Fluid pressure cylinder unit

Abstract

To effectively use high pressure gas to be discharged from a first chamber of a fluid pressure cylinder.SOLUTION: Each of fluid pressure cylinder units 101, 201, 301, 401 includes: lift cylinders 100, 400 having cylinder tubes 1 and piston rods 10, 310; accumulators 40, 340 having gas chambers 41 in which gas can be filled and liquid chambers 42 in which liquid can be filled; and first passages 30 communicating the first chambers with the gas chambers 41 of the accumulators 40, 340. Gas is filled in the first chambers and hydraulic fluid is supplied / discharged to / from second chambers to cause piston rods 10, 310 to reciprocate. In the first passages 30, check valves 50 are provided as valves allowing the flow only of the gas from the first chambers to the gas chambers 41 of the accumulators 40, 340.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fluid pressure cylinder unit. [Background technology]

[0002] Patent Document 1 discloses a fluid pressure cylinder having a cylindrical cylinder tube with a bottom having an opening at one end, a rod inserted into the cylinder tube, and a piston connected to the tip of the rod and dividing the inside of the cylinder tube into a rod side chamber filled with gas and a bottom side chamber to which hydraulic fluid is supplied and discharged. The rod side chamber is filled with gas, and hydraulic oil is supplied and discharged to the bottom side chamber. The fluid pressure cylinder extends by hydraulic oil pressure guided from a hydraulic source to the bottom side chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-176566 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a fluid pressure cylinder such as that described in Patent Document 1 is extended, the gas in the rod side chamber is pressurized and discharged to a tank, etc. This high-pressure gas is simply discharged to the tank, etc., and is not effectively utilized.

[0005] The present invention has been made in consideration of the above problems, and has an object to effectively utilize the high-pressure gas discharged from the first chamber of a fluid pressure cylinder. [Means for solving the problem]

[0006] The present invention is a fluid pressure cylinder unit comprising: a fluid pressure cylinder having a cylinder tube and a piston rod reciprocably provided within the cylinder tube dividing the interior of the cylinder tube into a first chamber and a second chamber; an accumulator having an air chamber that can be filled with a gas and a liquid chamber that can be filled with a liquid; and a first passage connecting the first chamber and the air chamber of the accumulator, wherein the first chamber is filled with gas and the piston rod reciprocates by supplying and discharging hydraulic fluid to and from the second chamber, and the first passage is provided with a valve that is capable of allowing only the flow of gas from the first chamber to the air chamber of the accumulator.

[0007] In this invention, when the fluid pressure cylinder is extended, the gas filled in the first chamber is pressurized and is guided through the first passage and the valve to the air chamber of the accumulator, thereby making it possible to effectively use the high-pressure gas discharged from the first chamber as the gas filled in the air chamber of the accumulator.

[0008] In the present invention, the second chamber and the fluid chamber of the accumulator are in communication with each other.

[0009] In this aspect of the invention, the second chamber and the fluid chamber of the accumulator communicate with each other, so that vibrations of an object driven by the fluid pressure cylinder can be absorbed by the accumulator.

[0010] The present invention is also characterized in that it further comprises a second passage connected between the first chamber and the valve in the first passage and communicating with the atmosphere, and the second passage is provided with a check valve that allows only the flow of gas from the atmosphere to the first passage.

[0011] In this invention, a drop in pressure in the air chamber of the accumulator is prevented.

[0012] The present invention is also characterized in that it further includes a third passage connected between the first chamber and the valve in the first passage, and the third passage is provided with a relief valve that opens when the pressure in the first passage reaches a predetermined pressure.

[0013] In this invention, the pressure in the air chamber of the accumulator is prevented from exceeding the set pressure.

[0014] In the present invention, the accumulator further includes a partition member that separates the air chamber from the liquid chamber, and the first passage, the valve, and the partition member are provided in the piston rod.

[0015] In this invention, the fluid pressure cylinder unit can be made compact.

[0016] Furthermore, the present invention is characterized in that when the fluid pressure cylinder is extended or contracted for the first time after the fluid pressure cylinder and the accumulator are connected, the gas in the first chamber is pressurized and filled into the air chamber of the accumulator.

[0017] In this invention, the air chamber is not filled with high-pressure gas before the operation of the fluid pressure cylinder, so the accumulator can be handled safely and easily. Effect of the Invention

[0018] According to the present invention, it is possible to effectively utilize the high-pressure gas discharged from the first chamber of the fluid pressure cylinder. [Brief description of the drawings]

[0019] [Figure 1] 1 is a circuit diagram of a fluid pressure cylinder unit according to an embodiment of the present invention. FIG. [Diagram 2] 5A to 5C are diagrams illustrating an operation of the fluid pressure cylinder unit according to the embodiment of the present invention and a state in which gas is charged into an accumulator. [Diagram 3] FIG. 4 is a circuit diagram of a fluid pressure cylinder unit according to a first modified example of the embodiment of the present invention. [Figure 4] FIG. 11 is a circuit diagram of a fluid pressure cylinder unit according to a second modified example of the embodiment of the present invention. [Diagram 5] FIG. 11 is a circuit diagram of a fluid pressure cylinder unit according to a third modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A fluid pressure cylinder unit 101 according to an embodiment of the present invention will be described with reference to the drawings. The fluid pressure cylinder unit 101 includes a fluid pressure cylinder and an accumulator 40 connected to the fluid pressure cylinder. In this embodiment, a case will be described in which the fluid pressure cylinder is a lift cylinder 100 that raises and lowers the forks of a forklift.

[0021] The lift cylinder 100 is a single-acting hydraulic cylinder. As shown in Fig. 1, the lift cylinder 100 has a cylinder tube 1, a piston rod 10 that is reciprocally provided in the cylinder tube 1 and divides the inside of the cylinder tube 1 into a rod side chamber 2 as a first chamber and an anti-rod side chamber 3 as a second chamber, a first passage 30 connected to the rod side chamber 2, and a main passage 20 connected to the anti-rod side chamber 3.

[0022] The piston rod 10 has a piston 11 slidably provided along the inner circumferential surface of the cylinder tube 1, and a rod 12 having one end connected to the piston 11 and the other end extending to the outside of the cylinder tube 1 and reciprocating. The rod side chamber 2 is filled with a gas such as air. Note that "filling" includes actively introducing gas into the rod side chamber 2 using a cylinder or the like, and mixing of gas into the rod side chamber 2 during assembly of the lift cylinder 100. Gas is discharged from the rod side chamber 2 through the first passage 30. Hydraulic oil as a hydraulic fluid is supplied and discharged to the anti-rod side chamber 3 through the main passage 20. Note that a liquid other than hydraulic oil, such as water, may be used as the hydraulic fluid.

[0023] A switching valve (not shown) is provided in the main passage 20, and by switching the switching valve, the main passage 20 is connected to a pump (not shown) or a tank (not shown). In the lift cylinder 100, hydraulic oil is supplied to and discharged from the anti-rod side chamber 3 through the main passage 20, causing the piston rod 10 to reciprocate. Specifically, when hydraulic oil is supplied from a hydraulic source to the anti-rod side chamber 3, the piston rod 10 moves upward (upward in FIG. 1), the lift cylinder 100 extends, and the fork and the luggage placed on the fork rise. When hydraulic oil is discharged from the anti-rod side chamber 3 to the tank due to the weight of the fork, the luggage, and the piston rod 10, the piston rod 10 moves downward (downward in FIG. 1), the lift cylinder 100 contracts, and the fork and the luggage descend.

[0024] The accumulator 40 has an air chamber 41 that can be filled with a gas and a liquid chamber 42 that can be filled with a liquid. The accumulator 40 is provided separately from the lift cylinder 100. The air chamber 41 and the liquid chamber 42 may be partitioned by a partition member such as a free piston or a bladder. The air chamber 41 is connected to the first passage 30, and the liquid chamber 42 is connected to a branch passage 21 that branches off from the main passage 20. In this way, the rod side chamber 2 and the air chamber 41 communicate with each other through the first passage 30, and the anti-rod side chamber 3 and the liquid chamber 42 communicate with each other through the main passage 20 and the branch passage 21. The first passage 30 is provided with a check valve 50 as a valve that can only allow the flow of gas from the rod side chamber 2 to the air chamber 41 of the accumulator 40. Instead of the check valve 50, a solenoid valve, a manual valve, or the like may be provided. The anti-rod side chamber 3 and the liquid chamber 42 may also communicate with each other through a passage provided in parallel with the main passage 20.

[0025] The fluid pressure cylinder unit 101 of this embodiment is assembled by connecting the lift cylinder 100 and the accumulator 40 under atmospheric pressure. Before the lift cylinder 100 and the accumulator 40 are connected, the air chamber 41 of the accumulator 40 is at atmospheric pressure and is not filled with high-pressure gas. The air chamber 41 of the accumulator 40 is filled with high-pressure gas by the initial operation of the lift cylinder 100 after the lift cylinder 100 and the accumulator 40 are connected.

[0026] Next, the charging of high-pressure gas into the air chamber 41 of the accumulator 40 will be described in detail.

[0027] 2(a)-(c) are diagrams showing the initial operation of the lift cylinder 100, and Fig. 2(a) shows the state before the initial operation of the lift cylinder 100 (in other words, immediately after the lift cylinder 100 and the accumulator 40 are connected). In this state, the lift cylinder 100 is in a fully contracted state due to the weight of the piston rod 10. The rod side chamber 2 and the air chamber 41 of the accumulator 40 are at atmospheric pressure, and the air chamber 41 is not filled with high-pressure gas.

[0028] The initial operation of the lift cylinder 100 is performed by supplying hydraulic oil from the hydraulic power source through the main passage 20 to the anti-rod side chamber 3 and extending (specifically, fully extending) the lift cylinder 100, as shown in Fig. 2(b). This causes the gas in the rod side chamber 2 to be pressurized, and as shown by the arrow on the right side of Fig. 2(b), the gas is guided to the air chamber 41 of the accumulator 40 through the first passage 30 and the check valve 50. Then, the air chamber 41 is filled with high-pressure gas until the pressure in the air chamber 41 reaches a set pressure.

[0029] After that, when the hydraulic oil is discharged from the anti-rod side chamber 3, as shown in FIG. 2(c), the lift cylinder 100 is fully contracted by the weight of the piston rod 10, and the initial operation of the lift cylinder 100 is completed. In this state, the volume of the rod side chamber 2 is increased compared to the state shown in FIG. 2(b), so the pressure in the rod side chamber 2 is reduced. However, since the check valve 50 is provided in the first passage 30, the gas filled in the air chamber 41 of the accumulator 40 is not led to the rod side chamber 2 through the first passage 30. Therefore, the pressure in the air chamber 41 of the accumulator 40 is maintained at the set pressure. The above-described operations in FIG. 2(a)-(c) may be performed before or after the fluid pressure cylinder unit 101 is mounted on the forklift. In addition, the operations in FIG. 2(a)-(c) may be performed during an operation test of the lift cylinder 100 or when air is bled from the anti-rod side chamber 3. Furthermore, in the case where a solenoid valve, a manual valve, or the like is provided instead of the check valve 50, it is sufficient that the rod side chamber 2 and the air chamber 41 of the accumulator 40 communicate with each other through the first passage 30 when the lift cylinder 100 is extended, and the communication between the rod side chamber 2 and the air chamber 41 of the accumulator 40 is blocked when the lift cylinder 100 is contracted. Even in this configuration, the solenoid valve, manual valve, or the like can only allow the flow of gas from the rod side chamber 2 to the air chamber 41 of the accumulator 40.

[0030] In normal operation of the lift cylinder 100, in which the fluid pressure cylinder unit 101 is mounted on a forklift to transport and handle cargo, the pressure in the rod side chamber 2 is lower than the pressure in the air chamber 41 of the accumulator 40 until the lift cylinder 100 reaches the maximum extension state, but the pressure in the air chamber 41 of the accumulator 40 is maintained by the check valve 50. When the lift cylinder 100 reaches the maximum extension state, the pressure in the rod side chamber 2 becomes the same as the state shown in FIG. 2(b) and is equal to the pressure in the air chamber 41 of the accumulator 40. In this way, in normal operation of the lift cylinder 100, the gas in the rod side chamber 2 is not led to the air chamber 41 of the accumulator 40. In other words, in the fluid pressure cylinder unit 101, after the lift cylinder 100 and the accumulator 40 are connected, the gas in the rod side chamber 2 is pressurized and filled into the air chamber 41 of the accumulator 40 only when the lift cylinder 100 is extended for the first time (specifically, fully extended).

[0031] In this way, in the initial operation of the lift cylinder 100, when the lift cylinder 100 extends, the gas filled in the rod side chamber 2 is pressurized and is guided to and filled in the air chamber 41 of the accumulator 40 through the first passage 30 and the check valve 50. This allows the high-pressure gas discharged from the rod side chamber 2 to be effectively used as the gas filled in the air chamber 41 of the accumulator 40.

[0032] In addition, since the air chamber 41 of the accumulator 40 is filled with high-pressure gas only at the initial operation of the lift cylinder 100, the air chamber 41 is not filled with high-pressure gas before the operation of the lift cylinder 100. Therefore, the accumulator 40 can be handled safely and easily. Furthermore, the accumulator 40 can be transported safely and easily. Furthermore, since the air chamber 41 of the accumulator 40 is filled with pressurized gas from the rod side chamber 2, there is no need to use a gas cylinder or the like to fill the air chamber 41 with high-pressure gas. Therefore, compared to the case where a gas cylinder or the like is used, the accumulator 40 can be handled safely and easily and the manufacturing cost is reduced.

[0033] Furthermore, in the fluid pressure cylinder unit 101, the anti-rod side chamber 3 and the fluid chamber 42 of the accumulator 40 communicate with each other through the main passage 20 and the branch passage 21, so that the fluctuation in pressure in the main passage 20 and the anti-rod side chamber 3 is absorbed by the accumulator 40. Therefore, even if an impact from the road surface acts on the lift cylinder 100 during transport of a load by a forklift, the vibration of the load can be absorbed by the accumulator 40. Therefore, it is possible to prevent the load from shifting during transport.

[0034] According to the above embodiment, the following advantageous effects are achieved.

[0035] In the lift cylinder 100, when the lift cylinder 100 is extended, the gas filled in the rod side chamber 2 is pressurized and is guided to and filled in the air chamber 41 of the accumulator 40 through the first passage 30 and the check valve 50. This makes it possible to effectively utilize the high-pressure gas discharged from the rod side chamber 2 as the gas filled in the air chamber 41 of the accumulator 40.

[0036] In the lift cylinder 100, the anti-rod side chamber 3 and the fluid chamber 42 of the accumulator 40 communicate with each other through the main passage 20. Therefore, the vibration of the object driven by the lift cylinder 100, such as luggage, can be absorbed by the accumulator 40.

[0037] In the fluid pressure cylinder unit 101, after the lift cylinder 100 and the accumulator 40 are connected, the air chamber 41 of the accumulator 40 is filled with high-pressure gas only at the initial operation of the lift cylinder 100, so the air chamber 41 is not filled with high-pressure gas before the operation of the lift cylinder 100. Therefore, the accumulator 40 can be handled safely and easily. In addition, the accumulator 40 can be transported safely and easily.

[0038] The following modified examples are also within the scope of the present invention, and it is possible to combine the configurations shown in the modified examples with the configurations described in the above-mentioned embodiments, or to combine the configurations described in the different modified examples below.

[0039] <Variation 1> In the above embodiment, the fluid pressure cylinder unit 101 includes the first passage 30 that communicates the rod side chamber 2 and the air chamber 41 of the accumulator 40. In addition, as shown in Fig. 3, the fluid pressure cylinder unit 201 according to the first modification includes the second passage 31 that is connected between the rod side chamber 2 and the check valve 50 in the first passage 30 and communicates with the atmosphere.

[0040] The second passage 31 communicates with the atmosphere through the filter 60. The second passage 31 is provided with a check valve 51 that allows only the flow of gas from the atmosphere to the first passage 30. Therefore, when the pressure in the rod side chamber 2 and the first passage 30 decreases (specifically, decreases below atmospheric pressure) when the lift cylinder 100 contracts, gas is supplied to the rod side chamber 2 and the first passage 30 through the filter 60, the second passage 31, and the check valve 51. This allows the gas in the rod side chamber 2 to be repeatedly charged into the air chamber 41 of the accumulator 40 every time the lift cylinder 100 extends. Therefore, a decrease in pressure in the air chamber 41 is prevented.

[0041] Further, the fluid pressure cylinder unit 201 includes a third passage 33 connected between the rod side chamber 2 and the check valve 50 in the first passage 30. The third passage 33 communicates with the atmosphere through a silencer 61. The third passage 33 is provided with a relief valve 52 that opens when the pressure in the first passage 30 reaches a predetermined pressure. When the relief valve 52 opens, the gas in the rod side chamber 2 and the first passage 30 is discharged to the atmosphere through the third passage 33 and the silencer 61. The pressure at which the relief valve 52 opens is set to be equal to the set pressure of the accumulator 40, for example. Therefore, the pressure in the rod side chamber 2 and the first passage 30 does not become higher than the set pressure of the accumulator 40. In other words, during the operation of the lift cylinder 100, the gas is prevented from filling the air chamber 41 of the accumulator 40 to more than the set pressure, and the pressure in the air chamber 41 is prevented from becoming more than the set pressure.

[0042] The third passage 33 may be connected to a tank instead of the atmosphere. It is not necessary to provide both the second passage 31 and the third passage 33, and only one of them may be provided. The filter 60 and the silencer 61 are not essential and may not be provided.

[0043] <Variation 2> In the above embodiment, in the fluid pressure cylinder unit 101, the anti-rod side chamber 3 and the fluid chamber 42 of the accumulator 40 communicate with each other through the main passage 20 and the branch passage 21. In contrast, as shown in FIG. 4, in the fluid pressure cylinder unit 301, the anti-rod side chamber 3 and the fluid chamber 42 of the accumulator 40 do not communicate with each other, and the fluid chamber 42 of the accumulator 40 is connected to another device (not shown) other than the lift cylinder 100 through the passage 221. Even in this configuration, the high-pressure gas discharged from the rod side chamber 2 can be effectively used as the gas filled in the air chamber 41 of the accumulator 40. In addition, the accumulator 40 can absorb vibrations of another device to which the accumulator 40 is connected.

[0044] <Variation 3> In the above embodiment, the accumulator 40 is provided separately from the lift cylinder 100. In contrast, in a fluid pressure cylinder unit 401 according to the third modification, the accumulator 40 is provided in the piston rod 10. Specifically, as shown in FIG. 5, the accumulator 240 has a free piston 43 as a partition member that partitions the air chamber 41 and the liquid chamber 42, and the first passage 30, the check valve 50, the free piston 43, and a passage 321 that communicates the anti-rod side chamber 3 and the liquid chamber 42 are provided in the piston rod 310. Even in this configuration, when hydraulic oil is supplied from the hydraulic source to the anti-rod side chamber 3 to extend the lift cylinder 400, the gas in the rod side chamber 2 is pressurized and is introduced through the first passage 30 and the check valve 50 into the air chamber 41 of the accumulator 340 to fill it. In addition, since the anti-rod side chamber 3 and the fluid chamber 42 of the accumulator 340 communicate with each other through the passage 321, the fluctuation in pressure in the main passage 20 and the anti-rod side chamber 3 is absorbed by the accumulator 340, and it is possible to prevent the collapse of the luggage during transportation. In this way, by providing the accumulator 340 in the piston rod 310, it is possible to make the fluid pressure cylinder unit 401 compact.

[0045] <Variation 4> In the above embodiment, in the fluid pressure cylinder unit 101, the rod side chamber 2 is filled with gas, and the rod side chamber 2 and the air chamber 41 communicate with each other. In addition, the anti-rod side chamber 3 and the liquid chamber 42 communicate with each other, and hydraulic oil is supplied and discharged to the anti-rod side chamber 3. Not limited to this, the fluid pressure cylinder unit 101 may be configured such that the anti-rod side chamber 3 is filled with gas, and the anti-rod side chamber 3 and the air chamber 41 communicate with each other, and the rod side chamber 2 and the liquid chamber 42 communicate with each other, and hydraulic oil is supplied and discharged to the rod side chamber 2. In this configuration, when the lift cylinder 100 contracts (specifically, fully contracts) for the first time after the connection between the lift cylinder 100 and the accumulator 40, the gas in the anti-rod side chamber 3 is pressurized and filled into the air chamber 41 of the accumulator 40. In addition, the fluid pressure cylinder unit 101 may be used in a vertically inverted orientation from that shown in FIG. 1.

[0046] <Variation 5> In the above embodiment, the case where the fluid pressure cylinder is the lift cylinder 100 that raises and lowers the forks of a forklift has been described. However, the fluid pressure cylinder is not limited to this, and may be a cylinder other than the cylinder mounted on a forklift, as long as one of the rod side chamber 2 and the anti-rod side chamber 3 is filled with gas and the piston rod 10 is reciprocated by supplying and discharging hydraulic fluid to the other. In addition, the fluid pressure cylinder may be a double-rod type cylinder.

[0047] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0048] The fluid pressure cylinder unit 101, 201, 301, 401 includes a lift cylinder 100, 400 as a fluid pressure cylinder having a cylinder tube 1, a piston rod 10, 310 that is reciprocatably provided within the cylinder tube 1 and divides the inside of the cylinder tube 1 into a first chamber and a second chamber, an accumulator 40, 240 having an air chamber 41 that can be filled with gas and a liquid chamber 42 that can be filled with liquid, and a first passage 30 that communicates the first chamber with the air chamber 41 of the accumulator 40, 340, the first chamber is filled with gas, and the piston rod 10, 310 reciprocates as hydraulic fluid is supplied and discharged to the second chamber, and a check valve 50 is provided in the first passage 30 as a valve that can only allow gas to flow from the first chamber to the air chamber 41 of the accumulator 40, 340.

[0049] In this configuration, when the lift cylinder 100, 400 is extended, the gas filled in the first chamber is pressurized and is guided through the first passage 30 and the check valve 50 to fill the air chamber 41 of the accumulator 40, 340. This makes it possible to effectively utilize the high-pressure gas discharged from the first chamber as the gas filled in the air chamber 41 of the accumulator 40, 340.

[0050] In the fluid pressure cylinder units 101, 201, 401, the second chamber and the fluid chamber 42 of the accumulator 40, 340 are in communication with each other.

[0051] In this configuration, the second chamber communicates with the fluid chamber 42 of the accumulator 40, 340. Therefore, the vibration of the object driven by the lift cylinder 100, 400 can be absorbed by the accumulator 40, 340.

[0052] In addition, the fluid pressure cylinder unit 201 further includes a second passage 31 that is connected between the first chamber in the first passage 30 and the check valve 50 and communicates with the atmosphere, and a check valve 51 is provided in the second passage 31 to allow only gas to flow from the atmosphere to the first passage 30.

[0053] In this configuration, a drop in pressure within the air chamber 41 of the accumulator 40 is prevented.

[0054] In addition, the fluid pressure cylinder unit 201 further includes a third passage 33 connected between the first chamber in the first passage 30 and the check valve 50, and the third passage 33 is provided with a relief valve 52 that opens when the pressure in the first passage 30 reaches a predetermined pressure.

[0055] In this configuration, the pressure in the air chamber 41 of the accumulator 40 is prevented from exceeding the set pressure.

[0056] In the fluid pressure cylinder unit 401, the accumulator 340 further has a free piston 43 as a partitioning member that partitions the air chamber 41 and the liquid chamber 42, and the first passage 30, the check valve 50, and the free piston 43 are provided within the piston rod 310.

[0057] With this configuration, the fluid pressure cylinder unit 401 can be made compact.

[0058] In the fluid pressure cylinder units 101, 201, 301, 400, when the lift cylinder 100, 400 is extended or contracted for the first time after the lift cylinder 100, 400 and the accumulator 40, 340 are connected, the gas in the first chamber is pressurized and filled into the air chamber 41 of the accumulator 40, 340.

[0059] In this configuration, the air chamber 41 is not filled with high-pressure gas before the operation of the lift cylinders 100, 400. Therefore, the accumulators 40, 340 can be handled safely and easily.

[0060] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments. [Explanation of symbols]

[0061] DESCRIPTION OF SYMBOLS 1···cylinder, 2···rod side chamber (first chamber, second chamber), 3···anti-rod side chamber (first chamber, second chamber), 10,310···piston rod, 30···first passage, 31···second passage, 32···third passage, 40,340···accumulator, 41···air chamber, 42···fluid chamber, 43···free piston (compartment member), 50···check valve (valve), 51···check valve, 52···relief valve, 100,400···lift cylinder (fluid pressure cylinder), 101,201,301,401···fluid pressure cylinder unit

Claims

1. A fluid pressure cylinder unit, a fluid pressure cylinder including a cylinder tube and a piston rod reciprocally provided within the cylinder tube and dividing the interior of the cylinder tube into a first chamber and a second chamber; An accumulator having an air chamber that can be filled with a gas and a liquid chamber that can be filled with a liquid; a first passage communicating the first chamber with the air chamber of the accumulator, The first chamber is filled with a gas, The piston rod reciprocates when hydraulic fluid is supplied to or discharged from the second chamber. the second chamber and the fluid chamber of the accumulator are constantly in communication with each other, a valve provided in the first passage for allowing only a flow of gas from the first chamber to the air chamber of the accumulator,

2. A fluid pressure cylinder unit as described in claim 1, a second passage connected between the first chamber and the valve in the first passage and communicating with the atmosphere; a check valve provided in the second passage for allowing only a flow of gas from the atmosphere to the first passage,

3. A fluid pressure cylinder unit as described in claim 1, a third passage connected between the first chamber and the valve in the first passage, a relief valve provided in the third passage and opening when the pressure in the first passage reaches a predetermined pressure;

4. 2. The fluid pressure cylinder unit according to claim 1, The accumulator further includes a partition member that partitions the air chamber and the liquid chamber, A fluid pressure cylinder unit, comprising: the first passage, the valve, and the partition member provided within the piston rod.

5. 2. The fluid pressure cylinder unit according to claim 1, a pressure adjusting unit configured to adjust the pressure of the fluid pressure cylinder in accordance with a pressure change amount of the fluid pressure applied to the fluid pressure cylinder and the pressure change amount of the fluid pressure applied to the fluid pressure cylinder;

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