JP2013083351A - U-packing with pressure accumulation preventive function and seal mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rod packing capable of returning pressure-accumulated pressure fluid to the pressure side of the rod packing in order to prevent the occurrence of failure due to abrasion or damage of the packing due to such a pressure accumulation phenomenon that the fluid leaking like oil film from the rod packing is sealed by a low-pressure side packing such as wiper ring and is accumulated between the two packings, in the packing of the rod part of a fluid pressure cylinder.SOLUTION: A discharge channel of the pressure-accumulated fluid is constituted by providing a protruded part in the axial direction on the outer circumferential surface of the rod packing and a recessed groove in the radial direction on the lip top part, the pressure-accumulated fluid is returned into the cylinder and, thereby, an accumulated pressure is kept low.

Description

  The present invention relates to a U-packing and sealing mechanism for sealing a rod portion that is mounted in an annular groove provided on an inner peripheral surface of a rod cover portion of a fluid pressure cylinder and seals fluid pressure. The present invention relates to a U-packing and a seal mechanism that can be suitably used for a rod packing having a pressure accumulation preventing function for a piston rod of a hydraulic breaker that is frequently used.

  Pressure close to the upper limit of the set pressure acts on the rod packing of the hydraulic cylinder using hydraulic pressure, but when the piston rod comes out, pressure acts on the bottom side of the piston, and the rod packing A relatively low pressure generated by the piping resistance on the side acts.

  Even in a fluid pressure cylinder, polyurethane rubber having excellent wear resistance and pressure resistance has been mainly used as a rod packing for a cylinder used under high pressure, high speed and high frequency conditions. The rod packing made of polyurethane rubber has excellent sealing performance because of the high contact surface pressure against the mating surface of the lip. However, since the deterioration of physical properties (such as compression set) due to heat generation is worse than that of NBR, Accumulation of leakage caused pressure accumulation between the rod packing and the oil lip of the wiper ring, leading to damage to the rod packing and wiper ring, as well as popping and breakage of the wiper ring.

  The single lip type wiper ring without wiper ring oil lip does not scrape off the oil film on the rod, so pressure buildup does not occur.However, the rod surface oil film is scraped off with dust and other foreign matter. The oil ring becomes larger due to repeated accumulation in a part of the ring, causing dripping and oil leakage.

  As a method of avoiding pressure accumulation due to oil lip, there is also a measure to guide the fluid accumulated between the rod packing and wiper ring as a drain to a tank etc., but this measure can be applied to equipment machinery, but industrial vehicles and When applied to construction machinery, there are problems such as an increase in the number of drain pipes, which is not realistic.

  In Patent Document 1, a small hole is provided in the oil lip of the wiper ring, the oil film on the surface of the rod is scraped off by the oil lip, a certain amount of oil is stored, and the function of returning the oil to the inside of the cylinder as an oil film is maintained. An invention is disclosed in which packing and wiper rings are prevented from being damaged by pressure accumulation by letting them pass through small holes.

  In order to compensate for the deterioration of the sealing performance of the rod packing under such high pressure, high speed, and high frequency conditions, a method in which a high pressure seal is additionally used on the pressure side of the rod packing has been used. As an example of such a seal, a ring-shaped seal having a substantially rectangular cross section provided with a slit on one side surface made of synthetic resin, an axial groove and a convex portion are alternately provided on the outer peripheral surface, and a slit is provided on one side surface. A slipper seal type buffer ring combined with a rubber back ring provided, or a concave groove on the top of the inner peripheral lip of a synthetic rubber U-shaped lip packing, and resin on the inner low pressure side corner Lip type buffering combined with a sex backup ring.

  Each of these seals cuts high fluid pressure as the primary seal and prevents high pressure from directly acting on the rod packing that becomes the secondary seal, thereby improving the sealing performance of the rod packing and the sliding resistance. It is lowered to reduce thermal deterioration of the packing material due to frictional heat and improve durability.

  For example, as disclosed in Patent Document 2, primary seals such as slipper seal type and lip type buffer rings are leaked from the primary seal and sealed with secondary seals such as rod packing. When the accumulated fluid becomes higher than the pressure acting on the primary seal, the primary seal is pushed up to the pressure side, passes through the flow path formed by the outer peripheral surface of the mounting groove and the concave groove of the buckling, and is provided on the pressure side surface. It returns to the cylinder chamber side through the flow path passing through the groove.

  Further, as disclosed in Patent Document 3, in the case of a lip type buffering, pressure accumulation fluid enters a concave groove provided on the outer peripheral surface of the base of the buffering from the bottom surface of the mounting groove, pushes up the outer peripheral lip, and It returns to the cylinder chamber side through the flow path passing through the concave groove at the top of the peripheral lip, functions so as not to cause the pressure accumulation phenomenon, improves the sealing performance of the U-packing that is the secondary seal, reduces the sliding resistance, and friction It is intended to reduce thermal deterioration of the material due to heat and improve durability.

  Patent Document 4 discloses a flow path for returning the accumulated fluid between the buffer ring of the type in which the outer peripheral base is not provided with a concave groove as the primary seal and the wiper ring serving as the tertiary seal to the buffering side. As an example, there is disclosed a seal system constituted by a U-packing in which a concave groove is provided at the front end of the inner peripheral lip portion and the front end of the outer peripheral lip portion.

  Since the hydraulic breaker slides at a high frequency of 100 to 600 times / min or more, the rod packing does not scrape the oil film sufficiently, and it is used under operating conditions where oil film leaks frequently and pressure is likely to accumulate. Yes.

  The hydraulic breaker is activated by driving the piston body by applying pressure from the hydraulic pump to the chisel side of the piston and adding the kinetic energy of the piston body to the chisel to crush concrete and rocks. By moving to the side, the fluid in the pressure chamber on the rod side is pressurized and accumulated in the accumulator built in the breaker, and when the pressure on the head side is switched, the piston body returns to the head side by the fluid pressure. As described above, since the pressure chamber on the rod side is always pressurized by the accumulator, the above-described primary seal is always pressed against the side surface of the low-pressure side groove, and it is inevitable that the accumulated pressure is difficult to return. It was.

  If the primary seal is a U-packing type structure, the inner peripheral lip and outer peripheral lip are always pressed simultaneously with the pressing on the side surface of the low pressure side groove. The contact force between the lip and the mating surface is increased, and the accumulated fluid between the secondary seal is difficult to return along with deterioration factors such as friction, wear, and heat generation. Deterioration factors such as wear and heat generation are brought about, and the accumulated pressure is also spread between the secondary seal and the tertiary seal (such as a wiper ring with an oil lip), causing a deterioration in the function of the entire rod packing system.

Japanese Utility Model Publication No. 09-411 Japanese Utility Model Publication No. 62-7029 JP 2008-144784 A JP 2001-355739 A

  The present invention is intended to solve the above-mentioned problems, and for example, returns accumulated pressure in a packing portion of a rod of a fluid pressure cylinder used under high-pressure, high-speed and high-frequency operating conditions such as a rod of a hydraulic breaker. It aims at making it easy and improving the sealing performance and durability of a rod packing.

The present invention is as follows.
(1) An inner peripheral lip that contacts the outer surface of the piston rod of the fluid pressure cylinder, an outer peripheral lip that is thinner than the inner peripheral lip, and a base that supports the inner peripheral lip and the outer peripheral lip. A trough is formed by the base, and is mounted in an annular groove provided on the inner peripheral surface of the rod cover portion of the fluid pressure cylinder to seal the fluid pressure from the piston side. In the packing, a plurality of convex portions extending in a direction substantially parallel to the axial direction of the piston in a region excluding the seal portion at the lip tip of the outer peripheral surface extending from the base portion to the outer peripheral lip, the top portion of the inner peripheral lip, and Each of the tops of the outer peripheral lips has a plurality of recesses extending in the radial direction of the piston, e.g., a recess groove, and a pressure accumulating fluid existing between the annular groove side part and the bottom part and the base part, U-packing, characterized in that it comprises a pressure accumulating distribution means for distributing to the plurality of recesses through the vicinity of the convex portion of the number.

  (2) The U-packing described in the above item (1), wherein the centers of the plurality of convex portions and the centers of the plurality of concave portions exist at substantially the same position at the central angle position.

  (3) The U-packing described in the above section (1) and the annular groove provided on the inner peripheral surface of the rod cover portion of the fluid pressure cylinder are attached to prevent foreign matter existing on the outer peripheral surface of the piston from entering. And a pressure accumulating and distributing means for distributing the working fluid existing in the space surrounded by the inner lip, the wiper ring, and the piston to the plurality of concave portions through the plurality of convex portions. A sealing mechanism characterized by

  According to the present invention, there is provided a U-packing that has a function of returning a pressure-accumulated fluid that has been scraped off by a secondary seal like an oil film to a rod-side pressure chamber while sufficiently maintaining the sealing performance against the original fluid pressure. Can do.

  The U packing according to the present invention basically maintains the basic performance as a rod packing having a high sealing function, and the second stage rod packing which is a secondary seal in which the oil film on the rod surface is located on the outside of the cylinder. The fluid pressure scraped and accumulated by the wiper ring with the oil lip can be returned to the cylinder.

FIG. 1 is a perspective view showing a U-packing according to Embodiment 1 in a partially cut state. FIG. 2 is a half sectional view showing a configuration example of a seal mechanism including the U packing according to the first embodiment. FIG. 3 is a half sectional view of the rod packing according to the first embodiment. FIG. 4 is a cross-sectional view illustrating a configuration example of a rod packing system including a U packing according to the second embodiment. FIG. 5 is a graph showing experimental data of accumulated pressure loss in each of the present invention example and the conventional example.

[Embodiment 1]
DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing the U-packing 1 according to the embodiment in a partially cut state, and FIG. 2 shows the U-packing 1, the buffer ring 9, and the wiper ring 10 according to the embodiment. FIG. 3 is a half sectional view of a rod packing (U packing) 1 according to the embodiment.

  In the following description, the U packing 1 according to the present invention is taken as an example when applied as a rod packing having a pressure accumulation preventing function for a hydraulic breaker rod that is frequently used under high pressure conditions.

As shown in FIG. 2, the buffer ring 9 and the wiper ring 10 are mounted in annular grooves 13 and 14 provided on the inner peripheral surface of the rod cover portion 12 of the fluid pressure cylinder 11, both of which are the same as known ones. Specifically, the buffer ring 9 is an annular seal member that has an action.
The wiper ring 10 has a function of absorbing impact pressure and a function of preventing dust and water from the outside from entering the cylinder.

Since these are well known to those skilled in the art, further explanation is omitted.
As shown in FIGS. 2 and 3, in this embodiment, the U packing according to the present invention is applied to the rod packing 1.

  As shown in FIGS. 1 and 2, the rod packing 1 is made of polyurethane rubber having an annular outer shape surrounding the outer peripheral surface of the piston rod 11 of the fluid pressure cylinder. Examples of the polyurethane rubber include RU910. The rod packing 1 seals the fluid pressure from the piston 11 side.

  As shown in FIGS. 1 and 2, the rod packing 1 includes an inner peripheral lip 2, an outer peripheral lip 3, a base portion 4, and a valley portion 5. The inner peripheral lip 2 contacts the outer surface of the piston 11 of the fluid pressure cylinder. The outer peripheral lip 3 is thinner than the inner peripheral lip 2. The base 4 supports the inner peripheral lip 2 and the outer peripheral lip 3. Furthermore, the valley 5 is formed by the inner peripheral lip 2, the outer peripheral lip 3 and the base 4.

  The rod packing 1 is movable in the annular groove 15 in the axial direction of the piston 11 in the annular groove 15 provided on the inner peripheral surface of the rod cover portion 12 of the fluid pressure cylinder. Installed.

  The rod packing 1 includes a plurality of (four in the present embodiment) convex portions 6 extending in a direction substantially parallel to the axial direction of the piston rod 11, the top portion 2 a of the inner peripheral lip 2, and the outer peripheral lip 3. Each of the tops 3a has a plurality of (four in the present embodiment) concave grooves 7 and 8 extending in the radial direction of the piston.

  The cross-sectional shape of the convex portion 6 may be a shape that is not easily crushed. For example, a semicircular shape is desirable in order to return the accumulated fluid to the rod-side pressure chamber and to manufacture the convex portion 6 easily and at low cost. In addition, if the base portion 4 side of the convex portion 6 has a rectangular base portion and a semicircular cross-section portion on the base portion, the accumulating fluid can be more reliably returned to the rod side pressure chamber. Is possible.

  The height of the convex portion 6 (projection height from the outer surface of the base portion 4) is 0.3 to 1 mm, and the width of the convex portion 6 is twice the height of the convex portion 6, that is, 0.6 to 2 mm. It is desirable to return the pressure-accumulated fluid scraped off by the secondary seal like an oil film to the rod-side pressure chamber while maintaining the sealing performance against the fluid pressure.

  Further, the convex portion 6 is formed in a region from the bottom portion 4a of the base portion 4 to the outer peripheral lip 3 except for the seal portion 3b of the outer peripheral lip 3, that is, a region from the bottom portion 4a to the vicinity of the seal portion 3b. . This is because when the convex portion 6 reaches the seal portion 3b and is formed, the sealing performance of the outer peripheral lip 3 against the fluid pressure cannot be maintained.

  The plurality of protrusions 6 and the plurality of recesses 7 and 8 are arranged so that the center position of each of the plurality of protrusions 6 and the center position of each of the plurality of recesses 7 and 8 are substantially the same at the central angle position. Is formed. Here, “substantially the same position at the central angle” means that the center position of the convex portion 6 is within the range where the concave portions 7 and 8 are formed. In the present embodiment, each of the plurality of convex portions 6 and the plurality of concave portions 7 and 8 is formed by four at a central angle of 90 degrees.

  Thereby, the working fluid existing between the side portion 15 a and the bottom portion 15 b of the annular groove 15 and the base portion 4 can be sequentially circulated to the plurality of concave portions 7 and 8 through the vicinity of the plurality of convex portions 6.

In the rod packing 1, the pressure packing fluid existing between the wiper ring 10 that is a secondary seal is subjected to the front pressure applied to the inner lip 2 of the rod packing 1, and the rod packing 1 has a side surface of the annular groove 15 on the low pressure side. Even in the state pressed by 15a, as shown by the arrow in FIG.
(I) If the front pressure is low, the gap formed by the rod packing 1 being pushed up toward the lips 2 and 3 by the accumulated fluid pressure,
(Ii) a flow path formed by the plurality of convex portions 6 and the annular groove 15 provided on the outer peripheral surface of the rod packing 1,
(Iii) a gap formed by acting on the distal end side of the outer peripheral lip 3 to push up the outer peripheral lip 3,
(Iv) a groove 8 formed at the top of the outer peripheral lip 3; and (v) a groove 7 formed at the top of the inner peripheral lip 2.
By returning the working fluid accumulated in the piston rod 11 side pressure chamber through the flow path passing through the cylinder, the accumulated pressure can be lowered and the sliding resistance can be lowered, and heat generation etc. can be suppressed and the rod packing 1 Deterioration of the material can be prevented.

  Further, the flow path for returning the stock pressure fluid to the pressure chamber on the piston rod 11 side in this way seals the front pressure because the contact portion between the bottom surface 15b of the annular groove 15 and the top portion 3a of the outer peripheral lip 3 has a check valve function. The function to perform is not impaired at all, and as the plurality of convex portions 6 are provided to the vicinity of the seal portion 3b of the outer peripheral lip 3, the outer peripheral lip 3 is more easily spread and the accumulated pressure fluid can be easily and reliably returned. .

  In addition, for example, since the concave portion is not provided in the base portion 4 in order to release the accumulated pressure, the convex portion 6 is formed, so that the rigidity of the base portion 4 is not lowered, and the sealing function of the front pressure is impaired at all. Absent.

  That is, the rod packing 1 is a second-stage rod that is a secondary seal in which the oil film on the surface of the piston rod 1 is located outside the cylinder while maintaining the basic performance as a rod packing having a high sealing function. The fluid pressure scraped and accumulated by the packing 1 and the wiper ring 10 with the oil lip can be returned into the cylinder.

  In this way, according to the present embodiment, the function of returning the pressure-accumulated fluid scraped off by the secondary seal like an oil film to the rod-side pressure chamber while maintaining the sealing performance against the original fluid pressure is provided. A packing 1, for example, a U packing 1 that can be suitably used for a rod packing 1 having a pressure accumulation preventing function for a piston rod 11 of a hydraulic breaker that is frequently used under high pressure conditions, and a seal using the U packing Mechanism 0 can be provided.

[Embodiment 2]
Embodiment 2 will be described. In the following description, portions that are different from the above-described first embodiment will be described, and the description of the same portions will be omitted by attaching the same reference numerals in the drawings.

  FIG. 4 is a cross-sectional view illustrating a configuration example of the seal mechanism 0-1 including the U packing 1 according to the second embodiment.

  The seal mechanism 0-1 is different from the seal mechanism 0 in that the U-packing 1 is used instead of the buffer ring 9 in the seal mechanism 0, that is, the two U-packings according to the present invention and the wiper ring 10 are used in combination. It is.

  In the seal mechanism 0, the U-packing 1 according to the present invention is used by being overlapped with the primary seal and the secondary seal, so that the primary side seal and the secondary side seal having high sealing performance can be sufficiently sealed. The pressure accumulation fluid sealed by the secondary seal made of the U packing 1 can be returned into the cylinder through the pressure accumulation return flow path of the primary seal also made of the U packing 1, and the durability of the seal mechanism 0-1 can be improved. Can be increased. As in the first embodiment, the primary seal can be returned from the secondary seal made of the U packing 1 to the accumulated pressure between the secondary seal made of the U packing 1 and the wiper ring 10 with the oil lip. Needless to say.

Next, the present invention will be described more specifically with reference to examples.
The U packing 1 shown in FIG. 1 having the following specifications is used as a rod packing having a pressure accumulation preventing function for a piston rod (inner diameter: 45 mm) of a hydraulic breaker frequently used under high pressure conditions. Was measured, and the pressure at which the accumulated pressure between the secondary seal and the wiper ring 10 with an oil lip began to be released was measured. The pressure at which the accumulated pressure began to drop was measured by applying pressure from the base 4 side of the rod packing 1 and measuring the pressure at which leakage started from the inner peripheral lip 2 side.

<U packing>
Material: Polyurethane rubber (RU910 etc.)
Inner lip 2 inner diameter, thickness: 44mm, 2.2-2.5mm
Outer lip 3 outer diameter, thickness: 57mm, 1.7-1.8mm
Height, length, width of convex part 6: 0.35mm, 3.5mm, 0.7mm
The depth and length of the recesses 7 and 8: 0.4 mm, 1.4 mm, and 0.9 mm
Inner diameter, outer diameter, thickness of base 4: 46.2mm, 55.6mm, 4.6-4.8mm
<Buffering 9>
Dimensions, Material: Rod diameter: 135.8, Material: Polyurethane rubber (RU910 etc.)
<Wiper ring 10>
Dimensions, Material: Rod diameter: 135.8, Material: Polyurethane rubber (RU910 etc.)
On the other hand, packing (existing packing) in which the convex part is not formed on the base as the conventional example 1, and SKY packing (the convex part is not formed on the base and the inner peripheral lip and the outer peripheral lip are used as the conventional example 2) With respect to the packing in which no recess was formed, the pressure was measured in the same manner as described above.

The results are shown graphically in FIG.
As shown in the graph of FIG. 5, according to the present invention, it is clear that the pressure at the beginning of the accumulated pressure drop can be significantly reduced.

  The U-packing according to the present invention returns the accumulator fluid to the cylinder pressure chamber side as a seal of the rod portion of the fluid pressure cylinder, and improves the sealing performance and durability as a rod packing system, for example, high pressure, high speed, high frequency It can be used for a rod packing seal mechanism under severe use conditions such as construction machines and hydraulic breakers used under certain conditions.

  The U packing according to the present invention is effective as, for example, a rod packing unit and a rod packing system, but by providing an axial protrusion on the outer peripheral surface of the rod packing, the U portion of the piston portion of the double acting hydraulic cylinder is provided. As a packing, there is a flow path that discharges reverse pressure (the generation mechanism is different from the pressure accumulation of the rod packing, both of which the pressure fluid acts from the bottom side of the rod packing), so the application to the piston packing is also effective Is.

0, 0-1 Seal mechanism 1 U packing 2 according to the present invention Inner lip 2a Top 3 Outer lip 3a Top 3b Seal 4 Base 4a Bottom 5 Valley 6 Convex 7, 8 Concave (concave)
9 Buffering 10 Wiper ring 11 Fluid pressure cylinder 12 Rod cover parts 13, 14, 15 Annular groove 15a Side part 15b Side part

Claims (3)

An inner peripheral lip that contacts the outer surface of the piston of the fluid pressure cylinder; an outer peripheral lip that is thinner than the inner peripheral lip; and a base portion that supports the inner peripheral lip and the outer peripheral lip. And a U-packing that is formed in the annular groove provided on the inner peripheral surface of the rod cover portion of the fluid pressure cylinder and seals the fluid pressure from the piston side.
A plurality of convex portions extending in a direction substantially parallel to the axial direction of the piston in a region excluding the seal portion at the lip tip of the outer peripheral surface extending from the base portion to the outer peripheral lip, and the top portion of the inner peripheral lip And a plurality of recesses extending in the radial direction of the piston at each of the top portions of the outer peripheral lip, and a working fluid existing between the side and bottom portions of the annular groove and the base portion, A U-packing comprising pressure accumulation flow means for flowing to a plurality of recesses in the previous period through the vicinity of a plurality of projections in the previous period.   The U-packing according to claim 1, wherein a center in the juxtaposed direction of the plurality of convex portions and a center in the juxtaposed direction of the plurality of concave portions are present at substantially the same position at a central angle position.   An oil lip that is attached to the U-packing according to claim 1 and an annular groove provided on an inner peripheral surface of a rod cover portion of the fluid pressure cylinder and prevents foreign matter existing on the outer peripheral surface of the piston from entering. The pressure accumulating and distributing means distributes the working fluid existing in the space surrounded by the inner lip, the wiper ring, and the piston to the plurality of grooves through the plurality of convex portions. Sealing mechanism.

Images