# Patent

## Title
Transformer

## Abstract

A transformer in which the high-voltage and low-voltage coils are easily laminated when they are alternately laminated in their axial directions, improving power efficiency. The transformer includes: a high-voltage coil including a wire wound around a cylindrical winding drum of a bobbin which is provided with flanges on both ends of the winding drum; a low-voltage coil formed of a flat plate member having an open ring shape, the low-voltage and high-voltage coils being alternately laminated in their axial directions; and a cover member which has a ring plate shape and is coaxially laminated on an outside of a laminate in an axial direction. The low-voltage coil is between the high-voltage coil and the cover member, and a wall portion protruding in the axial direction from the bobbin of the high-voltage coil and a wall portion protruding in the axial direction of the cover member are alternately disposed.

## Background
TECHNICAL FIELD
The present invention relates to a transformer used as a power transformer and the like in which large current flows through a low-voltage coil.
BACKGROUND ART
There has been generally used a transformer in which large current of 100 A or more flows through a low-voltage coil on a secondary side, for a power transformer or a DC-DC converter used for an electric car, a larger server or the like. In such a transformer, a flat metal plate having a small resistance is normally used for the low-voltage coil in order to accommodate increased current.
In the case where the low-voltage coil is formed of the flat metal plate, the low-voltage coil on the secondary side and a high-voltage coil on a primary side cannot have a layer winding structure, and thus there has been adopted a structure in which the low-voltage coil and the high-voltage coil are separately disposed. However, some of such structures have a problem of difficulty to obtain desired characteristics due to insufficient coupling.
Therefore, as illustrated in FIGS. 5 to 8, there has been conventionally used a transformer 10 in which a high-voltage coil 20 with a wire t wound around a winding drum 40a of a bobbin 40, and a low-voltage coil 30 formed of a flat plate member having an open ring shape, are alternately laminated in their axial directions, and cover members 50 each having a ring plate shape are coaxially laminated on outsides of the laminate in its axial direction. Note that reference character 40b denotes a flange of the bobbin 40. The reference numeral 60 denotes each of a pair of E ferrite cores surrounding the low-voltage coils 30 and the high-voltage coil 20 to form a figure-8 shaped closed magnetic path. The cover member 50 is an insulation member and interposed between the E-shaped ferrite core 60 and the low-voltage coil 30.
In the conventional transformer 10 configured as described above, the high-voltage coil 20 is sandwiched between the two low-voltage coils 30, so that coupling can be enhanced, thereby obtaining excellent characteristics.
The power transformer 10 having the above structure is also disclosed in Patent Literature 1, for example, recited below.
CITATION LIST
Patent Literature
Patent Literature 1: Japanese Patent Laid-Open No. 2001-267153
SUMMARY OF INVENTION
Technical Problem
In the transformer 10 having the conventional structure described above, in order to improve the characteristics by further enhancing the coupling, it is conceivable to adopt a structure in which the high-voltage coil 20 also has a divided structure and the divided high-voltage coils 20 sandwich the low-voltage coil 30, and the plurality of low-voltage coils 30 and high-voltage coils 20 are alternately laminated in the axial direction.
However, in the transformer 10 in which the plurality of low-voltage coils 30 and high-voltage coils 20 are alternately laminated in the axial direction, alignment is troublesome during assembly, which lowers work efficiency. Further, even when the alignment and assembly are successful, gaps are generated between the respective coils because of play in the axial direction, which causes displacement of the coils in a radial direction. Therefore, obtaining desired characteristics is difficult, which lowers product quality.
Further, in order to accommodate increased current, a sectional area is increased by increasing a plate thickness and a width of the low-voltage coil 30 formed of the flat plate member. However, in such a case, there is a problem of increased size of the transformer 10 itself.
The present invention has been made in view of such circumstances and an object thereof is to provide a transformer in which a high-voltage coil and a low-voltage coil are easily laminated when they are alternately laminated in their axial directions, and power efficiency can be improved.
Solution to Problem
In order to solve the above problems, the invention described in a first aspect of the invention is a transformer including: a high-voltage coil 2 including a wire 9 wound around a cylindrical winding drum 4a of a bobbin 4 which is provided with flanges 4b on both ends of the winding drum 4a; a low-voltage coil 3 formed of a flat plate member having an open ring shape, the low-voltage coil 3 and the high-voltage coil 2 being alternately laminated in axial directions of the low-voltage coil and the high-voltage coil; and a cover member 5 which has a ring plate shape and is coaxially laminated on an outside of a laminate in an axial direction. In the transformer, the low-voltage coil 3 is disposed between the high-voltage coil 2 and the cover member 5, and a wall portion 2a, 2b protruding in the axial direction from the bobbin 4 of the high-voltage coil 2 and a wall portion 5a protruding in the axial direction of the cover member 5 are alternately disposed along an inner circumferential surface of the low-voltage coil 3 to be positioned in a circumferential direction.
Further, in the invention described in a second aspect of the invention, in the invention described in the first aspect, two or more of the high-voltage coils are disposed in the axial direction, the low-voltage coil is disposed between the high-voltage coils, and the wall portions of the high-voltage coils are alternately disposed along the inner circumferential surface of the low-voltage coil to be positioned in the circumferential direction.
Further, in the invention described in a third aspect, in the invention described in first or second aspects, two or more of the low-voltage coils are coaxially laminated with an insulation sheet interposed between the low-voltage coils.
Advantageous Effects of Invention
According to the present invention described in the first to third aspects of the invention, a low-voltage coil is disposed between a high-voltage coil and a cover member to be laminated in an axial direction, and a wall portion protruding in the axial direction from a bobbin of the high-voltage coil, and a wall portion protruding in the axial direction of the cover member are alternately disposed along an inner circumferential surface of the low-voltage coil to be positioned in a circumferential direction. Thus, assembly work can be facilitated and displacement of the low-voltage coil in a radial direction can be prevented. Thereby, productivity can be improved, which can lead to an improvement of product quality.
According to the invention described in the second aspect of the invention, two or more of the high-voltage coils are disposed in the axial direction, the low-voltage coil is disposed between the high-voltage coils, and the wall portions of the high-voltage coils are alternately disposed along the inner circumferential surface of the low-voltage coil to be positioned in the circumferential direction. Thus, even when the plurality of high-voltage coils and low-voltage coils are laminated to be disposed, they can be easily assembled. As a result, productivity can be improved and a yield ratio can be improved.
According to the invention described in the third aspect of the invention, two or more of the low-voltage coils are coaxially laminated with an insulation sheet interposed between the low-voltage coils. Thus, current efficiency can be improved without increasing a thickness and a width of the low-voltage coil. Thus, large current transformer can be downsized.
Further, since the wall portion protruding from the bobbin of the high-voltage coil, and the wall portion protruding from the cover member come into contact with the inner circumferential surface of the low-voltage coil, even when the insulation sheet is interposed between the laminated low-voltage coils, the insulation sheet is not displaced in a radial direction, and thus the low-voltage coils can be prevented from contacting each other.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a sectional view of a transformer of an embodiment of the present invention in an axial direction in a state that it is not surrounded with E-shaped ferrite cores.
FIG. 2 is a perspective view illustrating a bobbin of a high-voltage coil and cover members used in the transformer of the embodiment of the present invention.
FIG. 3 is a perspective view illustrating the transformer of the embodiment of the present invention.
FIG. 4 is a perspective view illustrating a state that the transformer of FIG. 3 is exploded.
FIG. 5 is a sectional view of a conventional transformer in an axial direction in a state that it is not surrounded with E-shaped ferrite cores.
FIG. 6 is a perspective view illustrating a bobbin of a high-voltage coil and cover members in the transformer of FIG. 5.
FIG. 7 is a perspective view of the conventional transformer in which the high-voltage coil and a plurality of low-voltage coils are laminated.
FIG. 8 is a perspective view illustrating a state that the transformer of FIG. 7 is exploded.



DESCRIPTION OF EMBODIMENTS
FIGS. 1 to 4 each illustrate an embodiment of a transformer according to the present invention. The transformer 1 is generally composed of two high-voltage coils 2 as a primary side, three sets of low-voltage coils 3 as a secondary side, two cover members 5, and E-shaped ferrite cores 6 surrounding the high-voltage coils 2, the low-voltage coils 3, and the cover members 5 to form a closed magnetic path.
Herein, the low-voltage coil 3 is a flat plate member having an open ring shape which is formed by punching a copper plate. Both ends of the low-voltage coil 3 are integrally provided with terminals 3a extending outward. Further, an insulation sheet 7 is interposed between the two low-voltage coils 3, and the low-voltage coils 3 are coaxially laminated. Further, the insulation sheet 7 is formed of a flat plate member having a circular ring shape.
Further, the high-voltage coil 2 has an outside appearance of a substantially cylindrical shape. In the high-voltage coil 2, a bobbin 4 in which both ends of a cylindrical winding drum 4a having insulation property are provided with flanges 4b, and the bobbin 4 is wound with a triple insulated winding wire (wire) 9. Further, the high-voltage coil 2 is provided with wall portions 2a, 2b which come into contact with respective inner circumferential surfaces of the two low-voltage coils 3 when the set of the low-voltage coils 3 are laminated on both ends of the high-voltage coil 2 in the axial direction.
The wall portions 2a, 2b protrude outward in the axial direction from the bobbin 4 of the high-voltage coil 2, and the plurality (six in the figure) of wall portions 2a, 2b are formed at intervals in a circumferential direction of the inner circumferential surface of the low-voltage coil 3. Further, the wall portions 2a and 2b each have a height which is the same as a thickness of the set of low-voltage coils 3, are formed at the same intervals as each other, and alternately disposed in the circumferential direction of the low-voltage coil 3.
Further, on a peripheral portion of each flange 4b of the bobbin 4, there is formed a rotation stop member 8 protruding outward in the axial direction. The rotation stop members 8 are inserted into between the terminals 3a of the two low-voltage coils 3 and are alternately disposed such that one of the rotation stop members 8 comes into contact with inner ends of one of the terminals 3a, and the other rotation stop member 8 comes into contact with inner ends of the other terminals 3a when the set of low-voltage coils 3 are disposed between the two high-voltage coils 2.
The cover member 5 has a ring plate shape and has insulation property. The cover member 5 is provided with wall portions 5a which come into contact with the respective inner circumferential surfaces of the two low-voltage coils 3 when the set of low-voltage coils 3 are disposed between the high-voltage coils 2.
The wall portions 5a protrude outward in the axial direction from one end of the cover member 5, and the plurality (six in the figure) of wall portions 5a are formed at intervals in the circumferential direction of the inner circumferential surface of the low-voltage coil 3. The wall portions 5a have a height which is the same as the height of the wall portions 2a and 2b provided on both the ends of the bobbin 4 of the high-voltage coil 2, and are formed at the same intervals as the wall portions 2a and 2b. 
Further, the wall portions 5a of one of the cover members 5 and the wall portions 2a provided on one end of the bobbin 4 of the high-voltage coil 2 are alternately formed in the circumferential direction of the low-voltage coil 3, and the wall portions 5a of the other cover member 5 and the wall portions 2b provided on the other end of the bobbin 4 of the high-voltage coil 2 are alternately formed in the circumferential direction of the low-voltage coil 3.
Further, on a peripheral portion of the cover member 5, there are formed rotation stop members 8 protruding outward in the axial direction. The rotation stop members 8 are formed at positions where they come into contact with outer ends of the two terminals 3a of the two low-voltage coils 3 when the set of low-voltage coils 3 are disposed between the high-voltage coil 2 and the cover member 5.
When the transformer 1 configured as described above is assembled, first, the winding drum 4a of the bobbin 4 of one of the high-voltage coils 2 is wound with the triple insulated winding wire 9 by alpha winding, and then the winding drum 4a of the bobbin 4 of the other high-voltage coil 2 is wound with the triple insulated winding wire 9 extending from one of the high-voltage coils 2. Thus, the two high-voltage coils 2 with which one triple insulated winding wire 9 is continuously wound are prepared.
Next, as illustrated in FIG. 4, the set of low-voltage coils 3 are disposed such that they are sandwiched between the two high-voltage coils 2. At the same time, the wall portions 2a provided on one of the high-voltage coils 2, and the wall portions 2b provided on the other high-voltage coil 2 are fitted, the two high-voltage coils 2 are positioned, and also the low-voltage coil 3 is positioned at the same time because the wall portions 2a, 2b of the two high-voltage coils 2 come into contact with the respective inner circumferential surfaces of the two low-voltage coils 3.
Further, when the set of low-voltage coils 3 are disposed between the two high-voltage coils 2 to be assembled, the rotation stop member 8 provided on the flange 4b of the bobbin 4 of one of the high-voltage coils 2 comes into contact with the inner ends of the terminals 3a on one side of the two low-voltage coils 3, and the rotation stop member 8 provided on the flange 4b of the bobbin 4 of the other high-voltage coil 2 comes into contact with the inner ends of the terminals 3a on the other side of the two low-voltage coils 3. Thus, the set of low-voltage coils 3 are prevented from rotating in the circumferential direction.
Then, on both the ends in the axial direction of the laminated two high-voltage coils 2, the set of low-voltage coils 3 are disposed such that they are sandwiched between the high-voltage coil 2 and the cover member 5. At the same time, the wall portions 2a provided on one end side of the laminated high-voltage coils 2 are respectively fitted to the wall portions 5a of one of the cover members 5, and the wall portions 2b provided on the other end side of the high-voltage coils 2 are respectively fitted to the wall portions 5a of the other cover member 5. Accordingly, the cover members 5 are respectively positioned on the laminated high-voltage coils 2. Further, the wall portions 2a of the laminated high-voltage coils 2 and the wall portions 5a of the cover member 5, and the wall portions 2b of the laminated high-voltage coils 2 and the wall portions 5a of the cover member 5 come into contact with the respective inner circumferential surfaces of the two sets of low-voltage coils, and thus the two sets of low-voltage coils 3 are positioned at the same time.
Further, when the set of low-voltage coils 3 are disposed between the high-voltage coil 2 and the cover member 5 to be assembled, the rotation stop member 8 provided on the flange 4b of the bobbin 4 of the high-voltage coil 2 comes into contact with the insides of the terminals 3a on one side of the two low-voltage coils 3, and the two rotation stop members 8 provided on the circular edge of the cover member 5 come into contact with the outsides of the terminals 3a of one of the low-voltage coils 3. Thereby, the set of low-voltage coils 3 are prevented from rotating in the circumferential direction.
Then, the pair of E-shaped ferrite cores 6 surround the two high-voltage coils 2, the three sets of low-voltage coils 3, and the two cover members 5 to fit them with a binding member k, so that the assembly of the transformer 1 is completed.
In the transformer 1 configured as described above, the three sets of low-voltage coils 3 are respectively disposed between the two high-voltage coils 2 and between the high-voltage coils 2 and the cover members 5 to be laminated in the axial direction, and the wall portions 2a, 2b protruding in the axial direction from the bobbin 4 of the high-voltage coil 2, and the wall portions 5a protruding in the axial direction of the cover member 5 are alternately disposed along the inner circumferential surface of the low-voltage coil 3 to be positioned in the circumferential direction. Thus, assembly work can be facilitated and displacement of the sets of low-voltage coils 3 in the radial direction can be prevented. Thereby, productivity can be improved, which can lead to an improvement of product quality. Further, even when the bobbins 4 of the high-voltage coils 2 are an elliptical shape, for example, the high-voltage coils 2 can be positioned in the same direction as each other when they are laminated in their axial directions.
Further, since the low-voltage coils 3 are coaxially laminated with the insulation sheet 7 interposed therebetween, current efficiency can be improved without increasing the thickness and the width of the low-voltage coil 3. As a result, the large current transformer can be downsized.
Further, since the wall portions 2a, 2b protruding from the bobbins 4 of the high-voltage coils 2, and the wall portions 5a protruding from the cover members 5 come into contact with the respective inner circumferential surfaces of the three sets of the low-voltage coils 3, even when the insulation sheet 7 is interposed between the three sets of the low-voltage coils of each set of the low-voltage coils 3, the insulation sheet 7 is not displaced in a radial direction, and thus the low-voltage coils 3 can be prevented from contacting each other.
In the embodiment described above, the description is given to the case of the transformer 1 according to the present invention in which the two high-voltage coils 2 and the three sets of low-voltage coils 3 are alternately disposed and laminated in the axial direction. However, the present invention is not limited to this and the present invention can be configured by combining the more high-voltage coils 2 and low-voltage coils 3.
Further, the wire for forming the high-voltage coil 2 is not limited to the triple insulated winding wire 9 described above, and various kinds of wires can be used depending on specifications of the transformers.
As to the low-voltage coil 3, a wire having a large wire diameter can be used instead of the flat plate member having the open ring shape described above depending on magnitude of flowing current.
INDUSTRIAL APPLICABILITY
The present invention can be used for a large current transformer such as a power transformer or a DC-DC converter used for an electric car, a larger server or the like.
REFERENCE SIGNS LIST


    1 transformer
    2 high-voltage coil
    2a, 2b wall portion
    3 low-voltage coil
    4 bobbin
    4a winding drum
    4b flange
    5 cover member
    5a wall portion
    6 E-shaped ferrite core
    7 insulation sheet
    8 low-voltage coil rotation stop member
    9 wire
    10 transformer
    20 high-voltage coil
    30 low-voltage coil
    40 bobbin
    40a winding drum
    40b flange
    50 cover member
    60 E-shaped ferrite core
    t wire

## Claims

1. A transformer comprising:
high-voltage coils including a wire wound around a cylindrical winding drum of a bobbin which is provided with flanges on both ends of the winding drum;
low-voltage coils formed of a flat plate member having an open ring shape, the low-voltage coils and high-voltage coils being alternately laminated in axial directions of the low-voltage coils and high-voltage coils; and
a cover member which has a ring plate shape and is coaxially laminated on an outside of a laminate in an axial direction,
wherein one of the low-voltage coils are disposed between one of the high-voltage coils and the cover member, and a first set of wall portions protruding in the axial direction from the bobbin of one of the high-voltage coils and wall portions protruding in the axial direction of the cover member are alternately disposed along an inner circumferential surface of one of the low-voltage coils to be positioned in a circumferential direction;
wherein the first set of wall portions of the bobbin of one of the high-voltage coils each have a height which is the same as a thickness of the low-voltage coils, and are formed at same intervals as each other;
wherein the wall portions of the cover member have a height which is the same as the height of the first set of wall portions of the bobbin of one of the high-voltage coils; and
wherein another one of the low-voltage coils are disposed such that they are sandwiched between the high-voltage coils, and a second set of wall portions of the bobbin of one of the high-voltage coils and the wall portions of the bobbin of another one of the high-voltage coils are fitted, the high-voltage coils being positioned so that a second set of wall portions of the bobbin of one of the high-voltage coils and the wall portions of the bobbin of another one of the high-voltage coils come into contact with inner circumferential surfaces of adjacent ones of another one of the low-voltage coils.

2. The transformer according to claim 1, wherein two or more of the high-voltage coils are disposed in the axial direction, the low-voltage coils being disposed between the two or more high-voltage coils, and the wall portions of the bobbins of the two or more high-voltage coils being alternately disposed along the inner circumferential surface of the low-voltage coils to be positioned in the circumferential direction.

3. The transformer according to claim 1, wherein in the low-voltage coils, two or more of the flat plate members each having the open ring shape are coaxially laminated with an insulation sheet interposed between the flat plate members.

4. The transformer according to claim 2, wherein in the low-voltage coils, two or more of the flat plate members each having the open ring shape are coaxially laminated with an insulation sheet interposed between the flat plate members.