Patent Application
20200013536
The present disclosure relates to a reactor.
A reactor is one of the components used in a circuit that boosts/lowers a voltage. For example, JP 2011-119664A and JP 2009-246222A disclose a technique relating to a reactor including a coil and a magnetic core on which the coil is arranged. JP 2011-119664A and JP 2009-246222A state that an installation-side surface portion, which is to be located on an installation side when the reactor is installed, of an end core piece on which the coil is not arranged protrudes below an installation-side surface of a central core piece on which the coil is arranged, or a surface portion on a side opposite to the installation-side surface portion of the end core piece protrudes above a surface of the central core piece on a side opposite to the installation-side surface.
There is a demand for reducing vibration noise during driving of a reactor.
A reactor is driven by exciting a coil through the application of an electric current of a predetermined frequency to the coil. While being driven, the reactor may vibrate due to magnetostriction or electromagnetic attraction caused by the occurrence of a magnetic flux in a magnetic core, which may cause noise.
To address the problems described above, one of the objects of the present disclosure is to provide a reactor that can be reduced in size and can suppress vibration noise while being driven.
A reactor according to the present disclosure is a reactor including a coil having a wound portion; and a magnetic core having an inner core portion arranged inside the wound portion and an outer core portion arranged outside the wound portion. A bottom surface portion, which is to be located on an installation side when the reactor is installed, of the outer core portion protrudes below a bottom surface of the inner core portion. A top surface portion on a side opposite to the bottom surface portion of the outer core portion protrudes above a top surface of the inner core portion, and respective protrusion amounts are 20% or less of a height in a vertical direction of the inner core portion, and the outer core portion has a shape that is symmetrical with respect to a center line that divides the inner core portion into an upper portion and a lower portion.
The reactor of the present disclosure can be reduced in size and can suppress vibration noise while being driven.
The inventors of the present disclosure focused on the relationship between the drive frequency of a reactor and the natural frequency of a magnetic core, and investigated the influence of the drive frequency on the vibration characteristics of the reactor. As a result, the following findings were obtained.
In cases of reactors used in power conversion devices to be mounted in hybrid automobiles and electric automobiles, the drive frequency of an electric current applied to coils is generally within a range of 5 kHz to 15 kHz and particularly a range of about 5 kHz to 10 kHz. If the natural frequency of the magnetic core is close to this drive frequency, resonance will occur and vibration noise will thus increase. In particular, if the drive frequency is within an audible range (generally 20 Hz to 20 kHz), the problem of vibration noise will manifest.
With the reactors disclosed in JP 2011-119664A and JP 2009-246222A, the magnetic cores have a configuration in which the bottom surface portion of the outer core portion located on an installation side protrudes below the inner core portion, or the top surface portion on a side opposite to the bottom surface portion protrudes above the inner core portion. Accordingly, with this configuration, compared with a magnetic core that has the same volume and has a configuration in which the outer core portion does not protrude from the inner core portion, the length in a direction extending in the axial direction of the coil can be reduced, and the projection area of the installed reactor in a plan view can thus be reduced, thus making it possible to reduce the size of the reactor (see paragraphs [0013], [0051] and the like in JP 2011-119664A and paragraphs [0014] and the like in JP 2009-246222A, for example). The reactors disclosed in JP 2011-119664A and JP 2009-246222A are basically configured such that at least a bottom surface side of the outer core portion protrudes, and when the outer core portion has a protrusion, the protrusion amount is set such that the protrusion is flush with the outer peripheral surface of the coil (see paragraphs [0039], [0061],
The inventors of the present disclosure intensively investigated the vibration characteristics of conventional reactors as disclosed in JP 2011-119664A and JP 2009-246222A in which the outer core portion protrudes from the inner core portion. As a result, it was found that, compared with the case where the outer core portion does not protrude from the inner core portion, the natural frequency of the magnetic core was likely to decrease, and resonance occurred due to the natural frequency being close to the drive frequency, which resulted in an increase in vibration noise. As a result of intensive research, the inventors of the present disclosure found that the natural frequency decreased in the above-described conventional reactors mainly due to the protrusion amount of the bottom surface portion or top surface portion of the outer core portion being large relative to the inner core portion. In particular, it was found that, when the outer core portion was asymmetrical with respect to the center line that divides the inner core portion into an upper portion and a lower portion, the natural frequency was more likely to decrease.
Based on the above-mentioned findings, the inventors of the present disclosure recognized that it was important to suppress a decrease in the natural frequency in order to avoid resonance between the natural frequency of the magnetic core and the drive frequency, and devised the shape of the magnetic core to achieve the present disclosure.
First, embodiments of the disclosure of the present disclosure will be listed and described.
A reactor according to an aspect of the present disclosure is a reactor including a coil having a wound portion; and a magnetic core having an inner core portion arranged inside the wound portion and an outer core portion arranged outside the wound portion. A bottom surface portion, which is to be located on an installation side when the reactor is installed, of the outer core portion protrudes below a bottom surface of the inner core portion. A top surface portion on a side opposite to the bottom surface portion of the outer core portion protrudes above a top surface of the inner core portion, and respective protrusion amounts are 20% or less of a height in a vertical direction of the inner core portion, and the outer core portion has a shape that is symmetrical with respect to a center line that divides the inner core portion into an upper portion and a lower portion.
With the above-mentioned reactor, the bottom surface portion of the outer core portion protrudes below the inner core portion and the top surface portion thereof protrudes above the inner core portion, thus making it possible to reduce the length in a direction extending in the axial direction of the coil (wound portion) and reduce the projection area of the installed reactor. Accordingly, the footprint of the reactor is reduced, thus making it possible to reduce the size of the reactor. Furthermore, the protrusion amounts of the bottom surface portion and the top surface portion of the outer core portion are 20% or less of the height (i.e., the distance between the bottom surface and the top surface) of the inner core portion, thus making it possible to sufficiently suppress a decrease in the natural frequency of the magnetic core and make the natural frequency higher than the drive frequency (5 kHz to 15 kHz, or particularly 5 kHz to 10 kHz). Accordingly, resonance between the natural frequency and the drive frequency can be avoided by setting the natural frequency to be out of the drive frequency band. In addition, the outer core portion has a shape that is symmetrical with respect to the center line of the inner core portion, thus making it possible to effectively suppress the resonance. Therefore, resonance is less likely to occur, and vibration noise can be suppressed during driving of the reactor. Accordingly, the above-mentioned reactor can be reduced in size and can suppress vibration noise while being driven.
The protrusion amounts of the bottom surface portion and the top surface portion of the outer core portion are set to be 4% or more, or 8% or more, of the height of the inner core portion, for example, from the viewpoint of reducing the size of the reactor. On the other hand, the protrusion amounts are set to be 16% or less, 12% or less, or 10% or less, of the height of the inner core portion, for example, from the viewpoint of suppressing the vibration noise of the reactor.
The term “center line that divides the inner core portion into an upper portion and a lower portion” as used herein refers to an axis passing through the central position between the bottom surface and the top surface of the inner core portion. The term “symmetrical shape” satisfies the condition that the difference in the protrusion amounts between the bottom surface portion and the top surface portion of the outer core portion is 5% or less, and preferably 3% or less, of the height of the inner core portion.
In an embodiment of the above-mentioned reactor, a bottom surface and a top surface of the outer core portion are located on an inner peripheral side with respect to an outer peripheral surface of the wound portion of the coil.
When the bottom surface and the top surface of the outer core portion are located on the inner peripheral side with respect to the outer peripheral surface of the coil (wound portion), the height of the outer core portion is reduced. In this manner, the outer core portion can be reduced in height.
In an embodiment of the above-mentioned reactor, a natural frequency of the magnetic core is higher than a drive frequency.
Since the natural frequency of the magnetic core is higher than the drive frequency (e.g., 5 kHz to 10 kHz), the vibration noise can be suppressed. In particular, it is preferable that the natural frequency of the magnetic core is 10% or more higher than the drive frequency. For example, when the drive frequency is 10 kHz, the natural frequency is 11 kHz or more. In this case, the natural frequency of the magnetic core is sufficiently higher than the drive frequency, thus making it possible to significantly suppress the vibration noise. The natural frequency of the magnetic core is preferably higher than 10 kHz, and particularly preferably 11 kHz or more, for example, from the viewpoint of suppressing the vibration noise.
Hereinafter, specific examples of the reactor according to an embodiment of the disclosure of the present disclosure will be described with reference to the drawings. In the figures, components with the same name are denoted by the same reference numeral. The disclosure of the present disclosure is not limited to these embodiments and is defined by the scope of the appended claims, and all changes that fall within the same essential spirit as the scope of the claims are intended to be included therein.
A reactor 1 of Embodiment 1 will be described with reference to
The reactor 1 is installed to an installation target such as a converter case, for example. In this specification, the lower side of the reactor 1 (the coil 2 and the magnetic core 3 (the inner core portions 31 and the outer core portions 32)) in
As shown in
The winding wire is a coated wire (so-called “enameled wire”) including a conductor (e.g., copper) and an insulating coating (e.g., polyamideimide) covering the outer periphery of the conductor. The coil 2 may be formed of a single continuous winding wire, or formed by joining one end portion of one of the two wound portions 2c to one end portion of the other through welding. The coil 2 (wound portions 2c) of this embodiment is an edgewise coil obtained by winding a coated flat wire in an edgewise manner, and the wound portions 2c are formed in a quadrilateral tube shape. As shown in
As shown in
As shown in
As shown in
The inner core piece 31m is made of a material containing a soft magnetic material. Examples of the material for forming the inner core piece 31m include powder molded articles obtained by molding soft magnetic powder made of iron or an iron alloy (e.g., a Fe—Si alloy, a Fe—Si—Al alloy, or a Fe—Ni alloy), or coated soft magnetic powder that also includes insulated coatings, through compression molding, and composite materials containing soft magnetic powder and a resin. A thermosetting resin, a thermoplastic resin, a cold setting resin, or a low-temperature curing resin can be used as the resin for the composite material. Examples of the thermoplastic resin include polyphenylene sulfide (PPS) resin, polytetrafluoroethylene (PTFE) resin, a liquid crystal polymer (LCP), polyamide (PA) resin such as nylon 6 or nylon 66, polybutylene terephthalate (PBT) resin, and acrylonitrile-butadiene-styrene (ABS) resin. Examples of the thermosetting resin include unsaturated polyester resin, epoxy resin, urethane resin, and silicone resin. In addition, bulk molding compounds (BMCs) obtained by mixing calcium carbonate or glass fibers to unsaturated polyester, millable-type silicone rubber, millable-type urethane rubber, and the like can also be used. In this embodiment, the inner core piece 31m is constituted by a powder molded article.
As shown in
As shown in
In this embodiment, as shown in
Vibration characteristics of a reactor having the same configuration as that of Embodiment 1 described above (see
The dimensions (mm) of the reference model were set as follows (see
Height of outer core portion (H32): 42.0
Protrusion amount (h1, h2): 0
Thickness of outer core portion (D): 18.0
Width of outer core portion (W32): 70.5
Height of inner core portion (H31): 42.0
Width of inner core portion (W31): 22.5
Length of magnetic core (L): 82.5
The thickness D was a distance in the longitudinal direction between the inner end surface of the outer core portion 32 and the outer end surface on a side opposite to the inner end surface.
The length L was a length in the longitudinal direction between one end and the other end of the magnetic core 3.
The width W32 was a length in the width direction of the outer core portion 32.
The width W31 was a length in the width direction of the inner core portion 31.
Materials for forming the magnetic core 3 and their characteristics were set as follows.
Core pieces (inner core pieces 31 m, outer core portions 32)
Gaps 3 g
Under the above-mentioned conditions, the protrusion amounts h1 and h2 of the outer core portions 32 were varied, and the natural frequencies were determined through the CAE analysis. Table 1 and
It is clear from the results shown in Table 1 that the larger the protrusion amounts h1 and h2 of the outer core portions 32 were, the smaller the thickness D of the outer core portions 32 was, and the length L of the magnetic core 3 could thus be reduced.
It is clear from the results shown in Table 1 and
The reactor 1 of Embodiment 1 exhibits the following functions and effects.
Since the portions on the bottom surface 32b side and the top surface 32t side of the outer core portion 32 protrude from the inner core portion 31, the thickness D of the outer core portion 32 can be reduced in the case where the volume of the magnetic core is to remain the same, compared with the case where such portions do not protrude (h1, h2=0). Accordingly, the length L of the magnetic core 3 can be correspondingly reduced, and the projection area of the installed reactor 1 in a plan view can thus be reduced, thus making it possible to reduce the size of the reactor 1.
Since the protrusion amount h1 and h2 of the portions on the bottom surface 32b side and the top surface 32t side of the outer core portions 32 are 20% or less of the height H31 of the inner core portions, and the outer core portion 32 has a shape that is symmetrical with respect to the center line of the inner core portion 31, a decrease in the natural frequency of the magnetic core 3 can be sufficiently effectively suppressed. Accordingly, the natural frequency can be made higher than the drive frequency of the reactor 1 (5 kHz to 10 kHz), and resonance between the natural frequency and the drive frequency can be avoided, thus making it possible to suppress the vibration noise during driving of the reactor.
The protrusion amounts h1 and h2 of the portions on the bottom surface 32b side and the top surface 32t side of the outer core portion 32 are set to be 4% or more, or 8% or more, of the height of the inner core portion, for example, from the viewpoint of reducing the size of the reactor. On the other hand, the protrusion amounts h1 and h2 are set to be 16% or less, 12% or less, or 10% or less, of the height of the inner core portion, for example, from the viewpoint of suppressing the vibration noise of the reactor.
The reactor 1 of Embodiment 1 can be favorably used in constituent components of various types of converters such as vehicle-mounted converters (typically DC-DC converters) to be mounted in vehicles including hybrid automobiles, plug-in hybrid automobiles, electric automobiles, fuel cell automobiles, and the like, and converters for an air conditioner, and constituent components of power conversion devices.
Other configurations of the reactor 1 are listed below.
An interposed member (not shown) located between the coil 2 and the magnetic core 3 may be provided. The interposed member is made of an electrical insulating material and ensures electrical insulation between the coil 2 and the magnetic core 3.
Examples of the above-mentioned interposed member include an inner-side interposed member (not shown) to be located between the inner peripheral surface of the wound portion 2c and the outer peripheral surface of the inner core portion 31, and an outer-side interposed member (not shown) to be located between the end surface of the wound portion 2c and the inner end surface of the outer core portion 32. The inner-side interposed member serves to position the inner core portion 31 inside the wound portion 2c and prevents the inner peripheral surface of the wound portion 2c from coming into contact with the outer peripheral surface of the inner core portion 31, thus ensuring the insulation therebetween. On the other hand, the outer-side interposed member prevents the end surface of the wound portion 2c from coming into contact with the inner end surface of the outer core portion 32, thus ensuring the insulation therebetween.
Examples of a material for forming the interposed member include thermoplastic resins such as PPS resin, PTFE resin, a liquid crystal polymer, PA resin such as nylon 6 or nylon 66, and PBT resin. The interposed member can be produced using a known method such as injection molding.
A case (not shown) in which an assembly of the coil 2 and the magnetic core 3 is accommodated may be provided. This makes it possible to protect the assembly from the external environment (dust, corrosion, and the like) and protect it mechanically. When the case is made of metal, its entirety can be used as a heat dissipation path, and therefore, heat generated in the coil 2 and the magnetic core 3 can be efficiently dissipated to the external installation target, thus improving the heat dissipation properties. Examples of a material for forming the case include aluminum and aluminum alloys, magnesium and magnesium alloys, copper and copper alloys, silver and silver alloys, iron, steel, and austenitic stainless steel. The weight of the case can be reduced when it is made of aluminum, magnesium, or an alloy thereof. The case may also be made of resin.
In the case where the assembly is accommodated in the case, sealing resin for sealing the assembly accommodated in the case may be provided. This makes it possible to electrically and mechanically protect the assembly and to protect the assembly from the external environment. Epoxy resin, urethane resin, silicone resin, unsaturated polyester resin, PPS resin, or the like can be used as the sealing resin. A ceramic filler having high thermal conductivity, such as alumina or silica, may be mixed into the sealing resin from the viewpoint of improving the heat dissipation properties.
A molded resin portion (not shown) molded on the assembly of the coil 2 and the magnetic core 3 may be provided. In this case, the assembly can be integrated using the molded resin portion. This also makes it possible to electrically and mechanically protect the assembly and to protect the assembly from the external environment even in the case where the assembly is not accommodated in the case. The molded resin portion can be formed of epoxy resin, PPS resin, PA resin, or the like, for example.
A heat dissipation plate (not shown) may be provided on at least one of the bottom surface 2b and the top surface 2t of the coil 2. This makes it possible to efficiently dissipate heat generated in the coil 2 to the external installation target, thus improving the heat dissipation properties.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-044634 | Mar 2017 | JP | national |
This application is the U.S. national stage of PCT/JP2018/006787 filed on Feb. 23, 2018, which claims priority of Japanese Patent Application No. JP 2017-044634 filed on Mar. 9, 2017, the contents of which are incorporated herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/006787 | 2/23/2018 | WO | 00 |
