Corrosion-resistant magnet and magnetic adsorption device

Abstract

To provide a corrosion-resistant magnet with improved corrosion resistance, suitable for long-term use in high-humidity environments or underwater conditions, as well as a magnetic attractor equipped with the corrosion-resistant magnet.SOLUTION: A corrosion-resistant magnet 110 includes: a neodymium magnet 111 covered with a nickel layer 111a; and a zinc layer 112 formed on the nickel layer 111a. A magnetic attractor includes the corrosion-resistant magnet 110 and a yoke 181 that encases the corrosion-resistant magnet 110.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a corrosion-resistant magnet and a magnetic adsorption device.

Background Art

[0002] Permanent magnets such as neodymium, samarium cobalt, alnico, and ferrite currently in use are mainly manufactured on the premise of being used in the atmosphere, and have not been considered for use in high-humidity environments or seawater. In particular, for neodymium magnets, since neodymium (Ne), the main material, is a base metal with an electrode potential of around -2400 mV (SCE), when used in the atmosphere and moisture or water intrudes, a galvanic cell is formed with other metal materials and it becomes the anode part and dissolves and disintegrates. Therefore, it cannot be used without nickel plating on the surface. Thus, permanent magnets are premised on use in the atmosphere and have not been considered for use in seawater. And since the appearance of neodymium magnets, no corrosion prevention measures other than nickel plating on their surfaces have been taken.

[0003] The inventors of the present invention planned to use the adsorption force of a neodymium magnet as a means to attach an Al anode for cathodic protection in seawater instead of underwater welding. And in order to enhance the adsorption force of the neodymium magnet and prevent corrosion in seawater, the neodymium magnet was housed in a yoke and then further filled with a flexible zinc anode material to form a sacrificial anode layer and endow an electrochemically cathodic protection function, and developed a "magnetic adsorption device" (see Patent Document 1 below).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The above magnetic adsorption device is highly evaluated as a technology to replace conventional fixing means such as welding due to its high adsorption performance and ease of use. And, while it is desired to further expand its scope of application by taking advantage of its convenience, considering further long-term use in an environment with a lot of moisture or water, further improvement in the corrosion resistance of the magnet used in the device is required. For example, a neodymium magnet is suitable as the magnet. However, a neodymium magnet is made by sintering materials such as neodymium (Ne), boron (B), and ferrite (Fe). Since its surface is porous, moisture and water easily penetrate. When such penetration of moisture and water occurs, a dissimilar metal contact battery (galvanic cell) is formed between the materials, and the neodymium-rich part with a lower potential becomes the anode and dissolves. Therefore, as a measure to prevent the penetration of moisture and water, the neodymium magnet is used with its surface coated with a nickel plating layer. However, since the nickel plating layer itself is also porous and has a large number of pores on its surface, further improvement is required for further long-term use in a high-humidity environment or underwater.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a corrosion-resistant magnet having higher corrosion resistance that can withstand long-term use in a high-humidity environment or underwater, and a magnetic adsorption device including this corrosion-resistant magnet.

Means for Solving the Problems

[0007] In order to solve the above problems and achieve the related object, the present invention adopts the following aspects. (1) The corrosion-resistant magnet according to one aspect of the present invention is a permanent magnet whose entire surface is coated with a nickel film, a zinc film formed on the nickel film, and has the zinc Film covering the entire surface of the nickel film. (2) In the corrosion-resistant magnet according to the above (1), the zinc film may be a zinc plating. (3) In the corrosion-resistant magnet according to the above (1), the zinc coating may be a zinc tape.

[0008] According to the corrosion-resistant magnet described in the above (1) to (3), the pores on the surface of the nickel coating are covered by the zinc coating. Therefore, even when this corrosion-resistant magnet is used for a long time in a high-humidity environment or in water (including seawater), moisture and water will not reach the permanent magnet through the pores of the nickel coating, so that dissolution of the permanent magnet can be prevented. Accordingly, this corrosion-resistant magnet has high corrosion resistance that can withstand long-term use in a high-humidity environment or in water.

[0009] (4) The corrosion-resistant magnet according to another aspect of the present invention is The entire surface is a permanent magnet coated with a nickel coating, and a first insulating layer made of an epoxy resin formed on the nickel coating, and has such that the first insulating layer covers the entire surface of the nickel film. According to the corrosion-resistant magnet described in the above (4), the pores on the surface of the nickel coating are covered by the first insulating layer. Therefore, even when this corrosion-resistant magnet is used for a long time in a high-humidity environment or in water, moisture and water will not reach the permanent magnet through the pores of the nickel coating, so that dissolution of the permanent magnet can be prevented. Accordingly, this corrosion-resistant magnet has high corrosion resistance that can withstand long-term use in a high-humidity environment or in water.

[0010] (5) A magnetic adsorption device according to one aspect of the present invention is the corrosion-resistant magnet according to any one of the above (1) to (4), and a yoke that holds the corrosion-resistant magnet, and comprises. According to the magnetic adsorption device described in the above (5), the corrosion-resistant magnet thereof has high corrosion resistance that can withstand long-term use in a high-humidity environment or in water. Therefore, this magnetic adsorption device can be used for a long time in a high-humidity environment or in seawater.

[0011] (6) The magnetic adsorption device according to (5) above, a zinc anode layer covering the corrosion-resistant magnet may be further provided. According to the magnetic adsorption device described in (6) above, since the surface of the corrosion-resistant magnet is further covered by the zinc anode layer, it has higher corrosion resistance and can exhibit high magnetic adsorption performance over a long period.

[0012] (7) In the magnetic adsorption device described in (6) above, the following configuration may be adopted: the corrosion-resistant magnet is ring-shaped, the yoke has a back yoke portion that adsorbs to the corrosion-resistant magnet, an outer peripheral yoke portion that is integrally formed with the back yoke portion and surrounds the corrosion-resistant magnet, and an inner peripheral yoke portion that is disposed on the inner peripheral side of the corrosion-resistant magnet and is integrally formed with the back yoke portion. The zinc anode layer is formed between the outer peripheral surface of the corrosion-resistant magnet and the inner peripheral surface of the outer peripheral yoke portion, between the inner peripheral surface of the corrosion-resistant magnet and the outer peripheral surface of the inner peripheral yoke portion, and on the surface of the corrosion-resistant magnet opposite to the adsorption surface with the back yoke portion. is formed. According to the magnetic adsorption device described in (7) above, since the surface of the corrosion-resistant magnet is further covered by the zinc anode layer, it has higher corrosion resistance and can exhibit high magnetic adsorption performance over a long period.

[0013] (8) In the magnetic adsorption device described in (5) above, a second insulating layer made of epoxy resin formed on the surface of the corrosion-resistant magnet may be further provided. According to the magnetic adsorption device described in (8) above, since the surface of the corrosion-resistant magnet is further covered by the epoxy resin, it has higher corrosion resistance and can exhibit high magnetic adsorption performance over a long period.

[0014] (9) In the magnetic adsorption device described in (8) above, the following configuration may be adopted: The corrosion-resistant magnet is ring-shaped, and the yoke has a back yoke portion that adsorbs to the corrosion-resistant magnet, an outer peripheral yoke portion that is integrally formed with the back yoke portion and surrounds the corrosion-resistant magnet, and an inner peripheral yoke portion that is disposed on the inner peripheral side of the corrosion-resistant magnet and is integrally formed with the back yoke portion. The second insulating layer is formed between the outer peripheral surface of the corrosion-resistant magnet and the inner peripheral surface of the outer peripheral yoke portion, between the inner peripheral surface of the corrosion-resistant magnet and the outer peripheral surface of the inner peripheral yoke portion, and on the surface of the corrosion-resistant magnet opposite to the adsorption surface with the back yoke portion. According to the magnetic adsorption device described in (9) above, since the surface of the corrosion-resistant magnet is further covered by the second insulating layer, it has higher corrosion resistance and can exhibit high magnetic adsorption performance over a long period.

Effects of the Invention

[0015] According to each of the above aspects, it is possible to provide a corrosion-resistant magnet having higher corrosion resistance that can withstand long-term use in a high-humidity environment or underwater, and a magnetic adsorption device provided with this corrosion-resistant magnet.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

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Figure 11

[0017] Embodiments of the corrosion-resistant magnet and the magnetic adsorption device including the same of the present invention and various modifications thereof will be described below with reference to the drawings.

[0018] [Magnetic Adsorption Device] FIG. 1 is a diagram showing an embodiment of the present invention, and it is a longitudinal sectional view of the magnetic adsorption device 180 as seen in a cross-section including its central axis. FIG. 2 is an exploded perspective view of the magnetic adsorption device 180. The magnetic adsorption device 180 of this embodiment is particularly characterized by a corrosion-resistant magnetic adsorption structure 176 including a corrosion-resistant magnet 110. In the following description, first, the overall configuration of the magnetic adsorption device 180 will be described based on FIGS. 1 and 2, and then the details of the corrosion-resistant magnet 110 and the corrosion-resistant magnetic adsorption structure 176 will be continuously described.

[0019] As shown in FIG. 2, the magnetic adsorption device 180 according to this embodiment includes an adsorption device main body 180a and a nut 180b for fixing the adsorption device main body 180a to equipment or the like. The bolt 188 is screwed into the adsorption device main body 180a and used to adjust the adsorption force on the adsorption object by advancing and retreating the magnetic adsorption device 180 with respect to the adsorption object, and is an adsorption force adjustment member.

[0020] As shown in FIG. 2, the adsorption device main body 180a includes a corrosion-resistant magnetic adsorption structure 176 including a corrosion-resistant magnet 110 and a cap-shaped yoke 181 for accommodating the corrosion-resistant magnetic adsorption structure 176. In this FIG. 2, for the sake of explanation, only the corrosion-resistant magnet 110 in a ring shape in plan view among the corrosion-resistant magnetic adsorption structures 176 is illustrated. A screw shaft portion 186 is formed on the surface of the yoke 181 on the side opposite to the side facing the corrosion-resistant magnet 110.

[0021] As shown in FIG. 1, anticorrosion members 142a and 142b are provided in the gap between the yoke 181 and the corrosion-resistant magnet 110. Further, an anticorrosion member 142c is also provided on the lower surface of the corrosion-resistant magnet 110, that is, the surface that is exposed outward when accommodated in the yoke 181. In this embodiment, the corrosion-resistant magnet 110 and the anticorrosion members 142a, 142b, 142c, 142d (described later) covering the corrosion-resistant magnet 110 constitute the corrosion-resistant magnetic adsorption structure 176. The details of this corrosion-resistant magnetic adsorption structure 176 will be described later.

[0022] The yoke 181 has a configuration in which a disk-shaped back yoke portion 183 that adsorbs to the magnet surface on the back side of the corrosion-resistant magnet 110, a cylindrical outer peripheral yoke portion 184 having an inner peripheral surface facing the outer peripheral surface of the corrosion-resistant magnet 110, an inner peripheral yoke portion 185 having an outer peripheral surface facing the inner peripheral surface of the corrosion-resistant magnet 110, and a screw shaft portion 186 provided on the side of the back yoke portion 183 opposite to the surface that adsorbs to the corrosion-resistant magnet 110 are integrally formed. And the yoke 181 houses the corrosion-resistant magnetic adsorption structure 176 in a groove portion 181b in the shape of a ring in plan view formed by the back yoke portion 183, the outer peripheral yoke portion 184, and the inner peripheral yoke portion 185.

[0023] By providing the inner peripheral yoke portion 185 and the outer peripheral yoke portion 184 facing the inner periphery and the outer periphery of the ring-shaped corrosion-resistant magnet 110 as described above, the magnetic adsorption device 180 of the present embodiment is capable of obtaining a strong adsorption force. That is, by adopting such a double yoke structure, adsorption portions are formed between the corrosion-resistant magnet 110 and the inner peripheral yoke portion 185 and between the corrosion-resistant magnet 110 and the outer peripheral yoke portion 184, respectively, and the magnetic force of the corrosion-resistant magnet 110 can be efficiently utilized for adsorption. Specifically, the magnetic adsorption device 180 having the above-described double yoke structure can obtain an adsorption force about 1.7 times higher than that of a magnetic adsorption device having a configuration without the inner peripheral yoke portion 185 (single yoke structure). In the present embodiment, by adopting such a double yoke structure, the adsorption force is greatly improved without increasing the dimensions, and even a heavy equipment device can be fixed by the small magnetic adsorption device 180.

[0024] Also, as shown in FIG. 1, the groove portion 181b of the yoke 181 is formed to have a depth greater than the height of the corrosion-resistant magnetic adsorption structure 176. In a state where the corrosion-resistant magnetic adsorption structure 176 is housed in the yoke 181, the adsorption surfaces on the opening side of the outer peripheral yoke portion 184 and the inner peripheral yoke portion 185 protrude to the tip side (the adsorption target object 1000 side) from the surface of the corrosion-resistant magnetic adsorption structure 176. By protruding the yoke 181 more than the corrosion-resistant magnetic adsorption structure 176 in this way, it is possible to protect the corrosion-resistant magnetic adsorption structure 176 from friction and impact when the magnetic adsorption device 180 is adsorbed to the adsorption target 1000, and it is possible to prevent the corrosion-resistant magnetic adsorption structure 176 from wearing or cracking.

[0025] As shown in Fig. 2, the screw shaft portion 186 is integrally formed in a cylindrical shape with the yoke 181, and the extending direction of the screw shaft portion 186 coincides with the normal direction of the outer surface of the back yoke portion 183. On the outer peripheral surface of the screw shaft portion 186, a male screw portion 186a for screwing the nut 180b is formed. This screw shaft portion 186 functions as a member for attaching the magnetic adsorption device 180 to equipment (not shown) together with the nut 180b. That is, by inserting the screw shaft portion 186 into the bolt hole H of the support fitting (reference symbol S in Fig. 1) provided on the equipment and then fastening the nut 180b, it can be easily attached to the equipment or the like. The support fitting S in Fig. 1 extends toward the back side of the paper surface and is fixed to the equipment. Therefore, the equipment is fixed to the adsorption target 1000 by the magnetic adsorption device 180 fixed to the support fitting S with the nut 180b being magnetically adsorbed to the adsorption target 1000.

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

[0027] On the inner surface of the screw hole portion 181a, a female screw portion that screws with the male screw portion 189 of the bolt 188 is formed. Since the screw hole portion 181a penetrates the adsorption device main body 180a, by screwing a bolt 188 of sufficient length into the screw hole portion 181a, the tip of the bolt 188 can be made to protrude from the tip of the inner peripheral yoke portion 185. Also, by rotating the bolt 188 forward or backward around the axis, the protruding length of the bolt 188 from the adsorption surface of the yoke 181 can be freely adjusted.

[0028] The nut 180b screwed onto the male thread portion 186a of the screw shaft portion 186 is a locknut. In the case of the present embodiment, as shown in FIG. 2, a friction ring 187 coaxial with the screw hole of the nut 180b is provided. The friction ring 187 has a claw portion protruding toward the central portion side of the screw hole. By screwing the nut 180b onto the screw shaft portion 186, the claw portion comes into contact with the thread of the male thread portion 186a and deforms, and the male thread portion 186a is pressed by the reaction force generated by this deformation. Then, the free rotation of the nut 180b is restricted by the frictional force generated between the friction ring 187 and the male thread portion 186a, thereby preventing the nut 180b from loosening. Note that the anti-loosening structure of the nut 180b is not particularly limited, and various structures such as those using a spring washer, a double-nut structure, and a structure using a resin ring can be used in addition to the one using a friction ring.

[0029] As shown in FIG. 2, a plurality of screw hole portions (through holes) 183a penetrating the back yoke portion 183 and reaching the corrosion-resistant magnet 110 are formed in the back yoke portion 183. These screw hole portions 183a are used when accommodating the corrosion-resistant magnet 110 in the yoke 181. By inserting a bolt (not shown) through the screw hole portion 183a and protruding the tip of the bolt inside the yoke 181, the adsorption of the corrosion-resistant magnet 110 disposed on the opening side of the yoke 181 to the back yoke portion 183 is restricted. Thereby, when the corrosion-resistant magnet 110 is disposed, it is prevented from being drawn into the inside of the yoke 181 and colliding with the back yoke portion 183, and the corrosion-resistant magnet 110 is prevented from cracking or chipping due to the impact.

[0030] After the corrosion-resistant magnet 110 is adsorbed to the back yoke portion 183, an anticorrosion member 142d shown in FIG. 3 is provided in the screw hole portion 183a. As described above, the screw hole portion 183a is hardly used except for the assembly of the magnet during manufacturing or the removal of the magnet during disassembly. Therefore, after the corrosion-resistant magnet 110 is attached into the yoke 181, by disposing the anticorrosion member 142d in the screw hole portion 183a so as to be in contact with the corrosion-resistant magnet 110, corrosion of the corrosion-resistant magnet 110 can be effectively prevented. Further, since leakage of magnetic flux through the screw hole portion 183a can be reduced, the utilization efficiency of magnetic force can be increased, and magnetic force acting on other members can also be prevented. Incidentally, if the corrosion-resistant magnet 110 can be accommodated inside the yoke 181 without applying an impact thereto, the screw hole portion 183a may be omitted. In that case, since there is no through hole in the back yoke portion 183, the anticorrosion member 142d for filling the through hole is also unnecessary.

[0031] In the magnetic adsorption device 180 having the configuration described above, the height of the adsorption force by the corrosion-resistant magnet 110 having a strong magnetic force is controlled by the screw hole portion 181a formed in the screw shaft portion 186 provided to protrude from the back yoke portion 183 and the bolt 188 screwed into the screw hole portion 181a, so that the magnetic adsorption device 180 can be safely and surely adsorbed to the adsorption target.

[0032] That is, when the magnetic adsorption device 180 is adsorbed to the adsorption target 1000 as shown in FIG. 1, first, the bolt 188 is screwed into the screw hole portion 181a of the adsorption device main body 180a from the upper end of the screw shaft portion 186 so that the tip of the bolt 188 protrudes from the tip of the inner circumferential yoke portion 185. At this time, the protruding length of the bolt 188 can be exemplified as about 5 mm to 8 mm although it depends on the adsorption force of the magnetic adsorption device 180.

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

[0034] After that, when the head of the bolt 188 is rotated to retract the bolt 188, the gap between the magnetic adsorption device 180 and the object to be adsorbed 1000 gradually decreases, and accordingly, the attracting force between the two also increases. Then, when the bolt 188 is retracted to a position where its tip does not protrude from the inner peripheral yoke portion 185, as shown in FIG. 1, the adsorption surfaces of the outer peripheral yoke portion 184 and the inner peripheral yoke portion 185 come into contact with the object to be adsorbed 1000. Thereby, the magnetic adsorption device 180 is adsorbed to the object to be adsorbed 1000 on its adsorption surface.

[0035] On the other hand, when removing the magnetic adsorption device 180 from the object to be adsorbed 1000, in the adsorption state shown in FIG. 1, the bolt 188 is rotated about its axis to advance the tip portion of the bolt 188 toward the object to be adsorbed 1000 side. Then, a gap can be formed between the magnetic adsorption device 180 and the object to be adsorbed 1000. Since the corrosion-resistant magnet 110 used in the magnetic adsorption device 180 has an extremely strong adsorption force, it is difficult to directly pull it apart by hand. However, since the adsorption force of the magnetic adsorption device 180 is inversely proportional to the square of the gap between the yoke 181 and the object to be adsorbed 1000, it becomes possible to easily pull it apart by hand just by forming a gap of several millimeters. As described above, the magnetic adsorption device 180 of the present embodiment can be easily and safely attached to, detached from, or position-adjusted with respect to the object to be adsorbed 1000.

[0036] [Corrosion-Resistant Magnet and Corrosion-Resistant Magnetic Adsorption Structure] Continuing with the overall configuration described above, the details of the corrosion-resistant magnetic adsorption structure 176, which is particularly characteristic of the magnetic adsorption device 180 of this embodiment, will be described. In the following, in order to explain this feature in detail, the description will proceed including the development process from the magnetic adsorption device of the conventional structure to the configuration of this embodiment.

[0037] Cathodic protection is adopted as a countermeasure against corrosion of steel structures constructed in seawater. In this cathodic protection, an aluminum alloy anode (hereinafter: Al anode), which is a supply source of cathodic protection current, is attached to a steel object to be protected. And, as a means for this attachment, conventionally, underwater welding, which directly generates an arc and welds underwater, has been used. However, the inventors have confirmed that underwater welding induces a strength reduction of the steel sheet pile, which is high-tensile steel, in the case where the object to be protected is a steel sheet pile. Then, the inventors have advanced research to develop an alternative means for attaching the Al anode instead of underwater welding. And, a "magnetic adsorption device" has been developed which adsorbs the Al anode to the steel sheet pile using the strong magnetic force (adsorption force) possessed by neodymium magnets. Furthermore, the "Japan Magnetic Adsorption Method Association" has been established and efforts are being made to spread this technology.

[0038] In the process of developing the magnetic adsorption method, the inventors have confirmed the phenomenon that the neodymium magnets in the magnetic adsorption device are corroded and worn out, and investigated the cause. As a result, it was confirmed that since the nickel plating layer of the neodymium magnet has a low function as a protective layer, corrosion progresses from there if there are even the slightest scratches or defects despite applying cathodic protection using a zinc anode. Therefore, with the cooperation of Kagoshima University, a durability test of the neodymium magnet in seawater was carried out. As a result, it was confirmed that when a flaw occurs in the nickel plating layer, the neodymium magnet forms a galvanic cell with the object to be protected and becomes the anodic part and is severely consumed. In this galvanic cell, since the area ratio of the anodic part to the cathodic part is extremely large and the potential of the neodymium magnet is -2400 mV (SCE) and the object to be protected reaches the cathodic protection potential of around -900 mV (SCE), the potential difference (electromotive force) reaches 1500 mV and almost no cathodic polarization accompanies energization, so it was confirmed that a large corrosion current continues to flow.

[0039] Therefore, it was found that preventing the formation of this large-scale galvanic cell is necessary for the stable long-term use of neodymium magnets in seawater. At the beginning of the development, it was considered to strengthen the corrosion prevention function of the nickel plating layer, and electrolytic zinc plating (with a thickness of around 30 μm) was applied on top of the nickel plating layer to form a nickel-zinc composite plating layer. Then, as a result of conducting a salt spray test on this composite plating layer, it was confirmed that it has durability more than 10 times that of the case of the nickel plating layer alone.

[0040] However, when the processing quantity of neodymium magnets with electrolytic zinc plating is small, there is a situation where it is not cost-effective. Therefore, as an alternative measure, a configuration was adopted in which a zinc tape (with a thickness of 200 μm) is attached on top of the nickel plating layer to form a sacrificial anode layer. As a result of conducting a salt spray test on the configuration using this zinc tape, it was confirmed that the corrosion resistance is improved by more than 7 times compared to the case of applying electrolytic zinc plating. Therefore, it was confirmed that by strengthening the sacrificial anode function using a zinc tape, the corrosion caused by the galvanic cell can be reduced more significantly.

[0041] Attaching the zinc tape does not require special techniques or tools. By polishing and degreasing the nickel plating layer applied to the surface of the neodymium magnet, cutting the zinc tape into a predetermined shape and size, and attaching and adhering it, a zinc anode layer can be formed. Therefore, it can be carried out in a shorter time and at a lower cost than in the case of applying electrolytic zinc plating. The current zinc tape has a thickness of 200 μm, so it has a capacity 4 times that of HDZ55, which is the thickest standard of molten zinc plating. And since it also has a blocking function to seal the defective parts (micro pores) of the nickel plating layer, it can eliminate the potential difference between the neodymium magnet and the object to be protected, thereby preventing the formation of a galvanic cell.

[0042] Furthermore, aside from electrochemical means, it was considered that the formation of a galvanic cell could be prevented by physically isolating the neodymium magnet from the usage environment. Therefore, the functions of various commercially available insulating paints, lining materials, and fillers were investigated. As a result, it was found that a solvent-free epoxy resin paint sold under the name "Sigma Guard CSF650" by Amacoat in the United States has extremely excellent insulation and durability against seawater. When this solvent-free epoxy resin paint is used as a coating material for underwater use of neodymium magnets, it can impart extremely high durability and also has the following advantages. (1) It does not use solvents. (2) It has high coating properties at corners and edges. (3) It has high filling properties in damaged parts (open craters, omega craters). (4) Since the shrinkage of the coating film is low, cracks do not occur.

[0043] This solvent-free epoxy resin paint has also received high evaluations from the US Navy that adopted it, and information has been obtained that extremely long-term durability of over 100 years can be expected. Therefore, a sample in which a solvent-free epoxy resin paint was applied onto the nickel plating layer of a neodymium magnet to form an insulating layer, and a sample in which a solvent-free epoxy resin paint was filled around the neodymium magnet housed in a yoke to form an insulating layer (lining part) were fabricated. Then, these samples were subjected to a durability test by salt spray and confirmed. As a result, no changes were observed in the coating film part or the lining part around 1000 hours, and it was confirmed that high durability can be obtained over a long period. Furthermore, it was also confirmed that by appropriately combining electrochemical corrosion prevention measures (enhancing the sacrificial anode function) and physical corrosion prevention measures (forming an insulating film), the corrosion resistance of permanent magnets can be improved by several to several tens of times compared to the conventional level.

[0044] Through the above development process, the corrosion-resistant magnet of the present invention and the magnetic adsorption device including the same have been obtained. Embodiments and various modifications of these corrosion-resistant magnets and magnetic adsorption devices will be described below. First, each aspect of the corrosion-resistant magnet 110 will be described with reference to FIGS. 3 to 7. Subsequently, each aspect of the magnetic adsorption device 180 including the corrosion-resistant magnetic adsorption structure 176 will be described with reference to FIGS. 8 to 11.

[0045] FIG. 3 is a diagram for explaining the detailed structure of the corrosion-resistant magnetic adsorption structure 176 provided in the magnetic adsorption device 180, and is an enlarged view of part A in FIG. 1. The corrosion-resistant magnet 110 of the corrosion-resistant magnetic adsorption structure 176 has a neodymium magnet 111, a zinc coating 112 or a first insulating layer 113, and a zinc anode layer 142 or a second insulating layer 143.

[0046] The neodymium magnet 111 is an example of a permanent magnet, but is not limited thereto. That is, the permanent magnet to be used is not limited to the Nd-Fe-B-based permanent magnet, and includes not only RE-Fe-M-B (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, 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, Ta) iron-based rare earth permanent magnets, but also Sm-Co magnets, ferrite magnets, etc. can be adopted.

[0047] The neodymium magnet 111 is a thin ring-shaped component, having a pair of upper and lower surfaces, and an inner peripheral surface and an outer peripheral surface connecting between these upper and lower surfaces. The upper and lower surfaces of the neodymium magnet 111 are annular flat surfaces having the same inner diameter and outer diameter and being coaxial with each other. Also, the inner peripheral surface and the outer peripheral surface of the neodymium magnet 111 are annular and belt-shaped arc surfaces having the same height dimension and being coaxial with each other. When the neodymium magnet 111 is viewed in a cross section including its central axis, as shown in FIG. 3, substantially right-angled corners are formed at the connection portions between its upper surface and the inner peripheral surface and the outer peripheral surface. Similarly, when the neodymium magnet 111 is viewed in a cross section including its central axis, as shown in FIG. 3, substantially right-angled corners are also formed at the connection portions between its lower surface and the inner peripheral surface and the outer peripheral surface. The entire upper surface, lower surface, inner peripheral surface, and outer peripheral surface of the neodymium magnet 111 are covered with a nickel coating 111a. Also, all the corners of the neodymium magnet 111 described above are also covered with the nickel coating 111a. Note that a resin film may be adopted instead of the nickel coating 111a.

[0048] The entire surface of the neodymium magnet 111, that is, the entire surface of the nickel coating 111a, is covered with a zinc coating 112 or a first insulating layer 113. Here, the zinc coating 112 includes two forms: a case where it consists of an electrolytic zinc plating layer 112a and a case where it consists of a high-purity zinc tape 112b. Regarding the details of the above configuration, in addition to FIG. 3, FIGS. 4 to 7 will also be referred to for explanation. Note that FIG. 4 is a partially enlarged cross-sectional view in which part B of FIG. 3 is turned upside down, showing a form covered with the electrolytic zinc plating layer 112a (zinc coating 112). FIG. 5 is a partially enlarged cross-sectional view corresponding to FIG. 4, showing a form covered with a high-purity zinc tape 112b (zinc coating 112) instead of the electrolytic zinc plating layer 112a. FIG. 6 is a partially enlarged cross-sectional view corresponding to FIG. 4, showing a form covered with a first insulating layer 113 made of a solventless epoxy resin paint instead of the electrolytic zinc plating layer 112a.

[0049] First, in the configuration where the entire surface of the neodymium magnet 111 is coated with a zinc coating 112, there are two cases: when forming an electrolytic zinc plating layer 112a as shown in FIG. 4, or when covering it by pasting a high-purity zinc tape 112b as shown in FIG. 5. In either of these two means, the pores h of the nickel coating 111a can be covered and sealed. However, as described above, from the perspective of cost and the like, the form of FIG. 5 where the high-purity zinc tape 112b is pasted and covered is more preferable.

[0050] On the other hand, when the entire surface of the neodymium magnet 111 is covered with a first insulating layer 113 as shown in FIG. 6, the above-mentioned solventless epoxy resin paint is applied to the entire surface of the neodymium magnet 111, that is, the entire surface of the nickel coating 111a, and then this coating film is dried to form it. Also in this configuration, the pores h formed in the nickel coating 111a can be covered and sealed with the first insulating layer 113.

[0051] Note that it is inevitable for air to be mixed in during the mixing (stirring) of the solventless epoxy resin paint before application. If left as it is, it will cause bubbles to form in the first insulating layer 113 which is the coating film. In particular, when used as a lining material (filler) to cover the neodymium magnet 111 instead of painting as in this embodiment, it is required to eliminate the bubbles in the solventless epoxy resin paint. That is, in the lining material which is several times to 10 times thicker than the coating film thickness in the case of normal painting, the influence is significant when bubbles remain inside. Between the sound part with few bubbles and the unsound part with many bubbles, a difference in insulation function caused by the difference in coating thickness occurs, and it is likely to cause the progress of film deterioration. In addition, since the magnetic adsorption device 180 of this embodiment is used in a special way of being immersed in seawater for a long time, it is preferable to perform sufficient degassing to remove the bubbles in the solventless epoxy resin paint. Specifically, after applying a solvent-free epoxy resin paint to the entire surface of the neodymium magnet 111, that is, the entire surface of the nickel coating 111a, it is housed in a vacuum tank and dried as it is. Then, the bubbles (air) mixed in the solvent-free epoxy resin paint will dissipate outside the film, and it can be dried and solidified in a state where the bubbles have disappeared. As a result, a first insulating layer 113 that has no bubbles inside and equalizes the insulating function of each part can be formed, so that it can exhibit rock-solid insulation against seawater and prevent the corrosion progress of the neodymium magnet 111.

[0052] On the other hand, when pasting and coating the high-purity zinc tape 112b shown in FIG. 5 on the neodymium magnet 111, for example, the entire surface of the neodymium magnet 111 is coated by the process shown in FIG. 7. FIG. 7 is a diagram showing a method for manufacturing the corrosion-resistant magnet 110 according to the form shown in FIG. 5, indicating that the process proceeds in the order of (a), (b), and (c). First, the nickel coating 111a of the neodymium magnet 111 is polished and degreased. Subsequently, as shown in FIG. 7(a), one strip-shaped piece of the high-purity zinc tape 112b cut to a length sufficient to cover the entire circumference of the inner peripheral surface of the neodymium magnet 111 and one strip-shaped piece cut to a length sufficient to cover the entire circumference of the outer peripheral surface of the neodymium magnet 111 are each prepared. Then, each high-purity zinc tape 112b is pasted along the circumferential direction so as to cover the entire inner peripheral surface and the entire outer peripheral surface of the neodymium magnet 111.

[0053] Subsequently, as shown in FIG. 7(b), two annular pieces of the high-purity zinc tape 112b cut to have a width sufficient to cover the entire upper and lower surfaces of the neodymium magnet 111 are prepared. At this time, in the annular high-purity zinc tape 112b to be pasted later, the inner circumferential circle is cut to be slightly smaller and the outer circumferential circle is cut to be slightly larger so that no gap is generated between the high-purity zinc tape 112b pasted earlier and the inner and outer peripheral surfaces of the neodymium magnet 111. Then, each high-purity zinc tape 112b is coaxially pasted so as to cover the entire upper and lower surfaces of the neodymium magnet 111. Finally, as shown in FIG. 7(c), the inner and outer peripheral portions of the high-purity zinc tape 112b attached to the upper and lower surfaces of the neodymium magnet 111 are bent at right angles to cover the respective corners continuous with the upper and lower surfaces of the neodymium magnet 111. By this bending, each high-purity zinc tape 112b attached later can be attached so as to overlap on the high-purity zinc tapes 112b attached to the inner and outer peripheral surfaces of the neodymium magnet 111. In this way, the entire surface of the neodymium magnet 111, that is, the entire surface of the nickel coating 111a, is covered without gaps by the high-purity zinc tape 112b, and the corrosion-resistant magnet 110 can be obtained. As a result, as described with reference to FIG. 5, all the pores h can be sealed.

[0054] In order to use the corrosion-resistant magnet 110 obtained by the manufacturing method exemplified above in the magnetic adsorption device 180, the corrosion-resistant magnet 110 is first magnetically adsorbed at a predetermined coaxial position within the groove portion 181b of the yoke 181 by the above-described procedure. Thereafter, as illustrated in FIGS. 8 to 11, the surface of the corrosion-resistant magnet 110 is coated with the zinc anode layer 142 or the second insulating layer 143.

[0055] Here, FIG. 8 is a view showing the main part of the magnetic adsorption device 180 shown in FIG. 1 upside down, and is a longitudinal sectional view showing a case where the second insulating layer 143 formed of a solventless epoxy resin paint is formed. In this aspect, a solvent-free epoxy resin paint is filled in the gap between the inner peripheral surface of the corrosion-resistant magnet 110 and the outer peripheral surface of the inner peripheral yoke portion 185, and in the gap between the outer peripheral surface of the corrosion-resistant magnet 110 and the inner peripheral surface of the outer peripheral yoke portion 184, and it is solidified to form the second insulating layer 143. Further, on the surface of the corrosion-resistant magnet 110 facing the opening of the yoke 181 (in FIG. 8, the surface on the upper side of the corrosion-resistant magnet 110 on the paper surface), the second insulating layer 143 solidified from the solvent-free epoxy resin paint is also formed. According to the second insulating layer 143 formed on these three surfaces, it is possible to further improve the corrosion resistance by overlapping and covering the entire surface of the corrosion-resistant magnet 110 provided with corrosion resistance with the second insulating layer 143. Further, the second insulating layer 143 formed on the surface facing the opening of the yoke 181 is disposed on the inner side of the groove portion 181b, so that when the magnetic adsorption device 180 is adsorbed to the adsorption target 1000, it is disposed at a position separated from the adsorption target 1000 with a gap therebetween. Therefore, the second insulating layer 143 has an arrangement configuration in which damage due to direct contact with the adsorption target 1000 does not occur.

[0056] By the way, as described above, it is inevitable that air is mixed in during the mixing (stirring) of the solvent-free epoxy resin paint before application, and if left as it is, it will cause bubbles to form in the second insulating layer 143. In particular, when used as a lining material (filler) instead of painting as in this embodiment, it is required to eliminate the bubbles in the second insulating layer 143. That is, in the lining material which is several to 10 times thicker than the coating film thickness in the case of normal painting, the influence of the remaining bubbles inside is large, and between the sound portion with few bubbles and the unsound portion with many bubbles, an insulation function gap is caused by the difference in the coating thickness, and it is likely to cause the progress of film deterioration. In addition, since the magnetic adsorption device 180 of this embodiment is used in a special way of being immersed in seawater for a long time, it is preferable to perform sufficient degassing to remove the bubbles in the second insulating layer 143. Specifically, after storing the corrosion-resistant magnet 110 inside the yoke 181, it is filled and covered with a solvent-free epoxy resin paint, and then stored in a vacuum tank and dried as it is. Then, the air bubbles (air) mixed in the solvent-free epoxy resin paint will dissipate outside the film, so it can be dried and solidified in a state where the air bubbles have disappeared. As a result, a second insulating layer 143 that has no air bubbles inside and can equalize the insulation function of each part can be formed, so that it can exhibit rock-solid insulation against seawater and prevent the corrosion progress of the neodymium magnet 111.

[0057] FIG. 9 is a figure corresponding to FIG. 8, and is a longitudinal sectional view showing a case where a flexible zinc anode is filled around the corrosion-resistant magnet 110 to form a zinc anode layer (sacrificial anode layer) 142. The flexible zinc anode is obtained by mixing zinc powder or zinc alloy powder with a resin material or the like to form a paste.

[0058] In this embodiment, the flexible zinc anode is filled in the gap between the inner peripheral surface of the corrosion-resistant magnet 110 and the outer peripheral surface of the inner peripheral yoke portion 185, and in the gap between the outer peripheral surface of the corrosion-resistant magnet 110 and the inner peripheral surface of the outer peripheral yoke portion 184, and it is solidified to form the zinc anode layer 142. Further, on the surface of the corrosion-resistant magnet 110 facing the opening of the yoke 181 (in FIG. 9, the surface on the upper side of the corrosion-resistant magnet 110 on the paper surface), a zinc anode layer 142 solidified from the flexible zinc anode is also formed. The anticorrosion members 142a, 142b, and 142c are formed by the zinc anode layers 142 formed on these three surfaces. In this way, by covering the entire surface of the corrosion-resistant magnet 110 with the zinc anode layer 142 having corrosion resistance, it is possible to further improve the corrosion resistance. In addition, since the zinc anode layer 142 formed on the surface facing the opening of the yoke 181 is disposed on the inner side of the groove portion 181b, when the magnetic adsorption device 180 is adsorbed to the adsorption target 1000, it is disposed at a position separated from the adsorption target 1000 with a gap. Therefore, the zinc anode layer 142 has an arrangement configuration in which damage due to direct contact with the adsorption target 1000 does not occur.

[0059] Note that the zinc anode layer 142 may be at least in the form of a paste (paste-like) having viscosity during application, and may be solidified by heat treatment or drying treatment after application. Furthermore, the zinc anode layer 142 may not have conductivity during application, and may exhibit conductivity by heat treatment or drying treatment. Considering the anode potential, anode efficiency, amount of electrolytic products generated, and ease of handling, zinc is most suitable as the metal powder contained in this zinc anode layer 142.

[0060] The zinc anode layer 142 is preferably formed to have a thickness of 50 μm or more, more preferably 500 μm or more. Furthermore, if the thickness is 1 mm or more, it becomes a corrosion protection member capable of obtaining a corrosion protection effect over an extremely long period. By having such a configuration, a corrosion-resistant magnetic adsorption structure 176 provided with a sufficient amount of the corrosion protection member can be configured, so that it does not corrode even when used in water or seawater for a long period of time, and the adsorption force can be maintained.

[0061] FIG. 10 is a longitudinal sectional view showing a case where a solventless epoxy resin paint is applied around a corrosion-resistant magnet 110 coated with a high-purity zinc tape 112b to form a second insulating layer 143, which corresponds to a modified example of FIG. 8. That is, in the configuration described in FIG. 8, only the configuration of the corrosion-resistant magnet 110 is different, and the others are the same as the configuration of FIG. 8. FIG. 11 is a longitudinal sectional view showing a case where a flexible zinc anode is filled around a corrosion-resistant magnet 110 coated with a high-purity zinc tape 112b to form a zinc anode layer 142, which corresponds to a modified example of FIG. 9. That is, in the configuration described in FIG. 9, only the configuration of the corrosion-resistant magnet 110 is different, and the others are the same as the configuration of FIG. 9.

[0062] The gist of the corrosion-resistant magnet 110 and the magnetic adsorption device 180 described above is summarized below. (1) As shown in FIG. 3, the corrosion-resistant magnet 110 according to one aspect of the present invention is a neodymium magnet (permanent magnet) 111 coated with a nickel film 111a, and The zinc coating 112 formed on the nickel coating 111a, has. (2) As shown in FIG. 4, in the corrosion-resistant magnet 110 described in (1) above, the zinc coating 112 may be an electrolytic zinc plating layer (zinc plating) 112a. (3) As shown in FIG. 5, in the corrosion-resistant magnet 110 described in (1) above, the zinc coating 112 may be a high-purity zinc tape 112b.

[0063] (4) As shown in FIG. 6, the corrosion-resistant magnet 110 according to another aspect of the present invention is a neodymium magnet (permanent magnet) 111 coated with a nickel coating 111a, a first insulating layer 113 made of an epoxy resin formed on the nickel coating 111a, has.

[0064] (5) As shown in FIG. 1, the magnetic adsorption device 180 according to one aspect of the present invention is the corrosion-resistant magnet 110 described in any one of (1) to (4) above, a yoke 181 that holds the corrosion-resistant magnet 110, comprises.

[0065] (6) As shown in FIG. 3, the magnetic adsorption device 180 described in (5) above may further include a zinc anode layer 142 that covers the surface of the corrosion-resistant magnet 110.

[0066] (7) As shown in FIG. 1, the following configuration may be adopted in the magnetic adsorption device 180 described in (6) above: The corrosion-resistant magnet 110 is ring-shaped, the yoke 181 has a back yoke portion 183 that adsorbs to the corrosion-resistant magnet 110, an outer peripheral yoke portion 184 that is integrally formed with the back yoke portion 183 and surrounds the corrosion-resistant magnet 110, and an inner peripheral yoke portion 185 that is disposed on the inner peripheral side of the corrosion-resistant magnet 110 and is integrally formed with the back yoke portion 183, the zinc anode layer 142 Between the outer peripheral surface of the corrosion-resistant magnet 110 and the inner peripheral surface of the outer yoke portion 184, Between the inner peripheral surface of the corrosion-resistant magnet 110 and the outer peripheral surface of the inner yoke portion 185, The surface of the corrosion-resistant magnet 110 on the side opposite to the adsorption surface with the back yoke portion 183, is formed.

[0067] (8) As shown in FIG. 8, in the magnetic adsorption device 180 described in (5) above, A second insulating layer 143 made of an epoxy resin formed on the surface of the corrosion-resistant magnet 110 may be further provided.

[0068] (9) As shown in FIG. 8, the following configuration may be adopted in the magnetic adsorption device 180 described in (8) above: The corrosion-resistant magnet 110 is ring-shaped, The yoke 181 has a back yoke portion 183 that adsorbs to the corrosion-resistant magnet 110, an outer yoke portion 184 formed integrally with the back yoke portion 183 and surrounding the corrosion-resistant magnet 110, and an inner yoke portion 185 disposed on the inner peripheral side of the corrosion-resistant magnet 110 and formed integrally with the back yoke portion 183, The second insulating layer 143 is between the outer peripheral surface of the corrosion-resistant magnet 110 and the inner peripheral surface of the outer yoke portion 184, between the inner peripheral surface of the corrosion-resistant magnet 110 and the outer peripheral surface of the inner yoke portion 185, and the surface of the corrosion-resistant magnet 110 on the side opposite to the adsorption surface with the back yoke portion 183, is formed.

[0069] According to the corrosion-resistant magnet 110 described in the above (1) to (4), the pores h on the surface of the nickel film 111a are covered with the zinc film 112 or the first insulating layer 113. Therefore, even if this corrosion-resistant magnet 110 is used for a long time in a high-humidity environment or in water (including seawater), moisture and water will not reach the neodymium magnet 111 through the pores of the nickel film 111a, so the dissolution of the neodymium magnet 111 can be prevented. Therefore, this corrosion-resistant magnet 110 has high corrosion resistance that can withstand long-term use in a high-humidity environment or in water. And according to the magnetic adsorption device 180 described in the above (5) to (9), since it includes the corrosion-resistant magnet 110, it is possible to continuously exhibit high magnetic adsorption performance over a long period of time.

[0070] In addition, in each of the above embodiments, the shape of the adsorption surface of the outer peripheral yoke portion 184 with respect to the object to be adsorbed 1000 is a ring shape in a front view. However, the adsorption surface is not limited to a circular shape, and other shapes such as a rectangular shape or an elliptical shape may be adopted. For example, when a square frame shape is adopted as the shape of the adsorption surface, this square frame shape may be a square or a rectangle. Moreover, the magnetic adsorption device 180 of each of the embodiments described above can be used for various applications regardless of whether it is on land or in seawater. For example, in civil engineering and construction applications, it can be suitably used for the assembly of steel structures such as iron columns and iron plates, and the attachment of accessories to steel structures. In this application, conventionally, assembly and attachment have been performed using processing means such as welding, riveting, and bolt fastening. However, if the magnetic adsorption device of the present invention is adopted, these can be strongly adsorbed to obtain the same strength as the construction by the above processing means, so effects such as shortening the construction period and improving work efficiency can be obtained. Furthermore, since it can be removed as needed, when used for the installation of a work platform, etc., the withdrawal work can also be performed quickly.

Explanation of Reference Numerals

[0071] 110…Corrosion-resistant magnet 111…Neodymium magnet (permanent magnet) 111a…Nickel film 112…Zinc film 112b…High-purity zinc tape (zinc tape) 113…First insulating layer 142…Zinc anode layer 143…Second insulating layer 180…Magnetic adsorption device 181…Yoke 183…Back yoke part 184…Outer peripheral yoke part 185…Inner peripheral yoke part

Claims

1. A permanent magnet entirely coated with a nickel film, and a zinc film formed on the nickel film, characterized in that the zinc film covers the entire surface of the nickel film to form a corrosion-resistant magnet.

2. The corrosion-resistant magnet according to claim 1, wherein the zinc film is a zinc plating.

3. The corrosion-resistant magnet according to claim 1, wherein the zinc film is a zinc tape.

4. A permanent magnet entirely coated with a nickel film, and a first insulating layer made of an epoxy resin formed on the nickel film, characterized in that the first insulating layer covers the entire surface of the nickel film to form a corrosion-resistant magnet.

5. A corrosion-resistant magnet according to any one of claims 1 to 4, and a yoke holding the corrosion-resistant magnet, characterized in that it comprises a magnetic adsorption device.

6. The magnetic adsorption device according to claim 5, further comprising a zinc anode layer covering the corrosion-resistant magnet.

7. The corrosion-resistant magnet is ring-shaped, and the yoke has a back yoke portion that adsorbs to the corrosion-resistant magnet, an outer peripheral yoke portion formed integrally with the back yoke portion to surround the corrosion-resistant magnet, and an inner peripheral yoke portion disposed on the inner peripheral side of the corrosion-resistant magnet and formed integrally with the back yoke portion. The zinc anode layer is formed between the outer peripheral surface of the corrosion-resistant magnet and the inner peripheral surface of the outer peripheral yoke portion, between the inner peripheral surface of the corrosion-resistant magnet and the outer peripheral surface of the inner peripheral yoke portion, and on the surface of the corrosion-resistant magnet opposite to the adsorption surface with the back yoke portion. characterized in that the magnetic adsorption device according to claim 6 is formed.

8. The magnetic adsorption device according to claim 5, further comprising a second insulating layer made of an epoxy resin formed on the surface of the corrosion-resistant magnet. characterized in that

9. The corrosion-resistant magnet is ring-shaped, and the yoke has a back yoke portion that adsorbs to the corrosion-resistant magnet, an outer peripheral yoke portion formed integrally with the back yoke portion to surround the corrosion-resistant magnet, and an inner peripheral yoke portion disposed on the inner peripheral side of the corrosion-resistant magnet and formed integrally with the back yoke portion. The second insulating layer is formed between the outer peripheral surface of the corrosion-resistant magnet and the inner peripheral surface of the outer peripheral yoke portion, between the inner peripheral surface of the corrosion-resistant magnet and the outer peripheral surface of the inner peripheral yoke portion, and on the surface of the corrosion-resistant magnet opposite to the adsorption surface with the back yoke portion. characterized in that it is formed. The magnetic adsorption device according to claim 8, characterized in that...

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