JPH07192945A - Current transformer - Google Patents

Abstract

PURPOSE:To obtain a highly reliable current transformer excellent in performance which can be manufactured while eliminating the useless space by forming a U-shaped conductor, extending to the side edge of a U-shaped thin plate along the inner edge thereof, as a primary winding and fixing a clip lead terminal thereto. CONSTITUTION:The primary winding is provided by forming a U-shaped conductor 24 on the upper surface of a U-shaped thin plate 21 made of a dielectric synthetic resin, which is formed on top 15a of the base part of the drum bobbin 19, while extending to the side edge 23 of the thin plate 21 along the inner edge 22 thereof. An insulating sheet 25 having substantially identical profile to the thin plate 21 is then bonded thereto while partially exposing the end parts 24a, 24b of the conductor 24. Furthermore a clip lead terminal 27 is fixed to the side 15b at the base part so that the lead terminal 27 clips the base part 15 and the U-shaped thin plate while connecting with the end part 24a or 24b of the conductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current transformer surface-mounted on a circuit board of an electronic device, and more particularly to the structure of a primary winding of the current transformer.

[0002]

2. Description of the Related Art A coil transformer used as a current sensor is a current transformer. This is to detect a change in current on the primary side as an induced voltage having a magnification according to the turn ratio on the secondary side in phase.

In general, the surface mount type structure of the current transformer is a winding of a drum type coil bobbin which is composed of a base portion in which lead terminals are embedded, a winding frame portion for winding a winding, and an upper collar portion. A very thick copper wire is wound around the frame portion for one turn to form a primary winding, and a large number of secondary windings are wound around with a relatively thin insulation-coated conductor wire (generally about 100 to 200 turns), and each lead terminal is wired. .

The insulation between the primary winding and the secondary winding is processed by additionally processing an insulating tape or providing a middle collar on the winding frame.

A magnetic core of ferrite or the like is attached to this coil bobbin to form a current transformer.

FIG. 6 is a vertical sectional view showing an example of the structure of the conventional surface mount type current transformer.

In the figure, the drum type coil bobbin 2 of the current transformer 1 is made of an insulating synthetic resin, and is composed of an upper collar portion 3, a cylindrical winding frame portion 4, a base portion 5 and an intermediate collar portion 6, and a base portion. 5, lead terminals are embedded on the front and back side surfaces of the drawing.

In the upper area of the winding frame portion 4 of the drum type coil bobbin 2, the primary winding 7 of an extremely thick copper wire having a wire diameter of about 0.6 mm and having an insulation coating is wound one turn, and the middle brim portion 6 is provided. A secondary winding 8 having a wire diameter of about 0.1 mm is provided in the separated lower area.
It is wound about 0 turns, and each of them is entwined with a lead terminal and solder-dipped.

Further, the current transformer 1 is constructed such that E-type magnetic cores 9a and 9b are assembled as a magnetic core so as to face each other to form an EE-type day-type closed magnetic circuit. At this time, the central magnetic legs 10a and 10b of the E-shaped magnetic core are inserted into the fitting holes of the tubular winding frame portion 4, and the side magnetic legs 12a and 12b are attached so as to hold both side surface portions of the coil bobbin 4. To be done.

The E-type magnetic cores 9a and 9b are formed by press-molding and sintering ferrite powder, which is an oxide magnetic material.

[0011]

However, in the above-mentioned conventional current transformer 1, since the extremely thick copper wire is used as the primary winding, the automatic winding machine cannot be used and the manual winding work is inevitable. There is a problem that the process is complicated.

Further, when the extra-thick copper wire is wound and twisted on the lead terminal, the lead terminal may bend due to bending stress,
A w-like crack is likely to occur on the reel 4 in FIG.
There was a problem that it could cause the bobbin to crack.

Therefore, in order to solve the above problems, it is necessary to increase the wall thickness of the coil bobbin 2 and thicken the lead terminal, and it is necessary to design a coil bobbin with a lead terminal having a strong structure such as improved implantation strength. However, the cost was high.

Further, in order to secure the insulation, it is necessary to completely divide the area of the primary winding and the area of the secondary winding, which necessitates the middle flange portion 6 and causes an increase in size.

Since the primary winding 7 has only one turn,
There is a problem that the coupling area between the primary winding 7 and the secondary winding 8 is small and the coupling degree is poor.

The present invention has been made in view of the above circumstances, and provides a current transformer using a drum type coil bobbin and a winding structure, which is easy to manufacture, has no wasted space, and is excellent in reliability and performance. It is a thing.

[0017]

SUMMARY OF THE INVENTION According to the present invention, primary winding is performed on a drum type coil bobbin having a base portion, a tubular winding frame portion having a fitting insertion hole for inserting a magnetic core therethrough, and an upper collar portion. In a current transformer having a structure in which a wire and a secondary winding are wound and a magnetic core is inserted into the insertion hole, the planar shape is U-shaped so that the coil bobbin is inserted and laid on the upper surface of the base portion. A U-shaped conductor extending to the side edge along the inner edge of the U-shaped thin plate is formed on the surface of the insulating thin plate made of synthetic resin so as to surround the outer periphery of the winding frame, and this is used as the primary winding. In addition, an insulating sheet having substantially the same shape is adhered and fixed on the U-shaped thin plate so that the end portions of the conductor are partially exposed, and the side surface of the base portion is conductively connected to the end portion of the conductor while the base is being connected. Characterized in that a clip-type lead terminal is attached so as to sandwich the portion and the U-shaped thin plate together. By providing a current transformer, it is to achieve the above object.

Further, in the above current transformer, the lead electrode of the secondary winding is further used as a clip type lead terminal, and the side surface opposite to the side surface having the conductor end portion as the primary winding on the U-shaped thin plate surface. The above object is achieved by providing a current transformer characterized in that a conductor part for connecting a secondary terminal which is conductively connected to the clip type lead terminal is formed on the side.

[0019]

Since the U-shaped conductor extending along the inner edge of the U-shaped thin plate to the side edge portion replaces the conventional thick copper wire as the primary winding and the lead terminal is of the clip type, the thick copper is used. Eliminates the need for manual winding of wires and wiring to lead terminals.

Therefore, defects such as cracks in the coil bobbin and bending of the lead terminals during manual winding of the extra-thick copper wire are eliminated, and good reliability can be obtained without using a robust coil bobbin which has been conventionally required.

Further, since the U-shaped conductor is thin and the insulating sheet keeps good insulation between the primary winding and the secondary winding, it is insulated from the region of the winding frame portion as the primary winding. The intermediate collar part is unnecessary and space is saved.

On the other hand, since the coupling area between the U-shaped conductor as the primary winding and the secondary winding is large, the degree of magnetic coupling is large, and good performance improvement as a current sensor can be achieved.

If the lead electrode of the secondary winding is a clip-type lead terminal similar to that on the primary side, the consistency of the lead terminals is maintained and the base and U-shaped thin plate are provided from all sides. Since it will be crimped and sandwiched, the structural strength will increase.

The clip-type lead terminal is formed with two protrusions, and the protrusions sandwich and hold both the U-shaped thin plate and the base portion.

The U-shaped thin plate is formed so that the inner part hollowed out into a U shape matches the shape of the cylindrical winding frame on the upper surface of the base, and is inserted and laid on the upper surface of the base of the coil bobbin. In this case, it conforms to the top shape of the base.

[0026]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an exploded perspective view for explaining the structure of a drum type coil bobbin and a primary winding used in a current transformer according to the present invention, and FIG. 2 is a winding diagram showing a secondary winding wound on the drum type coil bobbin. It is a perspective view of the current transformer of the structure which mounted the E type magnetic core which rotated. FIG. 3 is a vertical sectional view of the current transformer.

The features of the present invention are, as shown in FIGS. 1, 2 and 3, a base portion 15 and a cylindrical winding frame portion 17 having a magnetic core insertion hole 16 formed therethrough. On the upper surface 15a of the base portion of the drum type coil bobbin 19 having the upper collar portion 18, a synthetic resin insulating U-shaped thin plate 21 having a U-shaped planar shape is provided on the surface of the winding portion 17 of the coil bobbin 19. Inner edge 2 of U-shaped thin plate 21 so as to surround the outer circumference
2, a U-shaped conductor 24 extending to the side edge portion 23 is formed and used as a primary winding, and an insulating sheet 25 of substantially the same shape is formed on the U-shaped thin plate 21 at the end of the conductor 24. Part 24
a and 24b are bonded and fixed so that they are partially exposed, are laid and laid, and further, the base part 15 and the U-shaped thin plate are conductively connected to the end part 24a or 24b of the conductor on the side part 15b of the base part. It has a structure in which a clip type lead terminal 27 is attached so as to sandwich 21 together.

The U-shaped conductor 24 is a substitute for the primary winding of a very thick copper wire, which conventionally requires a manual winding work and requires a strong coil bobbin, and the lead of the conductor 24 as the primary winding. It is the gist of the present invention that the conductive connection with the terminal is formed by sandwiching the clip type lead terminal 27. However, in the current transformer according to claim 1 of the present invention, the lead terminal on the secondary winding side is There is no particular limitation on the configuration.

For example, as in the conventional case, the lead terminals embedded in the base 15 may be formed so as to be twisted, but the compatibility with the primary winding and the clip type lead terminals are different from those of the base 15. Considering the advantage of sandwiching and crimping the U-shaped thin plate 21 together, the lead terminal on the secondary winding side is also the clip type lead terminal 2 like the current transformer 30 of FIG. 2 according to claim 2 of the present invention.
7b and a conductor part 29 for connecting a secondary terminal, which is conductively connected to the clip-type lead terminal 27b, on a side surface side 28 opposite to the side surface having the conductor end portion as the primary winding on the surface of the U-shaped thin plate 21. A structure in which is formed is desirable.

The coil is provided with a secondary winding, and the secondary side clip-type lead terminal 27b is entangled, and wiring processing is performed. At this time, the primary clip-type lead terminal 27 is also soldered and fixed to the conductor end portions 24a and 24b so as not to come off.

Finally, magnetic cores 31a, 31b such as ferrite
If combined, the current transformer 30 is obtained.

In this current transformer 30, as is apparent from FIG. 3, the coupling area between the U-shaped conductor 24 as the primary winding and the secondary winding 8 becomes large, so that the magnetic coupling degree becomes large and the current sensor As a result, good performance can be improved.

If the lead terminal of the secondary winding is a clip type lead terminal 27b similar to that on the primary side,
It is clear that the structural strength is increased because the lead terminals are kept in conformity and the base portion 15 and the U-shaped thin plate 21 are crimped and sandwiched from four sides.

Next, each member will be described in detail.

First, the U-shaped thin plate 21 is a phenol resin,
A copper clad laminate in which copper is thinly stretched on an insulating synthetic resin plate such as epoxy resin, PBT, or PET is etched to form a U-shaped conductor portion 24 and a conductor portion 29 for connecting a secondary terminal. Insulation sheet (thin plate) also made of synthetic resin on top 2
5 is fixed. The U-shaped conductor portion 24 may be formed by laminating by printing on ceramics.

The U-shaped thin plate 21 and the insulating sheet 25 are formed in such a manner that the inner part hollowed out in a U shape matches the shape of the cylindrical winding frame 17 on the upper surface of the base, and the upper surface of the base is shaped. Will be laid to fit.

Next, as the magnetic core to be mounted on the drum type coil bobbin 19, a columnar magnetic core may be simply inserted into the insertion hole 16, but usually the E type magnetic core 31 is used.
2a and 3b, the central magnetic leg of the E-shaped magnetic core is inserted into the insertion hole 16 as shown in FIGS.
It is general that the side magnetic legs of the shaped magnetic core are attached to both side surfaces of the coil bobbin to form a day-type closed magnetic circuit of EE type (or EI type).

The material of the magnetic core is not particularly limited, but usually ferrite is used. This ferrite is an oxide magnetic material, and has a relatively large resistance and a small high frequency loss, so it is widely used as a magnetic material for high frequencies. Nickel-based ferrite, nickel-cobalt-based ferrite, and nickel-zinc-based. There are types such as ferrite and manganese zinc-based ferrite. Other than ferrite, for example, a silicon steel plate is used.

Next, the drum type coil bobbin 19 is made of synthetic resin, for example, polybutylene terephthalate (PB).
T), polyethylene terephthalate (PET), phenol resin, etc. are injection-molded.

Further, the clip type lead terminals 27, 27b
Is generally an iron-based metal such as Kovar, 42 alloy or the like, or a copper-based metal such as copper-containing copper such as iron-containing copper is solder-plated, and two protrusions 27X and 27Y are formed. Both the U-shaped thin plate 21 and the base portion 15 are sandwiched and clamped together.

The secondary winding 8 is an insulating coated conductive wire such as an enamel coated conductive wire or a polyurethane coated conductive wire, and is normally wound 100 to 300 turns as a current transformer.

Incidentally, as a reminder, the shape of the drum type coil bobbin 19 is not particularly limited. For example, the shape of the cylindrical winding frame portion 17 has a rectangular cross section with the fitting insertion hole 16 as in the above embodiment. In addition to the rectangular column shape, for example, a circular cylindrical bobbin portion 17a such as a drum coil bobbin 19a shown in FIG. 5 may be used, or a circular upper collar portion 18a may be used. In this case, as shown in FIG. 4, the planar shape of the U-shaped thin plate 21a and the insulating sheet 25a placed on the upper surface of the base is also U-shaped, and the inner part is semicircular.

Further, the insulating sheet 25a in FIG. 5 differs from the clip type lead terminals 27, 2 in that the first embodiment is provided with the concave portion to form the adhesive with the clip lead terminal.
The side length at which the lead terminal is arranged so that the conductor portion to be bonded to 7b is exposed is set shorter than the base portion. Needless to say, the object of the present invention can be achieved even with the above configuration.

[0045]

Since the current transformer according to the present invention is constructed as described above, it has the following effects.

(1) It has an excellent effect that it is easy to manufacture because there is no need for winding and twisting the extra-thick copper wire of the primary winding which relied on manual work.

(2) It has an excellent effect that the bending of the lead terminal and the crack of the coil bobbin due to the bending stress of the extra thick copper wire can be avoided.

(3) The coil bobbin structure does not have to be robust, and has the excellent effect of increasing the degree of freedom in design.

(4) It has an excellent effect that it can be made thin as a whole and wasteful space is eliminated.

(5) It has an excellent effect that the coupling degree between the primary side and the secondary side is increased and the performance as a current transformer is improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view for explaining a structure of a drum type coil bobbin and a primary winding used in a current transformer according to the present invention,

FIG. 2 is a perspective view of a current transformer having a configuration in which a secondary winding is wound around the drum type coil bobbin and an EE type magnetic core is attached.

FIG. 3 is a vertical sectional view of the current transformer.

FIG. 4 is a perspective view showing a combination of another shape U-shaped thin plate and an insulating sheet according to the present invention.

FIG. 5 is a perspective view of a second drum-type coil bobbin according to the present invention, a U-shaped thin plate, and an insulating sheet.

FIG. 6 is a vertical sectional view showing a structure of a conventional current transformer.

[Explanation of symbols]

 1, 30 Current transformer 2, 19, 19a Drum type coil bobbin 3, 18 Upper flange part 4, 17 Cylindrical winding frame part 5, 15 Base part 6 Middle flange part 7 Primary winding 8 Secondary winding 9a, 9b E type magnetic core 10a, 10b Central magnetic leg 12a, 12b Side magnetic leg 15a Base part upper surface 15b Base part side part 16 Fitting insertion hole 21 U-shaped thin plate 22 U-shaped thin plate inner edge 23 Side edge 24 (U-shaped) Conductors 24a, 24b Ends of the conductor 24 25 Insulating sheets 27, 27b Clip type lead terminals 27x, 27y Protrusions 29 Secondary terminal connecting conductors 17a Cylindrical reel 18a Circular upper flange

Claims (2)

[Claims] 1. A primary winding and a secondary winding are wound on a drum type coil bobbin having a base portion, a tubular winding frame portion having a fitting insertion hole for inserting a magnetic core therethrough, and an upper collar portion. In a current transformer having a structure in which a magnetic core is inserted into the insertion hole while being rotated, a synthetic resin insulating thin plate having a U-shaped plane is inserted so as to be laid on the upper surface of the base of the coil bobbin. A U-shaped conductor is formed on the surface so as to surround the outer circumference of the winding frame part along the inner edge of the U-shaped thin plate and reaches the side edge part, and this is used as a primary winding, and on the U-shaped thin plate. An insulating sheet of substantially the same shape is bonded and fixed so that the end portions of the conductor are partially exposed, and the base portion and the U-shaped thin plate are sandwiched together while conductively connecting to the end portion of the conductor on the side surface portion of the base portion. The current transformer, which is equipped with a clip-type lead terminal as described above. 2. The lead electrode of the secondary winding is used as a clip-type lead terminal, and 1 on the surface of the U-shaped thin plate is used.
2. The current transformer according to claim 1, wherein a secondary terminal connecting conductor portion that is conductively connected to the clip-type lead terminal is formed on a side surface side opposite to a side surface having a conductor end portion as a secondary winding.