JP2010509555A - Active control of an acoustic cooling system. - Google Patents

Abstract

  Signal processing for generating a cancellation signal for noise generated by a first transducer 3 for cooling by generating sound waves, a second transducer 4 for cooling by generating sound waves, and an acoustic cooling system The acoustic cooling system having the unit 6. The second transducer 4 converts the cancellation signal into a sound that at least partially cancels the noise.

Description

  The present invention relates to a resonant cooling system, ie a cooling system that is resonated, thereby producing a pulsating air flow that can be directed towards an object to be cooled.

  Today, for example, technology exists in the case where electrical components are cooled by an acoustic resonance system. The most important component of this type of system is an acoustic transducer, such as a piezoelectric element, PVDF (polyvinylidine difluoride) material, a loudspeaker or some other electromagnetic or electrostatic transducer. If the transducer is connected to a resonator, such as an open resonant pipe or tube or a Helmholtz resonator, a pulsating air flow is generated.

  This air stream is used for cooling purposes, for example in electronic circuits and systems or in light emitters. The pulsating airflow is more effective for cooling than the laminar airflow obtained when the conventional cooling technique is used.

  A convenient output of an acoustic resonant cooler is turbulence at the outlet of the resonator. These provide the actual cooling. However, unavoidably, some periodic air movement remains, and we perceive this as sound or more particularly as noise.

  US Pat. No. 6,625,285 discloses an acoustic cooling system with a noise reduction function. The cooling system includes a temperature and pressure sensor that provides input values for driving an acoustic drive element that acts as a cooler. When the system is activated to cool the system, noise is detected by the microphone. The detected noise is then used to determine drive parameters for a loudspeaker that produces a sound that cancels the noise generated by the system.

  It is an object of the present invention to provide an improvement over the above and prior art techniques.

  A detailed object is to provide an acoustic cooling system that can efficiently cool warm objects and also keep the noise level of the system at a low level.

  Accordingly, an acoustic cooling system is provided having a first transducer that cools by generating sound waves and a second transducer that cools by generating sound waves. The signal processing unit generates a cancellation signal for the noise generated by the acoustic cooling system, and the second transducer converts the cancellation signal into a sound that at least partially cancels the noise.

  The cooling system of the present invention is advantageous in that noise is reduced without requiring the incorporation of any complex noise reduction means. Rather, noise cancellation is also performed by the component that performs the cooling. Preferably, the sound waves for each transducer are generated as a fluid and preferably the noise is completely cancelled.

  The acoustic cooling system may include a noise detector for detecting noise generated by the acoustic cooling system, the noise detector supplying a detected noise signal to the signal processing unit, and dynamic noise cancellation Is advantageous in that can be achieved.

  The signal processing unit may generate a predetermined cancellation signal, which is advantageous in that a simpler cooling system can be used.

  Each transducer may have a resonator that is advantageous in that the desired resonance can be obtained for each pulsating airflow.

  The second transducer can be excited by a signal obtained by nonlinear processing of the signal exciting the first transducer and offers the possibility of dealing with the nonlinearity of the transducer, ie the first It is possible to cancel noise with signal components in the harmonics of the fundamental frequency of the drive value for one transducer.

  The drive power of the second transducer can substantially correspond to the drive power of the first transducer, providing simple and efficient control of the second transducer. It will be understood that the drive power is the power used to generate the cooling exerted by the transducer.

  The resonators can extend in a generally parallel direction, or the resonators have corresponding openings that are oriented in generally opposite directions to provide a versatile and flexible configuration of the cooling system. Can be arranged.

  According to another aspect of the present invention, a method of driving an acoustic cooling system, the step of generating sound waves with a first transducer to cool, and the step of generating sound waves with a second transducer to cool. Generating a cancellation signal for noise generated by the acoustic cooling system by a signal processing unit; and converting the cancellation signal into sound that at least partially cancels the noise by the second transducer; Are provided.

  The method may further comprise detecting the noise generated by the acoustic cooling system with a noise detector.

  The method may also include providing a predetermined cancellation signal for the signal processing unit.

  The method of the present invention may further include directing acoustic waves from each transducer by a respective resonator.

  It should be noted that the method of the present invention can incorporate any of the features described above in connection with the cooling system of the present invention and has the same corresponding effect. The sound produced by the transducer can of course have any suitable frequency.

It is the schematic of the cooling system by 1st Example. It is the schematic of the cooling system by 2nd Example.

  Embodiments of the present invention will now be described, by way of example, with reference to the accompanying schematic drawings.

  FIG. 1 illustrates an acoustic cooling system 1 comprising two transducers 3, 4. Each transducer 3, 4 generates a sound wave for cooling, and has respective acoustic resonators 7, 8 having respective openings 10, 11. In the embodiment of FIG. 1, the resonators 7 and 8 are arranged in parallel to each other. The signal generator 13 sends a sine wave drive signal S 1 to the first transducer 3, and the same signal S 1 is sent to the second transducer via the nonlinear circuit 14 and the signal processing unit 6.

  The openings 10 and 11 are typically arranged to be directed toward a warm object (not shown) to be cooled, and a temperature sensor (not shown) takes the input value as the level of the drive signal S1. I.e. to the signal generator 13 for the determination of the level of cooling to be exerted by the system 1.

  When the system 1 is activated, noise is usually generated and the noise is detected by a noise detector 5 or a microphone. The detected noise is sent to the signal processing unit 6 as a signal ε.

The signal S1 sent from the signal generator 13 to the non-linear circuit 14 is converted by the non-linear circuit 14 into a signal S′1 including a harmonic frequency component of S1.
S′1 may be, for example, a periodic pulsed signal or a “sawtooth” signal.

  Of course, any suitable method of generating the signals S1 and S′1 can be used as long as the sound obtained from one of the signals can cancel the sound obtained from the other signal.

  For example, the two signals S1 and S′1 can be generated by searching from a look-up table having values ranging from sin (0) to sin (2π). Each signal is associated with a respective pointer that repeatedly traverses the lookup table, and since the pointers are different, a phase shifted sine wave signal is generated. One of the pointers can be traversed through the lookup table, for example at twice the speed of the other pointer, resulting in two overtone signals.

  In another variant, the two signals S1 and S′1 are generated by using a sine / cosine generator and assigning respective angle values to each signal S1, S′1. This makes it possible to generate an arbitrary phase for the signal only by adapting the two input values. Of course, it is also possible to use any other suitable trigonometric formula for generating a S1, S′1 signal whose phase shifted or overtone signal.

  The signal processing unit 6 has an adaptive control element 9 that adaptively filters S′1 by minimizing the correlation between the noise signal ε and the signal S′1. The resulting signal S ″ 1 is then used to drive the second transducer 4 to cancel the noise detected by the noise detector 5 and to perform cooling.

  That is, the signal S′1 is filtered by an adaptive filter, and the exact transfer function is determined by the output signal ε of the microphone. The criterion for adaptation is to make the correlation between ε and S′1 as small as possible. This is a known procedure in the field of adaptive filtering (either analog or digital). This can be performed in various ways that can be arbitrarily selected. By making ε as small as possible, the remainder of the original acoustic excitation signal at the microphone location (which results in unwanted noise) is minimized and unwanted noise is significantly reduced.

  Due to the relatively large wavelength of the acoustic wave (typically 34 cm at 1 kHz with respect to the atmosphere), complete noise cancellation at the exact location of the noise detector 5 is greater from the resonator outlets 10, 11. Provides improved noise characteristics over distance.

  Preferably, the second transducer 4 “follows” the first transducer 3 in terms of cooling output. If the first transducer 3 begins to work more securely for any reason, the second transducer 4 will automatically work in the same way. This means that if the cooling action of the first transducer 3 is done depending on the actual temperature of the object to be cooled (eg via a temperature sensor), the second transducer 4 responds accordingly. This means that its own cooling operation is automatically adapted.

  In one variant, the noise detector 5 is omitted, in which case the predetermined parameters for the noise cancellation signal are stored in the signal processing unit 6. The determination of these parameters preferably uses, for example, a temporary microphone at a specific distance from the system 1 and by determining the parameters such that noise at the position of the temporary microphone is offset. Performed during assembly of the cooling system 1.

  FIG. 2 illustrates a second embodiment in which the same components as in FIG. 1 have the same reference numerals. Here, the resonators 7 and 8 are disposed such that the openings 10 and 11 face in opposite directions, and the noise detector 5 is disposed on the side of the resonators 7 and 8.

  In practice, the detailed application of the cooling system 1 (especially its physical shape and the location of the object to be cooled) will determine which arrangement of the transducer / resonator is most appropriate.

  It should be noted that any suitable noise cancellation method principle can be used without departing from the scope of the present invention.

  Even if the system is described as having two transducers, as long as at least one of the transducers is configured to both cancel noise and provide cooling, any suitable Any number of transducers can be used.

  Preferably, the two transducers 3, 4 generate sound waves of a fluid (eg air), but the sound waves can be generated in any suitable medium.

Claims (12)

  An acoustic cooling system having a first transducer that cools by generating sound waves, the second transducer cooling by generating sound waves, and a cancellation signal for noise generated by the acoustic cooling system. An acoustic cooling system, wherein the second transducer converts the cancellation signal into a sound that at least partially cancels the noise.   The acoustic cooling system according to claim 1, further comprising a noise detector for detecting the noise generated by the acoustic cooling system, the noise detector supplying the detected noise signal to the signal processing unit. .   The acoustic cooling system of claim 1, wherein the signal processing unit generates a predetermined cancellation signal.   The acoustic cooling system according to claim 1, wherein each transducer has a resonator.   5. The acoustic cooling system according to claim 1, wherein the second transducer is excited by a signal obtained by nonlinear processing of a signal that excites the first transducer. 6.   The acoustic cooling system according to any one of claims 1 to 5, wherein the second transducer driving power substantially corresponds to the driving power of the first transducer.   The acoustic cooling system according to claim 4, wherein the resonator extends in an essentially parallel direction.   The acoustic cooling system according to any one of claims 4 to 6, wherein the resonators are arranged with corresponding openings that are oriented essentially in opposite directions. Generating a sound wave by a first transducer for cooling;
Generating sound waves by a second transducer for cooling;
Generating a cancellation signal for noise generated by the acoustic cooling system by a signal processing unit;
Converting the cancellation signal into a sound that at least partially cancels the noise by the second transducer;
A method of driving an acoustic cooling system comprising:   The method of claim 9, further comprising detecting the noise generated by the acoustic cooling system with a noise detector and providing the detected noise signal to the signal processing unit.   The method of claim 9, further comprising providing a predetermined cancellation signal for the signal processing unit.   12. A method as claimed in any one of claims 9 to 11 further comprising the step of directing sound waves from each transducer by a respective resonator.

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