JP2767702B2 - Voice coil bobbin - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voice coil bobbin for an electroacoustic transducer that is lightweight, has heat resistance and high elasticity, and has good dimensional stability against moisture.

(Prior Art) Conventionally, kraft paper has been used as a voice coil bobbin for an electroacoustic transducer. In recent years, with the spread of CDs, speakers with high sound quality and large input have been demanded. However, although kraft paper is lightweight, it has the drawback of poor heat resistance and water resistance. In order to eliminate this defect, a metal plate such as aluminum is also used as the voice coil bobbin.However, the metal plate becomes heavy as a bobbin, which not only reduces the efficiency as a speaker but also deteriorates the rising characteristics. There is a disadvantage that the sound quality is also deteriorated.

On the other hand, as a light and heat-resistant base material,
As shown in 59643, there is Nomex paper (manufactured by DuPont). Since Nomex paper is made of meta-aromatic polyamide fibers, the change in the moisture absorption of the paper is large with respect to the change in relative humidity, and the dimensional stability is poor.

It has been attempted to improve the dimensional stability of the bobbin by impregnating the base material with a phenolic resin having heat resistance for the purpose of improving the dimensional stability, and then performing heat treatment to improve the dimensional stability of the bobbin. In order to reduce the influence of humidity, it is necessary to increase the application amount of the impregnating agent, and it becomes difficult to manufacture a voice coil bobbin using a thin sheet.

In addition, as the amount of the impregnating agent applied increases, closed cells are easily generated inside the substrate, at the interface between the substrate and the impregnating agent, and in the impregnating agent layer. If a large input is applied to the voice coil without completely removing these bubbles, the bobbin will be deformed by the bubbles at a temperature lower than the heat-resistant temperature of the constituent materials due to the Joule heat generated from the coil, and the usage limit temperature for the voice coil will be reduced. descend. Therefore, heat treatment after impregnating Nomex with a heat-resistant resin such as a phenol resin causes a cost increase.

Therefore, the following method has been attempted for the purpose of preventing deformation of a voice coil bobbin using a nylon synthetic paper having an aromatic polyamide fiber as a base material due to moisture absorption and heat.

That is, as shown in Japanese Utility Model Publication No. 57-12639, a solvent type thermosetting resin is applied to one side of nylon synthetic paper, and after the solvent is volatilized, a heat treatment is applied to the thermosetting resin to form a thermosetting resin. After forming a film, the above-mentioned thermosetting resin is applied to the wire winding surface on the other surface of the nylon synthetic paper, and after the solvent is volatilized, a coil bobbin is formed in a cylindrical shape, and a solvent is added to the wire winding surface of the coil bobbin. A wire is wound while the thermosetting resin is reactivated, and then a heat treatment is performed, and the thermosetting resin is thermoset to form a thermosetting resin film. It is also a method of preventing deformation due to humidity.

(Problems to be Solved by the Invention) However, since the thermosetting resin does not penetrate into the inside of the nylon synthetic paper in this method, the thermosetting resin film is not formed on the cross section of the bobbin. Therefore, the bobbin deforms by absorbing moisture from the cross section. There was a problem that.

The present invention has been proposed in order to eliminate the above-mentioned drawbacks, and the object thereof is, as compared with a meta-based aromatic polyamide fiber, a para-aromatic polyamide fiber having a significantly lower water absorption as a main component. After impregnating the sheet-like nonwoven fabric substrate with a thermosetting resin such as a phenolic resin or a polyimide resin, it is subjected to a heat treatment to have light weight, heat resistance and high elasticity,
Another object of the present invention is to provide a voice coil bobbin having good dimensional stability with respect to moisture at a low cost.

(Means for Solving the Problems) In the present invention, a para-aromatic polyamide fiber having a tensile elastic modulus of 5,000 kg / mm ² or more and an equilibrium water absorption in a standard state of 7% or less as a main component, and a Kevlar pulp After adding a binder obtained by mixing ultra-highly beaten wood pulp, and impregnating a thermosetting resin such as a phenolic resin and / or a polyimide resin into a sheet-like nonwoven fabric substrate formed by a papermaking method, a heat treatment is performed. By performing the above, the above object is achieved.

(Action) In the present invention, a base material containing a para-aromatic polyamide fiber as a main component is used.

Since the voice coil bobbin has a remarkably low water absorption and high elasticity, the obtained voice coil bobbin has improved dimensional stability against moisture and high heat resistance.

In addition, the base material is impregnated with a heat-resistant resin, and as a result, the dimensional stability with respect to moisture is significantly better than that of the meta-based aromatic polyamide fiber, and the heat resistance and the high elasticity are lighter than metal. Voice coil.

(Example) In the present invention, an aqueous slurry obtained by mixing a para-aromatic polyamide fiber having high strength, high elastic modulus, high heat resistance and low water absorption with an appropriate binder is prepared, Form a wet paper with a paper machine having a netting, such as a short netting machine,
After drying, fiber paper is obtained by pressing with a hot roll as needed. The fiber paper is impregnated with a thermosetting resin solution and dried to obtain a voice coil bobbin material in an insufficient thermosetting state or a sufficient thermosetting state as required.

Para-aromatic polyamide fibers include paraphenylene terephthalamide fibers, polyparaphenylene 3-4, and diphenyl ether terephthalamide fibers, and have a tensile modulus of 5,000 kg / mm ² or more and a standard equilibrium water absorption. Fibers having a rate of 7% or less are suitable.

Suitable binders are those that have heat resistance and obtain the required paper strength at a low ratio. In addition, it should not inhibit adhesion of the impregnating thermosetting resin to the fiber. A hydrophilic pulp-like particle obtained from a metaphenylene isophthalamide polymer, which is generally called fibrid, or a highly highly fibrillated cellulose fiber can be used. The aqueous slurry is prepared by separately or simultaneously adding and dispersing the fibers and the binder to water in a suitable apparatus such as a pulper, a mixer or a beater.
Known dispersants and defoamers can be used. An appropriate slurry concentration is 0.1 to 1%.

Pressurization by the heat roll can be performed by a heat calendering apparatus in which a heated metal roll and an elastic roll such as heat-resistant paper are combined. In order to attach the thermosetting resin by impregnation in the post-process, pressurization, compression,
Fix it.

As the thermosetting resin, a resin having a heat resistance of 150 ° C. or more is suitable. That is, phenolic resins, epoxy resins, polyimide resins, and mixtures thereof. The curing step after the impregnation is performed by pressurizing with a heating roll to obtain a smooth surface. 50% impregnation of thermosetting resin
The following is desirable.

On the other hand, for the purpose of improving the adhesiveness, a thermoplastic resin (such as butyral resin) is added to the thermosetting resin, an inorganic or organic adhesive improving agent is applied on the thermosetting resin film, Modifying the coating with a surface treatment such as corona discharge treatment does not depart from the invention.

Example 1 A mixture of para-aromatic polyamide fiber, Kevlar 29 (manufactured by DuPont), 1.5 denier, 65 parts of 6 mm fiber length, 30 parts of Kevlar pulp (manufactured by DuPont), and 5 parts of ultra-highly beaten wood pulp were mixed and used as an aqueous solution. The slurry was prepared and 2 parts of a self-fixing reactive resin was added. This was paper-made using a circular paper machine, and subjected to a pressure treatment using a calender roll of a heated metal roll and a heat-resistant paper roll to obtain a base paper having a weight of 20 g / m ² and a thickness of 45 μm. When the tensile strength of the obtained base paper was measured,
The ratio between the MD direction (machine direction) and the CD direction (machine perpendicular direction) is
2.5: 1. This base paper is impregnated with a heat-resistant ferrule resin, and is pressed using a metal roll at 150 ° C. for 20 minutes to 250 ° C. for 2 minutes,
A heat treatment was performed to make the resin sufficiently cured to obtain a voice coil bobbin material.

Example 2 The same treatment as in Example 1 was performed using para-aromatic polyamide fiber Kevlar 149 (manufactured by DuPont), 1.5 denier, and fiber length of 3 mm to obtain a base paper having a weight of 25 g / m ² and a thickness of 47 μm. Was.
When the tensile strength of this base paper was measured, the ratio between the MD direction and the CD direction was 3: 1. This base paper was impregnated with a heat-resistant phenol resin to obtain a sufficiently cured state, and a voice coil bobbin material was obtained.

Conventional Example 1 Meta-based aromatic polyamide fiber paper, Nomex ^# 410
A voice coil bobbin material having a nominal thickness of 2 mils (manufactured by DuPont) was used.

The physical properties of the base fibers of Examples 1 and 2 and Conventional Example 1 are shown. As is clear from the table, the examples have significantly higher strength and elastic modulus than the conventional examples, have high heat resistance, have a small water absorption and thermal expansion coefficient, and have excellent dimensional stability against moisture and heat. Recognize.

The physical properties of the voice coil bobbin materials of Examples 1 and 2 and Conventional Example 1 are shown. By using the excellent fibers as described above, it is understood that the voice coil bobbin material of the example is significantly higher in both Young's modulus and propagation speed than the conventional example.

6 shows dimensional changes due to moisture absorption of the voice coil bobbin materials of Examples 1 and 2 and Conventional Example 1. Based on the dimensions after 24 hours in an atmosphere of 20 ° C. and 65% RH, the dimensions after 24 hours in an atmosphere of 46 ° C. and 97% RH are defined as the first moisture absorption treatment, and then in an atmosphere of 20 ° C. and 65% RH.
The dimension after time was defined as the first moisture release treatment, and the absorption and moisture release treatments were measured twice each.

In Examples 1 and 2, the dimensional change due to the moisture absorption and moisture release treatment was significantly smaller than that of the conventional example 1, and it can be seen that they were stable against the humidity change.

The surface of the voice coil bobbin material obtained in Examples 1 and 2 and Conventional Example 1 was coated with an adhesive for fixing a voice coil wire, and cut into a predetermined shape to obtain a voice coil bobbin. This was wound around a voice coil wire by a predetermined method, and an adhesive was cured at 180 ° C. for 30 minutes to obtain a voice coil having a diameter of 20 mm and a height of 16 mm.

The dimensional change of the voice coil obtained by the above method due to absorption and release of moisture is shown. 20% 65% of voice coil immediately after manufacturing
Based on the condition after standing for 24 hours in an RH atmosphere, the dimensions after 24 hours in a 46 ° C, 97% RH atmosphere and 24 hours in a 20 ° C, 65% RH atmosphere are defined as the first moisture absorption / release treatment, and this is repeated three times. The maximum deformation of a cylindrical voice coil from a perfect circle was measured.

Even in the state before the test immediately after being obtained after the heat treatment at 180 ° C. for 30 minutes during the manufacture of the voice coil, the deformation of the voice coils of Examples 1 and 2 is smaller than that of the conventional voice coil. It can be seen that the dimensional stability due to heat is excellent. In addition, even after the moisture absorption / release treatment, the voice coils of Examples 1 and 2 have a significantly smaller deformation amount than the conventional voice coil, and thus have excellent dimensional stability against humidity change.

No. 1 to No. 6 in FIG. 1 show the roundness diagrams of the voice coil as an example of the measurement results of the dimensional change due to moisture absorption and release of the voice coil.

In Examples 1 and 2, a voice coil bobbin material was manufactured by changing the impregnation amount of the heat-resistant phenol resin variously, and a voice coil having a diameter of 20 mm and a height of 16 mm was manufactured in the same manner as described above. A voice coil was similarly manufactured using the bobbin material of Conventional Example 1 and used for comparison. These were made into a 12 cm diameter, all-band loudspeaker by a predetermined method. All parts other than the voice coil were the same.

 An input resistance test was performed using these speakers.

In the conventional example, malfunction of the speaker occurred due to thermal deformation and bulging of the voice coil bobbin at 60 to 70 watts. When the temperature of the voice coil at this time is measured from the electric resistance, 25
0-280 ° C.

In the embodiment, the resin impregnation amount is appropriately adjusted. When the resin impregnation amount is 50% or less, the voice coil bobbin does not undergo thermal deformation or the like, and is approximately 90 watts.
Endured input.

When measuring the temperature of the voice coil at this time, 300 to 350
° C.

As described above, in the present embodiment, the input can be improved by about 20 W or more compared to the conventional example, and a voice coil bobbin with high heat resistance was obtained.

FIG. 2 shows the frequency characteristics of a 12 cm diameter full band speaker using the voice coil bobbin obtained in the first embodiment and the conventional example.

As compared with the conventional example, in Example 1, the high-frequency limit frequency was increased, and good results were obtained.

Example 3 Para aromatic polyamide fiber, Kevlar 29 fiber (same as in Example 1) 60 parts, Kevlar pulp (same as Example 1) 20 parts, metaphenylene isophthalamide fibrid (manufactured by Unitika) 20 The mixture was dispersed and mixed in water together with a small amount of a dispersant and an antifoaming agent to prepare an aqueous slurry, and produced in the same manner as in Example 1 to obtain a base paper having a weight of 25 g / m ² and a thickness of 45 μm. When the tensile strength of the obtained base paper was measured, the ratio between the MD direction and the CD direction was 2: 1. This base paper was impregnated with a phenol resin to obtain a voice coil bobbin material. It was confirmed that the obtained voice coil bobbin material also exhibited excellent characteristics as in Examples 1 and 2.

Example 4 Heat-resistant polyimide varnish and trainee were used on the base paper of Example 1.
^# 3000 (Toray) impregnated with a metal roll at 120 ° C
A pressurization and a heat treatment were performed for 10 minutes to 220 ° C. for 10 minutes to 290 ° C. for 15 minutes to make the resin sufficiently cured to obtain a voice coil bobbin material. Using the obtained bobbin material, a speaker was manufactured in the same manner as described above, and an input resistance test was performed.
Similar good results were obtained.

(Effects of the Invention) As described above, according to the present invention, a sheet-like nonwoven fabric base material mainly containing para-aromatic polyamide fibers is impregnated with a thermosetting resin such as a phenol resin and / or a polyimide resin. Since the voice coil bobbin is obtained by performing heat treatment, the voice coil bobbin has remarkably good dimensional stability against moisture, and has advantages that it is lighter than metal, and has excellent heat resistance, high elasticity and the like. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing the measurement of dimensional change with respect to moisture in terms of roundness, and FIG. 2 is a diagram comparing an embodiment of the present invention with a conventional example. It is a frequency characteristic figure.

Continued on the front page (72) Inventor Takashi Mikuniya 512 Miyazawa-cho, Akishima City, Tokyo Foster Electric Co., Ltd. (72) Inventor Meitaro Endo 422 Maeno, Mino City, Gifu Prefecture Daifuku Paper Co., Ltd. (56) References JP-A-54-123938 (JP, A) JP-A-55-173696 (JP, U) JP-B-61-59643 (JP, B2) JP-B-57-12639 (JP, B2) (58) Survey Field (Int.Cl. ⁶ , DB name) H04R 9/00-9/18 H04R 7/00-7/26

Claims (1)

(57) [Claims] 1. Main component is a para-aromatic polyamide fiber having a tensile modulus of 5,000 kg / mm ² or more and an equilibrium water absorption of 7% or less under standard conditions, mixed with Kevlar pulp and ultra-highly beaten wood pulp. And a heat treatment after impregnating a thermosetting resin such as a phenolic resin and / or a polyimide resin into a sheet-like nonwoven fabric substrate formed by a papermaking method. Voice coil bobbin for electro-acoustic transducer.