DE102017124348A1 - Method and device for detecting broken piezo material of an ultrasonic transducer of an ultrasonic assembly - Google Patents

Abstract

A refracted piezoelectric material in an ultrasonic transducer of an ultrasonic assembly of an ultrasonic device is detected by measuring a test piezo-coupling constant with a test scan of the ultrasonic assembly. The test piezo-coupling constant is compared with a previously measured baseline piezo-coupling constant. The piezoelectric material is determined to be broken if the test piezo-coupling constant is smaller than the baseline piezo-coupling constant by more than a predetermined value.

Description

area

The present invention relates to ultrasonic devices having an ultrasonic assembly, and more particularly, to detecting broken piezoelectric material of an ultrasonic transducer of the ultrasonic assembly.

background

This section contains background information regarding this disclosure that does not necessarily form the prior art.

Certain ultrasound devices have an ultrasound assembly that is energized by a power supply that is often also used to control the ultrasound device. An ultrasonic assembly includes an ultrasonic transducer and any component ultrasonically coupled to the ultrasonic transducer, typically a booster or amplifier and an ultrasonic sonotrode. Examples of such ultrasonic devices include ultrasonic welding equipment such as those used for welding together metal parts, those used for welding together plastic parts, and those used for sealing the ends of metal or plastic tubes (the latter being substantially the same as those used for welding Welding together metal or plastic parts are used).

1 FIG. 12 shows a model of an ultrasound assembly 102 and a power supply 104 of a conventional ultrasound device 100. It is understood that the ultrasound device 100 can be any type of ultrasound device having an ultrasound assembly that is energized by a power supply. Typical components of ultrasound assemblies 102 include an ultrasound transducer 106, a booster or amplifier 108, and an ultrasound sonotrode 110. Ultrasonic sonotrodes often have one or more ultrasound horn tips 112. Amplifier 108 and ultrasound sonotrode 110 are ultrasonically driven (FIG. directly or through another component) connected to an ultrasonic transducer 106. In the example of 1 For example, the amplifier 108 is attached to the ultrasound transducer 106, which establishes an ultrasound connection between the amplifier 108 and the ultrasound transducer 106, and the ultrasound sonotrode 110 is attached to the amplifier 108, thereby establishing an ultrasound connection between the ultrasound sonotrode 110 and the amplifier 108 generates an ultrasonic connection between the ultrasonic sonotrode 110 and the ultrasonic transducer 106 via the amplifier 108. It is understood that ultrasonic transducers are also known in the art as ultrasonic converters and both terms are used interchangeably. The power supply 104 is controlled by a controller 114, which includes a memory 116. It is understood that the controller 114 may be part of the power supply 104 or independent of the power supply 104. The ultrasonic device 100 will often include an anvil (not shown) upon which a workpiece to be processed is supported and in contact with an ultrasonic sonotrode tip 112 as it is processed. For example, when two metal or plastic parts are welded together, they are supported on the anvil and pressed together by the ultrasonic sonotrode tip during the welding process, which is ultrasonically vibrated against one of the parts to ultrasonically weld the two parts together.

The piezoelectric material of ultrasonic transducers may sometimes break, such as cracking in the piezoelectric material. This leads to an efficiency and gain loss of the ultrasonic transducer which is detrimental to the ultrasonic process. When a crack develops in the piezoelectric material, there is usually no visual way to detect this crack without disassembling the ultrasonic transducer, especially when the ultrasonic transducer has a housing. It is therefore desirable to recognize when the piezoelectric material of the ultrasonic transducer is broken. It is also desirable that a warning signal be provided when piezoelectric material of the ultrasonic transducer is detected as broken.

Summary

This section contains a general summary of the disclosure and does not fully disclose the full scope and all features.

According to an aspect of the present disclosure, a method of detecting broken piezoelectric material in an ultrasonic transducer of an ultrasonic assembly includes An ultrasonic device comparing a test piezo-coupling constant with a baseline piezo-coupling constant and determining that the piezoelectric material is refracted when the test piezo-coupling constant is smaller than the baseline piezo-coupling constant by more than a predetermined value. The test piezo-coupling constant is measured in the air with a test scan performed by a power supply of the ultrasonic device and compared with the baseline piezo-coupling constant previously measured.

In one aspect, the baseline piezo-coupling constant is established by performing a baseline scan of the ultrasound assembly in air with the ultrasound device power supply when it is known that the piezoelectric material of the ultrasound transducer is good, and by baseline piezo-coupling constant is measured with the baseline scan of the ultrasound assembly. In one aspect, the baseline piezo-coupling constant is stored in the memory of a controller as the baseline piezo-coupling constant, while the controller compares the test piezo-coupling constant to the baseline piezo-coupling constant and determines that the piezoelectric material is fractured. if the test piezo-coupling constant is smaller than the baseline piezo-coupling constant by more than a predetermined value. In one aspect, the controller provides a warning signal when piezoelectric material is determined to be broken.

Other areas of applicability will be apparent from the following description. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present invention.

list of figures

• 1 zeigt ein vereinfachtes Diagramm einer typischen Ultraschallvorrichtung aus dem Stand der Technik;
• 2 zeigt im Diagramm einen gemäß dem Stand der Technik üblichen Scan einer Ultraschallbaugruppe der Ultraschallvorrichtung gemäß 1; und
• 3 zeigt ein Flussdiagramm einer Steuerungsroutine gemäß eines Aspekts der vorliegenden Offenbarung zum Erkennen, ob piezoelektrisches Material eines Ultraschallwandlers einer Ultraschallvorrichtung gebrochen ist.

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present invention.

• 1 shows a simplified diagram of a typical ultrasonic device of the prior art;
• 2 shows in the diagram a conventional according to the prior art scan of an ultrasonic assembly of the ultrasonic device according to 1 ; and
• 3 FIG. 12 shows a flowchart of a control routine according to an aspect of the present disclosure for detecting whether piezoelectric material of an ultrasonic transducer of an ultrasonic device is broken.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Detailed description

Exemplary embodiments will be explained in more detail hereunder with reference to the accompanying drawings.

The following discussion refers to the ultrasound device 100 according to 1 However, it should be understood that the following applies to any ultrasonic device having an ultrasonic assembly that is energized by a power supply. In this regard, it is understood that according to an aspect of the present disclosure described below, the method of detecting that the piezoelectric material of the ultrasonic transducer 106 is different from methods used in prior art ultrasonic devices, and the characterization of 1 and 2 As prior art does not mean that the method described below belongs to the prior art.

According to one aspect of the present disclosure, a piezo-coupling coefficient Kz is measured to determine whether the piezoelectric material of the ultrasonic transducer 106 is broken. As is known in the art, the piezo-coupling coefficient describes the effectiveness with which the piezoelectric material of the ultrasonic transducer converts electrical energy into mechanical energy, and vice versa. The piezo-coupling coefficient Kz comes with a scan of the ultrasonic assembly 102 through the energy supply 104 measured as explained in detail below. More specifically, the piezo-coupling coefficient K _Z becomes a test scan of the ultrasonic assembly 102 measured when the ultrasonic transducer 106 must be checked to see if its piezoelectric material is broken. This piezo-coupling coefficient Kz is compared with a piezo-coupling coefficient Kz previously obtained with a baseline scan of the ultrasonic assembly 102 was measured. Here, the piezo-coupling coefficient Kz measured by the test scan is referred to as the test piezo-coupling coefficient K _Zt , and the piezo-coupling coefficient Kz measured by the baseline scan is referred to herein as the base lines Piezo-coupling coefficient K _Zb reference. When the test piezo-coupling coefficient Kzt is smaller than the base-line piezo-coupling coefficient K _Zb by more than a predetermined value, the piezoelectric material of the ultrasonic transducer is determined to be broken.

The piezo-coupling coefficient Kz is determined with certain during the scan of the ultrasonic assembly 102 measured parameters, and is calculated on the basis of these measured parameters. The term used here is a scan of the ultrasound assembly 102 is a frequency sweep of the ultrasonic assembly 102 through the energy supply 104 in which voltage and current flowing to the ultrasonic transducer 106 be passed in each frequency of the frequency sweep, be measured. The frequency steps of the frequency sweep depend on the desired fidelity, with frequency steps of 1 Hz being typical. As in 2 can be seen has a typical scan of the ultrasound module 102 a parallel resonance frequency present at the highest impedance and a series resonance frequency corresponding to the lowest impedance at a frequency below the parallel resonance. The frequency sweep is performed by a frequency range including the parallel resonance frequency and the series resonance frequency, and the range may be for the ultrasonic transducer 106 be determined heuristically or theoretically. A frequency range of +/- 10% of the nominal frequency of the ultrasonic transducer 106 is usually enough.

in der:

• Kz ist der Piezo-Kopplungskoeffizient;
• V_nom ist die Nennspannung der Energieversorgung;
• Gs ist die Verstärkung der Ultraschallbaugruppe;
• x₀ ist die Nominalamplitude des Ultraschallwandlers;
• η ist die Effizienz des Ultraschallwandlers;
• fp ist die Parallelresonanz-Frequenz der Ultraschallbaugruppe;
• f_S ist die Reihenresonanz-Frequenz des Ultraschallbaugruppe;
• Zp ist die Impedanz bei Parallelresonanz (V_P/I_P);
• Z_S ist die Impedanz bei Reihenresonanz (V_S/I_S);
• V_P ist die Spannung der Energieversorgung bei Parallelresonanz (gemessener Parameter);
• I_P ist die Stromstärke der Energieversorgung bei Parallelresonanz (gemessener Parameter);
• Vs ist die Spannung der Energieversorgung bei Reihenresonanz (gemessener Parameter);
• I_S ist die Stromstärke der Energieversorgung bei Reihenresonanz (gemessener Parameter).

The piezo-coupling coefficient Kz is calculated from the information of the scan as follows: $$K_Z=\frac{V_{nOm}}{G_S*x_0}*\sqrt{\frac{\eta }{\pi *f_P*f_S*Z_P*Z_S}}$$

in the:

• Kz is the piezo-coupling coefficient;
• V _nom is the rated voltage of the power supply;
• Gs is the gain of the ultrasound assembly;
• x ₀ is the nominal amplitude of the ultrasonic transducer;
• η is the efficiency of the ultrasonic transducer;
• fp is the parallel resonance frequency of the ultrasonic assembly;
• f _S is the series resonance frequency of the ultrasonic assembly;
• Zp is the parallel resonance impedance (V _P / I _P );
• Z _S is the impedance in series resonance (V _S / I _S );
• V _P is the voltage of the parallel resonance power supply (measured parameter);
• I _P is the current intensity of the parallel resonance power supply (measured parameter);
• Vs is the voltage of the power supply with series resonance (measured parameter);
• I _S is the current intensity of the power supply with series resonance (measured parameter).

in der:

• tan δ = der Piezo-Verlust-Koeffizient ist.

The efficiency of the ultrasonic transducer is calculated from the frequency scan as follows: $$\eta =\left(1-\frac{2}{\pi }*cOt\left(\frac{\pi *\left(f_P-f_S\right)}{2*f_P}\right)*tan\delta \right)*\left(1-\frac{f_P^2-f_S^2}{2\pi *f_P*f_S}*\sqrt{\frac{Z_S}{Z_P}}\right)$$

in the:

• tan δ = the piezo loss coefficient is.

It is understood that the parameters identified above as measured parameters are determined by the power supply 104 have been measured using sensors with which the power supply 104 configured in a known manner.

According to one aspect of the present disclosure, the baseline piezo-coupling _coefficient K _{Zb is} set by that of the controller 114 controlled power supply 104 Doing a baseline scan of the ultrasound assembly 102 in air with an intact ultrasonic transducer, and the controller 114 measures the piezo-coupling constant Kz with this baseline scan with this piezo-coupling constant K _Z as the baseline piezo-coupling constant K _Zb . This baseline scan is performed, for example, during initial assembly of the ultrasound device 100 or if the ultrasound device 100 first set up for operation, such as in a production plant. Subsequently, when it must be determined whether the piezoelectric material of the ultrasonic transducer 106 is broken, a test frequency scan of the ultrasonic assembly 102 through the energy supply 104 performed in air and the test piezo-coupling constant Kz is measured by the controller 114 , If the value of the test piezo-coupling constant K _Zt is smaller than the baseline piezo-coupling constant K _Zb by a predetermined _amount , the controller sets 114 determines that the piezoelectric material of the ultrasonic transducer is broken. In one aspect, the controller gives 114 a warning signal that the piezoelectric material of the ultrasonic transducer is broken. By way of example and not limitation, the warning signal may be a visual indication provided by the controller 114 is illuminated, a message on a screen of a user interface, such as the user interface 118 in phantom lines in 1 a message is sent to a remote monitoring system containing the ultrasound device 100 monitors, or any combination of all.

It is understood that one or more of the constants in the above equations need not be used in the calculations of the test piezo-coupling coefficient Kzt and the baseline piezo-coefficient K _Zb , as long as the calculations for determining the test piezoelectric Coupling coefficient Kzt and the baseline piezoelectric coefficient K _{Zb use the} same constants. For example, V _nom , G _s , x ₀ , and tan δ are all constants for a given power supply, an ultrasound assembly, and an ultrasound transducer and need not be used in the calculations to obtain the test piezo-coupling coefficient Kzt and the baseline piezoelectric To determine coefficients K _Zb for this given power supply, the ultrasonic assembly and the ultrasonic transducer.

3 shows a flowchart of a control routine, illustratively implemented in the controller 114 for the above-described method of detecting whether the piezoelectric material of the ultrasonic transducer 106 is broken. The control routine starts at 300. At 302 the control routine checks whether the piezoelectric material of the ultrasonic transducer 106 should be tested to determine if the piezoelectric material is broken. If not, the control routine returns to 302. If the piezoelectric material is to be tested, the control routine proceeds to 304, where the test piezo-coupling constant Kzt is one scan of the ultrasonic assembly 102 measured in air as described above. The control routine then proceeds to 306 where it compares the test piezo-coupling constant Kzt with the previously measured baseline piezo-coupling constant K _Zb and proceeds to 308. at 308 the control routine checks whether the test piezo-coupling constant Kzt is smaller than the baseline piezo-coupling constant K _Zb by more than a predetermined value. If not, the control routine determines that the piezoelectric material is not broken and goes back to 302. If the test piezo-coupling constant Kzt is smaller than the baseline piezo-coupling constant K _Zb by more than a predetermined value, the Control routine determines that the piezoelectric material is broken and proceeds to 310, where it provides a warning signal, as described above, and then ends at 312.

The foregoing description of the embodiments is for illustrative purposes and description only. It is not meant to be exhaustive or limit the revelation. Particular elements or features of a particular embodiment are not generally limited to this particular embodiment, but are interchangeable where applicable, and may be used in a selected embodiment, even if not explicitly shown or described. This can also be varied in different ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

As used herein, the term controller, control module, control system or the like refers to, forms part of or includes an application specific integrated circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, assigned, or groups) that executes code; a programmable logic controller, a programmable control system such as a processor-based control system that includes a computer-based control system, process control such as a PID controller, or other suitable hardware components that provide the described functionality or provide the described functionality when programmed with software described herein ; or a combination of parts or all of the above, such as in a one-chip system. The term module may include a memory (shared, dedicated, group) that stores the code executed by the processor. When referring to such a device performing a function, it will be understood that the device is configured to perform the function by, for example, appropriate logic, software, hardware or a combination thereof.

Spatially-related terms, such as "inside," "outside," "below," "below," "above," "higher," and the like, may be used for ease of description to refer to an element or feature reference to one or more other elements or to describe features as illustrated in the figures. Spatially related terms may encompass different orientations of the device used or operated, in addition to the orientations shown in the figures. For example, if the device in the figures is turned over, elements described will be oriented "below" or "below" other elements or features, then "above" the other elements or features. Thus, the term "under" may include both "over" and "under" orientation. The device may be otherwise oriented (rotated 90 ° or otherwise oriented) and the spatially related description terms used herein interpreted accordingly.

Claims (4)

A method of detecting broken piezo material in an ultrasonic transducer of an ultrasonic assembly of an ultrasonic device, comprising: Performing a test scan of the ultrasonic assembly in air with a power supply of the ultrasonic device, Measuring a test piezo-coupling constant with the test scan of the ultrasonic assembly, Comparing the test piezo-coupling constant with a previously measured baseline piezo-coupling constant and Determining that the piezoelectric material is refracted when the test piezo-coupling constant is smaller than the baseline piezo-coupling constant by more than a predetermined value. The method according to Claim 1 comprising establishing the baseline piezo-coupling constant by performing a baseline scan of the ultrasonic assembly in air with the power supply of the ultrasonic device when the piezoelectric material of the ultrasonic transducer is known to be intact and measuring the baseline piezo-coupling constant with the baseline scan the ultrasonic assembly. Method according to Claim 2 comprising, by the controller, storing the baseline piezo-coupling constant in a memory of a controller as the baseline piezo-coupling constant and comparing the test piezo-coupling constant with the baseline piezo-coupling constant, and determining that the piezoelectric material is refracted, if the test piezo-coupling constant is smaller than the baseline piezo-coupling constant by more than a predetermined value. The method according to Claim 3 comprising providing a warning signal by the controller after determining that the piezoelectric material is broken.

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