DE2205394A1 - ELECTROMECHANICAL FILTER - Google Patents

Description

STANDARD ELEKTRIK LORENZ AG

D. Klein-1

Electromechanical filter.

The invention relates to an electromechanical filter consisting of cylindrical filters arranged axially parallel to one another Flexural resonators, which are attached to a base plate in the vibration node with retaining wires and which are connected to one another by a coupling wire welded into the antinodes.

Electromechanical ^ filters of the type described above through the article by H.Albsmeier "A comparison of the possibility of realization electromechanical channel filter in the frequency range 12 kHz to 10 MHz ", Frequency, 25 (1971) 3, page 74 to 79, in particular page 79, Fig. 13, known. These Execution is designed so that the production and adjustment of the individual resonators as well as the assembly in an automated Manufacturing process can take place. Adjustment work on the fully assembled filter part should not be done more may be required.

Suitable materials for which the variation from batch to batch is within the permissible tolerance range are only very difficult and expensive to obtain. With the usual materials, when a material batch is changed, the filter bandwidth is influenced Requires subsequent adjustment work, since, depending on which materials are used in the filter manufacture, certain properties

January 28, 1972 ./.

vHy / An 309833/0604

D. Klein-1 - «sr -

fluctuate more or less strongly from batch to batch.

In a modern production of electromechanical filters of the type described above, the production of the Resonators in terms of length and cross-section as well as the adjustment to the resonance frequency fully in your hand. Yeah The modulus of elasticity and the material density, which determine the oscillation resistance of the resonators, are certain Subject to fluctuations. The modulus of elasticity fluctuates within a batch by only a few parts per thousand, from batch to batch, however, by ^ to ^ percent. The fluctuations in the Material density is around * 1 percent from batch to batch.

The situation is different with the coupling wire. Very high demands are placed on the uniformity of the wire cross-section posed. Ni-Fe-Mo alloys are often used for coupling wires. Such materials have good drawing properties on and thus low cross-sectional spread. However, wires made from such materials have the major disadvantage that their modulus of elasticity is strongly dependent on temperature and age. Constant modulus alloys, e.g. Ni-Fe-Mo-Be alloys, on the other hand, have a constant modulus of elasticity over a wide temperature range. at However, these alloys have the difficulty of matching the wire cross-section from batch to batch with the required Establish accuracy.

The invention is therefore based on the object of an electromechanical To create filters in which the properties of the resonator and coupling wire material fluctuate from batch to batch must be taken into account and compensated for during assembly.

309833/0604 · '·

D. Klein-1

2205'3 * §4

According to the invention, this object is achieved in that the width of the weld point depends on the fluctuating Properties of the bending resonators and the coupling wire is selected.

According to a further development of the invention, the width of the weld is then in the case of filters with flattened resonators chosen larger than the width of the flat.

The advantages achieved by the invention are that in the automated production of electromechanical Filter materials with the previously described fluctuations in their properties can be used.

The invention is explained in more detail below in conjunction with the drawings. Show it:

Fig.l shows a known electromechanical filter in perspective;

Fig.2a and

2b the front views of two cylindrical resonators, which are connected to one another via a coupling wire are connected.

Fig. 3a and

3b the front views of two cylindrical resonators provided with a longitudinal flattening, which are connected to one another via a coupling wire.

Fig. 1 shows an electromechanical filter known per se. A number of flattened cylindrical flexural resonators 2, 4, are axially parallel to one another on a base plate via holding wires 6 that engage in the vibration node 1 attached. The end resonators 2 are with it

309833/0604 ./.

D.Klein-l - * [-

'a flat area 2a running transversely to the direction of oscillation, on each of which an electrostrictive Converter element 3 is attached.

The actual filter resonators 4, however, are with a Flattened area 4a is provided, which is arranged parallel to the direction of oscillation on the underside of these resonators.

Both the end resonators 2 and the pilter resonators 4 are adjusted to the resonance frequency before assembly.

The individual resonators are coupled via a continuous coupling wire 5 with a round cross-section, which is welded to the resonators 4 in the area of the antinodes on the flats 4b. At the end resonators the welding takes place with the cylindrical outer surface.

Extensive investigations have now been made on how an electromechanical filter constructed in this way the deviations in the filter bandwidth caused by changes in the material properties by simple means could be offset. It is true that such a compensation could be achieved by changing the length of the coupling wires take place, however, due to the devices and gauges used in automatic production, it is not possible to carry out such a change in length without significant changes to the manufacturing equipment. The present invention therefore suggests changing the effective length of the coupling wires by changing the welding parameters .

2a and 2b show the effect of this measure on a pair of resonators with a circular cross-section. Fig.2a represents the one extreme case in which the connection between the resonators 4 and the coupling wire 5 is almost is punctiform. The resulting effective

309833/0604 ./.

D. Klein-l § *.

Coupling length \., _Λ can be changed by changing at least one

J \ -L

Set welding parameters (pressure, temperature, time) in such a way that the coupling wire 5 forms a flat connection with the resonators 4 and is welded to the circumference of the resonators 4 over a certain angular range in accordance with the penetration depth. The resulting effective coupling length! ". is in the other extreme case by 2 A1 _K1 shorter than the coupling length 1 _K1 · ° ie the variable length 2 Δ1 _K1 is relatively large in this case due to the gently rising surface curvature of the resonators at the connection point.

Another possibility is shown in FIGS. 3a and 3b. In this case, the resonators 4 are provided with flats 4a. In the one extreme case, the coupling wire 5 according to FIG. 3a is welded flat on and across the flattened areas 4a of the resonators 4 to the latter in a linear manner. This results in an effective length l "p of the coupling wire 5. With a change in at least one welding parameter, the coupling wire 5 forms an increasingly flat connection with the resonators 4 with a corresponding penetration depth, where these then contact the surface of the resonators adjacent to the flat 4a overlaps according to FIG. 3b. _{The effective coupling length 1 K2} resulting in this other extreme case is shorter by 2 Δ 1 _K2 than the coupling length 1 _K2 ^#

With the same penetration depth, the variable length 2 Δ 1 _{R2 is compared to the variable length 2 Δ 1 «.} significantly less, since the curvature of the resonator jacket surface adjacent to the flat 4a has a steeper course relative to the horizontal than in the contact area in the embodiment according to FIG

309833/0604

D. Klein-l _A - Sr-

Pig. 2 B. As a result, in the example of FIGS. 3a and 3b, there are slight fluctuations in the welding parameters around their Setpoints practically do not work. On the other hand, the range of variation extends from 2 Δ l “p with a corresponding design the filter completely off.

Claims
Bl. Drawings

309833/0604

Claims (1)

D. Small-1 '^ - Ψ " Claims. Electromechanical filter, consisting of cylindrical bending resonators arranged axially parallel to one another, which are fastened in the vibration nodes with holding wires on a base plate and which are connected to one another by a coupling wire welded into the vibration bellies, characterized in that the width of the weld point depends on the fluctuating properties of the Bending resonators and the coupling wire is selected. 2. Electromechanical filter according to claim 1, in which the bending resonators have a flat parallel to their axis and in which the coupling wire is welded over the entire width of the flat, characterized in that the width of the weld is greater than the width of the flat. January 28, 1972
vHy / An 309833/0604 Blank page