DE2443215C3 - Resonance element with constant natural frequency - Google Patents

Description

Oscillating crystals are usually used as frequency standards, i.e. single crystals that are in cut out certain directions and then by very precise mechanical shaping as well as by vapor deposition of other materials are trimmed to the nominal frequency. This is all complex and expensive. In addition, the mechanical suspension of the quartz crystal with regard to the demanded insensitivity to shock only with great difficulty

ωο = angular frequency of the natural oscillation, Li = primary inductance of the transformer, R \ = resonance resistance

is designated.

3. resonance element according to claim 2, characterized in that on the transformer core (7) two secondary windings (9,10) are applied.

4. resonance element according to claim 1 and one of the preceding claims, characterized in that that between ferrite ring core (5) and transformer (7) an adjustable inductive coupling element (11) is switched.

5. resonance element according to claim 1 and at least one of the preceding claims, characterized by two transformers (12, 12), which are connected via a coupling loop (8) in which one can be adjusted Mutual inductance (13) is to which ferrite ring core (5) are inductively coupled.

6. resonance element according to claim 1, characterized by an optionally after its sintering toroidal core annealed in a magnetic longitudinal field, which preferably consists of a stoichiometric Co-containing Ni-Zn ferrite and has a rectangular hysteresis loop.

7. resonance element according to claim 6, characterized by a ferrite ring core with the following Composition of its starting components:

50

51-62 mole percent Fe ₂ O ₃
0-25 mole percent ZnO
Remainder NiO
approx. 0.3-1% by weight CoO

55

8. resonance element according to claim 6 and 7, characterized by a ferrite ring core following Composition of its starting components:

57 mole percent Fe ₂ O ₃
12.5 mole percent ZnO
30.5 mole percent NiO
0.55 wt% CoO

9. Resonance element according to claim 1 and at least one of the preceding claims, characterized in that the ferrite _{ring core (5) L "un: ii and c} " NTZ "1958, H.4, pp 179-165 and" Philips Technisch! Rundschau «, 18 Jg. 1956/57, No. 10 pp. 277-312, it is known that ferrite ring cores made of a magnetostructural material, which are azimuthally prepolarized, can be excited to radial oscillations by an azimuthally directed alternating magnetic field. Attempts have already been made to create a low temperature dependence of the natural frequency by means of a suitable composition of the ferrite cores. The results achieved so far are, however, for high requirements, e.g. B. for frequency standards for electronic clocks, not yet satisfactory.

The present invention has the object based, in particular to create suitable resonance elements for electronic devices, their resonance frequency from external influences such as temperature changes, mechanical vibrations and the like is as independent as possible and as constant as possible over long periods of time, but in a simple manner in can be set to certain limits.

In the case of a resonance element with a ferrite ring core made of magnetostrictive material, the azimuthal pre-polarized and through an azimuthally directed alternating magnetic field to form radial oscillations can be excited, the natural frequency of which is independent of external influences adjustable within certain limits, The invention sees the solution to the problem posed-a ferrite ring core with a rectangular-like hysteresis loop before, by a magnetic field pulse whose strength is greater than the coercive force of the Ferrite material, is azimuthally prepolarized.

These resonance elements meet all the properties required at the beginning with regard to temperature independence and inability to flow through mechanical shocks.

The height of the field pulse can be a

Achieve fine tuning of the oscillation frequency. Since the

Ferrite ring core is driven inductively, is in

Difference to an oscillating crystal, the electrodes

, possesses, also no connection of the vibrating

Body with egg

Low-damping and shock-absorbing bracket

can be easily realized. The invention wire

explained in more detail below with reference to the drawing

, Shows in it

F i g. 1 shows a first embodiment of the object of the invention in a partially perspective and schematic representation;

F i g. 2 the electrical equivalent circuit diagram of the ■ resonance element according to FIG. 1;

^{3 shows} the locus of the impedance of the resonance circuit, the impedance being normalized to the value (OaL;

4 shows a second embodiment of the object according to the invention in a schematic representation

5 shows the electrical equivalent circuit diagram of the exemplary embodiment according to Fig. 4; ,O

6 tin third embodiment of the object according to the invention in a schematic representation

Fi'g-7 ^{e 'n} fourth embodiment of the article according to the invention in a schematic representation

Fig. 8 is a sketch of the locus of the impedance of the resonance circuit for the embodiment according to FIG. 7;

F i g. 9 a fifth embodiment of the subject matter according to the invention in a schematic representation;

10 shows the dependence of the natural frequency on the Temperature for several oscillators according to the invention which differ in their composition;

Fig. Π an embodiment for the temperature dependency the natural frequency of an oscillator according to the invention, a transducer and a transducer-transducer combination;

F i g. 12 shows an embodiment for the dependent wedge the natural frequency of an oscillator according to the invention on the level of the bias pulse.

In the first embodiment of a resonance element with constant natural frequency shown in Fig. 1, a toroidal core 5 made of magnetostrictive ferrite with a rectangular hysteresis loop is azimuthally prepolarized by a magnetic field pulse, the strength of which is greater than the coercive field strength Wr, and with a winding 6 with connections 1 2 provided, which - as in the in F i g. 1 is shown - in the extreme case can only consist of one turn. The ferrite ring core 5 can be excited to mechanical radial vibrations by an azimuthally directed alternating magnetic field, whereby it is always assumed that the ₄ s exciting field is smaller than the coercive field strength of the material.

Fig. 2 shows the electrical equivalent circuit diagram of the Resonance element according to FIG. 1, assuming that the line resistance is negligibly small. It means

L = basic inductance.
A: = electromechanical coupling factor. Q = quality of the mechanical vibration, y

W ₀ = angular frequency of the natural oscillation (ω _ο = 2π / ό).

In the case of usable ferrite cores, the clekiromechanical coupling factor k is in the order of magnitude of ν approximately 0.1, the quality of the mechanical oscillation in the order of 1000, whereby only ferrite cores are usable for which the condition A ^: Q> \ is fulfilled. The rule of thumb applies to the frequency / «:

VIII / ~ "(/" mm 'where d _a denotes the outer diameter of the ferrite ring core.

The locus of the impedance of the two-terminal pole results in _{a circle in the vicinity of ω 0} which, if the impedance is normalized to the value ω ₀ · L and under the assumption k ² · Q> 1, which also applies in the following, the center point coordinates k - ■ QIl or 1 and the diameter k ² ■ Q (see Fig. 3). The relationship between the resonance frequencies Ω or Q _{2 normalized to ω 0} and the quantities Q and k applies here:

where approximately Ωι = 1 and Ω ₂ y + applies

For the resonance resistance R] ' , the relationship R \' ^ k ² ■ Qü) _ü ■ L applies, which is why the inductance L must be correspondingly large if one has a given size of k ² ■ Q and the required resonance frequency f \ = / 0 wants to achieve the greatest possible resonance resistance R \. The inductance of the resonance element depends on the remanence permeability of the material, the geometric dimensions and the square of the number of turns. With regard to other important properties, such as B. the coupling factor, the quality and the temperature coefficient, the remanence permeability is only to a small extent freely selectable. Since the geometric dimensions are also fixed as a result of the required resonance frequency f \ or should be as small as possible for reasons of space, a high resonance resistance can consequently only be achieved with a correspondingly high number of turns.

However, since damping-free storage is problematic, especially with smaller ferrite ring cores, if several or many windings are to be passed through the ferrite ring core acting as an oscillator, - as in the second exemplary embodiment according to FIG. 4 and 5 is shown - the ferrite ring core 5 is inductively coupled by means of a coupling loop 8 to a transformer core 7, the primary inductance L \ must generally be so large that the condition

is satisfied. In addition, it must be ensured that the ohmic resistance in the coupling circuit is very small compared to Mi '. The secondary winding applied to the transformer core with the outputs 1, 2 is denoted by 9. Corresponding to the transmission ratio ü , the resolver resistance R / between the outputs 1, ^{2 is} greater than R by a factor of 2 than R] '.

The electrical equivalent circuit diagram of the arrangement according to FIG. 4 is in FIG. 5 shown.

Since a four-pole impedance is generally more favorable than a two-pole impedance in the construction of an oscillator circuit, according to the method shown in FIG. 6 another embodiment shown on the transformer core \ a second secondary winding 10 with outputs 3, ' can be applied.

Regardless of the Bev: h; il'fenhcit of the transformer 7 and the way it is wrapped can be wiped out lenitringkern 5 and the transformer 7 an adjustable , sound inductive coupling member 11 (see Fig. 7, durcl see the working point b / w. Zero crossing of the i F i g. 8 diagrammatically shown locus can be shifted towards approximately higher l-iequen / e'i. Whom

namely the Grundinduktivität L nor the inductance λ ■ L of the inductive coupling member 11 is added, the circle center point M of the locus moves parallel to the y-axis to the M *, where the resonance frequency moves to Ωι Ωι *. The following formula applies to the calculation of Ωι *:

U ₁ * =

Q | / 2 (/.+ D

2Q ² + k ² Q ² + 2 / .Q ² ~ \ - / .-

With regard to the uniqueness of the point of resonance must be there

, ie λ must not have such large values.

The adjustable inductive coupling element allows fine tuning of the resonance frequency.

Through the in F i g. 9, in which two transformer cores 12 are inductively coupled to the ferrite ring core 5 via a coupling loop 8 in which there is an adjustable mutual inductance 13, a larger range of variation can be achieved because this arrangement allows the center point M (see FIG. 8) can also be pushed under the x-axis. The secondary windings of the transformer cores 12 are denoted by 14.

As magnetostrictive materials with a rectangular hysteresis loop are preferred after their Sintering, optionally tempered in a longitudinal magnetic field, preferably overstoichiometric Co-containing Ni-Zn ferrites with a rectangular hysteresis loop and the following composition of their starting components:

51-62 mol% Fe ₂ O ₃
0-25 mol% ZnO
Remainder NiO
about 0.3 to 1% by weight CoO

is used, as this - as FIG. 10 shows for the following compositions - is a very good one have low temperature dependence of the natural frequency.

FIG. 10 shows the temperature dependence of the natural frequency for three ferrite ring cores labeled a, b and c in the table below, the curves a, b and c being assigned to the cores with the same name and having a parabolic course and the position of the maximum through the Co-content can be determined according to the area of application.

Core a

Fe2O3, mol% 57 57 57 NOK. Mol% 30.5 30.5 30.5 ZnO, mole% 12 pounds 12.5 12.5 CoO, wt% 0.475 0.55 0.625

The ferrite ring cores according to the table above were still in a magnetic one after sintering

ίο Longitudinal field annealed in order to impress the properties for the formation of a rectangular hysteresis loop. To control the temperature response and the values of Q and k , other additives, e.g. B. CaO, BaO, can be used.

The temperature response of the resonance frequency can, as shown in FIG. 11 is shown, flatten up to a curve d shown in dashed lines, if one compensates the curve marked with e of the temperature dependence of the natural frequency of the oscillator or ferrite ring core by a corresponding inductance-temperature curve / "of the transmitter material Natural frequency of the oscillator, as is the case in the example shown, the transformer must have a bell-shaped L- shape if the curve marked with ^ is to be obtained. The ferrite ring core measured in FIG. 11 had the following data:

L = 10 nH
k = 0.16
<? = 1200
/ "0 = 390 kHz.

Finally, FIG. 12 shows the with the aid of a ferrite ring core tempered in a magnetic field 6 mm outside diameter and the following composition of its starting components:

53.0 mole percent Fe ₂ O ₃
20.0 mole percent ZnO
27.0 mole percent NiO
0.64 wt% CoO

Determined dependence of the natural frequency on the level of the bias pulse Iv, where I _r is normalized to the coercive _{current / c of the ferrite ring core.} It can be seen that a variation of more than 1% is possible

The resonance element is expediently inserted in a hermetically sealed housing which is filled with a dry Gr%, for example nitrogen, or possibly evacuated. B. Dust or condensed moisture precipitates. Since magnetic interference fields can also affect the natural frequency, the housing should be made of a magnetically conductive material.

In addition 4 BkUt drawings

Claims (2)

Patent claims: 1. Resonance element with a ferrite ring core made of magnetostrictive material, which azimuthally pre-polarizes and can be excited to radial vibrations by an azimuthally directed alternating magnetic field whose natural frequency, which is independent of external influences, can be set within certain limits, characterized by a ferrite ring core (5) with a rectangular hysteresis loop, the by a magnetic field pulse, whose strength is greater than the coercive field strength of the ferrite core, is azimuthally prepolarized. 2. Resonance element according to claim 1, characterized in that the ferrite ring core (5) is inductively coupled to a transformer (7), where <y <\ Li > R \ and with is inserted into a closed with dry gas-filled or evacuated housing that consists of magnetically conductive material. 10 resonance element according to claim 9, characterized in that the housing is filled _{with N 2}