Magnetic marker

Abstract

To provide a magnetic marker capable of maintaining the magnetic function of the magnetic marker to some extent even when the pavement is damaged, such as when potholes are generated.SOLUTION: A magnetic marker 1 is embedded in the road surface for use in vehicle driving support such as automatic steering along the lane, lane run-off warning, etc. The magnetic marker is an aggregate of granular multiple magnets 10 with a diameter of 1 mm. Adjacent magnets 10 among the multiple magnets 10 are connected using foamed resin as a connecting material.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a magnetic marker disposed on a road to assist in the operation of a vehicle.

Background Art

[0002] Conventionally, a magnetic marker system for a vehicle that uses magnetic markers disposed on a road has been known (see, for example, Patent Document 1). Such a magnetic marker system is intended for a vehicle equipped with a magnetic sensor. By detecting magnetic markers disposed along a lane with the vehicle, various driving supports such as automatic steering control and lane departure warning are realized.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the road pavement deteriorates, there is a risk that the magnetic marker will fall off the road and the function of the magnetic marker will be lost at once.

[0005] The present invention has been made in view of the above conventional problems, and aims to provide a magnetic marker that has the possibility of maintaining the function of the magnetic marker even when the pavement is damaged.

Means for Solving the Problems

[0006] The present invention is a magnetic marker embedded in a road surface for use in assisting the operation of a vehicle, the magnetic marker is an aggregate of a plurality of magnets, and the plurality of magnets are connected so as to form a columnar shape, each of the plurality of magnets is a magnet in which magnetic powder is dispersed in a base material on the other hand, The material located in the gap between adjacent magnets among the plurality of magnets is a connecting material that connects adjacent magnets among the plurality of magnets, and the connecting material is more easily broken than each of the magnets among the plurality of magnets. It's on the magnetic marker.

[0007] The magnetic marker of the present invention is an assembly in which multiple magnets are connected to form a columnar shape. This magnetic marker is designed to easily separate into multiple parts if the connections between the magnets are damaged. For example, on a paved road surface, holes called potholes may form as cracks in the road surface progress. For example, if a pothole near a magnetic marker gradually enlarges and the magnetic marker becomes exposed on its inner surface, being able to separate a part of it as described above can reduce the risk of the entire magnetic marker immediately falling off the road. If even a part of the magnetic marker remains on the road side, it can partially maintain the magnetic function that the magnetic marker possesses.

[0008] Thus, the magnetic marker of the present invention has the excellent characteristic of being able to maintain its magnetic performance to some extent even if the paved road surface is damaged. [Brief explanation of the drawing]

[0009] [Figure 1] An explanatory diagram showing magnetic markers installed on a road in Example 1. [Figure 2] A cross-sectional view showing the road pavement structure in Example 1. [Figure 3] Diagram illustrating the internal structure of the magnetic marker in Example 1. [Figure 4] Diagram illustrating the internal structure of the magnetic marker in Example 2. [Figure 5] Cross-sectional view of the granular magnet in Example 2. [Figure 6] Diagram illustrating the guide member in Example 2. [Figure 7] Diagram illustrating the internal structure of the magnetic marker in Example 3. [Figure 8] A perspective view showing the magnetic marker in Example 4. [Figure 9] Diagram illustrating the cross-sectional structure of the magnetic marker in Example 4. [Figure 10]Explanatory drawing of another magnet sheet in Example 4. [Figure 11] Explanatory drawing of another joining method of the magnet sheet in Example 4. [Figure 12] Perspective view of the magnetic marker in Example 5. [Figure 13] Perspective view of another magnetic marker in Example 5. [Figure 14] Perspective view of the magnetic marker in Example 6. [Figure 15] Perspective view of the magnetic marker in Example 7. [Figure 16] Perspective view of another magnetic marker in Example 7. [Figure 17] Explanatory drawing of the marker bar in Example 8. [Figure 18] Explanatory drawing of the state where the magnetic marker is cut out from the marker bar in Example 8. [Figure 19(a)] Explanatory drawing of the state where the tip of the marker bar is inserted into the receiving hole in Example 8. [Figure 19(b)] Explanatory drawing of Step 1 of the procedure for separating the magnetic marker at the tip of the marker bar in Example 8. [Figure 19(c)] Explanatory drawing of Step 2 of the procedure for separating the magnetic marker at the tip of the marker bar in Example 8. [Figure 19(d)] Explanatory drawing of the procedure for separating and arranging the magnetic marker at the tip of the marker bar in the receiving hole in Example 8. [Figure 20] Perspective view of the magnetic marker provided with the wireless tag in Example 9. [Figure 21] Front view of the deployed shape of the secondary antenna in Example 9.

Mode for Carrying Out the Invention

[0010] (Example 1) This example shows a magnetic marker 1 that is placed on road 3 so that it can be detected by a magnetic sensor (not shown) attached to a vehicle. This magnetic marker 1 enables vehicle-side control to assist the driver's operation of the vehicle, or to achieve autonomous driving that does not depend on the driver's operation. This will be explained with reference to Figures 1 to 3.

[0011] The magnetic marker 1 in this example (Figure 1) is an embedded type magnetic marker and is installed (embedded) in a housing hole 30 with a depth of 30 mm provided in the road surface 3S. The magnetic marker 1 has a columnar shape with a diameter of 30 mm and a height of 20 mm. Since the height of the magnetic marker 1 is 20 mm relative to the depth of the housing hole 30 mm, the upper surface of the magnetic marker 1 placed in the housing hole 30 is set back about 10 mm from the road surface. After the magnetic marker 1 is housed in the housing hole 30, a polymer material such as asphalt or resin material is filled into it. As a result, a cover 31 made of asphalt or resin material is formed on the upper side of the magnetic marker 1.

[0012] The cross-sectional structure of a road 3 paved with asphalt, etc. (Figure 2) broadly consists of three layers: a subgrade 3C made of compacted soil, a base course 3B made of granular materials such as crushed stone or crushed stone run, and a surface layer 3A made of a heated asphalt mixture. The heated asphalt mixture is an asphalt mixture in which coarse aggregate 331, fine aggregate 332, filler, and asphalt are mixed while heated. The thickness of the surface layer 3A is, for example, about 10 cm.

[0013] The coarse aggregate 331 of the surface layer 3A is, for example, crushed stone with a particle size of 2.5 to 5 mm. The fine aggregate 332 is, for example, aggregate that passes through a 2.36 mm sieve and remains on a 0.075 mm sieve. The fine aggregate 332 is, for example, sand with a particle size of 0.075 to 2.36 mm. The filler, which is not shown in the illustration, is mineral powder that passes through a 0.075 mm sieve. The filler is, for example, stone powder made from powdered limestone.

[0014] The pavement of Road 3 is inevitably subject to deterioration such as potholes over time. Potholes are holes that occur when a portion of the surface layer 3A, which consists of a heated asphalt mixture, peels off from the road surface 3S. Potholes occur, for example, when the bonding structure between the coarse aggregates 331 in the heated asphalt mixture that makes up the surface layer 3A is damaged.

[0015] The magnetic marker 1 (Figure 3) is a roughly cylindrical molded product in which granular magnets 10 (hereinafter simply referred to as magnets 10) with a diameter of approximately 1 mm are dispersed in a molding material. In other words, the magnetic marker 1 is an aggregate of multiple granular magnets 10, with the molding material acting as a connecting material, and the multiple magnets 10 are connected so that they form a columnar shape as a whole. As described above, the external dimensions of the magnetic marker 1 are a diameter of 30 mm and a height of 20 mm. The magnetic marker 1 is magnetized after molding, so that the orientation of the magnetic poles of each magnet 10 is constant. Figure 3 is a perspective view showing a cross-section including the central axis of the columnar magnetic marker 1.

[0016] Magnet 10 is an isotropic ferrite plastic magnet in which magnetic powder of iron oxide, a magnetic material, is dispersed in a polymer material that forms the base material. The polymer material is, for example, nylon 12. In addition to nylon 12, other materials such as rubber, PPS (polyphenylene sulfide), and nylon 66 may also be used as the polymer material.

[0017] This magnet 10 has magnetic properties with a maximum energy product (BHmax) of 12 kJ / cubic meter. As a permanent magnet, the isotropic ferrite plastic magnet is resistant to corrosion because its magnetic material is iron oxide. Therefore, the magnetic marker 1, which includes this magnet 10, is less susceptible to magnetic force reduction due to corrosion and can be directly housed in the housing hole 30 provided in the road surface 3S.

[0018] The molding material that makes up the magnetic marker 1 is polystyrene, which is an example of a resin material. The magnetic marker 1 can be made, for example, by mixing granular magnets 10 into a material obtained by primary foaming raw material beads consisting of polystyrene and a hydrocarbon-based foaming agent, filling it into a mold (not shown), and molding it into a columnar shape. In the magnetic marker 1 of this example, the intermagnetic regions 100 that form the gaps between the granular magnets 10 are formed by expanded polystyrene (foamed plastic, foamed resin), which is an example of a porous foam. In other words, in the magnetic marker 1, adjacent granular magnets 10 are connected by expanded polystyrene as a connecting material. The expanded polystyrene as a connecting material is more porous than the magnets 10, which are isotropic ferrite plastic magnets. Easily breakable When an excessive external force is applied to the magnetic marker 1, the polystyrene foam, which is the connecting material, may break, causing the magnetic marker 1 to separate and disintegrate into multiple small pieces.

[0019] The magnetic marker 1 in this example has a surface magnetic flux density of 45 mT (millitesla) and magnetic flux density of approximately 8 μT at a height of 250 mm. Note that 250 mm is an example of the upper limit of the assumed mounting height range for magnetic sensors in vehicles.

[0020] One of the technical features of the magnetic marker 1 in this example is that the inter-magnet region 100 is a porous region formed of expanded polystyrene. Expanded polystyrene has a lower fracture strength than paving material and can be broken relatively easily. Thus, the magnetic marker 1 in this example has the characteristic that it can be easily separated into small pieces by the breakage of the expanded polystyrene that makes up the region 100 between the granular magnets 10.

[0021] If the magnetic marker 1 remained intact when it rolled onto the road surface 3S, it would detach from the road as a whole as the potholes or other obstacles expanded, resulting in a sudden loss of its magnetic function. However, with the magnetic marker 1 in this example, which has a structure that allows it to be separated into multiple small pieces, it is possible that a portion of it can be separated as the potholes or other obstacles expand, leaving the remaining portion on the road. Therefore, the magnetic marker 1 is likely to be able to maintain its magnetic function to some extent.

[0022] In this example, a magnetic marker 1 is shown with granular magnets 10, each with a diameter of 1 mm, dispersed throughout the marker. The size of the granular magnets 10 should be between 0.2 mm and 3.0 mm. As an example of granular magnets 10, spherical magnets with a diameter of 1 mm are shown, but they may also be rectangular or cubic in shape, or even granular with multiple protrusions, like a konpeito candy. The size of the granular magnets 10 can vary. Furthermore, the magnets 10 may be in powder form or in the form of irregularly shaped small pieces.

[0023] The molding material may be a resin material such as polyethylene, polypropylene, or polyurethane instead of polystyrene as in this example. Similar to the magnetic marker 1 in this example, the magnets 10 should be dispersed within a foamed resin (foam) made of these resin materials. For example, polyurethane stock can be poured into a mold pre-filled with granular magnets 10 and then foamed. This allows for the creation of a magnetic marker in which the magnets 10 are dispersed within a polyurethane foam, which is an example of a foam. Furthermore, biodegradable materials may be used as the resin material forming the foam.

[0024] The granular magnet 10 may be replaced with a ferrite rubber magnet or a sintered magnet instead of the isotropic ferrite plastic magnet used in this example. In this example, a columnar magnetic marker with a circular cross-section is used as an illustration. However, the cross-sectional shape is not limited to a circle. Columnar magnetic markers with triangular, square, pentagonal, or other cross-sectional shapes are also acceptable.

[0025] (Example 2) This example is based on the magnetic marker 1 of Example 1, but with a modified configuration of the aggregated granular magnets 10. This will be explained with reference to Figures 4 to 6. The magnetic marker 1 in this example is an aggregate of granular magnets 10 with a diameter of 1 mm, similar to Example 1 (Figure 4). In this magnetic marker 1, the granular magnets 10 are bonded to each other at the points where they are in contact externally, resulting in an overall columnar external shape. The dashed line in Figure 4 indicates a roughly cylindrical external shape.

[0026] In this example, asphalt, a polymer material, is used as the adhesive material for joining the magnets 10 together. The adhesive material in the magnetic marker 1 is located in the gaps between adjacent magnets 10 and serves as an example of a connecting material that links adjacent magnets 10. The asphalt adhesive material is arranged to cover the outer surface of the spherical granular magnets 10, but does not fill the gaps between adjacent granular magnets 10. As a result, an inter-magnet region 100 containing holes 108 is formed in the gaps between adjacent granular magnets 10.

[0027] Here, we show an example of how to manufacture the magnetic marker 1 in this example. A roughly spherical magnet 10 (Figure 5) with a diameter of 1 mm and an asphalt coating layer 107 on its outer surface is filled into a mold (not shown) having a space with a diameter of 30 mm and a depth of 20 mm, and then heated to soften the asphalt. The magnets 10 in the mold are bonded and joined together by the softened asphalt at the points where they are in contact with each other, thereby connecting them to form a columnar shape with a diameter of 30 mm and a height of 20 mm.

[0028] In the magnetic marker 1 of this example, the approximately spherical magnets 10 are in contact with each other, while gaps are created between adjacent magnets 10, forming holes 108. In this magnetic marker 1, the area in which adjacent magnets 10 are in contact and bonded to each other is small. Therefore, the magnetic marker 1 is easily broken and easily separated into small pieces.

[0029] Asphalt is also a paving material for road surfaces. In road surface paving, the gaps between adjacent aggregates are filled with asphalt. On the other hand, in this example, the magnetic marker 1 has gaps between the granular magnets 10, which are a substitute for aggregates, that are not filled with asphalt, and holes 108 are formed. Therefore, the magnetic marker 1 is more difficult to use than paving made of asphalt. too The breaking strength has decreased.

[0030] As the magnet 10, a granular magnet in which magnetic powder is dispersed in the asphalt base material may be used. In this case, the outer surface of the magnet 10 can be softened by heating it, thereby allowing adjacent magnets 10 to adhere to each other.

[0031] Alternatively, a bottomed cylindrical guide member 111 (Figure 6) may be prepared, granular magnets 10 may be filled inside the guide member 111, and then heated. After the magnets 10 are bonded to each other by heating, the guide member 111 may be removed, or it may remain as part of the magnetic marker 1.

[0032] In this example, asphalt is used as the adhesive material for bonding the magnets 10 together. However, the adhesive material is not limited to asphalt. Rubber, PPS (Polyphenyl Sulfide), nylon 66, nylon 12, etc., can also be used. The other components and effects are the same as in Example 1.

[0033] (Example 3) This example is based on the magnetic marker of Example 1, but with a modified molding material. This will be explained with reference to Figure 7.

[0034] This example uses a biodegradable material that decomposes over time as the molding material for the magnetic marker 1. In this magnetic marker 1, the intermagnetic region 100, which forms the gap between the magnets 10, is filled with the biodegradable material. The intermagnetic region 100 is a region where holes and cracks can form as the biodegradable material decomposes over time. Naturally, if the molding material in the intermagnetic region 100 decomposes and holes or cracks occur, the fracture strength of the magnetic marker 1 itself will decrease.

[0035] Examples of biodegradable materials that decompose over time include polymer materials that decompose due to the action of at least one of heat, light, or water, and biodegradable materials that are broken down into low-molecular-weight compounds in nature through the involvement of microorganisms.

[0036] Furthermore, as the molding material for magnetic marker 1, it is also advisable to use adhesive materials or tack materials that initially have high strength but gradually decrease in strength over time. Here, adhesive materials are those that are liquid before use and become solid over time. Tack materials are those that possess the properties of both liquids and solids, and are semi-solid and viscous. It can also be considered that the concept of adhesive materials in a broad sense includes adhesive materials in a narrow sense and tack materials in a broad sense.

[0037] As the adhesive or bonding material, it is also possible to use an adhesive material that has relatively high strength immediately after joining, but whose bonding strength gradually decreases over time. Alternatively, it is also possible to use a disassemblable adhesive or bonding material that has some kind of disassembly factor and has the characteristic of decreasing bonding strength or peeling off when a disassembly operation is performed to activate the disassembly factor. If the bonding strength of the adhesive material in the intermagnet region 100 decreases, the bond between adjacent magnets 10 weakens, making them more susceptible to cracks and other damage.

[0038] For example, the adhesive material may have a disintegration factor in the form of gas generation at the adhesive interface, and may lose its bonding strength through a disintegration operation such as ultraviolet irradiation. This adhesive material is used, for example, as the adhesive material for ultraviolet-release tapes called dicing tapes in semiconductor processes. For example, the adhesive material may be one containing a water-absorbing resin, which has a disintegration factor in the form of expansion of the water-absorbing resin, and whose bonding strength decreases through a disintegration operation such as water immersion. For example, the adhesive material may be one containing thermally expandable microcapsules, which has a disintegration factor in the form of expansion of microcapsules, and whose bonding strength decreases with heating. For example, the adhesive material may be a thermosetting / thermoplastic adhesive material, which has a disintegration factor in the form of softening / melting, and whose bonding strength decreases with a disintegration operation such as heating. For example, the adhesive material may have a disintegration factor in the form of brittleness of the adhesive material, and may become brittle and lose bonding strength due to heating or ultraviolet irradiation. For example, the adhesive material may be a hydrolyzable adhesive or adhesive material, which has a disintegration factor in the form of hydrolysis, and whose bonding strength decreases with a disintegration operation such as the supply of moisture. The adhesive material may be a moisture-absorbing release adhesive material, which has a disintegration factor in the form of moisture absorption and softening / melting, and whose bonding strength decreases with hot water immersion. For example, it may be an electromagnetic induction thermoplastic adhesive material that possesses a decomposition factor of softening and melting, and whose bonding strength decreases with electromagnetic induction heating. For example, it may be an easily peelable adhesive material that possesses a decomposition factor of mechanical fracture, and whose bonding strength decreases with a decomposition operation such as applying a vertical load. For example, it may be an adhesive material that possesses a decomposition factor of mechanical fracture, and whose bonding strength decreases with a decomposition operation such as applying a shear load.

[0039] Furthermore, for example, biodegradable materials may be used as the molding material for the magnetic marker. In addition, biodegradable adhesives or bonding materials may be used. By using biodegradable adhesives that decompose in nature, the bonding strength of the magnetic marker 1 can be gradually reduced after it is embedded. Moreover, if biodegradable adhesives are used, the disposal of the magnetic marker 1 becomes easier, and the cost of disposing of the magnetic marker 1 can be reduced. The other components and effects are the same as in Example 1.

[0040] (Example 4) This example is based on the magnetic marker of Example 1, but with a modified shape of the magnets constituting the magnetic marker 1. The external shape and installation method of the magnetic marker 1 are the same as in Example 1. This will be explained with reference to Figures 8 to 11.

[0041] The magnetic marker 1 in this example is the magnetic marker shown in Figures 8 and 9. Figure 8 is a perspective view showing the external appearance of the magnetic marker 1. Figure 9 is a cross-sectional view showing the structure of the cross section including the columnar central axis. The cross section in the same figure corresponds to the cross section of line AA in Figure 8.

[0042] The magnetic marker 1 in this example (Figure 8) is a columnar magnetic marker formed by laminating 30 mm diameter disc-shaped magnetic sheets (an example of magnetic pieces) 11 using an adhesive or bonding material. In other words, the magnetic marker 1 in this example is an assembly of disc-shaped permanent magnets, which are magnetic sheets 11. This magnetic marker 1 is a permanent magnet exhibiting a columnar external shape with a diameter of 30 mm and a height of 20 mm, similar to the magnetic marker in Example 1. The magnetic sheet 11 is formed in sheet form from an isotropic ferrite rubber magnet, in which iron oxide magnetic powder, a magnetic material, is dispersed in a polymer base material. The magnetic performance of this magnetic marker 1 is almost the same as that of the magnetic marker in Example 1. It is also possible to laminate magnetic sheets made of isotropic ferrite plastic magnets.

[0043] In magnetic marker 1 (Figures 8 and 9), a bonding layer 12 made of adhesive material or similar material is formed in the gap between adjacent magnetic sheets 11. If, for example, an adhesive material or similar material that does not harden over time is used as the adhesive material or similar material, adjacent small pieces will be easier to separate via the bonding layer 12. Alternatively, an adhesive material that hardens but is prone to fracture of the bonding layer 12 may be used. If the bonding layer 12 fractures, cracks will form between adjacent magnetic sheets 11, causing them to break and making it easier for the magnetic marker 1 to separate into multiple small pieces. The materials exemplified in Examples 2 and 3 can be used as the adhesive material or similar material.

[0044] After placing the magnetic marker 1 into its housing hole (reference numeral 30 in Figure 1), filling the housing hole 30 with a polymer material such as asphalt or resin material allows the shape of the magnetic marker 1 to be maintained by the polymer material. Therefore, even if the bonding force of the bonding layer 12 is lost over time, as long as the magnetic marker 1 remains in the housing hole 30, the magnetic marker 1 can be maintained as a single unit without separating into multiple small pieces.

[0045] Furthermore, as shown in Figure 10, it is also possible to provide a grid of concave grooves 112 on the surface of the magnet sheet 11 that constitutes the magnetic marker 1 in Figure 8. This magnet sheet 11 is easily subdivided by the concave grooves 112 acting as breaks. A magnetic marker formed by laminating these magnet sheets 11 can be easily separated into multiple small pieces, not only from the bonding layer 12, but also from the grooves 112 of each magnet sheet piece acting as breaks. In addition, when laminating the magnet sheet pieces in Figure 8, it is also possible to apply adhesive material only to the surface other than the concave grooves 112, or only to the concave grooves 112. In this case, the bonding area between adjacent magnet sheets 11 can be suppressed, and the bonding strength can be reduced.

[0046] As shown in Figure 11, adhesive material may be applied only to the X-shaped region 113 indicated by the dot hatch in the figure, on the surface of the magnetic sheet 11. In this case, by suppressing the bonding area between adjacent pieces of the magnetic sheet, the magnetic marker 1 becomes easier to separate into multiple small pieces.

[0047] Furthermore, adhesive materials may be omitted. The stacked state of the magnetic marker 1 can be maintained by the magnetic attraction force generated between adjacent magnetic sheets 11. The magnetic sheets 11 that make up the magnetic marker 1 have one side as a north pole and the other side as a south pole. Adjacent magnetic sheets 11 are stacked with their north pole surface and south pole surface facing each other. Therefore, adjacent magnetic sheets 11 are magnetically attracted to each other. A magnetic marker may also be an assembly of multiple magnetic sheets 11 that are magnetically connected to each other by the magnetic force of each magnetic sheet 11, which is a permanent magnet. The other components and effects are the same as in Example 1.

[0048] (Example 5) The magnetic marker 1 in this example is a magnetic marker that employs a guide member to maintain the stacked state of the magnetic sheet (an example of a magnetic piece) 11, based on Example 4. This will be explained with reference to Figures 12 and 13. The magnetic marker 1 in Figure 12 is constructed by holding a stacked state of magnetic sheets 11, similar to the magnetic marker of Example 4, by a cylindrical guide member 115 extending in the axial direction (an example of a predetermined direction). The guide member 115 is, for example, made by winding sheet paper, metal foil such as aluminum foil, or resin film into a cylindrical shape. The guide member 115 is preferably made of a material that is somewhat easily torn rather than a high-strength material. When the guide member 115 tears or breaks, the magnetic marker 1 becomes easier to separate into multiple small pieces. In the magnetic marker 1, two adjacent pieces of magnetic sheet 11 may be joined to each other using an adhesive material with weak bonding strength, or they may be attracted to each other solely by the magnetic force of the magnetic sheets 11.

[0049] The cylindrical guide member 115 may be a molded layer formed on the outer surface of a columnar body on which the magnetic sheets 11 are laminated. The molded layer is, for example, a layer made of a polymer material such as asphalt or a resin material. Examples of resin materials include rubber, PPS (Polyphenyl Sulfide), nylon 66, nylon 12, etc. The magnetic sheets 11 may be as illustrated in Figure 9. The guide member 115 may lose its shape by melting due to the action of moisture such as water or humidity or heat.

[0050] As shown in Figure 13, the molded layer forming an example of the guide member 115 may extend in the axial direction and does not necessarily have to be cylindrical. As shown in the same figure, it is also possible to provide multiple strip-shaped molded layers 116 extending in the axial direction at multiple locations in the circumferential direction on the outer surface of the cylindrical magnetic marker 1. Such molded layers 116 are effective in maintaining the laminated state of the magnetic sheets 11. Instead of the molded layers 116 in Figure 13, it is also possible to use strip-shaped tapes made of paper, metal foil such as aluminum foil, or resin film. It is preferable that the molded layer or tape is easily broken rather than having high strength. The molded layer 116 may lose its shape by melting due to the action of moisture such as water or humidity or heat. The other components and effects are the same as in Example 4.

[0051] (Example 6) This example is a magnetic marker that employs an axial guide member 117 to maintain the stacked state of the magnetic sheets (an example of magnetic pieces) 11, based on Example 4. This will be explained with reference to Figure 14.

[0052] The magnetic marker 1 in Figure 14 consists of a disc-shaped magnetic sheet 11 with a small hole in the center, held by a rod-shaped guide member 117 extending in the axial direction (an example of a predetermined direction). The magnetic sheet 11 is the same as the magnetic sheet of the magnetic marker in Example 4, except for the small hole in the center. The rod-shaped guide member 117 may be, for example, a rod made of paper or wood, or a rod made of polymer material solidified into a rod shape.

[0053] The paper or wooden rod used as the guide member 117 should be thin or have multiple slits along its axial direction, making it easily breakable. The rod made of polymer material may be hardened asphalt, or made of resin material such as rubber, PPS (Poly Phenylene Sulfide), nylon 66, or nylon 12. It is best to select a material that is easily breakable and of a suitable thickness. The guide member 117 may also lose its shape due to the action of moisture such as water or humidity or heat. Furthermore, the guide member 117 may be a long, slender magnetic rod with magnetic poles at both ends. The other components and effects are the same as in Example 4.

[0054] (Example 7) The magnetic marker 1 in this example is a magnetic marker formed by combining multiple columnar magnetic pieces 13, each with a fan-shaped cross-section, to form a cylindrical shape similar to that of other embodiments. This will be explained with reference to Figures 15 and 16.

[0055] In the magnetic marker 1 of Figure 15, the magnetic pieces 13 may be joined together using adhesive materials or other adhesive materials as exemplified in Examples 2 and 3, or they may be bound together using a strip-shaped belt or string. Alternatively, a cylindrical guide member as exemplified in Example 5 may be used. The belt may be made of paper, metal foil, or resin film wound in a ring shape, or it may be a molded layer made of polymer material. The string may be made of paper, metal, natural fibers, or chemical fibers, or it may be a string-like material formed by printing polymer material on its outer surface.

[0056] For example, if a very thin iron belt or string is used, it may lose its binding function due to oxidation and other aging changes after being installed on the road. Even if the binding function of the belt or string is lost, the columnar shape of the magnetic marker 1 can be maintained as long as it is housed in the housing hole 30 and its outer circumference is filled with asphalt or the like. The belt, string, guide member, or other member used to bind the columnar magnetic piece 13 with a fan-shaped cross-section may be one that loses its shape due to the action of water, humidity, heat, or other moisture.

[0057] Furthermore, as shown in Figure 16, a columnar body similar in shape to the magnet piece 13 in Figure 15 may be used, with the columnar body divided into multiple sections along the axial direction. This magnet piece 131 may also be a thin, fan-shaped magnetic sheet piece (an example of a magnet piece), like a slice of pizza. By stacking these thin, fan-shaped magnetic sheet pieces, a columnar body with a fan-shaped cross-section can be formed. The magnetic marker 1 in Figure 16 is a combination of these columnar bodies.

[0058] When forming columnar bodies with a fan-shaped cross-section, adhesive materials can be used, and when combining these columnar bodies to form a magnetic marker 1, they may be fastened together with belts, strings, or cylindrical guide members, or the columnar bodies may be joined together using adhesive materials. Alternatively, when forming columnar bodies, guide members such as mold layers or foils as exemplified in Example 5 can be used, and when combining the columnar bodies, they may be joined together using adhesive materials, or they may be fastened together with belts, strings, or cylindrical guide members. The columnar bodies with a fan-shaped cross-section may be formed by magnetically attracting fan-shaped magnetic sheet pieces, such as slices of pizza, to each other.

[0059] Thus, the magnetic marker 1 in this example is a magnetic marker with a structure that can be separated into multiple small pieces. With this magnetic marker 1, when the pavement is damaged and a pothole occurs, a portion of it can be separated in proportion to the expansion of the pothole. Therefore, even if a pothole occurs nearby, there is a high possibility that a portion of the magnetic marker 1 will remain on the road side, and it may be possible to maintain the magnetic function of the magnetic marker 1 to some extent.

[0060] Furthermore, while the coarse aggregate 331 forming the surface layer of the pavement has a particle size of, for example, 2.5 to 5 mm, the magnetic marker 1 has a diameter of 30 mm and a height of 20 mm. If the magnetic marker were to be a single unit, when a pothole occurs, there is a possibility that a magnetic marker larger than the coarse aggregate 331 could roll onto the road surface. On the other hand, with the magnetic marker 1 in this example, which has a structure that allows it to be separated into multiple small pieces, there is less risk of it rolling onto the road surface as a single unit. Because this magnetic marker 1 can be separated into multiple small pieces, it will only roll onto the road surface as small pieces that are equivalent in size to, or even smaller than, the coarse aggregate 331.

[0061] In this example, a columnar magnetic marker with a circular cross-section is used as an illustration. However, the cross-sectional shape is not limited to a circle. Columnar magnetic markers with triangular, square, pentagonal, or other cross-sectional shapes are also acceptable. Furthermore, the other components and effects are the same as in the other embodiments.

[0062] (Example 8) This example demonstrates a configuration that utilizes a structure that can be separated into multiple small pieces, allowing multiple magnetic markers to be handled as a single unit. This example relates to a marker rod 1R in which multiple magnetic markers 1 from Example 1 are connected. This will be explained using Figures 17 to 19(d).

[0063] The marker rod 1R (Figure 17) has a connecting surface 100 that connects two magnetic markers 1 in the axial direction, and is composed of multiple magnetic markers 1 as a whole. The connecting strength of the two magnetic markers 1 at the connecting surface 100 is set to be even lower than the strength required to separate the individual magnetic markers 1 into small pieces.

[0064] For example, as shown in Figure 18, if the marker rod 1R is placed on the workbench 105 so that its tip protrudes from the edge, and a force perpendicular to the tip is applied, the connecting surface 100 becomes the cutting surface, and the magnetic marker 1 can be cut out from the marker rod 1R. If the amount the tip protrudes from the edge of the workbench 105 is set to slightly exceed the height (total length) of the magnetic marker 1, the magnetic markers 1 can be cut out one by one efficiently.

[0065] Alternatively, a marker rod 1R can be used to house one magnetic marker 1 in each housing hole 30, as shown in Figures 19(a) to (d). With the tip of the marker rod 1R inserted into the housing hole 30, which has a diameter of 38 mm and a depth of 30 mm, for example, by about 13 to 18 mm (less than the height dimension of the magnetic marker 1) (Figure 19(a)), one magnetic marker 1 can be easily separated by rotating the rear end of the marker rod 1R (Figure 19(b)) (Figure 19(c)). The magnetic marker 1 separated from the marker rod 1R in this way falls to the bottom of the housing hole 30 due to its own weight and is housed there (Figure 19(d)).

[0066] For example, in the case of the magnetic markers of Example 1 and Example 2 (Figures 3 and 4), after fabricating the rod-shaped body, it is also possible to drill lateral holes or slits along the connecting surface 100. By drilling lateral holes or slits, the strength of the connecting surface 100 can be suppressed.

[0067] For example, in the case of the magnetic marker of Example 4 (Figure 8), the amount of adhesive material applied to the connecting surface 100 may be less than the amount of adhesive material applied to join adjacent magnet sheet pieces 11 on the magnetic marker 1. Alternatively, an adhesive material with lower bonding strength may be used as the adhesive material on the connecting surface 100. By selecting the amount and type of adhesive material in this way, the strength of the connecting surface 100 can be suppressed.

[0068] For example, in the magnetic marker of Example 5 (Figure 12), a guide member is used to hold the entire marker rod 1R, while reducing the breaking strength of the guide member at the point where it contacts the connecting surface 100. Various methods can be considered to reduce the breaking strength of the guide member, such as making a cut in the guide member or reducing the thickness of the guide member. Furthermore, at the point where the guide member corresponding to one of the adjacent magnetic markers 1 connects to the guide member corresponding to the other magnetic marker 1, a structure is provided to connect the former guide member and the latter guide member, and the strength of this structure is set to be low.

[0069] It should be noted that suppressing the strength of the connecting surface 100 is not an essential configuration. It is advisable to use a jig or similar device to cut out the magnetic markers 1 one by one from the marker rod 1R. By using a jig or similar device, the magnetic markers 1 can be efficiently cut out from the marker rod 1R, which has a substantially constant fracture strength in the axial direction. The other components and effects are the same as in Example 1.

[0070] (Example 9) This example shows an addition of a wireless tag 18 based on the magnetic markers of Examples 1 to 8. This will be explained with reference to Figures 20 and 21. In this example, the magnetic marker 1 (Figure 20) is based on the magnetic marker of Example 1, with a wireless tag 18 attached to its end face. The end face of the magnetic marker 1 has a diameter of 30 mm, while the wireless tag 18 has a cross-sectional shape of approximately 10 mm x 2 mm and a length of approximately 25 mm.

[0071] The wireless tag 18 is an electronic component in which an IC chip, a wireless communication antenna, and other components are housed in a case made of resin or the like. The wireless tag 18 operates by external power supply via radio waves and wirelessly outputs pre-stored information. The information output by the wireless tag 18 may include, for example, location information and road type information.

[0072] In this example, a secondary antenna 19 is provided on the outer circumferential surface and end face of the magnetic marker 1 to amplify the radio waves transmitted and received by the wireless tag 18. The secondary antenna 19 is formed by printing conductive ink on the outer surface of the magnetic marker 1. As shown in Figure 21, which is shown unfolded in a plane, the secondary antenna 19 has hook-shaped portions 194 that bend at a right angle at both ends. The hook-shaped portions 194 at both ends are bent in the opposite direction to the intermediate straight portion 191. The straight portion 191 extends radially from the end face, which is the mounting surface of the wireless tag 18, to the outer circumferential surface of the magnetic marker 1, and extends axially on the outer circumferential surface. The hook-shaped portions 194 are provided on the outer circumferential surface of the magnetic marker 1 so as to be aligned in the circumferential direction.

[0073] In the magnetic marker 1 shown in Figure 20, the wireless tag 18 is attached in contact with the linear portion 191 of the secondary antenna 19. The electromagnetic coupling between the communication antenna built into the wireless tag 18 and the secondary antenna 19 amplifies the radio waves transmitted and received by the wireless tag 18. The secondary antenna 19 may be an antenna made of copper foil, aluminum foil, etc., instead of a printed antenna made of conductive ink. If a metal foil antenna is used, it is preferable to use one that is sufficiently thin so as not to hinder the characteristic of the magnetic marker 1 that it can be separated into small pieces, or to configure it so that it can be easily peeled off from the outer surface of the magnetic marker 1.

[0074] Alternatively, a secondary antenna 19 may be used as a guide member to maintain the shape of the magnetic marker, which is an assembly of magnets. In this case, it is preferable that the linear portion 191 of the secondary antenna 19 be formed over the entire axial area on the outer surface of the magnetic marker 1. Furthermore, the other components and effects are the same as in the other embodiments.

[0075] Although specific examples of the present invention have been described in detail as shown in the examples above, these examples only disclose an example of the technology covered by the claims. Needless to say, the claims should not be interpreted restrictively based on the configuration or numerical values ​​of the specific examples. The claims encompass technologies obtained by various modifications, changes, or combinations of the above examples using prior art or the knowledge of those skilled in the art. [Explanation of Symbols]

[0076] 1 Magnetic marker 10 Magnets 100 Inter-magnet region 108 holes 111, 115, 117 Guide members 18 Wireless Tags 180 Groove 181 Tag Guard 19 Secondary antenna 3 road 3A Surface layer 3S road surface 30 Intake holes 331 Coarse aggregate 332 Fine aggregate

Claims

1. A magnetic marker embedded in the road surface for use in assisting vehicle operation, The magnetic marker is an assembly of multiple magnets, in which the multiple magnets are connected in a columnar shape. Each of the aforementioned plurality of magnets is a magnet in which magnetic powder is dispersed in a base material, A magnetic marker in which the material located in the gap between adjacent magnets among the plurality of magnets is a connecting material that connects adjacent magnets among the plurality of magnets, and the connecting material is a material that is more easily broken than each of the magnets among the plurality of magnets.

2. The magnetic marker in claim 1, wherein the connecting material is a foamed resin.

3. In claim 1 or 2, the material located in the gap between adjacent magnets among the plurality of magnets is a connecting material that connects adjacent magnets among the plurality of magnets, and the connecting material is an adhesive material or a tack material. The adhesive or bonding material is a magnetic marker that is a disassemblable adhesive or bonding material whose bonding strength decreases when disassembly factors are activated by a predetermined disassembly operation.

4. The magnetic marker according to claim 1 or 2, wherein the material located in the gap between adjacent magnets among the plurality of magnets is a connecting material that connects adjacent magnets among the plurality of magnets, and the connecting material is a biodegradable material.

5. A magnetic marker according to any one of claims 1 to 4, wherein a plurality of magnetic pieces are held in a columnar shape by a guide member extending in a predetermined direction.

6. The guide member in claim 5 is a magnetic marker which is a molded layer made of a polymer material formed on the outer surface of a columnar magnetic marker.

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