JP2009236538A - Reinforcing bar sensing method at time of cutting of cutting target containing reinforcing bar and cutter with reinforcing bar sensing means - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reinforcing bar sensing method capable of executing construction without breaking a reinforcing bar even when the position of the reinforcing bar in a reinforced concrete structure is unclear, and to provide a cutter with a reinforcing bar sensing means. <P>SOLUTION: In the method for cutting the reinforcing bar in the cutting target when the cutting target containing the reinforcing bar is cut by a cutting means, a first electrode is electrically connected to the cutting means, at least one second electrode is installed on the cutting target, an AC current is passed across the first and second electrodes to measure the impedance between the first and second electrodes and the contact of the cutting part of the cutting means with the reinforcing bar is sensed by a change in impedance. This reinforcing bar sensing method is used to perform construction without breaking the reinforcing bar in the reinforced concrete structure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reinforcing bar sensing method and a cutting apparatus provided with a reinforcing bar sensing means when a workpiece including a reinforcing bar is cut.

  In repair work and repair work on reinforced concrete structures, drilling with a core drill or cutting of a wall surface with a wall saw is performed. In these constructions, there is a possibility that the strength of the entire reinforced concrete structure may be lowered. Therefore, it is desired to perform the construction so as not to destroy the existing reinforcing bars in the structure.

  When the position of a reinforcing bar in a reinforced concrete structure is clearly known from a drawing or the like, it is possible to perform the work while avoiding the reinforcing bar. For example, using the cutting apparatus shown in Patent Document 1, it is possible to perform construction while accurately grasping the reinforcing bars.

JP 2000-354904 A

  However, there is a case where the position of the existing reinforcing bar cannot be clearly grasped in the reinforced concrete structure because the drawing is not stored, or the reinforcing bar is not necessarily arranged according to the design drawing even if there is a drawing. In such a case, there is a case where the reinforcing bar is accidentally destroyed in the repair work or the renovation work, or the construction is assumed to destroy the reinforcing bar.

  The present invention has been made based on the background as described above. Reinforcing bars that can be constructed without destroying the reinforcing bars even when the position of the reinforcing bars in the reinforced concrete structure is unknown. An object of the present invention is to provide a sensing method and a cutting device provided with a reinforcing bar sensing means.

  In order to solve the above problem, the present inventors have various methods for sensing without destroying the reinforcing bar even if the position of the reinforcing bar in the reinforced concrete structure to be enforced remains unknown. As a result of repeated studies, the present inventors have found that the reinforcing bar can be sensed by detecting a change in impedance measured when the cutting means and the surface of the reinforced concrete structure are energized, and the present invention has been conceived.

  That is, the present invention is a method for sensing a reinforcing bar in the workpiece when cutting a workpiece including a reinforcing bar by a cutting means, and electrically connecting a first electrode to the cutting means, At least one second electrode is installed on the workpiece, an alternating current is passed between the first electrode and the second electrode, and an impedance between the first electrode and the second electrode is measured. The reinforcing bar detecting method of detecting that the cutting portion of the cutting means is in contact with the reinforcing bar due to the change in impedance.

  Hereinafter, the method according to the present invention will be described in detail. FIG. 1 (A) shows a means for measuring the impedance between the first electrode and the second electrode by arranging the first electrode and the second electrode on the cutting means and the workpiece and energizing the alternating current. Show. Here, the cutting means used in the cutting operation is usually made of a current-carrying material such as steel, and a reinforcing bar is also a current-carrying material. On the other hand, many objects to be cut such as concrete are made of an insulating material. The present invention pays attention to the presence or absence of the electrical conductivity of these materials, forms a circuit constituting a capacitor by appropriately arranging electrodes, and measures the impedance in the system.

  In other words, when an AC circuit is formed by placing an electrode in contact with a current-carrying material, the material to be cut is an insulating material, and therefore serves as a capacitor in the circuit. The equivalent circuit shown in FIG. 1C is expressed assuming that FIG. 1A is an AC circuit. The workpiece that exists between the cutting means that is the energized material and the reinforcing bar, the workpiece that exists between the second electrode and the reinforcing bar, the point where the cutting means and the workpiece are in contact, and the second electrode The workpieces existing between the center portion are capacitors (C1, C2, C3), respectively.

  Here, the relationship as shown in the following formula 1 is established between the impedance (Z) and the capacitor (C). In Equation 1, j is an imaginary unit, and ω is an alternating angular frequency.

        Z = 1 / (j · ω · C) Equation 1

  As shown in FIG. 1B, when cutting progresses and the cutting means comes into contact with the reinforcing bar, the workpiece (C1) existing between the cutting portion of the cutting means and the reinforcing bar that has existed as a capacitor until then. Disappears as shown in FIG. As a result, the capacitance of the remaining capacitor (C2) is increased and the denominator of the above equation 1 is increased, and as a result, the impedance is lowered.

  Specifically, when the cutting part comes into contact with the reinforcing bar during the cutting operation, as shown in FIG. 2, the impedance is lowered and it is detected that the cutting part has come into contact with the reinforcing bar. Therefore, by interrupting the cutting operation at such time, the cutting operation can be performed without destroying the reinforcing bars.

  In the method according to the present invention based on the principle described above, the sensitivity for detecting the reinforcing bar is affected by the installation position of the second electrode and the like.

  That is, the distance between the point of contact between the cutting part of the cutting means and the object to be cut and the center of the second electrode should basically be a distance that enables rebar detection due to a decrease in impedance between the electrodes. Reinforcing bars can be sensed satisfactorily as long as the thickness of the workpiece is greater than the cover thickness. Here, the cutting portion refers to a portion where the cutting means cuts the workpiece. In addition, the distance between the point where the cutting part of the cutting means and the object to be cut contact and the center of the second electrode is the distance between the cutting part of the cutting means and the object to be cut. The distance from the point closest to the center to the center of the second electrode. If this distance is not sufficient, it is conceivable that the workpiece to be connected between the point where the cutting portion and the workpiece are in contact with the second electrode becomes a capacitor (C3 in FIG. 1D), The detection sensitivity is lowered and the reinforcing bars cannot be detected. Therefore, the distance is preferably equal to or greater than the cover thickness of the workpiece, and by taking a distance of at least 10 cm, the capacitor (C3) does not affect the change in impedance, and its action can be ignored. . Here, the cover thickness corresponds to the depth from the surface of the workpiece to the reinforcing bar. In addition, the longer the distance, the more preferable it is that the action of the capacitor (C3) can be ignored, but it is preferably 10 m or less in consideration of workability at the cutting site.

Then, the second electrode is preferably a contact area between the object to be cut is at least 0.001 m ² more 10 m ² or less. This is because, when the contact area is within the above range, the impedance change can be easily detected. When the contact area is smaller than 0.001 m ^2, the impedance of the capacitor (C2) becomes excessively high, so that it is easily affected by external noise, and it is difficult to detect a change in impedance. Conversely, when the contact area is larger than 10 m ^2, the impedance of the capacitor (C2) becomes excessively low, and it becomes difficult to detect the impedance change accompanying the reinforcing bar contact.

  The reinforcing bar sensing method according to the present invention requires at least one second electrode. As shown in FIG. 3 (A), when the reinforcing bars are arranged in only one direction with respect to the site where the workpiece is cut, only one second electrode is sufficient. On the other hand, as shown in FIG. 3 (B), when the reinforcing bars are arranged in two directions with respect to the part where the workpiece is cut, it is unclear which reinforcing bar the cutting part contacts. Therefore, two second electrodes are required to correspond to the reinforcing bars. In addition, when a plurality of reinforcing bars are arranged and overlapped with respect to a part where the workpiece is cut, it is unclear which reinforcing bar the cutting part contacts in the same manner as in FIG. In addition, the position of the reinforcing bar in the cut object may not be clearly understood. In these cases, a plurality of second electrodes may be used in order to correspond to the reinforcing bars, but as shown in FIGS. 4C and 4D, a circular or arcuate second electrode may be used. Good.

  Next, the first electrode in the present invention may be any electrode as long as it is electrically connected to the cutting means so that an impedance can be measured by forming an AC circuit, and does not require physical contact. . For example, the first electrode made of a brush-like current-carrying material is arbitrarily installed so as to come into contact with the rotational drive shaft of the cutting means.

  An AC power source and an impedance detector are provided between the first electrode and the second electrode. This is because AC is energized, the impedance between both electrodes is detected, and the rebar is sensed by the change. In the present invention, the AC power source is preferably capable of controlling the AC frequency between 10 kHz and 1000 kHz. The AC frequency is appropriately adjusted according to the material of the workpiece and the situation at the construction site, and any AC power source that can control the AC frequency within the above range may be used. Then, it is more preferable that it is 20 kHz-200 kHz.

  In addition, as a representative of the cutting means applicable to the cutting device according to the present invention, a core drill can be mentioned, but a drill, a wall saw, a wire saw, etc. may be used as long as it cuts an object to be cut. It may be an expression or a manual expression. The cutting portion of the cutting means is desirably a material that can detect impedance, for example, a metal material having electrical conductivity.

  On the other hand, as a workpiece to be cut, a reinforced concrete structure is representatively exemplified, but the workpiece exhibits a function as a capacitor in an AC circuit, and the reinforcing bar is embedded in the workpiece. As long as it is a thing, it is not limited to concrete but may be a material such as wood, urethane foam, ceramic, brick, or glass.

  As an apparatus used for the reinforcing bar sensing method described above, in a cutting apparatus having a cutting means for cutting an object to be cut, a first electrode electrically connected to the cutting means, and a surface of the object to be cut And at least one second electrode that can be installed on the AC power supply provided between the first electrode and the second electrode, and impedance detection means for detecting an impedance between the first electrode and the second electrode There is a cutting device characterized by comprising a reinforcing bar sensing means comprising: Each configuration of the cutting apparatus according to the present invention will be described below.

  First, as a representative of the cutting means applicable to the cutting apparatus according to the present invention, a core drill can be cited, but a drill, a wall saw, a wire saw, etc. may be used as long as it cuts an object to be cut. It may be an expression or a manual expression. The cutting portion of the cutting means is desirably a material that can detect impedance, for example, a metal material having electrical conductivity.

  Next, the first electrode in the present invention may be any electrode as long as it is electrically connected to the cutting means so that an impedance can be measured by forming an AC circuit, and does not require physical contact. . For example, the first electrode made of a brush-shaped energizing material is arbitrarily installed so as to be in contact with the rotational drive shaft of the cutting means.

And as a 2nd electrode applicable to the cutting device which concerns on this invention, what is necessary is just an electroconductive material of a structure which closely_contact | adheres to a to-be-cut object so that the detection of an impedance may become easy. The second electrode is preferably a contact area between the object to be cut is at least 0.001 m ² more 10 m ² or less. This is because, when the contact area is within the above range, the impedance change can be easily detected. When the contact area is smaller than 0.001 m ^2, the impedance of the capacitor (C2) becomes excessively high, so that it is easily affected by external noise, and it is difficult to detect a change in impedance. Conversely, when the contact area is larger than 10 m ^2, the impedance of the capacitor (C2) becomes excessively low, and it becomes difficult to detect the impedance change accompanying the reinforcing bar contact. Note that the cutting device according to the present invention requires at least one second electrode, and its shape may be circular or arcuate as long as the impedance can be easily detected.

  Furthermore, the distance between the point of contact between the cutting part of the cutting means and the workpiece and the center part of the second electrode basically needs to be a distance that enables rebar detection due to a decrease in impedance between the electrodes. Reinforcing bars can be sensed satisfactorily as long as the thickness of the workpiece is greater than the cover thickness. If this distance is not sufficient, it is conceivable that the workpiece to be connected between the point where the cutting portion and the workpiece are in contact with the second electrode becomes a capacitor (C3 in FIG. 1D), The detection sensitivity is lowered and the reinforcing bars cannot be detected. Therefore, the distance is preferably equal to or greater than the cover thickness of the workpiece, and by taking a distance of at least 10 cm, the capacitor (C3) does not affect the change in impedance, and its action can be ignored. . In addition, the longer the distance, the more the action of the capacitor (C3) can be ignored. However, in consideration of workability at the cutting site, the distance is preferably 10 m or less.

  As an AC power source applicable to the cutting apparatus according to the present invention, it is preferable that the AC frequency can be controlled between 10 kHz and 1000 kHz. The AC frequency is appropriately adjusted according to the material of the workpiece and the situation at the construction site, and any AC power source that can control the AC frequency within the above range may be used. Then, it is more preferable that it is 20 kHz-200 kHz.

  A typical example of the impedance detection means applicable to the cutting apparatus according to the present invention is an LCR meter. Moreover, a cheaper V monitor can be used by dividing the pressure. Furthermore, in order to clarify the change in impedance and facilitate rebar detection, impedance noise can be removed by a digital signal processing circuit, software processing, or the like.

  Further, in the present invention, the impedance change may be monitored and the cutting operation may be manually stopped. However, the cutting apparatus according to the present invention automatically stops the apparatus based on the impedance change subjected to the digital signal processing. Automatic control means can also be added.

  According to the reinforcing bar detecting method and the cutting apparatus provided with the reinforcing bar detecting means of the present invention, even when the position of the reinforcing bar of the object to be cut is unknown, the repairing or repairing work is not performed without destroying the reinforcing bar. Can be constructed.

First Embodiment: In order to clarify the features of the present invention, an embodiment will be described below. Here, the case where the drilling operation | work of a reinforced concrete structure is performed using the core drill apparatus 1 shown in FIG. 5 is demonstrated. The core drill apparatus 1 includes a motor main body 2 and a base 4 provided with a support shaft 3 that locks the motor main body 2 so that the motor main body 2 can be arranged vertically with respect to a surface for drilling the core drill and is slidable.

  At this time, the support shaft 3 extends vertically from the pedestal 4 fixed to the concrete 12 by the anchor bolt 11, and the handle 6 is rotated by passing the support shaft 3 through the engaging portion 5 connected to the motor body 2. Thus, the motor body 2 itself can be moved up and down by a rack and pinion method.

  A core drill 8 and a first electrode 9 were attached to the rotary drive shaft 7 extending from the motor body 2. The rotary drive shaft 7 and the core drill 8 are metallic and conductive, and the core drill 8 and the first electrode 9 are electrically connected.

  Here, the first electrode 9 was attached to the rotary drive shaft 7 as shown in FIG. FIG. 6A shows the relationship between the first electrode 9 and the rotary drive shaft 7 as a cross-sectional view cut in the horizontal direction with the concrete 12. The main body 60 of the first electrode 9 has a donut shape and is attached to the rotary drive shaft 7. FIG. 6B shows the relationship between the first electrode 9 and the rotary drive shaft 7 as a cross-sectional view cut in a direction perpendicular to the concrete 12. The main body 60 is fixed to the rotary drive shaft 7 by a retaining ring 61, and a rolling bearing 62 is attached to smoothly rotate the rotary drive shaft 7 even if the first electrode 9 is installed. The first electrode 9 forms an AC circuit by being electrically connected to the rotary drive shaft 7 by a brush 64 in the brush holder 63. The brush 64 is connected to the electric wire 14 and forms an AC circuit.

  On the other hand, the second electrode 10 is installed so as to contact the surface of the concrete 12 as shown in FIG. 5, and the distance from the point where the core drill 8 and the concrete 12 contact to the center of the second electrode 10 is equal to the concrete. The cover thickness was set to 90 cm so as to be 5 cm or more.

  The second electrode 10 used was a strip-like copper tape having a width of 5 cm and a length of 30 cm, with an adhesive attached to the back surface of the copper foil so that the surface of the concrete 12 could be easily contacted.

  The electric wire 14 electrically connects the first electrode 9 and the second electrode 10, and as shown in FIG. 5, a detector 15 (LCR meter manufactured by Hewlett-Packard Company) for measuring the impedance between both electrodes. 4284A, a measurement frequency range of 20 Hz to 1 MHz) and an AC power supply 16 for energizing AC (built in the LCR meter 4284A, frequency range of 20 Hz to 1 MHz) are connected.

  After the core drill device 1 and the second electrode 10 are installed on the concrete surface as described above, an alternating current is passed by the alternating current power source 16 under the condition of an alternating frequency of 100 kHz, and the impedance between the first electrode 9 and the second electrode 10 is set. While measuring, the core drill device 1 was used to cut the reinforced concrete structure.

  As shown in FIG. 2, the impedance value between the first electrode 9 and the second electrode 10 repeats up and down with a certain width for a certain period after the cutting operation is started, but a large change is recognized. Absent. This state indicates that the core drill 8 is cutting the concrete 12, but the core drill 8 is not in contact with the reinforcing bar.

  The impedance value decreased about 180 seconds after the start of cutting. Therefore, when the cutting operation was stopped, the reinforcing bars were visually confirmed from the bottom of the cavity generated by the cutting. That is, the decrease in the impedance value corresponds to the cutting portion of the core drill 8 coming into contact with the reinforcing bar. From the above results, according to the present invention, it was confirmed that the reinforcing bar in the reinforced concrete structure can be sensed by changing the impedance value.

Second Embodiment: Here, the same apparatus as that of the first embodiment is used, and the reinforcing steel in the case where the AC frequency is changed by cutting the reinforced concrete structure under the cutting conditions of 50 kHz, 80 kHz, and 100 kHz. The possibility of sensing was examined. Cutting conditions other than the AC frequency are the same as in the first embodiment.

  As shown in FIG. 7, in this embodiment, the impedance change by having contacted the reinforcing bar on the conditions with an alternating frequency of 80 kHz and 100 kHz was clearly recognized. Under the condition where the AC frequency was 50 kHz, the impedance change was slightly reduced due to the influence of the other implementation conditions except the AC frequency, but the rebar was not broken and no problem occurred in the cutting operation.

Third Embodiment: Next, using the same apparatus as in the first embodiment, the AC frequency is 80 kHz, the distance from the point where the core drill 8 and the concrete 12 contact to the center of the second electrode 10 (in FIG. 8) The cutting operation of the reinforced concrete structure was performed under the cutting conditions of 65 cm, 80 cm, and 90 cm as the distance between the electrodes), and the possibility of rebar detection was examined. Other cutting conditions are the same as those in the first embodiment.

  As shown in FIG. 8, in this embodiment, the impedance change when contacting the rebar according to the increase in the distance from the point where the core drill 8 and the concrete 12 contact to the center of the second electrode 10 increases. A tendency to increase was also observed. Under the condition of 65 cm, although the impedance change was slightly reduced due to the influence of the other implementation conditions, the rebar was not broken and no problem occurred in the cutting operation.

The figure which shows the outline | summary of the cutting device which concerns on this invention, and the relationship between this invention and a capacitor | condenser. The figure which shows the change of the impedance during cutting. The figure explaining the 2nd electrode of this invention. The figure explaining the 2nd electrode of this invention. Schematic of the core drill apparatus provided with the reinforcing bar sensing means according to the present invention. The figure explaining the 1st electrode of this invention. The figure which shows the change of the impedance corresponding to AC frequency. The figure which shows the change of the impedance corresponding to the distance between electrodes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core drill apparatus 2 Motor main body 3 Support shaft 4 Base 5 Engagement part 6 Handle 7 Rotation drive shaft 8 Core drill 9 First electrode 10 Second electrode 11 Anchor bolt 12 Concrete 13 Rebar 14 Electric wire 15 Impedance detector 16 AC power supply 60 Main body 61 Retaining ring 62 Rolling bearing 63 Brush holder 64 Brush

Claims (10)

A method of sensing a reinforcing bar in the workpiece when cutting the workpiece including the reinforcing bar with a cutting means,
Electrically connecting a first electrode to the cutting means, and installing at least one second electrode on the workpiece;
While passing an alternating current between the first electrode and the second electrode, and measuring the impedance between the first electrode and the second electrode,
Reinforcing bar detection method, wherein contact between the cutting portion of the cutting means and the reinforcing bar is detected by the change in impedance.   The reinforcing bar detection method according to claim 1, wherein a distance between a point at which the cutting portion of the cutting means and the workpiece are in contact with a center portion of the second electrode is equal to or greater than a cover thickness of the workpiece and 10 m or less.   The reinforcing bar sensing method according to claim 1 or 2, wherein a frequency of an alternating current passed between the first electrode and the second electrode is 10 to 1000 kHz. The second electrode and the rebar sensing method according to any one of claims 1 to 3, the contact area between the object to be cut to 0.001 m ² more 10 m ² or less. In a cutting apparatus having a cutting means for cutting a workpiece,
A first electrode electrically connected to the cutting means;
At least one second electrode that can be placed on the surface of the workpiece;
AC power source provided between the first electrode and the second electrode;
Impedance detection means for detecting impedance between the first electrode and the second electrode;
A cutting apparatus comprising a reinforcing bar sensing means comprising:   The cutting device according to claim 5, wherein a distance between a point where the cutting portion of the cutting means and the workpiece are in contact with a center portion of the second electrode is equal to or greater than a cover thickness of the workpiece.   7. The cutting apparatus according to claim 5, wherein the AC power source can control the AC frequency between 10 kHz and 1000 kHz. The second electrode, the cutting device according to any one of claims 5 to 7 the contact area between the object to be cut is 0.001 m ² or more 10 m ² or less.   The cutting device according to any one of claims 5 to 8, wherein the cutting means is a core drill.   The cutting apparatus according to claim 9, wherein the first electrode is electrically connected to a shaft portion that rotates the core drill.

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