JPS582009A - Bottled ferrite core - Google Patents

Abstract

PURPOSE:To set temperature coefficient of an inductance at 0+ or -60ppm/ deg.C., by offsetting positive inductance change of a bottled ferrite core against negative inductance change of a molded resin of trimmer. CONSTITUTION:An inductance change by expansion and shrink of a molded resin is given by DELTAL=alpha.l.(DELTAL1/DELTAd1).DELTAT...(1) Where alpha: thermal expansion coefficient of a molded resin, l: length of a molded resin between trimmer and retaining nut, DELTAL1/DELTAd1: inclination of variable curve at a point d1. Temperature coefficient TK DELTAT: temperature change. of a trimmer is given by TK=alpha.l.(DELTAL1/DELTAd1) (1/L)...(2) Hence, the temperature coefficient TK of a coil made of bottled ferrite core is positive as seen in Eq. (1). The temperature coefficient TK of trimmer is negative as seen in Eq. (2). If each absolute value is equal, the temperature coefficient of coil can be made zero value.

Description

[Detailed Description of the Invention] The present invention relates to molded coils used in filter circuits and tuning circuits in communication equipment, etc., and has realized a ferrite direct coil with an extremely small temperature coefficient (TK) of inductance as a pot-shaped coil. It is something to do.

FIG. 1 is a sectional view showing the general structure of a ferrite straight coil, and FIG. 2 is an enlarged view of section A in FIG. 1. 1
is a stationary core made of ferrite, and has a built-in coil 2. The central tubular n1d of the stationary core l is fitted into the center hole of the coil 2, and a magnetic gap G is formed. A supporting nut 3 is inserted and fixed into one end of the cylindrical portion 1d, and a trimmer 4 is threadedly supported by the nut 3. The trimmer 4 includes a trimmer core 41. made of a magnetic material. It is comprised of a threaded rod 42 that screws and supports the trimmer core 41 into the support nut 3 and an operating section 43. The trimmer core 41 has a cylindrical shape, for example, and is integrally fixed with a resin threaded rod 42 integrally molded with the operating portion 43 inserted therein. The inductance is adjusted by fitting a screwdriver into the operating part 43 and rotating it to move the trimmer core 41 up and down with respect to the support naso [3 to adjust the position of the trimmer core 41 with respect to the magnetic gap G. .

By the way, such a ferrite pot-shaped coil has a positive temperature coefficient, so conventionally it is used in a pair with a styrene film capacitor in a circuit, and the positive temperature coefficient of the ferrite pot-shaped coil and the negative temperature of the styrene film capacitor are It is used in such a way that the coefficients exactly cancel each other out. For example, the temperature coefficient of a styrene film capacitor is 115
Assuming 0 ppm/'C, the temperature coefficient of the flywheel coil is designed to be the center value +150 ppm/'C.

However, recently, with the miniaturization and cost reduction of equipment, the temperature coefficient of capacitors has become 0 ± 60 ppm/'.
The use of ceramic capacitors with a value of C is increasing, and therefore the temperature coefficient of the coil used in combination is also required to be close to zero.

To meet this requirement, in order to bring the temperature coefficient close to zero in the current ferrite pot-shaped coil, the relative temperature coefficient of the laerite material used (Tα = 4 and -L ) and the effective μ of the tuyurite core
2 The only way is to make the product of notch magnetic permeability (μe) as close to zero as possible.

° TK of core and coil = Tα・μe・old... (1) However, in this method, the relative temperature coefficient ゛rα is determined by the material of the thulite core, and there is a limit to reducing it, while the effective magnetic permeability If μe is made small, there is a problem that the Q of the coil cannot be made high.

Therefore, the present invention aims to solve this problem from a completely different perspective.To achieve this purpose, the present invention has the following objectives: In a stationary light pot type coil that uses a ferrite stationary core with an absolute value of 60 ppm/''C or more and has an inductance adjustment mechanism by inserting a straight trimmer, the positive inductance change due to temperature of the tuyurite stationary core and the trimmer. By selecting the coefficient of thermal expansion of the trimmer and its supporting means, the coefficient of thermal expansion of the resin part of the trimmer and its supporting means, and the dimensions of the trimmer core, so as to offset the negative inductance change caused by expansion and contraction of the mold resin part due to temperature. , the temperature coefficient of inductance is set to O±60 ppm/''C.

That is, in the present invention, by setting the temperature coefficient of the tsumelite pot-shaped core or the effective magnetic permeability μe high, +60 p p
m / ' Even if it is on CD, as a coil θ
This allows it to be set to ±60'p prn/''C.

When the trimmer 4 is moved relative to the support nut 3 using the point where the center C of the magnetic gap G and the center of the trimmer core 41 coincide with each other in the tuyurite pot-shaped coil having the structure shown in FIGS. 1 and 2 as a base point. No, move! 1. If the coil inductance variable amount ΔL with respect to the distance ad is not shown, the result will be as shown in FIG. 3. If the inductance L of the stationary coil is adjusted so that the center of the trimmer core 41 is aligned by dI with respect to the center C of the magnetic gap G of the Tyulite stationary core, the slight fluctuation of the trimmer core 41 in the vicinity of the d1 position will be Δd
With respect to +, the inductance changes by 5- by lL1 with a negative slope. Therefore, there is a difference in the thermal expansion coefficient of the ferrite coil γ and that of the molded resin parts such as the support nut 3 and the threaded rod 42 of the trimmer 4.As a result, the same inductance fluctuation occurs even when the trimmer coil γ 41 is displaced due to temperature changes. will occur.

The amount of change in inductance due to expansion and contraction of this molded resin part can be calculated by equation (2).

ΔL-α・"l'dr・ΔT ......(2) However, α: Thermal expansion coefficient of the molded resin part l Length of the molding 1' resin part of the nitrimer and support nut 4!-'・41 points The slope of the variable amount curve Δac.

ΔT: Amount of temperature change Further, the rate of change in inductance per 1° C., that is, the temperature coefficient TK due to the trimmer is expressed by equation (3).

Trimmer TK-α・J, 1L-+・-J-...
...(3) The temperature coefficient TK of the coil due to ΔtL + Muferite placement type γ is (1
) is a positive value, and the temperature coefficient TK of the trimmer is (3
) is a negative value, so by making their absolute values equal as in equation (4), the coefficient of the coil can be made zero.

1Tot-pe l-1cx-1! -4L'・"l-(
4) Δd,,L It would be ideal if the conditions of this equation could be completely satisfied, but in practice it is sufficient if it can be set within 0±60 ppm/''C.

Next, specific examples will be given and explained.

Tuyulite stationary core: Shape is 18φXll, material is M
n-Zn ferrite, μe-75, relative temperature coefficient is +0
．． 5~(1,1xlO/”c (center is +0.8t XIO) Temperature coefficient TK of coil with Ferrai I pot-shaped core:
+37.5~482.5p pm/”C (center +eop
pm/”C) This temperature coefficient is canceled out so that the center of TK becomes zero, that is, the temperature coefficient of the trimmer is TK--sopp m/
The constant of the trimmer should be selected so that "C" is achieved.

As a result, the following values were obtained.

7- α-I X 10-4/'c of the molded resin part can be easily realized by using, for example, polyacetal resin.

Further, a variable rate slope of 475 z 0.11/m can be easily realized by selecting the dimensions of the trimmer core.

As described above, according to the present invention, the thermal expansion coefficient of the molded resin part of the trimmer and the dimensions of the trimmer core are positively utilized to actively utilize the expansion and contraction caused by the temperature of the molded resin part of the trimmer for adjusting inductance and the supporting naso 1. By effectively selecting such factors, the temperature coefficient of the ferrite mold core can be canceled out, and the temperature coefficient of the ferrite-placed coil can be set to zero or O±60 p p m / which is practically acceptable for use in combination with a ceramic capacitor. Therefore, the temperature coefficient problem of the ferrite-based coil can be solved without sacrificing Q by reducing the effective magnetic permeability μe of the tuyurite-based core.

[Brief explanation of the drawing]

Fig. 1 is a fiffi sectional view showing an example of a ferrite-based coil to which the present invention is applied, Fig. 2 is an enlarged view of section A in the same figure, and Fig. 3 shows the amount of inductance change with respect to 1-JJ mom displacement. It is a diagram. In the figure, 1 is a pot ferrite core, 1d is a cylindrical part, and 2
is a coil, 3 is a support nut, 41 is a trimmer core, 42
numeral 43 is a threaded rod, and 43 is an operating section. Patent applicant: Fujitsu Ltd. Representative: Patent attorney Minoru Aoyagi 9- 8- Figure 1 Figure 3

Claims (1)

[Claims] In a ferrite direct coil that uses a tuyurite pot-shaped core with a positive temperature coefficient of inductance (magnetic permeability) and an absolute value of 60 ppm/''C or more, and has an inductance 11ti mechanism by inserting a trimmer, the ferrite stationary core is The coefficient of thermal expansion of the molded resin part of the trimmer and its support means and the dimensions of the trimmer core so that the positive inductance change due to temperature and the negative inductance change caused by expansion and contraction due to temperature of the molded resin part of the trimmer are offset. A thulite pot-shaped coil characterized in that the temperature coefficient of inductance is set to 0±60 ppm/°C by selecting .