Fluid pressure cylinder unit

Abstract

To facilitate the handling of a fluid pressure cylinder unit.SOLUTION: A fluid pressure cylinder unit 101 includes a lift cylinder 100 having a piston rod 10 which is provided reciprocatively in a cylinder tube 1 for partitioning the inside of the cylinder tube 1 into a rod chamber 2 and a bottom chamber 3, and driving a fork 80, a supply / discharge passage 20 connected to the bottom chamber 3, and a buffer 40 connected to the supply / discharge passage 20, the buffer 40 having a cylinder 41, a piston 51 provided reciprocatively in the cylinder 41 for partitioning the inside of the cylinder 41 into a first pressure chamber 43 and a second pressure chamber 42, a communication path 60 communicating between the first pressure chamber 43 and the second pressure chamber 42, and a spring 70 for energizing the piston 51 in a direction where the first pressure chamber 43 is shrunk, the bottom chamber 3 communicating with the first pressure chamber 43 or the second pressure chamber 42 through the supply / discharge passage 20.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a vehicle (forklift) including a vehicle body, a loading part supported by the vehicle body and capable of loading luggage, a lift cylinder for raising and lowering the loading part, and an accumulator communicable with the lift cylinder. The accumulator suppresses fluctuations in the pressure of the chamber by introducing and accumulating fluid when the pressure in the chamber of the lift cylinder rises, and discharging the accumulated fluid when the pressure in the chamber drops. By suppressing a rapid pressure change in the chamber in this way, vertical vibrations of the luggage loaded on the loading part are suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the lift cylinder described in Patent Document 1, a high-pressure gas is enclosed in an accumulator connected to the lift cylinder. Since there are legal regulations on high-pressure gases, it is not easy to transport an accumulator filled with a high-pressure gas, or to transport and use a gas cylinder of the high-pressure gas to be enclosed in the accumulator. Therefore, the lift cylinder described in Patent Document 1 is difficult to handle.

[0005] The present invention has been made in view of the above problems, and an object thereof is to facilitate the handling of a fluid pressure cylinder unit.

Means for Solving the Problems

[0006] The present invention relates to a fluid pressure cylinder unit, comprising a cylinder tube, and a piston rod reciprocably provided in the cylinder tube and partitioning the inside of the cylinder tube into a rod chamber and a bottom chamber, the fluid pressure cylinder for driving a driven object; a supply / discharge passage connected to the bottom chamber for supplying a working fluid to the bottom chamber or discharging the working fluid from the bottom chamber; and a shock absorber connected to the supply / discharge passage. The shock absorber includes a cylinder, a piston reciprocably provided in the cylinder and partitioning the inside of the cylinder into a first pressure chamber and a second pressure chamber, a communication passage communicating the first pressure chamber and the second pressure chamber, and a biasing member for biasing the piston in a direction in which the first pressure chamber contracts. The bottom chamber communicates with the first pressure chamber or the second pressure chamber through the supply / discharge passage.

[0007] In this invention, when an impact is applied to the driven object, the pressure in the bottom chamber increases, and the pressure in the first pressure chamber communicating with the bottom chamber also increases. As a result, the working fluid moves between the first pressure chamber and the second pressure chamber through the communication passage, and the piston of the shock absorber moves, thereby changing the volume of the bottom chamber. Thereby, the impact applied to the driven object is absorbed. Thus, in the fluid pressure cylinder unit, the shock applied to the driven object is absorbed by the shock absorber instead of an accumulator in which high-pressure gas is enclosed, so that handling becomes easy.

[0008] Further, the present invention is characterized in that the communication passage has a throttle portion for imparting resistance to the flow of the working fluid.

[0009] In this invention, since a damping force is exerted by the throttle portion, the impact applied to the driven object is more effectively absorbed.

[0010] Further, the present invention is characterized in that the shock absorber has a rod with a piston connected to the tip and reciprocably provided in the cylinder, and the rod is provided in the second pressure chamber.

[0011] In the present invention, the pressure-receiving areas of the pistons facing the first pressure chamber and the second pressure chamber are different due to the rods. As a result, the pistons are more likely to move due to the pressure changes in the first pressure chamber and the second pressure chamber, and the impact applied to the driven object is more effectively absorbed.

[0012] Further, the present invention is characterized in that the shock absorber is provided inside the fluid pressure cylinder.

[0013] In the present invention, the fluid pressure cylinder unit can be made compact.

Advantages of the Invention

[0014] According to the present invention, the handling of the fluid pressure cylinder unit can be facilitated.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0016] With reference to the drawings, a fluid pressure cylinder unit 101 according to an embodiment of the present invention will be described. The fluid pressure cylinder unit 101 includes a fluid pressure cylinder. In the present embodiment, the fluid pressure cylinder is a lift cylinder 100 that drives (lifts and lowers) a fork 80 as a driving target of a forklift, and a case where a pair of lift cylinders 100 is provided will be described.

[0017] The lift cylinder 100 is a single-acting hydraulic cylinder. As shown in FIG. 1, the lift cylinder 100 includes a cylinder tube 1 and a piston rod 10 that is reciprocally provided in the cylinder tube 1 and partitions the inside of the cylinder tube 1 into a rod chamber 2 and a bottom chamber 3.

[0018] The piston rod 10 includes a piston 11 slidably provided along the inner peripheral 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 chamber 2 is filled with a gas such as air. In the rod chamber 2, gas enters and exits, or is compressed, or expands according to the movement of the piston rod 10. Working oil as a working fluid is supplied and discharged to and from the bottom chamber 3 through a supply / discharge passage 20 described later. Note that, as the working fluid, a fluid such as water or a water-soluble substitute other than the working oil may be used.

[0019] The fluid pressure cylinder unit 101 includes a supply / discharge passage 20 connected to the bottom chamber 3 and a shock absorber 40 connected to the supply / discharge passage 20. For example, when the forklift drives over road surface irregularities during travel, an impact is applied to the fork 80, and there is a risk of the load on the fork 80 collapsing. The shock absorber 40 is for absorbing such an impact applied from the road surface to the fork 80.

[0020] The supply / discharge passage 20 is connected to both of the bottom chambers 3 of the pair of lift cylinders 100. The supply / discharge passage 20 has a hydraulic hose 21 (see FIG. 2) and a joint 22 (see FIG. 2), and is connected to a pump (not shown) or a tank (not shown) by a switching valve (not shown). That is, the supply / discharge passage 20 supplies hydraulic oil to the bottom chamber 3 or discharges hydraulic oil from the bottom chamber 3. In the lift cylinder 100, the piston rod 10 reciprocates when hydraulic oil is supplied to and discharged from the bottom chamber 3 through the supply / discharge passage 20. Specifically, when hydraulic oil is supplied from the pump to the bottom chamber 3, the piston rod 10 moves upward (the upper side in FIG. 1), the lift cylinder 100 extends, and the fork 80 and the load placed on the fork 80 rise. When the hydraulic oil is discharged from the bottom chamber 3 to the tank due to the self-weights of the fork 80, the load, and the piston rod 10, the piston rod 10 moves downward (the lower side in FIG. 1), the lift cylinder 100 contracts, and the fork 80 and the load descend. The pair of lift cylinders 100 extend and contract synchronously.

[0021] The shock absorber 40 is provided between the pair of lift cylinders 100 (see FIG. 2). The shock absorber 40 includes a cylinder 41, a piston rod 50 that is reciprocally provided in the cylinder 41 and divides the inside of the cylinder 41 into a first pressure chamber 43 and a second pressure chamber 42, a communication passage 60 that communicates the first pressure chamber 43 and the second pressure chamber 42, and a spring 70 as a biasing member that biases the piston rod 50 in the direction in which the first pressure chamber 43 contracts. In the present embodiment, the shock absorber 40 is formed separately from the lift cylinder 100, and as shown in FIG. 2, the shock absorber 40 and the lift cylinder 100 are connected to the supply / discharge passage 20 and provided adjacent to each other side by side.

[0022] The piston rod 50 has a piston 51 that is reciprocally movable within the cylinder 41 and divides the interior of the cylinder 41 into a first pressure chamber 43 and a second pressure chamber 42, and a rod 52 with the piston 51 connected to its tip and reciprocally movable within the cylinder 41. In this embodiment, the rod 52 is provided in the second pressure chamber 42 and extends outside the cylinder 41, and the second pressure chamber 42 is located above the first pressure chamber 43. In other words, in this embodiment, the second pressure chamber 42 is provided on the side of the rod 52. The supply / discharge passage 20 communicates with the first pressure chamber 43. That is, the bottom chamber 3 of the lift cylinder 100 communicates with the first pressure chamber 43 through the supply / discharge passage 20. The communication passage 60 is provided to penetrate the piston 51 in the axial direction and communicates the first pressure chamber 43 and the second pressure chamber 42. The communication passage 60 has an orifice 61 as a throttle portion that imparts resistance to the flow of the hydraulic oil. Therefore, resistance is imparted to the hydraulic oil moving between the first pressure chamber 43 and the second pressure chamber 42 through the communication passage 60 by the orifice 61. The spring 70 is provided in the second pressure chamber 42 so as to surround the rod 52 in the second pressure chamber 42.

[0023] Next, mainly referring to FIG. 3, the operation of the shock absorber 40 absorbing the impact applied to the fork 80 will be described in detail. FIG. 3 is a schematic diagram showing the operation of the shock absorber 40 absorbing the impact applied to the fork 80.

[0024] FIG. 3(a) shows a state before an impact is applied to the fork 80 during traveling in which the lift cylinder 100 is lifting the fork 80 and traveling. In this state, due to the self-weight of the fork 80 and the load, pressure acts on the bottom chamber 3 of the lift cylinder 100 via the piston rod 10. Since the bottom chamber 3 communicates with the first pressure chamber 43 of the shock absorber 40 through the supply / discharge passage 20, the piston 51 of the shock absorber 40 moves upward and floats from the bottom surface of the cylinder 41. At this time, in the shock absorber 40, the load due to the pressure in the first pressure chamber 43 is balanced with the resultant force of the load due to the pressure in the second pressure chamber 42 and the biasing force of the spring 70. In this state, the spring 70 is in a state with a compression allowance.

[0025] For example, when the forklift drives over the unevenness of the road surface during travel, an impact force F is applied to the fork 80 as shown in Fig. 3(b). Then, since a downward force acts on the piston rod 10 of the lift cylinder 100 via the fork 80, the pressure in the bottom chamber 3 and the first pressure chamber 43 of the shock absorber 40 communicating with the bottom chamber 3 increases, and a pressure difference is generated between the second pressure chamber 42 and the first pressure chamber 43 of the shock absorber 40. At this point, since almost no movement of the hydraulic oil occurs, the piston rod 10 does not move, and the piston rod 50 of the shock absorber 40 also does not move.

[0026] And in the shock absorber 40, when the pressure in the first pressure chamber 43 increases and the load due to the pressure in the first pressure chamber 43 exceeds the combined force of the load due to the pressure in the second pressure chamber 42 and the biasing force of the spring 70, as shown by the arrow A in Fig. 3(c), the hydraulic oil in the second pressure chamber 42 moves to the first pressure chamber 43 through the communication passage 60 and the orifice 61, and the piston rod 50 moves upward and the shock absorber 40 extends. As a result, since the first pressure chamber 43 expands and the pressure decreases, hydraulic oil is guided from the bottom chamber 3 of the lift cylinder 100 to the first pressure chamber 43 through the supply and discharge passage 20, and as shown by the arrow B in Fig. 3(c), the piston rod 10 moves downward and the bottom chamber 3 contracts. By contracting the lift cylinder 100 in this way, the impact applied to the fork 80 is absorbed. Note that in Fig. 3, the movement amounts of the piston rod 10 of the lift cylinder 100 and the piston rod 50 of the shock absorber 40 are exaggeratedly shown.

[0027] The movement amount of the piston rod 10 corresponds to the movement amount of the piston rod 50. Specifically, the bottom chamber 3 contracts by the withdrawal volume of the piston rod 50 from the cylinder 41 and the piston rod 10 moves. That is, the larger the movement amount of the piston rod 50, the larger the movement amount of the piston rod 10, so the impact applied to the fork 80 is more easily absorbed. When the impact applied to the fork 80 is absorbed, the hydraulic oil in the second pressure chamber 42 moves to the first pressure chamber 43 through the orifice 61, and the orifice 61 exerts a damping force, so the impact applied to the fork 80 is absorbed while being damped.

[0028] After the impact is absorbed, the pressure in the bottom chamber 3 of the lift cylinder 100 and the first pressure chamber 43 of the shock absorber 40 decreases. Then, due to the biasing force of the spring 70, the piston rod 50 of the shock absorber 40 moves downward, and the first pressure chamber 43 shrinks. As a result, hydraulic oil is guided from the first pressure chamber 43 to the bottom chamber 3 of the lift cylinder 100 through the supply and discharge passage 20, the piston rod 10 moves upward, the bottom chamber 3 expands, the lift cylinder 100 extends, and returns to the state shown in Fig. 3(a). When an impact is applied to the fork 80 again, the operations shown in Figs. 3(a)-(c) above are repeated.

[0029] Here, in the fluid pressure cylinder unit 101, it is also conceivable to use an accumulator filled with high-pressure gas instead of the shock absorber 40 to absorb the impact applied to the fork 80. However, since there are legal regulations on high-pressure gas, it is not easy to carry the accumulator filled with high-pressure gas, or to carry and use the gas cylinder of the high-pressure gas filled in the accumulator, and there are also problems such as the need for administrative approval. Therefore, such a fluid pressure cylinder unit 101 is difficult to handle.

[0030] On the other hand, in the fluid pressure cylinder unit 101 of the present embodiment, as described above, the impact applied to the fork 80 is absorbed not by an accumulator filled with high-pressure gas but by the shock absorber 40. Therefore, the handling of the fluid pressure cylinder unit 101 becomes easy.

[0031] In addition, since the communication passage 60 has an orifice 61 that imparts resistance to the flow of hydraulic oil, damping force is exerted by the orifice 61. Specifically, when an impact is applied to the fork 80 and the piston rod 50 of the shock absorber 40 moves upward and the pressure in the second pressure chamber 42 increases, resistance is imparted to the hydraulic oil that moves from the second pressure chamber 42 to the first pressure chamber 43 through the communication passage 60 by the orifice 61, thereby damping the impact. As a result, the impact applied to the fork 80 can be absorbed while being damped by the orifice 61, so that the impact applied to the fork 80 is more effectively absorbed. Further, when the shock absorber 40 absorbs the impact applied to the fork 80, the shock absorber 40 repeatedly extends and contracts, causing the piston rod 50 to reciprocate, and accordingly, the piston rod 10 of the lift cylinder 100 also repeatedly reciprocates, which may cause the fork 80 to vibrate. However, since the reciprocating motion of the piston rod 50 is damped by the orifice 61, vibration of the fork 80 is suppressed.

[0032] In addition, since the rod 52 of the shock absorber 40 is provided in the second pressure chamber 42, the pressure receiving areas of the piston 51 facing the first pressure chamber 43 and the second pressure chamber 42 are different. Specifically, the pressure receiving area of the piston 51 facing the first pressure chamber 43 is larger than the pressure receiving area facing the second pressure chamber 42 by the cross-sectional area of the rod 52. As a result, the piston 51 is more likely to move due to the pressure change between the first pressure chamber 43 and the second pressure chamber 42, and the amount of movement of the piston 51 increases. Therefore, the amount of movement of the piston rod 10 of the lift cylinder 100 increases, and the impact applied to the fork 80 is more effectively absorbed.

[0033] In addition, since the shock absorber 40 is connected to the supply / discharge passage 20, it can be attached as an attachment to an existing lift cylinder 100. Therefore, it can be easily replaced with an accumulator, and handling can be made easier.

[0034] In addition, the shock absorber 40 is provided side by side with the lift cylinder 100 in the supply / discharge passage 20. Therefore, the fluid pressure cylinder unit 101 can be made compact.

[0035] Note that the strength (spring constant) of the spring 70 is set, for example, to ensure the amount of movement of the piston 51 that can absorb the impact when the fork 80 is impacted and the bottom chamber 3 of the lift cylinder 100 shrinks.

[0036] According to the above embodiments, the following operational effects are achieved.

[0037] In the hydraulic cylinder unit 101, when an impact is applied to the fork 80, the bottom chamber 3 becomes high pressure, and the first pressure chamber 43 communicating with the bottom chamber 3 becomes high pressure. As a result, the hydraulic oil moves between the first pressure chamber 43 and the second pressure chamber 42 through the communication passage 60, and the piston 51 of the shock absorber 40 moves, causing the bottom chamber 3 to shrink. Thereby, the impact applied to the fork 80 is absorbed. In this way, in the hydraulic cylinder unit 101, since the impact applied to the fork 80 is absorbed by the shock absorber 40 instead of an accumulator in which high-pressure gas is enclosed, handling becomes easy.

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

[0039] <Modification Example 1> In the above embodiment, the bottom chamber 3 of the lift cylinder 100 communicates with the first pressure chamber 43 through the supply / discharge passage 20. However, it is not limited to this. As shown in FIG. 4, the bottom chamber 3 may communicate with the second pressure chamber 42 through the supply / discharge passage 20. When an impact force F is applied to the fork 80, the pressures in the bottom chamber 3 and the second pressure chamber 42 communicating with the bottom chamber 3 increase. Along with this, the pressure in the first pressure chamber 43 communicating with the second pressure chamber 42 also increases. When the load due to the pressure in the first pressure chamber 43 exceeds the resultant force of the load due to the pressure in the second pressure chamber 42 and the biasing force of the spring 70, the hydraulic oil in the second pressure chamber 42 moves to the first pressure chamber 43 through the communication passage 60 and the orifice 61, the piston rod 50 moves upward, and the shock absorber 40 extends. Then, the hydraulic oil is guided from the second pressure chamber 42 to the bottom chamber 3 through the supply / discharge passage 20, the bottom chamber 3 expands, the lift cylinder 100 extends, and the impact applied to the fork 80 is absorbed. After the impact is absorbed, the piston rod 50 moves downward due to the decrease in pressure in the first pressure chamber 43 and the biasing force of the spring 70, and the shock absorber 40 contracts.

[0040] In addition, in the above embodiment and this modification example, the rod 52 is provided to extend in the direction in which the piston 51 first moves (the upper side in FIGS. 1 and 4) when an impact is applied to the fork 80. In other words, the rod 52 is provided such that the pressure receiving area of the piston 51 in the direction in which it first moves (the second pressure chamber 42 side) when an impact is applied to the fork 80 becomes smaller, making it easier for the piston 51 to move.

[0041] <Modification Example 2> In the above embodiment, the inside of the cylinder 41 of the shock absorber 40 is partitioned into a first pressure chamber 43 and a second pressure chamber 42 by the piston 51. In addition to this, as shown in FIG. 5, the second pressure chamber 42 may be partitioned into a third pressure chamber 42a and a fourth pressure chamber 42b by the rod 52. The third pressure chamber 42a is partitioned by the piston 51, the outer peripheral surface of the rod 52, and the cylinder 41, and communicates with a tank (not shown in the figure) or the atmosphere through a passage (omitted in the figure). The fourth pressure chamber 42b is partitioned by the end face of the rod 52 and the cylinder 41. In this configuration, the communication passage 60 communicates the first pressure chamber 43 and the fourth pressure chamber 42b, and the spring 70 is provided in the fourth pressure chamber 42b to urge the piston 51 in the direction in which the first pressure chamber 43 contracts. Even with this configuration, the same effects as those of the above embodiment are achieved.

[0042] <Modification 3> In the above embodiment, the piston 51 is formed in a disk shape. However, the present invention is not limited to this, and as shown in FIG. 6, the piston 51 may be formed in a concave shape. In this configuration, the rod 52 has a base end portion (the upper end portion in FIG. 6) fixed to a device or the like, and a tip end portion (the lower end portion in FIG. 6) provided in the concave portion of the piston 51. The second pressure chamber 42 is partitioned by the concave portion of the piston 51 and the tip end portion of the rod 52. Even with this configuration, the same effects as those of the above embodiment are achieved.

[0043] <Modification 4> In the above embodiment, the shock absorber 40 is provided separately from the lift cylinder 100. On the other hand, in the fluid pressure cylinder unit 401 according to Modification 4, as shown in FIG. 7, the shock absorber 40 is provided inside the piston rod 310 of the lift cylinder 400. Specifically, a cylinder 41 of the shock absorber 40 is provided as a space inside the piston rod 310, and a piston rod 50 and a spring 70 are provided inside the cylinder 41. Further, the supply / discharge passage 20 has a first supply / discharge passage 20a connected to the bottom chamber 3 of the lift cylinder 100, and a second supply / discharge passage 20b that communicates the bottom chamber 3 and the first pressure chamber 43 of the shock absorber 40. Through the supply / discharge passage 20, hydraulic oil is supplied to the bottom chamber 3 or discharged from the bottom chamber 3.

[0044] In this configuration, when an impact force F is applied to the fork 80, the pressure in the bottom chamber 3 and the first pressure chamber 43 communicating with the bottom chamber 3 increases. When the load due to the pressure in the first pressure chamber 43 exceeds the combined force of the load due to the pressure in the second pressure chamber 42 and the biasing force of the spring 70, the hydraulic oil in the second pressure chamber 42 moves to the first pressure chamber 43 through the communication passage 60 and the orifice 61, and the piston rod 50 of the shock absorber 40 moves upward. Then, the hydraulic oil is guided from the bottom chamber 3 to the first pressure chamber 43 through the second supply / discharge passage 20b, the bottom chamber 3 shrinks, the lift cylinder 100 contracts, and the impact applied to the fork 80 is absorbed. In this way, by providing the shock absorber 40 inside the piston rod 310, the fluid pressure cylinder unit 401 can be made compact.

[0045] Also, the shock absorber 40 may be provided inside the cylinder tube 1 of the lift cylinder 100. Specifically, the shock absorber 40 may be provided on the bottom chamber 3 side inside the cylinder tube 1 of the lift cylinder 100. The shock absorber 40 is provided in the upside-down direction compared to the direction shown in FIG. 1 or FIG. 7 so that the first pressure chamber 43 communicates with the bottom chamber 3. The supply / discharge passage 20 has a first supply / discharge passage 20a connected to the bottom chamber 3 of the lift cylinder 100 and a second supply / discharge passage 20b communicating the bottom chamber 3 and the first pressure chamber 43. Through the supply / discharge passage 20, hydraulic oil is supplied to the bottom chamber 3 or discharged from the bottom chamber 3. Even with this configuration, the fluid pressure cylinder unit 401 can be made compact.

[0046] <Modification Example 5> In the above embodiment, the communication passage 60 has an orifice 61 that imparts resistance to the flow of the hydraulic oil, and the damping force is exerted by the orifice 61. However, the orifice 61 is not an essential component. As long as the shock absorber 40 can absorb the impact, the communication passage 60 may not have the orifice 61. Also, a relief valve may be provided instead of the orifice 61.

[0047] <Modification Example 6> In the above embodiment, the communication passage 60 is provided in the piston 51, and the spring 70 is provided in the second pressure chamber 42. However, the communication passage 60 is not limited to this. As long as it is configured to communicate the first pressure chamber 43 and the second pressure chamber 42, it may be provided in the cylinder 41 or outside the cylinder 41. Further, the spring 70 may be configured to bias the piston 51 in the direction in which the first pressure chamber 43 contracts, and may be provided outside the second pressure chamber 42 or outside the cylinder 41. For example, the spring 70 may be provided in the first pressure chamber 43 in a state where it is extended from its natural length.

[0048] <Modification Example 7> In the above embodiment, the communication passage 60 having the orifice 61 is provided in the piston 51. In addition to this, a passage having a check valve that allows only the flow of hydraulic oil from the first pressure chamber 43 to the second pressure chamber 42 may be provided in the piston 51.

[0049] <Modification Example 8> In the above embodiment, the case where the fluid pressure cylinder is the lift cylinder 100 that raises and lowers the fork 80 of the forklift has been described. However, the fluid pressure cylinder is not limited to this, and may be a cylinder mounted on industrial machinery other than forklifts. Further, the fluid pressure cylinder may be a double-rod type cylinder. Further, one or more fluid pressure cylinders may be provided in the fluid pressure cylinder unit 101.

[0050] The configuration, operation, and effects of the embodiment of the present invention configured as described above will be collectively described.

[0051] The fluid pressure cylinder units 101 and 401 include a cylinder tube 1, and a piston rod 10 or 310 that is reciprocally provided in the cylinder tube 1 and divides the interior of the cylinder tube 1 into a rod chamber 2 and a bottom chamber 3. A lift cylinder 100 or 400 serves as a fluid pressure cylinder for driving a fork 80 as a driving target. A supply / discharge passage 20 is connected to the bottom chamber 3 to supply or discharge the working fluid to or from the bottom chamber 3, and a shock absorber 40 is connected to the supply / discharge passage 20. The shock absorber 40 includes a cylinder 41, a piston 51 that is reciprocally provided in the cylinder 41 and divides the interior of the cylinder 41 into a first pressure chamber 43 and a second pressure chamber 42, a communication passage 60 that communicates the first pressure chamber 43 and the second pressure chamber 42, and a spring 70 that serves as a biasing member for biasing the piston 51 in a direction in which the first pressure chamber 43 contracts. The bottom chamber 3 communicates with the first pressure chamber 43 or the second pressure chamber 42 through the supply / discharge passage 20.

[0052] In this configuration, when an impact is applied to the fork 80, the bottom chamber 3 becomes high pressure, and the first pressure chamber 43 that communicates with the bottom chamber 3 becomes high pressure. As a result, the working fluid moves between the first pressure chamber 43 and the second pressure chamber 42 through the communication passage 60, and the piston 51 of the shock absorber 40 moves, thereby changing the volume of the bottom chamber 3. Thereby, the impact applied to the fork 80 is absorbed. Thus, in the fluid pressure cylinder units 101 and 401, the shock applied to the fork 80 is absorbed by the shock absorber 40 instead of an accumulator in which high-pressure gas is enclosed, so that handling becomes easy.

[0053] Further, in the fluid pressure cylinder units 101 and 401, the communication passage 60 has an orifice 61 that serves as a throttle portion for imparting resistance to the flow of the working fluid.

[0054] In this configuration, since a damping force is exerted by the orifice 61, the impact applied to the fork 80 is more effectively absorbed.

[0055] Also, in the fluid pressure cylinder units 101 and 401, the shock absorber 40 has a rod 52 with a piston 51 connected to its tip and is reciprocally provided in a cylinder 41. The rod 52 is provided in a second pressure chamber 42.

[0056] In this configuration, the pressure receiving areas of the piston 51 facing the first pressure chamber 43 and the second pressure chamber 42 are different due to the rod 52. As a result, the piston 51 is more likely to move due to the pressure changes in the first pressure chamber 43 and the second pressure chamber 42, and the impact applied to the fork 80 is absorbed more effectively.

[0057] Also, in the fluid pressure cylinder unit 401, the shock absorber 40 is provided in a lift cylinder 400.

[0058] In this configuration, the fluid pressure cylinder unit 401 can be made compact.

[0059] As described above, the embodiments of the present invention have been explained. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Explanation of Reference Numerals

[0060] 1... cylinder tube, 2... rod chamber, 3... bottom chamber, 10, 310... piston rod, 20... supply / discharge passage, 40... shock absorber, 41... cylinder, 42... second pressure chamber, 43... first pressure chamber, 51... piston, 52... rod, 60... communication passage, 61... orifice (throttle portion), 70... spring (biasing member), 80... fork (driven object), 100, 400... lift cylinder (fluid pressure cylinder), 101, 401... fluid pressure cylinder unit

Claims

1. A fluid pressure cylinder unit, a fluid pressure cylinder having a cylinder tube and a piston rod reciprocally disposed within the cylinder tube and dividing the interior of the cylinder tube into a rod chamber and a bottom chamber, the fluid pressure cylinder driving an object to be driven; a supply / discharge passage connected to the bottom chamber for supplying a working fluid to the bottom chamber or discharging a working fluid from the bottom chamber; a shock absorber connected to the supply / discharge passage, The buffer comprises: A cylinder; a piston that is reciprocally disposed within the cylinder and divides the interior of the cylinder into a first pressure chamber and a second pressure chamber; a communication passage that communicates the first pressure chamber with the second pressure chamber; a biasing member that biases the piston in a direction that reduces the size of the first pressure chamber, the shock absorber is actuated only by the flow of the working fluid through the supply and discharge passage, The bottom chamber is a fluid pressure cylinder unit that communicates with the first pressure chamber or the second pressure chamber through the supply / discharge passage.

2. 2. The fluid pressure cylinder unit according to claim 1, 10. A fluid pressure cylinder unit, wherein the communication passage has a throttle portion that applies resistance to the flow of the working fluid.

3. 2. The fluid pressure cylinder unit according to claim 1, the shock absorber has a rod, the piston being connected to a tip thereof, and the rod being reciprocally movable within the cylinder; The fluid pressure cylinder unit is characterized in that the rod is provided in the second pressure chamber.

4. 2. The fluid pressure cylinder unit according to claim 1, The fluid pressure cylinder unit is characterized in that the shock absorber is provided inside the fluid pressure cylinder.

5. A fluid pressure cylinder unit as described in claim 1, The communication passage passes through the piston and communicates the first pressure chamber with the second pressure chamber.

6. A fluid pressure cylinder unit as described in claim 1, The shock absorber is a fluid pressure cylinder unit provided adjacent to the fluid pressure cylinder.

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