JP2004028160A - Rod seal structure for hydraulic cylinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seal structure for a hydraulic cylinder having no stay of operating fluid in a space part between a first U-packing and a second U-packing. <P>SOLUTION: A piston 4 installed on a piston rod 5 is movably provided in a cylinder 1, the piston rod 5 is slidably sealed and supported through a wiper seal 5 disposed serially to the cylinder 1, and the first packing 13 and the second packing 14, and a back-up member 16 to regulate deformation of a lip part 13a for the first packing 13 is provided on the atmospheric side of it in this rod seal structure for a hydraulic cylinder. An oil returning means 19 is provided to return operating fluid invading into a space part S between the first packing 13 and the second packing 14 to the back-up member 16. <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. 3 and 4. This hydraulic cylinder moves a piston 4 that partitions two oil chambers 2 and 3 in 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. The oil pressure from an external oil pressure source (not shown) is supplied to the oil chamber 2 through the oil passage 7, By connecting the chamber 3 to an external tank (not shown) via an oil passage 8, the piston rod 5 is contracted, while the oil pressure from the oil pressure source is supplied to the oil chamber 3 via the oil passage 8, By connecting the chamber 2 to an external tank via an oil passage 7, the piston rod 5 is extended.
[0004]
As shown in FIG. 4, two annular grooves 10 and 11 and an annular notch 12 facing the outside of the cylinder 1 are provided in series on the inner periphery of the through hole 9 of the piston rod 5 in the cylinder 1. ing.
[0005]
The rod seal 6 described above is provided in the annular grooves 10 and 11 and the annular notch 12, that is, a first U-packing 13 made of urethane resin or the like is provided in the annular groove 10 on the oil chamber side. A second U packing 14 also made of urethane resin or the like is inserted in the annular groove 11, 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 rod 5. The hydraulic oil which is going to move out of the cylinder 1 through the gap is cut to prevent leakage to the second U packing 14 side.
[0010]
[Problems to be solved by the invention]
However, in the conventional hydraulic cylinder rod seal structure described above, the lip portion 13a of the first U-packing 13 is formed as a sharp protruding edge, and the protruding edge is slidably contacted with the outer periphery of the piston rod. Since the oil film adhering to the outer peripheral surface of 5 is cut off, if the lip portion 13a does not have a sharp protruding edge due to poor molding of the lip portion 13a, the above-described oil film cutting action may not be sufficiently performed. is assumed.
[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 transferred to the space S formed between the first U-packing 13 and the second U-packing 14. The back-up member 16 is cut again at the portion of the backup member 16 that is in sliding contact with the piston rod 5 during the compression stroke of the piston rod 5, so that the backup member 16 may accumulate in the space S.
[0012]
When the space S is fully filled with the above-mentioned hydraulic oil due to the repetition of the expansion and contraction operation of the piston rod, the pressure in the space S sharply increases thereafter, and the first pressure is increased by the pressure. Alternatively, the second 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]
In particular, in the above-described rod seal structure, since the backup member 16 is in sliding contact with the piston rod 5 with a large contact area, the hydraulic oil accumulated in the space S passes through the sliding contact portion and is There is a problem that it is difficult to return to the room 2 side.
[0014]
Therefore, an object of the present invention is to provide a seal structure for a hydraulic cylinder in which hydraulic oil is less likely to accumulate in a space between the first U packing 13 and the second U packing 14.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a piston attached to a piston rod movably in a cylinder, a wiper seal arranged in series with the cylinder, a first packing and a second packing. In the rod seal structure of the hydraulic cylinder, the piston rod is slidably and hermetically supported through the first packing, and a backup member is provided on the atmosphere side of the first packing to restrict the deformation of the lip portion. Oil return means is provided for returning hydraulic oil, which has entered the space between the first packing and the second packing, to the oil chamber side.
[0016]
In this case, the oil return means is preferably a plurality of helical grooves or straight grooves formed on the sliding surface of the backup member with the piston rod.
[0017]
The depth of the helical groove or the straight groove is preferably 50 μm to 10 μm.
[0018]
The helical groove or straight groove may have a U, V or U-shaped cross section.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, 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 with reference to FIGS.
[0020]
This rod seal structure is characterized in that the backup member 16 adjacent to the back side of the first U-packing 13 is provided with oil return means in the conventional hydraulic cylinder shown in FIGS. Other configurations are the same as those of the above-described conventional structure, and therefore, only the same reference numerals are given in the drawings, and description thereof will be omitted.
[0021]
That is, a plurality of helical grooves 19 are formed on the inner peripheral surface of the backup member 16 which is to be in sliding contact with the piston rod 5 over the entire circumference by knurling, and both ends of each groove are on both sides of the backup member 16. Open to the surface.
[0022]
The helical groove 19 is formed to have a depth of 50 μm to 10 μm. The reason is that when the depth of the groove 19 is deeper than 50 μm, the strength of the backup member 16 is reduced and the original reinforcing function cannot be achieved. This is because if it is shallower than 10 μ, the passage of hydraulic oil decreases.
[0023]
Further, the distance between adjacent grooves is set to 2 mm, and is formed so as to be inclined by 30 degrees with respect to the axis of the piston rod 5, but may be set to 45 degrees, 60 degrees or the like.
[0024]
Therefore, the hydraulic oil that has not been cut by the first U-packing 13 and has entered the space S returns to the back side of the first U-packing 13 through the helical groove 19 in the process of extending the piston rod 5, Due to the basic properties of the U packing 13, the U packing 13 is drawn into the oil chamber 2 side, so that the working oil does not accumulate in the space S.
[0025]
In the hydraulic cylinder configured as described above, since the lip portion 13a of the first U-packing 13 is in a state in which the protruding end edge is in sliding contact with the outer periphery of the piston rod 5, for example, the extension process of the piston rod 5 is performed. In this case, the piston rod 5 slides on the first U-packing 13 in a state where the oil film attached to the outer periphery is cut to an appropriate thickness, and the high pressure on the oil chamber 2 side is reduced by the lip portion 13a. The second U packing 14 is not affected.
[0026]
At this time, if the lip portion 13a does not have a sharp protruding edge due to a manufacturing error or the like for some reason, 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 penetrate into the space S formed.
[0027]
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.
[0028]
However, in the present embodiment, since the plurality of helical grooves 19 are formed on the inner peripheral surface of the backup member 16 adjacent to the back side of the U packing 13 and serving as a sliding contact portion with the piston rod 5, the first Hydraulic oil that has entered the space S without being cut by the U packing 13 returns to the back side of the first U packing through the helical groove 19 during the extension stroke of the piston rod, and the first U packing 13 Is drawn into the oil chamber 2 side due to the basic properties of, and the working oil does not accumulate in the space S.
[0029]
Further, in order to confirm the above effects, the piston rod was operated at 100 km and 400 km, and the pressure in the space at that time was measured. As a result, the pressure was 0 Mpa at 100 km and 0 Mpa at 400 km.
[0030]
By the way, when the backup member of the present embodiment is not used, it becomes 21 Mpa at 100 km and 34 Mpa at 400 km, confirming the effect of the present embodiment.
[0031]
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.
[0032]
Further, by forming a groove in the backup member 16 which has been conventionally used, the working oil which has entered the space can be returned to the oil chamber 2 side, so that it can be easily implemented without any special measures. it can.
[0033]
The present invention is not limited to the above-described embodiment, and can be embodied with the following modifications, for example.
[0034]
1) In the present embodiment, the helical groove 19 is used as the oil return means. Alternatively, a straight groove or a spiral groove may be used. Also, the cross-sectional shape of the groove can be set to any shape such as a V-shape, a U-shape, and a U-shape in cross-section.
[0035]
2) The interval and the number of grooves are not limited to the present embodiment, and may be arbitrarily changed. However, the change is limited to a range in which the lip portion 13a, which is the original function of the backup member 16, can be reinforced.
[0036]
3) In the present embodiment, the groove is adopted as the oil return means. However, the present invention is not limited to this. For example, minute concaves and convexes as the oil return means are provided on the inner peripheral surface of the backup member 16, and the concave portion is The hydraulic oil may be passed along.
[0037]
As a method of forming the irregularities, a method of forming minute irregularities on a molding surface of a mold for molding the backup member 16 by shot blasting or the like and transferring the irregularities to the backup member 16 can be used.
[0038]
In addition to the irregularities, the backup member 16 may be provided with a through hole extending from the space S to the lip 13a, and the through hole may be used as an oil return unit.
[0039]
4) In this embodiment, the cylinder for a 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.
[0040]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0041]
That is, according to the invention of each claim, even if the hydraulic oil enters the space formed by the first and second packings, it can be returned to the oil chamber side, so that the hydraulic oil is generated. A rapid pressure rise can be suppressed. Therefore, it is possible to reliably prevent the first or second packing from being damaged or the hydraulic oil leaking to the outside due to the increase in the pressure.
[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 partial plan view showing a part of the inner peripheral surface of the backup member.
FIG. 3 is a sectional view showing a conventional hydraulic cylinder.
FIG. 4 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 13a Lip portion 14 Second packing 15 Wiper seal 16 Backup member 19 Groove (oil return means)
S space part

Claims (4)

A piston attached to a piston rod is movably provided in a cylinder, and the piston rod is slidably sealed via a wiper seal arranged in series with the cylinder and a first packing and a second packing. In the rod seal structure of the hydraulic cylinder, which is provided with a back-up member for supporting and restricting deformation of the lip portion on the atmosphere side of the first packing, the back-up member is provided between the first packing and the second packing. A rod seal structure for a hydraulic cylinder, wherein oil return means is provided for returning hydraulic oil that has entered the space to the oil chamber side. The rod seal structure for a hydraulic cylinder according to claim 1, wherein the oil return means is a plurality of helical grooves or straight grooves formed on a sliding surface of the backup member with the piston rod. 3. The rod seal structure for a hydraulic cylinder according to claim 2, wherein the depth of the helical groove or the straight groove is 50 μm to 10 μm. 4. The rod seal structure for a hydraulic cylinder according to claim 2, wherein the helical groove or the straight groove has a U-shaped, U-shaped or U-shaped cross section.

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