JPS6098490A - Reverberator for musical instrument and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to a musical instrument made of a carbon fiber-reinforced resin sheet with a condensation resin as a matrix, which minimizes the increase in weight and improves acoustic characteristics. This invention relates to a soundboard and a method for manufacturing the same.

[Prior art]

Traditionally, soundboards for pianos and other instruments have been made of woods such as Ezo pine and spruce, which have well-aligned grain directions, but such natural materials are extremely expensive and require material selection, wood removal, and chiseling. It requires many complicated processes such as bonding, and wood has the disadvantage of poor yield. In addition, since the specific elastic modulus E/ψ (E: Young's modulus, ψ: density) is limited by the value unique to wood, it is impossible to expect sound characteristics beyond a certain level, and wood in particular has a high shear loss coefficient. As a result, the damping in the high frequency range is large, resulting in a blurred sound.

Therefore, recently, a core material made of low specific gravity such as foam is used, and fiber-reinforced resin sheets are laminated and bonded on both sides of the core material, or wood is used as the core material and fiber-reinforced resin sheets are laminated on both sides. Various types of soundboards having a sand inch structure made by bonding have been proposed. However, since the core material is made of single foam, its internal loss is large, resulting in insufficient volume, sound quality, and sound extension, especially in the high frequency range.

On the contrary, the problem was that the sound quality was blurred and the overall sound balance was poor. On the other hand, those with wood as the core material have a large E/9, extremely low internal loss in the low frequency range, and large high frequencies.

This also had the drawback of poor sound balance overall.

Therefore, as shown in FIG.
, 3, by joining a front plate 4 and a back plate 5 made of wood respectively.

We have already filed an application for a soundboard for musical instruments (Japanese Patent Application No. 166356/1982) which aims to control shear loss and improve sound quality. Although a soundboard having such a structure can provide a bright and balanced sound and improve the acoustic characteristics, it has the following problems.

In other words, carbon fiber reinforced resin sheets usually use prepreg with a matrix of high-temperature curing epoxy resin, so if you try to simultaneously cure and bond the prepreg by sandwiching uncured epoxy prepreg with wood and heating it, The moisture that evaporates from the wood when heated does not have an affinity with the epoxy resin, resulting in poor adhesion. Therefore, a sheet made of hardened carbon fiber reinforced resin. It was necessary to post-bond both the sheet and the wood with an adhesive (for example, an epoxy resin that cures at room temperature). Therefore, the adhesive layer increases the weight, and the loss coefficient of the wood part becomes large due to the adhesive penetrating into the wood part more than necessary, so that a sufficient effect cannot be obtained.

[Summary of the invention]

This invention was made in view of the points mentioned above.
Our goal is to provide a soundboard for musical instruments that minimizes the weight increase, does not increase the loss coefficient of the wood part, and provides good acoustic characteristics. It consists of a plate and a plurality of sheets made of carbon fiber reinforced resin having a matrix of condensed resin interposed between these single plates.

It is also an object of the present invention to interpose prepregs of uncured carbon fiber reinforced resin with condensation resin as a matrix between a plurality of wood veneers by aligning the fiber direction with the fiber direction of the veneers. Another object of the present invention is to provide a method for manufacturing a soundboard for a musical instrument, in which the prepreg is cured at the same time as these are integrated by heating and pressing.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

The 20th is a perspective view of essential parts showing an embodiment in which the musical instrument soundboard according to the present invention is applied to a piano soundboard. In the figure, a soundboard 10 is formed by joining a plurality of laminated plates 11 in the side direction thereof to form a plate-like body having predetermined bold letters.

The laminated board 11 is made of three wood veneers 12A and 12B.

12C and a carbon fiber reinforced resin sheet (13) having a matrix of condensation resin interposed between these veneers.
A, it has a structure in which it is laminated and bonded via 13n.

As each of the wood veneers 12A, 12B, and 12C, veneers of spruce, Japanese pine, Japanese cedar, etc. are used, and the fiber directions thereof are all aligned with the longitudinal direction of the laminate 11 as shown by arrow A. There is. The wood veneer 12A.

Two wood veneers 1 for the front side of 12B and 12C
The thickness of the boards 2A and 12C is preferably the same, about 2-411a, and the thickness of the central wood veneer 12B is preferably about 1-4 inches.
If the thickness of the wood veneer 12B in the center is 4n or more, the shear loss is too large, and if it is less than lii+, the veneer 12
B and the carbon fiber reinforced resin sheet) 13A.

Since the total thickness of the shear loss reduction layer consisting of 13B and 13B is reduced, the effect of improving the blurred sound peculiar to wood is reduced.

It is desirable that the carbon fiber reinforced resin sheets 13A and 13B have a thickness of about 0.05 to 0.5 yxrtr; if the thickness is less than 0.05 inch, the shear loss reinforcement effect will be small, and if it is more than Q, 5 m11, the weight will be reduced. increases too much.

The manufacturing method for these sheets 13A and 13B is to impregnate carbon fibers arranged parallel to each other in one direction with a condensation resin such as phenol resin, urea resin, or melamine resin using alcohol as a solvent as a matrix. The condensation resin may be cured by pre-curing, preparing an uncured continuous fiber bripreg sheet, and heat-pressing this with a hot press.

As a method for manufacturing the laminate 11, the above-mentioned uncured prepreg sheet is made, and this sheet is applied to the wood veneer 12A.
and 12B and between 12B and 12C, respectively, so that the fiber direction matches the fiber direction of the wood veneer,
These wood veneers 12A and 12B.

The 12C and prepreg sheets are held in a real press at 80'0 for 1 hour under a pressure of about 10kXi. As a result, the curing of the prepreg sheet and the adhesion of the cured sheet to the wood veneer are done in one step. , a laminate 11 can be obtained. Then, such a laminated board 11 is cut into a required size, and the sound board 1 is obtained by cutting the laminated board 11 into required dimensions and joining them together in the lateral direction.

Here, an uncured prepreg sheet made of a carbon fiber reinforced resin sheet with a matrix name of condensation resin is interposed between a plurality of wood veneers, and the curing of the sheet and adhesion to the wood veneer are performed. It has been found that by proceeding simultaneously, various effects listed below can be obtained. In other words, firstly, since a condensation resin is used as a matrix,
It has great affinity with wood veneers and provides good adhesion. Second, the resin will not penetrate into the wood veneer more than necessary, and the loss coefficient (-δ) of bending vibration in the direction of the wood veneer's end face (fiber direction) will not increase. Third, the resin will not penetrate into the wood veneer. Because the prepreg sheet fluidizes and hardens in a manner that conforms to the unevenness of the surface of the veneer, an adhesive layer with the minimum weight and a carbon fiber reinforced resin sheet layer with the maximum fiber content are formed. Fourth, since the condensation resin matrix has a higher elastic modulus than epoxy resins, etc., it is particularly effective in reinforcing shear loss in the direction of the butt end surface. the result.

Since shear loss in the direction of the butt end is small, damping in the high frequency range can be reduced.

Incidentally, the weight increase rate and the penetration of adhesive between the soundboard according to the present invention and the conventional soundboard made of a core material 1 front panel, a back panel, and a fiber-reinforced resin sheet with an epoxy resin matrix as shown in FIG. The thickness and loss factor (-δ) are shown in a table.

From the above table, it can be seen that the soundboard 1 having the above structure can minimize the increase in weight, and the sound is well extended throughout the entire tone, producing a bright and well-balanced sound. It is possible to improve the acoustic characteristics as

Although the above embodiment describes a case in which a laminate is manufactured using three wood veneers and two carbon fiber reinforced resin sheets, the present invention is not limited to this. and four carbon fiber reinforced resin sheets; in short, the resin sheets may be arranged symmetrically with respect to the center of the thickness of the laminate.

〔Effect of the invention〕

As explained above, the soundboard for a musical instrument according to the present invention includes a plurality of wood veneers, each of which is interposed between the wood veneers and positioned symmetrically with respect to the center of the thickness of the soundboard, and in the fiber direction. is manufactured by pressurizing and compressing a plurality of uncured carbon fiber reinforced resin prepreg sheets having a matrix of condensation resin that is almost the same as that of the wood veneer,
Good bonding strength can be obtained by increasing the minimum weight, and the penetration of the resin into the wood part is small, which prevents an increase in the loss coefficient of the wood part.In addition, the condensation resin has an excellent reinforcing effect on shear loss, and is suitable for high-frequency Damping in the range can be reduced, resulting in a brighter, more balanced sound and improved acoustic characteristics.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a conventional soundboard, and FIG. 2 is a perspective view of essential parts showing an embodiment in which the present invention is applied to a piano edge plate. 10...Soundboard, 11...Laminated board, 12A. 12B, 12C...wood veneer, 13A, 13B...
...Carbon fiber reinforced resin sheet. Patent applicant Nippon Musical Instruments Manufacturing Co., Ltd.

Claims (2)

[Claims] (1) A plurality of wood veneers and a plurality of carbon fiber-reinforced resin sheets interposed between these veneers and having a condensation resin as a matrix are integrally joined, and the carbon fiber reinforced The resin sheet is arranged symmetrically with respect to the center of the board thickness,
A sound board for a musical instrument, characterized in that the fiber direction thereof is the same as the fiber direction of the wood veneer. (2) A prepreg of uncured carbon fiber-reinforced resin with a matrix of condensed resin is placed between multiple wood veneers stacked with the grain direction aligned so that the fiber direction matches the fiber direction of the veneer. A sound board for a musical instrument, characterized in that the prepregs are inserted so as to be heated and hardened, and simultaneously integrated with the veneer.