EP3408036A1

EP3408036A1 - Method for exciting piezoelectric transducers and sound-producing arrangement

Info

Publication number: EP3408036A1
Application number: EP17700513.9A
Authority: EP
Inventors: Ralf Broszeit
Original assignee: Weber Ultrasonics GmbH
Current assignee: Weber Ultrasonics GmbH
Priority date: 2016-01-29
Filing date: 2017-01-12
Publication date: 2018-12-05
Also published as: US11065644B2; WO2017129415A1; CN108602093A; JP6935408B2; JP2019511954A; DE102016101660A1; US20190030568A1; CN108602093B

Abstract

Proposed is a method for exciting sound-wave producing transducers (7) which have operating frequencies defining a transducer frequency range, in which a generator (9) produces an electrical drive signal for the transducers (7), said electrical drive signal being fed to the transducers (7), wherein the generator (9) carries out frequency sweeps in a frequency sweep range between a minimum frequency (f_min) and a maximum frequency (f_max) with an adjustable sweep rate, with a target frequency (f_Ziel) being defined within said frequency sweep range, said method being characterized in that the minimum frequency (f_min), the maximum frequency (f_max) and the target frequency (f_Ziel) are selected in such a way that a first frequency difference (Δf₁) between the minimum frequency (fmin) and the target frequency (f_Ziel) differs in terms of magnitude from a second frequency difference (Δf₂) between the maximum frequency (f_max) and the target frequency (f_Ziel) within a number of frequency sweeps, and wherein the minimum frequency (f_min) and/or the maximum frequency (f_max) and/or the target frequency (f_Ziel) is/are modified after at least one frequency sweep in such a way that an arithmetic mean of the first frequency differences (Δf₁), formed over all frequency sweeps carried out, and an arithmetic mean of the second frequency differences (Δf₂), formed over all frequency sweeps carried out, are substantially the same in terms of magnitude.

Description

Method for excitation of piezoelectric transducers and

Sound generating arrangement

description

The invention relates to a method for excitation of ultrasonic transducers according to the preamble of claim 1. Such a method comprises excitation of at least one ultrasonic transducer, which is designed to generate sound waves and has operating frequencies which define a transducer frequency range. The method further uses a generator having an electrical connection to the ultrasonic transducer. The generator is designed to generate an electrical drive signal with a variable excitation frequency.

It is known to use piezoelectric crystals as ultrasonic transducers, in the present case also short: transducers. The crystals can be vibrated by an electrical signal and thereby emit sound waves in the ultrasound range. These emitted sound waves can be used, for example, to rid components of impurities. Preferably, the transducers are operated at a respective design-related resonant frequency. Frequently, several piezoelectric transducers are used whose resonant frequencies are more or less strong

differ from each other. On the one hand, attempts are made to achieve a greater frequency bandwidth of the transducers in order to be able to remove impurities of different sizes as well - the size of the dissolved impurities is in relation to the resonant frequency of the transducers. On the other hand, the superimposition of the vibrations of transducers with different resonant frequency makes the emitted sound wave field more homogeneous overall, which can have a positive effect on the quality of the cleaning.

It is already known, the excitation frequency for the operation of

piezoelectric transducer is not statically pretend, but the To vary the excitation frequency in time. This is called a sweep modulation. Previously known applications use sweep modulations with a frequency response that is within a fixed range

Pass area repeated. Frequency gradients are known in which the excitation frequency changes linearly with time. The signal of the excitation frequency may take the form of a sawtooth or the shape of a triangle.

EP 1 997159 B1 discloses a megasonic processing apparatus and method which uses megasonic processing apparatus of piezoelectric transducers operated at fundamental resonant frequencies of at least 300 kHz. In the method described, the excitation frequency for operating the piezoelectric transducers is varied within a range which covers all the fundamental resonance frequencies of the piezoelectric transducers used

includes piezoelectric transducer. This area of the sweep modulation goes over a frequency range ("converter range"), which of the

Basic resonant frequencies of the piezoelectric transducer is defined, up and down also. It is essential that the transducer range is symmetrically up or down during the sweep modulation of the excitation frequency above and below. This is to ensure that all basic resonance frequencies are excited by the drive signal.

In particular, this should take into account the fact that the resonance frequencies of the piezoelectric transducers can change due to temperature or age influences.

Similar devices and methods are also known from the documents US 2005/0003737 A1, US 2005/0098194 A1 and US 7,004,016 B1. In these documents, a sweep modulation is described in each case, which exceeds or falls below the range of the converter frequencies. The overshoot and undershoot of the transducer region is in each case configured symmetrically.

A problem with the known from the prior art method of sweep modulation is that the sweep modulation is a relatively large

Frequency deviation to the symmetrical excess or

Below the converter range to realize. Such a big one Frequency deviation is, however, with increasing losses in the power section of the

Generator, which provides the neces sary drive signals connected.

This creates a large heat loss in the generator, which can limit the maximum achievable amount of the frequency deviation in the sweep modulation. In addition, the frequency increases as the frequency increases

mechanical load on the sound transducers (ultrasonic transducers,

U ltraschallelemente, U ltraschallwand ler or Ähn liches). In addition, the problem arises in narrow band or high quality systems that the

Frequency sweep of the sweep modulation may not be too large, otherwise it could also be n o desired resonance frequencies or modes of vibration excited. In the worst case scenario, this could be the complete system

damaged or destroyed.

The invention has for its object to provide an improved method for r on the action of U ltraschallwandlern, which effectively utilizes the advantages of sweep modulation and at the same time avoids the previously beschriebenen problems.

This object is achieved by a method having the features of claim 1 and you rch a sound generating device having the features of claim 1 1. Advantageous developments emerge from the dependent claims.

On the part of the Applicant, it has been recognized that the method according to the invention is particularly advantageous for the excitation of the transducers when a number of pulses are applied to a frequency divider (sweep modulation)

Frequency difference between a minimum frequency at which the

Frequency sweep begins, and a target frequency differs in magnitude from a second frequency difference between a maximum frequency at which the frequency sweep ends and the target frequency. The target frequency is generally defined as a frequency that lies in the amount between the minimum and maximum frequencies. The minimum frequency and / or the maximum frequency and / or the target frequency will decrease

modified at least one frequency sweep so that an arith metic mean of the first differences, which over all carried out

Frequency sweeps is formed, and an arith metic mean of the second Differences, which is also formed over all frequency sweeps performed, are substantially equal in magnitude.

A frequency sweep of the excitation frequency is carried out between the minimum frequency and the maximum frequency, wherein the excitation frequency in the course of the frequency sweep substantially all values between the minimum frequency and the maximum frequency at least once. It is therefore within the meaning of the invention if the excitation frequency at the beginning of the frequency sweep equal in magnitude to the minimum frequency and at the end of the frequency sweep is equal in magnitude equal to the maximum frequency. Likewise, the reverse case is possible. It is also within the scope of the invention if the excitation frequency in the course of a frequency sweep several times equal to the minimum frequency and / or the maximum frequency.

To generate sound waves in the sense of the method according to the invention, a single transducer, preferably a piezoelectric transducer, can be used. This can have production-related irregularities of the layer thickness, so that the respective resonant frequency of transducers of the same type can be slightly different from each other. In addition, different regions of a single transducer may be exposed to different temperature effects, which may split its resonant frequency into slightly different partial resonant frequencies. Thus, a single transducer can also define a transducer frequency range or transducer in the sense mentioned above.

The frequency sweep of the sweep modulation is defined as the difference between the maximum frequency and the minimum frequency. The variation of the minimum frequency, the maximum frequency and / or the target frequency associated with the invention with a certain number of frequency sweeps from a total number of frequency sweeps brings with it the advantage that the frequency sweep is made smaller at substantially all frequency sweeps than it is at Prior art is described. This can minimize temperature losses in the power generating generator and at the same time reduce the probability of failure of the converter. Preferably, after completion of at least one frequency sweep, the minimum frequency and / or the maximum frequency are changed. This makes it possible to achieve a variation of the frequency sweep around the target frequency. A change in the minimum or maximum frequency is easy to implement in terms of control technology and does not require any increase

Circuit complexity.

According to a preferred embodiment of the method according to the invention, the minimum frequency, the maximum frequency and the target frequency are selected such that in a first frequency sweep the first frequency difference has a first magnitude (A) and the second frequency difference has a second magnitude (B). In a subsequent frequency sweep, at least the target frequency and preferably also the minimum frequency and the maximum frequency are modified such that the first frequency difference has the second magnitude (B) and the second frequency difference has the first magnitude (A), preferably the first magnitude and the second amount are different (A + B). Such an alternately symmetrically configured choice of

Frequency differences around the target frequency are considered by the applicant to be particularly advantageous. The excitation frequency can be increased again from the minimum frequency to the maximum frequency after each frequency sweep, so that the time course of the

Excitation frequency is sawtooth. A sequence of frequency differences over several frequency sweeps could thus have, for example, the amounts (AB-BA-AB-BA-AB-BA). A "running direction" of the change in the excitation frequency can also change after each frequency sweep, for example, after the maximum frequency has been reached, the excitation frequency can be reduced again, so that the time profile of the excitation frequency is triangular.And it is also within the scope of the invention, a combination of these two It is essential that the frequency differences during the respective frequency sweeps can have the abovementioned combinations of amounts.

Particularly preferably, after the completion of at least one frequency sweep, the target frequency is changed. This form of variation of the sweep modulation is particularly advantageous when the desired target frequency is not known exactly, but in the course of the process or in the During the frequency sweeps must first be determined. In this way, a desired operating point of the at least one ultrasonic transducer can be set flexibly and depending on the type of a specific requirement. According to an alternative embodiment, in the course of at least one frequency sweep, preferably all frequency sweeps, the excitation frequency of the drive signal is varied so that the drive signal the minimum frequency at a first time (t-ι), the target frequency at a second time (t ₂ ) and the maximum frequency at a third time (t ₃ ), wherein the second time is between the first and the third time, and wherein a first time difference between the first

Time and the second time and a second time difference between the second time and the third time are equal in magnitude. In other words, this means that during a frequency sweep, the target frequency can be reached substantially after exactly half of the entire duration of the frequency sweep. Conversely, this also means that the time profile of the drive signal f (t) has different slopes between the first time and the second time and between the second time and the third time if the target frequency is not exactly centered between the minimum frequency and the maximum frequency is. It is part of the

Although the process of the invention is not necessary that the first

Time difference and the second time difference are equal in magnitude. However, the magnitude equality can be particularly advantageous when a repetition rate of the sweep modulation is generated or triggered by a harmonic carrier signal, for example by a

sinusoidal carrier signal. In this case, the first time, the second time and the third time advantageously fall on characteristic points of the harmonic carrier signal, for example at turning points or extreme points.

The frequency change of the drive signal in the range of the second time point can be fluent (mathematically speaking: differentiable), but it can also be configured in the form of a mathematical discontinuity. Basically, the excitation frequency in the course of a frequency sweep can have almost any desired time course.

A particularly advantageous embodiment of the method according to the invention is present when the first and the second time difference are equal in magnitude. However, the method according to the invention is by no means limited thereto, but with a suitable choice of the minimum frequency, the maximum frequency and the target frequency, the first and second time difference may also be different in magnitude.

Preferably, the frequency sweep is selected such that in the course of at least one frequency sweep, preferably all frequency sweeps, a first derivative of the excitation frequency (or frequency change rate of the excitation frequency) after the time between the first time and the second time a constant first derivative amount and between the second time and the third time a constant second

Derivative amount. In circuit terms, this is easier to implement than a derivative or temporal change of the excitation frequency, which has a non-constant amount.

According to a preferred embodiment, the frequency sweep is selected such that in the course of at least one frequency sweep, preferably all frequency sweeps, the first derivative amount and the second derivative magnitude differ from one another.

If the time course of the drive signal f (t) between the first

Time and the second time as well as between the second time and the third time from each other has different slopes, may result in a graphic representation in an f (t) diagram with otherwise linear dependence of the frequency of the time a kink. The associated bending angle can be smaller or larger than 180 °.

Particularly preferably, at least one transducer, preferably a plurality of transducers, most preferably all transducers, are excited during a plurality, preferably all, frequency sweeps at a respective resonant frequency. This can increase the efficiency of the excitation. Particularly preferred is at least one transducer, preferably several transformers, most preferably all transducers, while meh rerer, preferably all, Frequenzdu rch runs at a respective resonant frequency of the same order, preferably at a respective fundamental resonant frequency, excited. In this form of the method, it is advantageous that the operating parameters of the transducers are comparable in the case of an excitation of all transducers having a resonant frequency of the same order, so that the homogeneity of the emitted acoustic wave field is increased. If converter at

Resonant frequencies of different order would be excited, resonance patterns with different spectral width could result, so that the superposition of the sound waves emitted by the individual transducers could possibly lead to inhomogeneities of the sound field. In a preferred embodiment of the invention, the target frequency is substantially selected according to a resonant frequency, preferably a fundamental frequency, of at least one transducer, and / or corresponding to a frequency in the transducer frequency range, preferably corresponding to a frequency that is at least some of arithmetic mean, preferably all, resonance frequencies in the converter frequency range is formed. Such a choice of the target frequency has the advantage that as far as possible all resonant frequencies or all resonance frequencies of an order are covered in the course of a frequency difference or over a large number of frequency sweeps. This again increases the efficiency of the excitation of the converters.

Further preferred features and embodiments of the invention will become apparent from the following description of embodiments with reference to the drawing.

FIG. 1 shows a sound generation arrangement according to the invention in FIG

schematic representation;

FIG. 2 shows a sweep modulation according to the prior art using an impedance-frequency diagram; FIG. 3 shows the sweep modulation from FIG. 1 on the basis of a corresponding frequency-time diagram;

FIG. 4 shows a sweep modulation according to the invention with reference to FIG

Impedance-frequency diagram;

FIG. 5 shows the frequency-time diagram of FIG

sweep modulation according to the invention; FIG. 6 shows a further aspect of the inventive sweep modulation according to FIG. 4 and FIG. 4 on the basis of an impedance-frequency diagram;

FIG. 7 shows the frequency-time diagram associated with FIG. 6; FIG. 8 shows a flow chart of a sweep modulation according to the invention;

FIG. 9 shows a sweep modulation according to the invention in an alternative embodiment on the basis of an impedance-frequency diagram; FIG. 10 shows a further aspect of the sweep modulation from FIG. 9 on the basis of an impedance-frequency diagram; and

FIG. 11 shows a further sweep modulation according to the invention in a frequency-time diagram.

FIG. 1 shows a sound generation arrangement according to the invention with reference to an application example in which the method according to the invention can be used, but without being limited to this application. In a tub 4, which is filled with water or other suitable cleaning medium 5, there are parts to be cleaned 6, which have dirt. At least one ultrasonic transducer 7 (solid line) is coupled to the trough 4 and the water (cleaning medium) 5 therein, which is designed to generate and deliver ultrasonic waves to the medium 5. These ultrasonic waves cause in a conventional manner, the cleaning of the parts 6 of the contaminants. It is within the scope of the invention, not to provide only one ultrasonic transducer 7, but a plurality of ultrasonic transducers (indicated by dashed lines in Figure 1).

The ultrasonic transducer 7 is in electrical and signaling technology

Active connection (via a line 8) with a (frequency) generator 9. The generator 9 has a signal unit 10, which is designed to generate a high-frequency excitation signal with a variable excitation frequency 1. The excitation signal is from the signal unit 10 and the

Generator 9 via the electrical operative connection 8, for example a

Signal line, transmitted to the ultrasonic transducer 7. The ultrasonic transducer 7 is thereby stimulated to generate (ultra-) sound waves, the

be coupled into the medium 5 according to the cleaning of the parts 6.

FIG. 2 schematically shows a method for modulating the excitation frequency 1 of the ultrasonic transducer 7 according to the prior art. FIG. 2 shows an impedance curve 3 of the ultrasound transducer 7, as the ultrasound transducer 7 usually has in the present context. The excitation frequency 1 generated by the generator 9 is varied between a minimum frequency f _min and a maximum frequency f _max .

Between the minimum frequency f _min and the maximum frequency f _max is a target frequency f _zie i. In the present example of FIG. 2, the impedance curve 3 has a local maximum 2 in the region of the target frequency f _zie . In this connection, one also speaks of a resonance frequency of the ultrasonic transducer 7 at the location of the local maximum 2. The excitation of the ultrasonic transducer 7 in the vicinity of its resonance frequency (s) increases the oscillation amplitude for a given excitation power and thus the effective efficiency of the sound conversion. It is known to excite ultrasonic transducers 7 in the region of their resonance frequency (s) in order to achieve the highest possible efficiency.

A first frequency difference Af-ι between the minimum frequency f _min and the target frequency f _zie i is equal in magnitude to a second in FIG

Frequency difference Af ₂ between the maximum frequency f _max and the

Target frequency f _zie i. In the prior art it is assumed that such a symmetrical, equal in terms of the same design of the minimum Frequency f _min and the maximum frequency f _max around the target frequency f _zie i leads to particularly good results.

FIG. 3 shows a time dependence of the excitation frequency 1 in a frequency-time diagram. This is taken from the prior art analogously to FIG. It can be seen that the first frequency difference Af-ι and the second frequency difference Af _2, as in Figure 2, are equal in magnitude.

A time t _zie i is defined as the time at which the excitation frequency 1 corresponds in magnitude to the frequency f _zie i. A time t _min is defined as the time at which the excitation frequency 1 corresponds in magnitude to the frequency f _min . A time t _max is defined as the time at which the excitation frequency 1 corresponds in magnitude to the frequency f _max . A first time difference At-ι is calculated from the difference between the time t _zei and the time t _min . A second time difference At _{2 is} calculated from the difference between the time t _max and the time t _Zie i - In Figure 3, the first time difference At-ι amount equal to the second time difference At ₂ .

A frequency sweep starts at time t _min and ends at

Time t _max , or vice versa. In FIG. 3, the excitation frequency 1 therefore has the form of a straight line during a frequency sweep.

From the prior art, various methods are known to perform this type of frequency modulation. If the excitation frequency 1 is reset to the minimum frequency f _min after the end of a frequency sweep, then this is called a sawtooth modulation. If the excitation frequency 1 after the end of a frequency sweep is not back to the minimum

Frequency f _min set, but starting from the maximum frequency f _max linearly reduced, it is called a triangular modulation. The

symmetrical embodiment of the modulation of the excitation frequency 1 around the target frequency around in the prior art method that a first derivative of the excitation frequency 1 during a frequency sweep is constant in magnitude. The minimum frequency f _min , the maximum frequency f _max and the target frequency f _ziei are regularly not changed according to the prior art after completion of a frequency sweep. This results in particular the aforementioned disadvantages regarding the Generator 9, which generator 9 generates the excitation frequency 1 and provides the excitation signal. These disadvantages include increased heat loss, which is generated in the generator 9 and in one

proportional relationship to the used frequency sweep of the sweep modulation is: A larger frequency deviation requires a larger

Waste heat.

FIG. 4 shows a method according to the invention for modulating the

Excitation frequency 1 for operation of the ultrasonic transducer 7 shown. The target frequency f _zie i is, as explained _above with reference to Figure 2, in the present embodiment in the range of a local maximum 2 of the impedance curve 3 of the ultrasonic transducer 7. The minimum frequency f _min is smaller in magnitude than the target frequency f _zie i, the maximum frequency In terms of amount, f _max is greater than the target frequency f _zie i. The maximum frequency f _max and the minimum frequency f _min are chosen such that the first

Frequency difference Af-ι amount is smaller than the second frequency difference Af ₂ . The target frequency f _zie i is therefore not centered between f _min and f _max .

The frequency-time diagram belonging to FIG. 4 is shown in FIG. The first time difference At-ι between the time t _zie i and the time t _min and the second time difference At ₂ between the time t _max and the time t _zie i are equal in magnitude. This requires that a first time derivative of the excitation frequency 1 in the range between t _min and t _zie i, at least in

arithmetic mean, is less than a first time derivative of

Excitation frequency 1 in the range between t _zie i and t _max . According to FIG. 4, the change in the excitation frequency 1 with time in the range from the time t _min to the time t _zie i as well as in the range from the time t _zie i to the time t _max always has the form of a straight line. In the present case, the slope of this straight line in the region between t _ze i and t _{max is} greater in magnitude than in the region between t _min and t _ze . In other words, this means that the ultrasonic transducer 7 is excited in the first region between t _min and t _zie i in the same time over a smaller frequency spectrum than in the range between t _zie i and t _max . One can also of a lesser

Frequency change rate in the first range between t _min and t _{ze ze} i speak in comparison to the second range between t _zie i and t _max . Since the time profile of the drive signal (excitation frequency f (t)) has different slopes between the first time t _min and the second time t _zie i and between the second time t _zie i and the third time t _max , the result is correspondingly graphic Representation in the f (t) diagram a kink. According to the embodiment in FIG. 5, the associated bending angle is less than 180 °.

FIG. 6 shows the same impedance curve 3 of the ultrasound transducer 7 in the impedance frequency diagram as FIG. 4. The target frequency _f.sub.zi is once again in the range of the local maximum 2 of the impedance curve 3 of the ultrasound transducer 7. It can be seen that in FIG. 6, contrary to FIG , the first frequency difference Af-i is greater in magnitude than the second frequency difference Af ₂ . This can be taken from the frequency-time diagram in FIG. Again, the two time differences At-ι and At ₂ are the same in terms of amount. The change of

Excitation frequency 1 over time again has the form of a straight line in the first range from t _min to tziei and in the second range from t _zie i to t _max . However, in contrast to FIG. 5, the first time derivative of the excitation frequency 1 in the first region between t _min and t _zie i is greater in magnitude than in the second region between t _zie i and t _max . In other words, in FIG. 7, the slope of the straight line is in the range between t _zei and t _max

smaller in absolute terms than in the range between t _min and t _zie i.

Since the time profile of the drive signal (excitation frequency f (t)) has different slopes between the first time t _min and the second time t _zie i and between the second time t _zie i and the third time t _max , the result is correspondingly graphic Representation in the f (t) diagram again a kink. According to the embodiment in FIG. 7, the associated bending angle is greater than 180 °. The relationship between the minimum frequency f _min , the maximum frequency f _max and the target frequency f _zie i and the impedance _curve 3 of the ultrasonic transducer shown in Figures 4 and 5 is used on average in about half of all frequency _sweeps . In about half of the other

Frequency sweeps, a combination of the corresponding parameters according to Figure 6 and Figure 7 is used. FIG. 8 shows an exemplary chronological sequence of individual steps of the method according to the invention. First, the minimum frequency f _min , the target frequency f _Zie i and the maximum frequency f _max are selected so that the amount of the first frequency difference Af-i = A and the amount of the second frequency difference Af ₂ = B. In a first frequency sweep, a drive signal with an excitation frequency 1 is equal to the minimum

Frequency f _min generated by the signal unit 10 of the generator 9 and transmitted to the ultrasonic transducer 7 (or the ultrasonic transducer). In the course of the first frequency sweep, the excitation frequency 1 is increased up to the maximum frequency f _max . After the end of a first frequency _sweep , the minimum frequency f _min , the target frequency f _Zie i and / or the maximum frequency f _max are varied so that the amount of the first frequency difference Af-ι now B and the amount of the second frequency difference Af _{2 is} now A. , The excitation frequency 1 is now reduced from the maximum frequency f _max to the minimum frequency f _min . This results in a triangular course of the drive signal or the excitation frequency 1 of the drive signal. As explained above, for example, the profile can also be sawtooth-shaped if the excitation frequency is increased again from the minimum frequency f _min after the end of the first frequency sweep.

It is obvious that also the maximum frequency f _max , or any other frequency within the frequency swept range, can serve as a starting point for the modulation of the excitation frequency 1. After the end of the second frequency sweep, the amounts of the two frequency differences are again selected as Af-i = A and Af ₂ = B. After the end of the third frequency sweep again accordingly Af-i = B and Af ₂ = A, etc.

In an arithmetic mean over all frequency sweeps, the first frequency difference Af-ι and the second frequency difference Af _{2 are} therefore magnitude

Λ + B

equal and each have the amount - ^ - on. In the frequency-time diagram, this means that the first time derivative of the excitation frequency 1 in the first range between t _min and t _zie i is approximately the same in magnitude as in the second range between t _zie i and t _max . The change of the excitation frequency 1 can not only have the form of a straight line in the frequency-time diagram, but also assume other types or courses. For example, the excitation frequency 1 can be changed quadratically with time, f = f (t ² ).

FIGS. 9 and 10 each show a further method according to the invention for modulating the excitation frequency 1 in an impedance-frequency diagram. In contrast to _FIGS. 2, 4 and 6, the target frequency f _Zie i is not approximately equal to the local maximum 2 of the impedance _{curve 3 of FIG}

Instead, the target frequency f _Zie i and correspondingly the minimum frequency f _min and the maximum frequency f _max can be anywhere on the impedance curve 3.

FIG. 11 shows a time profile of the change of the excitation frequency 1 for the case that the first time difference At-1 and the second time difference At ₂ are different in magnitude from each other. At a certain

Ratio between the first time difference At-ι and the second time difference At ₂ , it is also possible that the time course of the change of

Excitation frequency 1 within a frequency sweep has the shape of a straight line without kink, although the first frequency difference Af-i and the second frequency difference Af ₂ amount differ from each other.

Claims

claims

1. A method for the excitation of one or more, preferably

piezoelectric transducers (7), which transducers (7) are designed to generate sound waves and have operating frequencies which define a transducer frequency range,

in which a generator (9) having an electrical connection (8) to the transducers (7) and a frequency sweeping function for generating an electrical excitation signal with a variable excitation frequency (1), an electrical excitation signal for the

Transducer (7) generates which excitation signal is supplied to the transducers (7),

wherein the adjustable pass rate generator (9) performs a total number of frequency sweeps in a frequency swept range between a minimum frequency (f _min ) and a maximum frequency (f _m ax),

within which frequency swept range a target frequency (f ziei) is defined, characterized in that the minimum frequency (f _min ), the maximum frequency (f _max ) and the target frequency (f ziei) are chosen such that a first

Frequency difference (Af-i) between the minimum frequency (f _min ) and the target frequency (f ziei) at a first number of frequency sweeps from the total number of frequency sweeps, preferably at

Substantially all frequency sweeps, magnitude differs from a second frequency difference (Af ₂ ) between the maximum frequency (f _max ) and the target frequency (f ziei), and wherein the minimum frequency (f _min ) and / or the maximum frequency (f _max ) and / or the target frequency (f ziei) is changed after at least one frequency sweep so or that one over all performed

Frequency sweeps formed arithmetic mean of the first frequency differences (Af-ι) and on all performed Frequency sweeps formed arithmetic mean of the second frequency differences (Af ₂ ) in terms of amount are substantially equal.

2. The method of claim 1, wherein after completion of at least one of the minimum frequency (f _min ) and / or the maximum frequency (f _max ) is changed.

3. The method of claim 1 or 2, wherein the minimum frequency

(f _min ), the maximum frequency (f _max ) and the target frequency (f _Zie i) are chosen so that in a first frequency _sweep , the first frequency difference (Af-ι) has a first amount (A) and the second frequency difference (Af ₂ ) has a second amount (B), and in which in a subsequent frequency sweep at least the target frequency and preferably also the minimum frequency (f _min ) and the maximum frequency (f _max ) is modified so that the first

Frequency difference (Af-ι) has the second amount (B) and the second frequency difference (Af ₂ ) has the first amount (A),

wherein preferably the first amount (A) and the second amount (B) are different.

4. The method according to any one of claims 1 to 3, wherein the target frequency (fziei) is changed after completion of at least one frequency sweep.

5. The method according to any one of the preceding claims, wherein in the course of at least one frequency sweep, preferably all frequency sweeps, the excitation frequency (1) of the drive signal is varied so that the drive signal at a first time (t-ι) the minimum frequency (f _min ), at a second time (t ₂ ) the

Target frequency (f ziei) and at a third time (t ₃ ) has the maximum frequency (f _max ),

wherein the second time (t ₂ ) is between the first time (t-ι) and the third time (t ₃ ),

and wherein a first time difference (At-i) between the first time (ti) and the second time (t ₂ ) and a second time difference (At-i) between the second time (t ₂ ) and the d ritten Zeitpun kt (t ₃ ) are equal in magnitude.

6. The method of claim 5 wherein the frequency response is such

is chosen that in the course of at least one Frequenzdu rch run, preferably all Frequenzdu rch runs, a first derivative of the frequency after the time between the first time (t-ι) and the second time (t ₂ ) a constant first derivative amount and between the second time (t ₂ ) and the d ritten Zeitpun kt (t ₃ ) has a constant second derivative amount.

7. The method of claim 6, wherein said frequency response is selected to be such that at least one of them progresses

Frequency sweep, preferably all Frequenzdu rchläufe, the first derivative amount and the second derivative amount from each other.

8. The method according to any one of the preceding claims, wherein

while meh eral, preferably all, Frequenzdu rchläufe wen least one of the transducers (7), preferably meh er converter (7), most preferably all transducers (7), is excited at a respective resonant frequency.

9. The method according to claim 8, wherein currency rend meh rerer, preferably all, Frequenzdu rch runs at least one of the transducers (7),

Preferably, a plurality of transducers (7), most preferably all transducers (7), at a respective resonance frequency of the same order, preferably at a respective fundamental resonance frequency, is excited.

1 0. The method of claim 8 or 9, wherein the target frequency in

Substantially corresponding to a resonant frequency, preferably a fundamental resonance frequency, at least one transducer (7) is selected, and / or corresponding to a frequency in

Transducer frequency range, preferably according to a frequency, which is formed from an arithmetic averaging of at least some, preferably all, resonance frequencies in the transducer frequency range.

Sound generation arrangement comprising at least one, preferably piezoelectric transducer (7) and a generator (9) having an electrical connection (8) to the transducer (7), which generator (9) generates an electrical excitation signal for the transducer (7) is provided and a frequency sweeping function for generating an electrical excitation signal having a variable excitation frequency (1), which excitation signal for

Supply to the transducer (7) is provided,

which generator (9) is provided and designed to perform a total number of frequency sweeps in a frequency sweep range between a minimum frequency (fmin) and a maximum frequency (f _max ) at an adjustable sweep rate, within which sweep frequency range a target frequency (f ziei) is definable .

wherein the minimum frequency (f _min ), the maximum frequency (f _max ) and the target frequency (f ziei) are selectable such that a first

Frequency difference (Af-ι) between the minimum frequency (f _min ) and the target frequency (f ziei) in a first number of frequency sweeps from the total number of frequency sweeps, preferably at

Substantially all frequency sweeps, magnitude differs from a second frequency difference (Af ₂ ) between the maximum frequency (f _max ) and the target frequency (f ziei), and wherein the minimum frequency (f _min ) and / or the maximum frequency (f _max ) and / or the target frequency (f ziei) is changeable to at least one frequency sweep that an over all performed frequency sweeps formed arithmetic mean of the first frequency differences (f-i) and one performed on all frequency sweeps formed arithmetic mean of the second frequency difference (f ₂₎ in terms of magnitude are essentially the same.