as ceramics, heat-resistant glass, polycarbonate, LCP, polyimide, PPS or the like is used.

When an alternating current having a predetermined frequency is applied to the exciting coil 1A through the exciting circuit 30, a fluctuating magnetic field H is generated around the exciting coil 1A. When crossing 20b, an eddy current B is generated in the heat generating layer 20b of the heat-fixing belt 20 so as to prevent the change of the magnetic field H by electromagnetic induction. When this eddy current B flows through the heat generating layer 20b of the heat fixing belt 20, Joule heat is generated with electric power (W = I ² R) proportional to the resistance of the heat generating layer 20b, and the member to be heated (heating rotating body). The heat fixing belt 20 is heated.

  The frequency of the alternating current applied to the exciting coil 1A is set to, for example, 20 to 50 kHz. In this embodiment, the frequency of the alternating current is set to 30 kHz. Further, in the present embodiment, it has been confirmed that electromagnetic induction heating can be performed extremely well even when a low-cost parallel resonance type excitation circuit power source is used as the excitation circuit 30. Such a parallel resonance type high-frequency power source has a track record in an electromagnetic cooker or the like, and can be constructed at a low cost as a power source for electromagnetic induction heating, and is highly practical and versatile.

  Further, as the magnetic path forming member 41, a magnetic material such as iron, cobalt, nickel, and ferrite can be used, but the most desirable is soft ferrite. Soft ferrite has ferromagnetism, high magnetic permeability, and very high electric resistance, so that eddy current B due to electromagnetic induction does not flow easily. In addition, the hysteresis loss due to the alternating magnetic field is small, and it is most suitable for forming a magnetic path on the side opposite to the exciting coil 1A of the heat generating layer 20b. The magnetic path forming member 41 collects the magnetic flux generated by the exciting coil 1A and the surrounding magnetic flux having a high magnetic flux density of the reaction magnetic field caused by the eddy current to form a magnetic path, enabling efficient heating. At the same time, the magnetic flux leaks to the outside of the fixing device 10 to prevent the peripheral members from being unintentionally heated.

  Both end portions 41e in the circumferential direction of the magnetic path forming member 41 extend in the circumferential direction beyond the region facing the end portions 1Ae in the circumferential direction of the exciting coil 1A. That is, both ends 41e of the magnetic path forming member 41 extend beyond both ends 1Ae of the exciting coil 1A facing each other before and after the moving direction of the heat fixing belt 20 (circumferential direction).

FIG. 6 is a schematic explanatory diagram for explaining a preferable positional relationship between both end portions of the exciting coil 1A and both end portions of the magnetic path forming members facing each other.
As schematically shown in FIG. 6, the relationship between the width m2 of the magnetic path forming member 41 and the coil width m1 of the exciting coil 1A is set to satisfy m2> m1. This is because if m2 is shorter than m1, the magnetic path is not sufficiently formed, and there is a risk that the efficiency is reduced and induction to peripheral members occurs (of course, in the present invention, a leakage electromagnetic field shielding member is arranged). Therefore, the latter problem does not occur.) Table 2 below shows the measurement results of the magnetic flux density around the heating region in the case of m1 <m2 and m1> m2. As shown in Table 2 below, it can be seen that when m1 <m2, the leakage magnetic flux is small and a good shielding effect can be obtained.

  As described above, since both end portions 41e of the magnetic path forming member 41 extend beyond the region facing the exciting coil 1A and further in the circumferential direction of the heat fixing belt 20, the width of the magnetic path forming member 41 is increased. Is larger than the width (heating width) of the exciting coil 1A, and when the heat generating layer 20b induction heats a metal thinner than the skin depth δ, the reaction leaks from the opposite side of the exciting coil 1A across the heat generating layer 20b. Magnetic flux leakage due to a magnetic field can be more effectively prevented, a magnetic flux path with less leakage can be formed, and the shielding effect can be improved.

  In the present embodiment, the leakage electromagnetic field shielding member 6 characteristic of the present invention is disposed so as to surround the electromagnetic field generated from the exciting coil 1A in order to sufficiently reduce exposure to the human body due to the leakage electromagnetic field. The leakage electromagnetic field shielding member 6 is preferably a metal continuum. If it is a continuum, it cannot penetrate beyond the depth that the electromagnetic field can penetrate. Since the depth at which the electromagnetic field can enter is expressed by the mathematical formula shown in (Expression 1), if the thickness of the member is not less than the skin depth δ of (Expression 1), the electromagnetic field will not leak ( Almost close to 0).

  The leaked electromagnetic field shielding member 6 absorbs (induces) the leaked electromagnetic field. However, since it is induced in a metal material, an eddy current is generated in the metal. However, if the material has a sufficiently low resistance, the loss can be reduced to a level with no problem.

  The metal material used for the leakage electromagnetic field shielding member 6 must be a non-magnetic material. Magnetic materials need to have high resistance, and if they are high resistance, there is no danger of heat generation, but the design becomes sensitive because the electromagnetic field is changed. As a metal material used for the leakage electromagnetic field shielding member 6, it can be said that soft ferrite, which is a magnetic material, is also suitable in terms of characteristics, but it is difficult to make a continuous material, is heavy, and further increases in cost. Therefore, it is practically difficult to select a magnetic material.

  Therefore, as the nonmagnetic metal used for the leakage electromagnetic field shielding member in the present invention, silver, copper, aluminum, or an alloy containing a large amount thereof having a low specific resistance is preferable. In particular, aluminum that can realize low specific gravity at low cost is optimal, and can be said to be desirable as a suitable material for a leakage electromagnetic field shielding member. Also in this embodiment, aluminum is used as the material of the leakage electromagnetic field shielding member 6.

  In the present invention, the plate thickness of the leakage electromagnetic field shielding member is preferably 500 μm or more and 2 mm or less, more preferably 800 μm or more and 1.8 mm or less, and a commercial product when a plate thickness of 1.5 mm is selected if possible. Can be used to reduce costs. If the plate thickness is less than 500 μm, the shielding efficiency of the leakage electromagnetic field may be inferior. On the other hand, if the plate thickness exceeds 2 mm, not only is the material wasted, but the overall weight of the device is increased and the size is increased. Therefore, it is not preferable.

  FIG. 7 is a perspective view of the leakage electromagnetic field shielding member 6 used in this embodiment, and FIG. 8 is a plan view thereof. As shown in FIG. 7 and FIG. 8, the leakage electromagnetic field shielding member 6 is a member having one surface of a rectangular parallelepiped and an approximately U-shaped cross section. It has a shape protruding in the left-right direction on the drawing. The overhanging portion is referred to as an overhang portion 6a.

  The overhanging portion 6a is in a state where the distance from the exciting coil 1A is larger than the portion without the overhang (both ends in the longitudinal direction). Since the leakage electromagnetic field shielding member 6 affects the locus of the electromagnetic field formed by the exciting coil 1A, it also affects the induced current generated in the heat generating layer 20b by the electromagnetic field. Therefore, it is the gist of the present invention that the temperature distribution in the rotation axis direction of the heat fixing belt 20 can be made substantially constant by making the leakage electromagnetic field shielding member 6 in an appropriate shape.

In the case of the present embodiment, by properly providing the overhanging portion 6a, the distance between the leakage electromagnetic field shielding member 6 and the exciting coil 1A is in a state where the central portion is separated from the end portion of the exciting coil 1A. Yes. By forming the leakage electromagnetic field shielding member 6 in such a shape, the temperature distribution in the rotation axis direction of the heat fixing belt 20 can be made substantially constant.
Such verification of the operation and effect of the present invention will be left to the section of the fourth embodiment.

  As described above, the first embodiment, which is an exemplary aspect of the fixing device of the present invention, has been described. In the present invention, the arrangement relationship between the exciting coil 1A and the magnetic path forming member 41 with respect to the heat fixing belt 20 is as follows. The present invention is not limited to the embodiment. FIG. 9 is a schematic cross-sectional view of a fixing device 10 ′ according to a modification of the present embodiment. In this modification, only the arrangement relationship between the exciting coil and the magnetic path forming member is different from that of the first embodiment, and the configuration of other members including the leakage electromagnetic field shielding member 6 is the same as that of the first embodiment. . Therefore, in FIG. 9, the members having the same functions as those in the first embodiment are denoted by the same reference numerals as those in FIG.

  In the fixing device 10 ′ of this modification, the magnetic path forming member 41 ′ is disposed on the inner peripheral surface side of the heat fixing belt 20, and the exciting coil 1 </ b> A ′ is disposed on the outer peripheral surface side of the heat fixing belt 20. . That is, the fixing device 10 according to the first embodiment is one in which the arrangement relationship between the exciting coil and the magnetic path forming member is reversed (replaced) with the heating fixing belt 20 as a reference. Even when configured in this way, the same effects as those of the first embodiment can be obtained, and at the same time, the heat dissipation of the exciting coil 1A ′ can be improved.

<Second Embodiment>
FIG. 10 is a schematic cross-sectional view of the fixing device 50 according to the second embodiment, which is an exemplary aspect of the present invention. In the fixing device of the present embodiment, the configuration corresponding to the heating device is only different from that of the first embodiment, and other configurations are the same as those of the fixing device of the first embodiment. Therefore, in FIG. 10, members having the same functions as those in the first embodiment are denoted by the same reference numerals as those in FIG. 1, and a detailed description thereof is partially omitted. That is, portions not mentioned in the following description have the same configuration as that of the first embodiment.

  The fixing device of the present embodiment includes the heating device of the present invention, and a leakage electromagnetic field shielding member 16 is attached thereto as shown in FIG. In the present embodiment, in addition to the first magnetic path forming member (magnetic path forming member) 57 disposed opposite to the exciting coil 11A with the heat fixing belt (heating rotator) 20 interposed therebetween, the first magnetic path formation is also performed. A member 57 is provided with a second magnetic path forming member (second magnetic path forming member) 55 disposed opposite to the excitation coil 11 </ b> A and the heat fixing belt 20.

The fixing device 50 according to the second embodiment is intended to collect the magnetic flux generated by the exciting coil 11A more efficiently and raise the heating efficiency as compared with the first embodiment.
Specifically, as shown in FIG. 10, a thin hollow cylindrical heat-fixing belt 20 having a heat generating layer, and a pressure disposed so as to be in pressure contact with a lower outer peripheral surface of the heat-fixing belt 20 in the figure. A support member 22 is disposed at the center of the heat fixing belt 20.

  The support member 22 is in contact with the inner peripheral surface of the heat fixing belt 20 facing the pressure roll 23 (the lower portion of the inner periphery of the heat fixing belt 20 in the drawing) to form an elastic member 24 that forms a nip portion. On the opposite side (upper part of the inner periphery of the heat fixing belt 20 in the drawing), and a substantially semi-cylindrical ferrite first formed to follow the curved shape of the inner peripheral surface of the heat fixing belt 20. The two magnetic path forming member 55 is supported.

Furthermore, the upper part of the second magnetic path forming member 55 in the figure is formed so as to follow the curved surface shape of the inner peripheral surface of the heat fixing belt 20 through, for example, a hollow spiral coil 11A. The substantially semi-cylindrical coil support member 28 is disposed so as not to contact the inner peripheral surface of the heat fixing belt 20 and to face a part of the inner peripheral surface. The coil support member 28 has a projection 28A on the side facing the second magnetic path forming member 55 at the center thereof, and the excitation coil 11A is disposed in the projection 28A, thereby providing an excitation coil. 11A is sandwiched between the second magnetic path forming member 55 and the exciting coil 11A is held.
A first magnetic path disposed outside the heat fixing belt 20 facing the exciting coil 11A so as to face a part of the outer peripheral surface without contacting the outer peripheral surface of the heat fixing belt 20. A forming member 57 is provided.

  In the case of the fixing device 50 configured as described above, the second magnetic path forming member 55 disposed inside the heat fixing belt 20 with the exciting coil 11A and the heat fixing belt 20 interposed therebetween, and the outside of the exciting coil 11A. Since the first magnetic path forming member 57 and the second magnetic path forming member 57 are provided, the magnetic flux leaking from the exciting coil 11A can be collected and shielded more effectively.

  Further, both end portions 57e in the circumferential direction of the first magnetic path forming member 57 disposed outside the heat fixing belt 20 extend beyond the region facing the exciting coil 11A and further in the circumferential direction. Is formed.

  In this case, both circumferential end portions 57e of the first magnetic path forming member 57 disposed outside the heat fixing belt 20 extend in the circumferential direction beyond both end portions 11Ae of the exciting coil 11A facing each other. Therefore, similarly to the first embodiment, when the heat generating layer 20b induction heats a metal thinner than the skin depth δ, the magnetic flux generated by the reaction magnetic field leaks from the opposite side of the exciting coil 11A across the heat generating layer 20b. Leakage can be prevented more effectively and the shielding effect can be improved.

  In addition, the first magnetic path forming member 57 and the second magnetic path forming member 55 are arranged so as to face each other with the exciting coil 11A and the heat fixing belt 20 interposed therebetween, so that a high frequency power source that applies an alternating current to the exciting coil 11A is provided. It is possible to reduce the frequency of the excitation coil 11A and the number of turns of the excitation coil 11A. Further, it is possible to reduce the cost by reducing the size of the power source and the excitation coil 11A.

  FIG. 11 is a perspective view of the leakage electromagnetic field shielding member 16 used in this embodiment, and FIG. 12 is a plan view thereof. As shown in FIG. 11 and FIG. 12, the leakage electromagnetic field shielding member 16 is a member having one surface of a rectangular parallelepiped shape opened and having a substantially U-shaped cross section, and the longitudinal central portion of the surface facing the opening. Has a shape projecting outward (upward in the drawing). The overhanging portion is referred to as an overhang portion 16a.

The overhanging portion 16a is in a state where the distance from the exciting coil 11A is larger than the portion without the overhang (both ends in the longitudinal direction). That is, by appropriately providing the overhang portion 16a, the distance between the leakage electromagnetic field shielding member 16 and the excitation coil 11A is in a state where the center portion is separated from the end portion of the excitation coil 11A. By forming the leakage electromagnetic field shielding member 16 in such a shape, the temperature distribution in the rotation axis direction of the heat fixing belt 20 can be made substantially constant.
Such verification of the operation and effect of the present invention will be left to the section of the fourth embodiment.

  In this embodiment, the magnetic path forming member is formed by the two constituent members of the first magnetic path forming member 57 and the second magnetic path forming member 55. However, the magnetic path forming member includes the exciting coil 11A and the magnetic path forming member. What is necessary is just to have the part which opposes on both sides of the heat fixing belt 20, and what is necessary is just to arrange | position so that the magnetic path of the magnetic field which the coil 11A and the heat generating layer 20b may pinch | interpose.

  In the present embodiment, in order to improve the shielding effect, both end portions 55e in the circumferential direction of the second magnetic path forming member 55 arranged on the exciting coil 11A side extend beyond the region facing the exciting coil 11A. It is formed so as to extend in the circumferential direction.

  The second embodiment, which is an exemplary aspect of the fixing device of the present invention, has been described above. However, in the present invention, the arrangement relationship of the exciting coil 11A with respect to the heat fixing belt 20 is limited to that of the present embodiment. It is not something. FIG. 13 is a schematic cross-sectional view of a fixing device 50 ′ according to a modification of the present embodiment. This modification is different from the second embodiment only in the arrangement relationship between the exciting coil and the magnetic path forming member, and the configuration of other members including the leakage electromagnetic field shielding member 16 is the same as that in the second embodiment. Therefore, in FIG. 13, members having the same functions as those in the second embodiment are denoted by the same reference numerals as those in FIG.

  In the fixing device 50 ′ of this modification, the exciting coil 11A ′ and the coil support member 28 ′ are disposed on the outer peripheral surface side of the heat fixing belt 20, and the magnetic path forming member sandwiches the exciting coil 11A ′ and the heat fixing belt 20 as they are. Are arranged opposite each other. Even in such a configuration, the same effects as those of the second embodiment can be obtained, and at the same time, the heat dissipation of the exciting coil 11A ′ can be improved.

  In the present invention, it is the “magnetic path forming member” that is disposed opposite to the excitation coil across the heating rotator, facing the magnetic path forming member, and the excitation coil and the heating rotator. It is conceptually divided as a “second magnetic path forming member” to be arranged with the pin in between. Therefore, the magnetic path forming members opposed to each other in FIG. 13 are replaced with the reference numerals in FIG. 9 and the ones arranged on the inner peripheral surface side of the heat fixing belt 20 are the first magnetic path forming members (magnetic path forming members). 57 'and what is arranged on the outer peripheral surface side is a second magnetic path forming member (second magnetic path forming member) 55'.

<Third Embodiment>
FIG. 14 is a schematic cross-sectional view of a fixing device 70 according to a third embodiment, which is an exemplary aspect of the present invention. In the fixing device of the present embodiment, the configuration corresponding to the heating device is only different from that of the first embodiment, and other configurations are the same as those of the fixing device of the second embodiment. Therefore, in FIG. 14, members having the same functions as those in the first and second embodiments are denoted by the same reference numerals as in FIGS. 1 to 10, and a detailed description thereof is partially omitted. That is, portions not mentioned in the following description have the same configurations as those in the first and second embodiments.

The fixing device of the present embodiment includes the heating device of the present invention, and a leakage electromagnetic field shielding member 26 is attached thereto as shown in FIG.
The fixing device according to the present embodiment is configured to provide a heating device with high practicality in consideration of cost reduction, and a fixing device using the same, in which the fixing device according to the second embodiment is configured at a lower cost. It is. The fixing device 70 of the present embodiment is different from the fixing device 50 of the second embodiment in the form of the magnetic path forming member. In this embodiment, the amount of the magnetic path forming member is reduced. A cheaper and lighter heating device and a fixing device using the same are provided.

  As shown in FIG. 14, the fixing device of the present embodiment is disposed so as to be in pressure contact with a thin hollow cylindrical heat fixing belt 20 having a heat generating layer and a lower outer peripheral surface of the heat fixing belt 20 in the figure. And a pressure roller 23, and a support member 22 is disposed at the center of the heat fixing belt 20.

  The support member 22 is in contact with the inner peripheral surface of the heat fixing belt 20 facing the pressure roll 23 (the lower portion of the inner periphery of the heat fixing belt 20 in the drawing) to form an elastic member 24 that forms a nip portion. On the opposite side (upper part of the inner periphery of the heat fixing belt 20 in the drawing), and a substantially semi-cylindrical ferrite first formed to follow the curved shape of the inner peripheral surface of the heat fixing belt 20. One magnetic path forming member (magnetic path forming member) 77 is supported.

  Further, outside the heat fixing belt 20 facing the first magnetic path forming member 77, it is formed in a substantially semi-cylindrical shape so as to follow the curved shape of the outer peripheral surface of the heat fixing belt 20, and is formed in a hollow spiral shape. A coil support member 38 that holds the formed exciting coil 21 </ b> A is provided in non-contact with the outer peripheral surface of the heat fixing belt 20. Further, the first magnetic path forming member 77 and a second magnetic path forming member (first magnet) disposed opposite to each other with the exciting coil 21A and the heat fixing belt 20 interposed therebetween so as to surround the coil support member 38 that holds the exciting coil 21A. 2 magnetic path forming members) 75 are provided.

FIG. 15A is a side view in which only a portion corresponding to the heating device (excluding the leakage electromagnetic field shielding member 26) located in the upper part of the heating fixing belt 20 in the fixing device 70 according to the present embodiment is extracted. FIG. 14 is a cross-sectional view illustrating the cross section taken along the line HH ′ in FIG. FIG. 15B is a plan view in which only the exciting coil 21A in FIG. 15A is extracted.
In this embodiment, since the configuration other than the magnetic path forming member is substantially the same as that of the second embodiment, the description thereof is omitted, and the magnetic path forming member and its peripheral constituent members will be mainly described below.

  The exciting coil 21A is coiled by coiling 11 turns of litz wire, which is a bundle of 90 insulated wires (copper wire) having a diameter of 0.16 mm, which are insulated from each other, wound in a hollow spiral shape for 11 turns. It is. The hollow portion 1Ac of the exciting coil 21A is disposed on the convex portion 38A of the coil support member 38, and a curved shape is maintained following the curved surface shape of the surface of the coil support member 38.

  A second magnetic path forming member 75 is disposed on the upper surface of the exciting coil 21A in the figure so as to cover the exciting coil 21A in a shape substantially along the curved shape of the exciting coil 21A. The path forming member 75, the exciting coil 21 </ b> A, and the coil support member 38 are disposed so as to face the outer peripheral surface without contacting the outer peripheral surface of the heating and fixing belt 20 that moves around.

  A first magnetic path forming member 77 is disposed on the inner side of the heat fixing belt 20 along the inner peripheral surface of the heat fixing belt 20 so as to face the inner peripheral surface in a non-contact manner. The path forming member 77 and the second magnetic path forming member 75 are configured to face each other with the exciting coil 21A and the heat fixing belt 20 interposed therebetween.

  Further, the first magnetic path forming member 77 is supported by a support member 22 of a nonmagnetic insulating member or a nonmagnetic metal member (resin, aluminum, copper, etc.), and this support member 22 also forms a fixing nip. This is supported by receiving a load from the elastic member 24.

  Here, since the supporting member 22 supports the pressing load of the fixing nip, the supporting member 22 needs to be a member having high rigidity, high heat resistance, and high creep resistance, and is difficult to form with a resin material. It is desirable to be formed by. In the present embodiment, aluminum is used in consideration of cost, ease of manufacture, and rigidity. The reason why the non-magnetic metal such as aluminum or copper is used as the metal member is that the support member 22 generates an eddy current (eddy current B in FIG. 5) in the heating coil 20A and the heat generating layer 20b in the heat-fixing belt 20. If a magnetic metal is located at a position where a magnetic field is likely to act, heat is generated by the action of this magnetic field, and therefore, eddy current loss can be extremely reduced by employing a nonmagnetic metal having a large skin depth.

  Here, the 2nd magnetic path formation member 75 arrange | positioned at the exciting coil 21A side is comprised with the continuous body which covers the exciting coil 21A, as FIG.14 and FIG.15 shows. On the other hand, the first magnetic path forming member 77 arranged on the inner peripheral side of the heat fixing belt 20 is divided into a plurality of small piece arcuate members 77A, and the direction (heating) is substantially orthogonal to the rotation direction of the heat fixing belt 20. Thirteen pieces are arranged at an interval of 16 mm in the direction of the rotation axis of the fixing belt 20.

  A small arcuate member 77A of the first magnetic path forming member 77 has an arcuate shape with a thickness of 3 mm and a gentle curvature, and is along the longitudinal direction of the exciting coil 21A (the rotational axis direction of the heat fixing belt 20). The width is 10 mm. The small arcuate member 77A is placed on the support member 22 and is disposed so as not to contact the inner peripheral surface of the heat fixing belt 20 and to substantially correspond to the opposing surface of the exciting coil 21A along the inner peripheral surface. Has been. With the first magnetic path forming member 77 arranged in this way, for example, the magnetic path in the HH ′ cross section of FIG. 15 is formed as shown by the broken line of FIG. Here, FIG. 16 is a schematic cross-sectional view around the excitation coil 21A showing a magnetic path generated by the excitation coil 21A in the fixing device of the present embodiment.

  The reason why the small arcuate members 77A of the first magnetic path forming member 77 are spaced apart is to form a magnetic path by applying a magnetic flux evenly in the direction of the rotation axis of the heat fixing belt 20. What is necessary is just to design suitably the usage-amount of the 1st magnetic path formation member 77 which comprises the 1st magnetic path formation member 77 so that the electromagnetic induction to a surrounding metal member can be prevented with a smaller number.

  Below, the usage-amount of the 1st magnetic path formation member 77 in this 1st magnetic path formation member 77 is examined with reference to FIG. FIG. 17 is a graph showing the degree of induction of the first magnetic path forming member 77 to the support member 22 with respect to the usage amount of the first magnetic path forming member 77. The support member 22 is made of aluminum, and the inductivity of the support member 22 to the metal in the graph of FIG. 17 is smaller as it receives the electromagnetic induction action of the exciting coil 21A. This is a characteristic indicating that it is hardly affected.

  Further, the usage amount of the first magnetic path forming member refers to the total ratio of the length of the small bow member 77A in the same direction to the entire coil length of the exciting coil 21A. For example, when the usage amount is 100%, A state is shown in which the surface of the support member 22 is covered with the small bow member 77A by the same length as the coil length with respect to the coil length of the exciting coil 21A.

  In the case of this embodiment, the coil length is 350 mm, and a total of 13 pieces of small bow members 77A of the first magnetic path forming member 77 having a width of 10 mm are used. The amount is 10 × 13 mm / 350 mm × 100≈37%.

In the case where the inductive degree (0.9) of the dotted line in the figure is less than or equal to 0.9, the inductive action to the support member 22 is a region where the reactive power may increase and the efficiency of the power supply may be reduced. If the used amount of the forming member 77 is 30% or more, it exceeds this and it is understood that there is no problem. Further, if the usage amount is 30% or more, the leakage magnetic field is small, and induction to a metal component other than the support member 22 can be almost eliminated.
Therefore, also in the third embodiment in which the amount of the first magnetic path forming member 77 is reduced in this way, a heating device that can obtain a stable heating state and a fixing device using the same can be provided. .

  Further, in the present embodiment, at least the first magnetic path forming member 77 arranged on the heating and fixing belt 20 side has a plurality of small piece arcuate members 77A spaced from each other across the rotation axis direction of the heating and fixing belt 20. The small piece member 77A can be made small, so that it becomes easy to mold the small piece member 77A, and the dimensional accuracy can be easily obtained. In addition, it is possible to provide a heating device that can reduce the amount of ferrite used as an expensive magnetic path forming member, reduce the weight, and reduce the cost, and a fixing device using the heating device.

  As in the second embodiment, both circumferential ends 77e of the first magnetic path forming member 77 disposed on the inner peripheral side of the heat fixing belt 20 extend beyond the region facing the exciting coil 21A. Further, by forming it so as to extend in the circumferential direction, when the heat generating layer 20b induction-heats a metal thinner than the skin depth δ, the reaction magnetic field leaks from the opposite side of the exciting coil 21A across the heat generating layer 20b. Can effectively prevent the leakage of magnetic flux and improve the shielding effect.

  Further, the exciting coil 21A may be arranged inside the heat fixing belt 20, or the first magnetic path forming member 77 arranged outside the heat fixing belt 20 is constituted by a small piece arcuate member group, and heat fixing. You may comprise the 2nd magnetic path formation member 75 arrange | positioned inside the belt 20 with a continuous body.

  A perspective view of the leakage electromagnetic field shielding member 26 used in the present embodiment is shown in FIG. 18, and a plan view thereof is shown in FIG. As shown in FIG. 18 and FIG. 19, the leakage electromagnetic field shielding member 26 is a member having a rectangular parallelepiped shape whose one surface is open and has a substantially U-shaped cross-section, and the longitudinal central portions of both facing surfaces are outward. It has a shape protruding in the left-right direction on the drawing. The overhanging portion is referred to as an overhang portion 26a.

The overhanging portion 26a is in a state where the distance from the exciting coil 21A is larger than the portion without the overhanging (both ends in the longitudinal direction). That is, by appropriately providing the overhang portion 26a, the distance between the leakage electromagnetic field shielding member 26 and the excitation coil 21A is in a state where the center portion is separated from the end portion of the excitation coil 21A. By forming the leakage electromagnetic field shielding member 26 in such a shape, the temperature distribution in the rotation axis direction of the heat fixing belt 20 can be made substantially constant.
Such verification of the operation and effect of the present invention will be left to the section of the fourth embodiment.

<Fourth Embodiment>
FIG. 20 is a schematic cross-sectional view of a fixing device 90 according to a fourth embodiment, which is an exemplary aspect of the present invention. The overall configuration of the fixing device of this embodiment is similar to the fixing device of the third embodiment, and is substantially the same in cross-sectional view. Accordingly, in FIG. 20, members having the same functions as those in the first to third embodiments are denoted by the same reference numerals as in FIGS. 1 to 14, and a detailed description thereof is partially omitted. That is, portions not mentioned in the following description have the same configuration as in the first to third embodiments.

  The present embodiment is intended to provide a heating device having a high practicality in consideration of cost reduction, and a fixing device using the same, in which the fixing device of the third embodiment is configured at a lower cost. . The fixing device according to this embodiment is different from the configuration of the fixing device 70 shown in the third embodiment in the form of the magnetic path forming member. In this embodiment, the amount of the magnetic path forming member used is reduced. Thus, a cheaper and lighter heating device and a fixing device using the same are provided.

FIG. 21 is a side view in which only a portion corresponding to the heating device (excluding the leakage electromagnetic field shielding member 26) located in the upper part of the heating and fixing belt 20 in the fixing device 90 according to the present embodiment is extracted. It is the figure which looked at the same location as 15 (a) from the same direction. 22 is a sectional view taken along line JJ ′ of FIG. 21, and FIG. 23 is a sectional view taken along line KK ′ of FIG. FIG. 24A shows the positional relationship of the magnetic path forming member group in order to visually explain the meaning of the designation “zigzag arrangement” described later, which shows the positional relationship of the magnetic path forming members in the present embodiment. It is a side view showing typically. FIG. 24B is a plan view in which only the exciting coil 21A in FIG. 24A is extracted.
In this embodiment, since the configuration other than the magnetic path forming member is substantially the same as that of the third embodiment, the description thereof will be omitted, and the magnetic path forming member and its peripheral constituent members will be mainly described below.

  As shown in FIG. 20, in the present embodiment, a first magnetic path forming member (magnetic path forming member) 97 and a second magnetic path forming member (second magnetic path forming member) arranged to face each other. ) 95 is divided into a plurality of small piece arcuate members 97A and 95A, respectively, and the second magnetic path forming member 95 arranged on the exciting coil 21A side with an interval of 16 mm in the rotation axis direction of the heat fixing belt 20 Fourteen and thirteen first magnetic path forming members 97 arranged on the inner peripheral surface side of the heat fixing belt are arranged.

  The positional relationship between the first magnetic path forming member 97 and the second magnetic path forming member 95 is a so-called “staggered arrangement” as shown in FIG. 21 and FIG. The gaps 97As and 95As of the small arcuate members 95A and 97A are asymmetric with respect to the heat fixing belt 20, and the gap 97As of the small arcuate member 97A forming the first magnetic path forming member 97 is formed as the second magnetic path. The small arcuate members 95A forming the member 95 are arranged in a positional relationship such that they are substantially interpolated. In other words, each of the small arcuate member 95A and the small arcuate member 97A includes a gap 97As between each of the small arcuate members 97A and 95A in the opposing first magnetic path forming member 97 and the second magnetic path forming member 95. It arrange | positions so that it may correspond to 95As.

  More specifically, as shown in FIG. 24A, the center positions 95Ac and 97Ac of the small piece arcuate member 95A and the small piece arcuate member 97A correspond to the opposing first magnetic path forming member 97 and the first magnetic path forming member 97, respectively. The two magnetic path forming members 95 are arranged so as to substantially coincide with the centers of the gaps 97As and 95As of the small piece arcuate members 97A and 95A.

As described above, when the first magnetic path forming member 97 and the second magnetic path forming member 95 are divided into a plurality of small piece arcuate members 97A and 95A and arranged so as to be spaced from each other, the surrounding members due to leakage of the magnetic field can be obtained. The effects of electromagnetic induction can be considered.
Therefore, the verification results on the influence of electromagnetic induction on the surrounding members when the number of the small bow members 95A and 97A is changed to provide a gap will be described below.

First, a characteristic change depending on the number of small piece bow members 97A of the second magnetic path forming member 95 arranged on the exciting coil 21A side will be described with reference to FIGS. 25 and 26. FIG.
25 and 26 show electromagnetic induction when a metal member having a size equivalent to that of the exciting coil 21A is brought close to the distance of 5 to 10 mm from the exciting coil 21A when a constant alternating current is applied to the exciting coil 21A. It shows the result of investigating the influence of electromagnetic induction on surrounding metal members from change information such as the inductance value, resistance value, and phase difference between current and voltage. Correctly, FIG. 25 shows a change in the inductance value of the induction state when the metal member is brought close to the usage amount of the magnetic path forming member as a representative characteristic indicating the induction degree to the surrounding metal with respect to the ratio of covering the coil length. FIG. 26 is a graph showing a change in resistance value.

  For example, in the present embodiment, with respect to the coil length of 350 mm, the second magnetic path forming member 95 covers the exciting coil 21A by providing 14 small arch members 95A each having a width of 10 mm and providing a gap. This means that the number of magnetic path forming members used per unit / 350 mm = 40% (corresponding to 40% share area 40% on the horizontal axis).

  The metals close to the exciting coil 21A are aluminum and iron. When these metal members are brought close to each other, as shown in FIG. 25 and FIG. 26, if at least 40% or more of the magnetic path forming member is used, the electromagnetic field around the AC frequency component applied to the exciting coil 21A It can be seen that the effect of is a negligible level.

  Next, FIG. 27 shows the result of investigating the degree of influence of electromagnetic induction on the surrounding members of the first magnetic path forming member 97 in the same manner with the usage amount of the second magnetic path forming member 95 being 40%. The degree of influence of electromagnetic induction on the surrounding members of the first magnetic path forming member 97 is determined by the magnetic field of the exciting coil 21A and the eddy current B of the heat generating layer 20b when the supporting member 22 holding the member is made of metal such as aluminum or iron. The effect of the magnetic field H (see FIG. 5) on the support member 22 metal was investigated.

The inductivity to the support member 22 metal in the graph of FIG. 27 is a characteristic indicating that the smaller the electromagnetic induction effect is, the less the influence of the electromagnetic induction effect is. This is almost the same as the representative characteristics shown in FIGS. 25 and 26, and shows the ratio of the change in the inductance value and the resistance value in the inductive state when the metal member is brought closer. If the degree of induction is 0.9 or more as described above, the influence on the induction is at a level that can be ignored.
As shown in FIG. 27, when the first magnetic path forming member 97 is used in an amount of around 35%, the induction degree becomes 0.9 or more, and it has been found that the influence of electromagnetic induction on the surrounding members can be greatly reduced. .

  From the above-described verification results, it can be seen that the first magnetic path forming member 97 and the second magnetic path forming member 95 may be arranged with appropriate gaps between the first magnetic path forming member 97 and the second magnetic path forming member 95. It is also necessary to consider the heat distribution in the axial direction. For example, the first magnetic path forming member 97 and the second magnetic path forming member 95 are in the same positional relationship with respect to the rotation axis direction of the heat fixing belt 20 (so that each of the small piece arcuate members 95A and 97A faces each other). In the case of being arranged, the magnetic flux is applied to the portion where the first magnetic path forming member 97 and the second magnetic path forming member 95 are orthogonally projected onto the heat fixing belt (the portions where the small bow members 97A and 95A face each other). Concentrates and this part is heated excessively, resulting in a temperature difference (striped temperature unevenness). When such a heating device is applied to a fixing device, if the above temperature difference occurs, problems such as uneven coloring of a toner image to be fixed occur, which is not desirable.

  Therefore, as shown in FIG. 24, the small bow members 97A and 95A are arranged so that they do not have the same positional relationship with respect to the rotation axis direction of the heat fixing belt 20, and in particular, as shown in FIG. It is desirable to adopt a so-called “staggered arrangement” in which 97As and 95As are arranged to complement each other. As shown in FIG. 24, when the first magnetic path forming member 97 and the second magnetic path forming member 95 are arranged in a staggered manner, the magnetic field of the coil acts on the heat generating layer 20b of the heat fixing belt 20 evenly, and heat fixing. The temperature difference of the belt 20 can be reduced, and this enables stable heating without causing problems such as uneven coloring of the fixed image.

  Further, if the small bow members 97A and 95A in the first magnetic path forming member 97 and the second magnetic path forming member 95 are arranged so as to complement the gaps 95As and 97As, for example, the schematic diagram shown in FIG. As described above, they may be arranged so that their positions partially overlap each other. Here, FIG. 28 is a schematic diagram showing an example in which the opposing magnetic path forming members shown in FIG. 21 are arranged by increasing the amount of use of the small bow member (97A) of one (first magnetic path forming member 97). It is a side view. FIG. 28 shows an example in which the usage amount of the small piece arcuate member 97A forming the first magnetic path forming member 97 is increased as compared with the case shown in FIG. 21 of the present embodiment. You may arrange | position by increasing the usage-amount of the small arch-shaped member 95A which forms the member 95. FIG.

  As described above, when the magnetic path forming member is divided into small pieces and arranged as in the first magnetic path forming member 97A and the second magnetic path forming member 95A, the mutual positional relationship is as described above. Considering this, an appropriate magnetic path is formed, temperature unevenness due to concentration of magnetic flux is prevented, and the amount of expensive and heavy magnetic path forming members can be reduced. A heating device and a fixing device to which the heating device can be provided can be provided.

  Further, as shown in FIG. 23, the circumferential end portions 97e of the first magnetic path forming member 97 disposed on the inner peripheral side of the heat fixing belt 20 are moved beyond the region facing the exciting coil 21A. Further, by forming it so as to extend in the circumferential direction, the heat generating layer 20b is sandwiched when the heat generating layer 20b is induction-heated with a metal having a skin depth less than δ, as in the second to third embodiments. Thus, magnetic flux leakage due to the reaction magnetic field leaking from the side opposite to the exciting coil 21A can be more effectively prevented, and the shielding effect can be improved.

  The leakage electromagnetic field shielding member 26 used in this embodiment is the same as that used in the third embodiment, as shown in FIGS. 18 and 19. Therefore, as in the third embodiment, the temperature distribution in the direction of the rotation axis of the heat fixing belt 20 can be made substantially constant by forming the leakage electromagnetic field shielding member 26 in an appropriate shape also in this embodiment. The outstanding operation | movement and effect peculiar to this invention are show | played.

  In particular, in the present embodiment, the second magnetic path forming member 95 arranged outside the exciting coil 21A is not a continuous body, and the small arched members 95A are intermittently arranged at regular intervals. Electromagnetic field leaks to the outside although there is little. As is clear from the previous verification, the leakage electromagnetic field now does not affect the characteristics of the heating device, and it does not affect other metal members, but the influence of the electromagnetic field on the human body. However, it is desired to reduce the leakage as much as possible.

  In order to reduce the leakage electromagnetic field, a leakage electromagnetic field shielding member is generally provided. However, also in this embodiment, the leakage electromagnetic field is effectively shielded by the leakage electromagnetic field shielding member 26. Moreover, the leakage electromagnetic field shielding member 26 is characteristic of the present invention. In addition to the leakage electromagnetic field shielding effect, the excellent effect of uniforming the temperature distribution in the axial direction of the heat fixing belt 20 serving as a heating rotator is provided. Is played.

(Verification of action and effect of the present invention)
The operation and effect of the present invention will be verified.
First, in the fixing device of this embodiment, the temperature distribution in the rotation axis direction of the heat fixing belt 20 was measured after the fixing device was operated for 1 minute with the leakage electromagnetic field shielding member 26 removed. The results are shown graphically in FIG. As can be seen from the graph of FIG. 29, in the fixing device in which the leakage electromagnetic field shielding member 26 is not attached, the heat generation temperature is flat across the entire maximum sheet width, which is an ideal temperature distribution.

  However, as a result of the present inventors' study, it has been found that if the conventional leakage electromagnetic field shielding member is attached as it is, the electromagnetic field generated from the exciting coil 21A is affected, and this temperature distribution is disrupted. In the fixing device of the present embodiment, the result of performing the same test as described above using a straight conventional leakage electromagnetic field shielding member having no overhang in the longitudinal direction instead of the leakage electromagnetic field shielding member 26 is a graph shown in FIG. Is shown. Note that the leakage electromagnetic field shielding member (26 ') of the conventional example used for comparison has a shape shown in a perspective view in FIG.

  As can be seen from the graph of FIG. 31, when the leakage electromagnetic field shielding member 26 ′ of the conventional example is attached, the temperature rises at the end of the heat fixing belt 20 in the rotation axis direction, and the uniformity of the temperature distribution is impaired. . If the fixing device continues to move in this state, both ends of the leading edge when the recording material is inserted into the nip will cause overheating, or the center will be unfixed due to insufficient heat. There is a risk of getting lost.

  Next, the same test as described above was performed on the fixing device according to the fourth embodiment to which the leakage electromagnetic field shielding member 26 having a shape characteristic of the present invention was attached. The results are shown graphically in FIG. As can be seen from the graph of FIG. 32, by using the leakage electromagnetic field shielding member 26 in which the distance from the exciting coil 21 </ b> A is adjusted in advance so that the temperature distribution in the rotation axis direction of the heat fixing belt 20 is substantially constant. The heating temperature is flat across the entire maximum sheet width, and has an ideal temperature distribution.

  In any of the embodiments of the fixing device to which the heating device of the present invention described above is applied, the warm-up time can be made equal to 10 seconds or less, that is, almost equal to zero, and good fixing can be achieved. In addition, it is possible to reliably prevent the occurrence of defective peeling.

  That is, in the fixing device according to these embodiments, for example, in the case of the fixing device of the first embodiment, the pressure roll 23 is rotationally driven by the driving source at a process speed (rotational speed) of 140 mm / s. The heat fixing belt 20 is in pressure contact with the pressure roll 23 and is driven to rotate at a speed of 140 mm / s equal to the process speed of the pressure roll 23.

In the fixing device of each of the above embodiments, the recording material 27 on which the unfixed toner image 25 is transferred by a transfer device (not shown) is formed between the heat fixing belt 20 and the pressure roll 23. While the recording material 27 passes through 1Y and the recording material 27 passes through the nip portion 1Y, it is heated and pressurized by the heat fixing belt 20 and the pressure roll 23, whereby the unfixed toner image 25 is recorded. It is fixed on the surface.
At that time, in the fixing device of each of the above embodiments, the temperature of the heat fixing belt 20 is 160 ° C. at the inlet of the nip portion 1Y during the fixing operation due to the frequency of the high frequency current flowing through the exciting coils 1A, 11A, and 21A. It is controlled to about ~ 200 ° C.

  In such a fixing device, at the same time as the image forming signal is input, the pressure roll 23 starts rotating, and a high-frequency current is applied to the exciting coils 1A, 11A, and 21A. In the fixing device according to the first embodiment, for example, when 1000 W of electric power is applied to the exciting coil 1A, the temperature of the heat fixing belt 20 is about 8 seconds or less from room temperature due to induction heating. The fixing temperature is reached. That is, the warm-up is completed within the time required for the recording material 27 to move from the paper feed tray (not shown) to the fixing device 10. Therefore, in the fixing device of the first embodiment, the fixing process can be performed without waiting for the user. The same applies to the fixing devices of the second to fourth embodiments.

In general, when a recording material onto which a large amount of toner such as a color solid image has entered a thin paper of about 60 g / m ² enters the nip portion of the fixing device, the release of the toner and the surface of the heat fixing belt is released. Usually, the attractive force between the layers becomes strong, and it becomes difficult to peel off the recording material from the surface of the heat fixing belt. However, in the fixing device of each of the embodiments described above, the heat fixing belt 20 is formed so as to have a concave shape inside the nip portion 1Y while the shape of the heat fixing belt 20 is a convex shape outside the nip portion 1Y. .

  That is, the direction of the recording material 27 is wound around the pressure roll 23 inside the nip portion 1Y, and the direction of the heat fixing belt 20 is convex from the concave shape to the convex shape at the outlet portion of the nip portion 1Y. Therefore, the recording material 27 can not keep up with the rapid change in shape of the heat fixing belt 20 due to the stiffness (rigidity) of the recording material itself, and is naturally peeled off from the heat fixing belt 20. Is done. As a result, it is possible to reliably prevent the problem of peeling failure of the recording material 27.

  Although the heat fixing belt 20 in the above embodiment is formed in a thin cylindrical shape, the belt shape is naturally not limited to a cylindrical shape. For example, the heat fixing belt 20 extends between a plurality of rollers. A heat fixing belt may be formed by stretching the belt.

[Method of manufacturing heating apparatus]
The manufacturing method of the heating device of the present invention is a method of manufacturing the heating device of the present invention as described above. With reference to FIG. 1 and FIG. 2, if the heating device included in the fixing device of the first embodiment is taken as an example, the manufacturing method of the heating device of the present invention is:
A method of manufacturing a heating device for heating an endless heat fixing roll (heating rotator) 20 having at least a heat generating layer 20b that generates heat by electromagnetic induction action,
(A) The exciting coil 1A for inductively heating the heat fixing belt 20 is arranged along a part of the inner peripheral surface (in the present invention, the outer peripheral surface may be used) of the heat fixing belt 20,
(B) A leakage electromagnetic field shielding member 6 made of a nonmagnetic metal and configured to shield an electromagnetic field leaking from the periphery of the exciting coil 1A is arranged so as to surround the electromagnetic field generated from the exciting coil 1A. .
The shape of the leakage electromagnetic field shielding member 6: The distance between the leakage electromagnetic field shielding member 6 and the exciting coil 1A depends on the position of the heating fixing belt 20 in the rotation axis direction (the depth direction in FIG. 1). The shape is adjusted so that the temperature distribution at is almost constant.

In the manufacturing method of the heating device of the present invention,
The thickness of the heat generating layer 20b of the heat fixing belt 20 is made thinner than its skin depth, and the exciting coil 1A is formed on the surface of the heat fixing belt 20 to generate a variable magnetic field along the thickness direction of the heat generating layer 20b. Non-contact and formed by winding a wire along the surface,
(C) The fluctuation magnetic field generated by the eddy current flowing in the exciting coil 1A and the heat generating layer 20b is opposed to the exciting coil 1A across the heat fixing belt 20 and is not in contact with the surface of the heat fixing belt 20. You may further include the process of arrange | positioning the magnetic path formation member 41 formed in the following shape which forms a magnetic path and shields the magnetic field.
The shape of the magnetic path forming member 41: The surface of the magnetic path forming member 41 facing the exciting coil 1A is the outer peripheral surface shape of the heat fixing belt 20 (in the case where the exciting coil is arranged on the outer peripheral surface side, the inner peripheral surface shape). A shape formed to follow the shape.

  The steps (A), (B), and (C) are not particularly limited in their order, and may be appropriately selected in consideration of workability and the like. Of course, other steps may be included. Examples of other steps include a step of disposing the second magnetic path forming members (second magnetic path forming members) 55, 75, and 95 mentioned in the second to fourth embodiments.

  The shape of the leakage electromagnetic field shielding member 6 is preliminarily determined according to the position of the heating fixing roll (heating rotator) 20 in the rotation axis direction (depth direction in FIG. 1), and the distance between the leakage electromagnetic field shielding member 6 and the exciting coil 1A is heated and fixed. By adjusting the temperature distribution in the rotation axis direction of the belt 20 to be substantially constant, a heating device having a uniform temperature distribution in the axial direction of the heat fixing belt 20 can be manufactured.

  The shape of the leakage electromagnetic field shielding member specifically designed is not limited to the leakage electromagnetic field shielding member 6 shown in FIGS. 7 and 8 in the present invention. For example, the shape illustrated in the first to fourth embodiments or the modifications thereof (the distance between the leakage electromagnetic field shielding member and the excitation coil is greater in the center than in the end of the excitation coil. However, the relationship between the end portion and the center portion may be reversed depending on various conditions such as the characteristics of the exciting coil to be used and the arrangement of the members. Or it does not necessarily need to be left-right symmetric about the center part of the rotation axis direction of the heating rotating body. The point that the shape of the leakage electromagnetic field shielding member is appropriately adjusted so that the temperature distribution becomes substantially constant each time is important in the present invention.

  The fixing device of the fourth embodiment is replaced with an excitation coil (excitation coil length L2) having a shorter length (excitation coil length L1) in the width direction of the excitation coil 21A (rotational axis direction of the heat fixing belt 20). In addition, the fixing device from which the leakage electromagnetic field shielding member 26 was removed was subjected to a verification test similar to the “verification of the operation and effect of the present invention” described in the fourth embodiment. The results are as shown in the graph of FIG. As can be seen from the graph of FIG. 33, a sufficient heat generation temperature cannot be obtained at both axial ends of the heat fixing belt 20, and the effective heat generation width does not reach the maximum sheet width.

  When the leakage electromagnetic field shielding member is disposed in the fixing device in such a state, according to the manufacturing method of the present invention, the leakage electromagnetic field shielding member and the excitation coil 21A are arranged depending on the position of the heat fixing belt 20 in the rotation axis direction. The distance is designed by adjusting in advance so that the temperature distribution in the rotation axis direction of the heat-fixing belt 20 is substantially constant. As a result, it is conceivable to select a leakage electromagnetic field shielding member 26 ′ shown in FIG. 30 that is straight and has no overhang in the longitudinal direction. In this case, of course, the shape of the leakage electromagnetic field shielding member is adjusted according to various conditions such as the characteristics of the exciting coil to be used and the arrangement of the members, and is included in the concept of the manufacturing method of the present invention.

  Actually, an excitation coil (excitation coil length L2) in which the length (excitation coil length L1) in the width direction of the excitation coil 21A (rotational axis direction of the heating fixing belt 20) is further shortened from the fixing device of the fourth embodiment. For the fixing device in which the leakage electromagnetic field shielding member 26 is replaced with the leakage electromagnetic field shielding member 26 ′, the same verification test as described above was performed. The results are as shown in the graph of FIG. As can be seen from the graph of FIG. 34, the heat generation temperature that is insufficient at both ends in the axial direction of the heat fixing belt 20 increases, and the heat generation temperature is flat across the entire maximum sheet width, resulting in an ideal temperature distribution. Yes.

  In the manufacturing method of the present invention, the (A) and (C) processes other than the process of adjusting the shape of the leakage electromagnetic field shielding member (B) characteristic of the present invention and various other processes are conventionally known techniques. Accordingly, any manufacturing method can be adopted, and the present invention is not limited in any way.

[Image forming apparatus]
Hereinafter, an exemplary embodiment of the image recording apparatus of the present invention to which the heating apparatus of the present invention is applied will be described with reference to FIG. FIG. 35 is a schematic configuration diagram of an image recording apparatus 100 which is an exemplary aspect of the image recording apparatus of the present invention.

  As shown in FIG. 35, the image recording apparatus 100 includes, for example, a photosensitive drum 121 that rotates in the direction of arrow F, a charger 122 such as a corotron that charges the photosensitive drum 121 in advance, and each color component image information. Based on the above, an image writing device such as a laser scanning device (ROS) (not shown) that writes an electrostatic latent image corresponding to each color component on the surface of the photosensitive drum 121 (in this example, a beam is attached to the beam from the device) 123 And a rotary type developing device 124 in which developing devices 241 to 244 corresponding to the respective colors of yellow (Y), magenta (M), cyan (C) and black (K) are mounted on a rotary holder 245, and An electrostatic latent image for each color component of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the surface of the drum 121, and the rotary developing device 124. After each electrostatic latent image is visualized with the corresponding color toner of each developing device 241 to 244 in the image forming apparatus, primary transfer is sequentially performed on the intermediate transfer belt 130, and each color component toner image on the outer peripheral surface of the intermediate transfer belt 130 is overlaid. The transferred image is secondarily transferred onto the surface of the recording material P and fixed by the fixing device 160.

  Here, the recording material P is transported from the recording material tray 150 toward the predetermined transport path by the feed roll 151, and is temporarily stopped by the registration roll (registration roll) 152 in the transport path. The toner image is conveyed to the secondary transfer position 140 at a predetermined timing. Here, the transfer image (unfixed toner image) formed on the outer peripheral surface of the intermediate transfer belt 130 is secondarily transferred to the surface of the recording material P.

  After the secondary transfer, the recording material P is guided to the transport belt 153 and is transported to the fixing device 160 by the transport belt 153. When the secondary transfer process is completed, residual toner on the surface of the photosensitive drum 121 is cleaned by the drum cleaner 125, and residual toner on the outer peripheral surface of the intermediate transfer belt 130 is cleaned by the belt cleaner 141.

  In the image recording apparatus 100 configured as described above, in the present embodiment, the fixing device 160 of the present invention including the heating device of the present invention is used as the fixing device 160. By using the heating device or the fixing device of the present invention, the temperature in the direction perpendicular to the conveyance direction of the recording material P becomes substantially uniform at the nip portion of the fixing device, and a stable high-quality fixed image can be obtained. Obtainable. In addition, it is possible to provide an image recording apparatus that has a short warm-up time and can be stably fixed by heating.

  The image recording apparatus to which the present invention is applicable is not limited to the rotary type described above, and can be applied to various image recording apparatuses within the scope of the object of the present invention. For example, the same effects can be obtained even when applied to a so-called tandem type image recording apparatus.

  As described above, by providing the fixing device with the heating device of the present invention, it is possible to design an energy-saving fixing device that can reduce the warm-up time to 10 seconds or less. In addition, it is possible to design a highly practical heating apparatus that can realize cost reduction. By providing such a heating device or a fixing device, it is possible to provide an image recording apparatus that eliminates variations in fixing temperature in the direction perpendicular to the conveyance direction, has excellent stability and safety, and has an extremely short warm-up time. it can.

  In addition, according to the method for manufacturing a heating device of the present invention, the rotating shaft of the heating rotating body that is the object to be heated can be obtained simply by appropriately adjusting and designing the shape of the leakage electromagnetic field shielding member that is often required to be installed. The heating temperature distribution in the direction can be made substantially uniform.

1 is a schematic cross-sectional view of a fixing device according to a first embodiment that is an exemplary aspect of the present invention. FIG. 2 is a schematic enlarged sectional view for explaining a layer configuration of a heat fixing belt in the fixing device of FIG. 1. It is a model expanded sectional view for demonstrating the layer structure of the heat-fixing belt of a modification. It is a characteristic view which shows the relationship between the applied frequency for every copper layer thickness, and heat_generation | fever. FIG. 2 is an explanatory diagram for explaining a heating principle of a heat fixing belt in the fixing device of FIG. 1. It is a schematic explanatory drawing for demonstrating the suitable positional relationship of the both ends of an exciting coil, and the both ends of the magnetic path formation member which opposes. It is a perspective view which shows the leakage electromagnetic field shielding member in the fixing device of FIG. It is a top view which shows the leakage electromagnetic field shielding member in the fixing device of FIG. FIG. 9 is a schematic cross-sectional view illustrating a modification of the fixing device in FIG. 1. FIG. 6 is a schematic cross-sectional view of a fixing device according to a second embodiment which is an exemplary aspect of the present invention. It is a perspective view which shows the leakage electromagnetic field shielding member in the fixing device of FIG. It is a top view which shows the leakage electromagnetic field shielding member in the fixing device of FIG. FIG. 14 is a schematic cross-sectional view illustrating a modification of the fixing device in FIG. 13. FIG. 6 is a schematic cross-sectional view of a fixing device according to a third embodiment which is an exemplary aspect of the present invention. (A) is a side view of only a portion (excluding a leakage electromagnetic field shielding member) corresponding to the heating device, which is located at the upper part of the heating fixing belt in the fixing device of FIG. 14, and (b), It is the top view which extracted only the exciting coil in (a). FIG. 15 is a schematic cross-sectional view around an excitation coil representing a magnetic path generated by the excitation coil in the fixing device of FIG. 14. It is a graph which shows the induction | guidance | derivation degree to the support member with respect to the usage-amount of the 1st magnetic path formation member in the 1st magnetic path formation member of the fixing device of FIG. It is a perspective view which shows the leakage electromagnetic field shielding member in the fixing device of FIG. It is a top view which shows the leakage electromagnetic field shielding member in the fixing device of FIG. FIG. 6 is a schematic cross-sectional view of a fixing device according to a fourth embodiment which is an exemplary aspect of the present invention. FIG. 21 is a side view showing only a portion (excluding a leakage electromagnetic field shielding member) corresponding to the heating device, which is located in the upper part of the heating fixing belt in the fixing device of FIG. 20. It is JJ 'sectional drawing of FIG. It is KK 'sectional drawing of FIG. 20A schematically shows the positional relationship of the magnetic path forming member group in order to visually explain the meaning of the designation “staggered arrangement” indicating the positional relationship of the magnetic path forming members in the fixing device of FIG. It is a side view, (b) is the top view which extracted only the exciting coil in (a). FIG. 21 is a graph showing a change in inductance value in an induced state when a metal member is brought close to a usage amount of a second magnetic path forming member in the fixing device of FIG. 20. FIG. 21 is a graph showing a change in resistance value in an induced state when a metal member is brought close to a usage amount of a second magnetic path forming member in the fixing device of FIG. 20. FIG. 21 is a graph showing the degree of induction to the support member with respect to the amount of use of the first magnetic path forming member in the first magnetic path forming member of the fixing device of FIG. 20. It is a schematic side view which shows the example which increased and used the usage-amount of the one small piece arcuate member about the opposing magnetic path formation member shown by FIG. FIG. 21 is a temperature distribution diagram of heat generated by a fixing device in which a leakage electromagnetic field shielding member is removed from the fixing device of FIG. 20 when verifying the operation and effect of the present invention. It is a perspective view which shows the leakage electromagnetic field shielding member of the prior art example used in verification about the effect | action and effect of this invention. FIG. 31 is a temperature distribution diagram of heat generated by a conventional fixing device in which the leakage electromagnetic field shielding member shown in FIG. 30 is applied to the fixing device shown in FIG. FIG. 21 is a temperature distribution diagram of heat generated by the fixing device of FIG. 20 for verifying the operation and effect of the present invention. FIG. 21 is a temperature distribution diagram of heat generated by the fixing device using an exciting coil with a leakage electromagnetic field shielding member removed from the fixing device of FIG. 20 and a short length in the width direction. FIG. 31 is a heat generation temperature distribution diagram by the fixing device in which the leakage electromagnetic field shielding member of FIG. 30 is applied to the fixing device of FIG. 20 and an excitation coil having a short width in the width direction is used. 1 is a schematic configuration diagram of an image recording apparatus which is an exemplary embodiment of the present invention. It is a perspective view which shows an example of the conventional fixing device which employ | adopted the induction heating system. FIG. 37 is a cross-sectional view of a fixing roll in the fixing device of FIG. 36. FIG. 37 is a cross-sectional view showing a modification of the fixing device of FIG. 36 with only a fixing roll and a coil extracted.

Explanation of symbols

  1A, 11A, 21A: Excitation coil, 6, 16, 26: Leakage electromagnetic field shielding member, 10, 50, 70, 90, 160: Fixing device, 18, 28, 38: Coil support member, 20: Heat fixing belt (heating Rotating body), 22: support member, 23: pressure roll, 24: elastic member, 25: unfixed toner image, 27: recording material, 30: excitation circuit, 41: magnetic path forming member, 55, 75, 95 : Second magnetic path forming member (second magnetic path forming member), 57, 77, 97: first magnetic path forming member (magnetic path forming member), 100: image recording device, 121: photosensitive drum, 122: Charger: 124: rotary developing device; 125: drum cleaner; 130: intermediate transfer belt; 140: secondary transfer position; 141: belt cleaner; 150: recording material tray; 153: Conveyor belt, 241: Developer, 245: Rotating holder, 300: Fixing roll, 310: Coil, 320: Pressure roll

Claims (17)

A heating device for heating an endless heating rotating body having a heat generating layer that generates heat by at least electromagnetic induction,
An exciting coil for inductively heating the heating rotator is arranged along a part of the outer peripheral surface or the inner peripheral surface of the heating rotator,
A leakage electromagnetic field shielding member made of a non-magnetic metal for shielding an electromagnetic field leaking from around the excitation coil is disposed so as to surround the electromagnetic field generated from the excitation coil,
In addition, in the temperature distribution in the rotation axis direction when the distance between the leakage electromagnetic field shielding member and the excitation coil is the same at any position in the rotation axis direction of the heating rotator, the leakage electromagnetic field shielding is applied to a portion that becomes high in the temperature distribution in the rotation axis direction. The temperature distribution in the rotation axis direction of the heating rotator is substantially reduced by reducing the distance between the member and the excitation coil and / or increasing the distance between the leakage electromagnetic field shielding member and the excitation coil at a low temperature part. The distance between the leakage electromagnetic field shielding member and the excitation coil is adjusted to be constant, and the shape of the leakage electromagnetic field shielding member depends on the position of the heating rotator in the rotation axis direction. A heating device, wherein the heating device is formed so as to have a different distance from the exciting coil. The heating apparatus according to claim 1 the distance between the exciting coil and the leakage electromagnetic field shielding member, characterized in that towards the center portion is away from the end of the exciting coil. The leakage electromagnetic field shielding member, the heating device according to claim 1 or 2, characterized in that it consists of the following aluminum plate or aluminum alloy plate 2mm or thickness 500 [mu] m. The thickness of the heat generating layer of the heating rotator is thinner than the skin depth,
The excitation coil is formed by winding a wire along the surface in a non-contact manner with the surface of the heating rotator so as to generate a variable magnetic field along the thickness direction of the heat generating layer,
A magnetic path of a variable magnetic field generated by the exciting coil is formed so as to face the opposite side of the exciting coil across the heating rotating body and not in contact with the surface of the heating rotating body, thereby shielding the magnetic field. The heating device according to any one of claims 1 to 3, wherein a magnetic path forming member is provided. The heating rotator has an endless belt shape, rotates in a predetermined direction, and both ends of the magnetic path forming member extend beyond both ends of the opposing excitation coils before and after the rotation direction. The heating apparatus according to claim 4 , wherein the heating apparatus is provided. The heating apparatus according to claim 5 , wherein the heating rotator is cylindrical. The heating apparatus according to any one of claims 4 to 6 , wherein the magnetic path forming member is formed of soft ferrite. The heating layer of the heating rotator is formed of copper having a thickness of 2 to 15 μm mainly generating heat, and the frequency of the alternating current applied to the exciting coil is 20 to 100 kHz. The heating apparatus according to any one of claims 4 to 7 . A second magnetic path forming member that forms a magnetic path of a fluctuating magnetic field generated by the excitation coil and shields the magnetic field by facing the magnetic path forming member across the exciting coil and the heating rotator. The heating device according to any one of claims 4 to 8 , wherein is arranged. At least one of the magnetic path forming member and the second magnetic path forming member is composed of a small piece member group in which a plurality of small piece members are arranged with a predetermined gap therebetween in the rotation axis direction of the heating rotator. The heating apparatus according to claim 9 , wherein Both the magnetic path forming member and the second magnetic path forming member are constituted by the small piece member group, and each small piece of the small piece member group constituting the magnetic path forming member and the second magnetic path forming member. The members and the gaps formed by the two small piece members adjacent to each other in the small piece member group constituting the magnetic path forming member or the second magnetic path forming member facing each other are arranged so as to face each other. The heating device according to claim 10 , wherein Both the magnetic path forming member and the second magnetic path forming member are configured by the small piece member group, and the small piece member group of the magnetic path forming member and the small piece member group of the second magnetic path forming member. The heating apparatus according to claim 10 , wherein the gaps are arranged so as to complement each gap between the opposing small piece member groups. Each small piece member in the small piece member group that constitutes the magnetic path forming member and the second magnetic path forming member has a gap between each small piece member group on the other side facing the center in the rotation axis direction of the heating rotator. It is arrange | positioned so that it may correspond with the center in the said direction substantially, The heating apparatus of Claim 11 or 12 characterized by the above-mentioned. A heat-fixing belt having at least a heat generating layer and an outermost release layer, and a nip portion that is in contact with the heat-fixing belt and in which a recording material carrying an unfixed toner image is inserted and heated and pressed to fix are formed. A fixing device including a pressure member and a heating member for heating the heat fixing belt,
A fixing device wherein the heating member, wherein said a heating apparatus according to any one of claims 1 to 13, the heating fixing belt and the heating rotating body. At least an image forming means for forming an unfixed toner image on the surface of the recording material, and a nip through which the recording material on which the unfixed toner image is formed is inserted by contacting the heat fixing belt and the pressure member. An image forming apparatus comprising: a fixing unit having a portion formed thereon; and a heating member that heats the heating and fixing belt.
The heat-fixing belt has at least a heat generating layer and an outermost release layer, and
The image forming apparatus wherein the heating member is a heating apparatus according to any one of claims 1 to 13, heating rotator the heating fixing belt. A method of manufacturing a heating device for heating an endless heating rotator having at least a heat generating layer that generates heat by electromagnetic induction action,
An exciting coil for inductively heating the heating rotator is arranged along a part of the outer peripheral surface or inner peripheral surface of the heating rotator,
A heating apparatus comprising: a non-magnetic metal, and a leakage electromagnetic field shielding member having a shape described below for shielding an electromagnetic field leaking from around the excitation coil so as to surround the electromagnetic field generated from the excitation coil. Method.
-Shape of the leakage electromagnetic field shielding member: When a leakage electromagnetic field shielding member having an arbitrary shape is provided, the leakage electromagnetic field shielding member and the excitation coil in a temperature distribution in the temperature distribution in the rotation axis direction of the heating rotator Of the leakage electromagnetic field shielding member and the excitation coil with respect to a part that becomes low in temperature, the distance between the exciting electromagnetic coil and the excitation coil is increased. A shape in which the distance from the excitation coil is adjusted so that the temperature distribution in the rotation axis direction of the heating rotator is substantially constant. The thickness of the heat generating layer of the heating rotator is thinner than the skin depth,
The excitation coil is formed by winding a wire along the surface in a non-contact manner with the surface of the heating rotator so as to generate a variable magnetic field along the thickness direction of the heat generating layer, And,
A magnetic path of a variable magnetic field generated by the exciting coil is formed so as to face the opposite side of the exciting coil across the heating rotating body and not in contact with the surface of the heating rotating body, thereby shielding the magnetic field. The method for manufacturing a heating device according to claim 16 , further comprising a step of disposing a magnetic path forming member formed in the following shape.
-Shape of the magnetic path forming member: a shape formed so that the surface of the magnetic path forming member facing the excitation coil follows the inner peripheral surface shape or outer peripheral surface shape of the heating rotator.

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