Magnetic attraction device and conveying device

Abstract

To provide a magnetic attraction device capable of reliably determining attraction of a workpiece without any additional equipment such as a pressure reducing device. [Solution] The magnetic attraction device 100 of the present invention is a magnetic attraction device 100 in which a piston 50 equipped with a permanent magnet 70 is arranged axially movably inside a single-rod cylinder 10 having a head-side cylinder chamber H and a rod-side cylinder chamber L, and an attraction surface 11 that attracts a workpiece W by the magnetic force of the permanent magnet 70 of the piston 50 is formed adjacent to the axial end of the head-side cylinder chamber H, and is characterized in that a switching valve V is arranged to supply and discharge fluid pressure from a common pressure source (air tank T) to the head-side cylinder chamber H and the rod-side cylinder chamber L, and a detection means (magnetic sensor 15) can detect whether the piston 50 has moved in a direction away from the attraction surface 11 while fluid pressure is introduced from the pressure source into the head-side cylinder chamber H and the rod-side cylinder chamber L by the switching valve V.

Description

[Technical Field]

[0001] The present invention relates to a magnetic attraction device and a transport device having the magnetic attraction device at the tip of a transport arm. [Background technology]

[0002] As described in Patent Document 1 (Japanese Patent No. 7603109), a magnetic attraction device is known in which a piston equipped with a permanent magnet is disposed inside a cylinder. By supplying air to the upper space of the cylinder and moving the piston downward, a workpiece is magnetically attracted to the attraction surface at the bottom end of the cylinder. In addition, by supplying air to the lower space of the cylinder and moving the piston upward, the workpiece that was attracted to the attraction surface is released.

[0003] Whether or not a workpiece is adsorbed to the adsorption surface is determined by introducing a judgment pressure into the lower space of the cylinder. This judgment pressure is set to be smaller than the pressure that separates the piston that is adsorbed to the workpiece from the workpiece, and larger than the minimum rising pressure that moves the piston that is not adsorbed to the workpiece upward. When the piston moves upward due to the introduction of the judgment pressure, it is determined that a workpiece is not adsorbed to the adsorption surface.

[0004] Conversely, if the piston does not move upward, it is determined that the workpiece is adsorbed to the adsorption surface. The position of the piston (whether the piston has moved upward or not) is detected by a sensor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7603109 Summary of the Invention [Problem to be solved by the invention]

[0006] The magnetic attraction device of Patent Document 1 needs to generate a pressure that forcibly moves the piston up and down, as well as a judgment pressure that is smaller than this pressure. Generating the judgment pressure requires special auxiliary equipment, such as a pressure reducing device, which increases the complexity and cost of the structure. Furthermore, if there is a problem with the pressure reducing device, it may erroneously judge whether the workpiece is attracted. [Means for solving the problem]

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a magnetic attraction device that can reliably determine whether a workpiece has been attracted to a magnetic attraction device without the need for ancillary equipment such as a pressure reducing device.

[0008] In order to solve the above problems, the magnetic attraction device of the present invention is a magnetic attraction device in which a piston equipped with a permanent magnet is arranged axially movably inside a single-rod cylinder having a head-side cylinder chamber and a rod-side cylinder chamber, and an attraction surface that attracts a workpiece by the magnetic force of the permanent magnet of the piston is formed adjacent to the axial end of the head-side cylinder chamber, and is characterized in that a switching valve is arranged to supply and discharge fluid pressure from a common pressure source to the head-side cylinder chamber and the rod-side cylinder chamber, and detection means can detect whether the piston has moved in a direction away from the attraction surface while fluid pressure from the pressure source is introduced into the head-side cylinder chamber and the rod-side cylinder chamber by the switching valve. [Effects of the Invention]

[0009] According to the present invention, it is possible to reliably determine whether a workpiece has been adsorbed without using any additional equipment such as a pressure reducing device. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing the appearance of a magnetic adsorption device according to an embodiment of the present invention; [Figure 2] 1 is a vertical cross-sectional view showing an internal structure of a magnetic adsorption device according to an embodiment of the present invention. [Figure 3] 1 is a perspective view of a tip end of a transport arm of a transport device equipped with a magnetic adsorption device according to an embodiment of the present invention. [Figure 4] 10 is a flowchart showing a workpiece transport process by the transport device. [Figure 5] 10 is a vertical cross-sectional view of the magnetic adsorption device illustrating the downward movement of the piston when the switching valve is in the second position. FIG. [Figure 6] 10 is a vertical cross-sectional view of the magnetic attraction device for explaining the workpiece attraction confirmation operation. FIG. [Figure 7] 4 is a vertical cross-sectional view of the magnetic attraction device illustrating the upward movement of the piston when the switching valve is in the first position. FIG. [Figure 8] 10 is a vertical cross-sectional view of the magnetic attraction device illustrating the upward movement of the piston (workpiece detachment movement) when the switching valve is in the third position. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a magnetic attraction device and a conveyance device according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing the appearance of a magnetic attraction device 100. Fig. 2 is a vertical cross-sectional view showing the internal structure of the magnetic attraction device 100.

[0012] 3 is a perspective view of the tip of a transfer arm of a transfer device 200 equipped with a magnetic adsorption device 100 at the tip of the transfer arm 220. The tip of a robot arm is connected to a mounting hole 210 formed at the base end of the transfer arm 220.

[0013] 1 and 2, the magnetic adsorption device 100 has a single-rod cylinder 10. Inside the single-rod cylinder 10, a piston 50 is disposed so as to be movable in the axial direction (the vertical direction in FIG. 2).

[0014] A permanent magnet 70 is attached to the underside of the piston 50, and a seal ring 52 is attached to the outer circumferential surface of the piston 50. The single-rod cylinder 10 and the piston 50 are preferably made of a non-magnetic material such as an aluminum alloy.

[0015] An attraction surface 11 is formed adjacent to the lower end of the single-rod cylinder 10, i.e., the axial end of the head-side cylinder chamber H. The opening at the upper end of the single-rod cylinder 10 is closed by a rod cover 30.

[0016] The upper end of a piston rod 51 is slidably inserted into a rod hole 31 provided in the center of the rod cover 30. The upper surface of the piston 50 is connected to the lower end of the piston rod 51.

[0017] A seal ring 32 is disposed on the inner peripheral surface of the rod hole 31. The seal ring 32 prevents air leakage from the rod side cylinder chamber L.

[0018] 2, a head-side cylinder chamber H is formed below the piston 50, and a rod-side cylinder chamber L is formed above the piston 50. The rod-side cylinder chamber L is connected to an intake / exhaust hole 13 in the cylinder wall, and the head-side cylinder chamber H is connected to an intake / exhaust hole 14 in the cylinder wall.

[0019] The head side cylinder chamber H and the rod side cylinder chamber L are connected to an air tank T, which serves as a pressure source or air pressure supply means, via intake and exhaust holes 13, 14 and a switching valve V. Compressed air is supplied to the air tank T by an air pump P, which also serves as air pressure supply means, and air pressure Pa is constantly stored in the air tank T.

[0020] Switching valve The switching valve V is configured as a 5-port 3-position solenoid valve that can be switched to a first, second, or third position (indicated by circled numbers in Figure 2). The two ports on the left side are connected to the head-side cylinder chamber H and the rod-side cylinder chamber L. The three ports on the right side are connected to the air tank T and two silencers SL1 and SL2.

[0021] The switching valve V remains switched to the first position (neutral position) when the power is turned off. In this first position, the air tank T is connected to the head side cylinder chamber H and the rod side cylinder chamber L.

[0022] When the electromagnetic coil on one side (upper side) of the switching valve V is energized, the spool switches to the second position. In this second position, the air tank T is connected to the rod side cylinder chamber L, and the head side cylinder chamber H is connected to the silencer SL2.

[0023] When the electromagnetic coil on the opposite side (lower side) of the switching valve V is energized, the spool switches to the third position. In the third position, the head side cylinder chamber H is connected to the air tank T, and the rod side cylinder chamber L is connected to the silencer SL1.

[0024] Magnetic sensor A magnetic sensor 15 is attached to the outer surface of the lower end of the single-rod cylinder 10. This magnetic sensor 15 detects whether the permanent magnet 70 on the underside of the piston 50 has moved to the lower end of the single-rod cylinder 10.

[0025] The detection result of the magnetic sensor 15 is input to the control unit 90. The control unit 90 controls the transfer device 200 including the robot arm, the switching valve V, and the air pump P.

[0026] ●Control contents by the control unit The control contents by the control unit 90 will be explained below with reference to the flowchart in Fig. 4. First, in step S1, the transfer device 200 is positioned. This positioning is a process of moving the transfer device 200 above the workpiece W to be transferred.

[0027] In this movement process, the switching valve V may be in an OFF state (first position). In the first position, the head side cylinder chamber H and the rod side cylinder chamber L are connected to the air tank T, and air pressure Pa is introduced into each cylinder chamber H, L. There is a difference in pressure-receiving area between the cylinder chambers H, L corresponding to the cross-sectional area of ​​the piston rod 51, and this difference in pressure-receiving area causes the piston 50 to move upward.

[0028] In step S2, the transfer device 200 is lowered to approach the workpiece W. In this lowering step, the electromagnetic coil on one side (upper side) of the switching valve V is energized to switch the switching valve V to the second position.

[0029] 5, air pressure Pa is introduced into the rod-side cylinder chamber L, and air in the head-side cylinder chamber H is exhausted through the silencer SL2. The air pressure Pa moves the piston 50 downward as shown in FIG.

[0030] In step S3, the workpiece W is attracted by the magnetic attraction device 100 as shown in Fig. 5. As a result, the attraction surface 11 of the magnetic attraction device 100 is attracted to the upper surface of the workpiece W.

[0031] In step S4, the magnetic attraction device 100 is slightly raised by the transport device 200 as shown in Fig. 6. This causes the workpiece W to rise slightly above the ground G.

[0032] (Determined thrust generation) The reason for the slight lift is to confirm in step S5 that the workpiece W is securely attracted to the attraction surface 11 of the magnetic attraction device 100. In the state shown in FIG. 6, a judgment thrust is generated in step S5. The judgment thrust is the force that raises the piston 50 to confirm that the workpiece W is attracted to the attraction surface 11.

[0033] The judgment thrust is generated by switching the switching valve V back to the first position. This connects the head-side cylinder chamber H and the rod-side cylinder chamber L to the air tank T, and the same air pressure Pa is introduced into each cylinder chamber H, L. Then, due to the difference in the pressure-receiving area between the head-side cylinder chamber H and the rod-side cylinder chamber L, an upward pressure (judgment thrust) acts on the piston 50.

[0034] The upward thrust of the piston 50 due to this upward pressure (determined thrust) is significantly smaller than the upward thrust (see FIG. 8) due to the air pressure Pa in the head-side cylinder chamber H. Therefore, when the workpiece W is attracted to the attraction surface 11, the upward thrust of the piston 50 is weaker than the magnetic force acting between the workpiece W and the piston 50 (permanent magnet 70), and therefore the piston 50 cannot move upward.

[0035] Therefore, the magnetic sensor 15 detects that the permanent magnet 70 remains in the position shown in Figure 6. With the determined thrust applied to the piston 50, the process waits in this state for a predetermined time in step S6. A few seconds is sufficient for the predetermined time, but it may also be shorter than 1 second, for example, 0.5 seconds, or 10 seconds or more.

[0036] In step S7, it is determined whether or not the piston 50 has risen. If it is determined that the piston 50 has not risen, the workpiece W is transported to a predetermined position in step S8.

[0037] On the other hand, if the magnetic sensor 15 detects in step S7 that the piston 50 has risen with the judged thrust F as shown in FIG. 7, this means that the permanent magnet 70 failed to attract the workpiece W at the stage shown in FIG. 6, so in step S13 the conveying device 200 is raised once and the conveying process is repeated (return to step S1).

[0038] As described above, the magnetic attraction device 100 of this embodiment can reliably determine whether a workpiece W has been attracted to the magnetic pole without the need for ancillary equipment such as a pressure-reducing device. That is, the magnetic attraction device of Patent Document 1 may erroneously determine whether a workpiece has been attracted to the magnetic pole if there is a malfunction in the pressure-reducing device, but the magnetic attraction device 100 of this embodiment does not use a pressure-reducing device, and therefore the possibility of erroneously determining whether a workpiece has been attracted to the magnetic pole can be reduced. Furthermore, because a pressure-reducing device is not used, the cost of the magnetic attraction device 100 can be reduced.

[0039] In step S14, it is determined whether the retry count is four. If the retry count is four consecutive times, an alarm is generated in step S15 and the transport process is terminated. Since the workpiece W has failed to be attracted four consecutive times, the transport process is interrupted and the magnetic attraction device 100 is inspected. The alarm may be generated when the retry count is one or two times, rather than four consecutive times.

[0040] During the transport of the workpiece W in step S8, it is determined in step S9 whether the piston has risen. The determination in step S8 may be performed repeatedly and continuously during the transport of the workpiece W. If it is determined that the piston 50 has not risen, the workpiece W is accumulated at a predetermined position in step S10.

[0041] In this accumulation process, the switching valve V is switched to the third position with the magnetic attraction device 100 brought sufficiently close to the ground G as shown in Figure 8. This causes air pressure Pa to be introduced into the head-side cylinder chamber H, and air in the rod-side cylinder chamber L is exhausted through the silencer SL1.

[0042] As a result, the piston 50 is forced upward by the air pressure Pa against the magnetic force between the permanent magnet 70 and the workpiece W. As a result, the workpiece W is released from the attraction surface 11 by its own weight, as shown in FIG.

[0043] With the magnetic attraction device 100 held in the state shown in FIG. 8, the device waits for a predetermined time in step S11. This is to ensure that the workpiece W is released from the attraction surface 11. A few seconds is sufficient for the predetermined time, but the device may wait for less than one second, for example, 0.5 seconds, or for 10 seconds or more. Next, in order to prepare for the transport process of the next workpiece W, the transport device 200 is raised in step S12.

[0044] Although the above describes an embodiment of the present invention, it goes without saying that the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, the single-rod cylinder 10 is driven by air pressure. However, it is also possible to drive it by hydraulic pressure instead of air pressure. In this case, an oil tank and a hydraulic pump are provided as hydraulic pressure supply means, instead of the air tank T and air pump P. Furthermore, the magnetic sensor 15 may be mounted on the outside of the rod-side cylinder chamber L, rather than on the outside of the head-side cylinder chamber H as in the above embodiment. Furthermore, a limit switch LS that detects the movement of the piston rod 51 can be used instead of the magnetic sensor 15 (see FIGS. 7 and 8). The limit switch LS can be mounted on the transfer arm 220. Furthermore, the switching valve is not limited to an electromagnetic switching valve, and any type of switching valve can be used. Furthermore, a wide variety of transfer devices can be equipped with the magnetic attraction device 100, from small transfer devices using robot arms to large transfer devices such as gantry cranes. Furthermore, the number of magnetic attraction devices 100 used can be one or more. [Explanation of symbols]

[0045] 10: Single rod cylinder 11: Adsorption surface 13, 14: Intake and exhaust holes 15: Magnetic sensor 30: Rod cover 31: Rod hole 32: Seal ring 50: Piston 51: Piston rod 52: Seal ring 70: Permanent magnet 90: Control unit 100: Magnetic adsorption device 200: Conveyance device 210: Mounting hole 220: Transfer arm G: Ground H: Head side cylinder chamber L: Rod side cylinder chamber LS: Limit switch P: Air pump (air pressure supply means) Pa: Air pressure SL1, SL2: Silencer T: Air tank (air pressure supply means) V: Switching valve W: Work

Claims

1. A magnetic attraction device comprising: a single-rod cylinder having a head-side cylinder chamber and a rod-side cylinder chamber, a piston equipped with a permanent magnet disposed inside the cylinder so as to be movable in an axial direction; and an attraction surface formed adjacent to an axial end of the head-side cylinder chamber, which attracts a workpiece by the magnetic force of the permanent magnet of the piston; a switching valve is provided for supplying and discharging fluid pressure from a common pressure source to the head side cylinder chamber and the rod side cylinder chamber; a detecting means for detecting whether the piston has moved in a direction away from the adsorption surface while the same fluid pressure is introduced from the pressure source into the head-side cylinder chamber and the rod-side cylinder chamber by the switching valve.

2. 2. The magnetic adsorption device according to claim 1, wherein the detecting means is a magnetic sensor attached to the outside of the head-side cylinder chamber or the rod-side cylinder chamber.

3. 2. The magnetic attraction device according to claim 1, wherein said detecting means comprises a limit switch for detecting the movement of the piston rod of said single rod cylinder.

4. 2. The magnetic attraction device according to claim 1, wherein said pressure source is an air pressure supply means or a hydraulic pressure supply means.

5. 5. A transport device comprising a magnetic adsorption device according to claim 1, provided at the tip of a transport arm.

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