JPH04331600A - Diaphragm for electroacoustic converter and production thereof - Google Patents

Abstract

PURPOSE:To reinforce the center dome part of the diaphragm of an electroacoustic converter by suppressing the variation of the sensitivity, or a frequency response to the minimum. CONSTITUTION:A reinforcing film 7 is constituted of a material of the same quality with that of a diaphragm film 5, formed in the same shape with that of a center doom 2, and the center dome 2 is adhered to the formed face with an adhesive 6 constituted of a hot melt of the same quality with that of the diaphragm film 5, which is an organic solvent capable of being diluted. Thus, the variation of the sensitivity, or the frequency response due to the change of a temperature can be suppressed to the minimum, and the adhesive 6 is the organic solvent capable of being diluted so that is can be applied so as to be extremely thin, and then the quality and quantity of the center dome 2 can be make even.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a diaphragm for an electroacoustic transducer that converts vibrations such as sound into electrical signals, and more specifically, the present invention relates to a diaphragm for an electroacoustic transducer that converts vibrations such as sound into electrical signals. This invention relates to a diaphragm with minimal reinforcement and a method for manufacturing the same.

0002

2. Description of the Related Art Generally, it has been proposed to lower the resonant frequency of a diaphragm in, for example, a dynamic microphone or headphone in order to expand its low-frequency reproduction limit. This can be achieved by increasing the weight of the voice coil, reducing the thickness of the film in the sub-dome portion of the diaphragm, or changing the curvature of the sub-dome portion. However, the method of making the voice coil heavier causes an increase in vibration noise, and the method of changing the curvature of the sub-dome requires a lot of time and cost for designing the diaphragm, making it expensive. Therefore, a method of reducing the thickness of the sub-dome portion is widely practiced.

In this method, a film such as polyester is placed on a mold and heated and pressurized to make a thin diaphragm.If left as is, not only the thickness of the sub-dome part but also the center dome part becomes thinner, and The mechanical strength of the dome also becomes weaker, lowering the high frequency reproduction limit and making abnormal resonance more likely to occur. Therefore, the center dome part is reinforced by applying a resin or the like to the center dome part or by attaching a film of the same shape to the center dome part.

0004

[Problem to be Solved by the Invention] However, for example, in the case of a unidirectional dynamic microphone, the control method is inertial control, so an increase in the mass of the vibration system other than the voice coil causes vibration noise. Therefore, it is not possible to increase the strength by increasing the amount applied unnecessarily. Furthermore, if the weight added varies during manufacturing, variations in sensitivity and frequency response will occur. Therefore, the method of reinforcing by applying resin, etc., for example, when applying with a brush, requires highly precise work to ensure that the resin does not get on parts other than the center dome and that it is uniform, and requires skill. However, it is unsuitable for mass production.

Furthermore, the film is attached using an ultraviolet curing or epoxy adhesive after or at the same time as the diaphragm is molded, but this tends to cause individual differences in the adhesive layer. Even products of this type may have variations in frequency response and sensitivity. In addition, when the thickness increases, problems similar to those described above tend to occur, and there are also many manufacturing problems such as the tendency for the adhesive to ooze out and the formation of air bubbles within the adhesive layer. Furthermore, if the adhesive and film have different coefficients of thermal expansion, they may deform into a bimetallic shape due to temperature changes, which also has the disadvantage of causing variations in sensitivity and frequency response.

SUMMARY OF THE INVENTION An object of the present invention is to provide a diaphragm for an electroacoustic transducer in which the center dome portion is reinforced while minimizing variations in sensitivity and frequency response.

Another object of the present invention is to provide a method of manufacturing a diaphragm for an electroacoustic transducer having a reinforced center dome portion through simple steps.

[0008]

[Means for Solving the Problems] The present invention provides a diaphragm for an electroacoustic transducer having a center dome, in which the center dome is made of the same material as the diaphragm and is molded in the same shape as the center dome. It is characterized in that the reinforcing film is adhered to the diaphragm using an adhesive made of a hot melt adhesive that is the same as the diaphragm and can be diluted with an organic solvent.

The present invention also provides a method for manufacturing a diaphragm for an electroacoustic transducer having a center dome reinforced with a reinforcing film, in which the diaphragm is made of the same material as the diaphragm using a heating mold having a molding surface having the same shape as the center dome. A reinforcing film is formed into a center dome shape of the material, an adhesive made of hot melt that is the same as the diaphragm that can be diluted with an organic solvent is applied to the upper surface of this molded surface, and the molded surface of the reinforcing film is punched out. This method is characterized in that a punched reinforcing film is placed on the pressing surface of a heating die, a diaphragm film is covered thereon, and the reinforcing film is fixed to the diaphragm film by the heating die.

0010

[Operation] Since the diaphragm, reinforcing film, and adhesive are made of the same material, variations in sensitivity and frequency response due to temperature changes can be minimized, and the adhesive can be diluted with organic solvents. Therefore, it can be applied extremely thinly and the mass of the center dome can be made uniform. In addition, since it is a hot-melt adhesive, the reinforcing film can be attached to the diaphragm film during heat molding of the diaphragm film, so the reinforcing film with adhesive can be made separately, increasing productivity. can.

[0011] In the manufacturing method, the reinforcing film is coated with adhesive in advance and then die-cut, applied to the center dome of the diaphragm film, and fixed to the center dome by heat treatment. A diaphragm with a uniform dome mass can be manufactured extremely easily without requiring high precision. Furthermore, a conventional heating mold can be used to form the reinforcing film, and conventional manufacturing equipment can be used as is.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention shown in the drawings will be described.

FIG. 1 shows an embodiment of the diaphragm of the present invention, in which the diaphragm 1 includes a center dome 2, a sub-dome 3 formed to surround the outer periphery of the center dome 2,
A flat peripheral edge 4 formed on the outer periphery of this sub-dome 3
It is composed of a film 5 made of, for example, a polyester film having a thickness of about 9 μm, and a dome-shaped reinforcing film 7 attached to the center dome 2 via an adhesive 6. The adhesive 6 used is a polyester hot melt that can be diluted with an organic solvent. Further, as the reinforcing film 7, for example, a polyester film made of the same material as the film 5 and having a thickness of 25 μm is used.

The adhesive 6 is made with an organic solvent to an appropriate concentration, is applied to the inside of the reinforcing film 7, is attached to the upper surface of the center dome 2 of the film 5, and is cured by volatilizing the organic solvent. For example, if the adhesive is diluted with an organic solvent so that it forms an extremely thin layer of 1 μm or less when cured,
There is no variation in properties due to differences in layer thickness caused by coating methods.

Next, a method for manufacturing such a diaphragm will be explained with reference to FIGS. 2 to 7. First, a dome-shaped reinforcing film is made using a mold 11 for forming the diaphragm and a pressure pot 12 as shown in FIG. Mold 7. In order to mold the diaphragm 1, the mold 11 has a recess 13 having the same shape as the center dome 2 at the center of its upper surface, and a recess 14 having the same shape as the sub-dome 3 surrounding the outer periphery of the recess 13. ,
The outer periphery of the recess 14 has a flat portion 15 to form the peripheral edge 4.
It is being done. The pressurizing pot 12 has a substantially U-shaped cross section, has a pressurizing chamber 16 provided therein, and is positioned such that its open portion faces the upper surface of the mold 11 . The pressure pot 12 is fixed to a cylinder rod (not shown) or the like, and is configured to move up and down. An airtight O-ring 17 is attached to the edge of the open portion of the pressure pot 12. A pressurized air supply port 18 is formed on the side surface of the pressurized pot 12 for connection to a pressurized air supply source (not shown). Since these structures are the same as those of conventional thermoforming devices, detailed descriptions of their structures will be omitted.

[0016] Molding mold 11 heated to a preset temperature
The reinforcing film 7 is placed on top, the pressure pot 12 is lowered, and the reinforcing film 7 is sandwiched and fixed between the edges of the open part of the mold 11 and the pressure pot 12. Then, pressurized air is supplied into the pressurizing chamber 16 from the pressurized air supply port 18, and the recesses 13, 1 are formed on the upper surface of the mold 11 by air pressure and heat.
The reinforcing film 7 is formed into a shape according to 4. A plurality of reinforcing films 7 can be molded together as shown in the figure.

[0017] Reinforcing film 7 formed in this way
As shown in FIG. 3, the adhesive 6 as described above is applied to the central concave portion. The adhesive 6 may be applied to extend beyond the outer contour of the central recess.

Next, a pair of cutting dies 19 as shown in FIG.
20, punch out only the central concave portion of the reinforcing film 7. That is, the reinforcing film 7 is placed on a concave cutting die 19 having a through hole 21 with a diameter substantially equal to the diameter of the center dome 2 so that its central recess fits into the through hole 21, and the reinforcing film 7 is inserted into the through hole 21. By lowering the convex cutting die 20 having the matching punch 22 and fitting the punch 22 into the through hole 21, only the central concave portion of the reinforcing film 7 can be punched out.

Reinforcement film 7 formed in this way
As shown in FIG. 5, the film 5 is placed on the recess 13 of the mold 11 shown in FIG. 2, the film 5 is covered from above, and the pressure pot 12 shown in FIG. Mold 3. At this time, the reinforcing film 7 is also attached to the film 5 with the adhesive 6. At the same time, mold 1
The organic solvent of the adhesive 6 is volatilized by the heat of the adhesive 6, and the adhesive 6 is cured. As a result, as shown in FIG.
A center dome 2 and a sub-dome 3 to which a reinforcing film 7 is attached are formed at the center of the dome.

The film 5 formed in this way is
A pair of cutting dies 23 and 24 shown in FIG. 7 are used to punch out the outer diameter of the diaphragm 1 as shown in FIG. 1. That is, the film 5 is placed on a concave cutting die 23 having a through hole 25 having a diameter approximately equal to the outer diameter of the peripheral edge 4 of the diaphragm 1 so that its center portion is located at the center of the through hole 25. The diaphragm 1 can be punched out by lowering the convex cutting die 24 having a punch 26 fitted into the through hole 25 and fitting the punch 26 into the through hole 25.

As described above, the reinforcing film for the center dome 2 is cut out in advance with adhesive 6 applied thereto, applied to the center dome 2 of the film 5, and fixed to the center dome 2 by heat treatment. Because there are
A diaphragm 1 whose center dome 2 has a uniform mass can be manufactured extremely easily without requiring high precision. Furthermore, the conventional heating mold 11 can be used to form the reinforcing film 7, and conventional manufacturing equipment can be used as is.
It can be provided at low cost.

FIG. 8 is a graph showing the frequency response characteristics of a directional microphone using the diaphragm of the present invention, and FIG. 9 is a graph showing the frequency response characteristics of a directional microphone using the diaphragm of the present invention. This is a graph showing the frequency response characteristics of a directional microphone, where a is 0 with respect to the sound source.
° and b indicate the case where the angle is 135° with respect to the sound source. Comparing the characteristics of the two, the diaphragm of this invention has a rating of 50 to 10.
It can be seen that the low frequency limit around 0Hz is extended. Also,
Looking at the sensitivity of the microphone, 0db=1V/P
Based on a, it is −52 db in FIG. 8, while it is −54 db in FIG. 9, and the microphone in FIG. 8 also has high sensitivity.

[0023]

As described above, in the diaphragm of the electroacoustic transducer of the present invention, since the diaphragm, the reinforcing film, and the adhesive are made of the same material, the sensitivity due to temperature changes is reduced.
Variations in frequency response can be minimized, and since the adhesive can be diluted with an organic solvent, it can be applied extremely thinly, and the mass of the center dome can be made uniform. In addition, since it is a hot melt adhesive, the reinforcing film can be attached to the diaphragm film during heat molding of the diaphragm film, so the reinforcing film with adhesive can be made separately, increasing productivity. can.

[0024] In addition, in the method of manufacturing the diaphragm, adhesive is applied to the reinforcing film in advance, the mold is cut out, the film is applied to the center dome of the diaphragm film, and it is fixed to the center dome by heat treatment. Because
A diaphragm whose center dome has a uniform mass can be manufactured extremely easily without requiring high precision. In addition, conventional heating molds can be used to form the reinforcing film.
Since conventional manufacturing equipment can be used as is, it can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a diaphragm of the present invention.

FIG. 2 is a diagram for explaining a reinforcing dome forming process for explaining the method for manufacturing a diaphragm of the present invention.

FIG. 3 is a perspective view showing the reinforcing dome made in the molding process of FIG. 2;

FIG. 4 is a diagram for explaining the punching process of the reinforcing dome.

FIG. 5 is a diagram for explaining the process of forming the diaphragm together with the reinforcing dome.

6 is a perspective view showing the diaphragm and reinforcing dome made in the molding process of FIG. 5. FIG.

FIG. 7 is a diagram illustrating a punching process for punching out a diaphragm to a predetermined size.

FIG. 8 is a graph showing the frequency response characteristics of the diaphragm of the present invention.

FIG. 9 is a graph showing frequency response characteristics of a conventional diaphragm.

[Explanation of symbols]

1 Diaphragm 2 Center dome 3 Subdome 3 4 Peripheral area 5 Film 6. Adhesive 7 Reinforcement film 11 Molding mold 12 Pressure pot

Claims (2)

[Claims] 1. In a diaphragm for an electroacoustic transducer having a center dome, the center dome includes a reinforcing film made of the same material as the diaphragm and formed in the same shape as the center dome. 1. A diaphragm for an electroacoustic transducer, characterized in that the diaphragm is adhered to the diaphragm using an adhesive made of a hot melt adhesive that is the same as the diaphragm and is dilutable with a solvent. 2. A method for manufacturing a diaphragm for an electroacoustic transducer having a center dome reinforced with a reinforcing film, the method comprising: producing a diaphragm made of the same material as the diaphragm using a heating mold having a pressing surface having the same shape as the center dome; A reinforcing film is molded into the shape of the center dome, and an adhesive made of a hot melt adhesive similar to that of the diaphragm that can be diluted with an organic solvent is applied to the upper surface of the molded surface, and the molded surface of the reinforcing film is The electroacoustic device is characterized by punching, placing the punched reinforcing film on the pressing die surface of the heating die, covering it with a diaphragm film, and fixing the reinforcing film to the diaphragm film by the heating die. Method of manufacturing a transducer diaphragm.