JPH0344479B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an acoustic diaphragm, which can inexpensively manufacture a diaphragm made of ceramic into any desired shape. In general, ceramics have a large specific Young's modulus (E/ρ) and are inexpensive, so they are very suitable as acoustic diaphragms. However, on the other hand, there is a problem with brittleness, and in particular, a green core obtained by press-molding ceramic powder before sintering is extremely brittle, making it difficult to form a diaphragm from ceramic alone. In order to solve these problems, it has been proposed to create a composite plate material by thermally spraying ceramic such as alumina onto the surface of a light metal foil made of an Al alloy, and to use this material as an acoustic diaphragm (in particular, Kaisho
56-109096). However, as a material for light metal foil, E/
B, Be, etc., which have a large ρ value, cannot be used because of their poor brittleness, and Al-based metals, which have good brittleness even if their E/ρ value is small, must be used. For this reason, a sufficiently large E/ρ value could not be obtained as a composite plate material. On the other hand, powder such as ceramic or cermet is deposited on a template formed in the shape of a diaphragm by thermal spraying to form a thin plate of the same shape on the template, and then the thin plate is separated from the template to form a diaphragm. A method of manufacturing has been proposed (see Japanese Patent Application Laid-open No. 115097/1983). However, according to this method, the difference in thermal contraction between the thin plate and the template is used to separate the thin plate and the template.
In addition, the manufacturing process is complicated because the template is melted, and the thermal spraying equipment for spraying the powder as molten particles becomes expensive.
The drawback was that the manufacturing cost was extremely high. This invention was made in view of the above points, and its purpose is to form a diaphragm made of ceramic with a large specific Young's modulus into an arbitrary shape.
Another object of the present invention is to provide a method for manufacturing an acoustic diaphragm that can be manufactured at low cost. In order to achieve such an object, the present invention forms a mixture of pulp and ceramic fine particles into the shape of a diaphragm, then decarburizes it for a predetermined period of time to burn out the pulp, and then removes the ceramic. It was sintered to make a ceramic diaphragm. Hereinafter, this invention will be explained in detail with reference to Examples. FIG. 1 is a block diagram of a paper making apparatus for carrying out an embodiment of the method for manufacturing an acoustic diaphragm according to the present invention. In the figure, the first raw material tank 1 contains pulp 2.
is stored, and this pulp 2 flows into a mixing tank 5 through a pipe 4 by opening a regulating valve 3. This pulp 2 has been treated to remove as much lignin as possible to increase its surface area by fibrillating it so that the ceramic powder can easily adhere to it, and the degree of cation modification has been appropriately adjusted. There is. A finely divided ceramic powder 7 made of, for example, alumina (Al ₂ O ₃ ) is stored in the second raw material tank 6 , and this ceramic powder 7 is mixed through a pipe 9 by opening a regulating valve 8 . It is designed to flow into tank 5. The mixing ratio of the pulp 2 and the ceramic powder 7 is adjusted by operating the regulating valves 3 and 8. A stirring fan 10 is provided inside the mixing tank 5, and is rotated by the operation of a stirring motor 11. Pulp 2 and ceramic powder 7 flowing into mixing tank 5
are mixed by a stirring fan 10 to form a mixed suspension 12. Here, since the pulp 2 has a fibrillated surface, a large amount of ceramic powder adheres to it, and since the pulp 2 has an appropriate degree of cation modification, the ceramic powder adheres strongly. Then, the mixed suspension 12 stored in the mixing tank 5 is transferred to the pipe 1 by opening the regulating valve 13.
4 to the paper making tank 15. A water tank 18 is connected to the papermaking tank 15 via a water supply pipe 16 and a dewatering pipe 17, so that water circulates within the tank. That is, valve 1
Open 9 and 20 and connect the water pump 21 and dehydration pump 2.
2 is operated, the water in the water tank 18 is sent to the upper part of the papermaking tank 15, is dehydrated from the bottom, and moves from the top to the bottom in the tank. With the water circulating in this way, open the regulating valve 13 to pump a certain amount of mixed suspension 1.
2 is fed into the papermaking tank 15. The fed mixed suspension 12 flows downward together with water, but the papermaking tank 1
Paper is made by a paper making wire mesh 23 formed in the shape of a diaphragm provided in the paper making machine 5. And paper making tank 1
The concentration of the mixed suspension 12 in the paper-making wire mesh 23 gradually becomes thinner as the water circulates, but when this concentration reaches about 0.02% and the mixed suspension 12 is completely transferred to the paper-making wire mesh 23, the water supply is stopped. Stop the pump 21. When the dewatering pump 22 is operated continuously to completely remove the water in the tank, a diaphragm material 24 made of pulp and having ceramic powder adhered thereon, formed in the shape of a diaphragm, remains on the paper-making wire mesh 23. Then, when the diaphragm material 24 is in a water-containing state of about 3 to 4 times the weight of the anhydrous diaphragm material, the diaphragm material 24 and the papermaking wire mesh 23 are added to the papermaking tank 1.
Take it out from 5. After that, the diaphragm material 24 is removed from the paper wire mesh 23. Next, this diaphragm material 24 is molded with a mold. FIG. 2 is a sectional view of the mold. In the figure, 26 is an upper mold formed concavely in the shape of a diaphragm;
7 is a lower mold formed in a convex shape in the shape of a diaphragm. After setting the diaphragm material 24 on the lower mold 27, the upper mold 2
6 is lowered and molded, as shown in Figure 3,
A diaphragm material 24 accurately formed into a diaphragm shape is obtained. Next, the formed diaphragm material 24 is heated in a heating furnace. FIG. 4 is a sectional view of the heating furnace. In the figure, an inner container 30 also made of a refractory material is provided inside an outer container 29 made of a refractory material.
A heater 31 is wound around the outer circumferential surface of 0. Note that 32 is a partition plate provided in the inner container 30 and has a large number of pores, and 33 is a lid plate. Here, after placing the diaphragm material 24 on the partition plate 32 and covering it with the lid plate 33, the heater 31 is energized to heat the inside of the furnace. Increase the furnace temperature from 200℃ to 200℃/
When the temperature is raised to 600°C at a heating rate of h, the bulb portion of the diaphragm material 24 burns and carbonizes at around 400°C, and subsequently, the carbide gasifies and evaporates between 400°C and 600°C. , the vitrification component of the ceramic is melted. Then, it is held at 600°C for about 1 hour to decarburize. Then 600℃~1200℃ or
The temperature is increased to 1300 DEG C. at a heating rate of 150 DEG C. to 160 DEG C./h to sinter the ceramic. This compaction process shrinks and fills the pores created by the combustion of the pulp. In this manner, the pulp portion of the diaphragm material 24 is completely burned away, and only the ceramic portion remains after being sintered, so that a diaphragm made solely of ceramic is obtained. Other ceramic materials that can be used include those shown in the table below.

[Table] In the method of this example, the diaphragm material is formed using papermaking technology, so the material can be formed uniformly to a predetermined thickness. , can be easily formed into any shape. As described above, according to the method for manufacturing an acoustic diaphragm according to the present invention, after forming a mixture of pulp and ceramic fine particles into the shape of a diaphragm, the pulp portion is burnt out and the ceramic portion is sintered. To obtain a single ceramic diaphragm at low cost through a simple manufacturing process without using an expensive thermal spraying device such as the above, and without the need for a complicated process of separating a thermally sprayed thin plate and a template. Further, since it is possible to manufacture the ceramic powder without going through a green core state in which unsintered ceramic powder, which has extremely poor brittleness, is press-molded, workability is improved. Furthermore, since the diaphragm is made of ceramic alone, it can obtain a larger E/ρ value than conventional composite plates, and can be used in speakers and the like to greatly improve acoustic characteristics. In addition, by holding the mixture for a predetermined time at a temperature below the sintering temperature of the ceramic and at a temperature at which the pulp components can carbonize, the pulp components of the mixture gasify and evaporate, so that the ceramic components are not yet sintered. In this state, the pulp components are completely burned away.
Therefore, a ceramic diaphragm with high purity can be easily obtained. As described above, the present invention has many excellent effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a paper making apparatus used in an embodiment of the method for manufacturing an acoustic diaphragm according to the present invention, FIG. 2 is a sectional view of a mold, and FIG. 3 is a sectional view of a molded diaphragm material. FIG. 4 is a sectional view of the heating furnace. 2...Pulp, 5...Mixing tank, 7...Ceramic powder, 12...Mixed suspension, 15...Paper making tank, 18...Water tank, 21...Water pump, 22...
... Dehydration pump, 23 ... Paper wire mesh, 24 ... Diaphragm material, 26 ... Upper mold, 27 ... Lower mold, 29 ...
Outer container, 30... Inner container, 31... Heater, 32
...Partition board.

Claims (1)

[Claims] 1. A mixture production step of producing a mixture in which fine ceramic particles are attached to the surface of pulp fibers; A shape forming step of forming this mixture into the shape of a diaphragm; a decarburization step in which the mixture formed into a shape is held for a predetermined time at a temperature below the sintering temperature of the ceramic and at a temperature at which the pulp components are carbonized and then gasified; and after this decarburization step, the ceramic is sintered. A method for manufacturing an acoustic diaphragm, comprising a sintering step of sintering the ceramic component at a temperature higher than the sintering temperature.