WO2021227229A1

WO2021227229A1 - Inductor

Info

Publication number: WO2021227229A1
Application number: PCT/CN2020/101134
Authority: WO
Inventors: 刘钧; 冯颖盈; 姚顺; 徐金柱; 张宏伟
Original assignee: 深圳威迈斯新能源股份有限公司
Priority date: 2020-05-09
Filing date: 2020-07-09
Publication date: 2021-11-18
Also published as: CN111430111A

Abstract

Disclosed is an inductor, comprising a magnetic core and a winding, wherein the magnetic core comprises a middle magnetic core and side magnetic cores connected to two sides of the middle magnetic core, and the winding is wound around the middle magnetic core, the middle magnetic core being a ferrite core, and the side magnetic cores being iron powder cores. In the present invention, it is ensured that a magnetic core has a good magnetic conductivity, and the problem in traditional technology of an excessively high local temperature resulting from a magnetic loss being concentrated at an air gap of a magnetic core and a line of magnetic force cutting a heat-dissipation metal water channel is solved.

Description

An inductance

Technical field

The present invention relates to the technical field of magnetic elements, in particular to an inductor.

Background technique

The inductance used in the resonant network of the electric energy transmission system of the on-board charger is a resonant inductor, and the core material of the resonant inductor is mostly ferrite. In order to prevent magnetic saturation, an air gap is usually left on the magnetic core. Therefore, the magnetic loss of the resonant inductor is concentrated in the air gap, which causes the local temperature of the resonant inductor to be too high, which is not conducive to the heat dissipation of the entire resonant inductor, and the magnetic lines of force generated by the air gap will cut the water channel and generate heat. In addition, the resonant inductor is usually filled with heat dissipation glue in the cavity for heat conduction, which will not only increase the volume of the resonant inductor and reduce the power density, which is not conducive to integration and miniaturization, and its thermal conductivity is not good, which is further detrimental to the heat dissipation of the entire resonant inductor. .

Therefore, designing an inductor that can solve the heat dissipation problem in the above-mentioned related technologies is a technical problem to be solved urgently in the industry.

Summary of the invention

In order to solve the problem that the inductor is not easy to dissipate heat in the prior art, the present invention provides an inductor with good heat dissipation effect.

An inductor includes a magnetic core and a winding. The magnetic core includes a middle magnetic core and side magnetic cores connected to both sides of the middle magnetic core. The winding is wound on the middle magnetic core. The core is a ferrite core, and the side magnetic core is an iron powder core.

In an embodiment, the middle magnetic core is in the shape of an I-shape, and includes a middle column for winding the windings, and upper and lower columns connected to both ends of the middle column; the side magnetic cores are in a straight shape, The side magnetic cores are respectively connected to two ends of the upper side pillar and the lower side pillar.

In one embodiment, the middle magnetic core is I-shaped, and the side magnetic cores are C-shaped.

In an embodiment, the lengths of the middle magnetic core and the side magnetic cores are the same, and the heights of the middle magnetic core, the side magnetic cores, and the windings are the same.

In an embodiment, it further includes a substrate, which is attached and mounted on the bottom of the magnetic core.

In an embodiment, the length of the substrate is greater than the length of the bottom of the magnetic core, and the width of the substrate is greater than the width of the bottom of the magnetic core.

In an embodiment, the substrate is a ceramic substrate.

In an embodiment, the ceramic substrate is pasted on the bottom of the magnetic core through a thermally conductive glue.

In one embodiment, an epoxy board is further included, which is attached and installed on the top of the magnetic core.

In one embodiment, the inductor is a resonant inductor.

Compared with the prior art, the present invention has at least the following advantages:

First of all, by setting the core as the middle core and the side core, the middle core as the ferrite core, and the side core as the iron powder core, to ensure that the middle core has good magnetic permeability In the case of, the side magnetic core is not provided with an air gap opened to prevent magnetic saturation, thereby solving the problem of excessive local temperature caused by the concentration of magnetic loss in the air gap and the cutting of the metal water channel by the magnetic line of force.

Secondly, by arranging a ceramic substrate at the bottom of the magnetic core and windings, the magnetic core and windings dissipate heat through the ceramic substrate, which further improves the heat dissipation effect of the magnetic core and windings.

Description of the drawings

FIG. 1 is a schematic diagram of an exploded structure of an inductor in an embodiment of the present invention;

Fig. 2 is a semi-assembled schematic diagram of the ceramic substrate of the inductor in Fig. 1 bonded to the magnetic core;

Fig. 3 is a schematic diagram of the complete assembly structure of the inductor in Fig. 1;

4 is a schematic diagram of an exploded structure of an inductor in another embodiment of the present invention;

FIG. 5 is a semi-assembled schematic diagram of the ceramic substrate of the inductor in FIG. 4 and the magnetic core;

6 is a schematic diagram of the simulated magnetic field line distribution of the inductor magnetic force in an embodiment of the present invention;

FIG. 7 is a schematic diagram showing the equipotential magnetic field lines of a ferrite core with an air gap in the prior art;

FIG. 8 is a schematic diagram of the equipotential magnetic field lines with two air gaps in the ferrite core in the prior art;

Fig. 9 is a schematic diagram showing the equipotential magnetic lines of force with three air gaps in the ferrite core in the prior art;

Fig. 10 is a schematic diagram of equipotential magnetic field lines in an embodiment of the present invention.

Description of Reference Signs: 10, winding; 20, side magnetic core; 201, left side magnetic core; 202, right side magnetic core; 30, middle magnetic core; 301, upper side column; 302, center column 303, lower side column; 40, substrate; 50, epoxy board.

Detailed ways

In order to further illustrate the principle and structure of the present invention, the preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

It should be noted that although the present invention can be easily expressed in different forms of embodiments, what is shown in the drawings and will be described in detail in this specification is only some of the specific embodiments, and it is understood that this specification It should be regarded as an exemplary description of the principle of the present invention, and is not intended to limit the present invention to what is described herein.

Therefore, a feature pointed out in this specification will be used to describe one of the features of an embodiment of the present invention, rather than implying that each embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although certain features can be combined together to illustrate possible system designs, these features can also be used in other unspecified combinations. Thus, unless otherwise stated, the illustrated combinations are not intended to be limiting.

Referring to FIGS. 1-3, the present invention provides an inductor, which may be a resonant inductor, and is applied to a resonant network of a power transmission system of a vehicle-mounted charger. The inductor includes a magnetic core, a winding 10, a substrate 40 and an epoxy board 50. The magnetic core includes a middle magnetic core 30 and a side magnetic core 20, the middle magnetic core 30 is a ferrite core, and the side magnetic core 20 is an iron powder core. The side magnetic cores 20 are located on both sides of the middle magnetic core 30, and the winding 10 is wound on the middle magnetic core 30. The magnetic cores in the traditional technology are mostly ferrite cores. In order to prevent magnetic saturation, an air gap is left on the magnetic core. Therefore, during the energization process, the magnetic loss of the inductor will be concentrated around the air gap, which will cause eddy currents in the windings around the air gap, which in turn causes the temperature rise of the magnetic core around the air gap to increase, and the local temperature is too high, which is not conducive to the entire inductor. Heat dissipation. In addition, the magnetic field lines generated by the air gap will cut the metal water channel used for heat dissipation, and will also cause the winding to generate heat. In the present invention, the middle magnetic core 30 is set as a ferrite core, and the side magnetic core 20 is set as two different parts of an iron powder core. The middle ferrite core ensures good magnetic permeability, and the side iron core The powder core avoids the problem of excessive local temperature caused by the concentration of the magnetic circuit due to the opening of the air gap on the magnetic core, which is beneficial to the faster heat dissipation of the inductor. Detailed descriptions are given below.

Please refer to FIG. 1, the middle magnetic core 30 has an I-shaped shape, and includes a center pillar 302, an upper side pillar 301, and a lower side pillar 303. The upper side pillar 301 and the lower side pillar 303 have the same shape and size. One end of the center pillar 302 is connected to the middle of the upper side pillar 301, the other end of the center pillar 302 is connected to the middle of the lower side pillar 303, and the upper side pillar 301 and the lower side pillar 303 are located at both ends of the center pillar 302 symmetrically. The height of the center pillar 302 is smaller than the height of the upper side pillar 301 and the lower side pillar 303.

Please refer to FIG. 2, the winding 10 is wound on the center pillar 302, and the height of the winding 10 is flush with the height of the upper side pillar 301 and the lower side pillar 303.

Please refer to FIG. 1-2, the side magnetic core 20 is in a straight shape, that is, a rectangular parallelepiped shape. There are two side magnetic cores 20, and the two side magnetic cores 20 have the same shape and size. The two side magnetic cores 20 are completely symmetrically connected to the left and right sides of the middle magnetic core 30. The side magnetic cores 20 are symmetrically connected to the middle magnetic core 30, which is beneficial to uniform heat dissipation of the inductor. Specifically, the side magnetic core 201 on the left side is connected to the left side of the upper side column 301 and the left side of the lower side column 303 by adhesive, and the side magnetic core 202 on the right side is connected to the upper side column 301 and the lower side column 303 by adhesive. To the right. The length of the side magnetic core 20 is equal to the length of the middle magnetic core 30, and the height of the side magnetic core 20 is equal to the height of the upper leg 301, the lower leg 303, and the winding 10, so that the side magnetic core 20 is the same as the upper leg 301, The joints of the lower side pillars 303 are completely connected to form a complete magnetic circuit to avoid magnetic leakage. The side magnetic core 20 adopts an iron powder core, which has the characteristic of evenly distributing air gaps. Therefore, it is different from the traditional technology where a concentrated air gap for preventing magnetic saturation needs to be specially opened on the ferrite core.

Referring to FIG. 6, the air gaps evenly distributed on the iron powder core are very fine and spread over the entire iron powder core, so that the magnetic lines of force generated by the winding 10 can be evenly distributed on the side magnetic cores 20, so that the heat generated by the winding 10 It is evenly distributed on the side magnetic cores 20, thereby avoiding excessive local temperature on the inductor, which is beneficial for heat dissipation.

Please refer to FIGS. 4-5. In another embodiment, the middle magnetic core 30 is I-shaped, and the side magnetic cores 20 are C-shaped or [-shaped.

Please refer to Figures 1-4. The substrate 40 is a thermally conductive plate with good thermal conductivity. The substrate 40 is pasted on the bottom of the magnetic core through a thermally conductive glue. The thermally conductive glue serves to stick and fix the substrate 40. The thermal conductivity of the thermally conductive glue is lower than that of the ceramic substrate. 40. Therefore, the thickness of the thermal conductive adhesive should not exceed 2mm. Specifically, the substrate 40 is attached to the bottom surface of the upper side pillar 301, the lower side pillar 303, the side magnetic core 20 and the winding 10. The length of the substrate 40 is greater than the length of the bottom of the magnetic core, and the width of the substrate 40 is greater than the width of the bottom of the magnetic core. Setting the area of the substrate 40 slightly larger than the area of the magnetic core is beneficial to the heat dissipation of the magnetic core.

In a preferred embodiment, the substrate 40 is a ceramic substrate 40. The ceramic substrate 40 has good thermal conductivity and is easy to dissipate heat. In addition, the electromagnetic wire can be isolated, so that when the inductor is applied to the use environment of the metal water channel with heat dissipation or when the inductor is applied to the use environment of the motor, the ceramic substrate 40 can isolate the electromagnetic wire generated by the inductance and cut the heat dissipation metal water channel or electricity. The case, to avoid generating more heat. In a more preferred embodiment, the ceramic substrate 40 is an alumina (AL2O3) ceramic substrate 40.

Please refer to Figures 1, 3-4, the epoxy board 50 is attached to the top of the magnetic core. Specifically, the epoxy board 50 is located on the side magnetic core 20, the upper side pillar 301, the lower side pillar 303 and the winding 10. The epoxy board 50 is used to install and weld the inductor in the external environment, and is used to isolate electromagnetic, voltage, and current, and play the role of insulation safety. Two wire holes are provided on the epoxy board 50 for drawing out the winding wires at both ends of the winding.

The beneficial effects of using iron powder cores as side magnetic cores are illustrated below with examples.

All inductors in the traditional technology use ferrite as the magnetic core, and an air gap needs to be left on the ferrite. Assume that the side magnetic core 20 is provided with two air gaps on one side and 4 air gaps on both sides. Assuming that the magnetic loss of the inductor is A, the magnetic loss of each air gap is close to A/4. Assume that the area of one side of the side core 20 is S, the area of the two sides is 2S, the area at the air gap is s, and S/s>10. The heat loss per unit area at the air gap is A/4s. In the embodiment of the present invention, the side magnetic core 20 adopts an iron powder core. Under the same condition that the magnetic loss is A, and the heat is dissipated through the entire side magnetic core 20, the heat loss per unit area is A/2S. That is, local heat loss can be reduced by at least 5 times.

Please refer to Figs. 7-9. Fig. 7-9 is a schematic diagram of the equipotential simulation effect of the magnetic field lines with 1-3 air gaps on one side of the ferrite core 20 in the traditional technology, and the total air gap width remains unchanged. That is, the width of one air gap on one side is 1.5mm. There are 2 air gaps on one side, and the width of each air gap is 0.75mm. There are 3 air gaps on one side, and the width of each air gap is 0.5mm. The simulation result is its magnetic field line diagram, the darker the color indicates the stronger the magnetic field line. From the simulation results, the diffused magnetic flux around the air gap is obviously high, resulting in high local temperature around the air gap.

Please refer to FIG. 10, which is a schematic diagram of equipotential magnetic field lines using iron powder cores in an embodiment of the present invention. It can be seen from the simulation result that the magnetic lines of force are evenly distributed on the entire side magnetic core 20. That is, under the same magnetic loss conditions, the local magnetic field lines of the iron powder core are much smaller than that of the open air gap ferrite core. Reflected in the temperature rise, the local temperature rise of the iron powder core is significantly lower than that of the ferrite core.

The beneficial effects of laminating the ceramic substrate 40 on the bottom of the magnetic core will be described below with examples.

Please refer to Figures 2-3 and 5, the bottom of the inductor is provided with a ceramic substrate 40. The ceramic substrate 40 is very flat and can fit well on the heat dissipation metal water channel. The ceramic substrate 40 is directly attached to the heat-dissipating metal water channel so that the thermal resistance is very small, and the heat of the inductor can be effectively dissipated. The ceramic substrate 40 is aluminum oxide (AL2O3) ceramic, and its thermal conductivity is generally 25-30 W/m.K. Traditional technology uses thermally conductive adhesives for heat transfer. Generally, the thermal conductivity of thermally conductive adhesives with better thermal conductivity is 1 to 2W/m.K. Therefore, in comparison, the ceramic substrate 40 can better dissipate the heat of the inductor.

The relationship between thermal conductivity and thermal resistance is shown in the following formula:

In the above formula: R—The thermal resistance of the heat conductor, the unit is: °C/W;

d—The thickness of the heat conductor, in mm;

S—The heat conduction area of the heat conductor, the unit is: ㎡;

K—The thermal conductivity of the heat conductor, in W/m.K.

In a comparative embodiment, the length * width of the ceramic substrate 40 is: 50 mm*30 mm, the area S = 0.0015 square meters, and the area of the thermal conductive glue is the same as the area of the ceramic substrate 40. The thickness of the ceramic substrate 40 is d=1 mm, the thickness of the heat-dissipating glue is d=2 mm, the thermal conductivity of the ceramic substrate 40 is K=30 W/m.K, and the thermal conductivity of the thermal-conducting glue is 2 W/m.K. According to the above formula, the thermal resistance of the ceramic substrate 40 and the thermal conductive adhesive can be calculated as follows:

R ₁ -the thermal resistance of the ceramic substrate 40;

R ₂ —The thermal resistance of the thermally conductive adhesive.

The core loss of the resonant inductor is 40W, and the heat dissipation temperature difference between the ceramic substrate 40 and the thermal conductive adhesive is calculated according to the following formula:

T ₁ ＝P×R＝40×0.022＝0.88℃

T ₂ =P×R=40×0.67=26.8℃

T ₁ —The heat dissipation temperature difference of the ceramic substrate 40;

T ₂ —The heat dissipation temperature difference of the thermal conductive adhesive.

It can be seen that, in this embodiment, the use of the ceramic substrate 40 to dissipate heat can reduce the temperature rise on the magnetic core by 26.8-0.88=25.92° C. compared with the traditional use of thermally conductive glue for heat dissipation.

First, by setting the magnetic cores as the middle magnetic core 30 and the side magnetic cores 20, the middle magnetic core 30 as the ferrite core, and the side magnetic cores 20 as the iron powder core, it is ensured that the middle magnetic core 30 has In the case of good magnetic permeability, the side magnetic core 20 is not provided with an air gap to prevent magnetic saturation, thereby solving the problem of excessive local temperature caused by the magnetic loss concentrated in the air gap and the magnetic line of force cutting the metal water channel. problem.

Secondly, by providing a ceramic substrate 40 at the bottom of the magnetic core and the winding 10, the magnetic core and the winding 10 dissipate heat through the ceramic substrate 40, which further improves the heat dissipation effect of the magnetic core and the winding 10.

The above are only preferred and feasible implementations of the present invention and do not limit the protection scope of the present invention. The terms used are illustrative and exemplary rather than restrictive terms. Since the invention can be implemented in various forms without departing from the spirit or essence of the invention, it should be understood that the above-mentioned embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all changes and modifications falling within the scope of the claims or their equivalents shall be covered by the appended claims.

Claims

An inductor, comprising a magnetic core and a winding, the magnetic core comprising a middle magnetic core and side magnetic cores connected to both sides of the middle magnetic core, the winding is wound on the middle magnetic core, and the characteristic is , The middle magnetic core is a ferrite core, and the side magnetic core is an iron powder core.
The inductor according to claim 1, wherein the middle magnetic core is in an I-shape, and includes a middle column for winding the winding, and upper and lower columns connected to both ends of the middle column; the side The side magnetic cores are in-line, and the side magnetic cores are respectively connected to both ends of the upper side column and the lower side column.
The inductor of claim 1, wherein the middle magnetic core is in an I shape, and the side magnetic core is in a C shape.
The inductor of claim 2 or 3, wherein the middle magnetic core and the side magnetic core have the same length, and the middle magnetic core, the side magnetic core, and the winding have the same height .
The inductor according to claim 4, further comprising a substrate, which is attached to the bottom of the magnetic core.
The inductor of claim 5, wherein the length of the substrate is greater than the length of the bottom of the magnetic core, and the width of the substrate is greater than the width of the bottom of the magnetic core.
The inductor according to claim 6, wherein the substrate is a ceramic substrate.
8. The inductor of claim 7, wherein the ceramic substrate is attached to the bottom of the magnetic core through a thermally conductive adhesive.
5. The inductor of claim 1, further comprising an epoxy board, which is attached to the top of the magnetic core.
The inductor of claim 1, wherein the inductor is a resonant inductor.