Magnet gripper and industrial robot

Abstract

A magnet gripper (14) comprises a pair of pole shoes (16, 18), each of which has a magnetically attracting portion (32a) to which a workpiece (W) is magnetically attracted, and which are disposed spaced apart from one another in a first direction, a magnet (35) which is disposed between the pair of pole shoes (16, 18), a rotation mechanism (22) which rotates the magnet (35) about a rotation axis (C) in a second direction perpendicular to the first direction, and a yoke (36) which is disposed between the pair of pole shoes (16, 18) and which collects magnetic flux that is not directed toward the pole shoes (16, 18), wherein the yoke (36) is magnetically separated from the pair of pole shoes (16, 18).

Description

Magnetic grippers and industrial robots

[0001] The present invention relates to a magnetic gripper that uses magnetic force to hold a magnetic workpiece, and to an industrial robot.

[0002] A magnetic gripper generates a magnetic force to attract a magnetic workpiece such as steel. For example, in automobile factory production lines, magnetic grippers are attached to industrial robots that transport steel plates. The magnetic force of a magnetic gripper can locally magnetize a steel plate. When a metallic paint is applied to a magnetized steel plate, magnetic flakes become oriented in the magnetized portions of the steel plate, resulting in a problem of a pattern reflecting the magnetization distribution.

[0003] To solve this problem, a magnetic gripper with a demagnetization function has been proposed, as disclosed in JP 2021-515391 A. This magnetic gripper has a demagnetization electromagnetic coil in addition to a magnet that generates an attractive force. This magnetic gripper uses the demagnetization electromagnetic coil to magnetize a workpiece magnetized by a magnet, reversing the magnetic poles, thereby reducing the magnetic force of the steel plate.

[0004] However, the magnetic gripper of JP 2021-515391 A requires a demagnetizing electromagnetic coil and its control circuit in addition to a drive mechanism for driving the magnet, which causes the problem that the structure of the device and its control circuit become complicated.

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

[0006] One aspect of the following disclosure is a magnetic gripper comprising: a pair of pole shoes arranged spaced apart in a first direction, each having an attraction portion to which a workpiece is attracted; a magnetic flux source arranged between the pair of pole shoes and having a pair of magnetic poles that can be oriented in the first direction; a rotation mechanism that rotates the magnetic flux source around a rotation axis in a second direction perpendicular to the first direction; and a yoke arranged between the pair of pole shoes that collects magnetic flux that is not directed toward the pole shoes, wherein the yoke is magnetically separated from the pair of pole shoes.

[0007] Another aspect is a magnetic gripper comprising a pair of pole shoes arranged spaced apart in a first direction, each having an attraction portion to which a workpiece is attracted, a magnetic flux source arranged between the pair of pole shoes and having a pair of magnetic poles that can be oriented in the first direction, a rotation mechanism that rotates the magnetic flux source around a rotation axis that extends in a second direction perpendicular to the first direction, and a magnetic field sensor that detects the magnetic field of the pole shoe.

[0008] Yet another aspect resides in an industrial robot including the magnetic gripper of the above aspect and a robot arm to which the magnetic gripper is attached.

[0009] The magnetic gripper and industrial robot according to the above aspects can demagnetize a workpiece with a simple configuration.

[0010] The above objects, features and advantages will be easily understood from the following description of the embodiments, which is given with reference to the accompanying drawings.

[0011] FIG. 1 is a perspective view of an industrial robot according to a first embodiment. FIG. 2 is a perspective view showing the appearance of a magnetic gripper according to an embodiment that is attached to the industrial robot of FIG. 1. FIG. 3 is an exploded perspective view of the magnetic gripper of FIG. 2. Note that the housing is omitted from FIG. 3. FIG. 4 is a view showing a cross section of the magnetic gripper of FIG. 2. FIG. 5 is a cross section of the magnetic gripper of FIG. 2 taken along a plane perpendicular to the second direction at the position of the magnet, showing the orientation of the magnetic poles when the magnet angle of the magnet is 0°. FIG. 6A is a cross section showing the arrangement of the magnetic poles when the magnet is rotated to a magnetic angle of −θ in the cross section of FIG. 5. FIG. 6B is a cross section showing the arrangement of the magnetic poles when the magnet is rotated to a magnetic angle of +θ in the cross section of FIG. 5. FIG. 7 is a cross section showing the arrangement of the magnetic poles when the magnet is rotated to a magnetic angle of −90°. FIG. 8 is a graph showing the results of calculations using electromagnetic field analysis on the relationship between the magnetic angle θ of the magnet and the attractive force. FIG. 9 is an explanatory diagram showing a modified example of the magnet. Fig. 10 is a perspective view showing the appearance of a magnetic gripper according to the second embodiment. Fig. 11 is a perspective view showing a main part of the magnetic gripper of Fig. 10 in an exploded state. Fig. 12 is a cross-sectional view taken along line XII-XII in Fig. 10. Fig. 13 is a cross-sectional view taken along line XIII-XIII in Fig. 10, with some parts omitted. Fig. 14 is an exploded perspective view of a magnetic circuit member according to a modified example of the second embodiment.

[0012] First Embodiment As shown in Fig. 1, an industrial robot 10 according to an embodiment includes a robot arm 12 that is movable at multiple joints 12a, and a magnetic gripper 14 attached to the tip of the robot arm 12. Such an industrial robot 10 is used, for example, on a production line in an automobile factory to transport magnetic workpieces W, such as steel plates and various parts. The magnetic gripper 14 in Fig. 1 shows one form of a shape that is suitable for attracting a thin plate-like workpiece W.

[0013] The magnetic gripper 14 shown in Fig. 2 includes a first pole shoe 16, a second pole shoe 18, a magnetic force adjustment unit 20, a rotation mechanism 22, and a frame member 24. The magnetic gripper 14 attracts and holds the workpiece W with the first pole shoe 16 and the second pole shoe 18. In the following description, in order to clarify the shape and positional relationship of the components, the terms width direction, attraction direction, and front-rear direction shown in Fig. 2 are used to indicate three mutually perpendicular directions. The attraction direction is the direction in which an attraction force is generated on the workpiece W. The width direction is the direction in which the first pole shoe 16 and the second pole shoe 18 are separated from each other, and is also referred to as the first direction. The front-rear direction is the direction perpendicular to the attraction direction and the width direction.

[0014] Furthermore, the terms "second direction" and "third direction" are used to indicate the arrangement directions of the magnet 35 and the yoke 36, which will be described later. The second direction is the extension direction of the rotation axis C of the magnet 35, which will be described later, and the third direction is the extension direction of the tip wall 36a of the yoke 36. In the illustrated example, the front-rear direction coincides with the second direction and the attraction direction coincides with the third direction, but this is not limited thereto. For example, the magnet 35 and the yoke 36 can be arranged so that the attraction direction coincides with the second direction and the front-rear direction coincides with the third direction. Note that the width direction, the attraction direction, and the front-rear direction do not limit the arrangement direction of the magnetic gripper 14.

[0015] The first pole shoe 16 and the second pole shoe 18 are made of a ferromagnetic material, more preferably a soft magnetic material. The first pole shoe 16 is formed in the shape of a thin plate extending in the attraction direction. The first pole shoe 16 has a rectangular base 30 and legs 32 extending from the base 30. The legs 32 extend further in the front-to-rear direction than the base 30. The first pole shoe 16, which has the base 30 and the legs 32, has a T-shape when viewed in the width direction.

[0016] The first pole shoe 16 has an attraction portion 32a at the end of the leg portion 32 (the lower end in FIG. 2 ). The attraction portion 32a is a portion that emits magnetic flux toward the workpiece W and attracts the workpiece W by magnetic force. The thickness (dimension in the width direction) of the leg portion 32 gradually decreases toward the attraction portion 32a in order to concentrate the magnetic flux at the attraction portion 32a. As shown in FIGS. 3 and 5 , the first pole shoe 16 has a recess 33 in the base 30 that is recessed so as not to interfere with the cylindrical magnet 35. The recess 33 is formed with a curved surface that follows the radius of rotation of the magnet 35. The recess 33 may or may not come into contact with the magnet 35.

[0017] As shown in Figure 3, the second pole shoe 18 is formed in a similar shape to the first pole shoe 16, and therefore a detailed description of the second pole shoe 18 will be omitted. Note that, among the components of the second pole shoe 18, components similar to those of the first pole shoe 16 are denoted by the same reference numerals as the corresponding components of the first pole shoe 16. The second pole shoe 18 is disposed parallel to and spaced apart from the first pole shoe 16 in the width direction. A gap is formed between the first pole shoe 16 and the second pole shoe 18. In one embodiment, the width of the gap between the first pole shoe 16 and the second pole shoe 18 may be greater than the thickness of the first pole shoe 16 or the thickness of the second pole shoe 18.

[0018] The shapes of the first pole shoe 16 and the second pole shoe 18 are not limited to a T-shape. The first pole shoe 16 and the second pole shoe 18 may be, for example, an I-shape or an L-shape when viewed in the width direction.

[0019] A magnetic field sensor 80 is provided on the attraction portion 32a of the first pole shoe 16. The magnetic field sensor 80 detects the strength of the magnetic field flowing between the workpiece W and the first pole shoe 16. If the workpiece W is thin and the magnetic field generated by the first pole shoe 16 (and the second pole shoe 18) is too strong, there is a possibility that multiple workpieces W will be gripped while stacked. The magnetic field sensor 80 detects the strength of the magnetic field generated by the first pole shoe 16, thereby making it possible to detect the attraction of multiple workpieces W. The magnetic field sensor 80 may be provided on the second pole shoe 18, or on both the first pole shoe 16 and the second pole shoe 18. The attachment position of the magnetic field sensor 80 is not limited to the attraction portion 32a, and it may be provided anywhere on the path of the magnetic circuit formed by the first pole shoe 16 and the second pole shoe 18.

[0020] 2 , the magnetic force adjustment unit 20 is disposed between the first pole shoe 16 and the second pole shoe 18. The magnetic force adjustment unit 20 adjusts the magnetic field directed toward the first pole shoe 16 and the second pole shoe 18.

[0021] As shown in Figures 3 and 4, the magnetic force adjustment unit 20 includes a magnet assembly 34, a yoke 36, a first spacer 38, and a second spacer 40. Of these, the magnet assembly 34 is a cylindrical member including a magnet 35 as a magnetic flux source. The magnet assembly 34 has the magnet 35, a pin holder 42, and a magnet holder 44. As shown in Figure 3, the magnet 35 is sandwiched between the pin holder 42 and the magnet holder 44. The pin holder 42 and the magnet holder 44 are connected to the magnet 35 by a bolt 34a. This completes the magnet assembly 34.

[0022] The magnet 35 has a cylindrical shape. The magnet 35 is rotatable around a rotation axis C at its center. Here, a case will be described as an example in which the second direction, which is the extension direction of the rotation axis C, coincides with the front-to-rear direction. However, this embodiment is not limited to this, and the extension direction of the rotation axis C (second direction) may also be the attraction direction.

[0023] The magnet 35 is a permanent magnet and has a pair of magnetic poles by being magnetized in the radial direction. The magnet 35 has the center of its north pole (the part with the highest magnetic flux density) at a predetermined position in the circumferential direction on the outer circumferential surface 35 a, and the center of its south pole at a position 180° away from the north pole in the circumferential direction.

[0024] As shown in Figure 3, the magnet 35 has a front end surface 35b at one end in the second direction and a rear end surface 35c at the other end. The front end surface 35b and the rear end surface 35c are flat surfaces perpendicular to the second direction. A pin holder 42 is attached to the front end surface 35b, and a magnet holder 44 is attached to the rear end surface 35c. The pin holder 42 and the magnet holder 44 are connected to the magnet 35 by bolts 34a that pass through mounting holes 35d that pass through the magnet 35 in the second direction.

[0025] The length of the magnet 35 in the second direction may be increased or decreased as needed depending on the desired attractive force. Increasing the length of the magnet 35 in the second direction increases the magnetic flux emitted by the magnet 35, thereby providing a greater attractive force.

[0026] Furthermore, the shape of the magnet 35 is not limited to a cylindrical shape, and may be, for example, a plate-like shape extending along the rotation axis C. In this case, the plate-like magnet may be magnetized so that magnetic poles appear on the sides.

[0027] The pin holder 42 is a disk-shaped member having an outer diameter smaller than that of the magnet 35, and has a first pin 46 on its outer periphery. The first pin 46 is, for example, a parallel pin, and rotates integrally with the magnet 35. The first pin 46 restricts the rotation range of the magnet 35 by abutting against a second pin 57 (described later), thereby preventing the magnet 35 from rotating more than one full rotation. The pin holder 42 also has, at its center, a shaft protrusion 48 that protrudes short in the second direction coaxially with the rotation axis C. The shaft protrusion 48 is rotatably supported relative to the yoke 36 by a bushing 37 fixed to the yoke 36 (see FIG. 4 ).

[0028] The magnet holder 44 is fixed to the rear end surface 35c of the magnet 35. The magnet holder 44 is a cylindrical member having approximately the same outer diameter as the magnet 35 and is arranged coaxially with the magnet 35. As shown in FIG. 4 , the magnet holder 44 has an axial hole 44a extending along the rotation axis C at the end facing away from the magnet 35. The axial hole 44a accommodates the tip of the rotating shaft 52 of the motor 50 of the rotation mechanism 22. The magnet holder 44 and the rotating shaft 52 are fixed together by a setscrew 44c attached to the magnet holder 44. The setscrew 44c is screwed into a threaded hole 44b that penetrates from the side of the magnet holder 44 toward the axial hole 44a.

[0029] 3, the magnet holder 44 has a wear ring 54 on its outer periphery. The wear ring 54 is made of a material with low friction resistance and low wear, such as fluororesin or polyethylene resin. The wear ring 54 is disposed inside the inner diameter portion 56a of a cylindrical sleeve 56 and rotates while sliding inside the sleeve 56.

[0030] The yoke 36 is formed of a ferromagnetic material, preferably a soft magnetic material. As shown in FIG. 3 , the yoke 36 is C-shaped when viewed in the width direction (first direction) and includes a tip wall 36a, a first wall portion 36b, and a second wall portion 36c. The tip wall 36a extends in a third direction (the attraction direction in the illustrated example) perpendicular to the first and second directions. The tip wall 36a is located outward from a tip surface 35b of the magnet 35. The first wall portion 36b extends from a first end 36d of the tip wall 36a toward the magnet 35 in the front-rear direction (second direction), and the second wall portion 36c extends from a second end 36e of the tip wall 36a toward the magnet 35 in the front-rear direction (second direction).

[0031] As shown in Fig. 4, the first wall portion 36b and the second wall portion 36c sandwich the outer peripheral surface 35a of the magnet 35 from both sides in the third direction. The first wall portion 36b and the second wall portion 36c have a recess 36f, which has a curvature slightly larger than the radius of rotation of the outer peripheral surface 35a of the magnet 35, in a portion facing the magnet 35. The recess 36f is recessed so as not to interfere with the outer peripheral surface 35a of the magnet 35, and allows the magnet 35 to rotate. The magnet 35 may be in sliding contact with the recess 36f, or may not be in contact with the recess 36f.

[0032] 3, the yoke 36 has a second pin 57. The second pin 57 is, for example, a parallel pin, and is attached to the tip wall 36a of the yoke 36. The second pin 57 protrudes toward the magnet assembly 34 and restricts the rotation range of the magnet 35 by abutting against the first pin 46. If the motor 50 is configured as a stepping motor, the magnet angle θ (rotational position) at which the first pin 46 and the second pin 57 abut can be used to initialize the motor 50.

[0033] The first spacer 38 and the second spacer 40 are made of a non-magnetic material. In one embodiment, the non-magnetic material includes a paramagnetic material and a diamagnetic material. When viewed in the width direction, the first spacer 38 and the second spacer 40 have substantially the same C-shape as the yoke 36. The thickness (dimension in the first direction) of the first spacer 38 and the thickness (dimension in the first direction) of the second spacer 40 are the same and can be thinner than the thickness of the yoke 36. The first spacer 38 is disposed between the yoke 36 and the first pole shoe 16, and the second spacer 40 is disposed between the yoke 36 and the second pole shoe 18. As shown in FIG. 3 , the first spacer 38 and the second spacer 40 are fixed to the yoke 36 by bolts 58.

[0034] The first spacer 38 and the second spacer 40 weaken the magnetic coupling between the yoke 36 and the first pole shoe 16 and the second pole shoe 18, and magnetically separate them. When a workpiece W made of a ferromagnetic material is attracted to the first pole shoe 16 and the second pole shoe 18, the first pole shoe 16 and the second pole shoe 18 are magnetically coupled via the workpiece W. In this case, the yoke 36 is magnetically separated (magnetic coupling is weak) from the first pole shoe 16 or the second pole shoe 18. Therefore, magnetic flux does not easily pass through (short-circuit) the yoke 36, and the yoke 36 does not interfere with the attraction of the workpiece W.

[0035] Furthermore, when the magnetic poles of the magnet 35 face the first wall portion 36b and the second wall portion 36c of the yoke 36, most of the magnetic flux of the magnet 35 flows in a magnetic circuit that passes through the yoke 36. On the other hand, since the yoke 36 is magnetically separated, leakage of the magnetic field to the first pole shoe 16 and the second pole shoe 18 is prevented.

[0036] Furthermore, the first spacer 38 and the second spacer 40 seal the gap between the yoke 36 and the first pole shoe 16 and the second pole shoe 18, thereby preventing dust from entering the inside of the magnetic force adjustment unit 20. Note that the first spacer 38 and the second spacer 40 are not necessarily required as means for weakening the magnetic coupling between the yoke 36 and the first pole shoe 16 and the second pole shoe 18. In an embodiment, a gap may be provided instead of the first spacer 38 and the second spacer 40.

[0037] 3, the first wall portion 36b and the second wall portion 36c of the yoke 36 are fastened to the frame member 24 by bolts 60. The first pole shoe 16 and the second pole shoe 18 are fixed to the frame member 24 together with the yoke 36.

[0038] The frame member 24 has a partition wall 62, a first arm 64, and a second arm 66. The partition wall 62 is disposed between the first pole shoe 16, the second pole shoe 18, and the rotation mechanism 22. The partition wall 62 is formed in a plate shape perpendicular to the second direction, and its front surface 62a abuts against the rear portions 30a of the bases 30 of the first pole shoe 16 and the second pole shoe 18. The rotation mechanism 22 is fastened to the rear surface 62b of the partition wall 62. The partition wall 62 has a through hole 62c at its center that penetrates in the second direction. The through hole 62c is formed in a circular shape that is concentric with the rotation axis C of the magnet 35. A sleeve 56 is fitted into the through hole 62c.

[0039] As shown in Figure 3, the first arm 64 and the second arm 66 protrude in the second direction from the front surface 62a of the partition wall 62. The first arm 64 abuts against the end of the first pole shoe 16 in the attraction direction. A bolt 68 is attached to the first arm 64. The first arm 64 and the first pole shoe 16 are fastened together by the bolt 68. The second arm 66 abuts against the end of the second pole shoe 18 in the attraction direction. The second arm 66 and the second pole shoe 18 are fastened together by a bolt 70.

[0040] 5 , the yoke 36, the first spacer 38, and the second spacer 40 are disposed between the first arm 64 and the second arm 66. The yoke 36, the first spacer 38, the second spacer 40, the first pole shoe 16, the second pole shoe 18, and the frame member 24 form a housing chamber 72 that houses the magnet assembly 34. The rear of the housing chamber 72 is closed by the rotation mechanism 22.

[0041] 3, a plate-shaped fixing plate 74 may be attached to the frame member 24 as needed. The fixing plate 74 is used to attach an angle or the like that connects the industrial robot 10 and the magnetic gripper 14.

[0042] As shown in FIG. 4, the rotation mechanism 22 has a motor 50 and a housing 76. Various types of motors can be used for the motor 50, but a stepping motor, which can precisely adjust the magnet angle, is preferably used. The motor 50 has a rotating shaft 52 and rotates the magnet 35 via the rotating shaft 52. As shown in FIG. 3, the motor 50 is fixed to the rear surface 62b of the frame member 24 via a ring spacer 78.

[0043] 4, the housing 76 is a box-shaped member that protects the motor 50 by covering the periphery of the motor 50. In the above description, an example in which the motor 50 is used in the rotation mechanism 22 has been described, but this embodiment is not limited to this. In some embodiments, the rotation mechanism 22 may be configured by combining an air cylinder with various mechanisms (e.g., a cam mechanism or a rack mechanism) that convert the linear motion of the air cylinder into rotational motion.

[0044] The operation of the magnetic gripper 14 of this embodiment will be described below.

[0045] When the workpiece W is not being attracted, the magnet 35 is oriented as shown in Fig. 5. The magnetic pole direction P connecting the center of the north pole and the center of the south pole of the magnet 35 is aligned with the third direction of the yoke 36. The magnet angle θ of the magnet 35 shown in Fig. 5 is 0°. At a magnet angle of 0°, almost all of the magnetic flux of the magnet 35 is concentrated in the yoke 36. Note that the arrangement of the north and south poles at 0° may be reversed from that in the illustrated example.

[0046] The magnetic flux emitted from the north pole of the magnet 35 flows through the first wall portion 36b of the yoke 36 toward the front of the paper in FIG. 5, passes through the tip wall 36a (see FIG. 3), reaches the second wall portion 36c, flows toward the back of the paper in FIG. 5, and returns to the south pole of the magnet 35. In FIG. 5, a circle with a dot in the center represents magnetic flux flowing toward the front of the paper, and a circle with an X represents magnetic flux flowing toward the back of the paper. The yoke 36 is magnetically separated from the first pole shoe 16 by the first spacer 38 and from the second pole shoe 18 by the second spacer 40. Therefore, at a magnet angle of 0°, the magnetic flux of the magnet 35 does not leak to the first pole shoe 16 and the second pole shoe 18. Therefore, the first pole shoe 16 and the second pole shoe 18 do not generate an attractive force.

[0047] 6A, when the magnet 35 is rotated through a magnet angle of -θ, the north pole approaches the second pole shoe 18 and the south pole approaches the first pole shoe 16. As a result, part of the magnetic flux flows through the second pole shoe 18 and the first pole shoe 16, magnetizing the first pole shoe 16 and the second pole shoe 18 and generating a magnetic field in the attraction portion 32a. As a result, an attraction force due to the magnetic field is generated between the first pole shoe 16 and the second pole shoe 18.

[0048] As the absolute value of the magnet angle θ of the magnet 35 increases, the proportion of magnetic flux that flows from the magnetic pole of the magnet 35 toward the first pole shoe 16 and the second pole shoe 18 increases. When the absolute value of the magnet angle θ becomes 90°, almost all of the magnetic flux of the magnet 35 flows to the first pole shoe 16 and the second pole shoe 18, and the largest attractive force is generated in the first pole shoe 16 and the second pole shoe 18.

[0049] As shown in FIG. 8, when the absolute value of the magnet angle θ of the magnet 35 is increased within the range of 0° to 90°, an attractive force according to the absolute value of the magnet angle θ can be generated.

[0050] 7, when the magnet angle θ of the magnet 35 of the magnetic gripper 14 is set to −90° (or +90°), almost all of the magnetic flux generated by the magnet 35 is directed toward the first pole shoe 16 and the second pole shoe 18. In this case, the magnetic gripper 14 exerts the greatest adsorptive force.

[0051] 6B, when the magnet 35 of the magnetic gripper 14 is rotated to a magnet angle of +θ, the north pole approaches the first pole shoe 16 and the south pole approaches the second pole shoe 18. As a result, the attraction portion 32a of the first pole shoe 16 is magnetized to the north pole, and the second pole shoe 18 is magnetized to the south pole. In other words, the orientation of the magnetic poles between the first pole shoe 16 and the second pole shoe 18 is reversed compared to the case of the magnet angle of -θ in FIG. 6A.

[0052] Therefore, demagnetization using the magnetic gripper 14 is performed by moving the magnet 35 back and forth between magnetic angles +θ and -θ while gradually bringing the absolute value of the magnetic angle θ closer to 0°. As a result, the magnetic field between the first pole shoe 16 and the second pole shoe 18 that attract the workpiece W gradually decreases while the direction of the magnetic poles reverses, thereby demagnetizing the workpiece W. In this way, the magnetic gripper 14 of this embodiment can perform demagnetization only by rotating the magnet 35, without using an electromagnetic coil for demagnetization.

[0053] (Modification of the Embodiment) In the present embodiment, the number of magnets 35 serving as the magnetic flux source is not limited to one. As shown in the modification of FIG. 9 , the magnetic flux source may be configured by, for example, connecting a first magnet 35A, a second magnet 35B, and a third magnet 35C in the second direction. Note that FIG. 9 does not illustrate components other than the first magnet 35A, the second magnet 35B, the third magnet 35C, and the second pole shoe 18. In this case, the circumferential positions of the magnetic poles of the first magnet 35A, the second magnet 35B, and the third magnet 35C are aligned with one another, and they rotate integrally. According to this modification, the amount of magnetic flux generated by the magnetic flux source can be increased threefold, thereby increasing the attractive force of the magnetic gripper 14.

[0054] Another modification for increasing the magnetic flux of the magnets 35 is to increase the length of the magnets 35 instead of increasing the number of magnets 35. For example, if it is desired to triple the magnetic flux of the magnets 35 in FIG. 3, the length of the magnets 35 in the second direction is extended by three times. In this case as well, a greater attraction force can be obtained by the magnetic gripper 14.

[0055] In the above description, an example has been given in which a permanent magnet is used as the magnetic flux source, but the magnetic flux source should not be construed as being limited to this, and may be, for example, an electromagnetic coil, a superconductor, or any other means for generating magnetic flux.

[0056] Second Embodiment As shown in Fig. 10, this embodiment relates to a magnetic gripper 14A according to another configuration example. In the configuration of the magnetic gripper 14A, components common to the magnetic gripper 14 in Fig. 2 are denoted by the same reference numerals, and detailed descriptions thereof will be omitted.

[0057] The magnetic gripper 14A has a first pole shoe 16A, a second pole shoe 18A, a magnetic force adjustment unit 20A, a rotation mechanism 22, and a frame member 24A. The first pole shoe 16A and the second pole shoe 18A are attached to one side and the other side of the magnetic force adjustment unit 20A in the first direction, respectively. The first pole shoe 16A and the second pole shoe 18A in this embodiment have the same shape. Therefore, a description of the second pole shoe 18A will be omitted.

[0058] The first pole shoe 16A includes a base 30A and a leg 32. The base 30A is rectangular and extends in the vertical direction. The leg 32 extends from the lower end of the base 30A. An adsorption portion 32a is formed at the lower end of the leg 32. The shapes of the leg 32 and the adsorption portion 32a are similar to those of the leg 32 and the adsorption portion 32a described with reference to FIG. 2.

[0059] The base 30A is fixed to the side of the magnetic force adjustment unit 20A by fastening members such as screws or bolts through the four mounting holes 30c. Unlike the base 30 described with reference to Fig. 2, the base 30A of this embodiment does not have a recess 33 on the connection surface 30b that is attached to the magnetic force adjustment unit 20A. In other words, the connection surface 30b of the base 30A is configured as a flat surface. This first pole shoe 16A does not require processing to form the recess 33 in the base 30A, and this reduces the cost of the first pole shoe 16A, which is a consumable item.

[0060] The magnetic force adjustment unit 20A is attached to the front of the frame member 24A. The top, front, and bottom surfaces of the magnetic force adjustment unit 20A are covered by a casing 82, and both sides are covered by a first pole shoe 16A and a second pole shoe 18A. The casing 82 prevents dust and foreign matter from entering the interior of the magnetic force adjustment unit 20A, preventing malfunction of the magnetic force adjustment unit 20A. The casing 82 is made of a non-magnetic material. The casing 82 is removably fixed to a magnetic circuit member 84 (described later) by bolts 82a.

[0061] 11, the magnetic force adjustment unit 20A has a magnet assembly 34 and a magnetic circuit member 84 inside a casing 82. The magnet assembly 34 has a magnet 35, a pin holder 42, and a magnet holder 44, the configuration of which is as described with reference to FIG.

[0062] The magnetic circuit member 84 is integrally formed from a ferromagnetic material, more preferably a soft magnetic material. The magnetic circuit member 84 includes a first connecting portion 86, a second connecting portion 88, a yoke 90, a first connecting portion 92, and a second connecting portion 94. The first connecting portion 86 is a flat portion located on the left side of the magnetic circuit member 84 in FIG. 11 , the second connecting portion 88 is a flat portion located on the right side, and the yoke 90 is located between the first connecting portion 86 and the second connecting portion 88. The yoke 90 is sandwiched between the first connecting portion 86 and the second connecting portion 88 in the width direction.

[0063] 12 , the first connection portion 86 has a first outer portion 86a exposed on the side and a first inner portion 86b facing the yoke 90. The first outer portion 86a and the first inner portion 86b are formed by planes perpendicular to the first direction. A plurality of bolt holes 86c (four in the illustrated example) for fixing the first pole shoe 16A are formed in predetermined locations of the first outer portion 86a. The first pole shoe 16A abuts against and is fixed to the first outer portion 86a.

[0064] As shown in Fig. 11 , a first protrusion 106 is formed on the rear of the first outer portion 86a. The first protrusion 106 protrudes outward in the width direction from the first outer portion 86a of the first connecting portion 86. The first protrusion 106 extends in the up-down direction. The protrusion height of the first protrusion 106 in the width direction relative to the first outer portion 86a is equal to the thickness of the first pole shoe 16A (the dimension of the base 30A in the width direction). As shown in Fig. 10 , the first pole shoe 16A is attached to the front side of the first protrusion 106.

[0065] 12, a first recess 102 is formed in the first inner portion 86b of the first connecting portion 86 facing the yoke 90 so as not to interfere with the cylindrical magnet 35. The first recess 102 is formed by a curved surface that follows the radius of rotation of the magnet 35 about the rotation axis C.

[0066] 12 , the second connection portion 88 has a second outer portion 88a exposed on the side and a second inner portion 88b facing the yoke 90. The second outer portion 88a and the second inner portion 88b are formed by flat surfaces that are parallel to the front-rear direction and the up-down direction. Although not particularly shown, a plurality of bolt holes (not shown) for fixing the second pole shoe 18A are formed in predetermined locations of the second outer portion 88a. The second pole shoe 18A abuts and is fixed to the second outer portion 88a.

[0067] As shown in Fig. 11, a second protrusion 108 is formed on the rear of the second outer portion 88a. The second protrusion 108 protrudes outward in the width direction from the second outer portion 88a of the second connecting portion 88. The second protrusion 108 extends in the up-and-down direction. The protrusion height of the second protrusion 108 in the width direction relative to the second outer portion 88a is equal to the thickness of the second pole shoe 18A. As shown in Fig. 10, the second pole shoe 18A is attached to the front side of the second protrusion 108.

[0068] 12, a second recess 104 is formed in the second inner portion 88b of the second connecting portion 88 so as not to interfere with the cylindrical magnet 35. The second recess 104 is formed by a curved surface that follows the radius of rotation of the magnet 35 about the rotation axis C.

[0069] A first gap 96 is formed between the yoke 90 and the first connection portion 86. The first gap 96 is a gap formed by cutting out a magnetic material that forms the magnetic circuit member 84, and generates a large magnetic resistance between the yoke 90 and the first connection portion 86.

[0070] A second gap 98 is formed between the yoke 90 and the second connection portion 88. The second gap 98 is a gap formed by cutting out a magnetic material that forms the magnetic circuit member 84, and generates a large magnetic resistance between the yoke 90 and the second connection portion 88. In other words, the yoke 90 is substantially magnetically separated from the first connection portion 86 and the second connection portion 88 by the first gap 96 and the second gap 98.

[0071] 11 , the first coupling portion 92 is formed between the first connecting portion 86 and the yoke 90. The first coupling portion 92 is provided at each of the front end and rear end of the magnetic circuit member 84. The first coupling portion 92 is formed integrally with the first connecting portion 86 and the yoke 90, and couples the first connecting portion 86 and the yoke 90 together. The first coupling portion 92 maintains the spacing of the first gap portion 96 at a constant value. The first coupling portion 92 has a surface that is curvedly cut out so that the cross-sectional area is narrowed at the center in the width direction to prevent a decrease in magnetic reluctance.

[0072] The second coupling portion 94 is formed between the second connecting portion 88 and the yoke 90. The second coupling portion 94 is provided at each of the front end and rear end of the magnetic circuit member 84. The second coupling portion 94 is formed integrally with the second connecting portion 88 and the yoke 90, and couples the second connecting portion 88 and the yoke 90 to each other. The second coupling portion 94 maintains the spacing of the second gap portion 98 at a constant value. The second coupling portion 94 has a surface that is curvedly cut out so that the cross-sectional area is narrower at the center in the width direction to prevent a decrease in magnetic reluctance.

[0073] As shown in FIG. 13 , the yoke 90 has a C-shaped cross section when viewed in the width direction (first direction) and includes a tip wall 90a, a first wall portion 90b, and a second wall portion 90c. The tip wall 90a extends in the third direction (the attraction direction in the illustrated example). The tip wall 90a is located outward from the tip surface 35b of the magnet 35. The first wall portion 90b extends from the upper end of the tip wall 90a in the front-rear direction toward the frame member 24A and covers the upper part of the magnet 35. The second wall portion 90c extends from the lower end of the tip wall 90a in the front-rear direction toward the frame member 24A and covers the lower part of the magnet 35.

[0074] The first wall portion 90b and the second wall portion 90c sandwich the outer peripheral surface 35a of the magnet 35 from both sides in the third direction. The first wall portion 90b and the second wall portion 90c have a curved third recess 90d formed along the radius of rotation of the outer peripheral surface 35a of the magnet 35 in a portion facing the magnet 35. The third recess 90d is recessed so as not to interfere with the outer peripheral surface 35a of the magnet 35 and allows rotation of the magnet 35. The third recess 90d may be in sliding contact with the magnet 35 or may not be in contact with the magnet 35.

[0075] The yoke 90 has a second pin 57. The second pin 57 is, for example, a parallel pin that protrudes rearward from a tip wall 90a of the yoke 90. The second pin 57 abuts against the first pin 46, thereby restricting the rotation range of the magnet 35. If the motor 50 is configured as a stepping motor, the magnet angle θ (rotational position) at which the first pin 46 and the second pin 57 abut can be used to initialize the motor 50.

[0076] 12 and 13, a cylindrical housing space 100 is formed inside the magnetic circuit member 84, and is defined by a first recess 102, a second recess 104, and a third recess 90d. The magnet assembly 34 is rotatably housed in the housing space 100.

[0077] As described above, in the magnetic circuit member 84 of this embodiment, the first connecting portion 86, the second connecting portion 88, and the yoke 90 are integrally connected by the first connecting portion 92 and the second connecting portion 94. Therefore, the magnetic circuit member 84 can be handled as a single component, reducing the number of components and eliminating the need for an assembly process, which is ideal for suppressing manufacturing costs.

[0078] As shown in Figures 11 and 13, the frame member 24A is disposed between the rotation mechanism 22 and the magnetic force adjustment unit 20A. The frame member 24A has a partition wall 62. The partition wall 62 is formed in a plate shape perpendicular to the second direction, and its front surface 62a abuts against the magnetic circuit member 84. The rotation mechanism 22 is fastened to the rear surface 62b of the partition wall 62. The partition wall 62 has a through-hole 62c at its center that penetrates in the second direction. The through-hole 62c is formed in a circular shape that is concentric with the rotation axis C of the magnet 35. A sleeve 56 is attached to the through-hole 62c. The through-hole 62c accommodates the magnet holder 44 of the magnet assembly 34 and the rotation block 110 of the rotation mechanism 22 and guides their rotational motion.

[0079] A plurality of screw holes are formed in the upper part of the frame member 24A for connection to the robot arm 12 (FIG. 1) of the industrial robot 10. The magnetic gripper 14A is attached to the robot arm 12 via the frame member 24A.

[0080] The rotation block 110 is a cylindrical member attached to the rotation shaft 52 of the motor 50, and is connected to the magnet holder 44 of the magnet assembly 34. The rotation block 110 transmits the rotational force of the motor 50 to the magnet assembly 34.

[0081] The magnetic gripper 14A of this embodiment is configured as described above and operates as described below.

[0082] 12, in the non-attached state, the magnet 35 of the magnetic gripper 14A is arranged so that the center of its pair of magnetic poles faces the yoke 90. Magnetic field lines emitted from one magnetic pole of the magnet 35 are collected by the yoke 90 and flow to the other magnetic pole through the inside of the yoke 90, which has low magnetic resistance. Furthermore, magnetic field lines emitted to the outside of the yoke 90 short-circuit and flow inside the first connecting portion 86 or the second connecting portion 88. Therefore, the magnetic field lines of the magnet 35 flow only inside the magnetic circuit member 84, and no magnetic field lines are emitted from the first pole shoe 16A or the second pole shoe 18A, so that the workpiece W is not attracted.

[0083] The magnetic gripper 14A is placed in an attractive state by rotating the magnet 35 by 90° relative to the position of the magnet 35 in FIG. 12 . In the attractive state, the center line of the magnetic pole of the magnet 35 faces a first direction, and magnetic field lines emitted from one magnetic pole of the magnet 35 flow to the first pole shoe 16A through the first connection portion 86. The magnetic field lines are emitted from the attraction portion 32a of the first pole shoe 16A, flow through the workpiece W, and flow into the second pole shoe 18A. The magnetic field lines that flow into the second pole shoe 18A are returned to the other magnetic pole of the magnet 35 through the second connection portion 88. At this time, because the yoke 90 is magnetically separated from the first connection portion 86 and the second connection portion 88 via the first gap portion 96 and the second gap portion 98, most of the magnetic field lines flow to the workpiece W without short-circuiting the yoke 90. Therefore, the magnetic gripper 14A can attract the workpiece W with a strong attraction force.

[0084] The magnetic gripper 14A can be put into a non-attached state by returning the position of the magnet 35 to the position shown in Fig. 12. As with the magnetic gripper 14, the magnetization of the workpiece W that has been magnetized by attraction can be demagnetized by rotating the magnet 35 so that it oscillates around the position shown in Fig. 12 to a magnet angle of +θ (Fig. 6B) and a magnet angle of -θ (Fig. 6A) while gradually decreasing the oscillation angle range.

[0085] As described above, the magnetic gripper 14A of this embodiment can demagnetize the workpiece W simply by rotating the magnet 35, without the need for a demagnetizing electromagnetic coil, thereby simplifying the device configuration. Also, by integrating the magnetic circuit member 84, the magnetic gripper 14A can reduce the number of parts and assembly man-hours, allowing it to be manufactured at low cost. Furthermore, there is no need to form recesses 33 in the first pole shoe 16A and the second pole shoe 18A, which are consumables, and pole shoes designed and manufactured for other magnetic grippers can be reused, which is also effective in reducing running costs.

[0086] While the magnetic circuit member 84 is shown as being integrally formed from a magnetic material, the present embodiment is not limited to this, and the first connecting portion 86, the second connecting portion 88, and the yoke 90 may be formed from separate magnetic materials as shown in Fig. 14. In this case, the magnetic circuit member 84 may be formed by connecting the first connecting portion 86, the second connecting portion 88, and the yoke 90 together using a first gap member 114 and a second gap member 116 formed from a non-magnetic material that is C-shaped when viewed from the first direction.

[0087] In relation to the above disclosure, the following notes are further disclosed.

[0088] (Supplementary Note 1) One aspect of the disclosure is a magnetic gripper (14) comprising: a pair of pole shoes (16, 18) arranged spaced apart in a first direction, each having an attraction portion (32 a) to which a workpiece (W) is attracted; a magnetic flux source arranged between the pair of pole shoes and having a pair of magnetic poles that can be oriented in the first direction; a rotation mechanism (22) that rotates the magnetic flux source around a rotation axis (C) in a second direction perpendicular to the first direction; and a yoke (36, 90) arranged between the pair of pole shoes and collecting magnetic flux that is not directed toward the pole shoes, wherein the yoke is magnetically separated from the pair of pole shoes.

[0089] The above-mentioned magnetic gripper can generate a magnetic field between a pair of pole shoes according to the angle of the magnetic flux source by rotating the magnetic flux source (a magnet, for example). Furthermore, depending on the angle of the magnetic flux source, the magnetic poles can be reversed between the pair of pole shoes. Therefore, the above-mentioned magnetic gripper can demagnetize a workpiece simply by rotating the magnetic flux source without providing an electromagnetic coil for demagnetization, thereby simplifying the device configuration.

[0090] (Supplementary Note 2) In the magnetic gripper described in Supplementary Note 1, the yoke may have a tip wall (36 a) covering an outer side of a tip of the magnetic flux source in the second direction, a first wall portion (36 b) extending in the second direction from a first end (36 d) of the tip wall to cover an outer peripheral surface (35 a) of the magnetic flux source, and a second wall portion (36 c) extending in the second direction from a second end (36 e) of the tip wall to cover the outer peripheral surface of the magnetic flux source. When not performing attraction, this magnetic gripper can prevent leakage of a magnetic field by absorbing magnetic flux from the magnetic flux source (magnet) with the first wall portion and the second wall portion, thereby preventing attraction of foreign matter.

[0091] (Supplementary Note 3) The magnetic gripper according to Supplementary Note 1 or 2 may further include a pair of spacers (38, 40) made of non-magnetic materials sandwiching the yoke from the first direction, and the yoke may be connected to the pair of pole shoes via the pair of spacers. This magnetic gripper can achieve magnetic separation by weakening the magnetic coupling between the yoke and the pair of pole shoes using the spacers. Furthermore, the spacers can fill the gap between the yoke and the pole shoes to prevent dust from entering the rotating part of the magnetic flux source.

[0092] (Supplementary Note 4) In the magnetic gripper described in Supplementary Note 2, the yoke may have recesses (36f) curved along a radius of rotation of the magnetic flux source in the first wall portion and the second wall portion. This magnetic gripper allows the magnetic poles of the magnetic flux source to be disposed close to the yoke, thereby more effectively preventing leakage of the magnetic field.

[0093] (Supplementary Note 5) The magnetic gripper according to any one of Supplementary Notes 1 to 4 may further include a frame member (24) that connects the pair of pole shoes, the yoke, and the rotation mechanism. By connecting each component with the frame member, this magnetic gripper has excellent strength.

[0094] (Supplementary Note 6) The magnetic gripper described in Supplementary Note 5 may further include a first pin (46) that rotates integrally with the magnetic flux source, and a second pin (57) that is fixed to the pole shoe, the yoke, or the frame member and abuts against the first pin to restrict the rotation range of the magnetic flux source. By restricting the rotation range of the magnetic flux source, this magnetic gripper can improve operational reliability. Furthermore, the magnetic gripper can prevent angular misalignment by initializing the motor using the abutment position of the first pin and the second pin as a reference position.

[0095] (Supplementary Note 7) In the magnetic gripper according to any one of Supplementary Notes 1 to 6, the magnetic flux source may be formed in a circular shape when viewed from the second direction and may be magnetized in a radial direction perpendicular to the second direction. This magnetic gripper facilitates magnetic force adjustment according to the angle of the magnetic flux source due to the magnetic flux distribution in the circumferential direction, and can more reliably perform demagnetization operations.

[0096] (Supplementary Note 8) In the magnetic gripper according to any one of Supplementary Notes 1 to 7, the magnetic flux source may include a plurality of magnets coupled in the second direction and rotating together. This magnetic gripper can increase its attractive force.

[0097] (Supplementary Note 9) In the magnetic gripper according to any one of Supplements 1 to 8, the pair of pole shoes may include a first pole shoe (16A) and a second pole shoe (18A) facing the first pole shoe, a first connection portion (86) disposed between the magnetic flux source and the first pole shoe for transmitting the magnetic flux of the magnetic flux source to the first pole shoe, and a second connection portion (88) disposed between the magnetic flux source and the second pole shoe for transmitting the magnetic flux of the magnetic flux source to the second pole shoe, and the yoke may be disposed between the first connection portion and the second connection portion and magnetically separated from the first connection portion and the second connection portion via a first gap portion (96) and a second gap portion (98). This magnetic gripper does not require recesses in the first pole shoe and the second pole shoe to avoid interference with the rotational movement of the magnetic flux source, thereby reducing the cost of the first pole shoe and the second pole shoe, which are consumables.

[0098] (Supplementary Note 10) The magnetic gripper according to Supplementary Note 9 may include a magnetic circuit member (84) in which the first connection portion, the second connection portion, and the yoke are integrally connected via connecting portions (92, 94). This magnetic gripper can reduce the number of parts and the number of assembly steps.

[0099] (Supplementary Note 11) Another aspect is a magnetic gripper comprising: a pair of pole shoes each having an attraction portion to which a workpiece is attracted and arranged spaced apart in a first direction, a magnetic flux source arranged between the pair of pole shoes and having a pair of magnetic poles oriented in the first direction, a rotation mechanism that rotates the magnetic flux source about a rotation axis extending in a second direction perpendicular to the first direction, and a magnetic field sensor (80) that detects the magnetic field of the pole shoe. This magnetic gripper can detect the attraction of multiple stacked workpieces based on the magnetic field detected by the magnetic field sensor.

[0100] (Supplementary Note 12) Another aspect of the disclosure is an industrial robot (10) including the magnetic gripper according to any one of Supplementary Notes 1 to 11 and a robot arm (12) to which the magnetic gripper is attached. This industrial robot can attract and demagnetize a workpiece simply by rotating the magnetic flux source of the magnetic gripper, thereby simplifying the structure and reducing power consumption.

[0101] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention.

Claims

1. A magnetic gripper (14) comprising: a pair of pole shoes (16, 18) arranged at a distance in a first direction, each having an attraction portion (32a) to which a workpiece (W) is attracted; a magnetic flux source arranged between the pair of pole shoes and having a pair of magnetic poles that can be oriented in the first direction; a rotation mechanism (22) that rotates the magnetic flux source around a rotation axis (C) in a second direction perpendicular to the first direction; and a yoke (36, 90) arranged between the pair of pole shoes and collecting magnetic flux that is not directed toward the pole shoes, wherein the yoke is magnetically separated from the pair of pole shoes.

2. A magnetic gripper as described in claim 1, wherein the yoke has a tip wall (36a) covering the outside of the tip of the magnetic flux source in the second direction, a first wall portion (36b) extending in the second direction from a first end (36d) of the tip wall and covering an outer circumferential surface (35a) of the magnetic flux source, and a second wall portion (36c) extending in the second direction from a second end (36e) of the tip wall and covering the outer circumferential surface of the magnetic flux source.

3. A magnetic gripper as set forth in claim 1, further comprising a pair of spacers (38, 40) made of a non-magnetic material sandwiching the yoke from the first direction, the yoke being connected to the pair of pole shoes via the pair of spacers.

4. A magnetic gripper according to claim 2, wherein said yoke has a recess (36f) curved along a radius of rotation of said magnetic flux source in said first wall portion and said second wall portion.

5. A magnetic gripper according to claim 1, further comprising a frame member (24) connecting the pair of pole shoes, the yoke, and the rotation mechanism.

6. A magnetic gripper as described in claim 5, further comprising: a first pin (46) that rotates integrally with said magnetic flux source; and a second pin (57) that is fixed to said pole shoe, said yoke, or said frame member and abuts against said first pin to regulate the rotation range of said magnetic flux source.

7. A magnetic gripper according to claim 1, wherein said magnetic flux source is circular when viewed from said second direction and magnetized in a radial direction perpendicular to said second direction.

8. A magnetic gripper as claimed in claim 1, wherein said magnetic flux source comprises a plurality of magnets coupled in said second direction to rotate together.

9. A magnetic gripper as claimed in claim 1, wherein the pair of pole shoes comprises a first pole shoe (16A) and a second pole shoe (18A) facing the first pole shoe, a first connection portion (86) disposed between the magnetic flux source and the first pole shoe for transmitting the magnetic flux of the magnetic flux source to the first pole shoe, and a second connection portion (88) disposed between the magnetic flux source and the second pole shoe for transmitting the magnetic flux of the magnetic flux source to the second pole shoe, and the yoke is disposed between the first connection portion and the second connection portion, and is magnetically separated from the first connection portion and the second connection portion via a first gap portion (96) and a second gap portion (98).

10. A magnetic gripper according to claim 9, comprising a magnetic circuit member (84) in which the first connection portion, the second connection portion and the yoke are integrally connected via connecting portions (92, 94).

11. A magnetic gripper comprising: a pair of pole shoes arranged spaced apart in a first direction, each having an attraction portion to which a workpiece is attracted; a magnetic flux source arranged between the pair of pole shoes, the magnetic flux source having a pair of magnetic poles that can be oriented in the first direction; a rotation mechanism that rotates the magnetic flux source about a rotation axis that extends in a second direction perpendicular to the first direction; and a magnetic field sensor (80) that detects the magnetic field of the pole shoe.

12. An industrial robot (10) comprising: a magnetic gripper according to any one of claims 1 to 11; and a robot arm (12) to which the magnetic gripper is attached.

Images