JP5441537B2 - Diaphragm for electroacoustic transducer by water vapor pressure molding and manufacturing method thereof - Google Patents

Description

  The present invention relates to a diaphragm for an electroacoustic transducer by water vapor pressure molding, particularly a diaphragm made of metal, and a method for manufacturing the same.

  Conventionally, diaphragms for electroacoustic transducers can be manufactured from plate-like metal using pressure forming using air pressure, gas forming using gas pressure, hydraulic forming using hydraulic pressure, vacuum forming using vacuum pressure, and matching. Various manufacturing methods such as upper and lower mold forming using a mold have been used.

  In the manufacture of speaker metal cones by these various pressure forming processes for plate-like metal, the amount of spring back of the processed product is generally large as a result of room temperature processing, and mold correction and molding are required to obtain the specified molding. It is necessary to repeat. In order to improve this point, pressure forming is performed at a temperature near the recrystallization temperature of the workpiece (150 to 250 ° C.) so that the springback amount of the metal cone molded product is reduced and sufficient strength is satisfied. A method and apparatus have been proposed (see Patent Document 1).

  However, the following problems remain in common in any pressure molding. As for (1), in a cone-shaped molded product, a uniform thickness cannot be obtained in each part in the radial direction, the neck (inner periphery) is always the thinnest, and gradually increases from the intermediate part to the outer periphery. For this reason, it causes a partial reduction in strength and generation of an axisymmetric intense mode in the vibration mode. The (2) is that after the molding process, the molded product must be subjected to a surface treatment in a separate process in order to prevent surface corrosion.

JP-A-52-25617

  The problem to be solved by the present invention is that the manufacture of a diaphragm by pressure molding of a conventional plate-like metal requires mold correction and repetitive molding in order to reduce the amount of springback during room temperature pressure molding. In addition, since the thickness after molding becomes non-uniform throughout, the strength of the diaphragm is partially reduced, and an axisymmetric sudden mode is generated even in the vibration mode. It is necessary to perform surface treatment in the process.

  Therefore, the present invention does not generate a springback in the plate-shaped metal material despite the pressure forming, the thickness after forming is uniform in each part in the radial direction, and the partial strength is reduced or the partial shaft is formed. An object of the present invention is to provide an electroacoustic transducer diaphragm made of a plate-like metal, which can prevent the occurrence of a symmetric vibration mode, and can be subjected to surface treatment for corrosion prevention at the same time as pressure forming, and a method for manufacturing the same. To do.

According to the present invention, the diaphragm for electroacoustic transducers using the plate-like metal according to claim 1 is formed into a desired diaphragm shape by heating a plate-like metal having a concave surface together with pure water placed in the bottom of the concave surface. Sealed in the mold space for a predetermined time, and formed into the desired shape by the water vapor pressure that evaporates in the heated sealed space, creating a uniform thickness on the inner, intermediate and outer peripheral parts, and the molding side surface And an oxidized film formed thereon.
Moreover, according to this invention, the manufacturing method of the diaphragm for electroacoustic transducers by the plate-shaped metal of Claim 2 provides the process of providing a concave surface in a metal plate-shaped material, and the concave bottom or lower part of a plate-shaped material. A step of injecting pure water in an amount corresponding to the size of the plate-like material, a step of heating a formed female die having a desired diaphragm-shaped recess to a predetermined temperature equal to or higher than the boiling point of pure water, and a plate-like material A step of positioning the upper part of the space in the heated female mold together with pure water at the bottom of the concave surface; By sealing the plate-shaped material in a heated state with the water vapor pressure generated in the inner space of the formed female mold by sealing for a predetermined time according to the amount of the And a step of raising the upper mold after depressurizing the inner space of the mold and taking out the formed plate material. The features.
The diaphragm manufacturing method according to claim 3 is characterized in that the concave surface provided in the plate-like material is formed by making a substantially spherical area of the entire portion to be molded into a shallow spherical surface.

  According to the present invention, since the metal plate-like material is first pressure-formed in a heated state, the amount of springback is reduced, and pure water is put into the bottom or lower portion of the concave surface provided in the plate-like material. When heated and pressurized, the bottom or bottom of the concave surface touching the pure water is heated and pressurized later than the top of the concave surface exposed from the pure water, and eventually all the pure water is vaporized. Therefore, it is not thinner than the upper part, that is, the outer peripheral part, and is formed with a uniform thickness in each part in the radial direction as a whole. Furthermore, since a metal oxide film is formed on the surface of the molded product made of a metal plate material by water vapor generated during molding, surface treatment for preventing corrosion is applied simultaneously with molding.

FIG. 1 is a cross-sectional view showing a process of positioning a diaphragm plate material together with pure water placed on its concave surface in an upper part of a heated molding female inner space in an embodiment of a diaphragm manufacturing method according to the present invention. It is. FIG. 2 is a cross-sectional view showing a state in which pressure forming with water vapor is started by lowering the forming upper die onto the female die in the embodiment of FIG. FIG. 3 is a cross-sectional view showing a state in which the pressure molding is almost completed after shifting from the state of FIG. FIG. 4 is a cross-sectional view of the diaphragm material after pressure molding according to the present invention, and shows that the inner peripheral portion, the outer peripheral portion, and the intermediate portion have the same thickness. FIG. 5 is a frequency characteristic diagram comparing the acceleration frequency characteristics of the diaphragm according to the present invention and a conventional product formed by pressure air molding under the same conditions as in the present invention. FIG. 6 shows vibration modes of the conventional product and the product of the present invention, (a) shows the vibration mode of the conventional product, and (b) shows the vibration mode of the product of the present invention. 7A and 7B are infrared absorption analysis diagrams on the molding surface side of the conventional product and the product of the present invention. FIG. 7A shows the analysis product of the conventional product and FIG. FIG. 8 is a 5000 times enlarged cross-sectional photograph of the surface of the vibration plate of the present invention on the molding side, showing the formation of an oxide film on the surface.

  In order to achieve the object of the present invention, an embodiment of a method for producing an electroacoustic transducer diaphragm by steam pressure forming of a metal plate will be described with reference to FIGS.

  As an example, if a method for manufacturing a cone-type speaker diaphragm having a diameter of 10 cm according to the present invention using an aluminum foil having a thickness of 100 μm is shown, the plate-like material 1 is preferably preliminarily formed as shown in FIG. A shallow spherical concave surface 2 having a diameter of 10 cm or less is formed, and 5 cc of pure water 3 is poured into the bottom or lower portion of the concave surface 2. The amount of the pure water 3 is determined to be a value sufficient to expose the upper part of the concave surface 2 and to perform the steam pressure molding of the plate-like material 1 to be used.

  On the other hand, a forming female die 4 which is a lower die of a pressure forming die and has a concave portion 5 having a desired diaphragm shape is heated in advance to 200 ° C., which exceeds the boiling point of pure water and enables the formation of an aluminum foil. As shown in FIG. 1, the concave surface portion of the plate-like material 1 is installed on the upper part of the space in the concave portion 5 of the female mold 4 together with pure water.

  Next, as shown in FIG. 2, the flat mold 6 of the pressure mold is lowered, and the space in the recess 5 of the female mold 4 is sealed. The upper die 6 has an on-off valve 7 that communicates the space inside the recess and the outside space, but at this time, of course, it is closed. The sealing time under heating at 200 ° C. is set to 30 seconds. During this time, a load of 5 t is applied to the upper die 6, and the water vapor pressure generated by boiling pure water on the surface side of the concave surface 2 of the plate-like material 1 acts on the surface side of the plate-like material 1 accordingly. To do. However, in the initial stage of the sealing time, the lower part or the bottom part of the concave surface 2 of the plate-like material 1 does not have a temperature higher than the boiling point of pure water because pure water exists, and the upper part of the concave surface 2 exposed from the pure water. That is, the portion corresponding to the outer peripheral portion of the cone-shaped diaphragm first reaches a high temperature, and the molding proceeds from the outer peripheral portion first.

  In the final stage, as shown in FIG. 3, all of the pure water 3 becomes water vapor 3 ', and the bottom of the concave surface, that is, the portion corresponding to the inner peripheral portion of the diaphragm is exposed, reaches a high temperature and undergoes water vapor pressure molding. In this way, the portion corresponding to the inner peripheral portion of the diaphragm is heated and pressurized later than the upper concave portion corresponding to the outer peripheral portion, and as a result, both portions have a uniform thickness and the female concave portion 5 has a uniform thickness. Molded into a shape. After the elapse of 30 seconds, the on-off valve 7 is opened, the water vapor in the mold is exhausted under reduced pressure, the upper mold 6 is raised, and the diaphragm 10 made of the molded plate-like material 1 is removed from the mold.

  FIG. 4 is a cross-sectional view of the cone-shaped diaphragm 10 manufactured from the aluminum plate 1 by the above-described water vapor pressure forming of the present invention. Inner circumference part), B (intermediate part) and C (outer circumference part) are shown. As a result of using the aluminum plate-like material under the same conditions as the test sample, and making 1000 diaphragms 10 obtained by performing water vapor pressure molding under the same conditions, the average values of the measurements for all these samples were obtained. In A, B, and C, the same thickness of 0.083 mm was measured.

  For comparison, 1000 pieces of diaphragms having the same dimensions as described above were prepared by pressure forming using air pressure as an example of the prior art using an aluminum plate material having the same conditions as above, and the same three positions A to C as in FIG. When the thickness was measured for each of these, and an average value was taken, remarkable non-uniformity of 0.075 mm at position A, 0.083 mm at position B, and 0.090 mm at position C was found.

  FIG. 5 is a characteristic curve diagram comparing the diaphragm acceleration frequency characteristics of the conventional product and the present invention product. In the figure, the curve by the thick line shows the frequency characteristic of the product of the present invention, the curve by the thin line shows the frequency characteristic of the conventional product, and the peak dip due to resonance becomes large in the conventional product in the vicinity of 10 kHz and above, In the product of the present invention, the peak dip is kept small, which is clearly proof that the uniform thickness of the diaphragm prevents a partial reduction in strength.

  FIG. 6 shows vibration mode analysis diagrams of the conventional product and the product of the present invention near a frequency of 12.8 kHz. (A) is the product of the conventional product, (b) is the product of the present invention, and (a) shows the shaft. Symmetrical intense vibration modes have emerged, which is apparently due to a partial decrease in strength due to the non-uniform thickness of the diaphragm, but (b) is accompanied by a uniform thickness. A non-axisymmetric stable vibration mode can be confirmed.

  Finally, the presence or absence of a composition change on the pressure molding side surface of the conventional product and the product of the present invention is observed. 7A and 7B are infrared absorption analysis diagrams. FIG. 7A is a conventional product, FIG. 7B is a product of the present invention, and FIG. 8 is an enlarged cross-sectional photograph of the product of the present invention on the steam pressure molding side. As is clear by comparing (a) and (b) of FIG. 7, it was confirmed that the surface of the product of the present invention contains 43.2% of atoms indicating oxide O which is not present in the conventional product. The Also in the cross-sectional photograph of FIG. 8, a layer different from the aluminum base material is formed on the molding side surface of the product of the present invention, and it is clear from FIG. 7 (b) that this surface layer is an oxide film. It is.

  In the above embodiment, aluminum is shown as an example of the metal to be used. However, the present invention is not limited to aluminum, and is usually used as a diaphragm for an electroacoustic transducer, and includes other alloys including titanium, permalloy, and magnesium alloys. It is also applicable to metals and various alloys, and the amount of pure water, heating temperature, and sealing time are determined according to the dimensions and properties of the selected material. As for pure water, high-purity water can be substituted as long as it does not contain undesirable impurities.

DESCRIPTION OF SYMBOLS 1 Plate-like material 2 Concave surface 3 Pure water 4 Forming female die 5 Concave part 6 Upper die 7 On-off valve 10 Diaphragm

Claims (3)

  A plate-shaped metal having a concave surface is sealed together with pure water placed in the bottom of the concave surface in a heated mold-shaped mold space for a predetermined time, and molded into a desired shape by vapor pressure that evaporates in the heated sealed space. An electroacoustic transducer diaphragm made of a plate-like metal, comprising: an inner peripheral portion, an intermediate portion, and an outer peripheral portion having a uniform thickness, and an oxide film generated on a molding-side surface.   A step of providing a concave surface on a metal plate-like material, a step of injecting pure water in an amount corresponding to the size of the plate-like material into the bottom or lower portion of the concave surface of the plate-like material, and a formed female having a concave portion having a desired diaphragm shape A step of heating the mold to a predetermined temperature equal to or higher than the boiling point of pure water, a step of positioning the plate-like material together with pure water at the bottom of the concave surface in the heated upper part of the molded female mold, and a closed on-off valve By lowering the forming upper mold and sealing the forming female mold inner space containing the plate material for a predetermined time according to the amount of pure water, the plate material is heated by the water vapor pressure generated in the forming female mold inner space. And a step of removing the molded plate-shaped material by raising the upper die after depressurizing the molding female mold inner space by opening the on-off valve after a predetermined sealing time The manufacturing method of the diaphragm for electroacoustic transducers by a plate-shaped metal. 3. The method for manufacturing a diaphragm according to claim 2, wherein the concave surface provided on the plate-like material is formed by making a substantially spherical area of the almost entire area of the portion to be molded a shallow spherical surface.

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