JP2010105368A - Apparatus for producing soundboard - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for accurately producing a soundboard which is modified by heating and has desired physical properties. <P>SOLUTION: The soundboard manufacturing apparatus includes a preliminary humidity adjustment means for preliminarily adjusting the humidity of a woody soundboard material 1 to be the material of the soundboard 8, a heating chamber 2 for storing the soundboard material 1 which is humidity-adjusted preliminarily, first and second heaters 5a and 5b which are arranged on the respective front side and the back side of the soundboard material 1 in the heating chamber 2 and heat the soundboard material 1, first and second temperature sensors 6a and 6b for detecting the respective front and back temperatures T1 and T2 of the soundboard material 1, and a control means 7 which controls the first and second heaters 5a and 5b to make the detected front and back temperatures T1 and T2 of the soundboard material 1 be first and second prescribed temperatures TREF1 and TREF2, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  Conventionally, as a method for manufacturing a soundboard, for example, a method described in Patent Document 1 is known. In this production method, a raw material such as unprocessed or molded maple is placed in an autoclave filled with high-pressure steam at a temperature of 120 to 200 ° C. and a pressure of 0.2 to 1.6 MPa for 1 to 60 minutes. A soundboard is manufactured by leaving it to stand. As a result of reforming the soundboard material by such high-pressure steam treatment, the vibration characteristics are increased by increasing the Young's modulus of the soundboard material, lowering the loss tangent, lowering the density, etc., and increasing the acoustic conversion efficiency. We are trying to produce a soundboard that excels.

  However, in the above manufacturing method, since the soundboard material is only left for a predetermined time in high-pressure steam under the conditions of a predetermined temperature and pressure, only the overall temperature adjustment of the soundboard material can be performed. The actual temperature cannot be finely controlled. For this reason, the actual temperature of the soundboard material cannot be controlled to an appropriate temperature, and the physical properties of the soundboard material modified by heating cannot be obtained with high accuracy.

  The present invention has been made to solve such problems, and provides a soundboard manufacturing apparatus capable of accurately manufacturing a soundboard having desired physical properties modified by heating. With the goal.

Japanese Patent No. 3562517

  In order to achieve the above object, an invention according to claim 1 is a soundboard manufacturing apparatus for manufacturing a wooden soundboard that is used in an acoustic musical instrument and generates a musical sound by vibrating. Preliminary humidity control means for preliminarily adjusting the humidity of the wooden soundboard material that is the raw material, a heating chamber for storing the preconditioned humidity soundboard material, and a front surface and a back surface side of the soundboard material in the heating chamber, respectively, The first heater and the second heater for heating the plate material, the first temperature sensor and the second temperature sensor for detecting the surface temperature and the back surface temperature of the sound board material, respectively, and the detected surface temperature and the back surface temperature of the sound board material respectively. And control means for controlling the first heater and the second heater so that the first predetermined temperature and the second predetermined temperature are obtained.

  According to the soundboard manufacturing apparatus, the preliminarily conditioned soundboard material is heated by the first heater and the second heater in the heating chamber. By this heating, the crystallinity of cellulose constituting the soundboard material is increased, whereby the Young's modulus is increased, the equilibrium moisture content is decreased, and the hygroscopicity is decreased. Thereby, the degree of expansion / contraction (hereinafter referred to as “expansion / shrinkage ratio”) of the soundboard material due to dry and wet conditions can be reduced, and as a result, the dimensional stability of the soundboard can be improved.

  Further, according to the above-described soundboard manufacturing apparatus, the surface temperature and the back surface temperature of the soundboard material are detected by the first and second temperature sensors, respectively, and the detected surface temperature and back surface temperature are the first and second temperatures, respectively. The first and second heaters are controlled by the control means so that the second predetermined temperature is reached. Thus, since the detected actual surface temperature and back surface temperature can be finely controlled independently from each other so as to be the first and second predetermined temperatures, a soundboard having desired physical properties modified by heating can be obtained. Can be manufactured with high accuracy.

  According to a second aspect of the present invention, in the soundboard manufacturing apparatus according to the first aspect, the cooling means for cooling the heated soundboard material, and the soundboard material cooled by the cooling means is at least near the outer surface of the soundboard material. And humidity control means for adjusting the humidity so that internal compression stress remains.

  According to this configuration, the soundboard material that has been heat-treated and is in a completely dry state is cooled by the cooling means and then conditioned. With this humidity conditioning treatment, moisture enters from the surface of the soundboard material, but does not become uniform up to the inside of the soundboard material. Therefore, a moisture gradient is generated inside the soundboard material, and the expansion coefficient varies depending on the moisture gradient. Therefore, an internal stress of compression remains at least near the outer surface of the soundboard material. Due to the internal stress of the compression, the fine scratches existing near the outer surface of the soundboard are prevented from growing by the tensile stress, and the soundboard can be made difficult to break. As a result, as compared with the conventional soundboard, the sound characteristics of the soundboard are maintained well, so that the sound quality and volume of the musical instrument can be ensured. In addition, since the soundboard is hard to break, the maintenance cost for replacement and repair of the soundboard can be reduced.

  According to a third aspect of the present invention, in the soundboard manufacturing apparatus according to the first or second aspect, the first predetermined temperature and the second predetermined temperature are different from each other.

  According to this configuration, by heating the front and back surfaces of the soundboard material at different temperatures, the crystallinity of cellulose is made different between the front and back surfaces of the soundboard material, and the hygroscopicity and the expansion / contraction rate are made different accordingly. be able to. Thus, for example, when an acoustic piano soundboard is produced by joining a plurality of soundboard materials, the surface side to which the soundboard piece is attached is projected by setting the first predetermined temperature to a lower value. A so-called “strip” that curves in a shape can be formed easily and stably.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 and FIG. 2 show a heating device 11 in a manufacturing apparatus for a grand piano soundboard 8 (see FIG. 9) according to an embodiment of the present invention.

  The sound board 8 is produced by joining a plurality of sound board materials 1 and vibrates and generates a musical sound when a string is struck by a key depression.

  The heating device 11 includes a flat box-shaped heating chamber 2, a mesh belt 4 provided horizontally in the heating chamber 2, on which the soundboard material 1 is placed, and a plurality of first heaters 5a for heating the soundboard material 1. And a plurality of second heaters 5b, a first temperature sensor 6a and a second temperature sensor 6b for detecting the surface temperature T1 and the back surface temperature T2 of the soundboard material 1, respectively, and a control for controlling the first heater 5a and the second heater 5b. A device 7 is provided.

  The plurality of first and second heaters 5a and 5b are arranged at equal intervals on the upper and lower sides of the mesh belt 4 so as to be arranged along the length direction at intervals. The 1st and 2nd heaters 5a and 5b are comprised by the far-infrared heater which act | operates by ON / OFF, for example.

  The first and second temperature sensors 6a and 6b are directly attached to the center of the front and back surfaces of the soundboard member 1, respectively. Each of the first and second temperature sensors 6 a and 6 b is composed of, for example, a thermocouple, detects the surface temperature T <b> 1 and the back surface temperature T <b> 2 of the soundboard material 1, and outputs detection signals to the control device 7.

  The control device 7 is constituted by a microcomputer including a CPU, a ROM, a RAM, and an input / output circuit. As shown in FIG. 2, the control device 7 will describe the first and second heaters 5a and 5b later according to the surface temperature T1 and the back surface temperature T2 output from the first and second temperature sensors 6a and 6b. To control.

  In addition to the heating device 11 described above, the soundboard 8 manufacturing apparatus is not shown, but includes a preliminary humidity control device for preliminarily adjusting the humidity of the soundboard material 1, a cooling device for cooling the soundboard material 1, and the like. I have.

  Hereinafter, the manufacturing method of the soundboard 8 by the manufacturing apparatus having the above-described configuration will be described in detail. FIG. 3 shows the overall flow of the manufacturing process.

  In the first step 1 (illustrated as “S1”, the same applies hereinafter), the plurality of soundboard materials 1 are preliminarily conditioned (preliminary humidity adjusting step). The soundboard material 1 is made of a solid mesh material made of spruce or the like, and as shown in FIG. 4, for example, a length L = 1500 mm, a width W = 100 to 150 mm, and a thickness T = 11 mm as a standard length. It is a scale.

  Preliminary humidity control of the sound board 1 is performed by cutting a raw wood such as spruce into a plate shape, and then putting it in a preliminary humidity control chamber (not shown) of a preliminary humidity control device, and a predetermined temperature (for example, 50 to 100 ° C.) and It is carried out by forced drying under conditions of humidity (for example, 30 to 90%). As a result, the sound board 1 is adjusted to a predetermined moisture content of 10% or less, for example.

  Next, in step 2, the plurality of soundboard materials 1 conditioned in step 1 are heated (heating process). In this heating step, a plurality of soundboard materials 1 (only one is shown in FIG. 1) are mesh belts so that their length directions coincide with the arrangement direction of the plurality of first and second heaters 5a and 5b. After the heating chamber 2 is closed, the plurality of soundboard members 1 are heated by the first and second heaters 5a and 5b for a predetermined time. This predetermined time is, for example, 30 minutes to 30 hours, and is set to 25 hours in the present embodiment.

  FIG. 5 is a flowchart showing a heating control process executed by the control device 7 in order to control the heating by the first and second heaters 5a and 5b. This process is repeatedly executed every predetermined time (for example, 0.1 second). In this process, first, the first heater 5a is controlled in steps 11-14.

  In step 11, the surface temperature T1 detected by the first sensor 6a is a temperature obtained by subtracting a predetermined value ΔT (for example, 2 °) corresponding to hysteresis from the first predetermined temperature TREF1 (for example, 105 to 200 ° C.). It is determined whether it is lower than ΔT). When the determination result is YES, after the first heater 5a is operated (ON) (step 12), the process proceeds to step 15 described later.

  On the other hand, when the determination result in step 11 is NO, in step 13, it is determined whether or not the surface temperature T1 is higher than a temperature obtained by adding a predetermined value ΔT to the first predetermined temperature TREF1 (TREF1 + ΔT). When the determination result is YES, the first heater 5a is stopped (OFF) (step 14), and then the process proceeds to step 15.

  When the determination result of step 13 is NO, the process directly proceeds to step 15.

  By controlling the first heater 5a as described above, the surface temperature T1 detected by the first temperature sensor 6a is controlled to be the first predetermined temperature TREF1.

  Further, when the surface temperature T1 is in the range of (TREF1−ΔT) ≦ T1 ≦ (TREF1 + ΔT) (step 13: NO), the first heater 5a is maintained in the ON / OFF state immediately before the first heater 5a. Frequent switching of ON / OFF of 5a is prevented.

  Next, in steps 15-18, the second heater 5b is controlled.

  In step 15, the back surface temperature T2 detected by the second sensor 6b is a temperature obtained by subtracting a predetermined value ΔT from a second predetermined temperature TREF2 (for example, 105 to 200 ° C.) that is the same as the first predetermined temperature TREF1 (TREF2−ΔT). It is determined whether it is lower than or not. When the determination result is YES, after the second heater 5b is operated (step 16), this process is terminated.

  On the other hand, when the determination result in step 15 is NO, it is determined in step 17 whether or not the back surface temperature T2 is higher than a temperature (TREF2 + ΔT) obtained by adding a predetermined value ΔT to the second predetermined temperature TREF2. When the determination result is YES, the second heater 5b is stopped (step 18), and then this process is terminated.

  When the determination result of step 17 is NO, this process is ended as it is.

  By controlling the second heater 5b as described above, the back surface temperature T2 detected by the second temperature sensor 6b is controlled to be the second predetermined temperature TREF2.

  When the back surface temperature T2 is in the range of (TREF2−ΔT) ≦ T2 ≦ (TREF2 + ΔT) (step 17: NO), the ON / OFF state immediately before the second heater 5b is maintained, whereby the second heater Frequent switching of 5b ON / OFF is prevented.

  Returning to FIG. 3, in step 3, the heated soundboard material 1 is placed in a cooling chamber (not shown) of a cooling device and cooled under conditions of a predetermined temperature (for example, 20 ° C.) and humidity (for example, 50%) ( Cooling step). The sound board 1 is in a so-called completely dry state in which the moisture content is 0% by the heat treatment described above.

  Next, in step 4, the sound board 1 that has been subjected to the cooling process is conditioned to have a moisture content according to the usage environment (humidity adjustment process). In this case, moisture enters from the surface of the soundboard material 1 but does not become uniform up to the inside. Therefore, a moisture gradient is generated inside the soundboard material 1, and the expansion rate differs depending on the moisture gradient. Therefore, the outer surface of the soundboard material expands due to moisture absorption, while the other inner portion is completely dry. Will still maintain the contraction. As a result, expansion near the outer surface is constrained by the inner part due to the difference in expansion due to the moisture gradient inside the soundboard material. Stress remains.

  Next, in step 5, the soundboard 8 is assembled by joining the plurality of cooled soundboard materials 1 by width bonding (soundboard assembly process). Specifically, as shown in FIG. 6, after appropriately adjusting the length of the soundboard material 1, a plurality of soundboard materials 1 are joined together by width separation, and the outer peripheral portion thereof is cut off, as shown in FIG. 7. A soundboard 8 having a predetermined shape that matches the external shape of the grand piano is cut out.

  Next, in step 6, a plurality of sounding rods 9 are joined and attached to the back surface of the sounding plate 8 (sounding rod attaching step). These sounding rods 9 are obtained by processing a solid wood material made of spruce or the like. As shown in FIG. 8, the attachment surface 9 a is flat before being attached to the sounding plate 8. The sounding bar 9 is attached to the sounding board 8 so as to extend along a direction substantially perpendicular to the extending direction of the sounding board material 1, that is, a direction perpendicular to the grain of the sounding board material 1.

  Finally, in step 7, the soundboard 8 with the soundbar 9 attached is placed in a humidification chamber (not shown), humidified at a predetermined temperature (for example, 20 ° C.) and humidity (for example, 60%), and the moisture content is reduced. Increase to a predetermined value (humidification process). As a result, the soundboard 8 expands due to moisture absorption, but on the back side, the expansion is restrained by the soundbar 9, so that the surface of the soundboard 8 has a convex peel due to the difference in expansion between the front and back surfaces. The Thereby, the sound board 8 as shown in FIG. 9 and FIG. 10 is completed.

  As described above, according to the soundboard manufacturing apparatus of the present embodiment, the expansion and contraction rate of the soundboard material 1 due to dry and wet is increased by increasing the crystallization of cellulose constituting the soundboard material 1 by the heat treatment described above. As a result, the dimensional stability of the soundboard 8 can be improved.

  Further, when the sound board material 1 is heat-treated, the first and second heaters 5a and 5b are set so that the detected surface temperature T1 and back surface temperature T2 become the first predetermined temperature TREF1 and the second predetermined temperature TREF2, respectively. Control independently of each other. Thereby, the surface temperature T1 and the back surface temperature T2 of the soundboard material 1 can be finely controlled, and therefore the soundboard 8 having desired physical properties modified by heating can be manufactured with high accuracy.

  In addition, by subjecting the heat-treated soundboard material 1 to cooling / humidity treatment, fine scratches existing near the outer surface of the soundboard material 1 are pulled by the compression internal stress remaining near the outer surface of the soundboard material 1. Growth due to stress is prevented, and the soundboard 8 is difficult to break. As a result, the acoustic characteristics of the soundboard 8 can be maintained well, good sound quality and sound volume of the grand piano can be ensured, and maintenance costs for replacement and repair of the soundboard 8 can be reduced.

  In the heating control process of the above-described embodiment, the first predetermined temperature TREF1 and the second predetermined temperature TREF2 that are target temperatures of the surface temperature T1 and the back surface temperature T2 of the soundboard material 1 are set to the same temperature. For example, by setting the second predetermined temperature TREF2 to a temperature that is lower by about 10 ° than the first predetermined temperature TREF1, the expansion / contraction rate due to the dryness and humidity on the surface side of the soundboard member 1 may be further increased. As a result, when the peeling is formed, when the soundboard 8 is humidified, the soundboard 8 can be easily warped convexly on the surface side, and the peeling can be efficiently formed in a short time. Furthermore, since the expansion / contraction rate is different between the front and back of the soundboard 8 and the soundboard 8 as a whole is lowered, even if the humidity of the outside air changes, the peeling becomes difficult to deform, A peel having excellent stability can be obtained.

  In addition, this invention can be implemented in various aspects, without being limited to the embodiment described above. For example, in the embodiment, the internal stress of compression remains in the vicinity of the outer surface of the soundboard material 1 and the internal stress of tension remains in the inner portion by the cooling / humidification treatment after the heat treatment. You may make it the internal stress of compression remain in the whole sound board material 1. FIG.

  The embodiment is an example in which the present invention is applied to the production of a soundboard of a grand piano. However, the present invention is not limited to this, and is applied to a soundboard of other instruments such as an upright piano, a violin, and a guitar. It is possible. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

It is a figure which shows typically the heating apparatus among the manufacturing apparatuses of a soundboard. It is a figure which shows the structure of the control relationship of a heating apparatus. It is a figure which shows the flow of the manufacturing process of a soundboard. It is a perspective view of a sound board material. It is a flowchart which shows the heating control process performed with the control apparatus of FIG. It is a top view in the state where a plurality of soundboard materials were joined in a stripped manner. It is a top view of the soundboard after being cut out from a plurality of soundboard materials joined in the width direction. It is a top view for demonstrating the attachment process of a sounding stick. It is a top view which shows the manufactured sound board. FIG. 10 is a sectional view taken along line A-A ′ of FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sound board material 2 Heating chamber 5a 1st heater 5b 2nd heater 6a 1st temperature sensor 6b 2nd temperature sensor 7 Control apparatus (control means)
8 Soundboard T1 Surface temperature T2 Back surface temperature TREF1 First predetermined temperature TREF2 Second predetermined temperature

Claims (3)

A soundboard manufacturing apparatus for manufacturing a wooden soundboard that is used in an acoustic instrument and generates a musical sound by vibrating,
Preliminary humidity control means for preliminarily adjusting the humidity of the wooden soundboard material that is the material of the soundboard;
A heating chamber for storing the pre-humidified soundboard material;
A first heater and a second heater, which are respectively disposed on the front side and the back side of the soundboard material in the heating chamber, and heat the soundboard material;
A first temperature sensor and a second temperature sensor for detecting a surface temperature and a back surface temperature of the soundboard material, respectively;
Control means for controlling the first heater and the second heater, respectively, so that the detected surface temperature and back surface temperature of the soundboard material become the first predetermined temperature and the second predetermined temperature, respectively.
An apparatus for producing a soundboard, comprising: Cooling means for cooling the heated soundboard material;
Humidity control means for adjusting the humidity of the soundboard material cooled by the cooling means so that compression internal stress remains at least near the outer surface of the soundboard material;
The sound board manufacturing apparatus according to claim 1, further comprising:   The sound board manufacturing apparatus according to claim 1, wherein the first predetermined temperature and the second predetermined temperature are different from each other.

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