EP1113464A2 - Procédé de formation d'un micro-entrefer pour noyaux magnétiques - Google Patents

Procédé de formation d'un micro-entrefer pour noyaux magnétiques Download PDF

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Publication number
EP1113464A2
EP1113464A2 EP00127941A EP00127941A EP1113464A2 EP 1113464 A2 EP1113464 A2 EP 1113464A2 EP 00127941 A EP00127941 A EP 00127941A EP 00127941 A EP00127941 A EP 00127941A EP 1113464 A2 EP1113464 A2 EP 1113464A2
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EP
European Patent Office
Prior art keywords
core portion
core
mating
adhesive
gap spacing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00127941A
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German (de)
English (en)
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EP1113464A3 (fr
Inventor
Robert L. Billings
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcatel USA Sourcing Inc
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Alcatel USA Sourcing Inc
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Filing date
Publication date
Application filed by Alcatel USA Sourcing Inc filed Critical Alcatel USA Sourcing Inc
Publication of EP1113464A2 publication Critical patent/EP1113464A2/fr
Publication of EP1113464A3 publication Critical patent/EP1113464A3/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F3/00—Cores, Yokes, or armatures
    • H01F3/10—Composite arrangements of magnetic circuits
    • H01F3/14—Constrictions; Gaps, e.g. air-gaps
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores
    • H01F27/26—Fastening parts of the core together; Fastening or mounting the core on casing or support
    • H01F27/263—Fastening parts of the core together
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F21/00—Variable inductances or transformers of the signal type
    • H01F21/02—Variable inductances or transformers of the signal type continuously variable, e.g. variometers
    • H01F21/08—Variable inductances or transformers of the signal type continuously variable, e.g. variometers by varying the permeability of the core, e.g. by varying magnetic bias

Definitions

  • the invention relates to the field of magnetic core assemblies, and more particularly to a process for assembling cores for transformers, inductors and other magnetic devices with small but controllable gap spacing.
  • Transformers and inductors are often designed as one or more wire coils wound around a core.
  • the core defines a magnetic flux loop passing through the centerhole of the coil and closing outside the coil.
  • devices using closed loop cores are typically manufactured using two core portions that are mated together during assembly. Each core portion is itself open, so that a coil can be wound on one or more legs of the core before the core portions are mated together.
  • the coil or coils are pre-wound onto a non-magnetic bobbin, which is simply slipped onto the desired leg of one core portion before the core portions are mated together.
  • Cores can have many different shapes.
  • U-cores for example, are assembled from two U-shaped core portions, each with two legs protruding toward the opposite core portion.
  • One or more coils can be wound around one or both legs of the core portion before the core portions are mated together, the end surfaces of the legs of one core portion being placed into face-to-face contact with the end surfaces of the legs of the other core portion.
  • E-cores are assembled from two E-shaped core portions, each with three legs protruding toward the opposite core portion.
  • Cylindrically shaped cores are assembled from two cylindrical core portions, each having a center post protruding toward the other core portion. The coil(s) are typically wound around the center post before mating. Numerous other shapes exist. It will be appreciated that the two core portions that make up a complete core need not be symmetrical, although they often are.
  • Cores intended for operation above about 100 kHz are often fabricated from one of a number of ferrite materials.
  • Certain ferrites advantageously have very high permeability ( ⁇ ), for example ⁇ >10,000, allowing for very high inductance devices.
  • ⁇ very high permeability
  • the mating surfaces are ground to a high polish and the core portions are clamped together.
  • the operation is delicate because even a fingerprint can degrade the permeability.
  • a very thin layer of interfacial epoxy adhesive has been used between the mating surfaces of the core portions to hold them in place.
  • the effective permeability of magnetic devices with mated cores is very difficult to control during the manufacturing process. And since the inductance of a coil encircling the core is a function of the core permeability, the inductance of such a coil is also very difficult to control. Typically the inductance can be controlled only to within a tolerance of ⁇ 25% or so. In addition, the mating process itself degrades controllability even further, perhaps by yet another ⁇ 5%.
  • One way to control the permeability more precisely is to introduce an air gap within one leg of the core, typically the leg passing through the coil. Machinery currently exists which can grind this leg down on one of the mating core portions to within a much tighter tolerance.
  • Core permeability can alternatively be controlled by the simple process of testing and rejecting those cores that are not within the required tolerance specification. This process is expensive and wasteful, however, especially since it cannot be performed until after the core has already been assembled.
  • a magnetic device is assembled by first applying an adhesive to the end surface of a leg of one core portion, slipping a bobbin onto one of the legs (preferably a different leg) of the core portion, and mating the two core portions together. Then while observing the inductance of the coil, the two core portions are ground toward each other, gradually narrowing the adhesive-induced gap between the mating surfaces, until the desired inductance is achieved. The adhesive is then cured. Preferably the adhesive includes particulate matter to help resist the narrowing of the gap during the grinding process. The result is a "microgapped" core in which the effective permeability has been controlled to within a very tight tolerance.
  • the improvement in precision achieved due to the assembly process described herein is not limited to a reduction of the tolerance degradation that takes place during a conventional assembly process, but can also correct for permeability imprecision that might have existed in the unmated core portions themselves, prior to assembly.
  • Fig. 1 is a perspective diagram illustrating components of a transformer that can be assembled in accordance with features of the invention.
  • the components include first and second core portions 110 and 112, a bobbin 114, and a spring clamp 116.
  • the core 110/112 (collectively, 118) in the example of Fig. 1 has airindustry-standard shape known as EP-13. In this example the two core portions are symmetrical, so only core portion 112 will be described.
  • core portion 112 includes a center post, or leg, 120, about which the bobbin 114 will be placed during assembly.
  • a wall 122 Partially surrounding the center post 120 is a wall 122, partially cylindrical in shape, and spaced from the outer surface of the center post 120 sufficiently to permit insertion of the bobbin 114.
  • the outer wall 122 protrudes from an outer surface 124 of the core portion 112, toward the first core portion 110.
  • the end surface 126 of the center post 120 which will mate with a corresponding end surface 128 of center post 130 on the first core portion 110, is substantially co-planar with the end surface 132 of the wall 122 which will mate with the corresponding end surface 134 of the wall 136 of the first core portion 110.
  • each have unitary construction, and are made from a high-permeability ferrite material such as Nippon Ceramics NC-10 or TDK H5C2. These materials have a permeability of ⁇ 10,000, but they are specified only with a tolerance of ⁇ 30%.
  • the EP-13 core in the example of Fig. 1 is an example of a partially cylindrical core.
  • a "leg" of a core portion refers to any member of the core portion that protrudes toward the mating portion.
  • a “leg” need not be post-like, such as the center posts 120 and 130.
  • the walls 122 and 136 of the core portions 110 and 112 also constitute “legs” of such core portions.
  • a "rim" of a core portion refers to any mating member of the core portion other than a member that is encircled by the coil.
  • a “rim” member does not have to be circular in shape, or partially circular in shape such as the walls 122 and 136 of the core portions 110 and 112, nor must it even surround a central leg to any extent.
  • each of the outer legs constitute “rim” members as that term is used herein.
  • the bobbin 114 includes a central tube 138 having a centerhole 140 into which the center posts 120 and 130 can be inserted from opposite ends. Coils of wire (not shown) are wound around the tube 138. To help manage the winding, end stops 142 and 144 are disposed on opposite ends of the tube 138. In the particular example of Fig. 1, coils will be wound around the bobbin 114 so as to create a transformer having a single primary and two secondaries. Electrical connections are made via surface mount pins 148 on the bobbin 114.
  • the shape of the bobbin 114 is an industry-standard shape known as SEP-13, and it is made of a non-magnetic material such as phenolic.
  • Spring clamp 116 may be made, for example, from a nickel silver material.
  • Fig. 2 is a flow chart illustrating the significant steps performed in the assembly of the transformer of Fig. 1.
  • step 210 a coil or coils are wound onto the bobbin in a manner desired for the electrical purposes of the device. In the embodiment of Fig. 1, three coils are wound: one primary and two secondaries.
  • the step 210 can be performed either at the same location as the following steps, or at some other location and some earlier time.
  • an adhesive 150 (Fig. 1) is applied to one of the mating surfaces of one of the core portions 112.
  • the adhesive 150 preferably, but not necessarily, includes some hard particulate matter to improve controllability of the grinding process described below with respect to step 218.
  • An example adhesive is Zymet 517F, which is a thixotropic epoxy containing 3% by weight of 10 micron silica particles. Zymet 517F is available in premixed syringes for application.
  • step 214 the two core portions 110 and 112 are mated together around and through the coils and bobbin 114 (Fig. 1), and clamped together with the spring clamp 116.
  • the rim surface 132 of core portion 112 is "mated” with the corresponding rim surface 134 of core portion 110, as that term is used herein, although a very narrow gap spacing remains between the two surfaces due to the adhesive 150.
  • the two end surfaces 126 and 128 also remain spaced by a narrow gap. These two surfaces are nevertheless considered “mated”, as the term is used herein, inside the bobbin tube 138.
  • the effective permeability of the core 118 is observed.
  • observation of a characteristic such as permeability includes indirect observation of that characteristic, such as by observing an effect that is dependent upon the characteristic.
  • Permeability for example, can be "observed", as the term is used herein, by observing the inductance of a coil which is in sufficient proximity to the core to be affected by the effective permeability of the core.
  • the term "observing the inductance”, as used herein includes indirect observation of the inductance, such as by observing an effect that is dependent upon the inductance.
  • the effective permeability of the core 118 is observed by observing the inductance of the two secondary windings connected in series.
  • Fig. 3 schematically illustrates the test setup.
  • the transformer 310 includes a primary winding 312 having terminals 314 and 316.
  • the first secondary winding 318 has terminals 320 and 322, and the second secondary winding 324 has terminals 326 and 328.
  • terminals 322 and 326 are connected together and an inductance meter 330 is connected across terminals 320 and 328.
  • the inductance of any one of the windings 312, 318 and 324 is mathematically related to the effective permeability of the core 118
  • observation of the inductance of any one of the coils, or any two of the coils connected in parallel or series, or all three of the coils connected in various non-canceling ways will effectively constitute observation of the effective permeability of the core 118.
  • the coil whose inductance is observed in step 216 encircles the core 118, it will be appreciated that in another embodiment, the coil might instead be merely in sufficient proximity to the core so as to be affected measurably by the core permeability.
  • observation of an inductance is a particularly advantageous method of observing the effective core permeability, because usually it is the inductance, not the effective permeability of the core, which is specified in electronic circuits.
  • step 216 it is determined whether the effective permeability of the core 118 is within the desired tolerance. For the test setup of Fig. 3, this determination is made by determining whether the inductance read from inductance meter 330 is within a desired tolerance of a nominal inductance value. If it is not, then in step 218, the gap spacing is adjusted and the effective permeability of the core 118 is again observed (step 216). The process continues until the effective permeability of the core 118 is within the desired tolerance. In one embodiment, the observation step 216 and the adjustment step 218 are performed simultaneously and continuously until a desired permeability is reached, whereas in another embodiment, the two steps are performed in alternating manner.
  • the adjustment of gap spacing in step 218 can be performed in any of a number of ways.
  • the two core portions 110 and 112 are held tightly by apparatus which mechanically moves the cores toward or away from each other in sufficiently fine increments.
  • the two core portions 110 and 112 are simply ground toward each other.
  • the two core portions 110 and 112 are either rotated relative to each other or translated relative to each other, or both, in a plane parallel to their mating surfaces. This motion effectively "grinds" the two core portions toward each other.
  • the rotation and/or translation can be uni-directional, bi-directional or vibratory, and can be performed manually or by machine.
  • particulates in the adhesive 150 help resist the collapse of the adhesive structure, thereby slowing the narrowing of the gap spacing and improving controllability during the grinding process.
  • particulates should preferably be of a non-magnetic material such as silica, so they do not saturate magnetically during circuit operation.
  • the adhesive is cured while the gap spacing is maintained.
  • Curing is performed according to the instructions of the adhesive manufacturer, and may involve, for example, placing the assembly in a 170°C oven for 10 to 15 minutes, or applying RF heating.
  • virtually no curing takes place during the steps 216 and 218 of observing and adjusting, but in another embodiment, partial curing during these steps can be accommodated.
  • the curing process typically increases the permeability of the core 118 by approximately 10%, but the curing step does not significantly impact the precision of the device manufacturing process because the permeability increase during cure is predictable. Instead, the desired effective permeability targeted in steps 216 and 218 is merely reduced by the known percentage increase that will take place during the curing step 220.
  • step 222 the process is complete. It will be appreciated that not only has the process overcome the tolerance degradation that takes place during a conventional assembly process, but has also corrected for imprecision in the permeability of the raw core portions 110 and 112 as originally manufactured. The process permits magnetic devices to be tuned over a wide range, the upper limit being essentially the same permeability as that which the core 118 would exhibit when tightly clamped together without adhesive.
  • the adhesive 150 is applied only to the rim surface 132 of one of the core portions 112.
  • application of adhesive to one mating surface can be performed either directly or indirectly, for example by depositing adhesive onto the corresponding mating surface of the opposite core portion and then mating the two together.
  • no adhesive is applied to any mating surface that comes into close proximity with the coil or bobbin 114, so as to prevent any accidental bonding between the core 118 and the coil or bobbin 114. Otherwise the temperature coefficient of expansion of the combined structure might be indeterminate, thereby introducing an uncertainty into the circuit which may not be desired.
  • one end 142 or 144 of the bobbin 114 can be adhesive bonded if desired to the inside end section of the corresponding core portion 110 or 112.
  • the leg supporting the adhesive is the same as the leg encircled by the coil.
  • the invention can be used with a wide variety of symmetric and asymmetric core shapes.
  • E-cores for example, if the bobbin is placed on the center leg, then the adhesive can be applied to the end surfaces of the two outer legs.
  • cylindrical cores and the EP-13 core illustrated in Fig. 1 the surface(s) supporting the adhesive exists on opposite sides of the leg that is encircled by the coil. The substantially equal resistance exerted by the adhesive on both sides of the central leg therefore maintains the two mating surfaces of the central leg in substantially parallel planes. It is desirable, but not essential, that these two planes remain substantially parallel to avoid local saturation of part of the core.
  • a U-core which has two legs on each core portion, may receive the adhesive on the end surface of one leg and receive the bobbin on the other leg.
  • the mating surfaces inside the bobbin tube can be maintained in substantially parallel planes by applying the grinding force to the two core portions substantially co-axially with the legs supporting the adhesive.
  • Other accommodations will be apparent for other kinds of core shapes.
  • the invention can be used even where not all of the mating surfaces are co-planar with each other.
  • the invention can still be used even if the center post 120 or 130 of one or both of the core portions 110 and 112 has been shortened to create an intentional air gap between them.
  • equipment currently exists to achieve very small permeability tolerance in this situation, but the permeability tolerance can be improved even further through the use of the invention.
  • Fig. 4 is a perspective view of a magnetic device illustrating another aspect of the invention. It comprises first and second core portions 410 and 412, held together in an assembly 418 by a clamp 414.
  • the coil is internal to the assembly of Fig. 4, wound on a bobbin supported on a central leg similarly to the arrangement shown unassembled in Fig. 1.
  • a microgap spacing 416 between the mated surfaces of the core assembly 418 is maintained by particulate matter disposed in the gap 416.
  • the gap spacing is fixed by the particulate matter resisting against sustained force provided by the clamp 414, urging the two core portions 410 and 412 toward each other.
  • the device of Fig. 4 can be made by the same process as that set forth in the flow chart of Fig. 2, except that the particulate matter is applied to the mating surface in step 212 without adhesive, and the step 220 of curing the adhesive is replaced by a step of clamping the two core portions together to apply sustained force urging the two core portions toward each other.
  • a given signal, event or value is "responsive" to a predecessor signal, event or value if the predecessor signal, event or value influenced the given signal, event or value. If there is an intervening processing element, step or time period, the given signal, event or value can still be “responsive” to the predecessor signal, event or value. If the intervening processing element or step combines more than one signal, event or value, the signal output of the processing element or step is considered “responsive" to each of the signal, event or value inputs. If the given signal, event or value is the same as the predecessor signal, event or value, this is merely a degenerate case in which the given signal, event or value is still considered to be “responsive” to the predecessor signal, event or value. "Dependency" of a given signal, event or value upon another signal, event or value is defined similarly.
  • movement of two components “relative” to each other, and movement of one component “relative” to another, does not imply any restrictions about which component is moving relative to any absolute.
  • a statement that component A moves relative to component B is intended to include all of the following possibilities and to not select among them: that component A is stationary and component B is moves; that component B is stationary and component A moves; and that component A moves and component B move differently from component A.
  • the adhesive can be applied in between any one or more of any pair of the mating surfaces of any of the core portions, depending on requirements.
  • any and all variations described or suggested in the Background section of this patent application are specifically incorporated by reference into the description herein of embodiments of the invention.
  • the embodiments described herein were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Coils Or Transformers For Communication (AREA)
EP00127941A 1999-12-27 2000-12-21 Procédé de formation d'un micro-entrefer pour noyaux magnétiques Withdrawn EP1113464A3 (fr)

Applications Claiming Priority (2)

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US472572 1990-01-30
US47257299A 1999-12-27 1999-12-27

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EP1113464A2 true EP1113464A2 (fr) 2001-07-04
EP1113464A3 EP1113464A3 (fr) 2002-05-15

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1286371A2 (fr) * 2001-08-22 2003-02-26 Osram-Sylvania Inc. Procédé et pâte pour joindre des surfaces découpées de noyaux en ferrite pour lampes fluorescentes
EP1444707A1 (fr) * 2001-10-23 2004-08-11 DI/DT, Inc. Procede d'assemblage de circuit magnetique completement automatiquement
US20190214181A1 (en) * 2018-01-10 2019-07-11 Tdk Corporation Inductor element

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109994307B (zh) * 2019-04-17 2020-11-10 湖州师范学院求真学院 一种模压绕线电感器加工用自动输送线

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR773066A (fr) * 1934-05-08 1934-11-10 Perfectionnements apportés aux bobines d'inductance pour hautes fréquences, particulièrement à celles destinées aux appareils radioélectriques
GB723846A (en) * 1952-11-21 1955-02-09 Standard Telephones Cables Ltd Improvements in or relating to adjustable inductance coils
FR2184386A1 (fr) * 1972-05-15 1973-12-28 Cit Alcatel
JPS59168608A (ja) * 1983-03-14 1984-09-22 Murata Mfg Co Ltd フライバツクトランスの製造方法
EP0715323A1 (fr) * 1994-12-01 1996-06-05 Vlt Corporation Réglage de valeur d'inductance de composants magnétiques
JPH09208912A (ja) * 1996-02-01 1997-08-12 Toyo Commun Equip Co Ltd ギャップ形成用接着剤
US5745367A (en) * 1995-05-29 1998-04-28 Samsung Electro-Mechanics Co., Ltd. Fly back transformer, and its inductance adjusting method and device

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR773066A (fr) * 1934-05-08 1934-11-10 Perfectionnements apportés aux bobines d'inductance pour hautes fréquences, particulièrement à celles destinées aux appareils radioélectriques
GB723846A (en) * 1952-11-21 1955-02-09 Standard Telephones Cables Ltd Improvements in or relating to adjustable inductance coils
FR2184386A1 (fr) * 1972-05-15 1973-12-28 Cit Alcatel
JPS59168608A (ja) * 1983-03-14 1984-09-22 Murata Mfg Co Ltd フライバツクトランスの製造方法
EP0715323A1 (fr) * 1994-12-01 1996-06-05 Vlt Corporation Réglage de valeur d'inductance de composants magnétiques
US5745367A (en) * 1995-05-29 1998-04-28 Samsung Electro-Mechanics Co., Ltd. Fly back transformer, and its inductance adjusting method and device
JPH09208912A (ja) * 1996-02-01 1997-08-12 Toyo Commun Equip Co Ltd ギャップ形成用接着剤

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 009, no. 019 (E-292), 25 January 1985 (1985-01-25) & JP 59 168608 A (MURATA SEISAKUSHO:KK), 22 September 1984 (1984-09-22) *
PATENT ABSTRACTS OF JAPAN vol. 1997, no. 12, 25 December 1997 (1997-12-25) & JP 09 208912 A (TOYO COMMUN EQUIP CO LTD), 12 August 1997 (1997-08-12) *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1286371A2 (fr) * 2001-08-22 2003-02-26 Osram-Sylvania Inc. Procédé et pâte pour joindre des surfaces découpées de noyaux en ferrite pour lampes fluorescentes
EP1286371A3 (fr) * 2001-08-22 2003-10-29 Osram-Sylvania Inc. Procédé et pâte pour joindre des surfaces découpées de noyaux en ferrite pour lampes fluorescentes
EP1444707A1 (fr) * 2001-10-23 2004-08-11 DI/DT, Inc. Procede d'assemblage de circuit magnetique completement automatiquement
EP1444707A4 (fr) * 2001-10-23 2009-11-25 Power One Inc Procede d'assemblage de circuit magnetique completement automatiquement
US20190214181A1 (en) * 2018-01-10 2019-07-11 Tdk Corporation Inductor element
US11587717B2 (en) * 2018-01-10 2023-02-21 Tdk Corporation Inductor element

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