JP7554082B2 - transformer - Google Patents

Description

The present invention relates to a structure for fixing a transformer to an object on which it is to be installed.

In recent years, transformers have been used in the power supply circuits of various electronic devices, such as chargers. A transformer has, for example, a pair of core units, a primary coil unit, and a pair of secondary coil units. The primary coil unit is sandwiched between a pair of secondary coil units, and a pair of core units are provided to sandwich the secondary coil unit. Each unit is fixed in place with adhesive or by wrapping tape around the outer periphery of the core unit.

JP 2012-160616 A

When fixing such transformers to the object on which they are to be installed, leaf springs are often used. That is, the transformer is fixed by pressing the top surface of the core unit against the installation surface of the object with the leaf spring. In particular, for transformers that are placed in environments with severe vibration conditions, the force pressing the core unit by the leaf spring becomes large, and there is a concern that this will cause cracks in the core and, in some cases, break it.

The present invention was made to solve the above problems, and its purpose is to provide a transformer that can prevent core cracks.

The transformer of the present invention comprises a primary coil, a secondary coil having a bus bar and accommodating the primary coil inside, and a core formed around the secondary coil, the secondary coil being composed of a first resin body and a second resin body, the first resin body and the second resin body each having a fixing portion for fixing the transformer to an object to be installed, the second resin body being disposed above the first resin body, the fixing portion of the second resin body extending toward the first resin body, the bottom surface of the fixing portion of the second resin body being horizontal with the bottom surface of the fixing portion of the first resin body, and abutting the object to be installed .

The present invention makes it possible to obtain a transformer that can prevent core cracks.

1 is a perspective view showing an overall configuration of a transformer according to an embodiment; FIG. 2 is an exploded perspective view of the transformer according to the embodiment. FIG. 2 is a perspective view of the second resin body as viewed from the bottom. FIG. 2 is a plan view of a first resin body and a second resin body. 1 is a plan view of a state in which a first resin body and a second resin body are joined together. FIG. FIG. 13 is a diagram showing a state of stress applied to a core when a conventional transformer is fixed. 11A and 11B are diagrams illustrating a state of stress applied to a core when the transformer of the embodiment is fixed. FIG. 13 is a diagram showing the position of a fixing part in another embodiment. FIG. 13 is a diagram showing the position of a fixing part in another embodiment.

(composition)
The configuration of the transformer according to the present embodiment will be described with reference to the drawings. Fig. 1 is a perspective view showing the overall configuration of the transformer according to the present embodiment. Fig. 2 is an exploded perspective view of the transformer according to the present embodiment. Note that the winding axis direction of the electric wire is the height direction, and the side where the transformer 1 contacts the installation object is called the lower side, and the opposite side is called the upper side.

The transformer 1 is a device that converts the voltage level by utilizing electromagnetic induction. The transformer 1 of this embodiment is used in DC/DC converters, inverters, etc. As shown in Figures 1 and 2, the transformer 1 includes a primary coil unit 2, a secondary coil unit 3, and a core unit 4.

The primary coil unit 2 has an insulating bobbin 21 and an electric wire 22. The insulating bobbin 21 is made of an insulating resin. Examples of the types of resin include epoxy resin, unsaturated polyester resin, urethane resin, BMC (Bulk Molding Compound), PPS (Polyphenyl Sulfide), PBT (Polybutylene Terephthalate), and PET (Polyethylene Terephthalate). The insulating bobbin 21 has a ring shape with a circular hole 23 in the center. The insulating bobbin 21 has a recess on the outer periphery.

The electric wire 22 is composed of a single conductive member that is insulated with enamel or the like. The electric wire 22 is wound around a recess on the outer periphery of the insulating bobbin 21. Both ends of the electric wire 22 serve as input terminals 24. The pair of input terminals 24 extend toward the outside of the insulating bobbin 21 and are arranged side by side on one side of the transformer. The input terminals 24 are electrically connected to an external device. When power is supplied from the external device, a current flows through the electric wire 22.

The secondary coil unit 3 is composed of two parts, a first resin body 3A and a second resin body 3B. The secondary coil unit 3 is formed by separately molding the first resin body 3A and the second resin body 3B. The first resin body 3A and the second resin body 3B are made of resin, and the same type of resin as the insulating bobbin 21 of the primary coil unit 2 can be used.

The first resin body 3A and the second resin body 3B are joined facing each other to form the secondary coil unit 3. The secondary coil unit 3 is divided into two parts so that the primary coil unit 2 is sandwiched between the first resin body 3A and the second resin body 3B and housed within the secondary coil unit 3. The second resin body 3B is provided above the first resin body 3A. In other words, the first resin body 3A is provided at a position closer to the installation surface of the object on which the transformer 1 is to be installed than the second resin body 3B.

The first resin body 3A has a circular flat plate shape. A circular hole 32 of approximately the same size as the hole 23 of the insulating bobbin 21 is provided in the center of the first resin body 3A. This hole 32 is inserted into the middle leg 41 of the E-shaped core 4B described below. A mounting portion 33 is provided on the end face of the first resin body 3A opposite the end face that contacts the E-shaped core 4B. The mounting portion 33 is the end face on which the primary coil unit 2 is mounted.

Figure 3 is a perspective view of the second resin body 3B as viewed from the bottom. The second resin body 3B has a circular top cover 34 and a wall portion 35 extending from the edge of the top cover 34 toward the installation surface (downward) of the installation object, and the bottom surface is open. The primary coil unit 2 is accommodated in the space defined by the top cover 34 and the wall portion 35. The top cover 34 has a circular hole 36 of approximately the same size as the hole 23 of the insulating bobbin 21 and the hole 23 of the first resin body 3A. The middle leg 41 of the E-shaped core 4A is inserted into this hole 36. The hole 32 of the first resin body 3A, the hole 36 of the top cover 34, and the hole 23 of the insulating bobbin 21 of the primary coil unit 2 are arranged so that their central axes are coaxial.

The first resin body 3A and the second resin body 3B are integrally molded with the bus bar 5 and the fixing portion 31. "Integratedly molded" means that the bus bar 5 and the fixing portion 31 are fixed with resin by molding.

The bus bar 5 is composed of a single conductive member. The bus bar 5 has a ring shape, and this ring-shaped portion is covered with the resin that constitutes the first resin body 3A or the second resin body 3B. Both ends of the bus bar 5 become output terminals 51 and are exposed from the resin. That is, the first resin body 3A and the second resin body 3B each have two output terminals 51. In addition, a circular hole is provided at the tip of the output terminal 51 for connecting to a terminal of an external device.

The two output terminals 51a, 51b of the first resin body 3A extend outward from the side of the transformer 1 opposite the input terminal 24. The output terminals 51a, 51b are arranged side by side as shown in FIG. 4(a). The output terminal 51a is arranged in the center of the core unit 4 in the longitudinal direction and extends outward from the first resin body 3A (see FIG. 1). The output terminal 51b is provided between the output terminal 51a and the fixed portion 31c of the second resin body 3B.

The two output terminals 51c and 51d of the second resin body 3B extend outward from the side of the transformer 1 opposite to the input terminal 24. The output terminals 51c and 51d are arranged side by side as shown in FIG. 4(b). The output terminal 51 is arranged at the center of the longitudinal direction of the core unit 4 and extends outward from the first resin body 3A (see FIG. 1). The output terminal 51c is provided above the output terminal 51a, and the hole at the tip of the output terminal 51c overlaps with the hole at the tip of the output terminal 51a. The output terminal 51d is provided between the output terminal 51c and the fixed part 31b of the first resin body 3A. When the transformer 1 provided with the four output terminals 51a, 51b, 51c, and 51d is viewed from above, it appears to have three output terminals 51, as shown in FIG. 5.

The fixing portion 31 fixes the transformer 1 to the object on which it is to be installed. That is, the bottom surface of the fixing portion 31 abuts against the object on which it is to be installed. The fixing portion 31 is provided with a cylindrical collar 311. The outer periphery of the collar 311 is covered with resin and is molded integrally with the first resin body 3A or the second resin body 3B. The transformer is fixed to the object on which it is to be installed by inserting a fastener such as a bolt into the collar 311 and fastening it. In this embodiment, a total of four fixing portions 31 are provided, and the first resin body 3A and the second resin body 3B each have two fixing portions 31. The two fixing portions of the first resin body 3A are designated 31a and 31b, and the two fixing portions of the second resin body 3B are designated 31c and 31d.

The fixing parts 31a, 31b, 31c, and 31d extend toward the outside of the circular first resin body 3A. As shown by the dashed line in FIG. 4(a), the extension line of the fixing parts 31a and 31b does not pass through the center C of the first resin body 3A. Also, as shown by the dashed line in FIG. 4(b), the extension line of the fixing parts 31c and 31d does not pass through the center C of the second resin body 3B.

As shown in FIG. 4(a), the fixed parts 31a and 31b are arranged symmetrically with respect to the center C of the circular first resin body 3A. That is, the fixed part 31b is arranged at a position rotated 180 degrees from the position of the fixed part 31a. The fixed part 31a is arranged close to the outer leg 43 of the E-shaped core 4B on the side where the input terminal 24 is arranged.

The fixed portion 31b is located close to the outer leg 42 of the E-shaped core 4B on the side where the output terminals 51a, 51b of the busbar 5 are located. The fixed portion 31b is located close to the output terminal 51a of the busbar 5 with a space (dotted circle in FIG. 4(a) in between). The size of this space refers to the size of the output terminal 51d of the busbar 5 so that it can protrude between the fixed portion 31b and the output terminal 51a. The output terminal 51d is located in this space.

The fixed parts 31c and 31d of the second resin body 3B are arranged symmetrically with respect to the center C of the circular second resin body 3B, as shown in FIG. 4(b). That is, the fixed part 31d is arranged at a position rotated 180 degrees from the position of the fixed part 31c. The fixed part 31c is arranged close to the outer leg 42 of the E-shaped core 4B on the side where the input terminal 24 is arranged.

The fixed portion 31d is located close to the outer leg 43 of the E-shaped core 4B on the side where the output terminals 51c, 51d of the busbar 5 are located. The fixed portion 31c is located close to the output terminal 51c of the busbar 5 with a space (dotted circle in FIG. 4(b)) between them. The size of this space refers to the size of the output terminal 51b of the busbar 5 that allows it to protrude between the fixed portion 31c and the output terminal 51c. The output terminal 51b is located in this space.

In this way, the four fixing parts 31a, 31b, 31c, and 31d are provided at the four corners of the transformer 1. That is, when the center points of the collars of the fixing parts 31a, 31b, 31c, and 31d are connected by straight lines as vertices, the shape is roughly rectangular in plan view. In other words, the fixing parts 31a and 31b of the first resin body 3A or the fixing parts 31c and 31d of the second resin body 3B are provided at positions diagonal to each vertex.

The bottom surfaces of the fixing parts 31c and 31d are horizontal to the bottom surfaces of the fixing parts 31a and 31b and the installation surface. Therefore, the fixing parts 31c and 31d of the second resin body 3B arranged above the first resin body 3A extend downward along the wall part 35 of the second resin body 3B, that is, toward the first resin body 3A, and their tips extend outward.

The core unit 4 is made of a magnetic material, and may be, for example, a powder magnetic core, a ferrite core, or a laminated steel plate. In this embodiment, a ferrite core is used.

The core unit 4 is composed of a pair of E-shaped cores 4A and 4B. The E-shaped cores 4A and 4B are the same shape and size. The E-shaped cores 4A and 4B are roughly E-shaped, with a cylindrical center leg 41, a pair of outer legs 42 and 43 arranged to sandwich the center leg 41, and a yoke portion 44 connecting the center leg 41 and the pair of outer legs 42 and 43.

The E-shaped core 4B is placed opposite the installation surface of the object on which the transformer 1 is to be installed, and the E-shaped core 4A is placed on the upper surface of the E-shaped core 4B and joined. Specifically, the core unit 4 forms a closed magnetic circuit by facing the ends of the middle leg 41 and the pair of outer legs 42, 43 of the E-shaped cores 4A and 4B, and joining the middle leg 41 and the pair of outer legs 42, 43 with an adhesive or the like.

The middle leg 41 is inserted into the hole 23 of the insulating bobbin 21, the hole 32 of the first resin body 3A, and the hole 36 of the second resin body 3B. That is, the primary coil unit 2 and the secondary coil unit 3 are provided around the middle leg 41. The core unit 4 electromagnetically couples the electric wire 22 of the primary coil unit 2 and the bus bar 5 of the secondary coil unit 3.

The core unit 4 is wrapped around its outer periphery with tape 6, which secures each component so that it does not come apart. The contact surfaces of each component, such as the primary coil unit 2 and secondary coil unit 3, and the first resin body 3A and second resin body 3B, are fixed with adhesive.

(Action)
Next, the manner in which stress is applied when the transformer is fixed to an installation object will be described with reference to the drawings. Fig. 6 is a diagram showing the state of stress applied to the core of a transformer fixed by a leaf spring as in the conventional case. Fig. 7 is a diagram showing the state of stress applied to the core when the transformer of this embodiment is fixed.

As shown in FIG. 6, a conventional transformer is fixed by pressing down from the top of the E-shaped core 100A with a leaf spring. There is a space between the center leg 101 and the outer legs 102 and 103 of the E-shaped core 100A. And because the leaf spring presses down from the top of the E-shaped core 100A, the yoke part of the E-shaped core 100A, which forms the top of this space, is pressed down and bent. Therefore, stress is concentrated at the corners of the yoke part, and as shown in FIG. 6, there is a risk of cracks occurring at the corners of the yoke part of the E-shaped core 100A. In particular, when the transformer is installed in an environment with severe vibration conditions, it is necessary to press down more firmly with the leaf spring, which makes the E-shaped core 100A more likely to crack.

However, since the transformer 1 of this embodiment has fixing parts 31a, 31b, 31c, and 31d that are installed on the installation object, as shown in FIG. 7, the upper surface of the space is not pressed, and cracks can be prevented from occurring in the E-shaped core 4A. Also, although stress acts on the lower surface of the space, the yoke part 44 of the E-shaped core 4B is placed on the installation object. Therefore, instead of the stress being received by the space as in conventional transformers, the stress can be received by the yoke part 44 of the E-shaped core 4B, and the yoke part 44 does not bend. This makes it possible to prevent cracks from occurring in the E-shaped core 4B.

In addition, in this embodiment, not only the first resin body 3A but also the second resin body 3B has fixing portions 31c and 31d. Therefore, the primary coil unit 2 housed in the second resin body 3B is pressed by the second resin body 3B and is fixed more firmly.

Furthermore, the fixing parts 31a, 31b of the first resin body 3A and the fixing parts 31c, 31d of the second resin body 3B are arranged symmetrically with respect to the center C of each resin body 3A, 3B. Therefore, the resonant frequency can be increased compared to when the fixing parts 31a, 31b and the fixing parts 31c, 31d are arranged side by side on one side, and the transformer can be fixed more firmly.

(effect)
As described above, the transformer 1 of this embodiment includes the primary coil unit 2, the secondary coil unit 3 having the busbar 5 and accommodating the primary coil unit 2 therein, and the core unit 4 formed around the secondary coil unit 3. The secondary coil unit 3 is configured of a first resin body 3A and a second resin body 3B, and the first resin body 3A and the second resin body 3b each have a fixing portion 31 for fixing the transformer 1 to an object to which it is to be installed.

As a result, the transformer 1 can be fixed by the fixing portion 31 of the first resin body 3A and the second resin body 3B. In other words, it is no longer necessary to fix the transformer 1 to the installation object by pressing the top surface of the transformer 1 with a leaf spring, as in the conventional method. Therefore, no stress is applied to the E-shaped core 4A, and it is possible to prevent cracks from occurring in the core.

Furthermore, the first resin body 3A and the second resin body 3B each have a fixing portion 31, and the primary coil unit 2 is housed by being sandwiched between the first resin body 3A and the second resin body 3B. Therefore, when a bolt or the like is inserted into the fixing portions 31c, 31d of the second fixing portion 3B and screwed, the primary coil unit 2 is pressed toward the installation surface by the second resin body 3B. Therefore, the primary coil unit 2 is fixed more firmly, and the noise of the transformer 1 can be suppressed even under environments with severe vibration conditions.

The first resin body 3A and the second resin body 3B are molded integrally with the busbar 5 together with the fixing portion 31. This allows the fixing portion 31 and the busbar 5 to be fixed more firmly, improving the strength of the transformer 1 and enabling it to be made smaller. In addition, the process of fixing the busbar 5 can be omitted, improving productivity.

The first resin body 3A has an integrally molded fixed portion 31b and an output terminal 51a of the busbar 5 arranged in close proximity with a space between them. The second resin body 3B has an integrally molded fixed portion 31c and an output terminal 51c of the busbar 5 arranged in close proximity with a space between them. The size of this space is large enough to allow the output terminal 51b or 51d of the busbar 5 to protrude outward.

By providing a space between output terminal 51a and fixed portion 31b of busbar 5, and between output terminal 51c and fixed portion 31c of busbar 5, a mold can be inserted into the space during integral molding, and fixed portion 31 and busbar 5 can be integrally molded. Output terminals 51b and 51d are also arranged from the space. In this way, by arranging output terminals 51b and 51d in the space created by inserting a mold during integral molding, the space can be effectively utilized without dead space, and transformer 1 can be made smaller.

The first resin body 3A and the second resin body 3B are roughly circular in plan view, and two fixing parts 31 are provided on each of the first resin body 3A and the second resin body 3B. The fixing parts 31a, 31b provided on the first resin body 3A and the fixing parts 31c, 31d provided on the second resin body 3B are arranged symmetrically with respect to the center of the resin body, and when each fixing part is connected by a straight line in plan view, it has a roughly rectangular shape.

In this way, the four fixing parts 31a, 31b, 31c, and 31d are arranged at the four corners of the transformer 1, and further, the fixing parts 31a, 31b, 31c, and 31d of the first resin body 3A and the second resin body 3B are arranged diagonally. In other words, the first resin body 3A or the second resin body 3B does not fix only one side of the transformer 1. Therefore, the transformer 1 can be fixed more firmly, and noise generation can be suppressed even in environments with severe vibration conditions.

The second resin body 3B has a top cover 34 and a wall portion 35 extending from the edge of the top cover 34, and is disposed above the first resin body 3A, and the fixing portions 31c, 31d of the second resin body 3B extend along the wall portion 35. If the wall portion 35 were provided on the first resin body 3A, the height direction of the first resin body 3A would increase. As a result, the mold for molding the first resin body 3A would also become larger, increasing manufacturing costs.

On the other hand, as in this embodiment, the fixing parts 31c, 31d of the second resin body 3B arranged above the first resin body 3A need to extend to the installation surface. Therefore, even if the wall part 35 is provided in the second resin body 3B, the wall part 35 can be molded within the planned space of the mold, making effective use of the space and suppressing increases in manufacturing costs. In addition, since the fixing parts 31c, 31d extend downward along the wall part 35, the strength of the fixing parts 31c, 31d is improved compared to when they are provided alone without the wall part 35.

The E-shaped cores 4A and 4B are ferrite cores. Ferrite cores have low strength and are brittle. Therefore, if the transformer is fixed with a leaf spring as in the past, there is a high possibility that the pressure of the leaf spring will cause cracks in the ferrite core. Therefore, as in the transformer 1 of this embodiment, the first resin body 3A and the second resin body 3B have a fixing portion 31, so that even if ferrite cores are used for the E-shaped cores 4A and 4B, cracks can be prevented from occurring.

Furthermore, by arranging the fixing parts 31a, 31b so that their extension lines in the extension direction do not pass through the center C of the first resin body 3A, and the fixing parts 31c, 31d so that their extension lines in the extension direction do not pass through the center C of the second resin body 3B, the positions of the fixing parts 31a, 31b, 31c, 31d can be adjusted and they can be arranged near the core unit 4. To explain in more detail, when the extension lines of the fixing parts in the extension direction pass through the centers of the respective resin bodies, the adjustment of the positions of the fixing parts is in one direction in the extension direction of the fixing parts. On the other hand, as in this embodiment, if the extension line of the extension direction of the fixing parts 31a, 31b, 31c, and 31d is arranged so as not to pass through the center C of the first resin body 3A or the second resin body 3B, the positions of the fixing parts 31a, 31b, 31c, and 31d can be adjusted in other directions besides the extension direction, so that the fixing parts 31a, 31b, 31c, and 31d can be arranged in a position close to the core unit 4 without interfering with the bus bar 5, etc. Therefore, the fixing strength can be improved while increasing the degree of freedom of the transformer shape.

In addition, by arranging the fixing parts 31a and 31b so that their extension lines do not pass through the center C of the first resin body 3A, and the fixing parts 31c and 31d so that their extension lines do not pass through the center C of the second resin body 3B, it is possible to suppress an increase in the resonance point even when the vibration frequency is increased, resulting in a structure that is less prone to resonance.

Other Embodiments
In this specification, an embodiment of the present invention has been described, but this embodiment is presented as an example and is not intended to limit the scope of the invention. The above-mentioned embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. The embodiment and its modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and gist of the invention.

In this embodiment, the first resin body 3A and the second resin body 3B are molded integrally with the fixing portion 31 and the busbar, but the busbar 5 does not have to be molded integrally. In this case, the pair of busbars 5 are covered with insulating bobbins, and one busbar 5 is provided between the first resin body 3A and the primary coil unit 2, and the other busbar 5 is provided between the second resin body 3B and the primary coil unit 2.

The number and positions of the fixing parts 31 provided on the first resin body 3A and the second resin body 3B are not limited to the configuration of the embodiment. For example, as shown in FIG. 8(a), the number of fixing parts 31 provided on the first resin body 3A and the second resin body 3B may each be one. In this case, it is preferable that the fixing parts 31 provided on the first resin body 3A and the fixing parts 31 provided on the second resin body 3B are arranged in symmetrical positions with respect to the center.

Even if the first resin body 3A and the second resin body 3B each have two fixing parts 31, the fixing parts of each resin body do not have to be arranged symmetrically about the center as in this embodiment. For example, they may be provided on only one side as shown in FIG. 8(b).

Furthermore, in the first resin body and the second resin body in which the bus bar 5 is not integrally molded, as shown in FIG. 8(c), the output terminal 51d of the bus bar and the fixing portion 31 of the second resin body 3B may be arranged without providing a space between them. By molding the bus bar 5 as a separate body, the output terminal 51d of the bus bar 5 does not interfere with the second resin body 3B when molding it, preventing the mold from being inserted. This increases the degree of freedom in the arrangement position of the fixing portion 31.

The extensions of the fixing parts 31a and 31b do not pass through the center C of the first resin body 3A, and the extensions of the fixing parts 31c and 31d do not pass through the center C of the second resin body 3B (see FIG. 4). However, as shown in FIG. 9(a), the extensions of the fixing parts 31a and 31b may pass through the center C of the first resin body 3A. Also, as shown in FIG. 9(b), the extensions of the fixing parts 31c and 31d may pass through the center C of the first resin body 3B. Even if the fixing parts 31a, 31b, 31c, and 31d are arranged in this way, the resonant frequency can be increased as in the embodiment, and the transformer 1 can be firmly fixed while preventing damage to the core.

REFERENCE SIGNS LIST 1 Transformer 2 Primary coil unit 21 Insulating bobbin 22 Electric wire 23 Hole 24 Input terminal 3 Secondary coil unit 3A First resin body 3B Second resin body 31 Fixing portion 32 Hole 33 Mounting portion 34 Top cover 35 Wall portion 36 Hole 4 Core unit 4A, 4B E-shaped core 41 Center leg 42, 43 Outer leg 44 Yoke portion 5 Bus bar 51, 51a, 51b, 51c, 51d Output terminal 6 Tape 100 Transformer 100A, 100B E-shaped core 101 Center leg 102, 103 Outer leg

Claims (6)

A primary coil;
a secondary coil having a bus bar and accommodating the primary coil therein;
a core formed around the secondary coil;
Equipped with
The secondary coil is formed of a first resin body and a second resin body,
the first resin body and the second resin body each have a fixing portion for fixing the transformer to an object to be installed;
the second resin body is disposed above the first resin body,
The fixing portion of the second resin body extends toward the first resin body,
a bottom surface of the fixing portion of the second resin body is horizontal to a bottom surface of the fixing portion of the first resin body and abuts against the installation object ;
A transformer characterized by: the first resin body and the second resin body are integrally formed with the bus bar together with the fixing portion;
2. The transformer according to claim 1 . the first resin body or the second resin body has the fixing portion and the bus bar integrally molded therewith disposed with a space therebetween;
3. The transformer according to claim 2 . The first resin body and the second resin body have a generally circular shape in a plan view,
The fixing portion is provided in two pieces for each of the first resin body and the second resin body,
The two fixing portions provided on each resin body are arranged symmetrically with respect to the center of the resin body,
When viewed in a plan view with the fixing portions connected by straight lines, the fixing portion has a generally rectangular shape;
4. The transformer according to claim 1, wherein the second resin body has a top cover and a wall portion extending from an edge of the top cover ,
the fixing portion of the second resin body extends along the wall portion;
5. The transformer according to claim 1, wherein the core is a ferrite core;
6. A transformer according to claim 1, wherein

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