JP3620375B2 - Magnetic body installation method, magnetic marker, and vehicle information acquisition apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of installing a magnetic body used on a road for obtaining information represented by a magnetic field detected by a magnetic sensor mounted on a vehicle, a magnetic marker, and such a magnetic sign. The present invention relates to a vehicle information acquisition device that acquires information represented by a magnetic field generated from a body.
[0002]
[Prior art]
Conventionally, an automatic driving vehicle that performs steering control along a predetermined course set on a road has been proposed. In such an autonomous driving vehicle, the position (lateral position) of the vehicle in the width direction of the road is always detected, and steering control is performed based on the detected position so that the vehicle does not deviate from the predetermined course. I have to.
[0003]
As shown in FIG. 1, such an autonomous driving vehicle 10 is equipped with a magnetic sensor 12 that detects a magnetic field from a magnetic marker (magnetic marker) 100 laid on a predetermined course of a road R at a predetermined interval. doing. The magnetic field intensity from the magnetic marker 100 changes according to the distance from the magnetic marker 100. Accordingly, a deviation control (lateral position) of the vehicle 10 from the course is detected based on the magnetic field detected by the magnetic sensor 12, and the steering control is performed so as to guide the vehicle 10 onto the predetermined course based on the deviation. Is done.
[0004]
Incidentally, as described above, the magnetic marker 100 used for guiding the vehicle 10 based on the magnetic field intensity detected by the magnetic sensor 12 mounted on the vehicle 10 has, for example, a structure as shown in FIG. Then, as shown in FIG.
That is, in the magnetic marker 100, the magnet 120 is accommodated in a cylindrical case body 110 having a flange on the upper surface so as to fill the space of the case body 110. And the case body 110 is embedded in the road R so that the lower surface of the ridge may contact the road surface. As described above, since the magnetic marker 100 is embedded in the road R so that the position of the upper surface of the magnet 120 substantially matches the road surface position, the magnetic field strength at the road surface position can be obtained even with a relatively small magnet 120. Therefore, the magnetic sensor 12 of the vehicle 10 can detect a magnetic field strength (desired magnetic field strength) necessary and sufficient for detecting the position of the vehicle 10.
[0005]
[Problems to be solved by the invention]
By the way, it is generally known that the magnetic field intensity (vertical magnetic flux density) generated from the magnet 120 (magnetic material) attenuates in proportion to the cube of the distance from the magnet 120. Therefore, the intensity of the magnetic field generated from the magnetic marker 100 embedded as described above rapidly decreases as the distance from the road surface where the intensity becomes maximum is increased. In such a situation, a desired magnetic field strength can be obtained at a height position from the road surface of the magnetic sensor 12 installed in the vehicle 10, but the magnetic field strength on the road surface becomes relatively large and is scattered on the road surface ( Empty cans, nails, etc.) are easily attracted to the surface of the magnetic marker 100.
[0006]
Accordingly, a first problem of the present invention is to reduce the magnetic field strength on the road surface as much as possible while maintaining a state in which a desired magnetic field strength can be obtained at a height position from the road surface of the magnetic sensor installed in the vehicle. It is to provide a method for installing a magnetic material.
The second object of the present invention is to provide a magnetic marker that can be easily installed by such a magnetic substance installation method.
[0008]
[Means for Solving the Problems]
In order to solve the first problem, the present invention is used to obtain information represented by a magnetic field detected by a magnetic sensor mounted on a vehicle. In the method of installing a magnetic body on a road, the ratio of the distance from the magnetic body to the magnetic field strength is expressed as a distance-magnetic field strength point. On the contrary, the ratio of the change of the distance to the change of the magnetic field strength tends to be larger than the ratio of the change of the magnetic field strength to the change of the distance from the tendency of becoming larger than the change rate. The magnetic field generated by the magnetic body and its magnetic field strength should be installed so that the road surface is located at a distance from the magnetic body and the desired magnetic field strength can be obtained from the road surface at the installation height of the magnetic sensor. Configured to set the depth from the surface.
[0009]
The relationship between the magnetic field strength B generated from the magnetic material and the distance y is, for example, a curve connecting each distance-magnetic field strength point, which is a point determined by a pair of the magnetic field strength corresponding to the distance, as in the characteristic Q shown in FIG. Represented as: Such a characteristic Q can be regarded as attenuation such that the magnetic field strength B is proportional to the cube of the distance y from the magnetic material. In such a characteristic Q, at the distance-magnetic field strength point P1, the change rate of the magnetic field strength with respect to the change of the distance is larger than the change rate of the distance with respect to the change of the magnetic field strength. As the distance from the magnetic body increases (as the distance-magnetic field strength point P0 is approached), the rate of change in magnetic field strength with respect to the change in distance at each distance-magnetic field strength point decreases.
[0010]
On the other hand, at the distance-magnetic field strength point P2, the ratio of the change in the distance to the change in the magnetic field strength is larger than the ratio of the change in the magnetic field strength with respect to the change in the distance. As the distance from the magnetic body becomes smaller (as the distance-magnetic field strength point P0 is approached), the ratio of the change in distance to the change in magnetic field strength at each distance-magnetic field strength point becomes smaller.
[0011]
Therefore, in the above characteristic Q, the ratio of the change in the magnetic field strength with respect to the change in the distance tends to be larger than the ratio of the change in the distance with respect to the change in the magnetic field strength. There is a boundary distance-magnetic field strength point that changes to tend to be greater than the rate of change of the magnetic field strength. The distance between the boundary and the magnetic field strength point is a distance-magnetic field strength point P0 determined by the combination of the distance ym and the magnetic field strength Bm in the characteristic Q 1. This distance-magnetic field strength point P0 exists in a region where the characteristic curve Q expressed by the distance-magnetic field strength point is convex toward the origin 0 of the coordinate system.
[0012]
The road surface is located at a distance yR (≧ ym) from the magnetic body that is equal to or greater than the distance ym at the distance-magnetic field strength point P0, and a desired magnetic field strength Bs is obtained from the road surface at the installation height l1 of the magnetic sensor. Thus, the generated magnetic field strength Bo of the magnetic material and the depth l2 from the road surface to be installed are set.
In such a state, the magnetic field intensity generated from the magnetic material decreases rapidly between the distance l2 from the magnetic material embedded in the road to the road surface, while in the space from the road surface to the installation height l2 of the magnetic sensor. The change in magnetic field strength is relatively small. Therefore, the magnetic field strength BR on the road surface is relatively close to the desired magnetic field strength to be obtained at the installation height of the magnetic sensor. As a result, the magnetic field strength BR on the road surface can be reduced.
[0013]
In order to solve the first problem, the present invention provides a method for acquiring information represented by a magnetic field detected by a magnetic sensor mounted on a vehicle. In the method of installing the magnetic material used on the road, the distance from the magnetic material and the magnetic field strength at the distance from the magnetic material that is equal to or greater than the distance when the magnitude of the vector represented by the set is minimized. The magnetic field generated by the magnetic material and the depth from the road surface to be installed are set so that the desired magnetic field strength can be obtained at the installation height of the magnetic sensor from the road surface while the road surface is located at a distance. Composed.
[0014]
In the above-described characteristic Q (see FIG. 4) representing the relationship between the distance of the magnetic material and the magnetic field strength, a vector represented by a set of the distance y from the magnetic material and the magnetic field strength B at the distance y (y, The distance when B) is minimum is the distance ym at the point P0 on the characteristic Q. The magnetic field generated by the magnetic body is such that the road surface is located at a distance yR (≧ ym) from the magnetic body that is equal to or greater than this distance ym, and that the desired magnetic field strength Bs is obtained from the road surface at the installation height 11 of the magnetic sensor. The intensity Bo and the depth l2 from the road surface to be installed are set.
[0015]
In such a state, as in the case described above, the magnetic field intensity generated from the magnetic material decreases rapidly between the distance l2 from the magnetic material embedded in the road to the road surface, while the magnetic sensor is installed from the road surface. In the space up to the height l2, the change in magnetic field strength is relatively small. Therefore, the magnetic field strength BR on the road surface is relatively close to the desired magnetic field strength to be obtained at the installation height of the magnetic sensor. As a result, the magnetic field strength BR on the road surface can be made relatively small.
[0016]
Furthermore, in order to solve said 1st subject, this invention is for obtaining the information represented by the magnetic field detected by the magnetic sensor mounted in the vehicle, as described in Claim 3. In the method of installing the magnetic substance used on the road, the road surface is located at a distance from the magnetic substance at which the magnetic field intensity generated from the magnetic substance is ¼ or less, and the installation height of the magnetic sensor from the road surface. In order to obtain a desired magnetic field strength, the generated strength of the magnetic material and the depth from the road surface on which the magnetic material is to be installed are installed.
[0017]
A point on the characteristic curve Q (see FIG. 4) at which the intensity of the magnetic field generated from the magnetic material is ¼ is in the vicinity of the point P0. The road surface is located at a distance (for example, yR) from the magnetic body that is equal to or lower than the magnetic field strength at such a point, and the magnetic field strength is obtained so that a desired magnetic field strength can be obtained from the road surface at the installation height of the magnetic sensor. By setting the generated magnetic field Bo of the body and the depth from the road surface on which the body is to be installed, the magnetic field strength BR on the road surface can be made relatively small as in the case described above.
[0018]
In order to solve the second problem, the present invention acquires information represented by a magnetic field that is installed on a road and detected by a magnetic sensor mounted on a vehicle. In the magnetic marker used to do this, it has a cylindrical case body and a magnetic body accommodated in the case body, and the distance between the magnetic body and the upper surface of the case body is a distance from the magnetic body. In contrast, the ratio of the change in the magnetic field strength with respect to the change in the distance tends to be larger than the ratio of the change in the distance with respect to the change in the magnetic field strength. The distance change rate tends to be larger than the change rate of the magnetic field strength with respect to the change of the distance. The boundary distance is set to be equal to or greater than the distance at the magnetic field strength point, and is the same as the installation height of the magnetic sensor from the road surface. Away just as desired magnetic field intensity at a position spaced upwardly from the upper surface of the case body is obtained, configured to generate the magnetic field strength of the magnetic body is set.
[0019]
According to a fifth aspect of the present invention, in the magnetic marker used for acquiring information represented by a magnetic field installed on a road and detected by a magnetic sensor mounted on a vehicle, A case body and a magnetic body housed in the case body, and the distance between the magnetic body and the upper surface of the case body is a combination of the distance from the magnetic body and the magnetic field strength at that distance. Is set to be equal to or greater than the distance when the vector size is minimized, and at a position away from the upper surface of the case body by the same distance as the installation height of the magnetic sensor from the road surface. Thus, the generated magnetic field strength of the magnetic material is set so that a desired magnetic field strength can be obtained.
[0020]
Further, according to a sixth aspect of the present invention, in the magnetic marker used for acquiring information represented by a magnetic field installed on a road and detected by a magnetic sensor mounted on a vehicle, A case body and a magnetic body housed in the case body, and the distance between the magnetic body and the upper surface of the case body is such that the magnetic field intensity generated from the magnetic body is ¼ or less. The generated magnetic field strength of the magnetic body is set so that a desired magnetic field strength is obtained at a position away from the upper surface of the case body by a distance equal to the installation height of the magnetic sensor from the road surface. Configured to be set.
[0021]
According to each such magnetic marker, the magnetic marker is embedded in the road surface so that the upper surface of the case body coincides with the road surface, so that the road surface from the magnetic material embedded in the road as described above. The magnetic field intensity generated from the magnetic material decreases sharply during the distance 12 to reach, while the change in the magnetic field intensity is relatively small in the space from the road surface to the installation height 12 of the magnetic sensor.
[0022]
From the viewpoint that the magnetic body in the case body can be easily held without affecting the generated magnetic field, the present invention provides, as described in claim 7, the magnetic marker, the magnetic body and the case body. A nonmagnetic material can be accommodated in a space formed between the upper surface portion.
In addition, from the viewpoint of being able to absorb vibration transmitted from the road surface to the magnetic body, it is preferable that the non-magnetic body and the like are formed of an elastic member as described in claim 8.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The structure of a magnetic marker (magnetic marker) according to an embodiment of the present invention is, for example, as shown in FIG.
In the magnetic marker 100 shown in FIG. 5, for example, a rare earth (NdReB-based) magnet 112 is accommodated in a cylindrical case body 111 formed of a nonmagnetic material such as stainless steel or aluminum. Similar to the magnetic marker 100 shown in FIG. 2, a ridge is formed on the upper surface of the case body 111. The height of the magnet 112 is smaller than the length of the case body 111 in the vertical direction, and a non-magnetic body 113 serving as an elastic member such as urethane resin is filled between the upper surface of the magnet 112 and the upper surface portion of the case body 111. ing.
[0028]
The characteristic representing the relationship between the strength of the magnetic field generated from the magnet 112 of the magnetic marker 100 having the above structure and the distance is, for example, the characteristic Q1 shown in FIG. In this case, the generated magnetic field strength Bo (magnetic flux density) on the surface of the magnet 112 is 3.7 × 10 ⁻¹ Tesla (T), and the magnetic field strength Bs at a position of 240 millimeters (mm) from the surface of the magnet 112. Becomes the magnetic field intensity detected by the magnetic sensor 12 necessary for detecting the lateral position of the vehicle 10, for example, 2 × 10 ⁻⁴ Tesla (T).
[0029]
The installation height of the magnetic sensor 12 of the vehicle 10 is, for example, 190 millimeters (mm) from the road surface. In this case, the distance (240 mm) from the surface of the magnet 112 to a position where the magnetic field intensity (for example, 2 × 10 ⁻⁴ Tesla) necessary for detecting the lateral position of the vehicle 10 and the magnetic sensor of the vehicle from the road surface are obtained. The difference (50 millimeters) from the distance (190 millimeters) to the installation height of 12 is the distance from the surface of the magnet 112 to the road surface. That is, the distance from the upper surface of the magnet 112 to the upper surface portion of the case body 111 is 50 millimeters (mm).
[0030]
The magnetic marker 100 having the above structure is embedded in the road R as shown in FIG. That is, the case body 111 is embedded in the road R so that the lower surface of the bag of the case body 111 is in contact with the road surface. In this state, the distance l2 from the upper surface of the magnet 112 to the road surface is 50 millimeters (mm) (l2 = 50 mm). Further, since the distance l1 from the road surface to the magnetic sensor 12 of the vehicle 10 is 190 millimeters (mm) (l1 = 190 mm), the distance from the upper surface of the magnet 112 to the height position of the magnetic sensor 12 of the vehicle 10 is 240 millimeters. (Mm) (l1 + l2 = 240 mm). Therefore, when the vehicle 10 passes over the magnetic marker 100, the magnetic sensor 12 of the vehicle 10 calculates the magnetic field strength Bs (2 × 10 ⁻⁴ Tesla) necessary for detecting the lateral position of the vehicle 10. It can be detected.
[0031]
Thus, the magnetic field strength on the surface (exposed surface) of the magnetic marker 100 installed on the road R, that is, the magnetic field strength at a position away from the upper surface of the magnet 112 by 50 millimeters (mm) is 0.2 × 10 ^{−. 1} Tesla (T) (see characteristic Q1 shown in FIG. 7).
By embedding the magnetic marker 100 containing the magnet 112 having the characteristic Q1 in the above-described structure in the road R, the relationship between the distance from the magnet 112 and the magnetic field strength is expressed as a distance-magnetic field strength point (FIG. 7). (Refer to the above), the ratio of the change in the magnetic field strength with respect to the change in the distance tends to be larger than the change in the distance with respect to the change in the magnetic field strength. The road surface is located at a distance (50 millimeters) from the magnet 112 that is equal to or greater than the distance (20 millimeters) at the distance-magnetic field strength point P, which is a boundary that changes to a tendency to become larger than the ratio of the magnetic sensor 12. as desired magnetic field intensity at installation height (190 mm) (2 × ^{10 -4} Tesla) is obtained, of the magnet 112 Raw magnetic field (Bo = 3.7 × ^{10 -1} Tesla) and the depth from the installed road surface should be (50 millimeters) so that is set.
[0032]
Further, in the installation of such a magnet 112, when the magnitude of the vector represented by the set of the distance from the magnet 112 and the magnetic field strength at that distance is minimized (point P on the characteristic Q1 shown in FIG. 7). ) At a distance (50 mm) from the magnet 112 that is equal to or greater than the distance (20 mm), and a desired magnetic field strength (2 × 10) at the installation height (190 mm) of the magnetic sensor 12 from the road surface. ^-4 Tesla), the magnetic field intensity generated by the magnet 112 (Bo = 3.7 × 10 ⁻¹ Tesla) and the depth from the road surface to be installed (50 mm) are set. Also become.
[0033]
Furthermore, in the installation of such a magnet 112, a quarter of the magnetic field intensity (Bo = 3.7 × 10 ⁻¹ Tesla) generated from the magnet 112 (0.925 × 10 ⁻¹ Tesla: points in FIG. 7). The road surface is located at a distance (50 millimeters) from the magnet 112 that is equal to or less than the magnetic field strength in the vicinity of P), and the desired magnetic field strength (2 × 10 5) at the installation height (190 millimeters) of the magnetic sensor 12 from the road surface. ^-4 Tesla), the magnetic field intensity generated by the magnet 112 (Bo = 3.7 × 10 ⁻¹ Tesla) and the depth from the road surface to be installed (50 mm) are also set. Become.
[0034]
According to such an installation method of the magnetic marker 100, the change in the magnetic field strength in the road R (between the road surface and the depth of 50 mm) becomes very large (3.7 × 10 ⁻¹ Tesla → 0.2). × ^{10 -1} Tesla) on the other hand, the change in magnetic field strength in the space from the road surface to the magnetic sensor 12 is reduced (0.2 × ^{10 -1} Tesla → 2 × ^{10 -4} Tesla). The magnetic field intensity on the road surface is 0.2 × 10 ⁻¹ Tesla. With this magnetic field strength (magnetic flux density 0.2 × 10 ⁻¹ Tesla), it is difficult for magnetic materials such as empty cans and nails to be attracted to the surface of the magnetic marker 100, and even if they are attracted, they can be easily removed.
[0035]
The magnetic field intensity of each part when the magnetic marker 100 is installed on the road R according to a conventional installation method (see FIGS. 2 and 3) is shown as a comparative example.
The magnet 120 accommodated in the magnetic marker 100 has, for example, the characteristic Q2 shown in FIG. In this case, the magnetic field strength Bo on the surface of the magnet 120 is 1.3 × 10 ⁻¹ Tesla (T), and the magnetic field strength at a position of 190 millimeters (mm) from the surface of the magnet 120 is The detected magnetic field intensity at the magnetic sensor 12 necessary for detecting the directional position is, for example, 2 × 10 ⁻⁴ Tesla (T). In this case, since the magnetic marker 100 is installed so that the surface of the magnet 120 coincides with the road surface (see FIG. 3), the desired magnetic field strength of 2 × 10 ⁻⁴ Tesla is obtained at the installation height of the magnetic sensor 12. Is obtained. In this case, the magnetic field intensity on the surface of the magnetic marker 100 is 1.3 × 10 ⁻¹ Tesla.
[0036]
Therefore, according to the installation method of the magnetic marker 100 described in the above-described example (see FIGS. 5 and 6), the surface magnetic field of the magnetic marker 100 is smaller than that in the conventional installation method (see FIGS. 2 and 3). It can be much smaller (1 / 6.5).
Further, in the magnetic marker 100 according to the above-described example, the non-magnetic body 113 made of an elastic member such as urethane resin is housed between the magnet 112 housed in the case body 111 and the upper surface portion of the case body 111. The vibration transmitted from the road surface is absorbed by the nonmagnetic material 113. Therefore, the magnet 112 can be accommodated more stably in the case body 111.
[0037]
When embedding a magnetic marker on a so-called high-performance road R to which drainage pavement is applied, the following attention is required.
As shown in FIG. 8, the high function road R has a structure in which a base layer L1 and a surface layer L2 are laminated on a road bed L0. The surface layer L2 has drainage properties. And the waterproof layer L20 is provided between the surface layer L2 and the base layer L1 so that the water which permeate | transmitted the surface layer L2 which has drainage property does not approach into the base layer L1 and the road bed L0. With such a structure, water that has permeated through the surface layer L2 is guided to the drainage groove along the waterproof layer L20.
[0038]
When embedding the magnetic marker 100 on the high-performance road R having such a structure, it is unavoidable to install the magnetic marker 100 across the waterproof layer L20 (in the case of (2)) because the waterproof function is impaired. I must. Therefore, the magnetic marker 100 must be embedded in the surface layer L2 (in the case of (3)) or the base layer L1 (in the case of (1)).
[0039]
【The invention's effect】
As described above, according to the present invention according to claims 1 to 3, between the magnetic body embedded in the road and the road surface, the intensity of the magnetic field generated from the magnetic body depends on the distance. On the other hand, in the space from the road surface to the installation height of the magnetic sensor, the change according to the distance of the magnetic field strength is relatively small, and the magnetic field strength on the road surface is the magnetic field strength at the installation height of the magnetic sensor. Relatively close to. As a result, it is possible to reduce the magnetic field strength on the road surface as much as possible while maintaining a state in which a desired magnetic field strength can be obtained at a height position from the road surface of the magnetic sensor installed in the vehicle.
[0040]
Further, according to the present invention of claims 4 to 8, it is possible to realize a magnetic marker that can be easily installed by the above-described magnetic material installation method .
[Brief description of the drawings]
FIG. 1 is a diagram showing a relationship between a vehicle and a magnetic marker installed on a road.
FIG. 2 is a view showing an example of a conventional structure of a magnetic marker (magnetic marker).
FIG. 3 is a diagram showing an installation example of the magnetic marker shown in FIG. 2;
FIG. 4 is a characteristic diagram showing the relationship between magnetic field strength and distance of a general magnetic material.
FIG. 5 is a diagram illustrating a structure example of a magnetic marker according to an embodiment of the present invention.
6 is a diagram showing an installation example of the magnetic marker shown in FIG. 5. FIG.
7 is a characteristic diagram showing an example of characteristics of a magnet housed in the magnetic marker shown in FIG. 5 and a comparative example.
FIG. 8 is a diagram for explaining whether or not a magnetic marker embedding structure is possible;
[Explanation of symbols]
10 Vehicle 12 Magnetic Sensor 100 Magnetic Marker (Magnetic Marker)
111 Case body 112 Magnet 113 Non-magnetic body

Claims (8)

In a method for installing on a road a magnetic body used for acquiring information represented by a magnetic field detected by a magnetic sensor mounted on a vehicle,
In the characteristics that express the relationship between the distance from the magnetic body and the magnetic field strength as a distance-magnetic field strength point, the ratio of the change in the magnetic field strength with respect to the change in the distance is larger than the rate of the change in the distance with respect to the change in the magnetic field strength. Boundary distance where the rate of change in distance with respect to change in magnetic field strength tends to be greater than the rate of change in magnetic field strength with respect to change in distance-The road surface is located at a distance from the magnetic body that is equal to or greater than the distance at the magnetic field strength point In addition, a magnetic body installation method for setting the magnetic field intensity generated by the magnetic body and the depth from the road surface to be installed so that a desired magnetic field intensity can be obtained from the road surface at the installation height of the magnetic sensor. . In a method for installing on a road a magnetic body used for acquiring information represented by a magnetic field detected by a magnetic sensor mounted on a vehicle,
The road surface is located at a distance from the magnetic body that is equal to or larger than the distance when the magnitude of the vector represented by the combination of the distance from the magnetic body and the magnetic field strength at the distance is minimum, and the magnetic sensor from the road surface. The magnetic body installation method is such that the magnetic field intensity generated by the magnetic body and the depth from the road surface on which the magnetic body is to be installed are set so that a desired magnetic field strength can be obtained at the installation height of the magnetic body. In a method for installing on a road a magnetic body used for acquiring information represented by a magnetic field detected by a magnetic sensor mounted on a vehicle,
Magnetic field strength is generated so that a desired magnetic field strength can be obtained from the road surface at the installation height of the magnetic sensor, while the road surface is located at a distance from the magnetic body where the magnetic field strength generated from the magnetic body is ¼ or less. An installation method of a magnetic body in which the generation intensity of the body and the depth from the road surface to be installed are set. In a magnetic marker used to acquire information represented by a magnetic field installed on a road and detected by a magnetic sensor mounted on a vehicle,
A cylindrical case body;
A magnetic body housed in the case body,
The distance between the magnetic body and the upper surface of the case body represents the relationship between the distance from the magnetic body and the magnetic field strength as a distance-magnetic field strength point, and the ratio of the change in magnetic field strength to the change in distance is the change in magnetic field strength. On the contrary, the ratio of the change of the distance to the change of the magnetic field strength tends to be larger than the ratio of the change of the magnetic field strength to the change of the distance from the tendency of becoming larger than the ratio of the change of the distance to The magnetic field generated by the magnetic body is set to be equal to or greater than the distance, and the desired magnetic field strength is obtained at a position away from the upper surface of the case body by the same distance as the installation height of the magnetic sensor from the road surface. Is a magnetic marker. In a magnetic marker used to acquire information represented by a magnetic field installed on a road and detected by a magnetic sensor mounted on a vehicle,
A cylindrical case body;
A magnetic body housed in the case body,
The distance between the magnetic body and the upper surface of the case body is not less than the distance when the magnitude of the vector represented by the set of the distance from the magnetic body and the magnetic field intensity at the distance is minimum. And the generated magnetic field strength of the magnetic material is set so that a desired magnetic field strength is obtained at a position away from the upper surface of the case body by the same distance as the installation height of the magnetic sensor from the road surface. Magnetic marker. In a magnetic marker used to acquire information represented by a magnetic field installed on a road and detected by a magnetic sensor mounted on a vehicle,
A cylindrical case body;
A magnetic body housed in the case body,
The distance between the magnetic body and the upper surface of the case body is set to a distance at which the magnetic field intensity generated from the magnetic body is ¼ or less, and the distance from the road surface is equal to the installation height of the magnetic sensor. A magnetic marker in which the magnetic field intensity generated by the magnetic material is set so that a desired magnetic field strength is obtained at a position away from the upper surface of the body. The magnetic label according to any one of claims 4 to 6,
A magnetic marker in which a nonmagnetic material is accommodated in a space formed between the magnetic material and the upper surface of the case body. The magnetic label according to claim 7,
A magnetic marker in which the nonmagnetic material is formed of an elastic member.

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