Title of Invention	AMORPHOUS WOUND CORE TRANSFORMER
Abstract	Layer faces of a U-shaped core portion 101 comprising a first yoke portion la, and a first and a second leg portions Ic, Id at both sides of the first yoke portion of a wound core 1 are coated with a U-shaped cover 20. Windings are fitted to the leg portions Ic and Id coated with the U-shaped cover 20. A filter sheet 22, iS arranged inside a window portion 20d provideD in THE u-shaped cover 20, and a filter sheet 23 is disposed between each end of the U-shaped cover and the layered face of the core. A resin-coated layer is formed to cover the whole layer faces of a second yoke portion lb. A yoke cover 3 6 is attached to the layered face of the yoke portion lb by the resin forming the resin-coated layer. The filter sheets 22, 23 and yoke cover 3 6 are formed with felt.

Title of Invention

AMORPHOUS WOUND CORE TRANSFORMER

Abstract

Layer faces of a U-shaped core portion 101 comprising a first yoke portion la, and a first and a second leg portions Ic, Id at both sides of the first yoke portion of a wound core 1 are coated with a U-shaped cover 20. Windings are fitted to the leg portions Ic and Id coated with the U-shaped cover 20. A filter sheet 22, iS arranged inside a window portion 20d provideD in THE u-shaped cover 20, and a filter sheet 23 is disposed between each end of the U-shaped cover and the layered face of the core. A resin-coated layer is formed to cover the whole layer faces of a second yoke portion lb. A yoke cover 3 6 is attached to the layered face of the yoke portion lb by the resin forming the resin-coated layer. The filter sheets 22, 23 and yoke cover 3 6 are formed with felt.

Full Text	FIELD OF THE INVENTION The present invention relates to an amorphous core transformer using a wound core of a thin band of amorphous magnetic alloy. DESCRIPTION OF THE PRIOR ART An amorphous magnetic alloy is offered in the shape of a markedly thin band (strip) (e.g., nominal thickness of 0.02 5mm) and therefore, a core of a transformer using the amorphous magnetic alloy is generally obtained by winding. In order to manufacture the amorphous wound core transformer, for instance, a plurality of unit bodies of a predetermined length formed by cutting a thin band of a layered body are layered with a shift of a predetermined distance in a longitudinal direction, thereby to form a layer block. Then, a plurality of the thus-obtained layer blocks are sequentially wound around a frame and ends of the unit bodies in each layer block are butt-jointed or lap-jointed. Jointed portions are arranged stepwise at a yoke portion in the resulting rectangular wound core. In the present specification, one yoke portion without the jointed portions among two confronting yoke portions of the rectangular wound core will be named as a first yoke portion and, the other yoke portion with the jointed portions will be represented as a second yoke portion. Two leg portions extending in parallel between these fir^st and second yoke portions will be referred to as a first and a second leg portions. The leg portion here is a portion to be arranged in a window portion of windings fitted around the wound core, while the yoke portion is a portion placed projecting outside from the window portion of windings. Fig. 11 shows an example of a rectangular wound core 1., In Fig. 11, la and lb are the first and second yoke portions, and lc and Id are the first and second leg portions. A jointed portion J is formed in the second yoke portion lb. In the illustrated example, the wound core is constituted of four layer blocks and the jointed portion J formed in the second yoke portion lb comprises respective jointed portions J1-J4 of the first through fourth layer >locks. Jointed portions of a plurality of unit bodies constituting each layer block are distributed stepwise. The rectangular wound core manufactured as above is sent and annealed in an annealing furnace so as to remove warpings. After the core is annealed, the second yoke portion lb is opened at the jointed portion, then portions lbl, lb2 at both sides of the jointed portion of the second yoke portion lb and the first and second leg portions lc, Id are inserted in window portions of windings Wl, W2 respectively, so that the windings Wl, W2 are fitted with the first and second leg portions lc, Id respectively. A transformer is completed when the second yoke portion lb is closed after the fitting of windings. Since the amorphous magnetic alloy is easily deformed by its own weight, a reinforcing frame 2 of stainless steel or the like material is arranged at the innermost periphery of the wound core to reinforce the core. The reinforcing frame 2 is constituted of a large and a small U-shaped members 2A and 2B separable from each other. After the windings Wl, W2 are fitted while the member 2B is not attached, the member 2B is installed before the second yoke portion lb is closed. A protecting sheet of stainless steel band or the like is wound at the outermost periphery of the wound core 1. Both ends of the protecting sheet are welded in an overlapping state. The amorphous magnetic alloy is turned fragile subsequent to the annealing, causing the core to break at layer faces when the windings Wl, W2 are fitted. If the broken pieces are separated from the core and adhere to the windings or mixed with an insulation oil in a transformer case, the transformer is deteriorated in insulation performance and may be burnt in the worst case. Under the circumstances, the broken pieces should be sealed somehow not to be detached from the core of the transformer of this type. By way of example, Figs. 9A-9D and 10 show a conventional amorphous wound core transformer with means for sealing the broken pieces of amorphous magnetic alloy. A sequence of procedures of assembling the transformer by fitting the windings Wl, W2 to the annealed wound core 1 is indicated in Figs. 9A-9D. Fig. 10 represents a state of the wound core after the windings are fitted although the windings are not shown. In fitting the windings Wl, W2, as shown in Fig. 10, each layer face of a U-shaped core portion 101 consisting of the first yoke portion la, and the first and second leg portions 1c, Id at both sides of the portion la of the core 1 is covered with a U-shaped main cover 4 of an insulation paper, and an oil-resistant adhesive tape 5 is attached to peripheral edge portions of the U-shaped cover 4 and the core 1, whereby the main cover 4 is secured to the core 1 by the adhesive tape 5 and at the same time, the main cover 4 and the core 1 are sealed therebetween. Then, the second yoke portion lb of the core 1 is opened at the jointed portion and the windings Wl, W2 are fitted to the first and second leg portions lc, Id as in Fig. 9A. After the fitting, the member 2B of the reinforcing frame 2 is installed as in Fig. 9A. In Fig. 9A, 3 is a protecting plate arranged along the outermost periphery of the wound core. After the windings Wl, W2 are fitted at the first and second leg portions as in Fig. 9A, the second yoke portion lb is closed as in Fig. 9B. Both ends of the protecting plate 3 is overlapped and welded with each other. A corner cover 6 for covering the layer faces in the vicinity of inside corners between the second yoke portion lb of the core 1 and the first, second leg portions lc, Id and also an inner cover 7 for covering each layer face of the second yoke portion lb are set, and moreover, a band 8 is wound to the yoke portion lb and the inner cover 7 in the vicinity of the jointed portion of the second yoke portion lb. The corner cover 6, inner cover 7 and band 8 are bonded to the core. Further, as shown in Fig. 9C, a bag-like bottom cover 9 is placed to accommodate the second yoke portion lb with the corner cover 6, inner cover 7 and band 8, which is then fixed to the core by an adhesive tape 10 (referring to Fig. 10) . A main body 12 of the transformer having the windings Wl and W2 wound around the core is completed in this manner as shown in Fig. 9D. The main body 12 is kept in a case (not shown) . An insulation oil is filled in the case, so that the transformer obtained is an oil filled transformer. In the above example, all of the corner cover 6, inner cover 7 and band 8 are formed of insulation paper, while the bottom cover 9 is formed of insulation paper folded in three dimensions and bonded at required points. As is well known, the insulation oil is injected in vacuum in the oil filled transformer after the main body is accommodated in the case so as to let the oil permeate in the windings and the core. For facilitating the permeation of the insulation oil to the center of the core, a felt filter 11 is attached inside a window portion 9a of the bottom cover 9. As a result, the air inside the cover is smoothly exchanged with the insulation oil and, broken elements of the core are prevented from leaking outside through the window portion 9a in the above transformer. Although the windings Wl, W2 are fitted respectively to the first and second leg portions 1c, Id of the wound core 1 in the above example, the winding may sometimes be wound to either one of the leg portions. In such case, respective one leg portions of two wound cores 1 arranged side by side are disposed to face each other thereby to be used as one leg portion for fitting of the winding. In the conventional amorphous wound core transformer as described hereinabove, the main cover 4, corner cover 6, inner cover 7, band 8 and bottom cover 9 are provided to seal the broken pieces of the core. Broken pieces of the core are confined by completely covering the core with these covers and protecting plate 3. However, a large number of covers for covering the core inevitably increases a count of assembling steps and manufacturing costs. At the same time, the bottom cover 9 employed in the conventional amorphous wound core transformer is obtained by folding the insulation paper, which takes trouble and costs high. SUMMARY OF THE INVENTION An object of the present invention is therefore to provide an amorphous wound core transformer in which broken elements of a core can be confined only with a fewer number of kinds of covers without using a cover of a complicate shape. The present invention relates to a wound core transformer which is provided with a nearly rectangular wound core formed of a layered body of a thin amorphous magnetic alloy band and having a first and a second yoke portions and a first and a second leg portions extending between the first and second yoke portions, with a jointed portion at the second yoke portion, and a winding fitted to at least one of the leg portions of the wound core. In the present invention, each layered face of a U-shaped core portion consisting of the first yoke portion and the first and second leg portions at both sides of the first yoke portion is covered with a U-shaped cover, and the whole layered faces of the second yoke portion of the wound core are coated with a resin-coated layer. The U-shaped cover consists of a U-shaped coating portion formed in U shape and arranged conforming to each layer face of the U-shaped core portion, and an outer peripheral coating portion and an inner peripheral coating portion bent at outer peripheral edges and inner peripheral edges of the U-shaped core portion to cover the vicinity of end portions near layered faces of an outer peripheral face and an inner peripheral face of the U-shaped core portion and fixed to the outer peripheral face and inner peripheral face of the U-shaped core portion by adhesive tapes. The U-shaped cover has a window portion formed at a portion of the U-shaped coating portion corresponding to the first yoke portion. A first filter sheet is disposed between the window portion of the U-shaped cover and the layered face of the U-shaped core portion and bonded to a peripheral edge of the window portion. A second filter sheet disposed between each end of the U-shaped cover and the layered face of the U-shaped core portion is bonded to an inner face of the U-shaped cover and the layered face of the U-shaped core portion. The first and second filter sheets are formed of sheet-like material having permeabilities to air and oil and denseness prohibiting broken pieces generated from the wound core from passing through. A suitable resin resistant to oil and heat may be selected for the resin forming the resin-coated layer covering each layered face of the second yoke portion of the wound core. Considering workability, a thermosetting resin is preferred. The thermosetting resin used for forming the resin-coated layer is, for example, one-component epoxy thermosetting resin or two-component epoxy thermosetting resin. When the resin-coated layer covering the layered faces of the second yoke portion is formed of the thermosetting resin, the thermosetting resin not yet hardened is applied to the layered faces of the second yoke portion, then heated thereby to be hardened. In this case, it is not favorable if the resin not hardened yet deeply penetrates in the layered faces of the second yoke portion to distort the core. Therefore, the thermosetting resin forming the resin-coated layer is preferable to have a sufficiently high viscosity in a state not hardened (e.g., like paste) to suppress the penetration of the resin into the layered faces of the second yoke portion as much as possible. In the case where the resin-coated layer is formed of the thermosetting resin, in order to more perfectly coat the layered faces of the second yoke portion, it is better to arrange a yoke cover on the resin-coated layer and bond to each layer face of the second yoke portion by means of the resin forming the resin-coated layer. The yoke cover used here is formed of sheet-like material having flexibility to fit rough layered faces of the second yoke portion, with a feature absorbing/catching the not hardened thermosetting resin applied to the layered faces of the second yoke portion. Owing to the flexibility to fit the rough layered faces, each portion of the yoke cover is easily deformed in conformity with the rough layered faces when pressed to the layered faces of the core, and eventually brought in tight contact with the layered faces. Accordingly, no gap is generated between the yoke cover and the layered face. Meanwhile, the absorbing/catching property of the material absorbs and catches the resin not yet hardened (in a liquid state). These features are generally possessed by cloth (woven fabric or non-woven fabric) or porous material such as sponge or the like. A non-woven fabric such as felt, etc. is preferred as the material for the filter sheets and the yoke cover. As discussed hereinabove, when the resin-coated layer is formed to cover the whole of the layered faces of the second yoke portion, each layered face of the second yoke portion is covered with the resin-coated layer and, at the same time, the layered face is kept hard by the resin constituting the resin-coated layer. Accordingly, broken pieces of the core are prevented from leaking outside through the layered faces of the second yoke portion. Moreover, when the yoke cover having the flexibility and catching property to catch the not hardened resin is arranged on the above resin-coated layer and bonded to the layered faces of the second yoke portion by the resin forming the resin-coated layer, the resin not yet hardened is absorbed by the yoke cover, and therefore the adhesive applied to the layered faces of the second yoke portion is prevented from falling down. The layered faces are never left without the adhesive applied. Accordingly, the layered faces of the second yoke portion can be completely covered with the resin-coated layer, so that the broken pieces of the core are prevented from being separated from the layered faces of the yoke portion. Since the yoke cover has the feature to catch the not yet hardened resin, the resin applied to the layered faces is prevented from deeply penetrating into the layers of the core. In consequence, the core is prevented from being distorted at the setting time of the resin entering the layered faces. Further, since the layered face of the U-shaped core portion consisting of the first yoke portion and the first and second leg portions at both sides of the first yoke portion is coated with the U-shaped cover, broken pieces of the core are prevented from coming out of the layered face of the U-shaped core portion. As above, when the window portion is formed in the U-shaped cover and the filter sheet is arranged inside the window portion, and also the filter sheet is provided between each end of the U-shaped cover and the layered face of the core, the air inside the U-shaped cover is replaced with the oil through each fiIter sheet when the oil is vacuum-injected, letting the insulating oil smoothly enter the core. According to the present invention, the broken pieces of amorphous magnetic alloy can be prevented from being separated from the core only by the U-shaped cover or only by two kinds of covers, namely, U-shaped cover and the yoke cover. The conventionally used bottom cover or the like cover complicate in structure is not employed in the present invention, and therefore the cover is reduced in cost. As described hereinabove, a count of portions of the cover for covering the core is reduced and a count of assembling steps is decreased according to the present invention. In association with the effect of the elimination of the cover hard to process and complicate in shape, the amorphous wound core transformer can hence be decreased in cost. Accordingly the present invention provides an amorphous wound core transformer of a layered body of a thin amorphous magnetic alloy band which has a first and a second yoke portions, and a first and a second leg portions extending between the first and second yoke portions, and is provided with a nearly rectangular wound core having a jointed portion at the second yoke portion and a winding fitted to at least one leg portion of the wound core being characterized by including: a U-shaped cover which consists of a U-shaped coating portion formed in U shape and arranged conforming to each layered face of a U-shaped core portion composed of the first yoke portion and the first and second leg portions at both sides of the first yoke portion, and an outer peripheral coating portion and an inner peripheral coating portion bent at outer peripheral edges and inner peripheral edges of the U-shaped core portion to cover the vicinity of end portions near layered faces of an outer peripheral face and an inner peripheral face of the U-shaped core portion and fixed to the outer peripheral face and inner peripheral face of the U-shaped core portion by adhesive tapes, and which has a window portion formed at a portion of the U-shaped coating portion corresponding to the first yoke portion; a first filter sheet disposed between the window portion of the U-shapea cover and the layered face of the U-shaped core portion and bonded to a peripheral edge of the window portion; and a second filter sheet disposed between each end of the U-shaped cover and the layered face of the U-shaped core portion and bonded to an inner face of the U-shaped cover and the layered face of the U-shaped core portion, wherein a resin-coated layer is formed to cover the whole of layer faces of the second yoke portion of the wound core. BRIEF DESCRIPTION OF THE DRAWINGS These and other ob j ects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings throughout which like portions are designated by like reference numerals, and in which: Figs. 1A through ID are perspective views showing assembling procedures in sequence for a transformer according to the present invention by fitting windings to an annealed wound core. Fig. 2 is a perspective view of the wound core and a U-shaped cover installed in the wound core. Fig. 3 is a diagram explanatory of a process of mounting a yoke cover for covering layer faces of a second yoke portion of the wound core in the present invention. Fig. 4 is a sectional view indicating a structure mounting the yoke cover to the layer faces of the second yoke portion in the present invention. Fig. 5 is a plan view of an essential portion when the yoke cover is mounted to the second yoke portion of the wound core in the present invention. Fig. 6 is a right side view of Fig. 5. Fig. 7 is a perspective view of the wound core after windings are fitted to leg portions of the wound core used in the present invention, with the windings not shown. Figs. 8A and 8B are diagrams of frequency distributions of losses in a state of a single body of the core and after windings are fitted to the core and oil is vacuum-injected to the core in a conventional transformer and the transformer of the present invention. Figs. 9A through 9D are perspective views of assembling steps in sequence of assembling the conventional transformer by fitting windings to an annealed wound core. Fig. 10 is a perspective view of a state of the wound core after the windings are fitted to leg portions of the wound core used in the conventional transformer while the windings are not shown. Fig. 11 is a front view of a conventional structural example of the wound core. DETAILED DESCRIPTION OP THE PREFERRED EMBODIMENTS Figs. 1-7 show an example of the constitution of an amorphous wound core transformer according to the present invention. Figs. 1A-1D are perspective views indicating a sequence of assembling procedures of the transformer by fitting windings Wl and W2 to an annealed wound core 1. Fig. 2 is a perspective view of the wound core and a U-shaped cover installed in the wound core. Figs. 3 and 4 are a diagram explanatory of a mounting process for mounting a yoke cover covering a second yoke portion and a sectional view of an essential portion, respectively. Figs. 5 and 6 illustrate states in which the yoke cover is mounted to the second yoke portion, and Fig. 7 indicates a state of the wound core after windings are fitted at leg portions although the windings are not shown. The wound core 1 in the embodiment is the same as shown in Fig. 11, that is, a rectangular wound core having the first and the second yoke portions la and lb, and the first and the second leg portions lc and Id extending between the yoke portions. According to the present invention, prior to fitting of the windings Wl and W2, each layer face of a U-shaped core portion 101 comprising the first yoke portion la and the first and second leg portions lc and Id at both sides of the first yoke portion la of the wound core 1 are coated with a U-shaped cover 2 0 of an insulation paper, as shown in Fig. 2. The U-shaped cover 20 is constituted of a U- shaped coating portion 20a assuming a U shape conforming to each layered face of the U-shaped core portion 101 (in the same shape as each layered face and totally covering the whole of the layered faces of the U-shaped core portion 101) and arranged to trace the layered faces, an outer peripheral coating portion 20b and an inner peripheral coating portion 20c. The peripheral coating portion 20b, 20c is bent at outer peripheral ends, inner peripheral ends of the coating portion 20a to cover the neighborhood of end parts near the layered faces of an outer peripheral face, inner peripheral face of the U-shaped core portion. A window portion 20d is formed at a central portion of the U-shaped coating portion 20a corresponding to the first yoke portion la. A first filter sheet 22 is arranged inside the coating portion 2 0a of the U-shaped cover 20 to shut the window portion 20d. The first filter sheet 22 is bonded to a peripheral edge portion of the window portion 2 0d in a manner not to generate a gap between the first filter sheet 22 and the peripheral edge portion of the window portion 20d. Second filters 23, 23 are disposed inside both ends of the coating portion 20a of the U-shaped cover 20, which are bonded to the coating portion 20a and layered faces of the U-shaped core portion. The U-shaped cover 20 is disposed in such state that the U-shaped coating portion 20a faces the layered faces of the U-shaped core portion 101 of the wound core, and the outer and inner peripheral coating portions 20b and 20c respectively run along end portions near the layered faces of the outer and inner peripheral faces of the U-shaped core portion. The coating portions 20b ad 20c are fixed to the U-shaped core portion 101 by adhesive tapes 24 and 25 which are so arranged as to completely seal bonded portions between the coating portions 20b, 2 0c and, outer and inner peripheral faces of the U-shaped core portion. The first filter sheet 22 is simply butted to the layered face of the core without being bonded to the layered face. The filter sheets 23, 2 3 are bonded to the layered faces of the U-shaped core portion when the U-shaped cover 20 is installed to the U-shaped core portion. The first and second filter sheets 2 2 and 23 are formed of a sheet-like material having permeability to air and oil and denseness prohibiting broken pieces generated from the wound core from passing, preferably, non-woven fabric, portionicularly felt. The first filter sheet 22 is not bonded to the layer face of the core in order not to lose the air and oil permeability. Meanwhile, an adhesive for bonding the second filter sheets 23 to an inner face of the coating portion 20a of the U-shaped cover and the layered face of the U-shaped core portion 101 is used a little not to penetrate deep into the filter sheets 2 3, 2 3, or an adhesive of a kind not penetrating into the filter sheets is employed. After the U-shaped core portion 101 of the wound core 1 is covered with the U-shaped cover 2 0 as above, the second yoke portion lb of the wound core is opened right and left at the jointed portion J and the member 2B located at the side of the second yoke portion lb among the members 2A and 2B constituting the reinforcing frame 2 is detached. Thereafter, as shown in Fig. 1A, portions lbl and lb2 at both sides of the jointed portion J and the first and second leg portions lc and Id are inserted into the window portions of the windings Wl and W2, whereby the windings Wl and W2 are fitted to the first and second leg portions lc and Id. After the fitting of the windings Wl and W2 to the first and second leg portions lc and Id of the wound core, the member 2B of the reinforcing frame is installed as indicated in Fig. 3. In the example, the member 2B of the reinforcing frame is formed in U-shape having curved portions at both ends. A gap is generated between the member 2B and an end faces of the windings Wl, W2. As is clear from Fig. 3, spacers 31 of an insulating plate such as a pressboard or the like are inserted between an end face of the winding Wl, W2 in an axial direction and the member 2B to prevent the broken pieces of the core from entering the windings through the gap. Moreover, a filling material 3 3 of a square sponge is filled to shut a gap 32 formed between each end of the spacer 31 and each end of the member 2B (corner portion of the wound core at the side of the second yoke portion) to prevent the broken pieces of the core from entering the windings through the gap 32. While the spacers 31 and filling materials 3 3 are interposed between the member 2B of the reinforcing frame 2 and the windings Wl, W2 (in a state of Fig. 1A) , the jointed portion of the second yoke portion lb is closed as shown in Fig. IB, and both ends of the protecting plate 3 made of a stainless steel band, a silicon steel band or the like are overlapped and spot-welded. Then, as indicated in Figs. 1C and 4, a thermosetting resin not yet set is applied to the whole layer faces at both sides of the second yoke portion lb, spacers 31 and filling materials 33, thereby forming a resin-coated layer 35. A yoke cover 36 is placed on the resin-coated layer 35 and bonded to the layered faces at both sides of the second yoke portion lb, spacers 31 and filling materials 3 3 by the resin forming the resin-coated layer 35. For the resin forming the resin-coated layer 35, such a thermosetting resin that is supplied in a half set, paste-like state and hardened by heating is preferred. For instance, a bisphenol-series epoxy resin can be used. The thermosetting resin supplied in the half set state is once softened to liquid by heating and then hardened. The yoke cover 36 is formed of a sheet of material showing flexibility to the rough layered faces of the second yoke portion lb and absorbing/catching the resin when the resin applied to the layered faces of the second yoke portion is turned to liquid. Felt is preferable to form the yoke cover, similar to the filter sheet. The yoke cover 36 has a size enough to cover the whole of the layered faces of the second yoke portion lb. Although the yoke cover 36 may be formed in any optional shape, the illustrated yoke cover 36 is formed rectangular. When the resin-coated layer 35 is to be formed and the yoke cover 3 6 is to be bonded, after the paste-like thermosetting resin such as bisphenol-series epoxy resin, etc. is applied to each layer face of the second yoke portion lb, spacers 31 and filling materials 33, the yoke cover 3 6 is overlaid onto the applied resin and pressed to the layered faces of the second yoke portion. In this state, as in Fig. 5, each end portion of the yoke cover 3 6 is temporarily fixed by an adhesive tape 37 to the outer periphery of the second yoke portion of the wound core. Subsequently, the wound core with the windings are carried in and heated in a heating furnace to harden the resin, whereby the transformer main body is finished as in Fig. ID. In the completed state shown in Fig. ID, each layered face of the U-shaped core portion 101 consisting of the first yoke portion la and the first, second leg portions lc, Id of the wound core is covered with the U-shaped cover 20. Moreover, each layered face of the second yoke portion lb is covered not only with the resin-coated layer 35 applied and set there, but with the yoke cover 36. The second filter 2 3 disposed between each end of the U-shaped cover 20 and the core has an end portion 23a at the side of the second yoke portion lb exposed outside (referring to Fig. 2) . The resin forming the resin-coated layer 3 5 is once softened and turned to liquid when heated, and thereafter hardened. Therefore, the resin of the resin-coated layer 35 is apt to fall down from the layered faces of the second yoke portion lb when it is turned to liquid. A portion of the layered faces would be exposed if the resin dropped from the layered faces of the second yoke portion, possibly breaking the exposed portion. In the present invention, the liquid resin forming the resin-coated layer 35 is absorbed and caught by the yoke cover 36, thus prevented from falling down from the layered faces of the second yoke portion. In other words, the exposure of a portion of the layered faces of the second yoke portion is prevented. At the same time, since the yoke cover 36 is flexible to conform to the rough layered faces of the second yoke portion, the yoke cover 3 6 is kept in tight contact with the entire layered faces of the second yoke portion, so that the resin-coated layer 35 between the yoke cover and the layered face of the second yoke portion is maintained nearly constant in thickness. Consequently, the resin forming the resin-coated layer 35 is set while uniformly covering the whole layered faces of the second yoke portion lb. The resin of the resin-coated layer 35 is absorbed and caught by the yoke cover when the resin is turned to liquid. Therefore, the liquid resin never permeates deep between the layered faces of the second yoke portion. Only the vicinity of a surface of the layered faces of the second yoke portion is coated with the resin when the resin is set. Magnetic properties of the core are hence prevented from being deteriorated by a large stress brought about inside the second yoke portion of the core after the resin is set. In the above-described constitution, as indicated in Fig. 7, the layered faces of the U-shaped core portion 101 comprising the first yoke portion la and the first and second leg portions lc, Id are coated with the U-shaped cover 20, and further, the whole layered faces of the second yoke portion lb are coated with the resin-coated layer 35 and the yoke cover 36. Accordingly, broken pieces of amorphous magnetic alloy are perfectly prevented from being separated from the layer face of the core. Additionally, since the first filter sheet 22 is attached to the window portion 20d of the U-shaped cover 20 and the second f iIter sheets 23, 23 are arranged between ends of the U-shaped cover 20 and the layered face of the core, the insulation oil is replaced with the air in the wound core through the filter sheets 22 and 2 3 to permeate in the wound core when the oil is vacuum-injected after the transformer main body is accommodated in the case. According to the present invention, portionicularly, the layered faces of the second yoke portion are covered with the resin-coated layer thereby to prevent the broken pieces of the core from being separated from the layered faces of the second yoke portion. In consequence, end portions 23a and 23a of the second filters 23 and 23 at both ends of the U-shaped cover 20 are kept in a state exposed to the outside. The air in the wound core can accordingly be replaced with the insulation oil through the window portion 2 0a as well as through the filters 2 3 and 23 at both ends of the U-shaped cover, that is, the insulation oil is let to permeate into the core smoothly. In the wound core transformer, subsequent to the vacuum injection of oil, the wound core is deformed by a pressure difference inside and outside the core, resulting in a change of magnetic characteristics. The wound core is easy to deform portionicularly in the amorphous wound core transformer, and the deterioration of magnetic characteristics of the core after the vacuum injection of oil raises a problem. A ratio of a no-load loss ws of a single body of the wound core to a no-load loss we after the wound core with windings is subjected to vacuum injection of oil, i.e., we/ws is designated as a building factor B.F. A deterioration rate of the no-load loss of the core after the wound core is manufactured before the oil is vacuum-injected to the wound core thereby to complete a transformer is evaluated by this building factor B.F. As the building factor is closer to 1, magnetic characteristics of the material of the core can be utilized more for actual products. A frequency distribution of the no-load loss of the single body of the wound core is obtained in a plurality of amorphous wound core transformers in the conventional structure in which the layer faces of the second yoke portion of the wound core are not coated with resin as in Figs. 9 and 10. The result is a curve a' in Fig. 8A. A frequency distribution of the no-load loss after the oil is vacuum-injected to the same wound core with windings is indicated by a curve b' in Fig. 8B. In Fig. 8A, as' is a standard deviation of the no-load loss of the single of the wound core, and ae' is a standard deviation of the non-load loss after the oil is vacuum-injected to the wound core. The building factor B.F. of an average value of the no-load losses (average value of we/average value of ws) is 1.20, and the building factor B.F. of the standard deviation (=cre'/as') is 1*13. In contrast to the above, according to the present invention, since the entire layered faces of the second yoke portion lb are coated with the resin-coated layer, the frequency distribution of the no-load loss of the single body of the wound core is as shown in a curve a in Fig. 8B, and that after the vacuum-injection of oil is as represented by a curve b in Fig. 8B. The building factor B.F. of the average value of the no-load losses in this case is 1.10, while the building factor B.F. of the standard deviation is 0.86. In .other words, the building factor of the average value of the no-load losses is improved by 0.10 in the present invention, and the building factor of the standard deviation is improved by 0.27. The reason for this is supposed to be that the whole layered faces of the second yoke portion (yoke portion having the bonded portion) which is easiest to deform is covered with the resin-coated layer, thereby to restrict the deformation. According to the foregoing embodiment, the resin-coated layer 35 is formed to cover the whole of the layered faces of the second yoke portion, and at the same time, the yoke cover 36 is bonded to each layered face of the second yoke portion by using the resin forming the resin-coated layer 35 as an adhesive. If even the lowest viscosity of the resin forming the resin-coated layer 35 when the resin is not set is sufficiently high and consequently the resin does not deeply penetrate into layers of the second yoke portion lb, the yoke cover 3 6 may be omitted. As is described hereinabove, according to the present invention, broken pieces of amorphous magnetic alloy are perfectly prevented from being detached from the core by using only the U-shaped cover or only two kinds of covers, i.e., U-shaped cover and yoke cover, without using the conventionally employed cover complicated in structure, e.g., bottom cover or the like, or many kinds of covers. According to the present invention, not only because the cover hard to process and complicate in shape is eliminated, but because a count of portions of the cover for covering the wound core is reduced and a count of assembling steps is decreased, the amorphous wound core transformer can be obtained at reduced cost. Since the layered faces of the second yoke portion of the wound core are kept hard by the resin-coated layer to prevent the deformation of the wound core, the building factor indicating the change of characteristics after the wound core is manufactured before the oil is vacuum-injected thereby to complete the oil filled transformer is improved. The transformer shows low loss owing to the characteristic feature of the amorphous magnetic alloy. Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they deportion therefrom. WE CLAIM 1. An amorphous wound core transformer of a layered body of a thin amorphous magnetic alloy band which has a first and a second yoke portions, and a first and a second leg portions extending between the first and second yoke portions, and is provided with a nearly rectangular wound core having a jointed portion at the second yoke portion and a winding fitted to at least one leg portion of the wound core being characterized by including: a U-shaped cover which consists of a U-shaped coating portion formed in U shape and arranged conforming to each layered face of a U-shaped core portion composed of the first yoke portion and the first and second leg portions at both sides of the first yoke portion, and an outer peripheral coating portion and an inner peripheral coating portion bent at outer peripheral edges and inner peripheral edges of the U-shaped core portion to cover the vicinity of end portions near layered faces of an outer peripheral face and an inner peripheral face of the U-shaped core portion and fixed to the outer peripheral face and inner peripheral face of the U-shaped core portion by adhesive tapes, and which has a window portion formed at a portion of the U-shaped coating portion corresponding to the first yoke portion; a first filter sheet disposed between the window portion of the U-shaped cover and the layered face of the U-shaped core portion and bonded to a peripheral edge of the window portion; and a second filter sheet disposed between each end of the U-shaped cover and the layered face of the U-shaped core portion and bonded to an inner face of the U-shaped cover and the layered face of the U-shaped core portion, wherein a resin-coated layer is formed to cover the whole of layer faces of the second yoke portion of the wound core. 2. The amorphous wound core transformer according to claim 1 further comprising: a resin-coated layer formed of thermosetting resin to cover the whole of layered faces of the second yoke portion of the wound core; and a yoke cover arranged on the resin-coated layer covering each layered face of the second yoke portion and bonded to each layered face of the second yoke portion by the thermosetting resin forming the resin-coated layer, wherein said first and second filter sheets are made of sheet-like material having permeabilities to air and oil and denseness to prevent broken pieces generated from the wound core from passing through, and said yoke cover is made of sheet-like material having flexibility to fit rough layered faces of the second yoke portion and absorbing/catching the thermosetting resin applied to the layer faces of the second yoke portion which is not yet hardened. 3. The amorphous wound core transformer according to claim 1 or 2, wherein the filter sheets and the yoke cover are formed with felt. 4. An amorphous wound core transformer substantially as herein described with reference to Figures 1 to 8B of the accompanying drawings.

Full Text

FIELD OF THE INVENTION
The present invention relates to an amorphous core transformer using a wound core of a thin band of amorphous magnetic alloy. DESCRIPTION OF THE PRIOR ART
An amorphous magnetic alloy is offered in the shape of a markedly thin band (strip) (e.g., nominal thickness of 0.02 5mm) and therefore, a core of a transformer using the amorphous magnetic alloy is generally obtained by winding.
In order to manufacture the amorphous wound core transformer, for instance, a plurality of unit bodies of a predetermined length formed by cutting a thin band of a layered body are layered with a shift of a predetermined distance in a longitudinal direction, thereby to form a layer block. Then, a plurality of the thus-obtained layer blocks are sequentially wound around a frame and ends of the unit bodies in each layer block are butt-jointed or lap-jointed. Jointed portions are arranged stepwise at a yoke portion in the resulting rectangular wound core.
In the present specification, one yoke portion without the jointed portions among two confronting yoke

portions of the rectangular wound core will be named as a first yoke portion and, the other yoke portion with the jointed portions will be represented as a second yoke portion. Two leg portions extending in parallel between these fir^st and second yoke portions will be referred to as a first and a second leg portions. The leg portion here is a portion to be arranged in a window portion of windings fitted around the wound core, while the yoke portion is a portion placed projecting outside from the window portion of windings.
Fig. 11 shows an example of a rectangular wound core 1., In Fig. 11, la and lb are the first and second yoke portions, and lc and Id are the first and second leg portions. A jointed portion J is formed in the second yoke portion lb. In the illustrated example, the wound core is constituted of four layer blocks and the jointed portion J formed in the second yoke portion lb comprises respective jointed portions J1-J4 of the first through fourth layer >locks. Jointed portions of a plurality of unit bodies constituting each layer block are distributed stepwise.
The rectangular wound core manufactured as above is sent and annealed in an annealing furnace so as to remove warpings. After the core is annealed, the second yoke portion lb is opened at the jointed portion, then portions lbl, lb2 at both sides of the jointed portion of

the second yoke portion lb and the first and second leg portions lc, Id are inserted in window portions of windings Wl, W2 respectively, so that the windings Wl, W2 are fitted with the first and second leg portions lc, Id respectively. A transformer is completed when the second yoke portion lb is closed after the fitting of windings.
Since the amorphous magnetic alloy is easily deformed by its own weight, a reinforcing frame 2 of stainless steel or the like material is arranged at the innermost periphery of the wound core to reinforce the core. The reinforcing frame 2 is constituted of a large and a small U-shaped members 2A and 2B separable from each other. After the windings Wl, W2 are fitted while the member 2B is not attached, the member 2B is installed before the second yoke portion lb is closed. A protecting sheet of stainless steel band or the like is wound at the outermost periphery of the wound core 1. Both ends of the protecting sheet are welded in an overlapping state.
The amorphous magnetic alloy is turned fragile subsequent to the annealing, causing the core to break at layer faces when the windings Wl, W2 are fitted. If the broken pieces are separated from the core and adhere to the windings or mixed with an insulation oil in a transformer case, the transformer is deteriorated in insulation performance and may be burnt in the worst case. Under the

circumstances, the broken pieces should be sealed somehow not to be detached from the core of the transformer of this type.
By way of example, Figs. 9A-9D and 10 show a conventional amorphous wound core transformer with means for sealing the broken pieces of amorphous magnetic alloy. A sequence of procedures of assembling the transformer by fitting the windings Wl, W2 to the annealed wound core 1 is indicated in Figs. 9A-9D. Fig. 10 represents a state of the wound core after the windings are fitted although the windings are not shown.
In fitting the windings Wl, W2, as shown in Fig. 10, each layer face of a U-shaped core portion 101 consisting of the first yoke portion la, and the first and second leg portions 1c, Id at both sides of the portion la of the core 1 is covered with a U-shaped main cover 4 of an insulation paper, and an oil-resistant adhesive tape 5 is attached to peripheral edge portions of the U-shaped cover 4 and the core 1, whereby the main cover 4 is secured to the core 1 by the adhesive tape 5 and at the same time, the main cover 4 and the core 1 are sealed therebetween.
Then, the second yoke portion lb of the core 1 is opened at the jointed portion and the windings Wl, W2 are fitted to the first and second leg portions lc, Id as in Fig. 9A. After the fitting, the member 2B of the

reinforcing frame 2 is installed as in Fig. 9A. In Fig. 9A, 3 is a protecting plate arranged along the outermost periphery of the wound core.
After the windings Wl, W2 are fitted at the first and second leg portions as in Fig. 9A, the second yoke portion lb is closed as in Fig. 9B. Both ends of the protecting plate 3 is overlapped and welded with each other. A corner cover 6 for covering the layer faces in the vicinity of inside corners between the second yoke portion lb of the core 1 and the first, second leg portions lc, Id and also an inner cover 7 for covering each layer face of the second yoke portion lb are set, and moreover, a band 8 is wound to the yoke portion lb and the inner cover 7 in the vicinity of the jointed portion of the second yoke portion lb. The corner cover 6, inner cover 7 and band 8 are bonded to the core. Further, as shown in Fig. 9C, a bag-like bottom cover 9 is placed to accommodate the second yoke portion lb with the corner cover 6, inner cover 7 and band 8, which is then fixed to the core by an adhesive tape 10 (referring to Fig. 10) . A main body 12 of the transformer having the windings Wl and W2 wound around the core is completed in this manner as shown in Fig. 9D. The main body 12 is kept in a case (not shown) . An insulation oil is filled in the case, so that the transformer obtained is an oil filled transformer.

In the above example, all of the corner cover 6, inner cover 7 and band 8 are formed of insulation paper, while the bottom cover 9 is formed of insulation paper folded in three dimensions and bonded at required points.
As is well known, the insulation oil is injected in vacuum in the oil filled transformer after the main body is accommodated in the case so as to let the oil permeate in the windings and the core. For facilitating the permeation of the insulation oil to the center of the core, a felt filter 11 is attached inside a window portion 9a of the bottom cover 9. As a result, the air inside the cover is smoothly exchanged with the insulation oil and, broken elements of the core are prevented from leaking outside through the window portion 9a in the above transformer.
Although the windings Wl, W2 are fitted respectively to the first and second leg portions 1c, Id of the wound core 1 in the above example, the winding may sometimes be wound to either one of the leg portions. In such case, respective one leg portions of two wound cores 1 arranged side by side are disposed to face each other thereby to be used as one leg portion for fitting of the winding.
In the conventional amorphous wound core transformer as described hereinabove, the main cover 4, corner cover 6, inner cover 7, band 8 and bottom cover 9

are provided to seal the broken pieces of the core. Broken pieces of the core are confined by completely covering the core with these covers and protecting plate 3. However, a large number of covers for covering the core inevitably increases a count of assembling steps and manufacturing costs.
At the same time, the bottom cover 9 employed in the conventional amorphous wound core transformer is obtained by folding the insulation paper, which takes trouble and costs high. SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide an amorphous wound core transformer in which broken elements of a core can be confined only with a fewer number of kinds of covers without using a cover of a complicate shape.
The present invention relates to a wound core transformer which is provided with a nearly rectangular wound core formed of a layered body of a thin amorphous magnetic alloy band and having a first and a second yoke portions and a first and a second leg portions extending between the first and second yoke portions, with a jointed portion at the second yoke portion, and a winding fitted to at least one of the leg portions of the wound core.
In the present invention, each layered face of a

U-shaped core portion consisting of the first yoke portion and the first and second leg portions at both sides of the first yoke portion is covered with a U-shaped cover, and the whole layered faces of the second yoke portion of the wound core are coated with a resin-coated layer.
The U-shaped cover consists of a U-shaped coating portion formed in U shape and arranged conforming to each layer face of the U-shaped core portion, and an outer peripheral coating portion and an inner peripheral coating portion bent at outer peripheral edges and inner peripheral edges of the U-shaped core portion to cover the vicinity of end portions near layered faces of an outer peripheral face and an inner peripheral face of the U-shaped core portion and fixed to the outer peripheral face and inner peripheral face of the U-shaped core portion by adhesive tapes.
The U-shaped cover has a window portion formed at a portion of the U-shaped coating portion corresponding to the first yoke portion. A first filter sheet is disposed between the window portion of the U-shaped cover and the layered face of the U-shaped core portion and bonded to a peripheral edge of the window portion. A second filter sheet disposed between each end of the U-shaped cover and the layered face of the U-shaped core portion is bonded to an inner face of the U-shaped cover and the layered face of the U-shaped core portion.

The first and second filter sheets are formed of sheet-like material having permeabilities to air and oil and denseness prohibiting broken pieces generated from the wound core from passing through.
A suitable resin resistant to oil and heat may be selected for the resin forming the resin-coated layer covering each layered face of the second yoke portion of the wound core. Considering workability, a thermosetting resin is preferred. The thermosetting resin used for forming the resin-coated layer is, for example, one-component epoxy thermosetting resin or two-component epoxy thermosetting resin.
When the resin-coated layer covering the layered faces of the second yoke portion is formed of the thermosetting resin, the thermosetting resin not yet hardened is applied to the layered faces of the second yoke portion, then heated thereby to be hardened. In this case, it is not favorable if the resin not hardened yet deeply penetrates in the layered faces of the second yoke portion to distort the core. Therefore, the thermosetting resin forming the resin-coated layer is preferable to have a sufficiently high viscosity in a state not hardened (e.g., like paste) to suppress the penetration of the resin into the layered faces of the second yoke portion as much as possible.

In the case where the resin-coated layer is formed of the thermosetting resin, in order to more perfectly coat the layered faces of the second yoke portion, it is better to arrange a yoke cover on the resin-coated layer and bond to each layer face of the second yoke portion by means of the resin forming the resin-coated layer.
The yoke cover used here is formed of sheet-like material having flexibility to fit rough layered faces of the second yoke portion, with a feature absorbing/catching the not hardened thermosetting resin applied to the layered faces of the second yoke portion.
Owing to the flexibility to fit the rough layered faces, each portion of the yoke cover is easily deformed in conformity with the rough layered faces when pressed to the layered faces of the core, and eventually brought in tight contact with the layered faces. Accordingly, no gap is generated between the yoke cover and the layered face. Meanwhile, the absorbing/catching property of the material absorbs and catches the resin not yet hardened (in a liquid state). These features are generally possessed by cloth (woven fabric or non-woven fabric) or porous material such as sponge or the like.
A non-woven fabric such as felt, etc. is preferred as the material for the filter sheets and the

yoke cover.
As discussed hereinabove, when the resin-coated layer is formed to cover the whole of the layered faces of the second yoke portion, each layered face of the second yoke portion is covered with the resin-coated layer and, at the same time, the layered face is kept hard by the resin constituting the resin-coated layer. Accordingly, broken pieces of the core are prevented from leaking outside through the layered faces of the second yoke portion.
Moreover, when the yoke cover having the flexibility and catching property to catch the not hardened resin is arranged on the above resin-coated layer and bonded to the layered faces of the second yoke portion by the resin forming the resin-coated layer, the resin not yet hardened is absorbed by the yoke cover, and therefore the adhesive applied to the layered faces of the second yoke portion is prevented from falling down. The layered faces are never left without the adhesive applied. Accordingly, the layered faces of the second yoke portion can be completely covered with the resin-coated layer, so that the broken pieces of the core are prevented from being separated from the layered faces of the yoke portion.
Since the yoke cover has the feature to catch the not yet hardened resin, the resin applied to the layered faces is prevented from deeply penetrating into the layers

of the core. In consequence, the core is prevented from being distorted at the setting time of the resin entering the layered faces.
Further, since the layered face of the U-shaped core portion consisting of the first yoke portion and the first and second leg portions at both sides of the first yoke portion is coated with the U-shaped cover, broken pieces of the core are prevented from coming out of the layered face of the U-shaped core portion.
As above, when the window portion is formed in the U-shaped cover and the filter sheet is arranged inside the window portion, and also the filter sheet is provided between each end of the U-shaped cover and the layered face of the core, the air inside the U-shaped cover is replaced with the oil through each fiIter sheet when the oil is vacuum-injected, letting the insulating oil smoothly enter the core.
According to the present invention, the broken pieces of amorphous magnetic alloy can be prevented from being separated from the core only by the U-shaped cover or only by two kinds of covers, namely, U-shaped cover and the yoke cover. The conventionally used bottom cover or the like cover complicate in structure is not employed in the present invention, and therefore the cover is reduced in cost.

As described hereinabove, a count of portions of the cover for covering the core is reduced and a count of assembling steps is decreased according to the present invention. In association with the effect of the elimination of the cover hard to process and complicate in shape, the amorphous wound core transformer can hence be decreased in cost.
Accordingly the present invention provides an amorphous wound core transformer of a layered body of a thin amorphous magnetic alloy band which has a first and a second yoke portions, and a first and a second leg portions extending between the first and second yoke portions, and is provided with a nearly rectangular wound core having a jointed portion at the second yoke portion and a winding fitted to at least one leg portion of the wound core being characterized by including:
a U-shaped cover which consists of a U-shaped coating portion formed in U shape and arranged conforming to each layered face of a U-shaped core portion composed of the first yoke portion and the first and second leg portions at both sides of the first yoke portion, and an outer peripheral coating portion and an inner peripheral coating portion bent at outer peripheral edges and inner peripheral edges of the U-shaped core portion to cover the vicinity of end portions near layered faces of an outer peripheral face and an inner peripheral face of the U-shaped core portion and fixed to the outer peripheral face and inner peripheral face of the U-shaped core portion by adhesive tapes, and which has a window portion formed at a portion of the U-shaped coating portion corresponding to the first yoke portion;
a first filter sheet disposed between the window portion of the U-shapea cover and the layered face of the U-shaped core portion and bonded to a peripheral edge of the window portion; and
a second filter sheet disposed between each end of the U-shaped cover and the layered face of the U-shaped core portion and bonded to an inner face of the U-shaped cover and the layered face of the U-shaped core portion,
wherein a resin-coated layer is formed to cover the whole of layer faces of the second yoke portion of the wound core.

BRIEF DESCRIPTION OF THE DRAWINGS
These and other ob j ects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings throughout which like portions are designated by like reference numerals, and in which:
Figs. 1A through ID are perspective views showing assembling procedures in sequence for a transformer according to the present invention by fitting windings to an annealed wound core.
Fig. 2 is a perspective view of the wound core and a U-shaped cover installed in the wound core.
Fig. 3 is a diagram explanatory of a process of mounting a yoke cover for covering layer faces of a second yoke portion of the wound core in the present invention.
Fig. 4 is a sectional view indicating a structure mounting the yoke cover to the layer faces of the second

yoke portion in the present invention.
Fig. 5 is a plan view of an essential portion when the yoke cover is mounted to the second yoke portion of the wound core in the present invention.
Fig. 6 is a right side view of Fig. 5.
Fig. 7 is a perspective view of the wound core after windings are fitted to leg portions of the wound core used in the present invention, with the windings not shown.
Figs. 8A and 8B are diagrams of frequency distributions of losses in a state of a single body of the core and after windings are fitted to the core and oil is vacuum-injected to the core in a conventional transformer and the transformer of the present invention.
Figs. 9A through 9D are perspective views of assembling steps in sequence of assembling the conventional transformer by fitting windings to an annealed wound core.
Fig. 10 is a perspective view of a state of the wound core after the windings are fitted to leg portions of the wound core used in the conventional transformer while the windings are not shown.
Fig. 11 is a front view of a conventional structural example of the wound core. DETAILED DESCRIPTION OP THE PREFERRED EMBODIMENTS
Figs. 1-7 show an example of the constitution of an amorphous wound core transformer according to the

present invention. Figs. 1A-1D are perspective views indicating a sequence of assembling procedures of the transformer by fitting windings Wl and W2 to an annealed wound core 1. Fig. 2 is a perspective view of the wound core and a U-shaped cover installed in the wound core. Figs. 3 and 4 are a diagram explanatory of a mounting process for mounting a yoke cover covering a second yoke portion and a sectional view of an essential portion, respectively. Figs. 5 and 6 illustrate states in which the yoke cover is mounted to the second yoke portion, and Fig. 7 indicates a state of the wound core after windings are fitted at leg portions although the windings are not shown.
The wound core 1 in the embodiment is the same as shown in Fig. 11, that is, a rectangular wound core having the first and the second yoke portions la and lb, and the first and the second leg portions lc and Id extending between the yoke portions.
According to the present invention, prior to fitting of the windings Wl and W2, each layer face of a U-shaped core portion 101 comprising the first yoke portion la and the first and second leg portions lc and Id at both sides of the first yoke portion la of the wound core 1 are coated with a U-shaped cover 2 0 of an insulation paper, as shown in Fig. 2.
The U-shaped cover 20 is constituted of a U-

shaped coating portion 20a assuming a U shape conforming to each layered face of the U-shaped core portion 101 (in the same shape as each layered face and totally covering the whole of the layered faces of the U-shaped core portion 101) and arranged to trace the layered faces, an outer peripheral coating portion 20b and an inner peripheral coating portion 20c. The peripheral coating portion 20b, 20c is bent at outer peripheral ends, inner peripheral ends of the coating portion 20a to cover the neighborhood of end parts near the layered faces of an outer peripheral face, inner peripheral face of the U-shaped core portion. A window portion 20d is formed at a central portion of the U-shaped coating portion 20a corresponding to the first yoke portion la. A first filter sheet 22 is arranged inside the coating portion 2 0a of the U-shaped cover 20 to shut the window portion 20d. The first filter sheet 22 is bonded to a peripheral edge portion of the window portion 2 0d in a manner not to generate a gap between the first filter sheet 22 and the peripheral edge portion of the window portion 20d. Second filters 23, 23 are disposed inside both ends of the coating portion 20a of the U-shaped cover 20, which are bonded to the coating portion 20a and layered faces of the U-shaped core portion.
The U-shaped cover 20 is disposed in such state that the U-shaped coating portion 20a faces the layered

faces of the U-shaped core portion 101 of the wound core, and the outer and inner peripheral coating portions 20b and 20c respectively run along end portions near the layered faces of the outer and inner peripheral faces of the U-shaped core portion. The coating portions 20b ad 20c are fixed to the U-shaped core portion 101 by adhesive tapes 24 and 25 which are so arranged as to completely seal bonded portions between the coating portions 20b, 2 0c and, outer and inner peripheral faces of the U-shaped core portion.
The first filter sheet 22 is simply butted to the layered face of the core without being bonded to the layered face. The filter sheets 23, 2 3 are bonded to the layered faces of the U-shaped core portion when the U-shaped cover 20 is installed to the U-shaped core portion.
The first and second filter sheets 2 2 and 23 are formed of a sheet-like material having permeability to air and oil and denseness prohibiting broken pieces generated from the wound core from passing, preferably, non-woven fabric, portionicularly felt.
The first filter sheet 22 is not bonded to the layer face of the core in order not to lose the air and oil permeability. Meanwhile, an adhesive for bonding the second filter sheets 23 to an inner face of the coating portion 20a of the U-shaped cover and the layered face of the U-shaped core portion 101 is used a little not to

penetrate deep into the filter sheets 2 3, 2 3, or an adhesive of a kind not penetrating into the filter sheets is employed.
After the U-shaped core portion 101 of the wound core 1 is covered with the U-shaped cover 2 0 as above, the second yoke portion lb of the wound core is opened right and left at the jointed portion J and the member 2B located at the side of the second yoke portion lb among the members 2A and 2B constituting the reinforcing frame 2 is detached. Thereafter, as shown in Fig. 1A, portions lbl and lb2 at both sides of the jointed portion J and the first and second leg portions lc and Id are inserted into the window portions of the windings Wl and W2, whereby the windings Wl and W2 are fitted to the first and second leg portions lc and Id.
After the fitting of the windings Wl and W2 to the first and second leg portions lc and Id of the wound core, the member 2B of the reinforcing frame is installed as indicated in Fig. 3. In the example, the member 2B of the reinforcing frame is formed in U-shape having curved portions at both ends. A gap is generated between the member 2B and an end faces of the windings Wl, W2. As is clear from Fig. 3, spacers 31 of an insulating plate such as a pressboard or the like are inserted between an end face of the winding Wl, W2 in an axial direction and the

member 2B to prevent the broken pieces of the core from entering the windings through the gap. Moreover, a filling material 3 3 of a square sponge is filled to shut a gap 32 formed between each end of the spacer 31 and each end of the member 2B (corner portion of the wound core at the side of the second yoke portion) to prevent the broken pieces of the core from entering the windings through the gap 32.
While the spacers 31 and filling materials 3 3 are interposed between the member 2B of the reinforcing frame 2 and the windings Wl, W2 (in a state of Fig. 1A) , the jointed portion of the second yoke portion lb is closed as shown in Fig. IB, and both ends of the protecting plate 3 made of a stainless steel band, a silicon steel band or the like are overlapped and spot-welded.
Then, as indicated in Figs. 1C and 4, a thermosetting resin not yet set is applied to the whole layer faces at both sides of the second yoke portion lb, spacers 31 and filling materials 33, thereby forming a resin-coated layer 35. A yoke cover 36 is placed on the resin-coated layer 35 and bonded to the layered faces at both sides of the second yoke portion lb, spacers 31 and filling materials 3 3 by the resin forming the resin-coated layer 35.
For the resin forming the resin-coated layer 35, such a thermosetting resin that is supplied in a half set,

paste-like state and hardened by heating is preferred. For instance, a bisphenol-series epoxy resin can be used. The thermosetting resin supplied in the half set state is once softened to liquid by heating and then hardened.
The yoke cover 36 is formed of a sheet of material showing flexibility to the rough layered faces of the second yoke portion lb and absorbing/catching the resin when the resin applied to the layered faces of the second yoke portion is turned to liquid. Felt is preferable to form the yoke cover, similar to the filter sheet. The yoke cover 36 has a size enough to cover the whole of the layered faces of the second yoke portion lb. Although the yoke cover 36 may be formed in any optional shape, the illustrated yoke cover 36 is formed rectangular.
When the resin-coated layer 35 is to be formed and the yoke cover 3 6 is to be bonded, after the paste-like thermosetting resin such as bisphenol-series epoxy resin, etc. is applied to each layer face of the second yoke portion lb, spacers 31 and filling materials 33, the yoke cover 3 6 is overlaid onto the applied resin and pressed to the layered faces of the second yoke portion. In this state, as in Fig. 5, each end portion of the yoke cover 3 6 is temporarily fixed by an adhesive tape 37 to the outer periphery of the second yoke portion of the wound core. Subsequently, the wound core with the windings are carried

in and heated in a heating furnace to harden the resin, whereby the transformer main body is finished as in Fig. ID.
In the completed state shown in Fig. ID, each layered face of the U-shaped core portion 101 consisting of the first yoke portion la and the first, second leg portions lc, Id of the wound core is covered with the U-shaped cover 20. Moreover, each layered face of the second yoke portion lb is covered not only with the resin-coated layer 35 applied and set there, but with the yoke cover 36. The second filter 2 3 disposed between each end of the U-shaped cover 20 and the core has an end portion 23a at the side of the second yoke portion lb exposed outside (referring to Fig. 2) .
The resin forming the resin-coated layer 3 5 is once softened and turned to liquid when heated, and thereafter hardened. Therefore, the resin of the resin-coated layer 35 is apt to fall down from the layered faces of the second yoke portion lb when it is turned to liquid. A portion of the layered faces would be exposed if the resin dropped from the layered faces of the second yoke portion, possibly breaking the exposed portion. In the present invention, the liquid resin forming the resin-coated layer 35 is absorbed and caught by the yoke cover 36, thus prevented from falling down from the layered faces

of the second yoke portion. In other words, the exposure of a portion of the layered faces of the second yoke portion is prevented. At the same time, since the yoke cover 36 is flexible to conform to the rough layered faces of the second yoke portion, the yoke cover 3 6 is kept in tight contact with the entire layered faces of the second yoke portion, so that the resin-coated layer 35 between the yoke cover and the layered face of the second yoke portion is maintained nearly constant in thickness. Consequently, the resin forming the resin-coated layer 35 is set while uniformly covering the whole layered faces of the second yoke portion lb.
The resin of the resin-coated layer 35 is absorbed and caught by the yoke cover when the resin is turned to liquid. Therefore, the liquid resin never permeates deep between the layered faces of the second yoke portion. Only the vicinity of a surface of the layered faces of the second yoke portion is coated with the resin when the resin is set. Magnetic properties of the core are hence prevented from being deteriorated by a large stress brought about inside the second yoke portion of the core after the resin is set.
In the above-described constitution, as indicated in Fig. 7, the layered faces of the U-shaped core portion 101 comprising the first yoke portion la and the first and

second leg portions lc, Id are coated with the U-shaped cover 20, and further, the whole layered faces of the second yoke portion lb are coated with the resin-coated layer 35 and the yoke cover 36. Accordingly, broken pieces of amorphous magnetic alloy are perfectly prevented from being separated from the layer face of the core.
Additionally, since the first filter sheet 22 is attached to the window portion 20d of the U-shaped cover 20 and the second f iIter sheets 23, 23 are arranged between ends of the U-shaped cover 20 and the layered face of the core, the insulation oil is replaced with the air in the wound core through the filter sheets 22 and 2 3 to permeate in the wound core when the oil is vacuum-injected after the transformer main body is accommodated in the case.
According to the present invention, portionicularly, the layered faces of the second yoke portion are covered with the resin-coated layer thereby to prevent the broken pieces of the core from being separated from the layered faces of the second yoke portion. In consequence, end portions 23a and 23a of the second filters 23 and 23 at both ends of the U-shaped cover 20 are kept in a state exposed to the outside. The air in the wound core can accordingly be replaced with the insulation oil through the window portion 2 0a as well as through the filters 2 3 and 23 at both ends of the U-shaped cover, that is, the

insulation oil is let to permeate into the core smoothly.
In the wound core transformer, subsequent to the vacuum injection of oil, the wound core is deformed by a pressure difference inside and outside the core, resulting in a change of magnetic characteristics. The wound core is easy to deform portionicularly in the amorphous wound core transformer, and the deterioration of magnetic characteristics of the core after the vacuum injection of oil raises a problem. A ratio of a no-load loss ws of a single body of the wound core to a no-load loss we after the wound core with windings is subjected to vacuum injection of oil, i.e., we/ws is designated as a building factor B.F. A deterioration rate of the no-load loss of the core after the wound core is manufactured before the oil is vacuum-injected to the wound core thereby to complete a transformer is evaluated by this building factor B.F. As the building factor is closer to 1, magnetic characteristics of the material of the core can be utilized more for actual products.
A frequency distribution of the no-load loss of the single body of the wound core is obtained in a plurality of amorphous wound core transformers in the conventional structure in which the layer faces of the second yoke portion of the wound core are not coated with resin as in Figs. 9 and 10. The result is a curve a' in

Fig. 8A. A frequency distribution of the no-load loss after the oil is vacuum-injected to the same wound core with windings is indicated by a curve b' in Fig. 8B. In Fig. 8A, as' is a standard deviation of the no-load loss of the single of the wound core, and ae' is a standard deviation of the non-load loss after the oil is vacuum-injected to the wound core. The building factor B.F. of an average value of the no-load losses (average value of we/average value of ws) is 1.20, and the building factor B.F. of the standard deviation (=cre'/as') is 1*13.
In contrast to the above, according to the present invention, since the entire layered faces of the second yoke portion lb are coated with the resin-coated layer, the frequency distribution of the no-load loss of the single body of the wound core is as shown in a curve a in Fig. 8B, and that after the vacuum-injection of oil is as represented by a curve b in Fig. 8B. The building factor B.F. of the average value of the no-load losses in this case is 1.10, while the building factor B.F. of the standard deviation is 0.86. In .other words, the building factor of the average value of the no-load losses is improved by 0.10 in the present invention, and the building factor of the standard deviation is improved by 0.27. The reason for this is supposed to be that the whole layered faces of the second yoke portion (yoke portion having the

bonded portion) which is easiest to deform is covered with the resin-coated layer, thereby to restrict the deformation.
According to the foregoing embodiment, the resin-coated layer 35 is formed to cover the whole of the layered faces of the second yoke portion, and at the same time, the yoke cover 36 is bonded to each layered face of the second yoke portion by using the resin forming the resin-coated layer 35 as an adhesive. If even the lowest viscosity of the resin forming the resin-coated layer 35 when the resin is not set is sufficiently high and consequently the resin does not deeply penetrate into layers of the second yoke portion lb, the yoke cover 3 6 may be omitted.
As is described hereinabove, according to the present invention, broken pieces of amorphous magnetic alloy are perfectly prevented from being detached from the core by using only the U-shaped cover or only two kinds of covers, i.e., U-shaped cover and yoke cover, without using the conventionally employed cover complicated in structure, e.g., bottom cover or the like, or many kinds of covers.
According to the present invention, not only because the cover hard to process and complicate in shape is eliminated, but because a count of portions of the cover for covering the wound core is reduced and a count of assembling steps is decreased, the amorphous wound core

transformer can be obtained at reduced cost.
Since the layered faces of the second yoke
portion of the wound core are kept hard by the resin-coated
layer to prevent the deformation of the wound core, the
building factor indicating the change of characteristics
after the wound core is manufactured before the oil is
vacuum-injected thereby to complete the oil filled
transformer is improved. The transformer shows low loss
owing to the characteristic feature of the amorphous
magnetic alloy. Although the present
invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they deportion therefrom.

WE CLAIM
1. An amorphous wound core transformer of a layered body of a thin amorphous magnetic alloy band which has a first and a second yoke portions, and a first and a second leg portions extending between the first and second yoke portions, and is provided with a nearly rectangular wound core having a jointed portion at the second yoke portion and a winding fitted to at least one leg portion of the wound core being characterized by including:
a U-shaped cover which consists of a U-shaped coating portion formed in U shape and arranged conforming to each layered face of a U-shaped core portion composed of the first yoke portion and the first and second leg portions at both sides of the first yoke portion, and an outer peripheral coating portion and an inner peripheral coating portion bent at outer peripheral edges and inner peripheral edges of the U-shaped core portion to cover the vicinity of end portions near layered faces of an outer peripheral face and an inner peripheral face of the U-shaped core portion and fixed to the outer peripheral face and inner peripheral face of the U-shaped core portion by adhesive tapes, and which has a window portion formed at a portion of the U-shaped coating portion corresponding to the first yoke portion;
a first filter sheet disposed between the window portion of the U-shaped cover and the layered face of the U-shaped core portion and bonded to a peripheral edge of the window portion; and
a second filter sheet disposed between each end of the U-shaped cover and the layered face of the U-shaped core portion and bonded to an inner face of the U-shaped cover and the layered face of the U-shaped core portion,
wherein a resin-coated layer is formed to cover the whole of layer faces of the second yoke portion of the wound core.

2. The amorphous wound core transformer according to claim 1 further
comprising:
a resin-coated layer formed of thermosetting resin to cover the whole of layered faces of the second yoke portion of the wound core; and
a yoke cover arranged on the resin-coated layer covering each layered face of the second yoke portion and bonded to each layered face of the second yoke portion by the thermosetting resin forming the resin-coated layer,
wherein said first and second filter sheets are made of sheet-like material having permeabilities to air and oil and denseness to prevent broken pieces generated from the wound core from passing through, and said yoke cover is made of sheet-like material having flexibility to fit rough layered faces of the second yoke portion and absorbing/catching the thermosetting resin applied to the layer faces of the second yoke portion which is not yet hardened.
3. The amorphous wound core transformer according to claim 1 or 2, wherein the
filter sheets and the yoke cover are formed with felt.
4. An amorphous wound core transformer substantially as herein described with
reference to Figures 1 to 8B of the accompanying drawings.

Documents:

1478-mas-1997- abstract.pdf

1478-mas-1997- claims.pdf

1478-mas-1997- correspondence others.pdf

1478-mas-1997- correspondence po.pdf

1478-mas-1997- descripition complete.pdf

1478-mas-1997- drawings.pdf

1478-mas-1997- form 1.pdf

1478-mas-1997- form 4.pdf

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Patent Number

235135

Indian Patent Application Number

1478/MAS/1997

PG Journal Number

29/2009

Publication Date

17-Jul-2009

Grant Date

25-Jun-2009

Date of Filing

03-Jul-1997

Name of Patentee

DAIHEN CORPORATION

Applicant Address

1-11, TAGAWA 2-CHOME, YODOGAWA-KU, OSAKA-SHI, OSAKA.

Inventors:

#	Inventor's Name	Inventor's Address
1	KAORU OSAKO	C/O DAIHEN CORPORATION, 1-11, TAGAWA 2-CHOME, YODOGAWA-KU, OSAKA-SHI, OSAKA.
2	HIROTSUGU SAKAI	C/O DAIHEN CORPORATION, 1-11, TAGAWA 2-CHOME, YODOGAWA-KU, OSAKA-SHI, OSAKA
3	ATSUSHI IDEUE	C/O DAIHEN CORPORATION, 1-11, TAGAWA 2-CHOME, YODOGAWA-KU, OSAKA-SHI, OSAKA

PCT International Classification Number

H01F027/24

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	HEI 8-179438	1996-07-09	Japan