JP3068866B2 - Buried cable position measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indirect transmission of a signal current of a predetermined frequency from a transmission coil to a buried cable or a metal conduit (hereinafter, simply referred to as a cable) to generate an alternating magnetic field generated from the cable. The present invention relates to a buried cable position measuring instrument and a measuring method for searching a buried position of a cable and measuring a buried depth by detecting the buried position of the cable by detecting the receiving coil on the ground surface.

[0002]

2. Description of the Related Art In a conventional buried cable position measuring instrument, a transmitter and a receiver are separated from each other.
First, a transmitter is installed at a ground position immediately above a buried cable to be searched, and then a position is measured by detecting a magnetic field from the cable by a receiver at a location away from the transmitter.

[0003]

However, at first,
Since the position of the transmitter is unknown, the cable position is unknown.Therefore, it is necessary to temporarily set the transmitter at a position directly above it and then move the transmitter to an appropriate position based on the search result by the receiver. Was. This means, for example, after temporarily installing the transmitter, search for the point of maximum sensitivity at the receiver, and then set up the transmitter, or after searching for the point of maximum sensitivity at the receiver, It is a method of moving and installing it in a place where the reception sensitivity is further increased, and it is an indispensable work to prevent other buried objects from being erroneously searched. Also, in ordinary cable position measurement, the cable route is often tracked from the ground, and the operator must be away from the transmitter, so as a watchman of the transmitter, or change the transmission output during the measurement For example, personnel were required near the transmitter. In addition, buried objects parallel to the target cable,
For example, it is often necessary to check the presence and location of metal pipes such as gas pipes before digging the ground, and it is extremely difficult to conduct a quick and accurate search that includes them unless the conditions are adequately met. There was a drawback to say.

[0004]

A buried cable according to claim 1, wherein :
In the method for measuring the position of the cable, two transmission coils which are arranged in parallel with a distance between the centers thereof at the same height, and are differentially connected, and the combined magnetic field of the two transmission coils is zero When the center is located at a position and the receiving coil integrally disposed with the two transmitting coils is rotated by a predetermined angle around a straight line connecting the centers of the two transmitting coils as a rotation center axis. The burying depth of the buried cable is measured based on the magnetic field received by the receiving coil.

[0005]

According to the first aspect of the present invention, since the two transmitting coils and the receiving coil are integrally provided, the position of the buried cable can be easily measured by one person.
In addition, since the receiving coil is not directly affected by the magnetic field generated from the two transmitting coils, it is possible to receive only the magnetic field based on the current flowing through the buried cable,
The burial depth of the buried cable can be accurately measured.

[0006]

Next, the structure of an embodiment of the present invention will be described with reference to the drawings. The two sets of transmitting coils 3a and 3b are differentially connected and connected to a transmitting circuit 5, and the receiving coil 4 is connected to a receiving circuit 6
Are connected to the arithmetic circuit 7, and the arithmetic circuit 7 is connected to a display 8 for displaying numerical values and the like of the calculation results and an input unit 9 for setting specific numerical values and the like necessary for the calculations. In this case, the transmission coils 3a and 3b are opposed to the cable 1 which is disposed at a distance d perpendicular to the ground 2 and buried in the ground as shown in FIG. When the output of the transmitting circuit 5 is input to the differentially connected transmitting coils 3a and 3b, the transmitting coils 3a and 3b generate magnetic fields having the same magnitude and opposite directions. , An induced current i flows. The voltage induced in the receiving coil 4 by the magnetic field 11 generated by the induced current i is selected and amplified in a state where noise signals and the like are appropriately cut by the receiving circuit 6, digitized by the arithmetic circuit 7, and displayed on the display 8.

Next, a description will be given of a case where the magnetic field generated at one point of the cable by the transmission coils 3a and 3b is equal to the distance from the position immediately above the cable 1 to both the transmission coils 3a and 3b. FIG. 3 shows a magnetic field H generated at the point of the cable 1 by one transmission coil 3a.
The magnitudes of the magnetic poles generated at both ends of the transmission coil 3a are + qm and -qm, the length of the transmission coil 3a is 1, the vertical distance between the lower surface of the transmission coil 3a and the cable 1 is h, and the length of the transmission coil 3a and the cable 1 is If the horizontal distance is d / 2, the magnetic field H is a composite of the magnetic field H1 generated by + qm and the magnetic field H2 generated by -qm.

[0008]

(Equation 1)

(Equation 2)

(Equation 3)

(Equation 4)

(Equation 5) FIG. 4 shows a magnetic field H ′ generated at the point of the cable 1 by the other transmitting coil 3b. Transmission coil 3b
+ Qm, -q of each of the magnetic poles generated at both ends of
m, the length of the transmission coil 3b is 1, the vertical distance between the transmission coil 3b and the cable 1 is h, and the transmission coil 3b and the cable 1
Is the same value as in the case of the transmission coil 3a, and the magnetic field H ′ generated by this is + qm of the transmission coil 3b.
And a magnetic field H2 'generated by -qm.

[0009]

(Equation 6)

(Equation 7)

(Equation 8)

(Equation 9)

(Equation 10)

[Equation 11] Here, the magnetic field H0 generated at the point of the cable 1 is a composite of the magnetic field H and the magnetic field H '. Here, the y-direction components of the magnetic field H2 and the magnetic field H1' are canceled out because their directions are equal and opposite to each other. Similarly, the magnetic field H1 and the magnetic field H
Since the component in the y direction is also canceled for 2 ′, the magnetic field H
0 is a magnetic field of only the X-direction component. Due to the magnetic field H0, the magnetic flux Φ is linked to the cable 1 according to Faraday's law.

[0010]

(Equation 12) Voltage e is induced, and a current i flows. Next, a magnetic field generated at a point A located at an equal distance from each magnetic pole of the transmission coils 3a and 3b will be described. FIG. 5 shows a magnetic field H generated at point A by one transmission coil 3a.
Assuming that the magnitudes of the magnetic poles generated at both ends of the transmitting coil 3a are + qm and -qm, respectively, and the distance from each magnetic pole to the point A is r, the magnetic field H is the magnetic field H1 generated by + qm and -q
m and the magnetic field H2 generated by m.

[0011]

(Equation 13)

[Equation 14]

(Equation 15) FIG. 6 shows a magnetic field H 'generated at the point A by the other transmitting coil 3b. The magnitudes + qm and -qm of the magnetic poles generated at both ends of the transmission coil 3b and the distance r from each magnetic pole to the point A are the same as those in the case of the transmission coil 3a. 3b
The magnetic field H1 'generated by + qm and the magnetic field H2' generated by -qm are combined.

[0012]

(Equation 16)

[Equation 17]

(Equation 18)

[Equation 19] Here, the magnetic field H0 generated at the point of the cable 1 is a composite of the magnetic field H and the magnetic field H '. Since the x- and z-direction components of the magnetic field H1 and the magnetic field H2 are equal and opposite in direction. It is canceled and only the y-direction component is left.
Since the same can be said for the magnetic field H1 'and the magnetic field H2', the magnetic field H 'has only the y-direction component. Further, since the magnetic fields H and H 'have the same magnitude and are opposite in direction, they cancel each other out. Therefore, the magnetic field generated by the transmitting coils 3a and 3b does not exist at the point A.

Such a point exists on a straight line on a horizontal plane including the centers of the transmission coils 3a and 3b. Therefore, when the receiving coil 4 is arranged so that the coil axis is perpendicular to the straight line, parallel to the ground, and the center of the coil is on the straight line, the differentially connected transmitting coils 3a and 3b are connected to the cable 1
The receiving coil 4 can detect the magnetic field from the cable 1 and measure the position of the cable 1 without receiving the direct magnetic field from the transmitting coils 3a and 3b. Thus, the position just above the cable 1 can be found by finding the point where the received signal is maximum. In the buried cable position measuring device thus configured, the transmitting coils 3a and 3b and the receiving coil 4 At the position near the cable 1, the magnetic field generated by the transmission coils 3 a, 3 b at the position of the cable 1 increases. As a result, the induced current flowing through the cable 1 increases and the magnetic field generated from the cable 1 also increases.
In this state, the receiving coil 4 is also close to the cable 1, so that the received signal is increased. The magnitude of the received signal due to the movement of the measuring instrument is emphasized by the transmission / reception synergistic effect. effective.

Next, using this measuring instrument, the cable 1
A method for measuring the burial depth of the cradle will be described. FIG. 8 is a view from the side. Without changing the positional relationship between the coils shown in FIG. 3, the transmission coils 3a, 3b and the reception coil 4 are integrally formed by an angle θ in the clockwise direction in FIG. Assuming that the vertical distance from the lower surface of the transmitting coils 3a, 3b to the cable 1 is h in this state, each magnetic pole is
The magnetic field generated at the position

[0015]

(Equation 20)

(Equation 21)

(Equation 22)

(Equation 23)

(Equation 24)

(Equation 25)

(Equation 26)

[Equation 27] FIG. 9 shows this in a view from the cable section direction. At this time, the relationship between l Sinθ and the burial depth h of the cable 1 is

[0016]

[Equation 28] Then, the magnetic field H0 at the point of the cable 1 is

[0017]

(Equation 29) As shown in FIG. 2, a magnetic field is generated only in the X direction.
An induced current i corresponding to the magnetic field H0 flows through the cable 1 and the receiving coil 4

[0018]

[Equation 30] Voltage E1 is induced. Next, as shown in FIG. 10, the transmitting coils 3a and 3b and the receiving coil 4 are integrally rotated by an angle 2θ in the counterclockwise direction in the figure. As a result, the transmission coils 3a,
The axis of 3b forms an angle θ with respect to a straight line perpendicular to the ground. FIG. 11 is a cross-sectional view at this time. The magnetic fields generated by the magnetic poles of the transmission coils 3a and 3b at the position of the cable 1 are shown in FIG.
And as apparent from FIG.

[0019]

(Equation 31)

(Equation 32)

[Equation 33]

(Equation 34) Therefore, the resultant magnetic field H0 '

[0020]

(Equation 35) Becomes The induced current i is applied to the cable 1 by the magnetic field H0 '.
Flows, so that the receiving coil 4

[0021]

[Equation 36] K is induced by a voltage E2 which is a proportional constant. E measured earlier
From 1 and this E2, h is obtained as follows.

[0022]

(37) With this h, the burial depth up to the cable 1 can be calculated.

[0023]

According to the buried cable position measuring instrument of the present invention, the transmitter and the receiver, which have been conventionally separated, can be integrated, so that the transmitting and receiving operations can be performed by one operator. As a result, the position of the embedded cable can be measured quickly and accurately, and the depth of the embedded cable can be easily increased by measuring the magnetic field from the cable at two levels without changing the cable induced current. There is an effect that can be measured.

[Brief description of the drawings]

FIG. 1 is a perspective view including a block diagram showing a structure of a buried cable position measuring device according to an embodiment of the present invention.

FIG. 2 shows a buried cable 1 and a transmission coil 3a according to this embodiment;
FIG. 4 is a cross-sectional view illustrating a relationship between 3b and a receiving coil 4.

FIG. 3 is a cross-sectional view illustrating a magnetic field generated at a position of a cable 1 by each magnetic pole of transmission coils 3a and 3b of the present embodiment.

FIG. 4 is a cross-sectional view illustrating a magnetic field generated at the position of the cable 1 by each magnetic pole of the transmission coils 3a and 3b of the present embodiment.

FIG. 5 is a perspective view illustrating a magnetic field generated at a position at an equal distance from the magnetic pole of each of the transmission coils 3a and 3b according to the present embodiment.

FIG. 6 is a perspective view illustrating a magnetic field generated at a position at an equal distance from the magnetic pole of each of the transmission coils 3a and 3b according to the present embodiment.

FIG. 7 is a plan view illustrating a positional relationship between the transmission coils 3a and 3b and the reception coil 4 according to the present embodiment.

FIG. 8 is a cross-sectional view illustrating the relationship among the buried cable 1, the transmission coils 3a and 3b, and the reception coil 4 during depth measurement according to the present embodiment.

FIG. 9 shows transmission coils 3a and 3b at the time of depth measurement according to the present embodiment.
FIG. 3 is a cross-sectional view illustrating a magnetic field generated at the position of the cable 1 by each magnetic pole.

FIG. 10 is a cross-sectional view illustrating the relationship among the buried cable 1, the transmission coils 3a and 3b, and the reception coil 4 during depth measurement according to the present embodiment.

FIG. 11 shows transmission coils 3a and 3 during depth measurement according to the present embodiment.
FIG. 4 is a cross-sectional view for explaining a magnetic field generated at the position of the cable 1 by each magnetic pole b.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cable 2 Ground 3a Transmission coil 3b Transmission coil 4 Receiving coil 5 Transmitting circuit 6 Receiving circuit 7 Arithmetic circuit 8 Display circuit 9 Input section

Claims (1)

(57) [Claims] 1. Two transmission coils, each center of which is located at the same height, arranged in parallel with a space therebetween, and differentially connected, and a combined magnetic field of the two transmission coils becomes zero. When the center is located at a position and the receiving coil integrally disposed with the two transmitting coils is rotated by a predetermined angle around a straight line connecting the centers of the two transmitting coils as the rotation center axis, the reception is performed. A buried cable position measuring method for measuring a buried depth of a buried cable based on a magnetic field received by a coil.