JP2020128969A - Sonic speed measuring device for wood - Google Patents

Abstract

To provide a sonic speed measuring device for wood, for example, which allows even an unskilled worker to measure the accurate hardness of wood.SOLUTION: The sonic speed measuring device according to the present invention includes a sending probe 6 and a reception probe 8 to be inserted into wood separately by a predetermined distance. The sending probe 6 sends sound waves and the reception probe 8 receives sound waves. A sound wave added to the sending probe 6 is a sine wave, and the reception probe 8 receives the top of the first wave of the sine wave output from the sending probe 8. The time taken for a signal output from the reception probe 6 to reach the reception probe 8 is measured and the hardness of the wood is measured by the time.SELECTED DRAWING: Figure 1

Description

It is known that the material (hardness=Young's modulus) is measured if the density is known by measuring the velocity of a sound wave passing through the substance.
The present invention relates to a device that can easily and accurately measure the internal sound velocity of wood or the like. In particular, since the hardness can be measured at the logging site of the timber, the hardness can be measured before sending the timber to the sawmill, and can be sent to the sawmill after clearly indicating the quality and use of the timber.

In recent years, domestic timber has been frequently used for wooden construction, but as the forestry workers age, the equipment used for forestry is also required to be automated and IT. On the other hand, domestic cedar and cypress are softer than those made in the United States, and if the hardness can be known before sawing, whether it will be a pillar material or other depending on the hardness It is possible to make lumber according to the intended use.

An example of such a hardness measuring device is disclosed in Patent Document 1. This is to measure the Young's modulus of the wood from the propagation speed of the stress wave due to the impact of a hammer, etc., the database of the relationship between the Young's modulus and the density of the measured wood in advance, and the stress wave propagation speed of the wood. The Young's modulus, which is a hardness quality index, is obtained by measuring (sonic velocity).

Further, in the device disclosed in Patent Document 2, a transmission probe is applied to a test body, and a reception probe is provided at a position apart from the transmission probe by a specific distance. The emitted sound wave is received by the receiving probe, and the propagation velocity of the sound wave in the test body is measured. If the surface wave of the sound wave cannot be specified, or if the reflected wave has a known thickness of the object, a signal processing unit for calculating the sound velocity of the test object from the received signal is provided. This makes it possible to measure the propagation velocity of the sound wave of the test body in the substance.

JP, 2008-54550, A

JP, 2005-172528, A

The technique disclosed in the above Patent Document 1 discloses a method and an apparatus for measuring the Young's modulus of wood, but it is necessary to create a database of data showing the relationship between the Young's modulus of wood and the density. It is necessary to obtain a large number of this data in advance. For this reason, there is a problem that it takes time and effort to collect a large amount of data when putting it to practical use.
Also, the velocity of the stress wave due to the impact of a hammer or the like is shown in the sound velocity measurement, but when the shock wave from the hammer or the like is used, it is difficult to maintain a constant angle and impact force.

The technique disclosed in Patent Document 2 described above measures the sound velocity of a test body at the speed of ultrasonic waves, and even if the surface wave cannot be specified, if the thickness of the test body is known, the sound velocity of the reflected wave It is possible to measure. For this reason, the reception signal of the reception probe is discriminated into a longitudinal wave and a transverse wave.

The present invention focuses on the above points, and provides a sound velocity measuring device for wood or the like, which enables a worker to accurately and easily perform a sound velocity measuring operation with a simpler device.

The sound velocity measuring device of the present invention such as wood (herein, "wood etc." means wood, wood before use, wood used in wooden structures such as pillars) is separated by a predetermined distance. 2 is provided with a transmission probe and a reception probe (FIG. 2) which are driven into, the transmission probe has a mechanical conversion means for converting a sound wave electric signal into a vibration, and the reception probe has an electric conversion means for converting a sound wave into an electric signal. (Fig. 1)
The electric signal applied to the transmitting probe is a sound wave and has a waveform in which the differential value changes from positive to negative at the apex (sine wave or triangular wave), and the apex of the first wave of the signal emitted from the transmitting probe is received by the receiving probe. The time taken for the signal emitted from the transmitting probe to reach the receiving probe was measured, and the speed of sound of wood or the like was measured based on that time.

The wood hardness measuring device of the present invention has the following effects by the above means. That is, the sound wave applied to the wood or the like by the transmitting probe is received by the receiving probe, but at this time, not only the surface waves but also the countless reflected waves that have passed through the inside of the wood are received by the receiving probe. (Figure 4)
Further, when the transmitted wave is a continuous wave or a plurality of waves, more reflected waves are generated, and all except the first arriving signal become noise, which hinders accurate measurement. In this case, since the vertices of the signal to be transmitted and the vertices of the first wave are received by the receiving probe and the propagation time of the sound wave is measured by this, there is no influence of waveform deformation or noise due to the reflected wave.
Further, when the transmission signal is a square wave or a pulse wave, when the sound wave propagates inside the wood or the like, the reception waveform becomes dull and the rising point and the apex point become unclear, which causes an error (Fig. 5). However, since the transmitted wave is a 1-cycle SIN wave or triangular wave, the apex point is clear (Fig. 3).

By converting the standard sound velocity, density, and Young's modulus into a database for each type of wood, the quality of the wood, such as whether the wood to be measured is harder than standard or contains a lot of water, can be used. It can be specified.
Further, even if there is a softened wood inside due to corrosion or the like, it can be detected because the sound velocity becomes slower than the standard.

The transmitted signal has a low frequency in the sound wave region, but it is a SIN wave or triangular wave of only one cycle, and the peak of the first signal received by the receiving probe from only one peak point of this single wave. Since the arrival time of the sound wave from the transmitting probe to the receiving probe is measured by the time until, there is no influence of noise due to reflected waves. Further, since the measurement can be performed regardless of the frequency of the sound wave, the attenuation inside the wood or the like is small, and the signal attenuation due to the water content of the wood or the like is also small.

The shape of the sensor has an angle of 45 degrees between the driving part and the sensor for transmission and reception, respectively, and the probe and the sensor can be separated.
It is difficult to drive diagonally with good reproducibility when incorporating it into a device such as a harvester or when implanting the implant into wood or the like. The implant and the sensor of the present invention are fixed at a fixed angle (45 degrees). Therefore, the sensor angle can be constantly maintained at 45 degrees by driving the object vertically.
By setting the sensor at 45 degrees in this way, it becomes easy for the direct wave to reach and for the direct wave to become large, the sound wave that first arrives can be stably detected easily.
Further, in the case of a tree, a standing tree, a wooden structure, etc., it is difficult to measure using a small edge, but if the sensor has this shape, its sound velocity can also be measured.

When this sound velocity measurement system is incorporated in a wood production machine (heavy machinery such as a harvester), a transmission/reception sensor can be attached to a wood gripping tool of the heavy machinery to measure the sound velocity of wood at the same time as logging. Then, this heavy machine automatically cuts a tree, cuts branches, cuts to a predetermined length and loads it on a truck.In these operations, the sound velocity measurement measures the hardness of wood. Since the (Young's modulus) can be measured, by indicating which wood has which hardness, it is possible to carry in wood that already has hardness data when it is transported to a sawmill. As a result, it is possible to immediately determine the purpose of the sawmill at the sawmill, and it is possible to contribute to the creation of value such as wood and labor saving of the sawmill.

In such a shortage of forestry workers, it will be easy to promote automation. Further, it is possible to accurately measure the hardness of wood or the like without requiring the skill of a worker.

It is a block diagram which shows Example 1 of the sound velocity measuring apparatus of the wood etc. of this invention. FIG. 3 is a partially exploded side view of a transmission probe and a reception probe of the sound velocity measuring device for wood or the like according to the present invention. It is a graph which shows the transmission/reception signal state of Example 1 of the sound velocity measuring apparatus for wood etc. of the present invention. FIG. 3 is a cross-sectional view showing a state of transmission of sound waves in wood in Example 1 of the sound velocity measuring device for wood and the like according to the present invention. It is a figure which shows the received wave of a receiving probe when a square wave is used for an outgoing probe. It is a flow chart which shows operation of the control part in Example 1 of the hardness measuring device of the wood etc. of the present invention.

The invention according to claim 1 of the present invention comprises a transmitting probe and a receiving probe which are respectively driven into wood at a predetermined distance from each other, and the transmitting probe has a mechanical converting means for converting a sound wave electric signal into a vibration. Has an electric converting means for converting a sound wave into an electric signal, and the electric signal applied to the transmitting probe is a sound wave having a waveform whose differential value changes from positive to negative at the apex, It has a configuration in which the apex of a wave is received by a reception probe, the time taken for a signal emitted from the transmission probe to reach the reception probe, and the speed of sound of wood or the like is measured by the time. As a result, the effects of the invention described above are exhibited.

Hereinafter, a sound velocity measuring device for wood or the like according to the present invention will be described with reference to the drawings showing an embodiment. Reference numeral 1 denotes a main device, in which the following circuits and electronic parts are housed. A control unit 2 has a microprocessor (hereinafter referred to as “CPU”), a flash memory, and the like, and stores sound velocity data for wood and the like and arithmetic expressions. Reference numeral 3 denotes a command/display unit, which is made up of a combination of a liquid crystal panel and a touch panel. That is, the necessary data is displayed according to the operation of the CPU, and the operator performs the necessary operation via the touch panel. A signal generator 4 generates a sine wave of 20 hz to less than 20 kHz, and sends the sine wave to the controller 2. Reference numeral 5 denotes a transmission unit, which sends a signal to the transmission probe 6 according to an instruction from the control unit 2. Reference numeral 7 denotes a receiving unit, which sends a signal from the receiving probe 8 to the control unit 2.

Reference numeral 6 is a transmission probe, to which a sound wave signal is applied from the transmission unit 5. Reference numeral 8 denotes a receiving probe, which sends the received sound wave signal to the receiving unit 7. The transmitting probe 6 and the receiving probe 8 are driven into the wood 9 to be measured. Details of the transmission probe 6 and the reception probe 8 will be described with reference to FIG.

FIG. 2 is an exploded side view of the 6 transmit probe of FIG. 1 and the 8 receive probe of FIG. Here, the transmitting probe 6 and the receiving probe 8 have many common parts, and both will be described as common in the drawings. Both the transmitting probe 6 and the receiving probe 8 have main bodies 10 and 11 and driving portions 12 and 13. Since the driving portions 12 and 13 are portions to be driven into the timber 9 or the like in FIG. 1, the driving portions 12 and 13 have a shape that can be easily driven and removed, and the tips thereof are pointed. At the ends of the driving portions 12 and 13, there are provided brims 14 and 15 for insertion of a harvester (machine for forestry defined by the Forestry Agency) when driving 9 woods or the like in FIG. The brim portions 14 and 15 have a screw structure and can be freely attached to and detached from the main body 10 and 11 through 45 and 45 degree attachments of 20 and 21. When hammering by hand, the 45 and 45 degree attachments of 20 and 21 Remove 12 and 13 and hammer in the hammering part. The oscillators 16 and 17 made of a piezo element or the like are provided in the main bodies 10 and 11 of the transmitting probe and the receiving probe. Cases 18 and 19 that cover the oscillators 16 and 17 are provided in the main bodies 10 and 11. ing. Further, 45-degree attachments 20 and 21 for transmitting vibration are provided between the driving portions 12 and 13 and the vibrators 16 and 17, and a vibration isolator made of silicon rubber is provided between the cases 18 and 19 and the transmission portions 20 and 21. 22 and 23 are provided so that vibrations can be efficiently transmitted.

The sound velocity measuring device for wood or the like according to the present invention has the above-mentioned configuration, and its usage will be described below.
In a wood production machine such as a harvester, the probes 14 and 15 of the probe shown in FIG. 2 are held and driven vertically into wood or the like by hydraulic pressure.
When manually pushing the probe shown in FIG. 2 into wood or the like, remove the drive portions 12 and 13 shown in FIG. 2 from the 45° attachments 20 and 21 and vertically drive the target wood or the like, and then connect the 45° attachment and the main body. ..

Next, when incorporating it into a timber production machine such as a harvester, in addition to the power supply/transmission/reception cable, connect the communication line with the harvester, etc., perform the automatic measurement in response to the measurement instruction signal from the higher-level harvester, etc. Etc. to automatically communicate.
In the case of manual measurement, the command of the main device 1 and the display unit 3 are operated to instruct measurement start, and the measurement result is displayed. This will be described with reference to the flowchart of FIG. 6. In step 1 and step 2, the measurement start is waited, and if there is a measurement start instruction, the process proceeds to step 3 and the control unit 2 issues a command to the signal generator 4 to generate a sine wave. Then, it is transmitted to the transmitter 5. The transmitter 5 amplifies the sent sine wave signal and sends it to the oscillator 16 of the transmitting probe 6. At the same time, the time transmitted in step 4 is recorded in the memory in the control unit.

The oscillator 16 in the transmission probe 6 of FIG. 2 generates vibration by the sine wave, and transmits the sine wave vibration to the driving part 12 via the transmission part 20. The vibration is received by the vibrator 1717 of the reception probe 8 and generates an electric signal. This electric signal is converted from analog to digital by the receiving unit 7 and sent to the control unit 2. The control unit 2 finds the peak of the sine wave received in step 5 and records the time in the memory in step 6. There are several methods for finding the peak of a sine wave, but it is possible to easily differentiate the slope of the input wave and use the point at which its value changes from positive to negative as the peak. This state is shown in FIG. The first peak of the sine wave emitted from the transmission probe 6 is received by the reception probe 8, the first peak is captured, and the time passed through the wood 9 is measured.

From the difference between the transmission time data recorded in step 4 and the reception time data recorded in step 6, the time required to travel through the timber in step 7 can be known. The speed of the sound wave in the wood 9 can be known from the distance between the driving portions 12 and 13 of the transmitting probe 6 and the receiving probe 8 and the above time. The speed of the sound wave transmitted through the wood 9 is almost determined by the standard hardness of the wood for each kind of wood. Therefore, the data can be used to know how hard or soft the standard hardness is. The hardness data thus obtained is displayed on the pointing/display unit 3 in step 9. Then, in step 10, a series of operations ends.

Here, if a square wave is applied to the transmission probe 6, the reception wave received by the reception probe 8 becomes an irregularly disturbed wave as shown in FIG. As shown in FIG. 4, in addition to the sound wave emitted from the transmitting probe 6 directly entering the receiving probe 8, a wave reflected on the surface of the wood 9 or a wave disturbed by a knot of a tree is received. To enter. Therefore, when a square wave is used as the sound wave emitted by the transmission probe 6, the arrival time of the sound wave cannot be accurately measured.

In the above description, the hammering is used to drive the hammering into the driving parts 12 and 13 of the transmitting probe 6 and the receiving probe 8. However, the harvester of the machine defined by the Forestry Agency as a high-performance forestry machine Tree felling, pruning, beveling, and self-propelled machinery that consistently collects the sawn timber. Processors (forest roads, soil fields, etc.) It can also be attached to a self-propelled machine that continuously performs sweeping, measuring, and slicing) so that the hardness of wood can be automatically measured at the logging site.

Harvesters and processors are large machines, and when these are used, the vibrations generated by the engine and hydraulic equipment are transmitted to the transmitting probe 6 and the receiving probe 8 via cables. Since it is coupled to the transmission units 20 and 21 via 22 and 23, the transmission of vibration is small. Therefore, the reception probe 8 rarely catches vibration as noise.

As described above, the sound velocity measuring device for wood or the like according to the present invention automatically measures the sound velocity of sound waves transmitted through wood simply by driving the hammering parts 12, 13 of the transmitting probe 6 and the receiving probe 8 into the wood to be measured. Can be performed without requiring special skill. For this reason, it contributes to the promotion of forestry in the recent shortage of forestry workers. That is, even if the sound wave applied to the wood has a wave other than the surface wave, the peak of the sine wave is captured and measured, so that the measurement can be accurately performed.

1 Main Device 2 Control Section 3 Command/Display Section 4 Signal Generation Section 5 Transmitting Section 6 Transmitting Probe 7 Receiving Probe 8 Receiving Probe 9 Wood 10, 11 Main Body 12, 13 Driving Section 14, 15 Hammer Receiving Section 16 Oscillator 17 Microphone 18 , 19 Cases 20, 21 Transmission parts 22, 23 Vibration isolator

Claims (3)

Each of the transmitters has a transmitting probe and a receiving probe that are driven into the wood at a predetermined distance, and the transmitting probe has a mechanical converting means for converting a sound wave electric signal into a vibration, and the receiving probe has an electric converting means for converting a sound wave into an electric signal. And the electric signal applied to the transmission probe is a sound wave and has a waveform in which the differential value changes from positive to negative at the apex, and the apex of the first wave of the signal emitted from the transmission probe is received by the reception probe and transmitted. A sound velocity measuring device for wood and the like, which measures the time taken for a signal emitted from a probe to reach a receiving probe and measures the hardness of the wood based on the time. 2. The sound velocity measuring device for wood or the like according to claim 1, wherein the transmitting probe and the receiving probe are driven obliquely into the wood to be measured. The sound velocity measuring device for wood or the like according to claim 1, wherein each of the transmitting probe and the receiving probe is provided with a vibration isolator between a portion to be hammered into the target wood and the case to eliminate vibrations coming from the case.

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