US-12620382-B2 - Piezoelectric sound component having a case with stepped portion

US12620382B2US 12620382 B2US12620382 B2US 12620382B2US-12620382-B2

Abstract

A piezoelectric sound component is provided that includes a piezoelectric diaphragm and a case. The piezoelectric diaphragm is accommodated in the case. Moreover, a diaphragm 10 has a peripheral portion that includes a first peripheral portion and a second peripheral portion. The first peripheral portion is fixed to the case and the second peripheral portion is movable relative to the case. The case includes a step that is in positional agreement with the second peripheral portion in the thickness direction of the diaphragm. The step and the second peripheral portion define a clearance therebetween.

Inventors

Shungo Kanai
Tadashi Okuzawa
Toshiyuki Sakai
Yuta Okada

Assignees

MURATA MANUFACTURING CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20221216
Priority Date: 20210312

Claims (20)

1 . A piezoelectric sound component, comprising: a case having an internal space; and a piezoelectric diaphragm disposed in the internal space of the case and including a diaphragm and a piezoelectric member, the diaphragm having a middle portion and a peripheral portion that surrounds the middle portion with the piezoelectric member disposed on the middle portion, wherein the peripheral portion of the diaphragm includes a first peripheral portion fixed to the case and a second peripheral portion movable relative to the case, wherein the case includes a step that is in positional agreement with the second peripheral portion in a thickness direction of the diaphragm, and wherein the step and the second peripheral portion define a clearance therebetween.
2 . The piezoelectric sound component according to claim 1 , wherein the step is a projection or a recess of the case that extends in a widthwise direction that is perpendicular to the thickness direction.
3 . The piezoelectric sound component according to claim 1 , wherein: the case includes a lid and a case main body that has an opening and is fitted with the lid, such that the opening is closed with the lid, the case main body includes a first top wall facing a first main surface of the diaphragm and a first surrounding wall on an end of the first top wall, the lid includes a second top wall facing a second main surface of the diaphragm that opposes the first main surface and a second surrounding wall on an end of the second top wall, the step includes a first step that extends along the second peripheral portion in a manner to face the first main surfaces in the thickness direction, the first step extends from one of the first surrounding wall and the second surrounding wall, and the clearance includes a first clearance that is provided between a surface of the second peripheral portion and a surface of the first step, with the respective surfaces being oriented toward each other in the thickness direction.
4 . The piezoelectric sound component according to claim 3 , wherein: the surface of the second peripheral portion is either the first or second main surface of the diaphragm, and the surface that is oriented toward the surface of the second peripheral portion is a facing surface of the first step that is oriented toward the diaphragm.
5 . The piezoelectric sound component according to claim 4 , wherein the first clearance is defined by the first main surfaces of the diaphragm and the facing surface of the first step in a state in which the first main surface of the diaphragm is not in contact with the facing surface of the first step, or the first clearance is created between the first main surface of the diaphragm and the facing surface of the first step when the piezoelectric diaphragm vibrates in a state in which the first main surface of the diaphragm is in contact with the facing surface of the first step.
6 . The piezoelectric sound component according to claim 5 , wherein: the first clearance in the thickness direction has a width that is a distance between the first main surface of the diaphragm and the facing surface of the first step, and the width of the first clearance is less than or equal to 0.35 mm.
7 . The piezoelectric sound component according to claim 6 , wherein: the first clearance has a length in a direction in which the first and second main surfaces of the diaphragm extend that is a length of the first step in a direction in which main surfaces of the first step extend, and the length is greater than or equal to the width of the first clearance.
8 . The piezoelectric sound component according to claim 4 , wherein: the clearance includes a second clearance that is provided between two surfaces oriented toward each other in a direction in which the first and second main surfaces of the diaphragm extend, and one of the surfaces oriented toward each other is a surface of one of the first surrounding wall or the second surrounding wall that is fitted with the first step, and the other surface is a surface of the second peripheral portion.
9 . The piezoelectric sound component according to claim 8 , wherein: the second clearance is defined by a side surface of the second peripheral portion and an inner peripheral surface of the one of the first surrounding wall or the second surrounding wall that is fitted with the first step, and the first clearance and the second clearance are connected so as to cross each other.
10 . The piezoelectric sound component according to claim 4 , wherein: the step includes a second step that extends along the second peripheral portion in a manner so as to face the second main surface in the thickness direction, the second step is provided to the first surrounding wall or the second surrounding wall that is not fitted with the first step, the second step faces the first step, and the clearance includes a third clearance that is provided between a surface of the second step and a surface of the second peripheral portion, with the surfaces being oriented toward each other in the thickness direction.
11 . The piezoelectric sound component according to claim 10 , wherein: the surface of the second peripheral portion is the second main surface of the diaphragm, the surface that is oriented toward the surface of the second peripheral portion in the thickness direction is a facing surface of the second step, the facing surface of the second step is oriented toward the second main surface of the diaphragm, the third clearance is defined by the second main surface of the diaphragm and the facing surface of the second step, and the third clearance and a second clearance are connected so as to cross each other, with the second clearance being defined by a side surface of the second peripheral portion and an inner peripheral surface of the first surrounding wall or the second surrounding wall that is fitted with the second step.
12 . The piezoelectric sound component according to claim 11 , wherein: the third clearance has a width in the thickness direction that is a distance between the second main surface of the diaphragm and the facing surface of the second step, and the width of the third clearance is greater than the width of the first clearance.
13 . The piezoelectric sound component according to claim 1 , wherein the diaphragm comprises first and second main surfaces that oppose each other and are either circular or rectangular in a plan view thereof.
14 . The piezoelectric sound component according to claim 1 , wherein the first peripheral portion includes two or more portions that are fixed to the case.
15 . The piezoelectric sound component according to claim 14 , wherein the diaphragm comprises opposing main surfaces that are rectangular in a plan view thereof, and the first peripheral portion includes four corners of the diaphragm that are fixed to the case.
16 . The piezoelectric sound component according to claim 1 , wherein the positional agreement between the step and the second peripheral portion comprises the step overlapping the second peripheral portion in the thickness direction of the diaphragm.
17 . A piezoelectric sound component, comprising: a case having an internal space; and a piezoelectric diaphragm disposed in the internal space of the case and including a diaphragm and a piezoelectric member disposed on a main surface of the diaphragm, wherein the diaphragm comprises a rectangular shape in a plan view of the main surface and includes a peripheral portion that extends along sides of the rectangular shape of the diaphragm, wherein corners of the peripheral portion of the diaphragm are fixed to the case and sides of the peripheral portion between the corners are movable relative to the case, wherein the case includes a step that overlaps at least a portion of the sides of the peripheral portion in a thickness direction of the diaphragm, and wherein a space is provided between the step and the peripheral portion.
18 . The piezoelectric sound component according to claim 17 , wherein the step is a projection or a recess of the case that extends in a widthwise direction that is perpendicular to the thickness direction.
19 . The piezoelectric sound component according to claim 17 , wherein: the case includes a lid and a case main body that has an opening and is fitted with the lid, the case main body includes a first top wall facing the diaphragm and a first surrounding wall on an end of the first top wall, the lid includes a second top wall facing the diaphragm and a second surrounding wall on an end of the second top wall, the step extends from one of the first surrounding wall and the second surrounding wall, and the clearance includes a first clearance that is provided between a surface of the peripheral portion and a surface of the step, with the respective surfaces being oriented toward each other in the thickness direction.
20 . The piezoelectric sound component according to claim 19 , wherein: the surface of the peripheral portion is the main surface of the diaphragm, and the surface that is oriented toward the surface of the peripheral portion is a facing surface of the step that is oriented toward the main surface of the diaphragm.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of PCT Application No. PCT/JP2021/041201, filed Nov. 9, 2021, which claims priority to Japanese Patent Application No. 2021-040209, filed Mar. 12, 2021, the entire contents of each of which are hereby incorporated by reference in their entirety. TECHNICAL FIELD The present invention relates to a piezoelectric sound component. BACKGROUND Currently, sound components that generate warning sound and operation sound are used as buzzers and piezoelectric receivers in a wide range of applications, such as electronic devices, household appliances, and mobile phones. This leads a demand for piezoelectric sound components with excellent acoustic conversion efficiency. An example of a piezoelectric sound component is disclosed in WO2021/033376 (hereinafter “Patent Document 1”), which includes a diaphragm that has slits. Although an upper air chamber and a lower air chamber on the respective sides of the diaphragm are not sealed, air convection between the air chambers is suppressed such that the piezoelectric sound component produces large displacement and high acoustic pressure. In general, such piezoelectric sound components should include a thin diaphragm to exhibit excellent characteristics in relation to acoustic pressure or, more specifically, to produce large displacement and high acoustic pressure and to generate a low-frequency sound that is clearly audible. Moreover, the slits in the diaphragm of the piezoelectric sound component disclosed in Patent Document 1 are through-slits formed in the thickness direction of the diaphragm. Extra-fine slits are to be formed in a thin diaphragm such that the effect of suppressing air convection will not wear off. Unfortunately, it is difficult to form extra-fine slits, and component-to-component variations are likely to be produced. Furthermore, vibration of the diaphragm can cause deformation of slits, which would in turn become wider. In such a case, the piezoelectric sound component can fail to exhibit its acoustic pressure characteristics in a stable manner. SUMMARY OF THE INVENTION Accordingly, the exemplary aspects of the present invention provides a piezoelectric sound component that is designed with structural simplicity to exhibit excellent characteristics in relation to acoustic pressure without impairment of acoustic conversion efficiency. In an exemplary aspect, a piezoelectric sound component is provided that includes a piezoelectric diaphragm and a case. The piezoelectric diaphragm includes a diaphragm and a piezoelectric member. Moreover, the diaphragm has a middle portion and a peripheral portion surrounding the middle portion. The piezoelectric member is disposed on the middle portion. The case has an internal space with the piezoelectric diaphragm being disposed in the internal space. The peripheral portion of the diaphragm includes a first peripheral portion fixed to the case and a second peripheral portion movable relative to the case. The case includes a step that is in positional agreement with the second peripheral portion in a thickness direction of the diaphragm. Moreover, a clearance (or space) is defined between the step and the second peripheral portion. With such structural simplicity of the exemplary aspects, the piezoelectric sound component according to the present invention exhibits excellent characteristics in relation to acoustic pressure without impairing acoustic conversion efficiency. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an exploded perspective view of a piezoelectric sound component according to a first exemplary embodiment. FIG. 2 is a sectional view taken along line II-II in FIG. 1. FIG. 3 illustrates a case in the first embodiment. FIG. 4 is an enlarged view of Part A in FIG. 2. FIG. 5 illustrates the relationship between the width of a clearance in the first exemplary embodiment and the attenuation of acoustic pressure. FIG. 6 is a sectional view of a piezoelectric sound component according to a second exemplary embodiment. FIG. 7 is a sectional view of the piezoelectric sound component, illustrating a state in which a piezoelectric diaphragm in the second exemplary embodiment slides. FIG. 8 is a sectional view of a piezoelectric sound component according to a third exemplary embodiment. FIG. 9 is a sectional view of a piezoelectric sound component according to a fourth exemplary embodiment. FIG. 10 is a sectional view of a piezoelectric sound component according to a fifth exemplary embodiment. FIG. 11 is an exploded perspective view of a piezoelectric sound component according to a sixth exemplary embodiment. FIG. 12 illustrates a piezoelectric diaphragm in a comparative example. FIG. 13 illustrates a state in which the piezoelectric diaphragm in the comparative example vibrates. FIG. 14 illustrates the relationship between the width of slits in the comparative example and the attenuation of acoustic pressure. DETAILED DESCRIPTION OF EMBODIMENTS Here