Magnetic chuck

Abstract

SOLUTION: A magnet chuck 10 includes: a cylinder tube 12 having a workpiece suction surface 12c onto which a workpiece W is suctioned; a piston assembly 14 including a permanent magnet 42, being movable in an internal space 25 of the cylinder tube, and separating the internal space of the cylinder tube into a first pressure chamber 112 and a second pressure chamber 114; a first supply / discharge port 26 formed in the cylinder tube and communicating with the first pressure chamber; a second supply / discharge port 76 formed in the cylinder tube and communicating with the second pressure chamber; and a communication passage 71 providing communication between the first pressure chamber and the second pressure chamber.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a magnetic chuck. [Background technology]

[0002] There is known a magnetic chuck in which a permanent magnet is connected to a piston inside a cylinder and displaced together with the piston (see Patent Document 1). In such a magnetic chuck, the permanent magnet approaches a workpiece in response to the displacement of the piston under fluid pressure. As the permanent magnet approaches the workpiece, the workpiece is attracted and held. When the piston is displaced in a direction away from the workpiece, the workpiece is released. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 51-102174 Summary of the Invention [Problem to be solved by the invention]

[0004] When a high-temperature workpiece is attracted and held, it is conceivable that the members provided in the magnetic chuck may be damaged. Even when a high-temperature workpiece is attracted and held, it is preferable to suppress damage to the members provided in the magnetic chuck.

[0005] An object of the present invention is to provide a magnetic chuck having good heat resistance. [Means for solving the problem]

[0006] A magnetic chuck according to one embodiment of the present invention comprises a cylinder tube having a workpiece adsorption surface to which a workpiece is adsorbed, a piston assembly including a permanent magnet and movable within an internal space of the cylinder tube, separating the internal space of the cylinder tube into a first pressure chamber and a second pressure chamber, a first supply and exhaust port formed in the cylinder tube and communicating with the first pressure chamber, a second supply and exhaust port formed in the cylinder tube and communicating with the second pressure chamber, and a communicating passage communicating between the first pressure chamber and the second pressure chamber. Effect of the Invention

[0007] According to the present invention, a magnetic chuck having good heat resistance can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a front view showing a magnetic chuck according to a first embodiment. [Diagram 2] FIG. 1 is a cross-sectional view showing a magnetic chuck according to a first embodiment. [Diagram 3] FIG. 1 is a cross-sectional view showing a magnetic chuck according to a first embodiment. [Figure 4] FIG. 1 is an exploded perspective view showing a magnetic chuck according to a first embodiment. [Diagram 5] FIG. 6 is a cross-sectional view showing a magnetic chuck according to a second embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing a magnetic chuck according to a second embodiment. [Figure 7] FIG. 11 is a cross-sectional view showing a magnetic chuck according to a third embodiment. [Figure 8] FIG. 11 is a cross-sectional view showing a magnetic chuck according to a third embodiment. [Figure 9] FIG. 11 is a rear view showing the magnetic chuck according to the fourth embodiment. [Figure 10] FIG. 11 is a cross-sectional view showing a magnetic chuck according to a fourth embodiment. [Figure 11]FIG. 11 is a cross-sectional view showing a magnetic chuck according to a fourth embodiment. [Figure 12] FIG. 13 is a cross-sectional view showing a portion of a magnetic chuck according to a modified example of the fourth embodiment. [Figure 13] FIG. 13 is a block diagram showing a magnetic chuck according to a modified example of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic chuck according to the present invention will be described in detail below with reference to preferred embodiments and the accompanying drawings.

[0010] [First embodiment] A magnetic chuck according to a first embodiment will be described with reference to Figs. 1 to 4. Fig. 1 is a front view showing the magnetic chuck according to this embodiment. Figs. 2 and 3 are cross-sectional views showing the magnetic chuck according to this embodiment. Fig. 2 shows a state in which the piston assembly 14 is located at the top dead center. Fig. 3 shows a state in which the piston assembly 14 is located at the bottom dead center. Fig. 3 also shows a state in which a workpiece W is attracted to the magnetic chuck 10. Fig. 4 is an exploded perspective view showing the magnetic chuck according to this embodiment. In this specification, the surface of the magnetic chuck 10 on the upper side of the paper in Fig. 1 is referred to as the upper surface, and the surface of the magnetic chuck 10 on the lower side of the paper in Fig. 1 is referred to as the lower surface. The workpiece W is attracted to the lower surface side of the magnetic chuck 10.

[0011] 2 and 3, the magnetic chuck 10 according to the present embodiment includes a cylinder tube 12, a piston assembly 14, a bottom cover 18, and a latch yoke 20. The magnetic chuck 10 is attached to, for example, a distal arm of a robot (not shown).

[0012] A cylinder hole 24 is formed in the cylinder tube 12. The cylinder hole 24 penetrates the cylinder tube 12. The cross-sectional shape of the cylinder hole 24 is, for example, circular. That is, the cross-sectional shape of the cylinder hole 24 in a direction perpendicular to the central axis C of the cylinder tube 12 is, for example, circular. The central axis of the cylinder hole 24 coincides with the central axis C of the cylinder tube 12. The material of the cylinder tube 12 may be, for example, a paramagnetic metal such as an aluminum alloy, but is not limited to this.

[0013] As shown in FIG. 1, the cylinder tube 12 includes a first end 12d and a second end 12e. The first end 12d and the second end 12e are located opposite each other. The first end 12d includes a workpiece suction surface 12c to which the workpiece W is suctioned. As shown in FIG. 2 and FIG. 3, a fitting portion 22 that fits with a housing 86 described later is formed at the first end 12d of the cylinder tube 12. The outer shape of the cross section of the portion of the cylinder tube 12 excluding the fitting portion 22 is, for example, rectangular. The outer shape of the cross section of the fitting portion 22 of the cylinder tube 12 is, for example, circular.

[0014] A step 23 is formed at the tip of the fitting portion 22 of the cylinder tube 12, on which a second seal material 96 (described later) is attached. Also, a step 32 is formed at the upper side of the cylinder hole 24, with which a flange 20a (described later) formed on the latch yoke 20 engages.

[0015] The piston assembly 14 includes a seal holder 38 , a core yoke 40 , a permanent magnet 42 , a cover yoke 44 , and a ring plate 45 .

[0016] The seal holder 38 is formed in a disk shape. For example, a paramagnetic metal such as an aluminum alloy is used as the material of the seal holder 38, but the material is not limited thereto. A groove 39 is formed on the outer periphery of the seal holder 38. The groove 39 opens toward the outside in the circumferential direction of the seal holder 38. A piston seal 46 is attached to the groove 39. For example, a fluororubber is used as the material of the piston seal 46, but the material is not limited thereto. The piston seal 46 slides against the wall surface of the cylinder hole 24. A through hole 48 is formed in the center of the seal holder 38. An inward flange 50 that protrudes toward the center of the through hole 48 is formed in the through hole 48. An annular recess 51 is formed on the upper surface of the seal holder 38. The annular recess 51 opens toward the upper surface side of the magnet chuck 10. The portion between the through hole 48 and the annular recess 51 is the flange 41. The flange 41 protrudes toward the upper surface side of the magnetic chuck 10 .

[0017] The core yoke 40 is formed in a cylindrical shape as a whole. The core yoke 40 may be made of, for example, a ferromagnetic material such as steel, but is not limited thereto. A cylindrical protrusion 52 is formed in the center of the upper end of the core yoke 40. The cylindrical protrusion 52 protrudes toward the upper surface of the magnetic chuck 10. A bottomed screw hole 54 is formed in the core yoke 40. The screw hole 54 opens at the tip of the cylindrical protrusion 52. A recess 56 is formed in the lower portion of the core yoke 40. The recess 56 opens toward the lower surface of the magnetic chuck 10. The cross-sectional shape of the recess 56 is, for example, circular.

[0018] A cylindrical protrusion 52 of the core yoke 40 is inserted into a through hole 48 formed in the seal holder 38. The cylindrical protrusion 52 is inserted into a lower portion of the through hole 48. The cylindrical protrusion 52 fits into the through hole 48. The cylindrical protrusion 52 abuts against an inward flange 50 of the seal holder 38. A fixing screw 60 is inserted into the through hole 48. The fixing screw 60 is inserted from the upper side of the through hole 48. The fixing screw 60 is further inserted into a threaded hole 54 formed in the core yoke 40. The fixing screw 60 is screwed into the threaded hole 54. In this way, the seal holder 38 and the core yoke 40 are integrally connected.

[0019] A first seal 62 is attached to the base of the cylindrical protruding portion 52. The first seal 62 provides a seal between the seal holder 38 and the core yoke 40. The first seal 62 is made of, for example, fluororubber, but is not limited to, a material.

[0020] The permanent magnet 42 is formed, for example, in a cylindrical shape. The permanent magnet 42 is located on the outer periphery of the core yoke 40. As the permanent magnet 42, for example, a samarium-cobalt magnet is used, but is not limited thereto. The permanent magnet 42 is surrounded by the seal holder 38, the core yoke 40, the cover yoke 44, and the ring plate 45. The permanent magnet 42 is magnetized, for example, in a radial direction. The inner periphery side of the permanent magnet 42 is, for example, an N pole, and the outer periphery side of the permanent magnet 42 is, for example, an S pole. Note that the inner periphery side of the permanent magnet 42 may be an S pole, and the outer periphery side of the permanent magnet 42 may be an N pole. The permanent magnet 42 is divided, for example, in a circumferential direction. That is, the cylindrical permanent magnet 42 is configured by combining a plurality of fan-shaped magnet pieces (not shown). Note that the permanent magnet 42 may be configured by a single member. The permanent magnet 42 is not limited to a cylindrical shape. For example, the permanent magnet 42 may be formed in a square tube shape. That is, the rectangular cylindrical permanent magnet 42 may be formed by combining a plurality of flat magnet pieces.

[0021] The cover yoke 44 is formed in a cylindrical shape. The cover yoke 44 is located on the outer periphery of the permanent magnet 42. The material of the cover yoke 44 may be, for example, steel, which is a ferromagnetic material, but is not limited thereto. The outer periphery of the cover yoke 44 has a large diameter at the upper side and a small diameter at the lower side. That is, the cover yoke 44 includes a large diameter portion 64 and a small diameter portion 66. A step portion 65 exists between the large diameter portion 64 and the small diameter portion 66. Two annular grooves 68a, 68b are formed in the large diameter portion 64. The annular grooves 68a, 68b open toward the outside in the radial direction of the cover yoke 44. The annular grooves 68a, 68b are spaced apart from each other in the direction along the central axis C of the cylinder tube 12. Wear rings 70a, 70b are attached to the annular grooves 68a, 68b, respectively. The piston assembly 14 is guided and supported in the cylinder bore 24 via wear rings 70a and 70b. The wear rings 70a and 70b are made of, for example, polytetrafluoroethylene (PTFE). However, the material of the wear rings 70a and 70b is not limited to these materials.

[0022] The bottom cover 18 is provided with a bottom yoke 80, an outer yoke 82, and a housing 86.

[0023] The bottom yoke 80 is made of, for example, steel, which is a ferromagnetic material, but is not limited to this material. The bottom yoke 80 is, for example, cylindrical in shape. When the piston assembly 14 descends, the bottom yoke 80 enters the recess 56 of the core yoke 40 (see FIG. 3). A lower flange 80a is formed at the lower part of the bottom yoke 80. The lower flange 80a protrudes radially outward from the bottom yoke 80.

[0024] An outer yoke 82 is provided on the outside of the bottom yoke 80. The material of the outer yoke 82 may be, for example, steel, which is a ferromagnetic material, but is not limited thereto. The outer yoke 82 is formed, for example, in a cylindrical shape. An upper flange 82a is formed on the upper side of the outer yoke 82. The upper flange 82a protrudes radially outward from the outer yoke 82. An outer peripheral recess 82b is formed on the outer peripheral surface of the lower side of the outer yoke 82. The outer peripheral recess 82b is recessed radially inward from the outer yoke 82. A step 82c is formed on the inner peripheral surface of the lower side of the outer yoke 82.

[0025] An annular connecting plate 84 is provided between a lower flange 80a of the bottom yoke 80 and a step portion 82c of the outer yoke 82. The outer yoke 82 is fixed to the bottom yoke 80 by the connecting plate 84. The material of the connecting plate 84 is, for example, a paramagnetic metal such as an aluminum alloy, but is not limited to this.

[0026] The housing 86 is formed, for example, in a cylindrical shape. The material of the housing 86 may be, for example, a paramagnetic metal such as an aluminum alloy, but is not limited to this. The housing 86 is formed with a through hole 88 that penetrates in the vertical direction. The cross section of the through hole 88 is circular. A lower flange 90 is formed on the lower side of the through hole 88. The lower flange 90 protrudes radially inward from the through hole 88. The fitting portion 22 of the cylinder tube 12 is fitted into the through hole 88 of the housing 86.

[0027] As shown in Fig. 4, four tie rods 94 are inserted into insertion holes 35 formed in the housing 86. The tip end of each tie rod 94 is screwed into a threaded hole (not shown) formed in the cylinder tube 12. In this way, the cylinder tube 12 and the housing 86 are connected and fixed to each other. The upper flange 82a of the outer yoke 82 is clamped between the end face of the fitting portion 22 of the cylinder tube 12 and the lower flange 90 of the housing 86. In this way, the outer yoke 82 is connected and fixed to the cylinder tube 12 etc.

[0028] As described above, the step 23 is formed at the tip of the fitting portion 22 of the cylinder tube 12. The second seal material 96 is attached to the gap between the step 23 and the upper surface of the outer yoke 82. The second seal material 96 seals between the cylinder tube 12 and the outer yoke 82. The second seal material 96 is made of, for example, fluororubber, but is not limited to, a material.

[0029] A damper (lower damper 98) is attached between the lower end of the cylinder tube 12 and the upper surface of the outer yoke 82. The lower damper 98 is formed in an annular shape. The material of the lower damper 98 is, for example, fluororubber, but is not limited thereto. The upper surface of the lower damper 98 faces the annular recess 30 formed in the cylinder tube 12. When the piston assembly 14 descends to the bottom dead center, as shown in FIG. 3, the step portion 65 of the cover yoke 44 abuts against the lower damper 98. The lower damper 98 plays a role in mitigating the impact generated when the piston assembly 14 moves in the internal space 25. That is, the lower damper 98 plays a role in mitigating the impact when the piston assembly 14 descends to the bottom dead center. As shown in FIG. 4, a plurality of grooves 98a (a plurality of recessed grooves) are formed on the upper surface of the lower damper 98, from the inner peripheral end of the lower damper 98 to the outer peripheral end of the lower damper 98. The grooves 98a are formed, for example, at equal intervals in the circumferential direction of the lower damper 98. The grooves 98a serve to communicate a first fluid supply / discharge hole 28, which will be described later, with the cylinder bore 24. That is, the grooves 98a serve to communicate a first supply / discharge port 26, which will be described later, with a first pressure chamber 112, which will be described later. Even when the piston assembly 14 is located at the bottom dead center, the first fluid supply / discharge hole 28 communicates with the cylinder bore 24 via the grooves 98a. The grooves 98a also serve to communicate a second communication hole 74b, which will be described later, with the cylinder bore 24. That is, the grooves 98a also serve to communicate a first communication passage 71A, which will be described later, with the first pressure chamber 112.

[0030] The workpiece W is attracted to the lower surface of the magnetic chuck 10. The workpiece W may be, for example, an iron plate or the like, but is not limited thereto.

[0031] The latch yoke 20 is formed in a disk shape. For example, a ferromagnetic material such as steel is used as the material of the latch yoke 20, but the material is not limited thereto. A flange 20a is formed on the upper side of the latch yoke 20. The flange 20a protrudes radially outward from the latch yoke 20. The flange 20a engages with a step portion 32 formed on the upper side of the cylinder hole 24. A recess 102 is formed in the center of the latch yoke 20. The recess 102 opens toward the lower surface side of the magnet chuck 10. The cross section of the recess 102 is, for example, circular. The recess 102 includes a small diameter portion 102a and a large diameter portion 102b. The small diameter portion 102a is located on the upper side of the recess 102. The large diameter portion 102b is located on the lower side of the recess 102. When the piston assembly 14 rises, the head 60a of the fixing screw 60 is received in the small diameter portion 102a (see FIG. 2). The large diameter portion 102b is fitted with an upper damper 104. The upper damper 104 is formed in an annular shape. When the piston assembly 14 rises, as shown in FIG. 2, the flange 41 of the seal holder 38 comes into contact with the upper damper 104. The upper damper 104 plays a role in mitigating the impact when the piston assembly 14 rises. The upper damper 104 is made of, for example, fluororubber or the like, but is not limited thereto. An annular protrusion 106 is formed at the lower end of the large diameter portion 102b. The inner diameter of the annular protrusion 106 increases in a tapered manner toward the bottom. When the piston assembly 14 rises, the annular protrusion 106 enters the annular recess 51 formed in the seal holder 38. A recessed groove 21 is formed on the outer periphery of the latch yoke 20. The recessed groove 21 opens to the outside in the radial direction of the latch yoke 20. A latch yoke seal 27 is attached to the recessed groove 21. The latch yoke seal 27 may be made of, for example, fluororubber, but is not limited to, a material. A small diameter portion 20b is formed on the lower side of the latch yoke 20. A gap 114a exists between the outer peripheral surface of the small diameter portion 20b of the latch yoke 20 and the wall surface of the cylinder hole 24. The gap 114a is part of a second pressure chamber 114, which will be described later.

[0032] A groove 12b is formed on the upper side of the cylinder tube 12. The groove 12b opens toward the central axis C of the cylinder tube 12. A snap ring 16 is fitted into the groove 12b. The snap ring 16 is a ring-shaped retaining ring for preventing the latch yoke 20 from slipping out in the axial direction of the cylinder tube 12. The axial direction of the cylinder tube 12 is the direction along the central axis C. The material of the snap ring 16 is, for example, spring steel, but is not limited to this.

[0033] The internal space 25 of the cylinder tube 12 is separated into a first pressure chamber 112 and a second pressure chamber 114 by the piston assembly 14. The first pressure chamber 112 is a pressure chamber located below the piston seal 46 of the seal holder 38. The second pressure chamber 114 is a pressure chamber located above the piston seal 46 of the seal holder 38. The first pressure chamber 112 is located between the second pressure chamber 114 and the workpiece adsorption surface 12c.

[0034] The cylinder tube 12 is formed with a first supply / discharge port 26 for supplying / discharging a fluid to / from the first pressure chamber 112. The cylinder tube 12 includes a first side portion 12f and a second side portion 12g. The first side portion 12f and the second side portion 12g are located opposite each other with respect to the central axis C of the cylinder tube 12. The first supply / discharge port 26 is provided in the first side portion 12f of the cylinder tube 12. The cylinder tube 12 has a first side surface 13A and a second side surface 13B. The first side surface 13A and the second side surface 13B are located opposite each other. The first supply / discharge port 26 opens in the first side surface 13A of the cylinder tube 12. As the fluid, for example, a gas such as air is used, but is not limited thereto. A liquid such as water or oil may be used as the fluid. The temperature of the fluid is, for example, room temperature (about 25°C), but is not limited thereto. However, it is preferable that the temperature of the fluid is sufficiently lower than the temperature of the workpiece W so that the inside of the magnetic chuck 10 is cooled sufficiently.

[0035] A first fluid supply / drain hole 28 is formed inside the wall 12a of the cylinder tube 12. The first supply / drain port 26 is connected to the upper end of the first fluid supply / drain hole 28. The first fluid supply / drain hole 28 extends inside the wall 12a of the cylinder tube 12 along the axial direction of the cylinder tube 12. An annular recess 30 that opens toward the lower surface side of the magnetic chuck 10 is formed on the inner circumferential side of the fitting portion 22. The lower end of the first fluid supply / drain hole 28 reaches the annular recess 30. The first supply / drain port 26 communicates with the first pressure chamber 112 via the first fluid supply / drain hole 28. The first fluid supply / drain hole 28 has an opening 81b that communicates with the first pressure chamber 112. The opening 81b that communicates with the first pressure chamber 112 is provided in the first side portion 12f of the cylinder tube 12.

[0036] The cylinder tube 12 is provided with a second supply / discharge port 76 for supplying and discharging fluid to and from the second pressure chamber 114. The second supply / discharge port 76, like the first supply / discharge port 26, is provided in the first side portion 12f of the cylinder tube 12. The second supply / discharge port 76 opens in the first side surface 13A of the cylinder tube 12. The second supply / discharge port 76 is located above the first supply / discharge port 26.

[0037] A second fluid supply / drain hole 110 is formed inside the wall 12a of the cylinder tube 12. One end of the second fluid supply / drain hole 110 is connected to the second supply / drain port 76. The second fluid supply / drain hole 110 extends inside the wall 12a of the cylinder tube 12 toward the cylinder bore 24. The other end of the second fluid supply / drain hole 110 communicates with a gap 114a formed between the outer circumferential surface of the small diameter portion 20b of the latch yoke 20 and the wall surface of the cylinder bore 24. As described above, the gap 114a is a part of the second pressure chamber 114. The second supply / drain port 76 communicates with the second pressure chamber 114 via the second fluid supply / drain hole 110. The second fluid supply / drain hole 110 has an opening 81a communicating with the second pressure chamber 114. The opening 81a communicating with the second pressure chamber 114 is provided in the first side portion 12f of the cylinder tube 12.

[0038] A communication passage 71 that communicates between the first pressure chamber 112 and the second pressure chamber 114 is formed in the cylinder tube 12. The communication passage 71 includes a first communication passage 71A. The first communication passage 71A is formed inside the wall 12a of the cylinder tube 12. The first communication passage 71A is formed separately from the internal space 25 of the cylinder tube 12. The first communication passage 71A is provided in the second side portion 12g of the cylinder tube 12. As described above, the first side portion 12f and the second side portion 12g are located opposite to each other with respect to the central axis C of the cylinder tube 12. The first supply / discharge port 26 and the second supply / discharge port 76 are provided in the first side portion 12f of the cylinder tube 12, and the first communication passage 71A is provided in the second side portion 12g of the cylinder tube 12. The first supply / discharge port 26 and the second supply / discharge port 76 are disposed on the first side portion 12f of the cylinder tube 12, and the communication passage 71 is disposed on the second side portion 12g of the cylinder tube 12 for the following reason: That is, this is to suppress retention of fluid in the first pressure chamber 112 and the second pressure chamber 114, and to effectively cool each portion of the magnetic chuck 10 by the fluid.

[0039] The first communication passage 71A is provided with a flow rate adjustment valve 72, more specifically, a needle valve, for adjusting the flow rate of the fluid flowing through the first communication passage 71A. As described above, the second end 12e of the cylinder tube 12 is located opposite to the first end 12d including the workpiece suction surface 12c. The flow rate adjustment valve 72 is provided at the second end 12e. The flow rate adjustment valve 72 is attached to a recess 73 formed in the cylinder tube 12. The recess 73 opens toward the outside in the radial direction of the cylinder tube 12. The recess 73 opens at the second side surface 13B of the cylinder tube 12. The depth direction of the recess 73 is the radial direction of the cylinder tube 12. The cross section of the recess 73 in the axial direction of the cylinder tube 12 is, for example, circular. The recess 73 is formed with a step portion 73a on which a sealing material 75 described later is attached. A sealing material 75 is attached to the gap between the step portion 73a and the flow rate adjustment valve 72. The seal material 75 provides a seal between the cylinder tube 12 and the flow rate adjustment valve 72. As a material for the seal material 75, for example, fluororubber or the like is used, but the material is not limited to this.

[0040] The first communication passage 71A includes a first communication hole 74a and a second communication hole 74b. One end of the first communication hole 74a communicates with a gap 114a formed between the outer circumferential surface of the small diameter portion 20b of the latch yoke 20 and the wall surface of the cylinder bore 24. The first communication hole 74a, i.e., the communication hole, has an opening 79a communicating with the second pressure chamber 114. The opening 79a communicating with the second pressure chamber 114 is provided in the second side portion 12g of the cylinder tube 12. The other end of the first communication hole 74a opens at the bottom surface of the recess 73. The central axis of the first communication hole 74a and the central axis of the flow rate control valve 72 coincide with each other. The upper end of the second communication hole 74b opens at the side surface of the recess 73. The second communication hole 74b extends inside the wall 12a of the cylinder tube 12 toward the bottom of the cylinder tube 12. The lower end of the second communication hole 74b reaches the annular recess 30 formed in the cylinder tube 12. The first communication passage 71A communicates with the first pressure chamber 112 via a groove 98a formed in the lower damper 98. That is, the second communication hole 74b has an opening 79b that communicates with the first pressure chamber 112. The opening 79b that communicates with the first pressure chamber 112 is provided in the second side portion 12g of the cylinder tube 12.

[0041] The flow rate control valve 72 includes a body portion 72a and a core rod 72b. The body portion 72a is generally formed in a cylindrical shape. The core rod 72b is generally formed in a columnar shape. The core rod 72b is surrounded by the body portion 72a. The core rod 72b includes a large diameter portion 72b1 and a small diameter portion 72b2. The small diameter portion 72b2 is located at the tip of the core rod 72b. The small diameter portion 72b2 of the core rod 72b, i.e., the tip of the core rod 72b, is inserted into the first communication hole 74a. When the core rod 72b is rotated, the core rod 72b is displaced in the longitudinal direction of the core rod 72b. When the core rod 72b is displaced in the longitudinal direction of the core rod 72b, the size of the gap between the first communication passage 71A and the core rod 72b changes, and the flow rate of the fluid in the first communication passage 71A is adjusted. The size of the gap between the first communication passage 71A and the core rod 72b is set to be sufficiently small so that a sufficient pressure difference can be generated between the first pressure chamber 112 and the second pressure chamber 114 when the piston assembly 14 is driven. An annular groove 72b3 is formed in the core rod 72b. The annular groove 72b3 opens toward the outside in the radial direction of the core rod 72b. A seal material 77 is attached to the annular groove 72b3. The seal material 77 seals between the body portion 72a and the core rod 72b. The seal material 77 may be made of, for example, fluororubber, but is not limited to, a material.

[0042] The first supply / exhaust port 26 and the first communication passage 71A communicate with each other via the first pressure chamber 112. Even when the piston assembly 14 is at the bottom dead center, the state in which the first supply / exhaust port 26 and the first communication passage 71A communicate with each other via the first pressure chamber 112 is maintained, as shown in FIG.

[0043] The second supply / exhaust port 76 and the first communication passage 71A communicate with each other via the second pressure chamber 114. Even when the piston assembly 14 is at the top dead center, the state in which the second supply / exhaust port 76 and the first communication passage 71A communicate with each other via the second pressure chamber 114 is maintained, as shown in FIG.

[0044] In this manner, the magnetic chuck 10 according to the present embodiment is constructed.

[0045] Next, the operation of the magnetic chuck 10 according to this embodiment will be described with reference to Figures 2 and 3. The state shown in Figure 2, that is, the state in which the piston assembly 14 is located at the top dead center (ascending end), is defined as the initial state.

[0046] When the piston assembly 14 is located at the top dead center, the piston assembly 14 including the permanent magnet 42 is attracted to the latch yoke 20 by a predetermined magnetic attractive force.

[0047] Before the magnetic chuck 10 is put into use, for example, during transportation, the latch yoke 20 acts to hold the piston assembly 14 at the top dead center position even if no fluid is supplied to the magnetic chuck 10. This prevents the magnetic chuck 10 from attracting surrounding iron materials, thereby ensuring safety.

[0048] Next, while maintaining the magnetic chuck 10 in the initial state, for example, a robot (not shown) is driven to bring the magnetic chuck 10 into contact with the workpiece W. More specifically, the lower surface side of the magnetic chuck 10 is brought into contact with the workpiece W.

[0049] Next, by operating a switching valve (not shown), the supply of fluid into the second pressure chamber 114 is started, and the discharge of fluid from the first pressure chamber 112 is started. The supply of fluid into the second pressure chamber 114 is performed via the second supply / discharge port 76. The discharge of fluid from the first pressure chamber 112 is performed via the first supply / discharge port 26.

[0050] When the supply of fluid into the second pressure chamber 114 starts and the discharge of fluid from the first pressure chamber 112 starts, a pressure difference is generated between the first pressure chamber 112 and the second pressure chamber 114. Therefore, a force that tries to drive the piston assembly 14 downward acts on the piston assembly 14 according to the pressure difference between the first pressure chamber 112 and the second pressure chamber 114. At a stage where the force that tries to drive the piston assembly 14 downward does not exceed the magnetic attractive force acting between the latch yoke 20 and the piston assembly 14, the piston assembly 14 is held at the top dead center. As described above, the size of the gap between the core rod 72b of the flow rate control valve 72 and the first communication passage 71A is set to be sufficiently small, so that the pressure in the second pressure chamber 114 becomes sufficiently higher than the pressure in the first pressure chamber 112. When the force that tries to drive the piston assembly 14 downward exceeds the magnetic attractive force acting between the latch yoke 20 and the piston assembly 14, the piston assembly 14 starts to descend.

[0051] As the piston assembly 14 descends, the magnetic attractive force acting between the latch yoke 20 and the piston assembly 14 gradually decreases. Meanwhile, the magnetic attractive force acting between the bottom yoke 80 and the piston assembly 14 and the magnetic attractive force acting between the outer yoke 82 and the piston assembly 14 gradually increase.

[0052] As the piston assembly 14 further descends, the bottom yoke 80 enters the recess 56 of the core yoke 40. Thereafter, the step 65 of the cover yoke 44 abuts against the lower damper 98, and the piston assembly 14 reaches the bottom dead point (the lower end). When the piston assembly 14 is located at the bottom dead point, the magnetic flux density passing through the workpiece W becomes maximum, and the workpiece W is attracted and held by the magnetic chuck 10 with the maximum magnetic attraction force.

[0053] The workpiece W may be at room temperature or at a high temperature. When the workpiece W is attracted and held by the magnetic chuck 10, the heat of the workpiece W is transferred to the magnetic chuck 10. For example, fluororubber and the like used as materials for the first seal material 62, the second seal material 96, the piston seal 46, the lower damper 98, and the like cannot necessarily withstand extremely high temperatures. If the first seal material 62, the second seal material 96, the piston seal 46, the lower damper 98, and the like become extremely high in temperature, the first seal material 62, the second seal material 96, the piston seal 46, the lower damper 98, and the like may be damaged. In contrast, in this embodiment, the first pressure chamber 112 and the second pressure chamber 114 are communicated with each other via the communication passage 71 (the first communication passage 71A), so that the fluid continues to flow in the first pressure chamber 112 even when the piston assembly 14 is located at the bottom dead center. Therefore, according to this embodiment, the magnetic chuck 10 can be cooled by fluid, and damage to the first seal material 62, the second seal material 96, the piston seal 46, the lower damper 98, etc. can be prevented.

[0054] With the piston assembly 14 positioned at the bottom dead center, the workpiece W is transported to a predetermined position. That is, with the magnetic chuck 10 suction-holding the workpiece W, the workpiece W is transported to a predetermined position. After this, an operation is performed to release the workpiece W from the magnetic chuck 10. The operation to release the workpiece W from the magnetic chuck 10 is performed by operating a switching valve (not shown). Specifically, the supply of fluid into the first pressure chamber 112 is started, and the discharge of fluid from the second pressure chamber 114 is started. Even when the fluid is being supplied into the first pressure chamber 112 and the fluid is being discharged from the second pressure chamber 114, the fluid continues to flow in the first pressure chamber 112. Therefore, even when the fluid is being supplied into the first pressure chamber 112 and the fluid is being discharged from the second pressure chamber 114, the magnetic chuck 10 is cooled by the fluid.

[0055] When the supply of fluid into the first pressure chamber 112 starts and the discharge of fluid from the second pressure chamber 114 starts, a force that tries to drive the piston assembly 14 upward acts on the piston assembly 14 due to the pressure difference between the first pressure chamber 112 and the second pressure chamber 114. The piston assembly 14 is located at the bottom dead center until the force that tries to drive the piston assembly 14 upward exceeds the magnetic attractive force that works between the bottom yoke 80 and the piston assembly 14 and between the outer yoke 82 and the piston assembly 14. When the force that tries to drive the piston assembly 14 upward exceeds the magnetic attractive force that works between the bottom yoke 80 and the piston assembly 14 and between the outer yoke 82 and the piston assembly 14, the piston assembly 14 starts to rise.

[0056] The magnetic attraction force acting on the workpiece W gradually decreases as the piston assembly 14 rises, and the workpiece W is released from the attraction by the magnetic chuck 10. When the flange 41 of the seal holder 38 abuts against the upper damper 104, the rise of the piston assembly 14 ends. That is, the piston assembly 14 reaches the top dead center. In addition to the magnetic attraction force acting between the latch yoke 20 and the piston assembly 14, the differential pressure between the first pressure chamber 112 and the second pressure chamber 114 continues to be applied to the piston assembly 14, so that the piston assembly 14 is reliably held at the top dead center. Therefore, the piston assembly 14 does not unexpectedly descend and the workpiece W is not attracted. Even when the piston assembly 14 is held at the top dead center, a fluid continues to flow in the first pressure chamber 112. Therefore, even when the piston assembly 14 is held at the top dead center, the magnetic chuck 10 is cooled by the fluid.

[0057] Thus, according to the present embodiment, the first pressure chamber 112 and the second pressure chamber 114 are communicated with each other via the communication passage 71 (first communication passage 71A). Therefore, according to the present embodiment, each part of the magnetic chuck 10 is cooled by the fluid that continues to flow through the internal space 25 of the cylinder tube 12. Even when the piston assembly 14 is located at the bottom dead center, the fluid continues to flow through the first pressure chamber 112 and the second pressure chamber 114. Therefore, according to the present embodiment, even when a high-temperature workpiece W is adsorbed by the magnetic chuck 10, damage to the first seal material 62, the second seal material 96, the piston seal 46, the lower damper 98, and the like can be suppressed. Therefore, according to the present embodiment, a magnetic chuck 10 with good heat resistance can be provided.

[0058] [Second embodiment] Next, a magnetic chuck according to a second embodiment will be described with reference to Figs. 5 and 6. The same components as those in the magnetic chuck according to the first embodiment shown in Figs. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted or simplified. Figs. 5 and 6 are cross-sectional views showing the magnetic chuck according to this embodiment. Fig. 5 shows a state in which the piston assembly 14 is located at the top dead center. Fig. 6 shows a state in which the piston assembly 14 is located at the bottom dead center.

[0059] As shown in FIG. 5 and FIG. 6, a groove 116 is formed on the wall surface of the internal space 25 of the cylinder tube 12. In this embodiment, the communication passage 71 (second communication passage 71B) that communicates the first pressure chamber 112 and the second pressure chamber 114 is formed by the groove 116. In order to make it possible to generate a sufficient pressure difference between the first pressure chamber 112 and the second pressure chamber 114 when the piston assembly 14 is driven, the depth and width of the groove 116 that constitutes the second communication passage 71B are set to be sufficiently small. The second communication passage 71B is formed in the second side portion 12g of the cylinder tube 12, similar to the first communication passage 71A in the first embodiment. As described above, the first side portion 12f and the second side portion 12g are located opposite to each other with respect to the central axis C of the cylinder tube 12. The first supply / exhaust port 26 and the second supply / exhaust port 76 are provided in the first side portion 12f of the cylinder tube 12, and the second communication passage 71B is provided in the second side portion 12g of the cylinder tube 12.

[0060] The lower end of groove 116 constituting second communication passage 71B reaches lower damper 98 in which groove 98a is formed. First supply / discharge port 26 and second communication passage 71B communicate with each other via first pressure chamber 112. Even when piston assembly 14 is located at bottom dead center, the state in which first supply / discharge port 26 and second communication passage 71B communicate with each other via first pressure chamber 112 is maintained, as shown in FIG.

[0061] The upper end of the groove 116 faces the outer circumferential surface of the small diameter portion 20b of the latch yoke 20. As described above, a gap 114a is formed between the outer circumferential surface of the small diameter portion 20b and the wall surface of the cylinder bore 24. As described above, the gap 114a is a part of the second pressure chamber 114. The second supply / discharge port 76 and the second communication passage 71B communicate with each other via the second pressure chamber 114. Even when the piston assembly 14 is located at the top dead center, as shown in FIG. 5, the second supply / discharge port 76 and the second communication passage 71B maintain communication with each other via the second pressure chamber 114.

[0062] In the above, the case where the second communication passage 71B is formed by one groove 116 has been described as an example, but the present invention is not limited to this. The second communication passage 71B may be formed by a plurality of grooves 116. For example, a plurality of grooves 116 may be arranged at predetermined intervals in the circumferential direction of the cylinder bore 24.

[0063] In this manner, the communication passage 71 (second communication passage 71B) may be configured by the groove 116 formed on the wall surface of the internal space 25 of the cylinder tube 12. In this embodiment as well, each part of the magnetic chuck 10 is cooled by the fluid that continues to flow through the internal space 25 of the cylinder tube 12. That is, even when the piston assembly 14 is located at the bottom dead center, the fluid continues to flow through the first pressure chamber 112 and the second pressure chamber 114. Therefore, even when a high-temperature workpiece W is adsorbed by the magnetic chuck 10, damage to the first seal material 62, the second seal material 96, the piston seal 46, the lower damper 98, and the like can be suppressed. Therefore, in this embodiment as well, a magnetic chuck 10 with good heat resistance can be provided.

[0064] [Third embodiment] Next, a magnetic chuck according to a third embodiment will be described with reference to Figs. 7 and 8. The same components as those in the magnetic chuck according to the first or second embodiment shown in Figs. 1 to 6 are given the same reference numerals, and the description will be omitted or simplified. Figs. 7 and 8 are cross-sectional views showing the magnetic chuck according to this embodiment. Fig. 7 shows a state in which the piston assembly 14 is located at the top dead center. Fig. 8 shows a state in which the piston assembly 14 is located at the bottom dead center.

[0065] 7 and 8, the seal holder 38 is formed with a circular hole-shaped recess 85 that opens toward the upper surface side of the magnetic chuck 10. The circular hole-shaped recess 85 opens at the bottom surface of the annular recess 51. The central axis of the circular hole-shaped recess 85 coincides with the central axis of a through hole 87a described below. An example in which a plurality of circular hole-shaped recesses 85 are formed along the circumferential direction of the piston assembly 14 is shown in FIGS. 7 and 8.

[0066] The piston assembly 14 is further provided with a communication passage 71 (third communication passage 71C) that communicates between the first pressure chamber 112 and the second pressure chamber 114. The third communication passage 71C is formed by connecting a through hole 87a that passes through the seal holder 38, a through hole 87b that passes through the permanent magnet 42, and a through hole 87c that passes through the ring plate 45 to each other, but is not limited to this. The third communication passage 71C has an opening 83a that communicates with the second pressure chamber 114 and an opening 83b that communicates with the first pressure chamber 112. The diameter of the third communication passage 71C is set to be sufficiently small so as to enable a sufficient pressure difference to be generated between the first pressure chamber 112 and the second pressure chamber 114 when the piston assembly 14 is driven. Here, the diameter of the through hole 87a is set to be sufficiently small so as to generate a sufficient pressure difference between the first pressure chamber 112 and the second pressure chamber 114 when the piston assembly 14 is driven. The third communication passage 71C is formed at least between the central axis C of the cylinder tube 12 and the second side portion 12g. As described above, the first side portion 12f and the second side portion 12g are located opposite each other with respect to the central axis C of the cylinder tube 12. The first supply / exhaust port 26 and the second supply / exhaust port 76 are provided in the first side portion 12f of the cylinder tube 12, and the third communication passage 71C is provided at least between the central axis C of the cylinder tube 12 and the second side portion 12g. An example in which a plurality of third communication passages 71C are formed along the circumferential direction of the piston assembly 14 is shown in FIGS. 7 and 8.

[0067] The first supply / discharge port 26 and the third communication passage 71C communicate with each other via the first pressure chamber 112. Even when the piston assembly 14 is at the bottom dead center, the state in which the first supply / discharge port 26 and the third communication passage 71C communicate with each other via the first pressure chamber 112 is maintained, as shown in FIG.

[0068] The second supply / exhaust port 76 and the third communication passage 71C communicate with each other via the second pressure chamber 114. Even when the piston assembly 14 is at the top dead center, the state in which the second supply / exhaust port 76 and the third communication passage 71C communicate with each other via the second pressure chamber 114 is maintained, as shown in FIG.

[0069] In this manner, the communication passage 71 (third communication passage 71C) that communicates the first pressure chamber 112 and the second pressure chamber 114 may be formed in the piston assembly 14. In this embodiment as well, each part of the magnetic chuck 10 is cooled by the fluid that continues to flow through the internal space 25 of the cylinder tube 12. That is, even when the piston assembly 14 is located at the bottom dead center, the fluid continues to flow through the first pressure chamber 112 and the second pressure chamber 114. Therefore, even when a high-temperature workpiece W is attracted by the magnetic chuck 10, damage to the first seal material 62, the second seal material 96, the piston seal 46, the lower damper 98, and the like can be suppressed. Therefore, in this embodiment as well, a magnetic chuck 10 with good heat resistance can be provided.

[0070] [Fourth embodiment] Next, a magnetic chuck according to a fourth embodiment will be described with reference to Figs. 9 to 11. Fig. 9 is a rear view showing the magnetic chuck according to this embodiment. Figs. 10 and 11 are cross-sectional views showing the magnetic chuck according to this embodiment. Fig. 10 shows a state in which the piston assembly 14 is located at the top dead center. Fig. 11 shows a state in which the piston assembly 14 is located at the bottom dead center. The same components as those in the magnetic chucks according to the first to third embodiments shown in Figs. 1 to 8 are given the same reference numerals and their descriptions will be omitted or simplified.

[0071] In the magnetic chuck 10 according to the present embodiment, a directional control valve 134 is provided in the first communication passage 71Aa.

[0072] In the cylinder tube 12, a communication passage 71 that communicates between the first pressure chamber 112 and the second pressure chamber 114 is formed, similar to the cylinder tube 12 described above in the first to third embodiments. The communication passage 71 includes a first communication passage 71Aa. A portion of the first communication passage 71Aa is formed inside the wall 12a of the cylinder tube 12. The first communication passage 71Aa is formed separately from the internal space 25 of the cylinder tube 12. The first communication passage 71Aa is provided in the second side portion 12g of the cylinder tube 12, similar to the first communication passage 71A described above in the first embodiment.

[0073] The first communication passage 71Aa includes a first communication hole 74a. The first communication hole 74a in this embodiment is similar to the first communication hole 74a described above in the first embodiment.

[0074] The first communication passage 71Aa further includes a third communication hole 74c. A hole 118 is formed inside the wall 12a of the cylinder tube 12. The hole 118 extends inside the wall 12a of the cylinder tube 12 toward the bottom of the cylinder tube 12. The hole 118 penetrates the recess 73. A portion of the hole 118 located below the recess 73 constitutes the third communication hole 74c. An upper portion of the hole 118 is sealed by a sealing member 120. An upper end of the third communication hole 74c opens at a side surface of the recess 73. The third communication hole 74c extends inside the wall 12a of the cylinder tube 12 toward the bottom of the cylinder tube 12.

[0075] The first communication passage 71Aa further includes a fourth communication hole 74d. A lower end of the third communication hole 74c is connected to one end of the fourth communication hole 74d. The other end of the fourth communication hole 74d opens in the second side surface 13B of the cylinder tube 12.

[0076] The first communication passage 71Aa further includes a fifth communication hole 74e. An upper end of the fifth communication hole 74e communicates with a screw hole 130 described later. A lower end of the fifth communication hole 74e reaches an annular recess 30 formed in the cylinder tube 12. The first communication passage 71Aa communicates with the first pressure chamber 112 via a groove 98a formed in the lower damper 98, similar to the first communication passage 71A described above in the first embodiment. That is, the fifth communication hole 74e has an opening 79b communicating with the first pressure chamber 112. The opening 79b communicating with the first pressure chamber 112 is provided in the second side portion 12g of the cylinder tube 12.

[0077] A flow path block 122 is attached to the wall 12a of the cylinder tube 12. The flow path block 122 is attached to the second side portion 12g of the cylinder tube 12. In other words, the flow path block 122 is attached to the rear surface of the magnetic chuck 10. The flow path block 122 has a side surface 123A and a side surface 123B. The side surface 123A and the side surface 123B are located opposite to each other. The side surface 123A of the flow path block 122 contacts the second side surface 123B of the cylinder tube 12.

[0078] An intra-block flow path 124 is formed inside the flow path block 122. The first communication passage 71Aa further includes an intra-block flow path 124. The intra-block flow path 124 includes a sixth communication hole 74f. A step portion 144 to which a seal material 142 is attached is formed on a side surface 123A of the flow path block 122. One end of the sixth communication hole 74f opens at the step portion 144. The central axis of the sixth communication hole 74f coincides with the central axis of the fourth communication hole 74d. One end of the sixth communication hole 74f communicates with the fourth communication hole 74d. The other end of the sixth communication hole 74f opens at the bottom surface of a recess 132 described later. A seal material 142 is attached to the step portion 144. The seal material 142 seals between the second side surface 13B of the cylinder tube 12 and the side surface 123A of the flow path block 122. The material of the seal material 142 is, for example, fluororubber, but is not limited to this.

[0079] The intra-block flow path 124 further includes a seventh communication hole 74g. A hole 126 is formed inside the flow path block 122. The hole 126 extends upward inside the flow path block 122. The hole 126 penetrates a through hole 146, which will be described later. The hole 126 reaches a side surface of the recess 132. A portion of the hole 126 located between the through hole 146 and the recess 132 constitutes the seventh communication hole 74g. A lower portion of the hole 126 is sealed by a sealing member 128. An upper end of the seventh communication hole 74g opens at a side surface of the recess 132. A lower end of the seventh communication hole 74g opens at a side surface of the through hole 146.

[0080] A threaded hole 130 is formed inside the wall 12a of the cylinder tube 12. A tip end of a hollow bolt 154 (described later) is screwed into the threaded hole 130. One end of the threaded hole 130 communicates with the fifth communication hole 74e. The other end of the threaded hole 130 opens at the second side surface 13B of the cylinder tube 12. The threaded hole 130 forms a part of the first communication passage 71Aa.

[0081] A recess 132 is formed in the flow path block 122. The recess 132 opens at a side surface 123B of the flow path block 122. The depth direction of the recess 132 is the direction from the side surface 123B toward the side surface 123A. The bottom surface of the recess 132 forms a valve seat 132a against which a valve body 134c (described later) abuts.

[0082] A directional control valve 134 that controls the direction of the fluid flow is attached to the recess 132. A check valve 134A is used as the directional control valve 134. The check valve 134A has a support portion 134a, a spring 134b, and a valve body 134c. The valve body 134c can move relative to the support portion 134a. The valve body 134c moves in a direction along the central axis of the support portion 134a. That is, the valve body 134c moves in a depth direction of the recess 132. The spring 134b elastically biases the valve body 134c toward the valve seat 132a. When the pressure in the sixth communication hole 74f is higher than the pressure in the seventh communication hole 74g, the valve body 134c is subjected to the following first and second forces. The first force is a force applied to the valve body 134c according to the pressure difference between the seventh communication hole 74g and the sixth communication hole 74f. The second force is a force applied by the spring 134b to the valve body 134c. The direction of the first force and the direction of the second force are opposite to each other. When the first force is greater than the second force, the check valve 134A opens. That is, when the pressure in the sixth communication hole 74f becomes sufficiently higher than the pressure in the seventh communication hole 74g, the check valve 134A opens. When the first force is smaller than the second force, the check valve 134A is closed. Also, when the pressure in the sixth communication hole 74f is lower than the pressure in the seventh communication hole 74g, the check valve 134A is closed. The check valve 134A allows the flow of fluid from the second pressure chamber 114 toward the first pressure chamber 112 via the first communication passage 71Aa. The check valve 134A prevents the flow of fluid from the first pressure chamber 112 toward the second pressure chamber 114 via the first communication passage 71Aa.

[0083] A step 136 is formed in the recess 132, to which a snap ring (C-shaped retaining ring) 138 is attached. The snap ring 138 is attached to the step 136. The directional control valve 134 is fixed in the recess 132 by the snap ring 138.

[0084] A sealant 140 is attached to the directional control valve 134. The sealant 140 provides a seal between the directional control valve 134 and the recess 132. The material of the sealant 140 may be, for example, fluororubber, but is not limited to this.

[0085] A through hole 146 is formed in the flow path block 122. The central axis of the through hole 146 coincides with the central axis of the screw hole 130. A step 148 to which a seal material 150 is attached is formed in a side surface 123A of the flow path block 122. One end of the through hole 146 opens at the step 148. One end of the through hole 146 communicates with the screw hole 130. A recess 152 is formed in a side surface 123B of the flow path block 122 to accommodate a head 154a of a hollow bolt 154. The other end of the through hole 146 opens at the bottom surface of the recess 152.

[0086] The flow passage block 122 is attached to the wall 12a of the cylinder tube 12 by using a hollow bolt 154. The hollow bolt 154 is provided with a cavity 154b. The central axis of the cavity 154b coincides with the central axis of the hollow bolt 154. The hollow bolt 154 is formed with a hole 154c that reaches the cavity 154b. The central axis of the hole 154c intersects with the central axis of the cavity 154b. One end of the cavity 154b communicates with the seventh communication hole 74g via the hole 154c and the through hole 146. The other end of the cavity 154b communicates with the screw hole 130. A part of the block inner flow passage 124 is formed by the cavity 154b.

[0087] A gasket 156 is attached to the recess 152. The gasket 156 provides a seal between the hollow bolt 154 and the flow path block 122.

[0088] The thickness of the upper portion 122a of the flow path block 122 is thinner than the thickness of the other portions of the flow path block 122. A through hole 158 is formed in the upper portion 122a of the flow path block 122. The central axis of the through hole 158 coincides with the central axis of the recess 73. The recess 73 is a screw hole. The tip of the flow rate control valve 72 is screwed into the recess 73. The upper portion 122a of the flow path block 122 is attached to the wall 12a of the cylinder tube 12 by using the flow rate control valve 72.

[0089] When the supply of fluid into the second pressure chamber 114 starts and the discharge of fluid from the first pressure chamber 112 starts, a pressure difference is generated between the first pressure chamber 112 and the second pressure chamber 114. That is, a force that tries to drive the piston assembly 14 in a direction from the second pressure chamber 114 toward the first pressure chamber 112 acts on the piston assembly 14 in accordance with the pressure difference between the first pressure chamber 112 and the second pressure chamber 114. The first pressure chamber 112 communicates with the seventh communication hole 74g, and the second pressure chamber 114 communicates with the sixth communication hole 74f. Therefore, when a force that tries to drive the piston assembly 14 acts in a direction from the second pressure chamber 114 toward the first pressure chamber 112, a force that tries to open the check valve 134A acts on the check valve 134A. That is, a force that tries to open the check valve 134A acts on the check valve 134A in accordance with the pressure difference between the first pressure chamber 112 and the second pressure chamber 114. The check valve 134A opens when the pressure in the second pressure chamber 114 becomes sufficiently higher than the pressure in the first pressure chamber 112. That is, when the pressure in the sixth communication hole 74f becomes sufficiently higher than the pressure in the seventh communication hole 74g, the check valve 134A opens.

[0090] When the supply of fluid into the first pressure chamber 112 starts and the discharge of fluid from the second pressure chamber 114 starts, a pressure difference is generated between the first pressure chamber 112 and the second pressure chamber 114. That is, a force that tries to drive the piston assembly 14 in a direction from the first pressure chamber 112 toward the second pressure chamber 114 acts on the piston assembly 14 according to the pressure difference between the first pressure chamber 112 and the second pressure chamber 114. As described above, the first pressure chamber 112 communicates with the seventh communication hole 74g, and the second pressure chamber 114 communicates with the sixth communication hole 74f. Therefore, the pressure in the sixth communication hole 74f becomes lower than the pressure in the seventh communication hole 74g. Therefore, when a force that tries to drive the piston assembly 14 acts in a direction from the first pressure chamber 112 toward the second pressure chamber 114, the check valve 134A closes. When the directional control valve 134 is closed, after the piston assembly 14 reaches the top dead center (see FIG. 10), fluid stops flowing into the first pressure chamber 112. At this stage, since the workpiece W is released from the magnetic chuck 10, the magnetic chuck 10 is not heated by the workpiece W. That is, at this stage, it is not necessary to cool the magnetic chuck 10 by a fluid. Therefore, there is no particular problem even if fluid stops flowing into the first pressure chamber 112.

[0091] Thus, in this embodiment, when a force attempting to drive the piston assembly 14 acts in a direction from the first pressure chamber 112 to the second pressure chamber 114, the directional control valve 134 closes. According to this embodiment, since the directional control valve 134 is closed, waste of fluid can be prevented.

[0092] (Modification) Next, a magnetic chuck according to a modified example of this embodiment will be described with reference to Figs. 12 and 13. Fig. 12 is a cross-sectional view showing a part of the magnetic chuck according to this embodiment. Fig. 12 shows a state in which the piston assembly 14 is located at the top dead center. Fig. 13 is a block diagram showing the magnetic chuck according to this embodiment.

[0093] In the magnetic chuck 10 according to this modification, an electromagnetic directional control valve 134B is used as the directional control valve 134.

[0094] In the cylinder tube 12, a communication passage 71 that communicates between the first pressure chamber 112 and the second pressure chamber 114 is formed, similar to the cylinder tube 12 described above in the first to third embodiments. The communication passage 71 includes a first communication passage 71Ab. A part of the first communication passage 71Ab is formed inside the wall 12a of the cylinder tube 12. The first communication passage 71Ab is formed separately from the internal space 25 of the cylinder tube 12. The first communication passage 71Ab is provided in the second side portion 12g of the cylinder tube 12, similar to the first communication passage 71A described above in the first embodiment.

[0095] The first communication passage 71Ab includes a first communication hole 74a. The first communication hole 74a in this embodiment is similar to the first communication hole 74a described above in the first embodiment.

[0096] The first communication passage 71Ab further includes a third communication hole 74c. A hole 118 is formed inside the wall 12a of the cylinder tube 12. The hole 118 extends inside the wall 12a of the cylinder tube 12 toward the bottom of the cylinder tube 12. The hole 118 penetrates the recess 73. A portion of the hole 118 located below the recess 73 constitutes the third communication hole 74c. An upper portion of the hole 118 is sealed by a sealing member 120. An upper end of the third communication hole 74c opens on a side surface of the recess 73. The third communication hole 74c extends inside the wall 12a of the cylinder tube 12 toward the bottom of the cylinder tube 12. A lower end of the third communication hole 74c opens on a side surface of a port 160A described later.

[0097] A port 160A is formed in the wall 12a of the cylinder tube 12. The port 160A opens at the second side surface 13B of the cylinder tube 12. The port 160A communicates with the third communication hole 74c.

[0098] A port 160B is formed in the wall 12a of the cylinder tube 12. The port 160B is located below the port 160A. The port 160B opens at the second side surface 13B of the cylinder tube 12. The port 160B communicates with the fifth communication hole 74e.

[0099] 13, the electromagnetic directional control valve 134B is provided with ports 164A and 164B. The port 164A communicates with the port 160A via a flow passage 166A. The port 164B communicates with the port 160B via a flow passage 166B.

[0100] The electromagnetic directional control valve 168 is provided with ports 170A, 170B, and 170C. The port 170A is supplied with fluid via a flow path 172. The port 170B is connected to the second supply / discharge port 76 via a flow path 174A. The port 170C is connected to the first supply / discharge port 26 via a flow path 174B.

[0101] The control device 176 controls the magnetic chuck 10. The control device 176 includes, for example, a calculation unit (processing unit) (not shown) and a storage unit (not shown). The calculation unit is configured with, for example, a processor such as a CPU (Central Processing Unit). That is, the calculation unit is configured with a processing circuitry. The magnetic chuck 10 is controlled by the calculation unit executing a program stored in the storage unit.

[0102] The electromagnetic directional control valves 134B, 168 are switched by a signal supplied from a control device 176. The control device 176 switches the electromagnetic directional control valve 168 to supply fluid into the second pressure chamber 114 through the second supply / discharge port 76. When supplying fluid into the second pressure chamber 114 through the second supply / discharge port 76, the control device 176 switches the electromagnetic directional control valve 134B to allow the flow of fluid in the first communication passage 71Ab. That is, in this case, the control device 176 opens the electromagnetic directional control valve 134B to allow the flow of fluid in the first communication passage 71Ab. As a result, the fluid is introduced into the first pressure chamber 112 through the first communication passage 71Ab.

[0103] Furthermore, the control device 176 switches the electromagnetic directional control valve 168 to supply fluid into the first pressure chamber 112 via the first supply / discharge port 26. When supplying fluid into the first pressure chamber 112 via the first supply / discharge port 26, the control device 176 switches the electromagnetic directional control valve 134B to block the flow of fluid in the first communication passage 71Ab. That is, in this case, the control device 176 closes the electromagnetic directional control valve 134B to block the flow of fluid in the first communication passage 71Ab. This prevents fluid from flowing from the first pressure chamber 112 to the second pressure chamber 114 via the first communication passage 71Ab.

[0104] In this modification as well, when a force attempting to drive the piston assembly 14 acts in a direction from the first pressure chamber 112 to the second pressure chamber 114, the directional control valve 134 is closed. Therefore, in this modification as well, it is possible to prevent the fluid from being wasted.

[0105] [Modified embodiment] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention.

[0106] For example, the first embodiment may be combined with the second embodiment. That is, the magnetic chuck 10 may be provided with the first communication passage 71A and the second communication passage 71B.

[0107] Moreover, the first embodiment and the third embodiment may be combined. That is, the magnetic chuck 10 may be provided with the first communication passage 71A and the third communication passage 71C.

[0108] Moreover, the second embodiment and the third embodiment may be combined. That is, the magnetic chuck 10 may be provided with the second communication passage 71B and the third communication passage 71C.

[0109] Moreover, the first embodiment, the second embodiment and the third embodiment may be combined. That is, the magnetic chuck 10 may be provided with the first communication passage 71A, the second communication passage 71B and the third communication passage 71C.

[0110] Moreover, the fourth embodiment may be combined with the second embodiment. That is, the first communication passage 71Aa and the second communication passage 71B may be provided in the magnetic chuck 10. Moreover, the modified example of the fourth embodiment may be combined with the second embodiment. That is, the first communication passage 71Ab and the second communication passage 71B may be provided in the magnetic chuck 10.

[0111] Moreover, the fourth embodiment may be combined with the third embodiment. That is, the first communication passage 71Aa and the third communication passage 71C may be provided in the magnetic chuck 10. Moreover, the modified example of the fourth embodiment may be combined with the third embodiment. That is, the first communication passage 71Ab and the third communication passage 71C may be provided in the magnetic chuck 10.

[0112] The fourth embodiment may be combined with the second embodiment and the third embodiment. That is, the first communication passage 71Aa, the second communication passage 71B, and the third communication passage 71C may be provided in the magnetic chuck 10. The modified example of the fourth embodiment may be combined with the second embodiment and the third embodiment. That is, the first communication passage 71Ab, the second communication passage 71B, and the third communication passage 71C may be provided in the magnetic chuck 10.

[0113] The above embodiment can be summarized as follows.

[0114] The magnetic chuck (10) includes a cylinder tube (12) having a workpiece attracting surface (12c) to which a workpiece (W) is attracted, a piston assembly (14) including a permanent magnet (42) and movable within an internal space (25) of the cylinder tube and separating the internal space of the cylinder tube into a first pressure chamber (112) and a second pressure chamber (114), a first supply / discharge port (26) formed in the cylinder tube and communicating with the first pressure chamber, a second supply / discharge port (76) formed in the cylinder tube and communicating with the second pressure chamber, and a communication passage (71) communicating the first pressure chamber and the second pressure chamber. According to this configuration, since a communication passage communicating the first pressure chamber and the second pressure chamber is formed, a fluid continues to flow in the first pressure chamber and the second pressure chamber. Even when the piston assembly is located at the bottom dead center, the fluid continues to flow in the first pressure chamber and the second pressure chamber. Therefore, even when a high-temperature workpiece is attracted to the magnetic chuck, damage to the components of the magnetic chuck can be suppressed. Therefore, with this configuration, a magnetic chuck with good heat resistance can be provided.

[0115] The communicating passage may include a first communicating passage (71A, 71Aa, 71Ab), at least a portion of which is formed inside a wall (12a) of the cylinder tube, the first communicating passage being formed separately from the internal space of the cylinder tube, and the first communicating passage may have an opening (79b) communicating with the first pressure chamber and an opening (79a) communicating with the second pressure chamber.

[0116] The piston assembly may further include a damper (98) for absorbing impacts generated when the piston assembly is moved within the internal space, and the first communication passage may be connected to the first pressure chamber via a groove (98a) formed in the damper.

[0117] The first supply / discharge port may be in communication with the first pressure chamber via another groove (98a) formed in the damper.

[0118] A flow rate adjustment valve (72) for adjusting the flow rate of the fluid flowing through the first communication passage may be further provided. With this configuration, the flow rate of the fluid flowing through the first communication passage can be appropriately adjusted.

[0119] The cylinder tube may include a first end (12d) including the workpiece suction surface and a second end (12e) opposite to the first end, and the flow rate adjustment valve may be provided at the second end. With this configuration, a sufficient distance can be secured between the workpiece and the flow rate adjustment valve, and therefore damage to a sealant or the like provided at the flow rate adjustment valve can be sufficiently suppressed.

[0120] The first communication passage may include a communication hole (74a) having the opening that communicates with the second pressure chamber, and a central axis of the communication hole may coincide with a central axis of the flow rate adjustment valve.

[0121] The first communication passage (71Aa, 71Ab) may further include a directional control valve (134) for controlling a direction of fluid flow, the first pressure chamber being located between the second pressure chamber and the workpiece adsorption surface, the directional control valve opening when a force for driving the piston assembly acts in a direction from the second pressure chamber to the first pressure chamber, and closing when a force for driving the piston assembly acts in a direction from the first pressure chamber to the second pressure chamber. With this configuration, it is possible to prevent waste of fluid.

[0122] The directional control valve may be a check valve (134A), which allows the fluid to flow from the second pressure chamber toward the first pressure chamber via the first communication passage, and may block the fluid from the first pressure chamber toward the second pressure chamber via the first communication passage.

[0123] The device may further include a flow path block (122) attached to the wall of the cylinder tube, the first communication passage having an intra-block flow path (124) formed inside the flow path block, and the check valve may be provided in the flow path block.

[0124] The flow passage block may be attached to the wall of the cylinder tube by using a hollow bolt (154), and a cavity (154b) formed in the hollow bolt may form a part of the flow passage within the block. Such a configuration can contribute to the miniaturization of the magnetic chuck.

[0125] The directional control valve may be an electromagnetic directional control valve (134B) that is switched by a signal supplied from a control device, and when fluid is supplied into the second pressure chamber via the second supply / discharge port, the electromagnetic directional control valve may be switched so as to allow the flow of the fluid in the first communication passage, and when the fluid is supplied into the first pressure chamber via the first supply / discharge port, the electromagnetic directional control valve may be switched so as to prevent the flow of the fluid in the first communication passage.

[0126] The communication passage may include a second communication passage (71B) formed by a groove (116) formed in a wall surface of the internal space of the cylinder tube.

[0127] The communication passage may include a third communication passage (71C) formed in the piston assembly, and the third communication passage may have an opening (83b) communicating with the first pressure chamber and an opening (83a) communicating with the second pressure chamber.

[0128] The cylinder tube may include a first side portion (12f) and a second side portion (12g) located opposite each other with respect to a central axis (C) of the cylinder tube, the first supply / discharge port and the second supply / discharge port may be provided in the first side portion, and the communication passage may be provided at least in the second side portion or between the second side portion and the central axis. With this configuration, components of the magnetic chuck can be cooled more effectively, thereby providing a magnetic chuck with better heat resistance. [Explanation of symbols]

[0129] 10: Magnetic chuck 12: Cylinder tube 12a: wall 12b, 21, 39: groove 12c: Workpiece suction surface 12d: First end 12e: second end 12f: first side 12g: second side portion 13A: first side portion 13B: Second side 14: Piston assembly 16, 138: Snap ring 18: Bottom cover 20: Latch yoke 20a, 41: Flange 20b, 66, 72b2, 102a: Small diameter part 22: Fitting part 23, 32, 65, 73a, 82c, 136, 144, 148: Stepped section 24: Cylinder hole 25: Internal space 26: First supply / exhaust port 27: Latch yoke seal 28: First fluid supply / drain hole 30, 51: Annular recess 35: Insertion hole 38: Seal holder 40: Core yoke 42: Permanent magnet 44: Cover yoke 45: Ring plate 46: Piston seal 48, 87a~87c, 88, 146, 158: Through hole 50: Inward flange 52: Cylindrical protrusion 54: Screw hole 56, 73, 102, 132, 152: recessed 60: Fixing screw 60a, 154a: Head portion 62: First seal material 64, 72b1, 102b: Large diameter portion 68a, 68b, 72b3: Annular groove 70a, 70b: Wear ring 71: Connecting passage 71A, 71Aa, 71Ab: 1st communication path 71B: 2nd communication path 71C: Third communication passage 72: Flow rate control valve 72a: Body part 72b: Core rod 74a: First communication hole 74b: Second communication hole 74c: Third communication hole 74d: Fourth communication hole 74e: 5th communication hole 74f: 6th communication hole 74g: 7th communication hole 75, 77, 140, 142, 150: Sealing materials 76: Second supply / exhaust port 79a, 79b, 81a, 81b, 83a, 83b: Opening 80: Bottom yoke 80a, 90: Lower flange 82: Outer yoke 82a: Upper flange 82b: Outer circumferential recess 84: Connecting plate 85: Circular hole recess 86: Housing 94: Tie rod 96: Second seal material 98: Lower damper 98a, 116: Groove 104: Upper damper 106: Annular protrusion 110: second fluid supply / discharge hole 112: first pressure chamber 114: second pressure chamber 114a: gap 118, 126, 154c: Hole 120, 128: Sealing member 122: flow path block 122a: upper part 123A, 123B: Side surface 124: Flow passage inside block 130: Screw hole 134: Directional control valve 134A: Check valve 134B, 168: Electromagnetic directional control valve 154: Hollow bolt 154b: Cavity 156: Gasket 160A, 160B, 164A, 164B, 170A~170C: Ports 166A, 166B, 172, 174A, 174B: flow path 176: Control device C: Central axis W: Work

Claims

1. a cylinder tube having a workpiece suction surface on which a workpiece is suctioned; a piston assembly including a permanent magnet and movable within an internal space of the cylinder tube to separate the internal space of the cylinder tube into a first pressure chamber and a second pressure chamber; a first supply / discharge port formed in the cylinder tube and communicating with the first pressure chamber; a second supply / discharge port formed in the cylinder tube and communicating with the second pressure chamber; a communication passage that communicates the first pressure chamber and the second pressure chamber; Equipped with a magnetic chuck, wherein when fluid is discharged from the first pressure chamber through the first supply / discharge port, the fluid supplied to the second pressure chamber through the second supply / discharge port is also supplied to the first pressure chamber through the communicating passage, within a range in which the pressure of the first pressure chamber is lower than the pressure of the second pressure chamber.

2. 2. The magnetic chuck according to claim 1, the communication passage includes a first communication passage, At least a portion of the first communication passage is formed inside a wall of the cylinder tube, the first communication passage is formed separately from the internal space of the cylinder tube, The first communication passage has an opening communicating with the first pressure chamber and an opening communicating with the second pressure chamber.

3. A cylinder tube having a workpiece suction surface on which a workpiece is suctioned; a piston assembly including a permanent magnet and movable within an internal space of the cylinder tube to separate the internal space of the cylinder tube into a first pressure chamber and a second pressure chamber; a first supply / discharge port formed in the cylinder tube and communicating with the first pressure chamber; a second supply / discharge port formed in the cylinder tube and communicating with the second pressure chamber; a communication passage that communicates the first pressure chamber and the second pressure chamber; Equipped with the communication passage includes a first communication passage, At least a portion of the first communication passage is formed inside a wall of the cylinder tube, the first communication passage is formed separately from the internal space of the cylinder tube, the first communication passage has an opening communicating with the first pressure chamber and an opening communicating with the second pressure chamber, a damper for absorbing shock generated when the piston assembly is moved within the internal space; The first communication passage communicates with the first pressure chamber via a groove formed in the damper.

4. The magnetic chuck according to claim 3, The first supply / discharge port is in communication with the first pressure chamber via another groove formed in the damper.

5. The magnetic chuck according to any one of claims 2 to 4, The magnetic chuck further comprises a flow rate regulating valve for regulating a flow rate of the fluid flowing through the first communication passage.

6. A cylinder tube having a workpiece suction surface to which a workpiece is suctioned; a piston assembly including a permanent magnet and movable within an internal space of the cylinder tube to separate the internal space of the cylinder tube into a first pressure chamber and a second pressure chamber; a first supply / discharge port formed in the cylinder tube and communicating with the first pressure chamber; a second supply / discharge port formed in the cylinder tube and communicating with the second pressure chamber; a communication passage that communicates the first pressure chamber and the second pressure chamber; Equipped with the communication passage includes a first communication passage, At least a portion of the first communication passage is formed inside a wall of the cylinder tube, the first communication passage is formed separately from the internal space of the cylinder tube, the first communication passage has an opening communicating with the first pressure chamber and an opening communicating with the second pressure chamber, a flow rate regulating valve for regulating a flow rate of the fluid flowing through the first communication passage, The cylinder tube includes a first end including the workpiece adsorption surface and a second end opposite to the first end, The flow rate control valve is provided at the second end of the magnetic chuck.

7. 7. The magnetic chuck according to claim 6, the first communication passage includes a communication hole having the opening communicating with the second pressure chamber, a central axis of the communication hole and a central axis of the flow rate adjusting valve are aligned with each other.

8. A cylinder tube having a workpiece suction surface on which a workpiece is suctioned; a piston assembly including a permanent magnet and movable within an internal space of the cylinder tube to separate the internal space of the cylinder tube into a first pressure chamber and a second pressure chamber; a first supply / discharge port formed in the cylinder tube and communicating with the first pressure chamber; a second supply / discharge port formed in the cylinder tube and communicating with the second pressure chamber; a communication passage that communicates the first pressure chamber and the second pressure chamber; Equipped with the communication passage includes a first communication passage, At least a portion of the first communication passage is formed inside a wall of the cylinder tube, the first communication passage is formed separately from the internal space of the cylinder tube, the first communication passage has an opening communicating with the first pressure chamber and an opening communicating with the second pressure chamber, The first communication passage is further provided with a directional control valve that controls a direction in which the fluid flows, the first pressure chamber is located between the second pressure chamber and the workpiece suction surface, When a force attempting to drive the piston assembly acts in a direction from the second pressure chamber toward the first pressure chamber, the directional control valve opens, A magnetic chuck, wherein the directional control valve closes when a force attempting to drive the piston assembly acts in a direction from the first pressure chamber toward the second pressure chamber.

9. 9. The magnetic chuck according to claim 8, The directional control valve is a check valve, The check valve allows the fluid to flow from the second pressure chamber toward the first pressure chamber via the first communication passage, and prevents the fluid from flowing from the first pressure chamber toward the second pressure chamber via the first communication passage.

10. 10. The magnetic chuck according to claim 9, a flow path block attached to the wall of the cylinder tube, the first communication passage has an intra-block passage formed inside the passage block, The check valve is provided in the flow path block. A magnetic chuck.

11. The magnetic chuck according to claim 10, the flow passage block is attached to the wall of the cylinder tube using a hollow bolt; A magnetic chuck, wherein a cavity provided in the hollow bolt forms a part of the flow path within the block.

12. 9. The magnetic chuck according to claim 8, the directional control valve is an electromagnetic directional control valve that is switched by a signal supplied from a control device, when fluid is supplied into the second pressure chamber via the second supply / discharge port, the electromagnetic directional control valve is switched so as to allow the flow of the fluid in the first communication passage, and when fluid is supplied into the first pressure chamber via the first supply / discharge port, the electromagnetic directional control valve is switched so as to prevent the flow of the fluid in the first communication passage.

13. A cylinder tube having a workpiece suction surface on which a workpiece is suctioned; a piston assembly including a permanent magnet and movable within an internal space of the cylinder tube to separate the internal space of the cylinder tube into a first pressure chamber and a second pressure chamber; a first supply / discharge port formed in the cylinder tube and communicating with the first pressure chamber; a second supply / discharge port formed in the cylinder tube and communicating with the second pressure chamber; a communication passage that communicates the first pressure chamber and the second pressure chamber; Equipped with The magnetic chuck, wherein the communication passage includes a second communication passage constituted by a groove formed in a wall surface of the internal space of the cylinder tube.

14. The magnetic chuck according to any one of claims 1 to 13, the communication passage includes a third communication passage formed in the piston assembly, the third communication passage has an opening communicating with the first pressure chamber and an opening communicating with the second pressure chamber.

15. The magnetic chuck according to any one of claims 1 to 14, The cylinder tube includes a first side portion and a second side portion located opposite to each other with respect to a central axis of the cylinder tube, the first supply / exhaust port and the second supply / exhaust port are provided in the first side portion, The magnetic chuck, wherein the communication passage is provided at least in the second side portion or between the second side portion and the central axis.

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