System for generating ultrasonic acoustic vibrations with improved amplitude control - Patents.com
By using the predicted sudden vibration amplitude jump information in the drive control unit to adjust the frequency of ultrasonic vibration in real time, the problem of difficulty in quickly adjusting the ultrasonic vibration amplitude in the prior art is solved, and efficient and uniform material processing in high-speed material web processing is achieved.
Patent Information
- Application Number
- JP2024554680
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-03-15
- Filing Date
- 2023-03-06
- Publication Date
- 2025-03-21
AI Technical Summary
In the prior art, in high-speed material web processing, it is difficult to quickly adjust the ultrasonic vibration amplitude, resulting in limited processing speed and uneven material processing.
By using the predicted sudden vibration amplitude jump information in the drive control unit, the frequency of ultrasonic vibration is adjusted in real time to maintain the required vibration amplitude and frequency, quickly responding to high-speed movement and sudden changes of the material web.
In high-speed material web processing, the ultrasonic vibration amplitude and frequency are quickly and accurately adjusted, and the processing speed and uniformity of material processing are improved.
Smart Images
Figure 2025508158000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a system for generating ultrasonic acoustic vibrations, comprising a generator for generating an alternating voltage and a converter for converting the alternating voltage into ultrasonic acoustic vibrations. Such systems are known in principle. The converter usually comprises a piezoelectric element which converts the alternating voltage into mechanical vibrations, i.e. acoustic vibrations. The converter is often connected to a sonotrode which is designed to be excited by ultrasonic vibrations and to transmit them to the material to be processed, which is brought into contact with the sonotrode. [Background technology]
[0002] The converter, the sonotrode and an amplitude modulator, which may be arranged between the converter and the sonotrode, form an ultrasonic vibration unit. The converter, the sonotrode and, if applicable, the amplitude modulator, are adjusted relative to each other so that they can resonate at the same ultrasonic frequency.
[0003] The sonotrode usually has a sealing surface that is placed opposite a counter tool and is intended to process a material placed between the sonotrode and the counter tool.
[0004] For example, from DE 603 19 101 T2 a device is known in which, during processing, the material web is moved between a sonotrode and a counter tool and the sonotrode is pressed against the material web with a welding force. Whenever processing is not taking place, the sonotrode is moved away from the material web.
[0005] However, the constant back and forth movement of the sonotrode creates problems in guiding the material web, especially at very high web speeds, and high web speeds cannot be achieved because the sonotrode cannot be moved back and forth fast enough.
[0006] It has therefore already been proposed in DE 10 2017 107 617 A1 that the sonotrode should not be moved away from the material web when no processing is taking place, but instead should only reduce the vibration amplitude when no processing is taking place, so that during the welding interval the sonotrode is excited with a higher vibration amplitude than during the non-welding interval.
[0007] The device according to DE 10 2017 107 617 A1 therefore requires that the ultrasonic vibrations have a vibration amplitude A ist Record and calculate the desired vibration amplitude A soll Compared with the recorded vibration amplitude A ist The desired vibration amplitude A soll The control variable has a regulator that varies the control variable in order to approximate the
[0008] In principle, the generator that supplies the converter with an appropriate AC voltage to generate the ultrasonic vibrations can simply be switched off during intervals when no machining is taking place.
[0009] However, it has been shown that completely switching off the sonotrode means that when it is switched on again, i.e. at the start of the next interval in which the sonotrode processes the material web, it takes a relatively long time for the sonotrode to return to its desired steady state, resulting in a too long range in which the material web cannot still be optimally processed, especially at high web speeds.
[0010] Therefore, the desired vibration amplitude A in the absence of welding soll is greater than zero but is equal to the desired vibration amplitude A soll will be significantly smaller than
[0011] However, if the processing speed is further increased, the desired vibration amplitude A changes suddenly very rapidly in a very short period of time. soll This method and the associated rapid increase or decrease of the vibration amplitude is no longer possible, since it is no longer possible by regulation to adapt the vibration amplitude to the
[0012] EP 3 174 644 B1 describes an apparatus in which a rotating cylindrical counter tool has a raised portion, and welding is performed by means of ultrasonic waves only when the raised portion is positioned opposite the sonotrode. The apparatus has a triggering device which detects the position of the raised portion and an adjustment device which switches the adjustment ON or OFF depending on the result of the detection. However, the method described in EP 3 174 644 B1 requires the presence of a corresponding raised portion and is not suitable for apparatuses which do not have a raised portion or for which the vibration amplitude must be reduced whenever no welding is being performed.
[0013] Since known generators need to adapt the frequency f of the generated alternating voltage to the resonant frequency of the driven ultrasonic vibration unit, they usually have a frequency control module having a frequency control input and determining the frequency f of the generated alternating voltage U depending on a signal applied at the frequency control input.
[0014] EP 2705906 B1 describes a method in which the excitation frequency of an ultrasonic generator is controlled in such a way that the phase of the impedance of the vibration system is greater than 0°. Summary of the Invention [Problem to be solved by the invention]
[0015] Based on the above-mentioned state of the art, the present invention therefore aims to provide a system of the above-mentioned kind, which at least mitigates the above-mentioned drawbacks and allows for higher processing speeds and the sudden load changes associated therewith. [Means for solving the problem]
[0016] According to the invention, the problem is to convert an input signal into a manipulated variable signal. Control device is provided, and a desired vibration amplitude A soll is given as the input signal, and the manipulated variable signal is connected to the frequency control input. The system according to claim 1 is solved by:
[0017] The described ultrasonic vibration system is optimized for and resonates at a specific ultrasonic frequency, so excitation at a different frequency leads to a reduction in the amplitude of the ultrasonic vibrations.
[0018] According to the present invention, the desired vibration amplitude A soll is given as the input signal, the desired vibration amplitude A soll When A changes, the drive control unit causes an immediate change in the excitation frequency. ist and A soll There is no need to wait to detect a deviation between
[0019] The desired vibration amplitude A when the non-weldable area of the material moves between the sonotrode and the counter tool during the welding process, or when the weldable area of the material moves between the sonotrode and the counter tool with a reduced vibration amplitude and no welding takes place soll A sudden change in represents a disturbance to the regulating system that cannot be corrected quickly enough.
[0020] However, the desired vibration amplitude A soll Since both the time and magnitude of the sudden change in is known, this information can be used to determine the desired vibration amplitude A soll is used directly by the drive control unit which uses as its input signal.
[0021] When setting or programming the drive control unit, the difference between the frequency of the ultrasonic vibrations used during the welding process and the frequency used during the welding process, i.e. when the sonotrode is operated with a reduced vibration amplitude and the materials are not welded, can be determined in advance or experimentally. The drive control unit is then adjusted to the desired vibration amplitude A soll When a predicted sudden amplitude jump is detected, the manipulated variable signal can be set to reflect the required frequency jump, i.e., the determined frequency difference.
[0022] As a result of the controller's intervention, the system suddenly operates at the new operating frequency and, due to the correlation between operating frequency and vibration amplitude of the vibration system, at the new desired vibration amplitude.
[0023] Thus, the regulator does not have to adjust new operating parameters of the system and can immediately continue tuning in a substantially fully tuned state.
[0024] The adjustment device is It must react to all unexpected disturbances in the system, such as temperature changes or thickness variations in the web of material being processed.
[0025] The present invention According to , the frequency of the electrical alternating voltage U is used as the manipulated variable of the regulating device. Again, the regulating device must react to all unexpected disturbances in the system.
[0026] In this case, it is not necessary to vary the voltage at the generator: the amplitude of the ultrasonic vibrations can be achieved simply by changing the frequency of the electrical excitation voltage.
[0027] According to the present invention , the adjustment device outputs a control variable signal connected to the frequency control input. do In this way, the regulating device also uses the frequency control input of the frequency control module. For example, it is also possible that the control variable signal and the manipulated variable signal are added or that the manipulated variable signal is subtracted from the control variable signal and the sum or difference is connected to the frequency control input. In this case, the drive control unit also generates a manipulated variable signal that only represents a frequency offset value. Since the change in the desired vibration amplitude is known before the sudden change occurs, the required change in the excitation frequency f is directly initiated by the drive control unit using the preferred method described, without the regulating device having to take over the corresponding regulating task.
[0028] In a further preferred embodiment, the generator has two operating modes, where in a first operating mode only the regulating device is used and in a second operating mode both the regulating device and the drive control unit are used.
[0029] For example, the drive control unit may be used only during welding intervals or only during non-welding intervals, while otherwise any necessary interventions in the system are handled by the regulating device.
[0030] Therefore, in an alternative embodiment, the desired vibration amplitude A soll remains constant or does not change by more than a predetermined amount during a predetermined time interval, the first operating mode is used, and the desired vibration amplitude A soll It is provided that if changes by more than said predetermined amount during said predetermined time interval, said second mode of operation is used.
[0031] Further advantages, features and possible applications of the present invention will become apparent from the following description of preferred embodiments and the accompanying drawings. [Brief description of the drawings]
[0032] [Figure 1] FIG. 1 is a schematic diagram of an apparatus which may comprise a system according to the invention. [Diagram 2] FIG. 2 is a schematic diagram of the time dependence of vibration amplitude and force. [Diagram 3] FIG. 3 shows a schematic block diagram of a regulation device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Figure 1 shows a schematic diagram of an apparatus for intermittent ultrasonic processing of a material web. The material web 1 moves in the direction of the arrow between a sonotrode 2 and a counter tool 3. Both the sonotrode 2 and the counter tool 3 have a roller shape in this embodiment. The sonotrode 2 is pressed with a force F in the direction of the counter tool 3, so that the material web 1 is pressed together between the sonotrode 2 and the counter tool 3.
[0034] To operate the sonotrode, it is connected to a converter (not shown) which converts an alternating voltage into acoustic ultrasonic vibrations. For this purpose, an alternating voltage is transmitted from a generator (not shown) to the converter, which transmits the generated acoustic ultrasonic vibrations to the sonotrode 2.
[0035] The material web 1 is processed when the sonotrode 2 is pressed against the material web with a suitable welding force FA and the sonotrode is vibrated with a suitable vibration amplitude A.
[0036] However, there are applications in which only parts of the material web 1 are processed rather than the entirety of it.
[0037] In these cases, when no machining is taking place, the amplitude of the ultrasonic vibrations of the sonotrode is always reduced in the illustrated designs, and the material web is passed between the sonotrode and the counter tool, but no machining takes place due to the reduced amplitude of the ultrasonic vibrations.
[0038] This is shown diagrammatically in figure 2, which shows, in arbitrary units, both the vibration amplitude (solid line) and the welding force pressing the sonotrode towards the counter tool (dotted line). It can be seen that in interval I the vibration amplitude takes the value A and the force moving the sonotrode towards the counter tool takes the value FA. The actual machining takes place in interval I.
[0039] Before and after machining in interval I, both the vibration amplitude in interval II and the force pressing the sonotrode towards the counter tool are reduced to values B and FB. During movement interval II, no machining takes place. Now, between movement interval II and machining interval I, a ramp interval III is shown, in which the vibration amplitude increases and decreases continuously.
[0040] In this tilt interval III, conventional adjustment devices are unable to adjust the vibration amplitude rapidly enough at very high conveying speeds, with the result that undesirable machining can occur in the transfer interval II or insufficient machining takes place at the beginning of the machining interval I.
[0041] Therefore, the present invention provides a method for controlling the desired vibration amplitude A at least in the tilt interval III. soll to a manipulated variable signal, which is connected to the frequency control input of the frequency control module.
[0042] 3 shows an exemplary block diagram of an embodiment of a system according to the invention. A real tuned system 6 is usually subjected to a disturbance variable 9. The disturbance variable can for example be a length change in the system due to, for example, a temperature change.
[0043] In this example, a setpoint generator 4 defines a desired vibration amplitude 4. This is compared with the actual vibration amplitude, i.e. real signal 8 provided via a feedback signal, and the result of the comparison, for example as a difference, is made available to a regulating element 5.
[0044] When the regulating element 5 detects a deviation between the set point and the actual value, the manipulated variable signal 11 provided to the frequency control input of the controlled system 6 is modified.
[0045] So far the block diagram shows a known control method, however process related sudden changes in the oscillation amplitude of the set point can also result in sudden signal changes at the input of the regulating element.
[0046] According to the invention, the set value amplitude is also transmitted in parallel to the drive unit 10, which calculates a manipulated variable signal therefrom and adds it to the output of the regulating element 5, so that the sum of the manipulated variable signal generated by the drive unit and the manipulated variable signal generated by the regulating element is present at the frequency control input of the control path 6.
[0047] Process-related changes in the known target amplitude are therefore no longer regulated as disturbances but are rejected via the drive control unit. To prevent sudden interventions by the regulating element 5, i) a relatively gradual regulation can be ensured by the set of regulation parameters of the regulating element 5 (e.g. in the case of a PID controller, the D component is decreased and the I component is increased), or ii) the regulating element 5 can be stopped for a short time in case of a sudden change in the setpoint amplitude, or iii) a setpoint signal can be made available to the regulating element 5 at a slightly later point in time than to the control unit 10, so that the magnitude of the signal delay at the regulating element can be correlated with the dead time of the control path. As a result, the quality of control of the system can be significantly improved and the system can be used at very high web speeds. [Explanation of symbols]
[0048] 1 Material Web 2. Sonotrode 3 Mating tool 4 Setpoint Generator 5 Adjustment factors 6. Controlled Systems 7 Feedback Signal 8 Real Signals 9 Disturbance variables 10. Control Unit 11 Operated variable signals F force FA Welding Power A vibration amplitude I Interval II Movement Interval III Slope interval
Claims
1. A generator for generating an AC voltage U having a frequency f and a converter for converting said AC voltage into ultrasonic acoustic vibrations, said ultrasonic vibrations having a vibration amplitude A ist is detected and converted into the desired vibration amplitude A soll The detected vibration amplitude A ist The desired vibration amplitude A soll In a system for generating ultrasonic acoustic vibrations having an adjusting device for changing a manipulated variable in order to approximate a desired vibration amplitude A, the generator having a frequency control module having a frequency control input and determining the frequency f of the AC voltage U to be generated in response to a signal present at the frequency control input, a drive control unit is provided for converting an input signal into a manipulated variable signal, soll is provided as said input signal, and said manipulated variable signal is connected to said frequency control input.
2. 2. The system of claim 1, wherein the amplitude of the alternating voltage U is used as the manipulated variable.
3. 2. The system of claim 1, wherein said frequency of said electrical AC voltage is used as said manipulated variable.
4. 4. The system of claim 3, wherein said regulator outputs a control variable signal connected to said frequency control input.
5. 5. The system of claim 4, wherein the manipulated variable signal and the manipulated variable signal are added or the manipulated variable signal is subtracted from the manipulated variable signal and the sum or difference is connected to the frequency control input.
6. 6. The system according to claim 1, wherein the generator has two operating modes, in a first operating mode only the regulating device is used and in a second operating mode both the regulating device and the drive control unit are used.
7. The desired vibration amplitude A soll remains constant or does not change by more than a predetermined amount during a predetermined time interval, the first operating mode is used, and the desired vibration amplitude A soll 7. The system of claim 6, wherein said second mode of operation is used if changes more than said predetermined amount during said predetermined time interval.