Patent Grant
10312010
The present invention relates to coil components, and more specifically, to a coil component in which a drum core is housed in a through hole of a ring core (annular core).
In recent years, applications for electronic components have expanded and demands on stability against environmental fluctuation have been increasing. In particular, the adopted number of electronic components is ever increasing with movement toward computerization in the field of automobiles, and an electronic component such as a coil that does not break with respect to temperature fluctuation and vibration is desired. For a coil component, one with a structure in which a drum core, around which a winding wire is wound, is housed in a through hole of a ring core (or sleeve core) is known. For such a coil component including a core in which the drum core and the ring core are combined, there is, for example, an “inductance element” described in Patent Literature 1. The Literature discloses that by adopting a constitution of applying adhesive entirely along an inner circumferential surface of the ring core between an upper end flange and the drum core and the ring core, an impact does not concentrate at one specific portion but is substantially evenly dispersed between the drum core and the ring core.
[Patent Literature 1] Japanese Unexamined Patent Publication No. 2001-338818
However, as described in Patent Literature 1, although a method of applying the adhesive over the entire circumference of a gap between the ring core and the drum core can expect effects with respect to an impact, there are problems in that it is very difficult to evenly apply the adhesive over the entire circumference and in it being easily subjected to influence with respect to heat stress. For example, in the method of applying the adhesive over the entire circumference, the cores (drum core and ring core) cannot be easily positioned, and the gap between the cores becomes uneven and a large gap and a small gap are formed therebetween, where the extent/distribution of stress exerted on the cores may change depending on the size of the gap. In particular, when using a thick conductive wire, the position of the drum core may move by processing a lead wire of the conductive wire. Thus, it is not easy to obtain a coil component having both high reliability and stability of properties with the conventional method.
The present invention focuses on the above aspects, and aims to provide a coil component having a core structure in which a drum core and a ring core are combined, and having both high reliability and stability of properties.
Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.
The present invention is characterized by including a drum core having a pair of flange parts at both ends of a winding shaft; a conductive wire wound around the winding shaft; a ring core having a gap with respect to one of the flange parts as viewed in an axial direction of the winding shaft, and having a through hole housing the drum core therein; a terminal electrode electrically connected to the conductive wire; a first securing part provided at a part of the gap between the one flange part of the drum core and the ring core; and a second securing part provided at a part of a portion of the gap where the first securing part is not provided, and having a higher hardness than that of the first securing part.
According to one main aspect of the present invention, the first securing part covers an outer side of the second securing part. According to another aspect, a length of the first securing part in contact with an outer circumferential surface of the flange part of the drum core is 60% or more of a length of the outer circumferential surface of the flange part of the drum core. According to another further aspect, a hardness of the second securing part is greater than or equal to 50N/cm2 in Shore D hardness.
According to yet another further aspect, at least two or more second securing parts are provided. According to another further aspect: (1) at least two of the second securing parts are arranged at positions facing each other with respect to a center of the drum core; (2) The second securing parts are arranged line-symmetrically with respect to a line passing through a center of the drum core; (3) The second securing parts are arranged at equal intervals.
According to another further aspect, the first securing part and the second securing part are arranged on a flange part side opposite a surface on which the terminal electrode is mounted. The above described and other objects, features, and advantages of the present invention should be apparent from the following detailed description and the accompanying drawings.
According to the present invention, a coil component comprises: a drum core including a pair of flange parts at both ends of a winding shaft; a conductive wire wound around the winding shaft; a ring core having a gap with respect to one of the flange parts as viewed in an axial direction of the winding shaft, and having a through hole housing the drum core therein; a terminal electrode electrically connected to the conductive wire; a first securing part provided at a part of the gap between the one flange part of the drum core and the ring core; and a second securing part provided at a part of a portion of the gap where the first securing part is not provided, and having a higher hardness than that of the first securing part. Thus, the fluctuation in the distance between the drum core and the ring core can be suppressed, and the coil component having both high reliability and stability of properties can be obtained.
For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
Further aspects, features and advantages of this invention will become apparent from the detailed description which follows.
These and other features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings are greatly simplified for illustrative purposes and are not necessarily to scale.
The best mode for carrying out the present invention is described in detail below with reference to examples.
First, an example of the present invention is described with reference to
As shown in
Next, each portion constituting the coil component 10 is described in detail. As shown in
As shown in
Also, on an upper surface 30A side of the ring core 30, step differences (or grooves) 36A, 36B are provided so that an upper surface part 52A of the terminal electrodes 50A, 50B does not project out from the upper surface 30A, and step differences (or grooves) 38A, 38B for pulling out ends 46A, 46B of the winding wire 40 are formed. In the present example, as shown in
Next, the terminal electrodes 50A, 50B are described. The terminal electrodes 50A, 50B basically have a same configuration, and thus one terminal electrode 50A is described as an example. In the present example, the terminal electrode 50A is attached so as to lie along the outer circumferential surface 30C from the plane parts 34A, 34B of the ring core 30. As shown in
Such terminal electrode 50A is, for example, formed to a shape that can be attached to the ring core 30 by bending and caulking one metal plate including the side face 52, the upper surface part 52A, the nail parts 54A, 54B, the extended part 56, the connecting part 58, and the bottom surface part 52B at a predetermined position. In the illustrated example, the side face 52 lies along the plane part 34A of the ring core side surface, the upper surface part 52A lies along the step difference 36A of the ring core 30, the nail parts 54A and 54B lie along an inner circumferential surface 30D of the through hole 32 of the ring core 30, the bottom surface part 52B lies along a ring core bottom surface 30B, and the extended part 56 lies along the outer circumferential surface 30C of the ring core. It should be noted that in
Next, one example of a manufacturing method of the coil component 10 of the present example is described with reference to
Here, both ends 46A, 46B have the heights aligned to lie along the inner side of one flange part 24 of the drum core 20 (
Then, as shown in
The drum core 20, around which the winding wire 40 is wound and stripped of its coating 44 from the ends 46A, 46B in the above manner, is housed in the through hole 32 of the ring core 30, and positioned so that the respective centers coincide. In the positioning, the outer circumferential surfaces of the drum core 20 and the ring core 30 are image-recognized, and the position of the drum core 20 is adjusted. In this state, a UV adhesive is applied to two points between the outer circumferential surface of the flange part 24 of the drum core 20 and the inner circumferential surface of the ring core 30 using a dispenser from the upper surface side of the drum core 20, that is, the side opposite the mounting surface (upper surface 24A side of the flange part 24 in the present example), and cured with a UV lamp. In this case, the UV adhesive may be applied to one part of the terminal electrodes 50A, 50B. In the present example, the UV adhesive is applied so as to include the upper surface part 52A side of the terminal electrodes 50A, 50B.
The applied and cured UV adhesive becomes the second securing parts 60A, 60B. The second securing parts 60A, 60B are fixed at the position where the drum core 20 and the ring core 30 are positioned. The fluctuation in the position between subsequent steps and during a subsequently-conducted environment test, and the like thus can be suppressed. Also, in the illustrated example (see
Next, as shown in
Lastly, as shown in
Also, in the present example, as shown in
In the present example, two types of adhesives are used, where the adhesive with higher hardness after curing is used for the adhesive to become the second securing parts 60A, 60B than for the adhesive to become the first securing parts 62A, 62B, and the adhesive with lower linear coefficient of expansion after curing is used for the adhesive (thermosetting adhesive) to become the first securing parts 62A, 62B than for the adhesive to become the second securing parts 60A, 60B. If the second securing parts 60A, 60B have a Shore D hardness of greater than or equal to 50 N/cm2, the position of the core will not move. Also, the first securing parts 62A, 62B merely need to have a linear coefficient of expansion of lower than or equal to 2×10−5/K, and low-UV adhesive, thermosetting adhesive, and the like can be used. In addition, the conditions other than the linear coefficient of expansion include a glass transition point of greater than or equal to 150° C., and a viscosity before curing of greater than or equal to 80000 mPa·s. The thickness (depth) of the adhesive can be easily obtained even in one application, and the adhesive can be subjected to applications under high temperature of 150° C. when the above conditions are met.
<Test Samples>
Next, test samples of the present example are described. Coil components of a comparative example and test samples 1 to 6 were produced under the conditions shown in table 1 below, and variation (%) of inductance as well as defects after a heat cycle test were checked. The coil component 10 was a wound wire type inductor having a dimension of 10.5×10×5 mm, where Ni—Zn ferrite was used for the drum core 20 and the ring core 30, which are magnetic bodies. In this gap design between the drum core 20 and the ring core 30, the distance of the outer circumferential surface of the flange part 24 and the inner circumferential surface 30D of the ring core 30 was doubled, e.g., in a range of 0.22 to 0.3 mm. Also, a conductive wire of φ 0.43 mm with a polyamide imide coating (conductive wire itself was Cu) was used for the winding wire 40, and the number of windings was 15.5. Further, the UV adhesive having a hardness of 40 to 65 Shore D was used as an adhesive that can be cured in a short period of time with respect to the second securing parts 60A, 60B, and the epoxy adhesive having a hardness of 30 or 40 Shore D was used as a thermosetting adhesive used for the first securing parts 62A, 62B. Furthermore, a Cu plate having a thickness of 0.15 mm treated with Ni/Sn plating was used for the terminal electrodes 50A, 50B.
Specific test samples and comparative examples are described below. In this disclosure including the following description, multiple first securing parts are referred to collectively as the “first securing part”, and multiple second securing parts are referred to collectively as the “second securing part”, depending on the context.
In test sample 1, the dimension of the inner circumferential surface 30D of the ring core 30 was set at 10 mm, for example (the inner diameter can vary in combination with the outer diameter of the flange part and may be about 6 mm, about 10 mm, or the like, for example), the designed gap was set to 0.25 mm, and the design value of the inductance was 15 μH. With respect to the first securing parts 62A, 62B, the number of arrangements was two, the proportion was 40%, and the hardness was 30, and with respect to the second securing part 60 (wherein the second securing parts 60A, 60B, etc. are hereinafter referred to collectively as the second securing part 60), the number of arrangements was one, the proportion was 8%, and the hardness was 40. Also, the comparative example is similar to test sample 1 except that the designed gap was 0.3 mm, the designed inductance value was 14.7 μH, and the second securing part 60 was not provided.
In test sample 2, according to a similar method, the designed gap was 0.25 mm, and the designed value of the inductance was 15 μH. Test sample 2 was produced like test sample 1 except that the proportion was 60% for the first securing parts 62A, 62B. Test sample 3 was produced like test sample 2 except that the proportion was 80% for the first securing parts 62A, 62B, and the hardness was 50 for the second securing parts 60A, 60B.
In test sample 4, according to a similar method, the designed gap was 0.22 mm, and the designed value of the inductance was 15.4 μH. Test sample 4 was produced like test sample 3 except that the proportion was 90% for the first securing parts 62A, 62B, and the number of arrangements was two for the second securing parts 60A, 60B. Test sample 5 was produced like test sample 4 except that the proportion was 100% for the first securing part 62 and the number of arrangements was four, and the proportion was 16% for of the second securing parts 60A, 60B, 60C, 60D. Test sample 6 was produced like test sample 4 except that the hardness was 65 for the second securing parts 60A, 60B.
In Table 1, the size of the gap G was calculated as (ring core inner diameter D2−drum core flange part outer diameter D1)/2. Also, the proportion of the lengths of the first securing part and the second securing part making contact with the outer circumferential surface of the flange part 24 of the drum core 20 was indicated with the proportion of the lengths with respect to the outer circumference of the flange part 24 of the drum core 20 seen in a direction of the winding shaft 22 from the flange part 24. In the measurement, an angle of a range in which each of the first and second securing parts exist at the center of the flange part 24 of the drum core 20 was obtained at a magnification of 10 to 20 times using a factory microscope, and the proportion with respect to the entire outer circumference of the flange part 24 was obtained. For the first securing part 62, the angle of the range in which each securing part can be viewed when seen from the upper-surface side corresponding to the direction of the winding shaft 22 from the flange part 24 was obtained at the magnification described above. Moreover, for the second securing parts 60A, 60B, polishing was carried out in a range of 0.05 mm in the vertical direction with respect to the upper surface of the core having a lower height of the flange part 24 of the drum core 20 or the upper surface 30A of the ring core 30, and a range in which the second securing part can be viewed was obtained similarly from the upper-surface side or the polished surface. In addition, a Shore hardness test equipment D-type was used for the hardness, and the first and second securing parts were compared. With respect to a specific numerical value of hardness, each hardness was obtained after preparing a test sample having an outer dimension of φ 10 mm and a thickness of 2 mm with an adhesive for forming the second securing part, and performing a predetermined curing.
The variation of the inductance was calculated by a MAX value. The comparative example is an example in which an equivalent of the second securing part of the present example does not exist. Supplementing the inductance evaluation, it should be noted that the variation of inductance is caused by the variation in the gap. In such a case, an entirely even distance is preferably ensured between the outer circumferential surface of the drum core 20 and the inner circumferential surface of the ring core 30, where if the distance is not even, an area of close distance exists causing the inductance to become high. This becomes the variation caused by assembly precision. As the variation of inductance shifts toward the positive side of the designed value, the evaluation performed here obtains the proportion of the difference (size of shift) of the designed value and the maximum value. LCR meter 4285A frequency 100 kHz was used for the measuring instrument. Also, the heat cycle test evaluated the dimensional change before and after the test in 1000 cycles and 3000 cycles at a temperature of −55 to 150° C., and confirmed the presence/absence of change in either cycle. For such check, an area including the first securing part 62 was observed at a magnification of 50 times using a factory microscopic for an appearance change.
The following were confirmed from the results of the comparative example and the test samples shown in Table 1.
In the comparative example, variation in inductance was large. This is because the gap between the two cores has variation at some places when seen over the entire circumference. Also, in the heat cycle test, interfacial stripping was recognized between the drum core 20 or the ring core 30 and the first securing part 62. The thickness of the adhesive thus becomes thin in an area where the gap is large, which leads to defects due to the stress of thermal contraction/expansion.
In test sample 1, variation in inductance decreased even if the designed gap corresponding to the distance between the two cores was reduced. As the second securing parts were provided using the UV adhesive, it was found that the gap precision was satisfactory and that the variation of inductance could be reduced even if the gap was reduced. However, traces of crack were slightly found in the portion at the end in the length direction of the first securing parts 62A, 62B, which were determined to be microcracks. Changes were not found, however, between 1000 cycles and 3000 cycles, and no defects caused by the microcracks were also found. This is because the stress applied on the portion at the end of the first securing part 62 with the second securing part 60A as the trigger when the length in the circumferential direction of the portion where only the second securing part 60A exists was not sufficiently ensured.
In test sample 2, variation in the inductance improved, although slightly. This is because the positional stability was improved with increasing the length in the circumferential direction of the first securing part 62. Also, in test samples 2 to 6, the defects described above were all resolved. This is because the thickness in the height direction of the first securing part 62 was sufficiently ensured by increasing the length in the circumferential direction of the first securing part 62.
In test sample 3, variation in inductance was further reduced. This is because the positional precision further improved by adopting the second securing part 60A having a higher hardness than that of test sample 2.
In test samples 4 to 6, the designed gap was further reduced and variation in inductance was also kept low. This is because gap fluctuation was further reduced by increasing the proportion of the first securing part relative to the second securing part.
Test sample 5 was an example in which the first securing part was provided across the entire circumference, where variation was small and no defects were found in the tested sample size, but it should be taken in consideration that stress applies on a ridge portion of the core if formed across the entire circumference in a small component (smaller than or equal to 7 mm) where rounding of the ridge portion of the ring core 20 is difficult, for example.
According to a comparison between test sample 6 and test sample 4, it should be noted that an upper limit of the hardness of the second securing part does not need to be particularly provided, and no large change is found as long as the Shore D hardness is greater than or equal to 50; higher hardness does not need to be forcibly used and a range of up to about 100 is sufficient.
The examples according to the present invention have the following effects.
(1) The second securing parts 60A, 60B and the first securing part 62 are provided at one part of the gap G of the drum core 20 and the ring core 30, and the second securing parts 60A, 60B having a higher hardness than the first securing part 62 are adopted, so that fluctuation in the distance between the core members can be suppressed.
(2) Defects can be eliminated by setting the proportion of the first securing part 62 with respect to the length of the outer circumference of the drum core 20 to greater than or equal to 60%.
(3) Fluctuation (fluctuation in position between the cores) can be reduced by setting the Shore D hardness of the second securing parts 60A, 60B to greater than or equal to 50 N/cm2.
(4) The second securing part is provided in plural and are arranged opposite to each other with respect to the center C of the drum core 20, so that the gap can be further reduced and the stress applied on the ring core 30 can be evened out, thus reducing variation.
(5) The second securing parts 60A, 60B and the first securing parts 62A, 62B are provided on one flange part 24 side of the drum core 20 opposite the surface (bottom surface part 52B) on which the terminal electrodes 50A, 50B are mounted, and thus the mounting side (bottom surface part 52B) of the terminal electrodes 50A, 50B will not become contaminated.
(6) The first securing parts 62A, 62B cover the upper surface (outer side) of the second securing parts 60A, 60B, and thus the second securing parts 60A, 60B will not detach.
It should be noted that the present invention is not limited to the examples described in this disclosure, and various changes can be made within a scope not deviating from the gist of the invention. This includes, for example, the following.
(1) The shapes and dimensions shown in the above-discussed examples are examples, and may be appropriately changed as needed. For example, in the above-discussed examples, the outer cross-sectional shape of the ring core 30 is an oval shape in which one part of the circle is cut off, but it may be an octagon, a square, and the like, or may be a shape in which a corner is rounded to an extent that rotation does not occur.
(2) The pull-out configuration of the winding wire from the ring core 30 shown in the examples is also an example, and design changes can be appropriately made within a scope that similar effects are obtained.
(3) The shape of the terminal electrodes 50A, 50B shown in the examples and the joining mode with respect to the ends 46A, 46B of the winding wire 40 are also one example, and design changes can be appropriately made within a scope that similar effects are obtained.
(4) In the above-discussed examples, two second securing parts 60A, 60B are provided, but this is also an example, and the number and arrangement can be appropriately changed as long as two or more second securing parts are provided. For example, as in a coil component 10A shown in
(5) In the example, the UV adhesive to become the second securing parts 60A, 60B after being cured is applied to include three members being the outer circumference of the drum core, the inner circumference of the ring core, and the terminal electrode, but this is an example, and the second securing part does not necessarily need to be provided to include the terminal electrode.
(6) In the examples, the first securing parts 62A, 62B are provided to completely cover the upper surface of the second securing parts 60A, 60B, but this is an example, and they do not necessarily need to be arranged to cover the entire second securing part and may partially cover the second securing part. The second securing parts 60A, 60B merely need to at least make contact with either one of the first securing parts 62A, 62B. In either mode, the first and second securing parts will not detach from the component.
(7) Furthermore, in the examples described above, as shown in
(8) Alternatively, the range of the step differences 36A, 36B for caulking the terminal electrode may be narrowed as in a ring core 70A in the examples shown in
According to the present invention, a drum core including a pair of flange parts at both ends of a winding shaft, a conductive wire wound around the winding shaft, a ring core having a gap with respect to a flange part when seen in a winding shaft direction from one flange part, the ring core including the drum core in a through hole, a terminal electrode electrically connected to the conductive wire, a first securing part provided at one part of the gap between one flange part of the drum core and the ring core, and a second securing part provided at a part of a portion of the gap where the first securing part is not provided, and having a higher hardness than that of the first securing part are provided. Thus, fluctuation in distance between the drum core and the ring core can be reduced, allowing application to a coil component having both high reliability and stability of properties. In particular, it is suitable for application of a coil component for fields of automobiles and industrial machines as it excels in temperature resistance and impact resistance.
In the present disclosure where conditions and/or structures are not specified, a skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. Also, in the present disclosure including the examples described above, any ranges applied in some embodiments may include or exclude the lower and/or upper endpoints, and any values of variables indicated may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. Further, in this disclosure, “a” may refer to a species or a genus including multiple species, and “the invention” or “the present invention” may refer to at least one of the embodiments or aspects explicitly, necessarily, or inherently disclosed herein. The terms “constituted by” and “having” refer independently to “typically or broadly comprising”, “comprising”, “consisting essentially of”, or “consisting of” in some embodiments. In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.
The present application claims priority to Japanese Patent Application No. 2016-073417, filed Mar. 31, 2016, the disclosure of which is incorporated herein by reference in its entirety including any and all particular combinations of the features disclosed therein.
It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-073417 | Mar 2016 | JP | national |
| Number | Date | Country |
|---|---|---|
| 2001338818 | Dec 2001 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20170287614 A1 | Oct 2017 | US |
