Magnet gripper

Abstract

A magnet gripper (10) includes: a permanent electromagnet (M) having a first permanent magnet (12), a second permanent magnet (14), and a coil (16); a yoke (18); and pole pieces (20). The yoke (18) is in contact with the second permanent magnet (14). The pole piece (20) has a contact portion (20c) in contact with the yoke (18), and a holding portion (20h) extending from the contact portion (20c). A magnetic substance W can be held by magnetic force by end portions (20e) of the holding portions, the end portion being spaced apart from the contact portion (20c) in an extending direction (De) in which the holding portion (20h) extends from the contact portion (20c).

Description

Magnet Gripper

[0001] The present disclosure relates to a magnet gripper.

[0002] International Publication No. WO 2019 / 165228 discloses a magnetic coupling device. The magnetic coupling device includes an upper permanent magnet and a lower permanent magnet that serve as magnetic flux sources. A pole shoe magnetically coupled to the upper permanent magnet and the lower permanent magnet is provided. A lower portion of the pole shoe includes a workpiece contact interface that can be brought into contact with a workpiece. When the upper permanent magnet is rotated relative to the lower permanent magnet, the arrangement of the upper permanent magnet relative to the lower permanent magnet becomes an arrangement corresponding to an on-state or an off-state.

[0003] In the on-state, most of the magnetic flux of the upper permanent magnet and the lower permanent magnet is available to the workpiece at the workpiece contact interface of the pole shoe, and the workpiece is held by the magnetic coupling device in the on-state. In the off-state, most of the magnetic flux of the upper permanent magnet and the lower permanent magnet is not available to the workpiece at the workpiece contact interface of the pole shoe, and the workpiece is not held by the magnetic coupling device in the off-state.

[0004] In the magnetic coupling device disclosed in International Publication No. WO 2019 / 165228, the arrangement of the upper permanent magnet relative to the lower permanent magnet is controlled by an actuator. When changing the arrangement, the upper permanent magnet is rotated relative to the lower permanent magnet. Therefore, time for rotating the upper permanent magnet relative to the lower permanent magnet is required every time the workpiece is switched between a held state and a non-held state. This impairs the efficiency of work using magnetic force.

[0005] An object of the present disclosure is to solve the above-mentioned problems.

[0006] A first aspect of the present disclosure is a permanent electromagnet comprising: two first permanent magnets arranged side by side with their magnetization directions opposite to each other; two second permanent magnets arranged side by side with their magnetization directions opposite to each other; two coils each wound around the two second permanent magnets, each capable of reversing the magnetization direction of the two second permanent magnets by passing an electric current through them; two pairs of yokes each abutting the two second permanent magnets; and two pairs of pole pieces each abutting the two pairs of yokes and capable of holding a magnetic material by the magnetic force of the permanent electromagnet, wherein a first direction parallel to the magnetization directions of the two first permanent magnets intersects a second direction parallel to the magnetization directions of the two second permanent magnets, and the two yokes constituting each pair abut each of the two second permanent magnets along the second direction, and the two pole pieces constituting each pair Each gripper has a contact portion that abuts against each of the two yokes constituting the pair of yokes, and a holding portion that extends from each of the contact portions, and the magnetic material can be held by the magnetic force at the end of the holding portion that is spaced apart in the extending direction from the contact portion, and one of the two yokes constituting the first pair of yokes and one of the two yokes constituting the second pair of yokes each abut against one of the two first permanent magnets and face each other along the first direction, and the other of the two yokes constituting the first pair of yokes and the other of the two yokes constituting the second pair of yokes each abut against the other of the two first permanent magnets and face each other along the first direction, and the magnetic gripper is such that

[0007] A second aspect of the present disclosure is a magnet gripper comprising: a permanent electromagnet having a first permanent magnet whose magnetization direction is parallel to a first direction; a second permanent magnet whose magnetization direction is parallel to a second direction and different from that of the first permanent magnet; a coil wound around the second permanent magnet and capable of reversing the magnetization direction of the second permanent magnet by the flow of an electric current; a pair of yokes each abutting the second permanent magnet; and a pair of pole pieces each abutting the pair of yokes and capable of holding a magnetic material by the magnetic force of the permanent electromagnet, wherein the two yokes constituting the pair of yokes abut the second permanent magnet along the second direction, and the two pole pieces constituting the pair of pole pieces each have a contact portion that abuts the two yokes constituting the pair of yokes and a holding portion that extends from the contact portion, and the magnetic material can be held by the magnetic force at the ends of the holding portions spaced apart in the extending direction from the contact portion.

[0008] According to this disclosure, the efficiency of work utilizing magnetism can be improved.

[0009] The above-mentioned objectives, features, and advantages will be readily apparent from the following description of the embodiments, which will be illustrated with reference to the attached drawings.

[0010] Figures 1A, 1B, and 1C schematically show the configuration of the magnetic gripper according to the first embodiment and the magnetic circuit in the released state where the holding force that can hold the magnetic material is released. Figures 2A, 2B, and 2C schematically show the configuration of the magnetic gripper according to the first embodiment and the magnetic circuit in the held state where the magnetic material is held. Figures 3A, 3B, and 3C schematically show the configuration of the magnetic gripper according to the second embodiment and the magnetic circuit in the released state where the holding force that can hold the magnetic material is released. Figures 4A, 4B, and 4C schematically show the configuration of the magnetic gripper according to the second embodiment and the magnetic circuit in the held state where the magnetic material is held. Figures 5A, 5B, and 5C schematically show the configuration of the magnetic gripper according to the third embodiment and the magnetic circuit in the released state where the holding force that can hold the magnetic material is released. Figures 6A, 6B, and 6C schematically show the configuration of the magnetic gripper according to the third embodiment and the magnetic circuit in the held state where the magnetic material is held. Figures 7A and 7B schematically show the configuration and magnetic circuit of the magnet gripper according to Modification 1. Figures 8A and 8B schematically show the configuration and magnetic circuit of the magnet gripper according to Modification 2.

[0011] Robots may perform tasks such as supplying workpieces to industrial equipment. A magnetic gripper may be used as an end effector to hold the supplied workpieces. The robot performs tasks such as supplying workpieces using the magnetic force of the magnetic gripper.

[0012] (First Embodiment) Figures 1A, 1B, and 1C schematically show the configuration of the magnet gripper 10 according to the first embodiment and the magnetic circuit in the released state of the holding force that can hold the magnetic material W. Figure 1A shows a plan view of the magnet gripper 10. Figure 1B shows a front view of the magnet gripper 10. However, the permanent electromagnet M shown in Figures 1A and 1B is shown in a cross-sectional view. Figure 1C shows a side view of the magnet gripper 10. The magnet gripper 10 shown in Figures 1A, 1B, and 1C does not have a holding force for holding the magnetic material W.

[0013] The magnetic gripper 10 has a permanent electromagnet M. The permanent electromagnet M has a first permanent magnet 12, a second permanent magnet 14, and a coil 16. The first permanent magnet 12 is a neodymium magnet containing, for example, neodymium in addition to iron. The second permanent magnet 14 is a different magnet from the first permanent magnet 12, and is an alnico magnet containing, for example, aluminum, nickel, and cobalt in addition to iron.

[0014] The magnetization direction of the first permanent magnet 12 is parallel to the first direction D1. The magnetization direction of the second permanent magnet 14 is parallel to the second direction D2. The first direction D1 and the second direction D2 are parallel to each other.

[0015] The first permanent magnet 12 has a cylindrical shape with its axis in a first direction D1. The second permanent magnet 14 has a cylindrical shape with its axis in a second direction D2. The first permanent magnet 12 and the second permanent magnet 14 are arranged concentrically with respect to a common axis. The cylindrical first permanent magnet 12 is arranged to surround the cylindrical second permanent magnet 14. That is, the second permanent magnet 14 is housed in the hollow part of the first permanent magnet 12. This allows the permanent electromagnet M to be easily installed.

[0016] The coil 16 is wound around the second permanent magnet 14. In this embodiment, the coil 16 is wound around the entire second permanent magnet 14 and the first permanent magnet 12. In other words, the coil 16 is wound around the first permanent magnet 12 that surrounds the second permanent magnet 14. This allows the permanent electromagnet M to be easily installed. The coil 16 is connected to a power source (not shown). When a voltage is applied to the coil 16 and a current flows, the magnetization direction of the second permanent magnet 14 can be reversed. The magnetization direction of the first permanent magnet 12 does not reverse and remains fixed.

[0017] The magnetic gripper 10 further comprises a pair of yokes 18 and a pair of pole pieces 20. The pair of yokes 18 contact the first permanent magnet 12. The pair of yokes 18 also contact the second permanent magnet 14. The two yokes 18 constituting the pair of yokes 18 contact the first permanent magnet 12 along the first direction D1. The two yokes 18 constituting the pair of yokes 18 contact the second permanent magnet 14 along the second direction D2. As described above, the first direction D1 and the second direction D2 are parallel to each other. The pair of yokes 18 are made of ferromagnetic steel and pass through a magnetic flux B corresponding to the magnetic force generated by the permanent electromagnet M.

[0018] A pair of pole pieces 20 each abut against a pair of yokes 18. The pair of pole pieces 20 are made of ferromagnetic steel and allow a magnetic flux B corresponding to the magnetic force generated by the permanent electromagnet M to pass through them. The pair of pole pieces 20 can hold a magnetic material W by the magnetic force of the permanent electromagnet M. The surface of the magnetic material W may not be a flat plane. For example, a magnetic material W obtained by press-forming a steel plate may have an uneven surface. The magnetic material W may also be a cylindrical pipe. The pair of pole pieces 20 have a shape that allows them to hold a magnetic material W with a non-flat surface by the magnetic force of the permanent electromagnet M.

[0019] For example, a pair of pole pieces 20 that grasp and hold a granular magnetic material W may have a shape similar to the handle of tweezers. In that case, when the magnetic gripper 10 provides a holding force, the pair of pole pieces 20 move closer to each other in a closing direction due to magnetic force. When the holding force of the magnetic gripper 10 is released, the pair of pole pieces 20 move away from each other in an opening direction due to elastic force.

[0020] Each of the two pole pieces 20 constituting a pair of pole pieces 20 has a contact portion 20c and a holding portion 20h. The contact portion 20c contacts the yoke 18 at its contact surface 20s. The contact surface 20s faces the contact direction Dc. The contact direction Dc is parallel to the first direction D1 and the second direction D2. The holding portion 20h extends from the contact portion 20c in the extension direction De. The extension direction De intersects both the first direction D1 and the second direction D2. The pole piece 20 can hold the magnetic material W by the magnetic force of the permanent electromagnet M at the end 20e of the holding portion 20h that extends from the contact portion 20c in the extension direction De.

[0021] Figures 1A, 1B, and 1C illustrate the magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnetic gripper 10 in the released state described above. In the released state, the magnetization direction of the second permanent magnet 14 is opposite to that of the first permanent magnet 12. That is, the south pole of the second permanent magnet 14 is located closer to the north pole than the south pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the south pole than the north pole of the first permanent magnet 12.

[0022] The magnetic flux B traveling from the south pole to the north pole of the second permanent magnet 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that is in contact with the north pole of the second permanent magnet 14. The yoke 18 is also in contact with the south pole of the first permanent magnet 12, which is located close to the north pole of the second permanent magnet 14. The magnetic flux B exiting from the north pole of the second permanent magnet 14 passes through the yoke 18 and enters the south pole of the first permanent magnet 12.

[0023] The magnetic flux B traveling from the south pole to the north pole of the first permanent magnet 12 exits the north pole of the first permanent magnet 12 and passes through a yoke 18 that is in contact with the north pole of the first permanent magnet 12. The yoke 18 is also in contact with the south pole of the second permanent magnet 14, which is located close to the north pole of the first permanent magnet 12. The magnetic flux B exiting the north pole of the first permanent magnet 12 passes through the yoke 18 and enters the south pole of the second permanent magnet 14.

[0024] In other words, the magnetic circuit formed by the magnetic flux B in the released state of the magnetic gripper 10 is closed off by the first permanent magnet 12, the second permanent magnet 14, and a pair of yokes 18. In this case, even if a magnetic material W is placed near the released state of the magnetic gripper 10, the magnetic flux B does not pass through the magnetic material W in any way. Therefore, the magnetic gripper 10 does not possess the holding force necessary to hold the magnetic material W. Consequently, the magnetic gripper 10 does not hold the magnetic material W.

[0025] When a voltage is applied to the coil 16 of the permanent electromagnet M in the released magnetic gripper 10, a current flows through the coil 16 in a predetermined direction, thereby reversing the magnetization direction of the second permanent magnet 14. As a result, the magnetic gripper 10 can be provided with the holding force described above. Figures 2A, 2B, and 2C schematically show the configuration of the magnetic gripper 10 according to the first embodiment and the magnetic circuit in the holding state in which the magnetic material W is held.

[0026] Figure 2A shows a plan view of the magnetic gripper 10. Figure 2B shows a front view of the magnetic gripper 10. However, the permanent electromagnet M shown in Figures 2A and 2B is shown in a cross-sectional view. Figure 2C shows a side view of the magnetic gripper 10. The magnetization direction of the second permanent magnet 14 shown in Figures 2A and 2B is reversed as described above, and is therefore opposite to the magnetization direction of the second permanent magnet 14 shown in Figures 1A and 1B.

[0027] The magnetic gripper 10 shown in Figures 2A, 2B, and 2C has a holding force for holding the magnetic material W. Therefore, the magnetic gripper 10 is in a holding state, holding the magnetic material W. Figures 2A, 2B, and 2C illustrate the magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M possessed by the magnetic gripper 10 in the holding state.

[0028] In the held state, the magnetization direction of the second permanent magnet 14 is the same as the magnetization direction of the first permanent magnet 12. That is, the south pole of the second permanent magnet 14 is located closer to the south pole of the first permanent magnet 12 than the north pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the north pole of the first permanent magnet 12 than the south pole of the first permanent magnet 12.

[0029] The magnetic flux B traveling from the south pole to the north pole of the second permanent magnet 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that abuts against the north pole of the second permanent magnet 14. This yoke 18 is one of two yokes 18 that make up a pair of yokes 18. The magnetic flux B passing through this yoke 18 passes through the contact portion 20c of a pole piece 20 that abuts against this yoke 18 at the contact surface 20s. This pole piece 20 is one of two pole pieces 20 that make up a pair of pole pieces 20.

[0030] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of the other pole piece 20 of the pair of pole pieces 20 that make up the aforementioned pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0031] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts the other yoke 18 of the pair of yokes 18 at a contact surface 20s. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the second permanent magnet 14. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the second permanent magnet 14.

[0032] In this way, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of the second permanent magnet 14 is closed off by the second permanent magnet 14, a pair of yokes 18, a pair of pole pieces 20, and the magnetic material W. Similarly, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of the first permanent magnet 12 is closed off by the first permanent magnet 12, a pair of yokes 18, a pair of pole pieces 20, and the magnetic material W.

[0033] In other words, the magnetic flux B of the permanent electromagnet M passes through the magnetic material W. Therefore, the magnetic gripper 10 has a holding force corresponding to the magnetic force of the permanent electromagnet M. The magnetic gripper 10 is in a holding state in which the magnetic material W is held at the end 20e of the holding portion 20h by the holding force.

[0034] When a voltage is applied to the coil 16 of the magnetic gripper 10, which is in a holding state, a current flows through the coil 16 in the opposite direction to the predetermined direction, thereby reversing the magnetization direction of the second permanent magnet 14. As a result, the magnetic gripper 10 can enter the released state described above. Since the magnetic gripper 10 does not possess holding force, the magnetic material W detaches from the permanent electromagnet M.

[0035] By applying voltage to the coil 16 of the permanent electromagnet M, the magnetic gripper 10 can be easily and quickly switched between the released and held states. Therefore, the efficiency of work utilizing magnetic force can be improved compared to conventional methods. Furthermore, since a drive member for rotating the permanent magnet is not required as in conventional methods, the magnetic gripper 10 can be made smaller and vibrations associated with rotation can be suppressed. Therefore, the magnetic gripper 10 can be safely used as the end effector of the robot described above.

[0036] The magnetic gripper 10 may have two sets of the permanent electromagnets M described above. The two sets of permanent electromagnets M can be arranged side by side in a direction parallel to the extending direction De described above. In that case, a pair of yokes 18 will be in contact with each set of the two sets of permanent electromagnets M. A pair of pole pieces 20 will be in contact with each pair of yokes 18. The holding force that a magnetic gripper 10 with two sets of permanent electromagnets M can provide is approximately twice the holding force that a magnetic gripper 10 with one set of permanent electromagnets M can provide.

[0037] (Second Embodiment) Regarding the second embodiment, explanations that overlap with the first embodiment will be omitted. Figures 3A, 3B, and 3C schematically show the configuration of the magnet gripper 10 according to the second embodiment and the magnetic circuit in the released state of the holding force that can hold the magnetic material W. Figure 3A shows a plan view of the magnet gripper 10. Figure 3B shows a front view of the magnet gripper 10. However, the coil 16 of the permanent electromagnet M shown in Figures 3A and 3B is shown in a cross-sectional view. Figure 3C shows a side view of the magnet gripper 10. The magnet gripper 10 shown in Figures 3A, 3B, and 3C does not have a holding force for holding the magnetic material W.

[0038] The first permanent magnet 12 has a cylindrical shape with its axis in the first direction D1. The second permanent magnet 14 has a cylindrical shape with its axis in the second direction D2. The first permanent magnet 12 and the second permanent magnet 14 are placed side by side. In this embodiment, the first permanent magnet 12 and the second permanent magnet 14 are placed side by side in a direction intersecting the extending direction De to which the holding portion 20h of the pole piece 20 extends. However, the first permanent magnet 12 and the second permanent magnet 14 may be placed side by side in a direction parallel to the said extending direction De.

[0039] The coil 16 is wound around the second permanent magnet 14. In this embodiment, the coil 16 is not wound around the first permanent magnet 12. In this case, the length of the coil 16 can be shortened, thereby reducing the amount of heat generated when current flows through the coil 16. However, the coil 16 may be wound around the entire second permanent magnet 14 and the first permanent magnet 12.

[0040] Figures 3A, 3B, and 3C illustrate the magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnetic gripper 10 in the released state described above. In the released state, the magnetization direction of the second permanent magnet 14 is opposite to that of the first permanent magnet 12. That is, the south pole of the second permanent magnet 14 is located closer to the north pole than the south pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the south pole than the north pole of the first permanent magnet 12.

[0041] The magnetic flux B traveling from the south pole to the north pole of the second permanent magnet 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that is in contact with the north pole of the second permanent magnet 14. The yoke 18 is also in contact with the south pole of the first permanent magnet 12, which is located close to the north pole of the second permanent magnet 14. The magnetic flux B exiting from the north pole of the second permanent magnet 14 passes through the yoke 18 and enters the south pole of the first permanent magnet 12.

[0042] The magnetic flux B traveling from the south pole to the north pole of the first permanent magnet 12 exits the north pole of the first permanent magnet 12 and passes through a yoke 18 that is in contact with the north pole of the first permanent magnet 12. The yoke 18 is also in contact with the south pole of the second permanent magnet 14, which is located close to the north pole of the first permanent magnet 12. The magnetic flux B exiting the north pole of the first permanent magnet 12 passes through the yoke 18 and enters the south pole of the second permanent magnet 14.

[0043] In other words, the magnetic circuit formed by the magnetic flux B in the released state of the magnetic gripper 10 is closed off by the first permanent magnet 12, the second permanent magnet 14, and a pair of yokes 18. In this case, even if a magnetic material W is placed near the released state of the magnetic gripper 10, the magnetic flux B does not pass through the magnetic material W in any way. Therefore, the magnetic gripper 10 does not possess the holding force described above. Consequently, the magnetic gripper 10 does not hold the magnetic material W.

[0044] When voltage is applied to the coil 16 of the magnet gripper 10 in the released state, and a current flows through the coil 16 in a predetermined direction, the magnetization direction of the second permanent magnet 14 can be reversed. Thereby, the magnet gripper 10 can be provided with a holding force. FIGS. 4A, 4B and 4C are diagrams schematically showing the configuration of the magnet gripper 10 according to the second embodiment and the magnetic circuit in the holding state where the magnetic body W is held.

[0045] FIG. 4A is a plan view of the magnet gripper 10. FIG. 4B is a front view of the magnet gripper 10. However, the coil 16 of the permanent electromagnet M shown in FIGS. 4A and 4B is shown in a cross-sectional view. FIG. 4C is a side view of the magnet gripper 10. The magnetization direction of the second permanent magnet 14 shown in FIGS. 4A and 4B is reversed as described above, and thus is opposite to the magnetization direction of the second permanent magnet 14 shown in FIGS. 3A and 3B.

[0046] The magnet gripper 10 shown in FIGS. 4A, 4B and 4C has a holding force. Therefore, the magnet gripper 10 is in a holding state holding the magnetic body W. FIGS. 4A, 4B and 4C illustrate a magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M included in the magnet gripper 10 in the holding state. In the holding state, the magnetization direction of the second permanent magnet 14 is the same as the magnetization direction of the first permanent magnet 12. That is, the south pole of the second permanent magnet 14 is located closer to the south pole than the north pole of the first permanent magnet 12, and the north pole of the second permanent magnet 14 is located closer to the north pole than the south pole of the first permanent magnet 12.

[0047] The magnetic flux B traveling from the south pole to the north pole of the second permanent magnet 14 inside the second permanent magnet 14 exits from the north pole of the second permanent magnet 14 and passes through the yoke 18 abutting on the north pole of the second permanent magnet 14. The yoke 18 is one of the two yokes 18 constituting the pair of yokes 18. The magnetic flux B passing through the yoke 18 passes through the contact portion 20c of the pole piece 20 that abuts on the yoke 18 at the contact surface 20s. The pole piece 20 is one of the two pole pieces 20 constituting the pair of pole pieces 20.

[0048] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 exits to the outside of the magnetic gripper 10 through the end portion 20e. When the magnetic gripper 10 approaches or is in contact with the magnetic body W, the magnetic flux B passes through the magnetic body W. The magnetic flux B passing through the magnetic body W travels toward the end portion 20e of the holding portion 20h of the other pole piece 20 among the two pole pieces 20 constituting the pair of pole pieces 20 described above. The magnetic flux B passing through the magnetic body W enters the holding portion 20h of the pole piece 20 through the end portion 20e.

[0049] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 abuts against the other yoke 18 among the two yokes 18 constituting the pair of yokes 18 at the contact surface 20s. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 abuts against the S pole of the second permanent magnet 14. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the S pole of the second permanent magnet 14.

[0050] In this way, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of the second permanent magnet 14 is closed and formed by the second permanent magnet 14, the pair of yokes 18, the pair of pole pieces 20, and the magnetic body W. Similarly, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of the first permanent magnet 12 is closed and formed by the first permanent magnet 12, the pair of yokes 18, the pair of pole pieces 20, and the magnetic body W.

[0051] That is, the magnetic flux B of the permanent electromagnet M passes through the magnetic body W. Therefore, the magnetic gripper 10 has a holding force corresponding to the magnetic force of the permanent electromagnet M. The magnetic gripper 10 is in a holding state in which it holds the magnetic body W at the end portion 20e of the holding portion 20h by the holding force.

[0052] When a voltage is applied to the coil 16 of the magnetic gripper 10, which is in a holding state, a current flows through the coil 16 in the opposite direction to the predetermined direction, thereby reversing the magnetization direction of the second permanent magnet 14. As a result, the magnetic gripper 10 can enter the released state described above. Since the magnetic gripper 10 does not possess holding force, the magnetic material W detaches from the permanent electromagnet M.

[0053] By applying voltage to the coil 16 of the permanent electromagnet M, the magnetic gripper 10 can be easily and quickly switched between the released and held states. Therefore, the efficiency of work utilizing magnetic force can be improved compared to conventional methods. Furthermore, since a drive member for rotating the permanent magnet is not required as in conventional methods, the magnetic gripper 10 can be made smaller and vibrations associated with rotation can be suppressed. Therefore, the magnetic gripper 10 can be safely used as the end effector of the robot described above.

[0054] Furthermore, compared to the first embodiment, this embodiment allows for a larger distance between the first permanent magnet 12 and the second permanent magnet 14. This suppresses demagnetization of the second permanent magnet 14 by the first permanent magnet 12. Consequently, a higher holding force can be obtained.

[0055] (Third Embodiment) Regarding the third embodiment, explanations that overlap with the first and second embodiments will be omitted. Figures 5A, 5B, and 5C schematically show the configuration of the magnet gripper 10 according to the third embodiment and the magnetic circuit in the released state of the holding force that can hold the magnetic material W.

[0056] Figure 5A shows a plan view of the magnetic gripper 10. Figure 5B shows a front view of the magnetic gripper 10. However, the coil 16 of the permanent electromagnet M shown in Figures 5A and 5B is shown in a cross-sectional view. Figure 5C shows a side view of the magnetic gripper 10. The magnetic grippers 10 shown in Figures 5A, 5B, and 5C do not have a holding force for holding the magnetic material W.

[0057] The magnetic gripper 10 has a permanent electromagnet M. The permanent electromagnet M has two first permanent magnets 12, two second permanent magnets 14, and two coils 16. The magnetization direction of the first permanent magnets 12 is parallel to the first direction D1. The two first permanent magnets 12 are placed side by side so that their magnetization directions are opposite to each other. The magnetization direction of the second permanent magnets 14 is parallel to the second direction D2. The two second permanent magnets 14 are placed side by side so that their magnetization directions are opposite to each other.

[0058] The first permanent magnet 12 has a rectangular prism shape with its axis in a first direction D1. The second permanent magnet 14 has a cylindrical shape with its axis in a second direction D2. The first direction D1 intersects the second direction D2. Two coils 16 are wound around the two second permanent magnets 14, respectively. That is, one coil 16 is wound around one second permanent magnet 14. By applying a voltage to each coil 16 and causing a current to flow, the magnetization direction of each second permanent magnet 14 can be reversed.

[0059] The magnetic gripper 10 further comprises two pairs of yokes 18 and two pairs of pole pieces 20. Each pair of yokes 18 contacts one of the two second permanent magnets 14. That is, one pair of yokes 18 contacts one of the second permanent magnets 14. The two pairs of yokes 18 include a first pair of yokes 18 and a second pair of yokes 18. In this case, the two yokes 18 constituting the first pair of yokes 18 contact one of the two second permanent magnets 14 along the second direction D2. The two yokes 18 constituting the second pair of yokes 18 contact the other of the two second permanent magnets 14 along the second direction D2.

[0060] One of the two yokes 18 constituting the first pair of yokes 18 and one of the two yokes 18 constituting the second pair of yokes 18 each abut against one of the two first permanent magnets 12 and face each other along the first direction D1. The other of the two yokes 18 constituting the first pair of yokes 18 and the other of the two yokes 18 constituting the second pair of yokes 18 each abut against the other of the two first permanent magnets 12 and face each other along the first direction D1.

[0061] The two pairs of pole pieces 20 each abut against the two pairs of yokes 18. Assume that the two pairs of pole pieces 20 include a first pair of pole pieces 20 and a second pair of pole pieces 20. In that case, the two pole pieces 20 constituting the first pair of pole pieces 20 each abut against the two yokes 18 constituting the first pair of yokes 18. The two pole pieces 20 constituting the second pair of pole pieces 20 each abut against the two yokes 18 constituting the second pair of yokes 18.

[0062] Each pair of pole pieces 20 has four contact portions 20c and four holding portions 20h. Each contact portion 20c contacts the yoke 18 with a contact surface 20s. The contact surface 20s faces the contact direction Dc. The contact direction Dc is parallel to the first direction D1 or the second direction D2.

[0063] In this embodiment, the contact direction Dc is parallel to the second direction D2. Each holding portion 20h extends from the contact portion 20c in the extending direction De. The extending direction De intersects both the first direction D1 and the second direction D2. The pole piece 20 can hold the magnetic material W by the magnetic force of the permanent electromagnet M at the end portion 20e of the holding portion 20h that extends from the contact portion 20c in the extending direction De.

[0064] Figures 5A, 5B, and 5C illustrate the magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnetic gripper 10 in the released state described above. In the released state, the south pole of the second permanent magnet 14 is located closer to the north pole than the south pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the south pole than the north pole of the first permanent magnet 12.

[0065] The magnetic flux B traveling from the south pole to the north pole within one of the two second permanent magnets 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that is in contact with the north pole of the second permanent magnet 14. This yoke 18 is the other of two yokes 18 that make up the first pair of yokes 18 that are in contact with the second permanent magnet 14. This yoke 18 is also in contact with the south pole of one of the two first permanent magnets 12, which is located close to the north pole of the second permanent magnet 14. The magnetic flux B exiting from the north pole of the second permanent magnet 14 passes through the yoke 18 and enters the south pole of the first permanent magnet 12.

[0066] The magnetic flux B moving from the south pole to the north pole within the first permanent magnet 12 exits from the north pole of the first permanent magnet 12 and passes through a yoke 18 that is in contact with the north pole of the first permanent magnet 12. This yoke 18 is the other of two yokes 18 that make up the second pair of yokes 18 that are in contact with the other of the two second permanent magnets 14 described above.

[0067] The yoke 18 is in contact with the south pole of the other of the two second permanent magnets 14, which is located close to the north pole of the first permanent magnet 12. The magnetic flux B emanating from the north pole of the first permanent magnet 12 passes through the yoke 18 and enters the south pole of the second permanent magnet 14.

[0068] The magnetic flux B moving from the south pole to the north pole within the second permanent magnet 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that is in contact with the north pole of the second permanent magnet 14. This yoke 18 is one of the two yokes 18 that constitute the second pair of yokes 18. This yoke 18 is also in contact with the south pole of the other first permanent magnet 12, which is located in close proximity to the north pole of the second permanent magnet 14. The magnetic flux B exiting from the north pole of the second permanent magnet 14 passes through the yoke 18 and enters the south pole of the first permanent magnet 12.

[0069] The magnetic flux B moving from the south pole to the north pole within the first permanent magnet 12 exits from the north pole of the first permanent magnet 12 and passes through a yoke 18 that is in contact with the north pole of the first permanent magnet 12. This yoke 18 is one of the two yokes 18 that make up the first pair of yokes 18. This yoke 18 is also in contact with the south pole of the second permanent magnet 14, which is located in close proximity to the north pole of the first permanent magnet 12. The magnetic flux B exiting from the north pole of the first permanent magnet 12 passes through the yoke 18 and enters the south pole of the second permanent magnet 14.

[0070] In other words, the magnetic circuit formed by the magnetic flux B in the released state of the magnetic gripper 10 is closed off by the two first permanent magnets 12, the two second permanent magnets 14, and the two pairs of yokes 18. In this case, even if a magnetic material W is placed near the released state of the magnetic gripper 10, the magnetic flux B does not pass through the magnetic material W in any way. Therefore, the magnetic gripper 10 does not possess the holding force described above. Consequently, the magnetic gripper 10 does not hold the magnetic material W.

[0071] When a voltage is applied to the coil 16 of the released magnetic gripper 10, currents flow in opposite directions through the two coils 16, thereby reversing the magnetization directions of the two second permanent magnets 14. As a result, the magnetic gripper 10 can be provided with holding force. Figures 6A, 6B, and 6C schematically show the configuration of the magnetic gripper 10 according to the third embodiment and the magnetic circuit in the holding state in which the magnetic material W is held.

[0072] Figure 6A shows a plan view of the magnet gripper 10. Figure 6B shows a front view of the magnet gripper 10. However, the coil 16 of the permanent electromagnet M shown in Figures 6A and 6B is shown in a cross-sectional view. Figure 6C shows a side view of the magnet gripper 10. The magnetization directions of the two second permanent magnets 14 shown in Figures 6A and 6B are reversed as described above, and are therefore opposite to the magnetization directions of the two second permanent magnets 14 shown in Figures 5A and 5B.

[0073] The magnetic gripper 10 shown in Figures 6A, 6B, and 6C possesses a holding force. Therefore, the magnetic gripper 10 is in a holding state, holding the magnetic material W. Figures 6A, 6B, and 6C illustrate the magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M possessed by the magnetic gripper 10 in the holding state. In the holding state, the south pole of the second permanent magnet 14 is located closer to the south pole of the first permanent magnet 12 than the north pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the north pole of the first permanent magnet 12 than the south pole of the first permanent magnet 12.

[0074] The magnetic flux B traveling from the south pole to the north pole within one of the two second permanent magnets 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that abuts against the north pole of the second permanent magnet 14. This yoke 18 is one of two yokes 18 that make up a first pair of yokes 18 that abut against the second permanent magnet 14. The magnetic flux B passing through the yoke 18 passes through the contact portion 20c of a pole piece 20 that abuts against the yoke 18 at the contact surface 20s. This pole piece 20 is one of two pole pieces 20 that make up a first pair of pole pieces 20 that abut against the first pair of yokes 18.

[0075] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of the other pole piece 20 of the two pole pieces 20 constituting the first pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0076] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts the other yoke 18 of the two yokes 18 that constitute the first pair of yokes 18 at a contact surface 20s. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of one of the second permanent magnets 14 described above. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the second permanent magnet 14.

[0077] The magnetic flux B traveling from the south pole to the north pole within the other of the two second permanent magnets 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that is in contact with the north pole of the second permanent magnet 14. This yoke 18 is the other of two yokes 18 that constitute a second pair of yokes 18 that are in contact with the second permanent magnet 14.

[0078] The magnetic flux B passing through the yoke 18 passes through the contact portion 20c of the pole piece 20 that contacts the yoke 18 at the contact surface 20s. This pole piece 20 is the other pole piece 20 that is different from the other of the two pole pieces 20 that make up the second pair of pole pieces 20 that contact the second pair of yokes 18.

[0079] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of one of the two pole pieces 20 constituting the second pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0080] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts one of the two yokes 18 that constitute the second pair of yokes 18 with a contact surface 20s. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the other second permanent magnet 14. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the second permanent magnet 14.

[0081] In this way, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of each second permanent magnet 14 is closed off and formed by the second permanent magnet 14, a pair of yokes 18, a pair of pole pieces 20, and a magnetic material W.

[0082] The magnetic flux B traveling from the south pole to the north pole within one of the two first permanent magnets 12 exits from the north pole of the first permanent magnet 12 and passes through a yoke 18 that abuts against the north pole of the first permanent magnet 12. This yoke 18 is one of two yokes 18 that constitute the first pair of yokes 18. The magnetic flux B passing through the yoke 18 passes through the contact portion 20c of a pole piece 20 that abuts against the yoke 18 at the contact surface 20s. This pole piece 20 is one of two pole pieces 20 that constitute the first pair of pole pieces 20.

[0083] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of one of the two pole pieces 20 that constitute the second pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0084] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts one of the two yokes 18 that constitute the second pair of yokes 18 at a contact surface 20s. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the first permanent magnet 12 described above. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the first permanent magnet 12.

[0085] The magnetic flux B traveling from the south pole to the north pole within the other of the two first permanent magnets 12 exits from the north pole of the first permanent magnet 12 and passes through a yoke 18 that abuts against the north pole of the first permanent magnet 12. This yoke 18 is the other of two yokes 18 that constitute the second pair of yokes 18. The magnetic flux B passing through this yoke 18 passes through the contact portion 20c of a pole piece 20 that abuts against the yoke 18 at its contact surface 20s. This pole piece 20 is the other of two pole pieces 20 that constitute the second pair of pole pieces 20.

[0086] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of the other pole piece 20 of the two pole pieces 20 constituting the first pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0087] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts the other yoke 18 of the two pole pieces 20 constituting the first pair of yokes 18 at a contact surface 20s. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the other first permanent magnet 12 described above. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the first permanent magnet 12.

[0088] In this way, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of each first permanent magnet 12 is closed off and formed by the first permanent magnet 12, the two yokes 18, the two pole pieces 20, and the magnetic material W.

[0089] In other words, the magnetic flux B of the permanent electromagnet M passes through the magnetic material W. Therefore, the magnetic gripper 10 has a holding force corresponding to the magnetic force of the permanent electromagnet M. The magnetic gripper 10 is in a holding state in which the magnetic material W is held at the end 20e of the holding portion 20h by the holding force.

[0090] When a voltage is applied to each coil 16 of the magnetic gripper 10, which is in a holding state, a current flows through each coil 16 in the opposite direction to before, thereby reversing the magnetization direction of the second permanent magnet 14. As a result, the magnetic gripper 10 can enter the released state described above. Since the magnetic gripper 10 does not have a holding force, the magnetic material W detaches from the permanent electromagnet M.

[0091] By applying voltage to the coil 16 of the permanent electromagnet M, the magnetic gripper 10 can be easily and quickly switched between the released and held states. Therefore, the efficiency of work utilizing magnetic force can be improved compared to conventional methods. Furthermore, since a drive member for rotating the permanent magnet is not required as in conventional methods, the magnetic gripper 10 can be made smaller and vibrations associated with rotation can be suppressed. Therefore, the magnetic gripper 10 can be safely used as the end effector of the robot described above.

[0092] Compared to the first and second embodiments, this embodiment allows for a greater magnetic flux B to pass through the yoke 18 and pole piece 20, thus enabling a greater holding force of the magnetic gripper 10.

[0093] Furthermore, when the magnetic gripper 10 is in a state where it has holding power, four pole pieces 20 are provided through which the magnetic flux B generated by the magnetic force of the first permanent magnet 12 and the magnetic flux B generated by the magnetic force of the second permanent magnet 14 pass. Therefore, the holding power of the magnetic gripper 10 can be increased in this embodiment compared to the first and second embodiments which have two pole pieces 20. In other words, the magnetic gripper 10 with the same holding power can be made smaller in this embodiment compared to the first and second embodiments.

[0094] As mentioned above, the surface of the magnetic material W held by the magnetic gripper 10 may not be a flat plane. In that case, not all pole pieces 20 may be able to contact the magnetic material W. As in this embodiment, having more pole pieces 20 on the magnetic gripper 10 increases the likelihood that the magnetic gripper 10 will hold the magnetic material W.

[0095] According to this embodiment, a two-dimensional magnetic circuit is formed by the magnetic circuit formed by the magnetic flux B generated by the magnetic force of the first permanent magnet 12 and the magnetic circuit formed by the magnetic flux B generated by the magnetic force of the second permanent magnet 14. Therefore, even if the magnetic material W is a thin plate that is prone to magnetic saturation, the magnet gripper 10 can hold the magnetic material W.

[0096] As mentioned above, the first permanent magnet 12 is, for example, a neodymium magnet. Neodymium magnets are expensive. Compared to the first and second embodiments, this embodiment allows for a smaller volume ratio of the first permanent magnet 12 to the second permanent magnet 14. Therefore, the manufacturing cost of the magnet gripper 10 can be reduced.

[0097] The third embodiment described above may be modified as follows. In the following modifications, explanations that overlap with the above embodiment will be omitted. Also, in the figures used in the following modifications, components identical to those described in the above embodiment will be denoted by the same reference numerals.

[0098] (Modification 1) In the third embodiment described above, the two pairs of pole pieces 20 have four contact portions 20c and four holding portions 20h. Each holding portion 20h extends from the contact portion 20c in the extending direction De. The extending direction De is a direction that intersects with both the first direction D1 and the second direction D2.

[0099] However, as shown in Figures 7A and 7B, the extending direction De may be parallel to the second direction D2. The pole piece 20 can hold the magnetic material W by the magnetic force of the permanent electromagnet M at the end 20e of the holding portion 20h that extends in the extending direction De from the contact portion 20c. Figures 7A and 7B schematically show the configuration and magnetic circuit of the magnet gripper 10 according to Modification 1.

[0100] Figure 7A illustrates a magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnet gripper 10 in the released state described above. In the released state, the south pole of the second permanent magnet 14 is located closer to the north pole than the south pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the south pole than the north pole of the first permanent magnet 12. The magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnet gripper 10 in the released state according to this modified example 1 is the same as in the third embodiment.

[0101] In other words, the magnetic circuit formed by the magnetic flux B in the released state of the magnetic gripper 10 is closed off by the two first permanent magnets 12, the two second permanent magnets 14, and the two pairs of yokes 18. In this case, even if a magnetic material W is placed near the released state of the magnetic gripper 10, the magnetic flux B does not pass through the magnetic material W in any way. Therefore, the magnetic gripper 10 does not possess the holding force described above. Consequently, the magnetic gripper 10 does not hold the magnetic material W.

[0102] When a voltage is applied to the coil 16 of the released magnetic gripper 10, currents flow in opposite directions through the two coils 16, thereby reversing the magnetization directions of the two second permanent magnets 14. As a result, the magnetic gripper 10 can acquire a holding force. Figure 7B illustrates a magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnetic gripper 10 in the holding state. In the holding state, the south pole of the second permanent magnet 14 is located closer to the south pole of the first permanent magnet 12 than the north pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the north pole of the first permanent magnet 12 than the south pole of the first permanent magnet 12.

[0103] The magnetic flux B traveling from the south pole to the north pole within one of the two second permanent magnets 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that abuts against the north pole of the second permanent magnet 14. This yoke 18 is one of two yokes 18 that make up a first pair of yokes 18 that abut against the second permanent magnet 14. The magnetic flux B passing through the yoke 18 also passes through the contact portion 20c of a pole piece 20 that abuts against the yoke 18. This pole piece 20 is one of two pole pieces 20 that make up a first pair of pole pieces 20 that abut against the first pair of yokes 18.

[0104] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of the other pole piece 20 of the two pole pieces 20 constituting the first pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0105] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts the other yoke 18 of the two yokes 18 that constitute the first pair of yokes 18. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the second permanent magnet 14 described above. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the second permanent magnet 14.

[0106] The magnetic flux B traveling from the south pole to the north pole within the other of the two second permanent magnets 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that is in contact with the north pole of the second permanent magnet 14. This yoke 18 is the other of two yokes 18 that constitute a second pair of yokes 18 that are in contact with the second permanent magnet 14.

[0107] The magnetic flux B passing through the yoke 18 passes through the contact portion 20c of the pole piece 20 that abuts against the yoke 18. This pole piece 20 is the other pole piece 20 of the two pole pieces 20 that make up the second pair of pole pieces 20 that abut against the second pair of yokes 18.

[0108] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of one of the two pole pieces 20 constituting the second pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0109] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts one of the two yokes 18 that constitute the second pair of yokes 18. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the other second permanent magnet 14. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the second permanent magnet 14.

[0110] In this way, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of each second permanent magnet 14 is closed off and formed by the second permanent magnet 14, a pair of yokes 18, a pair of pole pieces 20, and a magnetic material W.

[0111] The magnetic flux B traveling from the south pole to the north pole within one of the two first permanent magnets 12 exits from the north pole of the first permanent magnet 12 and passes through a yoke 18 that abuts against the north pole of the first permanent magnet 12. This yoke 18 is one of two yokes 18 that constitute the first pair of yokes 18. The magnetic flux B passing through the yoke 18 passes through the contact portion 20c of a pole piece 20 that abuts against the yoke 18. This pole piece 20 is one of two pole pieces 20 that constitute the first pair of pole pieces 20.

[0112] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of the other pole piece 20 of the two pole pieces 20 constituting the first pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0113] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts the other yoke 18 of the two yokes 18 that constitute the first pair of yokes 18. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the other first permanent magnet 12 of the two first permanent magnets 12. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the first permanent magnet 12.

[0114] The magnetic flux B moving from the south pole to the north pole within the first permanent magnet 12 exits from the north pole of the first permanent magnet 12 and passes through a yoke 18 that abuts against the north pole of the first permanent magnet 12. This yoke 18 is the other of two yokes 18 that constitute the second pair of yokes 18. The magnetic flux B passing through this yoke 18 passes through the contact portion 20c of a pole piece 20 that abuts against this yoke 18. This pole piece 20 is the other of two pole pieces 20 that constitute the second pair of pole pieces 20.

[0115] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of one of the two pole pieces 20 that constitute the second pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0116] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts one of the two yokes 18 that constitute the first pair of yokes 18. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the first permanent magnet 12 described above. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the first permanent magnet 12.

[0117] In this way, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of the two first permanent magnets 12 is closed off and formed by the two first permanent magnets 12, two pairs of yokes 18, two pairs of pole pieces 20, and the magnetic material W.

[0118] In other words, the magnetic flux B of the permanent electromagnet M passes through the magnetic material W. Therefore, the magnetic gripper 10 has a holding force corresponding to the magnetic force of the permanent electromagnet M. The magnetic gripper 10 is in a holding state in which the magnetic material W is held at the end 20e of the holding portion 20h by the holding force.

[0119] When a voltage is applied to each coil 16 of the magnetic gripper 10, which is in a holding state, a current flows through each coil 16 in the opposite direction to before, thereby reversing the magnetization direction of the second permanent magnet 14. As a result, the magnetic gripper 10 can enter the released state described above. Since the magnetic gripper 10 does not have a holding force, the magnetic material W detaches from the permanent electromagnet M.

[0120] The magnetic gripper 10 according to this modified example 1 provides the same effects as the third embodiment.

[0121] (Modification 2) In the third embodiment described above, the extending direction De is a direction that intersects with both the first direction D1 and the second direction D2. However, as shown in Figures 8A and 8B, the extending direction De may be a direction parallel to the first direction D1. The pole piece 20 can hold the magnetic material W by the magnetic force of the permanent electromagnet M at the end 20e of the holding portion 20h that extends in the extending direction De from the contact portion 20c. Figures 8A and 8B are schematic diagrams showing the configuration and magnetic circuit of the magnet gripper 10 according to Modification 2.

[0122] Figure 8A illustrates a magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnet gripper 10 in the released state described above. In the released state, the south pole of the second permanent magnet 14 is located closer to the north pole than the south pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the south pole than the north pole of the first permanent magnet 12. The magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnet gripper 10 in the released state according to this modified example 2 is the same as in the third embodiment.

[0123] In other words, the magnetic circuit formed by the magnetic flux B in the released state of the magnetic gripper 10 is closed off by the two first permanent magnets 12, the two second permanent magnets 14, and the two pairs of yokes 18. In this case, even if a magnetic material W is placed near the released state of the magnetic gripper 10, the magnetic flux B does not pass through the magnetic material W in any way. Therefore, the magnetic gripper 10 does not possess the holding force described above. Consequently, the magnetic gripper 10 does not hold the magnetic material W.

[0124] When a voltage is applied to the coil 16 of the released magnetic gripper 10, currents flow in opposite directions through the two coils 16, thereby reversing the magnetization directions of the two second permanent magnets 14. As a result, the magnetic gripper 10 can acquire a holding force. Figure 8B illustrates a magnetic circuit formed by the magnetic flux B corresponding to the magnetic force of the permanent electromagnet M of the magnetic gripper 10 in the holding state. In the holding state, the south pole of the second permanent magnet 14 is located closer to the south pole of the first permanent magnet 12 than the north pole of the first permanent magnet 12. The north pole of the second permanent magnet 14 is located closer to the north pole of the first permanent magnet 12 than the south pole of the first permanent magnet 12.

[0125] The magnetic flux B traveling from the south pole to the north pole within one of the two second permanent magnets 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that abuts against the north pole of the second permanent magnet 14. This yoke 18 is one of two yokes 18 that make up a first pair of yokes 18 that abut against the second permanent magnet 14. The magnetic flux B passing through the yoke 18 also passes through the contact portion 20c of a pole piece 20 that abuts against the yoke 18. This pole piece 20 is one of two pole pieces 20 that make up a first pair of pole pieces 20 that abut against the first pair of yokes 18.

[0126] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of one of the two pole pieces 20 that constitute the second pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0127] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts one of the two yokes 18 that constitute the second pair of yokes 18. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the other second permanent magnet 14 of the two second permanent magnets 14. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the second permanent magnet 14.

[0128] The magnetic flux B from the south pole to the north pole of the second permanent magnet 14 exits from the north pole of the second permanent magnet 14 and passes through a yoke 18 that abuts against the north pole of the second permanent magnet 14. This yoke 18 is the other of two yokes 18 that constitute the second pair of yokes 18. The magnetic flux B passing through this yoke 18 passes through the contact portion 20c of a pole piece 20 that abuts against this yoke 18. This pole piece 20 is the other of two pole pieces 20 that constitute the second pair of pole pieces 20.

[0129] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of the other pole piece 20 of the two pole pieces 20 constituting the first pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0130] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts the other yoke 18 of the two yokes 18 that constitute the first pair of yokes 18. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the second permanent magnet 14 described above. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the second permanent magnet 14.

[0131] In this way, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of the two second permanent magnets 14 is closed off by the two second permanent magnets 14, two pairs of yokes 18, two pairs of pole pieces 20, and the magnetic material W.

[0132] The magnetic flux B traveling from the south pole to the north pole within one of the two first permanent magnets 12 exits from the north pole of the first permanent magnet 12 and passes through a yoke 18 that abuts against the north pole of the first permanent magnet 12. This yoke 18 is one of two yokes 18 that constitute the first pair of yokes 18. The magnetic flux B passing through the yoke 18 passes through the contact portion 20c of a pole piece 20 that abuts against the yoke 18. This pole piece 20 is one of two pole pieces 20 that constitute the first pair of pole pieces 20.

[0133] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of one of the two pole pieces 20 that constitute the second pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0134] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts one of the two yokes 18 that constitute the second pair of yokes 18. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the first permanent magnet 12 described above. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the first permanent magnet 12.

[0135] The magnetic flux B traveling from the south pole to the north pole within the other of the two first permanent magnets 12 exits from the north pole of the first permanent magnet 12 and passes through a yoke 18 that abuts against the north pole of the first permanent magnet 12. This yoke 18 is the other of two yokes 18 that constitute the second pair of yokes 18. The magnetic flux B passing through this yoke 18 also passes through the contact portion 20c of a pole piece 20 that abuts against this yoke 18. This pole piece 20 is the other of two pole pieces 20 that constitute the second pair of pole pieces 20.

[0136] The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the holding portion 20h of the pole piece 20. The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the end portion 20e and exits to the outside of the magnet gripper 10. When the magnet gripper 10 is approaching or in contact with the magnetic material W, the magnetic flux B passes through the magnetic material W. The magnetic flux B that has passed through the magnetic material W is directed toward the end portion 20e of the holding portion 20h of the other pole piece 20 of the two pole pieces 20 constituting the first pair of pole pieces 20. The magnetic flux B that has passed through the magnetic material W passes through the end portion 20e and enters the holding portion 20h of the pole piece 20.

[0137] The magnetic flux B passing through the holding portion 20h of the pole piece 20 passes through the contact portion 20c of the pole piece 20. The contact portion 20c of the pole piece 20 contacts the other yoke 18 of the two pole pieces 20 that constitute the first pair of yokes 18. The magnetic flux B passing through the contact portion 20c of the pole piece 20 passes through the yoke 18. The yoke 18 contacts the south pole of the other first permanent magnet 12. The magnetic flux B passing through the yoke 18 exits the yoke 18 and enters the south pole of the first permanent magnet 12.

[0138] In this way, the magnetic circuit formed by the magnetic flux B generated by the magnetic force of one of the first permanent magnets 12 is closed off by the first permanent magnet 12, one of the pairs of yokes 18, one of the pairs of pole pieces 20, and the magnetic material W. The magnetic circuit formed by the magnetic flux B generated by the magnetic force of the other first permanent magnet 12 is closed off by the first permanent magnet 12, the other of the pairs of yokes 18, the other of the pairs of pole pieces 20, and the magnetic material W.

[0139] In other words, the magnetic flux B of the permanent electromagnet M passes through the magnetic material W. Therefore, the magnetic gripper 10 has a holding force corresponding to the magnetic force of the permanent electromagnet M. The magnetic gripper 10 is in a holding state in which the magnetic material W is held at the end 20e of the holding portion 20h by the holding force.

[0140] When a voltage is applied to each coil 16 of the magnetic gripper 10, which is in a holding state, a current flows through each coil 16 in the opposite direction to before, thereby reversing the magnetization direction of the second permanent magnet 14. As a result, the magnetic gripper 10 can enter the released state described above. Since the magnetic gripper 10 does not have a holding force, the magnetic material W detaches from the permanent electromagnet M.

[0141] The magnetic gripper 10 according to this modified example 2 provides the same effects as the third embodiment.

[0142] With regard to the embodiments and modifications described above, the following additional information is disclosed.

[0143] (Note 1) The magnet gripper (10) of the present disclosure has a permanent electromagnet (M) having two first permanent magnets (12) arranged side by side with their magnetization directions opposite to each other, two second permanent magnets (14) arranged side by side with their magnetization directions opposite to each other, and two coils (16) wound around the two second permanent magnets respectively, which can reverse the magnetization direction of the two second permanent magnets when an electric current flows through them, and a permanent electromagnet (M) that contacts the two second permanent magnets respectively The device comprises two pairs of yokes (18) and two pairs of pole pieces (20) that abut against the two pairs of yokes and are capable of holding a magnetic material (W) by the magnetic force of the permanent electromagnet, wherein a first direction (D1) parallel to the magnetization directions of the two first permanent magnets intersects with a second direction (D2) parallel to the magnetization directions of the two second permanent magnets, and the two yokes constituting each pair of yokes abut against each of the two second permanent magnets along the second direction, and in front of each pair Each of the two pole pieces constituting the pole piece has a contact portion (20c) that abuts against the two yokes constituting each pair of yokes, and a holding portion (20h) that extends from the contact portion. The magnetic material can be held by the magnetic force at the end (20e) of the holding portion, which is spaced apart in the extending direction (De) from the contact portion. One of the two yokes constituting the first pair of yokes and one of the two yokes constituting the second pair of yokes each abut against one of the two first permanent magnets and face each other along the first direction. The other of the two yokes constituting the first pair of yokes and the other of the two yokes constituting the second pair of yokes each abut against the other of the two first permanent magnets and face each other along the first direction. With this configuration, the efficiency of work using magnetic force can be improved compared to conventional methods. Furthermore, even if the surface of the magnetic material is not a flat plane, the magnetic gripper can increase the likelihood of it holding the magnetic material. In addition, even if the magnetic material is a thin plate that is prone to magnetic saturation, the magnetic gripper can still hold the magnetic material.

[0144] (Note 2) The magnetic gripper described in Note 1, wherein the extending direction may be a direction that intersects with either the first direction or the second direction. With such a configuration, even if the surface of the magnetic material is not a flat plane, the possibility of the magnetic gripper holding the magnetic material can be increased.

[0145] (Note 3) The magnetic gripper described in Note 1, wherein the extending direction may be parallel to the first direction or the second direction. With such a configuration, even if the surface of the magnetic material is not a flat plane, the possibility of the magnetic gripper holding the magnetic material can be increased.

[0146] (Note 4) The magnet gripper of the present disclosure comprises a permanent electromagnet having a first permanent magnet whose magnetization direction is parallel to a first direction, a second permanent magnet whose magnetization direction is parallel to a second direction and different from that of the first permanent magnet, and a coil wound around the second permanent magnet that can reverse the magnetization direction of the second permanent magnet by the flow of an electric current; a pair of yokes that each abut against the second permanent magnet; and a pair of pole pieces that each abut against the pair of yokes and can hold a magnetic material by the magnetic force of the permanent electromagnet, wherein the two yokes constituting the pair of yokes abut against the second permanent magnet along the second direction, and the two pole pieces constituting the pair of pole pieces each have a contact portion that abuts against the two yokes constituting the pair of yokes, and a holding portion that extends from the contact portion, and the magnetic material can be held by the magnetic force at the ends of the holding portions spaced apart in the extending direction from the contact portion to the holding portion. With this configuration, the efficiency of work utilizing magnetism can be improved compared to conventional methods.

[0147] (Note 5) In the magnetic gripper described in Note 4, the two yokes constituting a pair of yokes may further abut the first permanent magnet along the first direction, the first permanent magnet and the second permanent magnet may be placed side by side, and the first direction and the second direction may be parallel to each other. With such a configuration, the magnetic gripper can be miniaturized.

[0148] (Note 6) In the magnetic gripper described in Note 5, the coil does not have to be wound around the first permanent magnet. With this configuration, the amount of heat generated when current flows through the coil can be suppressed.

[0149] (Note 7) In the magnetic gripper described in Note 5, the coil may be wound around the second permanent magnet and the first permanent magnet as a whole. With such a configuration, a permanent electromagnet can be easily provided.

[0150] (Note 8) In the magnetic gripper described in Note 7, the first permanent magnet may be arranged to surround the second permanent magnet. With such a configuration, a permanent electromagnet can be easily provided.

[0151] (Note 9) A magnet gripper as described in Note 4, wherein two of the first permanent magnets are arranged side by side with their magnetization directions opposite to each other, two of the second permanent magnets are arranged side by side with their magnetization directions opposite to each other, two of the coils are wound around the two of the second permanent magnets, two pairs of the yokes are in contact with the two of the second permanent magnets, two pairs of the pole pieces are in contact with the two pairs of the yokes, one of the two yokes constituting the first pair of the yokes and one of the two yokes constituting the second pair of the yokes are in contact with one of the two of the first permanent magnets and face each other along the first direction, and the other of the two yokes constituting the first pair of the yokes and the other of the two yokes constituting the second pair of the yokes are in contact with the other of the two of the first permanent magnets and face each other along the first direction. With this configuration, even if the surface of the magnetic material is not a flat plane, the likelihood of the magnetic gripper holding the magnetic material can be increased. Furthermore, even if the magnetic material is a thin plate that is prone to magnetic saturation, the magnetic gripper can still hold the magnetic material.

[0152] (Note 10) The magnetic gripper described in Note 9, wherein the extending direction may be a direction that intersects with either the first direction or the second direction. With such a configuration, even if the surface of the magnetic material is not a flat plane, the possibility of the magnetic gripper holding the magnetic material can be increased.

[0153] (Note 11) The magnetic gripper described in Note 9, wherein the extending direction may be parallel to the first direction or the second direction. With such a configuration, even if the surface of the magnetic material is not a flat plane, the possibility of the magnetic gripper holding the magnetic material can be increased.

[0154] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

Claims

1. A permanent electromagnet (M) having two first permanent magnets (12) arranged side by side with their magnetization directions opposite to each other, two second permanent magnets (14) arranged side by side with their magnetization directions opposite to each other, and two coils (16) wound around the two second permanent magnets, respectively, and capable of reversing the magnetization direction of each of the two second permanent magnets by passing an electric current through each of them; two pairs of yokes (18) that abut against the two second permanent magnets, respectively; and two pairs of pole pieces (20) that abut against the two pairs of yokes, respectively, and capable of holding a magnetic material (W) by the magnetic force of the permanent electromagnet, wherein a first direction (D1) parallel to the magnetization directions of the two first permanent magnets intersects with a second direction (D2) parallel to the magnetization directions of the two second permanent magnets, and the two yokes constituting each pair of yokes abut against each of the two second permanent magnets along the second direction, Each pair of pole pieces comprising the pole pieces each has a contact portion (20c) that abuts against the two yokes comprising the 2. A magnetic gripper according to claim 1, wherein the extending direction is a direction that intersects with both the first direction and the second direction.

3. A magnetic gripper according to claim 1, wherein the extending direction is parallel to the first direction or the second direction.

4. A magnet gripper comprising: a permanent electromagnet having a first permanent magnet whose magnetization direction is parallel to a first direction; a second permanent magnet whose magnetization direction is parallel to a second direction and different from that of the first permanent magnet; a coil wound around the second permanent magnet and capable of reversing the magnetization direction of the second permanent magnet by the flow of an electric current; a pair of yokes each in contact with the second permanent magnet; and a pair of pole pieces each in contact with the pair of yokes and capable of holding a magnetic material by the magnetic force of the permanent electromagnet, wherein the two yokes constituting the pair of yokes are in contact with the second permanent magnet along the second direction; and the two pole pieces constituting the pair of pole pieces each have a contact portion that is in contact with the two yokes constituting the pair of yokes, and a holding portion that extends from the contact portion, and the magnetic material can be held by the magnetic force at the ends of the holding portions spaced apart in the extending direction from the contact portion to the holding portion.

5. A magnetic gripper according to claim 4, wherein two yokes constituting a pair of yokes further abut the first permanent magnet in the first direction, the first permanent magnet and the second permanent magnet are placed side by side, and the first direction and the second direction are parallel to each other.

6. A magnetic gripper according to claim 5, wherein the coil is not wound around the first permanent magnet.

7. A magnetic gripper according to claim 5, wherein the coil is wound around the second permanent magnet and the first permanent magnet as a whole.

8. A magnetic gripper according to claim 7, wherein the first permanent magnet is arranged to surround the second permanent magnet.

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