JP2009232387A - Magnesium alloy-made dome type diaphragm for speaker and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diaphragm which is made using a magnesium alloy, has sufficient rigidity and can suppress split vibration, and to provide a manufacturing method thereof. <P>SOLUTION: The dome type diaphragm for a speaker is formed by press-machining a magnesium alloy plate. The diaphragm is configured so that its thickness is gradually reduced from the outer circumference toward the center and a thickness t<SB>2</SB>in the center of the diaphragm is 0.2-0.8 times the thickness t<SB>1</SB>of the outer circumference. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a loudspeaker diaphragm, and more particularly to a magnesium alloy loudspeaker dome diaphragm and a method of manufacturing the same.

  Japanese Patent Application Laid-Open No. 53-1517 (Patent Document 1) describes a dynamic speaker and a manufacturing method thereof. Japanese Unexamined Patent Publication No. 2007-43522 (Patent Document 2) describes a diaphragm for a speaker device. In these speaker diaphragms, rigidity is ensured by providing ribs on the resin diaphragm or by partially changing the thickness of the diaphragm. Thereby, the divided vibration generated in the diaphragm is reduced and the sound quality is improved.

  On the other hand, as a diaphragm for a speaker for high-pitched sound reproduction, paper, resin, and metals such as titanium and beryllium are generally used. Since paper and resin have low sound velocity, performance is insufficient for high sound reproduction.Although metals such as titanium and beryllium have high rigidity, titanium is slightly heavier and beryllium is extremely expensive. Generally not very popular. Among metals, magnesium and magnesium alloys (referred to as magnesium alloys in this specification) are very suitable for speaker diaphragms because of their light weight, large internal loss, and high specific rigidity. It is known to be a material. For this reason, in recent years, speaker diaphragms using magnesium alloys have been manufactured.

JP-A-53-1517 JP 2007-43522 A

  However, since the dome-shaped diaphragm of a loudspeaker mainly for reproducing high-frequency sound has a small diameter, the cone-shaped diaphragm having a relatively large diameter described in Japanese Patent Laid-Open Nos. 53-1517 and 2007-43522 is used. As described above, there is a problem that it is difficult to increase the rigidity by providing ribs.

  In addition, a diaphragm using a magnesium alloy is advantageous in suppressing split vibration because of its high specific rigidity, but a diaphragm with a constant thickness even when made of a magnesium alloy has sufficient rigidity. There is a problem that the divided vibration cannot be suppressed by increasing it. For this reason, even in a diaphragm using a magnesium alloy, divided vibration occurs in the high sound range, and the sound pressure in a specific frequency band in the audible range is high, or the sound pressure in a specific frequency band is low. May cause a problem in the reproducibility of the acoustic signal.

  Furthermore, there is a problem that it is very difficult to form a diaphragm having a changed thickness as described in JP 2007-43522 A by pressing a magnesium alloy plate.

  Accordingly, an object of the present invention is to provide a dome-shaped diaphragm for a speaker that uses a magnesium alloy and has sufficiently high rigidity and can suppress divided vibration, and a method for manufacturing the same.

  In order to solve the above-described problems, the present invention is a dome-shaped diaphragm for a speaker formed by pressing a magnesium alloy plate so that the thickness thereof gradually decreases from the outer periphery toward the center. The thickness at the center of the diaphragm is 0.2 to 0.8 times the thickness of the outer periphery.

  According to the dome-shaped diaphragm of the present invention configured as described above, the thickness gradually decreases from the outer periphery toward the center, and the thickness at the center of the diaphragm is 0.2 to 0.8 times the thickness of the outer periphery. Therefore, the rigidity is sufficiently high and the divided vibration can be suppressed.

In the present invention, preferably, the outer diameter of the dome-shaped diaphragm is r ₁ , the outer wall thickness is t ₁ , and the ratio of the center wall thickness to the outer wall thickness is α = (t ₂ / t ₁ ). The wall thickness t (r) at the point of the distance r from the outer periphery of the dome shape toward the central axis is formed approximately at t (r) = t ₁ −r · (1−α) t ₁ / r ₁ . ing.
According to the present invention configured as described above, since the bending stress acting on the diaphragm becomes substantially uniform, the divided vibration can be most effectively suppressed.

  The present invention also relates to a method for manufacturing a dome-shaped diaphragm according to the present invention, comprising the steps of preparing a magnesium alloy plate, and a die made of the magnesium alloy plate at a temperature of 100 to 250 ° C. And a step of sandwiching between the dies and the crease presser, and the magnesium alloy plate sandwiched between the dies and the crease presser is set to a temperature 50 to 150 ° C. higher than the temperature of the die and the crease presser and 150 to 300 And plastically deforming with a punch having a temperature of ° C.

  In the present invention configured as described above, the magnesium alloy plate sandwiched between the die and the wrinkle retainer is plastically deformed by the punch that has a temperature higher than that of the die and the wrinkle retainer. A diaphragm having a thin central part of the mold and a thick outer peripheral part is formed by press working.

  According to the present invention, using a magnesium alloy, it is possible to obtain a dome-shaped diaphragm for a speaker that has sufficiently high rigidity and suppresses divided vibration, and a manufacturing method thereof.

Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of a dome-shaped diaphragm according to an embodiment of the present invention. FIG. 2 is a graph showing an example of the thickness distribution of the dome-shaped diaphragm according to the embodiment of the present invention and the conventional dome-shaped diaphragm. FIG. 3 is a diagram illustrating a method for manufacturing a dome-shaped diaphragm according to an embodiment of the present invention.

  First, in order to suppress the divided vibration generated in the dome-shaped diaphragm, it is important to reduce the weight of the diaphragm without reducing the strength of the diaphragm. When the diaphragm receives an acoustic signal and vibrates, it receives air resistance on the entire surface of the diaphragm, so that it is considered that an evenly distributed load acts on the entire surface. Here, when considering the strength of the dome-shaped diaphragm as a cantilever fan-shaped plate with a fixed outer peripheral edge and an equally distributed load, a large bending moment acts on the fixed outer peripheral edge. It can be seen that the bending moment is reduced at the tip (center of the dome shape). Therefore, in a conventional dome diaphragm having a constant thickness as shown by a broken line in FIG. 2, a large bending stress acts near the outer periphery of the diaphragm, and the bending stress near the center decreases. That is, in a conventional diaphragm having a constant thickness, the vicinity of the center of the dome-shaped diaphragm has the same thickness as the peripheral portion of the diaphragm even though the acting bending moment is small.

  For this reason, it can be seen that the dome-shaped diaphragm having a constant thickness is thick even though the thickness near the center does not contribute to the improvement in strength, and the weight increases with respect to the strength. Therefore, by distributing the thickness of the diaphragm so that the bending stress acts more evenly from the outer periphery to the center of the dome-shaped diaphragm, the weight of the diaphragm is reduced without reducing the strength of the diaphragm. It is considered possible.

As described above, the inventor of the present invention uses a magnesium alloy having excellent material properties as a diaphragm for a speaker in order to construct a dome-shaped diaphragm that can sufficiently suppress the occurrence of divided vibration. Thus, it has been found that it is necessary to form a thicker outer peripheral portion and a thinner central portion. The dome-shaped diaphragm is configured such that the thickness gradually decreases from the outer periphery toward the center, and the thickness t _{2 at} the center of the diaphragm is 0.2 to 0.8 times the outer wall thickness t _1. There should be. Here, the thickness of the diaphragm means that the thickness of the diaphragm is measured in a direction parallel to the center axis of the dome shape.

  In addition, if the center plate thickness becomes too thin, the rigidity of the center portion becomes low, and split vibrations are more likely to occur, so it is necessary to maintain a certain plate thickness. It is necessary to make it 0.2 times or more the thickness of the part. Furthermore, when the thickness of the central portion exceeds 0.8 times the thickness of the outer peripheral portion, there is almost no difference from a diaphragm having a constant thickness, and the weight of the central portion becomes heavy, so that divided vibration is likely to occur.

  Furthermore, in order to effectively suppress the occurrence of divided vibration, the thickness of the diaphragm is changed so that an equal bending stress is applied to all parts of the diaphragm in a state where a uniform distributed load is applied to the entire diaphragm. By doing so, useless mass distribution can be avoided, and the occurrence of divided vibration can be most effectively suppressed. Therefore, a thickness distribution in which uniform bending stress acts is obtained, and a diaphragm having a thickness distribution substantially along this curve is formed.

That is, as indicated by a solid line in FIG. 2, the outer diameter of the dome-shaped diaphragm is r ₁ , the outer wall thickness is t ₁ , and the ratio of the center wall thickness to the outer wall thickness α = (t ₂ / t ₁ ). , The thickness t (r) at the point of the distance r from the outer periphery of the dome shape toward the central axis is approximately
t (r) = t ₁ −r · (1−α) t ₁ / r ₁ (Formula 1)
To be formed. In the example shown in FIG. 2, the outer diameter of the diaphragm is 30 mm, and the ratio α between the center wall thickness and the outer wall thickness is 0.5.

  Here, “to form so that the wall thickness is approximately t (r)” means that the thickness is within plus or minus 10% of the value represented by Formula 1 above. That is, it is ideal to change the plate thickness along the wall thickness obtained by the above formula, but it is difficult to make this value strictly when industrially manufacturing. As a result of the examination, it has been confirmed that the reproducibility of the acoustic signal can be maintained without detracting from the characteristics of the present invention if the error is plus or minus 10% of the wall thickness obtained by Formula 1.

Next, with reference to FIG. 3, the manufacturing method of the dome shape diaphragm by embodiment of this invention is demonstrated.
First, a magnesium alloy plate 1 punched into a disk shape as a material to be molded is prepared. As shown in FIG. 3A, the magnesium alloy plate 1 is placed on a wrinkle retainer 4 heated to a predetermined temperature. As shown in FIG. 3B, the magnesium alloy plate 1 placed on the wrinkle retainer 4 is sandwiched between dies 2 heated to a predetermined temperature and held for several seconds to bring the material to be molded to a predetermined temperature. Heat. In the present embodiment, the temperatures of the die 2 and the wrinkle retainer 4 are maintained at 100 ° C. to 250 ° C. Next, the die 2 and the wrinkle presser 4 are pushed down as shown in FIG. 3C and brought into contact with the punch 6 to form the magnesium alloy plate 1 into a dome shape. Preferably, the clearance between the punch 6 and the die 2 ensures a gap along a desired thickness distribution. However, in the press working in the present embodiment, the clearance between the punch and the die and the thickness of the molded diaphragm are not necessarily equal as in press forging (die forging).

  Here, the temperature of the punch 6 is kept at a temperature in the range of 150 ° C. to 300 ° C., which is 50 ° C. to 100 ° C. higher than the temperature of the die 2 and the wrinkle retainer 4. At the time of forming, the tip of the punch 6 first hits the magnesium alloy plate 1. At this time, since the temperature of the punch 6 is higher than that of the magnesium alloy plate 1, the central portion of the magnesium alloy plate 1 is heated. Thereby, the proof stress of the center part of the magnesium alloy plate 1 falls, the deformation | transformation of this part advances, and the center part of the magnesium alloy plate 1 is extended and becomes thin. Furthermore, the magnesium alloy plate 1 can be formed into a desired thickness distribution by adjusting the pressure of the wrinkle presser as necessary.

  By adjusting the temperature of the punch 6 and the temperature of the wrinkle restraint 4 in the overhanging process, which is one of the press processes, a dome-shaped diaphragm having a thickness distribution as expressed by the above formula 1 can be formed. That is, in the press working, the temperature of the die 2 and the wrinkle retainer 4 is set to 100 ° C. to 250 ° C., and the temperature of the punch 6 is in the range of 150 ° C. to 300 ° C. The dome-shaped diaphragm having the above thickness distribution can be obtained by molding at a high temperature.

  In addition, when the temperature of the die | dye 2 and the wrinkle presser 4 is lower than 100 degreeC, the ductility of the magnesium alloy plate 1 cannot fully be ensured, and an appropriate process cannot be performed. Further, when the temperature of the die 2 and the wrinkle retainer 4 is higher than 250 ° C., the magnesium alloy plate 1 becomes too soft and the material is broken. The temperature of the punch 6 is appropriately 150 ° C. to 300 ° C. However, if the temperature of the punch 6 is less than 150 ° C., the magnesium alloy plate 1 is not sufficiently softened and the thickness of the central portion cannot be reduced. Further, when the temperature of the punch 6 exceeds 300 ° C., the magnesium alloy plate 1 becomes too soft and breaks.

  Further, the temperature of the punch 6 is set 50 ° C. to 150 ° C. higher than the temperature of the die 2 and the wrinkle retainer 4. When the difference is smaller than 50 ° C., a sufficient thickness difference cannot be obtained. When the temperature difference exceeds 150 ° C., the proof stress difference between the high temperature portion and the low temperature portion becomes large and breaks.

  Further, in the present embodiment, the molding is performed in one stage, that is, performed by one press using a pair of punches and dies, but this may be performed in multiple stages. In this case, using a plurality of punches and dies having different shapes, pressing is performed several times to form a final shape. When performing in multiple stages, the diameter of the punch is gradually decreased from the largest, and finally the punch having a desired shape is pressed to obtain the final shape.

  Next, with reference to FIGS. 4 to 6, the result of actually forming the dome-shaped diaphragm by the manufacturing method described above will be described. FIG. 4 is a graph showing the thickness distribution of the dome-shaped diaphragm formed by the manufacturing method of the embodiment of the present invention and the thickness distribution of the dome-shaped diaphragm according to the comparative example. 5 and 6 are graphs showing frequency characteristics of speaker units configured using the dome-shaped diaphragm according to the embodiment of the present invention and the dome-shaped diaphragm according to the comparative example.

Example 1
A dome-shaped speaker diaphragm having an outer diameter of 30 mm and a height of 10 mm was formed using a magnesium alloy AZ31B wrought material having a thickness of 0.050 mm. During molding, H-SF-60 manufactured by Aida Engineering Co., Ltd. was used as the press machine. Moreover, the blank diameter of the magnesium alloy plate was 40 mm, the die and wrinkle holding temperature was 200 ° C., and the punch temperature was 250 ° C. The wrinkle holding pressure is changed during molding. The thickness distribution obtained by actually measuring the dome-shaped diaphragm for a speaker according to the embodiment of the present invention formed as described above is shown by a black circle in FIG. The wall thickness distribution of the dome-shaped diaphragm substantially conforms to Equation 1.

(Example 2)
A dome-shaped speaker diaphragm having an outer diameter of 25 mm and a height of 6 mm was formed using a magnesium alloy AZ31B wrought material having a thickness of 0.030 mm. At the time of molding, the press machine was H-SF-60 manufactured by Aida Engineering Co., Ltd., the blank diameter of the magnesium alloy plate was 35 mm, the die and wrinkle holding temperature was 170 ° C., and the punch temperature was 230 ° C. The wrinkle holding pressure is changed during molding. The thickness distribution obtained by actually measuring the dome-shaped diaphragm for a speaker according to the embodiment of the present invention formed as described above is shown by a black circle in FIG. Moreover, the thickness distribution calculated | required by Numerical formula 1 is shown with a dashed-dotted line.

(Comparative Example 1)
A dome-shaped speaker diaphragm having an outer diameter of 30 mm and a height of 10 mm was formed using a magnesium alloy AZ31B wrought material having a thickness of 0.050 mm. During molding, H-SF-60 manufactured by Aida Engineering Co., Ltd. was used as the press machine. The magnesium alloy plate was formed with a blank diameter of 40 mm, a die and wrinkle holding temperature of 200 ° C., and a punch temperature of 200 ° C. During the molding, molding was performed at a constant pressure without changing the wrinkle pressing pressure. The thickness distribution obtained by actually measuring the dome-shaped diaphragm for a speaker according to the comparative example formed as described above is shown by white circles in FIG. In Comparative Example 1, there is no difference between the die and the wrinkle presser and the temperature of the punch, so that the thickness at the outer peripheral portion and the central portion of the diaphragm is substantially the same. Moreover, in this comparative example, the tendency for thickness to become a little thick in the outer peripheral part was seen.

(Comparative Example 2)
A dome-shaped speaker diaphragm having an outer diameter of 25 mm and a height of 6 mm was formed using a magnesium alloy AZ31B wrought material having a thickness of 0.030 mm. During molding, H-SF-60 manufactured by Aida Engineering Co., Ltd. was used as the press machine. The magnesium alloy plate was formed with a blank diameter of 30 mm, a die and wrinkle holding temperature of 180 ° C., and a punch temperature of 180 ° C. During molding, molding was performed without changing the wrinkle pressure. The thickness distribution obtained by actually measuring the dome-shaped diaphragm for a speaker according to the comparative example formed in this way is shown by white circles in FIG. In Comparative Example 2, there is no difference between the die and the wrinkle presser and the punch temperature.

(Evaluation of performance)
The diaphragms according to Examples 1 and 2 and the diaphragms according to Comparative Examples 1 and 2 were incorporated in a dynamic speaker for a normal tweeter, and the frequency characteristics thereof were evaluated.
5 and 6 are graphs obtained by actually measuring the frequency characteristics. FIG. 5 is a graph of frequency characteristics of Example 1 and Comparative Example 1 which are dome-shaped diaphragms having an outer diameter of 30 mm. FIG. 6 is a graph of frequency characteristics of Example 2 and Comparative Example 2 of the present invention, which are dome-shaped diaphragms having an outer diameter of 25 mm.

  In any case, a large peak and dip are observed in the sound pressure level in the comparative example, whereas no large peak and dip are observed in the sound pressure level in the example. This indicates that the divided vibration is sufficiently suppressed in the dome-shaped diaphragms of Examples 1 and 2.

  According to the dome-shaped diaphragm of the embodiment of the present invention, it is possible to obtain a speaker that suppresses divided vibration and has excellent reproducibility of acoustic signals.

It is sectional drawing of the dome shape diaphragm by embodiment of this invention. It is a graph which shows an example of the thickness distribution of the dome shape diaphragm by embodiment of this invention, and the conventional dome shape diaphragm. It is a figure which shows the manufacturing method of the dome shape diaphragm by embodiment of this invention. It is a graph which shows the thickness distribution of the dome shape diaphragm formed by the manufacturing method of embodiment of this invention, and the thickness distribution of the dome shape diaphragm by a comparative example. It is a graph which shows the frequency characteristic of the speaker unit comprised using the dome shape diaphragm by embodiment of this invention, and the dome shape diaphragm by a comparative example. It is a graph which shows the frequency characteristic of the speaker unit comprised using the dome shape diaphragm by embodiment of this invention, and the dome shape diaphragm by a comparative example.

Explanation of symbols

1 Magnesium alloy plate 2 Dies 4 Wrinkle retainer 6 Punch

Claims (3)

A dome-shaped diaphragm for a speaker formed by pressing a magnesium alloy plate,
A dome-shaped diaphragm characterized in that the thickness is gradually reduced from the outer periphery toward the center, and the thickness at the center of the diaphragm is 0.2 to 0.8 times the thickness of the outer periphery. When the outer diameter of the dome-shaped diaphragm is r ₁ , the outer wall thickness is t ₁ , and the ratio of the center wall thickness to the outer wall thickness α = (t ₂ / t ₁ ), The thickness t (r) at a point of distance r toward the central axis is approximately
t (r) = t ₁ −r · (1−α) t ₁ / r ₁ ,
The dome-shaped diaphragm according to claim 1, wherein It is a manufacturing method of the dome shape diaphragm of Claim 1 or 2,
Preparing a magnesium alloy plate;
Sandwiching the magnesium alloy plate between a die and a crease pressed at a temperature of 100 to 250 ° C .;
The magnesium alloy plate sandwiched between the die and the wrinkle presser is made 50-150 ° C. higher than the die and wrinkle presser temperature and is plasticized with a punch having a temperature of 150-300 ° C. A step of deforming,
A method for manufacturing a dome-shaped diaphragm.

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