JP2009063874A - Method of manufacturing soundboard - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a soundboard which is capable of forming a camber efficiently and with a good precision, which gives an excellent stability to the formed camber and which is capable of improving acoustic characteristics. <P>SOLUTION: A method of manufacturing the soundboard includes a humidity conditioning step (step 1) which conditions the humidity of a plurality of flat wooden soundboard materials 2 to the predetermined water content, a heating processing step (step 2) which heats the surface and the back surface of a plurality of humidity conditioned soundboard materials 2 so that different quantity of heat is supplied to each of them, a soundboard assembly step (step 3) which assembles a soundboard 1 by using a plurality of heated soundboard materials 2, and a camber forming steps (steps 4 and 5) which form a camber on the soundboard 1 by humidifying and/or drying the assembled soundboard 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a soundboard used for musical instruments such as acoustic pianos, violins, and guitars.

  In general, an acoustic piano soundboard is not flat, but a curved plate with a gently curved convex surface on the side where the piece is attached, in order to efficiently convert string vibrations to air vibrations to generate musical sounds. Is formed. Such a shape is called a “spinning” in a piano soundboard, and is generally formed by a method called a natural stripping method. In this natural peeling method, a flat soundboard is first produced by transversely bonding a plurality of wooden soundboard materials. Next, the sound board is dried to a predetermined moisture content and contracted, and then a sound bar is bonded to the back surface. Thereafter, when the soundboard is placed under moisture absorption conditions and its moisture content is increased, a difference in expansion degree is generated between the front and back surfaces depending on the presence or absence of the soundbar, thereby forming a peeling.

  In addition, the present applicant has already proposed another peeling forming method in Patent Document 1. In this method, a plurality of wooden soundboard materials are glued together to produce one flat soundboard, which is then humidified until a predetermined moisture content is obtained. Next, the humidified soundboard is softened by heating and then sandwiched between two molds having a predetermined surface shape. In that state, the soundboard is heated and dried to a predetermined moisture content, whereby a peeling is formed.

  In the conventional natural peeling method described above, the peeling is formed by utilizing the moisture release and moisture absorption of the soundboard. Therefore, it takes a long time to obtain sufficient peeling, and the peeling can be efficiently formed. Can not. For the same reason, it is difficult to accurately obtain a predetermined amount of peeling because the size of the peeling greatly depends on the humidity and temperature of the outside air, the Young's modulus and moisture content of the soundboard material, and the like. If the specified amount of peeling is not obtained, the sound plane and the driving surface do not fit together exactly, causing a large stress on the sound board during joining, causing cracks in the sound board, and the cause of poor adhesion. At the same time, there is an excess or deficiency of the piece pressure (downward pressure acting on the piece from the string), and complicated work must be performed for the adjustment. In addition, even after the soundboard is manufactured, the moisture content of the soundboard is likely to change due to the humidity of the outside air, etc., and the peeling tends to be deformed by expansion and contraction accordingly. And cracks may occur.

  On the other hand, in the case of the peeling forming method of Patent Document 1, the peeling is forcibly formed in a state where one large soundboard is sandwiched between two molding dies, so that an apparatus for that purpose becomes a large scale. At the same time, the manufacturing cost increases. In addition, since the soundboard is softened and then heated and dried while being sandwiched between molds, internal stress tends to remain on the soundboard after molding. The plate may be deformed (rebound) to return to a flat state.

  The present invention has been made in order to solve such a problem, and can efficiently and accurately form the peeling, and can improve the acoustic characteristics while being excellent in the stability of the formed peeling. It aims at providing the manufacturing method of a soundboard.

JP-A-8-263053

  In order to achieve the above object, a soundboard manufacturing method according to claim 1 includes a humidity control step of adjusting a plurality of flat wooden soundboard materials to a predetermined moisture content, and a plurality of humidity-controlled soundboard materials. A heat treatment process for heating the front and back surfaces of the soundboard so that different amounts of heat are supplied, a soundboard assembly process for assembling a soundboard using a plurality of heated soundboard materials, and humidifying and And / or a peeling forming step of forming a peeling on the soundboard by drying.

  According to this soundboard manufacturing method, in the heat treatment step, the front and back surfaces of a plurality of soundboard materials are heated, and at that time, different amounts of heat are supplied to the front and back surfaces. Then, after assembling the soundboard using a plurality of heated soundboard materials in the soundboard assembling process, the assembled soundboard is humidified and / or dried in the peeling forming process to peel off the soundboard. Is formed.

  When the wooden soundboard material is heated, the cellulose of the soundboard material is crystallized. The crystallization of cellulose promotes its hydrophobization, which reduces the hygroscopicity of the soundboard material and suppresses the change in moisture content. Therefore, the degree of expansion and contraction due to moisture absorption and drying of the soundboard material. (Hereinafter referred to as “expansion / shrinkage ratio”) becomes low. Moreover, since the front and back surfaces of the soundboard material are heated with different amounts of heat, the degree of crystallization of cellulose differs between the front and back surfaces of the soundboard material, and the hygroscopicity and the expansion / contraction rate differ accordingly (becomes nonuniform).

  As described above, since the hygroscopicity and expansion / contraction rate of the front and back surfaces of the soundboard material are made non-uniform by heat treatment in advance, when the soundboard is humidified and / or dried in the peeling formation process, It tends to warp on one side of the back surface, and peeling tends to occur. As a result, the peeling can be efficiently formed in a short time as compared with the case where a normal soundboard material not subjected to heat treatment is used.

  In addition, even after the soundboard is manufactured, the hygroscopicity and the expansion / contraction rate are different between the front and back surfaces of the soundboard, and the soundboard as a whole is reduced. The peel is difficult to be deformed, and a peel having excellent stability can be obtained.

  Moreover, since the internal loss is reduced by crystallization of cellulose as a whole soundboard, the acoustic characteristics of the soundboard can be improved.

  According to a second aspect of the present invention, in the soundboard manufacturing method according to the first aspect, in the heat treatment step, a larger amount of heat is supplied to the rear surface side than the front surface side of the front and back surfaces of the plurality of soundboard materials. In the peeling process, the sounding bar is attached to the back of the sounding board, and the sounding board with the sounding bar is humidified to form a convex surface on the sounding board. And a humidifying step.

  According to this configuration, in the heat treatment step, by supplying a larger amount of heat to the back side of the soundboard material, the degree of crystallization of cellulose is increased on the back side, and the hygroscopicity and the expansion / contraction rate are reduced. For this reason, if the soundboard is humidified after attaching the sounding rod to the back surface of the soundboard in the peeling formation process, the surface side having a large expansion / contraction rate is likely to be deformed into a convex shape, so that peeling is easily formed. Can do.

  Further, the method for forming the above-described peeling is basically the same as the above-described natural peeling method. Therefore, according to the present invention, it is possible to use an existing production line based on the natural peeling method as it is, and without adding a large cost, only by adding equipment for heating the soundboard material. Soundboard can be manufactured.

  According to a third aspect of the present invention, in the soundboard manufacturing method according to the first or second aspect, in the heat treatment step, the surface temperature and the back surface of the plurality of soundboard materials are different from each other. It is characterized by heating to a temperature.

  According to this configuration, the temperature of the front and back surfaces of the soundboard material is controlled to different predetermined temperatures during the heat treatment. Thereby, the crystallization degree of cellulose on the front and back surfaces of the soundboard material, and consequently the hygroscopicity and expansion and contraction properties of the front and back surfaces, can be appropriately controlled, and thus a predetermined amount of peeling can be formed with high accuracy.

  According to a fourth aspect of the present invention, in the soundboard manufacturing method according to the first or second aspect, in the heat treatment step, the front and back surfaces of the plurality of soundboard materials are respectively heated for different predetermined times. To do.

  According to this configuration, in the heat treatment step, the front and back surfaces of the soundboard material are heated for different predetermined times. Therefore, as in the case of claim 2, the degree of cellulose crystallization on the front and back surfaces of the soundboard material, and consequently the hygroscopicity and expansion and contraction properties of the front and back surfaces, can be appropriately controlled, and a predetermined amount of peeling can be formed with high accuracy.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a soundboard of a grand piano to which the present invention is applied. As shown in the figure, the soundboard 1 is obtained by transversely bonding a plurality of wooden soundboard materials 2 and has the same shape as the planar shape of a grand piano. A plurality of sounding bars 3 are affixed to the lower surface of the sounding board 1, and a convex strip is formed on the sounding board 1 along the extending direction of the sounding board 3 as shown in FIG. Has been.

  Although not shown, a long piece and a short piece are attached to the upper surface of the soundboard 1, and a string is stretched in a state where the long piece and the short piece are engaged.

  In the following description, the surface of the soundboard 1 on the side where the peeling appears (projects) and the surface of the soundboard material 2 corresponding to the surface are referred to as “surface”, and the soundboard 1 on the opposite side thereof. The surface of the sound board 2 is referred to as “back surface”.

Hereinafter, the manufacturing method of the soundboard 1 will be described in detail. FIG. 3 shows a schematic flow of the process.
(1) In the first step 1 (illustrated as “S1”, the same applies hereinafter), the plurality of soundboard materials 2 are conditioned (humidity adjusting step). As shown in FIG. 4, the soundboard material 2 is formed of a solid plate made of spruce or the like, for example, a length L = 1500 mm, a width W = 100 to 150 mm, and a thickness T = 11 mm as a standard. It is long.

  The humidity control of the soundboard material 2 is performed by cutting a raw wood such as spruce into the plate shape described above, and then performing natural drying or forced drying. As a result, the sound board 2 is conditioned to a predetermined moisture content, for example, 10% or less.

(2) Next, in step 2, heat treatment is applied to the conditioned soundboard material 2 (heat treatment step). FIG. 5 shows a heat treatment apparatus 4 for performing this heat treatment. The heat treatment apparatus 4 includes a flat box-shaped heating chamber 5, a heat insulating material 6 made of foamed phenol or the like laid in the heating chamber 5, and a length direction ( A plurality of heaters 7 arranged at equal intervals along the horizontal direction in FIG. The heater 7 is composed of, for example, a far infrared heater.

  When performing the heat treatment, a plurality of sound board materials 2 (only one is shown in FIG. 5) conditioned in step 1 are arranged on the heat insulating material 6 with the back surface 2b facing upward, After closing the heating chamber 5, the heater 7 is operated for a predetermined time (for example, 20 hours). As a result of the sound board 2 being heated from the back surface 2b side, the amount of heat supplied from the heater 7 is larger on the back surface 2b side and smaller on the front surface side 2a, and accordingly, the back surface temperature during heating is It becomes higher than the surface temperature.

  For the purpose of the present invention, the back surface temperature and the surface temperature at this time are maintained within a predetermined temperature range, for example, 100 to 200 ° C., and the difference between the two temperatures is maintained within a predetermined range, for example, 10 ° C. or more. Is preferred. In this embodiment, the back surface temperature is set to 150 ° C., and the surface temperature is set to about 140 ° C.

  As a result of heating the back surface 2b side of the soundboard material 2 with a larger amount of heat by the heat treatment as described above, the closer to the back surface 2b, the more the crystallization of cellulose by heating proceeds. A hatched portion 8 in FIG. 6 indicates a portion having a particularly high degree of crystallization formed in the vicinity of the back surface 2b of the soundboard member 2.

(3) The subsequent steps 3 to 5 are basically the same as in the case of the natural peeling method. First, in step 3, the soundboard is assembled by transversely bonding the plurality of heat-treated soundboard materials 2 (soundboard assembly process). Specifically, as shown in FIG. 7, after appropriately adjusting the length of the soundboard material 2, a plurality of soundboard materials 2 are laterally bonded and the outer peripheral portion thereof is cut off, as shown in FIG. 8. The soundboard 1 having a predetermined shape that matches the external shape of the grand piano is cut out.

  In addition, when a curvature generate | occur | produces in the sound board material 2 by heat processing, a curvature is corrected before cross-bonding. Further, after the cutting, the front and back surfaces of the soundboard 1 are subjected to sanding for making them smooth.

(4) Next, in step 4, a plurality of sounding rods 3 are bonded and attached to the back surface of the soundboard 1 (sounding rod attaching step). These sounding rods 3 are obtained by processing a solid wood material made of spruce or the like. As shown in FIG. 9, the attachment surface 3 a is flat before being attached to the soundboard 1. The sounding rod 3 is attached to the sounding plate 1 so as to extend along a direction substantially perpendicular to the extending direction of the sounding plate material 2, that is, along the transverse direction of the sounding plate material 2.

(5) Finally, in step 5, the soundboard 1 to which the soundbar 3 is attached is placed in a humidification chamber (not shown), humidified under a predetermined condition, and the moisture content is increased to a predetermined value (humidification step) ). As a result, the soundboard 1 expands due to moisture absorption, but on the back side, the expansion is restrained by the soundbar 3, so that the surface of the soundboard 1 has a convex peel due to the difference in expansion between the front and back surfaces. The Thereby, the soundboard 1 as shown in FIG. 1 and FIG. 2 is completed.

  Moreover, according to this embodiment, the heat treatment of the soundboard material 2 increases the degree of crystallization of cellulose on the back surface side of the soundboard 1 and reduces the expansion / contraction rate. The difference in expansion between the front and back surfaces becomes larger, and peeling is more likely to occur. As a result, a predetermined amount of peeling can be efficiently formed in a short time compared to the case where a normal soundboard material that has not been subjected to heat treatment is used. Furthermore, since the surface temperature and the back surface temperature of the soundboard material 2 are controlled to different predetermined temperatures during the heat treatment, the degree of cellulose crystallization on the surface 2a and the back surface 2b of the soundboard material, and thus the hygroscopicity and expansion / contraction of the front and back surfaces. The rate can be controlled appropriately, so that the desired peeling can be accurately formed.

  Further, even after the soundboard 1 is manufactured, the hygroscopicity and the expansion / contraction rate are different between the front and back surfaces of the soundboard 1 and the soundboard 1 as a whole is reduced, so the humidity of the outside air changes. Even so, the peel is less likely to be deformed, and a peel having excellent stability can be obtained.

  Furthermore, since the internal loss of the soundboard 1 is reduced by crystallization of cellulose as a whole, the acoustic characteristics of the soundboard 1 can be improved. As a result of measuring the internal loss of the soundboard 1 manufactured according to the present embodiment, it was confirmed that the internal loss was reduced by about 10% compared to a normal soundboard in which the soundboard material was not subjected to heat treatment. It was.

  Moreover, the manufacturing method of the soundboard 1 of the present embodiment is the same as the natural peeling method except that the soundboard material 2 is heat-treated in advance. Therefore, it is possible to use an existing production line based on the natural peeling method as it is, and it is possible to produce the soundboard 1 without adding a significant cost simply by adding the heat treatment apparatus 4 described above. it can.

  In addition, the method of heat-processing the sound board material 2 is not restricted to what was shown in embodiment, As long as a big calorie | heat amount is supplied to the back surface 2b side of the sound board material 2, it can employ | adopt arbitrarily. For example, using the heat treatment apparatus 4, as shown in FIG. 5, after heating for a first predetermined time with the back surface 2b of the soundboard material 2 facing the heater 7, the soundboard material 2 is turned upside down and its surface Heating may be performed for a second predetermined time shorter than the first predetermined time with 2a facing the heater 7 side.

  FIG. 10 shows a heat treatment apparatus according to the second embodiment. This heat treatment apparatus 14 supports both ends in the length direction of the soundboard material 2 with support tools 16 and 16 made of a heat insulating material or the like, and the back surface 2b of the soundboard material 2 by the heaters 7 and 17 arranged on the upper and lower sides thereof. And the surface 2a can be heated simultaneously. According to this configuration, (a) the heat generation amount of the heater 7 on the back surface 2b side is set larger than the heat generation amount of the heater 17 on the front surface 2a side, and the operating times of both heaters 7 and 17 are set to the same predetermined time. In addition, (b) by setting the heat generation amounts of both the heaters 7 and 17 to be the same and setting the operation time of the heater 7 longer, a larger amount of heat can be supplied to the back surface 2b side.

  In the case of the above (a), as shown in FIG. 10, a back surface temperature sensor 18 and a surface temperature sensor 19 for detecting the back surface temperature and the surface temperature of the soundboard material 2 are provided, respectively, and the detected values are the back surface temperature. Further, the heat generation amount and ON / OFF of the heaters 7 and 17 may be feedback-controlled so that the target value of the surface temperature is obtained. Thereby, by controlling the back surface temperature and the surface temperature of the soundboard material 2 precisely to the target values, a predetermined amount of peeling can be obtained with higher accuracy.

  FIG. 11 shows a heat treatment apparatus according to the third embodiment. The heat treatment device 24 includes a cooling device 25 that cools the front surface 2a of the soundboard material 2 in addition to the heater 7 that heats the back surface 2b of the soundboard material 2. The cooling device 25 includes a cooling plate 26 on which the sound board 2 is placed with the surface 2a facing down, a water supply pipe 27 that is in contact with the lower surface of the cooling plate 26 and extends along the lower surface, An apparatus main body 28 for circulating cooling water in the water pipe 27 is provided. The cooling plate 26 and the water supply pipe 27 are made of stainless steel, for example. Further, the apparatus main body 28 incorporates a heat exchanger for cooling the cooling water returned from the water supply pipe 27, a pump (none of which is shown) for sending the cooling water to the water supply pipe 27, and the like. ing.

  According to this configuration, the back surface 2b of the soundboard material 2 is heated by the heater 7, and the cooling water is circulated in the water pipe 27 as indicated by the arrows in the figure, whereby the surface 2a of the soundboard material 2 is cooled by the cooling plate. 26 to cool. Thus, since the surface 2a of the soundboard material 2 is cooled by the cooling device 25 simultaneously with the heating of the back surface 2b of the soundboard material 2 by the heater 7, a large temperature difference is ensured between the front and back surfaces of the relatively thin soundboard material 2. Accordingly, the heat treatment of the sound board 2 can be performed more efficiently and reliably.

  Also in the present embodiment, a back surface temperature sensor and a surface temperature sensor (not shown) for detecting the back surface temperature and the surface temperature of the soundboard material 2 are provided, and the detected values are the target values of the back surface temperature and the surface temperature. As described above, the back surface temperature and the surface temperature of the soundboard material 2 may be controlled more finely by feedback control of the heat generation amount of the heater 7 and the pumping amount of the cooling device 25.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, the embodiment is an example in which the present invention is used in combination with the natural peeling method. However, the present invention is not limited to this, and any other method that forms a peeling by humidifying and / or drying a soundboard. For example, it can be used in combination with the peeling forming method described in Patent Document 1 described above.

  Further, the embodiment is an example in which the present invention is applied to a soundboard of a grand piano. However, the present invention is not limited to this, and the present invention is not limited to an upright piano, but is a musical instrument such as a violin or a guitar. Applicable to soundboard. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

It is a top view which shows the sound board of the grand piano to which this invention is applied. It is sectional drawing which follows the line II-II of FIG. It is a figure which shows the process of the manufacturing method of a soundboard. It is a perspective view of a sound board material. It is a figure which shows typically the heat processing apparatus of a sound board material. It is a partial expansion perspective view of the sound board material which heat-processed. It is a top view in the state where a plurality of sound board materials were pasted and bonded. It is a top view of the soundboard after being cut out from a plurality of soundboard materials that have been laterally bonded. It is a top view for demonstrating the attachment process of a sounding stick. It is a figure which shows typically the heat processing apparatus by 2nd Embodiment. It is a figure which shows typically the heat processing apparatus by 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sound board 2 Sound board material 2a The surface of a sound board material 2b The back surface of a sound board material 3 Sound bar 4 Heat processing apparatus 7 Heater 14 Heat processing apparatus 17 Heater 24 Heat processing apparatus

Claims (4)

A humidity control step of conditioning a plurality of flat wooden soundboard materials to a predetermined moisture content;
A heat treatment step of heating the front and back surfaces of the plurality of conditioned soundboard materials so that different amounts of heat are supplied;
A soundboard assembly process for assembling a soundboard using the heated soundboard materials,
A peeling forming step of forming a peeling on the soundboard by humidifying and / or drying the assembled soundboard;
A method for manufacturing a soundboard, comprising: In the heat treatment step, the front and back surfaces of the plurality of soundboard materials are heated so that a larger amount of heat is supplied to the back surface side than the front surface side,
The peeling formation step includes
A sounding rod mounting step for attaching a sounding rod to the back surface of the sounding board;
A humidifying step in which the surface side of the soundboard forms a convex peel by humidifying the soundboard attached with the soundbar;
The manufacturing method of the soundboard of Claim 1 characterized by the above-mentioned.   The heat treatment step, wherein the front surface and the back surface of the plurality of soundboard materials are heated so that the temperature of the front surface and the temperature of the back surface are different from each other, respectively. 2. A method for producing a soundboard according to 2.   The method of manufacturing a soundboard according to claim 1 or 2, wherein in the heat treatment step, the front surface and the back surface of the plurality of soundboard materials are heated for different predetermined times.

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