Cylinder device

Abstract

To provide a cylinder device which can generate sufficient thrust force even when expanding and contracting at high speed and achieve good mountability.SOLUTION: A cylinder device C of the invention includes: an expansion / contraction unit 1 having a cylinder 2, a rod 3, a piston 4 which divides the inside of the cylinder 2 into a rod side chamber 5 and a piston side chamber 6, and an outer shell 7 forming a tank 8 with the cylinder 2; a pump unit 20 having a pump 22 capable of supplying a liquid from the tank 8 to the rod side chamber 5; a variable relief valve 30 which provides resistance to flow of the liquid from the rod side chamber 5 to the tank 8; a first on-off valve 40 provided between the rod side chamber 5 and the piston side chamber 6; and a second on-off valve 41 provided between the piston side chamber 6 and the tank 8. A part of a passage connecting the rod side chamber 5 with the first on-off valve 40 or a part of a passage connecting the piston side chamber 6 with the first on-off valve 40 is formed by an outer pipe 50 disposed at the outside of the outer shell 7.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cylinder device. [Background technology]

[0002] Conventionally, this type of cylinder device has been used for the purpose of suppressing vibrations of an object to be damped. For example, a cylinder device is known that is installed between a car body and a bogie of a railway vehicle to suppress vibrations in the lateral direction relative to the direction of travel of the car body.

[0003] Such a cylinder device is used by being interposed between the bogie of a railway vehicle and a central pin located on the underside of the railway vehicle's body, and the output damping force or thrust can suppress vibrations of the body in the lateral direction relative to the direction of travel of the railway vehicle, improving the ride comfort of the railway vehicle.

[0004] The cylinder device includes, for example, a cylinder, an outer shell that covers the cylinder and forms a tank between the cylinder and the outer shell, an extension unit that has a rod that is inserted into the cylinder so as to be axially movable, and a piston that is inserted into the cylinder so as to be slidable and connected to the rod and that divides the inside of the cylinder into a rod-side chamber and a piston-side chamber, a pump unit that has a pump that is provided in a supply passage that connects the rod-side chamber and the tank and can supply liquid from the tank to the rod-side chamber and a motor that drives the pump, a variable relief valve that is provided in a discharge passage that connects the rod-side chamber and the tank, a first on-off valve that is provided in a first passage that connects the rod-side chamber and the piston-side chamber, and a second on-off valve that is provided in a second passage that connects the piston-side chamber and the tank, and thrust is generated by driving the pump to suppress vibration of the vehicle body (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7352710 Summary of the Invention [Problem to be solved by the invention]

[0006] Among the railway vehicles for which cylinder devices are used to control vibrations are those incorporated into train formations made up of trains with different destinations coupled together. When such train formations enter tunnels, the airflow at the coupling points within the train becomes turbulent, causing the car bodies to vibrate at high speed. When the car bodies vibrate at high speed and the telescopic unit expands and contracts, the pump flow rate may not be able to keep up with the change in volume within the cylinder, making it impossible for the cylinder device to suppress the vibration of the car body.

[0007] To increase the flow rate of a pump, it is sufficient to increase the size of the pump, but if the torque that the motor can output is small when only the pump is increased in size, the pump discharge pressure will decrease and the thrust force exerted by the cylinder device will be reduced, so it is necessary to increase the size of the motor as the pump increases.In this way, when a cylinder device is used in an application where there is a possibility that it will expand and contract at high speed due to an external force, it is necessary to increase the size of the pump unit.

[0008] If the pump unit is enlarged, the entire cylinder device will become larger, which will make it harder to mount on the object to be damped, so it is desirable to keep the diameter of the outer shell as small as possible to avoid enlarging the size of the cylinder device.

[0009] On the other hand, in conventional cylinder devices, because it is necessary to connect the rod-side chamber to the piston-side chamber, a pipe is housed in the tank between the cylinder and the outer shell, forming a passage that communicates with the rod-side chamber and is isolated from the tank, and this passage is used as part of the first passage to connect the first on-off valve to the rod-side chamber. In such conventional cylinder devices, because it is necessary to house the pipe in the tank and to ensure a passage area within the pipe, it is not possible to reduce the outer diameter of the outer shell to make the cylinder device more compact, even if it is desired to do so.

[0010] Therefore, in conventional cylinder devices, if the pump unit is made larger so that it can generate thrust even when it expands and contracts at high speed, there is a problem that the mountability on the object to be damped becomes poor.

[0011] Therefore, an object of the present invention is to provide a cylinder device that can exert sufficient thrust even when extending and retracting at high speed and that can be easily mounted. [Means for solving the problem]

[0012] In order to achieve the above-mentioned object, the cylinder device of the present invention comprises: a telescopic unit having a cylinder; a rod inserted into the cylinder so as to be movably in the axial direction; a piston inserted into the cylinder so as to be movably in the axial direction and connected to the rod, the piston dividing the interior of the cylinder into a rod-side chamber and a piston-side chamber; a cylindrical outer shell arranged on the outer periphery of the cylinder and forming a tank for storing liquid between the cylinder and the outer shell; a pump unit having a pump arranged between the rod-side chamber and the tank and capable of supplying liquid from the tank to the rod-side chamber and a motor for driving the pump; a variable relief valve arranged between the rod-side chamber and the tank and providing resistance to the flow of liquid from the rod-side chamber to the tank; a first on-off valve arranged between the rod-side chamber and the piston-side chamber; and a second on-off valve arranged between the piston-side chamber and the tank, wherein a part of a passage connecting the rod-side chamber and the first on-off valve or a part of a passage connecting the piston-side chamber and the first on-off valve is formed by an external piping arranged outside the outer shell.

[0013] According to the cylinder device configured in this manner, it is necessary to communicate the rod-side chamber with the piston-side chamber in order to switch between communication and cut-off between the rod-side chamber and the piston-side chamber using the first on-off valve. However, the passage connecting the rod-side chamber with the first on-off valve or part of the passage connecting the piston-side chamber with the first on-off valve is formed by external piping arranged outside the outer shell. Therefore, even if the capacity of the pump is increased and the motor is made larger to ensure thrust during high-speed extension and retraction, it is not necessary to install a pipe that runs the entire axial length of the tank inside the outer shell to communicate the rod-side chamber with the piston-side chamber. This means that the outer diameter of the outer shell can be reduced and the cylinder device can be made smaller.

[0014] The telescopic unit in the cylinder device may have an intermediate cylinder provided between the cylinder and the outer shell, covering at least a portion of the cylinder and forming an annular passage between the cylinder and the intermediate cylinder and communicating with the rod-side chamber, and the pump, the variable relief valve, and the first on-off valve may be connected to the rod-side chamber via the annular passage.

[0015] According to the cylinder device configured in this manner, by providing the intermediate cylinder, it is possible to easily form an annular passage between the cylinder and the outer shell that is in communication with the rod-side chamber. Furthermore, according to the cylinder device configured in this manner, it is only necessary to connect the pump unit and the adjustable relief valve to the annular passage, and the pump unit and the adjustable relief valve can be installed at any position in the circumferential direction and axial direction on the outer periphery of the outer shell. Therefore, the installation locations of the pump unit and the adjustable relief valve on the outer shell can be optimized depending on the installation target of the cylinder device, and the mountability of the cylinder device can be further improved.

[0016] In addition, the variable relief valve in the cylinder device may be attached to the outer periphery of the outer shell and include a discharge passage that connects the variable relief valve to the tank, and the discharge passage may be formed by a discharge pipe line that extends from the variable relief valve into the tank, and an annular tank passage that is provided in a ring that fits onto the outer periphery of the intermediate cylinder, connects to the discharge pipe line, and connects to a point within the tank at least below the liquid level.

[0017] According to the cylinder device configured in this manner, the flow rate of the liquid that has passed through the variable relief valve is reduced by the passage within the tank, while the liquid is discharged from below the liquid level in the tank. This prevents the liquid that has passed through the variable relief valve from drawing in gas within the tank, and prevents gas from entering the cylinder, thereby maintaining good damping force generation responsiveness of the cylinder device. [Effects of the Invention]

[0018] The cylinder device of the present invention can achieve both sufficient thrust even when extending and retracting at high speed and good mountability. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a side view of the cylinder device according to the embodiment. [Figure 2] FIG. 2 is a partially enlarged side view of the cylinder device according to the embodiment. [Figure 3] FIG. 2 is a cross-sectional view of a pump portion of the cylinder device according to the embodiment. [Figure 4] FIG. 2 is a cross-sectional view of a ring portion of the cylinder device according to the embodiment. [Figure 5] FIG. 10 is a partially enlarged vertical cross-sectional view of a cylinder device according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described below based on the embodiments shown in the drawings. As shown in Figures 1 and 2, the cylinder device C in one embodiment is configured to include an extension unit 1, a pump unit 20, an adjustable relief valve 30, a first on-off valve 40, a second on-off valve 41, and external piping 50. Although not shown in detail, the cylinder device C in this embodiment is installed between the carbody and bogie of a railway vehicle, with the target of vibration damping being a railway vehicle, and suppresses horizontal lateral vibration of the carbody relative to the direction of travel of the vehicle by the damping force it exerts when it extends or retracts. Note that the cylinder device C may also be used in vehicles or machinery other than railway vehicles, with the target of vibration damping being something other than a railway vehicle.

[0021] Each part will be described in detail below. As shown in Figures 1 and 2, the telescopic unit 1 includes a cylinder 2, a rod 3 inserted into the cylinder 2 so as to be movable in the axial direction, a piston 4 inserted into the cylinder 2 so as to be movable in the axial direction and connected to the rod 3, and dividing the interior of the cylinder 2 into a rod-side chamber 5 and a piston-side chamber 6, a cylindrical outer shell 7 arranged on the outer periphery of the cylinder 2 and forming a tank 8 for storing liquid between it and the cylinder 2, and an intermediate cylinder 9 covering the cylinder 2 from the left end to near the center.

[0022] The cylinder 2 is cylindrical, and an annular rod guide 10 is fitted into the inner periphery at the left end in FIG. 2, while a valve case 11 is fitted into the inner periphery at the right end in FIG. 2. The left end of the cylinder 2 is closed by the rod guide 10, and the right end of the cylinder 2 is closed by the valve case 11. An expanded diameter portion 2a, whose outer diameter is larger than that of the remaining portions, is formed on the outer periphery of the middle portion of the cylinder 2. Furthermore, the cylinder 2 has a through hole 2b penetrating the wall near the left end in FIG. 2.

[0023] A rod 3, which is movably inserted into the cylinder 2, is slidably inserted into the rod guide 10. One end of the rod 3 protrudes outside the cylinder 2, and the other end inside the cylinder 2 is connected to a piston 4, which is slidably inserted into the cylinder 2. A bracket 3a is provided at the other end of the rod 3, allowing it to be attached to a mounting portion provided on a bogie of a railway vehicle.

[0024] The interior of the cylinder 2 is divided by the piston 4 into a rod side chamber 5, through which the rod 3 is inserted, and a piston side chamber 6, through which the rod 3 is not inserted. The rod side chamber 5 and the piston side chamber 6 are filled with a liquid such as hydraulic oil. The piston 4 is provided with a flow rectifying passage 14 that allows the flow of liquid from the piston side chamber 6 to the rod side chamber 5, but blocks the flow of liquid from the rod side chamber 5 to the piston side chamber 6.

[0025] The rectifying passage 14 communicates the piston side chamber 6 and the rod side chamber 5, and is provided with a check valve 14a midway, so that it is set as a one-way passage that allows only the flow of hydraulic oil from the piston side chamber 6 to the rod side chamber 5.

[0026] Next, a cylindrical outer shell 7 is provided on the outer peripheral side of the cylinder 2, covering the outer peripheral surface of the cylinder 2. A rod guide 10 is fitted into the inner peripheral surface of the left end of the outer shell 7 in FIG. 2, and the left end of the outer shell 7 is closed by the rod guide 10. In addition, an annular seal case 12 is attached to the left end of the outer shell 7 in FIG. 2, stacked on the right side of the rod guide 10 in FIG. 2. The seal case 12 is provided with a dust seal 12a on its inner peripheral surface that slides against the outer peripheral surface of the rod 3, preventing dust and water from entering the telescopic unit 1.

[0027] The right end of the outer shell 7 in Fig. 2 is closed by a bottom cap 13. The bottom cap 13 is connected to the right end of the outer shell 7 by welding or the like, and is provided at its right end with a bracket 13a that enables attachment to an attachment portion (not shown) provided on the car body of a railway vehicle. Therefore, by utilizing the bracket 3a of the rod 3 and the bracket 13a of the bottom cap 13, the telescopic unit 1 of the cylinder device C can be attached between the car body and the bogie (not shown).

[0028] Then, when a bottom cap 13 is attached to the right end of the outer shell 7 and a seal case 12 is attached to the left end of the outer shell 7, the rod guide 10, cylinder 2 and valve case 11 housed in the outer shell 7 are sandwiched between the bottom cap 13 and the seal case 12 and fixed within the outer shell 7.

[0029] In this way, an annular tank 8 for storing liquid is formed between the outer shell 7 and the cylinder 2 housed within the outer shell 7. Specifically, the tank 8 is filled with the same liquid as that filled within the cylinder 2, as well as gas, and the pressure in the tank 8 is set to approximately atmospheric pressure.

[0030] 2, the valve case 11 is provided with a cylindrical fitting shaft 11a extending in the axial direction from the right end thereof, a vertical hole 11b opening at the right end of the fitting shaft 11a and communicating with the piston-side chamber 6, and a suction passage 19 that allows only the flow of fluid from the tank 8 toward the piston-side chamber 6. The suction passage 19 axially penetrates a portion of the valve case 11 avoiding the fitting shaft 11a, communicating between the tank 8 and the piston-side chamber 6, and is provided with a check valve 19a midway, making it a one-way passage that allows only the flow of hydraulic oil from the tank 8 toward the piston-side chamber 6.

[0031] The bottom cap 13 has a recess 13b whose inner diameter is reduced partway through, a notched groove 13c formed at the left end in FIG. 2 that connects the large-diameter portion of the recess 13b to the tank 8, a piston-side chamber communication passage 13d that opens from the tip of the recess 13b and leads to the lower end in FIG. 2, and a tank communication passage 13e that opens from the notched groove 13c and leads to the lower end in FIG. 2.

[0032] The fitting shaft 11a of the valve case 11 is fitted into the reduced diameter portion of the recess 13b of the bottom cap 13, and the bottom cap 13 radially positions the valve case 11 with respect to the outer shell 7 by fitting the fitting shaft 11a into the recess 13b. The piston-side chamber communicating passage 13d opens to the tip of the recess 13b and is connected to the piston-side chamber 6 through the vertical hole 11b of the valve case 11. One end of the suction passage 19 provided in the valve case 11 communicates with the recess 13b of the bottom cap 13 and is connected to the tank 8 via the recess 13b and the notched groove 13c. One end of the tank communicating passage 13e is connected to the tank 8 through the notched groove 13c facing the tank 8.

[0033] Next, the outer shell 7 has a hole 7a penetrating the wall thickness at the upper left side in Fig. 2, and a hole 7b penetrating the wall thickness at the lower part near the center in Fig. 2. Furthermore, a valve seat 15 for attaching the adjustable relief valve 30 to the outer shell 7 is attached to the outer periphery of the outer shell 7 in a ring-shaped position surrounding the hole 7a, and similarly, a seat 16 for attaching the pump unit 20 to the outer shell 7 is attached to the outer periphery of the outer shell 7 in a ring-shaped position surrounding the hole 7b.

[0034] Valve seat 15 is rectangular when viewed from the radial direction of outer shell 7, and has a curved surface that follows the outer periphery of outer shell 7 at its end facing the outer shell 7, and a flat surface at its end facing away from the outer shell for easy attachment of adjustable relief valve 30, and has hole 15a in its center that leads to hole 7a, as shown in Figure 2. When valve seat 15 is attached to the outer periphery of outer shell 7 with the curved surface facing the outer shell 7, hole 15a faces hole 7a and communicates with the inside of tank 8.

[0035] 1, 2, and 3, the base 16 has a base portion 16a that is disk-shaped when viewed from the radial direction of the outer shell 7 and whose surface facing the outer shell 7 is a curved surface that follows the outer periphery of the outer shell 7, a support portion 16b that is continuous with the side of the base 16a opposite the outer shell and has a flat mounting surface 16c on which the pump unit 20 is attached on the side opposite the outer shell, and a through-hole 16d that opens from the mounting surface 16c and passes through the support portion 16b and the base portion 16a, and when fixed to the outer periphery of the outer shell 7, the through-hole 16d faces the hole 7b directly, so that the through-hole 16d communicates with the inside of the tank 8. Note that the rod 3 is not shown in FIG.

[0036] The base 16a is cylindrical and has a curved surface 16a1 at its end on the outer shell 7 side that follows the outer periphery of the outer shell 7. Although the center of curvature of the curved surface 16a1 coincides with the center of the outer periphery of the outer shell 7, the axis Z passing through the center of the circular base 16a is shifted to the left from the axis Y of the outer shell 7 as shown in Figure 3, and therefore the axial length of the base 16a is longer on the left side in Figure 3 than on the right side in Figure 3.

[0037] The support portion 16b has a rectangular shape when viewed from below the outer shell 7 in FIG. 2, and as shown in FIG. 3, it is connected to the base 16a, which has a disk-shaped center, eccentrically to the left in FIG. 3. The right end of the support portion 16b in FIG. 3 is substantially flush with the right end of the base 16a in FIG. 3. However, because the length of the support portion 16b in the left-right direction in FIG. 3 is longer than the diameter of the base 16a, the support portion 16b protrudes leftward from the base 16a in FIG. 3. In this way, since the support portion 16b is connected eccentrically to the left in FIG. 3 relative to the base 16a, when the base 16 is attached to the outer shell 7, a line X that is perpendicular to the mounting surface 16c of the support portion 16b and passes through the center of the mounting surface 16c and an axis Y of the outer shell 7 are in a twisted position so as not to intersect with each other, and the mounting surface 16c is disposed at an offset position to the left in FIG. 3 relative to the outer shell 7.

[0038] The axis of through-hole 16d is aligned with line X, is perpendicular to mounting surface 16c, and is provided in base 16 so as to pass through the center of mounting surface 16c, and is provided at a position offset to the left of the center of base 16a in Fig. 3. Axis Z passing through the center of circular base 16a is offset to the left of axis Y of outer shell 7 in Fig. 3, and the thickness of base 16a along axis Z is thicker on the left side than on the right side, and through-hole 16d is offset from the center of base 16a to the left where the thickness is thicker, so that a decrease in the strength of base 16 due to the provision of through-hole 16d is reduced.

[0039] Next, the rod guide 10 is annular and is inserted into the inner periphery of the left end of the outer shell 7 in Figure 2, and is provided with a protruding portion 10a at the right end in Figure 2 that protrudes rightward. The outer diameter of the protruding portion 10a is reduced on the right end in Figure 2, which is the tip side, and is provided with a small diameter portion 10a1 on the tip side and a large diameter portion 10a2 on the base end side. The small diameter portion 10a1 of the rod guide 10 is fitted into the inner periphery of the left end of the cylinder 2 in Figure 2, and is fixed inside the outer shell 7 by being sandwiched between the cylinder 2 and a seal case 12 attached to the left end of the outer shell 7 in Figure 2.

[0040] The rod guide 10 is equipped on its inner periphery with a seal ring 10b that slides against the outer periphery of the rod 3, and a cylindrical bushing 10c. The seal ring 10b prevents liquid from leaking from inside the telescopic unit 1. The rod 3 is guided in its axial movement by the bushing 10c, so it can move smoothly in the axial direction relative to the cylinder 2 without any axial wobble.

[0041] 2 of the intermediate cylinder 9, which covers the cylinder 2 from its right end to its middle portion in FIG. 2, is fitted onto the outer periphery of the large diameter portion 10a2 of the rod guide 10. The right end of the intermediate cylinder 9 in FIG. 2 is fitted onto the outer periphery of the expanded diameter portion 2a of the cylinder 2.

[0042] The expanded diameter portion 2a of the cylinder 2 is provided with a flange 2a1 that faces the right end of the intermediate tube 9 in Figure 2, and when the intermediate tube 9 is fitted into the large diameter portion 10a2 of the rod guide 10 and the expanded diameter portion 2a, the flange 2a1 and the rod guide 10 restrict movement of the intermediate tube 9 relative to the cylinder 2 in the left-right direction in Figure 2, which is the axial direction.

[0043] The intermediate tube 9 has a hole 9a that penetrates radially through the upper wall thickness on the left in Figure 2, a hole 9b that penetrates radially through the lower wall thickness on the right in Figure 2, an annular socket 9c that protrudes radially from the outer periphery and surrounds the hole 9a, and an annular socket 9d that protrudes radially from the outer periphery and surrounds the hole 9b.

[0044] 2 is fitted onto the outer periphery of the expanded diameter portion 2a of the cylinder 2, and an annular passage P1 is formed between the intermediate cylinder 9 and the cylinder 2. The left end of the annular passage P1 in FIG. 2 is closed by fitting a rod guide 10 onto the left end of the intermediate cylinder 9, and the right end of the annular passage P1 in FIG. 2 is closed by fitting the expanded diameter portion 2a onto the right end of the intermediate cylinder 9, so that the annular passage P1 communicates with the inside of the rod-side chamber 5 via a through-hole 2b provided in the cylinder 2 but does not communicate with the inside of the tank 8. In this way, the annular passage P1 is formed by the cylinder 2 and the intermediate cylinder 9 that covers part of the outer periphery of the cylinder 2.

[0045] 1 and 2, the pump unit 20 includes a pump block 21 that includes a pump 22 and is attached to the mounting surface 16c of the base 16, and a motor 23 that is held by the pump block 21. The pump 22 is a one-way discharge pump that sucks liquid from the tank 8 and supplies the liquid to the rod-side chamber 5, and is, for example, a gear pump. The pump 22 may also be a two-way discharge pump, a piston pump, or the like.

[0046] The pump block 21 has a rectangular parallelepiped main body 21a having a flat mounting surface 21b facing the mounting surface 16c and fixed to the base 16, a pump accommodating section 21c that protrudes rightward from the right end of the main body 21a, which is on the lower, anti-rod side in Figure 2, and accommodates the pump 22 inside, a blind hole 21d that opens near the center of the mounting surface 21b, a suction passage 21e that opens from a portion of the mounting surface 21b facing the through hole 16d of the base 16 and leads to the suction port of the pump 22, a supply passage 21f that communicates between the discharge port of the pump 22 and the blind hole 21d, a pipe insertion hole 21g that opens upward in Figure 2 on the side of the main body 21a, closer to the outer shell 7 than the pump accommodating section 21c, and a branch passage 21h that communicates between the supply passage 21f and the pipe insertion hole 21g.

[0047] The motor 23 includes a rotor 23a and is attached to the left side of the main body 21a of the pump block 21 in FIG.

[0048] When main body 21a of pump block 21 is attached to mounting surface 16c of base 16, blind hole 21d and suction passage 21e face each other relative to through-hole 16d of base 16. In addition, blind hole 21d faces socket 9d in intermediate cylinder 9, so that cylindrical communication conduit 17 connects pump block 21 and intermediate cylinder 9, connecting supply passage 21f and annular passage P1 within intermediate cylinder 9. Communication conduit 17 is fixed to pump block 21 and intermediate cylinder 9 with one end fitted in blind hole 21d and the other end fitted in socket 9d.

[0049] Therefore, the supply passage 21f connected to the discharge port of the pump 22 is communicated with the rod side chamber 5 via the connecting pipe 17 and the annular passage P1. On the other hand, the pump 22 is communicated with the tank 8 via a suction passage 21e connected to the suction port of the pump 22. When the motor 23 is driven, the pump 22 can suck liquid from the tank 8 via the suction passage 21e and supply the liquid to the rod side chamber 5 through the supply passage 21f.

[0050] Next, the adjustable relief valve 30 is installed in a valve block 31 attached to the valve seat 15, and together with the valve block 31, constitutes a relief valve unit. The valve block 31 includes a valve housing 31a attached to the valve seat 15 while abutting against the flat surface of the valve seat 15, a cylindrical protrusion 31b protruding from the bottom of the valve housing 31a in Figure 2 and fitting into the hole 15a of the valve seat 15, two blind holes 31c and 31d opening upward from the lower end of the protrusion 31b in Figure 2, and an intra-block passage 31e opening from the bottom of the blind hole 31c and communicating with the bottom of the blind hole 31d.

[0051] When the valve block 31 is attached to the valve seat 15, the blind hole 31c, which faces the tank 8 via the hole 7a, faces the socket 9c of the intermediate cylinder 9 in the radial direction of the outer shell 7. One end of the intra-block passage 31e, which opens to the bottom of the blind hole 31c, and the hole 9a in the intermediate cylinder 9, which is surrounded by the socket 9c, are connected to each other by a communication pipe 18. One end of the communication pipe 18 is fitted into the blind hole 31c, and the other end is fitted into the socket 9c, and the communication pipe 18 is fixed to the valve block 31 and the intermediate cylinder 9.

[0052] One end of a cylindrical discharge pipe 32 is fitted into a blind hole 31d facing the tank 8 via the hole 7a. The discharge pipe 32 is attached to the valve block 31, extends radially from the outer shell 7, and protrudes into the tank 8. The other end of the discharge pipe 32 is fitted into a ring 33 attached to the outer periphery of the intermediate tube 9. The ring 33 is annular and fitted to the outer periphery of the intermediate tube 9. The ring 33 is provided with an annular groove 33a formed circumferentially on its inner periphery, an insertion hole 33b provided at a position radially opposite the blind hole 31d of the valve block 31 and opening from the bottom of the annular groove 33a and penetrating the wall thickness in the radial direction, and a discharge hole 33c that penetrates the wall thickness from the outer periphery of the lowest end portion in FIG. 2 and leads to the annular groove 33a.

[0053] When the ring 33 is fitted onto the outer periphery of the intermediate cylinder 9, the seal rings 33d and 33e attached to both sides of the annular groove 33a in the axial direction on the inner periphery of the ring 33 are tightly fitted onto the outer periphery of the intermediate cylinder 9. Therefore, when the ring 33 is fitted onto the outer periphery of the intermediate cylinder 9, the annular groove 33a and the discharge hole 33c form an in-tank passage P2.

[0054] The discharge pipe 32 is fitted into the insertion hole 33b of the ring 33, and the annular groove 33a of the ring 33 is connected to the other end of the intra-block passage 31e through the discharge pipe 32. The inside of the discharge pipe 32 is connected to the downward portion of the tank 8 in FIG. 2 via the intra-tank passage P2, and is also connected to the intra-block passage 31e of the valve block 31, so that the intra-block passage 31e is connected to the downward portion of the tank 8 via the discharge pipe 32 and the intra-tank passage P2.

[0055] The adjustable relief valve 30 is provided in the valve block 31 and midway through the intra-block passage 31e, and includes a valve element 30a that opens and closes the intra-block passage 31e, a spring 30b that biases the valve element 30a in a direction that closes the intra-block passage 31e, a pilot passage 30c that applies pressure to the valve element 30a in a direction that opens the intra-block passage 31e, and a solenoid 30d attached to the valve block 31 and that drives the valve element 30a. One end of the intra-block passage 31e is connected to the rod-side chamber 5 via the connecting pipe 18 and the annular passage P1, and the other end is connected to the inside of the tank 8 via the discharge pipe 32 and the intra-tank passage P2. Thus, a discharge passage EP is formed by the intra-block passage 31e, the connecting pipe 18, the annular passage P1, the through-hole 2b, the discharge pipe 32, and the intra-tank passage P2, and the adjustable relief valve 30 is provided midway through the discharge passage EP.

[0056] The pilot passage 30c in the adjustable relief valve 30 applies the pressure in the rod-side chamber 5 to the valve element 30a in the valve-opening direction. The solenoid 30d is attached to the left end of the valve block 31 in FIG. 2 and, although not shown in detail, includes a plunger 30d1, a coil that drives the plunger 30d1, a fixed iron core that attracts the plunger 30d1 when the coil is excited, and a frame 30d2 that accommodates the coil and the fixed iron core. When energized, the solenoid 30d drives the plunger 30d1 in a direction that protrudes from the frame 30d2, thereby applying a thrust to the valve element 30a of the adjustable relief valve 30 that presses the valve element 30a in the valve-opening direction against the biasing force of the spring 30b. The solenoid 30d can adjust the thrust depending on the amount of current supplied, and does not apply thrust to the valve element 30a when not energized.

[0057] In this way, the solenoid 30d can adjust the thrust applied to the valve element 30a depending on the amount of current supplied thereto, and can therefore adjust the valve opening pressure of the adjustable relief valve 30. In the present embodiment, the adjustable relief valve 30 minimizes its valve opening pressure when the amount of current supplied to the solenoid 30d is maximized, and maximizes its valve opening pressure when no current is supplied to the solenoid 30d. When the adjustable relief valve 30 is open, liquid is allowed to move from the rod side chamber 5 to the tank 8 via the discharge passage EP, and the valve opening pressure can be adjusted depending on the amount of current supplied to the solenoid 30d. Therefore, the adjustable relief valve 30 can control the pressure in the upstream rod side chamber 5 that is connected via the discharge passage EP by the amount of current supplied to the solenoid 30d.

[0058] Furthermore, the liquid that has passed through the adjustable relief valve 30 passes through the discharge pipe 32 and the in-tank passage P2 and is discharged below the tank 8 from the discharge hole 33c. Therefore, even if the cylinder device C is used in a horizontal position and the adjustable relief valve 30 is disposed above the outer shell 7, the liquid that has passed through the adjustable relief valve 30 can be discharged below the liquid level in the tank 8. Therefore, even if the adjustable relief valve 30 is disposed above the outer shell 7, it is possible to prevent the liquid that has passed through the adjustable relief valve 30 from being sprayed above the liquid level in the tank 8 and gas from being entrained in the liquid in the tank 8. Note that the positions at which the insertion hole 33b and the discharge hole 33c in the ring 33 are provided relative to the ring 33 can be changed as desired depending on the installation position of the adjustable relief valve 30 relative to the outer shell 7, and therefore, by forming the in-tank passage P2 using the ring 33, the discharge hole 33c can be easily provided below the liquid level in the tank 8 in accordance with the installation position of the adjustable relief valve 30. Furthermore, if the opening position of the discharge hole 33c of the ring 33 in the tank 8 is lower in the tank 8, the effect of preventing gas entrainment is increased, but if the opening position is at least below the liquid level S of the liquid O in the tank 8 as shown in Figure 4, the liquid that has passed through the adjustable relief valve 30 is discharged below the liquid level S, which makes it possible to prevent gas from being entrained in the liquid in the tank 8. Note that the rod 3 is not shown in Figure 4.

[0059] The first on-off valve 40 and the second on-off valve 41 are installed in a valve block 42 attached to the side surface of the bottom cap 13, which is located at the lower side in Figure 2, and together with the valve block 42, form an on-off valve unit. The valve block 42 is connected to the side of the bottom cap 13, and is provided with a pipe insertion hole 42a that opens from the end facing the pump unit 20, which is the left end in Figure 2, and faces the pipe insertion hole 21g of the pump block 21 in the axial direction of the outer shell 7, a first passage 42b that opens from the bottom of the pipe insertion hole 42a and leads to the upper end in Figure 2, and a second passage 42c that branches off from the middle of the first passage 42b and leads to the upper end in Figure 2.

[0060] The first on-off valve 40 is located midway through the first passage 42b, closer to the pipe insertion hole 42a than the connection point with the second passage 42c. The first on-off valve 40 includes a valve element 40a that has a communicating position that opens the first passage 42b and a blocking position that blocks the first passage 42b, a spring 40b that biases the valve element 40a toward the blocking position, and a solenoid 40c that applies a thrust to the valve element 40a against the biasing force of the spring 40b to move it to the communicating position. When the solenoid 40c is not energized, the valve element 40a is in the blocking position and blocks the first passage 42b. When the solenoid 40c is energized, the valve element 40a is in the communicating position and opens, opening the first passage 42b.

[0061] On the other hand, the second on-off valve 41 is provided midway through the second passage 42c. The second on-off valve 41 includes a valve element 41a that has a communicating position that opens the second passage 42c and a blocking position that blocks the second passage 42c, a spring 41b that biases the valve element 41a toward the blocking position, and a solenoid 41c that applies a thrust to the valve element 41a against the biasing force of the spring 41b to move it to the communicating position. When the solenoid 41c is not energized, the valve element 41a is in the blocking position and blocks the second passage 42c. When the solenoid 41c is energized, the valve element 41a is in the communicating position and opens, opening the second passage 42c.

[0062] When the valve block 42 in the on-off valve unit configured in this manner is connected to the bottom cap 13, the first passage 42b is connected to the piston-side chamber communicating passage 13d in the bottom cap 13, and the second passage 42c is connected to the tank communicating passage 13e. Furthermore, when the valve block 42 in the on-off valve unit is connected to the bottom cap 13, the pipe insertion hole 42a in the valve block 42 and the pipe insertion hole 21g in the pump block 21 face each other in the axial direction of the outer shell 7. An outer pipe 50 that connects the first passage 42b and the branch passage 21h is bridged between the pipe insertion hole 42a and the pipe insertion hole 21g that face each other in this manner.

[0063] The outer piping 50 is formed of a metal pipe, and by fitting one end into the pipe insertion hole 42a and the other end into the pipe insertion hole 21g, the outer piping 50 is disposed outside the outer shell 7 and fixed between the valve block 42 of the on-off valve unit and the pump block 21 of the pump unit 20. Note that the outer piping 50 may be formed of, for example, a flexible pressure-resistant hose instead of a pipe.

[0064] One end of the first passage 42b in which the first on-off valve 40 is provided communicates with the rod-side chamber 5 via the external piping 50, the branch passage 21h and the supply passage 21f in the pump block 21, the connecting pipe 17, the annular passage P1, and the through hole 2b, and the other end communicates with the piston-side chamber 6 via the piston-side chamber communicating passage 13d and the vertical hole 11b. Thus, when the first on-off valve 40 is opened, the rod-side chamber 5 and the piston-side chamber 6 are brought into communication with each other via the first passage 42b, and when the first on-off valve 40 is closed, the first passage 42b is shut off and communication between the rod-side chamber 5 and the piston-side chamber 6 via the first passage 42b is cut off.

[0065] Furthermore, one end of the second passage 42c in which the second on-off valve 41 is provided is connected to the piston side chamber 6 via the first passage 42b, the piston side chamber communicating passage 13d, and the vertical hole 11b, and the other end is connected to the tank 8 via the tank communicating passage 13e and the notched groove 13c. Therefore, when the second on-off valve 41 is opened, the piston side chamber 6 and the tank 8 are placed in a state of communication via the second passage 42c, and when the second on-off valve 41 is closed, the second passage 42c is shut off, and communication between the piston side chamber 6 and the tank 8 via the second passage 42c is cut off.

[0066] The cylinder device C is configured as described above, and the operation of the cylinder device C will be described below. First, the operation of the cylinder device C will be described in a state where the pump 22 is stopped and the first on-off valve 40 and the second on-off valve 41 are both closed. In a state where the pump 22 is stopped and the first on-off valve 40 and the second on-off valve 41 are both closed, the cylinder device C functions as a passive damper.

[0067] In the cylinder device C functioning as a passive damper, when the telescopic unit 1 is extended, the piston 4 moves leftward in FIG. 2 relative to the cylinder 2, thereby reducing the rod-side chamber 5 and expanding the piston-side chamber 6. In this case, the check valve 14a provided in the middle of the rectification passage 14 closes under pressure from the rod-side chamber 5, and the liquid in the contracted rod-side chamber 5 moves toward the tank 8 through the discharge passage EP formed by the intra-block passage 31e, the connecting pipe 18, the annular passage P1, the through hole 2b, the discharge pipe 32, and the intra-tank passage P2, and the variable relief valve 30.

[0068] Because resistance is provided to this movement of liquid by the adjustable relief valve 30, the pressure in the rod-side chamber 5 is adjusted to be higher than the tank 8 and equal to the valve opening pressure of the adjustable relief valve 30. Furthermore, the volume of the piston-side chamber 6 expands due to the movement of the piston 4, causing a shortage of liquid, but this shortage of liquid is supplied from the tank 8 to the piston-side chamber 6 via the suction passage 19 when the check valve 19a opens. Therefore, the pressure in the piston-side chamber 6 becomes approximately equal to the pressure in the tank 8.

[0069] In this way, when the telescopic unit 1 is extended, the pressure in the rod side chamber 5 acting on the rod side chamber side of the piston 4 becomes higher than the pressure in the piston side chamber 6 acting on the piston side chamber side of the piston 4, and the cylinder device C generates an extension-side damping force that hinders the extension of the telescopic unit 1. In addition, the liquid equivalent to the volume of the rod 3 withdrawn from the cylinder 2 is supplied from the tank 8 to the piston side chamber 6, thereby compensating for the volume of the rod 3 withdrawn from the cylinder 2. In addition, since the valve opening pressure of the variable relief valve 30 can be adjusted depending on the amount of current supplied to the solenoid 30d, the damping force generated by the cylinder device C when the telescopic unit 1 is extended can be adjusted.

[0070] When the liquid passes through the variable relief valve 30, the flow rate increases and it passes through the discharge pipe 32 and the tank internal passage P2 to reach the tank 8. However, the flow rate slows as the liquid passes through the annular groove 33a of the ring 33 that forms the tank internal passage P2, and the discharge hole 33c of the ring 33, which is the outlet end to the tank 8, opens below the tank 8. Therefore, the liquid that has passed through the variable relief valve 30 can be prevented from drawing in gas within the tank 8, and the intrusion of gas into the cylinder 2 can be prevented, thereby maintaining good damping force generation responsiveness of the cylinder device C.

[0071] Furthermore, the discharge hole 33c, which is the outlet end of the discharge passage EP, is located on the rod guide side of the tank 8 and is sufficiently separated from the suction passage 19 provided in the bottom cap 13 within the tank 8, which prevents liquid from being sucked into the cylinder 2 from the tank 8 via the suction passage 19 immediately after passing through the variable relief valve 30, which may entrain gas during the extension operation of the telescopic unit 1.

[0072] Therefore, in the cylinder device C of this embodiment, the intrusion of gas into the cylinder 2 can be more effectively suppressed, and the damping force generation responsiveness of the cylinder device C can be maintained even better.

[0073] Next, we will explain the operation when the telescopic unit 1 of the cylinder device C functions as a passive damper and is contracted. When the telescopic unit 1 is contracted, the piston 4 moves to the right in Fig. 2 relative to the cylinder 2, so the piston side chamber 6 is contracted and the rod side chamber 5 is expanded. In this case, the check valve 19a provided in the suction passage 19 is closed by the pressure in the piston side chamber 6, while the check valve 14a provided in the flow rectification passage 14 is opened by the pressure in the piston side chamber 6, so the liquid in the contracting piston side chamber 6 moves through the flow rectification passage 14 to the expanding rod side chamber 5.

[0074] Furthermore, when the telescopic unit 1 is retracted, the rod 3 enters the cylinder 2, and the cylinder 2 has an excess of liquid corresponding to the volume of the rod 3 entering the cylinder 2. This excess liquid in the cylinder 2 moves toward the tank 8 through the discharge passage EP and the adjustable relief valve 30, just as it did during the extension operation. Since the adjustable relief valve 30 provides resistance to this movement of liquid, the pressure in the rod-side chamber 5 is adjusted to be higher than the tank 8 and equal to the valve opening pressure of the adjustable relief valve 30. Furthermore, since the piston-side chamber 6 is in communication with the rod-side chamber 5 through the rectification passage 14, the pressure in the piston-side chamber 6 and the pressure in the rod-side chamber 5 become approximately equal.

[0075] In this way, when the telescopic unit 1 is retracted, the pressure in the rod side chamber 5 acting on the rod side chamber side of the piston 4 and the pressure in the piston side chamber 6 acting on the piston side chamber side of the piston 4 become approximately equal, but since the pressure receiving area receiving the pressure in the piston side chamber 6 is larger than the pressure receiving area receiving the pressure in the rod side chamber 5 of the piston 4, the cylinder device C generates a compression side damping force that hinders the retraction. The valve opening pressure of the variable relief valve 30 can be adjusted depending on the amount of current supplied to the solenoid 30d, so the damping force generated by the cylinder device C when the telescopic unit 1 is retracted can be adjusted to a high or low level. In addition, the liquid equivalent to the volume of the rod 3 entering the cylinder 2 is discharged from the cylinder 2 to the tank 8, thereby compensating for the volume of the rod 3 entering the cylinder 2.

[0076] In this way, the cylinder device C of this embodiment generates a damping force when it performs an extension / contraction operation, and functions as a damper that damps the vibration of the object to be damped. In the case of this cylinder device C, the cross-sectional area of ​​the rod 3 is half that of the piston 4, so that the pressure-receiving area on the rod-side chamber side of the piston 4 is half that of the piston-side chamber side. Therefore, the flow rate of liquid discharged from inside the cylinder 2 to the tank 8 via the adjustable relief valve 30 is equal when the cylinder device C is extended and when it is retracted. Therefore, if the valve opening pressure of the adjustable relief valve 30 is the same, the cylinder device C can exert equal damping force when the moving speed of the piston 4 is the same during extension and retraction.

[0077] Next, the operation of the cylinder device C when the pump 22 is stopped and the first on-off valve 40 or the second on-off valve 41 is opened will be described. When the pump 22 is stopped, the first on-off valve 40 is opened, and the second on-off valve 41 is closed, the cylinder device C functions as a one-sided damper that generates a damping force only during a contraction operation, and when the pump 22 is stopped, the first on-off valve 40 is closed, and the second on-off valve 41 is opened, the cylinder device C functions as a one-sided damper that generates a damping force only during an extension operation.

[0078] In the cylinder device C, when the pump 22 is stopped, the first on-off valve 40 is open, and the second on-off valve 41 is closed, when the telescopic unit 1 is extended, the piston 4 moves leftward in FIG. 2 relative to the cylinder 2, thereby reducing the rod-side chamber 5 and expanding the piston-side chamber 6. With the first on-off valve 40 open, the rod-side chamber 5 and the piston-side chamber 6 are in communication with each other via the first passage 42b, the external piping 50, the branch passage 21h, the supply passage 21f, the connecting pipe 17, the annular passage P1, the through-hole 2b, the piston-side chamber communicating passage 13d, and the vertical hole 11b. Therefore, liquid can freely move from the rod-side chamber 5 to the piston-side chamber 6. Furthermore, when the telescopic unit 1 is extended, the rod 3 retracts from the cylinder 2, and the liquid equivalent to the volume of the retracted rod 3 is supplied from the tank 8 via the suction passage 19. Therefore, when the telescopic unit 1 performs the extension operation, the pressure in the rod side chamber 5 and the piston side chamber 6 becomes equal to the tank pressure, so the cylinder device C becomes unloaded and performs the extension operation without resistance.

[0079] Next, we will explain the operation when the telescopic unit 1 of the cylinder device C is retracted when the pump 22 is stopped, the first on-off valve 40 is opened, and the second on-off valve 41 is closed. When the telescopic unit 1 is retracted, the piston 4 moves to the right in Fig. 2 relative to the cylinder 2, thereby reducing the piston side chamber 6 and expanding the rod side chamber 5. In this case, the check valve 19a provided in the suction passage 19 closes due to the pressure in the piston side chamber 6, while the rod side chamber 5 and the piston side chamber 6 are connected by the opening of the first on-off valve 40, so the liquid in the reduced piston side chamber 6 passes through the first on-off valve 40 and moves to the expanded rod side chamber 5.

[0080] Furthermore, when the telescopic unit 1 is retracted, the rod 3 enters the cylinder 2, and the cylinder 2 has an excess of liquid corresponding to the volume of the rod 3 entering the cylinder 2. This excess liquid in the cylinder 2 moves toward the tank 8 through the discharge passage EP and the adjustable relief valve 30, just as it did during the extension operation. Since the adjustable relief valve 30 provides resistance to this movement of liquid, the pressure in the rod-side chamber 5 is adjusted to be higher than the tank 8 and equal to the valve opening pressure of the adjustable relief valve 30. Furthermore, since the piston-side chamber 6 is in communication with the rod-side chamber 5 through the rectification passage 14, the pressure in the piston-side chamber 6 and the pressure in the rod-side chamber 5 become approximately equal.

[0081] Therefore, when the telescopic unit 1 is retracted, the pressure in the rod side chamber 5 acting on the rod side chamber side of the piston 4 and the pressure in the piston side chamber 6 acting on the piston side chamber side of the piston 4 become approximately equal, but since the pressure receiving area receiving the pressure in the piston side chamber 6 is larger than the pressure receiving area receiving the pressure in the rod side chamber 5 of the piston 4, the cylinder device C generates a compression side damping force that hinders the retraction. Note that the valve opening pressure of the variable relief valve 30 can be adjusted depending on the amount of current supplied to the solenoid 30d, so the damping force generated by the cylinder device C when the telescopic unit 1 is retracted can be adjusted to a high or low level. In addition, the liquid equivalent to the volume of the rod 3 entering the cylinder 2 is discharged from the cylinder 2 to the tank 8, thereby compensating for the volume of the rod 3 entering the cylinder 2.

[0082] In this way, when the pump 22 is stopped, the first opening / closing valve 40 is opened, and the second opening / closing valve 41 is closed, the cylinder device C functions as a one-sided damper that generates a damping force only during contraction operation.

[0083] On the other hand, in the cylinder device C when the pump 22 is stopped, the first on-off valve 40 is closed, and the second on-off valve 41 is open, when the telescopic unit 1 is extended, the piston 4 moves to the left in FIG. 2 relative to the cylinder 2, thereby reducing the rod-side chamber 5 and expanding the piston-side chamber 6. In this case, the check valve 14a provided in the middle of the rectification passage 14 closes due to the pressure in the rod-side chamber 5, so the liquid in the reduced-size rod-side chamber 5 moves toward the tank 8 through the discharge passage EP and the adjustable relief valve 30.

[0084] Because resistance is provided to this movement of liquid by the adjustable relief valve 30, the pressure in the rod-side chamber 5 is adjusted to be higher than the tank 8 and equal to the valve opening pressure of the adjustable relief valve 30. Furthermore, the volume of the piston-side chamber 6 expands due to movement of the piston 4, causing a shortage of liquid, but this shortage of liquid is supplied from the tank 8 to the piston-side chamber 6 via the second passage 42c, the first passage 42b, the piston-side-chamber communicating passage 13d, the vertical hole 11b, the tank communicating passage 13e, and the notched groove 13c when the second on-off valve 41 opens. Therefore, liquid can freely move from the tank 8 to the piston-side chamber 6, and the pressure in the piston-side chamber 6 becomes approximately equal to the pressure in the tank 8.

[0085] As described above, during the extension operation of the telescopic unit 1, the pressure in the rod side chamber 5 acting on the rod side chamber side of the piston 4 becomes higher than the pressure in the piston side chamber 6 acting on the piston side chamber side of the piston 4, and the cylinder device C generates an extension-side damping force that hinders the extension operation of the telescopic unit 1. Also, liquid equivalent to the volume of the rod 3 withdrawn from the cylinder 2 is supplied from the tank 8 to the piston side chamber 6, thereby compensating for the volume of the rod 3 withdrawing from the cylinder 2. Also, since the valve opening pressure of the variable relief valve 30 can be adjusted depending on the amount of current supplied to the solenoid 30d, the damping force generated by the cylinder device C during the extension operation of the telescopic unit 1 can be adjusted to a high or low level. As described above, the cylinder device C of this embodiment generates a damping force during the extension operation and functions as a damper that attenuates the vibration of the target to be damped.

[0086] Next, we will explain the operation when the telescopic unit 1 of the cylinder device C is retracted when the pump 22 is stopped, the first on-off valve 40 is closed, and the second on-off valve 41 is open. When the telescopic unit 1 is retracted, the piston 4 moves to the right in FIG. 2 relative to the cylinder 2, thereby reducing the piston side chamber 6 and expanding the rod side chamber 5. In this case, since the second on-off valve 41 is open, liquid can move freely between the piston side chamber 6 and the tank 8 through the second on-off valve 41. In addition, since the check valve 14a provided in the flow rectification passage 14 opens under the pressure of the piston side chamber 6, liquid in the reduced piston side chamber 6 moves via the flow rectification passage 14 to the expanded rod side chamber 5.

[0087] Furthermore, when the telescopic unit 1 is retracted, the rod 3 enters the cylinder 2, causing an excess of liquid in the cylinder 2 by the volume of the rod 3 entering the cylinder 2. This excess liquid in the cylinder 2 is discharged from the piston side chamber 6 to the tank 8 through the second on-off valve 41, so the liquid cannot pass through the discharge passage EP and the adjustable relief valve 30. Therefore, the pressure in the rod side chamber 5 and the piston side chamber 6 becomes the tank pressure, and the cylinder device C enters an unloaded state and performs retraction without resistance.

[0088] In this way, when the pump 22 is stopped, the first opening / closing valve 40 is closed, and the second opening / closing valve 41 is opened, the cylinder device C functions as a one-sided damper that generates a damping force only during extension operation.

[0089] Furthermore, as mentioned above, when the first opening / closing valve 40 is opened, the cylinder device C is in an unloaded state during extension operation, and when the second opening / closing valve 41 is opened, the cylinder device C is in an unloaded state during contraction operation. Therefore, when both the first opening / closing valve 40 and the second opening / closing valve 41 are opened, the cylinder device C is in an unloaded state during both extension and contraction, and no damping force is generated.

[0090] Next, we will explain the operation when the cylinder device C is made to function as an actuator. First, we will explain the case when the cylinder device C is made to exert thrust in the extension direction. When making the telescopic unit 1 exert thrust in the extension direction, which is the direction pushing it to the left in FIG. 2, the first on-off valve 40 is opened and the second on-off valve 41 is closed, while the pump 22 is driven and the valve opening pressure of the adjustable relief valve 30 is adjusted to be the thrust desired to be output to the cylinder device C. In this state, liquid is supplied from the pump 22 to the rod-side chamber 5, while the first on-off valve 40 is open, thereby communicating the rod-side chamber 5 and the piston-side chamber 6 via the first on-off valve 40, and the second on-off valve 41 is closed, thereby cutting off communication between the piston-side chamber 6 and the tank 8 via the second on-off valve 41.

[0091] Liquid is supplied from the pump 22 into the cylinder 2, and the pressure in the rod side chamber 5 and the piston side chamber 6 is adjusted to be equal to the valve opening pressure of the adjustable relief valve 30, so the telescopic unit 1 generates a thrust in the extension direction equal to the pressure difference multiplied by the pressure.The cylinder device C can adjust the pressure in the rod side chamber 5 and the piston side chamber 6 with the adjustable relief valve 30, so it can make the telescopic unit 1 exert a thrust in the extension direction and control this thrust.

[0092] On the other hand, a case where the cylinder device C is made to exert a thrust in the contraction direction will be described. When the telescopic unit 1 is made to exert a thrust in the contraction direction, which is a direction pushing it to the right in FIG. 2, the first on-off valve 40 is closed and the second on-off valve 41 is opened, while the pump 22 is driven and the valve opening pressure of the adjustable relief valve 30 is adjusted to be the thrust desired to be output to the cylinder device C. In this state, liquid is supplied from the pump 22 to the rod-side chamber 5, while the first on-off valve 40 is closed, cutting off communication between the rod-side chamber 5 and the piston-side chamber 6 via the first on-off valve 40, and the second on-off valve 41 is opened, connecting the piston-side chamber 6 to the tank 8 via the second on-off valve 41.

[0093] In this state, the first on-off valve 40 is closed, so liquid is supplied only to the rod side chamber 5 from the pump 22, and the pressure in the rod side chamber 5 is adjusted to the valve opening pressure of the adjustable relief valve 30, while the piston side chamber 6 is connected to the tank 8 via the second on-off valve 41, so the pressure in the piston side chamber 6 becomes the tank pressure. Therefore, if the tank pressure is considered to be 0, the telescopic unit 1 generates a rightward thrust of a value obtained by multiplying the pressure in the rod side chamber 5 by the pressure-receiving area on the rod side chamber side of the piston 4. And, because the cylinder device C can adjust the pressure in the rod side chamber 5 with the adjustable relief valve 30, it can make the telescopic unit 1 exert a thrust in the direction of contraction itself and control this thrust.

[0094] As described above, the cylinder device C of this embodiment comprises: the cylinder 2; the rod 3 inserted into the cylinder 2 so as to be movably in the axial direction; the piston 4 inserted into the cylinder 2 so as to be movably in the axial direction and connected to the rod 3, and dividing the interior of the cylinder 2 into a rod-side chamber 5 and a piston-side chamber 6; the telescopic unit 1 having the cylindrical outer shell 7 arranged on the outer periphery of the cylinder 2 and forming the tank 8 for storing liquid between the outer shell 7 and the cylinder 2; the pump unit 20 having the pump 22 arranged between the rod-side chamber 5 and the tank 8 and capable of supplying liquid from the tank 8 to the rod-side chamber 5 and the motor 23 for driving the pump 22; the variable relief valve 30 arranged between the rod-side chamber 5 and the tank 8 and providing resistance to the flow of liquid from the rod-side chamber 5 to the tank 8; the first on-off valve 40 arranged between the rod-side chamber 5 and the piston-side chamber 6; and the second on-off valve 41 arranged between the piston-side chamber 6 and the tank 8, and a part of the passage connecting the rod-side chamber 5 and the first on-off valve 40 is formed by the outer piping 50 arranged outside the outer shell 7. Since the outer piping 50 is installed in the unused space between the pump unit 20 and the on-off valve unit where nothing has been placed in the past, the installation of the outer piping 50 does not result in an increase in the size of the cylinder device C.

[0095] In the cylinder device C configured in this manner, the rod-side chamber 5 and the piston-side chamber 6 need to be communicated with each other in order to switch between communication and cut-off between the rod-side chamber 5 and the piston-side chamber 6 using the first on-off valve 40. However, because part of the passage connecting the rod-side chamber 5 and the first on-off valve 40 is formed by the external piping 50 arranged outside the outer shell 7, even if the capacity of the pump 22 is increased and the motor 23 is made larger to ensure thrust during high-speed extension and contraction, it is not necessary to install a pipe that connects the rod-side chamber 5 and the piston-side chamber 6 over the entire axial length of the tank 8 inside the outer shell 7, and the outer diameter of the outer shell 7 can be reduced. When the outer diameter of the outer shell 7 is reduced, the pump unit 20 and the adjustable relief valve 30 are disposed radially closer to the center of the cylinder device C by the amount of the reduced diameter of the outer shell 7, and the bottom cap 13 that closes the end of the outer shell 7 is also reduced in size in the radial direction, so the on-off valve unit is also disposed correspondingly closer to the center of the cylinder device C. Furthermore, since the outer piping 50 is placed in the unused space between the pump unit 20 and the on-off valve unit where nothing was previously placed, installation of the outer piping 50 does not result in an increase in size of the cylinder device C. As described above, according to the cylinder device C of this embodiment, even if the motor 23 is increased in size, use of the outer piping 50 makes it unnecessary to install a pipe that runs the entire axial length of the tank 8 inside the outer shell 7, allowing the outer diameter of the outer shell 7 to be reduced and the cylinder device C to be made more compact.

[0096] Therefore, according to the cylinder device C of the present embodiment, even if the pump unit 20 is increased in size, the diameter of the outer shell 7 can be reduced to avoid an increase in the overall size of the cylinder device C, so that sufficient thrust can be exerted even when extending and retracting at high speed, while also achieving good mountability. Also, since there is no need to install a passage in the bottom cap 13 for communicating the first on-off valve 40 with the rod-side chamber 5, the number of passages installed in the bottom cap 13 can be reduced, which is advantageous in that the bottom cap 13 can be made more compact.

[0097] The telescopic unit 1 in the cylinder device C of this embodiment is provided with an intermediate cylinder 9 that is disposed between the cylinder 2 and the outer shell 7, covers at least a portion of the cylinder 2, and forms an annular passage P1 between the cylinder 2 and the intermediate cylinder 9, which is in communication with the rod-side chamber 5. The pump 22, the variable relief valve 30, and the first on-off valve 40 are connected to the rod-side chamber 5 via the annular passage.

[0098] According to the cylinder device C configured in this manner, by providing the intermediate cylinder 9, it is possible to easily form the annular passage P1 that communicates with the rod-side chamber 5 between the cylinder 2 and the outer shell 7. Furthermore, according to the cylinder device C configured in this manner, it is only necessary to connect the pump unit 20 and the adjustable relief valve 30 to the annular passage P1, so the pump unit 20 and the adjustable relief valve 30 can be installed at any position in the circumferential direction and axial direction on the outer periphery of the outer shell 7. This makes it possible to optimize the installation locations of the pump unit 20 and the adjustable relief valve 30 on the outer shell 7 depending on the installation target of the cylinder device C, further improving the mountability of the cylinder device C. Furthermore, since the intermediate cylinder 9 does not need to cover the entire length of the cylinder 2 in accordance with the installation locations of the pump unit 20 and the adjustable relief valve 30 on the outer shell 7, the capacity of the tank 8 is not unnecessarily reduced.

[0099] Furthermore, the telescopic unit 1 in the cylinder device C of this embodiment has a base 16 that is attached to the outer periphery of the outer shell 7 and has a mounting surface 16c on which the pump unit 20 is attached, and a line X that is perpendicular to the mounting surface 16c and passes through the center of the mounting surface 16c and is in a twisted position with respect to the axis Y of the telescopic unit 1.

[0100] According to the cylinder device C configured in this manner, the line X that is perpendicular to the mounting surface 16c and passes through the center of the mounting surface 16c and the axis Y of the outer shell 7 are in a twisted position where they do not intersect with each other, and the mounting surface 16c is positioned at an offset position relative to the outer shell 7, so that the pump unit 20 attached to the base 16 can be attached at an offset position relative to the outer shell 7, making it easy to avoid interference between the pump unit 20 and other components in the installation target of the cylinder device C, further improving the mountability of the cylinder device C on the installation target.

[0101] In addition, if there is no need to radially offset the pump unit 20 from the outer shell 7 of the cylinder device C in this manner, a line Z that is perpendicular to the mounting surface 16c on the base 16 and passes through the center of the mounting surface 16c may be set to pass through the axis Y of the telescopic unit 1.

[0102] Furthermore, in the cylinder device C of this embodiment, the variable relief valve 30 is attached to the outer periphery of the outer shell 7 and is provided with a discharge passage EP that connects the variable relief valve 30 to the tank 8, and the discharge passage EP is formed by a discharge pipe line 32 that extends from the variable relief valve 30 into the tank 8, and an annular intra-tank passage P2 that is provided in a ring 33 that fits onto the outer periphery of the intermediate cylinder 9 and is connected to the discharge pipe line 32, and is also connected to a part of the tank 8 that is at least below the liquid level.

[0103] According to the cylinder device C configured in this manner, the flow rate of the liquid that has passed through the variable relief valve 30 is reduced by the tank internal passage P2, while the liquid is discharged from below the liquid level S of the liquid O in the tank 8. This prevents the liquid that has passed through the variable relief valve 30 from drawing in gas in the tank 8, and prevents gas from entering the cylinder 2, thereby maintaining good damping force generation responsiveness of the cylinder device C.

[0104]

[0047] In the above description, the first on-off valve 40 is attached to the bottom cap 13, but in cases where the rod guide 10 protrudes outward from the end of the outer shell 7 and the first on-off valve 40 is attached to the rod guide 10, as in the cylinder device C1 in a modified example shown in Fig. 5, or where the first on-off valve 40 is attached to the rod guide 10 of the outer shell 7 in the vicinity of the rod guide 10, part of the passage connecting the first on-off valve 40 to the piston side chamber 6 may be formed using the external piping 60 arranged outside the outer shell 7. Also, the first on-off valve 40 and the second on-off valve 41 are aggregated together in the valve block 42 to form an on-off valve unit, but the first on-off valve 40 and the second on-off valve 41 may be attached separately to the telescopic unit 1, or the first on-off valve 40 may be aggregated in the pump unit 20 or the valve block 31 that houses the adjustable relief valve 30.

[0105] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims. [Explanation of symbols]

[0106] 1 Telescopic unit, 2 Cylinder, 3 Rod, 4 Piston, 5 Rod side chamber, 6 Piston side chamber, 7 Outer shell, 8 Tank, 9 Intermediate cylinder, 16 Base, 16c Mounting surface, 20 Pump unit, 22 Pump, 23 Motor, 30 Adjustable relief valve, 32 Discharge pipe line, 33 Ring, 40 First on-off valve, 41 Second on-off valve, 50, 60 External piping, C, C1 Cylinder device, EP Discharge passage, O Liquid, P1 Annular passage, P2 Inner tank passage, S Liquid level

Claims

1. a telescopic unit including a cylinder, a rod inserted into the cylinder so as to be movably axially, a piston inserted into the cylinder so as to be movably axially and connected to the rod, the piston dividing the interior of the cylinder into a rod-side chamber and a piston-side chamber, and a cylindrical outer shell disposed on the outer periphery of the cylinder and forming a tank for storing liquid between the outer shell and the cylinder; a pump unit provided between the rod side chamber and the tank, the pump being capable of supplying liquid from the tank to the rod side chamber, and the pump being configured to drive a motor; a variable relief valve provided between the rod side chamber and the tank to provide resistance to the flow of liquid from the rod side chamber toward the tank; a first on-off valve provided between the rod side chamber and the piston side chamber; a second on-off valve provided between the piston-side chamber and the tank, A part of the passage connecting the rod side chamber and the first on-off valve or a part of the passage connecting the piston side chamber and the first on-off valve is formed by an outer pipe arranged outside the outer shell. A cylinder device characterized by:

2. the telescopic unit has an intermediate cylinder provided between the cylinder and the outer shell, covering at least a portion of the cylinder and forming an annular passage between the cylinder and the intermediate cylinder and communicating with the rod-side chamber, The pump, the variable relief valve, and the first on-off valve are connected to the rod side chamber via the annular passage.

2. The cylinder device according to claim 1.

3. The variable relief valve is attached to the outer periphery of the outer shell, a discharge passage that connects the variable relief valve to the tank; The discharge passage is a discharge line extending from the variable relief valve into the tank; an annular tank passage provided in a ring fitted to the outer periphery of the intermediate cylinder, which is in communication with the discharge pipe line and is in communication with at least a portion below the liquid level in the tank; 3. The cylinder device according to claim 2.

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