Coupling and clamping devices

Abstract

To increase coupling force or clamp force and achieve downsizing of a coupling device and a clamp device.SOLUTION: A coupling device includes a clamp cylinder 100 fixed to a reference member 1. The clamp cylinder 100 includes: a cylinder body 10; a first piston 20 and a second piston 30 which may reciprocate along a first direction relative to the cylinder body 10; and a biasing member 80 which drives the first piston 20 and the second piston 30 to one side in the first direction. The cylinder body 10 has: a first cylinder chamber 51 which drives the first piston 20 to the other side in the first direction; and a second cylinder chamber 52 which is formed separately from the first cylinder chamber 51 and drives the second piston 30 to the other side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present technology relates to coupling and clamping devices. [Background technology]

[0002] BACKGROUND ART Devices that fix a movable member such as a work pallet in a state of being aligned with a reference member such as a table of a machining center have been known in the past (for example, Patent Documents 1 and 2 listed below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 046039 [Patent Document 2] Utility Model Registration No. 3219695 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for increasing the connecting force of the connecting device or the clamping force of the clamping device, while there is also a demand for reducing the size of the connecting device.

[0005] An object of the present technology is to provide a connecting device and a clamping device that are miniaturized while increasing the connecting force or clamping force. [Means for solving the problem]

[0006] A connecting device according to the present technology is a connecting device that can connect a first member and a second member while positioning them relative to each other, and includes a fluid pressure cylinder fixed to the first member.

[0007] A clamping device according to the present technology is a clamping device capable of fixing a second member to a first member, and includes a fluid pressure cylinder fixed to the first member.

[0008] The fluid pressure cylinder includes a cylinder body, a first piston and a second piston reciprocatable along a first direction relative to the cylinder body, and a biasing member that drives the first piston and the second piston to one side in the first direction. The cylinder body has a first cylinder chamber that drives the first piston to the other side in the first direction, and a second cylinder chamber that is formed separately from the first cylinder chamber and drives the second piston to the other side. [Effects of the Invention]

[0009] According to the present technology, it is possible to reduce the size of the connecting device and the clamping device while increasing the connecting force or the clamping force. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a vertical cross-sectional view showing a first state (unclamped state) of a clamping device according to one embodiment. [Figure 2] FIG. 4 is a longitudinal sectional view showing a second state (clamped state) of the clamping device according to one embodiment. [Figure 3] 3 is an enlarged view of the periphery of an engaging ball in the clamp device shown in FIGS. 1 and 2. FIG. [Figure 4] FIG. 4 is a top view of the clamping device shown in FIGS. 1 to 3. [Figure 5] 5 is an enlarged vertical cross-sectional view showing the structure around a clamping chamber and an unclamping chamber of the clamping device shown in FIGS. 1 to 4. FIG. [Figure 6] FIG. 10 is a vertical cross-sectional view of a clamping device according to a modified example. [Figure 7] FIG. 7 is an enlarged view of part VII in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present technology will be described. Note that the same or corresponding parts are denoted by the same reference characters, and description thereof may not be repeated.

[0012] In the embodiments described below, when numbers, amounts, etc. are mentioned, the scope of the present technology is not necessarily limited to those numbers, amounts, etc., unless otherwise specified. Furthermore, in the embodiments described below, each component is not necessarily essential to the present technology, unless otherwise specified. Furthermore, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiments.

[0013] In this specification, the terms "comprise," "include," and "have" are open-ended. That is, when a certain feature is included, other features may or may not be included.

[0014] Furthermore, when geometric terms and terms expressing positional and directional relationships are used in this specification, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along," these terms allow for manufacturing errors and slight variations. When terms expressing relative positional relationships, such as "upper side" and "lower side," are used in this specification, these terms are used to indicate relative positional relationships in a single state, and the relative positional relationships can be reversed or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0015] In the following embodiments, a clamping device will be described as an example of a connecting device, but the scope of the present technology is not limited to a clamping device. The present technology is generally applicable to connecting devices that connect a first member and a second member while positioning them relative to each other. Specifically, the present technology is applicable to mechanisms for changing pallets in machine tools, changing chucks in lathes, and changing hands in robots, mechanisms for changing jigs in gear processing machines, measuring machines, inspection machines, cleaning machines, conveying devices, assembly devices, and welding devices, and mechanisms for changing molds in presses and injection molding machines.

[0016] 1 and 2 are longitudinal cross-sectional views showing a clamping device according to this embodiment, with Fig. 1 showing an unclamped state (first state) and Fig. 2 showing a clamped state (second state).

[0017] The clamping device of this embodiment is capable of fixing a movable member 2 (second member / fixed object) to a reference member 1 (first member / base body) and positioning the movable member 2 relative to the reference member 1 (left-right, up-down, and depth directions in Figures 1 and 2).

[0018] The reference member 1 (first member) is, for example, a table of a machining center, etc. The movable member 2 (second member) is, for example, a work pallet fixed to the table, etc.

[0019] A clamp cylinder 100 may be fixed to the reference member 1. A ring member 200 (annular member) may be fixed to the movable member 2. The clamp cylinder 100 and the ring member 200 are fixed to the reference member 1 and the movable member 2 by fixing members 300, 400 (bolts), respectively. The clamp cylinder 100 and the ring member 200 may also be fixed by fixing means other than the fixing members 300, 400.

[0020] The clamp cylinder 100 (fluid pressure cylinder) includes a cylinder body 10, a first piston member 20, a second piston member 30, a clamp chamber 40, an unclamping chamber 50, a steel ball 60 (engagement portion / engagement ball), a sealing member 70, and a biasing member 80.

[0021] The bottom of the cylinder body 10 is fitted into a hole 1A in the reference member 1. The position of the cylinder body 10 can be aligned by precisely adjusting the position and diameter of the hole 1A. The cylinder body 10 has a port 11A. A seal member 11B is provided around the port 11A. The port 11A communicates with an air flow path 3 provided in the reference member 1.

[0022] The first piston member 20 includes a piston portion 21, a rod portion 22, and an air passage 23. The air passage 23 includes a first portion 23A extending in the axial direction of the rod portion 22, and a second portion 23B extending from the first portion 23A in the radial direction of the rod portion 22 and opening at the outer peripheral surface of the rod portion 22.

[0023] A recess 31 is formed on the outer periphery of the second piston member 30. The second piston member 30 is fixed to the tip side of the rod portion 22 of the first piston member 20 by a fixing member 32 (bolt). This allows the rod portion 22 to connect the piston portion 21 of the first piston member 20 to the second piston member 30. Therefore, the first piston member 20 and the second piston member 30 can reciprocate integrally in the axial direction (first direction) relative to the cylinder body 10.

[0024] The clamp chamber 40 is formed above the piston portion 21 of the first piston member 20. More specifically, the clamp chamber 40 is formed between the upper surface of the piston portion 21 of the first piston member 20 and the cylinder body 10.

[0025] A clamping hydraulic fluid is supplied to the clamp chamber 40 from the air flow path 3 via the port 11A and the air passage 11C. This drives the first piston member 20 and the second piston member 30 to the fixed side (downward in the figure: one side in the first direction). The hydraulic fluid supplied to the clamp chamber 40 can be discharged from the air flow path 3 via the air passage 11C and the port 11A. Air, for example, is used as the clamping hydraulic fluid, but the hydraulic fluid is not limited to air. Hydraulic pressure may be used instead of air pressure.

[0026] The unclamping chamber 50 includes a first unclamping chamber 51 (first cylinder chamber) and a second unclamping chamber 52 (second cylinder chamber) that are spaced apart from each other. The first unclamping chamber 51 and the second unclamping chamber 52 are separated from each other with the clamping chamber 40 sandwiched between them. The first unclamping chamber 51 is formed below the piston portion 21 of the first piston member 20. More specifically, the first unclamping chamber 51 is formed between the bottom surface of the hole portion 1A of the reference member 1, the inner circumferential surface of the cylinder body 10, and the lower surface of the first piston member 20. The second unclamping chamber 52 is formed above the clamping chamber 40. More specifically, the second unclamping chamber 52 is formed between the cylinder body 10, the outer circumferential surface of the rod portion 22 of the first piston member 20, and the lower surface of the second piston member 30.

[0027] The first unclamping chamber 51 is supplied with unclamping hydraulic fluid from an air flow path 4 formed in the reference member 1. The unclamping hydraulic fluid supplied to the first unclamping chamber 51 is also supplied to the second unclamping chamber 52 via the air passage 23 of the first piston member 20. In the example of FIGS. 1 and 2 , the air flow path 4 and the first portion 23A of the air passage 23 are formed in a position that coincides with the axis of the clamp cylinder 100, but the air flow path 4 and the first portion 23A of the air passage 23 may also be formed in a position that is offset from the axis of the clamp cylinder 100.

[0028] When the working fluid is supplied to the unclamping chamber 50, the first piston member 20 and the second piston member 30 are driven to the release side (upper side in the figure: the other side in the first direction). The working fluid supplied to the unclamping chamber 50 can be discharged from the air flow path 4. As the working fluid for unclamping, air is used, for example, but the working fluid is not limited to air. Oil pressure may be used instead of air pressure.

[0029] The supply of the working medium to the unclamping chamber 50 is not limited to the mode in which it is supplied from the air flow path 4 to the first unclamping chamber 51. As a modified example, for example, the working medium may be supplied from the air flow path 4 to the second unclamping chamber 52, and the working medium may also be supplied from the second unclamping chamber 52 to the first unclamping chamber 51 via the air passage 23.

[0030] The steel balls 60 are held by the cylinder body 10 and are located on the inner circumferential side of the ring member 200. A plurality of steel balls 60 are provided so as to be lined up in the circumferential direction of the ring member 200. Each steel ball 60 is held by the cylinder body 10. Furthermore, each steel ball 60 is received in a recess 31 of the second piston member 30.

[0031] In the unclamped state (first state) shown in FIG. 1, the steel balls 60 do not protrude radially outward from the cylinder body 10 and do not press against the ring member 200. The first piston member 20 and the second piston member 30 are urged toward the unclamped side (upper side in FIG. 1), lifting the movable member 2. In this state, the movable member 2 can be removed and replaced. In the clamped state (second state) shown in FIG. 2, the steel balls protrude radially outward from the cylinder body 10 and press the ring member 200 against the reference member 1 (diagonally downward in FIG. 2).

[0032] The sealing member 70 includes a sealing member 71 provided on the outer periphery of the piston portion 21 of the first piston member 20, a sealing member 72 provided between the rod portion 22 of the first piston member 20 and the cylinder body 10, a sealing member 73 provided on the outer periphery of the second piston member 30, a sealing member 74 provided between the rod portion 22 of the first piston member 20 and the second piston member 30, and a sealing member 75 provided between the outer periphery of the cylinder body 10 and the reference member 1.

[0033] Sealing member 71 seals between clamping chamber 40 and first unclamping chamber 51. Sealing member 72 seals between clamping chamber 40 and second unclamping chamber 52. Sealing members 73 and 74 seal between second unclamping chamber 52 and the outside of cylinder body 10. Sealing member 75 seals between first unclamping chamber 51 and the outside of cylinder body 10.

[0034] The biasing members 80 are housed in the clamp chamber 40. The biasing members 80 illustrated in Figures 1 and 2 are coil springs arranged in the circumferential direction on the outer periphery of the rod portion 22. An elastic member such as a leaf spring may be used instead of the coil spring.

[0035] The biasing member 80 biases the piston portion 21 of the first piston member 20 and the cylinder body 10 in directions separating them from each other. The biasing member 80 drives the first piston member 20 downward. Therefore, in addition to the hydraulic fluid pressure for clamping into the clamp chamber 40, the biasing force of the biasing member 80 can ensure a clamping force for fixing the movable member 2. This can increase the clamping force of the clamp device.

[0036] Thus, in clamp cylinder 100, three cylinder chambers, namely, first unclamping chamber 51 (first cylinder chamber), second unclamping chamber 52 (second cylinder chamber), and clamping chamber 40 (third cylinder chamber), are formed along the vertical direction (first direction) in which reference member 1 (first member) and movable member 2 (second member) are aligned. Clamping chamber 40 is provided between first unclamping chamber 51 and second unclamping chamber 52.

[0037] The lower side of the first unclamping chamber 51 is defined by the reference member 1. The first unclamping chamber 51 and the clamping chamber 40 are separated by the piston portion 21 of the first piston member 20. The clamping chamber 40 and the second unclamping chamber 52 are separated by the cylinder body 10. The upper side of the second unclamping chamber 52 is defined by the second piston member 30.

[0038] As the second piston member 30 reciprocates, the steel balls 60 move in the radial direction (second direction), switching between an unclamped state and a clamped state.

[0039] Fig. 3 is an enlarged view of the vicinity of the steel ball 60 in the clamp cylinder 100. As shown in Fig. 3, the steel ball 60 is held in the holding portion 14 of the cylinder body 10. Also, an inclined surface 31A is provided on the upper side (movable member 2 side) of the recess 31 of the second piston member 30.

[0040] During clamping operation, the second piston member 30 is driven downward in Figure 3, and the steel ball 60 is pushed by the inclined surface 31A and presses the inclined surface 210 of the ring member 200 diagonally downward, thereby attracting the ring member 200 downward in Figure 3.

[0041] The cylinder body 10 has a reference surface 15. The detection port 13 opens onto the reference surface 15. In the clamped state, the contact surface 220 of the ring member 200 contacts the reference surface 15, closing the detection port 13 and preventing air supplied from the air flow path 6 (see FIG. 6 ). This increases the air pressure in the air flow path 6. Therefore, by measuring the air pressure in the air flow path 6, it is possible to detect whether the clamping operation is normal. Furthermore, by providing multiple detection ports 13, it is also possible to detect the inclination of the movable member 2.

[0042] During the unclamping operation, the second piston member 30, which is driven upward in Fig. 3, pushes up the movable member 2. When the movable member 2 is not clamped, the detection port 13 is open on the reference surface 15, and therefore, air supplied from the air flow path 6 leaks out.

[0043] Horizontal positioning is achieved by the inner tapered surface 230 of the ring member 200 abutting against the outer tapered surface 110 of the clamp cylinder 100 (cylinder body 10). When the ring member 200 is pulled downward during clamping operation, the abutment surface 220 of the ring member 200 abuts against the reference surface 15 of the cylinder body 10, thereby achieving positioning in the vertical direction. If the inner tapered surface 230 of the ring member 200 and the outer tapered surface 110 of the clamp cylinder 100 (cylinder body 10) are polygonally tapered, perfect positioning can be achieved by a single clamp cylinder 100.

[0044] FIG. 4 is a top view of the clamp cylinder 100. As shown in FIG. 4, the cylinder body 10 has a flange portion 16 that protrudes in a direction away from the central axis of the cylinder body 10. The cylinder body 10 is fixed to the reference member 1 by a fixing member 300 inserted into the flange portion 16. In the clamp cylinder 100, by providing multiple biasing members 80 in the circumferential direction, the total biasing force can be increased without excessively increasing the length of each biasing member 80. As a result, the clamp cylinder 100 can be made smaller, particularly in the height direction (the depth direction of the paper in FIG. 4).

[0045] Furthermore, as shown in FIG. 4, because the steel balls 60 are arranged on the outer periphery of the second piston member 30 that defines the second unclamping chamber 52, it is possible to increase the number of steel balls 60 arranged in the circumferential direction compared to when the steel balls 60 are arranged on the outer periphery of the rod portion 22 of the first piston member 20 (i.e., when the second piston member 30 is not present). As a result, it is possible to more accurately position the ring member 200 using the clamp cylinder 100. In addition, it is possible to reduce the surface pressure acting on each steel ball 60, allowing the steel balls 60 to be made smaller. As a result, it is possible to make the clamp cylinder 100 smaller, particularly in the height direction (the depth direction of the paper in FIG. 4).

[0046] FIG. 5 is an enlarged vertical cross-sectional view showing the structure around the clamping chamber 40 and the unclamping chamber 50 of the clamping cylinder 100. As shown in FIG.

[0047] 5, the cylinder body 10 includes a partition wall portion 10B that separates the clamping chamber 40 and the unclamping chamber 50, and a protruding portion 10C that protrudes downward (toward the first unclamping chamber 51) from the inner peripheral end of the partition wall portion 10B and guides the rod portion 22 of the first piston member 20. The cylinder body 10 defines a recessed portion 10A (first recessed portion) with the partition wall portion 10B as its bottom and the protruding portion 10C as its side wall. The recessed portion 10A faces the piston portion 21 of the first piston member 20.

[0048] The piston portion 21 of the first piston member 20 has a recess 20A (second recess) recessed in a direction away from the partition wall portion 10B. The recess 20A faces the partition wall portion 10B of the cylinder body 10.

[0049] The biasing member 80 is provided between the piston portion 21 of the first piston member 20 and the partition wall 10B. The biasing member 80 is housed in the space formed by the opposing recesses 10A, 20A. The biasing member 80 biases the partition wall 10B of the cylinder body 10 and the piston portion 21 of the first piston member 20 in a direction that separates them from each other.

[0050] The air passage 11C formed in the cylinder body 10 has a bent portion 11C1. The air passage 11C extends obliquely upward from the port 11A, bends at a substantially right angle at the bent portion 11C1, and extends obliquely downward from the bent portion 11C1 to reach the clamp chamber 40.

[0051] The biasing force of the biasing member 80, together with the air pressure supplied to the clamp chamber 40 from the air flow path 3, constitutes the clamping force of the clamp cylinder 100. Note that the clamping force may be constituted solely by the biasing force of the biasing member 80.

[0052] Air pressure from air flow path 4 is supplied to first unclamping chamber 51 and second unclamping chamber 52. First piston member 20 and second piston member 30 are driven toward the unclamping side (upward in FIG. 5 ) against the biasing force of biasing member 80. First piston member 20 and second piston member 30 rise until the tip of protruding portion 10C of cylinder body 10 abuts against a step portion formed in rod portion 22.

[0053] The second piston member 30 has a recess 30A (third recess) recessed in a direction away from the partition wall portion 10B of the cylinder body 10. The air passage 23, which connects the first unclamping chamber 51 and the second unclamping chamber 52, communicates with the second unclamping chamber 52 in a region located within the recess 30A. In the example of FIG. 5, the entire second portion 23B of the air passage 23 is located within the recess 30A. However, even if a portion of the second portion 23B of the air passage 23 in the height direction is located within the recess 30A, the air passage 23 should be interpreted as "communicating with the second unclamping chamber 52 in a region located within the recess 30A."

[0054] In this embodiment, the unclamping chamber 50 is divided into two parts, a first unclamping chamber 51 and a second unclamping chamber 52, and by driving the two parts, the first piston member 20 and the second piston member 30, the driving force on the unclamping side can be increased. The driving on the unclamping side is performed against the biasing force of the biasing member 80. Therefore, the biasing force of the biasing member 80 can be increased as the driving force on the unclamping side is increased. By increasing the biasing force of the biasing member 80, the driving force on the clamping side can be increased. As a result of the above, it is possible to increase the clamping force by the clamp cylinder 100.

[0055] In the present embodiment, a configuration has been exemplified in which one clamp chamber 40 is formed, a biasing member 80 is provided in the clamp chamber 40, and the unclamping chamber 50 is formed in two, but it is also possible to use a configuration in which the clamp chamber 40 is formed in two, one unclamping chamber 50 is formed, and the biasing member 80 is provided in the unclamping chamber 50.

[0056] Fig. 6 is a view showing a vertical cross section of a clamp cylinder 100 according to a modified example. The structure shown in Fig. 6 is naturally applicable to the clamp cylinder 100 shown in Figs. 1 to 5. In the example shown in Fig. 6, the cylinder body 10 has ports 12A and 13A. Seal members 12B and 13B are provided around the ports 12A and 13A, respectively. The ports 12A and 13A communicate with air flow paths 5 and 6 provided in the reference member 1, respectively.

[0057] The cylinder body 10 has air passages 12C and 13C that communicate with the ports 12A and 13A, respectively. The air passage 12C reaches the air blow chamber 90. The air blow chamber 90 is formed between the inner periphery of the cylinder body 10 and an insert member 91. The insert member 91 is fixed to the cylinder body 10 with a retaining ring 92. The air passage 13C opens to the outside of the cylinder body 10 via the detection port 13.

[0058] Figure 7 is an enlarged view of part VII in Figure 6. As shown in Figure 7, the air blow chamber 90 communicates with spaces A and B outside the cylinder body 10 via air passages 12D and 12E, respectively. Air supplied to the air blow chamber 90 is discharged from the air passages 12D and 12E toward spaces A and B. This makes it possible to prevent chips, coolant, and the like from entering the interior of the cylinder body 10.

[0059] Although the embodiments of the present technology have been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present technology is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0060] 1 Reference member, 1A Hole portion, 2 Movable member, 3, 4, 5, 6 Air flow path, 10 Cylinder body, 10A Recess, 10B Bulkhead portion, 10C Protrusion, 11A, 12A, 13A Port, 11B, 12B, 13B Seal member, 11C, 12C, 12D, 12E, 13C Air passage, 11C1 Bent portion, 13 Detection port, 14 Holding portion, 15 Reference surface, 16 Flange portion, 20 First piston member, 20A Recess, 21 Piston portion, 22 Rod portion, 23 Air passage, 23A First portion, 23B Second portion, 30 Second piston member, 30A Recess, 31 Recess, 31A Inclined surface, 32 Fixing member, 40 Clamp chamber, 50 Unclamp chamber, 51 First unclamping chamber, 52 Second unclamping chamber, 60 Steel ball, 70, 71, 72, 73, 74, 75 sealing member, 80 biasing member, 90 air blow chamber, 91 fitting member, 92 retaining ring, 100 clamp cylinder, 110 outer peripheral tapered surface, 200 ring member, 210 inclined surface, 220 abutment surface, 230 inner peripheral tapered surface, 300, 400 fixing member.

Claims

1. A coupling device capable of coupling a first member and a second member while positioning them relative to each other, the coupling device comprising: a fluid pressure cylinder fixed to the first member; the fluid pressure cylinder includes a cylinder body, a first piston and a second piston reciprocatable along a first direction relative to the cylinder body, and a biasing member that drives the first piston and the second piston toward one side in the first direction, the cylinder body includes a first cylinder chamber that drives the first piston to the other side in the first direction, and a second cylinder chamber that is formed separately from the first cylinder chamber and drives the second piston to the other side, The fluid pressure cylinder further includes a seal member provided on an outer periphery of the second piston, the seal member sealing between the second cylinder chamber and the outside of the cylinder body.

2. A coupling device capable of coupling a first member and a second member while positioning them relative to each other, comprising a fluid pressure cylinder fixed to the first member; the fluid pressure cylinder includes a cylinder body, a first piston and a second piston reciprocatable along a first direction relative to the cylinder body, and a biasing member that drives the first piston and the second piston toward one side in the first direction, the cylinder body includes a first cylinder chamber that drives the first piston to the other side in the first direction, and a second cylinder chamber that is formed separately from the first cylinder chamber and drives the second piston to the other side, The coupling device, wherein the biasing member is provided between the first cylinder chamber and the second cylinder chamber in the first direction.

3. A coupling device capable of coupling a first member and a second member while positioning them relative to each other, comprising a fluid pressure cylinder fixed to the first member; the fluid pressure cylinder includes a cylinder body, a first piston and a second piston reciprocatable along a first direction relative to the cylinder body, and a biasing member that drives the first piston and the second piston toward one side in the first direction, the cylinder body includes a first cylinder chamber that drives the first piston to the other side in the first direction, and a second cylinder chamber that is formed separately from the first cylinder chamber and drives the second piston to the other side, the cylinder body further includes a third cylinder chamber provided between the first cylinder chamber and the second cylinder chamber and configured to drive the first piston and the second piston to one side in the first direction, The biasing member is housed in the third cylinder chamber.

4. the cylinder body further includes a partition wall portion that separates the second cylinder chamber from the third cylinder chamber, The coupling device according to claim 3 , wherein the biasing member is provided between the partition wall and the first piston.

5. the cylinder body has a first recess recessed in a direction away from the first piston, the first piston has a second recess recessed in a direction away from the partition wall, The coupling device according to claim 4 , wherein the biasing member is provided to be received in the first recess and the second recess.

6. the fluid pressure cylinder further includes a rod portion extending along the first direction and connecting the first piston and the second piston; The coupling device according to claim 1 , wherein a passage that connects the first cylinder chamber and the second cylinder chamber is formed in the rod portion.

7. further comprising an annular member fixed to the second member; 7. The coupling device according to claim 1, wherein the fluid pressure cylinder further includes an engaging portion that can be positioned on an inner peripheral side of the annular member and that can switch between a first state in which the fluid pressure cylinder does not press the annular member and a second state in which the fluid pressure cylinder presses the annular member toward the first member in accordance with the reciprocating motion of the first piston and the second piston.

8. The coupling device according to claim 7 , wherein the engaging portion moves in a second direction perpendicular to the first direction in accordance with the movement of the second piston.

9. A clamping device capable of fixing a second member to a first member, the clamping device comprising a fluid pressure cylinder fixed to the first member, the fluid pressure cylinder includes a cylinder body, a first piston and a second piston reciprocatable along a first direction relative to the cylinder body, and a biasing member that drives the first piston and the second piston toward one side in the first direction, the cylinder body includes a first cylinder chamber that drives the first piston to the other side in the first direction, and a second cylinder chamber that is formed separately from the first cylinder chamber and drives the second piston to the other side, The clamping device, wherein the fluid pressure cylinder further includes a seal member provided on an outer periphery of the second piston, the seal member sealing between the second cylinder chamber and the outside of the cylinder body.

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