JPH0316840B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a manufacturing method for inexpensively manufacturing an acoustic diaphragm made of a material that is difficult to obtain through normal machining. In general, materials with a large Young's modulus and a small mass are preferred for diaphragms of speakers, etc., but such materials generally have poor brittleness and are extremely difficult to form into precise shapes through machining. difficult. For this reason, there is a method of manufacturing a diaphragm by spraying and depositing fine particles of a material suitable for a diaphragm at high speed on a template formed in the shape of a diaphragm to form a thin plate, and then separating this thin plate from the template. It has been proposed (see Japanese Patent Application Laid-Open No. 115097/1983). However, although such a method provides a diaphragm with excellent material quality and dimensional accuracy, it is very troublesome to separate the thin plate and template. In other words, to separate the formed thin plate from the template, there are two methods: one is to use the difference in thermal contraction between the thin plate material and the template material, and the other is to make the template made of a material that is easy to melt, such as copper, and then separate the thin plate from the template after forming the thin plate. A method of melting a template is used. However, in the former case, the difference in thermal expansion coefficient between the two materials must be sufficiently large, which limits the materials that can be used for the template. It is difficult to obtain, and even if it can be obtained, it will be very expensive. In addition, the latter method has the disadvantage that the work of melting the template is complicated and the template becomes a consumable item, resulting in high manufacturing costs. This invention has been made in view of the above points, and its purpose is to provide a method of manufacturing an acoustic diaphragm that can inexpensively manufacture a diaphragm made of a material with excellent acoustic properties. It is in. In order to achieve such an object, the present invention involves spraying metal, alloy, ceramic, or a mixture thereof onto a paper base material to form a coating, and then
It is designed so that only the base material is burned out. Hereinafter, this invention will be explained in detail with reference to Examples. FIG. 1 is a sectional view showing the state in which paper to be used as a base material is formed. In the figure, paper 1 is made of pulp or the like, and is wound into a roll around a core 2 in the form of a long belt. The mold is a cylindrical first lower mold 3;
A cylindrical second part is slidably inserted into the lower mold 3.
It consists of a lower mold 4 and a cylindrical upper mold 5. The upper surface of the second lower mold 4 is formed in a convex spherical shape, and the center portion of the lower surface of the upper mold 5 is formed in a concave spherical shape concentric with this convex spherical surface. Further, a punching cutter 6 having a blade portion at the lower end is slidably fitted into the outer peripheral surface of the upper mold 5. Paper 1 is inserted between the first lower mold 3 and upper mold 5 of such a mold, the second lower mold 4 is raised to form the paper 1 into a spherical surface, and then the first lower mold 3 and the upper mold 5 together to form a flange part around the spherical surface. After that, lower the punch cutter 6 to cut the paper 1 around the mold.
cut. When the upper and lower molds are separated and the molded paper is taken out, the base material 1 is shaped as shown in Figure 2.
0 is obtained. This base material 10 has approximately the same shape as the diaphragm to be manufactured. Next, powder of a metal suitable for the diaphragm material, such as B, Be, Ti, Mg, etc., is deposited on the base material 10 by plasma spraying. FIG. 3 is a block diagram of the plasma spraying apparatus, and FIG. 4 is a sectional view of the spray gun. The plasma spraying apparatus includes a power supply section 11, a cooling water tank 12, a working gas cylinder 13, a control device 14 that inputs electrical input, cooling water, and working gas from these and sends it out as a control output.
Powder feeding gas cylinder 15, powder feeding device 1 which inputs powder feeding gas and sends out metal powder at a predetermined pressure.
6, a thermal spray gun 17, etc. In addition,
18 is the electrical input, cooling water, and working gas to the thermal spray gun 1.
19 is a line for supplying metal powder to the thermal spraying gas 17, and 20 is a plasma jet. A cathode 21 made of thorium-tungsten alloy and a cathode 21 are provided in the nozzle portion of the thermal spray gun 17.
An anode 22 made of copper is provided concentrically forming a gas passage 23 on the outside of the anode 2.
A powder passage 24 is formed near the opening of 2. Then, a DC high voltage is applied between the cathode 21 and the anode 22 to generate an arc 25, and the gas passage 2
The working gas sent in from the nozzle 3 is made to undergo a violent swirling motion and flowed toward the outlet, and the arc 25 is stabilized so as to be narrowed to the nozzle central axis. As a result, the working gas is heated by the arc 25 and is ejected from the nozzle outlet as a high-velocity plasma jet 20. The metal powder is carried by the powder feed gas and passes through the powder passage 2.
It is blown into the jet from 4. While moving on the jet, this metal powder becomes molten, is given large thermal energy and kinetic energy, becomes molten particles 26, and is struck and bonded to the surface of the base material 10, as shown in FIG. A coating 28 made of a metal material suitable for the diaphragm is formed on the surface of the base material 10 in the same shape as the diaphragm.
Note that at this time, the temperature of the base material 10 is approximately 200° C. or lower, and the base material 10 is not damaged at this temperature. Next, the base material 10 on which the coating 28 has been formed is burned away. FIG. 6 shows a cross-sectional view of the heating furnace. In the figure, an inner container 31 made of stainless steel or the like is provided inside an outer container 30 made of fireproof material, and a heater 32 is wound around the outer peripheral surface of this inner container 31. Furthermore, a partition plate 33 having a large number of pores is provided inside the inner container 31, and the base material 10 on which the coating 28 is formed is placed on the partition plate 33. In addition, 34 is a lid plate. When the base material 10 is placed in the heating furnace and the heater 32 is energized to heat the inside of the furnace to 400°C or higher, the base material 10 made of paper is burned out and the coating 2
Only 8 remain. In this way, as shown in FIG. 7, a diaphragm made of a coating 28 having the same shape as the base material 10 is obtained. This diaphragm has excellent material properties, so when it is incorporated into a speaker or the like, a product with excellent frequency characteristics, transient characteristics, damping characteristics, etc. can be obtained. In addition, this diaphragm is formed from a paper base material that is easy to form into any shape, so
It can be easily formed into a desired shape. In the above embodiments, a thermal spraying device that uses plasma was explained, but in addition, a gas thermal spraying device that uses a combustion flame such as an oxygen-acetylene flame or an oxygen-propane flame as a heat source, and a thermal spraying device that uses arc heat due to arc discharge are also available. Electric arc thermal spraying equipment that uses as a heat source, explosive thermal spraying equipment that uses high-temperature, high-velocity flame generated when a mixed gas such as oxygen-acetylene explodes as a heat source, and wire explosive thermal spraying equipment that causes a discharge explosion by passing a large shock current through a wire, etc. can be used. In addition to the above-mentioned metals, alloys, ceramics, and cermets, which are mixtures of metals such as boron nitride and ceramics, can be used as thermal spray materials, that is, materials for the diaphragm. In particular, ceramics and cermets are suitable for this method because they are difficult to form into desired shapes. Furthermore, sintered products such as ceramics and cermets can be sintered when the base material is burned out or in a subsequent firing step. Note that the materials shown in the following table are suitable as ceramics.

[Table] As described above, according to the method for manufacturing an acoustic diaphragm according to the present invention, the work of removing the base material from the coating is extremely simple in order to burn off and remove the paper base material on which the coating is formed. Moreover, paper as a base material can be used to easily form the desired shape of the diaphragm, and the cost is also low, making it possible to manufacture a diaphragm made of a material with excellent acoustic properties at a low cost.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the state in which the base material is formed, Figure 2 is a front view of the molded base material, Figure 3 is a configuration diagram of the plasma spraying device, Figure 4 is a sectional view of the spray gun, and Figure 4 is a cross-sectional view of the spray gun. FIG. 5 is a sectional view of the base material with a sprayed coating formed on its surface, FIG. 6 is a sectional view of the heating furnace, and FIG. 7 is a front view of the coating that will become the diaphragm. 1... Paper, 3... First lower mold, 4... Second lower mold, 5
...Upper die, 6...Punching cutter, 10...Base material, 17...
Thermal spray gun, 20... plasma jet, 21... cathode, 22... anode, 23... gas passage, 24... powder passage, 28... coating, 30... outer container, 31... inner container,
32... Heater, 33... Partition plate.

Claims (1)

[Claims] 1 A base material made of paper is formed into the shape of a diaphragm, a coating is formed by spraying metal, alloy, ceramic, or a mixture thereof on the surface of this base material, and then the base material is burned out to form the above-mentioned A method of manufacturing an acoustic diaphragm that leaves only the coating.