A piezoelectric speaker

Abstract

The present invention discloses a piezoelectric speaker, comprising: a substrate, the substrate having a cavity extending therethrough; a supporting structure, arranged on the substrate and covering the cavity; a first driving structure, stacked on the supporting structure, the first driving structure comprising a first electrode layer and a first piezoelectric layer alternately stacked; a transmission structure, stacked on the driving structure; and a separation groove, the separation groove extending through the supporting structure and the driving structure to separate the first driving structure into a first piezoelectric driving part and a second piezoelectric driving part, the rigidity of the transmission structure being less than or equal to the rigidity of the driving structure, and the rigidity of the first driving structure being less than or equal to the rigidity of the supporting structure. Compared with the prior art, the present invention utilizes the separation groove to separate the first driving structure into a first piezoelectric driving part and a second piezoelectric driving part, the first piezoelectric driving part and the second piezoelectric driving part cooperate with each other, and the sound pressure level generated at the same time is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of loudspeakers, in particular to a piezoelectric loudspeaker. Background Art

[0002] As a commonly used electro-acoustic conversion device, loudspeakers have been widely used in smart terminal devices and are the key to realizing human-computer interaction interfaces. The miniaturization of electronic devices in smart terminals has driven the size of loudspeakers to become smaller and smaller. However, due to the small sound-emitting area of ​​miniaturized loudspeakers, it is difficult to achieve a high sound pressure level (SPL). Summary of the invention

[0003] The object of the present invention is to provide a piezoelectric speaker to solve the technical problems in the prior art, which can provide a higher sound pressure level.

[0004] The present invention provides a piezoelectric speaker, comprising:

[0005] A substrate, wherein a cavity is disposed through the substrate;

[0006] A support structure, disposed on the substrate and covering the cavity;

[0007] A first driving structure, stacked on the supporting structure, the first driving structure comprising alternately stacked first electrode layers and first piezoelectric layers;

[0008] A transmission structure, stacked on the first driving structure;

[0009] in:

[0010] It also includes a separation groove, which runs through the supporting structure and the first driving structure to separate the first driving structure into a first piezoelectric driving part and a second piezoelectric driving part. The stiffness of the transmission structure is less than or equal to the stiffness of the first driving structure, and the stiffness of the first driving structure is less than or equal to the stiffness of the supporting structure.

[0011] A piezoelectric speaker as described above, wherein preferably, the piezoelectric speaker further includes a slit penetrating the supporting structure and the first driving structure, the first driving structure includes a plurality of the first piezoelectric driving parts, and adjacent first piezoelectric driving parts are separated by the slit.

[0012] In the piezoelectric speaker as described above, preferably, a plurality of the first piezoelectric driving parts are annularly spaced by the slit and arranged outside the second piezoelectric driving part.

[0013] In the piezoelectric speaker as described above, preferably, the second piezoelectric driving unit is connected to the first piezoelectric driving unit or the substrate via a connecting beam.

[0014] In the piezoelectric speaker as described above, preferably, the first piezoelectric driving unit is controlled by a first electrical signal, and the second piezoelectric driving unit is controlled by a second electrical signal.

[0015] In the piezoelectric speaker as described above, preferably, the first electrical signal and the second electrical signal have equal phase difference and equal amplitude but opposite sign.

[0016] In the piezoelectric speaker as described above, preferably, the first electrical signal and the second electrical signal have the same amplitude and are consistent in sign, but have a phase difference of nπ.

[0017] In the piezoelectric speaker as described above, preferably, the first electrical signal or the second electrical signal is zero.

[0018] In the piezoelectric speaker as described above, preferably, the first piezoelectric driving unit and the second piezoelectric driving unit are driven by the same electrical signal.

[0019] A piezoelectric speaker as described above, wherein preferably, the piezoelectric speaker also includes a second driving structure stacked on the first driving structure, the second driving structure is embedded in a side of the transmission structure close to the first driving structure, the second driving structure is greater than or equal to the stiffness of the transmission structure, the stiffness of the supporting structure is greater than or equal to the stiffness of the second driving structure, the second driving structure includes alternately stacked second electrode layers and second piezoelectric layers, and the orthographic projection of the separation groove on the transmission structure falls on the second driving structure.

[0020] In the piezoelectric speaker as described above, preferably, the third piezoelectric driving unit and the first piezoelectric driving unit can be driven by the same electrical signal or by different electrical signals.

[0021] Compared with the prior art, the present invention utilizes a separation groove to separate the first driving structure into a first piezoelectric driving part and a second piezoelectric driving part. The first piezoelectric driving part and the second piezoelectric driving part work together to generate a higher sound pressure level at the same time. At the same time, due to the existence of the separation groove, the overall stiffness of the driving structure can be adjusted, reducing the self-limiting effect of the driving structure during vibration, thereby improving the maximum sound pressure output of the speaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a cross-sectional view of the first embodiment of the present invention;

[0023] Figure 2 is a bottom view of the first embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of a first connection mode of the driving structure of the first embodiment of the present invention;

[0025] Figure 4 is a schematic diagram of a second connection mode of the driving structure of the first embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the working state of the first embodiment of the present invention. Figure 1 ;

[0027] Figure 6 This is a schematic diagram of the working state of the first embodiment of the present invention. Figure 2 ;

[0028] Figure 7 This is a schematic diagram of the working state of the first embodiment of the present invention. Figure 3 ;

[0029] Figure 8 It is a cross-sectional view of the second embodiment of the present invention.

[0030] Description of reference numerals:

[0031] 10-substrate, 11-cavity;

[0032] 20- Support structure;

[0033] 30-first driving structure, 31-first piezoelectric driving unit, 32-second piezoelectric driving unit, 33-connecting beam, 34-second driving structure, 35-third piezoelectric driving unit, 36-first electrode layer, 37-second electrode layer, 38-first piezoelectric layer, 39-second piezoelectric layer;

[0034] 40- transmission structure;

[0035] 50-dividing slot;

[0036] 60-Slit. DETAILED DESCRIPTION

[0037] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, but should not be construed as limiting the present invention.

[0038] Embodiment 1

[0039] like Figure 1 As shown, an embodiment of the present invention provides a piezoelectric speaker, comprising a substrate 10, a supporting structure 20, a first driving structure 30 and a transmission structure 40, wherein:

[0040] A cavity 11 runs through the substrate 10, and the cavity 11 is a circular groove. Of course, it can also be set to a rectangular groove or a hexagonal groove or other special-shaped groove structures. In different usage scenarios, it can be adjusted according to usage needs, and is not limited here. In some embodiments, the material of the transmission structure 40 includes but is not limited to any of the following: a flexible substrate, a metal substrate or a non-metallic substrate. As a preferred method, the material of the above-mentioned flexible substrate can be selected from but is not limited to any of the following: polydimethylsiloxane (PDMS), polyethylene (PE) or polyimide (PI).

[0041] The support structure 20 is disposed on the substrate 10 and covers the cavity 11. The shape of the support structure 20 is adapted to the formation of the cavity 11. In some embodiments, the material of the support structure 20 includes but is not limited to any one of the following: SOI, SiN or a harder material such as metal.

[0042] The first driving structure 30 is stacked on the supporting structure 20. The first driving structure 30 includes alternately stacked first electrode layers 36 and first piezoelectric layers 38. When a corresponding control voltage is applied to the first piezoelectric layer 38, the first piezoelectric layer 38 converts electrical energy into mechanical energy, causing the first driving structure 30 to deform, thereby emitting sound waves of a corresponding frequency band. The overall stiffness of the first driving structure 30 cannot be too large to prevent insufficient out-of-plane displacement, nor can it be too small to prevent itself from producing arch warping. A specific preferred solution is that the stiffness of the first driving structure 30 is less than or equal to the stiffness of the supporting structure 20.

[0043] By applying different voltages to the first electrode layer 36 and the first piezoelectric layer 38, displacements of different degrees and directions can be generated, thereby flexibly adjusting the output sound. Those skilled in the art can know that the number of layers of the first electrode layer 36 and the first piezoelectric layer 38 can be adaptively changed according to actual conditions, and are not limited here. An insulating layer can also be provided.

[0044] In some embodiments, the material of the first piezoelectric layer 38 includes but is not limited to any one of the following: PZT piezoelectric ceramics, zinc oxide, aluminum nitride or lead magnesium niobate-lead titanate polyvinylidene fluoride, and the material of the first electrode layer 36 includes but is not limited to any one of the following: platinum, gold, chromium or aluminum.

[0045] The transmission structure 40 is stacked on the first drive structure 30. The transmission structure 40 is preferably a planar membrane structure. In order to avoid obstruction in the transmission of stress and strain, the overall stiffness of the transmission structure 40 is set to be relatively small. A specific preferred solution is that the overall stiffness of the transmission structure 40 is less than or equal to the overall stiffness of the first drive structure 30.

[0046] The piezoelectric speaker further includes a separation groove 50, which penetrates the support structure 20 and the first driving structure 30 along the axial direction of the cavity 11 to separate the first driving structure 30 into a first piezoelectric driving portion 31 and a second piezoelectric driving portion 32. The first piezoelectric driving portion 31 and the second piezoelectric driving portion 32 can be driven to move together by a driving control signal. At the same time, the rigidity of the transmission structure 40 is less than or equal to the rigidity of the first driving structure 30, and the rigidity of the first driving structure 30 is less than or equal to the rigidity of the support structure 20.

[0047] Through the above-mentioned implementation mode, the first piezoelectric driving unit 31 and the second piezoelectric driving unit 32 work together to generate a higher sound pressure level at the same time. At the same time, due to the existence of the separation groove 50, the overall stiffness of the first driving structure 30 can be adjusted, reducing the self-limiting effect generated by the first driving structure 30 during vibration, thereby improving the maximum sound pressure output of the speaker.

[0048] Furthermore, the first driving structure 30 includes a plurality of the first piezoelectric driving units 31, and adjacent first piezoelectric driving units 31 are separated by slits 60. Those skilled in the art may appreciate that the first driving structure 30 may also include only one first piezoelectric driving unit 31, and the first piezoelectric driving unit 31 is an integral annular structure, and the second piezoelectric driving unit 32 is disposed at the center of the annular structure.

[0049] Reference Figures 2 to 4 As shown, the second piezoelectric driving part 32 is located in the middle of the speaker structure, and a plurality of first piezoelectric driving parts 31 are arranged in a ring-shaped manner and at the outside of the second piezoelectric driving part 32. In some embodiments, six first piezoelectric driving parts 31 are provided, and the six first piezoelectric driving parts 31 are arranged in a ring-shaped manner with the second piezoelectric driving part 32 as the center and through the slit 60. The first piezoelectric driving part 31 and the second piezoelectric driving part 32 are separated by a separation groove 50, and the separation groove 50 is an annular groove. Those skilled in the art can know that the number and position of the first piezoelectric driving parts 31 can be adaptively changed according to actual conditions, and are not limited here.

[0050] Preferably, the piezoelectric speaker can selectively power on only the first piezoelectric driving unit 31 or the second piezoelectric driving unit 32. Since the first piezoelectric driving unit 31 and the second piezoelectric driving unit 32 are separated by the separation groove 50, the first piezoelectric driving unit 31 and the second piezoelectric driving unit 32 can be driven together or separately by an electrical signal. In some embodiments, at the first resonant frequency f of the piezoelectric speaker, 0 Previously, the first piezoelectric drive unit 31 and the second piezoelectric drive unit 32 were moved together by an electrical signal to generate a sound wave with a high sound pressure level, and the frequency range of the sound wave was 20 Hz-f 0Those skilled in the art will know that the first resonant frequency of the piezoelectric speaker is related to the structure of the piezoelectric speaker itself. 0 Determine the value.

[0051] The frequency range is f 0 -20kHz, the first piezoelectric drive unit 31 or the second piezoelectric drive unit 32 can be driven by an electrical signal alone, so that the speaker emits a frequency range of f 0 -20kHz sound wave. 0 Another benefit of exciting the first piezoelectric driving unit 31 or the second piezoelectric driving unit 32 alone is that the sound pressure level SPL at the resonant frequency can be effectively reduced, thereby reducing the THD corresponding to 1 / 2, 1 / 3, 1 / 4, ..., of the resonant frequency.

[0052] Further, refer to Figure 3 and Figure 4 As shown, the second piezoelectric driving part 32 is connected to the first piezoelectric driving part 31 or the substrate 10 via a connecting beam 33. The purpose of the connecting beam 33 structure is to facilitate the passage of circuits.

[0053] In some embodiments, the first piezoelectric drive unit 31 is controlled by a first electrical signal, and the second piezoelectric drive unit 32 is controlled by a second electrical signal, and the first electrical signal and the second electrical signal are preferably equal in amplitude but opposite in sign and have the same phase. In other embodiments, the first electrical signal and the second electrical signal are equal in amplitude and have the same sign, but have a phase difference of nπ.

[0054] In some embodiments, the first piezoelectric driving unit 31 and the second piezoelectric driving unit 32 are driven by the same electrical signal.

[0055] If the material of the first piezoelectric layer 38 is aluminum nitride, the first electrode of the first piezoelectric driving unit 31 can be connected to a positive alternating voltage (such as AC=Asin(2πft), A is the amplitude, >0, and f is the frequency)), and the second electrode can be grounded; the first electrode of the second piezoelectric driving unit 32 can be grounded, and the second electrode can also be connected to a positive alternating voltage, and the voltage is AC=Asin(2πft).

[0056] If the material of the first piezoelectric layer 38 is PZT, the first electrode of the first piezoelectric driving unit 31 can be connected to a positive alternating voltage and a positive direct voltage (such as AC+DC), and the second electrode can be grounded; the first electrode of the second piezoelectric driving unit 32 can be grounded, and the second electrode can be connected to AC+DC. Figure 3 As shown, the electrical signal for controlling the second piezoelectric driving unit 32 may be routed through a connecting beam 33 between the second piezoelectric driving unit 32 and the substrate 10 .

[0057] Or the circuit sends out an original signal, and retains a part of it through the conversion device. For example, AC=Asin(2πft), and the other part of the electrical signal is 180° different from the initial phase, such as AC=Asin(2πft+nπ), n=1,2,3,…, and some structures are as follows Figure 4 As shown, the electrical signal for controlling the second piezoelectric driving unit 32 can be routed through the connecting beam 33 between the second piezoelectric driving unit 32 and the first piezoelectric driving unit 31, and the electrode routing on the first piezoelectric driving unit 31 is electrically isolated from the routing of the second piezoelectric driving unit 32.

[0058] In some embodiments, the first piezoelectric driving unit 31 and the second piezoelectric driving unit 32 are driven by the same electrical signal, and the positive (or negative) electrode of the first piezoelectric driving unit 31 and the positive (or negative) electrode of the second piezoelectric driving unit 32 are electrically connected together at the outermost circle of the structure.

[0059] Reference Figures 5 to 7 As shown, one end of the first piezoelectric driving part 31 is connected to the substrate 10 and is in a clamped state, and the other end is relatively free; when the first piezoelectric driving part 31 (the first electrode layer 36 is omitted) is subjected to an electric field parallel to the vibration and sound generation direction of the piezoelectric speaker, due to the piezoelectric effect, telescopic movement will be generated in the plane. Since the stiffness of the first driving structure 30, the support structure 20 and the transmission structure 40 are inconsistent, and the relationship among the three is that the stiffness of the transmission structure 40 is less than or equal to the stiffness of the first driving structure 30, and the stiffness of the first driving structure 30 is less than or equal to the stiffness of the support structure 20, the first driving structure 30 adjacent to the transmission structure 40 is less than or equal to the stiffness of the first driving structure 30. The upper surface of a piezoelectric driving part 31 has a greater degree of expansion and contraction than the lower surface adjacent to the supporting structure 20. The surface of the transmission structure 40 adjacent to the first piezoelectric driving part 31 is the first surface, and the surface of the supporting structure 20 adjacent to the first piezoelectric driving part 31 is the second surface. The second surface has a smaller degree of expansion and contraction than the upper surface due to the restraining effect of the supporting structure 20 with greater rigidity. The rigidity of the transmission structure 40 is less than or equal to the rigidity of the first driving structure 30, and the expansion and contraction of the first surface is freer than that of the second surface. Therefore, the expansion and contraction degrees of the first surface and the second surface do not match, which will cause out-of-plane warping displacement of the entire device.

[0060] The two ends of the second piezoelectric driving part 32 are not supported by the substrate 10, and are both in a relatively free state, and can be relatively freely expanded and contracted. When subjected to the same electric field parallel to the vibration and sound generation direction of the piezoelectric speaker, the expansion and contraction degrees of the first surface and the second surface are not matched, and the edge area and the center area of ​​the second piezoelectric driving part 32 are also inconsistent in the outward warping of the surface (they may be concave, convex or flat). Together with the first piezoelectric driving part 31, the warping height of the entire device can be further increased, which can further increase the sound pressure level of the piezoelectric speaker.

[0061] Embodiment 2

[0062] The difference between this embodiment and the first embodiment is that the piezoelectric speaker further includes a second driving structure 34 stacked on the first driving structure 30, the second driving structure 34 includes a third piezoelectric driving unit 35, the second driving structure 34 is embedded in a side of the transmission structure 40 close to the first driving structure 30, the second driving structure 34 is greater than or equal to the stiffness of the transmission structure 40, and the stiffness of the support structure 20 is greater than or equal to the stiffness of the second driving structure 34. Specifically, refer to Figure 8 As shown, the third piezoelectric drive unit 35 is adjacent to the transmission structure 40, and the first piezoelectric drive unit 31 and the second piezoelectric drive unit 32 are adjacent to the support structure 20. Preferably, the second piezoelectric drive unit 32 may not be driven by an electrical signal. The structure of the third piezoelectric drive unit 35 is the same as that of the first piezoelectric drive unit 31, and the electric field direction of the third piezoelectric drive unit 35 is opposite to that of the first piezoelectric drive unit 31. The third piezoelectric drive unit 35 and the first piezoelectric drive unit 31 may be driven by the same electrical signal or by different electrical signals, and the positive projection of the separation groove 50 on the transmission structure 40 falls on the third piezoelectric drive unit 35.

[0063] In the first embodiment, the sum of the length of the first piezoelectric driving portion 31 extending from the edge to the center, the size of the separation groove 50 and the length of the second piezoelectric driving portion 32 is equal to the total size of the chip.

[0064] In the second embodiment, the advantage is that the sum of the length of the first piezoelectric driving part 31, the size of the separation groove 50 and the length of the third piezoelectric driving part 35 can be greater than the total size of the chip; it is obvious that when the length of the third piezoelectric driving part 35 becomes longer, the average height of the out-of-plane vibration of the entire chip will become larger, which can further improve the performance of the chip.

[0065] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings. The above are only preferred embodiments of the present invention, but the present invention is not limited to the scope of implementation shown in the drawings. Any changes made according to the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the protection scope of the present invention.

Claims

1. A piezoelectric speaker, include: A substrate, wherein a cavity is disposed through the substrate; A support structure, disposed on the substrate and covering the cavity; A first driving structure, stacked on the supporting structure, the first driving structure comprising alternately stacked first electrode layers and first piezoelectric layers; A transmission structure, stacked on the first driving structure; Features: The transmission structure further comprises a separation groove, wherein the separation groove passes through the support structure and the first driving structure to separate the first driving structure into a first piezoelectric driving part and a second piezoelectric driving part, wherein the rigidity of the transmission structure is less than or equal to the rigidity of the first driving structure, and the rigidity of the first driving structure is less than or equal to the rigidity of the support structure; The piezoelectric speaker further includes a slit penetrating the supporting structure and the first driving structure, the first driving structure includes a plurality of the first piezoelectric driving parts, and adjacent first piezoelectric driving parts are separated by the slit; A plurality of the first piezoelectric driving parts are arranged outside the second piezoelectric driving part through the slit annular interval; The piezoelectric speaker also includes a second driving structure stacked on the first driving structure, the second driving structure is embedded in a side of the transmission structure close to the first driving structure, the second driving structure is greater than or equal to the stiffness of the transmission structure, the stiffness of the supporting structure is greater than or equal to the stiffness of the second driving structure, the second driving structure includes alternately stacked second electrode layers and second piezoelectric layers, and the orthographic projection of the separation groove on the transmission structure falls on the second driving structure.

2. The piezoelectric speaker according to claim 1, Features: The second piezoelectric driving unit is connected to the first piezoelectric driving unit or the substrate through a connecting beam.

3. The piezoelectric speaker according to claim 1, Features: The first piezoelectric driving unit is controlled by a first electrical signal, and the second piezoelectric driving unit is controlled by a second electrical signal.

4. The piezoelectric speaker according to claim 3, Features: The first electrical signal and the second electrical signal have equal phase differences and equal amplitudes but opposite signs.

5. The piezoelectric speaker according to claim 3, It is characterized in that The first electrical signal or the second electrical signal is zero.

6. The piezoelectric speaker according to claim 1, Features: The first piezoelectric driving unit and the second piezoelectric driving unit are both driven by the same electrical signal.

7. The piezoelectric speaker according to claim 1, Features: The second driving structure and the first driving structure may be driven by the same electrical signal or by different electrical signals.

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