JPH09126767A - Position detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a measurement error of magnetic field intensity so as to improve precision in position detection of an object to be measured by preventing generation of induced current in the object to be measured. SOLUTION: A magnetic field generating device 1 provided with a transmitting coil 3 generating a magnetic field and an oscillator 4 supplying alternating current to the transmitting coil 3 is arranged in an observation reference position, the first receiving coil 8 and the second receiving coil 9 detecting the magnetic field generated from the magnetic field generating device 1 are inserted into a leading pipe 7, and the position of the leading pipe 7 is detected on the basis of the magnetic field intensity measured by the first and the second receiving coils 8, 9. A slit 14, which cuts off induced current generated in the outer circumference direction of the leading pipe 7 by means of the magnetic field of the transmitting coil 3, is formed in the leading pipe 7, and alternating current is fed to the transmitting coil 3 so as to generate a magnetic field, and then, intensity of the magnetic field is detected by means of the first and the second receiving coils 8, 9 in the leading pipe 7, and as a result, a relative position between the observation reference position and the leading pipe 7 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting method for measuring a magnetic field strength to detect a position between two points.

[0002]

2. Description of the Related Art Conventionally, in this type of position detecting method, a magnetic field generator is provided on one of the underground excavators at a reference position, and at the same time, a boring device (lead pipe) for the other underground excavator, which is the object to be measured. ) Is provided with a magnetic field detector, and the magnetic field generated by the magnetic field generator is detected by the magnetic field detector to measure the amount of relative displacement between one underground excavator and the other underground excavator. Japanese Unexamined Patent Publication (Kokai) No. 3-257316 discloses, for example, Japanese Patent Laid-Open No. 3-257316, in which a non-magnetic stainless steel is used for the tip pipe of the underground excavator and the influence of a magnetic substance on the magnetic field is suppressed.

[0003]

However, the present inventor has found that the above-described position detecting method has the following problems. That is, since the tip pipe of the underground excavator is made of stainless steel and has conductivity,
An induced current is generated in the outer peripheral direction of the leading conduit, and an induced magnetic field is generated in the direction opposite to the direction of the magnetic force lines of the magnetic field generated by the magnetic field generator. Therefore, the magnetic field inside the leading conduit is affected by the induced magnetic field, and the magnetic field strength is reduced. As a result, an error occurs in the measurement of the magnetic field strength, and the position detection accuracy of the object to be measured decreases.

The object of the present invention is to solve the above-mentioned problems.
It is an object of the present invention to provide a position detection method capable of reducing the measurement error of the magnetic field strength and improving the position detection accuracy of the measured object by preventing the generation of the induced current in the measured object. The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0005]

The outline of the invention disclosed in the present application will be briefly described as follows.
The position detection method of the present invention installs a magnetic field generation device including a transmission coil that generates a magnetic field at an observation reference position and an oscillator that supplies an alternating current to the transmission coil, and the magnetic field generation device from the magnetic field generation device A position detecting method in which a magnetic field detecting device having a receiving coil for detecting a generated magnetic field is inserted, and a position of the measured object is detected based on a magnetic field intensity measured by the magnetic field detecting device, the transmission to the measured object is performed. A slit for blocking an induced current generated in the outer peripheral direction of the object to be measured by the magnetic field of the coil is formed, an alternating current is applied to the transmitting coil, and a magnetic field is generated. The measurement is performed by the magnetic field detection device, and the relative position between the observation reference position and the object to be measured is detected.

Therefore, by forming a slit in the object to be measured and cutting off the induced current generated in the outer peripheral direction of the object to be measured by the magnetic field of the transmitting coil, the object to be measured is directed in the direction opposite to the magnetic field generated by the magnetic field generator. Generation of induced magnetic field, that is, induced noise, is prevented. Therefore, the measurement error of the magnetic field strength is reduced, and the detection accuracy of the position of the measured object is improved.

[0007]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. Here, FIG. 1 is a schematic configuration diagram of a position detection system according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a front conduit according to an embodiment of the present invention. Also, components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

In FIG. 1, in the position detection system, a magnetic field generator 1 is installed at an observation reference point (a target point of arrival of an excavator) in the ground. In the magnetic field generator 1, a transmission coil 3 for generating an alternating magnetic field having a predetermined frequency is mounted on a substantially L-shaped base 2, and the transmission coil 3 is provided above the transmission coil 3.
An oscillator 4 for supplying an alternating current is disposed in the transmission coil 3, and the transmission coil 3 and the oscillator 4 are connected by a conductive wire 5.

On the other hand, a tip conduit 7 is connected to the rear of the drill head 6 attached to the tip of the excavator to be measured,
A first receiving coil 8 and a second receiving coil 9 for detecting the magnetic field of the transmitting coil 3 are provided in the front conduit 7. The first and second receiving coils 8 and 9 are arranged so as to be separated from each other by a predetermined distance in the axial direction of the front conduit 7, and to have the center of the magnetic detection surface on the axial line. The first and second receiving coils 8 and 9 are connected to the first and second magnetic field strength meters 10 and 11, respectively, by the signal transmission cables 12 and 1, respectively.
3 are connected.

The first and second receiving coils 8 and 9 are also provided.
A slit 14 that blocks the induced current A due to the magnetic field of the transmitter coil 3 is formed in the longitudinal direction of the upper leading conduit 7. The slit 14 is closed by a member having no conductivity such as resin or ceramic in order to prevent dirt and water from entering the front conduit 7. Next, a position detecting method by the position detecting system will be described.

First, when an alternating current is applied to the transmitting coil 3 from the oscillator 4, the transmitting coil 3 generates a magnetic field. After that, the first receiving coil 8 and the second receiving coil 9 receive the magnetic field strength of the transmitting coil 3 and output an electric signal corresponding to the magnetic field strength to the first and second magnetic field strength meters 10, 1.
1 respectively.

Measuring signals of the magnetic field strength of the first and second magnetic field strength meters 10 and 11 and the first and second receiving coils 8 and
From the distance of the line segment connecting the nine, obtain the inclination angle of the line segment,
The displacement of the excavator with respect to the observation reference point and the distance between the two are detected from the inclination angle and the forward distance of the excavator.
In this case, since the slit 14 is formed in the longitudinal direction of the front conduit 7, the magnetic field of the transmitter coil 3 causes the front conduit 7 to move.
The induced current A generated in the outer peripheral direction of is cut off by the slit 14. As a result, an induced magnetic field in the axial direction of the front conduit 7, that is, an induced magnetic field (induced noise) in a direction opposite to the magnetic field generated by the magnetic field generator 1 is prevented from being generated by the induced current A. Therefore, the measurement error of the magnetic field strength is reduced, and the detection accuracy of the position of the front conduit 7 (object to be measured) can be improved.

As described above, the invention made by the present inventor is
Although the present invention has been specifically described based on the embodiments, it goes without saying that the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention.
Although the material of the leading conduit is not specified in this embodiment, the detection accuracy can be further improved by using a non-magnetic material such as stainless steel. Further, in the present embodiment, the slits are formed only at one place, but by forming the plurality of slits at symmetrical positions, the detection accuracy can be further improved.

[0014]

The effects obtained by the invention disclosed in the present application will be briefly described as follows.
According to the present invention, a slit is formed in the object to be measured, and the induced current generated in the outer peripheral direction of the object to be measured is blocked by the magnetic field of the transmission coil, so that the generation of the induced magnetic field (induced noise) in the object to be measured is prevented. Therefore, it is possible to improve the detection accuracy of the position of the measured object with respect to the observation reference position.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a position detection system used in a position detection method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a front conduit used in a position detecting method according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic field generator 2 Base 3 Transmitting coil 4 Oscillator 5 Conducting wire 6 Drill head 7 Leading conduit 8 First receiving coil 9 Second receiving coil 10 First magnetic field strength meter 11 Second magnetic field strength meter 12, 13 Signal Transmission cable 14 Slit A Induced current

Claims (1)

[Claims] 1. A magnetic field generator provided with a transmitter coil for generating a magnetic field at an observation reference position and an oscillator for supplying an alternating current to the transmitter coil, and a magnetic field generated by the magnetic field generator inside an object to be measured. In a position detection method of inserting a magnetic field detecting device having a receiving coil for detecting, and detecting the position of the measured object from the magnetic field strength measured by the magnetic field detecting device, the measured object has a magnetic field of the transmitting coil. By forming a slit for blocking an induced current generated in the outer peripheral direction of the measured object by applying an alternating current to the transmission coil to generate a magnetic field, the strength of the magnetic field is detected by the magnetic field detection in the measured object. A position detecting method, which comprises measuring with a device and detecting a relative position between the observation reference position and the object to be measured.