EP0421439B1 - Pulvérisateur à ultrason - Google Patents

Pulvérisateur à ultrason Download PDF

Info

Publication number
EP0421439B1
EP0421439B1 EP90119084A EP90119084A EP0421439B1 EP 0421439 B1 EP0421439 B1 EP 0421439B1 EP 90119084 A EP90119084 A EP 90119084A EP 90119084 A EP90119084 A EP 90119084A EP 0421439 B1 EP0421439 B1 EP 0421439B1
Authority
EP
European Patent Office
Prior art keywords
frequency
low
ultrasonic
switch
resonance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP90119084A
Other languages
German (de)
English (en)
Other versions
EP0421439A2 (fr
EP0421439A3 (en
Inventor
Gerhard Gaysert
Robert F. Wilson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eberspaecher Climate Control Systems GmbH and Co KG
Original Assignee
J Eberspaecher GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by J Eberspaecher GmbH and Co KG filed Critical J Eberspaecher GmbH and Co KG
Publication of EP0421439A2 publication Critical patent/EP0421439A2/fr
Publication of EP0421439A3 publication Critical patent/EP0421439A3/de
Application granted granted Critical
Publication of EP0421439B1 publication Critical patent/EP0421439B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207—Driving circuits
    • B06B1/0223—Driving circuits for generating signals continuous in time
    • B06B1/0269—Driving circuits for generating signals continuous in time for generating multiple frequencies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
    • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
    • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
    • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/70—Specific application
    • B06B2201/77—Atomizers

Definitions

  • the invention relates to an ultrasonic atomizer according to the preamble of claim 1.
  • Such an ultrasonic atomizer is known from US-A-3 885 902 and is used for example for parking heaters of vehicles.
  • the ultrasonic atomizer creates a fuel mist for the heating burner.
  • Ultrasonic atomizers are used for ultrasonic atomizers with an ultrasonic oscillator, which has an ultrasonic transducer, which is usually coupled to an amplitude transformer, which is provided at the free end with an atomizing plate or plate, the surface of which is supplied with liquid fuel to be atomized, via bores and channels which can be dimensioned large and therefore are not subject to the risk of clogging with dirt.
  • the fuel supply from a fuel supply takes place via a metering pump that works almost without back pressure, which is much simpler and cheaper than the high pressure pump with pressure regulator required in a pressure atomizer.
  • ⁇ and ⁇ are substance-related quantities, the following applies If you want to reduce the most common droplet diameter d h of an atomizing device, this is only possible by increasing the excitation frequency f a . Is z. B. f a increased to three times, d h decreases to half. In the case of heaters with a mixture preparation based on atomization, small drops are desirable, since the large surface area of the fuel associated with this enables rapid and intensive mixture formation.
  • an excitation frequency of 100 to 120 kHz is desirable. This is also practical in normal operation of a heater, but not when the heater is cold started at the lower limit of the temperature range, which is usually assumed at -40 ° C.
  • the power requirement of the ultrasonic atomizer rises 5 to 10 times at such low temperatures, since more atomization energy is required due to the increasing viscosity of the fuel. It is also with these high frequencies it is very difficult to throw off a cold and therefore highly viscous drop adhering to the atomizer plate in cold start operation.
  • the reliability of the atomization i.e. the security against atomization failure due to damping of the ultrasonic atomizer by highly viscous fuel with a given electrical excitation energy can be increased considerably if the frequency of the atomization is markedly reduced, e.g. B. to 40 kHz.
  • the losses in the material of the ultrasonic transducer which is usually chromium-nickel steel, then decrease and atomization is still possible at an acceptable power level. However, this is only at the price of larger drops. Conventionally, a compromise is therefore made between these opposite requirements and the atomization frequency is set at 50 to 60 kHz.
  • the ultrasonic oscillator Since the ultrasonic oscillator must be operated in resonance, its dimensions are determined by the excitation frequency.
  • the invention has for its object to provide an ultrasonic atomizer, which can be optimally operated both at operating temperature and at cold start temperatures, with as little additional effort as possible.
  • a temperature-dependent switch is made between a high resonance frequency when the heater is operating at the usual operating temperature and a low resonance frequency in cold start operation at a low temperature.
  • the different resonance frequencies between which the ultrasonic oscillator can be switched over may be fundamental oscillations of different oscillation modes of the ultrasonic oscillator, a fundamental oscillation and a harmonic of different oscillation modes of the ultrasonic oscillator, a fundamental oscillation and a harmonic of a same oscillation mode of the ultrasonic oscillator or different harmonics of the same Act the vibration mode of the ultrasonic transducer. It is preferable to choose a basic vibration and a suitable harmonic of the same vibration mode of the ultrasonic vibrator.
  • the ultrasonic oscillator is preferably excited to series resonance both in the low-frequency and in the high-frequency range.
  • the temperature threshold at which the excitation circuit switches from the delivery of the low-frequency to the delivery of the high-frequency excitation frequency is preferably 0 ° C.
  • the ultrasonic oscillator has piezoceramic disks provided with electrical excitation electrodes as ultrasonic transducers and an amplitude transformer adjoining the disks with an area of larger diameter in its area adjoining the disks and an area of smaller diameter between the area of larger diameter and the atomizing plate.
  • the area of smaller diameter and the atomizing plate are provided with an axial passage which is connected to a radial passage in the area of larger diameter which can be connected to a liquid supply, whereby a liquid line is formed up to the atomizing surface of the atomizing plate.
  • a controllable low-pass filter with a linear phase response is preferably used.
  • the excitation circuit has a phase latching circuit or PLL circuit, its voltage-controlled oscillator (VCO) and a frequency filter being switched to the low or high resonance excitation frequency.
  • VCO voltage-controlled oscillator
  • a frequency filter is preferably switched between two values depending on the temperature determined, which correspond to the low or high resonance excitation frequency which the excitation circuit emits to act on the ultrasonic oscillator.
  • a compensation device is connected in parallel to the ultrasound transducer, by means of which the ultrasound transducer is set to low-frequency or a high-frequency series resonance vibration is tuned.
  • a current sensor is assigned to the ultrasonic transducer, the output signal of which is fed to a first input of a phase detector which has a second input connected to the output of the voltage-controlled oscillator.
  • a high-gain low-pass filter is connected between the output of the phase detector and the input of the voltage-controlled oscillator and blocks the sum frequency component in the output signal of the phase detector.
  • the compensation device has two inductances, of which either one or the other can be connected in parallel to the converter by means of a switch, the two inductors being dimensioned such that the reactance of the capacitance inherent in the converter is in the lower or the upper resonance excitation frequency is compensated.
  • the compensation device has a parallel connection connected in parallel to the converter with a first inductance in one parallel branch and a series connection comprising a second inductance and a capacitor in the other parallel branch, and in that the parallel connection is in relation to that inherent in the converter Capacitance is dimensioned so that the reactance of the capacitor's own capacitance is compensated for at both the lower and the upper resonance excitation frequency.
  • the low-pass filter preferably has a gain in the range from approximately 50 dB to 100 dB.
  • the high-gain low-pass filter can be formed by an integrator.
  • the current sensor is preferably a resistor connected in series with the ultrasonic transducer.
  • a threshold value circuit is preferably connected between the current sensor and the first input of the phase detector, which only allows signals with a signal strength exceeding a predetermined threshold value, the threshold value being dimensioned such that it lies above the signal value reaching the input of the threshold value circuit with parallel resonance of the ultrasonic transducer .
  • the threshold circuit is preferably a threshold amplifier in the manner of a Schmidt trigger.
  • An impedance-adapting driver transformer can be connected between the output of the voltage-controlled oscillator and the ultrasonic transducer.
  • the sensor resistor can be connected in series with the secondary winding of the driver transformer.
  • a power amplifier can be connected between the output of the voltage-controlled oscillator and the primary winding of the driver transformer, which applies a square wave to the primary winding of the driver transformer.
  • the threshold value circuit preferably supplies a square-wave output signal.
  • a digital phase detector can be provided and a -90 ° phase shifter can be arranged between the output of the voltage-controlled oscillator and the second input of the phase detector.
  • the digital phase detector preferably has an EXCLUSIVE-OR circuit.
  • a multiplying phase detector is preferably provided and a -90 ° phase shifter is arranged between the output of the voltage-controlled oscillator and the second input of the multiplying phase detector.
  • a low-pass filter with a linear phase profile is preferably connected between the current sensor and the phase detector.
  • the ultrasonic vibrator 11 shown in cross section in FIG. 1 has an essentially axially symmetrical metal body 13, which is preferably made of chromium-nickel steel.
  • the metal body 13 has a disk region 15 of large diameter approximately in its longitudinal center.
  • Two disks made of piezzoelectric ceramic material are pushed onto a shaft area of the metal body 13 to the left of the disk area 15 in FIG. 1. They are pressed against the disk area by means of a screw nut 21 which is screwed onto a threaded part of the shaft area 17.
  • the ceramic disks 19 are provided with electrical connections, by means of which the ceramic disks 19 are supplied with electrical excitation energy, which sets them in mechanical vibrations.
  • an elongated area 25 small adjoins the disk area 15 Diameter.
  • the free end of the elongated area 25 is provided with an atomizing plate 27 of enlarged diameter.
  • the elongated region 25 has an axial passage 29 which is connected to a radial passage 31 in the disk region 15. By means of the passages 31 and 29, liquid fuel is brought from a fuel supply (not shown) onto the outer surface of the atomizing plate 27.
  • the disk area 15, the elongated area 25 and the atomizing plate 27 represent an amplitude transformer in the form of a mechanical impedance converter which has impedance jumps due to the changes in diameter.
  • Such an ultrasonic oscillator is capable of harmonics which, however, need not be frequency multiples of the fundamental oscillation due to the jumps in impedance.
  • FIG. 2 shows a profile of the impedance Z of an ultrasonic oscillator of the type shown in FIG. 1 as a function of the excitation frequency f a .
  • the combination of a longitudinally vibratable structure with the atomizing plate 27 capable of bending vibrations creates a vibratory system with several degrees of freedom and thus with different natural resonance frequencies which generally do not need to be in harmony with one another.
  • the resonance points that occur can be seen from the impedance curve shown in FIG. 2 above the excitation frequency.
  • the closely related series and parallel resonance points are characteristic.
  • the sharply defined fundamental oscillation f 1 lying at 49 kHz and the likewise sharply defined harmonic f 2 at 102 kHz can be used in the example shown.
  • the excitation circuit generating the electrical excitation energy is now carried out so that f 1 or f 2 can be excited as required.
  • the excitation circuit contains a self-oscillating oscillator, the frequency of which is determined by the connected load, namely the ultrasonic oscillator.
  • a self-oscillating oscillator the frequency of which is determined by the connected load, namely the ultrasonic oscillator.
  • These frequency windows can e.g. B. can be realized by switchable low-pass filters, which are located in the frequency control loop in the feedback path from the ultrasonic atomizer to the controllable oscillator.
  • f ' 88 kHz
  • the heater is now operated so that during the cold start, for. B. at temperatures below 0 ° C, the heater control device, which determines the temporal operation of the heater, a control signal for switching on the frequency window ⁇ f1 is given to the excitation circuit.
  • a temperature sensor reports to the heater control device that a predetermined temperature threshold has been exceeded.
  • the excitation circuit is now switched to the frequency window ⁇ f2 and thus to operation with f2.
  • the heater is operated with temperature control, in which there are temporary shutdowns according to a two-point control, the low frequency f 1 is only required for the first (cold) start.
  • the following frequent control starts in on / off operation can be done with f2, since the heater does not cool down so much during the breaks that a restart with f1 would be necessary.
  • FIG. 3A A first preferred embodiment of an ultrasonic atomizer according to the invention is shown in FIG. 3A.
  • Two tuning inductances Lo1 and Lo2 are arranged in parallel with an ultrasound transducer 33. Depending on the switching position of a controllable switch 35, either the tuning inductance Lo1 or the tuning inductance Lo2 is connected in parallel to the ultrasound transducer 33. This parallel connection is connected via connection points A and B in parallel to a series connection which has the secondary winding of a transformer 37 and a sensor resistor 39.
  • the two ends of the primary winding of the transformer 37 are connected to the output side of a power amplifier 41.
  • connection point between the secondary winding of the transformer 37 and the sensor resistor 39 is connected to the input of a threshold amplifier 45 via a low-pass filter 43, which has a linear phase response in the operating frequency range of the excitation circuit. Its output forms a first input 47 of a phase detector 49, the output of which is connected via a loop filter 51 to the input 53 of a voltage-controlled oscillator (VCO) 55.
  • VCO voltage-controlled oscillator
  • the output of the VCO 55 is on the one hand to the input of the power amplifier 41 and on the other hand connected via a -90 ° phase shifter to a second input 57 of the phase detector 49.
  • the loop filter 51 is designed as an integrating circuit with a high DC gain of at least about 50 dB, typically about 100 dB.
  • a differential amplifier 59 is provided, the inverting input of which is connected via a resistor 61 to the output of the phase detector 49 and via a series circuit comprising a resistor 63 and a capacitor 65 to the output of the differential amplifier 59.
  • the non-inverting input of the differential amplifier 59 is connected to the partial voltage point 67 of a voltage divider with resistors 69 and 71 connected between the two poles of a voltage supply source.
  • the inverting input of the differential amplifier 59 is connected to a wobble generator 79, specifically via a controllable switch 80.
  • a second phase detector 101 is connected between the output of the voltage-controlled oscillator 55 and the output of the threshold amplifier 45, the output signal of which is led to a first control input of a changeover switch 102.
  • a second control input of the changeover switch 102 is connected to the output of a temperature sensor 73, which gives a control signal to the changeover switch 102 when a predetermined temperature threshold is exceeded.
  • the low-pass filter 43 and the voltage-controlled oscillator 55 are each provided with an arrow to indicate that they can be switched between different frequencies. These arrows are over dashed lines with the Output of the switch 102 connected to show that the switching of the low-pass filter 43 and voltage-controlled oscillator 55 is controlled by the switch 102.
  • the controllable switch 80 is switched by the output signal of the second phase detector 101.
  • FIG. 7 shows an equivalent circuit diagram of such a converter. This consists of the parallel connection of a capacitor C0 to a series circuit with an inductance L1, a capacitor C1 and a resistor R1. With C0 the capacitance of the transducer is designated far below the resonance frequency minus C1. L1, C1 and R1 are not actual components, but electrical equivalents with which the function of a piezoelectric transducer that works near its resonant frequency can be represented. Usually one symbolizes with L1 the vibrating mass of the transducer, with C1 its elasticity and with R1 the mechanical, real resistance.
  • circuit in FIG. 3A is now considered in more detail with regard to function and dimensioning considerations.
  • the ultrasonic transducer 33 is connected in parallel with an inductance, the value of which is selected so that it forms a parallel resonance circuit with C0 at the series resonance frequency of the transducer 33, then this inductance and the capacitance C0 together form a very high resistance, so that they can be neglected.
  • the driver circuit therefore sees in the parallel connection of the converter 33 and the inductance a component with a purely ohmic resistance, corresponding to R1. Since the converter 33 appears together with the inductance as a structure with purely ohmic resistance, the current flowing through this parallel connection is in the resonance point of the converter 33, and only there, exactly in phase with the voltage driving the converter.
  • the inductor connected in parallel with the converter 33 is now, depending on the switch position of the switch 35, the inductance Lo1, which tunes the C0 of the converter 33 at f1 away, or the inductance Lo2, which tunes the C0 of the converter 33 away at f2.
  • These inductors are dimensioned accordingly f1 or f2.
  • the circuit shown in Fig. 3A uses the principle that the driver voltage and the converter current are in phase at the resonance point of the converter 33. It contains a circuit that has a type of phase lock loop with high DC loop gain to compare the phase of the converter drive voltage with the phase of the resulting converter current.
  • the circuit operates in a manner which automatically brings the frequency of the driver voltage to an operating point at which the converter voltage and the converter current are in phase, ie to the resonant frequency of the converter. Due to the high DC loop gain, the circuit can be on the exact resonance point of each converter "snap" provided that its resonant frequency is within the operating range selected for the circuit. There is no increase in phase error when the transducer resonant frequency approaches the limits of the operating range chosen for the circuit.
  • the voltage controlled oscillator 55 is designed to operate over a fixed frequency range that is wide enough to cover all possible deviations from the ideal series resonant frequency of the transducer. Such deviations can arise from the fact that the transducer is exposed to extreme temperature values, that the transducer is loaded with liquid to be atomized, through deposits on the transducer, aging of the transducer and the effect of manufacturing tolerances. Since the VCO 55 can only work in the defined frequency range, operation at undesired harmonic frequencies is not possible.
  • the output signal of the VCO 55 is buffered and amplified by the power amplifier 41 feeding the primary winding of the transformer 37.
  • the output transistors of the power amplifier 41 are operated as saturated switches, so that a square-wave output voltage results at the output of the power amplifier 41.
  • the transformer 37 increases the driving voltage to a value that is suitable for driving the converter with the desired power value.
  • the inductance of the secondary winding of the transformer 37 has a much higher value than the tuning inductance Lo1 or Lo2, so that the secondary winding of the transformer 37 has no influence on the tuning compensation of the nominal capacitance C0 of the converter 33.
  • the output voltage of the secondary winding of the transformer 37 is applied to the converter 33 via the sensor resistor 39, which has a low resistance value. Since the nominal capacitance Co of the converter 33 is almost completely eliminated by compensation through the tuning inductance Lo1 or Lo2, and without being influenced by the secondary winding of the transformer 37, the sensor resistor 39 sensing the converter current is not impaired by the high current which flows between the Tuning inductance Lo1 or Lo2 and the capacitance Co of the converter 33 circulates.
  • the sensor resistor 39 generates a signal in the line 75 connecting the sensor resistor 39 to the low-pass filter 43, which signal is proportional to the current flowing through the converter. At the series resonance frequency of converter 33, the current proportional signal on line 75 is exactly in phase with the converter driver voltage.
  • the current phase leads the voltage phase, so that the converter appears capacitive.
  • the current signal follows the driver voltage, so that the converter 33 appears to be inductive. Above the parallel resonance, the converter 33 appears capacitive again.
  • the driver voltage is a square wave signal
  • the resulting converter current is rich in harmonics. Since one task of the excitation circuit is to compare the phase of the converter driver voltage with that of the resulting current, it is necessary to remove all harmonics from the current signal in order to prevent the circuit from operating incorrectly. The use of a conventional low-pass filter to remove these harmonics would give the current signal a frequency-dependent phase shift and would therefore make the current signal useless for the intended one Make purpose.
  • a low pass filter with a linear phase response is therefore used in order to switch off the harmonics present in the current signal without impairing the phase of the signal of interest.
  • the low-pass filter 43 generates a negligible phase shift and damping over the entire operating frequency range of the VCO 55. Above the upper limit of the frequency operating range of the VCO 55, however, sharp damping sets in.
  • the output signal of the low-pass filter 43 which has a linear phase response, is a purely sinusoidal signal, which is the fundamental frequency component of the current signal on line 75. All harmonics resulting from the rectangular driver voltage have been removed.
  • This cleaned current signal is amplified with the aid of the threshold value amplifier 45 and used as one of the two input signals of the phase detector 49.
  • the threshold amplifier 45 serves two purposes. On the one hand, it amplifies the low-value signal present at the output of the low-pass filter 43 to a signal with a value as required by the phase detector 49. In the present circuit, it is favorable to use a type for the phase detector which needs a square wave as the input signal. Therefore, the gain of the threshold amplifier 45 is set to a very high value.
  • the second function of the threshold amplifier 45 is to prevent very low level current signals from passing through to the phase detector 49.
  • the current flowing through it is minimal. Because voltage and current even if parallel resonance is in phase, the circuit could try to lock onto the parallel resonance point. However, since this circuit is optimized for operation with series resonance, an incorrect mode of operation would result if the circuit latched onto the parallel resonance point. This is prevented by the fact that the threshold value of the threshold amplifier 45 is selected such that the current level for parallel resonance is below the threshold value. Therefore, the current signal occurring in parallel resonance cannot pass through the threshold amplifier 45 to the phase detector 49 and the circuit cannot attempt to lock onto the parallel resonance point.
  • the signal supplied to the second input 57 of the phase detector 49 corresponds to the converter driver voltage. It can be conveniently removed from the VCO output since there is only a very small phase difference between the output signal of the VCO 55 and the high voltage signal at the converter 33 itself, so that this signal can be used as the second input signal of the phase detector 49.
  • the phase detector 49 is preferably a multiplying analog phase detector or a "pseudo-analog" phase detector, ie a digital phase detector, the behavior of which is very similar to that of a multiplying analog phase detector, like a digital EXCLUSIVE OR logic circuit, since these Detector types have a high tolerance to electrical noise, which will be present due to the proportion of harmonics in the output signal of the excitation circuit.
  • a multiplying phase detector works with a nominal phase difference of 90 ° between its inputs if the phase error is 0 is. Therefore, a -90 ° phase shifter 77 is connected upstream of the second input 57.
  • the sequential phase detector is less recommended because of its sensitivity to noise.
  • the output signal of the phase detector 49 contains the sum and the difference of the two input frequencies which are fed to the phase detector 49.
  • the two input frequencies are the same, since the converter current must have the same frequency as the converter drive voltage, although there may be a phase difference between the two. Therefore, the difference is 0 Hz and the sum is twice the input frequency.
  • the loop filter 51 is used to suppress the sum frequency, leaving only the difference signal, which is a DC voltage signal, and is used as an input signal to control the frequency of the VCO 55.
  • the loop filter 51 is a low-pass filter that is designed in the form of an integrator, which is modified to ensure the loop stability, instead of a passive RC low-pass filter that is usually used.
  • the loop filter 51 serves two purposes.
  • the first purpose is to filter out the sum frequency component from the output signal of the phase detector 49, so that only a DC voltage remains as a control voltage at the input of the VCO 55.
  • the second purpose of the loop filter 51 is very important for the operation of this circuit. It consists in generating a very high DC gain within the loop. This high DC loop gain enables the circuit to snap to the exact resonant frequency of the converter. If the loop gain were low, the phase relationship between the two input signals of the phase detector 49 would not be constant 90 °. In the case of a conventional RC low-pass filter, as is often used as a loop filter, the phase relationship of the two input signals of the phase detector 49 would change from 0 ° at one end of the VCO range to 180 ° at the other end of the VCO range. A phase shift of 90 ° would only occur in the middle of the VCO frequency range.
  • the converter 33 would only be operated at its resonance frequency if it were very close to the center frequency of the VCO 55.
  • an amplifier with high DC voltage gain in the present case an integrator, which is connected between the phase detector 49 and the VCO 55, forces a constant phase shift of 90 ° between the two inputs of the phase detector 49, regardless of the frequency.
  • the integrator used for the loop filter 51 works as follows:
  • the voltage at the reference input (non-inverting input) of the operational amplifier 59 is set to the value at which the VCO 55 is operated at its center frequency, and this would produce a phase shift of 90 ° between the inputs of the phase detector 49. Since the integrator acts like an amplifier with high DC voltage gain when the loop is locked in, there is only a very small voltage deviation at the inverting input with respect to the reference voltage at the non-inverting input of operational amplifier 59 is required to cause the output signal of the integrator to transition from one extreme to the other extreme of the input voltage range of VCO 55.
  • phase detector 49 This means that the output signal of the phase detector 49 is always very close to its central point and therefore the inputs always have a phase distance of 90 °.
  • the phase change between the inputs of phase detector 49 is reduced by a factor that is equal to the DC gain of the integrator. And this is typically around 100 dB.
  • the integrating effect is generated by the action of the capacitor 65.
  • the linearly decreasing frequency characteristic of the integrator provides the desired low-pass filter effect. Since the loop is of the second order type, the basic integrator circuit with resistors 61 and 63 has been modified to ensure loop stability.
  • the circuit forms a second order phase lock loop or PLL circuit.
  • the loop input signal is the current signal from the converter.
  • the phase detector 49 compares the phase of this current signal with the phase of the VCO output signal, ie with the phase of the converter drive voltage signal and changes the frequency of the VCO 55 until a phase difference 0 ° appears between the voltage signal and the current signal. Since the operation in parallel resonance is blocked by the threshold amplifier 55, the circuit can only work with series resonance.
  • the excitation circuit described thus operates a piezoelectric transducer 33 exactly at its natural series resonance frequency, provided that this resonance frequency is within the predetermined frequency range of the VCO 55.
  • the circuit follows the changes in resonance frequency that may occur for the reasons given above. For the ability of the circuit to snap exactly to the resonance point of the converter 33, it makes no difference whether the resonance point is in the middle or at the limits of the working range of the VCO 55.
  • the circuit always drives converter 33 so that its voltage and current are in phase.
  • the low-pass filter 43 and the VCO 55 are, as already mentioned, in the embodiment shown in FIG. 3A switchable between a lower operating frequency range, which corresponds to the previously described frequency window ⁇ f1, and a higher operating frequency range, which corresponds to the previously mentioned frequency window ⁇ f2.
  • the switch 35 can be used to switch between the tuning inductances Lo1 and Lo2. The switchover between the two operating frequency ranges is controlled by the switch 102 from the output signal of the temperature sensor 73.
  • a temperature below a predetermined temperature threshold for example 0 ° C
  • an operating frequency range of the low-pass filter 43 and the VCO 55 is controlled in accordance with the frequency window ⁇ f 1 and the tuning inductance Lo1 the converter 33 is connected in parallel.
  • a working range of the low-pass filter 43 and the VCO 55 controlled according to the upper frequency window ⁇ f2 and the tuning inductance Lo2 the converter 33 connected in parallel.
  • the low-pass filter 43 and the VCO 55 are switched from the switch 102 to the low operating frequency range and the tuning inductance Lo1 is activated.
  • the switch 80 is closed.
  • the wobble generator 79 is therefore connected to the loop filter 51, and the VCO 55 is controlled to find the low resonance frequency f 1. If the resonance frequency f 1 is reached, which is determined by the second phase detector 101, the switch 80 opens and the circuit arrangement snaps onto the low resonance frequency.
  • the changeover switch 102 is released for switching over the low-pass filter 43 and VCO 55 as a function of the temperature sensor 73.
  • the changeover switch 102 switches the low-pass filter 43 and the VCO 55 to the high resonance frequency f2 and the tuning inductance Lo2 is activated. Since f2 is a harmonic of f1, the switch 80 can remain open. The circuit arrangement then snaps to f2 without wobbling again.
  • a timing element (not shown) can be provided which causes the changeover switch 102 to switch from f 1 to f 2 after a predetermined period of time.
  • such a timer can be provided instead of a temperature sensor.
  • the time constant of the timing element is dimensioned such that the ultrasonic oscillator is operated at f 1 for such a long time that the temperature threshold (not measured in this embodiment) is reliably reached even when the heater is switched on at a very low temperature.
  • the temperature sensor 73 and a timer are provided, it is advisable to give priority to the temperature sensor so that after switching on at low temperature the temperature threshold for the transition from f 1 to f 2 is definitely reached.
  • the time constant of the timing element can then be chosen to be correspondingly shorter.
  • FIG. 3B A second preferred embodiment of an ultrasonic atomizer according to the invention is shown in FIG. 3B.
  • This embodiment corresponds to the embodiment shown in FIG. 3A as far as the circuit part to the left of the connection points A and B is concerned. Only the circuit part to the right of these circuit points is different. In connection with FIG. 3B, only this circuit part to the right of the circuit points A and B is therefore described.
  • the two tuning inductances Lo1 and Lo2 are provided in FIG. 3A, of which, depending on the switching position of the switch 35 and thus under the control of the switch 102, one or the other tuning inductance is connected in parallel with the converter 33.
  • the powers to be switched with switch 35 are considerable. It can therefore be of It is an advantage to avoid such a switchover.
  • FIG. 3B Such a solution is shown in FIG. 3B.
  • the converter 33 on the one hand a tuning inductance Lo and on the other hand a series connection of a tuning inductance L2 and a capacitor C2 are connected in parallel.
  • the converter 33, the tuning inductors Lo and L2 and the capacitor C2 form a network that enables a series resonance of the converter 33 both at the low frequency f1 and at the high frequency f2.
  • This network is dimensioned so that on the one hand Lo and Co (see equivalent circuit in Figure 8) and on the other hand L2 and C2 each form a resonance at different frequency points. Both the Lo and Co as well as the resonance formed by L2 and C2 are at a suitable frequency point between f1 and f2.
  • both resonance circuits are connected together, two different parallel resonance frequencies arise.
  • One is below the normal resonance of Lo / Co and L2 / C2, while the other is above it.
  • the one parallel resonance frequency is chosen so that it lies at f1 and occurs when the capacitive reactance of the branch L2 / C2, which is capacitive below its own resonance frequency, with the inductive reactance of the branch Lo / Co, which is inductive below its own resonance frequency is to resonate with each other.
  • the result is a parallel resonance circuit of high impedance, which tunes the capacitance Co of the converter 33 away at f 1.
  • the second resonance point is chosen so that it lies at f2 and occurs when the inductive reactance of the branch L2 / C2, which is inductive above its own resonance frequency, with the capacitive reactance of the branch Lo / Co, which is capacitive above its own resonance frequency, resonates.
  • the result is a second parallel resonance circuit with high impedance, which tunes the Co of the converter 33 at f2.
  • this network also has a single series resonance. This is the series resonance of L2 and C2. With this series resonance, a very low resistance, almost like a short circuit, appears across the output of the driver generator. Usually this would be a problem. Not so in the present case, because this series resonance occurs at a frequency between f1 and f2.
  • the excitation circuit according to FIG. 3B never works at this frequency, since the two switchable frequency ranges of the VCO 55 do not include this frequency.
  • FIGS. 4 and 5 Two examples of a switchable VCO 55 according to the embodiments according to FIGS. 3A and 3B are shown in FIGS. 4 and 5.
  • the embodiment of a VCO 55 shown in FIG. 4 contains in block 81 all circuit components of a VCO with the exception of the components determining the frequency range. These consist of a capacitor 83 and a resistor 85, with which the width of the operating frequency range of the VCO 55 is set. In addition, a series connection with resistors 87 and 91 is provided, the total resistance of which determines the position of the operating frequency range on the frequency scale. The total resistance value of this series connection can be changed with the aid of a switching transistor 93 which is connected in parallel with the resistor 91. If transistor 93 is switched off, resistor 91 cooperates and becomes an operating frequency range causes in the lower frequency range, corresponding to the lower frequency window ⁇ f1.
  • FIG. 5 for a switchable VCO 55 is the same as the embodiment shown in FIG. 4, with the exception that the resistor 91 and the switching transistor 93 bridging it are not present, but the capacitor 83 has a further capacitor 95 is connected in parallel, which can be switched effective and ineffective using a controllable switch 97.
  • the operating frequency range of the VCO 55 corresponds to the lower frequency window ⁇ f1 or the upper frequency window ⁇ f2.
  • the control connection of the transistor 93 or the controllable switch 97 is brought into one or the other switching state in accordance with the output signal of the temperature sensor 73.
  • FIG. 6 An embodiment of a switchable low-pass filter 43 according to FIGS. 3A and 3B is shown in FIG. 6.
  • This low-pass filter has two stages and has a series inductance 99 and 101 and a main transverse capacitance 103 and 105 in each stage.
  • a parallel capacitance 107 or 109 is connected in parallel to the latter, which is connected in series with a controllable switch 111 or 113.
  • the control inputs of the controllable switches are controlled by a signal that from the output signal of the temperature sensor 73 depends.
  • the controllable switches 111, 113 are switched on or off.
  • the low-pass filter 43 is preferably designed as a phase-linear low-pass filter.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Special Spraying Apparatus (AREA)

Claims (10)

  1. Un pulvérisateur à ultrason destiné à la pulvérisation de liquides, particulièrement de carburant liquide dans le contexte d'appareils de chauffage, avec un oscillateur à ultrason (11), avec un transformateur à ultrason (19, 33) transformant l'énergie d'excitation électrique en oscillations à ultrason et avec une plaque de pulvérisateur (27) qui y est couplée, sur la surface de laquelle on amène du liquide à pulvériser provenant d'une réserve de liquide et avec une commutation d'excitation électrique au moyen de laquelle l'oscillateur à ultrason (11) est excité en oscillation de résonance, caractérisé en ce qu'un oscillateur à ultrason (11) pouvant produire des harmoniques, est prévu, la fréquence de la commutation d'excitation est commutable entre différentes fréquences de résonance (f₁, f₂) de l'oscillateur à ultrason, et qu'un dispositif de commande de commutation (73, 102) est prévu, qui incite la commutation d'excitation, selon un critère de température et/ou de temps, à fournir une fréquence correspondant à une fréquence de résonance de basse fréquence (f₁) et à fournir ensuite une fréquence de résonance de haute fréquence (f₂) de l'oscillateur à ultrason.
  2. Pulvérisateur à ultrason selon la revendication 1, caractérisé en ce que la commutation de la fréquence de la commutation d'excitation s'effectue en fonction du temps et/ou de la température.
  3. Pulvérisateur à ultrason selon au moins l'une des revendications 1 ou 2, caractérisé en ce que la fréquence d'excitation de la commutation d'excitation est commutable entre plusieurs oscillations fondamentales de modes d'oscillation différents, entre une oscillation fondamentale (f₁) et une oscillation harmonique (f₂) ou entre différentes oscillations harmoniques de l'oscillateur à ultrason (11).
  4. Pulvérisateur à ultrason selon au moins l'une des revendications 1 à 3, caractérisé en ce que le dispositif de commande de commutation (102) est pourvu d'un système temporaire, qui commande à l'expiration d'une durée de temps prédéterminée depuis le début du fonctionnement en fréquence de résonance à basse fréquence (f₁) la commutation à un fonctionnement de résonance à haute fréquence.
  5. Pulvérisateur à ultrason selon au moins l'une des revendications 1 à 4, caractérisé en ce que le dispositif de commande de commutation (73, 102) dispose d'un palpeur de température (73) pour la détection de la température utile, qui déclenche en cas de dépassement vers le bas ou vers le haut d'un seuil de température prédéterminé, la commutation sur fonctionnement de résonance à basse ou haute fréquence.
  6. Pulvérisateur à ultrason selon les revendications 4 et 5, caractérisé en ce que le pulvérisateur à ultrason démarre toujours au début de son fonctionnement en basse fréquence de résonance (f₁) et que la commutation à la fréquence de résonance supérieure (f₂) s'effectue ensuite en privilégiant la commande de commutation par le palpeur de température (73), à l'expiration de la durée de temps prédéterminée, ou, lorsqu'ensuite le seuil de température n'est pas encore atteint, après le dépassement par le haut du seuil de température.
  7. Pulvérisateur à ultrason selon au moins l'une des revendications 1 à 6, caractérisé en ce que la commutation d'excitation est pourvue d'un oscillateur commandé par tension (55), qui est alimenté en dépendance du dispositif de commande de commutation (73, 102) par une tension de commande atteignant la fréquence d'excitation à basse (f₁) ou à haute fréquence (f₂).
  8. Pulvérisateur à ultrason selon au moins l'une des revendications 1 à 7, caractérisé en ce que la commutation d'excitation dispose d'un filtre passe-bas pilotable (43), qui est commandé en fonction du dispositif de commande de commutation (73, 102) pour laisser passer uniquement la fréquence d'excitation à basse fréquence ou celle de basse et de haute fréquences.
  9. Pulvérisateur à ultrason selon la revendication 7 ou 8, caractérisé en ce que la commutation d'excitation est pourvue d'une commutation PLL avec un oscillateur commandé par tension (55) et d'un filtre passe-bas (43) et que la fréquence utile de l'oscillateur commandé par tension (55) et la fréquence de passage du filtre passe-bas (43) est commutable en fonction du dispositif de commande de commutation (73, 102) sur la fréquence d'excitation à basse (f₁) ou haute fréquence (f₂)
  10. Pulvérisateur à ultrason selon la revendication 9, caractérisé en ce qu'un dispositif de compensation (Lo1, Lo2, Lo, L2, C2) est couplé parallèlement au transformateur à ultrason (33) au moyen duquel le transformateur à ultrason (33) est accordé sur une oscillation de résonance série (f₁) à basse (f₁) ou à haute fréquence (f₂), qu'un senseur de courant (39) est associé au transformateur à ultrason (35) dont le signal de sortie est amené vers une première entrée (47) d'un comparateur de phase (49) qui présente une seconde entrée (57) reliée à la sortie de l'oscillateur commandé par la tension (55) et qu'entre la sortie du comparateur de phase (49) et l'entrée de l'oscillateur commandé par tension (55) est commuté un filtre passe-bas à forte amplification qui bloque la composante de la fréquence de sommation dans le signal de sortie du comparateur de phase.
EP90119084A 1989-10-05 1990-10-04 Pulvérisateur à ultrason Expired - Lifetime EP0421439B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3933300A DE3933300A1 (de) 1989-10-05 1989-10-05 Ultraschallzerstaeuber
DE3933300 1989-10-05

Publications (3)

Publication Number Publication Date
EP0421439A2 EP0421439A2 (fr) 1991-04-10
EP0421439A3 EP0421439A3 (en) 1992-03-18
EP0421439B1 true EP0421439B1 (fr) 1995-02-01

Family

ID=6390897

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90119084A Expired - Lifetime EP0421439B1 (fr) 1989-10-05 1990-10-04 Pulvérisateur à ultrason

Country Status (2)

Country Link
EP (1) EP0421439B1 (fr)
DE (2) DE3933300A1 (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004055326B3 (de) * 2004-11-16 2006-03-16 Webasto Ag Verfahren und Vorrichtung zur Erzeugung eines feinverteilten Kraftstoffnebels
NL1036416C2 (nl) * 2009-01-13 2010-07-14 Cooeperatieve Vereniging Easymeasure U A Werkwijze en inrichting voor overdracht van elektrische energie naar een transducer en toepassing van deze transducer ter behandeling van een fluidum.
WO2019198162A1 (fr) * 2018-04-10 2019-10-17 日本たばこ産業株式会社 Unité d'atomisation
CN108787299A (zh) * 2018-06-15 2018-11-13 江苏大学 一种气助式三参数威布尔低频超声雾化喷头
CN113364453B (zh) * 2020-03-06 2023-01-17 海能达通信股份有限公司 一种环路滤波器及锁相环
CN112641131A (zh) * 2020-11-27 2021-04-13 上海烟草集团有限责任公司 一种过滤效果可控的液雾过滤烟具
CN114468394A (zh) * 2022-02-15 2022-05-13 哈勃智能传感(深圳)有限公司 一种谐振频率提取方法、驱动方法及雾化系统

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH415137A (de) * 1962-01-29 1966-06-15 Exxon Research Engineering Co Elektronischer Oszillator mit einer durch ihn betriebenen Belastung mit mindestens einer Resonanzfrequenz
US3158928A (en) * 1962-03-30 1964-12-01 Aeroprojects Inc Method and means for operating a generating means coupled through a transducer to a vibratory energy work performing device
JPS5123342B2 (fr) * 1972-07-31 1976-07-16
DE3625149A1 (de) * 1986-07-25 1988-02-04 Herbert Dipl Ing Gaessler Verfahren zur phasengesteuerten leistungs- und frequenzregelung eines ultraschallwandlers sowie vorrichtung zur durchfuehrung des verfahrens
DE3625461A1 (de) * 1986-07-28 1988-02-04 Siemens Ag Erregerkreis fuer einen ultraschall-zerstaeuber
CS550488A3 (en) * 1987-08-17 1992-11-18 Satronic Ag Ultrasonic generator circuitry
EP0340470A1 (fr) * 1988-05-06 1989-11-08 Satronic Ag Procédé et circuit pour exciter un transducteur par ultrasons, et leur utilisation pour l'atomisation d'un liquide

Also Published As

Publication number Publication date
EP0421439A2 (fr) 1991-04-10
EP0421439A3 (en) 1992-03-18
DE3933300A1 (de) 1991-04-18
DE59008408D1 (de) 1995-03-16

Similar Documents

Publication Publication Date Title
EP0254237B1 (fr) Procédé d'ajustement de la puissance et de la fréquence d'un transducteur ultrasonore par commande de phase et dispositif pour l'application du procédé
DE2935282C2 (de) Drahtlose Temperaturmeßeinrichtung
DE2338503C3 (de) Schaltungsanordnung zum Erregen des Wandlers eines Ultraschall-Zerstäubers
DE2905132C2 (fr)
DE10122065B4 (de) Vorrichtung zur Erzeugung von Flüssigkeitströpfchen mit einer in Schwingungen versetzten Membran
DE2453153C2 (de) Spannungsgesteuerter Oszillator
EP0918383A2 (fr) Laser à pulsions avec contrÔle de la première pulsion
EP0329988B1 (fr) Générateur de puissance haute fréquence
EP0340470A1 (fr) Procédé et circuit pour exciter un transducteur par ultrasons, et leur utilisation pour l'atomisation d'un liquide
DE4322388C2 (de) Schaltungsanordnung zum sicheren Anschwingen von Ultraschalldesintegratoren
DE4412900C2 (de) Verfahren und Vorrichtung zum Feststellen des Einsetzens einer Überflutung eines Ultraschallzerstäubers
DE2849782A1 (de) Piezoelektrischer schwinger
EP0421439B1 (fr) Pulvérisateur à ultrason
DE2353840A1 (de) Oberflaechenwellenoszillator
EP0303944A1 (fr) Procédé et circuit pour l'excitation d'un vibrateur ultrasonore et leur application à la pulvérisation d'un liquide
DE19828622B4 (de) Breitbandoszillator mit automatischer Vorspannungssteuerung
WO2002040950A1 (fr) Procede et dispositif de mesure de niveau
EP1977190B1 (fr) Appareil de mesure de distance
DE2931602C2 (de) Erregerkreis für einen Ultraschall- Zerstäuber
EP2390634B1 (fr) Dispositif de fonctionnement d'une unité pivotante d'un résonateur à vibrations
DE2038435C3 (de) Oszillator
DE60125071T2 (de) Hochspannungsimpulsgenerator und mit solchem Generator ausgerüstete elektrische Versorgungseinrichtung
DE3222425A1 (de) Generator zum antrieb eines piezoresonators
DE60007740T2 (de) Frequenzgeneratorschaltung
DE2165725A1 (de) Piezoelektrisches schwingsystem fuer fluessigkeitszerstaeubung

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): DE FR GB IT NL SE

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): DE FR GB IT NL SE

17P Request for examination filed

Effective date: 19920309

17Q First examination report despatched

Effective date: 19940121

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

ITF It: translation for a ep patent filed

Owner name: BARZANO' E ZANARDO ROMA S.P.A.

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR GB IT NL SE

REF Corresponds to:

Ref document number: 59008408

Country of ref document: DE

Date of ref document: 19950316

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)

Effective date: 19950321

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19960717

Year of fee payment: 7

Ref country code: FR

Payment date: 19960717

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19960925

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19961031

Year of fee payment: 7

NLT1 Nl: modifications of names registered in virtue of documents presented to the patent office pursuant to art. 16 a, paragraph 1

Owner name: J. EBERSPAECHER GMBH & CO.

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19971004

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19971005

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19971031

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19980501

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19971004

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

Effective date: 19980501

EUG Se: european patent has lapsed

Ref document number: 90119084.3

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20021015

Year of fee payment: 13

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20040501

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20051004