JP2004019782A - Rod sealing structure of hydraulic cylinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing structure of a hydraulic cylinder, for preventing the pressure in a space part between a first U-shaped packing and a second U-shaped section from being increased suddenly even if operating fluid collects in the space. <P>SOLUTION: In this rod sealing structure of the hydraulic cylinder, a piston 4 fitted to a piston rod 5 is movably disposed in a cylinder 1, and the piston rod 5 is slidably sealed and supported in the cylinder 1 through a wiper seal 5, a first packing 13 and a second packing 14. The cylinder 1 intermediating between the first packing 13 and the second packing 14 is provided with a storing groove 21, and a pressure rise relief member 22 for relieving the pressure rise caused by operating fluid collecting in the space part S between the first packing 13 and the second packing 14 is inserted in the storing groove 21. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rod seal structure of a hydraulic cylinder provided with U packing for sealingly supporting a piston rod with respect to a cylinder.
[0002]
[Prior art]
Conventional hydraulic cylinders include, for example, those shown in FIGS. 2 and 3. This hydraulic cylinder moves a piston 4 that partitions two oil chambers 2 and 3 into a cylinder 1 whose both ends are closed. The piston 4 is arbitrarily provided, and a piston rod 5 having one end thereof attached to the cylinder 1 is made to penetrate through the cylinder 1. The piston rod 5 is made to penetrate the cylinder 1 in an oil-tight and slidable manner. A supporting rod seal 6 is provided.
[0003]
The cylinder 1 is provided with oil passages 7 and 8 communicating with the oil chambers 2 and 3, respectively, and supplies hydraulic oil from an external hydraulic source (not shown) to the oil chamber 2 through the oil passage 7. By connecting the oil chamber 3 to an external tank (not shown) via the passage 8, the piston rod 5 is contracted, and at the same time, the hydraulic oil from the hydraulic pressure source is supplied to the oil chamber 3 via the oil passage 8, By connecting the oil chamber 2 to an external tank via the oil passage 7, the piston rod 5 is extended.
[0004]
By the way, as shown in FIG. 3, two annular grooves 10 and 11 and an annular notch 12 facing the outside of the cylinder 1 are provided on the inner periphery of the through hole 9 of the piston rod 5 in the cylinder 1. .
[0005]
The rod seal 6 described above, that is, the first U-packing 13 made of urethane resin or the like in the annular groove 10 on the oil chamber side is provided in the annular grooves 10 and 11 and the annular notch 12. A second U packing 14 also made of urethane resin or the like is inserted in the annular groove 11 on the side, and a wiper seal 15 is inserted in the annular cutout 12.
[0006]
The first U-packing 13 has a lip portion 13a formed so as to have a sharp protruding edge, and when the oil chamber 2 side is at a high pressure, the back side of the lip portion 13a is inside the through hole 9. A backup member 16 made of nylon resin or the like that reinforces the lip portion 13a is arranged adjacently so as to prevent the lip portion 13a from biting.
[0007]
The second U-packing 14 has a lip portion 14a formed so as to have a sharp protruding edge, and the back side of the lip portion 14a has a through hole 9a when the oil chamber 2 side is at a high pressure. A backup member 17 made of nylon resin or the like that reinforces the second U-packing 14 is disposed adjacently so as to prevent the second U-packing 14 from biting into the inside.
[0008]
The wiper seal 15 includes a dust lip portion 15a facing outside and an oil lip portion 15b facing inside, and is formed integrally with a metal core 18, and the core 18 is attached to the annular notch. 12.
[0009]
In the rod seal structure configured as described above, especially when the oil chamber 2 side is at a high pressure, the first U-packing 13 functioning as a buffer seal is formed by the sharp protruding edge of the lip portion 13a and the through hole 9 and the piston. The hydraulic oil which is going to move out of the cylinder 1 through the gap with the rod 5 is cut to prevent the hydraulic oil from leaking to the second U packing 14 side.
[0010]
[Problems to be solved by the invention]
However, in the conventional hydraulic cylinder rod seal structure, the lip portion 13a of the first U-packing 13 has a sharp protruding edge, and the protruding edge is slid on the outer periphery of the piston rod. Since the oil film adhering to the outer peripheral surface of No. 5 is cut, if the lip portion 13a does not have a sharp protruding edge due to a molding defect or the like, it is assumed that the above-mentioned oil film cutting action is not sufficiently performed.
[0011]
In this case, the hydraulic oil that has not been cut by the first U-packing 13 during the extension stroke of the piston rod 5 is filled in the space S formed between the first U-packing 13 and the second U-packing 14. , And is cut again at the portion of the backup member 16 that slides on the piston rod 5 in the subsequent compression stroke, so that the backup member 16 may accumulate in the space S.
[0012]
Then, when the space S is filled with the above-mentioned hydraulic oil by repeating the expansion and contraction operation of the piston rod, the pressure of the space S rapidly increases thereafter, and the first or second pressure is increased by the pressure. There is a possibility that the U-packings 13 and 14 may be damaged or hydraulic oil may leak to the outside, thereby shortening the life of the seal structure itself.
[0013]
Therefore, an object of the present invention is to provide a hydraulic system in which even if hydraulic oil accumulates in the space S between the first U packing 13 and the second U packing 14, the pressure in the space S does not suddenly increase. An object of the present invention is to provide a cylinder seal structure.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a first packing, a second packing and a wiper in which a piston attached to a piston rod is movably provided in a cylinder, and is sequentially arranged in series with the cylinder. In a rod seal structure of a hydraulic cylinder that slidably seals and supports a piston rod via a seal, a storage groove is provided in a cylinder between a first packing and a second packing, and a first groove is provided in the storage groove. And a pressure rise reducing member for reducing a pressure rise caused by hydraulic oil accumulated in a space between the packing and the second packing.
[0015]
In this case, it is preferable that the pressure rise reducing member is a hollow O-ring, and is inserted into the storage groove so as not to always slide on the piston rod.
[0016]
Further, the pressure rise reducing member may be a ring body formed of urethane resin in an independently fired state.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment in which the present invention is embodied in a rod seal structure of a cylinder for a high-pressure construction machine will be described below with reference to the drawings.
[0018]
This rod seal structure is characterized in that a pressure rise relieving member is provided between the first U packing 13 and the second U packing 14 of the conventional hydraulic cylinder shown in FIGS. Since other configurations are the same as those of the above-described conventional structure, only the same reference numerals are given in the drawings, and description thereof will be omitted.
[0019]
That is, the storage groove having a rectangular cross section is provided at a substantially intermediate portion between the annular groove 10 in the cylinder 1 in which the first U-packing 13 is inserted and the annular groove 11 in which the second U-packing 14 is inserted. A hollow O-ring 22 is inserted into the storage groove 21 as a pressure rise reducing member.
The O-ring 22 is formed into an annular shape by fusing the ends of the PFA pipe to each other, and is always fixed to the storage groove 22 so that a part thereof is not exposed to the piston rod 5 side from the storage groove 22. It is fixedly inserted in a state of being elastically deformed.
[0020]
Therefore, after the space portion S formed by the first U-packing 13 and the second U-packing 14 is filled with the hydraulic oil, the O-ring 22 in the storage groove 21 is elastically deformed, so that It is designed to prevent sudden pressure rise.
[0021]
In the hydraulic cylinder configured as described above, the lip portion 13a of the first U-packing 13 is in a state in which its protruding end edge is in sliding contact with the outer periphery of the piston rod 5, so that, for example, the extension of the piston rod 5 In the process, the piston rod 5 slides on the first U-packing 13 in a state where the oil film adhered to the outer periphery thereof is cut to an appropriate thickness, and the lip portion 13a causes the oil chamber 2 side to move. The high pressure does not affect the second U packing 14.
[0022]
At this time, if the lip portion 13a does not have a sharp protruding edge due to a manufacturing error or the like, the above-described oil film cutting action is not sufficiently exerted, and the excess hydraulic oil is removed from the first U-packing 13. And the second U-packing 14 accumulates in the space S.
[0023]
When the advancing and retreating operation of the piston rod 5 is repeated in this state, the space S is filled with the working oil, and thereafter, a rapid pressure rise is attempted.
[0024]
However, in the present embodiment, the storage groove 21 is formed between the two annular grooves 10 and 11, and the hollow O-ring 22 is inserted into the storage groove 21. By deforming, the above-mentioned pressure rise can be absorbed.
[0025]
In order to confirm the above effects, the piston rod 5 was reciprocated 100 km and 400 km, and the pressure in the space S at that time was measured. When the pressure was 1 Mpa at 100 km and 1 Mpa at 400 km, respectively. Did not.
[0026]
Incidentally, when the hollow O-ring according to the present embodiment was not used, 21 Mpa at 100 km and 38 Mpa at 400 km, and the effect of the present embodiment was confirmed.
[0027]
Therefore, it is possible to surely prevent breakage of each U-packing due to a sudden increase in pressure as shown in the prior art and troubles such as oil leakage and extend the life.
[0028]
In addition, since the hollow O-ring 22 is inserted into the storage groove 21 so as not to be in sliding contact with the piston rod 5 at all, not only does the piston rod 5 not give extra resistance when moving forward and backward. Also, the durability of the O-ring 22 itself can be improved.
[0029]
The present invention is not limited to the above-described embodiment, but may be embodied with the following modifications, for example.
[0030]
1) As the pressure rise reducing member, in addition to the hollow O-ring 22 shown in the present embodiment, a urethane resin in an independently foamed state or another synthetic resin may be used. When used, the set pressure to be alleviated by changing the foaming ratio can be easily changed.
[0031]
2) The cross-sectional shape of the storage groove 21 is not limited to the rectangular shape, but may be a square shape or another shape.
[0032]
3) In the present embodiment, the cylinder for the high-pressure construction machine is shown, but the present invention is not limited to this, and it is needless to say that the cylinder may be embodied as a general hydraulic cylinder.
[0033]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0034]
1) According to the invention of each claim, a sudden pressure rise caused by the hydraulic oil accumulated in the space formed by the first and second U-packings is provided between the first and second U-packings. Can be suppressed by the pressure-relief member provided, the risk of damaging the first or second U-packing or causing leakage of hydraulic oil to the outside can be reliably prevented, and the rod seal structure itself can be prevented. Life can be extended.
[0035]
2) According to the second aspect of the present invention, the hollow O-ring is inserted into the storage groove so as not to be always in sliding contact with the piston rod, so that extra resistance is given when the piston rod moves forward and backward. Not only that, the durability of the O-ring itself can be increased.
[0036]
3) According to the third aspect of the invention, the set pressure to be alleviated by changing the foaming ratio can be easily changed.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part showing a rod seal structure of a hydraulic cylinder showing an embodiment of the present invention.
FIG. 2 is a sectional view showing a conventional hydraulic cylinder.
FIG. 3 is a sectional view of a main part showing a rod seal structure of a conventional hydraulic cylinder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder 4 Piston 5 Piston rod 13 First packing 14 Second packing 15 Wiper seal 21 Storage groove 22 O-ring (pressure rise reducing member)
S space part

Claims (3)

A piston attached to a piston rod is movably provided in a cylinder, and the piston rod is slidably and sealedly supported via a first packing, a second packing, and a wiper seal sequentially arranged in series with the cylinder. In the rod seal structure of a hydraulic cylinder, a storage groove is provided in a cylinder between the first packing and the second packing, and a space between the first packing and the second packing is provided in the storage groove. A rod seal structure for a hydraulic cylinder, wherein a pressure rise reducing member for mitigating a pressure rise caused by hydraulic oil accumulated in the cylinder is inserted. 2. The rod seal structure for a hydraulic cylinder according to claim 1, wherein the pressure rise reducing member is a hollow O-ring, and is inserted into the storage groove so as not to always contact the piston rod. 2. The rod seal structure for a hydraulic cylinder according to claim 1, wherein the pressure rise reducing member is a ring body formed of urethane resin in an independently fired state.

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