JPH0446513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a diaphragm for a speaker.

[Conventional technology]

It is desirable for speaker diaphragms to have a large specific elastic modulus E/ρ (E: Young's modulus, ρ: density), that is, to have a large rigidity and be lightweight, and various materials, shapes, and manufacturing methods have been studied. . For example, light metals (aluminum, aluminum alloys, titanium, titanium alloys) are often used as diaphragm materials, especially in speakers for medium and high frequencies. Press molding is applied as a manufacturing method for such light metal diaphragms, and they can be manufactured in large quantities relatively easily and at low cost. However, beryllium, beryllium alloys, boron compounds, ceramics, etc., which have performance superior to the light alloys mentioned above, have extremely low extensibility and are difficult to press, so these diaphragms are manufactured using vacuum deposition, ion plating, etc. Manufactured by However, it is not possible to obtain an inexpensive diaphragm because the manufacturing equipment is expensive and the working time is long.

Therefore, as one method for manufacturing these materials, as shown in Japanese Patent Application Laid-Open No. 115098/1982, molten diaphragm material (powder for thermal spraying) is sprayed at high pressure onto a mold having a desired diaphragm shape. After forming a film (thin plate) on the surface of the mold by so-called thermal spraying,
A method has been proposed in which a diaphragm is manufactured by separating the two and further re-molding this thin plate at high temperature and pressure. According to the above patent publication, in FIG. 4, a cross-sectional configuration diagram showing a conventional thermal spraying apparatus, compressed air and combustion gas are supplied to supply pipes 12 and 13 of a thermal spraying apparatus 11, respectively, and a nozzle 1 is
A flame 14 of approximately 1000 to 3000°C is generated from 1a, and a thermal spraying powder 16 of boron nitride cermet, which is a diaphragm material, is supplied from the supply pipe 15. The thermal spraying powder 16 is radiated forward by compressed air, and the combustion gas is emitted. It is melted by the flame 14 and pulverized by compressed air to become particles.
These particles in a molten state collide with the surface of a dome-shaped mold 17 placed in front of the thermal spraying device 11, are pressed, cooled, and instantly solidified. By repeating this process, the thermal spraying powder 16 is deposited in layers on the mold 17 to form a film (thin plate) 18. When the thin plate 18 reaches a predetermined thickness, the thermal spraying is stopped, and then the thin plate 18 and the mold 17 are separated. The particles of this thin plate 18 are connected by mechanical bonds, and also contain air bubbles, which is a characteristic of a thermally sprayed film. These bubbles are not necessarily harmful because they add loss inside the diaphragm, which can reduce the sharpness of the self-resonance of the diaphragm. However, in order to obtain a diaphragm that requires even more rigidity,
In addition to the above process, a high-temperature, high-pressure pressing process is carried out. That is, after the thin plate 18 is separated from the mold 17, it is inserted into the molds 19 and 20 having the dome-shaped unevenness shown in the cross-sectional view of FIG.
The diaphragm is manufactured by pressing at 2000℃ and press pressure of approximately 1000Kg. The diaphragm thus obtained has high rigidity because the diaphragm material (sprayed powder) is recrystallized and the air inside the bubbles is released.

[Problem that the invention seeks to solve]

However, if there are variations in the thickness of the diaphragm or if the precision of the mold is poor, uneven gaps between the diaphragm and the mold will occur, and cracks will occur in the diaphragm when pressurized. Therefore, press mold 1
9 and 20 must be precisely made to have the same shape as the diaphragm, and must have the same thermal expansion as the diaphragm. The mold had to be manufactured with carbon or ceramics in consideration of heat resistance, and the reaction with the diaphragm had to be suppressed, so the mold was limited. Furthermore, cracks occur if a temperature difference occurs between the mold and the diaphragm during the temperature raising and cooling steps, so this step had to be carried out gradually. Furthermore, it is necessary to raise the temperature of a mold with a large heat capacity, which requires a large amount of electric power, and the manufacturing equipment also requires a press mechanism. There is also the problem that the shape of the diaphragm is limited during press processing, and pressure may not be applied uniformly depending on the shape. As mentioned above, there are problems in that it requires highly accurate press molds and equipment, requires long working hours, requires a large amount of electricity, and has poor workability.Furthermore, depending on the shape of the diaphragm, pressing cannot be performed. The dot was hot.

The present invention was made to solve these problems, and an object of the present invention is to easily manufacture a speaker diaphragm having high rigidity with good workability.

[Means for solving problems]

The speaker diaphragm of the present invention comprises a process of spraying and depositing boron carbide (B ₄ C) as a diaphragm material onto a mold having a diaphragm shape as thermal spray powder to form a film, and releasing this film from the mold. In an argon atmosphere,
It is manufactured through a process of heating and firing at 1500 to 2300°C and sintering.

[Effect]

In this invention, the diaphragm is sintered by heating and firing using a high-frequency induction heating method, for example, so there is no need for a press mold with high precision as in a high-temperature, high-pressure press, and the shape of the diaphragm is also limited. Workability is improved without any problems. In addition, the particles in the diaphragm progress metallurgically to sinter and increase its rigidity.

〔Example〕

Figures 1 and 2 each relate to an embodiment of the present invention; Figure 1 is a cross-sectional configuration diagram of a plasma spraying apparatus for forming a diaphragm coating, and Figure 2 is a cross-sectional configuration diagram showing a high-frequency induction heating apparatus. It is a diagram. For the diaphragm, a film (thin plate) having the shape of a diaphragm is first manufactured using a plasma spraying apparatus 1 shown in FIG.
The thermal spraying apparatus 1 has an electrode 1a and a nozzle 1b, and a mixed gas 1c, which is a mixture of N ₂ or Ar gas and an appropriate amount of H ₂ gas, is introduced between the electrode 1a and the nozzle 1b. By applying power from a power source connected to a terminal between the electrode 1a and the nozzle 1b, the mixed gas 1c is ionized and becomes a plasma flame 1d.
This plasma flame has a temperature of 20000℃ and a flow rate of 3000℃.
It reaches m/sec. Therefore, if thermal spray powder, which is the diaphragm material, in this case boron carbide 2, is introduced into this from the supply port 3, it will easily melt, collide at high speed with the mold 4 having the desired diaphragm shape, adhere, cool, and It is solidified and deposited to form a film (thin plate) 5.

In addition, the film (thin plate) 5 formed in this way
can be easily separated from the mold 4 by smoothing the surface of the mold in advance and selecting an appropriate material.
As a result, a thin plate 5 made of boron carbide having a desired shape can be formed and separated. Since this thin plate 5 is formed by mechanically depositing boron carbide particles for the most part, the bonding force between the particles is relatively weak and it contains 5 to 20% of air bubbles. As mentioned above regarding conventional diaphragms, these bubbles are not necessarily harmful. However, if a higher specific modulus is required,
It is necessary to strengthen the bonds between boron carbide particles, reduce bubbles, and increase E. Therefore, in this invention, in addition to the above steps, a heating and firing step is added. That is, the dome-shaped thin plate 5 manufactured in the above process, for example, having an outer diameter of 65 mm, a thickness of 140 μm, and a porosity of 15%, is placed in a carbon cylinder 6 shown in FIG.
This was placed in a container 7 in an argon atmosphere, and fired using a high frequency induction heater 8 at a temperature of 1500 to 2300°C, in this case 2100°C, for about 60 minutes. In this heating and firing, the particles of the thin plate 5 progressed in sintering in accordance with the firing temperature, the number of air bubbles decreased, and the bonding force between the particles increased and the rigidity increased. Figure 3 is a characteristic diagram showing the relationship between firing temperature and specific elastic modulus (E/ρ). In the figure, the vertical axis represents the relative value of E/ρ when the value of E/ρ of the untreated sample is taken as 1. , the horizontal axis represents the firing temperature. As is clear from this figure, as the firing temperature increases, the bonding between particles increases, resulting in an increase in E/ρ, which becomes approximately three times that of the untreated sample at approximately 2200°C, reaching almost saturation. did.

Furthermore, when the firing temperature is below 1000℃, there is almost no effect, when it is above 1500℃, the increase in E/ρ becomes noticeable, and when it is above 2300℃, deformation may occur, so 1500 to 2300℃ is preferable, and ~2200℃ is optimal. Furthermore, as is clear from Figure 3, the value of E/ρ has a correlation with the firing temperature, and by controlling the firing temperature, it is possible to manufacture various diaphragms with the desired E/ρ value. .

Note that if the firing atmosphere is air or _N2 atmosphere, the boron carbide thin plate 5 will be oxidized and its strength will be reduced. Furthermore, in a vacuum, the weight of the thin plate 5 after firing is approximately 10% less than the weight before firing, which suggests that evaporation of boron carbide is occurring. Accordingly
Ar atmosphere is preferable.

Furthermore, although a high frequency induction heating method was used in this embodiment as a heating method, resistance wire heating can also of course be used.

〔Effect of the invention〕

As explained above, this invention includes a process of thermally spraying and depositing boron carbide (B ₄ C) as a diaphragm material on a mold having a diaphragm shape as thermal spray powder to form a film, and releasing this film from the mold. In an argon atmosphere,
The process of heating and firing at 1,500 to 2,300°C for sintering has the effect of making it possible to easily manufacture a speaker diaphragm with an excellent specific modulus of elasticity with good workability.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional configuration diagram showing a plasma spraying apparatus according to an embodiment of the present invention, FIG. 2 is a cross-sectional configuration diagram also showing a heating device, and FIG. 3 is a characteristic diagram showing the relationship between firing temperature and specific elastic modulus. , FIG. 4 is a sectional view showing a conventional thermal spraying apparatus, and FIG. 5 is a sectional view showing a press mold. In the figure, 1 is a plasma spraying device, 2 is a powder for thermal spraying, 4 is a mold, 5 is a film (thin plate), and 8 is a high frequency induction heater. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 Step of thermally spraying boron carbide (B ₄ C) as a diaphragm material as thermal spray powder onto a mold having a diaphragm shape and depositing it to form a film, and releasing this film from the mold and heating it in an argon atmosphere at 1500 ~ A method for manufacturing speaker diaphragms that involves heating and sintering at 2300℃.