Magnetic attraction device

Abstract

To provide a magnetic attraction device that can demonstrate its intrinsic attraction force even when the surface shape of an object to be attracted is not flat.SOLUTION: A magnetic attraction device 180 includes a neodymium magnet 111 and a yoke 181 that holds the neodymium magnet 111. The yoke 181 has a back yoke unit 183 that attracts the neodymium magnet 111 and an outer peripheral yoke unit 184 that is formed integrally with the back yoke unit 183 and surrounds the neodymium magnet 111. An attraction surface 184a of the outer peripheral yoke unit 184 includes a first curved surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic attraction device. [Background technology]

[0002] There is a known technology in which a yoke is attached to one side of a magnet that has a north pole and a south pole, thereby increasing the magnetic flux density on the other side and doubling the adhesive force. An example of the application of such a technology is disclosed in, for example, Patent Document 1 listed below. In the magnetic attraction device described in Patent Document 1, one side of a corrosion-resistant magnet made of a neodymium magnet is attached to a back yoke portion and the outer periphery is covered with a yoke. The other side of the corrosion-resistant magnet faces the object to be attracted. This magnetic attraction device can double the attraction force to the object to be attracted, so that the high magnetic force of the neodymium magnet can be effectively used to exert an extremely high attraction force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5090781 Summary of the Invention [Problem to be solved by the invention]

[0004] The magnetic attraction device is highly regarded as an alternative technology to conventional fixing methods such as welding, due to its high attraction performance and ease of use. It is desirable to take advantage of its convenience and expand the range of its use, but one problem arises due to the use of magnetic force. That is, when a flat attraction surface is prepared in advance, such as the attraction object described in the above Patent Document 1, the original attraction force of the magnetic attraction device can be exerted by utilizing the flat surface. On the other hand, when a curved surface such as the outer circumferential surface of a circular pipe is to be used as the attraction surface, a partial gap inevitably occurs between the flat magnet and the curved surface, and the original attraction force cannot be fully utilized. This problem occurs not only when the attraction object has a convex curved surface, but also when the attraction object has a concave curved surface. Therefore, it has been desired to be able to exert the original attraction force regardless of the surface shape of the attraction object and to be able to use it in a wider variety of applications.

[0005] The present invention has been made in consideration of the above circumstances, and has an object to provide a magnetic attraction device that can exert its inherent attraction force even when the surface shape of the object to be attracted is not flat. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the above object, the present invention employs the following aspects. (1) One aspect of the present invention is a magnetic adsorption device comprising a permanent magnet and a yoke that holds the permanent magnet, the yoke having a back yoke portion that adsorbs the permanent magnet and an outer peripheral yoke portion that is formed integrally with the back yoke portion and surrounds the permanent magnet, and the adsorption surface of the outer peripheral yoke portion includes a first curved surface. According to the magnetic attraction device described in (1) above, the attraction surface has a first curved surface that matches the surface shape of the object to be attracted, so the attraction surface can be placed on the object without any gaps. As a result, the decrease in attraction force due to the gaps can be suppressed, and the original attraction force of the permanent magnet can be exerted.

[0007] (2) In the magnetic attraction device described in (1) above, the first curved surface may include a curved shape that forms a part of the outer circumferential surface or the inner circumferential surface of a hollow sphere. In other words, a configuration may be adopted in which the first curved surface is curved in a convex shape approaching the permanent magnet or moving away from the permanent magnet in both a cross section including one of two intersecting axes that are perpendicular to each other when the attraction surface is viewed opposite to each other and a cross section including the other of the two intersecting axes. In the case of the magnetic attraction device described in (2) above, the attraction surface of the magnetic attraction device can be overlapped without any gaps regardless of whether the surface shape of the object to be attracted is a convex spherically curved surface or a concave spherically curved surface.

[0008] (3) In the magnetic attraction device described in (1) above, the first curved surface may include a curved shape that forms a part of the outer circumferential surface or the inner circumferential surface of a cylinder. In other words, in a cross section including one of two intersecting axes that are perpendicular to each other when the attraction surface is viewed opposite to each other, the first curved surface may be curved in a convex shape that faces toward or away from the permanent magnet, and in a cross section including the other of the two intersecting axes, the first curved surface may be linear. In the case of the magnetic attraction device described in (3) above, the attraction surface of the magnetic attraction device can be overlapped without any gaps even if the surface shape of the object to be attracted is a convex cylindrical curved surface or a concave cylindrical curved surface.

[0009] (4) In the magnetic adsorption device described in any one of (1) to (3) above, the following configuration may be used: the permanent magnet is ring-shaped; an inner yoke portion penetrating the permanent magnet is integrally formed with the back yoke portion; and the adsorption surface of the inner yoke portion includes a second curved surface. In the case of the magnetic attraction device described in (4) above, the attraction surfaces of both the first and second curved surfaces, which are adapted to the surface shape of the object to be attracted, can be overlapped with the object without any gaps, and as a result, the improvement in the attraction force due to the provision of the inner yoke portion can be effectively achieved.

[0010] (5) In the magnetic adsorption device described above in (4), the first curved surface and the second curved surface may have the same curved shape with the same radius of curvature. In the case of the magnetic attraction device described in (5) above, the gap between the first curved surface and the second curved surface and the surface shape of the object to be attracted can be easily and highly accurately managed. Effect of the Invention

[0011] According to the above aspect of the present invention, the attraction surface of the outer yoke portion is configured to include a first curved surface, so that the permanent magnet can exert its inherent attraction force even if the surface shape of the object to be attracted is other than flat. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a first embodiment of the present invention, and is a vertical sectional view of a magnetic attraction device taken along a cross section including a central axis thereof. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a cross-sectional view of the magnetic attraction device taken along line AA in FIG. [Figure 4] FIG. 1 is a cross-sectional view illustrating a case where a conventional magnetic attraction device is attracted to the outer circumferential surfaces of a plurality of types of steel pipes having different outer diameters, the cross-sectional view being perpendicular to the pipe axis of the steel pipes. [Diagram 5] 5 is an enlarged view of part B in FIG. 4, and is a cross-sectional view showing a gap that occurs when a conventional magnetic attraction device is fixed to the outer circumferential surface of a steel pipe. [Figure 6] FIG. 1 is a cross-sectional view illustrating a case where a conventional magnetic attraction device is attracted to the inner peripheral surfaces of a plurality of types of steel pipes having different inner diameters, the cross-sectional view being perpendicular to the pipe axis of the steel pipes. [Figure 7] 7 is an enlarged view of part C in FIG. 6, and is a cross-sectional view showing a gap that occurs when a conventional magnetic attraction device is fixed to the inner peripheral surface of a steel pipe. [Figure 8] FIG. 2 is a cross-sectional view showing a case where the magnetic adsorption device of the first embodiment is fixed to the outer circumferential surface of the steel pipe, the cross-sectional view being perpendicular to the axis of the steel pipe. [Figure 9] FIG. 11 is a cross-sectional view showing a modified example of the magnetic attraction device of the first embodiment, in which the magnetic attraction device according to the modified example is fixed to the inner peripheral surface of a steel pipe. [Figure 10] FIG. 11 is a diagram showing a second embodiment of the present invention, and is a perspective view of an attraction surface of a yoke of a magnetic attraction device. [Figure 11] FIG. 13 is a diagram showing a modified example of the magnetic attraction device of the second embodiment, and is a perspective view of an attraction surface of a yoke of the magnetic attraction device. [Figure 12] FIG. 10 is a diagram showing a third embodiment of the present invention, and is a side view of a yoke of a magnetic adsorption device. [Figure 13] 11 is a side view illustrating the movement of the yoke when the magnetic attraction device is fixed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the magnetic attraction device of the present invention will be described with reference to the accompanying drawings.

[0014] (First embodiment) Fig. 1 is a diagram showing the first embodiment, and is a vertical cross-sectional view of a magnetic attraction device 180 seen along a cross section including its central axis. Fig. 2 is an exploded perspective view of the magnetic attraction device 180. Fig. 3 is a diagram showing the magnetic attraction device 180, and is a cross-sectional view taken along line AA in Fig. 1. 1, the magnetic attraction device 180 of this embodiment is particularly characterized by the shape of the attraction surface that attracts the attraction target 1000. In the following explanation, first, the overall configuration of the magnetic attraction device 180 will be explained mainly with reference to FIGS. 2 and 3, and then the features of the attraction surface will be explained.

[0015] 2, the magnetic attraction device 180 according to this embodiment includes an attraction device main body 180a and a nut 180b for fixing the attraction device main body 180a to equipment or the like. The bolt 188 is used by being screwed into the attraction device main body 180a, and is an attraction force adjustment member for adjusting the attraction force with respect to the attraction target by moving the magnetic attraction device 180 toward and away from the attraction target.

[0016] As shown in Fig. 2 and Fig. 3, the attraction device main body 180a includes a Nd-Fe-B permanent magnet (hereinafter referred to as a neodymium magnet) 111 that is ring-shaped when viewed from above, and a cap-shaped yoke 181 that houses the neodymium magnet 111. A screw shaft portion 186 is formed on the surface of the yoke 181 opposite to the surface that faces the neodymium magnet 111. Furthermore, corrosion-resistant members 142a and 142b are provided in the gap between the yoke 181 and the neodymium magnet 111. In this embodiment, the neodymium magnet 111 and the corrosion-resistant members 142a and 142b that come into contact with the neodymium magnet 111 constitute a corrosion-resistant magnet 176.

[0017] The permanent magnets constituting the corrosion-resistant magnet 176 are not limited to Nd-Fe-B permanent magnets, but may be iron-based rare earth permanent magnets represented by RE-Fe-MB (RE is at least one rare earth element selected from the group consisting of Nd, Y, La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and M is at least one element selected from the group consisting of Co, Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, and Ta), Sm-Co magnets, ferrite magnets, and the like. These permanent magnets may have a resin film or a plating film formed on the surface.

[0018] 3, the corrosion-resistant members 142a and 142b are both formed in a ring shape in a planar cross-sectional view, and respectively cover the outer and inner peripheral surfaces of the neodymium magnet 111. The corrosion-resistant members 142a and 142b in this embodiment are flexible corrosion-resistant members, and in this example, are flexible zinc anodes formed in a paste state by mixing zinc powder or zinc alloy powder with a resin material or the like.

[0019] The flexible corrosion-resistant member may be in a paste (putty) form that is viscous at least when applied. In other words, it may be solidified by a heating treatment or drying treatment after application. Furthermore, it may not be conductive when applied, but may become conductive by a heating treatment or drying treatment. Furthermore, when the anode potential, anode efficiency, amount of electrolytic product generated, and ease of handling are taken into consideration, zinc is the most suitable metal powder to be contained in the flexible corrosion-resistant member.

[0020] The anticorrosive members 142a, 142b are preferably formed to a thickness of 50 μm or more, and more preferably to a thickness of 1 mm or more. If the anticorrosive members 142a, 142b are formed to a thickness of 1 mm or more, the anticorrosive effect can be obtained for an extremely long period of time. With such a configuration, the magnetic adsorption device 180 of this embodiment can be used in severe corrosive environments such as underwater or in the sea without causing corrosion of the neodymium magnet 111.

[0021] Conventionally used plating film thicknesses (approximately 5 to 20 μm) present almost no problems when used in the atmosphere, but do not provide sufficient corrosion protection in severe corrosive environments such as underwater or in the sea, and there is a risk of the neodymium magnet 111 corroding. In contrast, if a corrosion-resistant member with a thickness in the above-mentioned range is provided, a corrosion-resistant magnet with a sufficient amount of corrosion-resistant member can be constructed, and it will not corrode even if used underwater or in seawater for a long period of time, and its adsorptive power can be maintained.

[0022] The yoke 181 is configured by integrally forming a disk-shaped back yoke portion 183 that is attracted to the magnetic surface on the back side of the neodymium magnet 111, a cylindrical outer peripheral yoke portion 184 having an inner peripheral surface facing the outer peripheral surface of the neodymium magnet 111, an inner peripheral yoke portion 185 having an outer peripheral surface facing the inner peripheral surface of the neodymium magnet 111, and a screw shaft portion 186 provided on the side of the back yoke portion 183 opposite to the surface that is attracted to the neodymium magnet 111. The yoke 181 accommodates the corrosion-resistant magnet 176 in a groove portion 181b that is ring-shaped in a plan view and is formed by the back yoke portion 183, the outer peripheral yoke portion 184, and the inner peripheral yoke portion 185.

[0023] As described above, the inner yoke portion 185 and the outer yoke portion 184 are provided on the inner and outer periphery, respectively, of the ring-shaped neodymium magnet 111, so that the magnetic attraction device 180 of this embodiment is able to obtain a strong attraction force. In other words, by adopting such a double yoke structure, an attraction portion is formed between the neodymium magnet 111 and the inner yoke portion 185, and between the neodymium magnet 111 and the outer yoke portion 184, so that the magnetic force of the neodymium magnet 111 can be efficiently used for attraction. Specifically, the magnetic attraction device 180 with the double yoke structure configured as described above can obtain an attractive force that is approximately 1.7 times higher than that of a magnetic attraction device with a single yoke structure that does not have the inner peripheral yoke portion 185. In this embodiment, by adopting the double yoke structure in this manner, the attractive force is greatly improved without increasing the dimensions, and even heavy equipment can be installed with a small magnetic attraction device.

[0024] Furthermore, as shown in FIG. 1, the groove portion 181b of the yoke 181 is formed to a depth greater than the height of the neodymium magnet 111, and when the corrosion-resistant magnet 176 is housed in the yoke 181, the attraction surfaces 184a, 185a on the opening sides of the outer peripheral yoke portion 184 and the inner peripheral yoke portion 185 protrude toward the tip side (toward the object to be attracted 1000) beyond the surface of the neodymium magnet 111. By having the yoke 181 protrude beyond the neodymium magnet 111 in this manner, the neodymium magnet 111 can be protected from friction and impact when the magnetic attraction device 180 is attracted to the object to be attracted 1000, and the neodymium magnet 111 can be prevented from wearing out or cracking.

[0025] The screw shaft portion 186 is formed in a cylindrical shape integral with the yoke 181, and the extension direction of the screw shaft coincides with the normal direction of the outer surface of the back yoke portion 183. A male screw portion 186a for screwing the nut 180b is formed on the outer circumferential surface of the screw shaft portion 186. The screw shaft portion 186 functions as a member for attaching the magnetic adsorption device 180 to equipment and the like together with the nut 180b. That is, the screw shaft portion 186 can be easily attached to the equipment and the like by inserting it into a bolt hole H of a support bracket (reference symbol S in FIG. 1) provided on the equipment and then fastening it with the nut 180b. Note that the support bracket S in FIG. 1 extends toward the back side of the paper and is fixed to the equipment. Therefore, the equipment is fixed to the attraction target 1000 by the magnetic adsorption device 180 fixed to the support bracket S with the nut 180b being magnetically attracted to the attraction target 1000.

[0026] A threaded hole 181a is formed in the threaded shaft portion 186, penetrating the threaded shaft portion 186 in the axial direction. As shown in Fig. 1, the threaded hole 181a coaxially penetrates the back yoke portion 183 and the inner peripheral yoke portion 185 of the yoke 181. That is, the threaded hole 181a is formed penetrating the suction device main body 180a in the height direction.

[0027] A female thread is formed on the inner surface of the screw hole 181a to screw into the male thread 189 of the bolt 188. Since the screw hole 181a penetrates the suction device main body 180a, by screwing a bolt 188 of sufficient length into the screw hole 181a, the tip of the bolt 188 can be made to protrude from the tip of the inner yoke part 185. In addition, by rotating the bolt 188 forward or backward about its axis, the protruding length of the bolt 188 from the suction surface 185a can be freely adjusted.

[0028] The nut 180b screwed onto the male threaded portion 186a of the screw shaft portion 186 is a locking nut, and in this embodiment, as shown in FIG. 2, a friction ring 187 is provided coaxially with the screw hole of the nut 180b. The friction ring 187 has a claw portion protruding toward the center of the screw hole, and when the nut 180b is screwed onto the screw shaft portion 186, the claw portion comes into contact with the thread of the male threaded portion 186a and deforms, and the reaction force generated by this deformation presses the male threaded portion 186a. The friction force generated between the friction ring 187 and the male threaded portion 186a restricts the free rotation of the nut 180b, preventing the nut 180b from loosening. The anti-loosening structure of the nut 180b is not particularly limited, and in addition to using a friction ring, various structures can be used, such as a structure using a spring washer, a double nut structure, and a structure using a resin ring.

[0029] The back yoke portion 183 is formed with a plurality of screw holes (through holes) 183a that penetrate the back yoke portion 183 and reach the neodymium magnets 111. These screw holes 183a are used when housing the neodymium magnets 111 in the yoke 181, and by inserting a bolt (not shown) into the screw hole 183a and leaving the tip of the bolt protruding inside the yoke 181, the neodymium magnets 111 arranged on the opening side of the yoke 181 are restricted from being attracted to the back yoke portion 183. This prevents the neodymium magnets 111 from being pulled into the inside of the yoke 181 and colliding with the back yoke portion 183 when the neodymium magnets 111 are arranged, causing the neodymium magnets 111 to crack or chip due to the impact.

[0030] After the neodymium magnet 111 is attracted to the back yoke portion 183, a corrosion-resistant member (not shown) is provided in the screw hole portion 183a. As described above, the screw hole portion 183a is hardly used except for assembling the magnet during manufacturing or removing the magnet during disassembly. Therefore, by disposing a corrosion-resistant member in the screw hole portion 183a so as to come into contact with the neodymium magnet 111, corrosion of the neodymium magnet 111 can be effectively prevented. In addition, since the leakage of magnetic flux through the screw hole portion 183a can be reduced, the utilization efficiency of the magnetic force can be improved and the magnetic force can be prevented from acting on other members. Note that if the neodymium magnet 111 can be accommodated inside the yoke 181 without applying an impact to the screw hole portion 183a, the screw hole portion 183a may be omitted. In that case, since there is no through hole in the back yoke portion 183, there is no need for a corrosion-resistant member to fill the through hole.

[0031] In the magnetic adsorption device 180 having the configuration described above, the strength of the adsorption force of the neodymium magnet 111 having strong magnetic force can be controlled by means of the screw hole portion 181a formed in the screw shaft portion 186 protruding from the back yoke portion 183 and the bolt 188 screwed into the screw hole portion 181a, thereby enabling the magnet to be safely and reliably attracted to an object to be attracted.

[0032] 1, first, a bolt 188 is screwed into a screw hole 181a of an attraction device main body 180a from an upper end of a screw shaft portion 186, and the tip of the bolt 188 is made to protrude from the tip of the inner yoke portion 185. At this time, the protruding length of the bolt 188 depends on the attraction force of the magnetic attraction device 180, but can be, for example, 5 mm to 8 mm.

[0033] Then, the magnetic attraction device 180 with the tip of the bolt 188 protruding is brought close to the object to be attracted 1000. Then, the tip of the protruding bolt 188 hits the surface of the object to be attracted 1000, preventing contact between the magnetic attraction device 180 and the object to be attracted 1000, and the magnetic attraction device 180 and the object to be attracted 1000 are held in a state separated from each other via a gap. At this time, the magnetic attraction device 180 is attracted to the object to be attracted 1001 with a weak force or is not attracted at all.

[0034] Thereafter, when the head of the bolt 188 is rotated to move the bolt 188 back, the gap between the magnetic attraction device 180 and the object to be attracted 1000 gradually decreases, and the force of attraction between the two also increases. When the bolt 188 is moved back to a position where the tip of the bolt 188 does not protrude from the inner yoke part 185, the attraction surfaces of the outer yoke part 184 and the inner yoke part 185 come into contact with the object to be attracted 1000, as shown in FIG. 1. This causes the magnetic attraction device 180 to be attracted to the object to be attracted 1000 at its attraction surface. In this way, in the process of attracting the magnetic attraction device 180 to the object to be attracted 1000, the magnetic attraction device 180 can be automatically positioned around the central axis CL of FIG. 1. Details of this will be described later in the description of FIG. 8.

[0035] On the other hand, when removing the magnetic attraction device 180 from the object to be attracted 1001, in the attracted state shown in Fig. 1, the bolt 188 is rotated about its axis to advance the tip of the bolt 188 toward the object to be attracted 1000. Then, a gap can be formed between the magnetic attraction device 180 and the object to be attracted 1000. The neodymium magnet 111 used in the magnetic attraction device 180 has an extremely strong attractive force, making it difficult to directly separate them by hand, but since the attractive force of the magnetic attraction device 180 is inversely proportional to the square of the gap between the yoke 181 and the object to be attracted 1000, simply forming a gap of a few millimeters makes it easy to separate them by hand. As described above, the magnetic attraction device 180 of this embodiment can be attached to and detached from the attraction target 1000, or the position thereof can be adjusted easily and safely.

[0036] Following the overall configuration described above, the features of the magnetic attraction device 180 of this embodiment will be described in turn. In this magnetic attraction device 180, the shape of the tips of the outer peripheral yoke portion 184 and the inner peripheral yoke portion 185, more specifically, the shape of the attraction surface that contacts the object to be attracted 1000, is particularly distinctive. In the following, in order to provide a detailed explanation of the action and effect based on this feature, the present invention will be described in comparison with a magnetic attraction device of a conventional structure.

[0037] First, all magnets currently on the market are designed to be attached to a smooth surface. Therefore, the yoke of a conventional magnetic attraction device inevitably has a flat surface as its attraction surface. When a conventional magnetic attraction device with such a flat surface as its attraction surface is used to attract an object with a cylindrical or spherical curvature (such as a water intake pipe, a water supply pipe, a penstock, a steel pipe sheet pile, a steel pipe pile, a tank, etc.), a partial gap inevitably occurs between the object and the attraction surface. As mentioned above, the attraction force is inversely proportional to the square of the gap between the yoke and the object to be attracted, so even if it is only partial, it is not desirable from the viewpoint of attraction force to have a gap.

[0038] This problem will be explained using the conventional magnetic adsorption device shown in Figs. 4 to 7. Fig. 4 is a diagram for explaining the case where a magnetic adsorption device is attached to the outer peripheral surfaces of a plurality of types of steel pipes having different outer diameters, and is a cross-sectional view perpendicular to the pipe axis of the steel pipes. Fig. 5 is an enlarged view of part B in Fig. 4, and is a cross-sectional view showing a gap that occurs when a conventional magnetic adsorption device is fixed to the outer peripheral surface of a steel pipe. Fig. 6 is a diagram for explaining the case where a conventional magnetic adsorption device is attached to the inner peripheral surfaces of a plurality of types of steel pipes having different inner diameters, and is a cross-sectional view perpendicular to the pipe axis of the steel pipes. Fig. 7 is an enlarged view of part C in Fig. 6, and is a cross-sectional view showing a gap that occurs when a conventional magnetic adsorption device is fixed to the outer peripheral surface of a steel pipe.

[0039] The conventional magnetic adsorption device shown here has a configuration partially similar to the magnetic adsorption device 180 of this embodiment, but in Figs. 4 to 7, only the adsorption device main body 180aC corresponding to the adsorption device main body 180a is shown in order to clarify the difference between the two. As shown in Fig. 5, the adsorption surfaces 184aC and 185aC of this conventional adsorption device main body 180aC are both flat. These adsorption surfaces 184aC and 185aC are ring-shaped flat surfaces coaxial with each other. The adsorption surface 184aC is formed at the tip of the outer circumferential yoke portion 184C, and the adsorption surface 185aC is formed at the tip of the inner circumferential yoke portion 185C. These adsorption surfaces 184aC and 185aC are arranged in the same plane perpendicular to the central axis CL of the adsorption device main body 180aC. Therefore, if the surface to be adsorbed is flat, these adsorption surfaces 184aC and 185aC can be in contact with the surface to be adsorbed without any gaps and adsorbed.

[0040] On the other hand, when the attracted surface has a convex circular curvature, that is, when the attracted surface is the outer circumferential surface of a steel pipe 1001 as shown in FIG. 4, a gap g shown in FIG. 5 is generated according to the outer diameter of the steel pipe 1001. Here, as the outer diameter of the steel pipe 1001 becomes smaller, it deviates from the flat state more. Therefore, in the case of FIG. 4, the gap g becomes larger in the order of the outer diameter of φ2000 mm, φ1000 mm, and φ600 mm. Here, a calculation example of the specific value of the gap g is shown in Table 1 below. When the size of the gap g is D (mm), the radius of the outer shape of the outer yoke part 184C of the conventional magnetic attraction device is C (mm), and the radius of the attracted surface is r (mm), the size of the gap g D (mm) is expressed by the following formula 1.

[0041] [Table 1]

[0042] D=C 2 / (2×r)...(Formula 1)

[0043] 5, when the attracted surface has a curvature forming a convex cylindrical surface, the gap g becomes larger as it moves away from the central axis CL, and the attracted surface is essentially only attracted at two points on the attracting surface, attracting surface 185aC of inner peripheral yoke portion 185C and attracting surface 184aC of outer peripheral yoke portion 184C. Therefore, the attracting force is significantly lower than when the attracted surface is attracted to a flat attracted surface. Furthermore, when a conventional magnetic adsorption device is attached to an adsorbed surface having a convex spherical curvature, even the two adsorption points on the adsorption surface 184aC that were in contact with the adsorbed surface are lost, resulting in a more significant decrease in adhesive force.

[0044] The above problem also occurs, and becomes even more severe, when the surface to be attached has a curvature forming a concave cylindrical surface. That is, when the surface to be attached is the inner peripheral surface of a steel pipe 1001 as shown in Fig. 6, a gap g shown in Fig. 7 occurs according to the inner diameter of the steel pipe 1001. Here, as the inner diameter of the steel pipe 1001 becomes smaller, it deviates from the flat state more, so in the case of Fig. 6, the gap g becomes larger in the order of inner diameters of φ2000 mm, φ1000 mm, and φ600 mm. 7, when the attracted surface has a curvature forming a concave cylindrical surface, the gap g becomes larger as it approaches the central axis CL, and the attracted surface is substantially in contact only at two points on the attracting surface 184aC of the outer peripheral yoke portion 184. Therefore, the attracting surface 185aC of the inner peripheral yoke portion 185 is completely separated from the attracted surface, and the outer peripheral yoke portion 184 also has only two points in contact with the attracted surface. Therefore, in this case as well, the attracting force is significantly reduced compared to when the attracting surface is attracted to a flat attracted surface.

[0045] In addition, when a conventional magnetic attraction device is attached to a target surface having a concave spherical curvature, the attraction surface 185aC of the inner peripheral yoke portion 185C is completely separated from the target surface, so it is difficult to obtain a sufficient attraction force. Incidentally, although the attraction surfaces 184aC, 185aC of the conventional magnetic attraction device are both circular in Fig. 4 to Fig. 7, even if these are changed to a box-shaped yoke having a rectangular shape, the problem of the decrease in the attraction force cannot be solved. For the reasons explained above, the attachment points of conventional magnetic attraction devices have been limited to flat surfaces. Therefore, attachment to objects having cylindrical or spherical curvature has not been considered, limiting the scope of application of magnetic attraction devices. However, as exemplified above, in actual situations, the surfaces of objects to be attracted often have cylindrical or spherical curvature. Therefore, if conventional magnetic attraction devices are to be applied, it may be possible to grind the surfaces to be attracted having curvature to form flat surfaces in advance, but this would require a great deal of effort, which would lead to another problem.

[0046] In contrast to the conventional magnetic adsorption device, the magnetic adsorption device 180 of this embodiment can be adsorbed without any gaps, as shown in FIG. 8. FIG. 8 is a cross-sectional view of a cross section perpendicular to the axis of the steel pipe 1001, showing a case where the magnetic adsorption device 180 is fixed to the outer circumferential surface of the steel pipe 1001. In FIG. 8, the axis direction of the steel pipe 1001 is perpendicular to the paper surface. Therefore, the outer circumferential surface of the steel pipe 1001 is a curved surface on the convex side when viewed perpendicular to the paper surface of FIG. 8, forming an adsorbed surface having a curvature forming a convex cylindrical surface. In this figure, for the sake of explanation, only the adsorption device body 180a of the magnetic adsorption device 180 is shown.

[0047] As shown in FIG. 8, the suction device body 180a of this embodiment has suction surfaces 184a and 185a that are both concavely curved. The suction surface 184a is formed at the tip of the outer circumferential yoke portion 184, and the suction surface 185a is formed at the tip of the inner circumferential yoke portion 185. When viewed facing each other, the suction surface (first curved surface) 184a and the suction surface (second curved surface) 185a form ring-shaped surfaces that are coaxial with each other. On the other hand, when viewed from the side (or when viewed in a cross section perpendicular to the axis of the steel pipe 1001), the suction surfaces 184a and 185a form concavely curved surfaces. The shapes and orientations of the suction surfaces 184a and 185a are determined so that both are included in the same concavely curved surface formed on the inner circumferential surface of a cylinder. Therefore, the suction surfaces 184a and 185a have the same curved shape with the same radius of curvature.

[0048] 8, the direction approaching the neodymium magnet 111 as viewed from the positions of the attracting surfaces 184a, 185a is defined as the approaching direction, and the direction away from the neodymium magnet 111 is defined as the separating direction. In this case, the attracting surfaces 184a, 185a move toward the approaching direction as they approach the central axis CL, and on the other hand, the farther they move away from the central axis CL, the more they move toward the separating direction.

[0049] 8, the attracting surface 184a is furthest away in the separating direction at its left end position, gradually approaches the position of the neodymium magnet 111 as it approaches the central axis CL toward the right side of the paper, and reaches the position furthest away in the approaching direction at the position of the central axis CL. Next, as the attracting surface 184a passes the position of the central axis CL and moves away from the central axis CL toward the right side of the paper, it gradually moves away from the position of the neodymium magnet 111, and reaches the position furthest away in the separating direction at the right end position. The left end position and right end position of the attracting surface 184a are at the same positions in the separating direction. Similarly, the attracting surface 185a is also furthest away in the separation direction at its left end position, and gradually approaches the position of the neodymium magnet 111 as it approaches the central axis CL toward the right side of the paper, and reaches the position furthest away in the approach direction at the position of the central axis CL. Then, as the attracting surface 185a passes the position of the central axis CL and moves away from the central axis CL toward the right side of the paper, it gradually moves away from the position of the neodymium magnet 111, and reaches the position furthest away in the separation direction at the right end position. The left end position and the right end position of the attracting surface 185a are the same position in the separation direction. However, since the attracting surface 185a is closer to the central axis CL than the attracting surface 184a, when viewed in the cross section of FIG. 8, the left end position and the right end position of the attracting surface 185a are closer to the approach direction than the left end position and the right end position of the attracting surface 184a. That is, the adsorption surface 185a is disposed at a position recessed further back than the adsorption surface 184a.

[0050] On the other hand, when the suction device main body 180a is viewed in a cross section including the axis of the steel pipe 1001 and perpendicular to the paper surface of FIG. 8, the suction surfaces 184a, 185a are both linear and parallel to the axis of the steel pipe 1001. In this way, the attraction surfaces 184a, 185a are in close contact with the outer circumferential surface of the steel pipe 1001 without any gaps when viewed in a cross section perpendicular to the axis of the steel pipe 1001 and when viewed in a cross section parallel to the axis of the steel pipe 1001. Therefore, the attenuation of the attraction force that attenuates with the square of the gap does not occur at any position in the circumferential direction of the attraction device main body 180a. Therefore, the magnetic force of the neodymium magnet 111 can be effectively utilized without waste, and the strong attraction force inherent to the magnetic attraction device 180 can be exerted. Therefore, it is possible to provide the magnetic attraction device 180 that can be firmly attracted to an attraction target surface having a circular curvature, such as a water intake pipe, a water supply pipe, a penstock, a steel pipe sheet pile, a steel pipe pile, a tank, etc.

[0051] Furthermore, as described above, according to the magnetic attraction device 180, in the process of attracting the magnetic attraction device 180 to the steel pipe 1001, the magnetic attraction device 180 can be automatically positioned around the central axis CL in FIG. That is, the steel pipe 1001 illustrated in Fig. 8 has a cylindrical shape with a central axis perpendicular to the paper surface, and therefore the attracted surface has an arc shape in the cross section of Fig. 8, but has a linear shape in the cross section perpendicular to the paper surface. Therefore, when a direction perpendicular to a point on the attracted surface is set to coincide with the central axis CL of the magnetic attraction device 180, the shape of the attracted surface when viewed in a cross section including the central axis CL differs from one another at each circumferential position around the central axis CL.

[0052] Similarly, the attracting surface 184a of the magnetic attraction device 180 is also in an arc shape having the same radius of curvature as the attracted surface of the steel pipe 1001 in the cross section of FIG. 8, but on the other hand, in the cross section perpendicular to the paper, it is in a straight line shape like the attracted surface of the steel pipe 1001. Therefore, at each circumferential position around the central axis CL, the shape of the attracting surface 184a when viewed in a cross section including the central axis CL is different from each other. The same is true for the attracting surface 185a, which is in an arc shape having the same radius of curvature as the attracted surface of the steel pipe 1001 in the cross section of FIG. 8, but in the cross section perpendicular to the paper, it is in a straight line shape like the attracted surface of the steel pipe 1001. Therefore, at each circumferential position around the central axis CL, the shape of the attracting surface 185a when viewed in a cross section including the central axis CL is different from each other.

[0053] As explained above, the cross-sectional shapes of both the attracted surface and the attracting surfaces 184a, 185a of the steel pipe 1001 are different at each circumferential position about the central axis CL. Therefore, although the attracted surface and the attracting surfaces 184a, 185a of the steel pipe 1001 have cross-sectional shapes with the same curvature, they will not come into close contact with each other unless their rotational positions along the circumferential direction about the central axis CL coincide. However, in the magnetic attraction device 180 of this embodiment, the strong attraction force of the neodymium magnet 111 strongly presses the attraction surfaces 184a, 185a against the attracted surface of the steel pipe 1001, so that even if the positions of the attraction surfaces 184a, 185a around the central axis CL are slightly misaligned with respect to the attracted surface of the steel pipe 1001, the attraction surfaces 184a, 185a automatically rotate while being guided by the inclined surface of the attracted surface of the steel pipe 1001, and finally the attraction surfaces 184a, 185a come into perfect contact with the attracted surface of the steel pipe 1001. In this way, the magnetic attraction device 180 can be attached without any gaps without requiring any special process, so that the attraction force of the neodymium magnet 111 can be exerted without loss.

[0054] In addition, Figure 8 shows an example of a configuration in which the pipe is adsorbed to the outer peripheral surface of the steel pipe 1001, but this configuration is not limited to this, and it is also possible to adopt a configuration in which the pipe is adsorbed to the inner peripheral surface of the steel pipe 1001, as shown in the modified example in Figure 9. In the suction device main body 180a of this modification, as shown in FIG. 9, the suction surfaces 184b and 185b are both convex curved surfaces. The suction surface 184b is formed at the tip of the outer circumferential yoke portion 184, and the suction surface 185b is formed at the tip of the inner circumferential yoke portion 185. When viewed facing each other, the suction surface (first curved surface) 184b and the suction surface (second curved surface) 185b are ring-shaped surfaces that are coaxial with each other. On the other hand, when viewed from the side (or when viewed in a cross section perpendicular to the axis of the steel pipe 1001), the suction surfaces 184b and 185b are convex curved surfaces. The shapes and orientations of the suction surfaces 184b and 185b are determined so that both are included in the same convex curved surface formed on the outer circumferential surface of the cylinder. Therefore, the suction surfaces 184b and 185b have the same curved shape with the same radius of curvature.

[0055] 9, the direction approaching the neodymium magnet 111 as viewed from the positions of the attracting surfaces 184b, 185b is defined as the approaching direction, and the direction away from the neodymium magnet 111 is defined as the separating direction. In this case, the attracting surfaces 184b, 185b move more toward the separating direction as they approach the central axis CL, and conversely, the more they move away from the central axis CL, the more they move toward the approaching direction.

[0056] 9, the attracting surface 184b is closest to the approaching direction at its left end position, and as it approaches the central axis CL toward the right side of the paper, it gradually moves away from the position of the neodymium magnet 111, and reaches the position closest to the separating direction at the position of the central axis CL. Next, as it passes the position of the central axis CL and moves away from the central axis CL toward the right side of the paper, the attracting surface 184b gradually approaches the position of the neodymium magnet 111, and reaches the position closest to the approaching direction at the right end position. The left end position and right end position of the attracting surface 184b are at the same positions in the approaching direction. Similarly, the attracting surface 185b is closest to the approaching direction at its left end position, and as it approaches the central axis CL toward the right side of the paper, it gradually moves away from the position of the neodymium magnet 111, and reaches the position closest to the separating direction at the position of the central axis CL. Next, the attracting surface 185b gradually approaches the position of the neodymium magnet 111 as it passes the position of the central axis CL and moves away from the central axis CL toward the right side of the paper, and reaches the position closest to the approaching direction at the right end position. The left end position and the right end position of the attracting surface 185b are the same position in the separating direction. However, since the attracting surface 185b is closer to the central axis CL than the attracting surface 184b, when viewed in the cross section of FIG. 9, the left end position and the right end position of the attracting surface 185b protrude in the separating direction more than the left end position and the right end position of the attracting surface 184b. That is, the adsorption surface 185b is disposed at a position protruding outward from the adsorption surface 184b.

[0057] On the other hand, when the suction device main body 180a is viewed in a cross section including the axis of the steel pipe 1001 and perpendicular to the paper surface of FIG. 9, the suction surfaces 184b and 185b are both linear and parallel to the axis of the steel pipe 1001. In this way, the attraction surfaces 184b, 185b are in close contact with the inner circumferential surface of the steel pipe 1001 without any gaps when viewed in a cross section perpendicular to the axis of the steel pipe 1001 and when viewed in a cross section parallel to the axis of the steel pipe 1001. Therefore, the attenuation of the attraction force that attenuates with the square of the gap does not occur at any position in the circumferential direction of the attraction device main body 180a. Therefore, even in this modified example, the magnetic force of the neodymium magnet 111 can be effectively utilized without waste, and the strong attraction force that is inherent to the magnetic attraction device 180 can be exerted.

[0058] As described above, the magnetic attraction device 180 can automatically position the magnetic attraction device 180 around the central axis CL in Fig. 9 during the process of attracting the magnetic attraction device 180 to the steel pipe 1001. The mechanism is the same as that described for the configuration in Fig. 8. That is, in the magnetic attraction device 180 of this embodiment, the attraction surfaces 184b, 185b are strongly pressed against the attracted surface of the steel pipe 1001 by the high attraction force of the neodymium magnet 111, so even if the position of the attraction surfaces 184b, 185b around the central axis CL is slightly shifted with respect to the attracted surface of the steel pipe 1001, the attraction surfaces 184b, 185b will automatically rotate while being guided by the inclined surface of the attracted surface of the steel pipe 1001. That is, the inclined surface included in the attraction surfaces 184b, 185b and the inclined surface included in the attracted surface of the steel pipe 1001 will rotate while rubbing against each other until the two surfaces match. As a result, the attraction surfaces 184b, 185b match the attracted surface of the steel pipe 1001 without any gaps. In this way, the magnetic attraction device 180 can be attached without any gaps without requiring any special process, so that the attraction force of the neodymium magnet 111 can be exerted without impairing it.

[0059] Second embodiment A second embodiment of the magnetic attraction device of the present invention will be described below with reference to Fig. 10. Fig. 10 is a perspective view of attraction surfaces 184c, 185c of a yoke 181 provided in a magnetic attraction device 180 of the second embodiment, and other components are omitted for the sake of explanation. In the first embodiment, the suction surfaces 184a, 185a after fixing are configured as two-dimensional curved surfaces that appear curved only when viewed in a cross section perpendicular to the pipe axis of the steel pipe 1001. In contrast, the suction surfaces 184c, 185c in this embodiment are configured as three-dimensional curved surfaces. That is, the suction surfaces 184c, 185c are concave curved surfaces that have the same shape as the suction surfaces 184a, 185a shown in FIG. 8 in all cross sections including the central axis CL. Therefore, in FIG. 10, when viewed in a cross section including the curved line S1 along the suction surfaces 184c, 185c and the central axis CL, and when viewed in a cross section including the curved line S2 along the suction surfaces 184c, 185c and the central axis CL, the suction surfaces 184c, 185c have the same cross-sectional shape as the suction surfaces 184a, 185a shown in FIG. 8. The shapes and orientations of the adsorption surfaces 184c and 185c are determined so that they are both included in the same concave curved surface formed on the inner circumferential surface of the hollow sphere, and therefore, the adsorption surfaces 184c and 185c have the same curved shape with the same radius of curvature.

[0060] By employing the yoke 181 having these attraction surfaces 184c, 185c in the magnetic attraction device 180, even if the surface to be attracted of the object is a convex spherical surface, the entire surface can be brought into close contact with no gap. Therefore, in this embodiment, the attenuation of the attraction force that attenuates with the square of the gap does not occur at any position in the circumferential direction of the attraction device main body 180a. Therefore, in this embodiment as well, the magnetic force of the neodymium magnet 111 can be effectively utilized without waste, and the strong attraction force that is inherent to the magnetic attraction device 180 can be exerted.

[0061] In addition, in Fig. 10, the configuration in which the shape of the adsorption surfaces 184c, 185c is a part of a concave spherical surface in order to adsorb to a convex spherical surface is illustrated as an example, but the present invention is not limited to this configuration. For example, as shown in the modified example of Fig. 11, the shape of the adsorption surfaces 184d, 185d may be a part of a convex spherical surface in order to adsorb to a concave spherical surface. The adsorption surfaces 184d, 185d of this modified example are three-dimensionally configured as convex curved surfaces. That is, the adsorption surfaces 184d, 185d are convex curved surfaces that have the same shape as the adsorption surfaces 184b, 185b shown in Fig. 9 in all cross sections including the central axis CL. Therefore, in Fig. 11, when viewed in a cross section including the curved line S1 along the adsorption surfaces 184d, 185d and the central axis CL, and when viewed in a cross section including the curved line S2 along the adsorption surfaces 184d, 185d and the central axis CL, the adsorption surfaces 184d, 185d have the same cross-sectional shape as the adsorption surfaces 184b, 185b shown in Fig. 9. The shapes and orientations of the adsorption surfaces 184d, 185d are determined so that both are included in the same convex curved surface formed on the outer circumferential surface of the hollow sphere. Therefore, these adsorption surfaces 184d, 185d have the same curved shape with the same radius of curvature.

[0062] By employing the yoke 181 having these attraction surfaces 184d, 185d in the magnetic attraction device 180, even if the surface to be attracted of the object is a concave spherical surface, the object can be brought into close contact with the object over the entire surface without any gaps. Therefore, in this embodiment, the attenuation of the attraction force that attenuates with the square of the gap does not occur at any position in the circumferential direction of the attraction device main body 180a. Therefore, in this modified example as well, the magnetic force of the neodymium magnet 111 can be effectively utilized without waste, and the strong attraction force inherent to the magnetic attraction device 180 can be exerted.

[0063] Third embodiment A third embodiment of the magnetic attraction device of the present invention will be described below with reference to Fig. 12 and Fig. 13. Fig. 12 is a side view of a yoke of the magnetic attraction device of this embodiment. Fig. 13 is a side view illustrating the movement of the yoke when the magnetic attraction device is fixed. In the first and second embodiments, the magnetic attraction device has an attraction surface that has only one of a concave curved surface and a convex curved surface. In contrast, in the present embodiment, as shown in Fig. 12, the magnetic attraction device has both a concave curved surface and a convex curved surface in accordance with the surface to be attracted of the object to be attracted. With this configuration, as shown in Fig. 13, the magnetic attraction surfaces 184e and 185e of the magnetic attraction device 180 can be attracted to the object to be attracted 1002 having a surface to be attracted that has both a concave curved surface and a convex curved surface without any gaps.

[0064] The object to be attracted 1002 is a steel material that is long in the direction perpendicular to the plane of the page in Fig. 13, and has a corrugated outer surface when viewed in a cross section perpendicular to the longitudinal direction, as shown in Fig. 13. When a conventional magnetic attraction device having a flat attraction surface is attracted to such a corrugated attraction surface, a gap is created. In contrast, the magnetic attraction device 180 of this embodiment has a corrugated attraction surface 184e and a convex attraction surface 185e, and therefore can adhere closely to the attracted surface without any gaps.

[0065] That is, the adsorption surface 184e is formed at the tip of the outer peripheral yoke portion 184, and has a corrugated concave-convex curved surface that matches the corrugated adsorbed surface. On the other hand, the adsorption surface 185e is formed at the tip of the inner peripheral yoke portion 185, and has a convex curved surface that matches the concavely curved portion of the adsorbed surface. When viewed facing each other, the adsorption surface (first curved surface) 184e and the adsorption surface (second curved surface) 185e form ring-shaped surfaces that are coaxial with each other. The other configurations are the same as those described in the first embodiment. When the magnetic adsorption device 180 of this embodiment is attached to a surface to be attracted, as shown in FIG. 13, it is possible to obtain an adjustment effect in which the concave-convex curved surface of the magnetic adsorption device 180 and the concave-convex curved surface of the surface to be attracted naturally match each other by utilizing the magnetic adsorption force.

[0066] That is, the high attractive force of the neodymium magnet 111 strongly presses the attractive surfaces 184e, 185e against the attracted surface of the object to be attracted 1002, so even if the central axis CL of the attractive surfaces 184e, 185e is slightly misaligned with respect to the wavy attracted surface, the attractive surfaces 184e, 185e automatically move while being guided by the inclined surface of the attracted surface, and finally the attractive surfaces 184e, 185e match the attracted surface without any gaps. In this way, the magnetic attraction device 180 can be attached without any gaps without requiring any special process, so the attractive force of the neodymium magnet 111 can be exerted without loss.

[0067] The gist of each of the above-described embodiments will be summarized below. (1) As illustrated in FIG. 1, one embodiment of the present invention is a magnetic adsorption device 180 including a neodymium magnet (permanent magnet) 111 and a yoke 181 that holds the neodymium magnet 111, wherein the yoke 181 has a back yoke portion 183 that adsorbs the neodymium magnet 111 and an outer peripheral yoke portion 184 that is formed integrally with the back yoke portion 183 and surrounds the neodymium magnet 111, and an adsorption surface 184a of the outer peripheral yoke portion 184 includes a first curved surface. According to the magnetic attraction device 180 described in (1) above, the attraction surface 184a has a first curved surface that matches the surface shape of the steel pipe (object to be attracted) 1001, so that the attraction surface 184a can overlap the steel pipe 1001 without any gaps. As a result, the decrease in the attraction force due to the gaps can be suppressed, so that the original attraction force of the neodymium magnet 111 can be exerted.

[0068] (2) As illustrated in Figures 10 and 11, in the magnetic adsorption device 180 described in (1) above, the first curved surface may include a curved shape forming a part of the outer circumferential surface or inner circumferential surface of a hollow sphere. In other words, a configuration may be adopted in which the first curved surface is curved in a convex shape approaching the neodymium magnet 111 or in a direction away from the neodymium magnet 111 in both a cross section including one of two intersecting axes (curved lines S1, S2) that are perpendicular to each other when the adsorption surface 184a is viewed opposite to each other and a cross section including the other of the two intersecting axes (curved lines S1, S2). In the case of the magnetic adsorption device 180 described in (2) above, regardless of whether the surface shape of the object to be adsorbed is a convex spherically curved surface or a concave spherically curved surface, the adsorption surface 184a of the magnetic adsorption device 180 can be overlapped without any gaps.

[0069] (3) As illustrated in Figures 8 and 9, in the magnetic adsorption device 180 described in (1) above, the first curved surface may include a curved shape forming a part of the outer peripheral surface or inner peripheral surface of a cylinder. In other words, a configuration may be adopted in which, in a cross section including one of two intersecting axes (curved lines S1, S2) that are perpendicular to each other when the adsorption surface 184a is viewed opposite to each other, the first curved surface is curved in a convex shape facing toward or away from the neodymium magnet 111, and in a cross section including the other of the two intersecting axes, the adsorption surface (first curved surface) 184a is linear. In the case of the magnetic attraction device 180 described in (3) above, regardless of whether the surface shape of the attraction target is a convex cylindrical curved surface or a concave cylindrical curved surface, the attraction surface 184a of the magnetic attraction device 180 can be overlapped without any gaps.

[0070] (4) As illustrated in Figures 8 and 9, the magnetic adsorption device 180 described in any one of (1) to (3) above may be configured as follows: the neodymium magnet 111 is ring-shaped; an inner yoke portion 185 penetrating the neodymium magnet 111 is integrally formed with the back yoke portion 183; and the adsorption surface 185a of the inner yoke portion 185 includes a second curved surface. In the case of the magnetic attraction device 180 described in (4) above, the attraction surface (first curved surface) 184a and the attraction surface (second curved surface) 185a, which are adapted to the surface shape of the object to be attracted, can be overlapped without any gaps. As a result, the improvement of the attraction force due to the provision of the inner yoke portion 185 can be effectively achieved.

[0071] (5) As illustrated in Figures 8 and 9, in the magnetic adsorption device 180 described in (4) above, the adsorption surface (first curved surface) 184a and the adsorption surface (second curved surface) 185a may have the same curved shape with the same radius of curvature. In the case of the magnetic attraction device 180 described in (5) above, the gap between the attraction surface (first curved surface) 184a and the attraction surface (second curved surface) 185a and the surface shape of the object to be attracted can be easily and accurately controlled.

[0072] In the above-mentioned embodiments, the entire suction surfaces 184a-184e constitute a curved surface (first curved surface), and the entire suction surfaces 185a-184e constitute a curved surface (second curved surface). However, the present invention is not limited to this embodiment, and only a part of the suction surfaces 184a-184e may constitute a curved surface (first curved surface), and only a part of the suction surfaces 184a-184e may constitute a curved surface (second curved surface). In other words, the suction surfaces 184a-184e and the suction surfaces 184a-184e may be configured to partially include a discontinuous portion due to a flat surface, a concave or convex corner, or the like, connected to the curved surface, on the premise that at least a part of the suction surfaces 184a-184e has a curved surface.

[0073] In addition, in each of the above-described embodiments, the shape of the adsorption surfaces 184a to 184e is a ring shape when viewed from the opposite side, but it is not limited to a circle, and other shapes such as a rectangle, an ellipse, etc. may be adopted. For example, when a rectangular frame shape is adopted as the shape of the adsorption surfaces 184a to 184e, this rectangular frame shape may be a square or a rectangle.

[0074] Moreover, the magnetic adsorption device 180 of each embodiment described above can be used for various applications, whether on land or underwater. For example, in civil engineering and construction applications, it can be suitably used for assembling steel structures such as iron poles and iron plates, and attaching accessories to steel structures. In this application, assembly and attachment have traditionally been performed using processing means such as welding, riveting, and bolt fastening, but by adopting the magnetic adsorption device of the present invention, these can be strongly adsorbed to obtain the same strength as construction using the above processing means, thereby obtaining effects such as shortening the construction period and improving work efficiency. Furthermore, since it can be removed as necessary, if it is used for setting up a work scaffold, removal work can also be performed quickly. [Explanation of symbols]

[0075] 111...Neodymium magnet (permanent magnet) 180...Magnetic adsorption device 181…York 183…Back yoke 184…Outer yoke part 184a...adsorption surface, first curved surface 185a...adsorption surface, second curved surface 185…Inner yoke part

Claims

1. A magnetic adsorption device comprising a permanent magnet and a yoke that holds the permanent magnet, the yoke has a back yoke portion that is attracted to the permanent magnet, and an outer periphery yoke portion that is integrally formed with the back yoke portion and surrounds the permanent magnet, The suction surface of the outer yoke portion includes a first curved surface. A magnetic adsorption device characterized by:

2. The first curved surface includes a curved shape that forms a part of the outer circumferential surface or the inner circumferential surface of a hollow sphere.

2. The magnetic adsorption device according to claim 1.

3. The first curved surface includes a curved shape that forms a part of an outer circumferential surface or an inner circumferential surface of a cylinder.

2. The magnetic adsorption device according to claim 1.

4. The permanent magnet is ring-shaped, An inner yoke portion that passes through the permanent magnet is integrally formed with the back yoke portion, The suction surface of the inner yoke portion includes a second curved surface.

4. The magnetic adsorption device according to claim 1, wherein the magnetic adsorption device is a magnetically adsorbed device.

5. The first curved surface and the second curved surface have the same curved shape with the same radius of curvature.

5. The magnetic adsorption device according to claim 4.

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