JP2005285639A - Induction heating device and image forming device equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating device in which occurrence of magnetic field inter-linkage to a core material and occurrence of inverted magnetic field in the core material can be prevented even if thickness of the conductive exothermic layer of a heating roller is made as thin as that of the surface skin thickness δ or less, and in which shortening of temperature rising time is possible with a high heating efficiency. <P>SOLUTION: This induction heating device is provided with the heating roller 1 which is composed of a core material 11 installed at the center part of the rotation, a heat resistant retaining layer 12 installed at the outer peripheral side of the core material 11, and an conductive exothermic layer 13 that is installed at the outer peripheral side of the heat resistant retaining layer 12 and that exotherms in the fluctuating magnetic field, and also provided with a magnetic field generating means which is arranged so as to cover a part of the outer peripheral part of the heating roller 1 and which generates the fluctuating magnetic field, while at the part not covered by the magnetic field generating means, the heating roller 1 is constituted to conduct the heat generated by the conductive exothermic layer 13 to a heated material member, and the heat resistant retaining layer 12 is constituted to be formed with non-conductive material that is dispersed with magnetic particles 16 in its inside. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device in dry electrophotographic equipment, a drying device in wet electrophotographic equipment, a drying device in an ink jet printer, an induction heating device suitably used for an erasing device for rewritable media, and an image including the induction heating device. The present invention relates to a forming apparatus.

  In a heating device, for example, a fixing device in dry electrophotographic equipment, a drying device in wet electrophotographic equipment, a heating device for erasing device for rewritable media, etc., a halogen lamp is provided inside a heating roller having a hollow core material such as aluminum, A configuration in which a heating roller is heated by a halogen lamp is widely used. The method using such a halogen lamp has a problem that the rise at the start of heating is slow and the warm-up time is long.

  Therefore, a conductive heating layer is provided on the heating roller, an alternating magnetic field is applied to the conductive heating layer by magnetic field generating means to generate eddy current, and the heating roller is heated by Joule heat due to the eddy current, as shown in FIG. Inductive heating apparatus 100 has attracted attention. The induction heating apparatus 100 includes a heating roller 101, a heating coil 2 that is a magnetic field generating unit disposed so as to surround a part of the outer peripheral portion of the heating roller 101 to heat the heating roller 101, and a high-frequency current to the heating coil 2. Excitation circuit 7 for flowing heat, temperature detecting element 8 for detecting the heat generation temperature of the heating roller 101, and pressure roller 3 in contact with the lower end portion of the outer peripheral surface of the heating roller 101. As shown in FIG. 21, the heating roller 101 is provided by sequentially laminating a cylindrical core member 111 positioned at the rotation center of the heating roller 101 and an outer peripheral surface of the core member 111 in an outward direction. The heat-resistant holding layer 112, the conductive heat generating layer 113, the elastic layer 114, and the surface release layer 115 are configured. The core material 111 is made of iron, or a metal such as stainless steel or aluminum. The heat-resistant holding layer 112 is formed of a heat-resistant sponge, the conductive heat generating layer is formed of a metal sleeve made of nickel or soft iron, the elastic layer 114 is formed of heat-resistant silicon rubber, and the surface release layer 115 is made of a Teflon-based material.

  In the conventional induction heating device 100 described above, the heating roller 101 having the conductive heat generation layer 113 is induction-heated by the heating coil 2 and is brought into contact with the heating roller 101 and the pressure roller 3 heated to a certain temperature. By passing a recording paper 5 that is a heated material having an unfixed toner image 6 through a certain nip portion 4, the recording paper 5 is heated to fix the toner image 6.

  In the above-described conventional induction heating apparatus 100, in order to speed up the rise at the start of heating of the recording paper 5, it is necessary to shorten the temperature rising time by induction heating of the conductive heat generating layer 113 as much as possible. It is desired to reduce the heat capacity of the heat generating layer 113. As one of means for reducing the heat capacity, a method of replacing the heating roller with a belt can be considered. However, this method has a problem that a mechanism for preventing meandering is newly required. Therefore, in the conventional induction heating apparatus 100 using a heating roller, an attempt is made to reduce the thickness of the conductive heat generating layer 113 from the viewpoint of reducing the heat capacity of the conductive heat generating layer 113 (for example, Patent Document 1). (See the fixing device described in 1).

  In the fixing device described in Patent Document 1, in order to shorten the heating time and secure the mechanical strength, the thickness of the conductive heat generating layer is the depth at which the magnetic field penetrates into the conductive heat generating layer, which will be described later. It is characterized by having a composite structure in which the conductive heat generating layer is backed up by a low heat conductive layer and a high heat conductive cylindrical rigid body.

In the induction heating apparatus shown in FIG. 20 as well, from the viewpoint of making the conductive heat generating layer 113 as thin as possible, the thickness of the conductive heat generating layer 113 is made smaller than the “skin thickness” to make the conductive heat conductive layer 113 thinner. It is possible to reduce the heating time by reducing the heat capacity of the heat generating layer 113.
JP 2002-49261 A

In general, in induction heating in which an eddy current is generated in a heat generating member such as metal using an alternating magnetic field and heat is generated by the eddy current, the electric field induced in the heat generating member is expressed by the following formula (1) from the surface of the heat generating member. It is known to enter by a depth of δ. This δ is referred to as “skin thickness”. Here, σ ₁ is the conductivity of the heat generating member, μ ₁ is the relative magnetic permeability of the heat generating member, μ ₀ is the magnetic permeability in vacuum, and f is the frequency.

δ = {2 / (σ ₁ · μ ₁ · μ ₀ · 2πf)} ^1/2 ―― (1)
Incidentally, in the conventional induction heating apparatus 100 shown in FIG. 20 as described above, the thickness of the conductive heat generating layer 113 of the heating roller 101 shown in FIG. Is made thinner than the skin thickness δ, the heat capacity of the conductive heat generating layer 113 can be reduced, so that the temperature raising time can be shortened. However, since the thickness of the conductive heat generating layer 113 of the heating roller 101 is equal to or less than the skin thickness δ, a part of the magnetic field 41 (leakage magnetic flux 43) generated by the magnetic field generating means 102 as shown in FIG. Passes through the conductive heat generating layer 113 and the heat resistant holding layer 112 and is linked to the core material 111. Under this condition, an eddy current is generated in the core material 111 in a direction that cancels the interlinking magnetic field, and the core material 111 itself self-heats due to the eddy current, and at the same time cancels the magnetic field 41 generated by the magnetic field generating means 102. A magnetic field (reversal magnetic field 44) is generated. The reversal magnetic field 44 reaches the conductive heat generating layer 113 again and interlinks to weaken the total magnetic field interlinked with the conductive heat generating layer 113, thereby reducing the heat generation amount of the entire conductive heat generating layer 113, that is, the heat generation efficiency. Will be reduced. That is, even if it can contribute to shortening of the temperature rise time by reducing the thickness of the conductive heat generating layer 113 to the skin thickness δ or less and reducing the temperature rise time, the heating efficiency is deteriorated. There is a problem that power consumption increases during continuous printing. In this regard, the same applies to the fixing device described in Patent Document 1.

  Therefore, the present invention has been made to solve the above-described problem. Even if the thickness of the conductive heat generation layer of the heating roller is reduced to the skin thickness δ or less, the magnetic field linkage to the core material can be reduced. An object of the present invention is to provide an induction heating apparatus that can prevent the generation of a reversal magnetic field in a core material and that can shorten the heating time with high heating efficiency.

  The induction heating apparatus of the present invention made to solve the above problems includes a core material provided at the center of rotation, a heat resistant holding layer provided on the outer peripheral side of the core material, and an outer peripheral side of the heat resistant holding layer. A heating roller comprising at least a conductive heating layer that generates heat in a varying magnetic field, and a magnetic field generating means for generating the varying magnetic field disposed so as to surround a part of an outer peripheral portion of the heating roller. An induction heating device configured to transmit heat generated by the conductive heating layer to a material to be heated in a portion that is not surrounded by the magnetic field generation means, the heat resistant holding layer Is formed of a non-conductive material in which conductive particles are dispersed.

  When the thickness of the conductive heating layer of the induction heating device is smaller than the skin thickness δ, a part of the magnetic field (leakage magnetic flux) generated by the heating coil passes through the conductive heating layer. Covers heat-resistant holding layer. Since magnetic particles are mixed in the heat-resistant holding layer, the leakage magnetic flux interlinks with the mixed and dispersed magnetic particles. Therefore, eddy currents are generated in the magnetic particles, but since the magnetic particles are dispersed, the path of the eddy current loop generated in each magnetic particle is minute, and the shape of each magnetic particle The magnetic particles absorb the magnetic field without generating heat because the dispersed positions or the direction of the particles are different. Therefore, it is possible to prevent the leakage magnetic flux that is a part of the magnetic field generated by the heating coil from interlinking with the core material, and to prevent the generation of a reversal magnetic field in the core material.

  In the above induction heating device, instead of the heat-resistant holding layer of the heating roller, a magnetic shielding layer that is located on the core material side and formed of a nonconductive material in which conductive particles are dispersed, and The heat roller may be provided with a heat-resistant elastic layer that is located on the conductive heat generating layer side and formed of a non-conductive material without including conductive particles.

  In the induction heating apparatus including the heating roller provided with a magnetic shielding layer and a heat-resistant elastic layer, the length of the magnetic shielding layer of the heating roller in the rotation axis direction is greater than or equal to the length of the conductive heating layer in the rotation axis direction. In addition, the end of the magnetic shielding layer and the end of the conductive heat generating layer may be configured not to overlap. Further, when the mechanism for supporting the rotation of the heating roller is configured, the heating roller rotation support member may support the core material having the magnetic shielding layer formed on the surface thereof. Further, when a heating roller rotation driving member such as a gear is used as a medium for transmitting the rotation operation to the core material of the heating roller, the heating roller rotation driving member passes through the magnetic shielding layer and passes through the core material. You may comprise so that it may latch directly on. Moreover, you may make it provide the slit formed in the rotating shaft direction in the said magnetic shielding layer of the said heating roller.

  In each of the induction heating devices described above, an outer circumferential surface of the core member of the heating roller may be provided with an annular groove portion that goes around the outer periphery or a linear groove portion that is parallel to the rotation axis direction.

  Another induction heating device of the present invention is a heating roller comprising at least a core material provided at the center of rotation and a conductive heating layer provided on the outer peripheral side of the core material and generating heat in a varying magnetic field. And a magnetic field generating means for generating the fluctuating magnetic field, which is disposed so as to surround a part of the outer peripheral portion of the heating roller, and wherein the heating roller is electrically conductive at a portion not surrounded by the magnetic field generating means. An induction heating apparatus configured to transmit heat generated by the heat generating layer to a material to be heated, wherein the core material is formed of a non-conductive material.

  In the present invention, an image forming apparatus can be configured using the induction heating apparatus having the above-described features as a fixing apparatus.

  The induction heating device of the present invention generates a heat in a variable magnetic field provided on a core provided at the rotation center, a heat-resistant holding layer provided on the outer peripheral side of the core, and an outer peripheral side of the heat-resistant holding layer. A heat roller comprising at least a conductive heat generating layer, and a magnetic field generating means for generating a variable magnetic field disposed so as to surround a part of the outer peripheral portion of the heat roller, and a heat resistant holding layer of the heat roller However, it is formed of a nonconductive material in which conductive particles are dispersed. Therefore, even if the thickness of the conductive heat generating layer of the heating roller is made thinner than the skin thickness δ, it is possible to prevent the magnetic field linkage to the core material and the generation of the reversal magnetic field in the core material, and the high heating efficiency. Thus, it is possible to provide an induction heating apparatus capable of shortening the heating time.

  In the heating roller of the induction heating device, instead of the heat-resistant holding layer, a magnetic shielding layer that is located on the core material side and is formed of a non-conductive material in which conductive particles are dispersed, and a conductive heating layer When the heat roller is provided with a heat-resistant elastic layer that is located on the side and formed of a non-conductive material without containing conductive particles, the respective portions of the heat-resistant holding layer are manufactured by forming two layers. Can be facilitated, and the cost can be reduced. Further, by changing the hardness of the two layers, the amount of deformation at the nip portion where the heating roller is in contact with the material to be heated can be adjusted.

  In the induction heating apparatus provided with the magnetic shielding layer and the heat-resistant elastic layer on the heating roller, the length of the magnetic shielding layer of the heating roller in the rotation axis direction is equal to or greater than the rotation axis direction length of the conductive heating layer, If the end of the magnetic shielding layer and the end of the conductive heat generation layer are configured not to overlap, the magnetic field that goes around the end of the conductive heat generation layer and tries to interlink with the core reaches the core. The magnetic particles of the magnetic shielding layer can be linked to each other before the eddy current, and the eddy current of the core material can be suppressed. Therefore, the heat generation and the generation of the reversal magnetic field in the core material can be more effectively suppressed.

  Further, when configuring the mechanism for supporting the rotation of the heating roller, if the core material with the magnetic shielding layer formed on the surface is supported by the heating roller rotation support member, the core material is covered with the magnetic shielding layer. As a result, the strength against bending is increased, and the deflection generated at the nip portion where the heating roller is in contact with the material to be heated can be reduced. Therefore, the core portion can be reduced in diameter and thickness. Further, when a heating roller rotation driving member such as a gear is used as a medium for transmitting the rotation operation to the core material of the heating roller, the heating roller rotation driving member is directly locked to the core material through the magnetic shielding layer. When configured to prevent damage to the magnetic shielding layer such as cracks caused by the rotational torque of the heating roller rotation driving member, which is likely to occur when the heating roller rotation driving member such as a gear is locked to the magnetic shielding layer. Can do. Further, if the magnetic shielding layer is provided with a slit formed in the direction of the rotation axis, even if the magnetic shielding layer is thermally expanded by heat from the conductive heat generating layer, the expansion can be absorbed by the slit. It is possible to prevent damage to the magnetic shielding layer due to the difference in thermal expansion of the core material.

  In each of the induction heating devices described above, if the outer circumferential surface of the core material of the heating roller is provided with an annular groove portion that circulates around the outer periphery or a linear groove portion that is parallel to the rotation axis direction, a vortex generated on the outer peripheral surface side of the core material. Since the path of the current loop is shortened, eddy currents in the core material can be suppressed, and more effective heat generation and generation of a reversal magnetic field in the core material can be suppressed.

  Another induction heating device of the present invention is a heating roller comprising at least a core material provided at the center of rotation, and a conductive heating layer provided on the outer peripheral side of the core material and generating heat in a varying magnetic field, and The heating roller is arranged so as to surround a part of the outer peripheral portion of the heating roller, and includes a magnetic field generating means for generating a variable magnetic field, and the heating roller generates a conductive heating layer in a portion not surrounded by the magnetic field generating means. An induction heating apparatus configured to transmit heat to a material to be heated, wherein the core material is formed of a non-conductive material. For this reason, eddy current due to the magnetic field interlinking with the core material is not generated, so that the generation of heat and the reverse magnetic field in the core material can be suppressed.

  According to the image forming apparatus of the present invention, since the induction heating apparatus having the above-described features is provided, an image with high quality can be output.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of an induction heating device in the present embodiment. In FIG. 1, an induction heating apparatus 10 according to the present embodiment includes a heating roller 1 and a heating coil (magnetic field generating means) arranged so as to surround a part of the outer peripheral portion of the heating roller 1 in order to heat the heating roller 1. 2. An excitation circuit 7 for supplying a high-frequency current to the heating coil 2, a temperature detection element 8 for detecting the heat generation temperature of the heating roller 1, and a pressure roller 3 in contact with the lower end portion of the outer peripheral surface of the heating roller 1. Except for the heating roller 1, it is the same as the conventional induction heating device 100 described above. As shown in FIG. 4, the heating roller 1 includes a core material 11 positioned at the center of rotation of the roller 1, and a heat resistant holding layer 12 that is provided on the outer peripheral side of the core material 11 in order and stacked outward. The conductive heating layer 13, the elastic layer 14, and the surface release layer 15 are configured.

  The core material 11 has a cylindrical shape or a columnar shape, and is formed of a metal such as iron, stainless steel, or aluminum. In the present embodiment, the core material 11 is a cylindrical shape having a thickness of 3 mm and is made of aluminum. is there.

  The heat-resistant holding layer 12 is provided for suppressing deformation of the heating roller 1 at the nip portion 4 which is a contact portion between the heating roller 1 and the pressure roller 3, and is made of silicon sponge or the like which is a nonconductive material. Although it is formed, other materials may be used as long as they are nonconductive materials having heat resistance or heat insulation and flexibility. In the present embodiment, the heat-resistant holding layer 12 has a thickness of 5 mm and is made of silicon rubber that is a non-conductive material.

  In the heat-resistant holding layer 12, magnetic particles 16 made of nickel-zinc ferrite powder having a diameter of 1 mm or less are mixed in silicon rubber so as to be evenly dispersed. As the magnetic particles 16, copper-zinc ferrite powder, conductive powder having magnetism such as iron or nickel, or conductive powder such as carbon or aluminum can be used. Care must be taken when mixing these magnetic particles 16 into the silicon rubber, so that the individual particles are dispersed or dispersed so that the magnetic particles 16 do not form a large chain. Is to be mixed in an insulated state.

  The conductive heating layer 13 is a heating element that generates heat based on the principle of induction heating by an alternating magnetic field generated by the heating coil 2, and has a thickness of 30 μm to 100 μm in order to shorten the heating time. . As a material for the conductive heat generating layer 13, in order to generate heat by induction heating, stainless steel such as SUS430 or a conductive metal having magnetism such as iron is generally used, but a material having a particularly high relative permeability is suitable. Yes, a silicon steel plate, an electromagnetic steel plate, nickel steel, or the like may be used. Even a non-magnetic material can be used as long as it has a high resistance value such as SUS304 stainless steel because it can generate heat by induction heating. Furthermore, the above-described material having a high relative magnetic permeability may be arranged in a nonmagnetic material such as ceramic or resin so as to have conductivity. Further, in order to increase the calorific value, it may be composed of a composite material composed of a plurality of materials. In the present embodiment, the conductive heat generating layer 13 is made of nickel and has a thickness of 40 μm. According to the above-described equation (1), when nickel is used as the heat generating member, when the frequency f is 40 kHz, the above-described skin thickness δ is 0.1 mm or more. The thickness of the layer 13 is thinner than the skin thickness δ.

  The elastic layer 14 is provided in order to improve the adhesion between the melted toner and the surface release layer 15, and the material is heat-resistant silicon rubber (LTV, RTV, HTV) or the like. In the present embodiment, the elastic layer 14 has a thickness of 400 μm and is made of silicon rubber (LTV).

  The surface release layer 15 has a role of preventing the toner whose viscosity is lowered by being heated at the nip portion 4 from adhering to the heating roller 1, and is a copolymer of PFA (tetrafluoroethylene and perfluoroalkyl vinyl ether). ) And PTFE (polytetrafluoroethylene). In the present embodiment, the surface release layer 15 has a thickness of 30 μm and is formed of PFA (Teflon).

  The upper end portion of the pressure roller 3 is in contact with the heating roller 1 to form a nip portion 4 through which the recording paper 5 that is a material to be heated passes. The pressure roller 3 includes a cored bar formed of iron, stainless steel, or aluminum and a heat-resistant elastic layer formed of silicon rubber or the like on the outer peripheral surface of the cored bar. A surface release layer made of PFA or PTFE may be formed on the surface of the pressure roller 3. The pressure roller 3 is pressed against the heating roller 1 by an elastic member such as a spring (not shown), and a nip portion 4 having a width of about 7 mm is formed between the pressing roller 3 and the heating roller 1.

  The heating coil 2 (magnetic field generating means) has a shape as shown in FIG. 2 and generates an alternating magnetic field to cause the conductive heating layer 13 of the heating roller 1 to generate heat. As shown in FIG. 1, the heating coil 2 is disposed so as to surround the outer peripheral portion of the heating roller 1. By installing the heating coil 2 outside the heating roller 1 as described above, the heating coil 2 can be easily cooled against the radiant heat from the heating roller 1 as compared with the case where it is installed inside the heating roller 1. be able to. Therefore, the amount of heat generated by the copper loss of the heating coil 2 itself, which increases at a high temperature, can be suppressed, so that a reduction in heating efficiency can be prevented.

  The material used for the heating coil 2 is required to have heat resistance, but in the present embodiment, 30 litz wires with a diameter of 0.3 mm are twisted (enameled wires are stranded) Is used. In order to suppress the copper loss generated in the heating coil 2, it is recommended that the total resistance value of the heating coil 2 is 0.5Ω or less, preferably 0.1Ω or less. A plurality of heating coils 2 may be arranged according to the size of the recording paper 5 to be fixed.

  The excitation circuit 7 is used for flowing a high-frequency current through the heating coil 2, and FIG. 3 shows its circuit configuration. This circuit configuration is a kind of circuit configuration called a half bridge type SEPP system.

  In the excitation circuit 7, a capacitor 7a is connected in series with the heating coil 2, a switching element 7b is connected in series to the heating coil 2 and the capacitor 7a, and a switching element 7c is connected in parallel. ing. The two switching elements are alternately turned on and off at a predetermined frequency through the control circuit 7d in the figure, and thereby heated by the resonance phenomenon of the circuit formed by the heating coil 2 and the capacitor 7a. A high-frequency current flowing through the coil 2 is generated. In the figure, 7e is a rectifier circuit and 7f is an oscillation circuit. An alternating magnetic field is generated by applying a high-frequency current of 20 kHz or more to the heating coil 2 using the excitation circuit 7. When this alternating magnetic field is linked to the conductive heat generating layer 13 of the heating roller 1, an eddy current is generated in the conductive heat generating layer 13, and the conductive heat generating layer is caused by Joule heat due to the resistance of the conductive heat generating layer 13 itself. 13 generates heat. The temperature control of the heating coil 2 is performed by adjusting the output of the excitation circuit 7 based on the detection signal of the temperature detection element 8 that is arranged in the vicinity of the entrance of the nip portion 4 and is composed of, for example, a thermistor. A series of temperature detection and temperature control by power control is controlled by a control circuit unit (not shown) in the excitation circuit 7.

  Next, operation | movement of said induction heating apparatus 10 is demonstrated. The induction heating device 10 first warms up and switches to the main operation after the warm-up is completed. In the warm-up, the switching element 7b and the switching element 7c of the excitation circuit 7 are repeatedly turned on and off at a predetermined frequency, whereby a high-frequency alternating current is applied to the heating coil 2. By this high frequency current, a high frequency alternating magnetic field is generated in the heating coil 2, and this alternating magnetic field is linked to the conductive heat generating layer 13 of the heating roller 1, thereby generating an eddy current in the conductive heat generating layer 13. As a result, the heating roller 1 generates heat. The amount of heat generated at this time is about 1000 W. Then, the heating roller 1 starts to rotate and the pressure roller 3 is driven to rotate. The surface temperature of the heating roller 1 is constantly detected by the temperature detecting element 8, and when the surface temperature of the heating roller 1 reaches a predetermined temperature of 180 ° C., the warm-up is completed, and the frequency of the alternating current applied to the heating coil 2 is determined. While switching to the main operation, the surface temperature of the heating roller is maintained at a predetermined temperature in the main operation. Under this state, the recording paper 5 on which the unfixed toner image is transferred is conveyed to the nip portion 4, and the toner image is melted and fixed by the heat of the heating roller 1 and the pressure of the pressure roller 3. A robust image is formed by being fixed on the top.

  In the induction heating apparatus 10 described above, as described above, the heat-resistant holding layer 12 is formed of a non-conductive material in which the magnetic particles 16 are dispersed, and thus has the following effects. That is, the conductive heat generating layer 13 is made of nickel, has a thickness of 40 μm, and is thinner than the skin thickness δ as described above. Therefore, as shown in FIG. 5, a part of the magnetic field 41 (leakage magnetic flux 42) generated by the heating coil 2 passes through the conductive heat generating layer 13 and reaches the heat resistant holding layer 12. Since the magnetic particles 16 are mixed in the heat-resistant holding layer 12, the leakage magnetic flux 42 is linked to the mixed and dispersed magnetic particles 16. Therefore, although eddy currents are generated in the magnetic particles 16, since the magnetic particles 16 are dispersed, the path of the eddy current loop generated in each magnetic particle 16 is very small, and each magnetic material Since the shape of the particles, the dispersed positions, the direction of the particles, and the like are different, the magnetic particles 16 absorb the magnetic field without generating heat. Therefore, the leakage magnetic flux 42 which is a part of the magnetic field 41 generated by the heating coil 2 can be prevented from interlinking with the core material 11, and the generation of a reversal magnetic field in the core material 11 can be prevented. Therefore, according to the above induction heating device, even when the thickness of the conductive heat generating layer of the heating roller is reduced to the skin thickness δ or less, the magnetic field linkage to the core material and the generation of the reversal magnetic field in the core material are prevented. In addition, it is possible to provide an induction heating apparatus capable of shortening the temperature raising time with high heating efficiency.

  In the induction heating apparatus 10 described above, the magnetic particles 16 are mixed evenly into the heat-resistant holding layer 12, but as shown in FIG. You may do it. Thus, by dispersing and mixing the magnetic particles 16 in the vicinity of the core material 11, a decrease in the rubber hardness of the silicon rubber of the heat-resistant holding layer 12 can be suppressed, and the core material 11 can be formed without impairing the necessary deformation at the nip portion 4. It is possible to prevent the magnetic field from interlinking.

  In the induction heating apparatus 10, instead of the heat-resistant holding layer 12 formed on the heating roller 1, as shown in FIG. 7, the magnetic shielding layer 17 laminated in two layers from the outer surface of the core material 11 toward the outside. And the heat-resistant elastic layer 18 may be formed on the heating roller 1. Of these two layers, the magnetic shielding layer 17 has a thickness of 4 mm and is mainly composed of silicon rubber which is a non-conductive material, and the magnetic particles 16 which are conductive particles are mixed and dispersed inside the silicon rubber. Let it form. The heat-resistant elastic layer 18 has a thickness of 6 mm, does not include the magnetic particles 16, and is formed only from a silicone rubber sponge. As described above, by forming the corresponding portion of the heat-resistant holding layer 12 into two layers, manufacturing of each layer can be facilitated, and cost reduction can be achieved. Further, by changing the hardness of the two layers, the deformation amount in the nip portion 4 where the heating roller 1 is in contact with the recording paper 5 can be adjusted. As the non-conductive material used for the magnetic shielding layer 17, in addition to the above silicon rubber, engineering resin materials such as polyimide, PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PBS (polybutylene terephthalate) are used. ) Etc., or ceramic may be used. Further, as a material used for the heat resistant elastic layer 18, silicon rubber may be employed.

  In the above induction heating apparatus in which the heating roller 1 includes the magnetic shielding layer 17 and the heat-resistant elastic layer 18, the length of the magnetic shielding layer 17 in the rotation axis direction is the rotation of the conductive heating layer 13 as shown in FIG. You may comprise so that it may be more than an axial direction length and the edge part of the magnetic shielding layer 17 and the edge part of the electroconductive heat generating layer 13 may not overlap. For example, the length of the conductive heat generating layer 13 is 318 mm, and the length of the magnetic shielding layer 17 is 330 mm. By configuring in this way, the magnetic particles 16 of the magnetic shielding layer 17 wrap around from the end of the conductive heat generating layer 13 and try to link the magnetic material to the core material 11 before reaching the core material 11. Since the eddy current of the core material 11 can be suppressed, the heat generation and the generation of the reversal magnetic field in the core material 11 can be more effectively suppressed.

  In the induction heating apparatus provided with the magnetic shielding layer 17 and the heat-resistant elastic layer 18 on the heating roller 1, the magnetic shielding layer 17 is formed on the surface as a mechanism for supporting the rotation of the heating roller 1, as shown in FIG. You may comprise the core material 11 made so that the heating roller rotation support member 19 may support. For example, the core material 11 is formed of aluminum having a thickness of 1.5 mm, and the magnetic shielding layer 17 is formed so as to cover the surface of the core material 11. The magnetic shielding layer 17 is made of polyimide reinforced with 4 mm thick glass fiber. The heating roller rotation support member 19 uses a ball bearing, and the heating roller rotation support member 19 is installed so that the ball bearing is in contact with the surface of the magnetic shielding layer portion 17. By doing so, since the core material 11 is covered with the magnetic shielding layer 17 and the strength against bending is increased, the deflection generated in the nip portion 4 where the heating roller 1 is in contact with the recording paper 5 can be reduced. The material 11 can be reduced in diameter and thinned.

  Since the diameter of the heating roller 1 is not changed when the core material 11 is reduced in diameter or thinned, if the core material 11 can be reduced in diameter, the distance between the conductive heating layer 13 and the core material 11 becomes longer. Accordingly, since the amount of generation of the reversal magnetic field in the core material 11 is reduced, the content of the magnetic particles 16 in the magnetic shielding layer 17 can be reduced. In addition, the thinning of the core material reduces the volume of the portion where the eddy current that causes the generation of the reversal magnetic field is generated, so that the influence of the reversal magnetic field can be reduced. The content of body particles can be reduced.

  In the induction heating apparatus provided with the magnetic shielding layer 17 and the heat-resistant elastic layer 18 on the heating roller 1, as shown in FIG. 10, a heating roller rotation driving member 20 such as a gear serves as a medium for transmitting the rotation operation to the core material 11. The heating roller rotation driving member locking portion 20 a of the heating roller rotation driving member 20 such as a gear may be directly locked to the core material 11 through the magnetic shielding layer 17. By doing in this way, it originates in the rotational torque of the heating roller rotation drive member 20 which is easy to occur when the heating roller rotation drive member locking part 20a of the heating roller rotation drive member 20 such as a gear is locked to the magnetic shielding layer. It is possible to prevent damage to the magnetic shielding layer 17 such as cracks.

  In the induction heating apparatus provided with the magnetic shielding layer 17 and the heat-resistant elastic layer 18 on the heating roller 1, as shown in FIG. 11, the magnetic shielding layer 17 is provided with a slit 21 formed in the rotation axis direction. Also good. In FIG. 11, the number of the slits 21 is one, but the number of the slits 21 may be two as shown in FIG. 12, and the magnetic shielding layer 17 itself may be divided into a plurality of blocks. In FIG. 11, the width of the slit 21 is about 1 mm and the depth is the same as the thickness of the magnetic shielding layer 17. However, the depth of the slit 21 may be made shallower than the thickness of the magnetic shielding layer 17. Good. Further, the slit 21 may be formed in a spiral shape. By doing in this way, even if the magnetic shielding layer 17 is thermally expanded by the heat from the conductive heat generating layer 13, this expansion can be absorbed by the slit 21, and the thermal expansion difference between the magnetic shielding layer 17 and the core material 11. It is possible to prevent the magnetic shielding layer 17 from being damaged.

  In each of the induction heating devices described above, on the outer peripheral surface of the core material 11 of the heating roller 1, as shown in FIG. 13, an annular groove part that goes around the outer periphery, or a line parallel to the rotation axis direction as shown in FIG. A groove portion may be provided. Alternatively, a spiral groove (not shown) may be provided. By doing so, since the path of the eddy current loop generated on the outer peripheral surface side of the core material 11 is shortened, the eddy current of the core material 11 can be suppressed, and more effective heat generation and reversal magnetic field in the core material 11 can be achieved. Can be suppressed.

  Next, induction heating apparatuses in other embodiments other than those described above will be described with reference to FIGS. 15 to 18. The other embodiments other than those described above are almost the same as the first embodiment described above. The difference is that the core material 11 of the heating roller 1 is formed of a non-conductive material instead of a metal. Is a point. FIG. 15 shows a cross section of the heating roller 1. In FIG. 15, the core material 11 is formed of polyimide, but may be formed of engineering plastics such as PPS, PEEK, PBT, etc., as long as the material has heat resistance and strength. Moreover, in order to improve mechanical strength, it is desirable to mix glass fiber 30% or more. Moreover, you may comprise with inorganic materials, such as a ceramic.

  FIG. 16 shows the magnetic coupling efficiency between the heating coil 2 and the heating roller 1 in the case of the heating roller using polyimide as the core material and the heating roller using aluminum according to the first embodiment described above. It is a graph of the result of having measured. The vertical axis represents the magnetic coupling efficiency, and the horizontal axis represents the frequency of the coil current flowing through the heating coil 2. FIG. 16 shows that the magnetic coupling efficiency is better when the core material is non-conductive polyimide than when the core material is conductive aluminum. In addition, when the core material is conductive, it is necessary to use it in an area where the magnetic coupling state is good, and thus it is understood that the coil current of the heating coil 2 needs to be set to a higher frequency. Even when a magnetic shielding layer and a heat-resistant elastic layer were used instead of the heat-resistant holding layer, the measurement results of the magnetic coupling efficiency between the heating coil 2 and the heating roller 1 were the same as described above. Therefore, according to the induction heating device in the other embodiment described above, since the core material is formed of a non-conductive material, an eddy current in the core material is not generated by a magnetic field interlinked with the core material. Heat generation and reversal magnetic field generation in the core material can be suppressed.

  In the induction heating apparatus using the non-conductive material polyimide as the core material, the magnetic coupling efficiency is improved as described above, so that it is not necessary to flow a high-frequency coil current to the heating coil 2. Therefore, it is possible to use a simple excitation circuit 31 or excitation circuit 32 with one output side switching element as shown in FIGS. Thus, it is possible to provide an induction heating apparatus with high heating and high rate.

  Next, a color image forming apparatus in which the induction heating apparatus of the present invention is used will be described.

  A color image forming apparatus in which the induction heating apparatus of the present invention is used is a so-called tandem printer in which four color visible image forming units 50 are arranged along a recording medium conveyance path as shown in FIG. Specifically, four sets of visible image forming units 50Y are arranged along the recording paper conveyance path that connects the supply tray 70 of the recording paper P (material to be heated) and the fixing device 80 using the induction heating device of the present invention. , 50M, 50C, and 50B are provided, and each color toner is multiplex-transferred onto the recording paper P conveyed by the recording paper conveying means 60 of the endless belt, and then fixed by the fixing device 80 to form a full-color image. To form. The recording paper transporting means 60 includes an endless transport belt 33 that is stretched by a pair of drive rollers 61 and an idling roller 62 and that is rotated at a predetermined peripheral speed (134 mm / s in this embodiment). The recording paper is electrostatically adsorbed on the belt and conveyed. Each visible image forming unit 50 is provided with a charging roller 52, a laser beam irradiation means 53, a developing device 54, a transfer roller 55, and a cleaner 56 around the photosensitive drum 51, and the developing device of each unit. Each contains toner of yellow (Y), magenta (M), cyan (C), and black (B). Each visible image forming unit forms a toner image on the recording paper P by the following process. That is, after the surface of the photosensitive drum 51 is uniformly charged by the charging roller 52, the surface of the photosensitive drum 51 is laser-exposed according to image information by the laser light irradiation means 53 to form an electrostatic latent image. Thereafter, the developing device 54 develops the toner image with respect to the electrostatic latent image on the photosensitive drum 51 and conveys the visualized toner image by the transfer roller 55 to which a bias voltage having a polarity opposite to that of the toner is applied. Transfer is sequentially performed on the recording paper P conveyed by the means 60.

  Thereafter, the recording paper P is peeled off from the transport belt 63 by the curvature of the driving roller 61 and then transported to the fixing device 80. Therefore, an appropriate temperature and pressure are given by the fixing roller maintained at a predetermined temperature. Then, the toner is dissolved and fixed on the recording paper P to form a robust image.

  The induction heating device described above is not limited to the fixing device described above, but can also be used as a heating device such as a drying device in a wet electrophotographic apparatus, a drying device in an inkjet printer, or an erasing device for rewritable media.

  The induction heating device of the present invention can be effectively used as a fixing device in dry electrophotographic equipment, a drying device in wet electrophotographic equipment, a drying device in an inkjet printer, an erasing device for rewritable media, or the like.

It is a block diagram of the induction heating apparatus of this invention. It is a perspective view of a heating coil. It is a circuit block diagram of an excitation circuit. It is a cut perspective view of a heating roller. It is explanatory drawing of an effect | action of a heating roller. It is sectional drawing of the heating roller of the example from which the structure of a heat-resistant holding layer differs. It is sectional drawing of a heating roller provided with a magnetic shielding layer and a heat-resistant elastic layer. It is sectional drawing of the heating roller which made the rotation-axis direction length of the magnetic shielding layer longer than the electroconductive heat generating layer. It is sectional drawing of the heating roller comprised so that the core material in which the magnetic shielding layer was formed in the surface may support a heating roller rotation support member. It is sectional drawing of the heating roller which latched the heating roller rotation drive member directly to the core material. It is a disassembled perspective view of the heating roller provided with the slit in a magnetic shielding layer. It is a disassembled perspective view of the heating roller of the other example provided with the slit in the magnetic shielding layer. It is a perspective view of the core material provided with the annular groove part. It is a fragmentary perspective view of the core material provided with the linear groove part. It is sectional drawing of the heating roller in which the core material was formed with the nonelectroconductive material. It is the graph which showed the magnetic coupling efficiency of a heating coil and a heating roller. It is a circuit configuration of a simplified excitation circuit. It is a circuit configuration of another example of a simplified excitation circuit. It is a block diagram of the color image forming apparatus in which the induction heating apparatus of this invention is used. It is a block diagram of the induction heating apparatus of a prior art example. It is a cutting perspective view of the heating roller of the induction heating device of the conventional example. It is explanatory drawing of an effect | action of the heating roller of the induction heating apparatus of a prior art example.

Explanation of symbols

1 Heating roller 2 Heating coil (magnetic field generating means)
3 Pressure roller 4 Nip part 5 Recording paper (heated material)
6 Toner Image 7 Excitation Circuit 7a Capacitor 7b Switching Element 7c Switching Element 7d Control Circuit 7e Rectification Circuit 7f Oscillation Circuit 8 Temperature Detection Element 10 Induction Heating Device 11 Core Material 12 Heat Resistant Holding Layer 13 Conductive Heating Layer 14 Elastic Layer 15 Surface Release Layer 16 Magnetic particle 17 Magnetic shielding layer 18 Thermal insulation elastic layer 19 Heating roller rotation support member 20 Heating roller rotation driving member 20a Heating roller rotation driving member locking portion 21 Slit 22 Annular groove portion 23 Linear groove portion 24 Eddy current loop 25 Eddy current Loop 31 Excitation circuit 31a Capacitor 31b Switching element 31d Control circuit 31e Rectifier circuit 31f Oscillation circuit 32 Excitation circuit 32a Capacitor 32b Switching element 32d Control circuit 32e Rectification circuit 32f Oscillation circuit 41 Magnetic flux 42 Leakage magnetic flux 43 Leakage magnet 44 Inverted magnetic flux 50 Visible image forming unit 50Y Visible image forming unit 50M Visible image forming unit 50C Visible image forming unit 50B Visible image forming unit 51 Photosensitive drum 52 Charging roller 53 Laser light irradiation means 54 Developer 55 Transfer Roller 56 Cleaner 60 Recording paper conveying means 61 Driving roller 62 Idling roller 63 Conveying belt 70 Supply tray 80 Fixing device 100 Induction heating device 101 Heating roller 111 Core material 112 Heat resistant holding layer 113 Conductive heat generating layer 114 Elastic layer 115 Surface release layer P Recording paper

Claims (9)

A core material provided at the center of rotation, a heat-resistant holding layer provided on the outer peripheral side of the core material, and a conductive heating layer provided on the outer peripheral side of the heat-resistant holding layer and generating heat in a variable magnetic field A heating roller and a magnetic field generating means for generating the fluctuating magnetic field disposed so as to surround a part of the outer peripheral portion of the heating roller, and the heating at a portion not surrounded by the magnetic field generating means An induction heating device configured such that a roller transmits heat generated by the conductive heating layer to a heated material,
The induction heating device, wherein the heat-resistant holding layer is formed of a non-conductive material in which magnetic particles are dispersed.   Instead of the heat-resistant holding layer, a magnetic shielding layer that is located on the core material side and is formed of a non-conductive material in which conductive particles are dispersed, and a conductive layer that is located on the conductive heat generation layer side and is conductive. The induction heating apparatus according to claim 1, wherein the heating roller includes a heat-resistant elastic layer formed of a non-conductive material without containing particles.   The length of the magnetic shielding layer in the rotation axis direction is not less than the length of the conductive heat generation layer in the rotation axis direction, and the end of the magnetic shielding layer and the end of the conductive heat generation layer do not overlap. The induction heating apparatus according to claim 2 configured.   The induction heating apparatus according to claim 2 or 3, wherein a heating roller rotation support member supports the core member having the magnetic shielding layer formed on a surface thereof.   The induction heating apparatus according to claim 4, wherein a heating roller rotation driving member serving as a medium for transmitting a rotation operation to the core material is configured to pass through the magnetic shielding layer and be directly locked to the core material.   The induction heating apparatus according to any one of claims 2 to 5, further comprising a slit formed in the magnetic shielding layer in a rotation axis direction.   The induction heating device according to any one of claims 1 to 6, further comprising an annular groove portion that makes a round around the outer periphery or a linear groove portion that is parallel to the rotation axis direction on the outer peripheral surface of the core member. A heating roller comprising at least a core material provided at the center of rotation and a conductive heating layer provided on the outer peripheral side of the core material and generating heat in a varying magnetic field, and a part of the outer periphery of the heating roller The heating roller is arranged to surround and includes a magnetic field generating means for generating the varying magnetic field, and the heating roller uses the heat generated by the conductive heating layer as a material to be heated at a portion not surrounded by the magnetic field generating means. An induction heating device configured to communicate,
The induction heating apparatus, wherein the core material is formed of a non-conductive material. An image forming apparatus comprising the induction heating device according to claim 1.

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