Coil and method for manufacturing coil

A coil of an embodiment is formed by winding a winding conductor in which a conductive conductor is molded by a resin, wherein the winding conductor has the resin filled to a surface of the conductor without leaving any spaces.

TECHNICAL FIELD

The present disclosure relates to a coil and a method of manufacturing a coil.

BACKGROUND ART

A coil is formed for example by winding a litz wire obtained by intertwining a plurality of enamel strands (thin wires) or winding a conductor such as a lower half rectangular wire having a rectangular cross section or a round wire having a circular cross section. The periphery of the conductor and the outer periphery of the coil are covered by a resin.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF INVENTION

Problem Solved by Invention

However, degradation of the insulation property of conductors and coils lead to reduction in the performance of the coils.

Thus, there is provided a coil exhibiting excellent insulation property and a method of manufacturing such coil.

Solution to Problem

A coil of an embodiment is formed by winding a winding conductor in which a conductive conductor is molded by a resin, wherein the winding conductor has the resin filled to a surface of the conductor without leaving any spaces.

EMBODIMENTS OF INVENTION

First Embodiment

A first embodiment will be described hereinafter based on the drawings. Elements that are substantially identical in the description of the embodiments are identified with identical reference symbols and are not re-described.

A litz wire used in a coil comprises a multiconductor magnet wire (winding conductor) formed by intertwining a plurality of enamel strands (thin wire). The litz wire is being widely used as a magnet wire for coils used in high-frequency electric appliances. As the frequency of current conducted through the litz wire becomes greater, the loss becomes greater due to the increase in AC resistance caused by the skin effect.

The litz wire is used in the coils of high frequency electric appliances to suppress the increase of AC resistance by fragmenting the skin current by dividing the conductor into multiple wires using enamel lines having an insulation coating. A round litz wire having a circular cross section is generally used however, a rectangular litz wire having a rectangular cross section is also used to increase the coil occupancy when the coils of the electrical appliance are wound.

Thus, there is provided a coil having excellent insulation property and a method of manufacturing such coil.

FIG. 1is a perspective view schematically illustrating an exemplary structure of a coil10indicated as one example of an embodiment.FIG. 2is a cross sectional view illustrating the structure at portion A of the coil10ofFIG. 1. Coil10is configured by a litz wire12being a wiring conductor obtained by intertwining and bundling thin wires, that is, strands made of copper for example. The coil10is configured by tightly winding the litz wire in a whorl so as to form concentric ellipses having a cavity at the center with the entire structure being hardened by a resin. The portion A inFIG. 1corresponds to a basic unit of the litz wire12andFIG. 2illustrates the basic structure of the litz wire12constituting the coil10. The litz wire12used in the coil10is a multiconductor magnet wire (winding conductor) obtained by intertwining and bundling a plurality of mutually insulated conductive strands14(thin wires) such as enamel lines provided with insulation coating for example.

As shown inFIG. 2, the litz wire12includes a first unit litz wire16obtained by intertwining a plurality of strands14. Further, a second unit litz wire18is formed by intertwining a plurality of first unit litz wires16. The litz wire12is formed by covering the periphery of the second unit litz wires18with a lashing band22and a surrounding band24.

A strong aramid fiber tape for example is used as the lashing band22. The lashing band22is shaped like a paper tape and is wound around the second unit litz wires18to lash the first unit litz wires16or the strands14constituting the second unit litz wires18so that they are not disassembled. The lashing band22is wound around the second unit litz wires18so that gaps G are formed between the wound lashing bands22as shown in the later describedFIG. 4 (a).

The surrounding band24is wound around and covers the second unit litz wires18lashed by the lashing band22. The surrounding band24is formed by hardening a later described nonwoven tape32impregnated with a later described resin liquid38. In this case, the nonwoven tape32is raised as one example of a material capable of allowing penetration and permeation of the later described resin liquid38and capable of being wound around the second unit litz wires18during the later described manufacturing process flow of the coil10. The material constituting the surrounding band24is not limited to the nonwoven tape32as long as the material possesses these properties.

In the second unit litz wires18, insulative hardened resin20(resin) exists without leaving any spaces between the plurality of strands14or the plurality of first unit litz wires16. The hardened resin20exists without leaving any spaces between the strands14, the lashing band22, and the surrounding band24and further between the first unit litz wires16, the lashing band22, and the surrounding band24. That is, the second unit litz wire18is formed by hardening and integrally solidifying the plurality of strands14or the plurality of first unit litz wires16with the later described resin liquid38and is three dimensionally integrated and solidified by the hardened resin20. Further, the litz wire12is obtained by solidifying the strands14, the first unit litz wires16, the second unit litz wires18, the lashing band22, and the surrounding band24with the hardened resin20without leaving any spaces. That is, the coil10and the litz wire12that constitutes the coil10are configured by filling and molding the hardened resin20between the strands14and in the periphery of the strands14without leaving any spaces.

A resin with high thermal conductivity, that is, with high heat dissipating property may be employed as the hardened resin20, that is, the later described resin liquid38. A resin obtained by adding a micro-sized and highly thermal conductive filler such as alumina or boron nitride to an epoxy resin for example as an additive that imparts high thermal conductivity is used as a resin having high thermal conductivity. When a resin with high thermal conductivity is employed, the coil10and the litz wire12constituting the coil10are configured so that hardened resin20with high thermal conductivity, that is, high heat dissipating property is filled between the plurality of strands14, between the plurality of first unit litz wires16, between the strands14, lashing band22, and the surrounding band24, and further between the first unit litz wires16, the lashing band22, and the surrounding band24without leaving any spaces. Thus, because the interior of the formed coil10and the litz wire12constituting the coil10are filled with the hardened resin20having high thermal conductivity and high heat dissipating property without leaving any spaces and their outer periphery are covered by the surrounding band24hardened by the hardened resin20having high heat dissipating property, the coil10as a whole is caused to have high thermal conductivity and high heat dissipating property.

Next, a description will be given on a method of manufacturing the coil10.FIGS. 3 to 9are figures for explaining the manufacturing method of the coil10and each illustrate one phase of the manufacturing process flow.FIG. 3illustrates one phase of the manufacturing process flow of the litz wire12constituting the coil10andFIG. 3 (a)is a perspective view andFIG. 3 (b)is a cross sectional view.FIG. 4illustrates one phase of the manufacturing process flow of the litz wire12constituting the coil10andFIG. 4 (a)is a perspective view andFIG. 4 (b)is a cross sectional view.FIG. 5illustrates one phase of the manufacturing process flow of the litz wire12constituting the coil10andFIG. 5 (a)is a perspective view andFIGS. 5 (b)and5(c) are cross sectional views.

First, an intertwined litz wire30a(litz wire) is prepared as shown inFIGS. 3 (a)and3(b). The intertwined litz wire30ais formed by forming the first unit litz wires16by intertwining the strands14and thereafter intertwining the first unit litz wires16. The intertwined litz wire30ahardened by the hardened resin20corresponds to the second unit litz wire18.

Next, as shown inFIGS. 4 (a)and4(b), the intertwined litz wire30ais lashed by winding the lashing band22around the intertwined litz wire30ato form a lashed litz wire30b(litz wire). The lashing band22is wound around the intertwined litz wire30aso as to form gaps, that is, spaces. In this state, the intertwined litz wire30ais exposed from the gaps of the wound lashing band22. The lashing band22is an aramid paper tape for example and thus, does not allow permeation of the later described resin liquid.

Next, as shown inFIGS. 5 (a)and5(b), the nonwoven tape32is wound around the lashed litz wire30bto form a surrounded litz wire30c(litz wire). In this case, the nonwoven tape32is wound around the lashed litz wire30bso as not to form any gaps between the wound nonwoven tapes32. The nonwoven tape32allows penetration and permeation of the later described resin liquid38.

The nonwoven tape32includes a hardening accelerator of the later described resin liquid38. Amines, imidazoles, phosphine, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and its organic acid salt, ammonium or phosphonium compound or the like are used as the hardening accelerator.

In case the nonwoven tape32is strong enough to lash the intertwined litz wire30a, that is, strong enough to prevent the strands14and the first unit litz wires16from disassembling, it is possible to omit the lashing of the intertwined litz wire30aby the lashing band22. That is, it is possible to form the surrounded litz wire30d(litz wire) shown inFIG. 5 (c)by winding the nonwoven tape32around the intertwined litz wire30awithout leaving any spaces as shown inFIGS. 3 (a)and3(b). In this case, it is possible to omit the lashing by the lashing band22and thus, simplifies the process flow to contribute in reduction of manufacturing cost. Further, in the coil10and the litz wire12constituting the coil10in this case, the surrounding band24is wound around the second unit litz wires18and the lashing band22does not exist between the second unit litz wires18and the surrounding band24. The remaining structures are the same.

Next, as shown inFIG. 6, the surrounded litz wire30cis wound around a winding core material34to form the surrounded litz wire30cinto a coil shape. The winding core material34is formed of wood for example. The surrounded litz wire30cwound around the winding core material34in a coil shape is referred to as a coil10bas shown inFIG. 7.

After removing the coil10bfrom the winding core material34, the coil10bis immersed in a resin container36filled with the resin liquid38as shown inFIG. 7. The filling of the resin liquid38into the coil10bis facilitated by placing the resin container36in a space having a pressure lower than the atmospheric pressure. As described earlier, the nonwoven tape32allows permeation of the resin liquid38. Further, the lashing band22is wound around the intertwined litz wire30aso as to form gaps between the lashing bands22as shown inFIG. 4. Thus, the resin liquid38permeates the nonwoven tape32to reach into the surrounded litz wire30cand further between the first unit litz wires16and between the strands14through the gaps G of the wound lashing bands22. Thus, the resin liquid38is filled without leaving any spaces between the first unit litz wires16or between the strands14in the second unit litz wire18, and further between the lashing band22, the nonwoven tape32, the strands14, the second unit litz wires18and the like.

As described above, the nonwoven tape32includes the hardening accelerator of the resin liquid38. The coil10bis immersed in the resin liquid38, and after the resin liquid38has permeated sufficiently into the nonwoven tape32and the surrounded litz wire30c, the resin liquid38in the nonwoven tape32hardens through reaction with the hardening accelerator. Thus, the surrounding band24hardened by the resin is formed as shown inFIG. 8. Since the hardening accelerator is only contained in the nonwoven tape32, only the resin liquid38at the nonwoven tape32portion hardens and the interior resin liquid38covered by the nonwoven tape32is left unhardened. That is, the inner region covered by the nonwoven tape32and located between the first unit litz wires16inside the second unit litz wire18, the strands14, and the lashing band22is filled with the resin liquid38prior to being hardened, that is, the unhardened resin40. The coil in this state is referred to as coil10dand the litz wire constituting the coil10dis referred to as the surrounded litz wire30e. The surrounded litz wire30econstituting the coil10dis configured so that the unhardened resin40is filled between the strands14and between the first unit litz wires16inside the surrounded litz wire30eand the outer periphery of the surrounded litz wire30eis covered by nonwoven tape32hardened by the resin liquid38, that is, the surrounding band24as shown inFIG. 8.

Next, the coil10din the above described state which has been taken out of the resin container36is illustrated inFIG. 9. The structure of the surrounded litz wire30econstituting coil10dis illustrated inFIG. 8as described above.FIG. 8illustrates the cross sectional structure of portion B ofFIG. 9. The periphery of the surrounded litz wire30econstituting the coil10dis covered by the surrounding band24hardened by the resin liquid38as described above. Thus, even when the coil10dis taken out of the resin container36, it is possible to prevent the resin liquid38inside the coil10d, that is, the unhardened resin40from leaking to the exterior and the unhardened resin40is held without leaving any spaces in the inside of the coil10dcovered by the surrounding band24.

Next, the coil10dis put into a heat drying furnace42as shown inFIG. 9. The entirety of the coil10dis thermally dried by the heat drying furnace42to thereby harden the unhardened resin40of the coil10d. The hardening of the surrounding band24is facilitated at the same time. The coil10illustrated inFIG. 1can be manufactured through the above described process steps.

In the process step illustrated inFIG. 7, the hardening accelerator is contained only in the nonwoven tape32portion and the resin liquid38of this portion alone is hardened for the following reason. Suppose the hardening accelerator of the resin liquid38is not contained in the nonwoven tape32portion. In such case, the resin liquid38of the nonwoven tape32portion is not hardened even in case the coil10bis immersed in the resin liquid38inside the resin container36. When the coil10is taken out of the resin container36in this state, the unhardened resin40inside the coil10will leak to the outside by passing through the nonwoven tape32since the nonwoven tape32allows permeation of the resin liquid. Thus, in case the resin liquid38is hardened by the heat drying furnace42in this state, the hardened resin20is absent in the litz wire12constituting the coil10and spaces are created between the strands14, the first unit litz wires16, the second unit litz wires18, the lashing band22, the surrounding band24, and the like. The insulation property of the coil10becomes reduced when such spaces exist.

On the other hand, in order to harden the resin liquid38without containing the hardening accelerator in the nonwoven tape32, the resin liquid is hardened by methods such as applying heat with the coil10placed inside the resin container36. However, when such method is taken, the resin liquid38becomes hardened along with the resin container36containing the coil10, thereby causing the coil10to be integrated with the resin container36and preventing the coil10from being taken out of the resin container36. Further, the hardened resin becomes filled in the cavity in the center of the coil10and the cavity becomes blocked by the hardened resin. The hardening accelerator is contained in the nonwoven tape32to harden the resin liquid38in this portion alone for the above described reasons. That is, the nonwoven tape32turns into the surrounding band24hardened by the resin by containing the hardening accelerator therein and possesses a function of retaining a state in which the resin liquid38is filled inside the coil10bwithout leaving any spaces when the coil10bis immersed in the resin container36filled with the resin liquid38and the interior of the coil10bis impregnated with the resin liquid38. It is thus, possible to obtain coil10with improved insulation property without leaving any spaces between the strands14, the first unit litz wires16, the second unit litz wires18, the lashing band22, and the surrounding band24inside the coil10.

The coil10according to the above described embodiment provides the following effects.

In the coil10of the embodiment and the litz wire12constituting the coil10, the hardened resin20is filled and molded without leaving any spaces between the strands14and in the periphery of the strands14. Thus, the insulation property of the coil10is improved to exert excellent insulation property even when the coil10is used in high frequency electric appliances for example.

Further, in the coil10and the litz wire12constituting the coil10, the strands14, the first unit litz wires16, the second unit litz wires18, the lashing band22, and the surrounding band24are integrally solidified by the hardened resin20without leaving any spaces to provide a three-dimensionally secured structure. That is, in the coil10and the litz wire12constituting the coil10, the hardened resin20is filled, solidified, and molded without leaving any spaces between the strands14and in the periphery of the strands14. Thus, generation of gaps and peeling voids are suppressed in the coil10to provide excellent insulation property.

The periphery of the coil10and the litz wire12constituting the coil10of the embodiment are covered by the surrounding band24formed of nonwoven tape32hardened by the resin. Thus, the insulation property between the litz wires12as well as the mechanical strength of the coil10are improved.

In the coil10and the litz wire12constituting the coil10of the embodiment, a resin having high thermal conductivity, that is, high heat dissipating property may be employed as the hardened resin20, that is, the resin liquid38. In this case, because the coil10exhibits excellent heat dissipating property, it is possible to prevent damaging of the coil10, etc. even when abnormal heat is produced for example at the coil10.

According to the manufacturing method of the coil10of the embodiment, the hardening accelerator of the resin liquid38is contained in the nonwoven tape32. The coil10bbeing manufactured is immersed in the resin liquid38, and the resin liquid38at the nonwoven tape32hardens through reaction with the hardening accelerator after the resin liquid38has sufficiently permeated into the surrounded litz wire30c. Thus, the inner region of the coil10is filled with resin liquid38which is not hardened, that is, the unhardened resin40and the outer periphery of the unhardened resin40is covered by nonwoven tape32hardened by the resin liquid38, that is, the surrounding band24. That is, it is possible to create a situation in which the outer periphery of the unhardened resin40in the inner region of the coil10is covered by the surrounding band24solidified by the resin and the unhardened resin40is confined therein. It is thus, possible to prevent the unhardened resin40in the inner region of the coil10from leaking even when the coil10being manufactured is taken out of the resin container36. As a result, it is possible to obtain the coil10and the litz wire12constituting the coil10in which the hardened resin20is filled and molded without leaving any spaces between the strands14and in the periphery of the strands14. It is thus, possible to manufacture a coil10exhibiting excellent insulation property even when the coil10is applied to a high-frequency electric appliance for example.

The above description was given through an example in which a rectangular litz wire was used as the litz wire12of the embodiment. However, the litz wire12is not limited to a rectangular litz wire. A round litz wire may be used for example.

Second Embodiment

A second embodiment will be described hereinafter with reference to the drawings. In the description of the embodiment, elements that are substantially identical are identified with identical reference symbols and are not re-described.

FIG. 10is a perspective view schematically illustrating an example of a configuration of a coil110presented as one example of the embodiment.FIG. 11is a cross sectional view illustrating portion A of the coil110ofFIG. 10. Coil110is configured by a multiconductor wire112formed of copper for example. The coil110is configured by tightly winding the multiconductor wire112in a whorl so as to form concentric ellipses having a cavity at the center and the entire structure is hardened by a resin. The portion A inFIG. 10corresponds to a basic unit of the multiconductor wire112andFIG. 11illustrates the basic structure of the multiconductor wire112constituting the coil110. The multiconductor wire112used in the coil110is a plurality of, for example, two mutually insulated conductive strands114, for example, a winding conductor formed of a plurality of enamel lines provided with an insulation coating.

As shown inFIG. 11, the multiconductor wire112comprises a plurality of strands114. The periphery of the multiconductor wire112is covered by a lashing band122and a surrounding band124.

A strong aramid fiber tape is used for example as the lashing band122. The lashing band122is shaped like a paper tape and is used to lash the strands114so that the strands114are not disassembled. As shown in the later describedFIG. 13 (a), the lashing band122is wound around the multiconductor wire112so as to form gaps G (corresponding to spaces) between the wound lashing bands122.

The surrounding band124is wound around and covers the multiconductor wire112lashed by the lashing band122. The surrounding band124is obtained by impregnating a later described nonwoven tape132with a later described resin liquid138(corresponding to liquid resin) and hardening the resin liquid138. In this case, the nonwoven tape132is given as an example of a material which allows penetration and permeation of the later described resin liquid138and which is capable of being wound around the multiconductor wire112in the later described manufacturing process flow of the coil110. The material constituting the surrounding band124is not limited to the nonwoven tape132as long as it possesses the above described properties.

An insulative hardened resin120(resin) exists without leaving any spaces between the plurality of strands114. Further, the hardened resin120exists without leaving any spaces between the strands114, the lashing band122, and the surrounding band124as well. That is, the entirety of the coil110is integrated and secured three-dimensionally by the hardened resin120from the inside to the outside. The lashing band122and the surrounding band124are also solidified without leaving any spaces by the hardened resin120. That is, the coil110and the multiconductor wire112constituting the coil110are provided with a structure in which the hardened resin120is filled and molded without leaving any spaces between the strands114and in the periphery of the strands114.

A resin with high thermal conductivity, that is, high heat dissipating property may be employed as the hardened resin120, that is, the later described resin liquid138. A resin obtained by adding a micro-sized and highly thermal conductive filler such as alumina or boron nitride to an epoxy resin for example as an additive that imparts high thermal conductivity is used as a resin having high thermal conductivity. When employing a resin having a high thermal conductivity, the coil110and the multiconductor wire112constituting the coil110are configured so that hardened resin120having high thermal conductivity, that is, high heat dissipating property is filled between the plurality of strands114, between the strands114, the lashing band122, and the surrounding band124, and further to the outer peripheral surface of the coil110. Thus, the inside of the formed coil110and the multiconductor wire112constituting the coil110are filled with the hardened resin120having high thermal conductivity, that is, high heat dissipating property without leaving any spaces, and the outer periphery of the formed coil110and the multiconductor wire112constituting the coil110are covered by the surrounding band124hardened by the hardened resin120having high heat dissipating property and thus, the entire coil110exhibits high thermal conductivity and high heat dissipation property.

Further, because there is very little amount of voids which are prone to become insulation defects and adhesion of the conductor portion and the resin is good, it is possible to obtain high insulation performance.

Next, a description will be given on the method of manufacturing the coil110.FIGS. 12 to 18are diagrams for explaining the manufacturing method of the coil110and each indicate one phase of the manufacturing process flow.FIG. 12indicates one phase of the manufacturing process flow of the multiconductor wire112constituting the coil110.FIG. 13indicates one phase of the manufacturing process flow of the multiconductor wire112constituting the coil110andFIG. 13 (a)is a perspective view andFIG. 13 (b)is a cross sectional view.FIG. 14indicates one phase of the manufacturing process flow of the multiconductor wire112constituting the coil110andFIG. 14 (a)is a perspective view, andFIGS. 14 (b)and14(c) are cross sectional views.

Next, as shown inFIGS. 13 (a)and13(b), the strands114are lashed by winding the lashing band122around the strands114to form the multiconductor wire112. The lashing band122is wound so as to form gaps, that is, spaces. In this state, the strands114are exposed from the gaps between the wound lashing bands122. Because the lashing band122is an aramid paper tape for example, the later described resin liquid is not allowed to permeate therethrough. That is, the lashing band122does not allow permeation of the unhardened resin liquid.

Then, as shown inFIGS. 14 (a)and14(b), the nonwoven tape132is wound around a lashing line130b. In this case, the nonwoven tape132is wound around the lashing line130bso as not to form any gaps between the wound nonwoven tapes132. The nonwoven tape132allows penetration and permeation of the later described resin liquid138.

The nonwoven tape132includes a hardening accelerator (corresponds to a resin hardening accelerator) of the later described resin liquid138. Amines, imidazoles, phosphine, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and its organic acid salt, ammonium or phosphonium compound or the like are used as the hardening accelerator.

In case the nonwoven tape132is strong enough to lash the strands114, that is, strong enough to prevent the strands114from disassembling, it is possible to omit the lashing of the strands114by the lashing band122. That is, as shown inFIGS. 14 (a)and14(b), it is possible to form the multiconductor wire112shown inFIG. 14 (c)by winding the nonwoven tape132around the strands114without leaving any spaces. In this case, it is possible to omit the lashing by the lashing band122and thus, simplifies the process flow to contribute in reduction of manufacturing cost. Further, in the coil110and the multiconductive wire112constituting the coil110in this case, the periphery of the strands114is covered by the surrounding band124. The remaining structures are the same.

Next, as shown inFIG. 15, the multiconductor wire112is spirally wound around a winding core material134to form the multiconductor wire112in a coil shape. The winding core material34is made of wood for example. The multiconductor wire112wound around the winding core material134in a coil shape is referred to as a coil110bas shown inFIG. 16

After removing the coil110bfrom the winding core material134, the coil110bis immersed in a resin container136filled with the resin liquid138as shown inFIG. 16. The filling of the resin liquid138into the coil110bis facilitated by placing the resin container136in a space having a pressure lower than the atmospheric pressure. As described earlier, the nonwoven tape132allows permeation of the resin liquid138. Further, the lashing band122is wound around the strands114so as to form gaps G between the lashing bands122as shown inFIG. 13. Thus, the resin liquid138permeates the nonwoven tape132to reach the outer peripheral surface (surface) of the strands114and further between the strands114through the gaps G of the wound lashing bands122. Thus, resin liquid138is filled without leaving any spaces between the strands114and further between the lashing band122, the nonwoven tape132, and the strands114.

As described above, the nonwoven tape132includes the hardening accelerator of the resin liquid138. The coil110bis immersed in the resin liquid138, and after the resin liquid138has permeated sufficiently into the nonwoven tape132and the multiconductor wire112, the resin liquid138in the nonwoven tape132hardens through reaction with the hardening accelerator. Thus, the surrounding band124hardened by the resin is formed as shown in the later describedFIG. 17. Since the hardening accelerator is only contained in the nonwoven tape132, only the resin liquid138of the nonwoven tape132portion hardens and the interior resin liquid138covered by the nonwoven tape132is left unhardened. That is, the inner region covered by the nonwoven tape132and located between the strands114and the lashing band122is filled with the resin liquid138prior to being hardened, that is, the unhardened resin140. When the coil in this state is referred to as coil110d, the multiconductor wire112constituting the coil110dis configured so that the unhardened resin140is filled between the strands114inside the multiconductor wire112and the outer periphery of the multiconductor wire112is covered by the nonwoven tape132hardened by the resin liquid138, that is, the surrounding band124as shown inFIG. 17.

Next, the coil110din the above described state which has been taken out of the resin container136is illustrated inFIG. 18. The structure of the multiconductor wire112constituting the coil110dis illustrated inFIG. 17as described above.FIG. 17illustrates the cross sectional structure of portion B ofFIG. 18. The periphery of the multiconductor wire112constituting the coil110dis covered by the surrounding band124hardened by the resin liquid138. Thus, even when the coil110dis taken out of the resin container136, it is possible to prevent the resin liquid138inside the coil110d, that is, the unhardened resin140from leaking to the exterior and the unhardened resin140is held without leaving any spaces in the inside of the coil110dcovered by the surrounding band124.

Next, the coil110dis put into a heat drying furnace142as shown inFIG. 18. The entirety of the coil110dis thermally dried by the heat drying furnace142to thereby harden the unhardened resin140of the coil110d. The hardening of the surrounding band124is facilitated at the same time. The coil110illustrated inFIG. 10can be manufactured through the above described process steps.

In the process step illustrated inFIG. 16, the hardening accelerator is contained only in the nonwoven tape132portion and the resin liquid138of this portion alone is hardened for the following reason. Suppose the hardening accelerator of the resin liquid138is not contained in the nonwoven tape132portion. In such case, the resin liquid138of the nonwoven tape132portion is not hardened even in case the coil110bis immersed in the resin liquid138inside the resin container136. When the coil110is taken out of the resin container136in this state, the unhardened resin140inside the coil110will leak to the outside by passing through the nonwoven tape132since the nonwoven tape132allows permeation of the resin liquid138. Thus, in case the resin liquid138is hardened by the heat drying furnace142in this state, the hardened resin120is absent in the multiconductor wire112constituting the coil110and spaces are created between the strands114, the lashing band122, the surrounding band124, and the like. The insulation property of the coil110becomes reduced when such spaces exist.

On the other hand, in order to harden the resin liquid138without containing the hardening accelerator in the nonwoven tape132, the resin liquid138is hardened by methods such as applying heat with the coil110placed inside the resin container136. However, when such method is taken, the resin liquid138becomes hardened along with the resin container136containing the coil110, thereby causing the coil110to be integrated with the resin container136and preventing the coil110from being taken out of the resin container136. Further, the hardened resin becomes filled in the cavity in the center of the coil110and the cavity becomes blocked by the hardened resin. The hardening accelerator is contained in the nonwoven tape132to harden the resin liquid138in this portion alone for the above described reasons. That is, the nonwoven tape132turns into the surrounding band124hardened by the resin by containing hardening accelerator in the nonwoven tape132and possesses a function of retaining a state in which the resin liquid138is filled inside the coil110bwithout leaving any spaces when the coil110bis immersed in the resin container136filled with the resin liquid138and the interior of the coil110bis impregnated with the resin liquid138. It is thus, possible to obtain coil110with improved insulation property without leaving any spaces between the strands114, the lashing bands122, and the surrounding bands124inside the coil110.

The coil110according to the above described embodiment provides the following effects.

In the coil110and the multiconductor wire112constituting the coil110of the embodiment, hardened resin120is filled and molded between the strands14and in the periphery of the strands14without leaving any spaces. Thus, the insulation property of the coil110is improved and excellent insulation property is exerted even when the coil110is used in a high-frequency electric appliances for example.

Further, in the coil110and the multiconductor wire112constituting the coil110, the strands114, the lashing band122, and the surrounding band124are integrally solidified by the hardened resin120without leaving any spaces to provide a three-dimensionally secured structure. That is, in the coil110and the multiconductor wire112constituting the coil110, the hardened resin120is filled, solidified, and molded between the strands114and in the periphery of the strands114without leaving any spaces. Thus, generation of gaps and peeling voids are suppressed in the coil110to provide excellent insulation property.

The periphery of the coil110and the multiconductor wire112constituting the coil110of the embodiment are covered by the surrounding band124formed of the nonwoven tape132hardened by the resin. Thus, the insulation property between the multiconductor wires112as well as the mechanical strength of the coil110are improved.

In the coil110and the multiconductor wire112constituting the coil110of the embodiment, a resin having high thermal conductivity, that is, high heat dissipating property may be employed as the hardened resin120, that is, the resin liquid138. In this case, because the coil110exhibits excellent heat dissipating property, it is possible to prevent damaging of the coil110, etc. even when abnormal heat is produced for example at the coil110.

According to the manufacturing method of the coil110of the embodiment, the hardening accelerator of the resin liquid138is contained in the nonwoven tape132. The coil110bbeing manufactured is immersed in the resin liquid138and the resin liquid138at the nonwoven tape132hardens through reaction with the hardening accelerator after the resin liquid138has sufficiently permeated into the multiconductor wire112. Thus, the inner region of the coil110is filled with resin liquid138which is not hardened, that is, the unhardened resin140and the periphery of the unhardened resin140is covered by nonwoven tape132hardened by the resin liquid138, that is, the surrounding band124. That is, it is possible to create a situation in which the periphery of the unhardened resin140in the inner region of the coil110is covered by the surrounding band124solidified by the resin and the unhardened resin140is confined therein. It is thus, possible to prevent the unhardened resin140of the inner region of the coil110from leaking even when the coil110being manufactured is taken out of the resin container136. As a result, it is possible to obtain the coil110and the multiconductor wire112constituting the coil10in which the hardened resin120is filled and molded without leaving any spaces between the strands114and in the periphery of the strands114. It is thus, possible to manufacture a coil110having excellent insulation property.

The foregoing embodiment described an example in which a rectangular line having a substantially rectangular cross section obtained by bundling two strands114aand114bwas used, however, a single strand114having a substantially rectangular cross section may be used as shown inFIG. 19 (a). Even when such strand114is used, the resin liquid138permeates to the surface of the strand114as illustrated inFIG. 19 (b)by winding the nonwoven tape132around the strand114and immersing the strand114in the resin container136as was the case in the embodiment. Then, by thermally treating the strand114, it is possible to obtain the multiconductor wire112with excellent insulation property as shown inFIG. 19 (c). It is thus, possible to manufacture the coil110having excellent insulation property.

The above description was given through an example in which a rectangular wire having a rectangular cross section was used as the multiconductor wire112in the embodiment. However, multiconductor wire112is not limited to a rectangular wire. A round wire having a circular cross section for example may be used instead.