Active lead-free piezoelectric buzzer

Abstract

The invention discloses an active lead-free piezoelectric buzzer, and belongs to the technical field of buzzers, the active lead-free piezoelectric buzzer comprises a shell, a vibrating body and a driving circuit, the vibrating body and the driving circuit are packaged in the shell, the vibrating body is formed by bonding a KNN piezoelectric plate and a metal substrate, the lead content of the KNN piezoelectric plate is smaller than 1000 ppm, a resonance cavity is formed in the shell, a sound hole is formed in the top of the shell, the vibrating body is fixed below the resonance cavity, and the driving circuit is connected with the driving circuit. The drive circuit is a built-in integrated circuit board, and the integrated circuit board is fixed to the bottom of the shell through a clamping groove and connected with the KNN piezoelectric plate through a lead. According to the piezoelectric buzzer, the KNN piezoelectric plate with the lead content smaller than 1000 ppm and the metal substrate are bonded to form the vibrating body, the optimized resonance cavity structure and the built-in driving circuit are matched, the problems that a traditional piezoelectric buzzer is serious in lead pollution, unstable in acoustic performance, low in integration degree and the like are solved, and the piezoelectric buzzer has the advantages of being environmentally friendly, free of lead, stable in acoustic performance, high in integration degree, reliable in structure and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of buzzer, and particularly relates to an active lead-free piezoelectric buzzer. BACKGROUND

[0002] As a core electro-acoustic transducer based on the inverse piezoelectric effect, the typical structure of the active piezoelectric buzzer includes three modules of a piezoelectric sheet, a driving circuit and an acoustic resonance cavity. Under the trend of miniaturization and green manufacturing of electronic products, the application demand of the device in the fields of Internet of Things terminals, smart home, medical equipment and the like continues to grow, but the existing technology has the following systematic defects:

[0003] Firstly, the environmental friendliness of the material faces a fundamental challenge. The current mainstream piezoelectric material adopts lead zirconate titanate (PZT) ceramic, which has a lead content of more than 15000 ppm. Although the RoHS directive exemption temporarily maintains production, with the European Union ECHA including lead in the list of substances of very high concern (SVHC), the traditional technology route has become unsustainable.

[0004] Secondly, the acoustic structure design is mismatched with the characteristics of lead-free materials. The existing technology such as CN111179892B discloses a high sound pressure level piezoelectric buzzer, which improves the sound pressure level through a multi-section sound cover structure, but the acoustic cavity parameters (such as height, diameter, etc.) are designed for PZT materials, and cannot adapt to the frequency response characteristics (usually 3-5 kHz) of lead-free materials such as potassium sodium niobate (KNN). This leads to a 10-15 dB drop in sound pressure level and a shift in resonant frequency when directly replacing the material, which seriously affects the reliability of the device.

[0005] Thirdly, the circuit integration restricts the development of device miniaturization. The traditional scheme mostly adopts an external multi-resonant oscillator drive, which not only increases the complexity of circuit layout, but also causes additional power consumption. Tests show that the discrete component scheme increases the overall power consumption by 20%-30%, and cannot achieve 3-12V wide voltage adaptation, which greatly limits the application in portable devices.

[0006] In addition, the existing manufacturing process has obvious shortcomings. PZT and metal substrate mostly use high-temperature sintering process, while KNN material needs low-temperature bonding, but conventional epoxy resin bonding will cause interface stress concentration, and is prone to delamination failure under frequent vibration conditions. At the same time, the wall thickness design of the resonance cavity lacks optimization, and excessive thickness will reduce the sound radiation efficiency, and excessive thinness will result in insufficient mechanical strength.

[0007] Therefore, it is necessary to propose an active lead-free piezoelectric buzzer to solve the above technical problems. SUMMARY

[0008] The active lead-free piezoelectric buzzer has the advantages of environmental protection, stable acoustic performance, high integration, reliable structure and the like.

[0009] To achieve the above object, the present application provides the following scheme: an active lead-free piezoelectric buzzer, comprising a shell, a vibrating body and a driving circuit packaged in the shell, the vibrating body is composed of a KNN piezoelectric sheet and a metal substrate, the lead content of the KNN piezoelectric sheet is less than 1000 ppm, a resonance cavity is arranged in the shell, an acoustic hole is arranged at the top, the vibrating body is fixed below the resonance cavity, the driving circuit is an integrated circuit board, the integrated circuit board is fixed to the bottom of the shell through a clamping groove and connected to the KNN piezoelectric sheet through a lead wire.

[0010] The above structure aims to provide an active lead-free piezoelectric buzzer, which is composed of a KNN piezoelectric sheet with a lead content less than 1000 ppm and a metal substrate, and cooperates with an optimized resonance cavity structure and an embedded driving circuit, to solve the problems of traditional piezoelectric buzzer, such as serious lead pollution, unstable acoustic performance, low integration and the like, and has the advantages of environmental protection, stable acoustic performance, high integration, reliable structure and the like.

[0011] Further, the material of the KNN piezoelectric sheet is potassium sodium niobate-based ceramic. In some optional schemes of the present application, the material of the KNN piezoelectric sheet is potassium sodium niobate-based ceramic, which has good piezoelectric performance and environmental protection characteristics, can ensure the acoustic performance and environmental protection requirements of the buzzer, and provides a basic material for subsequent performance optimization.

[0012] Further, the piezoelectric constant d33 of the KNN piezoelectric sheet is greater than or equal to 120 pC / N, and the frequency response range is 3 kHz-5 kHz. In some optional schemes of the present application, the piezoelectric constant d33 of the KNN piezoelectric sheet is greater than or equal to 120 pC / N, and the frequency response range is 3 kHz-5 kHz, which ensures the efficient acoustoelectric conversion efficiency of the buzzer in a specific frequency band, solves the problems of insufficient output sound pressure and frequency response mismatch caused by lead-free material substitution, and improves the acoustic performance.

[0013] Further, the metal substrate is a copper-zinc alloy substrate with a thickness of 0.05 mm-0.1 mm, and is bonded to the KNN piezoelectric sheet by an epoxy resin adhesive. In some optional schemes of the present application, the copper-zinc alloy substrate with a thickness of 0.05 mm-0.1 mm is selected and bonded to the KNN piezoelectric sheet by an epoxy resin adhesive, which optimizes the material and structural parameters of the metal substrate, solves the interface matching problem between the lead-free piezoelectric material and the metal substrate, and improves the mechanical reliability and acoustic performance stability of the device.

[0014] Further, the shell comprises a shell body and a bottom cover, and the bottom cover is buckled with the shell body. In some optional schemes of the present application, the buckling structure of the shell body and the bottom cover avoids the low assembly efficiency caused by traditional screw fixation, facilitates disassembly during later maintenance, and improves the assembly and maintenance efficiency.

[0015] Further, the top wall of the shell body is inwardly protruded with a support ring, and the support ring is abutted with the vibration body to form the resonance cavity. In some optional schemes of the present application, the support ring of the top wall of the shell body is abutted with the vibration body to form the resonance cavity, realizes the accurate positioning and fixation of the vibration body, constructs the resonance cavity with specific geometric parameters, and improves the sound energy conversion efficiency and simplifies the assembly process.

[0016] Further, the resonance cavity is a cylindrical cavity with a height of 8mm-10mm, a diameter of 15mm-20mm, and a cavity wall thickness of 0.5mm-1mm. In some optional schemes of the present application, the resonance cavity is limited to a cylindrical cavity with a height of 8mm-10mm, a diameter of 15mm-20mm, and a cavity wall thickness of 0.5mm-1mm, which optimizes the geometric parameters of the resonance cavity, solves the problem of acoustic matching of lead-free piezoelectric materials, and improves the sound energy conversion efficiency.

[0017] Further, the clamping groove is at least one concave groove arranged on the inner wall of the shell body, and is used for fixing the integrated circuit board. In some optional schemes of the present application, the groove is designed to fix the integrated circuit board, realizes the compact installation of the driving circuit module, solves the problem of low space utilization rate in the shell caused by the traditional external fixation mode, and improves the overall integration.

[0018] Further, the integrated circuit board integrates a multi-resonance oscillation circuit and connects an external power supply through a positive lead and a negative lead. In some optional schemes of the present application, the integrated circuit board integrates a multi-resonance oscillation circuit and connects an external power supply through a positive lead and a negative lead, realizes the miniaturization and modularization of the driving circuit, reduces external wiring, reduces circuit impedance matching difficulty, and avoids signal transmission loss.

[0019] Further, the working voltage range of the integrated circuit board is 3V-12V, and the output square wave frequency is 4kHz±10%. In some optional schemes of the present application, the working voltage range of the integrated circuit board is limited to 3V-12V, and the output square wave frequency is 4kHz±10%, which solves the problems of high power consumption and poor frequency stability of the traditional buzzer caused by the non-integrated driving circuit, and improves the consistency and adaptability of the acoustic performance.

[0020] Compared with the prior art, the present application at least discloses the following beneficial effects:

[0021] The application provides an active lead-free piezoelectric buzzer and an integrated structure of an assembly and a driving circuit thereof, and the active lead-free piezoelectric buzzer is formed by bonding a KNN piezoelectric sheet with a lead content less than 1000 ppm and a metal substrate to form a vibration body, and is matched with an optimized resonance cavity structure and a built-in driving circuit, so that the problems of the traditional piezoelectric buzzer, such as serious lead pollution, unstable acoustic performance and low integration, are solved, and the active lead-free piezoelectric buzzer has the advantages of environmental protection, stable acoustic performance, high integration and reliable structure. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 Structure diagram of the active lead-free piezoelectric buzzer Figure One ;

[0024] Figure 2 Structure diagram of the active lead-free piezoelectric buzzer Figure Two ;

[0025] Figure 3 Exploded view of the active lead-free piezoelectric buzzer

[0026] Figure 4 Structure diagram of the shell of the active lead-free piezoelectric buzzer.

[0027] In the figure: 1, shell; 11, shell body; 12, support ring; 13, clamping groove; 14, resonance cavity; 15, sound hole; 2, bottom cover; 3, positive lead; 4, negative lead; 5, integrated circuit board; 6, vibration body; 61, KNN piezoelectric sheet; 62, metal substrate. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0030] REFERENCE Figure 1 Figure 4As shown, the embodiment provides an active lead-free piezoelectric buzzer, including a shell 1, a vibration body 6 and a driving circuit. The vibration body 6 is fixed below a resonance cavity 14 inside the shell 1 and is formed by bonding a KNN piezoelectric sheet 61 and a metal substrate 62, wherein the lead content of the KNN piezoelectric sheet 61 is less than 1000 ppm. An acoustic hole 15 is formed at the top of the shell 1, and a resonance cavity 14 is arranged inside. The volume of the resonance cavity 14 can be adjusted according to acoustic requirements, for example, by changing the height or diameter of the cavity to achieve different frequency response characteristics. The vibration body 6 is fixed below the resonance cavity 14, and the driving circuit is an integrated circuit board 5. The integrated circuit board 5 is fixed to the bottom of the shell 1 through a clamping slot 13 and is connected to the KNN piezoelectric sheet 61 through a lead wire.

[0031] The shell 1 can be made of ABS or PC engineering plastic by injection molding. The volume of the resonance cavity 14 can be adjusted according to acoustic requirements, for example, by changing the height or diameter of the cavity to achieve different frequency response characteristics. The KNN piezoelectric sheet 61 of the vibration body 6 is preferably a potassium sodium niobate ceramic material, and its thickness is usually 0.2-0.5mm. Silver electrodes are used for electrical connection through screen printing. In addition to copper-zinc alloy, stainless steel or titanium alloy can also be used for the metal substrate 62, and the thickness can be extended to 0.03-0.15mm to adapt to different stiffness requirements. The bonding process can use epoxy resin, silicone or acrylic adhesive, and the curing temperature is controlled at 80-150℃ to ensure the interface bonding strength. In addition to clamping, the integrated circuit board 5 can also be fixed by screws or hot melt column positioning. The lead wire connection includes welding, conductive adhesive bonding or spring contact and other implementation schemes.

[0032] The technical scheme adopts low-lead KNN piezoelectric material to meet environmental protection requirements while maintaining piezoelectric performance. The design of the built-in integrated circuit board 5 simplifies the external circuit connection. The multi-resonant circuit can directly drive the piezoelectric sheet to produce vibration, and the vibration is amplified by the optimally designed resonance cavity 14 and then radiates sound waves from the acoustic hole 15. Compared with traditional lead-containing piezoelectric buzzers, this structure has a significant advantage in material compatibility. The combination of KNN piezoelectric sheet 61 and metal substrate 62 of a specific thickness can match the output characteristics of the driving circuit, avoiding the decline in acoustic performance caused by material replacement. The geometric parameters of the resonance cavity 14 and the position of the vibration body 6 are cooperatively designed to effectively solve the problem of acoustic energy loss caused by the change in acoustic impedance of lead-free materials.

[0033] Further optimization scheme, the material of KNN piezoelectric sheet 61 is potassium sodium niobate ceramic.

[0034] In one embodiment, the potassium sodium niobate-based ceramic is a lead-free piezoelectric material represented by the chemical formula (K,Na)NbO3, which is prepared by a solid state reaction method. The material is prepared by mixing high purity K2CO3, Na2CO3 and Nb2O5 powders as raw materials, ball milling, pre-sintering, secondary ball milling, granulation, molding and sintering processes. The sintering temperature is controlled in the range of 1100-1200°C, and the holding time is 2-4 hours, so that a ceramic body with a density of ≥95% can be obtained. As a preferred embodiment, the piezoelectric properties can be adjusted by doping a small amount of metal oxide (such as Ta2O5 or Sb2O5), and the doping amount is controlled between 0.2-0.8wt%. After polarization treatment, the crystal structure of the ceramic sheet formed thereby exhibits an orthorhombic phase and has stable piezoelectric properties.

[0035] In this embodiment, the potassium sodium niobate-based ceramic is used as the piezoelectric sheet material, which has the following advantages: first, the lead content of the material is less than 1000ppm, fully meeting the RoHS directive requirements for the limitation of harmful substances, solving the environmental pollution problem of traditional PZT materials; second, through component optimization and doping modification, the piezoelectric constant d33 can reach more than 120pC / N, the frequency response characteristics match the working frequency band of 3kHz-5kHz of the buzzer, ensuring the sound-electric conversion efficiency; in addition, the difference between the thermal expansion coefficients of the material and the copper-zinc alloy substrate is less than 15%, which can reduce the interfacial stress when bonded by epoxy resin and improve the structural reliability of the vibration body 6. Therefore, this technical solution not only realizes environmental performance, but also guarantees the acoustic performance and service life of the buzzer.

[0036] Further optimization scheme, the piezoelectric constant d33 of the KNN piezoelectric sheet 61 is ≥120pC / N, and the frequency response range is 3kHz-5kHz. Among them, the piezoelectric constant d33 reflects the ability of the material to produce strain along the polarization direction under the action of the electric field, and this parameter directly affects the sound pressure output efficiency of the buzzer; the frequency response range limits the effective working sound wave frequency band of the device. In one embodiment, the piezoelectric constant can be optimized by adjusting the sintering process of the KNN ceramic (such as using a two-step sintering method to control the grain size) or doping modification (such as adding manganese, antimony and other elements); the frequency response range is determined by the matching degree of the piezoelectric sheet thickness and the metal substrate 62, for example, when the thickness of the KNN piezoelectric sheet 61 is 0.2mm, the combination with the 0.08mm copper-zinc alloy substrate can achieve a 4kHz center frequency.

[0037] In the embodiment, the technical solution solves the problems of insufficient output sound pressure and frequency response mismatch caused by lead-free material replacement by setting the lower limit of piezoelectric performance and the working frequency band. Compared with the traditional lead-containing piezoelectric buzzer, under the condition of keeping d33≥120pC / N, the environmental protection requirement is met, and the working frequency of the driving circuit is accurately matched to 3kHz-5kHz, thereby avoiding the decrease of energy conversion efficiency caused by the increase of dielectric loss of lead-free material. Experiments show that the KNN piezoelectric sheet 61 with the parameters can make the buzzer reach a sound pressure level output of more than 85dB under a driving voltage of 5V, and the harmonic distortion rate is less than 5%.

[0038] In a further optimized scheme, the metal substrate 62 is a copper-zinc alloy substrate with a thickness of 0.05mm-0.1mm, which is bonded to the KNN piezoelectric sheet 61 by an epoxy resin adhesive.

[0039] In a specific embodiment, the copper-zinc alloy substrate has high mechanical strength and good electrical conductivity, wherein the copper content is preferably 60%-70%, and the zinc content is 30%-40%. The thickness of the alloy substrate is controlled within the range of 0.05mm-0.1mm, which ensures the structural strength and does not excessively increase the overall weight. The epoxy resin adhesive uses a two-component epoxy system, and the curing temperature is controlled at 80°C-120°C, and the curing time is 30-60 minutes. As a preferred embodiment, the thickness of the bonding layer is controlled within 10μm-20μm to ensure good sound energy transmission efficiency. It should be understood that in actual application, the surface of the substrate can be sandblasted to increase the roughness, thereby improving the bonding strength.

[0040] In the embodiment, the technical solution solves the interface matching problem between the lead-free piezoelectric material and the metal substrate 62 by optimizing the material and structural parameters of the metal substrate 62. The copper-zinc alloy substrate has a small difference in thermal expansion coefficient with the KNN piezoelectric sheet 61, which can reduce the interface stress caused by temperature change; the precisely controlled thickness and bonding process ensure efficient transmission of vibration energy, avoiding the problem of resonance frequency deviation caused by insufficient stiffness of the traditional stainless steel substrate. Compared with the prior art, the scheme significantly improves the mechanical reliability and acoustic performance stability of the device while maintaining the environmental protection characteristics.

[0041] In a further optimized scheme, the shell 1 includes a shell body 11 and a bottom cover 2, and the bottom cover 2 is buckled to the shell body 11.

[0042] Specifically, the shell body 11 and the bottom cover 2 are connected in a snap-fit manner, and the snap-fit structure can adopt mechanical connection modes such as buckle type, threaded type, or elastic clamping type. As a preferred embodiment, the bottom edge of the shell body 11 is provided with an annular flange, and the inner side of the bottom cover 2 is provided with a corresponding annular groove, and quick assembly is realized by rotating or pressing. It should be understood that in actual application, a sealing ring or a dispensing process can be added to the contact surface of the shell body 11 and the bottom cover 2 to improve the waterproof performance. Thus, the structure avoids the low assembly efficiency problem caused by traditional screw fixing, and facilitates disassembly during later maintenance.

[0043] The technical scheme solves the maintenance difficulty problem caused by the traditional buzzer shell 1 integrally formed by designing a modular shell 1. Among them, the snap-fit structure simplifies the assembly process while ensuring mechanical strength, and the cooperation gap between the shell body 11 and the bottom cover 2 can be controlled within 0.05mm, ensuring the sealing of the acoustic cavity. Compared with the prior art, the scheme realizes detachability while maintaining the integrity of the shell 1. When the driving circuit or the vibration body 6 needs to be repaired, only the bottom cover 2 needs to be separated to operate, avoiding overall scrap. Further, the mechanical stress generated by the snap-fit structure is uniformly distributed on the contact surface, effectively reducing the energy loss in the vibration transmission process.

[0044] Further optimization scheme, the top wall of the shell body 11 is inwardly protruding with a support ring 12, the support ring 12 abuts with the vibration body 6 to form a resonance cavity 14.

[0045] In one specific embodiment, the support ring 12 is an annular protruding structure, the height of which matches the installation position of the vibration body 6, and the relative position between the vibration body 6 and the shell body 11 is limited by the mechanical support. As a preferred embodiment, the support ring 12 can be made of plastic material integrally injection molded with the shell body 11, and the inner diameter thereof is slightly larger than the diameter of the vibration body 6 to reserve an assembly gap, and the ring width is 1mm-2mm to ensure the structural strength. Further, a buffer gasket (such as a silica gel layer) can be provided on the top of the support ring 12 for absorbing vibration transmission and reducing mechanical noise. The resonance cavity 14 formed thereby is a closed cavity structure, and its volume is determined by the height of the support ring 12 and the effective vibration area of the vibration body 6, which directly affects the sound wave resonance frequency.

[0046] The technical scheme realizes accurate positioning and fixing of the vibrating body 6 through the support ring 12, and constructs a resonance cavity 14 with specific geometric parameters. In terms of technical effects, firstly, the size deviation problem of the cavity of the traditional buzzer caused by adhesive positioning is solved, and the consistency of the height of the resonance cavity 14 is ensured through the rigid support structure; secondly, the face contact mode of the support ring 12 and the vibrating body 6 is more conducive to improving the vibration transmission efficiency than the point fixing, and the damping effect of the glue layer on high-frequency vibration is avoided; finally, the support ring 12 is integrally formed, which simplifies the assembly process and reduces the assembly time by more than 30% compared with the split fixing piece. Through testing, the sound pressure level of the buzzer with the structure can reach 85dB±2dB at a working frequency of 4kHz, which is about 8% higher than that of the comparative sample without the support ring 12.

[0047] Further optimization scheme, the resonance cavity 14 is a cylindrical cavity, the height is 8mm-10mm, the diameter is 15mm-20mm, and the cavity wall thickness is 0.5mm-1mm. Among them, the cylindrical cavity is formed by the support ring 12 on the top wall of the shell body 11 and the vibrating body 6. In one specific embodiment, the height of the cylindrical cavity is preferably 9mm, the diameter is preferably 18mm, and the cavity wall thickness is preferably 0.8mm. As a preferred embodiment, the cavity wall thickness of the resonance cavity 14 can be controlled by the injection molding process, and the tolerance range is controlled within ±0.05mm. For example, the cavity wall thickness can be designed with variants of 0.6mm, 0.7mm or 0.9mm to meet different sound pressure output requirements.

[0048] In this embodiment, the technical scheme solves the problem of acoustic matching of lead-free piezoelectric materials by limiting the geometric parameters of the resonance cavity 14. Among them, the size range of the cylindrical cavity and the frequency response range(3kHz-5kHz) of the KNN piezoelectric sheet 61 form an acoustic resonance match, thereby improving the sound energy conversion efficiency. Further, the cavity wall thickness in the range of 0.5mm-1mm can ensure the structural strength while reducing the sound wave attenuation, compared with the multi-section sound cover structure in the prior art, the acoustic cavity structure is simplified and the acoustic properties of lead-free materials are adapted. In one specific embodiment, the combination of a cavity height of 8mm-10mm and a diameter of 15mm-20mm can optimize the standing wave formation conditions of sound waves in the cavity, so that when the KNN piezoelectric sheet 61 with d33≥120pC / N is used, the sound pressure level is improved by about 15%.

[0049] Further optimization scheme, the clamping groove 13 is at least one concave groove arranged on the inner wall of the shell body 11, used for fixing the integrated circuit board 5.

[0050] In one specific embodiment, the concave groove can adopt a single-sided opening U-shaped structure or a double-sided opening through structure, with a groove depth preferably 1.2-1.5 times the thickness of the integrated circuit board 5, and a groove width controlled within the range of 0.1-0.3 mm from the circuit board gap. As a preferred implementation, the inner wall of the concave groove can be provided with anti-skid lines or elastic protrusions to enhance the fixing stability. Further, the number of concave grooves can be set to 2-4 symmetrically distributed groove bodies according to the size of the circuit board, for example, one pair of groove bodies on each of the opposite sides of the shell 1, to achieve horizontal fixation of the circuit board through multi-point limiting.

[0051] In the present embodiment, the technical solution directly forms the concave clamping groove 13 structure inside the shell body 11, omitting the mounting holes and auxiliary supports required for traditional screw fixation, so that the integrated circuit board 5 can be slid into the groove body longitudinally and achieve precise positioning. Compared with the prior art, this structure not only simplifies the assembly process, but also avoids the problem of circuit board displacement caused by loose screws, while the concave groove forms a wrapping type fixation to the edge of the circuit board, effectively reducing the collision noise between the circuit board and the shell 1 in the transportation or vibration environment. In one specific embodiment, the design achieves compact installation of the drive circuit module through structural integration, solving the problem of low space utilization inside the shell 1 caused by traditional external fixation.

[0052] Further optimization scheme, the integrated circuit board 5 integrates a multi-resonant circuit, including transistors, resistors, capacitors and other elements, and connects to an external power supply through the positive lead 3 and the negative lead 4.

[0053] The multi-resonant circuit can adopt a double-transistor symmetric structure or an integrated circuit chip, wherein the transistor is preferably an NPN type triode, the resistance value range is 1kΩ-10kΩ, and the capacitance value range is 0.01μF-0.1μF. The positive lead 3 and the negative lead 4 can adopt tinned copper wire with a wire diameter of 0.2mm-0.5mm, welded to the power input end of the integrated circuit board 5. As a preferred implementation, the working frequency of the multi-resonant circuit is realized by adjusting the RC time constant, and the frequency can be fine-tuned by a variable resistor or an adjustable capacitor.

[0054] The technical solution integrates the multi-resonant circuit into the integrated circuit board 5, achieving miniaturization and modularization of the drive circuit. Compared with the traditional scheme of externally connected oscillator, the integrated design reduces external wiring, reduces circuit impedance matching difficulty, and avoids signal transmission loss. Since standardized electronic components are used, the circuit stability is improved, and consistency control is facilitated during batch production. The wide design of the working voltage range of 3V-12V enables it to adapt to the needs of different power supply environments.

[0055] Further optimization scheme, integrated circuit board 5 working voltage range is 3V-12V, output square wave frequency is 4kHz±10%.

[0056] Integrated circuit board 5 integrates a multi-resonant oscillation circuit, which contains transistors, resistors, capacitors and other components, and is connected to an external power supply through positive lead 3 and negative lead 4. Among them, the working voltage range is realized by adjusting the resistance value in the multi-resonant oscillation circuit, which can be configured by variable resistance or fixed resistance network; the output square wave frequency is determined by the RC time constant of the multi-resonant oscillation circuit, in which the capacitor can be a ceramic capacitor or a thin film capacitor, and the resistor can be a metal film resistor or a carbon film resistor. As a preferred embodiment, the transistor is selected as an NPN type triode, and the collector-emitter voltage meets the 12V voltage resistance requirement; further, the square wave frequency stability is realized by temperature compensation capacitor or high precision resistor, and the frequency deviation is controlled within ±10%.

[0057] The technical scheme limits the working voltage range and output frequency of the integrated circuit board 5, solves the problems of high power consumption and poor frequency stability caused by the non-integrated driving circuit of the traditional buzzer. In a specific embodiment, the 3V-12V wide voltage design adapts to various power supply environments, avoiding additional voltage conversion circuit; the 4kHz±10% square wave output directly matches the resonant frequency of the KNN piezoelectric sheet 61, and the frequency tolerance is realized by circuit parameter optimization, ensuring efficient driving of lead-free piezoelectric materials. Compared with the prior art, this scheme simplifies external connection while maintaining the advantage of miniaturization, reduces system power consumption, optimizes driving parameters for lead-free piezoelectric characteristics, and improves the consistency of acoustic performance.

[0058] In the description of the present application, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the present application.

[0059] The above-described embodiments are only preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. An active lead-free piezoelectric buzzer, comprising a housing (1), a vibrating element (6) encapsulated within the housing (1), and a driving circuit, characterized in that, The vibrator (6) is composed of a KNN piezoelectric sheet (61) bonded to a metal substrate (62). The KNN piezoelectric sheet (61) has a lead content of less than 1000 ppm. The housing (1) has a resonant cavity (14) inside and a sound outlet (15) at the top. The vibrator (6) is fixed below the resonant cavity (14). The driving circuit is a built-in integrated circuit board (5). The integrated circuit board (5) is fixed to the bottom of the housing (1) through a slot (13) and connected to the KNN piezoelectric sheet (61) through a lead wire.

2. The active lead-free piezoelectric buzzer according to claim 1, characterized in that, The KNN piezoelectric element (61) is made of potassium sodium niobate-based ceramic.

3. The active lead-free piezoelectric buzzer according to claim 1 or 2, characterized in that, The piezoelectric constant d33 of the KNN piezoelectric element (61) is ≥120pC / N, and the frequency response range is 3kHz-5kHz.

4. The active lead-free piezoelectric buzzer according to claim 1 or 2, characterized in that, The metal substrate (62) is a copper-zinc alloy substrate with a thickness of 0.05mm-0.1mm, and is bonded to the KNN piezoelectric sheet (61) by epoxy resin adhesive.

5. The active lead-free piezoelectric buzzer according to claim 1, characterized in that, The housing (1) includes an outer shell body (11) and a bottom cover (2), the bottom cover (2) being fastened to the outer shell body (11).

6. The active lead-free piezoelectric buzzer according to claim 5, characterized in that, The top wall of the outer shell (11) has an inwardly protruding support ring (12), which abuts against the vibrator (6) to form the resonance cavity (14).

7. The active lead-free piezoelectric buzzer according to claim 6, characterized in that, The resonating cavity (14) is a cylindrical cavity with a height of 8mm-10mm, a diameter of 15mm-20mm, and a wall thickness of 0.5mm-1mm.

8. The active lead-free piezoelectric buzzer according to claim 1, characterized in that, The slot (13) is at least one concave groove provided on the inner wall of the outer shell body (11) for fixing the integrated circuit board (5).

9. The active lead-free piezoelectric buzzer according to claim 1, characterized in that, The integrated circuit board (5) integrates a multivibrator circuit and is connected to an external power supply through a positive lead (3) and a negative lead (4).

10. The active lead-free piezoelectric buzzer according to claim 9, characterized in that, The operating voltage range of the integrated circuit board (5) is 3V-12V, and the output square wave frequency is 4kHz±10%.

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