JP3877591B2 - Packing detection method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a filling detection method and apparatus for detecting a filling state of concrete into a mold made of, for example, precast concrete.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a structure of a building employs a method in which a reinforcing bar is placed inside a formwork made of precast concrete (hereinafter referred to as precast concrete formwork) and concrete is filled there. In recent years, the shape of precast concrete formwork has become complex due to diversification of design, etc., and a method that can easily detect whether the concrete is properly filled up to the end of the complex shape by nondestructive inspection is desired. It is rare.
[0003]
For example, as a method currently commercialized, for example, there is one disclosed in Japanese Patent Laid-Open No. 10-197467.
FIG. 9 is a configuration diagram of the concrete filling confirmation device disclosed in the publication. In this figure, it has a pair of gauge terminals 1a and 1b as electrodes provided at intervals, and a resistor 2 connected between the gauge terminals 1a and 1b, and is provided in a concrete placement space. Three electric resistance sensors 1 arranged at intervals of each other, a battery 3 for applying a constant voltage between the gauge terminals 1a and 1b of each electric sensor 1, a multipoint changeover switch 4, a detector 5 and a personal computer 6, and includes a detection device 7 that sequentially converts the output of each electric resistance sensor 1 into a voltage and displays each voltage value.
[0004]
Then, when concrete is placed in the placement space and the placement portion of each electric resistance sensor 1 is filled with concrete, the pair of gauge terminals 1a and 1b of each electric resistance sensor 1 is wetted in contact with the concrete and is in a conductive state. Therefore, the resistance value between the gauge terminals 1a and 1b changes. And the change of the resistance value between the gauge terminals 1a and 1b at this time is detected by the detection device 7. Thereby, the filling state of concrete can be grasped based on this detection result.
[0005]
As another method, a thermocouple is arranged in a precast concrete mold, and the concrete filling state is discriminated by a temperature change using a difference in specific heat between air and concrete.
[0006]
[Problems to be solved by the invention]
By the way, the above-mentioned conventional concrete filling confirmation apparatus has the following problems.
That is, in what is disclosed in Japanese Patent Application Laid-Open No. 10-197467, the change in the resistance value when the concrete contacts the electrode is not constant due to the hardness of the water contained in the concrete and the influence of the ambient temperature. It is necessary to take a reference value (reference) on site every time. In addition, due to the characteristics of the sensor, once the concrete contacts and gets wet, it cannot be detected even if the concrete subsequently moves to form a cavity. Further, it cannot be detected until the subsequent solidification process, and it is impossible to accurately grasp the demolding time of the mold.
[0007]
Also, in the method of detecting the filling condition of concrete using the difference in specific heat between air and concrete using a thermocouple, if the temperature difference between concrete and temperature is small, the filling condition of concrete should be detected accurately. I can't. In particular, in a building buried in the ocean, the interior is filled with seawater, so detection by a temperature difference is difficult.
[0008]
The present invention has been made in view of such circumstances, and shows a filling state of a filler such as concrete into a predetermined space, such as a closed space and an open space, where filling cannot be easily confirmed by visual observation or the like. An object of the present invention is to provide a packing detection method and apparatus that can be detected accurately and easily.
[0009]
[Means for solving the problems]
According to a first aspect of the present invention, there is provided a filling detection method that applies a sinusoidal excitation signal whose frequency changes with time in a predetermined range to a sensor element that converts electrical energy into mechanical energy, and fills the detection means. A filling detection method for observing temporal changes in frequency characteristics due to contact with an object, wherein the detection means is applied in a state where the excitation signals are applied to a plurality of sensor elements connected in parallel and having different natural frequencies. It is characterized in that the completion of the filling of the filler and the subsequent condensing process are detected by observing a temporal change in the frequency characteristic due to the contact with the filler.
[0010]
According to this method, the sensor element that converts an electrical signal into mechanical vibration is vibrated by a sinusoidal vibration signal, and the frequency characteristic of the sensor element is detected by changing the frequency in an arbitrary range. The filler is detected by utilizing the fact that the frequency characteristics change when the filler such as concrete comes into contact with the sensor element. This change in the frequency characteristic of the sensor element can be detected with high sensitivity near the natural frequency of the sensor element. Therefore, detection of concrete filling in the space and its setting process can be detected by a plurality of sensor elements having different natural frequencies when detecting the filling of concrete and detecting the process of setting of concrete.
[0011]
In addition, since a plurality of sensor elements are connected in parallel, only two wires are required for these sensor elements, and it is not affected by temperature, concrete temperature, water hardness, etc. The concrete filling and setting process can be detected with high accuracy. Further, since the vibration characteristics of each sensor element are known in advance, it is not necessary to set a reference value in the field. In addition, the vibration frequency characteristics of the sensor element change depending on the specific gravity and viscosity of the substance in contact with the sensor element, so if this amount of change is measured, the filled substance is a gas, liquid, or solid Can be identified. Furthermore, by setting the frequency range of the excitation signal applied to the sensor element to be close to the natural frequency of the sensor element, it is possible to accurately measure the type and state change of the substance.
[0012]
According to a second aspect of the present invention, there is provided a filling material detection device that repeatedly generates a detection means having a sensor element that converts electrical energy into mechanical energy, and a sine wave electrical signal whose frequency changes over time within a predetermined range. Excitation signal generating means for generating an excitation signal, and frequency characteristic reflected signal output means for outputting a reception signal reflecting the frequency characteristic of the detection means when the excitation signal is applied to the detection means And multiplying means for multiplying the received signal from the frequency characteristic reflecting signal output means by the excitation signal from the excitation signal generating means, and the detection means is a natural frequency connected in parallel. A plurality of sensor elements having different characteristics.
[0013]
According to this configuration, the sensor element is excited by the sine wave excitation signal to the detection means formed by connecting a plurality of sensor elements having different natural frequencies in parallel, and the frequency is changed in an arbitrary range. The frequency characteristic is detected, and the filler is detected by utilizing the fact that the frequency characteristic changes when the filler such as concrete comes into contact with the sensor element. This change in the frequency characteristic of the sensor element can be detected with high sensitivity near the natural frequency of the sensor element. Further, the amplitude of the received signal can be detected with high accuracy by multiplying the excitation signal and the received signal.
Therefore, it is possible to detect the concrete filling in the space and the setting process with high precision by using multiple sensor elements with different natural frequencies when detecting the filling of concrete and detecting the setting process of concrete. it can.
[0014]
According to a third aspect of the present invention, there is provided the packing detection device according to the second aspect, wherein the excitation signal generating means is configured to vary a range in which the frequency of the excitation signal is changed. A variable means is provided.
[0015]
According to this configuration, since the frequency range can be varied, various types of fillers (air, water, concrete, etc.) can be identified with a single detection means.
[0016]
According to a fourth aspect of the present invention, there is provided a filling material detection apparatus according to any one of the second to third aspects, wherein the sensor element is a piezoelectric element.
[0017]
According to this configuration, an inexpensive filling detection device can be provided by using a piezoelectric element as the sensor element.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of a filling detector according to an embodiment of the present invention. In this figure, the filling detection device according to the present embodiment includes a synchronization signal generator 10, a variable frequency oscillator 11, an amplifier 12, a resistor 13, a piezoelectric speaker (detection means) 14, and a differential amplifier 15. And a quadrant multiplier 16 and a low-pass filter 17. In this case, the synchronization signal generator 10, the variable frequency oscillator 11, and the amplifier 12 constitute an excitation signal generating means. The resistor 13 and the differential amplifier 15 constitute frequency characteristic reflecting signal output means. The 4-quadrant multiplier 16 corresponds to multiplication means.
[0019]
The synchronization signal generator 10 generates a synchronization signal for repeatedly operating the variable frequency oscillator 11. The variable frequency oscillator 11 generates a sinusoidal electric signal whose frequency continuously changes in a predetermined frequency range (for example, 1 kHz to 20 kHz). That is, every time a synchronization signal is output from the synchronization signal generator 10, a sine wave signal is repeatedly generated from an initial frequency (for example, 1 kHz). The amplifier 12 amplifies the sine wave signal generated by the variable frequency oscillator 11 to a level at which the piezoelectric speaker 14 can be driven and outputs it (this output is referred to as an excitation signal Vr).
[0020]
The piezoelectric speaker 14 is formed by using a piezoelectric element, and converts an electrical signal into a mechanical signal and outputs it. Here, FIG. 2 is a configuration diagram of the piezoelectric speaker 14, (a) is a side view, (b) is an overall perspective view, and (c) is a side view of the piezoelectric element. The piezoelectric speaker 14 includes two piezoelectric elements (sensor elements) 14a and 14b having different natural frequencies, and a damping material 14c such as a foamed rubber material. The two piezoelectric elements 14a and 14b are the damping material 14c. It is joined with the appearance that turns their backs through each other.
[0021]
The damping material 14c is for preventing vibrations of the two piezoelectric elements 14a and 14b from affecting each other. Each of the piezoelectric elements 14a and 14b includes a piezoelectric ceramic 20 and a diaphragm 21. The piezoelectric element 14a has a natural frequency in the range of 3 kHz to 5 kHz, and the piezoelectric element 14b has a natural frequency in the range of 100 Hz to 2 kHz. Further, the attachment of the piezoelectric speaker 14 to the apparatus main body is performed by a sensor support member 22 as shown in FIG. The sensor support member 22 has one support portion 22 a that supports the piezoelectric speaker 14.
[0022]
The piezoelectric speaker 14 shown in FIG. 2 has a shape in which the piezoelectric elements 14a and 14b are joined to each other with the damping material 14c facing each other. However, as shown in FIG. An arranged shape is also conceivable. In this case, the sensor support member 23 includes support portions 23a and 23b that support the piezoelectric elements 14a and 14b, respectively.
[0023]
Returning to FIG. 1, the resistor 13 is inserted in series between the amplifier 12 and the piezoelectric speaker 14, and a voltage corresponding to the current flowing through the piezoelectric speaker 14 is generated at both ends thereof. Since the amplitude and phase of the current flowing through the piezoelectric speaker 14 change according to the change in frequency, the voltage appearing at both ends of the resistor 13 reflects the frequency characteristics of the piezoelectric speaker 14. The differential amplifier 15 amplifies the voltage generated at both ends of the resistor 13 and outputs the amplified voltage (this output is referred to as a reception signal Vi). The 4-quadrant multiplier 16 multiplies the excitation signal Vr output from the amplifier 12 by the reception signal Vi output from the differential amplifier 15 to remove the influence of noise on these signals.
[0024]
The low-pass filter 17 outputs a signal (output voltage Vo) obtained by removing cos (2ωt + α + β) described below from the output signal of the 4-quadrant multiplier 16. The output voltage Vo is a signal reflecting the frequency characteristics (amplitude and phase) of the piezoelectric speaker 14 with respect to the frequency change of the excitation signal Vr. At this time, if there was nothing in contact with the surface of the piezoelectric speaker 14, a peak was found at a frequency (4.7 kHz) near the natural frequency of the piezoelectric element 14a constituting the piezoelectric speaker 14 as shown in FIG. A voltage appears. When concrete is filled around the piezoelectric speaker 14 from this state, the vibration characteristics of the piezoelectric element 14a constituting the piezoelectric speaker 14 change, and the peak voltage position becomes 3.3 kHz as shown in FIG. As it changes, the amplitude decreases.
[0025]
On the other hand, since the piezoelectric element 14b constituting the piezoelectric speaker 14 has a natural frequency in the range of 100 Hz to 2 kHz, a voltage having a peak at about 3 kHz appears as shown in FIG. At the end of concrete setting, as shown in FIG. 8, the peak voltage position changes to about 1 to 2 kHz and the amplitude decreases. Thus, the completion of the concrete filling and the subsequent setting process can be easily detected from the change in the peak voltage.
[0026]
The operation principle will be described using mathematical expressions as follows.
Here, it is assumed that Vr = Asin (ωt + α) and Vi = Bsin (ωt + β). However, A and B are amplitudes, ωt is a frequency, and α and β are phase shifts.
Vr × Vi = Asin (ωt + α) × Bsin (ωt + β)
= AB [cos (β-α) -cos (2ωt + α + β)] / 2 (1)
[0027]
The cos (β−α) portion of the expression (1) is a direct current component that changes in accordance with the phase difference, and includes the amplitude component of the reception signal Vi. The cos (2ωt + α + β) portion is a signal having a frequency twice that of the original excitation signal Vr and the reception signal Vi. Since the required frequency characteristic information is the amplitude (magnitude) of the received signal Vi, only cos (β−α) in the equation (1) is sufficient. Therefore, the component of cos (2ωt + α + β) may be removed by passing through the low-pass filter 17. In this way, frequency characteristics appear in the form of voltage in the output voltage Vo.
[0028]
Next, the operation of the packing detection apparatus having the above configuration will be described.
A variable frequency oscillator 11 generates a sine wave whose frequency changes in an arbitrary range. The generated sine wave signal is amplified by the amplifier 12 and input to the piezoelectric speaker 14 as the excitation voltage Vr, and mechanical vibration is generated. When mechanical vibration is generated in the piezoelectric speaker 14, a voltage corresponding to the current flowing through the piezoelectric speaker 14 is generated at both ends of the resistor 13, and this voltage is amplified by the differential amplifier 15 and the received signal Vi is output. The received signal Vi and the excitation voltage Vr output from the amplifier 12 are multiplied by the four-quadrant multiplier 16, and the cos (2ωt + α + β) component is removed from the output by the low-pass filter 17 to output the output voltage Vo. Is obtained.
[0029]
This output signal Vo is a signal reflecting the frequency characteristics (amplitude and phase) of the piezoelectric speaker 14 with respect to the frequency change of the excitation signal. If the concrete is not in contact with the surface of the piezoelectric speaker 14, the output of the piezoelectric speaker 14 A voltage having a peak at a frequency in the vicinity of the natural frequency appears (FIG. 5). When concrete is filled around the piezoelectric speaker 14 in this state, the vibration characteristics of the piezoelectric speaker 14 change and the position and magnitude of the peak voltage change (FIG. 6). When the concrete congeals, the vibration characteristics of the piezoelectric speaker 14 change and the position and magnitude of the peak voltage further change (FIG. 8).
[0030]
As described above, according to the filling detection apparatus of the present embodiment, the piezoelectric speaker 14 formed by connecting two piezoelectric elements 14a and 14b having different natural frequencies in parallel is vibrated by a sinusoidal vibration signal. At the same time, the frequency characteristics of the piezoelectric elements 14a and 14b are detected by changing the frequency within an arbitrary range, and the concrete is detected by utilizing the change in frequency characteristics when the concrete contacts the piezoelectric elements 14a and 14b. To do. Changes in the frequency characteristics of the piezoelectric elements 14a and 14b can be detected with high sensitivity in the vicinity of the natural frequencies of the piezoelectric elements 14a and 14b. Further, the amplitude of the reception signal Vi can be detected with high accuracy by multiplying the excitation signal Vr and the reception signal Vi.
[0031]
Therefore, the detection of concrete filling in the space and its setting process are accurately detected by the two piezoelectric elements 14a and 14b having different natural frequencies when detecting the filling of the concrete and when detecting the setting process of the concrete. can do.
[0032]
In the present embodiment, since the two piezoelectric elements 14a and 14b constituting the piezoelectric speaker 14 are connected in parallel, only two wires are required for the piezoelectric elements 14a and 14b. The concrete filling and setting process can be detected with high accuracy without being affected by the hardness of the water used. Further, since the vibration characteristics of each of the piezoelectric elements 14a and 14b are known in advance, it is not necessary to set a reference value in the field. Further, the piezoelectric elements 14a and 14b are inexpensive, and the amplifiers 12, 13 and the four-quadrant multiplier 16 are also inexpensive, so that the cost of the apparatus can be reduced.
[0033]
Further, since the vibration frequency characteristics of the piezoelectric elements 14a and 14b change depending on the specific gravity or viscosity of the substance in contact with the piezoelectric elements 14a and 14b, if the amount of change is measured, whether the filled substance is a gas, a liquid, or a solid It is possible to identify whether this is the case.
Furthermore, by setting the frequency range of the excitation signal Vr applied to the piezoelectric elements 14a and 14b to be close to the natural frequency of the piezoelectric elements 14a and 14b, it is possible to accurately measure the type and state change of the substance.
[0034]
In the above embodiment, a sine wave of a single frequency range is used. However, a frequency range switch (not shown, corresponding to frequency range variable means) for switching the frequency range is provided, and a plurality of frequency ranges are provided. A sine wave may be alternatively selected. In this case, the variable frequency oscillator 11 has a function of repeatedly generating a sine wave signal in the frequency band in the range switched by the frequency range switch. In this way, by selecting sine waves in multiple frequency ranges, the optimum frequency range for measurement can be selected according to the physical characteristics such as the structure and material of the precast concrete formwork. This allows for more accurate measurements.
[0035]
In the above embodiment, the two piezoelectric elements 14a and 14b are used. However, the number is not limited to this number, and may be three or more. Of course, it goes without saying that each natural frequency is different.
In the above embodiment, the detection of the filling state in a closed space such as a precast concrete formwork of concrete has been described. However, the detection of the filling state in a formwork made of other wooden formwork or steel plate is described. Needless to say, it can be used for the above.
[0036]
【The invention's effect】
As described above, according to the present invention, a plurality of sensor elements having different natural frequencies are connected in parallel, and each is excited by a sinusoidal excitation signal, and the frequency is changed in an arbitrary range. Since each frequency characteristic is detected and the frequency characteristics change when the filler contacts each other, the filler such as concrete is detected, so the filler such as concrete in the space Can be detected with high accuracy.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a filler detection device according to an embodiment of the present invention.
2 is a configuration diagram of a piezoelectric speaker used in the filler detection device of FIG.
FIG. 3 is a view showing a piezoelectric speaker used in the filling material detection apparatus of FIG. 1 and a sensor support member for attaching the piezoelectric speaker to the apparatus main body.
FIG. 4 is a view showing another example of a piezoelectric speaker used in the filler detection apparatus of FIG. 1 and a sensor support member for attaching the piezoelectric speaker to the apparatus main body.
FIG. 5 is a diagram showing an example of a measurement result obtained by the filling detection apparatus of FIG. 1, and is an output voltage waveform diagram when there is no concrete in the precast concrete formwork.
6 is a diagram showing an example of a measurement result obtained by the filling detector of FIG. 1, and is an output voltage waveform diagram when concrete is filled in a precast concrete formwork. FIG.
7 is a diagram showing an example of a measurement result obtained by the filling detector of FIG. 1, and is an output voltage waveform diagram immediately after the concrete is filled in the precast concrete formwork. FIG.
FIG. 8 is a diagram showing an example of a measurement result obtained by the filler detection device of FIG. 1, and is an output voltage waveform diagram after completion of setting of the concrete filled in the precast concrete formwork.
FIG. 9 is a configuration diagram of a conventional concrete filling confirmation apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Synchronous signal generator 11 Variable frequency oscillator 12 Amplifier 13 Resistance 14 Piezoelectric speaker (detection means)
14a, 14b Piezoelectric element (sensor element)
14c Damping material 15 Differential amplifier 16 Four-quadrant multiplier 17 Low-pass filter 20 Piezoelectric ceramic 21 Diaphragm 22, 23 Sensor support member

Claims (4)

Applying a sinusoidal excitation signal whose frequency changes over time within a specified range to the sensor element that converts electrical energy into mechanical energy, and the temporal change in the frequency characteristics due to the contact of the filler with the detection means A method for detecting a filling material to be observed, wherein a time characteristic of a frequency characteristic due to a filling material coming into contact with the detecting means in a state where the excitation signal is applied to a plurality of sensor elements having different natural frequencies connected in parallel. A filling detection method characterized by detecting the completion of filling of the filling and the subsequent setting process by observing a change. Detection means having a sensor element for converting electrical energy into mechanical energy, and excitation signal generation means for repeatedly generating a sinusoidal electric signal whose frequency changes over time within a predetermined range to generate an excitation signal A frequency characteristic reflecting signal output means for outputting a reception signal reflecting the frequency characteristic of the detecting means when the excitation signal is applied to the detecting means; and a received signal from the frequency characteristic reflecting signal output means And a multiplying unit that multiplies the excitation signal from the excitation signal generating unit, and the detection unit includes a plurality of sensor elements connected in parallel and having different natural frequencies. Filling detection device. 3. The filling detection device according to claim 2, wherein the excitation signal generating means includes frequency range variable means for changing a range in which the frequency of the excitation signal is changed. 4. The filling detection apparatus according to claim 2, wherein the sensor element is a piezoelectric element.

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