TECHNICAL FIELD
[0001] The present invention relates to a method of manufacturing a diaphragm made of resin
film and to a loudspeaker and an electronic appliance including the diaphragm.
BACKGROUND ART
[0002] As mobile telephones and laptop computers have been marketed, the demand for manufacturing
loudspeakers for use in those appliances at higher productivity is increased. In response
to the demand, a conventional method of manufacturing a diaphragm installed in the
loudspeaker often employs an air-pressure forming technique which has a low cost.
[0003] Fig. 6 is a cross-sectional view of a conventional diaphragm manufacturing apparatus
501 for manufacturing a diaphragm employing the air-pressure forming technique as
is depicted in Patent Document 1.
[0004] The manufacturing apparatus 501 includes a molding die 1 having a molding pattern
for forming a predetermined shape of the diaphragm and a second molding die 2 facing
the molding die 1. The molding dies 1 and 2 which are heated up sandwich a resin film
3 between the dies 1 and 2. Then, air is introduced from a duct 4 provided in the
second molding die 2 so as to shape the resin film 3 along the first molding die 1
with a pressure of the air.
[0005] The predetermined molding pattern has a deep recess corresponding to a recess 1A
provided in the molding die 1. When the resin film 3 is pressed onto the recess 1A
in the molding die 1, the resin film 3 may be stretched out excessively and broken
off.
[0006] In order to prevent any damage on the resin film 3, the air introduced from the duct
4 is gradually adjusted in its pressure so as to stretch the resin film 3 moderately.
However, this process takes a long period of time during the molding of the resin
film 3 and accordingly decreases the productivity of the diaphragm.
Patent Document 1:
JP3-133616A
SUMMARY OF THE INVENTION
[0007] A diaphragm has a predetermined shape having a projecting portion and a recessed
portion opposite to the projection portion. The diaphragm has a first surface and
a second surface opposite to the first surface, the first surface having the projecting
portion, the second surface having the recessed portion therein. A first molding die
has a surface having a molding pattern having a recess to shape the projecting portion
of the diaphragm. A second molding die has a surface having a projection facing the
recess of the first molding die. The surface of the second molding die has a duct
therein for blowing out the air. A resin film is placed between the first molding
die and the second molding die while the first molding die and the second molding
die are located away from each other. The first molding die and the second molding
die contact the resin film. The resin film is attached to the surface of the first
molding die by a pressure of the air blown out from the duct.
[0008] The diaphragm can be manufactured at high productivity by this method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009]
Fig. 1 is a cross-sectional view of a diaphragm according to an exemplary embodiment
of the present invention.
Fig. 2 is a cross-sectional view of a diaphragm manufacturing apparatus of the diaphragm
according to the embodiment.
Fig. 3 is a cross-sectional view of the diaphragm manufacturing apparatus according
to the embodiment.
Fig. 4 is a cross-sectional view of the diaphragm manufacturing apparatus according
to the embodiment.
Fig. 5 is a partial cross-sectional view of an electronic appliance according to the
embodiment.
Fig. 6 is a cross-sectional view of a conventional apparatus for manufacturing a diaphragm.
REFERENCE NUMERALS
[0010]
- 5
- First Molding Die
- 6
- Projection
- 7
- Second Molding Die
- 8
- Molding Die
- 9
- Resin Film
- 10
- Recess
- 13
- Duct
- 15
- Chamber
- 51
- First Heater
- 52
- Second Heater
- 101
- Diaphragm
- 101C
- Projecting Portion
- 101D
- Recessed Portion
- 102
- Magnetic Gap
- 103
- Magnetic Circuit
- 104
- Voice Coil
- 301
- Electronic Appliance
- 302
- Case
- 401
- Loudspeaker
DETAIL DESCRIPTION OF PREFERRED EMBODIMENT
[0011] Fig. 1 is a cross-sectional view of a diaphragm 101 according to an exemplary embodiment
of the present invention. The diaphragm 101 is made of a resin film having a predetermined
shape having surface 101A and surface 101B opposite to surface 101A. The surface 101A
of the diaphragm 101 has a projecting portion 101C projecting. The surface 101B of
the diaphragm 101 has a recessed portion 101D opposite to the projecting portion 101C.
[0012] Fig. 2 is a cross-sectional view of an apparatus 1001 for manufacturing the diaphragm
according to the embodiment. The apparatus 1001 includes a first molding die 5 having
a surface 5A and a second molding die 7 having a surface 7A facing the surface 5A
of the first molding die 5. A molding pattern 8 is formed at the surface 5A of the
first molding die 5 for defining the shape of the diaphragm 101. The second molding
die 7 has a projection 6 provided on the surface 7A. The molding pattern 8 at the
surface 5A of the first molding die 5 has a recess 10 therein. A hole 11 extends from
the recess 10 and passes through the first molding die 5. The first molding die 5
has a first outer rib 12 projects from surface 5A and surrounds the recess 10. A first
heater 51 is mounted onto the surface 5B of the first molding die 5 opposite to the
surface 5A for heating up the fist molding die 5.
[0013] The projection 6 of the second molding die 7 faces the recess 10 provided in the
first molding die 5. The projection 6 has a duct 13 provided therein for emitting
gas, such as air. The second die 7 has a second outer rib 14 projects from surface
7A and surrounds the projection 6. A second heater 52 is mounted onto a surface 7B
of the second molding die 7 opposite to the surface 7A for heating up the second molding
die 7.
[0014] A method of manufacturing the diaphragm 101 according to the embodiment will be described
below.
[0015] First, as shown in Fig. 2, both the first molding die 5 and the second molding die
7 are heated up to a temperature higher than a glass transition point of the resin
film 9. According to the embodiment, the resin film 9 is made from polyetherimide
(PEI). More specifically, both the first molding die 5 and the second molding die
7 are heated by the heaters 51 and 52 to 230°C, which is higher than 220°C of the
glass transition point of PEI. Then, while the first molding die 5 and the second
molding die 7 are located away from each other, the resin film 9 is placed and held
between the first molding die 5 and the second molding die 7. At this moment, a portion
of the resin film 9 providing the diaphragm 101 is precisely positioned on the molding
pattern 8.
[0016] Then, as shown in Fig. 3, the first molding die 5 and the second molding die 7 move
relatively close to the resin film 9 to contact the resin film 9. The resin film 9
contacts the projection 9 of the second molding die 7 and is heated and softened by
the heat of both the first molding die 5 and the second molding die 7. Then, air is
sucked from the hole 11 to attach the softened resin film 9 onto the surface 5A at
the molding pattern 8 of the first molding die 5. At this moment, the resin film 9
has a stress to be urged towards the projection 6, accordingly being pulled from an
outside of a chamber 15 to an inside of the chamber 15. Then, the first outer rib
12 and the second outer rib 14 contact the resin film 9 between the ribs 12 and 14
to produce the chamber 15 sealed between the first molding die 5 and the second molding
die 7
[0017] Then, as shown in Fig. 4, the resin film 9 is pressed relatively against the surface
5A of the first molding die 5 with the second outer rib 14. At this moment, a gap
6A is provided between the resin film 9 and the projection 6. Air is blown out from
the duct 13 provided in the projection 6 of the second molding die 7 across the gap
6A to the chamber 15 while the air is sucked from the hole 11. The blown air presses
the resin film 9 directly against the molding pattern 8 at the surface 5A of the first
molding die 5. This process transfers the shape of the molding pattern 8 to the resin
film 9. At this moment, the resin film 9 has a stress towards the duct 9, hence being
slightly displaced from the outside of the chamber 15 to the inside of the chamber
15.
[0018] Then, the temperature of the resin film 9 between the molding dies 5 and 7 is reduced
to a temperature lower than the glass transition point, and then, the first molding
die 5 and the second molding die 7 are removed away from each other. Then, the air
is blown from the hole 11 so as to remove, from the first molding die 5, the resin
film 9 having the shape transferred from the molding pattern 8, thus providing the
diaphragm 101 having the predetermined shape.
[0019] In the manufacturing apparatus 1001 according to the embodiment, the resin film 9
is pulled into the recess 10 with the projection 6 moving into the recess 10 before
being pressed against the surface 5A of the first molding die 5 with the second outer
rib 14, as shown in Fig. 3. This process prevents the resin film 9 from being stretched
excessively when the air blown from the duct 13 attaches the resin film 9 onto the
molding pattern 8 particularly onto the recess 10. Thus, while the conventional manufacturing
apparatus 501 shown in Fig. 6 stretches the resin film 3 with air for a long period
of time, the manufacturing apparatus 1001 according to the embodiment manufactures
the diaphragm 101 favorably.
[0020] The duct 13 blows the air from the projection 6 facing the recess 10 in the first
molding die 5. The air blown out from the duct 13 in the projection 13 attaches the
resin film 9 uniformly onto the recess 10, thereby transferring the shape of the recess
10 properly to the resin film 9. The air blown out from the duct 13 in the projection
6 produces a stress that urges the resin film 9 towards the projection 6, thus pulling
the resin film 9 to the inside of the chamber 15. This process prevents the resin
film 9 from breaking due to an excessive stretching of the resin film 9, provides
the diaphragm 101 with predetermined quality. Alternatively, the duct 13 blowing the
air can be located at a position on the surface 7A other than the position of the
projection 6, providing the effect of the projection 6 that pulling the resin film
9 inward, as shown in Fig. 3.
[0021] In the manufacturing apparatus 1001 according to the embodiment, before the first
molding die 5 and the second molding die 7 contacts the resin film 9, both the first
molding die 5 and the second molding die 7 are heated up to the temperature higher
than the glass transition point of the resin film 9, thereby softening the resin film
9 as the resin film 9 approaches the first molding die 5 and the second molding die
7. As shown in Fig. 4, the temperature of the resin film 9 is higher than the glass
transition point when the resin film 9 contacts the molding pattern 8 at the surface
5A of the first molding die 5. The first molding die 5 and the second molding die
7 press against each other while the air blown out from the duct 13, as shown in Fig.
4. This operation transfers the shape of the molding pattern 8 to the resin film 9
for a short time, thus increasing a productivity of the diaphragm 101.
[0022] Both the first molding die 5 and the second molding die 7 are heated up by heaters
51 and 52 mounted onto the surface 5B of the first molding die 5 and the surface 7B
of the second molding die 7, respectively. As shown in Figs. 3 and 4, while approaching
the resin film 9, the molding dies 5 and 7 are removed from the heaters 51 and 52
and approach the resin film 9. As the molding dies 5 and 7 are removed away from the
heaters 51 and 52, respectively, temperature gradually falls. The temperature of the
molding dies 5 and 7 however remain higher than the glass transition point when the
shape of the molding patter 8 is transferred to the resin film 9 sandwiched between
the molding dies 5 and 7 as shown in Fig. 4. Then, the air blown out from the duct
13 for transferring the shape of the molding pattern 8 to the resin film 9 lowers
the temperature of the molding dies 5 and 7 with the resin film 9 quickly to a temperature
less than the glass transition point of the resin film 9, thus curing the resin film
9 having the shape transferred from the molding pattern 8. Thus, the manufacturing
apparatus 1001 according to the embodiment can manufacture the diaphragm 101 at high
productivity inexpensively without an extra device for cooling down the resin film
9.
[0023] In the manufacturing apparatus 1001 according to the embodiment, the pressure applied
to the resin film 9 due to the air blown out from the duct 13 is higher than 0.8 MPa
and lower than a level damaging the resin film 9. This pressure presses the resin
film 9 more tightly against the molding pattern 8 at the recess 10 of the molding
die 5. Accordingly, even if the shape of the molding pattern 8 is intricate, the shape
can be transferred accurately to the resin film 9 and ensures the high productivity
of the diaphragm 101 while reducing production failure of diaphragms 101.
[0024] Fig. 5 is a partial cross-sectional view of an electronic appliance 301 according
to the embodiment. The electronic appliance 301 is a portable appliance, such as a
mobile telephone, which includes a case 302 and a loudspeaker 401 mounted to the case
302. The loudspeaker 401 includes a diaphragm 101 produced by the manufacturing apparatus
1001, a magnetic circuit 103 having a magnetic gap 102, and a voice coil 104 coupled
to the diaphragm 101. The voice coil 104 is located in the magnetic gap 102 and is
displaced in response to a current applied to the coil so as to vibrate the diaphragm
101 emitting sound. Since the diaphragm 101 is manufactured at higher productivity
without being stretched out excessively, the diaphragm 101 has high performance as
well as a physical strength while being inexpensive. Thus, loudspeaker 401 has high
performance and provides the electronic appliance 301 with high quality and a low
cost.
INDUSTRIAL APPLICABILITY
[0025] A manufacturing method according to the present invention provides a diaphragm at
high productivity and particularly favorable for manufacturing a diaphragm having
a small size and an intricate shape.
1. A method of manufacturing a diaphragm having a predetermined shape having a projecting
portion and a recessed portion opposite to the projection portion, the diaphragm having
a first surface and a second surface opposite to the first surface, the first surface
having the projecting portion, the second surface having the recessed portion therein,
said method comprising:
providing a first molding die having a surface, the surface of the first molding die
having a molding pattern having a recess to shape the projecting portion of the diaphragm;
providing a second molding die having a surface, the surface of the second molding
die having a projection facing the recess of the first molding die, the surface of
the second molding die having a duct therein for blowing out the air;
placing a resin film between the first molding die and the second molding die while
the first molding die and the second molding die are located away from each other;
causing the first molding die and the second molding die to contact the resin film;
and
attaching the resin film to the surface of the first molding die by a pressure of
the air blown out from the duct.
2. The method according to claim 1, wherein the duct is provided in the projection.
3. The method according to claim 1,
wherein said causing the first molding die and the second molding die to contact the
resin film comprises providing a chamber between the first molding die and the second
molding die, said method further comprising
pulling the resin film into the chamber by the pressure of the air blown out from
the duct.
4. The method according to claim 1, further comprising
heating the first molding die and the second molding die to a temperature higher than
a glass transition point of the resin film before said placing the resin film between
the first molding die and the second molding die.
5. The method according to claim 4, wherein
said heating the first molding die and the second molding die comprises:
heating the first molding die with a first heater mounted onto a surface of the first
molding die opposite to the surface of the first molding die; and
heating the second molding die with a second heater mounted onto a surface of the
second molding die opposite to the surface of the second molding die, and
said causing the first molding die and the second molding die to contact the resin
film comprises:
moving the first molding die from the first heater to the resin film; and
moving the second molding die from the second heater to the resin film.
6. The method according to claim 1, wherein the pressure of the air is higher than 0.8
MPa.
7. A diaphragm manufactured by the method according to any one of claims 1 to 6.
8. A loudspeaker comprising:
the diaphragm according to claim 7;
a magnetic circuit having a magnetic gap; and
a voice coil placed in the magnetic gap and coupled with the diaphragm.
9. An electronic appliance comprising:
the loudspeaker according to claim 8; and
a case having the loudspeaker mounted thereto.