JP6303593B2 - Reactor - Google Patents

Description

  The present invention relates to a reactor, and more particularly to a reactor in which a casting resin is injected into a case in which a coil is accommodated.

  A reactor including a coil is used for a power conversion device such as a DC-DC converter mounted on a vehicle such as a hybrid vehicle, an electric air vehicle, or a fuel cell vehicle. The structure of the reactor is disclosed in Patent Document 1, for example. In this type of conventional general reactor, a coil through which a magnetic core (core) is inserted is accommodated in a case, and a space inside the case is filled with casting resin (sealing resin). The casting resin has a role of maintaining the insulating properties of the coil and a role of suppressing a temperature rise of the coil. The casting resin penetrates between the coil turns.

JP 2012-253384 A

  In the reactor, when the coil is energized, the coil is vibrated due to the interaction between adjacent coil turns and the influence of the vibration of the vehicle on which the reactor is mounted. Then, stress is applied to the casting resin due to the vibration of the coil, and a gap may be formed between the coil and the casting resin. Then, a crack occurs in the casting resin from a portion where the void is formed, or a crack that has already occurred progresses. Then, the role of the casting resin for suppressing the temperature rise of the coil may not be sufficiently fulfilled, and the appearance of the reactor may be impaired.

  The problem to be solved by the present invention is to provide a reactor having a casting resin in which a void is prevented from being generated between the coil and the casting resin due to vibration of the coil.

  In order to solve the above-described problems, a reactor according to the present invention includes a coil formed by winding a wire in which the surface of a conductor wire is covered with an insulating coating layer, a case in which the coil is accommodated, and a filling in the case. And a layer made of at least one buffer resin formed between the casting resin and covering the surface of the strand, the buffer resin having a temperature of 50 ° C. The present invention is summarized in that it has a tensile elastic modulus lower than that of the casting resin and less than 2000 MPa, and has a glass transition temperature lower than that of the casting resin.

  Here, the tensile elastic modulus at 50 ° C. of the buffer resin is preferably 500 MPa or less.

  And the glass transition temperature of the said buffer resin is good in it being -40 degrees C or less.

  Moreover, it is preferable that the layer which consists of said buffer resin has the thickness of the range of 0.8-50 micrometers.

  The buffer resin may contain a curable resin.

  In the reactor concerning this invention, it has a layer which consists of buffer resin between casting resin and the strand which comprises a coil. The buffer resin has the tensile modulus as described above, is softer than the casting resin, and is easily deformed by the vibration of the coil. Thus, when the coil vibrates, the buffer resin relieves stress applied from the coil to the casting resin. As a result, a gap is less likely to occur between the casting resin and the coil. Further, since the buffer resin has a glass transition temperature lower than that of the casting resin, the function of the buffer resin that suppresses the formation of a gap between the coil and the casting resin is maintained even in a low temperature environment.

  Here, when the tensile elastic modulus at 50 ° C. of the buffer resin is 500 MPa or less, the effect of relaxation of stress during coil vibration by the buffer resin and the suppression of void formation by the buffer resin are further enhanced.

  And when the glass transition temperature of the buffer resin is -40 ° C or lower, the function of the buffer resin to suppress the gap formation between the casting resin and the coil is good even in a low temperature region of about -40 ° C. Demonstrated.

  Further, when the layer made of the buffer resin has a thickness in the range of 0.8 to 50 μm, the stress applied from the coil to the resin can be effectively relieved, and the buffer resin fills the space between the coil turns. This prevents the filling of the casting resin from being hindered.

  And when buffer resin contains curable resin, it is easy to coat | cover buffer resin in the layer form on the surface of the strand which comprises a coil.

It is a perspective view which shows the reactor concerning one Embodiment of this invention. The casting resin is not shown. It is sectional drawing of the said reactor (the hatching which shows a cross section is abbreviate | omitting suitably). It is a perspective view which shows the assembly of the coil and magnetic core which comprise the said reactor. It is a figure which shows the AA cross section of the said coil typically.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Overall structure of the reactor>
1-4, the reactor 1 concerning one Embodiment of this invention and the coil 10 which comprises the reactor 1 are shown. Reactor 1 has the same shape as the reactor described in Patent Document 1 except for the presence of buffer resin 50 described later. Hereinafter, the overall structure of the reactor 1 will be briefly described.

  As shown in FIGS. 1 and 2, the reactor 1 basically has a structure in which a combination of a coil 10 and a magnetic core 20 is accommodated in a case 30.

  As shown in FIGS. 3 and 4, the coil 10 is formed by spirally winding an element wire 11 in which the outer periphery of a conductor wire 11 a is covered with an insulating coating layer 11 b. The coil 10 has an overall shape in which two straight portions 10a, 10a are aligned in the winding direction. A layer made of a buffer resin 50 is further provided on the outer periphery of the insulating coating layer 11 b of the strand 11. The buffer resin 50 will be described in detail later.

  The conductor wire 11a is made of metal such as copper or copper alloy, aluminum or aluminum alloy, for example. The insulating coating layer 11b is made of an enamel material typified by polyamideimide, for example. Moreover, as a shape of the strand 11, it is preferable that it is a flat wire from a viewpoint of raising cooling (heat dissipation) property and raising the density of winding. The coil 10 is preferably formed as a square coil having a shape obtained by rounding the corners of a prism, from the viewpoint of ease of fixing and the like.

  The coil 10 is a combined body in which the magnetic core 20 is inserted into the hollow portion of each linear portion 10 a and is accommodated in the case 30. The magnetic core 20 has a structure in which, for example, a core portion 21 made of a magnetic material and a gap portion 22 made of a nonmagnetic material are alternately connected. In the combined body, an insulator may be appropriately interposed between the coil 10 and the magnetic core 20 (not shown).

  The case 30 has a bottom surface 31 on which a combination of the coil 10 and the magnetic core 20 is placed and fixed, and a side wall surface 32 erected on the outer periphery of the bottom surface 31, and an upper portion of the side wall surface 32 facing the bottom surface 31. Is provided with an opening 33. The bottom surface 31 is preferably made of a metal such as aluminum or an aluminum alloy so as to have high thermal conductivity, and the side wall surface 32 is preferably made of a resin material from the viewpoint of insulation. Further, between the bottom surface 31 and the side wall surface 32, a packing (not shown) for preventing the casting resin 40 from leaking is provided as appropriate.

  The combined body of the coil 10 and the magnetic core 20 is accommodated in the case 30 through the opening 33, is placed on the bottom surface 31, and is integrally fixed to the bottom surface 31. The coil 10 is fixed to the bottom surface 31 via a resin material having adhesiveness. As described above, the coil 10 is integrally fixed to the bottom surface 31 of the case 30, so that the efficiency of cooling (heat radiation) of the coil 10 is enhanced.

  The space inside the case 30 that accommodates the combined body of the coil 10 and the magnetic core 20 is filled with a casting resin 40. The casting resin 40 fills the space between the coil 10 and the side wall surface 32 of the case 30 and also fills the space between the coil turns (each pitch of the spiral) of the coil 10. The casting resin 40 has an effect of maintaining insulation of the coil 10 and an effect of cooling (dissipating heat) the coil 10 that generates heat when energized. Here, the insulation of the coil 10 includes not only the insulation of the entire coil 10 but also the insulation between coil turns.

  The casting resin 40 may be made of any insulating resin composition, but in a highly fluid state, there is no gap in the space between the coil 10 and the side wall surface 32 of the case 30 or the space between the coil turns. It is preferable to use a curable resin as a main component in that it can be solidified after infiltrating and filling. Examples of the curable resin include a thermosetting resin, a photocurable resin (particularly an ultraviolet curable resin), a moisture curable resin, and a two-component reaction curable resin. Examples of the resin species include silicone resin, acrylic resin, epoxy resin, urethane resin, phenol resin, unsaturated polyester resin, polyurea resin, and the like. These may be used alone or in combination of two or more. Furthermore, additives such as coloring pigments, viscosity modifiers, anti-aging agents, fillers (inorganic fillers), storage stabilizers, and dispersants may be added to the curable resin. In particular, the filler is effective in increasing the thermal conductivity of the casting resin 40.

  In addition, the reactor 1 appropriately includes members necessary for operation and control, such as a terminal 81 and various sensors 82. The assembled reactor 1 is fixed to a predetermined attachment site such as in the DC-DC converter at the bottom surface 31 of the case 30. A cooling mechanism may be appropriately provided at the attachment site that contacts the bottom surface 31. In this case, the coil 10 is cooled by the cooling mechanism via the bottom surface 31 and the casting resin 40.

<Buffer resin>
The reactor 1 according to the present embodiment covers the surface of the strand 11, a layer made of the buffer resin 50 is formed, and the buffer resin 50 is interposed between the strand 11 and the casting resin 40. Has characteristics. The buffer resin 50 is made of an insulating resin composition, has a tensile elastic modulus lower than that of the casting resin 40 and less than 2000 MPa at 50 ° C., and has a glass transition temperature lower than that of the casting resin 40. Have.

  In the reactor 1, when an alternating current is input to the coil 10, an interaction occurs between the coil turns, and a vibration occurs between the coil turns. The vibration is further increased under the condition that the magnitude of the current input to the coil 10 changes. Further, the coil 10 is also vibrated by the vibration of the vehicle or the like on which the reactor 1 is mounted. When such a vibration occurs in the coil 10, if the coil 10 does not have a layer made of the buffer resin 50 on the surface of the strand 11 and is in direct contact with the casting resin 40, the coil 10 Stress is applied to the mold resin 40, and the casting resin 40 is peeled off from the surface of the coil 10, and a gap is easily generated between the casting resin 40 and the coil 10. When such voids are generated, cracks occur in the casting resin 40 starting from the voids, or cracks that have already occurred are developed. Then, the function of the casting resin 40 that promotes cooling (heat radiation) of the coil 10 is impaired, and the appearance of the reactor 1 is deteriorated.

  However, in this reactor 1, since the buffer resin 50 is interposed between the coil 10 and the casting resin 40, a gap is generated between the coil 10 and the casting resin 40 when the coil 10 vibrates. Is suppressed. That is, the buffer resin 50 has a lower tensile elastic modulus than that of the casting resin 40, so that it is softer than the casting resin 40, and when force is applied by vibration of the coil 10, It is more susceptible to elastic deformation than the casting resin 40. Then, even if the coil 10 vibrates, the buffer resin 50 is elastically deformed, so that the vibration is absorbed or reduced, and the stress applied from the coil 10 to the casting resin 40 is relaxed. This makes it difficult for the casting resin 40 to be peeled off from the surface of the wire 11 of the coil 10 covered with the buffer resin 50, and makes it difficult to form a gap between the wire 11 of the coil 10 and the casting resin 40. . Further, in the case of a general reactor, in view of the degree of vibration generated in the coil, if the buffer resin 50 has a tensile modulus of elasticity of less than 2000 MPa at 50 ° C., the coil is elastically deformed in this manner. The effect of relaxing the stress application to the casting resin 40 due to the vibration of 10 can be sufficiently exhibited. Here, the reference temperature of 50 ° C. relating to the tensile modulus is assumed to be a temperature when the reactor 1 is used in a general environment.

  Further, the buffer resin 50 has a glass transition temperature lower than that of the casting resin 40. Since the tensile elastic modulus of the resin material is remarkably increased at a low temperature with the glass transition temperature as a boundary, the buffer resin 50 has a glass transition temperature lower than that of the casting resin 40, so that the glass transition temperature of the buffer resin 50 is almost the same. Even in a low temperature region similar to the above, the state in which the buffer resin 50 has a lower tensile elastic modulus than the casting resin 40 is easily maintained, and the formation of voids between the casting resin 40 and the coil 10 is easily suppressed. Also, when subjected to a thermal shock in which a low temperature and a high temperature are alternately repeated, the formation of similar voids is easily suppressed. The tensile modulus of the resin is a parameter depending on the temperature, but the relationship between the tensile modulus of the two types of resins is often maintained even when the temperature changes. The buffer resin 50 having a tensile elastic modulus lower than 40 can be regarded as maintaining a state having a tensile elastic modulus lower than that of the casting resin 40 up to a low temperature comparable to the glass transition temperature of the buffer resin 50.

  From the viewpoint of effectively suppressing void formation between the coil 10 and the casting resin 40, the buffer resin 50 preferably has a tensile modulus of elasticity of 500 MPa or less at 50 ° C., and a tensile elasticity of 15 MPa or less. It is more preferable to have a rate. The lower the tensile elastic modulus of the buffer resin 50, the greater the above effect can be exhibited. Therefore, there is no particular lower limit on the preferred value, but from the viewpoint of availability, etc., the tensile elasticity is generally about 0.01 MPa or more. It is practical to use a resin having a rate at 50 ° C. The tensile elastic modulus of the buffer resin 50 and the casting resin 40 can be measured by a known method such as a method defined in ASTM D638.

  It is preferable that the glass transition temperature of the buffer resin 50 is −40 ° C. or lower. Then, the soft state of the buffer resin 50 (a state in which it is easily elastically deformed) is maintained until a low temperature of about −40 ° C., and the effect of suppressing the gap formation between the casting resin 40 and the coil 10 by the buffer resin 50 is achieved. It is because it is maintained. The glass transition temperatures of the buffer resin 50 and the casting resin 40 may be measured by a known method, and in particular, the change in the tensile elastic modulus is accurately reflected, and tan δ by dynamic mechanical analysis (DMA). It is preferable to measure by the method.

  The layer made of the buffer resin 50 preferably has a thickness of 0.8 μm or more. This is because the effect of suppressing the formation of a gap between the casting resin 40 and the coil 10 is easily exhibited by the elastic deformation of the buffer resin 50. On the other hand, when considering the distance between coil turns in a general reactor, the thickness of the layer made of the buffer resin 50 is preferably 50 μm or less. If it is thicker than this, the buffer resin 50 fills the space between the coil turns, which may hinder the penetration of the casting resin 40 between the coil turns. When a plurality of layers made of the buffer resin 50 are formed by laminating, these values relating to the preferred thickness are applied to the total of each layer. The thickness of the layer made of the buffer resin 50 can be evaluated by observing the cross section of the wire 11 constituting the coil 10 with a microscope or the like. Moreover, when forming the layer which consists of buffer resin 50 using the liquid containing the buffer resin 50 so that it may mention later, the thickness of a layer is adjusted by adjusting the quantity of the liquid used and the density | concentration of the buffer resin 50 in a liquid. Can be controlled.

  With respect to the buffer resin 50, the specific resin species is not particularly limited as long as it has the above-described tensile elastic modulus and glass transition temperature. Examples include silicone resins, acrylic resins, epoxy resins, urethane resins, phenol resins, unsaturated polyester resins, polyurea resins, and the like. These may be used alone or in combination of two or more. Among the above, the silicone resin is preferable from the viewpoint of easy control of the curing reaction and many types of solvents that can be used. The buffer resin 50 may further contain additives such as coloring pigments, viscosity modifiers, anti-aging agents, fillers (inorganic fillers), storage stabilizers, and dispersants. In addition, when these additives are added to the buffer resin 50, the tensile elastic modulus and the glass transition temperature of the buffer resin 50 defined above are values obtained in a state where the additive is added.

  The buffer resin 50 preferably comprises a curable resin. Then, the buffer resin 50 in an uncured state is brought into contact with the surface of the wire 11 constituting the coil 10 to form a film and then cured, whereby a layer made of the buffer resin 50 is simply formed. It can be formed thin on the surface of the film. As a specific method, after the coil 10 is molded, the coil 10 is immersed in a liquid containing an uncured buffer resin 50 before being inserted into the case 20 or housed in the case 30, taken out, and then cured. You can do it. Alternatively, after the coil 10 is combined with the magnetic core 20 and accommodated and fixed in the case 30, the liquid containing the uncured buffer resin 50 is injected into the case 30 and the excess liquid is discharged from the case 30. It can be cured. A layer made of the buffer resin 50 may be formed on the long strand 11 before forming the coil 10. However, in order to avoid peeling of the buffer resin 50 layer at the time of forming the coil 10, the layer made of the buffer resin 50 is formed after the coil 10 is formed rather than at the stage of the long strand 11. desirable. Further, in order to prevent the buffer resin 50 from interfering with the fixing of the coil 10 to the bottom surface 31 of the case 30 through the adhesive layer, the liquid containing the buffer resin 50 is removed while the coil 10 is fixed in the case 30. The method of discharging after injecting into the case 30 is most preferable. In this case, the buffer resin 50 also adheres to members other than the coil 10 exposed inside the case 30, but this is not a problem because it does not have a special influence in terms of preventing cracking of the casting resin 40.

  Even when the buffer resin 50 does not contain a curable resin, the buffer resin 50 is included in the same manner as in the case of the curable resin in a state where the buffer resin 50 is dissolved and diluted with a volatile solvent. A layer made of the buffer resin 50 can be formed on the surface of the strand 11 by bringing the solution into contact with the surface of the strand 11 to form a film and removing the solvent by drying. The thickness of the buffer resin 50 layer to be formed can be controlled by adjusting the concentration of the buffer resin 50 in the liquid to be used, regardless of whether the buffer resin 50 is curable or not. .

  In the above, one type of buffer resin 50 is used, and only one layer made of the buffer resin 50 is formed on the surface of the strand 11 of the coil 10. Two or more layers may be laminated on the surface. Further, another resin layer such as an adhesive layer may be interposed between the wire 11 and the casting resin 40.

  Examples of the present invention and comparative examples are shown below. In addition, this invention is not limited by these Examples.

<Preparation of test sample>
A reactor having a structure as shown in FIG. 1 was prepared, and a buffer resin solution diluted with a solvent was injected into the case. Thereafter, the buffer resin was discharged from the case, and the inside of the case was dried. Then, a casting resin (epoxy resin, “EC-508” manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., tensile elastic modulus at 50 ° C.:>4,000 MPa, glass transition temperature: 125 ° C.) is injected into the case and cured. Then, reactors according to Examples 1 to 6 and Comparative Example 2 were produced. Table 1 summarizes the types of the buffer resin used, the tensile modulus at 50 ° C., the glass transition temperature, and the thickness of the buffer resin layer. The thickness of the buffer resin layer was controlled by the concentration of the buffer resin in the solvent. In Comparative Example 1, a buffer resin was not used, and after casting the reactor of FIG.

The specific buffer resin used is as follows.
Silicone resin (Examples 1 to 4): “TSE3062” manufactured by Momentive
Styrene-ethylene-propylene-styrene copolymer (SEPS) (Example 6): “Septon 2007” manufactured by Kuraray Co., Ltd.
Epoxy resin (Comparative Example 2): “EC-1200M” manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.

The physical property values of the buffer resin and the casting resin are measured by the following methods.
-Tensile modulus (50 ° C): ASTM D638
Glass transition temperature: tan δ method by DMA

<Test method>
[Evaluation of cracks caused by thermal shock]
About each reactor, the cycle which energizes each 1.5 hours at -40 degreeC and 150 degreeC was repeated 500 times. Thereafter, it was visually confirmed whether or not the casting resin was cracked. The presence or absence of cracks was confirmed on the surface of the casting resin and on the cut surface. A case where no cracks occurred on the surface or the cut surface was judged as acceptable “◯”, and a case where cracks occurred on at least one of the surface or the cut surface was regarded as unacceptable “x”.

<Test results>
In Table 1, about the reactor concerning each Example and a comparative example, the characteristic of buffer resin and the result of evaluation of a crack are shown.

  According to Table 1, in the reactor according to Comparative Example 1 that does not have the layer made of the buffer resin on the surface of the coil wire, cracking occurred in the casting resin in the crack evaluation test after applying the thermal shock. On the other hand, in the reactors according to Examples 1 to 6, no cracking occurred in the casting resin. In Examples 1 to 6, a buffer resin having a tensile modulus of less than 2000 MPa and a glass transition temperature of −40 ° C. or less is interposed between the coil and the casting resin, so that the coil vibrates when energized. Even so, it is interpreted that the stress applied to the casting resin is relaxed by the buffer resin.

  On the other hand, in the reactor according to Comparative Example 2, although a buffer resin having a lower tensile elastic modulus than the casting resin is interposed between the coil and the casting resin, the value of the tensile elastic modulus is as large as 2000 MPa, Further, the glass transition temperature is higher than −40 ° C., which is the temperature at the low temperature of the thermal shock test. This interprets that the stress applied to the casting resin when the coil vibrates, particularly at low temperatures, does not sufficiently relax the buffer resin, leading to cracking of the casting resin.

10 Coil 11 Wire 20 Magnetic core 30 Case 31 Bottom surface 32 Side wall surface 40 Cast resin 50 Buffer resin

Claims (4)

A coil formed by winding an element wire whose surface is covered with an insulating coating layer;
A case containing the coil;
A casting resin filled in the case and filling the space between the coil and the side wall surface of the case and the space between the coil turns of the coil ;
From at least one layer of buffer resin different from the insulating coating layer, which is formed between the casting resin and covering the surface of the wire including the portion where the adjacent coil turns face each other And a layer
The buffer resin, at 50 ° C., the lower than casting resin, and having a tensile modulus of less than 2000 MPa, Ri name of a resin composition having a glass transition temperature lower than the casting resin,
The reactor is characterized in that the layer made of the buffer resin has a thickness in the range of 0.8 to 50 μm .   The reactor according to claim 1, wherein the buffer resin has a tensile elastic modulus at 50 ° C. of 500 MPa or less.   The reactor according to claim 1, wherein the buffer resin has a glass transition temperature of −40 ° C. or lower. The reactor according to any one of claims 1 to 3 , wherein the buffer resin includes a curable resin.

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