Gas pulse generating device

Abstract

An air pulse generating device comprises a membrane structure operated at an ultrasonic operation frequency and a resonant cavity formed on one side of the membrane structure. Resonance is formed in the resonant cavity. The frequency response of the acoustic characteristic of the gas pulse generating device has a peak at the ultrasonic operating frequency due to the resonant cavity.

Description

Technical Field

[0001] The invention relates to a gas pulse generating device, in particular to a gas pulse generating device with a resonance chamber embedded therein. Background Art

[0002] Unless otherwise indicated, the practices described below are not prior art within the patent scope of the present invention, and the contents of this paragraph should not be included in the prior art.

[0003] Speaker drivers and rear enclosures are two major design challenges in the speaker industry. Existing speakers have difficulty covering the entire audio frequency band (e.g., 20 Hz to 20 KHz). In order to produce high-fidelity sound with a sufficiently high sound pressure level, the radiation / movement surface and volume / size of the rear enclosure of existing speakers must be large enough.

[0004] Air-pulse generating (APG) devices have been taught to overcome the design challenges faced by existing loudspeakers. However, previously disclosed APG devices generate airflow pulses. For loudspeaker applications (or air flow applications), this airflow needs to be efficiently converted into air pressure. Summary of the invention

[0005] Therefore, the main purpose of the present invention is to provide a gas pulse generating device to improve the deficiencies of the prior art.

[0006] An embodiment of the present invention provides an air pulse generating device, comprising a membrane structure, operating at an ultrasonic operating frequency; and a resonance chamber, formed on one side of the membrane structure; wherein resonance is formed in the resonance chamber; wherein, due to the resonance chamber, the frequency response of the acoustic characteristics of the air pulse generating device has a peak value at the ultrasonic operating frequency.

[0007] The beneficial effect of the present invention is that the present invention utilizes a resonant chamber to make the frequency response of acoustic impedance form a peak at the ultrasonic operating frequency, thereby effectively generating air pressure and further enhancing the sound pressure level. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0009] Figure 2 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0010] Figure 3 A resonant chamber according to an embodiment of the present invention.

[0011] Figure 4 FIG. 4 is a frequency response of a resonant chamber according to an embodiment of the present invention.

[0012] Figure 5 A resonant chamber according to an embodiment of the present invention.

[0013] Figure 6 FIG. 4 is a frequency response of a resonant chamber according to an embodiment of the present invention.

[0014] Figure 7 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0015] Figure 8 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0016] Fig. 9 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0017] Fig.10 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0018] Fig.11 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0019] Fig.12 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0020] Fig.13 FIG. 4 is a schematic diagram of an APG device according to an embodiment of the present invention.

[0021] Fig.14 FIG. 1 is a top view of a membrane structure of an APG device according to an embodiment of the present invention.

[0022] Fig.15 FIG. 4 is a top view of a cover structure of an APG device according to an embodiment of the present invention.

[0023] The reference numerals are as follows:

[0024] 10,90:Membrane structure

[0025] 10,20,30,40,50,60,70,80,82: Gas pulse generating device

[0026] 101,103: Petals

[0027] 102: Petal pair

[0028] 112: Virtual Valve

[0029] 115,115a,115b: Resonance chamber

[0030] 116,117: Cavity

[0031] 131,133,134: Anchoring part

[0032] 150,850,92: Cover structure

[0033] 151: wall

[0034] 202,204,206: Direction

[0035] 701,702:Reflector

[0036] 703,704: End

[0037] 713,715,716,723: Export

[0038] H116,H117:Distance DETAILED DESCRIPTION

[0039] The following inventions filed by the applicant are incorporated herein by reference in their entirety and become part of this specification: US Patent No. 11,323,797 regarding dynamic vent (DV), Patent No. 11,943,585 regarding APG device, and Application No. 18 / 829,245 regarding tooth-shaped flap edges.

[0040] In an APG device, a pair of opposing petals (e.g., U.S. Pat. No. 11,943,585 or Figure 1 or Figure 2 The flaps (flaps 101, 103) shown are manufactured by etching a film layer made of silicon or other suitable material, and are actuated by applying a voltage to a piezoelectric material (such as PZT) covering the pair of flaps. The pair of opposing flaps are used to generate common mode motion according to a signal SM and differential mode motion according to a pair of signals ±SV, thereby performing the functions of ultrasonic modulation and demodulation, respectively. This ultrasonic modulation and demodulation to baseband results in air mass movement (through a virtual valve 112 between the flap pair 101-103 at baseband frequencies). This air pump can be used as an audio speaker (to pump air bidirectionally at audio frequencies to produce audio sound waves), or as a unidirectional air pump for other applications (such as forced air cooling).

[0041] Airflow through the valve increases as the pressure differential across the valve increases. The instantaneous pressure on each side of the valve is generated by the movement of the flaps, which locally compress or expand the air. In order to increase the flow through the valve 112, patent No. 11,943,585 discloses that a cap with outlets is located above the flaps, and the cap forms a small chamber near the flaps with a size much smaller than the wavelength and has a small outlet to restrict the airflow. This causes a greater degree of compression / expansion of the air in the chamber and increases the pressure differential across the valve, thereby inducing greater airflow. As described in patent No. 11,943,585, this cap is not absolutely necessary, and considerable airflow can be achieved even without the cap.

[0042] An alternative method of increasing the local pressure variation around the valve is proposed here, rather than restricting the airflow in and out of the compression chamber. Resonant air cavities can be designed on one or both sides of the flap to increase the local ultrasonic pressure by confining the ultrasonic energy within the cavity. The resonance can be a Helmholtz resonance or a standing wave resonance. When the air mass at the outlet forms a mass-spring system with the volume of air in the chamber (the air volume acts as a spring), a Helmholtz resonance occurs at a specific frequency. When the acoustic reflector is at a preferred distance from the flap, so that the sound wave is reflected at the reflector, the reflected wave is superimposed with the incident wave to form constructive interference regions with high amplitude oscillating pressure (antinodes) and destructive interference regions with minimum pressure (nodes), and standing wave resonance occurs. At Figure 1 or Figure 2 In the embodiment shown, a pair of flaps 101 and 103 have a Helmholtz resonance chamber 115 on one side with an outlet 713. On the other side, Figure 2 The standing wave cavity 116 and the acoustic reflector 702 are shown, and the acoustic reflector 702 is separated from the petal by a distance H116.

[0043] In the present invention, the terms "chamber" and "cavity" are used interchangeably.

[0044] As described in Patent No. 11,943,585, Figure 1 and Figure 2The APG device 10 and 20 includes a membrane structure 104, the membrane structure 104 includes a flap pair 102, and the flap pair 102 includes flaps 101 and 103. The flaps 101 and 103 have anchoring portions 131 and 133, respectively. The flap pair 102 performs differential mode motion to form an opening 112 or a virtual valve 112, wherein "virtual valve" is used to emphasize the ability of the flap pair to be controlled to open or close, and "opening" is used to emphasize the state of controlling the flap pair, especially when the virtual valve is opened.

[0045] The flaps 101 and 103 generate ultrasonic pressure bidirectionally outwards from the flaps to the cavities 115 and 116 based on the common-mode displacement of the common-mode signal SM at the ultrasonic modulation / operating frequency, but with opposite polarities in these two directions. The effect of the Helmholtz resonance or standing wave resonance is to increase the ultrasonic pressure magnitude while maintaining opposite polarities on both sides of the flap. The flaps are also driven by the differential-mode signals ±SV superimposed on the common-mode signal, resulting in the opening of the virtual valve 112. The opening of the valve 112 is aligned in time with the pressure difference generated by the common-mode displacement, so that the pressure difference on both sides of the flap results in a net airflow (through the valve 112 during the ultrasonic cycle of the common-mode displacement).

[0046] In one embodiment, the ultrasonic modulation / operation frequency of the common mode signal (or modulated drive signal) SM may be 192kHz; and based on the differential mode motion, the demodulation frequency of the differential mode signal (or demodulated drive signal) SV may be 96kHz, which is half of the ultrasonic modulation / operation frequency.

[0047] The detailed working principle of the petal pair driven by the common / differential mode signal SM / SV and the common / differential mode motion and (de)modulation operation to generate ultrasonic pulses has been described in Patent No. 11,943,585 and will not be repeated here. In addition, the demodulation signal SV can be provided by the driving circuit disclosed in Application No. 18 / 396,678, and the modulation signal SM can be provided by the driving circuit disclosed in Patent No. 12,107,546. For the sake of brevity, it will not be repeated here.

[0048] In addition, the APG device 10 / 20 further includes a covering structure 150, and the outlet 713 is formed in the covering structure 150. The covering structure 150 may be a lid, a cover, etc. The covering structure 150 may be made by 3D printing or made of metal or silicon (for example, by a semiconductor process), but is not limited thereto. Figure 1 and Figure 2 As shown, the Helmholtz resonance chamber 115 is formed between the membrane structure 104 and the cover structure 150. The outlet 713 is in communication with the Helmholtz resonance chamber 115.

[0049] Helmholtz resonance

[0050] Acoustic simulation of a Helmholtz cavity ( Figure 3 ) shows the pressure distribution near the Helmholtz resonance based on the input velocity at the bottom of the chamber 115, where the bottom of the chamber 115 represents the location of the flaps 101 and 103. It can be seen that the pressure inside the chamber is very high, and the pressure decreases at the outlet. Figure 4 The input acoustic impedance is shown as a function of the frequency looking into the chamber from the position of the input volume velocity (or just input velocity). In this case, the maximum value of the acoustic impedance corresponds to the Helmholtz mode (designed to be approximately 192 kHz, the ultrasonic operating frequency, in this case) and can be designed to be close to the common mode signal (e.g., SM) frequency by controlling the size of the outlet and the cavity. Maximizing the acoustic impedance at the ultrasonic operating frequency minimizes the ultrasonic energy propagating outward from the flap and maximizes the pressure accumulation near the virtual valve, so that the air through the valve flows as expected. At the same time, the ultrasonic impedance of the resonant chamber at the baseband frequency should be kept low, typically lower than other impedances of the system (e.g., the valve or connected acoustic chamber) to avoid hindering the baseband airflow.

[0051] from Figure 3 and Figure 4 It has been demonstrated that a Helmholtz resonant chamber causes a peak in the frequency response of the acoustic impedance of an APG device (eg, 10 or 20) at an ultrasonic operating frequency (eg, 192 kHz).

[0052] Standing wave resonance

[0053] Standing wave reflectors can also be used to improve airflow. Figure 2 ) is reflected from the reflector 702 and superimposed with the subsequent cycles of the ultrasonic waves generated by the flaps. These reflections cause resonances to form in the cavity, which leads to increased pressure and increased airflow through the valve 112. The optimal distance H116 of the reflector 702 from the plane of the flaps 101, 103 depends mainly on the ultrasonic wave length in the air.

[0054] In one embodiment, the reflector 702 is a hard rigid wall, whose characteristic acoustic impedance is much higher than that of air. When the ultrasonic wave travels along the direction 202 and reaches the reflector, the ultrasonic wave is reflected along the direction 204 without changing its polarity; in order to achieve in-phase summation of pressure at the flap, the total two-way distance between the flap and the reflector should be a multiple of the corresponding wavelength λ of the ultrasonic operating frequency, so the optimal distance H116 between the reflector and the flap should be approximately Nλ / 2, where N is a positive integer.

[0055] Figure 5 The pressure magnitude distribution of a simulated standing wave cavity with N = 1 is shown, where the high pressure antinode is located in the plane of the reflector 702 and the petals, and the low pressure node is located in the center of the cavity. Periodic boundary conditions are used to simulate an array of such petals, and a small outlet is set at the reflector 702, however, the directivity section below describes the possibility of other outlet configurations. The input acoustic impedance seen from the position of the input velocity is a function of frequency ( Figure 6 ), which exhibits several peaks, the first peak corresponding to the Helmholtz mode and the second peak corresponding to the λ / 2 standing wave mode near the common mode frequency (192kHz in this case). On the other hand, the impedance dip near 96kHz corresponds to destructive interference, as described in Patent No. 11,943,585, which helps to further suppress the differential mode pressure generated by the valve movement.

[0056] It is worth noting that, depending on the configuration of the outlet, the standing wave configuration can be designed to have a higher quality factor (sharper impedance peak) than the Helmholtz configuration. Since the standing wave configuration does not require narrow walls, viscous losses can be significantly reduced. As described later in the directivity section, the radiation (loss) of the ultrasound can be reduced by placing the outlet on the side rather than on a reflector. This has the advantage of containing a larger proportion of the ultrasound energy in the cavity with less dissipation. However, a higher quality factor may result in the pressure taking more time to reach a steady-state level, and may also increase sensitivity to changes in resonant frequency due to temperature, humidity, or other factors. (The acoustic impedance simulation does not take into account open valves.) However, in the presence of an open valve, airflow through the valve will reduce the quality factor and may be significantly lower than Figure 6 The values ​​shown.

[0057] The resonant frequency of the standing wave may be affected by the holes or other outlets required for baseband airflow and deviate from the given Nλ / 2 condition. The anchoring areas 131 and 133 of the flaps also present different acoustic impedances to ultrasound compared to the movable flaps and together affect the optimal distance for resonance.

[0058] Increased ultrasound to baseband conversion

[0059] The ultrasound waves contained by the Helmholtz or standing waves increase the local ultrasonic acoustic pressure difference, resulting in airflow at a higher baseband frequency. When the valve is open, air flows across the valve from one side of the cavity to the other, resulting in a reduced pressure gain or quality factor (ratio Figure 4 and Figure 6 The damping or loss mechanism of the low (shown) is described in detail below. Figure 4 and Figure 6 The effect of the valve was not modeled. However, this achieves the desired goal of improving the efficiency of the conversion or demodulation of ultrasonic waves to baseband waves. Therefore, an air cavity with high acoustic impedance at the common mode operating frequency is beneficial.

[0060] At the same time, another effect is to reduce the emission of unwanted ultrasonic frequencies. In patent No. 11,943,585, the generated ultrasonic waves are emitted and not recaptured as described herein, resulting in high intensity unwanted ultrasonic waves being emitted along with the baseband waves. For health and safety reasons, it is generally desirable to limit the emitted ultrasonic energy to a certain threshold level; this enhanced ultrasound to baseband conversion simultaneously improves the baseband output and reduces the possible harmful emission of high amplitude ultrasound.

[0061] Directivity

[0062] For standing wave resonance, since the wavelength of ultrasonic waves is significantly smaller than that of baseband waves, ultrasonic waves have higher directivity than baseband waves. When the array or the size of the petals 101 and 103 is larger than the wavelength of ultrasonic waves, ultrasonic waves propagate toward the reflector with minimal lateral propagation loss. On the contrary, the demodulated baseband waves have a lower frequency and propagate like spherical waves, and more acoustic energy is directed to the reflector. Figure 2lateral to direction 206. Accordingly, slits, holes, or other openings in or around the reflector may be designed off-axis relative to ultrasound to achieve both ultrasound suppression and baseband transmission from these openings. Large openings near the perimeter may be beneficial for maintaining high baseband airflow. This allows for greater design freedom because the openings can be designed for baseband and decoupled from ultrasound requirements. In the case of the outlet described in patent No. 11,943,585 or the aforementioned Helmholtz chamber, a narrow outlet is required to accommodate ultrasound, but this also results in significant resistive losses; in contrast, a standing wave acoustic cavity can be designed with a larger opening to achieve low baseband losses while confining ultrasound within the cavity.

[0063] Various embodiments

[0064] Other embodiments may provide a standing wave resonant cavity or a Helmholtz cavity on one or both sides of the petal. The configuration of the standing wave cavity on both sides of the petal is shown in Figure 7 . Figure 7 An APG device 30 is shown with standing wave resonant cavities (116, 117) and reflectors 701, 702 on either side of the petal. Distances H116 and H117 can each be close to the Nλ / 2 condition, depending on other effects that affect frequency. From a manufacturing perspective, this embodiment may be preferred because it does not require the manufacture and assembly of three-dimensional patterns with small features with the chamber.

[0065] The standing wave cavity can also be partially filled with solid material (e.g. Figure 8151 of the APG device 40) to confine the sound waves laterally to a smaller area, such as a small area directly above the valve. Local air pressure is generated by the displacement of the flaps - for a given displacement, the lateral volume reduction of the cavities 116 and 117 results in a larger pressure change, which is beneficial to the airflow through the valve. Because the pressure wave is confined and can be directed close to the valve, the reflected ultrasonic waves reflected in ineffective areas (such as the anchor and the flap area near the anchor) are minimized. This has the effect of improving the rate of conversion of ultrasonic energy to baseband (fewer reflections are required, with a lower quality factor, but high airflow can still be obtained), and is beneficial to achieving high sound pressure levels at high frequencies with minimal delay or decay time. In addition, the filling material can also give the reflector more structural rigidity. However, the cavity should be wide enough to avoid increasing the viscous resistance of the airflow, thereby causing unwanted acoustic losses. To achieve baseband airflow in this embodiment, the openings of wall 151 or reflectors 701 and 702 may be spaced in the out-of-page direction.

[0066] For standing waves, consider using a soft boundary ultrasonic reflector. Fig. 9 A narrow slot with W715 and W716 (which are much smaller than the wavelength) at the outlets 715 and 716 of the APG device 50 and entering the open space may cause an impedance mismatch at the open boundary at the end of the slot, causing the ultrasound to reverse polarity when reflected from the slot-to-open boundary - in this case, the optimal distance from the petals 101 and 103 to the ends 703 / 704 is about λ(N / 2+1 / 4), and the ends 703 or 704 may refer to the ends of the channels 715 or 716. Compared to a rigid reflector that requires a distance of λ / 2, the fundamental wavelength of this embodiment is λ / 4, so a smaller device size can be achieved.

[0067] Notice, Fig. 9 The APG device 50 may include resonant chambers 115a and 115b. In one embodiment, the resonant chambers 115a and 115b may be Helmholtz resonant chambers, but are not limited thereto.

[0068] Although Figure 1 and Figure 2 The outlet of the Helmholtz chamber is shown as being located directly above flaps 101 and 103 , but the outlet may be located elsewhere. Fig.10 The outlet 717 is shown to be located above the anchors 131 and 133, rather than above the flaps. The acoustic impedance can still be adjusted to maximize the impedance of the ultrasonic common mode frequency. In this case, no walls are required between adjacent flap pairs, which can facilitate manufacturing.

[0069] structure

[0070] The resonant chamber walls may be made of solid material forming part of the loudspeaker module (e.g. copper traces or printed circuit boards for electrical routing), or of a cover (e.g. stainless steel, brass) for protection from mechanical, chemical, dust or other undesirable substances. They may also be designed as part of a structural component, such as in an earbud or headphone. In this case, the integration of such an acoustic resonant chamber adds little cost.

[0071] Non-rigid, flexible reflectors are also possible and can be made from polymers such as polyimide, polyethylene and polyvinyl chloride, which can be easily and inexpensively added to the speaker package. The optimal position of these flexible reflectors may vary depending on the mass and stiffness.

[0072] The standing wave reflector may also have a slight concave curvature towards the petals 101, 103 or have inwardly curved ends to help confine the ultrasound waves within the cavity.

[0073] In addition, the APG device of the present invention may include multiple outlets and flap pairs. For example, Fig.11 The APG device 70 or a cover structure according to an embodiment of the present invention is shown in FIG. The APG device 70 may have a plurality of outlets formed on the cover structure (eg, a cover or a lid). Fig.12 and Fig.13 1 is a cross-sectional view of an APG device 80 and 82 according to an embodiment of the present invention. The APG device 80 and 82 includes a plurality of flap pairs 102 and a plurality of outlets 723. Fig.12 , the outlet 723 is formed and aligned with the virtual valve or opening 112 (i.e., located above the virtual valve or opening 112). The APG devices 80 and 82 include a plurality of flap pairs 102 and a plurality of outlets 723. Fig.13The outlet 723 is formed and aligned with the anchor 134 (ie, located above the anchor 134). A Helmholtz resonance chamber can be formed between the cover structure 850 and the membrane structure 104 of the APG device 80 / 82 to enhance the air pressure or sound pressure level of the APG device 80 / 82.

[0074] Fig.14 FIG. 1 is a top view of a membrane structure 90 of an APG device according to an embodiment of the present invention. Fig.15 1 is a top view of a cover structure 92 of an APG device according to an embodiment of the present invention. The membrane structure 90 and the cover structure 92 can be applied to the APG devices 80 and 82. The alignment of the outlet 723 relative to the flap pair 102 can be designed according to actual needs.

[0075] In short, the present invention utilizes a resonant chamber to make the frequency response of acoustic impedance peak at the ultrasonic operating frequency, thereby effectively generating air pressure and thereby enhancing the sound pressure level.

[0076] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the claims of the present invention should fall within the scope of the present invention.

Claims

1. A gas pulse generating device, comprising: a membrane structure operating at an ultrasonic operating frequency; and a resonant chamber formed on one side of the membrane structure; Wherein, resonance is formed in the resonance chamber; Among them, because of the resonant chamber, the frequency response of the acoustic characteristics of the air pulse generating device has a peak at the ultrasonic operating frequency.

2. The gas pulse generating device according to claim 1, wherein: This resonance is a Helmholtz resonance.

3. The gas pulse generating device according to claim 1, wherein: The acoustic property is acoustic impedance.

4. The gas pulse generating device according to claim 1, comprising: a cover structure; Wherein, the resonance chamber is formed between the membrane structure and the cover structure.

5. The gas pulse generating device according to claim 4, wherein: An outlet is formed in the cover structure and communicates with the resonant chamber.

6. The gas pulse generating device according to claim 5, in, The membrane structure includes a pair of petals, the pair of petals being used to perform differential mode motion to form a virtual valve; Wherein, the outlet is located above the virtual valve.

7. The gas pulse generating device according to claim 5, wherein: The outlet is located above an anchoring portion of a flap of the membrane structure.

8. The gas pulse generating device according to claim 1, comprising: a first resonant chamber formed on a first side of the membrane structure; as well as A second resonant chamber is formed on a second side of the membrane structure, the second side being opposite to the first side.

9. The gas pulse generating device according to claim 8, comprising: a first outlet, communicating with the first resonant chamber; as well as A second outlet is communicated with the second resonant chamber.

10. The gas pulse generating device according to claim 1, comprising: a resonant cavity; wherein the resonant chamber is formed on a first side of the membrane structure; The resonant cavity is formed on a second side of the membrane structure, and the second side is opposite to the first side.

11. The gas pulse generating device according to claim 10, comprising: a reflector; Wherein, the resonant cavity is formed between the membrane structure and the reflector.

12. The gas pulse generating device according to claim 11, wherein: The distance between the membrane structure and the reflector is a half wavelength corresponding to the ultrasonic operating frequency or an integral multiple of the half wavelength.

13. The gas pulse generating device according to claim 1, wherein: This resonance is a standing wave resonance.

14. The gas pulse generating device according to claim 1, wherein: The membrane structure includes a pair of petals, which are used to perform common mode motion and differential mode motion.

15. The gas pulse generating device according to claim 1, comprising: a first resonant cavity formed on a first side of the membrane structure; as well as a second resonant cavity formed on a second side of the membrane structure, the second side being opposite to the first side; A first standing wave resonance is formed in the first resonance cavity, and a second standing wave resonance is formed in the second resonance cavity.

16. The gas pulse generating device according to claim 15, comprising: a first reflector and a second reflector; The first resonant cavity is formed between the membrane structure and the first reflector, and the second resonant cavity is formed between the membrane structure and the second reflector.

17. The gas pulse generating device according to claim 1, wherein: The membrane structure includes a plurality of petal pairs and a plurality of outlets.

18. The gas pulse generating device according to claim 17, wherein: The plurality of outlets are located above a plurality of openings formed by differential mode motion of the plurality of flap pairs.

19. The gas pulse generating device according to claim 17, wherein: The plurality of outlets are located above the plurality of anchoring portions of the plurality of flap pairs.

20. The gas pulse generating device according to claim 17, comprising: A cover structure, wherein The plurality of outlets are formed in the cover structure.

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