Transformer

Abstract

To prevent localized temperature increases in a transformer core.SOLUTION: In a transformer (1), when a first core (10) and a second core (20) are combined with each other, a center leg portion that is inserted into the coil (30) and an outer peripheral portion that is formed around the coil (30) and sandwiches the center leg portion are formed, and when the transformer (1) is viewed in plan from the first core (10) side, the outer peripheral portion has a heat reduction portion (11) that covers the inner circumference of the coil (30) in at least the first core (10).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a transformer. [Background technology]

[0002] Patent Document 1 discloses an iron core including a first core body having a central leg portion formed in the center, and a second core body that is butted against the first core body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 51-57217 Summary of the Invention [Problem to be solved by the invention]

[0004] When the iron core disclosed in Patent Document 1 is used as a transformer core and the second iron core body is grounded to a cooling surface, the temperature gradient throughout the core becomes large. For example, the temperature of the first iron core body near the part in contact with the central leg core is higher than the surface temperature of the second iron core body grounded to the cooling surface. Considering the magnetic properties of the core and the heat resistance of the components, it is desirable to have a small temperature gradient throughout the core, but due to space restrictions in which the transformer is installed, it can be difficult to cool the entire core so that the temperature is uniform. One aspect of the present disclosure aims to prevent a local temperature rise in a transformer core. [Means for solving the problem]

[0005] In order to solve the above problems, a transformer according to a first aspect of the present disclosure is a transformer including a coil, a first core, and a second core, wherein, when the first core and the second core are combined with each other, a center leg portion that is inserted into the coil and an outer periphery portion that is formed around the coil and sandwiches the center leg portion are formed, and when the transformer is viewed in a plane from the first core side, the outer periphery has a heat reduction portion that covers an inner periphery of the coil, at least in the first core.

[0006] According to the above configuration, by providing the heat reduction portion on the outer periphery, the cross section through which the magnetic flux passes is enlarged, the magnetic flux density is reduced, and the amount of heat generated is reduced, compared to when the heat reduction portion is not provided. Also, the amount of heat dissipation is increased compared to when the heat reduction portion is not provided. Therefore, it is possible to prevent the temperature in the vicinity of the center leg from rising locally.

[0007] In the transformer according to aspect 2 of the present disclosure, when the transformer is viewed in plan from the first core side, the width of the outer circumferential portion other than the heat reduction portion is smaller than the width of the inner circumferential portion of the coil.

[0008] According to the above-described configuration, the width of the outer periphery other than the heat generation reduction portion is made smaller than the inner periphery of the coil, thereby making it possible to reduce material costs.

[0009] In the transformer according to the third aspect of the present disclosure, when the transformer is viewed in plan from the first core side, the heat reduction portion covers the inner periphery of the coil and is also covered by the outer periphery of the coil.

[0010] According to the above configuration, since the heat generation reduction portion is smaller than the outer periphery of the coil, the provision of the heat generation reduction portion does not affect the mounting area of ​​the transformer on the board.

[0011] In the transformer according to the fourth aspect of the present disclosure, when the transformer is viewed in plan from the first core side, the heat reduction portion has a circular shape concentric with the coil or a rectangular shape concentric with the coil.

[0012] According to the above configuration, the heat reduction portion is in the shape of a circle concentric with the coil or a rectangle concentric with the coil, so that the number of areas through which magnetic flux does not pass can be reduced, and material costs can be reduced.

[0013] In the transformer according to a fifth aspect of the present disclosure, the first core is an I core, and the second core is an E core having the center leg portion.

[0014] According to the above configuration, since the first core and the second core are EI cores, the gap tolerance can be reduced more than in the case where they are PQ cores. Effect of the Invention

[0015] According to one aspect of the present disclosure, local temperature rise in the core of the transformer can be prevented. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view illustrating a configuration example of a transformer according to an embodiment of the present disclosure. [Diagram 2] 2 is a schematic side view of a first core and a second core constituting the transformer of FIG. 1. [Diagram 3] 2 is a plan view of the transformer in FIG. 1 as viewed from the first core side. [Figure 4] FIG. 1 is a perspective view illustrating a configuration of a comparative example of a transformer according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An embodiment of the present disclosure will be described in detail below. Fig. 1 is a perspective view showing an example of a configuration of a transformer according to an embodiment of the present disclosure. The transformer 1 shown in Fig. 1 includes a first core 10, a second core 20, and a coil 30. The bottom surface of the second core 20 is disposed on a substrate 40.

[0018] The first core 10 and the second core 20 are formed of a magnetic material. The first core 10 and the second core 20 are, for example, a ferrite core formed from ferrite, or a dust core formed from a powder material by compression molding. In the example shown in Fig. 1, the first core 10 is an I-core formed in an I-shape, and the second core 20 is an E-core formed in an E-shape.

[0019] The coil 30 includes a primary coil and a secondary coil wound around a bobbin. Details of the coil 30, such as the bobbin, input / output terminals, etc., are omitted in Fig. 1. Hereinafter, the X-axis direction, Y-axis direction, and Z-axis direction of the transformer 1 will be defined as shown by the arrows in Fig. 1.

[0020] Fig. 2 is a schematic side view of the first core and the second core constituting the transformer shown in Fig. 1. The second core 20 has a center leg 21 and an outer leg 22. The center leg 21 has, for example, a substantially elliptical cylindrical shape, and is inserted into the coil 30, not shown in Fig. 2.

[0021] The first core 10 and the second core 20 are used in combination. Combining the first core 10 and the second core 20 means that both ends of the outer leg 22 and the center leg 21 of the second core 20 are brought into contact with the bottom surface of the first core 10, or are faced to the bottom surface of the first core 10 with a predetermined gap provided. In a state in which the first core 10 and the second core 20 are combined, the outer leg 22 of the second core 20 forms an outer circumferential portion 50 that covers the periphery of the coil 30 together with the first core 10, as shown in FIG. 1. The outer circumferential portion 50 sandwiches the center leg 21. The center leg 21 and the outer circumferential portion 50 form a substantially closed magnetic path.

[0022] Fig. 3 is a plan view of the transformer shown in Fig. 1 as seen from the first core side. As shown in Fig. 3, the first core 10 has a heat generation reduction portion 11 that is bulged out more than other portions near the portion in contact with the center leg portion 21. In plan view, the heat generation reduction portion 11 has a concentric shape with the coil 30, and its diameter is larger than the width of the inner circumference 31 of the coil 30 and smaller than the width of the outer circumference 32 of the coil 30. In other words, in plan view, the heat generation reduction portion 11 covers the inner circumference 31 of the coil 30 and is covered by the outer circumference 32 of the coil 30.

[0023] In a plan view, the heat generation reduction portion 11 being concentric with the coil 30 means that when the inner circumference 31 and the outer circumference 32 of the coil 30 are substantially circular, the center of the heat generation reduction portion 11 coincides with the inner circumference 31 and the outer circumference 32 of the coil 30. Note that when the inner circumference 31 and the outer circumference 32 of the coil 30 are substantially rectangular or substantially elliptical, the heat generation reduction portion 11 is considered to be concentric with the coil 30 when the center of the heat generation reduction portion 11 coincides with the center of gravity of the substantially rectangular or substantially elliptical shape.

[0024] The width in the Y-axis direction of the outer circumferential portion 50 other than the heat reduction portion 11 is approximately the same as the width in the Y-axis direction of the center leg portion 21. In other words, when the transformer 1 is viewed in plan from the first core 10 side, the width in the Y-axis direction of the outer circumferential portion 50 other than the heat reduction portion 11 is smaller than the width in the Y-axis direction of the inner periphery 31 of the coil 30.

[0025] 4 is a perspective view showing a comparative example of a transformer according to an embodiment of the present disclosure. The transformer 100 shown in FIG. 4 is different from the transformer 1 in that a third core 101 that does not have a heat reduction portion 11 is provided instead of the first core 10.

[0026] In the transformer 100 of the comparative example, the second core 20 and the third core 101 are combined to form a substantially closed magnetic path. In the transformer 100, the magnetic flux density is higher in the vicinity of the center leg 21 of the third core 101 than in other parts, and the vicinity is more likely to generate heat. The second core 20 dissipates heat to the substrate 40, but the third core 101 is more likely to retain heat than the second core 20. Therefore, in the transformer 100, the vicinity of the center leg 21 of the third core 101 is more likely to become locally hot.

[0027] The core of the ferrite molded product has a temperature characteristic in which the energy loss decreases up to a certain temperature and increases after the certain temperature. In the transformer 100 of the comparative example, the analysis confirmed that the temperature at which the energy loss is inflection occurs near the center leg 21 of the third core 101.

[0028] In the transformer 1 according to an embodiment of the present disclosure, the heat generation reduction portion 11 is provided in the vicinity of the center leg 21 of the first core 10. The heat generation reduction portion 11 has a width in the Y-axis direction wider than other portions of the first core 10. Therefore, in the heat generation reduction portion 11, the cross section through which the magnetic flux passes is wider than the vicinity of the center leg 21 of the third core 101, so that the magnetic flux density is smaller, the iron loss is smaller, and the amount of heat generated is smaller. In addition, by providing the heat generation reduction portion 11, the first core 10 has a larger surface area than the third core 101, and the amount of heat dissipation is increased. Therefore, the first core 10 can prevent localized temperature rises compared to the third core 101. As a result, when the first core 10 and the second core 20 are formed using a material having temperature characteristics such as ferrite, the entire core can be designed to fall within a temperature range with small energy loss.

[0029] Another possible method for reducing the magnetic flux density near the center leg 21 of the first core 10 is to increase the width of the center leg 21 in the X-axis and Y-axis directions, but this would require increasing the size of the coil 30 through which the center leg 21 is inserted, which would increase the mounting area of ​​the transformer. In the transformer 1, the magnetic flux density is reduced by providing a heat reduction section 11 that is larger than the inner circumference 31 and smaller than the outer circumference 32 of the coil 30 near the center leg 21 of the first core 10, so there is no need to increase the size of the coil 30 and the impact on the mounting area of ​​the transformer is small.

[0030] The inductance superposition characteristic of the transformer 1 is improved more than that of the transformer 100. In the transformer 1, the first core 10 has the heat reduction portion 11, so that the effective cross-sectional area is larger than that of the third core 101. The gap of the transformer 1 is made wider than that of the transformer 100 in order to adjust the inductance to a targeted value. As a result, the magnetic flux density of the transformer 1 can be made smaller than that of the transformer 100.

[0031] The transformer 1 is easier to position when mounted on a substrate than the transformer 100. The transformer 1 has a heat reduction portion 11 in the first core 10, and therefore has a larger surface area to be attracted to a suction nozzle used when mounting the transformer 1 on a substrate 40 than the transformer 100.

[0032] (Modification) In the above embodiment, the first core 10 is an I core, and the second core 20 is an E core. However, the combination is not limited to the above embodiment, as long as the first core 10 and the second core 20 are combined to form a center leg 21 and an outer circumferential part 50, and a substantially closed magnetic path is formed. For example, the first core 10 may be an E core having a heat reduction part 11 on the outer leg. When the first core 10 is an E core, the second core 20 may be an I core. Also, the first core 10 may be a P core, and the second core may be a Q core. When the first core 10 and the second core 20 are combined with an I core and an E core as in the above embodiment, the tolerance of the gap dimension between the first core 10 and the second core 20 can be made smaller than when the first core 10 and the second core 20 are combined with a P core and a Q core.

[0033] In the above embodiment, the heat reduction portion 11 provided in the first core 10 has a shape concentric with the coil 30, but is not limited thereto. For example, the heat reduction portion 11 may have a rectangular or elliptical shape concentric with the coil 30.

[0034] In the above embodiment, the heat generation reduction portion 11 provided in the first core 10 is smaller than the width of the outer periphery 32 of the coil 30, but is not limited thereto. For example, it is permissible to make the heat generation reduction portion 11 larger than the width of the outer periphery 32 of the coil 30 as long as the transformer 1 mounted on the substrate 40 does not interfere with the surroundings. As long as the mounted transformer 1 does not interfere with the surroundings, a heat dissipation portion through which magnetic flux does not pass may be further provided in the heat generation reduction portion 11. For example, as long as the mounted transformer 1 does not interfere with the surroundings, a heat dissipation protrusion may be provided in the Z-axis direction or the like from the heat generation reduction portion 11.

[0035] In the above embodiment, the first core 10 is provided with the heat generation reduction portion 11, but the heat generation reduction portion 11 may be provided in the outer leg portion 22 of the second core 20 at a position near the middle leg portion 21. In the above embodiment, the second core 20 is disposed on the substrate 40, and heat is dissipated from the second core 20 to the substrate 40. However, in a situation where heat dissipation from the second core 20 to a cooling surface such as the substrate 40 cannot be expected, providing the heat generation reduction portion 11 in the outer leg portion 22 of the second core 20 can prevent the vicinity of the middle leg portion 21 of the outer leg portion 22 from becoming locally hot.

[0036] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0037] 1. Transformer 10 First Core 11 Heat reduction section 20 Second Core 21 Middle leg 30 Coil 31 Inner circumference 32 Circumference 50 Outer periphery

Claims

1. A transformer comprising a coil, a first core and a second core, When the first core and the second core are combined with each other, A center leg portion that is inserted into the coil; an outer circumferential portion formed around the coil and sandwiching the center leg portion; a heat generation reducing portion that covers an inner periphery of the coil and is disposed on at least the first core when the transformer is viewed in a plan view from the first core side.

2. 2. The transformer according to claim 1, wherein, when the transformer is viewed in a plan view from the first core side, a width of the outer circumferential portion other than the heat reduction portion is smaller than a width of an inner circumferential portion of the coil.

3. 2. The transformer according to claim 1, wherein, when the transformer is viewed in plan from the first core side, the heat reduction portion covers an inner periphery of the coil and is also covered by an outer periphery of the coil.

4. 2. The transformer according to claim 1, wherein, when the transformer is viewed in a plan view from the first core side, the heat reduction portion has a circular shape concentric with the coil or a rectangular shape concentric with the coil.

5. the first core is an I core, 2. The transformer according to claim 1, wherein the second core is an E core having the center leg.

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