Magnet gripper

Abstract

This magnet gripper (10) grips a workpiece (W) by suction and comprises: a permanent electromagnet (12) that includes a first permanent magnet (12a) and a second permanent magnet (12b); a coil (14) that is wound around the outer periphery of at least the second permanent magnet and can reverse the magnetization direction of the second permanent magnet by the flow of current; a yoke (16) accommodating the permanent electromagnet therein; and a display sheet (30) which changes color when the magnetization direction of the second permanent magnet is reversed, and which has a medium (30a) in which optical crystals of magnetic particles are used.

Description

Magnetic Gripper

[0001] The present disclosure relates to magnetic grippers.

[0002] Japanese Patent Laid-Open Publication No. 60-130106 discloses a permanent electromagnetic attractor in which a low-coercive force magnet is magnetized in the same direction as a high-coercive force magnet when attracting a magnetic material, and when not attracting, the low-coercive force magnet is magnetized in the opposite direction to the high-coercive force magnet.

[0003] The magnetic force generated by the electro-permanent magnet cannot be visually detected from the appearance of the magnetic gripper, which poses a problem in that it is impossible to determine whether the magnetic gripper is in a state where it can attract a workpiece.

[0004] The present disclosure aims to solve the above-mentioned problems.

[0005] An aspect of the present disclosure is a magnetic gripper that attracts a workpiece, comprising: a permanent electromagnet including a first permanent magnet and a second permanent magnet; a coil wound around at least the outer periphery of the second permanent magnet and capable of reversing the magnetization direction of the second permanent magnet when a current flows through it; a yoke that houses the permanent electromagnet inside; and a display sheet that has a medium using a photonic crystal made of magnetic particles and changes color in response to the reversal of the magnetization direction of the second permanent magnet.

[0006] According to the present disclosure, it is possible to determine whether or not the magnetic gripper is in a state in which it can attract a workpiece.

[0007] Fig. 1 is a diagram schematically showing an example of the configuration of a magnetic gripper that attracts a workpiece. Figs. 2A and 2B are diagrams schematically showing an example of the configuration of a display sheet. Figs. 3A and 3B are diagrams schematically showing magnetic flux corresponding to the magnetic force generated by a permanent electromagnet. Figs. 4A and 4B are diagrams schematically showing other examples of the configuration of a magnetic gripper.

[0008] FIG. 1 is a diagram schematically illustrating an example configuration of a magnetic gripper 10 that attracts a workpiece W. The magnetic gripper 10 has a permanent electromagnet 12, a coil 14, a yoke 16, a cover member 20, and a display sheet 30. The magnetic gripper 10 may further be provided with a connector for connecting to a power source, an adapter for attaching the magnetic gripper 10 to a robot arm, and the like, but these are not shown in FIG. 1 . The permanent electromagnet 12 includes a first permanent magnet 12 a and a second permanent magnet 12 b. In this embodiment, as shown in FIG. 1 , the first permanent magnet 12 a and the second permanent magnet 12 b are arranged adjacent to each other.

[0009] Specifically, the cylindrical first permanent magnet 12a covers the outer peripheral surface of the cylindrical second permanent magnet 12b. That is, the second permanent magnet 12b is housed in the hollow portion of the first permanent magnet 12a. The first permanent magnet 12a is a neodymium magnet containing, for example, neodymium in addition to iron. The second permanent magnet 12b is an alnico magnet containing, for example, aluminum, nickel, and cobalt in addition to iron.

[0010] The coil 14 is wound around at least the outer periphery of the second permanent magnet 12b. In this embodiment, as shown in FIG. 1, the coil 14 is wound around the outer periphery of the first permanent magnet 12a, which is disposed further outward from the second permanent magnet 12b. The coil 14 is electrically connected to a power source (not shown). When a voltage is applied to the coil 14 and a current flows, the magnetization direction of the second permanent magnet 12b can be reversed.

[0011] The yoke 16 houses the electro-permanent magnet 12 inside. The yoke 16 is made of steel, which is a ferromagnetic material, and passes magnetic flux corresponding to the magnetic force generated by the electro-permanent magnet 12. The yoke 16 has a top yoke 16t, a bottom yoke 16b, and an outer yoke 16u. The top yoke 16t and the bottom yoke 16b are arranged in a direction that intersects with the magnetization direction of the first permanent magnet 12a and the second permanent magnet 12b.

[0012] A non-magnetic body Nm is disposed between the top yoke 16t and the outer yoke 16u. The non-magnetic body Nm is made of, for example, stainless steel. The top yoke 16t and the non-magnetic body Nm are held by the outer yoke 16u and a pad Rd disposed on the outer periphery of the outer yoke 16u.

[0013] Assume that the magnetization direction of the second permanent magnet 12b is opposite to that of the first permanent magnet 12a. In this case, by applying a voltage to the coil 14 and causing a current in a predetermined direction to flow through the coil 14, the magnetization direction of the second permanent magnet 12b can be reversed to match the magnetization direction of the first permanent magnet 12a. If the workpiece W is a magnetic body, the workpiece W is attracted toward the top yoke 16t by the magnetic force generated by the permanent electromagnet 12 and is attracted to the magnetic gripper 10.

[0014] Even after the application of voltage to the coil 14 is stopped and the current flowing through the coil 14 is stopped, the magnetic force attracting the workpiece W is maintained. Therefore, the workpiece W continues to be attracted to the magnetic gripper 10.

[0015] Thereafter, a voltage is applied to the coil 14, causing a current to flow through the coil 14 in the opposite direction to the above-mentioned predetermined direction, thereby reversing the magnetization direction of the second permanent magnet 12b to the opposite direction to the magnetization direction of the first permanent magnet 12a. Since the magnetic force generated by the electro-permanent magnet 12 no longer acts on the workpiece W, the magnetic gripper 10 is released from attraction of the workpiece W. Even after the application of voltage to the coil 14 is stopped and the current flowing through the coil 14 is stopped, the magnetic gripper 10 remains released from attraction of the workpiece W.

[0016] The outer yoke 16u extends in a direction intersecting the top yoke 16t and the bottom yoke 16b. In this embodiment, as shown in FIG. 1 , the outer yoke 16u surrounds and covers the permanent electromagnet 12 and the coil 14. The outer yoke 16u contacts the non-magnetic material Nm and the bottom yoke 16b. The cover member 20 surrounds and covers the outer yoke 16u. The cover member 20 also covers the bottom yoke 16b.

[0017] The display sheet 30 is provided on at least one of the outer surface of the top yoke 16t and the outer surface of the cover member 20 that covers the outer yoke 16u. In other words, the display sheet 30 is provided on the outside of the yoke 16. In this embodiment, the display sheet 30 is provided on both the outer surface of the top yoke 16t and the outer surface of the cover member 20 that covers the outer yoke 16u.

[0018] The display sheet 30 includes a medium using photonic crystals made of magnetic particles and a light-blocking sheet laminated on the medium. The medium contains a large number of magnetic particles dispersed in a liquid. When magnetic flux passes through the medium, the spacing between the particles changes. This changes the wavelength of the reflected light when the photonic crystals made of particles Bragg reflect light incident on the medium from the outside. In other words, the color of the light reflected from the medium changes depending on whether or not magnetic flux passes through the medium. The stronger the magnetic flux passing through the medium, the shorter the wavelength of the reflected light from the medium, so the color displayed by the display sheet 30 approaches green, blue, or purple.

[0019] Depending on the reversal of the magnetization direction of the second permanent magnet 12b, the magnetic flux corresponding to the magnetic force generated by the electro-permanent magnet 12 may or may not pass through the medium. Therefore, depending on the reversal of the magnetization direction of the second permanent magnet 12b, the color shown by the display sheet 30 changes. In other words, the display sheet 30 is provided at a position where the color changes depending on the reversal of the magnetization direction of the second permanent magnet 12b.

[0020] 2A and 2B, the light-shielding sheet has a window portion, and areas other than the window portion block external light from entering the medium. The worker can visually recognize the change in color shown by the indicator sheet 30 through the window portion. This allows the worker to determine whether the magnetic gripper 10 is in a state where it can attract the workpiece W.

[0021] 2A and 2B are diagrams schematically showing an example configuration of the display sheet 30. As described above, the display sheet 30 has a medium 30a and a light-shielding sheet 30b. As shown in Fig. 2A and 2B, the light-shielding sheet 30b is laminated on the medium 30a and has a window portion 30t. The window portion 30t is formed by cutting out a circular portion of the light-shielding sheet 30b.

[0022] The window 30t transmits light incident on the medium 30a and light reflected from the medium 30a. This makes it easier to determine whether the magnetic gripper 10 is in a state where it can attract the workpiece W. When the magnetic flux corresponding to the magnetic force generated by the permanent electromagnet 12 passes through the medium 30a, the window 30t is preferably positioned at a position where a stronger magnetic flux passes through the medium 30a. This makes the color change shown by the indicator sheet 30 clearer.

[0023] 3A and 3B are diagrams schematically illustrating the magnetic flux Mb corresponding to the magnetic force generated by the permanent electromagnet 12. Note that in Figs. 3A and 3B, the cover member 20 and the pad Rd of the magnetic gripper 10 shown in Fig. 1 are omitted.

[0024] 3A shows the magnetic flux Mb when the magnetization direction of the second permanent magnet 12b is opposite to that of the first permanent magnet 12a. Most of the magnetic flux Mb emitted from the first permanent magnet 12a enters the second permanent magnet 12b, and most of the magnetic flux Mb emitted from the second permanent magnet 12b enters the first permanent magnet 12a. In other words, much of the magnetic flux Mb is confined within the electro-permanent magnet 12 and the yoke 16.

[0025] A portion of the magnetic flux Mb emitted from the first permanent magnet 12a passes through the yoke 16 rather than the second permanent magnet 12b and returns to the first permanent magnet 12a. However, the magnetic flux Mb passing through the first permanent magnet 12a, the second permanent magnet 12b, the top yoke 16t, the outer yoke 16u and / or the bottom yoke 16b hardly exits the yoke 16. Therefore, as described above, almost no magnetic flux Mb passes through the medium 30a of the display sheet 30 (not shown) that is provided outside the yoke 16. In addition, because almost no magnetic flux Mb passes through the workpiece W (not shown) that is located outside the outer yoke 16u, the workpiece W is not attracted to the magnetic gripper 10.

[0026] 3B shows the magnetic flux Mb when the magnetization direction of the second permanent magnet 12b is the same as the magnetization direction of the first permanent magnet 12a. Unlike in FIG. 3A, almost no magnetic flux Mb enters the second permanent magnet 12b from the first permanent magnet 12a. Almost no magnetic flux Mb enters the first permanent magnet 12a from the second permanent magnet 12b.

[0027] Most of the magnetic flux Mb emitted from the first permanent magnet 12a returns to the first permanent magnet 12a. Most of the magnetic flux Mb emitted from the second permanent magnet 12b returns to the second permanent magnet 12b. More of the magnetic flux Mb passing through the first permanent magnet 12a, the second permanent magnet 12b, the top yoke 16t, the outer yoke 16u, and / or the bottom yoke 16b exits the yoke 16 than in FIG. 3A. In this way, the magnetic flux Mb exiting the yoke 16 affects the workpiece W (not shown), which is a magnetic material, and the medium 30a of the display sheet 30 (not shown), which contains magnetic particles.

[0028] The indicator sheet 30 is provided on the outer surface of the top yoke 16t and the outer surface of the cover member 20 that covers the outer yoke 16u. Therefore, a strong magnetic flux Mb passes through the medium 30a of the indicator sheet 30. Because the wavelength of the light reflected from the medium 30a becomes shorter, the color shown by the indicator sheet 30 approaches green, blue, or purple. Furthermore, because the strong magnetic flux Mb passes through a workpiece W (not shown) located outside the outer yoke 16u, the workpiece W can be attracted to the magnetic gripper 10. In this way, it is possible to determine at a glance whether the magnetic gripper 10 is in a state where it can attract the workpiece W, based on the color shown by the indicator sheet 30.

[0029] The above-described embodiment may be modified as follows: In the following modifications, explanations that overlap with the embodiment will be omitted.

[0030] (Variation 1) In the above-described embodiment, the display sheet 30 is provided on the outer surface of the top yoke 16t and the outer surface of the cover member 20 that covers the outer yoke 16u, but this is not limited to this. Figures 4A and 4B are schematic diagrams showing other configuration examples of the magnetic gripper 10. In the example shown in Figure 4A, the cover member 40 thinly covers the top yoke 16t. In this case, the display sheet 30 is provided not on the outer surface of the top yoke 16t, but on the outer surface of the cover member 40 that covers the top yoke 16t.

[0031] 4B , the cover member 20 does not completely cover the outer yoke 16u, leaving a portion of the outer yoke 16u exposed. Specifically, the example shows a portion of the outer surface of the outer yoke 16u exposed. In this case, the display sheet 30 is provided on the exposed outer surface of the outer yoke 16u, not on the outer surface of the cover member 20 that covers the outer yoke 16u.

[0032] 4A and 4B, when a large amount of magnetic flux Mb is projected outside the yoke 16, a strong magnetic flux Mb passes through the medium 30a of the display sheet 30. Therefore, it is possible to determine at a glance whether the magnetic gripper 10 is in a state where it can attract the workpiece W, based on the color shown by the display sheet 30.

[0033] (Variation 2) In the above-described embodiment, the first permanent magnet 12a and the second permanent magnet 12b included in the permanent electromagnet 12 are arranged adjacent to each other. However, the first permanent magnet 12a and the second permanent magnet 12b do not have to be arranged adjacent to each other. For example, the first permanent magnet 12a and the multiple second permanent magnets 12b included in the permanent electromagnet 12 may be arranged so that the magnetization direction of the first permanent magnet 12a intersects with the magnetization direction of each of the second permanent magnets 12b.

[0034] By applying a voltage to the coil 14 and causing a current to flow through the coil 14 in a predetermined direction, the magnetization direction of the second permanent magnet 12b can be reversed. This causes the magnetic gripper 10 to enter a state in which it is unable to attract the workpiece W, which is a magnetic body. In this case, most of the magnetic flux Mb emitted from the first permanent magnet 12a enters the second permanent magnet 12b, and most of the magnetic flux Mb emitted from the second permanent magnet 12b enters the first permanent magnet 12a. In other words, most of the magnetic flux Mb is trapped within the electro-permanent magnet 12 and the yoke 16. Therefore, almost no magnetic flux Mb escapes outside the yoke 16.

[0035] By applying a voltage to the coil 14 and causing a current to flow in a predetermined direction through the coil 14, the magnetization direction of the second permanent magnet 12b can be reversed. This enables the magnetic gripper 10 to attract the workpiece W, which is a magnetic body. In this case, almost no magnetic flux Mb enters the second permanent magnet 12b from the first permanent magnet 12a. Almost no magnetic flux Mb enters the first permanent magnet 12a from the second permanent magnet 12b.

[0036] Most of the magnetic flux Mb emitted from the first permanent magnet 12a returns to the first permanent magnet 12a. Most of the magnetic flux Mb emitted from the second permanent magnet 12b returns to the second permanent magnet 12b. Therefore, much of the magnetic flux Mb exits the yoke 16. The magnetic flux Mb exiting the yoke 16 affects the workpiece W, which is a magnetic body, and the medium 30a of the display sheet 30, which contains magnetic particles. In this case, it is possible to determine at a glance whether the magnetic gripper 10 is in a state where it can attract the workpiece W, based on the color shown by the display sheet 30.

[0037] The following additional notes are disclosed regarding the above-described embodiment and modifications.

[0038] (Supplementary Note 1) The magnetic gripper (10) of the present disclosure is a magnetic gripper that attracts a workpiece (W), and includes a permanent electromagnet (12) including a first permanent magnet (12 a) and a second permanent magnet (12 b), a coil (14) wound around at least the outer periphery of the second permanent magnet and capable of reversing the magnetization direction of the second permanent magnet when a current flows through it, a yoke (16) that houses the permanent electromagnet, and an indicator sheet (30) that has a medium (30 a) using a photonic crystal made of magnetic particles and changes color in response to the reversal of the magnetization direction of the second permanent magnet. With this configuration, it is possible to determine whether the magnetic gripper is in a state where it can attract a workpiece.

[0039] (Supplementary Note 2) In the magnetic gripper according to Supplementary Note 1, the display sheet may include the medium and a light-shielding sheet (30b) laminated on the medium, and the light-shielding sheet may have a window (30t) that transmits light incident on the medium and light reflected from the medium. With this configuration, the color change indicated by the display sheet becomes clearer.

[0040] (Supplementary Note 3) In the magnetic gripper according to Supplementary Note 1 or 2, the yoke may include a top yoke (16t) through which a magnetic flux (Mb) corresponding to the magnetic force generated by the electro-permanent magnet passes, the workpiece is attracted toward the top yoke by the magnetic force, and the indicator sheet may be provided on the outer surface of the top yoke or on the outer surface of a cover member (40) covering the top yoke. With this configuration, it is possible to determine at a glance whether the magnetic gripper is in a state where it can attract a workpiece, based on the color shown by the indicator sheet.

[0041] (Supplementary Note 4) In the magnetic gripper according to Supplementary Note 1 or 2, the yoke may include a top yoke (16t) and an outer yoke (16u) through which a magnetic flux (Mb) corresponding to the magnetic force generated by the electro-permanent magnet passes, the workpiece is attracted toward the top yoke by the magnetic force, the outer yoke extends in a direction intersecting the top yoke, and the indicator sheet may be provided on the outer surface of the outer yoke or on the outer surface of a cover member (20) covering the outer yoke. With this configuration, it is possible to determine at a glance whether the magnetic gripper is in a state where it can attract a workpiece, based on the color shown by the indicator sheet.

[0042] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

Claims

1. A magnetic gripper (10) for attracting a workpiece (W), comprising: a permanent electromagnet (12) including a first permanent magnet (12a) and a second permanent magnet (12b); a coil (14) wound around at least the outer periphery of the second permanent magnet and capable of reversing the magnetization direction of the second permanent magnet when a current flows through it; a yoke (16) for accommodating the permanent electromagnet inside; and a display sheet (30) having a medium (30a) using a photonic crystal made of magnetic particles, the display sheet changing color in response to the reversal of the magnetization direction of the second permanent magnet.

2. A magnetic gripper as described in claim 1, wherein the display sheet has the medium and a light-shielding sheet (30b) laminated on the medium, and the light-shielding sheet has a window portion (30t) that transmits light incident on the medium and light reflected from the medium.

3. A magnetic gripper as set forth in claim 1 or 2, wherein the yoke includes a top yoke (16t) through which magnetic flux (Mb) corresponding to the magnetic force generated by the permanent electromagnet passes, the workpiece is attracted toward the top yoke by the magnetic force, and the display sheet is provided on the outer surface of the top yoke or the outer surface of a cover member (40) covering the top yoke.

4. A magnetic gripper as set forth in claim 1 or 2, wherein the yoke includes a top yoke (16t) and an outer yoke (16u) through which magnetic flux (Mb) corresponding to the magnetic force generated by the permanent electromagnet passes, the workpiece is attracted toward the top yoke by the magnetic force, the outer yoke extends in a direction intersecting the top yoke, and the display sheet is provided on the outer surface of the outer yoke or the outer surface of a cover member (20) covering the outer yoke.

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