MANUFACTURING METHOD FOR NARROW-TYPE DIAPHRAGM AND THIN-TYPE DIAPHRAGM, SPEAKER-USE DIAPHRAGM MANUFACTURED USING SAME MANUFACTURING METHOD, SPEAKER, ELECTRONIC APPARATUS, AND MOVABLE DEVICE

• US 20140241565A1
• Filed: 05/01/2014
• Published: 08/28/2014
• Est. Priority Date: 01/25/2012
• Status: Active Grant

• Current Assignee: PANASONIC AUTOMOTIVE SYSTEMS CO., LTD. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: JIN, YOHEI
• Granted Patent: US 9,173,036 B2
• Time in Patent Office: Days
• US Class Current: 381/388
• CPC Class Codes: H04R 2307/021 Diaphragms comprising cellulose-like materials, e.g. wood, paper, linen
• CPC Class Codes: H04R 31/003 for diaphragms or their outer suspension
• CPC Class Codes: H04R 7/04 Plane diaphragms
• CPC Class Codes: H04R 9/025 Magnetic circuit

Abstract

After beaten, pulp is mixed with a filler to obtain a mixture of the pulp and the filler. Additives are added to the mixture, which is made into pater and then hot-pressed. The filler content of the mixture is in the range of 20 wt % to 80 wt %. After the additives are added, a polymeric viscosity improver with high viscosity is added to produce a narrow diaphragm or a thin compact diaphragm with high aspect ratio. These diaphragms have high rigidity and a wide reproduction frequency range.

Claims

1. A method of manufacturing a narrow diaphragm or a thin diaphragm, the method comprising, in the sequence set forth:

beating pulp;

mixing the beaten pulp with a filler so as to form a mixture of the beaten pulp and the filler;

adding a paper-strengthening agent and a sizing agent as additives to the mixture;

making paper from the mixture containing the additives; and

drying the paper by hot-pressing;

wherein a content of the filler in the mixture is in a range of 20 wt % to 80 wt %, inclusive, when the mixture is formed; and

a polymeric viscosity improver with high viscosity is added after the additives are added and before making the paper.

2. The method according to claim 1, wherein the viscosity improver is made of a polymeric material having a molecular weight of 5,000,000 or greater.

3. The method according to claim 1, wherein the viscosity improver has a viscosity of 12,000 mPa·

s/25°

C. or greater.

4. The method according to claim 1, wherein adding the additives, an added amount of the viscosity improver is in a range of 0.1% to 5%, inclusive, of a total weight of the mixture.

5. The method according to claim 1, wherein the viscosity improver is either cationic or zwitterionic.

6. The method according to claim 1, wherein the beaten pulp has a beating degree in a range from 200 ml to 700 ml, inclusive, according to Canadian standard freeness.

7. The method according to claim 1, wherein the beaten pulp has a fiber length of not less than 0.8 mm and not more than 3 mm.

8. The method according to claim 1, wherein the diaphragm has a density in a range from 0.40 g/cm³ to 1.00 g/cm³, inclusive.

9. The method according to claim 1, wherein

when mixing the beaten pulp and the filler, fine fibrillated fibers are mixed with the beaten pulp and the filler to form the mixture;

and

a content of the fine fibrillated fibers in the mixture is in a range from 1 wt % to 30 wt %, inclusive.

10. The method according to claim 9, wherein the fine fibrillated fibers have a beating degree of 200 ml or less.

11. The method according to claim 1, wherein the pulp contains bamboo fibers obtained from bamboos of one year old or more.

12. The method according to claim 11, wherein a lignin content of the bamboo fibers is 20 wt % or less.

13. The method according to claim 1, wherein the filler is at least one of mica, plant opal, and metal fiber.

14. A loudspeaker diaphragm manufactured by the method of manufacturing the narrow diaphragm or the thin diaphragm according to claim 1, wherein the filler is contained in a range from 20 wt % to 80 wt %, inclusive.

15. A loudspeaker comprising:

the loudspeaker diaphragm as defined in claim 14;

a frame;

a magnetic circuit connected to the frame;

a voice coil disposed in a magnetic gap of the magnetic circuit and fixed in a center of the loudspeaker diaphragm; and

an edge joining the loudspeaker diaphragm and the frame.

16. An electronic apparatus comprising:

a video display unit;

an outer frame enclosing the video display unit; and

the loudspeaker as defined in claim 15 and accommodated inside the outer frame.

17. A movable device comprising:

a driving device;

a body member including the driving device; and

the loudspeaker as defined in claim 15 and mounted in the body member.