DE1280988B - Mechanical flexural oscillator - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

H03h

German class: 21 a4 -10

Number: 1280988

File number: P 12 80 988.0-35 (S 85316)

Filing date: May 21, 1963

Opening day: October 24, 1968

Mechanical flexural oscillator

The invention relates to a mechanical flexural oscillator, which by platelets made of electrostrictive Material for a transducer for the transition from electrical vibrations to mechanical flexural vibrations and vice versa and preferably designed as a converter of a multi-part electromechanical Filter is provided, and in the case of the plate made of electrostrictive material predominantly within the area delimited by two neighboring vibration nodes in the course of the flexural vibrator are arranged.

According to the Austrian patent specification 224 163, it is already a flexural transducer, among other things become known, which is designed as a double-plate bending crystal and which consists essentially of a Single crystal consists of zinc oxide, with excitation electrodes being provided on two surfaces of the crystal are. For this arrangement, however, it is essential that the entire flexural oscillator from one electrostrictive material.

Furthermore, a tuning fork-shaped arrangement is known in which the vibration excitation by im Tuning fork foot arranged electrostrictively active elements takes place. For the perfect function In this arrangement, however, it is imperative to use an oscillating one designed as a tuning fork Element to use.

Furthermore, a mechanical flexural oscillator has already been proposed, which by platelets made of electro-sensitive material to a transducer for the transition of electrical vibrations on mechanical flexural vibrations and vice versa and preferably designed as a converter multi-part electromechanical filter is provided and for which it is essential that at least each a plate with at least approximately perpendicular to the longitudinal axis of the flexural oscillator Platelet level and preferably within that bounded by two neighboring nodes of vibration Area is arranged on both sides of the neutral fiber of the flexural oscillator, and that this preferably lying in a cross-sectional plane of the flexural oscillator platelets in a to Platelet plane perpendicular direction are polarized in opposite directions. With this older proposal, assumed, for example, in the case of rod-shaped flexural oscillators, flexural oscillations due to utilization to stimulate the so-called longitudinal piezo effect, including at least two electrostrictive plates Material are arranged directly in the course of a flexural oscillator and the vibration excitation takes place in such a way that the one plate Applicant:

Siemens Aktiengesellschaft, Berlin and Munich, 8000 Munich 2, Witteisbacherplatz 2

Named as inventor:

Dr.-Ing. Dietwalt Thierbach, 8000 Munich;

Josef Adamietz, 8131 Traubing

Chen is subjected to stretching, while the other plate is shortened at the same time. How yourself shows, such flexural vibrators are then relative to mechanical vibration sensitive if the dimension lying in the direction of oscillation, for example due to the required natural resonance frequency is relatively small; it also complicates this requirement because of the relatively small soldering area still available, so is the manufacture such flexural oscillator.

The invention is based on the problem of the aforementioned difficulties in proportion easy way to counter and flexural oscillators with relatively high mechanical stability create.

Based on a mechanical flexural oscillator, which is made by electrostrictive plates Material for a transducer for the transition from electrical vibrations to mechanical flexural vibrations and vice versa and preferably designed as a converter of a multi-part electromechanical Filter is provided, and in the case of the plate made of electrostrictive material predominantly within the area delimited by two neighboring vibration nodes in the course of the flexural vibrator are arranged, this object is achieved according to the invention in that in the flexural oscillator a slot is provided which extends from the outer limit to approximately in the area of the with respect to bending vibrations occurring neutral fiber that extends into this slot at least a plate provided with excitation electrodes of electrostrictive material is introduced, which in a manner known per se with a pre-polarization running perpendicular to the excitation electrodes is provided, and that at least between one of the excitation electrodes and the flexural oscillator an electrically insulating intermediate layer lies.

The invention is explained in more detail below on the basis of exemplary embodiments.

809 628/1374

3 4

Fig. 1 shows a mechanical bending process then the platelets 6 and 10 because of the Schwinger, which occurs from a continuous steel part 5 when the steel part 5 cools consists, which is provided with a slot 7. Shortened in length under a mechanical pre-slit 7 is a plate 6 from an electrostric voltage, which is expediently chosen so that a tive ceramic (such as lead zirconate). 5 intimate connection of the platelets 6 and 10 with the The electrostrictive plate 6 is on which the steel part comes about.

Steel part facing sides with metallic layers In Figs. 3 and 4 are exemplary embodiments

th 8 and 9, preferably provided with silver layers, in which the excitation die For example, by vapor deposition in a vacuum, electrodes are not electrostrictively inactive, but rather are applied to the ceramic plate. Between an electrostrictively active material is used. see the silver layer 9 and the steel part 5 is located. The transducer according to FIG. 3 consists of

a plate 10 made of an electrically non-conductive one continuous steel part 5, in which a slot 7 is made of material which is milled from quartz glass in the exemplary embodiment. In the oscillation nodes 11 and 12 there is. In the oscillation nodes 11 and 12, wires are in turn fastened, which fasten metallic wires 14 and 15 to the holder, which are used for coupling 15 of the oscillator in a housing. These wires and the GeFilters or the anchoring of the oscillator in the housing are not shown in the drawing for the purpose of tying up with further flexural transducers of a multi-part seren overview. In the slot 7 a housing, not shown in detail, is used. On two are separated by a silver layer 28 the silver layer ^ is a lead wire 16 on plates 20 and 21 made of an electrostrictive solder, which leads to a terminal 1. Soldered in ao terial. A further supply guide wire 31 is connected to the silver layer 28 and is attached to a terminal 1 wire 17 which leads to a connection terminal 3. In the vibration node 12 is a leads on the steel part. In order not to adversely affect the quality of the oscillator to a terminal 3 leading lead, the lead wires 16 wire 30 are attached. The polarization of the platelets 16 and 17 is advantageously formed from a material that is as light as possible and is opposite to that of the platelet 21 and is flexible. Through the dashed line 13, as indicated by the arrows 24 and 25, the dotted line 13 is still what is known as the neutral one. If an interchangeable fiber of the oscillator is indicated at the terminals 1 and 3, under which the voltage U is applied, then stretching is to be understood as an example plane in which the tensile and compressive forces occurring during the oscillation in the positive half-wave of both platelets 20 reverse their sign 30 and 21 under the influence of the electric field. while they increase in the negative half-wave

In Fig.2 is a view in the longitudinal direction pull together, causing the oscillator to bend it vibrations shown in FIG. 1 are excited, net, in the event that the terminals 1 The embodiment according to FIG. 4 is

and 3 an alternating voltage U is applied. By means of a further development of the FIG. 3 the arrow 18 shown is an electrostrictive plate oscillator in such a way that the oscillator is indicated in addition to impressed polarization, the example of the ceramic plate 20 and 21 formed in the positive half-wave of the electrical excitation system with a further alternating voltage with the electrical Field direction is provided electrostrictively active system. This agrees, in the negative half-wave of the elec- 40 consists of the ceramic platelets 22 and 23, which is oriented in Irish alternating voltage opposite to the field, a further slot T arranged in the steel part 5. According to this polarisa- are introduced. The polarization of the platelets 22 tion expands the electrostrictive platelets 6 and 23 is again directed in the opposite direction, as the influence of the electric field from. Since it is indicated by the arrows 26 and 27. Zwi-Schwinger made of a continuous steel part see 45 the platelets 22 and 23 is a silver layer, are exerted by the expansion of the platelet 6 29, on which a lead to a terminal 2 'bending forces on the oscillator, which thus the connecting wire 32 is soldered on. The silver layer 28 separating the plates in accordance with the surfaces 20 and 21 which are valid for the elastic line is bent according to laws. If the polar connection wire leading to a terminal 1 'did the interchangeable 50 31 applied to terminals 1 and 3 provided. Reversing from the oscillation node 12 of the steel voltage U , the plate 6 pulls itself together, and another connecting wire 30 leads to one, whereby the oscillator is in the disconnected terminal 3 '.

opposite direction deflects. If you attach an input to terminals Γ and 3 '

supply state is no longer shown in FIG. AC input voltage U _c , then the oscillator performs If the frequency of the AC voltage U at least 55 in the manner already described flexural oscillation at approximately the natural frequency of the gene. On the basis of these flexural vibrations, whoever-vibrator agrees, then the latter carries out the platelets 22 and 23 expansions and stamped flexural vibrations in the cycle of the applied contractions, so that because of the alternating voltage, symmetrically to the piezoelectric effect between the silver layer one through the Vibration nodes 11 and 12 fixed 60 29 and the steel part 5 an alternating voltage level. whose frequency corresponds to the frequency of the excite-The electrostrictive plate 6 as well as that from the voltage and the plate 10 existing on the Klem quartz glass can be fixed in the transducer by men 2 'and 3' as output alternating voltage U _{a ab-soldering.} For this it can be taken.

however, the quartz glass plate 65 is also required. In the exemplary embodiment of FIG to be provided with metallic coverings. It is also electrostrictively active on both sides of the system possible, the platelets 6 and 10 against each other by shrinking neutral fibers of the oscillator to be fixed in the steel part 5. Arranged at this offset. Practically the same electrical ones

Properties can be achieved when the electrostrictively active systems are exactly opposite one another, or if they are only on one side of the neutral fiber at a suitable distance from each other are arranged.

The F i g. 5 shows the electrical equivalent circuit diagram for the case that the oscillator is operated with two poles (cf. FIGS. 1 to 3). Between the terminals 1 and 3 there is an impedance behavior that can be represented by a series resonant circuit with the inductance L, the capacitance C and a loss resistance R, to which a capacitance C ₁₁ is connected in parallel.

The electrical equivalent circuit diagram of an oscillator operated as a quadrupole (corresponding to FIG. 4) is shown in FIG. 6 shown. A transverse capacitance C _{pt is} connected downstream of the input terminals Γ and 3 ', in the series branch there is a lossy series resonant circuit with the inductance L', the capacitance C "and the loss resistance R ', and at the output there is a parallel capacitance C _{n 2} in the transverse branch. Between the terminals 2 'and 3' an output alternating _{voltage TJ a} always occurs when the natural frequency of the oscillator at least approximately corresponds to the frequency of the input alternating voltage U _0.

In the F i g. 7 to 9 are shown tuning fork-shaped flexural oscillators, their use primarily is advantageous at relatively low frequencies, since there the greater length of a constant frequency Flexural oscillator may have a disruptive effect.

In the embodiment of FIG. 7 lie between the fork prongs of a tuning fork-shaped one Flexural oscillator 35 has two plates 36 and 37 made of an electrostrictive ceramic, the polarization of which in the direction of arrows 39 and 40 is directed in the opposite direction. One of the plates 36 and 37 separating them Silver layer 38 leads a connecting wire 41 to a terminal 1. Another connecting wire 44 is direct attached to the steel part of the tuning fork and leads to a clamp 3. There is a point in the tuning fork base is in which practically no movements occur, a retaining wire 42 is expediently attached there, which is used to anchor the tuning fork in a housing not shown in detail. When putting on an alternating voltage to the terminals 1 and 3, the electrostrictively active platelets 36 and 37 subjected to expansions and contractions because of the firm connection of these Plate with the tuning fork prongs are transferred to the tuning fork. The tuning fork will always stimulated to vibrations when their natural frequency matches the frequency of the terminals 1 and 3 applied alternating voltage at least approximately match.

The one shown in FIG. The tuning fork resonator shown in FIG. 8 is essentially the same as that shown in FIG. 7th shown match. However, the electrostrictively active system is in one in the connector of the two fork prongs provided slot 43. Due to the structure, the in the F i g. 7 and 8 shown tuning fork resonators are only operated with two poles, so that their behavior can be traced back to the electrical equivalent circuit diagram of FIG.

The behavior of a four-pole can be compared with the one shown in FIG. 9 achieve tuning fork resonator shown. Here, a slot 5 is provided in the connecting piece of the two fork prongs of a tuning fork 45, in which the excitation systems are introduced. The excitation systems consist of two electrostrictive active platelets 46 and 47, between which a spacer 53 made of an electrically non-conductive material (e.g. quartz glass) and its polarization, for example in the direction of the arrows 48 and 49 is selected. From the to the plate

ίο 46 applied silver layer 50 leads a connecting wire 54 leads to a clamp 1 'from the silver layer 51 applied to the plate 47 a connecting wire 55 to a connecting terminal 2 '. Another lead 56 is directly connected to the Steel part connected and leads to a connector 3 '. The tuning fork 45 is at rest in turn a retaining wire 42 is attached.

If an input AC voltage U _c is applied to terminals 1 'and 3', its frequency is approximately equal to

so the natural frequency of the tuning fork coincides, then these flexural vibrations lead to the beat of the applied AC voltage. Due to these vibrations, the electrostrictive plate 47 becomes stretched and contracted, so that between the silver layer 51 and the steel part 45 an alternating voltage occurs, which are taken as output alternating voltage at terminals 2 'and 3' can. This can be used in FIG. 9 tuning fork resonator shown on the equivalent circuit of the F i g. 6 lead back. Practically the same electrical conditions are achieved when the electrostrictively active systems and the spacer 53 between the two fork prongs (similar to F i g. 7) are arranged.

In the embodiment of FIG. 10 a slot 7 is provided in a continuous steel part 5, in which four electrostrictive plates 60, 61, 62 and 63 are placed one behind the other are. The electrostrictive platelets are separated from one another by layers of silver 65, 66 and 67. A connecting wire 68 leads from the silver layer 65 to a terminal 1 ', from which the silver layer 67 leads a connecting wire 69 to a connecting terminal 2 ', and from the silver layer 66 a connecting wire leads 70 to a terminal 3 ', which also has a further connecting wire 71 with the steel part 5 in electrically conductive connection. As a rule, the connecting wire 71 is in one of the vibration nodes 11 or 12 soldered to the steel part. Because of the conductive connection via wires 70 and 71 the silver layer 66 is at the same electrical potential as the oscillator 5. The polarization the electrostrictive platelet is chosen so that two adjacent platelets are opposite are polarized, as indicated, for example, by arrows 73 to 76.

An AC input voltage applied to terminals 1 'and 3' generates an output alternating voltage between terminals 2 'and 3' in the manner already described whenever the frequency of the AC input voltage with the natural frequency of the flexural vibrator at least approximately matches. An oscillator constructed according to FIG. 10 has the advantage, among other things, of that only one slot has to be provided in the steel rod, which increases the mechanical strength of the transducer elevated. Its electrical equivalent circuit diagram corresponds to the circuit shown in FIG.

In a further development of the one shown in FIG The oscillator can, for example, be a further pair of platelets separated by a metallic intermediate layer be mounted in the slot 7, the electromechanical coupling factor of that of the other platelets deviates. Such an arrangement then enables the acceptance in a simple manner an additional signal voltage that can be used to control other devices.

In Fig. 11 a flexural oscillator is shown, whose vibration excitation takes place via the so-called transverse piezoelectric effect. in the Steel partS a slot 7 is provided into which an electrostrictively active plate 80 is soldered. On the electrostrictive plate 80 are excitation electrodes 81 and 82 in the form of silver layers applied, which via lead wires 83 and 84 with the terminals 1 and 3 in connection stand. The polarization of the electrostrictive plate 80 is indicated by the arrow 84. At ao Applying an alternating voltage to the terminals 1 and 3, the plate 80 is stretched and contracted. Because of the transversal effect, this movement has elongations and shortenings of the electrostrictive ceramic 80, which in the direction of movement of the mechanical expansion of the Oscillator 5 lie and thus stimulate this to flexural vibrations. The one selected in FIG Representation corresponds to a two-pole oscillator and can be increased by another system of the same type an oscillator working as an electric quadrupole. This excitation system can also be used analogously in the case of those shown in FIGS Use tuning fork-shaped transducers and is preferred when only narrow ones Filter bandwidths are required.

Claims (1)

Patent claims: 1. Mechanical flexural oscillator, which is formed by platelets made of electrostrictive material Converter for the transition from electrical vibrations to mechanical flexural vibrations and vice versa and preferably designed as a converter of a multi-part electromechanical Filter is provided, and in the case of the plate made of electrostrictive material predominantly within the area bounded by two neighboring vibration nodes in the course of the Flexural vibrators are arranged, characterized in that in the flexural vibrator (5) a slot (7) is provided which extends from the outer limit to approximately in the area of the with regard to bending vibrations occurring neutral fiber (13) that extends into this slot (7) at least one with excitation electrodes (8, 9) provided plate (6) electrostrictive material is introduced, which is known per se Way with a pre-polarization running perpendicular to the excitation electrodes (8, 9) (18) is provided, and that at least between one of the excitation electrodes (9) and the Flexural oscillator (5) has an electrically insulating intermediate layer (10). 2. Mechanical flexural oscillator according to spoke 1, characterized in that two opposite polarized platelets (20, 21) separated by an electrically conductive layer (28) electrostrictive material introduced into the slot (7) arranged in the flexural oscillator (5) are. 3. Mechanical flexural oscillator according to claim 1 or 2, characterized in that im Flexural oscillator (5) has two slots located only on one side of the neutral fiber (13) are, in the provided with excitation electrodes plates made of electrostrictive material are introduced. 4. Mechanical flexural oscillator according to claim 1 or 2, characterized in that in the flexural oscillator (5) on both sides of the neutral fiber (13) lying slots (7, 7 ') are arranged, in the plate provided with excitation electrodes (22, 23, 24, 25) made of electrostrictive material are introduced. 5. Mechanical flexural oscillator according to one of the preceding claims, characterized in that that the flexural oscillator has the shape of a tuning fork resonator (35) and that the with Plates (36, 37) of electrostrictive material provided with excitation electrodes between the two forks are arranged (Fig. 7). 6. Mechanical flexural oscillator according to one of the preceding claims, characterized in that that the flexural oscillator has the shape of a tuning fork resonator (35) and that the with Plates (36, 37) made of electrostrictive material and provided with excitation electrodes in an im Connecting piece of the two fork prongs lying slot (43) are introduced. 7. Mechanical flexural oscillator according to claim 5 or 6, characterized in that between the electrostrictive plates (46, 47) a spacer (53) made of an electrically insulating material, preferably quartz glass, is arranged (Fig. 9). 8. Mechanical flexural oscillator according to one of the preceding claims, characterized in that that in the slot (7) provided in the flexural oscillator with excitation electrodes (81, 82) provided plate (80) made of electrostrictive material is introduced, the Vibration excitation takes place perpendicular to the desired mechanical expansion. 9. Mechanical flexural oscillator according to one of the preceding claims, characterized in that that the platelets (60, 61, 62, 63) made of electrostrictive material several times by electrical conductive intermediate layers (65, 66, 67) are divided (Fig. 10). 10. Mechanical flexural oscillator according to one of the preceding claims, characterized in that that the plate provided with excitation electrodes (ζ. Β. 24, 25) from electrostrictive Material are introduced into the slot (7) arranged in the flexural oscillator (5) in such a way that they are under a mechanical preload of a given size. Considered publications:
Austrian Patent No. 224163;
U.S. Patent No. 1781,513. 1 sheet of drawings 809 628/1374 10.68 © Bundesdruckerei Berlin