阅读说明：本技术 用于确定超声波焊接工艺状态的设备 (Device for determining the state of an ultrasonic welding process ) 是由 菲利克斯·克里马斯 托马斯·赫青 路茨·雷曼 丹尼尔·泽曼 加布里埃尔·艾尔茨 扬斯·托耶 于 2020-03-31 设计创作，主要内容包括：本发明涉及一种借助于超声波工具(303)实现的用于确定超声波焊接工艺的状态的设备(305),包括被设置用于采集超声波工具(303)的电气控制信号的传感器装置(316)；和被设置用于获取控制信号的信号特征,以及基于参照信号曲线和所获取的信号特征确定超声波焊接工艺状态的评价装置(315)。本发明此外涉及一种带有超声波焊接装置的布置和一种方法。(The invention relates to a device (305) for determining the state of an ultrasonic welding process, realized by means of an ultrasonic tool (303), comprising a sensor arrangement (316) arranged for acquiring electrical control signals of the ultrasonic tool (303); and an evaluation device (315) which is provided for detecting a signal characteristic of the control signal and for determining the state of the ultrasonic welding process on the basis of the reference signal profile and the detected signal characteristic. The invention further relates to an arrangement with an ultrasonic welding device and to a method.)

1. An apparatus (305) for determining the state of an ultrasonic welding process, implemented by means of an ultrasonic tool (303), comprising:

a sensor arrangement (316) arranged for acquiring electrical control signals of the ultrasonic tool (303); and

an evaluation device (315) is provided for acquiring a signal characteristic of the control signal and for determining the state of the ultrasonic welding process on the basis of the reference signal profile and the acquired signal characteristic.

2. The device (305) of claim 1, comprising,

a first interface arranged for connection with an output of an ultrasonic generator;

a second interface arranged for connection with a signal input of an ultrasonic tool (303);

a signal path electrically connecting the first interface and the second interface together;

wherein the sensor device (316) is arranged for measuring the electrical control signal on the signal path in a non-invasive manner.

3. The device (305) according to claim 1 or 2, wherein the sensor arrangement (316) comprises a voltage meter (316) for measuring a voltage signal and/or a current converter (319) for measuring a current signal.

4. The device (305) according to any one of the preceding claims, comprising

A switching element (307) arranged in the signal path and provided for interrupting the signal path in order to electrically disconnect the first interface from the second interface, and

a signal generator (311) arranged for generating a control signal for the ultrasonic tool (303) and controlling the ultrasonic tool (303) when the switching element (307) interrupts the signal path.

5. An apparatus (305) according to claim 4, wherein the switching element (307) is arranged to interrupt the signal path when the sensor means (316) knows that the ultrasound generator (301) is not sending a control signal to the ultrasound tool (303).

6. The device (305) according to claim 4 or 5, wherein the signal generator (311) is arranged for generating a control signal for the ultrasonic tool (303) by means of small signal control.

7. The device (305) according to any one of claims 4 to 6, wherein the sensor arrangement (316) is arranged for measuring an electrical signal on a signal path when a signal generator of the device (305) controls the ultrasonic tool (303) through the signal path.

8. The device (305) according to claim 7, wherein the evaluation means (315) is arranged for determining the equivalent parameter based on an electrical signal measured when a signal generator (311) of the device (305) controls the ultrasonic tool (303) through a signal path.

9. The device (305) according to any one of claims 4 to 8, wherein the signal generator (311) is arranged for generating a control signal based on an operating signal of the sonotrode (301), in particular having a frequency between ± 2kHz of the operating frequency of the sonotrode (301).

10. The device (305) according to any one of claims 4 to 9, comprising a discharge switching element (313) electrically connected to the signal path and arranged for short-circuiting the ultrasonic tool (303) in an on-state such that residual charges within the ultrasonic tool (303) can be drained.

11. An arrangement with an ultrasonic welding device (300) and an apparatus (305) according to any one of claims 1 to 10, wherein the apparatus (305) is connected between an ultrasonic generator (301) of the ultrasonic welding device (300) and an ultrasonic tool (303) of the ultrasonic welding device (300).

12. A method for determining the status of an ultrasonic welding process comprising:

measuring (405) an electrical control signal of the ultrasonic tool (303) by means of the sensor device (316); and is

Signal characteristics of the control signal are acquired (406) by an evaluation device (315), and

the state of the ultrasonic welding process is determined (407) by an evaluation device (315) on the basis of the reference signal profile and the acquired signal characteristics.

13. The method according to claim 12, comprising disconnecting the sonotrode (301) from the ultrasonic tool (303) by means of a switching element (307).

14. The method according to claim 13, comprising generating a control signal by the signal generator (311) and controlling the ultrasonic tool (303) when the ultrasonic generator (301) is disconnected from the ultrasonic tool (303).

15. The method of claim 14, comprising determining equivalent parameters for the welding device based on the generated control signal based on the state of the ultrasonic welding process.

Technical Field

The invention relates to a device, an arrangement and a method for determining the state of an ultrasonic welding process.

Background

The ultrasonic welding process of metals uses an ultrasonic tool (or US oscillating system) for welding different metal pairs. The process is fast, energy-saving and reliable.

Fig. 1 is a schematic diagram showing an ultrasonic welding apparatus 100.

The ultrasonic welding apparatus 100 includes an oscillation generator 103, i.e., a transducer; a welding head 105, i.e. an oscillating part in contact with the weld metal 107 and possibly one or more intermediate pieces; so-called "horns" are used for amplitude transformation or for support. The transducer usually consists of a series of piezoelectric ceramic exciters which are electrically contacted and preloaded by an additional component.

The generator 101 is connected to a transducer and generates, in the ultrasonic range (20-100kHz), a sinusoidal alternating voltage that is converted by a piezoelectric ceramic exciter into mechanical oscillations of the same frequency. The design of the transducer, horn and horn 105 are programmed such that they are tuned to the frequency generated by the generator 101 after half-wave synthesis and they oscillate within or near the resonance of the eigenmode. In the resonance state, the entire ultrasonic oscillation system can operate in an optimum manner in terms of energy.

The electromechanical ultrasonic oscillation system can be illustrated as a mechanical equivalent diagram of operation in resonance, see fig. 2a, and allows to derive equivalent parameters for characterizing the ultrasonic oscillation system: mass m_mBy means of springs c_mAnd a damper d_mCombined with the environment. Harmonic forces F act on the right. These components represent the mechanical component of the ultrasonic oscillator moving in resonance with displacement x.

The parameters denoted m are the modal parameters of the excitation mode. The mechanical domain and the electrical domain of the piezoelectric exciter are coupled together by a transmitter a. Here, Cp is a capacitance of the piezoelectric exciter, and Rp represents a loss resistance of the piezoelectric exciter, which is, however, generally so small as to be negligible and can be simplified to Rp — 0. In the mechanical equivalent diagram, the voltage U and the charge Q are proportional to the mechanical force F and the mechanical displacement x through the transmitter a.

Thus, it can be seen from the figure that the alternating voltage u (t) applied to the piezoelectric exciter results in a mechanical oscillation with a displacement x (t).

Instead of mechanical equivalent parameters, the ultrasonic oscillator can also be shown by eigenmodes in the form of an electrical equivalent, see fig. 2 b. The modal mass m here_mCorresponding to inductance, damping dm to resistance, transmitter a to transformer, and stiffness c_mCorresponding to the inverse of the capacitance. Here, the speed of the mechanical oscillation i is represented as an electrical parameter proportional to the current.

If it is now assumed that the transmission coefficient a is constant, the electrical equivalent diagram can be simplified further and the parameter R can be used_m、C_mAnd L_mSee, fig. 2 c.

The electrical equivalent diagram can also be used in industry for characterizing oscillating structures.

The oscillating system is applied to the welding process as follows: the oscillating movement of the horn 105 is transmitted to the welding pair to be welded, i.e. the weld metal 107, through the contact surface of the horn 105. They may for example be cables consisting of plied wires and contact members. The oscillating movement of the welding heads 105 is transmitted to the strand so that they move relative to the contact part fixed by the pressing device. The rapid movement of the welding couple ensures firstly the cleaning of the surface, thus removing the oxide layer. The diffusion process between the process pairs is accelerated by the ultrasonic oscillation, so that, depending on the application, the cold-welded material-bonded connection of the welding pairs occurs within a few seconds.

Disclosure of Invention

The object of the invention is to specify an advantageous concept for determining the state of an ultrasonic welding process.

In the soldering process there are different phases of the cleaning process, diffusion process and joining process composition, which can be evaluated, for example, by the impedance, the distortion factor or the proportion of certain higher harmonic frequency components. From this, an index can be derived that can be used for process quality assessment.

According to a first aspect, the object is achieved by an apparatus for determining the state of an ultrasonic welding process, which is realized by means of an ultrasonic tool, comprising a sensor device which is provided for acquiring electrical control signals of the ultrasonic tool; and an evaluation device which is provided for acquiring a signal characteristic of the control signal and for determining the state of the ultrasonic welding process on the basis of the reference signal profile and the acquired signal characteristic.

This reference signal profile can be pre-stored in a memory. The evaluation device can be provided for reading the reference signal profile from the memory. The electrical control signals are used to control the ultrasonic tool to perform the ultrasonic welding process. The generator is capable of controlling the ultrasonic tool through the control signal.

The present invention thus relates to a system-independent device and process diagnostic system for ultrasound processes, which is capable of operating independently of the device and is "invisible" to the generator from an electrical point of view. This makes it possible to both characterize the oscillating system and to evaluate the welding process without intervention in the welding process and to carry out it independently of the type of device.

One function is to observe the welding process and to collect the electrical endquantity current and voltage applied to the ultrasonic oscillator during welding without thereby affecting the weld. This system is not visible to the generator during welding.

The measured variable measured when measuring the electrical control signal can be a time-dependent variable. The welding, which is usually carried out under different conditions, does not differ significantly in its mean value or in its individual fourier transformation throughout the welding process, but only in the form of its curve, it being advantageous if the physical variable is plotted as a function of time to acquire a time-dependent measured variable.

Applications of fourier analysis may include applications of short-term fourier analysis from which the temporal correlation of amplitude, frequency or other quantities can be determined. The individual windowed portions of the short-term fourier analysis can use suitable windowing functions, in particular flat-top windows for the calculation of the amplitude and rectangular windows for the calculation of the frequency or the phase. Zero-filling and interpolation can also be used, in particular when calculating the frequency in the case of short-term fourier analysis with small window variables.

In one embodiment, the apparatus comprises a first interface arranged for connection with an output of an ultrasound generator; a second interface configured to connect with a signal input of the ultrasonic tool, a signal path electrically connecting the first interface and the second interface; wherein the sensor means are arranged for measuring the electrical control signal on the signal path in a non-invasive manner.

This may show an intelligent intermediate switching system. The intelligent intermediate switching system is implemented between a generator and a transducer and includes sensors for current and voltage measurements. The intensity distribution with which the different harmonics occur in one of the measured vibrations can be described by the curve characteristic variables distortion factor, shape factor and crest factor. These all characterize the shape of the curve of the alternating variable.

Ultrasonic welding devices generally use frequency as a control variable for their control circuit. The manipulated variable is set to keep the manipulated variable constant or to be changed in a targeted manner in the process. Typical adjustable quantities are active power introduced into the system, deflection or core admittance of the welding head (estimated from the electrical parameters) or phase difference between current and voltage. This adjustment is responsible for ensuring that in the example of reduced friction contamination caused by grease, such as hand cream, the operating frequency of the generator is set for values lower than for clean samples. In order to understand the influence of the determined welding settings and welding conditions on the frequency of the manipulated variable, the frequency response of the admittance and the frequency response of the core admittance can be examined. By means of a smaller friction in the welding area, the resonance (determined by the mechanical series oscillating circuit) shifts to lower frequencies. If the starting value of the frequency is higher than resonance, the frequency of such contaminated welding parts must be set to a lower value than the frequency of the welding parts that are not installed, in order to set the deflection to the same desired value.

When adjusting the device, the deflection of the welding head does not have to be taken into account in the control loop. When the deflection is set to a target value, it can be evaluated by means of an electrical variable. If a mechanical variable is measured in addition to the electrical variable, a cross-domain quantity, such as the core admittance, can be calculated. The value of the core admittance is determined by the velocity amplitude/voltage amplitude. To determine its phase, it may be necessary to synchronize the electrical and mechanical measurements.

In one embodiment, the sensor device comprises a voltage probe for measuring a voltage signal, and/or a current converter for measuring a current signal.

In one embodiment, the device comprises a switching element arranged in the signal path and provided for interrupting the signal path in order to electrically disconnect the first interface and the second interface, and a signal generator provided for generating a control signal for the ultrasonic tool and for controlling the ultrasonic tool when the switching element interrupts the signal path.

The signal generator may be a small signal frequency generator unit with an integrated amplifier. The switching element may be a relay.

Another function of the device is to be able to generate a small-signal control of the ultrasonic oscillator between the welds when the welding system is in an idle state, during which the electrical-quantity current and the electrical-quantity voltage are also measured (impedance measurement). Equivalent parameters can be determined from the impedance measurements and used for ultrasonic oscillator characterization. The small signal control for impedance measurement can be implemented as a modified sine wave (also referred to as a "frequency sweep") between 2kHz with the operating frequency. In the small-signal control process, the ultrasonic oscillator is decoupled from the generator by a relay circuit and coupled with an amplifier integrated into the intermediate switching system.

Direct analysis of the device state is achieved by measuring the frequency response of the admittance. The unloaded oscillatory system is thus excited at different frequencies with a constant voltage, and the system response is measured in the form of a current (i.e. by low voltage-sweeping the frequency-dependent admittance of the piezoelectric exciter which is loaded with the oscillatory system). The frequency dependent admittance of a loadless oscillatory system results from the relationship between current response and voltage. The state of the oscillating system can be characterized by this frequency response. Since the oscillating system is composed of parallel and series oscillating circuits, resonance and antiresonance occur in the operating frequency range. The frequencies, where they occur, their spacing, their width and value, the phase between them in the frequency range-all these quantities give information about the state of the oscillating system. A defective piezo exciter has, for example, a small frequency separation between resonance and antiresonance. Improperly installed systems can exhibit frictional losses such as are seen in the frequency response.

In one embodiment, the switching element is provided for interrupting the signal path if the sensor detection device knows that the ultrasonic generator is not sending a control signal to the ultrasonic tool. Thus, in the pause state of the control, further measurements can be carried out with the signal generator as a source of ultrasound.

In one embodiment, the signal generator is configured to generate a control signal for the ultrasonic tool by means of a small-signal control. The calculation of the necessary parameters can be achieved in a simplified manner by small-signal control.

In one embodiment, the sensor device is provided for measuring an electrical signal on the signal path when a signal generator of the device controls the ultrasonic tool via the signal path. This can help to obtain a reference curve, since the signal generator can provide predefined values.

In one embodiment, the evaluation device is provided for determining the equivalent parameter on the basis of an electrical signal measured when a signal generator of the device controls the ultrasonic tool via the signal path. This can cause an update of the model by means of small-signal control.

The oscillating system can be modeled by an electromechanical equivalent circuit diagram. By comparing the system response of the equivalent circuit diagram with the measured frequency response, equivalent parameters of the circuit diagram can be determined. A model consisting of four equivalent parameters can very well approximate the frequency response of an ultrasonic welding device. These parameters are: capacitance of the piezoelectric exciter, capacitance of the mechanical oscillator, inductance of the mechanical oscillator and resistance of the mechanical oscillator (here the mechanical parameters inertia, stiffness and damping are converted to analog electrical parameters capacitance, inductance and resistance as contained in the impedance describing the generator load). In this way, changes in the oscillation system, in particular slow changes in the piezoelectric exciter, can be detected.

The calculation of the equivalent parameters can also be carried out for a loaded oscillating system, i.e. when the welding head is pressed against the welded component with a normal force and is thus additionally damped. The frequency response can also be measured in the welding process, wherein the excitation voltage is significantly lower than the welding voltage in the kilovolt range and thus does not interfere with the welding process, but merely superposes. The instantaneous frequency component of the frequency response measurement may be filtered out at the time of the current measurement if the instantaneous frequency of the frequency response measurement is not close to the instantaneous operating frequency. In this case, the evaluation unit can use fourier analysis.

In one embodiment, the signal generator is arranged for generating the control signal based on an operating signal of the sonotrode, in particular having a frequency between ± 2kHz of the operating frequency of the sonotrode.

In one embodiment, the device comprises a discharge switching element which is electrically connected to the signal path and is provided for short-circuiting the ultrasonic tool in a conductive state, so that residual charges within the ultrasonic tool can be discharged.

According to a second aspect, the object is achieved by an arrangement with an ultrasonic welding device and an apparatus according to the first aspect, wherein the apparatus is connected between an ultrasonic generator of the ultrasonic welding device and a transducer of the ultrasonic welding device.

According to a third aspect, the technical problem is solved by a method for determining the status of an ultrasonic welding process, the method comprising:

measuring an electrical control signal of the ultrasonic tool by a sensor device; and is

Acquiring signal characteristics of the control signal through an evaluation unit; and is

The state of the ultrasonic process is determined by an evaluation unit on the basis of the reference signal curve and the acquired signal characteristics.

In one embodiment, the measurements are performed during the welding process. This may enable the welding process to be monitored.

In one embodiment, the method includes disconnecting the sonotrode from the ultrasonic tool via the switching element.

In one embodiment, the method includes generating, by the sonotrode, a control signal and controlling the ultrasonic tool while the sonotrode is disconnected from the ultrasonic tool.

In one embodiment, the method includes determining equivalent parameters for the welding device based on the generated control signal based on the determined state of the ultrasonic welding process.

In this way, reference values for determining the measured curve can be generated and a model can be developed, on the basis of which the signal generator and the evaluation unit operate.

The invention is described in more detail below with reference to the figures and examples. The figures show:

FIG. 1 is a schematic illustration showing an ultrasonic welding apparatus;

FIG. 2a is a mechanical equivalent diagram showing an ultrasonic welding device;

FIG. 2b is an electrical equivalent diagram showing the mechanical equivalent diagram according to FIG. 2 a;

FIG. 2c is an electrical small signal equivalent diagram showing the mechanical equivalent diagram according to FIG. 2 a;

FIG. 3 is a schematic diagram illustrating an ultrasonic welding apparatus according to one embodiment; and is

FIG. 4 is a flow diagram illustrating a method according to one embodiment.

Detailed Description

FIG. 3 shows a schematic diagram of an ultrasonic welding apparatus 300 in accordance with an exemplary embodiment. The ultrasonic welding apparatus 300 includes an ultrasonic generator 301 and an ultrasonic tool 303. A device 305 is connected between the ultrasonic generator 301 and the ultrasonic tool 303. The device 305 comprises a relay circuit with a switching element 307 for disconnecting the positive path between the ultrasonic generator 301 and the ultrasonic tool 303.

Direct analysis requires a device 305 that has an additional voltage source to provide a voltage for frequency response (sweep) in addition to the ultrasonic generator 301. In order to be able to excite the piezoelectric exciter separately from the ultrasonic generator 301, a high-voltage relay is also required as an electrical circuit. In order to be able to use such monitoring in production, the device must be able to identify the interval between welds in order to carry out a measurement at a suitable point in time, wherein the connection between the ultrasound generator 301 and the piezoelectric exciter is disconnected and the piezoelectric exciter is instead excited by the voltage source of the device. In another embodiment, the system may be integrated into the control and regulation circuitry of the generator.

A signal generator 311, which can generate a control signal for the ultrasonic tool 303, can be switched on via the relay 309. This generation process is here based on a small-signal equivalent model.

The ultrasound generator 301 can be coupled to the oscillating system by means of a relay circuit, or the signal generator 311, here an amplifier of the analysis system, can be coupled to the oscillating system. This is done by disconnecting the wires, i.e. the positive poles of the signal paths, and connecting them to various relay switches.

In another exemplary embodiment, the oscillation system can be short-circuited for a few milliseconds between the switching process of the oscillation system to the ultrasound generator 301 or the signal generator 311 by closing the discharge switching element 313, in order to be able to discharge the residual charge present in the ultrasound tool 303. This prevents short term current spikes on the sonotrode 301 and small signal control once they are reconnected to the oscillating system.

The relay circuit and the modified sine wave are controlled or generated in a software manner. The point in time for the switching of the respective switching elements 307, 309, 313 of the relay circuit is realized by observation of the process. The output state is an observation of the weld. For this purpose, a switching element (which may also be a plurality of parallel switching elements depending on the required power) is closed, so that the ultrasound generator 301 is connected to the ultrasound tool 303.

At the start of the weld, a trigger is activated and the software identifies the start and end points of the weld and stores the measured voltage and current profiles for subsequent evaluation. After the welding is completed, the process pause is utilized and the software switches the "generator-ultrasonic oscillator" to the "small signal-ultrasonic oscillator" through the "short-circuit-ultrasonic oscillator". That is, the switching element 307 opens the signal path, the switching element 313 generates a short-term short circuit so as to discharge the residual charge, and then opens again, and then the switching element 309 turns on the signal generator 311 so that it provides the control signal to the ultrasonic tool 303.

The modified sine wave is now applied to the ultrasonic tool 303 by the signal generator 311 for a duration of several seconds to less than 1 second, depending on the process pause. After the impedance measurement has ended, the software switches the switching elements 309, 313, 307 again to the output state in the reverse order and connects the ultrasound generator 301 with the ultrasound tool 303.

The conversion and evaluation takes place in an evaluation unit 315, here a microcontroller. The measurement of the electrical control signal, whether from the ultrasonic generator 301 or the signal generator 311, is effected by a sensor arrangement 316 comprising a voltage measuring instrument 317, in particular a voltage probe, and a current converter 319, which enables non-invasive measurement.

Fig. 4 shows a flow diagram of a method according to an embodiment.

In a first step 401, a transparent observation mode is used. That is, the switching element 307 is switched so that the ultrasonic generator 301 can provide the ultrasonic tool 303 with an electrical control signal.

In a second step 402, the welding is triggered, i.e. the evaluation unit identifies that welding has occurred. This can be achieved by monitoring of the voltage meter 317.

In step 403, welding is started. Here, the welding process is observed noninvasively. For this purpose, the current is measured by a converter 319 and the voltage is measured at a voltage measuring device 317.

In step 404, a break in the welding process is identified, as described in step 402.

In step 405, an impedance measurement is then performed, and then switching back to a transparent observation mode so as not to interfere with the welding.

In parallel with this, the results of the measured impedance measurements are evaluated in step 406 and signal characteristics are acquired therefrom. In this case, the evaluation unit 315 determines the derivation of an index for the weld quality, an equivalent parameter, and represents a representation of the ultrasonic oscillation system. In another embodiment, step 406 occurs after step 405.

In step 407, the state of the ultrasonic welding process is determined by the evaluation unit 315 on the basis of the reference signal profile and the acquired signal characteristics. For this purpose, the reference signal profile is preset as a setpoint value and a comparison is made whether the determined signal characteristic lies within a predetermined range around the setpoint value.

List of reference numerals

100 ultrasonic welding device

101 generator

103 oscillation generator

105 welding head

107 weld metal

201 Trolley

202 environment

300 ultrasonic welding device

301 ultrasonic generator

303 ultrasonic tool

305 device

307 switching element

309 relay

311 signal generator

313 discharge switching element

315 evaluation device

316 sensor device

317 voltage measuring instrument

319 current converter

400 flow chart

401-

m_mQuality of

c_mSpring

d_mDamper

Force F

x displacement

a transformer

Cp capacitance

Rp loss resistance

U voltage

Charge of Q

i mechanical oscillation