Oscillator manufacturing apparatus and manufacturing method of oscillator

Abstract

To provide an oscillator manufacturing apparatus having a curved part having a three-dimensional curved surface profile and capable of manufacturing an oscillator with a highly symmetrical shape while a surface ruggedness transfer to the curved surface is suppressed, and a manufacturing method of the oscillator.SOLUTION: A manufacturing apparatus of an oscillator including a curved surface having a three-dimensional curved surface includes a mold 10 including a counterbore part 11 that is a recessed part formed on an upper surface 10a facing a heat source, and a cavity 12 that is a recessed part formed on a bottom surface 11a of the counterbore part 11. The counterbore part 11 is a part in which a plate material 100 made of a reflow material constituting the oscillator is disposed. A maximum diameter of the cavity 12 is smaller than a maximum diameter of the bottom surface 11a of the counterbore part 11. A manufacturing method of the oscillator includes the steps of: setting the plate material 100 in a mold 10 having the counterbore part 11; softening the plate material 100 by the heat source; evacuating the cavity 12; and forming a three-dimensional curved surface by different pressure deformation.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a vibrator manufacturing apparatus and a vibrator manufacturing method for a vibrator having a three-dimensional curved surface. [Background technology]

[0002] Conventionally, BRG is known as an inertial sensor that uses a vibrator with a three-dimensional curved surface that vibrates in wine-glass mode. BRG is an abbreviation for Bird-bath Resonator Gyroscope. This type of vibrator has a Q value that represents the vibration state of 10 6 Since the above level is achieved, higher accuracy than conventional methods is expected. As a method for manufacturing this type of vibrator, for example, the method described in Patent Document 1 can be given.

[0003] The method for manufacturing a vibrator described in Patent Document 1 involves preparing a mold that has a recess and a support portion protruding from the center of the bottom of the recess and that can evacuate the interior of the recess, and a reflow material such as quartz glass, and placing the reflow material on the recess and heating it with a flame or the like while reducing the pressure inside the recess. As a result, a portion of the reflow material that has been softened by heating is pulled into the recess, and the center of the softened portion is supported by the support portion, making it possible to manufacture a vibrator that has a curved surface portion with a three-dimensional curved surface and a cylindrical connection portion with a bottom that is recessed toward the center of the hemispherical portion formed by the curved surface portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2018 / 0079129 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, in order to further improve precision in BRG, it is important to reduce the resonant frequency difference Δf in the wine-glass mode where n = 2. In order to reduce the resonant frequency difference Δf in BRG, it is necessary to process the vibrator into a highly symmetrical shape. To manufacture a vibrator with a highly symmetrical shape, it is necessary to control the heat input to the reflow material as evenly as possible when heating the reflow material, so that it deforms evenly.

[0006] Various heat sources have been proposed for processing reflow materials such as quartz glass, but the flame of a gas burner is the most effective for achieving the temperature and temperature rise rate required for melting and deforming the glass. However, it is difficult to completely control the flame shape of a gas burner, so it is not possible to evenly distribute the heat input to the reflow material by flame control.

[0007] Therefore, a method can be considered in which the recess of the mold used to manufacture the vibrator is curved to match the three-dimensional curved shape of the curved surface portion, and the shape of the vibrator is controlled by melting and deforming the reflow material while bringing it into contact with the curved surface of the recess. However, with this manufacturing method, the surface irregularities present on the curved surface of the mold recess are transferred to the surface of the curved surface portion of the resulting vibrator, resulting in a decrease in the Q value of the vibrator.

[0008] In view of the above, the present disclosure aims to provide a vibrator manufacturing apparatus and a method for manufacturing a vibrator that has a curved surface portion with a three-dimensional curved shape and is capable of manufacturing a vibrator with a highly symmetrical shape while suppressing the formation of surface irregularities on the curved surface portion. [Means for solving the problem]

[0009] According to one aspect of the present disclosure, a vibrator manufacturing apparatus includes: A vibrator manufacturing apparatus for manufacturing a vibrator (2) having a curved surface portion (21) having a three-dimensional curved surface, The mold (10) has a counterbore portion (11) formed on an upper surface (10a) facing a heat source for softening a plate material (100) made of a reflow material, which is a recess in which the plate material is placed, a cavity (12) formed on a bottom surface (11a) of the counterbore portion, and an air vent (14) formed in the cavity and connected to a negative pressure source for creating a negative pressure in a space closed by the plate material and the cavity, The maximum diameter of the counterbore is larger than that of the plate material. The cavity has a maximum diameter smaller than the bottom surface of the counterbore.

[0010] This vibrator manufacturing apparatus has a mold including a counterbore portion, which is a recess formed on the top surface facing a heat source, a cavity, which is a recess formed on the bottom surface of the counterbore portion and has a maximum diameter smaller than that of the bottom surface, and an air vent formed in the cavity and connected to a negative pressure source. In this vibrator manufacturing apparatus, a plate made of a reflow material placed in the counterbore portion is heated by the heat source, and the enclosed space formed by the plate and the cavity is depressurized by the negative pressure source, thereby melting a portion of the plate and deforming the plate due to the pressure difference between the inside and outside of the enclosed space. The mold having the counterbore portion is structured so that the hot airflow generated by the heat source is retained in the counterbore portion, which makes the heat input to the plate more uniform compared to a mold without a counterbore portion, making it possible to manufacture highly symmetrical vibrators without having the entire molten portion of the plate come into contact with the wall surface of the cavity.

[0011] According to another aspect of the present disclosure, a method for manufacturing a vibrator includes: A method for manufacturing a vibrator (2) having a curved surface portion (21) having a three-dimensional curved surface, A mold (10) is provided with a countersunk portion (11) which is a recess formed on an upper surface (10a) facing a heat source, a cavity (12) which is a recess formed on a bottom surface (11a) of the countersunk portion and has a maximum diameter smaller than that of the bottom surface, and an air hole (14) formed in the cavity and connected to a negative pressure source; preparing a plate material (100) and placing it in the counterbore; creating a negative pressure in the closed space formed by the plate material and the cavity using a negative pressure source connected to the vent hole; The method includes softening the plate material with a heat source, and deforming the plate material by a pressure difference between the inside and outside of the enclosed space to form a curved surface portion.

[0012] This vibrator manufacturing method uses a mold having a counterbore portion, which is a recess formed on the top surface facing a heat source; a cavity, which is a recess formed on the bottom surface of the counterbore portion and has a maximum diameter smaller than that of the bottom surface; and an air vent formed in the cavity and connected to a negative pressure source. A plate made of a reflow material is then placed in the counterbore portion, and the plate is softened by a heat source while the pressure inside the cavity is reduced by a negative pressure source. The differential pressure deforms the plate to form a curved surface. Because this manufacturing method uses a mold with a counterbore portion, the hot airflow generated by the heat source is retained in the counterbore portion, and heat input to the plate is more uniform than with a mold without a counterbore portion. Therefore, this manufacturing method makes it possible to manufacture a highly symmetrical vibrator without contacting the entire molten portion of the plate with the wall surface of the mold cavity.

[0013] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view illustrating an example of an inertial sensor. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 2 is a top view showing a mold used in manufacturing the vibrator according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] 4 is an explanatory diagram illustrating the formation of a vibrator using the mold of FIG. 3. FIG. [Figure 6] FIG. 10 is a diagram showing a vibration model in which the rim of the vibrator has a completely symmetrical shape. [Figure 7] FIG. 10 is a diagram showing a vibration model in which the rim of the vibrator has an elliptical shape. [Figure 8] FIG. 10 is an explanatory diagram of the height position of the vibrator. [Figure 9] 10A and 10B are diagrams showing the results of comparing the roundness of the rims of vibrators according to an example and a comparative example. [Figure 10] FIG. 10 is a diagram showing the results of comparing the circularity of pillars in vibrators according to an example and a comparative example. [Figure 11] FIG. 10 is a diagram showing the results of comparing the axial misalignment of the rims in the vibrators of the example and the comparative example. [Figure 12] FIG. 10 is a diagram showing the results of comparing the axial misalignment of pillars in the vibrators of the example and the comparative example. [Figure 13] 10A and 10B are schematic diagrams showing an estimated mechanism of reduction in symmetry of a vibrator in a vibrator manufacturing method of a comparative example. [Figure 14] 10A to 10C are schematic diagrams illustrating an estimated mechanism for improving the symmetry of a vibrator in a vibrator manufacturing method according to an embodiment. [Figure 15] 10A and 10B are schematic diagrams showing an estimated mechanism of reduction in symmetry of a vibrator in a manufacturing method of a vibrator according to another comparative example. [Figure 16] FIG. 10 is an explanatory diagram of the radius of the rim of the vibrator. [Figure 17] FIG. 10 is a diagram illustrating an example of the variation of the rim radius of a transducer in azimuth. [Figure 18] 10A and 10B are explanatory diagrams of indices for evaluating the symmetry of the rim of a vibrator. [Figure 19] FIG. 10 is a diagram showing the results of comparing the coefficients of four-fold symmetry in the vibrators of the example and the comparative example. [Figure 20] FIG. 10 is a top view showing a first modified example of a mold used in manufacturing a vibrator according to the embodiment. [Figure 21] FIG. 10 is a top view showing a second modified example of the mold used in manufacturing the vibrator according to the embodiment. [Figure 22] FIG. 10 is a top view showing a third modified example of a mold used in manufacturing a vibrator according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following embodiments, identical or equivalent parts will be denoted by the same reference numerals.

[0016] (Embodiment) A vibrator manufacturing apparatus and a vibrator manufacturing method according to an embodiment will be described. First, a BRG will be described as a representative example of an inertial sensor in which a vibrator is used.

[0017] [Inertial Sensor] 1, the inertial sensor 1 has a vibrator 2 and a mounting substrate 3, and is equipped with a sensor element in which the vibrator 2 is mounted on the mounting substrate 3. The inertial sensor 1 can detect an angular velocity applied to the inertial sensor 1 and a rotation angle based on a change in electrostatic capacitance between, for example, a part of the thin-walled vibrator 2 that can vibrate in a first vibration mode and a second vibration mode and a plurality of first electrode portions 51 of the mounting substrate 3.

[0018] As shown in FIG. 2 , the vibrator 2 is a micro-vibrator having a three-dimensional, approximately symmetrical structure, including a curved surface portion 21 having a three-dimensional curved surface outline of a substantially hemispherical shape and a bottomed, cylindrical connection portion 22 extending from the apex of the imaginary hemisphere formed by the curved surface portion 21 toward the center of the hemisphere. The surface of the vibrator 2 with a larger outer diameter is the front surface, and the opposite surface is the back surface. When viewed from the back surface, the tip surfaces of the pillar-shaped connection portions 22 form the mounting surface, which is connected to the mounting substrate 3. For example, a conductive film (not shown) is formed on both the front and back surfaces of the vibrator 2, allowing voltage application from the mounting substrate 3. For example, a rim 23, which is the end of the curved surface portion 21 opposite the connection portion 22, is arranged to face multiple first electrode portions 51 of the mounting substrate 3, which will be described later. The rim 23 vibrates in a resonant mode due to electrostatic force generated between the first electrode portion 51 and the rim 23.

[0019] The vibrator 2 is made of a reflow material such as glass containing additives, such as quartz glass or borosilicate glass, metallic glass, or silicon glass. The vibrator 2 is not limited to the aforementioned examples of materials, as long as it is made of glass capable of forming the curved surface portion 21 and the connecting portion 22 and vibrating in wine-glass mode. The vibrator 2 is manufactured, for example, by processing and shaping a plate 100 made of a reflow material using a mold 10 (described later). The curved surface portion 21 and the connecting portion 22 are thin-walled components on the order of micrometers, with thicknesses of 10 μm to 100 μm. The vibrator 2 has a millimeter-sized shape, for example, with the height direction parallel to the thickness direction of the mounting substrate 3 being 2.5 mm and the outer diameter of the surface side of the rim 23 being 5 mm. The vibrator 2 may also be referred to as a "resonator" or a "micro-vibrator," for example. The vibrator 2 is manufactured using a mold 10 having a counterbore portion 11, which will be described later. Therefore, the curved surface portion 21 and the connecting portion 22 have a highly symmetrical shape compared to conventional vibrators, and the Q value of the vibration is 10. 5 That's all.

[0020] As shown in FIGS. 1 and 2, the mounting substrate 3 includes a lower substrate 4 and an upper substrate 5, which are bonded together. For example, the mounting substrate 3 can be obtained by forming grooves 41 and wiring (not shown) in the lower substrate 4, which is made of borosilicate glass, an insulating material, and then anodically bonding the upper substrate 5, which is made of silicon, a semiconductor material, to the lower substrate 4 and patterning the resulting substrate. The mounting substrate 3 can be formed, for example, by performing dry etching such as DRIE on the upper substrate 5 after anodically bonding, thereby forming a plurality of first electrode portions 51 and second electrode portions 52. DRIE is an abbreviation for Deep Reactive Ion Etching.

[0021] The multiple first electrode portions 51, for example, face the rim 23 of the vibrator 2 and are arranged at equal intervals apart so as to form a ring on the plane of the mounting substrate, with an electrode film (not shown) formed on the upper surface of each. The multiple first electrode portions 51, for example, have wires (not shown) connected to the electrode film (not shown) and are electrically connected to an external circuit board or the like, thereby enabling control of their potential. Each of the multiple first electrode portions 51 is spaced a predetermined distance from the rim 23 of the vibrator 2 and each forms a capacitor with the vibrator 2, making it possible to detect the capacitance between them. Some of the multiple first electrode portions 51 serve as detection electrodes that detect capacitance, and others serve as drive electrodes that apply an electrostatic force to the rim 23 of the vibrator 2.

[0022] 1, the second electrode unit 52 has a frame shape surrounding the plurality of first electrode units 51, and has an electrode film (not shown) formed on its upper surface, to which a wire (not shown) is connected. The second electrode unit 52 is connected to a conductive film (not shown) of the vibrator 2 by a wiring (not shown) or the like, and is configured to be able to apply a voltage.

[0023] The above is the basic configuration of the inertial sensor 1. This inertial sensor 1 uses a highly symmetrical oscillator 2 obtained by the manufacturing method described below, and therefore has a configuration with high sensor accuracy.

[0024] [Method for manufacturing vibrator] Next, a method for manufacturing the vibrator 2 will be described with reference to Figures 3 to 5. In Figure 3, the portion of the outer periphery of a mold 10 (described later) that is covered by a plate material 100 is indicated by a broken line.

[0025] 3, a plate material 100 that forms the base of the vibrator 2 and a mold 10 for forming the curved surface portion 21 and the connecting portion 22 are prepared. The plate material 100 is made of any reflow material that can be softened by heating and deformed and processed by differential pressure, such as quartz glass with a thickness of 100 μm. The plate material 100 is arranged so as to close the cavity 12 of the mold 10.

[0026] First, the mold 10 will be described. As shown in FIG. 4, the mold 10 has a countersunk portion 11, which is a recess recessed from an upper surface 10a facing a heat source that heats the plate material 100, and a cavity 12, which is a recess formed in a bottom surface 11a of the countersunk portion 11. The mold 10 further has, for example, columnar support portions 13 formed within the cavity 12, and an air vent 14 that communicates with the cavity 12 and is connected to a negative pressure source (not shown). The mold 10 is made of any material that has a higher heat resistance temperature than the plate material 100, does not react with the softened plate material 100, and has a thermal conductivity equal to or higher than a predetermined value, such as carbon or boron nitride. The mold 10 corresponds to a vibrator manufacturing device used to manufacture the vibrator 2.

[0027] The countersunk portion 11 is a portion where the plate material 100 is placed, and is, for example, circular when viewed from the normal direction to the top surface 10a, i.e., when viewed from the top surface, has a symmetrical outer shape. The countersunk portion 11 is a recess provided for the purpose of reducing the variation in heat input to the plate material 100 and improving the symmetry of the curved surface portion 21 and the connection portion 22. The estimated mechanism by which the countersunk portion 11 improves the symmetry of the vibrator 2 will be described later. For example, the maximum diameter of the outer shape of the countersunk portion 11 when viewed from above is set to be equal to or less than twice the maximum diameter of the plate material 100. This is because it is believed that if the planar size of the countersunk portion 11 is made too large compared to the planar size of the plate material 100, the effect of reducing the variation in heat input to the plate material 100 will be reduced. For example, when the thickness of the plate material 100 is 100 μm, the countersunk portion 11 has a depth of about 0.5 mm, where the depth is the distance from the top surface 10a to the bottom surface 11a in a direction normal to the top surface 10a of the mold 10. Note that the countersunk portion 11 may have a depth greater than 0.5 mm as long as it is deep enough to prevent the plate material 100 from protruding above the top surface 10a.

[0028] The cavity 12 is a recess formed on the bottom surface 11a of the countersunk portion 11 and has a diameter smaller than that of the bottom surface 11a. As shown in FIG. 5 , for example, the cavity 12 is a space that forms a three-dimensional curved surface when the plate material 100 is heated and softened by flame F from a heat source H. The plate material 100 is decompressed by evacuating the closed space formed by the plate material 100 and the cavity 12 using a negative pressure source (not shown) connected to the vent holes 14. The portion softened by the flame F deforms toward the cavity 12 due to the pressure difference, forming the curved surface portion 21 and the connecting portion 22. The cavity 12 is, for example, a roughly bowl-shaped recess, with a columnar support portion 13 protruding from the center. The cavity 12 also has a plurality of vent holes 14, which are through-holes connected to the negative pressure source, formed near the support portions 13.

[0029] The support pillar 13 is formed, for example, at the center of the cavity 12 and has a cylindrical shape. The support pillar 13 provides support when a portion of the plate material 100 softened by the flame F is deformed by differential pressure, and is used to form the connection portion 22. The height of the support pillar 13 from its base to its tip surface is set to a level that does not protrude from the cavity 12, for example.

[0030] The ventilation holes 14 are through holes used to reduce the pressure inside the cavity 12. For example, a plurality of ventilation holes 14 are formed at positions that do not come into contact with the softened portion of the plate material 100. For example, when a plurality of ventilation holes 14 are formed, they are arranged evenly when viewed from above so that the pressure inside the cavity 12 is not reduced unevenly.

[0031] The above is the basic configuration of the mold 10. Using the mold 10 with the counterbore portion 11 formed, the plate material 100 is set in the counterbore portion 11 so that it covers the cavity 12. Then, the plate material 100 is heated by the flame F of the heat source H, and the cavity 12 is made negative pressure, thereby deforming the plate material 100 under differential pressure and forming the curved surface portion 21 and the connection portion 22. At this time, since the mold 10 has the counterbore portion 11, unevenness in the differential pressure deformation is suppressed compared to when a mold without the counterbore portion 11 is used, and the curved surface portion 21 and the connection portion 22 have highly symmetrical shapes. This will be described in more detail later.

[0032] Then, for example, laser light is irradiated onto the plate material 100 on which the curved surface portions 21 and the connecting portions 22 are formed, and unnecessary portions outside the curved surface portions 21 are cut and removed. Thereafter, a conductive film is formed on the front and back surfaces of the plate material 100 from which the unnecessary portions have been removed, for example, by any film formation method such as sputtering, thereby making it possible to manufacture the vibrator 2 having highly symmetrical curved surface portions 21 and connecting portions 22.

[0033] [Symmetry and vibration characteristics of the vibrator] Next, a description will be given of the symmetry of the shape and vibration characteristics of the vibrator 2. In Figures 6 and 7, the outline of the rim 23 when viewed from above is shown by a solid line in a vibration model to be described later.

[0034] When the rim 23 of the vibrator 2 is a perfect circle in top view and the vibrator 2 as a whole has a perfectly symmetrical shape (hereinafter referred to as "perfectly symmetrical" for convenience), and the vibrator 2 is vibrated in a wine glass mode with n=2, the vibration model is expressed as shown in Fig. 6, for example. The perfectly symmetric vibrator 2 has a spring constant k along its vibration direction in top view, as shown in Fig. 6, for example. x , k y and the damping coefficient C x , C y These two objects are connected to mass point m and can be regarded as a two-degree-of-freedom vibrating body that vibrates on a two-dimensional plane. The two-dimensional plane here means a plane along the surface of the mounting substrate 3 on which the multiple first electrode portions 51 are formed. The spring constant k x , k y are the spring constant and damping coefficient C in the vibration axis x and y, respectively. x , C y are the damping coefficients of vibration in the vibration axes x and y, respectively.

[0035] The vibrator 2 shown in Figure 6 has an ideal perfectly symmetrical structure and a uniform thickness. In this case, the perfectly symmetrical vibrator 2 has a mass of m on the vibration axis x. x The mass on the vibration axis y is m y Then, the mass is m x =my , and the spring constant is k x =k y Therefore, in principle, the perfectly symmetrical vibrator 2 has a resonant frequency f x is the resonant frequency f on the vibration axis y y The resonance frequency difference between the x and y vibration axes in the wine-glass mode of n=2 is Δf=|f x -f y | is 0. The resonance frequency f is 1 / 2π×(k×m) 0.5 It is calculated using the formula:

[0036] In contrast, an actual vibrator 2 has unavoidable asymmetry. For example, the vibrator 2 has an asymmetrical elliptical structure in which the diameter of the rim 23 on the vibration axis x is larger than the diameter on the vibration axis y when viewed from above. In this case, the vibration model of the vibrator 2 in the wine glass mode with n=2 is expressed as shown in Figure 7. The vibrator 2 with this asymmetrical structure has a mass m x ≠m y , and the spring constant is k x ≠k y Therefore, the resonant frequency difference Δf = |f x -f y | does not become 0. In other words, a vibrator 2 with an asymmetric structure generates a resonance frequency difference Δf according to the asymmetry of the shape. In order to improve the vibration characteristics of the vibrator 2, it is effective to reduce the resonance frequency difference Δf, that is, to make the shapes of the curved surface portion 21 and the connecting portion 22 closer to perfect symmetry.

[0037] [Symmetry of the oscillator] Next, the results of the symmetry evaluation of the example and the comparative example will be explained, using the vibrator 2 manufactured using the mold 10 having the countersunk portion 11 as an example and a vibrator manufactured using a conventional mold without the countersunk portion 11 as a comparison example.

[0038] In the symmetry evaluation, for example, as shown in Figure 8, a flat reference plane P S The vibrator 2 is placed so that the lower surface 23a of the rim 23 is in contact with the reference plane P SThe normal direction to the vibrator 2 was defined as the height direction Z, and the position in the height direction Z was defined as the height position. Evaluation was carried out for four indices, namely, "rim roundness," "pillar roundness," "rim axis misalignment," and "pillar axis misalignment," for each height position of the vibrator 2.

[0039] For ease of explanation, the surface of the vibrator 2 with the larger outer diameter will be referred to as the front surface 2a, the surface opposite the front surface 2a will be referred to as the back surface 2b, and the surface of the connection portion 22 located opposite the bottom surface 22a of the recess on the front surface 2a side will be referred to as the "mounting surface 22b."

[0040] The height position (unit: μm) is the reference plane P S was set to 0 μm, and the direction toward the apex of the curved surface portion 21 was set to positive. The evaluation results of rim roundness, pillar roundness, rim axis deviation, and pillar axis deviation shown in Figures 9 to 12 are plots of average values ​​of n=30 for both the example and the comparative example. The evaluation of the above four indexes was performed by measuring the dimensions of each part of the photographed image of the glass vibrator.

[0041] The rim circularity is calculated for each height position using the following formula (1). According to formula (1), the smaller the rim circularity value, the more symmetric the vibrator. The maximum diameter, minimum diameter, and average diameter of curved surface portion 21 in formula (1) refer to the maximum, minimum, and average diameters of curved surface portion 21 in a two-dimensional plane when viewed from above, respectively.

[0042] Rim roundness (%) = (maximum diameter of curved surface portion 21 - minimum diameter of curved surface portion 21) / average diameter of curved surface portion 21 × 100 (1) As shown in Figure 9, the rim roundness of the comparative example had a maximum value of approximately 0.262, a minimum value of approximately 0.173, and an average value of 0.226 across the entire height range. On the other hand, the rim roundness of the example had a maximum value of approximately 0.174, a minimum value of approximately 0.054, and an average value of approximately 0.114, which were smaller than those of the comparative example across the entire height range. This result shows that the outer shape of the front surface 2a side of the curved portion 21 of the example is closer to a perfect circle than that of the comparative example.

[0043] The pillar circularity is calculated for each height position using the following formula (2). According to formula (2), the smaller the pillar circularity value, the more symmetric the vibrator. The maximum diameter, minimum diameter, and average diameter of connection portion 22 in formula (2) refer to the maximum, minimum, and average diameters, respectively, of the diameter on the front surface 2a side of connection portion 22 in a two-dimensional plane when viewed from above.

[0044] Pillar roundness (%) = (maximum diameter of connection portion 22 - minimum diameter of connection portion 22) / average diameter of connection portion 22 × 100 (2) As shown in Figure 10, the pillar circularity of the comparative example had a maximum value of approximately 2.490, a minimum value of approximately 0.708, and an average value of 1.590 across the entire height range. On the other hand, the pillar circularity of the example had a maximum value of approximately 1.167, a minimum value of approximately 0.478, and an average value of approximately 0.856, which were smaller than those of the comparative example across the entire height range. This result shows that the outer shape of the front surface 2a side of the connection portion 22 of the example is closer to a perfect circle than that of the comparative example.

[0045] The rim axis deviation is calculated for each height position using the following formula (3). According to formula (3), the smaller the value of the rim axis deviation, the more symmetric the vibrator. The center position of the mounting surface 22b in formula (3) refers to the center position of the mounting surface 22b in a two-dimensional plane when viewed from above. This also applies to formula (4) described below. Furthermore, the rim averaged circle refers to a circle averaged so that the outer shape of the surface 2a side of the curved surface portion 21 when viewed from above becomes a perfect circle.

[0046] Rim axis deviation (%) = |deviation amount between the center position of the mounting surface 22b and the center position of the rim averaging circle| / (radius of the rim averaging circle) × 100 (3) As shown in Figure 11, the rim axis misalignment of the comparative example had a maximum value of approximately 1.020, a minimum value of approximately 0.453, and an average value of 0.697 across the entire height range. On the other hand, the rim axis misalignment of the example had a maximum value of approximately 0.456, a minimum value of approximately 0.346, and an average value of approximately 0.390, which were smaller values ​​than the comparative example across the entire height range. This result shows that, when viewed from above, the curved surface portion 21 of the example has a shape that is closer to a perfect circle with its central axis at the center position of the mounting surface 22b overall, compared to the comparative example.

[0047] The pillar axis misalignment is calculated for each height position using the following formula (4). According to formula (4), the smaller the pillar axis misalignment value, the more symmetric the vibrator is. The pillar averaged circle in formula (4) refers to a circle averaged so that the outer shape of the front surface 2a of the connection portion 22 when viewed from above becomes a perfect circle.

[0048] Pillar axis deviation (%) = |deviation between the center position of the mounting surface 22b and the center position of the pillar averaging circle| / (radius of the pillar averaging circle) × 100 (4) As shown in Figure 12, the pillar axis misalignment of the comparative example had a maximum value of approximately 2.054, a minimum value of approximately 0.565, and an average value of 1.350 across the entire height range. On the other hand, the pillar axis misalignment of the example had a maximum value of approximately 1.838, a minimum value of approximately 0.395, and an average value of approximately 0.903, which were smaller values ​​than the comparative example across the entire height range. This result shows that, when viewed from above, the connecting portion 22 of the example has a shape that is closer to a perfect circle with its central axis at the center position of the mounting surface 22b as a whole, compared to the comparative example.

[0049] As described above, the vibrator 2 of the example had smaller values ​​than the comparative example for the four evaluation indexes of rim roundness, pillar roundness, rim axis misalignment, and pillar axis misalignment, and had high symmetry in the shapes of the curved surface portion 21 and the connection portion 22. This is the effect of using the mold 10 having the counterbore portion 11. The reason why the counterbore portion 11 improves the symmetry of the shape of the vibrator 2 is presumably because the heat input to the plate material 100 is made more uniform than when a mold without the counterbore portion 11 is used.

[0050] Specifically, for example, as shown in FIG. 13 , the vibrator of the comparative example is manufactured by setting a plate material 100 in a mold 200 that does not have a counterbore portion 11 and heating the plate material 100 with a flame from a heat source (not shown). The mold 200 has, for example, a cavity 201, which is a recess formed in an upper surface 200a that faces the heat source, and a support portion 202 formed within the cavity 201 and protruding from the center of the cavity 201. Because the mold 200 does not have the counterbore portion 11, the plate material 100 is set on the upper surface 200a so as to cover the entire cavity 201. When the plate material 100 is heated with a flame (not shown), for example, as shown by hatching in FIG. 13 , it is thought that the heat input to the mold 200 is not uniform like an elliptical shape, but rather is biased. This causes variations in the heat input to the plate material 100, and it is presumed that uneven deformation due to the heat input also occurs in the differential pressure deformation when the cavity 201 is put under negative pressure.

[0051] On the other hand, in the example, as shown by hatching in Fig. 14, for example, the mold 10 has the countersunk portion 11, and it is thought that the heat input to the mold 10 is uniform like a circle that follows the outer shape of the countersunk portion 11. This is presumably because the hot air flow caused by the flame remains in the recess formed by the countersunk portion 11, and the heat input to the mold 10 is more uniform than in the mold 200 that does not have the countersunk portion 11. For this reason, it is thought that the heat input to the plate material 100 is more uniform than in the comparative example, and uneven deformation during differential pressure deformation is suppressed, resulting in improved symmetry of the shape of the obtained vibrator 2.

[0052] The method described in Patent Document 1 uses a mold 300 including a lower mold 310 having a cavity 311, support posts 312, and ventilation holes 313, and an upper mold 320 having a through-hole 321, as shown in FIG. 15 . This method sandwiches a plate material 100 between the molds 300, heats the plate material 100 with flame F from a heat source H, and creates a negative pressure in the cavity 311 to form a three-dimensional curved surface through differential pressure deformation. However, since the upper mold 320 is positioned closer to the heat source H than the plate material 100, the mold 300 has a structure in which variations in heat input to the upper mold 320 also affect the heat input to the plate material 100, as shown by hatching and arrows in FIG. 15 . For this reason, it is considered difficult to obtain a highly symmetrical vibrator 2 using a mold structure in which the plate material 100 is sandwiched between multiple molds, such as the mold 300.

[0053] Next, the relationship between the symmetry of the rim 23 of the vibrator 2 and the resonant frequency difference Δf in the wine glass mode where n=2 will be described.

[0054] For example, as shown in Fig. 16, the radius of the rim 23 of the vibrator 2 when viewed from above is r, and if the outer shape of the rim 23 is not a perfect circle, the radius r varies for each orientation as shown in Fig. 17. Here, the radius r of the rim 23 is the distance from the center C of the rim averaged circle to the rim 23 in the radial direction with the center C as the axis. Furthermore, the orientation is assigned, for example, from 0° to 360° clockwise, with any direction when viewed from above (for example, the 12 o'clock direction) being set as 0°.

[0055] In the non-patent document Microsystem Technologies (2021) 27:789-799, an investigation into the relationship between the n-fold symmetry (n: integer greater than or equal to 1) of a vibrator and the resonant frequency difference Δf in the wine-glass mode for n = 2 revealed that four-fold symmetry significantly affects Δf. N-fold symmetry means that when a vibrator is rotated by (360 / n)° around the center C of the rim-averaged circle, the outer shapes of the rim 23 before and after the rotation completely overlap. For example, when a four-fold symmetric vibrator 2 is rotated by 90° around the center C of the rim-averaged circle, the outer shapes of the rim 23 before and after the rotation completely overlap. The rim radius of an actual vibrator has a seemingly random distribution, as shown in Figure 17, but can be decomposed into periodic waves by Fourier transform.

[0056] For example, the radius r of the rim 23 shown in FIG. 17 can be expressed by the following equation (5) by performing a Fourier transform.

[0057] r=a0+a1sinθ+a2sin2θ+a3sin3θ+a4sin4θ+a5sin5θ+a6sin6θ+a7sin7θ+a8sin8θ...(5) In equation (5), sinθ to sin8θ correspond to one-fold to eight-fold symmetry, respectively. a0 is the average radius of the rim 23, i.e., the radius of the rim-averaged circle. a1 to a8 are coefficients corresponding to one-fold to eight-fold symmetry. The smaller the value, the smaller the corresponding n-fold symmetry. When a1 to a8 are all zero, the rim 23 is a perfect circle without n-fold symmetry. In other words, the smaller the values ​​of a1 to a8, the more symmetric the shape of the rim 23. By graphing the coefficients obtained from equation (5), it is possible to evaluate whether the n-fold symmetry is small, as shown in Figure 18, for example. Note that Figure 18 shows a bar graph with the "n-fold" portion of n-fold symmetry on the horizontal axis and the values ​​of coefficients a1 to a8 on the vertical axis. For ease of viewing, results other than one-fold, four-fold, and eight-fold symmetry are omitted. As mentioned above, it has been reported that the smaller the four-fold symmetry of a vibrator, the smaller the resonant frequency difference Δf. Here, "small four-fold symmetry" means that the coefficient a4 is small. When the coefficient of four-fold symmetry for the vibrators of the example and the comparative example was compared at n=30, the results shown in FIG. 19 were obtained.

[0058] In the vibrator of the comparative example, the maximum value of the coefficient of four-fold symmetry was approximately 57, the minimum value was approximately 19, and the average value was approximately 36. On the other hand, in the vibrator 2 of the example, the maximum value of the coefficient of four-fold symmetry was approximately 31, the minimum value was approximately 0, and the average value was approximately 9. This result shows that the vibrator 2 of the example has a smaller four-fold symmetry and a smaller resonant frequency difference Δf than the comparative example, and therefore has improved vibration characteristics.

[0059] According to this embodiment, a vibrator manufacturing apparatus for a vibrator 2 uses a mold 10 having a counterbore portion 11, which is a recess formed in an upper surface 10a facing a heat source, and a cavity 12 formed in a bottom surface 11a of the counterbore portion 11, the cavity 12 having a maximum diameter smaller than that of the counterbore portion 11. This vibrator manufacturing apparatus has a structure in which the cavity 12 is formed within the bottom surface 11a of the counterbore portion 11, where the plate material 100 is placed, and therefore the heat input to the mold 10 and therefore the plate material 100 is more uniform than in a case in which the counterbore portion 11 is not formed. As a result, the symmetry, particularly the four-fold symmetry, of the curved surface portion 21 and the connection portion 22 of the three-dimensional curved surface shape is small, and a vibrator 2 with improved vibration characteristics can be manufactured. Furthermore, since the mold 10 does not require the plate material 100 to be pressed against the inner wall surface of the cavity 12 to be molded, the surface irregularities of the inner wall surface of the cavity 12 are prevented from being transferred to the curved surface portion 21 of the vibrator 2 manufactured using the mold 10, and a decrease in the Q value of the vibration is suppressed.

[0060] (First Modification) The mold 10 may have a polygonal shape in which the outer shape of the countersunk portion 11 is line-symmetric or point-symmetric when viewed from above, as shown in Fig. 20, for example. In this case, when a rectangular plate material 100 is used, the corners of the countersunk portion 11 engage with the corners of the plate material 100 to function as positioning portions 111 that suppress misalignment of the plate material 100. In Fig. 20, the outer shape of the countersunk portion 11 is shown by a two-dot chain line to make it easier to see.

[0061] In this way, from the viewpoint of easily equalizing the heat input from the heat source H to the mold 10, the countersunk portion 11 may have an outer shape that is line-symmetric or point-symmetric when viewed from above, and is not limited to a circular shape, but may have other shapes such as a triangular shape or a pentagonal shape. The plate material 100 is also not limited to a rectangular plate shape, but may have other shapes such as a polygonal plate or a disk. Furthermore, although the above describes an example in which the corners of the countersunk portion 11 serve as the positioning portions 111, the present invention is not limited to this, and even if a portion of the outer periphery of the countersunk portion 11 other than the corners is fitted with the plate material 100, it functions as the positioning portion 111.

[0062] This modification also provides a vibrator manufacturing apparatus and a method for manufacturing a vibrator 2 that can obtain the same effects as those of the first embodiment. Furthermore, a part of the outer periphery of the countersunk portion 11 serves as a positioning portion 111 that fits with the plate material 100, thereby providing the effect of suppressing positional displacement of the plate material 100 during processing.

[0063] (Second Modification) 21 , the mold 10 may have a recess 15 on the bottom surface 10b opposite to the top surface 10a, and may have a heat storage structure in which heat is likely to accumulate in the mold 10 during heating by the heat source H. In this case, the portions of the bottom surface 10b of the mold 10 that come into contact with other members, etc. are limited to the protrusions 16, which limits the escape route for heat and makes it easy for heat to accumulate in the mold 10 during heating by the heat source H. For this reason, the heat input to the mold 10, and therefore the heat input to the plate material 100, is more uniform than when the bottom surface 10b does not have the recess 15, making it possible to manufacture a vibrator 2 with improved symmetry of the curved surface portions 21 and the connecting portions 22.

[0064] The planar size, depth, shape, forming locations, number, etc. of the recesses 15 are not limited to the example shown in FIG. 21, and can be changed as appropriate.

[0065] This modification also provides a vibrator manufacturing apparatus and a method for manufacturing a vibrator 2 that can achieve the same effects as those of the first embodiment. Furthermore, since the mold 10 has the recess 15 on the lower surface 10b, the mold 10 has a structure that makes it easy to store heat, and the heat input to the plate material 100 is more uniform, which is expected to have the effect of further improving the symmetry of the vibrator 2.

[0066] (Third Modification) The mold 10 is not limited to a mold in which the cavity 12 has a substantially bowl-like shape, and may have a substantially cylindrical shape (a square shape in cross section) as shown in Fig. 22, for example. In this case, when forming the curved surface portion 21 in the plate material 100, the contact area with the inner wall surface of the cavity 12 is reduced, making it difficult for the surface irregularities on the inner wall surface of the cavity 12 to be transferred to the curved surface portion 21. Therefore, it is possible to suppress a decrease in the Q value of vibration caused by the transfer of the surface irregularities to the curved surface portion 21.

[0067] This modification also provides a vibrator manufacturing apparatus and a method for manufacturing the vibrator 2 that can achieve the same effects as those of the first embodiment.

[0068] The first to third modified examples can be freely combined.

[0069] (Other embodiments) Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one, or less than one, are also within the scope and spirit of the present disclosure.

[0070] It goes without saying that in each of the above embodiments, the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle. Furthermore, in each of the above embodiments, when numerical values ​​such as the number, values, amounts, and ranges of the components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle. Furthermore, in each of the above embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., unless they are specifically stated or are clearly limited to a specific shape, positional relationship, etc. in principle. [Explanation of symbols]

[0071] 2... vibrator, 21... curved surface portion, 10... mold, 10a... upper surface, 11... counterbore portion, 11a... bottom surface of counterbore portion, 12... cavity, 14... vent hole, 100... plate material, 111... positioning portion

Claims

1. A vibrator manufacturing apparatus for manufacturing a vibrator (2) having a curved surface portion (21) having a three-dimensional curved surface, The mold (10) includes a countersunk portion (11) formed on an upper surface (10a) facing a heat source for softening a plate material (100) made of a reflow material, the countersunk portion being a recess in which the plate material is placed, a cavity (12) being a recess formed on a bottom surface (11a) of the countersunk portion, and an air vent (14) formed in the cavity and connected to a negative pressure source for creating a negative pressure in a space closed by the plate material and the cavity, the countersunk portion has a maximum diameter larger than that of the plate material, The cavity has a maximum diameter smaller than that of the bottom surface of the countersunk portion.

2. The vibrator manufacturing apparatus according to claim 1 , wherein the counterbore portion has an outer shape that is point-symmetric when viewed from a direction normal to the upper surface.

3. The vibrator manufacturing apparatus according to claim 2 , wherein the counterbore portion has a circular outer shape when viewed from a direction normal to the upper surface.

4. The vibrator manufacturing apparatus according to claim 1 , wherein the counterbore portion has an outline that is line-symmetrical when viewed from a direction normal to the upper surface.

5. 2. The vibrator manufacturing apparatus according to claim 1, wherein the counterbore portion has a positioning portion (111) that fits into a part or all of an outer periphery of the plate material when the plate material is placed.

6. 6. The vibrator manufacturing apparatus according to claim 1, wherein the depth of the recessed portion is greater than the thickness of the plate material.

7. A method for manufacturing a vibrator (2) having a curved surface portion (21) having a three-dimensional curved surface, A mold (10) is provided with a countersunk portion (11) which is a recess formed on an upper surface (10a) facing a heat source, a cavity (12) which is a recess formed on a bottom surface (11a) of the countersunk portion and has a maximum diameter smaller than that of the bottom surface, and an air hole (14) formed in the cavity and connected to a negative pressure source; preparing a plate material (100) and placing it in the counterbore; creating a negative pressure in the closed space formed by the plate material and the cavity using a negative pressure source connected to the air vent; softening the plate material with the heat source, and deforming the plate material by a pressure difference between inside and outside the closed space to form the curved surface portion.

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