Core coil having a improved temperature characteristic

[57] ABSTRACT

The temperature characteristics of a core and winding assemblage are improved by including within the magnetic circuit of the core an auxiliary core which is composed of a mixture of magnetic powders of various Curie points, whereby the inductance of the core assemblage remains constant over a wide range of temperature.

Claims, 8 Drawing Figures

<img file="US3663913A_D0001.tif" />

Patented May 16, 1972 3,663,913

Sheets-Sheet 1

<td> FIG.I M·' 3 FIG.3 ³</td><td> FIG.2 : 3 J J jig ^F,G'⁴ I ² INVENTORS. UMAKI KATO a HISAO NISHINO BY</td>

AGENT

Patented May 16, 1972

3,663,913

Sheets-Sheet 2

FIG.5

<img file="US3663913A_D0002.tif" />

INVENTORS.

UMAKI KATO a HISAO NISHINO

<img file="US3663913A_D0003.tif" />

AGENT

Patented May 16, 1972

3,663,913

Sheets-Sheet 3

<img file="US3663913A_D0004.tif" />

HISAO NISHINO

<img file="US3663913A_D0005.tif" />

AGENT

Patented May 16, 1972

Sheets-Sheet 4

3,663,913

FIG.7

<img file="US3663913A_D0006.tif" />

BY

<img file="US3663913A_D0007.tif" />

AGENT

Patented May 16, 1972 3,663,913

Sheets-Sheet 5

FIG.8

<img file="US3663913A_D0008.tif" />

AGENT

3,663,913

CORE COIL HAVING A IMPROVED TEMPERATURE CHARACTERISTIC

This is a continuation-in-part of our copending application Ser. No. 786,080, filed Dec. 23, 1968, now abandoned.

This invention relates to improved magnetic cores for coil windings, and more particularly to cores having inductances which vary in a linear manner over a wide range of temperature.

Generally, the inductance of a magnetic core used with coil windings will vary with temperature, the change in inductance in almost all instances being non-linear over large temperature changes, and being linear only within small changes in temperature.

However, in electronic equipment used in computers, communications, radar and the like, wherein oscillators, filters and the like must operate within closely defined limits, it is imperative that the inductance of the magnetic cores be either constant or vary at a predictable linear rate over a wide range of temperature.

It is an object of this invention to provide a magnetic core for use with a coil which has an inductance which remains constant over a wide range of temperature.

It is another object of this invention to provide a magnetic core for use with a coil which has an inductance which varies linearly over a wide range of temperatures.

It is still another object of this invention to provide a magnetic core for use with a coil which has an inductance which is either constant or varies linearly over a wide range of temperature that is economical to manufacture.

These and further objects and advantages of the present invention are achieved, in general, through the use of an auxiliary core composed of magnetic material whose Curie temperature, the temperature above which the molecular forces of magnetism of paramagnetic bodies cease to exist, is lower than . that of the magnetic material of the core, the auxiliary core ' being arranged in series with the magnetic circuit ofthe core in some instances, and in parallel with the magnetic circuit of the core in other instances.

The novel features that are considered characteristic of this invention are set forthwith particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing wherein:

FIG. 1 is a cross-sectional view in perspective of an E-type core and associated winding in accordance with the principles of this invention;

FIG. 2 is a cross-sectional view in perspective of a pot-type core and associated winding in accordance with the principles of this invention;

FIG. 3 is a cross-sectional view in perspective of a ring-type core and associated winding in accordance with the principles of this invention;

FIG. 4 is a partial sectional view in perspective of a rod-type core and associated winding in accordance with the principles of this invention; and

FIGS. 5 through 8 graphically compare variations of inductance, in percent, with temperature of cores which are modified in accordance with the principles of this invention with cores which are not modified in accordance with the principles of this invention.

Similar reference numerals represent similar parts throughout the several views of the drawing.

While different shapes and configurations of cores and associated coils are illustrated, the similar parts of the various coil assemblages are designated by the same reference numeral.

Referring to FIG. 1, there is illustrated a cross sectional per- 70 spective view of an E-type of core and winding in accordance with the principles of this invention. An E-type of core 1 composed of magnetic material supports a coil 2 which fills up completely the window of the core. The center leg of the Etype core is cut short a predetermined amount and an auxilia- 75 ry core 3 is positioned within the space provided. The auxiliary core 3 is made of magnetic material whose Curie temperature is lower than the Curie temperature of the magnetic material of which the E-type core is made.

Referring to FIG. 2, there is illustrated a cross-sectional view in perspective of a pot-type core and associated winding in accordance with the principles of this invention. A pot-type of core 1 composed of magnetic material supports a coil 2 which fills up the window of the core. The center leg of the pot-type core is cut short a predetermined amount and an auxiliary core 3 is positioned within the space provided. The auxiliary core 3 is made of magnetic material whose Curie temperature is lower than the curie temperature of the magnetic material of which the pot-type core is made.

In the embodiments illustrated in FIGS. 1 and 2, the auxiliary core 3 is shown as being in the center leg. It is to be understood that the auxiliary core 3 may also be positioned in one or both of the outer legs; or, the auxiliary core 3 may be 2q positioned in each of the legs.

Referring to FIG. 3, there is illustrated a ring-type core and associated winding. A ring-type core 1 supports an auxiliary core 3 and a winding 2 which is positioned around both the core 1 and the auxiliary core 3.

Referring now to FIG. 4, there is illustrated a rod-type core and associated winding. A rod-type core 1 supports a winding 2, an auxiliary core 3 positioned around the core 1 and the winding 2. The Curie temperatures of the auxiliary cores 3 are again lower than the Curie temperature of the cores 1.

In FIGS. 1 and 2, the auxiliary core 3 is in series in the magnetic circuit of the core. In FIGS. 3 and 4, the auxiliary core 3 is in parallel in the magnetic circuit ofthe core.

Referring specifically to the embodiment of FIG. 2, a core 1 of IEC type 26-16 composed of Mn - Zn ferrite having a με 35 of 250 and a Curie point or temperature of 170° C. has a temperature characteristic represented by curve 1 of FIG. 5. The combining of an auxiliary core 3 having a thickness of 30μ with the conventional core 1, as illustrated in the embodiment of FIG. 2, causes a change of the temperature characteristics ⁴⁰ of the assemblage, as shown by curve 2 of FIG. 5. In this assemblage, the auxiliary core was composed of 2-gram adhesive and 1.5 gram Mn — Zn ferrite powder, the powder being a mixture of powders of various Curie points as follows:

Curie Point of Powder (°C.)

Ratio in weight

-5 -10 -15 -20 -25 -30 -35

Curie Point of Powder (°C.)

Ratio in weight where the radius of the particles=9μ; and the total weight equals 1.5 grams.

In determining the characteristics of the core, the coil 2 had 60^v100 turns, and carried 1 ma at IKHz. A Maxwell bridge was used as the measuring apparatus.

Referring again to the embodiment of FIG. 2, a core 1 of IEC type 26-16 composed of Mn - Zn ferrite having an μβ of 250 and a Curie point of 168° C. has a temperature characteristic represented by curve 1 of FIG. 6. The combining of an auxiliary core 3 having a thickness of 40μ with the conventional core 1, as illustrated in the embodiment of FIG. 2, causes a change of the temperature characteristics of the assemblage, as shown by curve 2 of FIG. 6. In this assemblage, the auxiliary core was composed of 2-gram adhesive and 1.5 gram Mn — Zn ferrite powder, the powder being a mixture of powders of various Curie points as follows:

3,663,913

601

502

403

203.5

104.5

-10 5.55

-307.5 where the radius of the particles == 7μ; and the total weight equals 1.5 grams.

The conditions under which the characteristics of the core were determined were the same as those of the first noted example.

Referring still again to the embodiment of FIG. 2, a core 1 of IEC type 26-16 composed of Mn - Zn ferrite, having an με of 250 and a Curie point of 168° C. has a temperature characteristic represented by curve 1 of FIG. 7. The combining of an auxiliary core 3 having a thickness of 40 μ with the conventional core 1, as illustrated in the embodiment of FIG. 2, causes a change of the temperature characteristics of the assemblage, as shown by curve 2 of FIG. 7. In this assemblage, the auxiliary core was composed of 2-gram adhesive and 1.5 gram Mn - Zn ferrite powder, the powder being a mixture of powders of various Curie points as follows:

Curie Point of Powder (° C.)

Ratio in weight —20 where the radius of the particles=7/x; and the total weight equals 1.5 grams. 35

The conditions under which the characteristics of the core were determined were the same as those of the first noted example.

An examination of the curves of FIGS. 6 and 7 will reveal that, with the exact same core, different characteristics can be 40 obtained by using auxiliary cores composed of powders having different Curie points. In a similar manner, the assemblages of FIGS. 1, 3 and 4 can provide cores having characteristics which vary from the characteristics of the core 1 by a desired amount to provide a core assemblage having improved temperature characteristics.

Obviously many modifications and variations of the present invention are possible in the light of the above teaching. It is therefore, to be understood that the invention may be practiced otherwise than as specifically described herein.