JP2013254970A - Reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor which can be arranged to have a desired inductance with no gap.SOLUTION: The reactor 1 comprises a core unit 10, and an inductor 20 disposed outside a part of the core unit. In the reactor 1, a closed magnetic circuit extending through the core unit is formed in response to magnetic excitation of the inductor. The core unit is substantially formed from a material having relative magnetic permeability of 5-50 when electric current forced to pass through the inductor is zero. The core unit includes, as its constituent material, soft magnetic powder. The soft magnetic powder is made of at least one selected from iron, cobalt and nickel, and an iron-based alloy.

Description

  The present invention relates to a reactor. In particular, the present invention relates to a reactor having no gap in the core portion.

  In recent years, hybrid vehicles have been put into practical use from the viewpoint of protecting the global environment. A hybrid vehicle is a vehicle that includes an engine and a motor as drive sources and travels using one or both of them. In such a hybrid vehicle, the direct current of the battery is converted into alternating current by an inverter, and the alternating current is supplied to a motor for traveling. In particular, recent hybrid vehicles are equipped with a boost converter to reduce the size of the battery and motor. The boost converter has a role of boosting the voltage of the battery and supplying it to the inverter (motor), and a role of reducing the regenerative current from the generator (motor) to the battery voltage and charging the battery. The reactor can store electric energy as magnetic energy and is used as one of the components of the boost converter.

  For example, as shown in FIG. 7, such a reactor 1 includes a core portion 10 and a coil 20, and forms a closed magnetic path through the core portion 10 by exciting the coil 20. Moreover, the core part 10 is comprised from the core piece 15 and the gap material 16 (patent document 1 FIG. 1 as literature which shows the form of a similar core part).

More specifically, the ring-shaped core portion 10 is configured by combining a plurality of core pieces 15 and gap members 16 as described below. The core portion 10 includes a pair of U-shaped core pieces 15u having a rectangular end face, and four I-shaped core piece 15 _i. Each U-shaped core piece 15 _u is arranged so that the end faces thereof face each other, and two I-shaped core pieces 15 _i are arranged side by side between each end face of the U-shaped core piece 15 _u. . As the material constituting the core piece 15, for example, a magnetic material such as a laminated steel plate is used.

  In addition, a gap for adjusting the magnetic permeability of the core portion is formed in the core portion 10 in order to set the reactor inductance to a desired value without causing magnetic saturation in the core portion 10. The gap is formed by sandwiching the gap material 16 between the core pieces and joining the core piece 15 and the gap material 16 together. The gap is formed of a nonmagnetic material having a relative permeability close to 1. In addition to the gap material 16 made of an inorganic material, the gap may be an air gap. Since the reactor inductance is defined by the gap distance formed in the closed magnetic circuit, this gap distance needs to be maintained with high accuracy. Therefore, a plate made of a non-magnetic material with high hardness such as alumina is often used for the gap material 16.

  And the coil 20 is provided in a part of outer periphery of such a core part 10. FIG. The coil 20 is formed by winding a winding 21. If current is passed through the coil 20 to excite it, a closed magnetic path passing through the core piece 15 and the gap member 16 is formed along the annular core portion 10.

JP 2004-241475 A

  However, in the core portion provided with the gap, problems of noise and leakage magnetic flux occur.

  When the reactor coil is excited, an electromagnetic attractive force acts on the core piece. Therefore, vibration is generated particularly at the joint portion between the core piece and the gap member, and noise is generated from the reactor due to the vibration.

  In addition, when a gap is provided in the core part, the gap material has a smaller magnetic permeability than the core piece, so that the magnetic flux leaks to the outside of the core part. For example, as shown in FIG. 6 (B), the magnetic flux (arrow) bends and leaks outside the gap material 16 at a location where the gap material 16 is sandwiched between the core pieces 15. When the coil 20 is formed on the outer periphery of the core portion 10, leakage magnetic flux enters the coil 20 and causes eddy current loss in the coil 20. For this reason, conventionally, a space is provided between the outer periphery of the core portion 10 and the inner periphery of the coil 20 so that the leakage magnetic flux does not affect the coil 20.

  On the other hand, if all of the core part is composed of laminated steel plates and the gap is eliminated, there is a problem that when the coil is excited, the core part is magnetically saturated and the reactor inductance cannot be adjusted to a predetermined range. is there.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a reactor that can have a desired inductance without having a gap.

  As a result of studying the configuration of the reactor without providing a gap, the present inventors have obtained the knowledge that the entire core portion may be substantially composed of a predetermined low magnetic permeability material and complete the present invention. It came to.

  The reactor of the present invention is a reactor that includes a core portion and a coil that is disposed outside a part of the core portion, and a closed magnetic path that passes through the core portion is formed by excitation of the coil. And the said core part is substantially comprised with the material whose relative magnetic permeability is 5-50.

The reactor according to the present invention eliminates the gap in the core portion of the conventional reactor, and the core portion is substantially made of a low magnetic permeability material. Therefore, the problem of noise due to the gap can be reduced. In addition, since the leakage magnetic flux is eliminated by eliminating the gap, if the core part having the same size as the conventional one is used, the space between the core part and the coil can be reduced, so that the outer dimension of the reactor can be reduced. If the outer dimensions of the coil constitute the same reactor, a larger core part can be used. Since the reactor occupies a considerably large volume among the components of the boost converter, if the reactor can be downsized, the effect of reducing the installation space of the boost converter is great. Furthermore, since the entire core portion is substantially made of a predetermined low permeability material, it is possible to avoid the occurrence of a magnetic saturation in the core portion when the coil is excited, and to obtain the required inductance. it can. The relative permeability μ _r is a ratio μ / μ ₀ between the material permeability μ and the vacuum permeability μ ₀ (vacuum permeability μ ₀ = 4π × 10 ⁻⁷ ).

  As one form of this invention reactor, it is desirable to make a core part into a compacting body.

  If the core part is a green compact, the core part can be molded into various three-dimensional shapes, and a material with low magnetic permeability can be obtained to achieve the above-described predetermined relative magnetic permeability. Is possible.

  As one form of this invention reactor, it is preferable to make a core part into a sintered compact.

  If the core part is a sintered body, the core part can be formed into various three-dimensional shapes, and a material having a low magnetic permeability can be obtained to achieve the above-described predetermined relative magnetic permeability. It is.

  As one form of this invention reactor, it is desirable to make a core part into the shaping | molding hardening body which shape | molded the mixture of magnetic powder and fluid resin, and hardened the resin of the obtained molded object.

  If the core part is a molded and hardened body, the core part can be formed into various three-dimensional shapes, and a material having a low magnetic permeability can be obtained and the above-described predetermined relative magnetic permeability can be realized. It is.

  In addition, as one form of this invention reactor, it is preferable to make a core part into the structure provided with an inner core, an outer core, and a connection core. The inner core is located inside the coil. The outer core is located outside the coil. The connecting core covers the both ends of the coil and connects the inner core and the outer core.

  Such a so-called pot-type core part can directly or indirectly contact part or substantially all of the outer peripheral surface of the coil with the core part, so that the contact area between the core part and the coil can be increased. it can. Therefore, when the coil is energized, the heat generated from the coil is conducted to the core part, so that it can be efficiently radiated from the entire core part.

  According to the reactor of the present invention, the magnetic saturation of the core portion can be suppressed while eliminating the gap that has been conventionally provided. As a result, it is possible to reduce the problems of reactor noise and leakage magnetic flux, which have become problems due to the existence of the gap.

It is a partial notch perspective view which shows an example of this invention reactor. An example of the reactor of the present invention having a pot-type core part is shown, (A) is an external perspective view, (B) is a longitudinal sectional view, and (C) is a transverse sectional view. It is a disassembled perspective view of the reactor of FIG. It is explanatory drawing which shows the approximate dimension of the reactor used for the trial calculation example. It is a graph which shows the relationship between the electric current at the time of exciting the reactor which has a core part from which a relative permeability differs, and an inductance. It is a schematic explanatory drawing which shows the relationship between the magnetic flux which passes a core part, and a coil, (A) shows this invention reactor, (B) shows the conventional reactor. It is a partial notch perspective view which shows the conventional reactor.

  Hereinafter, the configuration of the reactor of the present invention will be described in more detail.

[Core part]
A core part is a location where a closed magnetic circuit is formed when a coil is excited. Specific examples of the core part used in the reactor of the present invention include an annular core part and a pot-type core part.

(Annular core)
As an example of an annular core part, as shown in FIG. 1, the core part 10 which consists of a cylindrical body is mentioned. The core portion 10 is configured as an integral molded body, and is not formed by joining a plurality of core pieces. If the core part 10 is formed of an integral molded body, the labor of joining a plurality of core pieces can be saved.

  Compared with the core portion of FIG. 7, the characteristics of the core portion used in the present invention can be understood well. In a conventional reactor, each core piece is joined with a gap material interposed therebetween, and a coil 20 is formed so as to cover an arrangement position of the gap material. In the reactor 1 of the present invention, a gap is not formed in a portion where the coil 20 is formed in the core portion 10 as well as a portion where the coil 20 is formed.

  Such a cylindrical core part 10 can be obtained by using sintering, compacting or injection molding, which will be described later.

(Pot type core part)
As an example of the pot-type core portion, as shown in FIGS. 2 and 3, the pot-shaped core portion is composed of a cylindrical inner core 11, a hollow cylindrical outer core 12, and a pair of disk-shaped connecting cores 13. The core part 10 is mentioned. Among these, the connection core 13 includes an upper connection core 13U that covers the upper end of the coil 20, and a lower connection core 13L that covers the lower end of the coil 20. The outer diameter of the outer core 12 and the outer diameters of the two connecting cores 13U and 13L are substantially the same.

  When assembling the reactor, as shown in FIG. 3, a coil 20 having a winding wound in a hollow cylindrical shape is prepared in advance, and the coil 20 is fitted inside the outer coil 12. The upper and lower end surfaces of the outer coil 12 are formed with notches 121 for pulling out both ends of the winding 21 constituting the coil 20, and the coil 20 is placed so that both ends of the winding 21 are fitted into the notches 121. Position in the outer core 12. Next, the inner core 11 is positioned and joined on the center part of the lower connecting core 13L, and the outer core 12 in which the coil 20 is fitted is joined on the lower connecting core 13L. At that time, the inner core 11 is fitted inside the coil 20. Then, the upper connecting core 13U is joined on the outer core 12, and the coil 20 is accommodated in the core portion 10. The cores 11, 12, and 13 can be joined with bolts or an adhesive. In the reactor 1 of the present invention using the pot-type core portion, a closed magnetic path that returns to the inner core through the inner core 11, the upper connecting core 13U, the outer core 12, and the lower connecting core 13L is formed. At that time, no gap is formed in the middle of the closed magnetic circuit.

  In the reactors of FIGS. 2 and 3, the reactor can be divided by the inner core, the outer core, and the connecting core, but various variations can be considered. For example, when the inner core and the upper connecting core are integrated, and the outer core and the lower connecting core are integrated, or the outer core is divided into the upper outer core and the lower outer core, the upper outer core and the upper connecting core are integrated, For example, the lower outer core and the lower connecting core are integrated.

  In the case of the pot-type core portion, the inner core, the outer core, and the connecting core can all be obtained by using sintering, compacting, injection molding, or casting, which will be described later.

(Relative permeability)
The core part as described above is made of a low permeability material having a relative permeability of 5 to 50. Conventionally, the relative magnetic permeability of the electromagnetic steel sheet used for the core portion of the reactor is about 4000 to 8000, and the relative permeability of the green compact is about 400 to 600. With such a high magnetic permeability material, it is difficult to configure the core without providing a gap. However, in the reactor of the present invention, the problem of magnetic saturation of the core portion is solved without providing a gap by configuring the entire core portion with a low permeability material having a relative permeability of 5 to 50.

  Here, “the core part is substantially composed of a low magnetic permeability material” means that there is substantially no inductance adjusting part (gap) made of a material having a magnetic permeability different from that of the core part material in the middle of the closed magnetic path. Say. For example, when a core part is comprised with the joined body of a several core piece, an adhesive agent will intervene in this joining location. The adhesive is usually non-magnetic, but the adhesive here is not for adjusting the inductance of the reactor, but merely for joining the core pieces together. Therefore, even if the adhesive is present in the middle of the closed magnetic path, in such a case, it is considered that the core portion is substantially composed of a low magnetic permeability material.

  In the present invention, the range of the relative magnetic permeability is defined as described above, but it is preferable that the entire core portion is made of a substantially uniform magnetic permeability material. Theoretically, for example, a part of the core part may be made of a low permeability material with a relative permeability of 5 and the remaining part of the core part may be made of a low permeability material with a relative permeability of 50, but the entire core part is almost uniform. If it is made of a material having a high magnetic permeability, the magnetic flux passes uniformly through the core portion, and the problem of leakage magnetic flux can be more effectively solved.

(Adjustment method of permeability)
In order to adjust the magnetic permeability of the constituent material of the core part and adjust the relative magnetic permeability within the above specified range, the following method is exemplified. In any case, if the size of the core portion increases, it is preferable to lower the magnetic permeability of the material constituting the core portion.

<For sintered body>
When obtaining a core part with a sintered body, usually, a mixed powder of a soft magnetic powder, a nonmagnetic powder and a binder resin is mixed, and the mixed powder is molded and then sintered at a high temperature. During sintering, the binder resin almost disappears, and the soft magnetic powder and the nonmagnetic powder are sintered. Therefore, a core portion made of a low magnetic permeability material can be obtained by adjusting the mixing ratio of the soft magnetic powder and the nonmagnetic powder. In addition, the magnetic permeability of the constituent material of the core part can be adjusted by changing the pressure when forming the mixed powder. There is a tendency that the permeability of the core portion can be lowered when the blending amount of the nonmagnetic powder is large or when the molding pressure of the mixed powder is low.

Soft magnetic powders include Fe, Co, Ni, Fe-based alloy powders such as Fe-Si, Fe-Ni, Fe-Al, Fe-Co, Fe-Cr, Fe-Si-Al, or rare earth metals Powder, ferrite powder, etc. can be used. As the non-magnetic powder, non-magnetic non-metallic powders such as Al ₂ O ₃ and SiO ₂ can be used in addition to non-magnetic metal powders such as Cu, Al, and Si. As the binder resin, a thermoplastic resin, a non-thermoplastic resin, or a higher fatty acid can be suitably used.

<For green compact>
When obtaining a core part with a green compact, usually a soft magnetic powder having an insulating coating provided on the surface and a binder resin are mixed, and the mixed powder is molded and then fired at a temperature lower than the heat resistance temperature of the insulating coating. In this case, the core part made of a low magnetic permeability material can be obtained by changing the mixing ratio of the soft magnetic powder and the binder resin. In addition, the magnetic permeability of the constituent material of the core part can be adjusted by changing the pressure when forming the mixed powder. There is a tendency that the permeability of the core portion can be lowered when the amount of the binder resin is large or when the molding pressure of the mixed powder is low. Unlike the core portion of the sintered body, the binder resin remains in the core portion of the green compact, and insulation between the soft magnetic powders is maintained. Therefore, eddy current loss can be reduced compared with the core part of a sintered compact, and it is suitable for use when a coil is supplied with a high frequency.

  As the soft magnetic powder, the same soft magnetic powder as that of the sintered body can be used. Examples of a method for producing such a powder include an atomizing method (gas, water) and a mechanical pulverization method. The insulating coating formed on the soft magnetic powder is preferably composed of a phosphoric acid compound, a silicon compound, a zirconium compound or a boron compound. As the binder resin, a thermoplastic resin, a non-thermoplastic resin, or a higher fatty acid is preferably used.

<In the case of molded hardened body>
When the molded cured body is used as the core portion, there are injection molding and cast molding as methods for obtaining the molded cured body. Injection molding is usually performed by mixing soft magnetic powder (and, if necessary, non-magnetic powder) and a flowable binder resin, pouring the mixed fluid into a mold under pressure, and then molding the binder resin. Is cured. On the other hand, in cast molding, a mixed fluid similar to that of injection molding is obtained, and then the mixed fluid is injected into a mold without applying pressure to be molded and cured. In any molding technique, a thermosetting resin such as an epoxy resin, a phenol resin, or a silicone resin is preferably used as the binder resin. When a thermosetting resin is used as the binder resin, the molded body is heated to thermoset the resin. However, the binder resin may be cured by using a room temperature curable resin or a low temperature curable resin and leaving the molded body at a room temperature to a relatively low temperature. In addition, after injection molding, the molded body may be heat-treated at a high temperature to sinter soft magnetic powders or soft magnetic powder and nonmagnetic powder (MIM: Metal injection molding). Even when using injection molding or cast molding, if not sintered, soft magnetic powder (nonmagnetic powder) and binder resin are mixed, and if sintered, soft magnetic powder and nonmagnetic powder The magnetic permeability of the material constituting the core part can be adjusted by changing the blending of.

〔coil〕
A coil is provided on the outer periphery of such a core portion. This coil is formed by winding a winding. This winding is typically composed of a metal wire having an insulating coating. The cross-sectional shape of the winding may be a circle or a polygon such as a rectangle or a hexagon. For example, in the reactor of FIGS. 1 and 2, a coil 20 is formed by winding a rectangular metal winding 21 having a rectangular cross section into a so-called edgewise winding. The form of the coil may be a form adapted to the outer shape of the core part around which the winding is wound. For example, in the reactor of FIG. 1, since the winding part of the coil 20 in a core part is quadrangular prism shape, the form of a coil is also hollow prismatic shape. On the other hand, in FIG. 2, since the inner core has a columnar shape, the form of the coil 20 is also cylindrical. The metal wire constituting the winding is preferably highly conductive, and copper and copper alloys can be suitably used. The insulating coating can be a coating such as enamel.

  Such a coil is preferably fixed to the core portion with an adhesive in order to reduce noise caused by vibration of the coil when excited. For example, an epoxy resin or a urethane resin can be used as such an adhesive.

[Other configurations]
These reactors of the present invention preferably include an insulator at a portion where the coil and the core portion come into contact with each other.

  A large current may flow through the coil. Therefore, it is necessary to prevent dielectric breakdown that occurs between the coil and the core part, and it is also necessary to reduce the loss associated with the eddy current generated on the surface of the core part. If an insulator is provided in the part where a coil and a core part contact, between a coil and a core part can be insulated more reliably and the generation | occurrence | production of the dielectric breakdown and eddy current can be prevented. Examples of the insulating material forming the insulator include resins such as PPS (Poly Phenylene Sulfide polyphenylene sulfide) and LCP (Liquid Crystal Polymer liquid crystal polymer). Further, an inorganic filler may be added to such a resin in order to better transfer the heat of the coil to the core portion. Examples of the inorganic filler include insulating materials such as glass (silicon dioxide), alumina (aluminum oxide), and titanium oxide. The amount of such inorganic filler added may be appropriately selected. It is easy to arrange such an insulator so as to be integrated by combining divided pieces, which is preferable.

[Example 1]
The reactor according to the present invention and the conventional reactor were produced, and the characteristics of both were evaluated. Here, the reactor of FIG. 1 was produced as the reactor of the present invention, and the reactor of FIG. 7 was produced as the conventional reactor. As shown in FIG. 4 (representing a conventional reactor), the size of the manufactured reactor is as follows: the major axis outer dimension Lo of the core part 10 is about 80 mm, the major axis inner dimension Li of the core part 10 is about 40 mm, and the core part 10 is The short axis inner dimension Wi is about 20 mm, and the outer width Wc of the coil 20 is about 80 mm.

  First, the core part of the reactor of the present invention is produced. Prepare water atomized pure iron powder (average particle size of about 100 μm) as soft magnetic powder and polyethylene as binder resin. These iron powder and polyethylene are mixed so that polyethylene is 5 to 80% by mass with respect to the iron powder. The mixed powder is filled into a predetermined mold and molded at a molding pressure of 980 MPa. Then, the compact is heat-treated at 250 ° C. for 60 minutes to obtain a compacted compact. The cylindrical body integrally formed by this compacting is the core portion of the reactor of the present invention.

  On the other hand, in the case of a conventional reactor, a pair of U-shaped core pieces and four I-shaped core pieces are produced by a laminated body of silicon steel plates. And each core piece is made into a core part by joining via the alumina plate used as a gap. A total of six alumina plates are used.

  A coil is provided outside each obtained core part. The coil is formed by winding a winding of a rectangular copper wire with an insulating coating. The winding has a cross-sectional width of about 1 mm and a thickness of about 5 mm, and the number of turns of the coil is 50 turns.

  Here, first, the inductance (self-inductance) of the conventional reactor is measured. The inductance was measured using an LCR meter manufactured by Agilent Technologies. The inductance of the reactor is proportional to the square of the number of turns of the coil and inversely proportional to the magnetic resistance. Further, the magnetic resistance is proportional to the magnetic path length of the closed magnetic path, and is inversely proportional to the product of the magnetic permeability of the constituent material of the core part and the cross-sectional area of the core part. Therefore, by determining the inductance, it is possible to determine the permeability of the laminated steel plate and the alumina plate as viewed on average in the core portion. As a result, the average relative permeability of the core portion of the conventional reactor was about 30.

  Next, the magnetic permeability was measured about the constituent material of each obtained core part. The permeability was measured using a BH tracer manufactured by Riken Denshi Co., Ltd.

  In the case of the green compact, the relationship between the resin amount ratio, the filling rate, and the relative magnetic permeability was as shown in Table 1. “Resin amount ratio” is “resin mass / total mass of resin and iron powder”, and “filling ratio” is “iron powder volume / total volume of resin and iron powder” after molding the mixed powder.

  On the other hand, in the core portion of the conventional reactor, the relative permeability of the laminated steel sheet was 4000 to 5000, and the relative permeability of the alumina plate was 1.

Next, since the average relative permeability μ _r of the core portion of the conventional reactor was about 30, a reactor of the present invention was prepared using a compacted body having a relative permeability μ _r of 30 in Table 1. , relative permeability mu _r in Table 1 were prepared comparing React with a powder compact of 100. The core part of the comparative reactor is a compacted body integrally molded in the same manner as the core part of the reactor of the present invention. And it supplied with electricity to the coil of each reactor, and calculated | required the relationship between the electric current and inductance in that case. The result is shown in FIG.

This graph, relative permeability mu _r indicates the inductance when the current I = 0 in the 30 as 1. The shaded area in this graph is the required inductance specification range. As is apparent from the graph, it can be seen that the current-inductance characteristics are within the required specification range in the reactor of the present invention. In contrast, in the comparative reactor, it can be seen that the current-inductance characteristics deviate greatly from the specification range, particularly when the current value is low.

From the above, it can be seen that the reactor of the present invention can be adjusted to a predetermined inductance without providing a gap. And since the gap is not provided, it seems that the problem of the noise at the time of exciting a reactor and the magnetic flux leakage has improved greatly. For example, if there is no gap in the reactor, the magnetic flux does not affect the coil 20 because the magnetic flux passes through the inside of the core portion 10 as shown in FIG.

  It should be noted that the above embodiments can be modified as appropriate without departing from the gist of the present invention. The scope of the present invention is not limited to the above embodiments.

  The reactor of the present invention can be suitably used as a component of a boost converter such as a hybrid vehicle or an electric vehicle.

1 Reactor
10 Core part
11 Inner core 12 Outer core 13 Linked core
13U Upper connecting core 13L Lower connecting core
121 Notch
15 core pieces
15u U-shaped core piece 15i I-shaped core piece 16 Gap material
20 coils
21 Winding

Claims (1)

A reactor including a core part and a coil disposed on the outside of a part of the core part, wherein a closed magnetic path passing through the core part is formed by excitation of the coil;
The core portion is substantially composed of a material having a relative permeability of 5 to 50 when a current passing through the coil is 0,
A reactor in which the core portion includes soft magnetic powder as a constituent material, and the soft magnetic powder is at least one selected from Fe, Co, Ni, and Fe-based alloys.

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