JP7680931B2 - Cylinder Unit - Google Patents

Description

The present invention relates to a cylinder device.

Conventionally, this type of cylinder device has been used, for example, as a vibration damping device for railway vehicles that suppresses vibrations in the left-right direction relative to the direction of travel of the car body. A vibration damping device for railway vehicles is composed of multiple cylinder devices interposed between the car body and the bogie, and suppresses vibrations of the car body by the thrust or damping force exerted by the cylinder devices.

A conventional cylinder device is, for example, composed of a cylinder, a piston slidably inserted into the cylinder, a rod inserted into the cylinder and connected to the piston, a rod side chamber and a piston side chamber partitioned by the piston within the cylinder, a tank, and an electromagnetic relief valve provided midway through a damping passage connecting the rod side chamber and the tank (see, for example, Patent Document 1).

Conventional cylinder devices use an electromagnetic relief valve to control the pressure inside the cylinder, adjusting the thrust or damping force generated by the cylinder device to suppress vibrations in the body of the railway vehicle.

Furthermore, conventional cylinder devices are provided with a passageway that passes through a damping valve downstream of the electromagnetic relief valve, and a bypass path that is parallel to the passageway, and a switching valve can be used to select and switch between the passageway and the bypass path. In conventional cylinder devices configured in this way, when large vibrations are input, the switching valve selects the passageway in which the damping valve is provided, and the damping valve exerts a high damping force, making it possible to suppress vibrations of the car body of the railway vehicle even in the event of large vibration input.

JP 2019-043296 A

However, in conventional cylinder devices, when large vibrations are input and the pressure inside the cylinder becomes very high, high pressure acts on the electromagnetic relief valve, so an electromagnetic relief valve that can withstand high pressure must be used. This requires measures such as increasing the thickness of the components of the electromagnetic relief valve to ensure the strength of the electromagnetic relief valve, which increases the weight of the electromagnetic relief valve, and creates problems such as an increase in the weight and cost of the entire cylinder device.

Therefore, the present invention aims to provide a cylinder device that can reduce weight and costs.

The cylinder device of the present invention is characterized by comprising a cylinder filled with liquid, a piston inserted axially movably into the cylinder and dividing the interior of the cylinder into a rod side chamber and a piston side chamber, a cylinder body having a rod inserted axially movably into the cylinder and connected to the piston, a tank for storing liquid, a first opening/closing valve for switching between communication between the rod side chamber and the piston side chamber and between communication between the piston side chamber and the tank, a damping passage through which the liquid passes when the cylinder body is extended or retracted, a bypass damping passage parallel to the damping passage, a damping valve provided in the damping passage, a bypass damping passage damping valve provided in the bypass damping passage, and a directional control valve provided upstream of the damping valve, which opens the damping passage and closes the bypass damping passage when the pressure on the upstream side is less than a predetermined pressure, and closes the damping passage and opens the bypass damping passage when the pressure on the upstream side is equal to or greater than the predetermined pressure.

Another cylinder device of the present invention includes a cylinder filled with liquid, a piston inserted axially movably into the cylinder and dividing the interior of the cylinder into a rod side chamber and a piston side chamber, a cylinder body having a rod inserted axially movably into the cylinder and connected to the piston, a tank for storing liquid, a first opening/closing valve for switching between communication between the rod side chamber and the piston side chamber and between blocking communication, a second opening/closing valve for switching between communication between the piston side chamber and the tank and between blocking communication, a damping passage through which the liquid passes when the cylinder body is expanded or contracted, and a bypass damping valve arranged in parallel with the damping passage. It is characterized by comprising a damping passage, a damping valve provided in the damping passage, a bypass damping passage damping valve provided in the bypass damping passage, a damping passage opening/closing valve provided upstream of the damping passage damping valve, which opens the damping passage when the upstream pressure is less than a predetermined pressure and closes the damping passage when the upstream pressure is equal to or greater than the predetermined pressure, and a bypass damping passage opening/closing valve provided upstream of the bypass damping passage damping valve in the bypass damping passage, which closes the bypass damping passage when the upstream pressure is less than the predetermined pressure and opens the bypass damping passage when the upstream pressure is equal to or greater than the predetermined pressure.

With this cylinder device, when the upstream pressure during extension and retraction reaches or exceeds a predetermined pressure, the directional control valve blocks the damping passage and opens the bypass damping passage, or when the upstream pressure during extension and retraction reaches or exceeds a predetermined pressure, the damping passage opening/closing valve blocks the damping passage and the bypass damping passage opening/closing valve opens the bypass damping passage. This prevents the damping valve from being exposed to high pressure, protecting the damping valve, while still allowing the bypass damping passage damping valve to exert a damping force.

In addition, a cylinder device equipped with a damping passage opening/closing valve that is provided upstream of the damping valve in the damping passage and opens and closes the damping passage, and a bypass damping passage opening/closing valve that is provided upstream of the bypass damping passage damping valve in the bypass damping passage and opens and closes the bypass damping passage, allows switching between the damping passage and the bypass damping passage with multiple lightweight and small opening/closing valves, and the entire device can be made smaller by appropriately arranging the opening/closing valves.

The cylinder device may further include a common passage connected to the piston side chamber, a first passage having one end connected to the rod side chamber via a damping passage and connected to the piston side chamber via a common passage and provided with a first on-off valve, a second passage having one end connected to the piston side chamber via the common passage and connected to the tank and provided with a second on-off valve, and a common passage on-off valve provided in the common passage.

With a cylinder device configured in this manner, not only can an increase in the weight of the components of the damping passage and damping valve be avoided, but by providing a common passage opening/closing valve, the first passage, second passage, first opening/closing valve, and second opening/closing valve can be prevented from being exposed to high pressure, so that an increase in the weight of the components of the first passage, second passage, first opening/closing valve, and second opening/closing valve can be avoided, and the weight and cost of the entire device can be reduced more effectively.

FIG. 2 is a diagram showing the cylinder device when mounted on a railway vehicle. FIG. 2 is a hydraulic circuit diagram of the cylinder device according to the first embodiment. FIG. 4 is a hydraulic circuit diagram of a cylinder device in a first modified example of the first embodiment. FIG. 11 is a hydraulic circuit diagram of a cylinder device in a second modified example of the first embodiment. FIG. 11 is a hydraulic circuit diagram of a cylinder device according to a second embodiment.

The present invention will be described below based on the embodiment shown in the drawings. Note that the same reference numerals are used for configurations common to the cylinder devices C1, C2, C3, and C4 of each embodiment described below, and in order to avoid duplication of explanation, detailed explanations of the configurations described in the explanation of the first embodiment will be omitted in the explanations of the other embodiments. Note that in this embodiment, the cylinder devices C1, C2, C3, and C4 are used to damp vibrations of the car body B of the railway vehicle V, but the cylinder devices C1, C2, C3, and C4 may be used for purposes other than damping vibrations of the railway vehicle V.

First Embodiment
As shown in Fig. 1, the cylinder device C1 in the first embodiment is interposed between a car body B and a bogie T of a railway vehicle V, and is used for vibration control of the car body B. In the case of the railway vehicle V, the cylinder device C1 is connected to a pin P hanging down below the car body B, and is interposed in parallel in pairs between the car body B and the bogie T. The bogie T holds the wheels W rotatably, and a suspension spring CS is interposed between the car body B and the bogie T, and the car body B is elastically supported from below, allowing the car body B to move laterally relative to the bogie T.

As shown in FIG. 2, the cylinder device C1 includes a cylinder body 1, a tank 8 for storing liquid, a first opening/closing valve 12, a second opening/closing valve 14, a damping passage 21 through which liquid passes when the cylinder body 1 expands or contracts, a bypass damping passage 25 arranged in parallel with the damping passage 21, a variable relief valve 22 as a damping valve provided in the damping passage 21, a bypass damping passage damping valve 26 provided in the bypass damping passage 25 and providing a greater resistance to the flow of liquid than the variable relief valve 22, and a directional control valve 28.

The components of the cylinder device C1 of the first embodiment will be described in detail below. As shown in FIG. 2, the cylinder body 1 includes a cylinder 2 filled with liquid, a piston 3 inserted axially movably into the cylinder 2 to divide the cylinder 2 into a rod side chamber 5 and a piston side chamber 6, a rod 4 inserted axially movably into the cylinder 2 and connected to the piston 3, and an outer cylinder 7 covering the cylinder 2 and the outer periphery of the cylinder 2. The cylinder device C1 is interposed between the car body B and the bogie T, with the cylinder 2 connected to the car body B of the railway vehicle V and the rod 4 connected to the bogie T.

The openings at the left end side in FIG. 2 of the cylinder 2 and the outer tube 7 that covers the cylinder 2 are closed by an annular rod guide 9, and the openings at the right end side in FIG. 2 of the cylinder 2 and the outer tube 7 are closed by a bottom cap 10 that fits over both. In this way, the annular gap between the cylinder 2 and the outer tube 7 is closed by the rod guide 9 and the bottom cap 10, forming a tank 8 that stores liquid.

The rod 4, which is inserted movably into the cylinder 2, is slidably inserted into the rod guide 9, and the axial movement of the rod 4 is guided by the rod guide 9. One end of the rod 4 protrudes outside the cylinder 2 through the rod guide 9, and the other end inside the cylinder 2 is connected to the piston 3, which is inserted movably into the cylinder 2.

The outer circumference of the rod 4, the gap between the rod guide 9 and the cylinder 2, the gap between the rod guide 9 and the outer tube 7, the gap between the cylinder 2 and the bottom cap 10, and the gap between the outer tube 7 and the bottom cap 10 are each sealed with sealing members (not shown). This keeps the inside of the cylinder 2 and the tank 8 sealed.

The rod side chamber 5 and piston side chamber 6, which are partitioned by the piston 3 in the cylinder 2, are filled with liquid, and the tank 8 is filled with gas in addition to storing the liquid. Note that there is no particular need to compress and fill the gas in the tank 8 to create a pressurized state. The liquid is, for example, hydraulic oil, but it may be a liquid other than hydraulic oil.

Although not shown, the cylinder device C1 is interposed between the bogie and the car body, with the rod 4 connected to one of the bogie and the car body of the railway vehicle V and the cylinder 2 connected to the other of the bogie and the car body. Since the cylinder device C1 is set to a single rod type, it is easier to ensure the stroke length compared to a double rod type cylinder device, and the overall length of the cylinder device C1 is shorter, improving the mountability on the railway vehicle V. In addition, the left end of the rod 4 in FIG. 2 and the bottom cap 10 that closes the right end of the cylinder 2 are equipped with mounting parts (not shown), so that this cylinder device C1 can be interposed between the car body B and the bogie T of the railway vehicle V.

As shown in FIG. 2, the cylinder device C1 of the first embodiment is provided with a straightening passage 18 that allows only flow from the piston side chamber 6 to the rod side chamber 5. The straightening passage 18 may be provided in a location other than the piston 3. Furthermore, the cylinder device C1 of this example is provided with a suction passage 19 that allows only flow from the tank 8 to the piston side chamber 6.

The damping passage 21 has one end connected to the rod side chamber 5 and the other end connected to the tank 8, communicating the rod side chamber 5 with the tank 8. A damping valve is provided in the damping passage 21. In the cylinder device C1 of this embodiment, the damping valve is a variable relief valve 22 capable of changing the valve opening pressure. In this example, the variable relief valve 22 is a proportional electromagnetic relief valve equipped with a solenoid, and is capable of adjusting the valve opening pressure according to the amount of current supplied, and is configured to minimize the valve opening pressure when the amount of current is maximized, and maximize the valve opening pressure when no current is supplied. More specifically, although not shown in detail, the variable relief valve 22 mainly comprises a valve body 22a that opens and closes the damping passage 21, a housing (not shown) that houses the valve body 22a and has a valve hole that is connected to the damping passage 21, a spring 22b that urges the valve body 22a in the valve closing direction, a solenoid 22c that exerts a thrust that urges the valve body 22a in the valve opening direction when energized, and a pilot passage 22d that is provided so that the pressure upstream of the valve body 22a acts on the valve body 22a as a pilot pressure to urge the valve body 22a in the valve opening direction by the pilot pressure.

The damping valve may be any damping valve that is equipped with a driving source such as a solenoid that drives a valve body and can adjust the damping force (thrust) exerted by the cylinder device C1. In addition to the variable relief valve 22, it may be a variable throttle valve that can change the flow path area by driving a spool with a driving source such as a solenoid, or as disclosed in JP 2017-82874 A, a valve unit that has a passage in which an opening/closing valve and a passive valve are provided and a passage in which a variable relief valve is provided in parallel, and that opens and closes the opening/closing valve and controls the opening pressure of the variable relief valve with a single driving source such as a solenoid.

The bypass damping passage 25 has one end connected to the rod side chamber 5 and the other end connected to the tank 8, and communicates with the rod side chamber 5 and the tank 8 in parallel with the damping passage 21. The bypass damping passage 25 is provided with a bypass damping passage damping valve 26. In the illustrated example, the bypass damping passage damping valve 26 is a variable orifice whose opening area can be adjusted by manual operation, but it may be a fixed orifice or a relief valve.

In the cylinder device C1 of this embodiment, the directional control valve 28 is a two-position, three-port directional control valve that includes a valve body 28a located in the damping passage 21 on the rod side chamber upstream of the connection point between the variable relief valve 22 as a damping valve and the first passage 11, a pilot passage 28d that applies the pressure on the rod side chamber upstream of the directional control valve 28 as pilot pressure to the valve body 28a, and a spring 28e that biases the valve body 28a against the pilot pressure.

The valve body 28a has a damping passage connection position 28b that connects the damping passage 21 and blocks the bypass damping passage 25, and a bypass damping passage connection position 28c that blocks the damping passage 21 and connects the bypass damping passage 25.

The pilot passage 28d guides the pressure upstream of the directional control valve 28 of the damping passage 21 to act on the valve body 28a. The valve body 28a is always biased by the force of the pressure to take the bypass damping passage communication position 28c. In contrast, the spring 28e biases the valve body 28a to take the damping passage communication position 28b. Therefore, the valve body 28a takes the damping passage communication position 28b until the force of the pressure applied to the valve body 28a exceeds the biasing force of the spring 28e, and when the pressure increases and the force pressing the valve body 28a exceeds the biasing force of the spring 28e, the valve body 28a takes the bypass damping passage communication position 28c. When the pressure upstream reaches or exceeds a predetermined pressure, the directional control valve 28 switches from the damping passage communication position 28b to the bypass damping passage communication position 28c.

As described above, when the pressure in the upstream rod side chamber 5 is less than a predetermined pressure, the directional control valve 28 opens the damping passage 21 and allows the liquid to flow to the tank 8 through the variable relief valve 22. On the other hand, when the pressure in the upstream rod side chamber 5 is equal to or greater than the predetermined pressure, the directional control valve 28 selects the bypass damping passage 25 and allows the liquid to flow to the tank 8 through the bypass damping passage damping valve 26. Therefore, when the pressure in the rod side chamber 5 exceeds the predetermined pressure, no liquid flows through the variable relief valve 22, which serves as a damping valve. The predetermined pressure, which is the upstream pressure at which the directional control valve 28 closes the damping passage 21, is set to be at least less than the pressure that the variable relief valve 22 can withstand.

In addition, in order to protect the hydraulic circuit, the cylinder device C1 of the first embodiment is provided with a protective passage 29 that connects the rod side chamber 5 to the tank 8 in parallel with the damping passage 21 and the bypass damping passage 25, and a relief valve 30 provided in the protective passage 29. When the pressure in the rod side chamber 5 reaches a preset upper limit pressure, the relief valve 30 opens to discharge the liquid from within the cylinder body 1 to the tank 8, preventing the pressure in the cylinder body 1 from becoming excessive and protecting the cylinder device C1.

Furthermore, in the cylinder device C1 of the first embodiment, a first passage 11 is provided between the direction switching valve 28 and the variable relief valve 22 as a damping valve, which is located in the middle of the damping passage 21, one end of which is connected to the rod side chamber 5, and the other end of which is connected to a common passage 27 connected to the piston side chamber 6. The first passage 11 is connected to the rod side chamber 5 via the damping passage 21 and the direction switching valve 28, and is connected to the piston side chamber 6 via the common passage 27. Thus, the first passage 11 communicates with the rod side chamber 5 and the piston side chamber 6. In addition, a first opening/closing valve 12 is provided in the first passage 11. The first on-off valve 12 is an electromagnetic on-off valve, and has a communication position that connects the rod side chamber 5 and the piston side chamber 6, and a blocking position that blocks communication between the rod side chamber 5 and the piston side chamber 6. When energized, the first passage 11 is opened to connect the rod side chamber 5 and the piston side chamber 6, and when deenergized, the first passage 11 is blocked to block the rod side chamber 5 and the piston side chamber 6. In this way, the first on-off valve 12 switches between communication and blocking between the rod side chamber 5 and the piston side chamber 6.

The cylinder device C1 of this example also includes a second passage 13, one end of which is connected to the common passage 27 connected to the piston side chamber 6, and the other end of which is connected to the tank 8. The second passage 13 communicates between the piston side chamber 6 and the tank 8 via the common passage 27, and a second on-off valve 14 is provided in the second passage 13. The second on-off valve 14 is an electromagnetic on-off valve, and has a communication position that communicates between the piston side chamber 6 and the tank 8, and a blocking position that blocks communication between the piston side chamber 6 and the tank 8. When energized, the second passage 13 is opened to connect the piston side chamber 6 and the tank 8, and when deenergized, the second passage 13 is blocked to block the piston side chamber 6 and the tank 8. In this way, the second on-off valve 14 switches between communication and blocking between the piston side chamber 6 and the tank 8.

In this way, the first passage 11 branches off from the damping passage 21 upstream of the variable relief valve 22 and downstream of the directional control valve 28 and is connected to the common passage 27, and the second passage 13 branches off from the common passage 27 and is connected to the tank 8.

The cylinder device C1 configured in this manner operates as follows. When the first opening/closing valve 12 and the second opening/closing valve 14 are in the shutoff position, and the cylinder body 1 is extended by receiving an external force, liquid is pushed out from the compressed rod side chamber 5. Then, liquid is supplied from the tank 8 through the suction passage 19 to the expanding piston side chamber 6. During this extension operation, if the pressure in the rod side chamber 5 upstream of the directional control valve 28 of the damping passage 21 is less than a predetermined pressure, the directional control valve 28 closes the bypass damping passage 25 and opens the damping passage 21, so that the cylinder device C1 exerts a damping force that suppresses the extension of the cylinder body 1 by providing resistance to the flow of liquid pushed out from the cylinder 2 with the variable relief valve 22. The opening pressure of the variable relief valve 22 can be changed by adjusting the amount of current supplied to the variable relief valve 22, so that the cylinder device C1 of this embodiment makes it possible to adjust the damping force on the extension side.

In addition, when the pressure in the rod side chamber 5 during extension exceeds a predetermined pressure, the directional control valve 28 blocks the damping passage 21 and opens the bypass damping passage 25, so that the cylinder device C1 exerts a damping force that suppresses extension by providing resistance to the flow of liquid pushed out from inside the cylinder 2 with the bypass damping passage damping valve 26.

On the other hand, when the first opening/closing valve 12 and the second opening/closing valve 14 are in the shutoff position, when the cylinder body 1 contracts due to an external force, liquid moves from the compressed piston side chamber 6 to the expanding rod side chamber 5 via the rectifying passage 18. Also, when the cylinder device C1 contracts, the rod 4 enters the cylinder 2, so that the liquid in the cylinder 2 is in excess of the volume of the rod 4 entering the cylinder 2 and is pushed out of the cylinder 2. During this contraction operation, if the pressure in the rod side chamber 5 upstream of the directional control valve 28 of the damping passage 21 is less than a predetermined pressure, the directional control valve 28 blocks the bypass damping passage 25 to communicate with the damping passage 21, so that the cylinder device C1 exerts a damping force that suppresses the contraction of the cylinder body 1 by providing resistance to the flow of liquid pushed out from the cylinder 2 with the variable relief valve 22. And, since the opening pressure of the variable relief valve 22 can be changed by adjusting the amount of current supplied to the variable relief valve 22, the cylinder device C1 of this embodiment allows adjustment of the damping force on the contraction side.

In addition, when the pressure in the rod side chamber 5 during contraction exceeds a predetermined pressure, the directional control valve 28 blocks the damping passage 21 and opens the bypass damping passage 25, so that the cylinder device C1 exerts a damping force that suppresses the contraction of the cylinder body 1 by providing resistance to the flow of liquid pushed out from inside the cylinder 2 with the bypass damping passage damping valve 26.

In the case of this cylinder device C1, the cross-sectional area of the rod 4 is half that of the piston 3, and the pressure-receiving area on the rod side chamber 5 side of the piston 3 is half that of the piston side chamber 6 side. Therefore, the flow rate of liquid discharged from inside the cylinder 2 through the damping passage 21 or bypass damping passage 25 to the tank 8 is equal when the cylinder device C1 is extended and when it is contracted. Therefore, the cylinder device C1 can exert the same damping force if the moving speed of the piston 3 is the same on both sides of the extension and contraction.

In addition, both the first and second valves 12 and 14 are in the cut-off position when not energized, and in the event of a failure that causes the power supply to be unavailable, the cylinder device C1 in this example always exerts a damping force against expansion and contraction as described above, so it functions as a passive damper.

In addition, in the cylinder device C1 of this example, when the first opening/closing valve 12 is in the communication position and the second opening/closing valve 14 is in the cutoff position, the rod side chamber 5 and the piston side chamber 6 are communicated through the first passage 11, but the communication between the piston side chamber 6 and the tank 8 through the second passage 13 is cut off. In this state, when the cylinder body 1 is contracted by an external force, the liquid equivalent to the volume of the rod 4 entering the cylinder 2 is pushed out from the rod side chamber 5 toward the damping passage 21, so that a damping force that suppresses the contraction of the cylinder body 1 is exerted by the variable relief valve 22 or the bypass damping passage damping valve 26 selected by the directional control valve 28 according to the pressure of the rod side chamber 5. On the other hand, in this state, when the cylinder body 1 extends, liquid moves from the contracting rod side chamber 5 to the expanding piston side chamber 6 through the first passage 11, and the liquid equivalent to the volume of the rod 4 leaving the cylinder 2 is supplied from the tank 8 to the cylinder 2 through the suction passage 19. Therefore, in this case, the liquid does not flow to the damping passage 21 or the bypass damping passage 25, and the pressure inside the cylinder 2 becomes tank pressure, so the cylinder device C1 does not exert a damping force.

Furthermore, in the cylinder device C1 of this example, when the first on-off valve 12 is in the shutoff position and the second on-off valve 14 is in the communication position, the communication between the rod side chamber 5 and the piston side chamber 6 through the first passage 11 is cut off, but the piston side chamber 6 and the tank 8 are communicated through the second passage 13. When the cylinder body 1 is extended under external force in this state, the liquid is pushed out from the rod side chamber 5 toward the damping passage 21 as the rod side chamber 5 contracts, and a damping force that suppresses the extension of the cylinder body 1 is exerted by the variable relief valve 22 or the bypass damping passage damping valve 26 selected by the directional control valve 28 according to the pressure of the rod side chamber 5. On the other hand, when the cylinder body 1 contracts in this state, liquid moves from the contracting piston side chamber 6 to the expanding rod side chamber 5 through the straightening passage 18, and the liquid of the volume of the rod 4 entering the cylinder 2 is discharged from the piston side chamber 6 to the tank 8 through the second passage 13. Therefore, in this case, the liquid does not flow to the damping passage 21 or the bypass damping passage 25, and the pressure inside the cylinder 2 becomes tank pressure, so the cylinder device C1 does not exert a damping force. In this way, the cylinder device C1 can function as a one-sided damper that exerts a damping force by selecting either extension or contraction.

In this way, when the first opening/closing valve 12 is in the open position and the second opening/closing valve 14 is in the shutoff position, and when the first opening/closing valve 12 is in the shutoff position and the second opening/closing valve 14 is in the open position, as described above, the cylinder device C1 is in a mode in which it exerts a damping force only in either extension or contraction. Therefore, for example, if this mode is selected, when the direction in which the damping force is exerted is a direction in which the vibration of the bogie T of the railway vehicle V causes the car body B to vibrate, the cylinder device C1 can be made to be a one-sided damper so as not to exert a damping force in such a direction. Therefore, with this cylinder device C1, semi-active control based on Karnop's skyhook theory can be easily realized, so that the cylinder device C1 can function as a skyhook semi-active damper.

In addition, when the first on-off valve 12 and the second on-off valve 14 are open, the rod side chamber 5 and the piston side chamber 6 are connected to the tank 8, the pressure in the rod side chamber 5 and the pressure in the piston side chamber 6 become the tank pressure, and the cylinder device C1 is in an unloaded state in which no damping force is generated even when the cylinder body 1 is extended or contracted.

The opening pressure of the relief valve 30 provided in the protective passage 29 is higher than the above-mentioned predetermined pressure, and in the cylinder device C1 of the first embodiment, when the pressure in the cylinder 2 reaches the opening pressure of the relief valve 30, the liquid moves to the tank 8 not only through the bypass damping passage damping valve 26 but also through the relief valve 30, so that the pressure in the cylinder 2 is prevented from becoming excessive and the cylinder device C1 is protected.

As described above, the cylinder device C1 of the first embodiment includes a cylinder 2 filled with liquid, a piston 3 inserted axially movably into the cylinder 2 and dividing the cylinder 2 into a rod side chamber 5 and a piston side chamber 6, a cylinder body 1 having a rod 4 inserted axially movably into the cylinder 2 and connected to the piston 3, a damping passage 21 through which liquid passes when the cylinder body 1 expands and contracts, a bypass damping passage 25 parallel to the damping passage 21, a variable relief valve (damping valve) 22 provided in the damping passage 21, a bypass damping passage damping valve 26 provided in the bypass damping passage 25, and a directional control valve 28 provided upstream of the variable relief valve (damping valve) 22, which opens the damping passage 21 and closes the bypass damping passage 25 when the upstream pressure is less than a predetermined pressure, and closes the damping passage 21 and opens the bypass damping passage 25 when the upstream pressure is equal to or greater than the predetermined pressure.

In the cylinder device C1 configured in this manner, when the pressure in the rod side chamber 5 during extension and contraction reaches or exceeds a predetermined pressure, the directional control valve 28 blocks the damping passage 21 and communicates with the bypass damping passage 25. In this manner, in the cylinder device C1, when the pressure in the cylinder 2 reaches or exceeds a predetermined pressure when the cylinder body 1 expands or contracts due to the input of large vibration, the directional control valve 28 blocks the damping passage 21, preventing the variable relief valve 22 as a damping valve from being exposed to high pressure, thereby protecting the variable relief valve 22, while allowing the bypass damping passage damping valve 26 to exert a damping force. Therefore, since it is not necessary to adopt a variable relief valve 22 that can withstand high pressure, it is possible to avoid an increase in the weight of the components of the variable relief valve 22 and the damping passage 21 in order to ensure the strength of the variable relief valve 22 and the damping passage 21. As described above, according to the cylinder device C1 of this embodiment, the weight and cost of the entire device can be reduced.

The damping passage 21 connects the inside of the cylinder 2 to the tank 8, and the downstream side of the variable relief valve 22 is always at tank pressure. Since no high pressure acts from the downstream side, if the directional control valve 28 is used to block the damping passage 21 upstream of the variable relief valve 22, the variable relief valve 22 will not be exposed to high pressure.

The specified pressure, which is the upstream pressure at which the directional control valve 28 blocks the damping passage 21, is set to a pressure lower than the variable relief valve 22 can withstand, so that the variable relief valve 22 is not subjected to high pressure that would cause the variable relief valve 22 to deteriorate, and the variable relief valve 22 can be used safely.

The pressure flow characteristics of the bypass damping passage damping valve 26 can be set independently of the pressure flow characteristics of the variable relief valve 22, but a situation in which the pressure inside the cylinder 2 becomes very high is considered to be a situation in which large vibrations are input to the cylinder body 1. Therefore, in a situation in which the directional control valve 28 blocks the damping passage 21, it is advisable to set the pressure flow characteristics of the bypass damping passage damping valve 26 so that the bypass damping passage damping valve 26 exerts a damping force higher than the damping force that can be exerted by the variable relief valve 22, thereby sufficiently damping the vibrations of the vehicle body B.

As in the cylinder device C2 of the first modified example of the first embodiment shown in FIG. 3, in addition to the directional control valve 28, the common passage 27 may be provided with a common passage opening/closing valve 31 that opens and closes the common passage 27. The common passage opening/closing valve 31 includes a valve body 31a provided in the common passage 27, a pilot passage 31d that applies the pressure of the common passage 27 on the piston side chamber side of the common passage opening/closing valve 31 as pilot pressure to the valve body 31a, and a spring 31e that biases the valve body 31a against the pilot pressure.

The valve body 31a has a communication position 31b that communicates with the common passage 27 and a blocking position 31c that blocks the common passage 27. The pilot passage 31d guides the pressure of the piston side chamber 6 to act on the valve body 31a. The valve body 31a is always biased to take the blocking position 31c by the force of the pressure. In contrast, the spring 31e biases the valve body 31a to take the communication position 31b. Therefore, the valve body 31a takes the communication position 31b until the force of the pressure that the valve body 31a receives exceeds the biasing force of the spring 31e, and when the pressure increases and the force pressing the valve body 31a exceeds the biasing force of the spring 31e, the valve body 31a takes the blocking position 31c. Then, when the pressure of the piston side chamber 6 becomes equal to or higher than the second predetermined pressure, the common passage opening and closing valve 31 switches from the communication position 31b to the blocking position 31c.

As described above, when the pressure in the piston side chamber 6 is less than the second predetermined pressure, the common passage on-off valve 31 opens the common passage 27 to enable the first on-off valve 12 in the first passage 11 and the second on-off valve 14 in the second passage 13, and when the pressure in the piston side chamber 6 is equal to or greater than the second predetermined pressure, it closes the common passage 27 to prevent the first on-off valve 12 in the first passage 11 and the second on-off valve 14 in the second passage 13 from being exposed to high pressure. The second predetermined pressure, which is the pressure in the piston side chamber 6 at which the common passage on-off valve 31 closes the common passage 27, is set to be at least less than the pressure that the first on-off valve 12 and the second on-off valve 14 can withstand. In addition, the common passage opening/closing valve 31 may use the pressure in the rod side chamber 5 as a pilot pressure, similar to the directional control valve 28. In that case, the common passage opening/closing valve 31 opens the common passage 27 when the pressure in the rod side chamber 5 is less than the second predetermined pressure, and closes the common passage 27 when the pressure in the rod side chamber 5 is equal to or greater than the second predetermined pressure, thereby preventing the first opening/closing valve 12 and the second opening/closing valve 14 from being exposed to high pressure.

When the common passage 27 is blocked by the common passage opening/closing valve 31 and the damping passage 21 is blocked by the directional control valve 28, the cylinder device C2 functions as a passive damper and exerts a damping force against the expansion and contraction of the cylinder body 1 by the bypass damping passage damping valve 26 or the bypass damping passage damping valve 26 plus the relief valve 30.

According to the cylinder device C2 of the first modified example of the first embodiment configured in this manner, not only can it be avoided to increase the weight of the components of the variable relief valve 22 and the damping passage 21 to ensure the strength of the variable relief valve 22 and the damping passage 21 as a damping valve, but also, by providing a common passage opening and closing valve 31, it is possible to prevent the first passage 11, the second passage 13, the first opening and closing valve 12, and the second opening and closing valve 14 from being exposed to high pressure, so that it is possible to avoid an increase in the weight of the components of the first passage 11, the second passage 13, the first opening and closing valve 12, and the second opening and closing valve 14. Therefore, according to the cylinder device C2 of this embodiment, the weight and cost of the entire device can be reduced more effectively.

Even if a common passage opening/closing valve 31 is provided in the common passage 27, when the first opening/closing valve 12 and the second opening/closing valve 14 are open, the rod side chamber 5 and the piston side chamber 6 in the cylinder 2 are connected to the tank 8, so the pressure in both the rod side chamber 5 and the piston side chamber 6 is tank pressure. This means that the common passage opening/closing valve 31 does not shut off the common passage 27, and the cylinder device C2 can be unloaded.

The second predetermined pressure, which is the pressure in the piston side chamber 6 or the rod side chamber 5 at which the common passage opening/closing valve 31 closes the common passage 27, and the predetermined pressure, which is the pressure in the rod side chamber 5 at which the directional control valve 28 closes the damping passage 21, may be set to the same value or may be set independently.

Also, as in the cylinder device C3 of the second modified example of the first embodiment shown in FIG. 4, in addition to the configuration of the cylinder device C1 of the first embodiment, a supply passage 16 that connects the tank 8 and the rod side chamber 5, a pump 15 provided in this supply passage 16 to suck up liquid from the tank 8 and discharge it to the rod side chamber 5, and a check valve 17 provided on the discharge side of the pump 15 in the supply passage 16 to prevent the flow of liquid from the rod side chamber 5 toward the tank 8 may be provided.

The pump 15 is driven by a motor 20 controlled by a controller (not shown) and is a pump that discharges liquid in only one direction. The pump 15 is also installed in the supply passage 16 with its suction port facing the tank 8 and its discharge port facing the rod side chamber 5. When driven by the motor 20, the pump 15 sucks liquid from the tank 8 and supplies the liquid to the rod side chamber 5.

As mentioned above, the pump 15 discharges liquid in only one direction and does not switch rotation directions, so there is no problem with the discharge volume changing when the rotation direction is switched, and an inexpensive gear pump or the like can be used.

Furthermore, since the rotation direction of the pump 15 is always the same, the motor 20, which is the driving source that drives the pump 15, does not require high responsiveness to rotation switching, and therefore a cheaper motor 20 can be used. The check valve 17 is provided to prevent liquid from flowing back toward the pump 15 when the cylinder device C3 is forcibly expanded or contracted by an external force.

Next, when the cylinder device C3 configured as described above is to exert a desired thrust in the extension direction, the motor 20 is rotated to supply liquid from the pump 15 into the cylinder 2, while the first opening/closing valve 12 is set to the communication position and the second opening/closing valve 14 is set to the blocking position. Then, the rod side chamber 5 and the piston side chamber 6 are placed in communication with each other, liquid is supplied from the pump 15 to both, the piston 3 is pushed to the left in FIG. 4, and the cylinder device C3 exerts a thrust in the extension direction. When the pressure in the rod side chamber 5 and the piston side chamber 6 exceeds the opening pressure of the variable relief valve 22, the variable relief valve 22 opens and the liquid is discharged to the tank 8 through the damping passage 21. Therefore, the pressure in the rod side chamber 5 and the piston side chamber 6 is adjusted to be equal to the opening pressure of the variable relief valve 22, which is determined by the amount of current applied to the variable relief valve 22. The cylinder device C3 exerts a thrust in the extension direction equal to the difference in pressure-receiving area between the piston side chamber 6 side and the rod side chamber 5 side of the piston 3 multiplied by the pressure in the rod side chamber 5 and the piston side chamber 6.

On the other hand, when the cylinder device C3 is to exert a desired thrust in the contraction direction, the motor 20 is rotated to supply liquid from the pump 15 into the rod side chamber 5, while the first on-off valve 12 is set to the shutoff position and the second on-off valve 14 is set to the open position. Then, the piston side chamber 6 and the tank 8 are placed in communication and liquid is supplied from the pump 15 to the rod side chamber 5, so that the piston 3 is pushed to the right in FIG. 4 and the cylinder device C3 exerts a thrust in the contraction direction. Then, as described above, by adjusting the amount of current applied to the variable relief valve 22, the cylinder device C3 exerts a thrust in the contraction direction that is the product of the pressure-receiving area on the rod side chamber 5 side of the piston 3 and the pressure in the rod side chamber 5. In this way, the cylinder device C3 can function as an actuator.

In addition, when the rod 4 moves to the left in FIG. 4 due to an external force with the first on-off valve 12 open and the second on-off valve 14 closed, the cylinder device C3 does not exert a force in the direction that prevents the movement of the rod 4, that is, in the contraction direction, regardless of whether the pump 15 is driven or not. In this case, when the pump 15 is driven, the discharge flow rate of the pump 15 cannot keep up with the volume change in the cylinder 2 that decreases when the rod 4 retreats from the cylinder 2, but liquid is supplied from the tank 8 to the cylinder 2 through the suction passage 19. In addition, in this case, when the pump 15 is not driven, liquid equivalent to the volume of the rod 4 retreating from the cylinder 2 is supplied from the tank 8 to the cylinder 2 through the suction passage 19. In any case, in this case, the pressure in the cylinder 2 is the tank pressure, so the cylinder device C3 does not exert a damping force in the direction that prevents the movement of the rod 4, that is, in the contraction direction.

When the rod 4 moves to the right in FIG. 4 due to an external force with the first on-off valve 12 open and the second on-off valve 14 closed, the liquid pushed out of the cylinder 2 by the rod 4 entering the cylinder 2 is returned to the tank 8 through the damping passage 21, regardless of whether the pump 15 is driven or not. In this case, the pressure in the cylinder 2 is controlled to the desired pressure by the variable relief valve 22, so the cylinder device C3 can exert a force in the direction that prevents the movement of the rod 4, that is, in the extension direction.

On the other hand, when the rod 4 moves to the right in FIG. 4 due to an external force with the first on-off valve 12 closed and the second on-off valve 14 open, the cylinder device C3 does not exert a force in a direction that prevents the movement of the rod 4, that is, in the extension direction, regardless of whether the pump 15 is driven or not. In this case, when the pump 15 is driven, the discharge flow rate of the pump 15 cannot keep up with the volume change in the rod side chamber 5 that increases when the rod 4 enters the cylinder 2, but liquid is supplied from the piston side chamber 6 to the rod side chamber 5 through the straightening passage 18. In addition, as the rod 4 enters the cylinder 2, the liquid in the cylinder 2 is excessive by the volume of the rod 4 entering the cylinder 2, but the piston side chamber 6 on the compression side passes through the second passage 13, and this excess liquid is discharged to the tank 8. In this case, even when the pump 15 is not driven, the liquid in the rod side chamber 5 that increases when the rod 4 enters the cylinder 2 is supplied from the piston side chamber 6 through the straightening passage 18, just as when the pump 15 is driven. The excess liquid volume that the rod 4 has entered into the cylinder 2 is discharged from the compressed piston side chamber 6 to the tank 8 via the second passage 13. In either case, the pressure in the cylinder 2 becomes the tank pressure, so the cylinder device C3 does not exert a damping force in the direction that impedes the movement of the rod 4, that is, in the extension direction.

When the rod 4 moves to the left in FIG. 4 due to an external force with the first on-off valve 12 closed and the second on-off valve 14 open, the liquid pushed out from the rod side chamber 5 is returned to the tank 8 through the damping passage 21 regardless of whether the pump 15 is driven or not. In this case, the pressure in the rod side chamber 5 is controlled to the desired pressure by the variable relief valve 22, so the cylinder device C3 can exert a force in the direction that prevents the movement of the rod 4, that is, in the contracting direction.

In other words, when the first on-off valve 12 is opened and the second on-off valve 14 is closed, or when the first on-off valve 12 is closed and the second on-off valve 14 is opened, the cylinder device C3 exerts a damping force in only one direction, either extension or contraction, in response to vibration input from an external force, regardless of the driving status of the pump 15.

Therefore, in the present example, when the direction of the force exerted is a direction in which the vehicle body B is vibrated due to the vibration of the bogie T of the railway vehicle V, the cylinder device C3 can function as a one-sided damper so as not to exert force in such a direction. Therefore, this cylinder device C3 can easily realize semi-active control based on Karnop's Skyhook theory, and can also function as a semi-active damper.

And, as can be understood from the explanation of the cylinder device C1 of the first embodiment, even in this cylinder device C3, it can function as a damper only by opening and closing the first opening and closing valve 12 and the second opening and closing valve 14. In other words, even in a situation where the pump 15 is driven by the motor 20, when the cylinder device C3 is forcibly expanded and contracted by an external force, it can function as a skyhook semi-active damper or a passive damper, and the damping force can be adjusted by adjusting the opening pressure of the variable relief valve 22. In this way, the cylinder device C3 not only functions as an actuator, but can also function as a damper only by opening and closing the first opening and closing valve 12 and the second opening and closing valve 14, regardless of the driving state of the motor 20. And, the direction in which the cylinder device C3 should exert a thrust or a damping force is controlled only by opening and closing the first opening and closing valve 12 and the second opening and closing valve 14, and when the direction in which the thrust and the damping force should be exerted are the same, the opening and closing states of the first opening and closing valve 12 and the second opening and closing valve 14 are the same. Therefore, in the cylinder device C3, the state of the actuator and the skyhook semi-active damper can be switched without stopping and driving the pump 15 or performing the troublesome and abrupt switching operation of the first opening/closing valve 12 and the second opening/closing valve 14. Therefore, the cylinder device C3 is a system with high responsiveness and reliability.

The cylinder device C3 configured in this manner is provided with a directional control valve 28, so that, like the cylinder device C1, when a large vibration is input to the cylinder body 1 and the pressure in the rod side chamber 5 becomes high above a predetermined pressure, the directional control valve 28 shuts off the damping passage 21 to protect the variable relief valve 22 as a damping valve, while the bypass damping passage damping valve 26 exerts a damping force that prevents the expansion and contraction of the cylinder body 1. Therefore, even in the cylinder device C3 in the second modified example of the first embodiment, it is possible to avoid an increase in the weight of the components of the variable relief valve 22 and the damping passage 21 to ensure the strength of the variable relief valve 22 and the damping passage 21, and the weight and cost of the entire device can be reduced. In addition, the cylinder device C3 may be provided with a common passage opening and closing valve 31 in the common passage 27, in which case the first opening and closing valve 12 and the second opening and closing valve 14 can also be protected, so that the weight and cost of the entire device can be further reduced.

Second Embodiment
As shown in FIG. 5 , the cylinder device C4 in the second embodiment differs from the cylinder device C1 in that, instead of the directional control valve 28 in the configuration of the cylinder device C1 in the first embodiment, a damping passage opening/closing valve 33 is provided upstream of the variable relief valve 22 serving as a damping valve in the damping passage 21 to open and close the damping passage 21, and a bypass damping passage opening/closing valve 34 is provided upstream of the bypass damping passage damping valve 26 in the bypass damping passage 25 to open and close the bypass damping passage 25.

As described above, the cylinder device C4 is provided with a damping passage opening/closing valve 33 that opens and closes the damping passage 21, and a bypass damping passage opening/closing valve 34 that opens and closes the bypass damping passage 25, instead of the directional control valve 28.

The damping passage opening/closing valve 33 is provided with a valve body 33a provided in the damping passage 21 on the rod side chamber side upstream of the connection point between the variable relief valve 22 as a damping valve and the first passage 11, a pilot passage 33d that applies the pressure on the rod side chamber side of the damping passage 21 from the damping passage opening/closing valve 33 as a pilot pressure to the valve body 33a, and a spring 33e that biases the valve body 33a against the pilot pressure. In the cylinder device C4, the first passage 11 is connected at one end to the rod side chamber 5 via the damping passage 21 and the damping passage opening/closing valve 34, and at the other end to the piston side chamber 6 via the common passage 27.

The valve body 33a has a communication position 33b that communicates with the damping passage 21 and a blocking position 33c that blocks the damping passage 21. The pilot passage 33d guides the pressure of the rod side chamber 5 to act on the valve body 33a. The valve body 33a is always biased to take the blocking position 33c by the force of the pressure. In contrast, the spring 33e biases the valve body 33a to take the communication position 33b. Therefore, the valve body 33a takes the communication position 33b until the force of the pressure that the valve body 33a receives exceeds the biasing force of the spring 33e, and when the pressure increases and the force pressing the valve body 33a exceeds the biasing force of the spring 33e, the valve body 33a takes the blocking position 33c. Then, when the pressure of the rod side chamber 5 becomes equal to or greater than the predetermined pressure, the damping passage opening/closing valve 33 switches from the communication position 33b to the blocking position 33c.

The bypass damping passage opening/closing valve 34 is provided with a valve body 34a located in the bypass damping passage 25 on the rod side chamber side upstream of the bypass damping passage damping valve 26, a pilot passage 34d that applies the pressure on the rod side chamber side of the bypass damping passage 25 from the bypass damping passage opening/closing valve 34 as pilot pressure to the valve body 34a, and a spring 34e that biases the valve body 34a against the pilot pressure.

The valve body 34a has a blocking position 34b for blocking the bypass damping passage 25 and a communicating position 34c for communicating with the bypass damping passage 25. The pilot passage 34d guides the pressure of the rod side chamber 5 to act on the valve body 34a. The valve body 34a is always biased to take the communicating position 34c by the force of the pressure. In contrast, the spring 34e biases the valve body 34a to take the blocking position 34b. Therefore, the valve body 34a takes the blocking position 34b until the force of the pressure applied to the valve body 34a exceeds the biasing force of the spring 34e, and when the pressure increases and the force pressing the valve body 34a exceeds the biasing force of the spring 34e, the valve body 34a takes the communicating position 34c. Then, when the pressure of the rod side chamber 5 becomes equal to or higher than the predetermined pressure, the bypass damping passage opening/closing valve 34 switches from the blocking position 34b to the communicating position 34c.

As described above, when the pressure in the rod side chamber 5 is less than a predetermined pressure, the damping passage opening/closing valve 33 opens the damping passage 21 to allow liquid to pass through the variable relief valve 22, and the bypass damping passage opening/closing valve 34 blocks the bypass damping passage 25 to prevent liquid from passing through the bypass damping passage damping valve 26. On the other hand, when the pressure in the rod side chamber 5 is equal to or greater than a predetermined pressure, the damping passage opening/closing valve 33 blocks the damping passage 21 to prevent the variable relief valve 22 from being exposed to high pressure, and the bypass damping passage opening/closing valve 34 communicates with the bypass damping passage 25 to allow liquid to pass through the bypass damping passage damping valve 26. In other words, the damping passage opening/closing valve 33 and the bypass damping passage opening/closing valve 34 in the cylinder device C4, like the directional control valve 28 in the cylinder device C1, communicate with the damping passage 21 and block the bypass damping passage 25 when the pressure in the rod side chamber 5 is less than a predetermined pressure during the extension and contraction operations of the cylinder body 1, and block the damping passage 21 and communicate with the bypass damping passage 25 when the pressure in the rod side chamber 5 becomes equal to or greater than the predetermined pressure.

In this way, in the cylinder device C4, when the cylinder body 1 expands and contracts due to the input of large vibrations and the pressure inside the cylinder 2 becomes high above a predetermined pressure, the damping passage opening/closing valve 33 closes the damping passage 21, preventing the variable relief valve 22 as a damping valve from being exposed to high pressure and protecting the variable relief valve 22, while the bypass damping passage opening/closing valve 34 opens the bypass damping passage 26 and allows the bypass damping passage damping valve 26 to exert a damping force. Therefore, since it is not necessary to adopt a variable relief valve 22 that can withstand high pressure, it is possible to avoid an increase in the weight of the components of the variable relief valve 22 and the damping passage 21 in order to ensure the strength of the variable relief valve 22 and the damping passage 21. As described above, according to the cylinder device C4 of this embodiment, the weight and cost of the entire device can be reduced.

In addition, the cylinder device C4 of the second embodiment is provided with a damping passage opening/closing valve 33 that is provided upstream of the variable relief valve 22 serving as a damping valve in the damping passage 21 and opens the damping passage 21 when the upstream pressure is below a predetermined pressure and closes the damping passage 21 when the upstream pressure is equal to or greater than the predetermined pressure, and a bypass damping passage opening/closing valve 34 that is provided upstream of the bypass damping passage damping valve 26 in the bypass damping passage 25 and closes the bypass damping passage 25 when the upstream pressure is below the predetermined pressure and opens the bypass damping passage 25 when the upstream pressure is equal to or greater than the predetermined pressure. In this way, when comparing the cylinder device C4 of the second embodiment equipped with the damping passage opening/closing valve 33 and the bypass damping passage opening/closing valve 34 with the cylinder device C1 of the first embodiment equipped with one two-position three-port directional control valve 28, the damping passage opening/closing valve 33 and the bypass damping passage opening/closing valve 34 are lighter and smaller than the directional control valve 28, and can be arranged separately in the hydraulic circuit constituting the cylinder device C4, so that the damping passage opening/closing valve 33 and the bypass damping passage opening/closing valve 34 have a high degree of freedom in arrangement. Therefore, by optimizing the arrangement of the damping passage opening/closing valve 33 and the bypass damping passage opening/closing valve 34, the valve block forming the hydraulic circuit can be made small. As described above, according to the cylinder device C4 of the second embodiment, the damping passage 21 and the bypass damping passage 25 can be switched by the lightweight and small damping passage opening/closing valve 33 and the bypass damping passage opening/closing valve 34, and the entire device can be made small by appropriately arranging the opening/closing valves.

In addition, the cylinder device C4 of the second embodiment is simply changed from the directional control valve 28 to the damping passage opening/closing valve 33 and the bypass damping passage opening/closing valve 34, so the damping passage opening/closing valve 33 and the bypass damping passage opening/closing valve 34 can be applied instead of the directional control valve 28 of the cylinder device C2 of the first modified example of the first embodiment and the cylinder device C3 of the second modified example.

Although the preferred embodiment of the present invention has been described in detail above, modifications, variations, and changes are possible without departing from the scope of the claims.

1: Cylinder body, 2: Cylinder, 3: Piston, 4: Rod, 5: Rod side chamber, 6: Piston side chamber, 8: Tank, 11: First passage, 12: First opening/closing valve, 13: Second passage, 14: Second opening/closing valve, 21: Damping passage, 22: Variable relief valve (damping valve), 25: Bypass damping passage, 26: Bypass damping passage damping valve, 27: Common passage, 28: Directional switching valve, 31: Common passage opening/closing valve, 33: Damping passage opening/closing valve, 34: Bypass damping passage opening/closing valve, C1, C2, C3, C4: Cylinder device

Claims (3)

a cylinder body including: a cylinder filled with liquid; a piston inserted into the cylinder so as to be axially movable and dividing the interior of the cylinder into a rod side chamber and a piston side chamber; and a rod inserted into the cylinder so as to be axially movable and connected to the piston;
A tank for storing the liquid;
a first on-off valve that switches between communication and cut-off between the rod side chamber and the piston side chamber;
a second on-off valve that switches between communication and cut-off between the piston side chamber and the tank;
a damping passage through which the liquid passes when the cylinder body is extended or retracted;
a bypass damping passage arranged in parallel with the damping passage;
a damping valve provided in the damping passage;
a bypass damping passage damping valve provided in the bypass damping passage;
a directional control valve that is provided upstream of the damping valve and that opens the damping passage and blocks the bypass damping passage when the pressure on the upstream side is lower than a predetermined pressure, and that blocks the damping passage and opens the bypass damping passage when the pressure on the upstream side is equal to or higher than the predetermined pressure. a cylinder body including: a cylinder filled with liquid; a piston inserted into the cylinder so as to be axially movable and dividing the interior of the cylinder into a rod side chamber and a piston side chamber; and a rod inserted into the cylinder so as to be axially movable and connected to the piston;
A tank for storing the liquid;
a first on-off valve that switches between communication and cut-off between the rod side chamber and the piston side chamber;
a second on-off valve that switches between communication and cut-off between the piston side chamber and the tank;
a damping passage through which the liquid passes when the cylinder body is extended or retracted;
a bypass damping passage arranged in parallel with the damping passage;
a damping valve provided in the damping passage;
a bypass damping passage damping valve provided in the bypass damping passage;
a damping passage opening/closing valve that is provided in the damping passage upstream of the damping valve and opens the damping passage when the pressure on the upstream side is lower than a predetermined pressure and closes the damping passage when the pressure on the upstream side is equal to or higher than the predetermined pressure;
a bypass damping passage opening/closing valve that is provided upstream of the bypass damping passage damping valve in the bypass damping passage and that blocks the bypass damping passage when a pressure on the upstream side is lower than a predetermined pressure and opens the bypass damping passage when the pressure on the upstream side is equal to or higher than the predetermined pressure. a common passage communicating with the piston side chamber;
a first passage having one end communicating with the rod side chamber via the damping passage and the other end communicating with the piston side chamber via the common passage, the first opening/closing valve being provided therein;
a second passage having one end communicating with the piston side chamber via the common passage and the other end communicating with the tank, the second opening/closing valve being provided therein;
The cylinder device according to claim 1 or 2, further comprising a common passage opening/closing valve provided in the common passage.

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