Transformer and method for manufacturing transformer

Abstract

The present invention provides: a transformer in which an insulating sheet is employed in certain locations in a bobbin and a core winding part, thereby allowing a smaller form factor to be achieved while preserving the coil shape; and a method for manufacturing said transformer. A transformer 10 according to the present invention comprises a coil assembly 65, insulation sheets 40, and cores 50. The coil assembly 65 includes: a coil 20 formed by winding covered wires 21 in a rounded-off rectangular shape so as to yield mutually opposed left and right linear parts 22, 22, an upper connection part 23a connecting the upper ends of the linear parts, and a lower connection part 23b connecting the lower ends of the linear parts; an upper bobbin 30a in which are formed recessed grooves 31 that cover the inner peripheral surface and the side surface of the upper connection part; and a lower bobbin 30b in which are formed recessed grooves that cover the inner peripheral surface and the side surface of the lower connection part. Said insulation sheets 40 have electric insulation properties and are wound around the linear parts of the coil, and said cores 50 are composed of directional electromagnetic steel plates 51 and are wound in a spiral shape from above the insulation sheet.

Description

Transformer and method for manufacturing the same

[0001] The present invention relates to a transformer having a coil wound with a grain-oriented electromagnetic steel sheet in a roll shape with an insulating sheet interposed therebetween, and to a method for manufacturing the same.

[0002] Known transformers for voltage and current transformation include a cylindrical core wound around a coil wound in a generally rounded rectangular shape. For example, a transformer disclosed in Patent Document 1 has a coil wound around an electrically insulating resin bobbin with a coated wire wound in a generally rectangular shape, and a core made of grain-oriented electromagnetic steel sheet wound around the bobbin. Also, a transformer disclosed in Patent Document 2 has an insulating sheet wound around a generally rounded rectangular coil, and a grain-oriented electromagnetic steel sheet coil wound around the insulating sheet.

[0003] JP-A-8-51034 Patent No. 7442885

[0004] The transformer in Patent Document 1 employs a bobbin with a rounded rectangular shape and grooves formed on the outer periphery to ensure coil winding, insulation, and creepage distance. Because the resin bobbin is a molded resin product, its thickness must be 0.8 mm to 1.5 mm to ensure strength and insulation heat resistance. In other words, the radial thickness of the resin bobbin is 1.6 mm to 3.0 mm. A thicker resin bobbin directly leads to a larger transformer. If the transformer size is specified, the diameter of the coated wire of the coil used must be reduced by the thickness of the resin bobbin, resulting in increased loss due to temperature rise and increased voltage fluctuation characteristics.

[0005] The transformer of Patent Document 2 does not use a bobbin, but winds the coil in a roughly rounded rectangular shape, and insulates the coil from the core with an insulating sheet wrapped around the straight portions of the coil. However, when winding thin coated wire, such as that used in transformers with a capacity of 1 kVA or less, it is extremely difficult to wind the coil in an orderly manner without breaking the winding. Furthermore, it is not possible to provide taps in the coil.

[0006] An object of the present invention is to provide a transformer and a manufacturing method thereof that can be made smaller while maintaining the coil shape by using insulating sheets in some parts around the bobbin and core.

[0007] The transformer of the present invention comprises: a coil formed by winding a coated wire in a rounded rectangular shape so as to have opposing left and right straight portions, an upper connecting portion connecting the upper ends of the straight portions, and a lower connecting portion connecting the lower ends of the straight portions; an upper bobbin having a groove formed therein covering the inner peripheral surface and side surface of the upper connecting portion; and a lower bobbin having a groove formed therein covering the inner peripheral surface and side surface of the lower connecting portion; an insulating sheet having electrical insulation properties and wound around the straight portions of the coil; and a core made of grain-oriented electromagnetic steel plate and wound in a spiral shape from above the insulating sheet.

[0008] It is desirable that the upper and lower bobbins have creepage distance securing projections protruding from their inner peripheries for positioning the core.

[0009] At least one of the upper bobbin and the lower bobbin is preferably formed on a side surface thereof with a tap lead-out portion through which a tap led out from a coil passes.

[0010] The transformer may be a current transformer and may include a conductor wound on the insulating sheet side between the insulating sheet and the core, and a second insulating sheet wound between the conductor and the core.

[0011] Furthermore, the present invention provides a method for manufacturing a coil assembly, which includes: a coil formed by winding a coated wire in a rounded rectangular shape so as to have opposing left and right straight portions, an upper connecting portion connecting the upper ends of the straight portions, and a lower connecting portion connecting the lower ends of the straight portions; an upper bobbin having a recessed groove formed therein covering the inner peripheral surface and side surface of the upper connecting portion; and a lower bobbin having a recessed groove formed therein covering the inner peripheral surface and side surface of the lower connecting portion, the method comprising the steps of: preparing the upper bobbin and the lower bobbin; a pair of side jigs having linear recessed grooves formed on their outer peripheries; a side spacer jig that holds the pair of side jigs at a predetermined distance; and a pair of bobbin spacer jigs that hold the upper bobbin and the lower bobbin at a predetermined distance; a bobbin-jig assembly is formed by placing the upper bobbin above the side spacer jig with the groove facing upward, placing the lower bobbin below the side spacer jig with the groove facing downward, and placing the side jigs on the left and right of the side spacer jig with the groove facing outward, and attaching the bobbin spacer jigs to the front and rear of the side spacer jig so that the upper bobbin and the lower bobbin are spaced a predetermined distance apart; hooking a covered wire onto one of the upper bobbin, the lower bobbin, and the side jig, and rotating the bobbin-jig assembly around the left-right and top-bottom centers of the side spacer jig as a rotation center, thereby winding the covered wire around the grooves of the upper bobbin, the lower bobbin, and the side jig, to form a coil; After the coil is formed, the rotation of the bobbin / jig assembly is stopped, one of the bobbin spacer jigs and the side spacer jigs is removed, and then the side jig is removed while leaving the other bobbin spacer jig in place, thereby obtaining the coil assembly.

[0012] The method for manufacturing a transformer of the present invention includes winding an electrically insulating sheet around the straight portion of the coil assembly manufactured as described above, removing the other bobbin spacer jig, and spirally winding a core made of a grain-oriented electromagnetic steel sheet around the insulating sheet.

[0013] In addition, the method for manufacturing a transformer of the present invention includes winding an electrically insulating sheet around the straight portion of the coil assembly manufactured as described above, removing the other bobbin spacer jig, the upper bobbin, and the lower bobbin, and then spirally winding a core made of a grain-oriented electromagnetic steel sheet around the insulating sheet.

[0014] The transformer is a current transformer, and after the insulating sheet is wound around the transformer and before the core is wound around the transformer, a conductor is wound around the insulating sheet, and a second insulating sheet is further wound around the conductor.

[0015] According to the transformer and the manufacturing method of the present invention, the straight portion of the coil where the core is wound can be made of only insulating sheet. In addition, the upper connecting portion of the coil is housed in the groove of the upper bobbin, and the lower connecting portion is housed in the groove of the lower bobbin, so the coil will not come apart, and taps can be easily provided.

[0016] FIG. 1 is a perspective view of a transformer according to an embodiment of the present invention. FIG. 2 is an exploded front view of a bobbin / jig assembly. FIG. 3 is an exploded right side view of the bobbin / jig assembly. FIG. 4 is a perspective view of the bobbin / jig assembly. FIG. 5 is a front view showing a state in which a coil has been wound around the bobbin / jig assembly. FIG. 6 is a front view showing a state in which one bobbin spacer jig, a side spacer jig, and a side jig have been removed from the bobbin / jig assembly. FIG. 7 is a front view showing a state in which an insulating sheet has been wound around a straight portion of the coil. FIG. 8 is a cross-sectional view of the coil taken along line E-E in FIG. 7, where (a) is a cross-sectional view during winding of the insulating sheet, and (b) is a cross-sectional view of a state in which the insulating sheet has been tightened. FIG. 9 is a front view showing a state in which the other bobbin spacer jig has been removed. FIG. 10 is a front view of a transformer obtained by winding a core. FIG. 11 is an end view of a bobbin constructed from bobbin segments, with (a) the bobbin segments integrated and (b) the bobbin segments disengaged. FIG. 12 is a front view of a bobbinless transformer. FIG. 13 is an end view of a bobbin of a two-phase winding transformer. FIG. 14 is a side view of a side jig for a two-phase winding transformer. FIG. 15 is an end view of an embodiment in which the side jig for a two-phase winding transformer is constructed from side jig segments, with (a) the side jig segments integrated and (b) the side jig segments disengaged. FIG. 16 is a perspective view of a primary insulating sheet and a secondary insulating sheet. FIG. 17 is a cross-sectional view showing the state in which insulating sheets are wound around the primary and secondary coils of a two-phase winding transformer. FIG. 18 is a perspective view of a current transformer in the middle of manufacture, with conductors arranged on insulating sheets. FIG. 19 is a perspective view showing the state in which conductors are wound. Fig. 20 is a cross-sectional view of the current transformer taken perpendicular to the straight portion, and Fig. 21 is a perspective view of the current transformer of the present invention.

[0017] A transformer 10 according to one embodiment of the present invention will be described below with reference to the drawings. For ease of understanding, in this specification and the drawings, the upper bobbin 30a at the front side of the transformer 10 in FIG. 1 will be referred to as the "upper" and the lower bobbin 30b at the rear side will be referred to as the "lower." In other words, the upper side of the front view in FIG. 10 will be referred to as the "upper" and the lower side as the "lower." Similarly, the left side in FIG. 10 will be referred to as the "left," the right side as the "right," the front side as the "front," and the rear side as the "rear." Of course, these directions are used for the purpose of explanation and do not specify the direction or manner of use of the transformer 10.

[0018] 1 is a perspective view of a transformer 10 according to one embodiment of the present invention. The transformer 10 is, for example, a power transformer, and is configured by disposing a cylindrical core 50 in which a grain-oriented electromagnetic steel sheet 51 is spirally wound around the outer periphery of a coil 20 wound in a rounded rectangular shape, with an insulating sheet 40 interposed therebetween. Reference numerals 30a and 30b denote upper and lower bobbins that hold connecting portions 23a and 23b of the coil 20.

[0019] <Coil 20> The coil 20 constituting the transformer 10 can be, for example, a single-phase winding in which a portion of the primary coil and a portion of the secondary coil are shared, and is formed by winding a coated wire 21 such as an enameled copper wire with an insulating coating. A two-phase winding in which the primary coil and the secondary coil are separate coils will be described in a modified example, but the primary coil and the secondary coil can be wound with insulation between them. The coil 20 can be wound into a substantially rounded rectangle with opposing straight portions 22, 22, as shown in Figures 5 and 6 (described later). The straight portions 22, 22 are the portions around which the insulating sheet 40, as shown in Figures 7 and 9, and the core 50, as shown in Figures 1 and 10, are wound. 1, the straight portions 22, 22 are connected by rounded connecting portions 23a, 23b (upper connecting portion and lower connecting portion), but the arc shape, curvature, and radius of curvature of the connecting portions 23a, 23b are not limited to this as long as they have rounded corners, and the space between the corners may be arc-shaped, elliptical, or linear. In this specification, this type of coil 20 shape is also referred to as a rounded rectangle.

[0020] <Upper bobbin 30a, lower bobbin 30b> The upper bobbin 30a and the lower bobbin 30b are attached to the upper and lower opposing connecting portions 23a, 23b of the coil 20 from the inside. The upper bobbin 30a and the lower bobbin 30b are made of electrically insulating resin, and as best shown in Figures 1 to 4, particularly Figure 4, a groove 31 is formed inward from the outer periphery. The groove 31 is a groove that covers the inner periphery and side surfaces of the connecting portions 23a, 23b of the coil 20. The groove 31 has a pair of front and rear lateral walls 32, 32 that form the side surfaces, and a bottom wall 33 that forms the bottom surface 34 of the groove 31. It is desirable that the groove 31 have a cross-section that tapers toward the bottom surface so that the coil 20 can be wound in a shape that is close to a circular cross-section. In this embodiment, as shown in Figure 3, the groove 31 is an isosceles trapezoid (half of a hexagon) whose width tapers toward the bottom surface 34.

[0021] The upper bobbin 30a and the lower bobbin 30b have tap lead-out portions 35 formed on the side walls 32, through which the taps 24 drawn from the coils 20 pass. The illustrated tap lead-out portions 35 are notched recesses formed in the side walls 32.

[0022] Furthermore, the upper bobbin 30a and the lower bobbin 30b have a creepage distance ensuring protrusion 36 protruding from the bottom wall 33 to position the core 50 on the side opposite the recessed groove 31 and ensure a creepage distance with the coil 20. Specifically, the end face of the core 50 abuts against the creepage distance ensuring protrusion 36 to position the core 50 on the straight portion 22 of the coil 20 and maintain a constant distance to the edge of the insulating sheet 40 wound around the straight portion 22. As best shown in FIG. 2 , the creepage distance ensuring protrusion 36 is a U-shaped protrusion in cross section that has a hollow claw insertion hole 37 protruding from the center of the bottom wall 33. The claw insertion hole 37 is formed in the creepage distance ensuring protrusion 36 because, in this embodiment, it also serves as an attachment portion for attaching bobbin spacer jigs 70a, 70b used when winding the coil 20.

[0023] <Insulating sheet 40> As shown in Figures 1, 7, 9, and 10, an insulating sheet 40 is wrapped around the straight portions 22, 22 of the coil 20. The insulating sheet 40 insulates the coil 20 from the core 50. As shown in the cross-sectional view of Figure 8, the insulating sheet 40 is a thin sheet made of an electrically insulating material. For example, the insulating sheet 40 can be made of aramid paper (Nomex (registered trademark) manufactured by DuPont) woven with aramid fibers made of aromatic polyamide resin, or a polyester film.

[0024] The insulating sheet 40 is formed to have a width that allows it to be wound around the straight portion 22 and is at least wider than the grain-oriented electromagnetic steel sheets 51 that form the core 50. In order to ensure a creepage distance between the coil 20 and the core 50, it is desirable that the width of the insulating sheet 40 be at least 5 mm (2.5 mm on each side) longer than the width of the grain-oriented electromagnetic steel sheets 51. Furthermore, in order to provide an insulating effect, the length of the insulating sheet 40 is such that it wraps around the outer periphery of the straight portion 22 at least once, preferably 1.2 to 2 times.

[0025] After the insulating sheet 40 is wrapped around the straight portion 22, it is preferable to fasten it with a fixing means such as tape (not shown) to prevent it from coming undone.

[0026] As will be described later, during the process of assembling the transformer 10, after the coil 20 is wound (FIGS. 5 and 6), the upper and lower bobbins 30a and 30b are held at a predetermined distance by the bobbin spacer jigs 70a and 70b until the insulating sheet 40 is wound. This prevents the straight portion 22 of the coil 20 from bending or loosening. Therefore, the insulating sheet 40 is wound around the straight portion 22 with the bobbin spacer jigs 70a and 70b still attached. On the other hand, when winding the core 50, the bobbin spacer jigs 70a and 70b must be removed. At this time, the straight portion 22 of the coil 20 must be reinforced by the insulating sheet 40 to prevent bending or loosening. Therefore, the insulating sheet 40 must have a certain strength. For this reason, the insulating sheet 40 is preferably 0.1 mm to 0.5 mm thick, and more preferably 0.2 mm to 0.4 mm thick.

[0027] <Core 50> The core 50 is formed on the insulating sheet 40 that is wound around the straight portion 22 of the coil 20. The core 50 is formed by winding a grain-oriented electromagnetic steel sheet 51 in a spiral shape around the insulating sheet 40, as shown in Fig. 1. It is desirable to perform an annealing heat treatment on the grain-oriented electromagnetic steel sheet 51 in advance.

[0028] The transformer 10 configured as described above does not require a bobbin on the straight portion 22, and can be made smaller by directly winding the insulating sheet 40 and the core 50. On the other hand, the shape of the coil 20 can be secured by attaching the upper bobbin 30a to the upper connecting portion 23a and the lower bobbin 30b to the lower connecting portion 23b.

[0029] <Manufacturing Method> The transformer 10 of the present invention can be manufactured according to the procedures shown in FIGS.

[0030] FIG. 2 shows the upper bobbin 30a, the lower bobbin 30b, and jigs 70, 80, and 90 for winding the coil 20 between the upper bobbin 30a and the lower bobbin 30b.

[0031] The jigs include side jigs 90, 90 around which the coil 20 is wound, a side spacer jig 80 that holds the side jigs 90, 90 at a predetermined distance, and bobbin spacer jigs 70 (70a, 70b) that hold the bobbins 30a, 30b at a predetermined distance.

[0032] 3 and 4, the side jig 90 has a linear groove 91 formed on the outer periphery. The groove 91 is continuous with the grooves 91 of the upper bobbin 30a and the lower bobbin 30b, and the covered wire 21 of the coil 20 is wound around the groove 91. The cross-sectional shape of the groove 91 can be the same as the cross-sectional shape of the grooves 31 of the upper bobbin 30a and the lower bobbin 30b.

[0033] 4 and 5, when winding the coil 20, the side jigs 90 are attached to the left and right sides of the side spacer jig 80. On the inner periphery of the side jig 90, attachment pieces 92 for attaching to the side spacer jig 80 are formed to protrude in the front-to-rear direction, and fastening holes 93 are opened in the attachment pieces 92.

[0034] <Side spacer jig 80> The side spacer jig 80 is a jig that holds the side jigs 90 at a predetermined interval. The side spacer jig 80 has a roughly rectangular parallelepiped shape that is thicker than the upper bobbin 30a and the lower bobbin 30b. The side spacer jig 80 has screw holes (not shown) formed on its side surface for screwing the side jig 90. The side spacer jig 80 also has rotating shaft mounting holes 81 formed in the left-right and top-bottom central portions when viewed from the front. The illustrated rotating shaft mounting hole 81 is a grooved hole into which a motor rotating shaft 100 (e.g., with a key) such as that shown in FIG. 4 is fitted when winding the coil 20.

[0035] <Bobbin spacer jig 70 (70a, 70b)> The bobbin spacer jig 70 is a jig that holds the upper bobbin 30a and the lower bobbin 30b at a predetermined distance, and also integrates the bobbins 30a, 30b with the side jig 90 and the side spacer jig 80 to form the bobbin / jig assembly 60.

[0036] 2 to 4, the bobbin spacer jig 70 is a jig with inwardly protruding bobbin locking claws 73. In the illustrated embodiment, the jig has a rectangular parallelepiped jig body 71 to which an L-shaped metal fitting 72 having the bobbin locking claws 73 is attached. The jig body 71 and the L-shaped metal fitting 72 are fastened with screws 74.

[0037] The jig body 71 has a rotary shaft mounting hole 75 formed in the center thereof, which is aligned with the rotary shaft mounting hole 81 of the side spacer jig 80 .

[0038] <Bobbin / Jig Assembly 60> With regard to the bobbins 30a, 30b and jigs 70, 80, 90 configured as described above, as shown in Fig. 2A, the side jig 90 is brought close to both sides of the side spacer jig 80 with the grooves 91 facing outward, and attached by screws or the like. Also, as shown in Fig. 3, the upper bobbin 30a is positioned with the grooves 31 facing upward and the lower bobbin 30b with the grooves 31 facing downward, and the bobbins 30a, 30b are brought close to the side spacer jig 80 from above and below as indicated by arrow B. Then, the bobbin spacer jigs 70a, 70b are brought close to the side spacer jig 80 from the front and rear as indicated by arrow C, and the bobbin locking claws 73 of the bobbin spacer jigs 70a, 70b are inserted into the claw insertion holes 37 (see Fig. 2) of the bobbins 30a, 30b as indicated by arrow D. As a result, the bobbin / jig assembly 60 shown in FIG. 4 is formed.

[0039] As shown in FIGS. 2 to 4, the bobbin / jig assembly 60 has a configuration in which the recessed grooves 31 of the bobbins 30a, 30b and the recessed grooves 91 of the side jigs 90, 90 are continuous in the circumferential direction.

[0040] <Winding the coil 20> As shown in Fig. 4, the motor shaft 100 is inserted into the aligned shaft mounting holes 75, 81 of the obtained bobbin / jig assembly 60. The coated wire 21 is wound around a reel or the like, and one end 25a is pulled out from the tap pull-out portion 35 of the upper bobbin 30a (or the lower bobbin 30b) and hung in the groove 31, for example, as shown in Fig. 5.

[0041] From this state, by driving the motor, the bobbin / jig assembly 60 rotates around the rotary shaft mounting holes 75, 81 as the center of rotation, and the covered wire 21 is wound into the recessed grooves 31, 91. If a tap is required on the covered wire 21 during the winding, the rotation of the bobbin / jig assembly 60 is stopped, the tap is formed, and the covered wire 21 is pulled out from the tap pull-out portion 35. Then, when the coil 20 has been wound a predetermined number of times, the rotation of the bobbin / jig assembly 60 is stopped, the covered wire 21 is cut, and the end 25b of the coil 20 is hooked on the tap pull-out portion 35 as shown in FIG. 5. The bobbin / jig assembly 60 is then removed from the rotary shaft 100 of the motor. This completes the coil 20 winding process. The portion of the coil 20 that fits into the groove 91 of the side jig 90 is the straight portion 22, and the portions that fit into the grooves 31 of the bobbins 30a, 30b are the upper connecting portion 23a that connects the upper ends of the straight portions 22, 22, and the lower connecting portion 23b that connects the lower ends of the straight portions 22, 22.

[0042] <Removing the jigs 70, 80, 90> As shown in Figure 6, some of the jigs 70, 80, 90 are removed from the bobbin / jig assembly 60 (Figure 5) around which the coil 20 has been wound. Specifically, one of the bobbin spacer jig 70a (the rear jig in Figure 6) is left, and the other jigs 70b, 80, 90 are removed. The reason for leaving one of the bobbin spacer jig 70a is to hold the upper bobbin 30a and the lower bobbin 30b at a predetermined distance and to prevent the straight portion 22 of the coil 20 from bending or slackening until the insulating sheet 40 is wound.

[0043] The order of removal of the jigs is as follows: first, pull out the front bobbin spacer jig 70b toward you. Next, release the screws connecting the side spacer jig 80 and side jig 90, and pull out the side spacer jig 80 toward you. Then, for the left and right side jigs 90, shift the right side jig 90 to the left and pull it out toward you. Similarly, shift the left side jig 90 to the right and pull it out toward you. This results in a coil assembly 65 in which the upper bobbin 30a and lower bobbin 30b are held at a predetermined distance by the rear bobbin spacer jig 70a, as shown in Figure 6.

[0044] <Winding the Insulating Sheet 40> As shown in FIG. 7, the insulating sheet 40 is wound around the straight portion 22 of the coil 20 of the coil assembly 65 shown in FIG. 6. As shown in FIG. 7, the insulating sheet 40 is wound as far as possible so that it extends above or below the creepage distance securing protrusions 36 protruding inward from the bobbins 30a, 30b. As a result, when the core 50 is wound around the insulating sheet 40, an end of the insulating sheet 40 extends beyond the core 50, forming a protruding portion 41 (see FIG. 10), which corresponds to the creepage distance. After the winding is completed, one end of the insulating sheet 40 is attached to the straight portion 22 of the coil 20 with a fixing means such as tape, and the insulating sheet 40 is wound one or more times as shown in FIG. 8(a). Then, the insulating sheet 40 is tightened as shown by arrow F, and tension is applied to the coil 20 so that the cross section of the straight portion 22 approaches a substantially circular shape, as shown in FIG. 8(b). After this, the free end of the insulating sheet 40 may be fixed with a fixing means such as tape. As shown in FIG. 8, insulating sheets 40 are wrapped around both straight portions 22, 22, respectively.

[0045] <Removing the rear bobbin spacer jig 70a> By attaching the insulating sheet 40, the straight portion 22 is reinforced and prevented from bending or loosening. Therefore, in this state, it is possible to remove the rear bobbin spacer jig 70a that remains on the coil assembly 65. Even after removing the bobbin spacer jig 70a, the strength of the insulating sheet 40 keeps the straight portion 22 in a straight state, as shown in FIG.

[0046] <Winding the Core 50> Finally, the grain-oriented electromagnetic steel sheet 51 is wound around the insulating sheet 40. The grain-oriented electromagnetic steel sheet 51 can be wound, for example, as described in Patent Document 2, but the method is not limited to this. The core 50 formed by winding the grain-oriented electromagnetic steel sheet 51 is wound so that its end faces abut against the creepage distance securing protrusions 36, 36 protruding inward from the bobbins 30a, 30b, as shown in Figures 1 and 10. This prevents the core 50 from protruding beyond the creepage distance securing protrusions 36, so that the protruding portions 41 of the insulating sheet 40 can ensure the creepage distance of the insulation.

[0047] After the winding of the grain-oriented electromagnetic steel sheet 51 is completed, the end of the grain-oriented electromagnetic steel sheet 51 may be fixed to the peripheral surface of the core 50 by welding or the like. Figures 1 and 10 show the manufactured transformer 10.

[0048] The transformer 10 of the present invention employs bobbins 30a and 30b in some parts, but employs insulating sheet 40 instead of a bobbin for the portion around which core 50 is wound. This allows the shape of coil 20 to be maintained by bobbins 30a and 30b, while core 50 is wound around the portion where there is no bobbin, thereby enabling core 50 to be miniaturized. This allows the transformer 10 to be miniaturized.

[0049] <Modifications> Modifications of the present invention will now be described.

[0050] <Transformer 10 without Bobbins 30a, 30b> In the above embodiment, the bobbins 30a, 30b remain in the final transformer 10 ( FIG. 10 ). However, the bobbins 30a, 30b can be removed during manufacturing. For example, in FIG. 11 , the bobbins 30a, 30b are configured to be separable into left and right halves (reference numerals 39a, 39b). The left and right bobbin segments 39a, 39b can be integrated with bolts or the like. The bobbins 30a, 30b formed by integrating the left and right bobbin segments 39a, 39b are used to perform the insulating sheet winding process shown in FIG. 7 . Then, after removing the bobbin spacer jig 70a as shown in FIG. 9 , the bobbin segments 39a, 39b are disconnected from each other, and the bobbins 30a, 30b are removed from the coil 20 as shown in FIG. 12 . As described above, the straight portion 22 of the coil 20 maintains its straight state due to the strength of the insulating sheet 40, so that the coil 20 of the coil assembly 65 maintains its rounded rectangular shape as shown in FIG.

[0051] Thereafter, the core 50 may be wound as shown in Fig. 10. After the core 50 has been wound, the bobbins 30a and 30b may be removed.

[0052] According to this embodiment, the bobbins 30a and 30b do not remain in the transformer 10, which allows for a smaller and lighter transformer 10. Furthermore, since the bobbin segments 39a and 39b do not remain in the transformer 10, they do not need to be electrically insulating and can be made of, for example, metal and reused.

[0053] <Two-Phase Winding Transformer> In the case where the primary coil 20a and the secondary coil 20b are two-phase windings of separate coils (see FIG. 17), as shown in FIG. 13, the bobbins 30a, 30b have an insulating wall 38 protruding from the bottom surface 34 of the groove 31, dividing the groove 31 in half (31a and 31b). Similarly, as shown in FIGS. 14 and 15, the side jig 90 also has an insulating wall 94 protruding from the groove 91, dividing the groove 91 in half (91a and 91b). In FIGS. 14 and 15, the side jig 90 can also be divided into left and right halves (90a, 90b). Then, using the bobbins 30a, 30b and the side jigs 90, 90, the bobbin-jig assembly 60 is assembled so that the grooves 31a, 91a are aligned and the grooves 31a, 91a are aligned.

[0054] In the bobbin / jig assembly 60, the primary coil 20a is wound in one of the grooves 31a, 91a, and the secondary coil 20b is wound in the other groove 31b, 91b. Then, as shown in Figure 5, after winding the coil 20, the bobbin spacer jig 70b and the side spacer jig 80 are removed, leaving the bobbin spacer jig 70a. The side jigs 90, 90 are also removed. In this embodiment, the side jig 90 is made up of side jig segments 90a, 90b that can be separated into left and right halves, so it is sufficient to remove them one by one.

[0055] For example, the insulating sheet 40 wrapped around the straight section 22 can also be a primary insulating sheet 40a and a secondary insulating sheet 40b bent into an approximately U-shape, as shown in Figure 16. First, remove the side jig segment 90a and insert the primary insulating sheet 40a so that one end of the primary insulating sheet 40a enters the resulting gap. Then, remove the side jig segment 90b and insert the secondary insulating sheet 40b so that one end of the secondary insulating sheet enters the resulting gap (see Figure 17).

[0056] 17, the primary coil 20a is wrapped with the primary insulating sheet 40a, the secondary coil 20b is wrapped with the secondary insulating sheet 40b, and the entire assembly is then covered with the insulating sheet 40c from the outside. This achieves insulation between the primary coil 20a and the secondary coil 20b. After that, the bobbin spacer jig 70a is removed and the core 50 is wound using the same procedure as in FIGS. 9 and 10.

[0057] 13 can be separated into left and right halves as shown in FIG. 11, and can be removed from the coil assembly 65 to obtain a two-phase winding transformer 10 without a bobbin.

[0058] <Current Transformer 110> The transformer 10 described above is a power transformer. However, the current transformer 110 can be fabricated in a similar manner by interposing an insulated conductor 111 between the coil 20 and the core 50 so as to encase the coil 20. The conductor 111 is, for example, a copper plate, and as shown in FIG. 18, has a generally U-shaped cross section, with terminals 112 serving as lead wires formed on its edge. After winding the insulating sheet 40 around the coil 20 as shown in FIG. 9, the conductor 111 is fitted to encase the coil 20 as shown in FIG. 18 (insulating sheet 40 is not shown), and the tip of the conductor 111 is bent to fit the coil 20 as shown in FIGS. 19 and 20. The tips of the conductors 111 are spaced slightly apart to create a gap 113 as shown in FIG. 20. Then, second insulating sheet 42 (not shown in FIG. 21) is wrapped around the outer periphery of conductor 111 as shown in FIG. 20, and core 50 is then wrapped around it as shown in FIGS. 20 and 21. Current transformer 110 configured in this manner can be used in various power supply devices, such as wireless power transfer devices that transfer power at high frequency between an electric vehicle and a home by transferring power charged in a storage battery from a solar panel.

[0059] The current transformer 110 may have a configuration that does not include the bobbins 30a and 30b described above.

[0060] The above description is for the purpose of explaining the present invention, and should not be construed as limiting the invention described in the claims or narrowing its scope. Furthermore, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications are possible within the technical scope described in the claims.

[0061] REFERENCE SIGNS LIST 10 Transformer 20 Coil 21 Covered wire 22 Straight portion 23a Upper connecting portion 23b Lower connecting portion 30a Upper bobbin 30b Lower bobbin 31 Groove 36 Creepage distance securing protrusion 37 Claw insertion hole 40 Insulating sheet 50 Core 51 Grain-oriented electromagnetic steel plate 60 Jig assembly 65 Coil assembly 70 (70a, 70b) Bobbin spacer jig 73 Bobbin locking claw 80 Side spacer jig 90 Side jig 91 Groove 110 Current transformer

Claims

1. A transformer comprising: a coil formed by winding a coated wire in a rounded rectangular shape so as to have opposing left and right straight sections, an upper connecting section connecting the upper ends of the straight sections, and a lower connecting section connecting the lower ends of the straight sections; an upper bobbin having a groove formed therein that covers the inner surface and side of the upper connecting section; and a lower bobbin having a groove formed therein that covers the inner surface and side of the lower connecting section; an insulating sheet having electrical insulation properties and wound around the straight sections of the coil; and a core made of grain-oriented electromagnetic steel sheet and wound in a spiral shape from above the insulating sheet.

2. The transformer according to claim 1, wherein the upper bobbin and the lower bobbin have creepage distance securing protrusions protruding from their inner peripheries to position the core.

3. The transformer according to claim 2, wherein at least one of the upper bobbin and the lower bobbin is formed with a tap lead-out portion on a side surface through which a tap led out from a coil passes.

4. The transformer according to any one of claims 1 to 3 is a current transformer and comprises a conductor wound on the insulating sheet side between the insulating sheet and the core, and a second insulating sheet wound between the conductor and the core.

5. A method for manufacturing a coil assembly including a coil formed by winding a coated wire into a rounded rectangular shape so as to have opposing left and right straight portions, an upper connecting portion connecting the upper ends of the straight portions, and a lower connecting portion connecting the lower ends of the straight portions, an upper bobbin having a recessed groove formed therein covering the inner peripheral surface and side surface of the upper connecting portion, and a lower bobbin having a recessed groove formed therein covering the inner peripheral surface and side surface of the lower connecting portion, the method comprising: preparing the upper bobbin and the lower bobbin, a pair of side jigs having a linear recessed groove formed on the outer periphery, a side spacer jig that holds the pair of side jigs at a predetermined distance, and a pair of bobbin spacer jigs that hold the upper bobbin and the lower bobbin at a predetermined distance; a bobbin-jig assembly is formed by placing the upper bobbin above the side spacer jig with the groove facing upward, placing the lower bobbin below the side spacer jig with the groove facing downward, and placing the side jigs on the left and right of the side spacer jig with the groove facing outward, and attaching the bobbin spacer jigs to the front and rear of the side spacer jig so that the upper bobbin and the lower bobbin are spaced a predetermined distance apart; hooking a covered wire onto one of the upper bobbin, the lower bobbin, and the side jig, and rotating the bobbin-jig assembly around the left-right and top-bottom centers of the side spacer jig as a rotation center, thereby winding the covered wire around the grooves of the upper bobbin, the lower bobbin, and the side jig, to form a coil; After the coil is formed, the rotation of the bobbin / jig assembly is stopped, one of the bobbin spacer jigs and the side spacer jigs is removed, and then the side jig is removed while leaving the other bobbin spacer jig in place, thereby obtaining the coil assembly.

6. A method for manufacturing a transformer, comprising winding an electrically insulating sheet around the straight section of the coil assembly manufactured by the manufacturing method described in claim 5, removing the other bobbin spacer jig, and then spirally winding a core made of grain-oriented electromagnetic steel sheet around the insulating sheet.

7. The method for manufacturing a transformer according to claim 6, wherein the transformer is a current transformer, and after winding the insulating sheet and before winding the core, a conductor is wound on the insulating sheet, and then a second insulating sheet is wound on top of the conductor.

8. A method for manufacturing a transformer, comprising winding an electrically insulating sheet around the straight section of the coil assembly manufactured by the manufacturing method described in claim 5, removing the other bobbin spacer jig, the upper bobbin, and the lower bobbin, and then spirally winding a core made of grain-oriented electromagnetic steel sheet around the insulating sheet.

9. The method for manufacturing a transformer according to claim 8, wherein the transformer is a current transformer, and after winding the insulating sheet and before winding the core, a conductor is wound on the insulating sheet, and then a second insulating sheet is wound on top of the conductor.

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