JP3807733B2 - Hydraulic cylinder seal structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a hydraulic cylinder which is provided on the cylinder side and seals a sliding gap between the piston rod and the cylinder, or which is provided on the piston side and seals a sliding gap between the cylinder and the piston rod. The present invention relates to a sealing device.
[0002]
[Prior art]
As a conventional hydraulic cylinder, for example, there are those shown in FIGS. 5 and 6, and this hydraulic cylinder moves a piston 4 that divides two oil chambers 2 and 3 into a cylinder 1 that is closed at both ends. A piston rod 5 provided at one end of the piston rod 5 is freely passed through the cylinder 1, and a sliding gap between the piston rod 5 and the cylinder 1 is provided in a penetrating portion of the piston rod 5 in the cylinder 1. A seal structure 6 is provided for oil-tightly and slidably sealing.
[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 chamber 3 to an external tank (not shown) via the oil passage 8, the piston rod 5 is contracted, while operating oil from the hydraulic source is supplied to the oil chamber 3 via the oil passage 8. The piston rod 5 is extended by communicating the oil chamber 2 with an external tank via the oil passage 7.
[0004]
Meanwhile, as shown in FIG. 6, two annular grooves 10 and 11 and an annular notch 12 facing the outside of the cylinder 1 are provided in the inner periphery of the through hole 9 of the piston rod 5 in the cylinder 1. .
[0005]
In the annular grooves 10 and 11 and in the annular notch 12, the above-described seal structure 6, that is, the 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 made of urethane resin or the like and a back-up ring 17 on the back side thereof are inserted into the annular groove 11, and a wiper seal 15 is inserted into the annular notch 12.
[0006]
The first U-packing 13 functions as a buffer seal that receives high pressure on the oil chamber side, and has a lip portion 13 a that is in sliding contact with the surface of the piston rod 5.
[0007]
The second U-packing 14 controls the thickness of the oil film that adheres to the surface of the piston rod 5 and exits to the atmosphere to an appropriate value, and also has a lip portion 14a that is in sliding contact with the surface of the piston rod 5. is doing.
[0008]
Further, a backup ring made of nylon resin or the like that reinforces the second U-packing 14 so as to prevent the back side of the lip portion 14a from biting into the through-hole 9 when subjected to high pressure on the oil chamber 2 side. 17 are arranged adjacent to each other.
[0009]
Although not shown, the wiper seal 15 includes a dust lip portion that faces the outside and an oil lip portion that faces the inside. The wiper seal 15 is formed integrally with a metal core, and the core is connected to the annular notch. It is fitted to the part 12.
[0010]
In the seal structure 6 configured as described above, when the oil chamber 2 side becomes high pressure, the first U-packing 13 functions as a buffer seal, and the through-hole 9 and the piston rod at the protruding edge of the lip portion 13a. The hydraulic oil that is about to move to the second U-packing 14 side through the gap with the first U-packing 14 is cut to a predetermined film pressure, and only an oil film having a predetermined thickness is sent to the second U-packing 14.
[0011]
[Problems to be solved by the invention]
However, the conventional hydraulic cylinder seal structure 6 has the following problems.
[0012]
That is, the backup ring 17 disposed adjacent to the back side of the second U-packing 14 is intended to prevent the back side of the lip portion 14a from biting into the through hole 9 side, and thus has a rectangular cross section. In addition, the inner diameter is set to have an allowance so that the inner peripheral surface and the surface of the piston rod 5 do not slide strongly when inserted into the annular groove 11.
[0013]
For this reason, when the backup ring 17 does not have the shape as designed due to a cause of molding failure or the like, specifically, when the inner diameter is smaller than the design value, or is assembled in an eccentric state in the annular groove 11. If attached, the entire inner peripheral surface of the backup ring 14 or a part of the inner peripheral surface strongly slides on the surface of the piston rod 5 and scrapes off the oil film on the surface of the piston rod 5.
[0014]
In this case, there is a concern that the surface of the piston rod 5 is in a so-called dry state, and the lip portion 14a is worn or damaged, causing hydraulic oil leakage.
[0015]
Accordingly, an object of the present invention is to provide a hydraulic cylinder seal structure in which a backup ring disposed adjacent to the second U-packing does not scrape off the oil film formed on the piston rod surface by sliding strongly against the piston rod surface. Is to provide.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, according to one aspect of the present invention, a piston attached to a piston rod is movably provided in a cylinder, and the above-described object is provided via a packing and a backup ring that are arranged adjacent to each other. In the sealing structure of a hydraulic cylinder that seals the sliding gap between the piston rod and cylinder, the long side that is the contact surface of the backup ring with the packing is inclined toward the packing side toward the outside, and this inclined surface is the direction of the backup ring. The backup ring is deformed in the diameter-expanding direction by the axial force applied to the packing toward the front .
[0019]
Further, according to another aspect of the present invention, a piston attached to a piston rod is movably provided in the cylinder, and the cylinder and the piston are interposed between a packing and a backup ring that are arranged adjacent to each other. In the seal structure of the hydraulic cylinder that seals the sliding gap of the back side, the long side that is the contact surface with the packing in the backup ring is an inclined surface that faces inward toward the packing side, and this inclined surface is used for packing toward the backup ring. The backup ring is also deformed in the reduced diameter direction by the applied axial force .
[0021]
A plurality of lubricating grooves extending in the radial direction may be provided on the inclined surface of the backup ring.
[0022]
In each of the above means, one place of the backup ring may be cut in the radial direction.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is embodied in a high-pressure construction machine cylinder seal structure will be described with reference to the drawings.
[0024]
The sealing structure of this hydraulic cylinder is such that the second U-packing 14 toward the backup ring 17 is arranged between the second U-packing 14 and the backup ring 17 of the conventional hydraulic cylinder 1 shown in FIGS. In order to deform the backup ring 17 in the diameter-expanding direction by the axial force applied to the ring, the backup ring 17 has a feature in that an inclined surface 18 is provided, and other configurations are the same as the conventional structure described above. Therefore, only the same reference numerals are given in the drawing, and the description thereof is omitted.
[0025]
That is, in one embodiment of the present invention, as shown in FIG. 1, the inner surface of the backup ring 17 is in contact with the back surface of the second U-packing 14, and the inclined surface 18 is formed on the inner surface of the backup ring 17. .
[0026]
In this case, the back surface of the second packing 14 may be a vertical surface or an inclined surface 18a as shown.
[0027]
In addition, the long side used as the contact surface with the 2nd U packing 14 in the back-up ring 17 arrange | positioned adjacent to the back side of the 2nd U packing 14 makes the inclined surface 18 which goes to the 2nd U packing 14 side outward. The backup ring 17 is formed in a trapezoidal shape, and the backup ring 17 is deformed in the diameter-enlarging direction by an axial force applied to the second U-packing 14 toward the backup ring 17 by the inclined surface 18. .
[0028]
As shown in FIG. 2, the inclined surface 18 of the backup ring 17 is provided with a plurality of lubrication grooves 19 extending in the radial direction at predetermined intervals, and in contact with the second U-packing 14. In this case, hydraulic oil penetrates into the lubrication groove 19 to significantly reduce the frictional resistance between them.
[0029]
In addition, the backup ring 17 is cut in a radial direction at one portion like a C-shaped ring, for example, and easily expands in diameter when an axial force is applied from the second U-packing 14. It is like that.
[0030]
Therefore, when an axial force (indicated by the arrow P) generated due to the hydraulic load generated by the cylinder expansion / contraction operation is applied to the second U-packing 14, the distribution by the inclined surfaces 18, 18a or the inclined surface 18 alone is performed. The backup ring 17 is easily deformed in the diameter expansion direction by a so-called wedge action.
[0031]
In the hydraulic cylinder 1 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, for example, In the extension stroke, the piston rod 5 slides and moves on the first U-packing 13 with the oil film attached to the surface thereof being cut to an appropriate thickness, and the lip portion 13a causes the oil chamber 2 side to move. The high pressure is prevented from directly affecting the second U-packing 14.
[0032]
Therefore, a reduced pressure is applied to the second U-packing 14, and an axial force P generated due to the hydraulic load, that is, a force that pushes the second U-packing 14 to the atmosphere side is generated. .
[0033]
At this time, since the backup ring 17 has a long side that becomes a contact surface with the second U-packing 14 as an inclined surface 18 toward the second U-packing 14 toward the outer side, the second U-packing 14 is in the atmosphere. When pushed to the side, the wedge ring action causes the backup ring 17 itself to move outward along the inclined surface 18 and deforms so that the entire diameter expands, and as shown in FIG. An appropriate gap is formed between the surface and the surface of the piston rod 5.
[0034]
As described above, according to the present embodiment, when an axial force in the direction of the backup ring 17 is applied to the second U-packing 14, the backup ring 17 itself is deformed in the diameter increasing direction using this force. Therefore, for example, even when the inner diameter of the backup ring 17 becomes smaller than a design value due to a manufacturing error or the like, the sliding contact state between the inner peripheral surface and the piston rod 5 surface is relaxed by the above-described diameter expansion action, An appropriate gap can be formed.
[0035]
Accordingly, as shown in the conventional example, the entire circumference or a part of the inner circumferential surface of the backup ring 17 is slidably brought into sliding contact with the surface of the piston rod 5 to scrape off the oil film on the surface of the piston rod 5 and wear the lip portion 14a. It is possible to reliably prevent malfunctions that cause hydraulic oil leakage due to damage.
[0036]
Even when the backup ring 17 is assembled in the annular groove 11 in an eccentric state, it is aligned by the deformation in the above-mentioned diameter expansion direction, and thus the same operation and effect as described above are exhibited.
[0037]
In addition, since the backup ring 17 can be deformed in the diameter expansion direction by making the long side of the backup ring 17 the inclined surface 18 , the backup ring 17 itself can be easily manufactured and can be implemented at low cost.
[0038]
Further, since a plurality of lubricating grooves 19 are provided on the inclined surface 18 of the backup ring 17 at a predetermined interval, the backup ring 17 moves smoothly along the inclined surface 18 by the hydraulic oil supplied into the lubricating groove 19. Can be made.
[0039]
Moreover, since one place of the backup ring 17 is cut | disconnected, the deformation | transformation to said diameter expansion direction can be performed smoothly.
[0040]
In addition, this invention is not limited to the said embodiment, For example, it can also be changed and embodied as follows.
[0041]
1) In the above-described embodiment, the packing 14 and the backup ring 17 provided on the cylinder 1 side have been described. Of course, the packing 22 and the backup ring 23 provided on the piston 4 side may be embodied.
[0042]
In this case, as shown in FIG. 4, since the packing 22 and the backup ring 23 are inserted into the annular groove 21 provided in the piston 4, the long side serving as the contact surface of the backup ring 23 with the packing 22. Is an inclined surface 24 directed inward toward the packing 22 , and the backup ring 23 itself is deformed in the diameter-reducing direction by the inclined surface 24.
[0043]
In this case, when an axial force in the direction of the backup ring 23 is applied to the packing 22, the backup ring 23 itself is deformed in the reduced diameter direction by the wedge action, and the degree of sliding contact of the backup ring 23 with the cylinder 1 is increased. Can be adjusted.
[0044]
Accordingly, the outer peripheral surface of the backup ring 23 is in strong sliding contact with the inner peripheral surface of the cylinder 1 and scrapes off the oil film on the inner peripheral surface of the cylinder 1, so that the lip portion of the backup ring 23 and the packing 22 is worn or damaged. It is possible to surely prevent the malfunction of being performed.
[0045]
2) In the above embodiment, the second U-packing 14 is embodied. However, the first U-packing 13 having back application may be embodied.
[0047]
4) In the above embodiment, only the long side of the backup ring 17 on the second U packing 14 side is the inclined surface, but the long sides on both sides may be the inclined surface 18. In this case, erroneous assembly when the backup ring 17 is assembled in the annular groove 11 can be prevented.
[0048]
5) In the present embodiment, the high pressure construction machine cylinder is shown, but the present invention is not limited to this, and it is needless to say that the present invention may be embodied in a general hydraulic cylinder.
[0049]
【The invention's effect】
The present invention has the following effects.
[0050]
1) According to the invention of claim 1, the back-up ring itself is deformed in the diameter-enlarging direction using the axial force applied to the packing toward the back-up ring direction, and the sliding contact degree of the back-up ring with the piston rod is adjusted. Therefore, for example, the inner peripheral surface of the backup ring strongly contacts the piston rod surface and scrapes off the oil film on the piston rod surface, so that the lip of the backup ring and packing is worn or damaged. It is possible to reliably prevent a malfunction that causes leakage.
[0051]
2) According to the invention of claim 2 , it is possible to adjust the degree of sliding contact of the backup ring with respect to the cylinder by deforming the backup ring itself in the diameter reducing direction by utilizing the axial force applied to the packing toward the backup ring direction. So, for example, the outer peripheral surface of the backup ring is in sliding contact with the inner peripheral surface of the cylinder and scrapes off the oil film on the inner peripheral surface of the cylinder, and the lip portion of the backup ring and packing is worn or damaged. Can be reliably prevented.
[0052]
3) According to the invention of the claims, it is possible to deform the backup ring in enlarged or reduced in diameter direction by an inclined surface of the long side of the backup ring can be easily manufactured backup ring itself, inexpensively implemented it can.
[0053]
4) According to the invention of claim 3, since a plurality of lubrication grooves are provided at predetermined intervals on the inclined surface of the backup ring, when hydraulic oil is supplied into the lubrication groove, the backup is performed along the inclined surface. The ring can be moved smoothly.
[0054]
5) According to the invention of claim 4 , since one part of the backup ring is cut in the radial direction, the backup ring can be smoothly deformed in the diameter-expanding or diameter-decreasing direction.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part showing a sealing structure of a hydraulic cylinder showing an embodiment of the present invention.
FIG. 2 is a plan view showing a backup ring.
3 is a cross-sectional view of the main part showing the operating state of the backup ring in the hydraulic cylinder seal structure shown in FIG. 1;
FIG. 4 is a cross-sectional view of a main part showing a sealing structure of a hydraulic cylinder showing another embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a conventional hydraulic cylinder.
FIG. 6 is a cross-sectional view of a main part showing a rod seal structure of a conventional hydraulic cylinder.
[Explanation of symbols]
1 Cylinder 4 Piston 5 Piston rod 14 Second packing 17 Backup ring 18, 18a Inclined surface 24 Inclined surface

Claims (4)

A hydraulic cylinder seal in which a piston attached to a piston rod is movably provided in the cylinder, and a sliding clearance between the piston rod and the cylinder is sealed via a packing and a backup ring disposed adjacent to the cylinder. In the structure, the long side, which is the contact surface with the packing in the backup ring, is inclined toward the packing side toward the outer side, and the diameter of the backup ring is expanded by the axial force applied to the packing toward the backup ring on this inclined surface. A hydraulic cylinder seal structure characterized by being deformed in a direction. A hydraulic cylinder is provided in which a piston attached to a piston rod is movably provided in a cylinder, and a sliding clearance between the cylinder and the piston is sealed through a packing and a backup ring arranged adjacent to the piston. In the seal structure, the long side, which is the contact surface with the packing in the backup ring, is inclined toward the packing side toward the inside, and the backup ring is compressed by the axial force applied to the packing toward the backup ring on this inclined surface. A hydraulic cylinder seal structure characterized by being deformed in a radial direction. The seal structure for a hydraulic cylinder according to claim 1 or 2, wherein a plurality of lubricating grooves extending in a radial direction are provided at predetermined intervals on the inclined surface of the backup ring. The hydraulic cylinder seal structure according to any one of claims 1 to 3, wherein the backup ring is cut at one place in a radial direction.

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