JP2005353872A - Fixed inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixed inductor which is small-sized, made lightweight and obtaining stable inductance and appropriate DC superimposing characteristics by providing a proper air gap. <P>SOLUTION: A fixed inductor comprises a stick-like core 1, a coil 5 winding an insulating coating electrical wire 2 around the stick-like core 1, and an angular sleeve core 3 for housing the coil 5 therein. The inductor is mechanically provided with an air gap G by providing recessed portions 1a or projecting portions on both end faces of the stick-like core 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a fixed inductor, and more particularly to a fixed inductor used in a digital amplifier.

  FIG. 12 shows a schematic circuit diagram of a fixed inductor used in the digital amplifier. FIG. 12A is a circuit schematic diagram according to a SEPP (Single Ended Push Pull) system, and FIG. 12B is a circuit schematic diagram according to a BTL (Balanced Transformer Less) system. In the figure, IC is an integrated circuit, AMP is a digital amplifier, L and C are fixed inductors and capacitors constituting a low-pass filter LPF, and SP is a speaker. As described above, the SEPP circuit method requires one set of LPFs for one channel, and the BTL circuit method requires two sets of LPFs for one channel.

  Fixed inductors used in digital amplifiers are connected to each speaker, and direct current superposition characteristics at a large current are required to improve sound quality. Furthermore, there is a demand for miniaturization of fixed inductors accompanying the miniaturization of equipment. In such a case, a toroidal coil using a toroidal core is shown as a fixed inductor conventionally used as shown in FIG. In the toroidal coil 50, a copper wire 52 having an insulating coating is wound around a toroidal core 51 formed of a ferrite magnetic material in a toroidal shape, and the lead wire 53 is connected to an external circuit.

  This toroidal coil 50 has a closed magnetic circuit configuration in order to prevent adverse effects such as external radiated radio waves from affecting other parts as the digital amplifier is downsized. Since the core material has a magnetic susceptibility (μ = 10 or less), there is a problem in that leakage magnetic flux is generated from the wound portion of the winding and disturbs the peripheral circuit. In addition, it is difficult to wind the ring-shaped toroidal core when performing the winding work, and further, a fixing mechanism for fixing to the mounting board is required, so that downsizing of components is hindered. there were.

  As a fixed inductor other than the toroidal coil, there is a fixed inductor 60 as shown in FIG. 14 that has a closed magnetic circuit, can be easily wound, and can be easily mounted on a mounting board. FIG. 14 shows a case where a winding 56 in which an insulating coated wire is wound around a drum core 55 provided with an external terminal 58 is housed in a pot-shaped core 57. However, the fixed inductor 60 has a problem that heat generation is large and a direct current superimposition characteristic cannot be obtained sufficiently. .

Also, as a fixed inductor used in the BTL output system, Patent Document 1 in which two fixed inductors are housed in one housing case and Patent Document 2 in which a spring core is housed in an EE type core are disclosed. However, these have a large shape, and further miniaturization is required.
JP2003-151832A (P6222) JP 2003-077734 A (P6114)

  In response to the above requirements, the fixed inductor of the present invention aims to provide a fixed inductor that is small and light in weight, and that can provide a stable inductance and suitable DC superposition characteristics by providing an appropriate air gap. .

  In order to solve the above-described problems, the present invention provides a fixed inductor including a rod-shaped core, a coil in which an insulating coated wire is wound around the rod-shaped core, and a rectangular sleeve core that houses the coil. Any one of the convex portions is provided.

  The fixed inductor of the present invention is a fixed inductor having a rod-shaped core, a coil in which an insulating coated electric wire is wound around the rod-shaped core, and a rectangular sleeve core that accommodates the coil. By providing recesses or protrusions on both end faces of the rod, even if the position of the rod-shaped core is shifted to one side, a minimum mechanical air gap can be obtained by the recess or protrusion on one end, and stable inductance And DC superposition characteristics are obtained.

  A fixed inductor according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is an exploded perspective view of a fixed inductor according to a first embodiment of the present invention. FIG. 2 shows a cross-sectional view of the fixed inductor 10 shown in FIG.
As shown in FIGS. 1 and 2, the fixed inductor 10 according to the first embodiment includes a rod-shaped core 1 made of a magnetic body having a circular cross section provided with fan-shaped round recesses 1 a on both end surfaces, and a rod-shaped core 1. A coil 5 in which an insulating coated electric wire is wound to provide a winding 2, a rectangular sleeve core 3 made of a magnetic material that penetrates the inside of the coil 5, and an end of the winding 2 are extended to form an external terminal 2a. The base 3 made of an insulating resin that holds the external terminal 2a is provided.

FIG. 3 shows a cross-sectional view of the fixed inductor 11 according to the second embodiment of the present invention.
As shown in the cross-sectional view of FIG. 3, in the second embodiment, the shape of the concave end surface of the rod-shaped core 1 according to the first embodiment is changed to a round concave portion 1b provided with a step.
The rod-shaped core 1 which is a 1st Example tends to lack the front-end | tip part of the fan-shaped recessed part 1a. Therefore, in the second embodiment, the strength of the tip portion is increased, and the difference is that round recesses 1b provided with steps on both end faces of the rod-like core 1 are formed. Others are the same as the first embodiment.
Thus, in the second embodiment, the coil 5 is formed on the rod-shaped core 1 having round recesses with steps on both end faces of the rod-shaped core having a circular cross section. As a result, the strength of the tip surface of the recess 1b can be increased, and troubles such as tipping and chipping at the tip portion during molding of the rod-shaped core and handling such as work can be prevented.

FIG. 4 is a cross-sectional view showing the positional relationship between the coil of the fixed inductor and the rectangular sleeve core.
FIG. 4A shows a fixed inductor 11 according to a second embodiment of the present invention, and FIG. 4B shows a fixed inductor 30 using a general rod-shaped core 31.
As shown in FIG. 4A, the fixed inductor 11 of the present invention forms a coil 5 using a rod-shaped core 1 provided with round recesses 1b having steps on both end faces. When the coil 5 is displaced in the longitudinal direction Δt from the center position of the rectangular sleeve core 3, the tip of the concave portion 1 b comes into contact with the inner surface 3 a of the rectangular sleeve core. At that time, the air gap G is mechanically formed by the recess 1 b provided in the rod-shaped core 1.

  For example, as shown in FIG. 4B, in the coil 35 using a general rod-shaped core 31 such as a flat end 31a having no recesses at both ends, the coil 35 is displaced in one direction Δ When the end face 31a of the rod-shaped core 31 approaches (or comes into contact with) the inner side surface 3a of the rectangular sleeve core 3 at time t, the air gap G becomes extremely small and the inductance changes abruptly.

FIG. 5 shows a change in inductance and a change in DC superimposition characteristics due to the displacement of the coil.
As shown in FIG. 5, the horizontal axis represents the coil positional deviation Δt, and the vertical axis represents the inductance change rate (%) and the DC superposition change rate (%). However, when the coil is located at the center position of the rectangular sleeve, the initial value is the reference, and the maximum positional deviation is the inner surface 3a on both sides of the rectangular sleeve core.
The characteristics 11A and 11B are an inductance change rate and a DC superposition change rate obtained by changing the size of the concave portion 1b in the fixed inductor 11 according to the second embodiment of the present invention shown in FIG.
The characteristic 30 is an inductance change rate and a DC superposition change rate of the general fixed inductor 30 shown in FIG.

As shown in FIG. 5, in the inductance change rate and the DC superposition characteristic change rate, the change in the general fixed inductor 30 rapidly increases as the end surface 31 a of the rod-shaped core 31 approaches the inner surface 3 a of the sleeve core 3. In contrast, the fixed inductors 11A and 11B according to the second embodiment of the present invention change greatly as the tip of the recess 6a approaches the inner surface 3a of the sleeve core 3, but the air gap G is mechanically formed by the recess. Therefore, the change is smaller than that of the general fixed inductor 30.
The difference between the characteristics 11A and 11B depends on the size of the recess. For example, the recess shape of the characteristic 11A has a depth of 2.5 mm and a diameter of 4 mmφ, and the recess shape of the characteristic 11B has a depth of 2.5φ and a diameter of 2 mmφ. It is. As described above, since the air gap G is mechanically increased by providing a large recess shape (area within the recess), it is possible to reduce the characteristic change (inductance change rate and DC superposition change rate) due to the displacement of the coil. it can. It goes without saying that this phenomenon is a change in the left and right objects with the coil as the boundary of the square sleeve core.

Next, FIG. 6 shows the relationship between the BIAS current (A) flowing through the fixed inductor and the inductance change rate.
As shown in FIG. 6, the horizontal axis indicates the BIAS current (A) flowing through the fixed inductor, and the vertical axis indicates the inductance change rate (%). The coil position is the center position of the rectangular sleeve, and the initial value (reference) is when no BIAS current flows.
As a result, as shown in FIG. 6, for example, the BIAS current when the inductance change rate is −10% is approximately 9 (A) in the general fixed inductor 30, whereas the fixed inductor 11 </ b> A according to the embodiment of the present invention. 12.7 (A), 11B is 12 (A), and a large BIAS current can be passed through the fixed inductor by increasing the recess.
This is suitable as a fixed inductor for a digital amplifier that requires a large current.

The fixed inductor used in this measurement had an inductance L of 13 μH, an inner dimension of the square sleeve of 13 mm × 11.5 mm, a rod-shaped core diameter of 6 mmφ, and a length of 12 mm.
Here, it is desirable that the size and shape of the recess (air gap G) are determined according to the inductance and DC superimposition characteristics required for the fixed inductor.

FIG. 7 is a cross-sectional view of the fixed inductor 12 according to the third embodiment of the present invention.
As shown in FIG. 7, the third embodiment is similar to the second embodiment in that the strength of the end of the rod-shaped core 1 is increased, and fan-shaped convex portions 1c are formed on both end faces of the rod-shaped core 1. Different points. Others are the same as the first embodiment. As described above, in the third embodiment, the both end surfaces of the rod-shaped core 1 are fan-shaped convex portions 1c, so that the strength of the rod-shaped core tip portion is obtained, the moldability of the rod-shaped core is facilitated, and the cost is lower. Parts can be used.

FIG. 8 is an exploded perspective view of the fixed inductor 13 according to the fourth embodiment of the present invention.
As shown in FIG. 8, the fourth embodiment is provided with the rod-like core 1 (recesses 1a, 1b or protrusions 1c formed on both end faces of the core) used in the first, second, and third embodiments. ), A plurality of coils 5 are stacked vertically, for example, as in the embodiment of FIG. 8, and two fixed inductors are formed as one fixed inductor.
Thus, the fourth embodiment is a fixed inductor suitable for a circuit in which a plurality of fixed inductors are configured as one fixed inductor as in the BTL output system of a digital amplifier.

FIG. 9 is a longitudinal sectional view of the fixed inductor 14 according to the fifth embodiment of the present invention.
As shown in FIG. 9, the fifth embodiment uses a square pot core 7 in which the upper portion of the square sleeve core 3 is closed in the fixed inductor 13 according to the fourth embodiment. Others are the same as the fourth embodiment.
By changing from the rectangular sleeve core 3 to the rectangular pot-shaped core 7, it is possible to prevent the influence of the magnetic flux leakage from the upper surface and the influence of the intrusion from the external magnetic field.

FIG. 10 is an exploded perspective view of the fixed inductor 15 according to the sixth embodiment of the present invention. FIG. 11A is a perspective view of a rod-shaped core used in the fixed inductor 15 according to the sixth embodiment and a perspective view of a coil using the rod-shaped core.
The fixed inductor 15 according to the sixth embodiment of the present invention is one in which two fixed inductors are formed with one core and is suitable for a BTL output type digital amplifier, and is higher than the fourth and fifth embodiments. This can be suppressed.

As shown in FIG. 11 (a), a fixed inductor 15 according to a sixth embodiment of the present invention is a core having a quadrangular cross section in which the central axis made of ferrite is orthogonal and the planar shape is formed in a cross shape. 16 is used.
The core 16 includes a winding shaft 17-1 extending in the X-axis direction and a winding shaft 17-2 extending in the Y-axis direction, which are formed in a cross shape. 1d is formed. In addition, as the shape of each end face of the core, any one of the concave portions or the convex portions used in the first, second, and third embodiments may be used. In addition, in the embodiment, a core having a quadrangular cross section is used, but a round or elliptical shape may be used.

  Then, as shown in FIG. 11B, the winding is wound around the winding axis 17-1 extending in the X-axis direction, the first coil 18 is wound with an insulating coated wire, and the winding axis 17-2 extending in the Y-axis direction. The second coil 19 is wound with an insulating coated wire. Then, the winding terminals of the first coil 18 and the second coil 19 are extended to be external terminals 18a and 19a. Thus, the coil 20 which comprises two fixed inductors with the one core 16 is formed.

  As shown in FIG. 10, the coil 20 is housed in the rectangular pot core 7 used in the fourth embodiment, and the insulating resin that holds the external terminals 18 a and 19 a of the coil 20 is formed in the bottom side opening of the rectangular pot core 7. A fixed inductor 15 in which two fixed inductors are formed as one fixed inductor is formed using the base 4. Thus, the fixed inductor 15 of the sixth embodiment is one in which two fixed inductors are formed by using the coil 20 in which two coils 18 and 19 are formed in one core 16 and the square pot core.

  As described above, the fixed inductor of the present invention has a flat end face that does not have a recess or projection by using a core in which a recess or projection that becomes an air gap is formed at each end of a rod-shaped core. As compared with the case where a simple core is used, a large current (BIAS current) that can be passed through the fixed inductor can be obtained and a change in inductance can also be reduced. Moreover, even if the coil is displaced from the center position of the rectangular sleeve core or the rectangular pot core, a fixed inductor can be obtained in which the inductance and the direct current superposition characteristics are small.

  Although the embodiments of the fixed inductor of the present invention have been described above, the present invention is not limited to these embodiments. For example, the shape of the concave portion or the convex portion provided at both ends of the rod-shaped core is not limited to the embodiment. The cross-sectional shape of the rod-shaped core may be a round shape, an oval shape, a quadrangular shape, or a polygonal shape. And although the coil | winding terminal was hold | maintained using the base, you may provide and connect an external terminal and an external electrode to the base beforehand. Further, the internal coil, the sleeve core, or the pot core may be directly fixed to the circuit board by bonding or the like without using the base or the like.

The exploded perspective view of the fixed inductor which is the 1st example of the present invention is shown. FIG. 2 shows a cross-sectional view of a fixed inductor according to the first embodiment of FIG. 1. The cross-sectional view of the fixed inductor which is the 2nd example of the present invention is shown. The cross-sectional view which shows the positional relationship of the coil of a fixed inductor and a square sleeve core is shown. The cross-sectional view (a) of the fixed inductor which is the 2nd example of the present invention, and the cross-sectional view (b) using a general core. The change of the inductance by the position shift of a coil and the change of direct current superposition are shown. . FIG. 6 shows the relationship between the BIAS current (A) passed through the fixed inductor and the inductance change rate. FIG. 6 shows a cross-sectional view of a fixed inductor according to a third embodiment of the present invention. The disassembled perspective view of the fixed inductor which is the 4th Example of this invention is shown. The longitudinal cross-sectional view of the fixed inductor which is the 5th Example of this invention is shown. The disassembled perspective view of the fixed inductor which is the 6th Example of this invention is shown. The rod-shaped core (a) used for the fixed inductor which is the 6th Example of this invention, and the perspective view (b) of the coil are shown. The schematic circuit diagram of the fixed inductor used for a digital amplifier is shown. Inductor using a conventional toroidal core. Inductors using conventional drum and pot cores

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rod-shaped core 2 Winding 3 Rectangular sleeve core 4 Base 5 Coil 1a, 1b Concave part 1c Convex part

Claims (5)

In a fixed inductor comprising a rod-shaped core, a coil in which an insulating coated wire is wound around the rod-shaped core, and a rectangular sleeve core that houses the coil,
The rod-shaped core is provided with either a concave portion or a convex portion on both end faces, and a fixed inductor. In a fixed fixed inductor comprising a rod-shaped core, a coil in which an insulating coated electric wire is wound around the rod-shaped core, and a rectangular sleeve core that houses the coil,
The rod-shaped core uses a core having a cross-shaped planar shape with a central axis orthogonal to each other. Each end surface is provided with either a concave portion or a convex portion, and an insulating coated electric wire is wound around a portion extending in the X-axis direction. A fixed inductor, wherein a first coil is provided, and a second coil is formed by winding an insulating coated wire around a portion extending in the Y-axis direction. The fixed inductor according to claim 1, wherein a plurality of the coils are stacked vertically and stored in the rectangular sleeve core. The fixed inductor according to any one of claims 1 to 3, wherein the rectangular sleeve core is a rectangular pot core whose one surface is closed. The fixed inductor according to any one of claims 1 to 4, wherein a base for holding the end of the coil is provided on one surface of the open-ended square sleeve core.

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