JPS61170689A - Detector for joint position of buried cast iron pipe - Google Patents

Abstract

PURPOSE:To detect easily and surely the joint position of a pipe by moving a magnetic sensor along the pipe, comparing the pattern of a detection signal with a standard pattern, discriminating the presence or absence of the joint and calculating thereafter the joint position by arithmetic operation. CONSTITUTION:The magnetic sensor 1 is moved by a moving means 3 along the cast iron pipe 4 and the differential signal which is shifted in the phase is outputted therefrom. The pattern of the differential signal and the change pattern stored in a storage means 7 are compared and collated by a means 8 for calculating the joint position and whether the patterns coincide or not is discriminated. The means 8 calculates the position of the joint 9 by the arithmetic operation using the relation between the magnetic pole position and the end position of the pipe 4 if both patterns coincide and the joint 9 exists within the moving section of the sensor 1.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is used to detect the position of a joint when there is a need to know the position of a joint for maintenance management of buried cast iron pipes for city gas supply, etc. (Conventional technology and its problems) A so-called metal detection device is a conventional device that can detect buried cast iron pipes. This device mainly utilizes the property that the earth's magnetism is affected by buried metal lumps, causing disturbances and local changes.This disturbance is detected by a differential magnetic sensor, and the signal is detected for signals exceeding a certain amount. This system generates sound with a frequency corresponding to the amount of sound, and it is known that metal exists under the place where the highest frequency is generated. However, although this device works effectively on things like constituent soil clods, when it comes to long objects like pipes, it reacts strongly only near the ends, causing the device to act as if there were two lumps. Effective detection is difficult because the way the earth's magnetic field is disturbed varies greatly depending on the relative angle between the axial direction of the tube and the direction of the earth's magnetic field. In particular, in the case of buried cast iron pipes that connect many pipes, disturbances in the geomagnetic field do not appear at each connection point, that is, at the joint position, and the cast iron pipes have their own residual magnetism that cannot be detected by the magnetic sensor. Although an acoustic change appears, the poles of residual magnetism do not match the joint position, and there is also interaction between the poles of adjacent pipes, so it is difficult to detect the joint position with the metal detector. be.

The present invention is configured by rationally using a differential magnetic sensor,
The purpose of this invention is to enable detection of the joint position of a buried cast iron pipe, which is difficult to detect with the conventional metal detection devices described above.

(Means for Solving the Problems) In order to achieve the above-mentioned objects, the present invention provides a differential magnetic sensor, a means for moving the magnetic sensor, a position sensor, and a relationship between the signals of the magnetic sensor and the position sensor. measurement and recording means for measuring and recording the signal of the magnetic sensor as a change pattern with respect to position; and storage means for storing a standard pattern for comparison with the measured and recorded change pattern.

The gist of the present invention is to provide a joint position calculation means for calculating the joint position, and a means for outputting the results of the calculation. A detailed explanation will be given below based on an example.

Reference numeral 1 denotes a differential magnetic sensor, and the magnetic sensor 1 has a pair of sensor parts 2 and 2' separated by an appropriate distance.

Reference numeral 3 denotes a means for moving the magnetic sensor 1, and the moving means 3 is configured as a cart, for example, as shown in the figure. This transportation means 3
is made of non-magnetic material in order not to disturb the surrounding static magnetism. The direction of the differential magnetic sensor 1 when moving by the moving means 3 is arbitrary. For example, in FIG. 1, the differential magnetic sensor 1 is installed in the moving means 3 so that the direction connecting the sensor parts 2 and 2' is parallel to the axial direction of the cast iron pipe 4, but the sensor part It may be installed so that the direction connecting 2 and 2' is perpendicular to the axial direction.

It may be installed at an appropriate angle between these. Also sensor 2,
The distance between 2' may be fixed or adjustable. Next, reference numeral 5 denotes a position sensor provided on the moving means 3, and this position sensor 5 detects the position of the magnetic sensor 1 during movement.

The specific configuration of the position sensor 5 may be arbitrary, such as a pulse type or a hood type. Reference numeral 6 denotes a measuring and recording means for correlating the signals of the magnetic sensor 1 and the position sensor 5 and measuring and recording the signal of the magnetic sensor 1 as a change pattern for one position. In addition to the pattern of the level itself, it may be a pattern in which this pattern is subjected to mathematical processing such as differential processing, filter processing, level expansion/reduction, reference axis correction, or graphical conversion processing. Reference numeral 7 denotes a storage means for storing a standard pattern for comparison with the measured and recorded change pattern, and the standard pattern is created by prior measurement or the like. This standard pattern can be created in an appropriate format corresponding to the format of the measured and recorded change pattern.

Reference numeral 8 denotes a joint position calculation means for comparing and collating the measured and recorded change pattern with the standard pattern, determining the presence or absence of a joint 9 based on whether or not they match, and calculating the position of the joint 9 when it is present. 10 is such a judgment.

This is a means for outputting calculation results. The output means 10 is a display device or a printer that displays the judgment and calculation results numerically and graphically on a CRT or liquid crystal display.

A recording device such as a memory device is appropriately selected and configured. In addition, the above measurement recording means 6. The storage means 7° joint position calculation means 8 and the output means 10 can be constructed by a microcomputer system.

(Function) In the above configuration, when the differential magnetic sensor 1 is moved along the cast iron pipe 4 by the moving means 3 as shown in FIG. A pair of detection signals on the same curve shifted from each other is obtained, and the magnetic sensor 1
outputs these difference signals. Although the detection signal pair is depicted as a sine wave in the figure, the actual signal pair has a complicated shape influenced by many magnetisms other than the cast iron pipe 4.

However, since the influence on the magnetic sensor 1 from a place farther away than the cast iron pipe 4 appears in the same shape on each sensor section 2, 2', it is canceled out and almost eliminated in the difference signal between them. . By moving the magnetic sensor 1 in this manner, the measurement recording means 6 records a change pattern of the detection signal with respect to the position of the magnetic sensor 1.

By the way, the cast iron pipe 4 is magnetized by the influence of the magnetic field around the pipe 1 during the manufacturing process, but the inventors (・well, that N-8
It was discovered that the poles do not appear at both ends like a normal bar magnet, but appear at a position 15 to 20% of the total length from the end.

Therefore, the change pattern of the detection signal from the magnetic sensor 1 itself becomes a curve that has a peak on the positive and negative sides on the magnetic pole appearing at the position, and then passes through a zero point between the magnetic poles and reverses the polarity.

Of course, this change pattern depends on the condition of the cast iron pipe 4,
It varies depending on conditions such as the relative positional relationship such as the angle of the magnetic sensor 1 with respect to the distance, and the distance between the sensor sections 2 and 2'.

Therefore, in the present invention, the standard pattern stored in the storage means 7 according to such conditions and the measured and recorded variation pattern are compared and verified by the joint position calculation means 8, and it is determined whether or not they match. The presence or absence of the joint 9 can be determined by comparing the two patterns, which may be performed on the entire pattern, or after performing the above-mentioned processes to more clearly express the characteristics of the joint 9. You can also do it with The latter allows for more reliable determination and calculations described below.If the two patterns match in this way and the joint 9 is present within the movement range of the magnetic sensor 1, the joint position calculation means 8 then performs the above-mentioned calculation. The position of the joint 9 can be calculated by calculation using the relationship between the magnetic pole position and the end position of the cast iron pipe 4, that is, the position of the joint 9. The above judgment and calculation results can be displayed or recorded via the appropriate output means 10 as described above.

Comparisons, reproductions, etc. can also be made later.

In the above case, a large number of standard patterns that serve as standards for the comparison and verification are stored in the storage means 7 in accordance with the various conditions, and one of the measurement conditions is selected depending on the conditions near the section to be measured. It is also possible to select the

It is also possible to select a plurality of measurement conditions. By doing this, the sensitivity can be improved depending on the amount of residual magnetism of the cast iron pipe 4, the depth of burial, etc.

Effects such as making the shape of the pattern clear can be measured, and in the latter case in particular, the influence of disturbances can be reduced and detection accuracy can be improved.

(Effects of the Invention) As described above, the present invention does not detect the entire joint based only on the high and low levels of the detection signal of the differential magnetic sensor, but also moves the magnetic sensor along the cast iron pipe using a moving means. The change in the level of the detection signal due to movement is grasped as a pattern for one position, and the presence or absence of a joint is determined by comparing this pattern with a standard turn prepared in advance.

Since the joint position is then calculated by calculation, the joint position, which has been extremely difficult to detect with conventional metal detectors, can be easily and reliably detected.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the overall configuration of the present invention, FIG. 2 is a detailed explanatory diagram of the present invention, and FIG. 3 is an illustration of a conventional example. Code 1...Magnetic sensor, 2.2'...Sensor part, 3
...Moving means, 4...Cast iron pipe, 5...Position sensor, 6...Measurement recording means, 7...Storage means, 8...
Joint position WI! Calculation means, 9...Joint, 10...Output means.

Claims (1)

[Claims] A differential magnetic sensor, a moving means for the magnetic sensor, a position sensor, and a measurement recording means for associating the signals of the magnetic sensor and the position sensor and measuring and recording the signal of the magnetic sensor as a change pattern with respect to position. , a storage means for storing a standard pattern for comparison and comparison with the measured and recorded change pattern; and a storage means for comparing and comparing the measured and recorded change pattern with the standard pattern, and determining the presence or absence of a joint based on whether or not they match. , a joint position detection device for a buried cast iron pipe, characterized in that it is provided with a joint position calculation means for calculating the position when there is a joint position, and a means for outputting the determination and calculation results.