EP2124484A1

EP2124484A1 - Method of producing diaphragm and speaker and electronic device using the diaphragm

Info

Publication number: EP2124484A1
Application number: EP07828237A
Authority: EP
Inventors: Masashi Kawabe; Hironori Tabata; Shinichi Yamanaka; Koji Sano
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2007-04-12
Filing date: 2007-09-18
Publication date: 2009-11-25
Also published as: JP2008263416A; CN101690268A; WO2008129695A1; JP4367515B2

Abstract

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. The diaphragm can be manufactured at high productivity by this method.

Description

TECHNICAL FIELD

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

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.
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.
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.
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.
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

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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.
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.
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.
A method of manufacturing the diaphragm 101 according to the embodiment will be described below.
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.
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
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.
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.
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.
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.
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.
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.
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.
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

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.

Claims

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.
The method according to claim 1, wherein the duct is provided in the projection.
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.
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.
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.
The method according to claim 1, wherein the pressure of the air is higher than 0.8 MPa.
A diaphragm manufactured by the method according to any one of claims 1 to 6.
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.
An electronic appliance comprising:
the loudspeaker according to claim 8; and

a case having the loudspeaker mounted thereto.