JP4051074B2 - How to dry wood - Google Patents

Description

  The present invention relates to a method for drying wood.

As domestic structural materials such as pillar materials, domestically-produced cedar and hinoki core-supported square materials such as cypress have been used. Increased. However, such a cored square member is liable to be cracked during drying, and similarly to the back split material, the dimensional stability after construction and construction is poor, which causes a problem. For this reason, the use of laminated wood having excellent dimensional stability is also increasing.
In recent years, a high-temperature drying method has been developed and spread to prevent cracking of the material surface that occurs during drying of cedar and cypress cored squares. In this high temperature drying method, it is said that the surface cracking is reduced by forming a drying set on the surface layer by drying at a dry bulb temperature of 120 ° C. in the initial stage of drying. According to the high temperature drying method, cracks on the surface of the material are relatively reduced, but it is not sufficient.

Further, the high temperature drying method has a problem that internal cracks are likely to occur. Internal cracking in the high temperature drying method is considered to be caused by the shrinkage of the inner layer due to drying due to an increase in tensile stress due to the constraint of the tangential direction and the surface drying set.
In addition, cracking of the material surface is considered to occur in the initial stage of high-temperature drying, when the duration of the dry-bulb temperature of 120 ° C is not sufficient, the so-called drying set formation layer is shallow and tensile stress is still present on the surface layer. ing.
In order to prevent cracking of the material surface, if the duration of the dry bulb temperature of 120 ° C. is excessively increased, the layer of the drying set is deepened, but the drying speed is fast, so that the portion inside the surface of the drying set layer is 120. It is said that due to the dry-bulb temperature of ℃, the inner layer rapidly begins to shrink, and the inner layer is strongly restrained by the surface drying set, which increases the tensile stress and causes internal cracking (patent) Reference 1)

By the way, in order to elucidate how long it is appropriate to maintain the condition of the dry bulb temperature of 120 ° C. in the initial stage of drying, which has an effect of suppressing cracking of the material surface, generally, the test material is dried during drying. A slicing method is used which is taken out from the room and measures the open strain. In this slicing method, the drying stress of each slice at each time point of drying is estimated to estimate the appropriate duration of the dry bulb temperature of 120 ° C. ing.
However, when the test material is taken out and measured from the high-temperature drying chamber, the internal stress generated during the drying of the material to be dried in the drying chamber is not continuously measured directly, so the change in the stress cannot be grasped. Therefore, it is difficult to estimate to what point during drying it is appropriate to maintain the condition of the dry bulb temperature of 120 ° C. In addition, as the drying conditions, application of conditions other than setting the dry bulb temperature to 120 ° C. in the initial stage of drying can be considered, and the drying conditions are various. Therefore, it is difficult to grasp appropriate drying conditions only by the slice method.
In addition, the moisture content and the material temperature inside the wood during drying are measured, and when the moisture content reaches the fiber saturation point, the dry bulb temperature is lowered, the stress is relieved, and the wood is dried to suppress internal cracking. Is known (see Patent Document 2). However, the drying method judges the stress based on indirect information such as the moisture content and the material temperature inside the wood. Again, since the behavior of wood during drying is not directly measured, the behavior in which internal cracks occur is not instantaneously measured, so the control range must be widened.

JP 2004-190957 A JP 2001-287206 A

Therefore, the objective of this invention is providing the drying method of the timber which can find the drying conditions which can suppress a surface crack and / or an internal crack.
In addition, the object of the present invention is to be able to easily measure displacement caused by expansion and / or contraction of the wood being dried, and to efficiently dry the wood while suppressing material surface cracks and / or internal cracks. It is to provide a method of drying wood that can be performed.

  In the present invention, a pair of displacement gauge fixing jigs are fixed to two adjacent side faces of a square bar, and a displacement gauge fixed between the pair of displacement gauge fixing jigs measures a displacement generated in the square bar during drying. The above object is achieved by providing a method for drying wood, characterized in that the square bar is dried.

  Further, the present invention provides a displacement generated in a square member during drying by a pair of displacement meter fixing jigs fixed to two adjacent side surfaces of the square member and fixed between the pair of displacement meter fixing jigs. The square is dried while measuring, and based on the measurement result of the displacement generated in the square, a drying schedule that can reduce the material surface crack and / or internal crack is set, and the same square is dried according to the drying schedule. The above object is achieved by providing a method for drying wood, which is characterized by being performed.

According to the wood drying method of the present invention, it is possible to find a drying condition capable of suppressing material surface cracking and / or internal cracking.
Further, according to the method for drying wood according to the present invention, displacement caused by expansion and / or contraction of the wood being dried can be easily measured. Or wood can be efficiently dried while suppressing internal cracks.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
For carrying out the method for drying wood according to the present invention, a drying apparatus having a drying chamber capable of controlling temperature and humidity is preferably used. FIG. 1 shows an example of such a drying apparatus, and the wood 10 accommodated in the drying chamber 1 can be dried under the control of the temperature and humidity in the drying chamber 1. The wood drying apparatus in FIG. 1 includes a drying chamber 1 that houses wood 10 to be dried, a spraying mechanism 2 that injects steam into the drying chamber 1, and a heating mechanism 3 that heats the air in the drying chamber 1. The air supply mechanism 4 for introducing outside air into the drying chamber 1 and the exhaust mechanism 5 for exhausting the air in the drying chamber 1 to the outside are provided. The temperature in the drying chamber 1 is controlled by appropriately controlling the vaporization by the vaporization mechanism 2, the heating by the heating mechanism 3, the air supply by the air supply mechanism 4, and the air exhaust by the exhaust mechanism 5 by opening and closing valves, etc. The humidity can be controlled to a desired temperature and humidity. A conventionally well-known mechanism etc. can be employ | adopted for the point which is not demonstrated especially.

  In the method of the present invention, for example, as shown in FIG. 2, a pair of displacement gauge fixing jigs 6A, 6A are fixed to two side surfaces 10A, 10A adjacent to each other, and the pair of displacement gauges is fixed. A displacement meter 7A is fixed between the jigs 6A and 6A. In the present embodiment, a pair of displacement meter fixing jigs and displacement meters is taken as a set, and two pairs of displacement meter fixing jigs and displacement meters are fixed at different locations in the longitudinal direction of the square member 10. .

One set, the displacement gauge fixing jigs 6A and 6A and the displacement gauge 7A, is mainly intended for monitoring a dimensional change of a portion where an internal crack of wood occurs. These displacement gauge fixing jigs 6A and 6A are preferably fixed to the center region M in the width direction on the two adjacent side surfaces 10A and 10A of the square member 10 as shown in FIG. The central region M in the width direction of each side surface 10A is a central region when the width of each side surface 10A is divided into three equal parts.
The other set, the displacement gauge fixing jigs 6B and 6B and the displacement gauge 7B, is mainly intended for monitoring the formation state of the drying rig set on the surface layer of wood. As shown in FIG. 3B, the displacement gauge fixing jigs 6B and 6B are fixed to a region S near the corner portion C formed by the two side surfaces on the two side surfaces 10A and 10A adjacent to each other. It is preferable. The region S in each side surface 10A is a region located on the corner C side with respect to the central region M in the width direction when the width of each side surface 10A is equally divided into three regions.

  The pair of displacement meter fixing jigs 6A and 6A and the pair of displacement meter fixing jigs 6B and 6B are fixed so as to sandwich the corner C formed by the two side surfaces 10A and 10A adjacent to each other. Square material is fast drying in the vicinity of the corner of the cross section, it can quickly measure the behavior of the material to be dried, which causes cracking of the surface, internal cracks, especially internal cracks are likely to occur in the inner layer near the corner, This is because measuring the change in the tangential distance of the annual rings is an important point.

  Each of the displacement meter fixing jig 6A and the displacement meter fixing jig 6B is preferably fixed to a portion separated by 10 cm or more from each of both ends in the longitudinal direction of the square member 10, and more preferably fixed to a portion separated by 30 cm or more. To do. It is preferable that the displacement meter fixing jig 6A and the displacement meter fixing jig 6B are separated by 3 cm or more in the longitudinal direction of the square bar.

The displacement meter fixing jig 6A has a strip-like shape in plan view, is brought into contact with the side surface 10A of the wood at the center in the longitudinal direction, and is fixed to the side surface 10A with a fixing tool such as a screw 62. A fixing portion 61 is provided. In the longitudinal direction of the displacement gauge fixing jig 6A, the front and rear portions 63 and 64 positioned before and after the fixing portion 61 are separated from the side face 10A in a state where the displacement gauge fixing jig 6A is fixed to the side face 10A. ing. On the other hand, the displacement meter fixing jig 6B has a form in which the front and rear portions 63 and 64 are removed from the displacement meter fixing jig 6A, and the entire portion is a fixing portion 61 that is abutted and fixed to the side surface 10A. Yes.
The portion where the displacement gauge fixing jigs 6A and 6B are fixed to the side surface 10A is fixed so that there is no displacement between the side surface 10A and the surface of the displacement gauge fixing jigs 6A and 6B facing the side surface 10A. That is, the determination is made based on the position of the fixing portion 61 (particularly the center position of the fixing tool such as the screw 62).

As the displacement meter 7A (7B), use various devices that can measure the change in the distance between the pair of displacement meter fixing jigs 6A, 6A (6B, 6B) facing each other across the corner C. Can do. The displacement meter can output a change in the distance between the pair of displacement gauge fixing jigs 6A and 6A (6B and 6B) as a change in electrical resistance, voltage, current, and the like.
In this embodiment, as shown in FIGS. 2 and 3, a clip-type displacement meter having a central portion 71 with a built-in strain gauge and arc-shaped arm portions 72, 72 extending in front and rear thereof is used. ing. The clip-type displacement meter of the present embodiment can output a change in the distance L (see FIG. 3A) between both ends 73 and 73 of the arm part as a change in electrical resistance, voltage, current, and the like. is there.
As the clip-type displacement meter and the displacement meter fixing jig, the clip-type displacement meter “RA-5SH” of Tokyo Sokki Kenkyujo Co., Ltd. and a dedicated displacement have the configurations shown in FIGS. 2 and 3, respectively. The meter mounting jig PS3-1468 can be used particularly preferably. As shown in FIG. 4, the displacement meter mounting jig has claws 66 that are engaged with both end portions 73 of the clip-type displacement meter at both end portions in the width direction of the side surface 10 </ b> A of the square member 10. The clip-type displacement meter is fixed between a pair of displacement meter mounting jigs in a state where the distance L between the both end portions is narrower than the distance in the natural state.
The pair of displacement meter fixing jigs fixes the displacement meter by positioning the end of a displacement meter (such as a clip-type displacement meter) at a portion other than the end in the same direction as the width direction of the side surface 10A. It may be a thing.

In the present invention, the displacement gauge fixing jig and the displacement gauge are fixed to the square bar, and the square bar is dried while measuring the displacement generated in the square bar during drying based on the information output from the displacement gauge.
The displacement generated in the square bar is recorded, for example, by connecting the displacement gauges 7A and 7B to a data logger, and at the same time being able to visually recognize an electrical signal (voltage change, etc.) output from the displacement gauges 7A and 7B. ) And output to a monitor or printer. In the example shown in FIG. 1, each of the displacement meters 7A and 7B is electrically connected to a control calculation unit 8 that is mainly composed of a personal computer and also has a function as a data logger. , The electrical signals from the displacement meters 7A and 7B are converted into a change amount (displacement amount) of the distance L between both ends of the clip-type displacement meter by a predetermined calculation, and the change amount (displacement amount) is Are output continuously on the display means 9 and / or the printer 11 and continuously recorded, and a predetermined command is input from the input means 12 while observing the displayed displacement amount. Thus, the temperature and humidity in the drying chamber 1 can be appropriately changed to desired values.

  In the drying method of the present invention, the result of measuring the displacement generated in the square bar during drying as described above is immediately reflected in the drying, and the drying is performed while controlling the drying conditions of the square bar based on the measurement result. be able to. As the control of the drying conditions based on the measurement result, for example, from a high temperature drying step with a dry bulb temperature of 118 to 122 ° C. (preferably 120 ° C.), a drying step with a lower dry bulb temperature (for example, a dry bulb temperature of 100 to 115 ° C.). The amount of displacement measured by the displacement gauge fixing jigs 6B and 6B and the displacement meter 7B (hereinafter also referred to as the displacement amount of the short axis) has almost reached equilibrium from the viewpoint of preventing cracking of the material surface. The amount of displacement measured by the displacement meter fixing jigs 6A and 6A and the displacement meter 7A (hereinafter also referred to as the displacement amount of the long axis) from the viewpoint of confirming that (driving set) and preventing internal cracks In order to prevent the temperature from rapidly decreasing, for example, the dry bulb temperature may be gradually decreased after the amount of displacement of the minor axis reaches substantially parallel.

  Further, in the drying method of the present invention, the square bar is dried while measuring the displacement generated in the square bar during drying as described above, and the measurement result of the displacement generated in the square bar obtained during the drying is measured. Based on the above, it is also possible to set a drying schedule that can reduce the surface cracking and / or internal cracking, and to dry the same square material according to the drying schedule. For example, a plurality of square timber lumbered from the same tree species collected from the same production area and in the same dry state is suitable for the square timber by performing drying while measuring the displacement generated in the square timber for some of them. If the drying schedule is set, the same drying result can be obtained by drying the remaining squares with the same drying schedule without particularly measuring the displacement during drying. That is, in the present invention, from the displacement obtained by measuring the dimensional change of the cross-section that occurs during the drying of the wood, the wood drying rate, moisture content, drying stress, etc. are estimated, and material surface cracks and internal cracks are generated. It is also possible to elucidate the displacement, and to establish a drying method that suppresses material cracks and internal cracks under appropriate drying conditions.

Hereinafter, the present invention will be described in more detail based on experimental examples. However, the present invention is not limited to the following examples.
(Preliminary test 1)
2 and FIG. 3 (b) on two adjacent side surfaces of a cedar pillar material (core-supported square material, without splitting, regular square material with a cross-sectional dimension of 11.5 cm × 11.5 cm, length of 300 cm) as a material to be dried. As shown, a pair of displacement meter fixing jigs 6B and 6B were fixed, and a displacement meter 7B was fixed between them. The displacement gauge fixing jigs 6B and 6B are fixed at a position of 100 cm from one end (the end face of the cedar) in the longitudinal direction of the cedar pillar material, and from the corner C formed by the two side surfaces to the center of the fixing screw 62. Was fixed at a position where the distance was 27 mm.
Moreover, as shown in FIG.2 and FIG.3 (a), the displacement gauge fixing jig | tool is the same 2 side surface as the 2 side surface which fixed the said pair of displacement gauge fixing jigs 6B and 6B in the same cedar pillar material. A pair of displacement gauge fixing jigs 6A and 6A were fixed at a distance of 5 cm from the fixing positions of 6B and 6B. The displacement gauge fixing jigs 6A and 6A were fixed so that the distance from the corner C formed by the two adjacent side surfaces to the center of the fixing screw 62 was 57.5 mm. And the displacement meter 7A was fixed between these displacement meter fixing jigs 6A, 6A.

Then, the cedar pillar material was dried under the control of the dry bulb temperature and the wet bulb temperature according to the drying schedule shown in the graph of FIG. Then, the dimensional change (short axis displacement) of the column material measured by the displacement meter 7B and the dimensional change (long axis displacement amount) of the column material measured by the displacement meter 7A were recorded in the data logger.
The drying schedule shown in FIG. 5 will be described.
Water vapor was sprayed into the dryer, and initial cooking was performed at 96 ° C. for 8 hours. The initial steaming is performed in order to relieve the stress in the wood and suppress the occurrence of cracks by homogenizing the wood moisture and softening the wood. Subsequently, after the temperature of the dry bulb was raised to 116 ° C. and held for 2 hours, the dry bulb temperature was raised to 120 ° C. to proceed with drying, and the dry bulb temperature was maintained at 120 ° C. until the end of drying. The drying time was 72 hours.
Each displacement measured in this drying schedule will be described.
The amount of displacement of the short axis suddenly shifted to the negative side after about 12 hours from the start of drying, showing the progress of shrinkage, and almost reached an equilibrium state at about 30 hours from the start of drying. The high temperature drying time to reach the parallel state (120 ° C. duration including 116 ° C. dry bulb temperature) was 22 hours. On the other hand, the displacement amount of the long axis showed a remarkable positive displacement after cooking. This is thought to be due to the thermal expansion of the wood. After about 14 hours from the start of drying, it suddenly shifted to the negative side, became negative after about 30 hours from the start of drying, and showed a significant negative displacement until about 36 hours after the start of drying.
After 72 hours from the start of drying, the test material was taken out from the dryer and observed. No cracks were observed on the surface of the material, but when the cross section of the square was observed by sawing the portion where the displacement gauge was attached, Cracking was observed.

  From these results, 20 hours, which is the duration of the dry bulb temperature of 120 ° C., until 30 hours after the start of drying when the displacement of the short axis is in an equilibrium state, is a sufficient time for forming a drying set that suppresses cracking on the material surface. It can be said that. It is estimated that during this 20 hours, the tensile stress on the material surface side has disappeared and it has been converted to compressive stress, and the shrinkage to the inner layer has progressed, and the short axis displacement has reached an equilibrium state. It is presumed that there was no material cracking. Even after 30 hours have elapsed after the start of drying (20 hours as the duration of the dry bulb temperature 120), the long axis displacement is maintained until about 36 hours from the start of drying by continuing the condition of the dry bulb temperature of 120 ° C. It showed a significant negative displacement, and then gradually displaced. Internal cracking is caused by the fact that the drying at the dry bulb temperature of 120 ° C. continues for about 30 hours after the start of the drying set formation in which the short axis displacement is in an equilibrium state. It is thought that a part of the inner layer progressed and internal cracks occurred due to a sudden increase in tensile stress. From this result, in order to suppress internal cracks, about 30 hours after the start of drying when the short axis displacement is in an equilibrium state (after drying at a dry bulb temperature of 120 ° C. for 20 hours), the dry bulb temperature is lowered and dried. It is thought that reducing the speed will prevent internal cracking.

(Preliminary test 2)
Two pairs of displacement gauge fixing jigs and displacement gauges are used on the same cedar pillar material as used in preliminary test 1, and displacement gauge fixing jigs 6B and 6B and displacements in preliminary test 1 are arranged on two common side surfaces. Fixed in the same manner as in 7B. Then, using these two displacement meters (both for measuring the displacement of the short axis), the occurrence of cracking of the material due to lack of the duration of the dry bulb temperature of 120 ° C. was verified. The drying schedule at that time and the amount of displacement of both short axes are shown in the graph of FIG. The drying schedule is steaming as shown in the graph for 14 hours after the start of drying, 14 hours after the start of drying, after raising the temperature to 120 ° C. and continuing for 12 hours (26 hours after the start of drying), the dry bulb temperature The temperature was lowered to 105 ° C., and after 2 hours, the temperature was again raised to the dry bulb temperature of 120 ° C. and continued for 6 hours (about 34 hours after the start of drying), and then the dry bulb temperature was 90 ° C. for 24 hours (58 hours after the start of drying). Then, 105 degreeC was complete | finished in 35 hours (93 hours of drying).
After completion, the material surface was taken out from the dryer and the material surface was observed, and cracks penetrating through one surface of the material surface were observed. Internal cracks were not observed due to material cracks. As a result, when the duration of the dry bulb temperature of 120 ° C. is 12 hours, none of the displacements measured by the two displacement meters has reached the equilibrium state, and fluctuates in the subsequent change of the dry bulb temperature. This clearly indicates that the material surface cracking occurred because the drying set was not sufficiently formed on the surface layer.

Preliminary tests 1 and 2 can prevent cracks and internal cracks that occur during drying of squares, especially cedar and cypress pillars (regular squares).
(1) Continue to dry at a high temperature (for example, 120 ° C.) until the short axis displacement is almost in an equilibrium state to prevent cracking of the material surface.
(2) Decreasing the temperature of the dry bulb from the point when the equilibrium is reached to avoid shrinkage of the inner layer due to rapid drying, and (3) so that the subsequent displacement of the major axis does not suddenly change to the negative side. Observing the displacement, it can be seen that it is important to suppress the occurrence of internal cracks by controlling the dry bulb temperature.

Example 1
Preliminary test 1 and two adjacent side surfaces of a cedar pillar material immediately after sawing produced by Tochigi as a material to be dried (core-supported square material, no split split, regular square material with a cross-sectional dimension of 11.5 cm × 11.5 cm, length of 300 cm) Similarly, the displacement meter 7A and the displacement meter 7B were fixed.
And this cedar pillar material was dried. FIG. 7 is a graph showing the history of dry bulb and wet bulb temperatures and the history of displacement of the short axis and the long axis during the drying.
The cedar wood generally has a high moisture content in the raw material, and each has a large variation in water content. For this reason, it is an important point for good drying to reduce variation in the initial stage of drying and to make each individual dried state (water content) uniform. In particular, a large variation in the moisture content of the surface layer affects the cracking of the material.
In this Example 1, after maintaining the condition of dry bulb and wet bulb temperature 70 ° C. for 6 hours so that the water content of all the surface layers is as uniform as possible, the dry bulb temperature 70 ° C., wet bulb temperature 67 ° C., Pretreatment of drying and humidity conditioning was performed for 18 hours under the condition of a relative humidity of 87%. Then, it was steamed at 95 ° C. for 6 hours. By the above pretreatment, it is considered that the dry state of the surface layer of the wood becomes uniform in the total number of wood, and the drying set can be formed uniformly in a short time in the subsequent drying at a dry bulb temperature of 120 ° C.

  And it heated up to 120 degreeC from 30 hours after the drying start. The short-axis displacement is about 42 hours after the start of drying, that is, when 120 ° C. is maintained for 12 hours, and is becoming equilibrium. Since the progress of shrinkage is becoming equilibrium, the dry bulb temperature is lowered to 116 ° C. Lasted for hours. After that, the displacement of the short axis changed in the same manner as when the dry bulb temperature was changed to 116 ° C. (42 hours after the start of drying), and the formation of the drying set was confirmed. Thereafter, in order to suppress the occurrence of internal cracks, the dry bulb temperature is lowered to 112 ° C. 46 hours after the start of drying, the dry bulb temperature 108 ° C. after 50 hours, and the dry bulb temperature 105 ° C. after 68 hours. In addition, the wet bulb temperature was also gradually lowered and the drying proceeded. The drying time was 144 hours. When the test material was observed after the drying was finished, no material surface cracks and internal cracks were observed.

(Example 2)
The cedar pillar material having the same production area and the same form as the cedar pillar material used in Example 1 was dried by controlling the dry bulb temperature and the wet bulb temperature to be exactly the same as the drying in Example 1. A displacement meter was not attached. When the wood was observed after drying, no cracks on the surface and internal cracks were observed.

Thus, according to this invention, the drying conditions which can suppress a material surface crack and / or an internal crack can be found, and the wood which suppressed the material surface crack and / or the internal crack can be dried.
Note that only one of the displacement meter for measuring the displacement amount of the short axis and the displacement meter for measuring the displacement amount of the long axis may be fixed for drying. The two side surfaces to be fixed between the displacement meter fixing jigs may be different between the displacement meter for measuring the amount and the displacement meter for measuring the displacement amount of the long axis. Further, the displacement meter can be fixed to two, three, or four corners instead of fixing to one of the four corners of the square member. FIG. 8 is a diagram illustrating an example in which four corners are fixed. When a displacement meter is fixed to a plurality of corners, it is preferable to set the drying conditions so that no risk of material cracking or internal cracking is observed with any displacement meter.

It is a schematic diagram which shows an example of the drying apparatus of the wood which can be used for implementation of this invention. It is a perspective view which shows the state which fixed the displacement meter fixing jig and the displacement meter to the to-be-dried material. It is a cross-sectional view showing a state in which a displacement meter fixing jig and a displacement meter are fixed to a material to be dried. It is sectional drawing which shows the displacement gauge fixing jig for the displacement measurement of a short axis, and its fixed state. 4 is a graph showing a drying schedule and displacement history in preliminary test 1. It is a graph which shows the drying schedule in the preliminary test 2, and the history of a displacement. It is a graph which shows the drying schedule in Example 1, and the history of displacement. It is a cross-sectional view of the timber which shows the other embodiment of this invention.

Explanation of symbols

6A, 6B Displacement meter fixing jig 7A, 7B Displacement meter 10 Square material 10A, 10A Two adjacent side surfaces

Claims (7)

  A pair of displacement gauge fixing jigs are fixed to two adjacent side faces of the square bar, and the square bar is measured while measuring the displacement generated in the square bar during drying by a displacement meter fixed between the pair of displacement gauge fixing jigs. A method for drying wood, comprising drying the wood.   The wood drying method according to claim 1, wherein drying is performed while controlling drying conditions based on a measurement result of displacement generated in the square bar.   The wood drying method according to claim 1 or 2, wherein the pair of jigs for fixing the displacement meter is fixed to a central region in the width direction on each of two adjacent side surfaces of the square bar.   The wood drying method according to claim 1 or 2, wherein the pair of displacement gauge fixing jigs are fixed at positions near the corners formed by the two side surfaces on each of two adjacent side surfaces of the square member.   A pair of the displacement gauge fixing jig and the two displacement gauges are fixed, and one set of the displacement gauge fixing jig is fixed to the center region in the width direction on each of two adjacent side surfaces of the square member, and the other The wood drying method according to claim 3 or 4, wherein the set of displacement gauge fixing jigs is fixed to a region close to a corner portion formed by the two side surfaces on each of two adjacent side surfaces of the square member.   The method for drying wood according to any one of claims 1 to 5, wherein a clip-type displacement meter is used as the displacement meter. A pair of displacement gauge fixing jigs are fixed to two adjacent side faces of the square bar, and the square bar is measured while measuring the displacement generated in the square bar during drying by a displacement meter fixed between the pair of displacement gauge fixing jigs. Based on the measurement result of the displacement generated in the square bar obtained at the time of drying, a drying schedule that can reduce the surface cracks and / or internal cracks is set, and according to the drying schedule, the same square bar A method for drying wood, comprising drying the wood.

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