Magnetic attraction device

Abstract

This magnetic attraction device (1) comprises: a cylinder tube (7), the bottom surface of which is an attraction surface (3) that attracts a workpiece, and which is provided with a pressure chamber (5) in the interior thereof; a piston (11) that is provided with a permanent magnet (9), the piston (11) moving up and down within the pressure chamber (5); a control unit (13) that, when attracting the workpiece (W), moves the piston (11) to the lower end of the pressure chamber (5) and causes the workpiece (W) to be attracted to the attraction surface (3) by the magnetic force of the permanent magnet (9); and a magnetic sensor (15) that detects the position of the piston (11). The control unit (13) moves the piston (11) upward if the workpiece (W) is not attracted to the attraction surface (3) after the piston (11) is moved to the lower end of the pressure chamber (5), and the control unit (13) determines whether the workpiece (W) is attracted to the attraction surface (3) according to whether the magnetic sensor (15) has detected that the piston (11) has moved upward.

Description

Magnetic Adsorption Device

[0001] The present disclosure relates to a magnetic attraction device.

[0002] Patent Document 1 describes a magnetic chuck that attracts and holds a workpiece using the force of a permanent magnet. In the magnetic chuck of Patent Document 1, the workpiece is attracted to an attracting surface at the bottom end of a cylinder tube when the piston is at bottom dead center. The attracted workpiece is detected by a photoelectric sensor or proximity sensor provided on the side of the cylinder tube.

[0003] JP 2022-41872 A

[0004] However, in the conventional magnetic chuck described above, since the photoelectric sensor is provided on the side of the cylinder tube, if there is a hole in the workpiece where the light directly below the sensor hits, the light is not reflected and it is not possible to detect the presence or absence of the workpiece. Similar problems also occur when the workpiece is smaller than the bottom surface of the cylinder tube or when a proximity sensor is provided instead of the photoelectric sensor.

[0005] One aspect of the present disclosure is a magnetic adsorption device comprising: a cylinder tube whose bottom surface is an adsorption surface for adsorbing a workpiece and which has a pressure chamber inside; a piston equipped with a permanent magnet and which moves up and down within the pressure chamber; a control unit which, when adsorbing the workpiece, moves the piston to the lower end of the pressure chamber and adsorbs the workpiece to the adsorption surface using the magnetic force of the permanent magnet; and a sensor which detects the position of the piston; wherein, after moving the piston to the lower end of the pressure chamber, if the workpiece is not adsorbed to the adsorption surface, the control unit moves the piston upward, and determines whether the workpiece is adsorbed to the adsorption surface based on whether the sensor detects that the piston has moved upward.

[0006] According to a magnetic attraction device according to an aspect of the present disclosure, whether or not a workpiece is attracted to the attraction surface is determined based on whether or not a sensor detects that the piston has moved upward. Therefore, even if the workpiece has a hole or is smaller than the bottom surface of the cylinder tube, the presence or absence of the workpiece can be detected.

[0007] According to one aspect of the present disclosure, the presence or absence of a workpiece can be detected even if the workpiece has a hole or is smaller than the bottom surface of the cylinder tube.

[0008] FIG. 1 is a perspective view showing the structure of a magnetic attraction device according to the first embodiment. FIG. 2 is a cross-sectional view showing the structure of a magnetic attraction device according to the first embodiment. FIG. 3A is a perspective view showing the structure of a carry-out device equipped with a magnetic attraction device according to the first embodiment. FIG. 3B is a plan view showing the structure of the bottom of a carry-out device equipped with a magnetic attraction device according to the first embodiment. FIG. 4 is a flowchart showing the processing procedure for workpiece carry-out processing by a carry-out device equipped with a magnetic attraction device according to the first embodiment. FIG. 5 is a diagram for explaining the operation of a piston descending in the magnetic attraction device according to the first embodiment. FIG. 6 is a diagram for explaining the operation of the magnetic attraction device according to the first embodiment when attracting a workpiece. FIG. 7 is a diagram for explaining the operation of a piston ascending in the magnetic attraction device according to the first embodiment. FIG. 8 is a diagram for explaining the operation of the magnetic attraction device according to the first embodiment when stacking workpieces. FIG. 9 is a cross-sectional view showing the structure of a magnetic attraction device according to a second embodiment.

[0009] First Embodiment Magnetic Adsorption Device A magnetic adsorption device according to this embodiment will now be described with reference to the drawings. FIG. 1 is a perspective view showing the structure of the magnetic adsorption device, and FIG. 2 is a cross-sectional view. As shown in FIGS. 1 and 2 , the magnetic adsorption device 1 according to this embodiment includes a cylinder tube 7 having a pressure chamber 5 therein, a piston 11 equipped with a permanent magnet 9 and moving up and down within the pressure chamber 5, a control unit 13 that, when adsorbing the workpiece W, moves the piston 11 to the lower end of the pressure chamber 5 to attract the workpiece W to the adsorption surface 3 using the magnetic force of the permanent magnet 9, and a magnetic sensor 15 that detects the position of the piston 11. After moving the piston 11 to the lower end of the pressure chamber 5, if the workpiece W is not adsorbed to the adsorption surface 3, the control unit 13 moves the piston 11 upward, and determines whether the workpiece W is adsorbed to the adsorption surface 3 based on whether the magnetic sensor 15 detects that the piston 11 has moved upward.

[0010] The cylinder tube 7 is made of a paramagnetic metal such as an aluminum alloy and has a rectangular parallelepiped shape as shown in Fig. 1. As shown in Fig. 2, the bottom surface of the cylinder tube 7 forms an attraction surface 3 that attracts the workpiece W, and the cylinder tube 7 has a pressure chamber 5 inside. The pressure chamber 5 has a cylindrical shape and is separated into an upper space 17 and a lower space 19 by a piston 11 provided inside.

[0011] An upper air intake / exhaust hole 21 that communicates with the upper space 17 and supplies / exhausts air, and a lower air intake / exhaust hole 23 that communicates with the lower space 19 and supplies / exhausts air, are formed on one side of the cylinder tube 7. The upper air intake / exhaust hole 21 is opened when the piston 11 is raised, and air is supplied to the upper air intake / exhaust hole 21 when the piston 11 is lowered. The lower air intake / exhaust hole 23 is opened when the piston 11 is raised, and air is supplied to the lower air intake / exhaust hole 23 when the piston 11 is lowered.

[0012] Furthermore, two mounting grooves 25 (FIG. 1) are formed on the side surface opposite the side surface on which the upper air intake and exhaust hole 21 and the lower air intake and exhaust hole 23 are formed, and the magnetic sensor 15 is attached to the mounting grooves 25. Since the mounting grooves 25 are formed in the vertical direction, the magnetic sensor 15 can be attached to the side surface of the cylinder tube 7 at any desired position in the vertical direction.

[0013] The piston 11 has a cylindrical shape and is provided with a ferromagnetic core yoke and the like in addition to the permanent magnet 9, and is provided so as to be able to move up and down inside the pressure chamber 5. The piston 11 also has a seal member 27 that contacts the inner surface of the pressure chamber 5, and separates the pressure chamber 5 into an upper space 17 and a lower space 19.

[0014] The magnetic sensor 15 is a sensor that detects the position of the piston 11 by detecting the magnetism of the permanent magnet 9, and when the piston 11 moving inside the cylinder tube 7 approaches and detects the magnetism of the permanent magnet 9, it outputs a detection signal to the control unit 13. As shown in Figure 2, the magnetic sensor 15 is attached to the upper part of the side surface of the cylinder tube 7, so when the piston 11 rises, it detects the magnetism of the permanent magnet 9 and outputs a detection signal to the control unit 13. However, the magnetic sensor 15 does not have to be attached to the upper part of the side surface of the cylinder tube 7, and may be attached to the lower side.

[0015] When attracting the workpiece W, the control unit 13 executes control to move the piston 11 to the lower end of the pressure chamber 5 and attract the workpiece W to the attraction surface 3 by the magnetic force of the permanent magnet 9. After moving the piston 11 to the lower end of the pressure chamber 5, the control unit 13 determines whether the workpiece W is attracted to the attraction surface 3 based on whether the piston 11 moves upward and the magnetic sensor 15 detects the magnetism of the permanent magnet 9.

[0016] Specifically, the control unit 13 supplies air at a pressure P1 from the upper supply and exhaust port 21 to the upper space 17, and then discharges the air from the lower space 19 through the lower supply and exhaust port 23 to move the piston 11 to the lower end of the pressure chamber 5, and then supplies air at a predetermined determination pressure P from the lower supply and exhaust port 23 to the lower space 19, and moves the piston 11 upward when the workpiece W is not adsorbed to the suction surface 3. At this time, the determination pressure P is set to be smaller than the pressure that separates the piston 11 that is adsorbed to the workpiece W from the workpiece W, and larger than the minimum rising pressure that moves the piston 11 that is not adsorbed to the workpiece W upward.

[0017] That is, when the workpiece W is adsorbed, the piston 11 will not move upward even if air at the determination pressure P is supplied, and when the workpiece W is not adsorbed, the piston 11 moves upward by discharging the air in the upper space 17 from the upper air supply / exhaust hole 21 by supplying air at the determination pressure P. Therefore, if the piston 11 does not move upward and the magnetic sensor 15 does not detect the magnetism of the permanent magnet 9, it can be determined that the workpiece W is adsorbed. On the other hand, if the piston 11 moves upward and the magnetic sensor 15 detects the magnetism of the permanent magnet 9, it can be determined that the workpiece W is not adsorbed.

[0018] In this way, after moving the piston 11 to the lower end of the pressure chamber 5, the control unit 13 supplies air at the judgment pressure P and determines that the workpiece W is adsorbed to the suction surface 3 if the piston 11 does not move upward, and determines that the workpiece W is not adsorbed to the suction surface 3 if the piston 11 moves upward.

[0019] The control unit 13 is configured by a computer having a memory, a processor such as a CPU (Central Processing Unit), and various interfaces. The memory and various interfaces are connected to the processor via a bus. The control unit 13 executes control to determine whether or not the workpiece W is adsorbed to the adsorption surface 3 by having the processor execute a program stored in the memory. The control unit 13 also controls a compressor (not shown) and the like to control the pressure of air supplied to the pressure chamber 5.

[0020] [Carry-Out Device] FIG. 3A is a perspective view showing the structure of a carry-out device equipped with a magnetic adsorption device according to this embodiment, and FIG. 3B is a plan view showing the structure of the bottom of the carry-out device. As shown in FIGS. 3A and 3B , the carry-out device 31 includes a carry-out arm 33, a magnetic adsorption device 1, and multiple suction pads 35. The carry-out device 31 can move in the left-right direction X, the front-back direction Y, and the up-down direction Z by operating a drive unit (not shown). Furthermore, the carry-out device 31 can rotate horizontally around a central axis extending in the up-down direction by operating the drive unit. While FIG. 3B shows only one magnetic adsorption device 1, multiple devices may be included. When the workpiece is large or non-magnetic, the suction pads 35 and the magnetic adsorption device 1 are used together to adsorb the workpiece.

[0021] [Workpiece Carry-Out Processing] Next, a description will be given of the workpiece carrying-out processing by the carrying-out device 31 including the magnetic attraction device 1 according to this embodiment. Fig. 4 is a flowchart showing the processing procedure of the workpiece carrying-out processing.

[0022] 4, in step S101, the carry-out device 31 moves to the position of the workpiece W to be carried out and performs positioning. That is, the carry-out device 31 moves to the position of the X and Y coordinates that indicate the position of the workpiece W, and stops at a position directly above the workpiece W.

[0023] In step S103, the carrying-out device 31 descends from a position directly above the workpiece W to a position where the attraction surface 3 of the magnetic attraction device 1 provided on the carrying-out device 31 contacts the workpiece W.

[0024] In step S105, the magnetic attraction device 1 attracts the workpiece W. When the carry-out device 31 is lowered in step S103, the piston 11 is located at the upper end (top dead center) of the pressure chamber 5. Therefore, as shown in FIG. 5 , the control unit 13 supplies air at pressure P1 from the upper air supply and exhaust port 21 to the upper space 17 and exhausts air from the lower space 19 through the lower air supply and exhaust port 23, thereby lowering the piston 11. Pressure P1 is the pressure required to lower the piston 11. When the piston 11 moves to the lower end (bottom dead center) of the pressure chamber 5, the workpiece W is attracted to the attraction surface 3 by the magnetic force of the permanent magnet 9.

[0025] In step S107, the carrying-out device 31 slightly rises to check whether the workpiece W is being attracted to the attraction surface 3. For example, the carrying-out device 31 rises by 30 mm.

[0026] In step S109, the control unit 13 supplies air at a determination pressure P, which is in a slightly rising state and is used to determine whether or not the workpiece W is adsorbed to the adsorption surface 3, from the lower supply and exhaust port 23 to the lower space 19 as shown in FIG. 6. The determination pressure P is set to be smaller than the pressure that separates the piston 11 that is adsorbed to the workpiece W from the workpiece W, and larger than the minimum rising pressure that moves the piston 11 upward when the workpiece W is not adsorbed. In other words, the determination pressure P is a pressure at which the piston 11 does not move if the workpiece W is adsorbed, and moves upward if the workpiece W is not adsorbed. This determination pressure P is set taking into consideration the magnetic force of the permanent magnet 9, the weight of the piston 11 and the permanent magnet 9, the sliding resistance when the piston 11 moves, and the like.

[0027] In step S111, the control unit 13 waits for a short time, for example, 0.4 seconds, and monitors the movement of the piston 11 caused by the supply of air at the determination pressure P.

[0028] In step S113, the control unit 13 determines whether the piston 11 has risen, and if the piston 11 has risen, the process proceeds to step S115, and if the piston 11 has not risen, the process proceeds to step S121. When the workpiece W is not attracted, the piston 11 rises due to air at the determination pressure P as shown in FIG. 7, so the magnetic sensor 15 detects the magnetic force of the permanent magnet 9 provided on the risen piston 11 and outputs a detection signal. Therefore, if the control unit 13 receives a detection signal from the magnetic sensor 15 after the short time period of step S111 has elapsed, the control unit 13 determines that the piston 11 has risen. On the other hand, if the control unit 13 does not receive a detection signal from the magnetic sensor 15 after the short time period of step S111 has elapsed, the control unit 13 determines that the piston 11 has not risen.

[0029] In step S115, the carry-out device 31 rises to reattach the workpiece W since the workpiece W is not being adsorbed.

[0030] In step S117, the control unit 13 determines whether the number of retries due to failure to adsorb the workpiece W is the fourth, which is the predetermined number. If the number of retries is not the fourth, that is, if it is the third or less, the process returns to step S101 to retry adsorption of the workpiece W, and if it is the fourth retries, the process proceeds to step S119. Note that the number of retries does not have to be four, and may be any number other than four.

[0031] In step S119, since the control unit 13 has not been able to adsorb the workpiece W even after three retry attempts, it issues an alarm and terminates the workpiece carrying-out process according to this embodiment.

[0032] In step S121, the carrying-out device 31, which has adsorbed the workpiece W, transports the adsorbed workpiece W and moves it to the accumulation position.

[0033] In step S123, the control unit 13 determines whether or not the piston 11 has risen during the transport of the workpiece W, and monitors the state of the piston 11 even during the transport of the workpiece W. If the piston 11 has risen, the process proceeds to step S125, and if the piston 11 has not risen, the process proceeds to step S127.

[0034] In step S125, the control unit 13 determines that the workpiece W has come off during transport, generates an alarm, and ends the workpiece carrying-out process according to this embodiment.

[0035] In step S127, the control unit 13 accumulates the workpieces W at the accumulation position to which the workpieces W have been moved. Specifically, as shown in Fig. 8, the control unit 13 supplies air at a pressure P2 from the lower air supply and exhaust hole 23 to the lower space 19 in order to separate the piston 11, which is adsorbed to the workpieces W, from the workpieces W, and exhausts air from the upper space 17 through the upper air supply and exhaust hole 21. This causes the piston 11 to rise, and the workpieces W are released from the adsorption surface 3 and accumulated.

[0036] In step S129, the control unit 13 waits for a short time, for example, 0.2 seconds, to confirm that the workpiece W has been reliably released. However, the short time of 0.2 seconds may be changed.

[0037] In step S131, when the accumulation of the workpieces W is completed, the carrying-out device 31 rises and ends the workpiece carrying-out process according to this embodiment.

[0038] Effect of First Embodiment As described above in detail, the magnetic attraction device 1 according to this embodiment moves the piston 11 upward when the workpiece W is not attracted to the attraction surface 3 after moving the piston 11 to the lower end of the pressure chamber 5, and determines whether the workpiece W is attracted to the attraction surface 3 based on whether the magnetic sensor 15 detects that the piston 11 has moved upward. This makes it possible to detect the presence or absence of the workpiece W even when the workpiece W has a hole or is smaller than the bottom surface of the cylinder tube.

[0039] Furthermore, the magnetic attraction device 1 according to this embodiment supplies air at a predetermined determination pressure P to the lower space 19 after moving the piston 11 to the lower end of the pressure chamber 5, and moves the piston 11 upward if the workpiece W is not adsorbed to the attraction surface 3. The determination pressure P is set to be smaller than the pressure that separates the piston 11 that is adsorbed to the workpiece W from the workpiece W, and larger than the minimum rising pressure that moves the piston 11 upward if the workpiece W is not adsorbed to the workpiece W. As a result, if the workpiece W is adsorbed, the piston 11 does not move, and if the workpiece W is not adsorbed, the piston 11 moves upward. Therefore, by supplying air at the determination pressure P, it is possible to determine whether the workpiece W is adsorbed.

[0040] Furthermore, the magnetic attraction device 1 according to this embodiment determines that the workpiece W is attracted to the attraction surface 3 if the piston 11 does not move upward after moving the piston 11 to the lower end of the pressure chamber 5, and determines that the workpiece W is not attracted to the attraction surface 3 if the piston 11 moves upward. This makes it possible to determine whether or not the workpiece W is attracted based on the movement of the piston 11, so that the presence or absence of the workpiece W can be detected even if the workpiece W has a hole or is smaller than the bottom surface of the cylinder tube.

[0041] The carrying-out device 31 is also equipped with the magnetic attraction device 1 according to this embodiment. As a result, the carrying-out device 31 is equipped with the magnetic attraction device 1 that can accurately detect the presence or absence of the workpiece W, and therefore can reliably carry out the carrying-out of the workpiece W.

[0042] Second Embodiment A second embodiment of the present invention will now be described with reference to the drawings. In the drawings, identical parts are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 9 , a magnetic attraction device 50 according to this embodiment differs from the first embodiment in that it further includes an elastic member 52. The elastic member 52 is formed of a spring having an elastic force that moves the piston 11 upward when the workpiece W is not attached to it. The elastic force is set to be smaller than the force that separates the piston 11 that is attached to the workpiece W from the workpiece W. In other words, when the workpiece W is attached to it, the piston 11 does not move, and when the workpiece W is not attached to it, the piston 11 moves upward due to the elastic force of the elastic member 52. When the piston 11 moves upward, the piston 11 is detected by the magnetic sensor 15, as in the first embodiment.

[0043] In the magnetic attraction device 50 according to this embodiment, when attracting the workpiece W in step S105 of FIG. 4 , air at pressure P1 is supplied from the upper air supply / exhaust port 21 and exhausted from the lower air supply / exhaust port 23, as in the first embodiment, to lower the piston 11. Subsequently, in step S109 in the first embodiment, air at the determination pressure P is supplied, but in this embodiment, since the elastic member 52 is provided, it is not necessary to supply air at the determination pressure P. That is, in this embodiment, when the control unit 13 stops the supply of air at pressure P1, the piston 11 moves upward due to the elastic force of the elastic member 52 unless the workpiece W is attracted to the attraction surface 3. Therefore, in the magnetic attraction device 50 according to this embodiment, the workpiece carrying-out process can be executed by deleting step S109 of FIG.

[0044] Effect of Second Embodiment As described above in detail, the magnetic attraction device 50 according to this embodiment further includes an elastic member 52 having an elastic force that moves the piston 11 upward when the workpiece W is not attached to it. The elastic force is set to be smaller than the force that separates the piston 11, which is attached to the workpiece W, from the workpiece W. After the control unit 13 moves the piston 11 to the lower end of the pressure chamber 5, if the workpiece W is not attached to the attraction surface 3, the elastic member 52 moves the piston 11 upward by its elastic force. As a result, if the workpiece W is attached to it, the piston 11 does not move, and if the workpiece W is not attached to it, the piston 11 moves upward. Therefore, it is possible to determine whether the workpiece W is attached or not by the movement of the piston 11 caused by the elastic member 52.

[0045] Although the embodiments of the present disclosure have been described above, the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

[0046] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2023-105856, filed on June 28, 2023, the entire disclosure of which is incorporated herein by reference.

Claims

1. A magnetic adhesion device comprising: a cylinder tube whose bottom surface is an adhesion surface for adsorbing a workpiece and which has an internal pressure chamber; a piston equipped with a permanent magnet and which moves up and down within the pressure chamber; a control unit which, when adsorbing the workpiece, moves the piston to the lower end of the pressure chamber to adsorb the workpiece to the adhesion surface by the magnetic force of the permanent magnet; and a sensor which detects the position of the piston; wherein after the piston has been moved to the lower end of the pressure chamber, if the workpiece is not adsorbed to the adhesion surface, the control unit moves the piston upward and determines whether or not the workpiece is adsorbed to the adhesion surface depending on whether or not the sensor detects that the piston has moved upward.

2. The magnetic adsorption device according to claim 1, wherein the piston separates the pressure chamber into an upper space and a lower space, and the control unit moves the piston to the lower end of the pressure chamber and then supplies air of a predetermined determination pressure to the lower space, and moves the piston upward when the workpiece is not adsorbed to the adsorption surface, and the determination pressure is set to be smaller than the pressure that separates the piston adsorbed to the workpiece from the workpiece and larger than a minimum rising pressure that moves the piston not adsorbed to the workpiece upward.

3. A magnetic adsorption device as described in claim 1, further comprising an elastic member having an elastic force that moves the piston, which is not adsorbed to the workpiece, upward, wherein the elastic force is set to be smaller than a force that pulls the piston, which is adsorbed to the workpiece, away from the workpiece, and when the workpiece is not adsorbed to the adsorption surface after the control unit has moved the piston to the lower end of the pressure chamber, the elastic member moves the piston upward by the elastic force.

4. The magnetic adsorption device according to any one of claims 1 to 3, wherein the control unit determines that the workpiece is adsorbed to the adsorption surface if the piston does not move upward after moving the piston to the lower end of the pressure chamber, and determines that the workpiece is not adsorbed to the adsorption surface if the piston moves upward.

5. A discharge device equipped with a magnetic adsorption device according to any one of claims 1 to 3.

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