JPH03245697A - Manufacture of diaphragm for speaker - Google Patents

Abstract

PURPOSE:To reduce generation of cracks by applying plasma flame spraying of a ceramics to the die of a prescribed shape whose surface is processed smoothly so as to form a film, polishing smoothly the surface of the film, removing the forming from the die and baking the film in an inactive gas. CONSTITUTION:A plasma flame spraying device 1 is used to manufacture at first a film of a prescribed shape. The plasma flame spraying device 1 is provided with an electrode 1a and a nozzle 1b and a mixture gas 1c mixing gaseous hydrogen of a proper quantity in gaseous argon or nitrogen is introduced between the electrode 1a and the nozzle 1b. Then power is applied between the electrode and the nozzle to ionize the mixture gas thereby forming a plasma flame. Since the plasma flame has high temperature and a high speed, when a B4C whose mean particle diameter is 10-50micron being a diaphragm material is introduced from a supply port 3 into the plasma flame, the material is molten, collides with the die 4, is adhered, cooled, solidified and deposited and the film 5 made of B4C is formed. Then the surface is smoothed by using #320-600 Emily polishing paper.

Description

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

[Prior Art] Figures 4 and 5 are diagrams showing a method of manufacturing a speaker diaphragm disclosed in Japanese Patent Application Laid-open No. 60-1691, respectively. FIG. 5 is a cross-sectional view showing the above-mentioned coating firing apparatus. That is, the diaphragm is first manufactured into a film having a dome shape, for example, using a plasma spraying apparatus (1) shown in FIG.

The above plasma spraying apparatus (1) has an electrode (1a) and a nozzle (1b), between which a mixed gas (I
C) is introduced. Then, the electrode (18) and the nozzle (1
b) By applying electric power in between, the above-mentioned mixed gas is ionized and becomes a plasma flame. Since this plasma flame has high temperature and high speed, the molten elbow powder, which is the material of the diaphragm, is fed into the plasma flame through the supply port (
When poured from step 3), it melts, collides with the mold (4), adheres, cools, solidifies and deposits to form a film (5), which is separated from the mold.

As shown in Figures 1 and 2, the surface of the film obtained in this way becomes a smooth surface corresponding to the surface of the mold (4) due to the crushing of the molten thermal spray powder on side A of the side of the mold. . On the other hand, surface B on the side surface of the thermal spraying device is not crushed so much that the surface has severe irregularities corresponding to the particle size of the molten particles. The coating (5) in this state as sprayed has relatively weak bonding between powder particles and low mechanical strength, which is an important characteristic of the diaphragm, E/ρ (E: Young's modulus, ρ:
Therefore, as shown in the partially enlarged view of FIG. 2, the thermally sprayed coating (5) is placed in a carbon cylinder, for example, and fired at 1000 DEG C. to 2300 DEG C. in an argon gas atmosphere. By applying this treatment, the bond between the particles is significantly strengthened, and a diaphragm with a large E/p value can be obtained.

[Problems to be Solved by the Invention] In the conventional method for manufacturing a diaphragm, the diaphragm was made by releasing and firing the coating (5) while it was sprayed. However, as shown in (1-1) in Figure 1 and (2-1) in Figure 2, in the as-sprayed coating (5), the surface B on the opposite side of the mold (4) is extremely uneven. When it is vibrated as a diaphragm, cracks tend to form in the concave portions, and the cracks spread from these buds, making it unable to withstand large vibrations.

Furthermore, as shown in Fig. 6, in the case of a dome-shaped diaphragm,
It is necessary to wind the voice coil (9) around the rising part of the diaphragm, but if the surface is extremely uneven, there are problems such as the insulation film of the coil being torn at the edges.

This invention was made to solve the above problems, and an object thereof is to manufacture a highly reliable speaker diaphragm with less occurrence of cracks.

[Means for Solving the Problems] A method for manufacturing a speaker diaphragm according to the present invention includes: 1) forming a film in a predetermined shape by plasma spraying ceramics on a mold having a predetermined shape and having a smooth surface; The surface of this film is polished to a smooth surface, then released from the mold, and the film is fired in an inert gas at, for example, 1000°C to 2400°C to form a diaphragm.

[Function] Polishing the surface of the film in this invention smoothes the surface roughness of the film, suppresses the occurrence and propagation of cracks, and strengthens the bond between the voice coil and the film, resulting in high performance and high performance. A reliable speaker diaphragm can be obtained.

[Embodiment] Figures 4 and 5 show an apparatus used in the manufacturing method of the present invention, which is similar to the apparatus used in the conventional manufacturing method. That is, in manufacturing the diaphragm of the present invention, a plasma spraying apparatus (1) shown in FIG. 4 is used, and a coating having a predetermined shape is first manufactured. The plasma spraying apparatus (1) has an electrode (1a) and a nozzle (1b), between which a mixed gas (1c) of nitrogen or argon gas mixed with an appropriate amount of hydrogen gas is introduced. By applying electric power between the electrode and the nozzle, the mixed gas is ionized and becomes a plasma flame. Since this plasma flame has a high temperature and high speed, if B and C, which are diaphragm materials with an average particle size of 10 to 50 microns, are put into the flame from the supply port (3), they will melt.
It collides with the mold (4), adheres, cools, and solidifies to form a B4C film (5). Specifically, the surface of the film formed using B and C powders with an average particle size of 17 microns is shown in Figure 2 (2
As shown in -1), the surface B on the side surface of the thermal spraying device has less crushing and unevenness corresponding to the particle size of the molten B4C particles, resulting in the roughness measurement results shown in (3-1) in Figure 3. As expected, the 10-point average roughness Rz is approximately 5 microns, resulting in a highly uneven surface.

Therefore, in order to make the surface smooth, it was polished with #320-600 Emily polishing paper. Although the B4C particles are harder than the abrasive used in Emily abrasive paper, the bonds between the B4C particles in the sprayed coating are relatively weak and can be easily smoothed.

FIG. 2 (2-2) is a partially enlarged view of the coating of the present invention after polishing. FIG. 3 (3-3) shows the measurement results of the surface roughness of the film of the present invention when polished with #400 Emily polishing paper; Rz in this case was about 1 micron. Also, instead of using abrasive paper, alumina, SIC
, 5IO2 or the like was sprayed using compressed air to make the surface smooth.

After polishing in this way, it is removed from the mold (4).The surface that was in contact with the mold (4) corresponds to the surface roughness of the mold (4) as in the conventional case, and in the example, it is shown in Fig. 3. The roughness as shown in (3-2) was 0.5 micron. Note that the surface of the film (5) can be polished after release from the mold, but since this film is fragile, it is necessary to use a jig adapted to the shape. Otherwise, it may crack during the polishing process, so it is better to perform polishing before releasing the mold, and the film after releasing the mold (5)
The bond between the powder particles is relatively weak and the mechanical strength is low. Therefore, E/ρ (E: Young's modulus, ρ: density), which is an important characteristic of the diaphragm, is also small. Therefore, the film after mold release (5
) is the same as before, using vacuum or nitrogen in the firing furnace (7),
In an inert atmosphere such as argon, as shown in Fig. 5, it was placed in a carbon cylinder (6) and heated by a heating source (B) for 100 minutes.
Calculate at 0°C to 2300°C. As a result, the bond between the particles becomes significantly stronger and the E/ρ value becomes larger.

Figure 7 shows the relationship between the roughness Rz of the polished surface B and the bending strength of the diaphragm when fired at 2000°C in an argon atmosphere.The bending strength is the same for the strip-shaped sample as for the dome-shaped diaphragm. The three-point bending method was used to measure the products manufactured using this method. As is clear from this result, the smaller the surface roughness, the greater the bending strength. Samples without polishing (
Rz (approximately 5 microns) is 25 Kg/m♂, but as the surface becomes smoother by polishing, the bending strength increases, and when Rz becomes 1 micron, the bending strength becomes approximately 30 Kg/Oboro Il+1. In this way, the bending strength increases as the surface becomes smoother, so it is better to make it smoother in terms of strength, but since it is expensive, it is desirable to decide the degree of polishing depending on the purpose.

Note that in the film after firing, the bond between the B4C particles is strong and the hardness of the B4C particles is large, so polishing after firing is extremely difficult.

Since the diaphragm of the present invention manufactured in this way has a smooth surface, cracks are less likely to occur, and high-amplitude vibration is possible. In addition, the adhesion between the voice coil and the film is good, making it possible to apply high input power.For example, compared to conventional unpolished diaphragms, the amplitude and input resistance of a diaphragm polished to an Rz of 1 micron are improved. Both about 3
I was able to increase it by 0%. Although B4C is used as the material for the diaphragm in this embodiment, similar effects can be obtained with other ceramics or a mixed material of ceramics and metal.

[Effects of the Invention] As described above, the present invention involves forming a film by plasma spraying ceramics on a mold having a predetermined shape and having a smooth surface, and then polishing the surface of the film to make it smooth, and then releasing it. Since the film was molded and fired in an inert gas, it was possible to obtain a high-performance speaker diaphragm with little cracking, high reliability, and high amplitude and input resistance.

[Brief explanation of drawings]

FIG. 1 shows the surface roughness of diaphragm coatings formed by the manufacturing method of the present invention and the conventional manufacturing method, and shows (1-1
) is the conventional one, and (1-2) is the one of this invention. FIG. 2 is a partially enlarged cross-sectional view showing the roughness of each of the above-mentioned films, (2-1) is the conventional one, and (2-2) is the one of the present invention. Figure 3 shows the measurement data of surface roughness before and after polishing, (3-1) is before polishing of surface B in Figure 2, (3-3)
) is the measurement data of surface A in FIG. 2 after polishing, and (3-2) is the measurement data of surface A in FIG. Fig. 4 is a sectional view showing a conventional plasma spraying device and the spraying state of the present invention, Fig. 5 is a sectional view showing a firing device, and Fig. 6 is a sectional view showing a voice coil bonded to a dome-shaped diaphragm. The side view and FIG. 7 are characteristic diagrams showing the relationship between surface roughness and bending strength of the diaphragm. In the figure, (4) is the mold, and (5) is the film. 1 Figure-1-2 Figure 2m) Front) 1 1 Maro bond-3-2 Figure Figure Figure Figure Figure 2 3 4 8 surface roughness Rz (μri procedure amendment form (voluntary)

Claims (4)

[Claims] (1) After forming a film by plasma spraying ceramics on a mold with a predetermined shape and a smooth surface, the surface of this film is polished to a smooth shape, then the mold is released, and this film is inert. A method for manufacturing a speaker diaphragm characterized by firing it in a gas. (2) Ceramics to be plasma sprayed are boron carbide (
B_4C) The method for manufacturing a speaker diaphragm according to claim 1. (3) Manufacture of a speaker diaphragm according to claim 1, in which the surface of the film obtained by plasma spraying of ceramics is polished with abrasive paper using an abrasive such as alumina, Emily, SIC, etc. Method. (4) The method for manufacturing a speaker diaphragm according to claim 1, wherein the surface of the coating obtained by plasma spraying of ceramics is polished by spraying powder of alumina, SIC, SIO_2, etc.