JPH07122672B2 - Magnetic field distribution measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention magnetically detects the configuration of an electrically conductive piping system buried in the ground, such as a gas pipe, a power cable or a telephone cable. The present invention relates to a device for measuring a planar distribution of a magnetic field, which is used for that purpose.

(Prior Art) A conventional method for detecting the position of an electrically conductive buried pipe, buried cable, or the like (hereinafter generically referred to as a buried pipe) buried in the ground, that is, the position directly above and the buried depth. For this reason, the magnetic detection method is often used because it is simple and has relatively high detection accuracy and can be applied to various places. In such a magnetic detection method, the method most often used is to apply an alternating current to the buried pipe and detect from the distribution of the magnetic field created by this alternating current on the ground surface.In this case, the alternating current is applied to the buried pipe. There are a direct method in which an alternating current source is directly connected and flowing, and an indirect method in which an induction current is generated in a buried pipe by utilizing electromagnetic induction.

The conventional method will be briefly described with reference to the accompanying drawings. First, in the method shown in FIG. 7, a pair of magnetic sensors S1 and S2 having similar magnetic detection characteristics are arranged so that their detection directions are parallel to each other. Then, the detector L that is integrally formed with a fixed distance d is used. According to this method, the magnetic field components in the horizontal direction are detected by the magnetic sensors S1 and S2 while moving the detector L along the ground surface E, and the position where the detected magnetic field becomes maximum is the position directly above the buried pipe P. Judgment, and then from the outputs B1 and B2 of the magnetic sensors S1 and S2, the buried depth r1
Is calculated.

r1 = d × B2 / (B1-B2) Next, the method shown in FIG. 8 uses a detector L'provided with a single magnetic sensor S. This method is similar to the above-mentioned method. While moving the detector L ′ along the ground surface E, the magnetic sensor S detects the horizontal magnetic field component, and after determining that the position where the detected magnetic field is maximum is the position directly above the buried pipe P, The detector L'is further moved until the output of the sensor S becomes half of the maximum detection output, and the moving distance is detected as the embedding depth r1. It is shown by the following equation that the horizontal magnetic field component B3 at a point horizontally separated by the embedding depth r1 from the position just above is half of the maximum detection magnetic field B1 at the position just above.

Since the latter method uses a single magnetic sensor, it has the advantage of not causing an error due to the difference in the characteristics of the pair of magnetic sensors, unlike the former method, but it has a maximum magnetic field in order to obtain the burial depth. The sensor has to be moved again after the detection, which has a drawback that the measurement operation is complicated.

(Problems to be Solved by the Invention) In the conventional method described above, for a piping system that spreads two-dimensionally or three-dimensionally, in each case, every point While measuring the magnetic field, it is assumed that the buried pipe exists alone in a straight line, and that the magnetic field created around it has a cylindrical distribution. It is detecting.
However, in the actual piping system, it is rare that the buried pipe exists alone in a straight line.Therefore, there is a branch pipe, and it is raised or lowered to avoid other buried pipes. It composes a complicated piping system, and the distribution of the magnetic field is complicated in such a piping system.Therefore, the detection error of the position directly above the buried pipe becomes large, and the There is a problem that the error in the calculation of the burial depth on the premise of detection also becomes large, and the operator cannot know the degree of the error.

In order to solve the above-mentioned problems, the present inventor applies an alternating current directly or indirectly to an electrically conductive piping system buried in the ground, and the magnetic field created on the surface of the ground causes the piping to flow. In the method for detecting a system, a distribution of the magnetic field on a plane parallel to the surface of the earth is measured as a component in which two axes are orthogonal to each other in the three axial directions, and from the plane distribution of at least one of the components, A method for detecting a piping system was proposed in another application. (Refer to the description and drawings attached to the application for the patent application (1) filed on July 9, 1988.) The measurement of the plane distribution of the magnetic field component can be performed, for example, by measuring a magnetic sensor having a corresponding detection axis on a plane. It may be arranged vertically and horizontally, or a plurality of magnetic sensors having corresponding detection axes may be provided in a row, and the magnetic sensors may be moved in a direction perpendicular to the row direction, or a single detection axis may be provided. Alternatively, it can be performed by scanning a small number of magnetic sensors vertically and horizontally on a plane.

The method of (1) allows the fastest measurement because it does not need to move the magnetic sensor at all, but it has the advantage and disadvantage that the device becomes very large, and the method of (2) has the minimum number of magnetic sensors. Therefore, it is economical, but there is a trade-off that it takes too long to move.

An apparatus to which the above method or method, especially the method is applied,
That is, an apparatus in which a sensor unit that stores a plurality of magnetic sensors is provided in a protruding manner in the lateral direction of the apparatus main body that is configured to be movable by the moving means can perform measurement relatively efficiently and is practical.

However, in such a device, if the projecting length of the sensor unit is increased in order to increase the lateral width that can be measured at one time, it is inconvenient to carry, and it becomes impossible to perform measurement in a place where the road width of the measurement site is narrow. If the protruding length of the sensor unit is shortened in order to prevent this, the horizontal width that can be measured at one time becomes narrow, a wide planar distribution cannot be obtained, and the detection accuracy of the buried pipe, especially deep buried There is a problem that the detection accuracy of the pipe becomes poor.

The present invention aims to solve the above problems.

(Means for Solving the Problems) The structure of the present invention will be described with reference to FIGS. 1 to 6 corresponding to the embodiments. First, the apparatus according to claim 1 is a plane of a magnetic field. In a device for measuring distribution, a sensor unit accommodating a magnetic sensor is provided in a protruding manner in a lateral direction of a device body configured to be movable by a moving means, and a bending portion is configured in the sensor unit to enable folding. It is composed.

Next, the device described in the second item is the same as the device described in the first item,
The refraction direction of the sensor unit in the refraction part is horizontal.

Next, the device described in the third item is the same as the device described in the first item,
The refraction direction of the sensor unit in the refraction section is the vertical direction.

Next, the device described in the fourth item is the same as the device described in the first item,
The refraction part is formed in one place of the sensor unit.

Next, the device described in the fifth item is the same as the device described in the first item,
The refraction part is formed at a plurality of locations in the sensor unit.

Next, the device described in the sixth item is the same as the device described in the first item,
The sensor unit is provided with means for detecting folding.

Next, in the device described in the seventh item, in the device of the first item, the sensor unit is provided with a means for fixing in a folded state.

(Operation and Embodiment) The operation of the present invention as described above will be described below with reference to the drawings corresponding to the embodiment.

In FIG. 1, reference numeral 1 indicates an apparatus main body configured to be movable by a moving means 2 such as a wheel.
The sensor unit 4 storing the magnetic sensor 3 in the lateral direction of the
The sensor unit 4 is provided with a refraction portion 5 so as to be foldable. In the device body 1, a signal processing system 6 for processing a magnetic detection signal from the magnetic sensor 3 to derive a planar distribution of a predetermined magnetic field, a display means 7 for measuring results, and the like,
The control means 8 and a part of the magnetic sensor 3 are stored. Further, the apparatus main body 1 is provided with a handle 9 for moving it by the moving means 2, a driving means such as an electric motor, and a movement amount detecting means 10 such as an encoder. The magnetic sensor 3 stored in the sensor unit 4 is, for example, as shown in FIG.
As shown in FIG. 2, the two axes have detection axes X, Y, and Z in the directions of three orthogonal axes that are in the horizontal plane, and a plurality of them are arranged in the sensor unit 4 with the detection axes aligned. As a result, the magnetic field can be detected at a plurality of locations along the sensor unit 4. Although not shown, the magnetic sensor 3 is singular or small in number, and is configured to be movable along the sensor unit 4 so that the magnetic field can be detected at a plurality of locations along the sensor unit 4. It may be configured. Of course, the magnetic sensor 3 does not have to have a configuration having detection axes in all three orthogonal directions.
Further, in the illustrated example, the sensor unit 4 is the device main body 1
Although the protrusions are provided on both sides, the configuration may be such that only one side is provided.

In the above configuration, by moving the device body 1 on the ground surface along the buried pipe estimated based on, for example, the description of the piping diagram, the detection AC current flowing in the buried pipe is on the ground surface. It is possible to measure a plurality of magnetic fields generated along the sensor unit 4 at regular intervals, and a predetermined amount is determined from the measurement of the magnetic field and the amount of movement of the apparatus body 1 that can be measured by the movement amount detecting means 10 such as the encoder. It is possible to measure the planar distribution of the magnetic field in the range.

At this time, when the road width or the like at the measurement site is narrow and the sensor unit 4 cannot move as shown in FIG. As shown by a solid line in FIG. 4B or an imaginary line in FIG. 4B, the sensor unit 4 portion on the tip side of the bending portion 5 is folded toward the apparatus main body 1 side and an appropriate fixing means (not shown) is provided. ), The sensor unit 4 is fixed in this state, and the lateral projection length of the sensor unit 4 as a whole is shortened in this way to narrow the lateral width of the entire device. With the magnetic sensor 3 in 4, the above-mentioned measurement can be performed even in a narrow space.

The refraction direction of the sensor unit 4 in the refraction part 5 is the first
It may be vertical as shown in FIGS. 3, 3 and 5, or may be horizontal as shown in FIG. Further, the refraction part 5 can be formed at one place as shown in FIGS. 1, 3, and 4, or at two places or more as shown in FIG. In the case of the latter configuration, the lateral projection length of the sensor unit 4 and the lateral width of the entire device can be adjusted in smaller increments, which makes it more appropriate in a measurement site of various widths. It can be adjusted.

Next, if the sensor unit 4 is folded in all the refraction parts 5, the lateral width of the entire device becomes the smallest, and it becomes easy to carry. Not only in the sensor unit 4 protruding laterally from the device body 1, but also in the device body 1,
In the configuration in which the sensor unit 4 and the series of magnetic sensors are provided, it is possible to perform the measurement in the above-mentioned holding state.

FIG. 6 is a system explanatory view showing an example of a measuring system in the device of the present invention. This measuring system uses a multiplexer 11 to convert a plurality of signals from a plurality of magnetic sensors 3 into an A / D converter. 1
2, the output signal of the A / D converter 12 and the output signal of the movement amount detecting means 10 are processed by the CPU 13, and a predetermined processing result is displayed on the display means 7. Further, the sensor unit 4 is provided with a folding detection switch 14 such as a mechanical type or a magnetic type for each of the refraction portions 5, etc., and an effective magnetic sensor 3, that is, an unfolded sensor is provided by a signal from the folding detection switch 14. Identify the magnetic sensor 3 in the unit 4,
Based on this, by performing the above-described measurement only with the effective magnetic sensor 3, it is possible to prevent the inconvenience that the output of the magnetic sensor 3 whose detection axis does not face the predetermined direction is taken into the measurement system.

(Effect of the invention) As described above, according to the present invention, a sensor unit is provided so as to project in the lateral direction of the apparatus main body configured to be movable by the moving means, and the sensor unit is provided by one or a plurality of magnetic sensors stored in the sensor unit. Since it is possible to measure the magnetic field at multiple points along the unit, measure the magnetic field created by the alternating current flowing in the buried pipe system on the ground surface by performing such measurement while moving the main body of the device. Therefore, there is an effect that even in a complicated piping system in which there are branches, rises, and falls, it is possible to measure them with high accuracy. In particular, according to the present invention, since the sensor unit is provided with a refraction portion so as to be foldable and the sensor unit can be folded or unfolded, the protrusion length of the sensor unit, that is, the lateral width of the entire device can be adjusted. , It is possible to carry out appropriate measurement at any time regardless of the width of the road at the measurement site, etc. Also, folding the sensor unit in all the refraction parts has the effect of making it easy to carry. . Thus, the present invention makes it possible to increase the efficiency of excavation work for buried pipes such as gas pipes and water pipes, and at the same time prevent accidents due to damage to the buried pipes due to erroneous excavation, thus ensuring safety. It has a great effect on the economic and economic aspects.

[Brief description of drawings]

FIG. 1 is an explanatory perspective view showing an example of the constitution of the present invention, and FIG.
FIG. 2A is an explanatory perspective view showing an example of a single magnetic sensor applied to the apparatus of the present invention, and FIG. 2B is an example of an arrangement method of a plurality of magnetic sensors in a sensor unit of the apparatus of the present invention. It is an explanatory plan view showing. Figure 3 (a), (b)
Is an explanatory front view showing the operation of the apparatus of FIG. 1, FIG. 4 is an explanatory perspective view showing another example of the constitution of the present invention, and FIGS. 5 (a) and 5 (b) are constitutions of the present invention. FIG. 6 is a schematic front view showing still another example of FIG. 6, and FIG. 6 is a system explanatory view showing a magnetic field measurement system in the apparatus of the present invention. Further, FIG. 7 (a),
(B), FIG. 8 (a), (b) is an explanatory view showing a conventional buried pipe detection method. Reference numeral 1 ... Device body, 2 ... Moving means, 3 ... Magnetic sensor, 4 ... Sensor unit, 5 ... Refraction part, 6 ... Signal processing system, 7 ... Display means, 8 ... Control means, 9 ... Handle, 10 ... Moving amount detecting means, 11 ... Multiplexer, 12
…… A / D converter, 13 …… CPU, 14 …… Folding detection switch.

Claims (7)

[Claims] 1. An apparatus for measuring a planar distribution of a magnetic field, comprising:
A magnetic field is characterized in that a sensor unit accommodating a magnetic sensor is projectingly provided in a lateral direction of an apparatus main body that is configured to be movable by a moving unit, and that the sensor unit includes a refraction portion and is configured to be foldable. Planar distribution measuring device 2. The apparatus for measuring the planar distribution of a magnetic field according to claim 1, wherein the refraction direction of the sensor unit in the refraction section is horizontal. 3. The apparatus for measuring the plane distribution of a magnetic field according to claim 1, wherein the refraction direction of the sensor unit in the refraction section is a vertical direction. 4. The apparatus for measuring the planar distribution of a magnetic field according to claim 1, wherein the refraction part is formed at one location of the sensor unit. 5. The apparatus for measuring the planar distribution of a magnetic field according to claim 1, wherein the refraction portion is formed at a plurality of locations on the sensor unit. 6. The apparatus for measuring the planar distribution of a magnetic field according to claim 1, wherein the sensor unit is provided with means for detecting folding. 7. The apparatus according to claim 1, wherein the sensor unit is provided with means for fixing the sensor unit in a folded state.