SU698674A1 - Ultrasonic generator with frequency self-tuning - Google Patents

Description

one

The invention relates to ultrasound technology, the field of mechanical engineering and electronic instrumentation, and can be used, in particular, in ultrasonic technological installations for welding microcontacts of semiconductor devices and integrated circuits.

Ultrasonic generators containing a power amplifier, an acoustic sensor mounted on the non-operating end of the converter, and a feedback circuit 1 are known.

However, these generators are difficult to configure and unreliable.

The closest to the invention in its technical essence is an ultrasonic oscillator with automatic frequency control, containing a series-connected master oscillator of independent excitation, a power amplifier, and an acoustic transducer, which form a feedback circuit with two acoustic sensors installed along

both sides of the mechanical oscillation assembly, two logarithmic amplifiers, the outputs of which are connected to the inputs of the differential stage, the output of which is connected to the frequency control input of the master oscillator of the independent excitation.

However, in this generator it is impossible to precisely adjust the frequency to the resonance of the acoustic transducer.

The aim of the invention is to ensure the rigid maintenance of the resonant mode of operation of the acoustic transducer.

The goal is achieved by the introduction of two rectifiers, an adder and a subtractive device.

Claims (2)

FIG. 1 schematically shows the distribution of the amplitudes of mechanical oscillations and two points A and B located on either side of the oscillation node O in idling mode (points U and Uj.) And in the load mode (points and I and 2.); in fig. 2 A functional diagram of an auto-tuning ultrasound generator. The ultrasonic generator contains an independent excitation generator 1 connected in series, a power amplifier 2, an acoustic transducer 3 and two acoustic sensors 4 forming a feedback circuit, connected respectively via rectifiers 5 and 6 to the inputs of the adder 7 and the subtractor 8, the outputs of which connected, respectively, to the inputs of the logarithmic amplifier 9 and 10, the outputs of the logarithmic amplifiers 9 and 10 are connected to the inputs of the differential stage 11, the output of which is connected to the control input and a frequency oscillator 1. Works ultrasound generator as follows. The master oscillator 1 of independent excitation generates a signal with a frequency corresponding to the often resonant acoustic transducer 3. This signal is amplified to the desired value by power amplifier 2 and fed to acoustic transducer 3 to excite it. Ultrasonic oscillations arising in this case in the transducer 3 excite an electrical signal in the acoustic sensors 4. Acoustic sensors 4 are installed on either side of the mechanical oscillation assembly at such a distance from each other that, under the most unfavorable operating conditions of the converter 3 for the load, the node does not go beyond the limits of sensors 4. To satisfy this condition and to obtain the maximum slope converting the amplitude of the mechanical oscillations into an electrical signal; the distance between the sensors 4 must satisfy the condition:,. Split (1) s - distance between sensors h - sequence number of the node along the axis of the converter, starting from the shaft of the active element; hi is the maximum possible change in the resonant length of the wave in the transducer; v is the value of the dead zone of the sensor. Further, the signals from the acoustic sensor 4 are rectified by rectifiers 5 and 6, the output of which is proportional to the amplitudes of the input signals and does not depend on their frequency and phase relation. From each rectifier 5 and 6, the signals are fed to the adder 7 and the subtractive device 8, producing, respectively, algebraic addition and algebraic subtraction of two input signals. The output terminal of the adder 7, equal to the sum of the amplitudes of the signals taken from the acoustic sensors 4, goes to the logarithmic amplifier 9, and the output signal from the subtractor 8, equal to the difference of the amplitudes of the same signals, goes to the logarithmic amplifier 10. From the output of the logarithmic amplifiers 9 and 10 Prologized sum and spread of the input signals of the feedback circuit are fed to the differential stage 11, where the logarithm of the sum from the logarithm of the difference of the input signals is subtracted. The output signal of the differential stage 11 is defined by the expression: Bbix-g - V og VUz (2) or U-1-KUg where and days is the output signal of the feedback circuit; (J is the amplitude of the signal taken from the first (conditional sensor); Ij is the amplitude of the signal taken from the second sensor. The signal AND output from the output of the differential stage 11 is fed into the frequency control circuit of the master oscillator 1 to adjust it to the resonant frequency of the acoustic transducer 3 This signal unambiguously determines both the direction of departure of the resonant wavelength and its absolute value, which follows from the consideration of the triangles and (Fig. 1), where the equality can be written: Ug OB-l H is the amount of care of the resonance length waves at work on the load. From this we find: and; -. and Enter in the expression (5) the coefficient Y. г constant for each particular acoustic transducer and determining the position of the mechanical vibration node relative to acoustic sensors 1 and 2 in idle mode course, we can write the equality: and; 2 uniquely defining the direction and magnitude of the departure of the resonant wavelength in the acoustic transducer. Having transcribed this expression, we obtain an expression that determines the equivalent value of the output signal of the feedback circuit (3). The coefficient K is introduced into the subtractor 8 by changing the transmission coefficient at the corresponding input. All nodes in the frequency control circuit process the amplitudes of the signals taken from the two acoustic sensors, regardless of their frequency and phase relation. Consequently, the self-tuning range depends only on the design parameters of the transducer, in particular, on the distance between acoustic sensors. Therefore, the ultrasonic sound generator allows for rapid replacement of acoustic transducers without additional tuning of the feedback circuits and ensures high accuracy in maintaining the resonant mode of operation of the ultrasound unit. The invention Ultrasonic oscillator with frequency control, containing a series-connected master oscillator of independent excitation, power amplifier, acoustic transducer, forming a feedback circuit two acoustic sensors installed on both sides of the mechanical oscillation node, two logarithmic amplifiers, the outputs of which are connected to the differential inputs cascade, the output of which is connected to the frequency control input of the master oscillator of independent excitation -. nor, characterized by what | In order to ensure the rigid maintenance of the resonant mode of operation of the acoustic transducer, two rectifiers, as well as an adder and a subtractive device, are introduced into the device, the inputs of which are rectified in parallel with two acoustic sensors, and their outputs are connected to the inputs of logarithmic amplifiers. Sources of information taken into account during the examination 1. Donskoy A. F., Keller O. K., Kratysh G. S. Ultrasonic electro-technological installations. Energy, 1968, p. 171-174. 2. USSR author's certificate number 492313, cl. B 06 B 1/02, 1974. fuz. / fvj i 5i