JP2005150413A - Core for power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a core for power source that can reduce eddy currents even when the core is not constituted in a laminated structure. <P>SOLUTION: The core 1 for power source is formed in an E-shape, and characterized in that a plurality of slit-shaped grooves 4a and 4b are formed on the periphery of its middle leg 3 in the lengthwise direction. The slit-shaped grooves 4a and 4b, which are formed in an even number, are formed in slitted shapes at the positions at which the grooves 4a and 4b become symmetrical about the lateral center line 5 of the end face of the core 1 when the grooves 4a and 4b are viewed from the end face of the middle leg 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an E-shaped power supply core used for a switching power supply or the like.

  Conventionally, as this type of power supply core, for example, there is one shown in FIG. In FIG. 7, the power source core 100 has an E shape when viewed from the side, and integrally includes a core outer foot 101 on both sides and a core middle foot 102 therebetween, and the core middle foot 102 has a cylindrical shape. The outer leg 101 has a cylindrical surface on the inner surface side.

The E-shaped power supply core 100 is assembled in such a way that two cores are attached as a set, and a coil wound around a bobbin is attached to the core middle leg 102 and the end faces of the core legs are brought together. The power source core 100 is manufactured by a sintering method after molding a core material.
JP-A-7-302720

  However, in such a conventional power supply core, as shown in FIG. 8A, when the coil 103 having the number of turns N1 is attached to the core middle leg 102 and the voltage V is applied, the core middle leg 102 A voltage Vc of (1 / N1) is generated along the outer periphery of the eddy current and an eddy current i flows. That is, assuming that the resistance value on the circumference of the core middle leg 102 is R, an eddy current of i = Vc / R flows on the outer circumference of the core middle leg 102, resulting in a core loss.

  FIG. 8B is an equivalent circuit when the coil 103 is attached to the power source core 100 and the voltage V is applied. The core middle leg 102 is equivalent to the coil 104 having one turn with respect to the coil 103. The voltage Vc = V · (1 / N1) generated in the equivalent winding 104 is applied to the electric resistance R of the core, and the eddy current i flows to cause loss.

  Further, in the case of the transformer structure, since the magnetic flux generated by the leakage inductance in addition to the eddy current and the core are linked and a transient large eddy current flows, the loss further increases. In order to prevent such eddy current, the core may have a laminated structure such as a silicon steel plate. However, since the power source core of the sintering method is easily broken, it is difficult to adopt the laminated structure. Further, when a laminated structure such as a silicon steel plate is adopted for the power source core, there is a problem that the assembly of the transformer becomes complicated and it takes time to manufacture.

An object of the present invention is to provide a power supply core that can reduce eddy current without using a laminated structure.

In order to achieve this object, the present invention is configured as follows. The present invention is a power supply core having an E shape, and is characterized in that one or a plurality of slit grooves are formed in the longitudinal direction on the outer periphery of the core middle leg. Here, an even number of slit grooves are formed at positions and shapes that are line-symmetric with respect to the horizontal center line passing through the core end surface when viewed from the end surface of the core middle leg.

  According to the power supply core of the present invention, the slit groove is formed on the outer periphery of the core middle leg, thereby increasing the electrical resistance on the outer circumference of the core with respect to the voltage generated on the outer periphery of the core middle leg, and the eddy current Can be reduced.

In addition, when combining two E-type power cores by forming an even number of slit grooves at positions and shapes that are symmetrical with respect to the horizontal center line passing through the core end surface when viewed from the end surface of the core middle leg Even if the orientation of the core changes, it can be combined so that the slit groove of the core midfoot always matches, especially the core midfoot part is fitted with a coil wound around the bobbin, and the outside can not be seen after assembly Since the slit grooves are always combined so as to coincide with each other, inspection after assembly is unnecessary, and productivity can be improved.

  FIG. 1 is an explanatory view showing an embodiment of a power supply core according to the present invention. This embodiment is characterized in that one slit groove is formed. 1A is a perspective view, and FIG. 1B is a plan view.

  In FIG. 1, a power source core 1 is manufactured by molding after molding from a powdery core material having a predetermined component, and a core outer foot 2 is integrally formed on both sides, The core middle leg 3 is integrally formed.

  The core middle leg 3 has a cylindrical shape and forms one slit groove 4 in the longitudinal direction of the outer peripheral surface. The depth of the slit groove 4 is about half of the radius of the core middle leg 3 so that the sectional area of the slit groove 4 is within a range not exceeding about 10% with respect to the sectional area of the core middle leg 3. The shape of the slit groove 4 is determined, and the reduction of the core cross-sectional area is minimized.

  As described above, in the power supply core 1 of the present invention, the slit groove 4 is formed in the outer peripheral longitudinal direction of the core middle leg 3, so that two sets of the power supply core 1 of the present invention shown in FIG. The transformer structure is assembled by combining the slit grooves 4 so as to overlap each other at the end face of the foot 3 and attaching the coil wound around the bobbin to the core middle foot 3 in this state.

  In such a transformer structure using two sets of power supply cores 1 of the present invention, when a voltage is applied to a coil attached to the core middle leg 3 via a bobbin, the core middle leg 3 is equivalent to one turn. As a coil, if the coil fraction is N1, Vc = V. A voltage of (1 / N1) is applied, and an eddy current flows on the outer periphery of the coil middle leg 3.

  The eddy current at this time is determined by the electric resistance depending on the length of the outer periphery of the core middle leg 3, but in the present invention, the slit groove 4 is formed by forming the slit groove 4 on the outer periphery of the core middle leg 3. The length of the outer periphery of the core middle leg 3 is increased by the amount formed, and the resistance value is increased by the length passing through the slit groove 4. Therefore, by providing the slit groove 4, the eddy current flowing on the outer periphery of the core middle leg 3 can be reduced.

  FIG. 2 is an explanatory view showing another embodiment of the power supply core according to the present invention. This embodiment is characterized in that two slit grooves are formed.

  In FIG. 2, the power core 1 is integrally formed with core outer legs 2 on both sides thereof, and a core middle leg 3 is integrally formed therebetween. Slit grooves 4 a and 4 b are formed in the longitudinal direction on the outer periphery of the core middle leg 3. As shown in the plan view of FIG. 2B, the slit grooves 4a and 4b are formed so as to be symmetrical with respect to the lateral center line 5 with respect to the core end surface as viewed from the core end surface of the core middle foot 3. .

  In this way, the slit grooves 4a and 4b are formed in the core midfoot 3 so as to be symmetrical with respect to the horizontal center line 5, so that the core surfaces are aligned using two sets of power supply cores 1 shown in FIG. When assembling the two power supply cores 1 with the core surfaces facing each other, regardless of whether the core orientation is the front side or the back side in FIG. 3 can be assembled so that the slit grooves 4a and 4b formed in 3 coincide with and overlap with the slit grooves 4a and 4b of the power supply core 1 which is the counterpart.

  In this case, if the slit grooves of the core do not match, leakage magnetic flux is generated from the end face of the mating core where the slit groove is located and jumps into the winding to increase the loss. It is important to match.

  For this reason, in the assembly of the transformer structure using two sets of power supply cores 1 in FIG. 2, the core surface side can be assembled without considering the orientation of the two sets of power supply cores 1, and the transformer structure is assembled. In the state, the core middle leg 3 is not visible from the outside because the coil wound around the bobbin is attached, but the slit grooves 4a and 4b formed in the core middle leg 3 are always in the two power cores 1. Since the alignment is possible, an inspection operation for confirming the state of the slit groove after the assembly is not necessary, thereby facilitating the assembly and improving the workability.

  Of course, the depth of the two slit grooves 4a and 4b in the embodiment of FIG. 2 is substantially half of the radius of the core midfoot 3, and the sectional area of the two slit grooves 4a and 4b is also in the core. The shape does not exceed 10% of the circular cross section of the foot 3.

  In the embodiment of FIG. 2, when the dimensions of the two slit grooves 4a and 4b are the same as the slit groove 4 of FIG. 1, for example, in the embodiment of FIG. The amount of increase is twice that of FIG. 1, and accordingly, the embodiment of FIG. 2 has a greater effect of reducing the eddy current.

  FIG. 3 is an explanatory view showing another embodiment of the power supply core according to the present invention. This embodiment is characterized in that three slit grooves are formed.

  In FIG. 3, the power supply core 1 of the present invention has a core outer foot 2 integrally formed on both sides and a core middle foot 3 formed integrally therebetween, and the core middle foot 3 has a cylindrical shape. Three slit grooves 4a, 4b, 4c are formed at equal intervals on the outer periphery.

  The depth of the slit grooves 4 a to 4 c is approximately one half of the radius of the core middle leg 3, and the total sectional area of the three slit grooves 4 a to 4 c is equal to the circular section of the core middle leg 3. The shapes of the slit grooves 4a to 4c are determined so as not to exceed 10% of the area.

  In the embodiment of FIG. 3, the length of the outer periphery of the core middle leg 3 is increased by the amount of the three slit grooves 4 a to 4 c, thereby increasing the electrical resistance. The eddy current flowing on the outer periphery can be reduced.

  FIG. 4 is an explanatory view showing another embodiment of the power supply core according to the present invention. In this embodiment, two slit grooves are formed. In FIG. 4, the power core 1 is integrally formed with core outer legs 2 on both sides, and a core middle leg 3 is integrally formed therebetween, and the core middle leg 3 is positioned at a position opposite to the core outer leg 2. That is, the slit grooves 4a and 4b are formed at a position where the horizontal center line 5 passes.

  Also in the embodiment of FIG. 4, the slit grooves 4a and 4b of the core middle leg 3 are formed symmetrically with respect to the center line 5 in the horizontal direction. When assembling so that the core surfaces face each other, regardless of whether the orientation of the power source core is the front side or the back side in FIG. Can be assembled so that the positions overlap.

  FIG. 5 is an explanatory view showing another embodiment of the power supply core according to the present invention. This embodiment is also characterized in that four slit grooves are formed. In FIG. 5, the power supply core 1 is integrally provided with core outer legs 2 on both sides, and a core middle leg 3 is integrally provided therebetween, and the outer circumference of the core middle leg 3 is equally spaced in the circumferential direction. Four slit grooves 4a, 4b, 4c, 4d are formed in the longitudinal direction.

  The slit grooves 4a to 4d are formed so as to be line symmetric with respect to the center line 5 passing through the core end surface of the power source core 1 in the lateral direction. Therefore, even in the power supply core 1 of FIG. 5, when assembling the two sets of power supply cores 1 so that the core surfaces face each other, the front side or the back side in FIG. Regardless of the orientation, when two sets of power supply cores 1 are combined on the core surface side, the slit grooves 4a to 4d formed on the outer circumference of the core middle legs 3 of the two cores must be assembled so as to always coincide with the other slit grooves. Can do.

  Further, the depth of the slit grooves 4a to 4c in FIG. 5 is approximately half of the radius of the core middle leg 3, and the total sectional area of the four slit grooves 4a to 4d is approximately the circular sectional area of the core middle leg 3. It is formed to be within 10%.

  FIG. 6 is an explanatory view showing another embodiment of the present invention, which is characterized by including a rectangular core middle leg. In FIG. 6, the power supply core 11 has a pair of core outer legs 12 formed on both sides, and a core middle leg 13 formed integrally therebetween.

  The core outer leg 12 and the core middle leg 13 have a rectangular shape when viewed from the core end face side in FIG. And about the core middle leg 13 located in the center, the two slit grooves 14a and 14b are formed in the longitudinal direction in the inner peripheral surface facing the core outer leg 12, for example.

  Here, as the depth of the slit grooves 14a and 14b provided in the rectangular core middle leg 13, for example, if the core middle leg 13 is a square, the depth is approximately one quarter of the length of one side thereof. Yes. The total cross-sectional area of the two slit grooves 14a and 14b has a shape that does not exceed approximately 10% of the rectangular cross-sectional area of the core midfoot 13.

  In the embodiment of FIG. 6 as well, since the two slit grooves 14a and 14b are formed on the outer periphery of the rectangular core intermediate leg 13, the length of the outer periphery of the core intermediate leg 13 is reduced to the slit grooves 14a and 14b. The length is increased by the amount formed, and the electrical resistance is increased by that amount, whereby the eddy current can be reduced.

In the power supply core of the present invention, the number and shape of the grooves formed on the outer periphery of the core middle leg can be appropriately determined as necessary. In this case, what is required is the total area of the slit grooves. May be within a range that does not exceed approximately 10% of the cross-sectional area of the core midfoot before the slit groove is formed. As described above, since the formation area of the slit groove is within 10% of the cross-sectional area of the core middle leg before the slit groove is formed, the reduction of the cross-sectional area of the core middle leg is minimized.

Explanatory drawing which showed embodiment of the core for power supplies by this invention which formed one slit groove | channel Explanatory drawing which showed other embodiment of the core for power supplies by this invention which formed two slit grooves Explanatory drawing which showed other embodiment of the core for power supplies by this invention which formed three slit grooves Explanatory drawing which showed other embodiment of the core for power supplies by this invention which formed two slit grooves Explanatory drawing which showed other embodiment of the core for power supplies by this invention which formed four slit grooves Explanatory drawing which showed other embodiment of the core for power supplies by this invention provided with the rectangular core midfoot Explanatory drawing of conventional E-type power supply core Illustration of eddy current generated in power supply core

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11: Core for power supplies 2, 12: Core outer leg 3, 13: Core middle leg 4, 4a-4d, 14a, 14b: Slit groove 5: Center line

Claims (2)

A power supply core having an E shape, wherein one or a plurality of slit grooves are formed in a longitudinal direction on an outer periphery of a core middle leg.
  2. The power supply core according to claim 1, wherein an even number of slit grooves are formed at positions and shapes that are axisymmetric with respect to a lateral center line passing through the core end surface when viewed from the end surface of the core middle leg. Power supply core.

Images