JP2005108654A - Litz wire and exciting coil, and induction heating device using above - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a litz wire structure capable of responding to the higher efficiency and the higher frequency of a coil and reducing high frequency resistance by a proximity effect, an exciting coil capable of having high efficiency and reducing cost by using the litz wire, and an induction heating device, a high frequency transformer, and a coil inductance using the exciting coil. <P>SOLUTION: The litz wire is made of a plurality of twisted insulation coating conductors, a hollow litz wire A1 has the cross-section center of the litz wire as a hollow part or with a core member other than the insulation coating conductors. A double hollow litz wire A2 is made by twisting the plurality of litz wires A1 as secondary wires, with its cross-section center as a hollow part or with a core member other than the secondary wires. The exciting coil has such litz wires formed into a coil shape. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a litz wire, an exciting coil using the litz wire, and an induction heating device.

  For convenience, a fixing device (image heating device) that is provided in an image forming apparatus such as a copier or printer and heat-fixes a toner image on a recording material will be described as an example.

  In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, printing paper, electrophotographic process, electrostatic recording process, magnetic recording process, etc. Induction heating device (electromagnetic induction) as a fixing device that heats and fixes an unfixed image (toner image) of the target image information formed and supported on a recording paper by a transfer method or a direct method as a permanently fixed image on the recording material surface Heating type heating device).

  The induction heating device generates an alternating magnetic flux by supplying an alternating current (high-frequency current) from the exciting circuit to the exciting coil, and causes the alternating magnetic flux to act on the induction heat generating member (conductor such as metal, magnetic material, resistor). Then, an eddy current is induced, and the member to be heated is heated by causing the induction heat generating member to generate heat by Joule heat (due to the specific resistance of the induction heat generating member) due to the eddy current.

  For example, Patent Documents 1 and 2 disclose an induction heating fixing device that induces a current in a fixing roller by magnetic flux and generates heat by Joule heat. This makes it possible to directly heat the fixing roller by using the generation of induced current, and achieves a fixing process that is more efficient than a heat roller type fixing device using a halogen lamp as a heat source.

  In such an induction heating apparatus, the resistance of the exciting coil is an important component that directly determines the efficiency of the induction heating apparatus. In high-frequency propagation, due to the skin effect determined by the physical properties of the conductor, more current flows closer to the outer periphery of the conductor cross section, and the current density decreases as it goes inside. In order to reduce the influence due to the skin effect, a so-called litz wire obtained by twisting a large number of thin insulated conductors, for example, a copper wire (thinned copper wire) having an insulating film, is used as the element wire (for example, (See Patent Documents 3 and 4).

  In such a litz wire, the individual skin wires are twisted so that the outer periphery and the center of the wire bundle are evenly alternated to suppress the skin effect. Further, in view of the magnetic distribution when formed as a coil, each strand is twisted and formed in a spiral shape so as to alternate with the generated magnetic field without unevenness.

The current that flows in the winding of the coil configured using such a litz wire as a coil wire flows near the surface of the conductor due to the skin effect. The skin depth σ [m] into which electromagnetic waves penetrate is σ = 503 × (ρ / fμ) ^{1/2 with} the frequency f [Hz], permeability μ and specific resistance ρ [Ωm] of the excitation circuit.
Given by.

  When the material of the conductor is copper, it becomes 446 μm to 199 μm at a frequency of 20 kHz to 100 kHz around 100 ° C. Since the skin depth σ is a value at which the electric field strength of the electromagnetic wave becomes 1 / e, in reality, if the thickness is about twice this, all the energy flows, and the absorber is efficient. However, the current density in the central portion is reduced, and the thickness is substantially wasted. Actually, it becomes 1 / e at the distance of σ from the surface. Therefore, if a large number of copper wires having a radius sufficiently smaller than σ (about σ / 2 or less) are bundled, the effective cross-sectional area does not decrease. It can be used. For example, many strands having an outer diameter of 0.3 mm or less are twisted and used.

  The skin effect can be dealt with by thinning the strands, but for the proximity effect, it is necessary to increase the distance between the strands. For this reason, in order to reduce the high frequency resistance of the coil, the wire of the litz wire is thinned, and the wire is packed in the same volume by being composed of a large number of wires, increasing the space factor and reducing the conductor resistance, For the two purposes of improving the coil formability and the ease of assembly as a unit, the coil was pressed to form the desired shape.

For this reason, the insulation of the coil windings at different turns depends only on the thickness of the insulating layer of the litz wire itself, and the insulating film is set to be somewhat thick (usually 10 μm or more compared to 5 to 7 μm). As a result, the pinhole occurrence rate is suppressed, an increase in high-frequency resistance due to the proximity effect is suppressed, and reliability for press molding has been secured.
Japanese Utility Model Publication No. 51-109736 Japanese Patent Publication No. 5-9027 JP 2002-373774 A JP 2003-47252 A

  However, in a higher frequency application, it is necessary to use a thinner litz wire. In such a case, the insulating layer of the strand (insulating coated conductor) must be thinned. In particular, a litz wire used for an application such as an induction heating fixing device is required to have high heat resistance of an insulating layer from the usage environment.

  For this reason, in the case of a litz wire using a thin strand corresponding to high frequency, it is necessary to remove the coating when the litz wire terminal treatment is performed. However, because of its high heat resistance, it is impossible to remove the coating by ordinary soldering treatment, and it is difficult to remove the coating only in the desired area due to capillary action in the treatment with chemicals, and mechanical peeling becomes difficult. For this reason, there is a problem that it is difficult to adopt a thin wire structure.

  In addition, since the insulation layer of the wire becomes thin and the conductors of the wire are used in close proximity to each other, there is a problem that a decrease in effective area due to the proximity effect at high frequencies cannot be ignored. .

  Therefore, the present invention can achieve higher efficiency and lower costs by using a litz wire structure that can cope with higher efficiency and higher frequency of the coil and that can reduce high frequency resistance due to the proximity effect, and the litz wire. An exciting coil is provided. The present invention also provides an induction heating device, a high frequency transformer, and a coil inductance using the exciting coil.

  The present invention is a litz wire, an exciting coil and an induction heating device using the litz wire, a high-frequency transformer, and a coil inductance, characterized by the following configuration.

  (1) A litz wire comprising a plurality of insulated coated conductors, wherein the central portion of the cross section of the litz wire is a hollow portion or a core member other than the insulated coated conductor. line.

  (2) The insulation coated conductor is a primary strand, and is a litz wire composed of a plurality of twisted wires, and the central portion of the cross section of the litz wire is a hollow portion or a core member other than the insulation coated conductor A litz wire characterized in that a secondary strand is used, and a plurality of the secondary strands are combined.

  (3) The insulation coated conductor is a primary strand, and is a litz wire made of a plurality of twisted wires, and the central portion of the cross section of the litz wire is a hollow portion or a core member other than the insulation coated conductor A litz characterized by comprising a secondary strand and a plurality of strands of the secondary strand, the central portion of the cross section being a hollow portion or a core member other than the secondary strand line.

  (4) The insulation coated conductor is a primary strand, the litz wire composed of a plurality of twisted strands is a secondary strand, and the center portion of the cross section is hollow. A litz wire characterized by being a part or a core member other than a secondary strand.

  (5) The litz wire according to any one of (1) to (4), wherein the insulating coated conductor is an insulated wire having a diameter of 0.3 mm or less by covering the copper wire with an insulating coating. Here, the diameter may be a copper wire diameter or a conductor diameter including an insulating coating (usually 20 μm in thickness).

  (6) The insulating coated conductor has a layer structure of at least three cross sections, the outermost layer is an insulator layer, the intermediate layer is an electrically conductive layer, and the inner core layer has a volume resistivity higher than that of the intermediate layer. The litz wire according to any one of (1) to (4), which is composed of a high layer.

  (7) The litz wire according to any one of (1) to (6), wherein the core member is a heat pipe or a cooling member.

  (8) An exciting coil, wherein the Litz wire according to any one of (1) to (7) is formed in a coil shape.

  (9) The exciting coil according to (8), characterized in that an insulating layer is provided between the layers of the litz wire that circulates as a coil for each turn.

  (10) An induction heating apparatus comprising the exciting coil according to (8) or (9) as a high frequency coil for inducing an eddy current in an induction heat generating member to generate heat.

  (11) A high-frequency transformer comprising the exciting coil according to (8) or (9).

  (12) A coil inductance comprising the exciting coil according to (8) or (9).

  According to the present invention described above, the use of the Litz wire structure, which can cope with higher efficiency and higher frequency of the coil, and can reduce the high frequency resistance due to the proximity effect, and the Litz wire are excellent in workability, It was possible to provide an exciting coil that is high in efficiency and reduced in cost and capable of handling high frequencies. In addition, an induction heating device, a high-frequency transformer, and a coil inductance using the exciting coil could be provided.

  FIG. 1 is a schematic cross-sectional view of an induction heating fixing apparatus as an example of an induction heating apparatus according to the present invention.

(1) Overall Configuration of Induction Heating Fixing Device 10 is a fixing unit (heating unit), and 20 is a pressure roller. Both the members 10 and 20 are arranged in parallel vertically so that they are pressed against each other to form a fixing nip portion N. It is formed.

  In the fixing unit 10, 11 is a cylindrical / flexible fixing sleeve, 12 is a cylindrical guide member in which the fixing sleeve 11 is loosely fitted, and 13 corresponds to the fixing nip portion N of the guide member 12. A heat conductive member provided along the length of the guide member on the lower surface portion, 14 is a magnetic field generating assembly disposed on the substantially right half side of the guide member 12 in the drawing, and 17 is an additive inserted into the guide member 12. A pressure rigid stay 18 is an insulating member that insulates the magnetic field generating assembly 14 from the pressure rigid stay 15. The magnetic field generating assembly 14 includes an exciting coil (fixing coil, heating coil) 15 and a magnetic core 16.

  The fixing sleeve 11 is an electromagnetic induction heat generating member, and includes a cylindrical metal layer made of a ferromagnetic material such as nickel, iron, ferromagnetic SUS, or nickel-cobalt alloy as an electromagnetic induction heat generating layer, and an elastic layer sequentially formed on the outer side thereof. It has a composite layer structure having flexibility in the entire laminated release layer.

  The pressure roller 20 is composed of a cored bar 21 and a heat-resistant / elastic material layer 222 such as silicone rubber, fluororubber, or fluororesin that is concentrically and integrally formed around the cored bar. Both ends of the core metal 21 are rotatably supported between the chassis side metal plates (not shown) of the apparatus.

  The fixing unit 10 is arranged above the pressure roller 20 in parallel with the pressure roller 20 with the good heat conductive member 13 facing downward, and both ends of the pressure rigid stay 7 are respectively connected to pressure springs (not suitable). In FIG. The pressurizing rigid stay 17 is in contact with the inner bottom surface of the guide member 12, and the good heat conductive member 13 on the lower surface of the guide member 12 presses the fixing sleeve 11 with the pressing rigid stay 17 pressed. A fixing nip portion N having a predetermined width is formed between the fixing sleeve 11 and the pressure roller 20 by pressing against the elasticity of the elastic material layer 22 on the upper surface of the roller 20.

  The pressure roller 20 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the fixing sleeve 11 by the frictional force between the pressure roller 20 and the outer surface of the fixing sleeve 11 in the fixing nip portion N by the rotation driving of the pressure roller 20, and the inner surface of the fixing sleeve 11 is in the fixing nip N. The outer periphery of the guide member 12 is rotated in a clockwise direction as indicated by an arrow with a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 20 while sliding in close contact with the lower surface of the good heat conducting member 13. Since the end portion of the fixing sleeve 11 is received by a flange member (not shown), the movement of the fixing sleeve 11 along the length of the guide member with the rotation of the fixing sleeve 11 is restricted.

  In order to reduce the mutual sliding frictional force between the lower surface of the heat conductive member 13 and the inner surface of the fixing sleeve 11 in the fixing nip portion N, the lower surface of the heat conductive member 13 and the inner surface of the fixing sleeve 11 in the fixing nip portion N are reduced. A lubricant such as heat-resistant grease may be interposed therebetween, or the lower surface of the good heat conductive member 13 may be covered with a lubricant member. This is because the surface slipperiness is not good as in the case where aluminum is used as the good heat conducting member 13 or the finishing process is simplified, and the inner surface of the sliding fixing sleeve 11 is damaged and fixed. This prevents the durability of the sleeve 11 from deteriorating.

  An excitation circuit (not shown) is connected to the excitation coil 15 of the magnetic field generating assembly 14. The excitation circuit can generate a high frequency of 20 kHz to 500 kHz by a switching power supply. The exciting coil 15 generates an alternating magnetic flux by an alternating current (high frequency current) supplied from an exciting circuit. The alternating magnetic flux is guided to the magnetic core 16 and acts on the electromagnetic induction heat generating layer of the fixing sleeve 11 to generate an eddy current in the electromagnetic induction heat generating layer. This eddy current generates Joule heat (eddy current loss) in the electromagnetic induction heating layer due to the specific resistance of the electromagnetic induction heating layer. That is, the rotating fixing sleeve 11 is induction-heated at the portion of the magnetic field generating assembly 14 and goes around the fixing nip portion N, and the fixing nip portion N is heated.

  Reference numeral 19 denotes a temperature sensor such as a thermistor, which is disposed on the outer surface of the guide member 12 at a position near the good heat conductive member on the downstream side in the rotation direction of the fixing sleeve 11 relative to the good heat conductive member 13 of the guide member 12. The inner surface temperature of the fixing sleeve 11 is detected. The temperature of the fixing nip N is controlled so that a predetermined temperature is maintained by controlling the current supply from the excitation circuit to the excitation coil 15 by the temperature control system including the temperature sensor 19.

  Thus, the fixing sleeve 11 is rotated, and the electromagnetic induction heat generation of the fixing sleeve 11 is performed as described above by supplying power from the excitation circuit to the excitation coil 15, and the fixing nip portion N rises to a predetermined temperature and is adjusted in temperature. In the state, the recording material P on which the unfixed toner image t conveyed from the image forming unit (not shown) is formed is directed upward between the fixing sleeve 11 and the pressure roller 20 of the fixing nip N. In other words, the toner image is introduced so as to face the fixing sleeve surface, and in the fixing nip portion N, the image surface is brought into close contact with the outer surface of the fixing sleeve 11 and the fixing nip portion N is nipped and conveyed together with the fixing sleeve 1. In the process in which the recording material P is nipped and conveyed together with the fixing sleeve 11 through the fixing nip N, the fixing sleeve 11 is heated by electromagnetic induction heat generation, and the unfixed toner image t on the recording material P is heated and fixed. The When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing sleeve 11 and discharged and conveyed. The heat-fixed toner image on the recording material is cooled to a permanently fixed image after passing through the fixing nip.

  The good heat conducting member 13 has an effect of making the temperature distribution in the longitudinal direction uniform. For example, when small-size paper is passed, the heat amount of the non-paper passing portion of the fixing sleeve 11 is transferred to the good heat conducting member 13. By heat conduction in the longitudinal direction of the good heat conducting member 13, the heat amount of the non-sheet passing portion is transferred to the small size sheet passing portion. Thereby, the effect of reducing the power consumption at the time of passing small size paper is also acquired.

  A thermoswitch 30 is disposed at a position facing the heat generation area of the fixing sleeve 11 due to the action of the alternating magnetic flux generated by the magnetic field generating assembly 14, and serves to block power supply to the exciting coil 15 during runaway. Yes.

(2) Excitation coil 15
FIG. 2 is an external perspective model view of the exciting coil 15. This exciting coil 15 uses a double hollow litz wire A2 according to the present invention as a coil wire (winding) and is wound for 12 turns to form a boat-shaped exciting coil 15.

  FIG. 3 is an explanatory diagram of the structure of the double hollow litz wire A2 used here. (A) is the expansion cross-sectional model figure of the insulation coating conductor a used as a primary strand, and the thing of this example is the insulated wire which gave the insulation coating 2 to the copper wire 1 of about φ0.3 mm or less. A hollow litz wire A1 is formed by combining the primary strands a from six and making the central portion of the cross section as shown in the enlarged cross section model diagram of FIG. This hollow litz wire A1 is made into a secondary strand, and this is combined from 6 pieces, and the double hollow litz wire A2 which made the hollow cross-section center part like the enlarged cross-sectional model figure of (c) is made is created. This double hollow litz wire A2 is used as a coil wire to form an exciting coil 15 as shown in FIG.

  In view of the magnetic distribution when formed as a coil, the primary strand a of the hollow litz wire A1 in FIG. 3B is also arranged so that the individual strands forming the coil alternate with the generated magnetic field without unevenness. The secondary strand A1 of the double hollow litz wire A2 in (c) is also twisted in a spiral shape as shown in the model diagram in (d).

  FIG. 4 shows an enlarged cross-sectional model view of a conventional densely wound litz wire as a structural comparison example. (A) is a densely wound litz wire A3 in which seven insulated wires a as primary wires are combined. (B) is a double densely wound litz wire A4 in which this densely wound litz wire A3 is used as a secondary strand and is combined from 7 wires.

  The hollow litz wire A1 formed by twisting the six primary strands a in FIG. 3 (b) described above is a densely wound litz wire A3 that is matched with the seven primary strands a in FIG. 4 (a). Is formed by removing one strand a from the center, and the inside is hollow.

  The current flowing in the coil winding flows near the surface of the conductor due to the skin effect at a high frequency (about 20 kHz to 100 kHz) at which induction heating is performed. At the same time, due to the proximity effect, the current density on the surfaces facing each other between the strands decreases.

  Accordingly, the direct current resistance of the coil winding is high when the hollow litz wire having a small number of strands is used. However, as the frequency increases to 10 kHz and 100 kHz, the relative value of the resistance is reversed, and the densely wound litz wire with many strands has a higher resistance than the hollow litz wire with few strands.

  Moreover, the insulation coating thickness for each strand of the hollow litz wire is also set to be thick (10 to 20 μm) in order to make it less susceptible to the influence of adjacent electric wires and to suppress an increase in resistance due to the effect of the proximity effect.

  When the thickness of the insulation coating can be ensured, the exciting coil 15 affects the hollow litz wire constituting the coil winding due to the influence of pressure in order to obtain ease of handling such as assembly and transportation as a coil. The moldability may be improved by applying pressure from the outside to the extent that it is not.

  As shown in (c) and (d) of FIG. 3, the hollow litz wire A1 is considered as one strand, and this is used as a secondary strand, and the structure of a double hollow litz wire A2 twisted in the hollow is further formed. As a result, the high-frequency characteristics can be dramatically improved and the coil weight can be reduced. Furthermore, it is possible to reduce the amount of the primary strand a to be used, thereby reducing the cost.

  In induction heating, the distance between the exciting coil 15 and the fixing sleeve 11 that is the object to be heated is very important, and the strength and accuracy of the exciting coil 15 are required to keep the distance constant. In addition, while assembling as a fixing unit, the assembly of the exciting coil 1 and the ease of transportation greatly affect the assembly man-hours. Therefore, the double hollow litz wire A is circulated around the press die and the hollow wire is affected. Formability is improved by applying pressure from the outside to such an extent that it is not applied.

  FIG. 5 (a) is a hollow litz wire A5 in which the hollow litz wire A1 of FIG. 3 (b) is used as a secondary strand and further combined with seven wires, and FIG. 5 (b) is a view of FIG. ) Is a hollow litz wire A6 in which six densely wound litz wires A3 are used as secondary strands and are combined in a hollow shape. The hollow litz wires A5 and A6 in the form as shown in FIGS. 5A and 5B also have the same effect as the above-described double hollow litz wire A2. The same effect can be obtained even if the hollow litz wire A1 of FIG. 3B is used as a coil wire as it is.

  In this embodiment, as an example, a six-stranded hollow litz wire A1 of the primary strand a, a seven-stranded densely wound litz wire A3 of the primary strand a, and the litz wire A1 or A3 as a secondary strand. The number of primary strands a and the number of secondary strands A1 or A3 are arbitrary depending on the application and cost. Actually, it is possible to use three or more primary strands / secondary strands where practical, up to about 30.

  The hollow part of the hollow litz wire and the double hollow litz wire do not have to be completely hollow. For the purpose of eliminating deformation at the time of press molding of the coil using this litz wire, logistics transportation, and deformation at the time of management, A litz wire configuration in which a core member other than the primary strand or the secondary strand constituting the litz wire is present in the portion can also be used. As the core member, for example, a wire made of an insulator such as glass fiber, Teflon (registered trademark) (tetrafluoroethylene resin), polyimide, polyamideimide, polyurethane, or the like can be used.

  As a specific example, (a) in FIG. 6 is the one in which the core wire b is present in the hollow portion of the hollow litz wire A1 in (b) in FIG. 3, and (b) is the double hollow litz in (c) in FIG. The core wire b is present in the hollow portion of each hollow litz wire A1 as a secondary strand of the wire A2, and the large-diameter core wire c is also formed in the large-diameter hollow portion of the central portion of the double hollow litz wire A2. (C) shows the core wire b in the hollow part of each hollow litz wire A1 as the secondary strand of the hollow litz wire A5 in FIG. 5 (a), (d) shows the figure. 5 (b), in which a large-diameter core wire c is present in the large-diameter hollow portion at the center of the hollow litz wire A6.

  The core wires b and c are, for example, a PDA polymer material having high thermal conductivity as a cooling member, a resin to which a carbon filament is added, aluminum, a heat pipe, and the like.

  The current flowing in the coil winding flows near the surface of the conductor due to the skin effect at a high frequency (about 20 kHz to 100 kHz) at which induction heating is performed. At the same time, due to the proximity effect, the current density on the surfaces facing each other between the strands decreases. In addition, since the resistivity of the metal increases as the temperature rises, the skin effect is alleviated as the coil temperature rises. However, the increase in resistance value is the most effective, and the efficiency is still worse. Therefore, it becomes necessary to cool the coil efficiently.

  With such a configuration, by using the cooling member as in the above example as the core wire b · c to be present in the hollow portion of the hollow litz wire as in the examples of FIGS. It is possible to suppress the increase in resistance due to the noise and improve the high frequency characteristics.

  Furthermore, as described above, in induction heating, it is very important to make the distance between the exciting coil 15 and the fixing sleeve 11 that is the object to be heated constant, and in order to keep the distance constant, the strength and accuracy of the coil. Therefore, the coil is minimally pressed. Although a large pressing pressure could not be applied only with the hollow structure, it is possible to improve the moldability during pressing by providing core wires b and c such as a heat conducting member (cooling member) in the hollow portion. ing.

  7A to 7F show various structural models of the insulated coated conductor a as the primary strand. These examples have a layer structure of at least three layers in cross section, the outermost layer a3 is a coating insulator layer of several μm, the intermediate layer a2 is an electrically conductive layer, and the inner core layer a1 is more than the intermediate layer. It is an insulating coated conductor composed of a layer having a high volume resistivity.

For the insulating layer a3, urethane polymer material, polyimide, polyamideimide, PTFE, inorganic polymer, or the like is used depending on the use environment. On the other hand, there is a tendency for thinning in high frequency applications, and when an insulator with a high heat resistance grade is used, it is difficult to remove the insulation coating for terminal processing or the like. Insulating layer a3 in each example of (a) ~ (c) is, UE (urethane), PI (polyimide), EI (ester imide), AI (amideimide), or SiO _2. The insulating layer a3 in each example of (d) to (f) is UE, PI, EI, AI, glass (glass-based insulating material) or SiO ₂ .

  As shown in (b), as the core layer a1 and the intermediate layer a2, by providing Cu as a clad layer on the Al core, the decrease in resistivity at high frequency is suppressed, and the workability at the time of insulation peeling is remarkably improved. It becomes possible. For example, at a frequency of 1 MHz, the skin depth of Cu is about 49.6 μm, and in the conventional method, the wire diameter must be 0.05 mm or less. In addition to making it difficult to insulate thin wires, there are various problems in assembling, such as the wire becomes soft, the assembling property is impaired when it is configured as a coil, and the wire becomes easy to bite. there were.

  Here, an example is shown in which an Al core, for example, 50 μm, is coated with about 25 μm of Cu. In such a case, the wire diameter is about 0.10 μm, and it becomes relatively easy to produce an electric wire with high workability such as easy mechanical peeling. A structure with good moldability can be obtained even when pressing. Moreover, what is necessary is just to set so that the resistivity of the conductor of a center part and the conductor of an outer peripheral part may become lower than the resistivity of the conductor of a center part, such as Ag coating of Cu core like (a). Further, the core a1 is not a conductor, and an insulator such as PI, PTFE, nylon, glass fiber or the like may be used as in each of the examples (c) to (f).

  In such a case, the insulating layer coating of the litz wire may be performed after the terminal treatment.

  When a litz wire is used as a coil wire to wrap around the coil 15 and the coil is overlapped, the voltage per turn is applied to the insulating layer of the coil, that is, the insulating layer of the strand. become.

  The exciting coil used in the induction heating fixing device has a width as large as the width of the paper to be passed, and the number of turns for obtaining a necessary inductance is small because the area of the coil is large. However, since the applied voltage at the time of driving the coil is as high as 500V to 1000V, the voltage applied per turn of the coil wire is as high as 50V or more. Further, as the frequency to be used increases, the line capacity increases. Therefore, the Litz wire that is circulated as a coil is insulated between layers for each turn, and in order to reduce the capacitance between the lines, the insulating member is configured to be sandwiched for each lap of the Litz wire that is circulated as a coil. As the insulating member, nomex tape, PI, polyamideimide, PTFE, urethane polymer material, or the like is used. You may comprise so that a distance may be ensured by standing a rib in a coil holder instead of pinching a tape etc.

  FIG. 8 shows an example of a high-frequency transformer 100 in which a litz wire is used as a coil according to the present invention, where (a) is an external perspective model diagram, (b) is a cross-sectional model diagram, and (c) is a plan view. 101 is a transformer coil, and the hollow litz wire A1 as shown in FIG. 3 (b), the double hollow litz wire A2 as shown in (c), and the hollow as shown in FIGS. 5 (a) and 5 (b). Litz wires A5, A6, and litz wires A1, A2, A5, and A6 in which core members b and c as shown in FIGS. 6A to 6D exist are wound. The primary strand a of the litz wire can be made of an Al core, such as a Cu clad, as described in the third embodiment.

  The litz wire according to the present invention is effective when used for various other things such as a coil and a coil inductance.

  Here, as a manufacturing point of a thing like a hollow litz wire A1, A2, A5, and A6, for example, a method of putting a cored bar and twisting it up and then pulling out the cored bar can be adopted. Long ones can be manufactured by removing the cored bar while twisting the litz wire. As another method, since the heat-resistant temperature of the litz wire is high (at least 180 ° C. or higher), a resin material that dissolves by baking at 150 to 180 ° C. is used as a core material, and a normal twist is used. After performing, baking etc. can be considered.

Cross-sectional model diagram of an induction heating fixing device as an example of an induction heating device according to the present invention Appearance perspective model of exciting coil Structure diagram of double hollow litz wire Expanded cross-sectional model of a conventional densely wound litz wire as a structural comparison example (A) and (b) are enlarged cross-sectional model views of other structural examples of hollow litz wires, respectively. (A)-(d) is an expanded cross-sectional model figure of the form which made the core member exist in the hollow part of a hollow litz wire, respectively. Various structural model diagrams of insulated coated conductors as primary wires Diagram of high-frequency transformer of Example 5

Explanation of symbols

  15 .... excitation coil, A1, A2, A5, A6 ... hollow litz wire, a ... strand (primary strand, insulated conductor), b ... c ... core member

Claims (12)

  A litz wire comprising a plurality of twisted insulation-coated conductors, wherein the central portion of the cross-section of the litz wire is a hollow portion or a core member other than the insulation-coated conductor.   A litz wire composed of a plurality of stranded wires with an insulation coated conductor as a primary strand, the center of the cross section of the litz wire being a hollow portion or a core member other than the insulation coated conductor A litz wire, characterized in that the wire is a secondary strand, and is composed of a plurality of twisted secondary strands.   A litz wire composed of a plurality of stranded wires with an insulation coated conductor as a primary strand, the center of the cross section of the litz wire being a hollow portion or a core member other than the insulation coated conductor A litz wire, characterized in that it is made of a plurality of strands of secondary strands, and the central portion of the cross section is a hollow portion or a core member other than the secondary strands.   The insulation coated conductor is a primary strand, the litz wire composed of a plurality of twisted strands is a secondary strand, and the center portion of the cross section is a hollow portion. A litz wire characterized by being a core member other than a secondary strand.   The litz wire according to any one of claims 1 to 4, wherein the insulating coated conductor is an insulated electric wire having a diameter of 0.3 mm or less by covering the copper wire with an insulating coating.   The insulating coated conductor has a layer structure of at least three layers in cross section, the outermost layer is an insulator layer, the intermediate layer is an electrically conductive layer, and the inner core layer is a layer having a higher volume resistivity than the intermediate layer. The Litz wire according to any one of claims 1 to 4, wherein   The litz wire according to any one of claims 1 to 6, wherein the core member is a heat pipe or a cooling member.   8. An exciting coil, wherein the Litz wire according to claim 1 is formed in a coil shape.   The exciting coil according to claim 8, wherein an insulating layer is provided between the layers of the litz wire that circulates as a coil for each turn.   An induction heating apparatus comprising the exciting coil according to claim 8 or 9 as a high-frequency coil that generates heat by inducing an eddy current in an induction heat generating member.   A high frequency transformer comprising the exciting coil according to claim 8.   A coil inductance comprising the exciting coil according to claim 8.

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