JP2011096744A - Inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inductor reducing leakage flux in a gap by a method for preventing deterioration of safety due to heat generation without impeding miniaturization and thinning of the inductor. <P>SOLUTION: Force F is applied to a piezoelectric element inserted into the gap with magnetic attraction generated in the gap 7 when excitation current flows to an excitation coil 4 and is generated in a magnitude proportional to a magnitude of the excitation current so as to generate power. Then, the current is made to flow in a cancellation coil 6 by the power and cancellation magnetic flux Φc is generated. The prescribed cancellation magnetic flux Φc can be generated and a diameter of winding of the cancellation coil 6 can freely be selected without considering a diameter of the excitation coil 4 and the size of the excitation current, so that the cancellation coil 6 can be miniaturized, thereby installation properties of the cancellation coil 6 are improved and also the miniaturization and thinning of the reactor 1 are not impeded. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inductor having a gap provided in a core, and more particularly, to an inductor in which a piezoelectric element is inserted into a gap and magnetic characteristics are improved by using electric power supplied from the piezoelectric element.

  Conventionally, in inductors such as reactors and choke coils, a large current flows through a coil (hereinafter referred to as an exciting coil) that is provided with a gap in the core in order to improve the magnetic saturation characteristics of the core and is wound around the core a predetermined number of times. In this case, the magnetic resistance in the gap is increased to prevent magnetic saturation from occurring in the core. However, if a gap is provided in the core, there is a problem that leakage magnetic flux is generated from the gap, and the leakage magnetic flux affects the electronic devices installed around the reactor or the choke coil, causing malfunctions such as malfunction of the electronic devices. .

  In order to prevent the influence of this leakage flux, the leakage flux is prevented from leaking outside the case by inserting a reactor or a choke coil into a case made of a soft magnetic material such as iron and shielding it. ing. However, in such a method, it is difficult to reduce the size and thickness of the reactor and the choke coil by providing the case, and there is a problem that the reduction of the size and thickness of the electric device provided with the reactor or the choke coil is hindered.

  As a method for solving such a problem, a coil wound so that a magnetic flux in the direction opposite to the leakage magnetic flux generated in the gap (hereinafter referred to as a canceling magnetic flux) is generated in the vicinity of the gap of the core (hereinafter referred to as a canceling magnetic flux). (Referred to as Patent Document 1) or a plurality of foils made of a soft magnetic material slightly larger than the gap cross-sectional area are inserted into the gap. Thus, a method for reducing leakage magnetic flux (for example, see Patent Document 2) has been proposed.

  Patent Document 1 discloses a large current inductor in which an exciting coil is wound around a toroidal core provided with a gap, and a canceling coil that generates a canceling magnetic flux is disposed in the vicinity of the gap. And the exciting coil are connected in series. The magnetic flux generated in the toroidal core increases as the exciting current flowing through the exciting coil increases, and this increases the leakage flux, but the canceling coil is connected in series with the exciting coil, so as the exciting current increases. Since the canceling magnetic flux generated by the canceling coil is also increased, the leakage magnetic flux can be reduced with good followability to the operation of the inductor.

  However, in this method, since the canceling coil is connected in series with the exciting coil, the exciting current flowing through the exciting coil also flows through the canceling coil. Since the excitation current is usually large (for example, 10 (A)), the winding used for the excitation coil (generally copper wire is used) takes into account the heat generated by the flowing excitation current and the resistance value change. The wire diameter is determined. For example, a winding with a relatively large wire diameter, such as 1.5 mm or 2.0 mm, is selected. Is the winding of the cancellation coil through which the same excitation current flows equal to the excitation coil? It is necessary to make the wire diameter larger than that.

  The canceling coil needs to have several tens to several hundreds of turns to generate a canceling magnetic flux that can cancel out the leakage magnetic flux. However, as described above, the winding diameter of the canceling coil is large. The cancellation coil becomes very large. For this reason, there is a problem that it is difficult to dispose the canceling coil in the vicinity of the gap of the inductor, and even if it can be disposed, it becomes an obstacle to downsizing and thinning of the inductor.

  On the other hand, Patent Document 2 discloses that an inductor in which an exciting coil is wound around a toroidal core having a gap is slightly larger than the gap cross-sectional area, has a small coercive force such as iron or silicon steel, and has a magnetic permeability. A plurality of foils made of a large soft magnetic material are stacked and inserted into the gap. Since the foil formed of the soft magnetic material is larger than the gap cross-sectional area, the leakage magnetic flux generated in the gap is drawn into the toroidal core through the foil formed of the soft magnetic material, so that the leakage magnetic flux can be reduced. At the same time, since the soft magnetic material foil to be inserted is slightly larger than the gap cross-sectional area, it does not hinder the downsizing / thinning of the inductor.

  However, in such a method, an eddy current is generated when the leakage magnetic flux passes through the soft magnetic material foil. Therefore, the soft magnetic material foil may generate heat due to eddy current loss and heat the toroidal core. There was a problem in securing.

Japanese Patent Laid-Open No. 11-121239 (pages 2 and 3, FIG. 1) Japanese Patent Laid-Open No. 11-121240 (page 2, FIG. 1)

  The present invention solves the above-described problems and provides an inductor that reduces leakage magnetic flux in the gap in a manner that does not hinder downsizing and thinning of the inductor and that does not cause a decrease in safety due to heat generation. For the purpose.

  The present invention solves the above-mentioned problems, and the inductor of the present invention inserts a piezoelectric element that generates electricity when pressure is applied to the gap provided in the core, and arranges the voltage generated by the piezoelectric element in the vicinity of the gap. When applied to the canceling coil, the canceling magnetic flux for canceling the leakage magnetic flux generated from the gap is generated from the canceling coil to reduce the leakage magnetic flux.

  The inductor according to the present invention generates power by applying a force to the piezoelectric element inserted in the gap by a magnetic attraction force generated in the gap when the exciting current flows through the exciting coil and generated in proportion to the magnitude of the exciting current. And the generated voltage is applied to the canceling coil to generate a canceling magnetic flux. Since the current flowing through the cancellation coil is much smaller than the excitation current, the wire diameter of the cancellation coil winding can be freely selected if a predetermined cancellation magnetic flux can be generated. Can be downsized, the installation of the cancellation coil is improved, and the downsizing / thinning of the inductor is not hindered.

  In addition, the leakage magnetic flux generated in the gap is reduced by canceling with the canceling magnetic field generated by the canceling coil, so it is possible to prevent heat generation due to eddy current loss that occurs when the leakage magnetic flux passes through the soft magnetic material. Inductor safety can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the reactor which is 1st Example of this invention, (A) is principal part sectional drawing of a reactor, (B) is the schematic of a cancellation coil, (C) is DD in (B). It is sectional drawing. It is a figure explaining the principle of the leakage magnetic flux reduction in 1st Example of this invention, (A) is an explanatory drawing of the leakage magnetic flux in a gap, (B) is explanatory drawing of the force added to a piezoelectric element, (C) is It is explanatory drawing of a cancellation magnetic flux. It is a figure explaining the phase relationship of the leakage magnetic flux and the cancellation magnetic flux in 1st Example of this invention, (A) is the phase relationship diagram 1 which represents the phase of leakage magnetic flux and the output voltage of a piezoelectric element, (B) is FIG. 3 is a phase relationship diagram 2 showing the phases of the leakage magnetic flux, the output voltage before / in the adjusting means, and the phase of the canceling magnetic flux. It is a block diagram of the adjustment circuit which adjusts the period and phase of the cancellation magnetic flux in 1st Example of this invention. It is explanatory drawing of the choke coil which is 2nd Example of this invention, (A) is principal part sectional drawing of a choke coil, (B) is the schematic of a cancellation coil, (C) is the principle of leakage magnetic flux reduction. FIG.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, as an Example, it demonstrates as an example the inductor used and the choke coil used for the reactor used for a power factor improvement etc. for an air conditioner etc., a noise filter, an inverter circuit, etc. is mentioned as an example. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the spirit of the present invention.

  FIG. 1 shows the configuration of a reactor according to the first embodiment. As shown in the sectional view of the main part of FIG. 1A, the reactor 1 includes an E-type core 2, an I-type core 3, an exciting coil 4, a piezoelectric element 5, and a canceling coil 6. ing. Although not shown in the figure, insulating paper that is wound around the exciting coil 4 to insulate the E-type core 2 and I-type core 3 from the exciting coil 4, a bottom plate for attaching the reactor 1 to an electric device, and a reactor Lead wires, terminals, and terminal blocks for connecting 1 to a control board of an electric device are provided.

  The E-type core 2 is formed by laminating soft magnetic materials such as silicon steel plates and has a substantially E-shape when viewed from the front and has a predetermined depth dimension. The E-shaped core 2 includes a middle leg 2a provided at the center and outer legs 2b provided on both sides thereof. The middle leg 2a is compared with the outer leg 2b as shown in FIG. And short. Further, the width dimension of the middle leg 2a is 2H, which is twice the width dimension H of the outer leg 2b.

  The I-type core 3 is formed by laminating soft magnetic materials such as silicon steel plates, and has a substantially rectangular parallelepiped shape with a predetermined dimension. The thickness dimension of the I-type core 3 is the same as the width dimension H of the outer leg 2b of the E-type core 2, and the depth dimension of the I-type core 3 is the same as the depth dimension H of the E-type core 2. FIG. As shown to (A), the end surface of the front-end | tip part of the outer leg 2b of the E type | mold core 2 is joined with the corresponding surface of the I type | mold core 3 by welding etc., and the core which has a magnetic path of length 12 is formed. The

Further, a gap 7 is formed by the front end surface of the middle leg 2a of the E-type core 2 and the corresponding surface of the I-type core 3 as shown in FIG. By providing the gap 7, the magnetic resistance in the gap 7 is increased to prevent magnetic saturation from occurring in the core, thereby improving the magnetic saturation characteristics of the reactor 1. The gap 7 has a width H that is the width of the middle leg 2 a of the E-type core 2, a height that is a distance l 1 between the tip of the middle leg 2 a and the lower surface of the I-type core 3, and a depth dimension of The size is the same as the depth of the E-type core 2.

  The exciting coil 4 is formed by winding an insulated wire, a so-called magnet wire, in which a polyester insulating coating is provided on a conductor such as copper in a predetermined number of times / shape. As described above, the exciting coil 4 is wound with insulating paper formed of an insulator such as paper at a position where it contacts the E-type core 2 and the I-type core 3. The core 3 and the exciting coil 4 are insulated.

  The piezoelectric element 5 is an element formed by sandwiching a piezoelectric body, which is a kind of dielectric material such as polyvinylidene fluoride (PVDF), which is a kind of plastic, or lead zirconate titanate, which is a kind of ceramic, between two electrodes, Generally, it is also called a piezo element. The piezoelectric element 5 has a piezoelectric effect that converts an applied force into a voltage, and the generated voltage value increases as the applied force increases. As shown in FIG. 1A, the piezoelectric element 5 is inserted in the gap 7 of the reactor 1, and the size is equal to the cross-sectional area S of the middle leg 2a of the E-type core 2 (= the tip end area of the middle leg 2a). A plurality of the piezoelectric bodies stacked are sandwiched between two electrodes, and have substantially the same dimensions as l1 which is the dimension of the gap 7.

  The canceling coil 6 is provided with a polyester insulating coating on a conductor such as copper as shown in the schematic diagram of the canceling coil in FIG. 1B and the DD cross-sectional view in FIG. A coil portion 6a is formed by winding a winding 6c, which is a so-called magnet wire, in a predetermined number of times / shape, and a coil portion 6a is formed with a predetermined length at the beginning and end of winding 6c. Lead wires 6b are formed to be pulled out from the portion 6a and to be connected to the piezoelectric element 5. As shown in FIG. 1A, the canceling coil 6 is installed in the vicinity of the gap 7, more specifically, so as to surround a part of the middle leg 2 a of the E-type core 2 and the piezoelectric element 5.

  Next, the principle of reducing the leakage magnetic flux generated in the gap 7 of the reactor 1 by the operation of the piezoelectric element 5 and the canceling coil 6 will be described with reference to FIGS. When an exciting current, which is an alternating current, flows through the exciting coil 4, the direction of the exciting current is such that the middle leg 2 a of the E-type core 2 → the gap 7 → the I-type core 3 → the outer leg 2 b of the E-type core 2 in this order. Magnetic flux passes through the core. At this time, as indicated by an arrow in FIG. 2A, a part of the magnetic flux flowing through the core leaks outside the gap 7 to generate a leakage magnetic flux Φm. In FIG. 2A, the description of the piezoelectric element 5 and the canceling coil 6 is omitted for easy understanding of the generation state of the leakage magnetic flux.

  On the other hand, as shown in FIG. 2B, in the gap 7, the magnetic attraction force generated by the magnetic flux passing through the E-type core 2 and the I-type core 3 (depending on the direction of the excitation current, the middle leg of the E-type core 2). The force F is applied to the piezoelectric element 5 inserted in the gap 7 by generating a force that attracts each other with the tip surface of 2a being the N pole / I type core 3 and the corresponding surface of the N pole / I-type core 3 being the S pole or vice versa. .

  When a force F is applied to the piezoelectric element 5, a voltage is generated in the piezoelectric element 5. When this voltage is applied to the canceling coil 6 connected to the piezoelectric element 5 and a current flows through the canceling coil 6, a canceling magnetic flux Φc is generated in the canceling coil 6 as shown by an arrow in FIG. To do. The magnitude of the canceling magnetic flux Φc can be adjusted to the same magnitude as the leakage magnetic flux Φm by determining the number of turns of the winding 6c according to the voltage value applied to the canceling coil 6, but the phase of the canceling magnetic flux Φc is Since it deviates from the leakage flux Φm, the leakage flux Φm cannot be canceled out by the cancellation flux Φc unless the phase is adjusted separately. Next, a method for adjusting the phase will be described.

  FIG. 3 is a waveform diagram for explaining the phase relationship between the leakage magnetic flux Φm and the canceling magnetic flux Φc. FIG. 3A shows the waveform of the leakage magnetic flux Φm and the output voltage Ec of the piezoelectric element 5, and FIG. The waveforms of Φm, the output voltage Ec1 / Ec2 before and during the adjusting means described later, and the canceling magnetic flux Φc are shown. 3 (A) / (B), the horizontal axis represents time (ωt) and the vertical axis represents amplitude. Here, in order to mainly explain the phase relationship, the vertical axis is an arbitrary value and is a unit. Is omitted.

  The leakage flux Φm is in phase with the magnetic flux passing through the core, and the magnetic flux passing through the core of the reactor 1 is generated by the exciting current (alternating current) flowing through the exciting coil 4, so that the magnetic flux flowing through the core and the exciting current are in phase. It becomes. Therefore, the leakage magnetic flux Φm has the same phase as the exciting current, and the waveform of the leakage magnetic flux Φm becomes the leakage magnetic flux Φm50 as shown in FIG. Further, the direction of the magnetic flux passing through the core of the reactor 1 is reversed between the case where the amplitude value of the leakage magnetic flux Φm is positive and the case where it is negative.

  On the other hand, the force F applied to the piezoelectric element 5 is the same as the magnetic attraction force generated in the gap 7 regardless of the direction of the magnetic flux passing through the core of the reactor 1 (= direction of the leakage magnetic flux Φm). A force F having the same magnitude is generated regardless of whether the amplitude of the leakage flux Φm is on the plus side or the minus side. Therefore, the output voltage Ec generated by the piezoelectric element 5 in response to the force F has the same phase as the force F, and the waveform of the output voltage Ec is DC biased to the plus side as shown in FIG. The output voltage Ec51 has a period of ½ with respect to the waveform of Φm.

  Even if this output voltage Ec is applied to the cancellation coil 6, the generated cancellation magnetic flux Φc becomes a magnetic flux in only one direction, and the leakage magnetic flux Φm cannot be canceled sufficiently. Therefore, an adjusting circuit shown in FIG. 4 is inserted between the piezoelectric element 5 and the canceling coil 6 to correct the DC bias of the output voltage Ec and adjust the period / phase to leak the magnetic flux from the canceling coil 6. Adjustment is made to generate a canceling magnetic flux Φc that can sufficiently cancel Φm.

  As shown in FIG. 4, the adjustment circuit includes a capacitor 8 (capacitance is arbitrary) for cutting a direct current component of the output voltage Ec, and a phase inversion composed of an operational amplifier as well as a period changing means 9a composed of an operational amplifier. It is comprised by the adjustment means 9 which consists of a means 9b. Since both the period changing unit 9a and the phase inverting unit 9b are well-known techniques, detailed description thereof is omitted, and only the respective effects are described here.

  The output voltage Ec generated by the piezoelectric element 5 becomes a corrected output voltage Ec1 whose DC bias is corrected by the capacitor 8, and the waveform thereof becomes a corrected output voltage Ec1 (52) as shown in FIG. Next, this corrected output voltage Ec1 is doubled by the period changing means 9a of the adjusting means 9 to become the corrected output voltage Ec2, and the waveform thereof is corrected output voltage Ec2 (53) as shown in FIG. become that way.

  Further, the corrected output voltage Ec2 is applied to the canceling coil 6 as a corrected output voltage Ec3 whose phase is inverted by 180 ° by the phase inverting means 9b of the adjusting means 9. The current flowing through the canceling coil 6 by the corrected output voltage Ec3 has a waveform whose phase is delayed by 90 ° from the corrected output voltage Ec3. At this time, the canceling magnetic flux Φc generated from the canceling coil 6 is also a current flowing through the canceling coil 6. Since the phase is the same, the waveform of the canceling magnetic flux Φc becomes a canceling magnetic flux Φc54 as shown in FIG.

As shown in FIG. 3B, the waveform of the canceling magnetic flux Φc54 has the same amplitude and period as the waveform of the leakage magnetic flux Φm waveform 50, and has a phase that is 180 ° different. Therefore, the leakage flux Φm is canceled by the cancellation flux Φc, and the leakage flux Φm can be greatly reduced.
The adjustment circuit described above is provided with amplitude adjusting means for adjusting the amplitude of the output voltage Ec of the piezoelectric element 5 so that the magnitude of the canceling magnetic flux Φc generated in the canceling coil 6 matches the magnitude of the leakage magnetic flux Φm. May be.

Next, a method of determining the number of turns of the cancellation coil 6 for generating the cancellation magnetic flux Φc that cancels the leakage magnetic flux Φm will be described with reference to FIG. In the following description, the piezoelectric body constituting the piezoelectric element 5 is a polyvinylidene fluoride having a thickness of 30 (μm) and a power generation efficiency of 100 (mW / m ² ) when a force of 500 (N) is applied. (PVDF) is used, and the case where this piezoelectric element 5 is inserted in the reactor 1 which can obtain inductance: 3 (mH) by exciting current: 10 (A) is mentioned as an example, and is demonstrated. It should be noted that the method described below can be similarly applied to other reactors and choke coils.

As shown in FIG. 1A, the specifications of the reactor 1 are as follows: exciting current I: 10 (A), inductance L: 3.0 (mH), exciting coil winding number N: 56 (turns), gap dimension 11: 2.0 (mm), magnetic path length l2: 94 (mm), which is a path when magnetic flux passes through the core, E-type core middle leg cross-sectional area S: 576 (mm ² ), vacuum permeability μ Assuming that ₀ : 4π × 10 ⁻⁷ (H / m) and the relative permeability μ _s : 7,000, the number of turns of the canceling coil 6 is calculated.

First, the force F applied to the piezoelectric element 5 is obtained. The magnetic resistance Rm of the core of the reactor 1 is expressed by “Equation 1” using the gap dimension l1, the magnetic path length l2, the E-shaped core leg cross-sectional area S, the vacuum permeability μ _{0 and the} relative permeability μ _s. It can be obtained by an expression.

  The magnetic flux Φ passing through the magnetic path can be obtained by the formula 2 using the magnetic resistance Rm, the exciting current I, and the exciting coil winding number N.

Accordingly, the magnetic flux density B at the middle leg 2a of the E-type core 2 is obtained by using the magnetic flux Φ and the cross-sectional area S of the E-type core middle leg. Using the magnetic flux density B at the middle leg 2a of the E-type core 2, the cross-sectional area S of the E-type core middle leg, and the magnetic permeability μ _{0 of the} vacuum, each can be obtained by the “Equation 3”.

By substituting the above-mentioned specification (numerical value) into the formula for obtaining the force F applied to the piezoelectric element 5 of the “Equation 3”, the force F actually applied to the piezoelectric element 5 is obtained as shown in the “Equation 4”. The force F applied to the piezoelectric element 5 is calculated to be 50 (N) at the maximum.

Next, the power generation amount W at the piezoelectric element 5 is obtained. As described above, since the thickness of the piezoelectric body is 30 (μm) and the dimension l1 of the gap 7 is 2.0 (mm), 60 piezoelectric bodies are stacked in consideration of the thickness of the terminal attached to the piezoelectric body. Thus, the calculation is performed assuming that the piezoelectric element 5 is formed. Since the power generation efficiency of one piezoelectric body is 100 (mW / m ² ) when a force of 500 (N) is applied as described above, the power generation efficiency per unit force is 0.2 (mW / m ² N )

Since the piezoelectric element 5 has the same size as the cross-sectional area S of the middle leg 3a of the E-type core 2, the total area of the piezoelectric bodies when 60 piezoelectric bodies are stacked is 3.5 × 10 ⁻² (m ² ). Therefore, power generation efficiency per unit force: 0.2 (mW / m ² N), total area of the piezoelectric body: 3.5 × 10 ⁻² (m ² ), force F applied to the piezoelectric element 5: 50 (N) As shown in “Expression 5”, the power generation amount W at the piezoelectric element 5 is calculated as 0.35 (mW).

  Next, the number of turns n of the cancellation coil 6 is obtained. The canceling magnetic flux Φc generated in the canceling coil 6 can be obtained by the equation (6) using the inductance Lc of the canceling coil 6 and the current Ic flowing through the canceling coil 6.

  The output voltage Ec of the piezoelectric element 5 can be obtained by differentiating the canceling magnetic flux Φc with respect to time as shown in “Expression 7”.

  The current Ic flowing through the canceling coil 6 can be obtained by the equation (8) using the power generation amount W in the piezoelectric element 5 and the output voltage Ec of the piezoelectric element 5.

  Therefore, the canceling magnetic flux Φc generated in the canceling coil 6 can be obtained by the “Expression 9” from the “Expression 6”, the “Expression 7”, and the “Expression 8”.

On the other hand, the leakage flux Φm in the gap 7 is calculated as an actual value assuming that 1% of the magnetic flux Φ generated in the reactor 1 leaks, and as shown in the “Equation 10”, 3 × 10 ⁻⁴ (Wb) Become.

Here, the leakage magnetic flux Φc = cancellation magnetic flux Φc that can cancel the leakage magnetic flux Φm is generated by substituting the actual numerical value into the mathematical expression 11 obtained by modifying the mathematical expression 9 as the leakage magnetic flux Φm = cancellation magnetic flux Φc. The inductance Lc of the cancellation coil 6 that can be obtained can be obtained, and the value is 5.25 × 10 ⁻⁷ (H).

Further, the inductance Lc of the canceling coil 6 uses the vacuum permeability μ _{0, the} number of turns n of the canceling coil 6, the cross-sectional area S ′ of the canceling coil 6, and the winding width l ′ of the canceling coil 6. It can be obtained by the “Expression 12” equation.

  Since the canceling coil 6 is wound around the middle leg 2a and the gap 7 of the E-type core 2, the cross-sectional area S ′ of the coil 6 = the cross-sectional area S of the E-type core middle leg, the winding width l of the canceling coil 6 '= Gap dimension l1 and by substituting an actual numerical value into "Formula 13" obtained by modifying "Formula 12", the number of turns n of the canceling coil 6 can be obtained. Become.

  As described above, the number of turns of the canceling coil 6 that generates the canceling magnetic flux Φc is required to be about 600 times. Next, the shape when the actual canceling coil 6 is created with this number of turns and the installation property to the reactor 1 will be described. The actual value of the current Ic flowing through the canceling coil 6 is 70 (μA) when calculated by substituting a numerical value into the “Equation 8”.

  Thus, since the value of the current Ic is very small, the influence of the heat generation of the canceling coil 6 and the change in resistance value due to the current Ic is small, so that the winding 6c of the canceling coil 6 should use an insulated wire having a small wire diameter. Can do. For example, when the wire diameter of the winding 6c is 0.1 (mm) and the number of turns is 600, as shown in FIG. 1 (C), the number of turns per layer is 75 (turns). Thus, the dimensions of the cancellation coil 6 can be set to a winding width: 7.5 (mm) and a thickness of the coil portion 6a: 0.8 (mm), and can be installed in the vicinity of the gap 7 of the reactor 1. It can be a size.

  Next, the reduction of leakage flux in the choke coil according to the second embodiment will be described. The method for matching the phases of the leakage magnetic flux and the canceling magnetic flux and the method for obtaining the number of turns of the canceling coil are the same as those described in the first embodiment, and therefore detailed description thereof is omitted, and the choke coil configuration is omitted. Only the principle of reducing leakage flux will be described.

  FIG. 5 shows the configuration of a choke coil according to the second embodiment. As shown in the cross-sectional view of the main part in FIG. 5A, the choke coil 10 includes a toroidal core 11, a winding 12, a piezoelectric element 13, and a canceling coil 14. Although not shown, a case for attaching the choke coil 10 to an electric device, a lead wire and a terminal for connecting to a control board of the electric device, and a heat-resistant tube covering the lead wire are provided.

  The toroidal core 11 is made of a soft magnetic material such as iron-based amorphous and has a donut shape. Specifically, a soft magnetic material having a predetermined magnetic permeability and formed into a thin plate shape is wound up to form a donut shape, and a gap 15 is formed in a part of the toroidal core 11. The magnetic saturation characteristics of the choke coil 10 are improved by providing the magnetic resistance in the gap 15 and preventing magnetic saturation from occurring.

  The winding 12 is a so-called magnet wire in which a polyester insulating coating is provided on a conductor such as copper, and is wound around the toroidal core 11 a predetermined number of times. A magnetic flux is generated in the toroidal core 11 when an exciting current flows through the winding 12. The piezoelectric element 13 is the same as the piezoelectric element 5 described in the first embodiment, and the cross-sectional area of the toroidal core 10 is inserted into the gap 15 of the choke coil 10 as shown in FIG. A plurality of piezoelectric bodies having the same size as that of the gap 15 are sandwiched between two electrodes and have substantially the same dimensions as the gap 15.

  As shown in the schematic diagram of the canceling coil in FIG. 5B, the canceling coil 14 is formed by winding a winding made of an insulated wire in which a polyester insulating coating is provided on a conductor such as copper in a predetermined number of times / shape. The coil portion 14a is formed, and a lead wire 14b for connecting a part of the winding start and end of the winding with a predetermined length from the coil portion 14a and connecting to the piezoelectric element 13 is formed. . As shown in FIG. 5A, the canceling coil 14 is installed in the vicinity of the gap 15, and more specifically, is installed so as to surround a part of the toroidal core 10 and the piezoelectric element 13.

  Next, the principle of reducing the leakage magnetic flux generated in the gap 15 in the second embodiment by the operation of the piezoelectric element 13 and the canceling coil 14 will be described with reference to FIG. When an exciting current that is an alternating current flows through the winding 12, the magnetic flux passes through the toroidal core 11 clockwise or counterclockwise depending on the direction of the exciting current. At this time, as indicated by an arrow in FIG. 5C, a part of the magnetic flux flowing through the toroidal core 11 leaks outside the gap 15 to generate a leakage magnetic flux Φm ′.

  On the other hand, in the gap 15, the magnetic attraction force generated by the magnetic flux passing through the toroidal core 11 (depending on the direction of the excitation current, one of the toroidal cores 11 in the vicinity of the gap 15 becomes an N pole and the other attracts each other. Force F ′ is applied to the piezoelectric element 13 inserted in the gap 15.

  When a force F ′ is applied to the piezoelectric element 13, a voltage is generated in the piezoelectric element 13. When this voltage is applied to the canceling coil 14 connected to the piezoelectric element 13 and a current flows through the canceling coil 13, a canceling magnetic flux Φc ′ is generated from the canceling coil 14 as indicated by an arrow in FIG. Will occur. The magnitude of the canceling magnetic flux Φc ′ can be adjusted to the same magnitude as the leakage magnetic flux Φm ′ by determining the number of turns of the winding in accordance with the current flowing through the canceling coil 6. The phase shift with respect to the leakage magnetic flux Φm ′ is adjusted by inserting the adjusting circuit shown in FIG. 4 between the piezoelectric element 13 and the canceling coil 14 and using the same method as described in the first embodiment. . Accordingly, the leakage flux Φm ′ is canceled by the cancellation flux Φc ′, and the leakage flux Φm ′ can be greatly reduced.

  As described above, according to the present invention, the piezoelectric element inserted in the gap by the magnetic attraction force generated in the gap when the exciting current flows through the exciting coil and generated in a magnitude proportional to the magnitude of the exciting current. Power is generated by applying force, the generated voltage is applied to the canceling coil, and a current is passed through the canceling coil to generate a canceling magnetic flux. Therefore, the wire diameter of the canceling coil winding can be freely selected if a predetermined canceling magnetic flux can be generated without considering the wire diameter of the exciting coil and the magnitude of the excitation current. The coil can be reduced in size, and the installation property of the canceling coil is improved, and the downsizing / thinning of the inductor is not hindered.

  In addition, the leakage magnetic flux generated in the gap is reduced by canceling with the canceling magnetic field generated by the canceling coil, so it is possible to prevent heat generation due to eddy current loss that occurs when the leakage magnetic flux passes through the soft magnetic material. Inductor safety can be increased.

  In the above-described embodiment, the reactor including the E-type core and the I-type core is described as the first embodiment, and the choke coil including the toroidal core having a donut shape is described in the second embodiment. Instead of the reactor, the reactor may have a core shape using two E-type cores, a U-type or a C-type core and an I-type core. As for the choke coil, the shape of the toroidal core may be a square, a rectangle or an ellipse.

  In the first and second embodiments, the soft magnetic material is laminated or wound to form the core. However, the present invention is not limited to this, and a magnetic material such as ferrite is compacted. The core formed by may be used.

  In the first and second embodiments, the case where the canceling coil is installed around the gap of the core has been described. However, the canceling coil is part of the vicinity of the gap, for example, FIG. It may be arranged only on the gap right side (the outer peripheral side of the toroidal core 11) of the toroidal core 11 of A) so as to cancel only the magnetic flux leaking in one direction such as the outside of the inductor.

DESCRIPTION OF SYMBOLS 1 Reactor 2 E type core 2a Middle leg 2b Outer leg 3 I type core 4 Exciting coil 5 Piezoelectric element 6 Canceling coil 6a Coil part 6b Lead wire 6c Winding 7 Gap 8 Capacitor 9 Adjustment means 9a Period change device 9b Phase inversion device DESCRIPTION OF SYMBOLS 10 Choke coil 11 Toroidal core 12 Winding 13 Piezoelectric element 14 Counter coil 14a Coil part 14b Lead wire 15 Gap

Claims (2)

A core made of a magnetic material and having a gap in part, an exciting coil wound around the core, a piezoelectric element disposed in the gap, and connected to the piezoelectric element and disposed in the vicinity of the gap With a cancellation coil,
An inductor characterized in that leakage magnetic flux generated in the gap is canceled by canceling magnetic flux generated in the canceling coil.   The inductor according to claim 1, further comprising an adjustment circuit for adjusting the cancellation magnetic flux between the piezoelectric element and the cancellation coil.