JPH069115U - Vase core - Google Patents

Abstract

(57) [Abstract] [Purpose] Leakage magnetic flux is less likely to occur, and the effective permeability can be adjusted very easily. [Structure] A core 1 includes an annular outer foot core portion 2 provided on an outer periphery, an annular middle foot core portion 3 having a bottomed concave portion or a through hole at a central portion, an outer foot core portion and a middle foot. It is composed of a bottom surface core part 4 connecting the core part, and the annular middle foot core part 3 is
It has parts 3a and 3b having different heights which are separated from each other in the circumferential direction. A pair of two such cores 1 are mounted, coils are mounted inside, and the cores are butted against each other and relatively rotated, thereby changing the effective gap amount and adjusting the effective magnetic permeability.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pot core for a high frequency transformer or a high frequency power choke coil used in a switching power supply device or the like.

[0002]

[Prior art]

 In general, high frequency power transformers (especially transformers for flyback type switching power supplies), choke coils, etc. on which DC current is superimposed, and those for the purpose of positively utilizing the electromagnetic energy stored in the coil , A so-called cored structure that has a magnetic body in its magnetic path in terms of the function it performs, and is not a so-called closed magnetic path in which the magnetic path is entirely filled with a magnetic body, but a part of the magnetic path is a non-magnetic body or an air gap. The so-called open magnetic circuit structure is adopted. FIG. 11 shows an example thereof, in which 21 is a core, 22 is a coil, and 23 is an air gap provided in a part of the core 21.

The reason why the above-mentioned open magnetic circuit structure is adopted is that in the cored coil, as shown in FIG. 12, the magnetic body is saturated by the superposed direct current I and the inductance L is reduced. That is, as shown in FIG. 13, the saturation current I _S depends on the effective magnetic permeability μ * of the core magnetic body, and the effective magnetic permeability is determined by the gap amount.

Therefore, in designing the coil, the size of the magnetic material, the effective permeability and the number of turns of the winding are determined from the superposed current value to be flowed and the electromagnetic energy amount to be stored, and the inductance value is set to a desired value during manufacture. It is common to adjust the gap amount so that

There are the following two ways to provide the air gap, and each has advantages and disadvantages. A transformer and a choke coil, which is generally represented by an EI (or EE) type core, has a so-called middle foot core portion into which the coil is fitted and an outer foot core portion that forms a magnetic path outside the coil. There are two ways to provide an air gap: one that provides a gap only in the metatarsal core portion, and one that provides a gap in both the metatarsal core portion and the outer foot core portion. The former has the merit that leakage magnetic flux is less likely to occur because the air gap is confined in the coil, and is particularly useful as a countermeasure against high frequency noise, but on the other hand, the gap amount cannot be adjusted when assembled. There is a trouble in adjusting that polishing and assembly measurement are repeated several times. On the other hand, the latter is the opposite, and it is very easy to adjust the gap length by inserting a non-magnetic spacer into the outer foot core while measuring the inductance as assembled, but from the outer foot core The magnetic flux leakage causes interference such as electromagnetic noise.

[0006] Therefore, a vase-shaped core is given as one having the advantages of both of the above. Fig. 14 shows a typical shape of a vase-shaped core. 25 is an annular outer foot core part provided on the outer periphery, 26 is a middle foot core part, and the outer foot core part 25 and the middle foot core are shown. The bottom core portion 27 is connected to the portion 26. A recess 28 deviated from the center C is provided on the front end surface of the middle foot core portion 26.

FIG. 15 shows a structure in which a pair of cores are abutted with each other and a coil 29 is incorporated therein, and the abutted cores are relatively rotated to face each other as shown in FIG. The relative positional relationship of the recesses 28, that is, the overlapping area of the recesses changes, and the effective magnetic permeability can be adjusted.

However, conventionally, it has been considered as a core for obtaining a simple inductance that does not superimpose a direct current, and the problem of magnetic flux saturation of the core remains.

On the other hand, as represented by the terms light, thin, short, and small, in order to meet the demand for miniaturization and high performance of electronic devices, a DC low voltage required from a commercial power supply (AC 100V or 200V) or a battery inside the device. There has been a general trend to adopt a switching method for the (stabilized) power supply unit for converting (for example, 3V or 5V) to the conventional series regulator method.

Since the switching power supply can be downsized more by increasing the conversion frequency, the frequency has been increased year by year, but electromagnetic noise is the main one because of the problems associated with it. As one of the solutions, a so-called planar core has been developed in which the middle leg of the vase-shaped core is hollowed out into a cylindrical shape to form an annular shape.

[0011]

[Problems to be solved by the device]

 However, this planar core also has a structure in which two cores of the same shape are butted against each other to form a magnetic path. Therefore, when trying to adjust the inductance while assembled as a coil, the inner leg core part and the outer part There is no choice but to use a method in which the cores of the foot have the same length, and there is a gap of the same size in both the middle and outer foot cores, which is especially a problem with electromagnetic noise. It was not possible to prevent the leakage magnetic flux in the gap part of the.

The present invention is intended to solve the above problems, and provides a vase-shaped core in which leakage magnetic flux is less likely to occur and the effective magnetic permeability can be easily adjusted by changing the effective gap amount. With the goal.

[0013]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention comprises a pair of cores of the same shape that are used in abutment with each other. A vase-shaped core consisting of a ring-shaped middle foot core that is a recess or a through hole, and a bottom core that connects the outer foot core and the middle foot core. It is configured such that it has parts of different heights that are separated by directions.

Further, an inclined portion whose height gradually changes is provided at the boundary between the portions having different heights.

[0015]

[Action]

 According to the above configuration, the gap is formed only at the abutting portion of the metatarsal core portion, and since there is no magnetic flux leakage in the gap portion of the outer foot core portion, the problem of electromagnetic noise is solved.

Further, regarding the adjustment of the effective magnetic permeability, when two pairs of cores are butted against each other, both cores are relatively rotated to be effective when the low height portions of the metatarsal core portions face each other. The amount of gap is minimized and therefore the effective permeability is maximized. On the contrary, the effective gap amount becomes maximum when the low height part of the metatarsal core part faces the high part of the metatarsal core part of the mating core, and therefore the effective magnetic permeability becomes minimum. In the intermediate state, the amount of effective gap increases in proportion to the increase in the area where the low-height parts of each metatarsal core face each other, and conversely the effective permeability decreases.

This can be proved also by the following approximate expression for obtaining the effective gap amount of the magnetic circuit in which the gap is not uniform. Gap = (∫G _S ds) ÷ S Gap: Effective gap amount G _S : Individual gap amount when the gap surface is divided into minute areas S: Total area of the gap surface

Therefore, the maximum and minimum values (variable range) of the effective magnetic permeability of the core during assembly can be adjusted by appropriately selecting the height and area of the high and low parts of the midfoot core. If the number of turns of the winding is determined, the variable range of the DC current value and the inductance value that can be superimposed can be obtained.

[0019]

【Example】

 Hereinafter, embodiments will be described in detail with reference to the drawings. FIG. 1 shows one of a pair of cores of the same shape used in abutment with each other in a pot-shaped core according to a first embodiment of the present invention. The core 1 is composed of an annular outer foot core portion 2 provided on the outer periphery, an annular middle foot core portion 3 having a central portion having a bottomed recess, an outer foot core portion 2 and a middle foot core portion 3. It consists of the bottom core part 4 which runs. The annular metatarsal core portion 3 is composed of portions having different heights divided in the circumferential direction, that is, a portion 3a having a high height from the bottom core portion 4 and a portion 3b having a low height. FIG. 1B is a developed view of the metatarsal core portion 3.

Although it has been described that the central portion of the metatarsal core portion 3 has a bottomed recess, this portion may be a through hole in some cases. Although not shown, a hole for drawing out a lead wire of a coil inserted between the outer foot core portion 2 and the middle foot core portion 3, for example, a through hole formed in the bottom surface core portion 4, or There are slit-shaped openings and the like formed in the diameter direction of the bottom surface core portion 4. Since this hole does not directly affect the function and effect of the present invention, it is omitted in the following drawings.

FIG. 2 is a development view of the metatarsal core parts 3 facing each other when two cores 1 of FIG. 1 are butted against each other. When the cores are relatively rotated, FIG. As shown in FIG. 2 (b), when the low-height portions 3b face each other, and when the low-height portions 3b face the high-core portion 3a of the opponent core, as shown in FIG. The part 3b and the high part 3a of the opponent core may partially face each other. In the case of, since the high-height portions 3a face each other and approach each other, the effective gap amount is minimized, and thus the effective permeability is maximized. In the case of, the area far from the partner core becomes the widest, so the effective gap amount becomes maximum, and therefore the effective permeability becomes minimum. In the case of, the effective gap amount is determined by the area where the low-height portions face each other, and the effective permeability is determined.

As can be seen from the above description, the gap forming portion is only the abutting portion of the metatarsal core portion 3, and when the coil is mounted, it is confined in the coil, so that the leakage magnetic flux is less likely to occur. Then, the effective magnetic permeability can be easily adjusted by relatively rotating the butted cores.

FIG. 3 shows a second embodiment of the present invention, in which a sloped portion 5 having a gradually changing height is formed at the boundary between the portions 3a and 3b of the metatarsal core 3 having different heights. Is provided.

The advantages of providing the inclined portion 5 are as follows. First, the change in effective permeability when the butted cores are relatively rotated is more gradual than the change in the solid line without the inclined portion, as shown by the broken line in FIG. Adjustment becomes easy. In the two cases, when the inclined portion is not provided, when the relative position shown in FIG. 5 is reached, the magnetic force lines concentrate at the corner A of the high-height portion 3a and the core partially becomes magnetically saturated. Whereas the corner is obtuse or arcuate, such magnetization saturation is less likely to occur. Although it is an obtuse angle, of course, magnetization saturation is less likely to occur in an arc-shaped continuous curved surface rather than in a broken line discontinuous point.

FIG. 6 shows a third embodiment of the present invention, in which the annular metatarsal core part 3 is divided into three kinds of parts 3a, 3b, 3c having different heights which are divided in the circumferential direction. It consists of Here, the operation of the portion 3c having the highest height will be described. If a small gap area (corresponding to the highest height area 3c) that is smaller than the total magnetic path area is provided in the magnetic path with a certain gap, the small gap area will be generated when the DC superimposed current is small. When the area works effectively and the inductance value becomes large, and the DC superimposed current increases and the small gap area becomes the magnetization saturation state, it operates as a choke coil having an inductance value that depends on other areas with a large gap amount. To do. That is, the inductance characteristic as shown by the broken line in FIG. 8 is obtained. Therefore, a choke coil that uses a core with such a shape can obtain a higher inductance value in a small current region than a choke coil that uses a core in which the entire metatarsal core is of uniform height. In addition, compared to a coil that has a high inductance value in the entire current region, the core does not saturate even when a larger current flows and the required inductance is maintained in the large current region. In this embodiment, the above features are added to the effects of the first embodiment.

FIG. 7 shows a fourth embodiment in which an inclined portion 5 is provided at the boundary between the highest portion 3c and the intermediate height portion 3a of the embodiment shown in FIG. By providing the inclined portion 5, there is an effect that the inductance characteristic can be made a gentle curve as shown by the solid line in FIG.

A slope 5 is also provided at the boundary between the lowest part 3b and the intermediate height part 3a, either alone or in combination with the slope shown in FIG. 7, so that the change in effective permeability is moderate. Good.

FIG. 9 shows a fifth embodiment of the present invention in which an intermediate core portion 6 is provided between the outer foot core portion 2 and the middle foot core portion 3. It is the same as the first embodiment that the metatarsal core portion 3 has portions of different heights that are divided in the circumferential direction. As shown in FIG. 9C, the transformer coil 9 is mounted in the groove 7 between the outer foot core portion 2 and the middle foot core portion 6, and the intermediate core portion 6 and the middle foot core portion 3 are A choke coil 10 is mounted in the groove 8 between and.

As described above, when the set of the transformer and the choke coil is incorporated in one pot-shaped core, when the outer leg core portion 2 and the intermediate core portion 6 are assembled together due to the characteristics required of the transformer. The shape and dimensions must be such that no air gap is created. Then, the middle foot core portion 3 is provided with the configurations of the first to fourth embodiments so that the respective operational effects can be obtained.

Further, FIG. 10 shows a sixth embodiment of the present invention, in which a groove 11 for mounting a short ring is provided on the tip surface of the intermediate core portion 6 of the fifth embodiment. is there. In the vase-shaped core of the present embodiment, which constitutes an integrated structure of the transformer and the choke, the intermediate core portion 6 has a structure that serves as both the magnetic path of the transformer and the magnetic path of the choke, and the magnetic flux generated by the operation of the transformer. When there is a large imbalance in the magnetic flux generated by the action of the choke and the choke, the outer foot core 2 is part of the choke magnetic path, or the middle foot core 3 is part of the transformer magnetic path. It may cause malfunction and instability as a power supply device due to mutual interference between the transformer and the choke. As a measure to prevent such a problem, insert the short ring 12 into the groove 11 provided on the tip surface (sliding surface) of the intermediate core portion 6 as shown in FIG. 10 (c). Thus, the magnetic flux generated by the operation of the transformer and the magnetic flux generated by the operation of the choke can be prevented from entering the middle foot core portion 3 and the outer foot core portion 2, and mutual interference can be effectively eliminated.

[0031]

[Effect of device]

 As described above, according to the present invention, since the gap forming portion is confined in the coil mounted on the pot-shaped core, leakage magnetic flux is less likely to occur, and the abutted core is relatively By turning to, the effective gap amount can be changed and the effective permeability can be easily adjusted.

[Brief description of drawings]

FIG. 1 is a perspective view of a core according to a first embodiment of the present invention and an exploded view of a metatarsal core.

FIG. 2 is a diagram showing adjustment of an effective gap amount in the example.

FIG. 3 is a development view of a metatarsal core portion according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a relative rotation angle of the upper and lower cores and an effective magnetic permeability in the example.

FIG. 5 is a diagram showing a problem in the case where an inclined portion is not provided at a boundary portion of portions having different heights of the middle foot core portion.

FIG. 6 is a development view of a metatarsal core portion according to a third embodiment of the present invention.

FIG. 7 is a development view of a metatarsal core portion according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between a DC superimposed current value and an inductance in the third and fourth embodiments.

FIG. 9 is a configuration diagram of a core and a coil mounting diagram thereof according to a fifth embodiment of the present invention.

FIG. 10 is a configuration diagram of a core and a coil mounting diagram thereof according to a sixth embodiment of the present invention.

FIG. 11 is a diagram showing a conventional example of a high frequency power transformer.

FIG. 12 is a diagram showing a relationship between a DC superimposed current value and an inductance in the conventional example.

FIG. 13 is a diagram showing a relationship between effective magnetic permeability and saturation current in the conventional example.

FIG. 14 is a perspective view of a conventional example of a pot-shaped core.

FIG. 15 is a coil mounting diagram of the conventional example.

FIG. 16 is a diagram showing adjustment of effective magnetic permeability in the conventional example.

[Explanation of symbols]

1 ... Core, 2 ... Outer foot core part, 3 ... Middle foot core part,
3a ... High part, 3b ... Low part, 4 ... Bottom core part, 5 ... Inclined part, 6 ... Intermediate core part, 11 ... Short ring groove.

Claims (6)

[Scope of utility model registration request] 1. A pair of cores of the same shape which are used for butting against each other, each core having an annular outer leg core portion provided on the outer periphery and a central portion serving as a bottomed recess or through hole. A vase-shaped core consisting of an annular middle foot core part and a bottom core part connecting the outer foot core part and the middle foot core part, wherein the annular middle foot core part is divided in its circumferential direction. A vase-shaped core characterized by having portions with different heights. 2. A sloped portion whose height gradually changes is provided at a boundary between portions having different heights.
Vase core as described. 3. The vase-shaped core according to claim 1, wherein the annular metatarsal core portion is composed of three types of portions having different heights which are divided in the circumferential direction. 4. A sloped portion whose height gradually changes is provided in at least one of a boundary portion between a highest portion and a middle height portion or a boundary portion between a middle height portion and a lowest height portion. The vase-shaped core according to claim 3, wherein 5. The vase-shaped core according to claim 1, further comprising an intermediate core portion between the outer foot core portion and the middle foot core portion. 6. The vase-shaped core according to claim 5, further comprising a groove for mounting a short ring on a tip surface of the intermediate core portion.