JP3874383B2 - Oil seal structure of hydraulic shock absorber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil seal structure for a hydraulic shock absorber that is mounted on a vehicle to improve riding comfort, and more particularly to an oil seal structure for a hydraulic shock absorber that prevents oil lip of an oil seal from running out.
[0002]
[Prior art]
A hydraulic shock absorber mounted on a vehicle prevents hydraulic oil from leaking from between a piston rod and a rod guide that guides and supports the piston rod, and further to a reservoir via a reflux passage provided in the rod guide. An oil seal that functions to return is provided.
[0003]
FIG. 5 is a partial sectional view showing an oil seal structure of a conventional hydraulic shock absorber having such an oil seal. This hydraulic shock absorber is provided so as to close the upper end of the cylinder 1 and the piston rod 2 that goes in and out of the cylinder 1, and slidably guides and supports the piston rod 2 through the bush 3 in the center hole 4a. And a ring-shaped rod guide 4.
[0004]
Further, an outer shell 5 that forms a reservoir R is provided on the outer peripheral side of the cylinder 1, and an upper member of the outer shell 5 is provided as an attachment member for the rod guide 4 between the outer shell 5 and the flange portion 4 b of the rod guide 4. The skirt portion 6a at the lower end of the seal protective case 6 is fixed so as to be held in an oiltight manner.
[0005]
Further, a ring-shaped oil seal 7 is attached inside the seal protection case 6 above the installation site of the rod guide 4. The oil seal 7 has a holding piece 7a that is fitted and held on the inner periphery of the seal protective case 6, and the whole or part of the insert metal 8 is embedded in the holding piece 7a.
[0006]
The insert metal 8 forms a ring-shaped body having an L-shaped cross section as a whole, and a part of the insert metal 8 extends to the continuous portion of the dust lip 7b and the oil lip 7c. The holding piece 7a is provided integrally with the dust lip 7b and the oil lip 7c.
[0007]
Here, a gap P is provided on the side where the holding piece 7a and the oil lip 7c face each other. The inner peripheral surfaces of the dust lip 7b and the oil lip 7c are in oil-tight contact with the outer periphery of the piston rod 2.
[0008]
Garter springs 9 and 10 are fitted on the outer peripheral sides of the dust lip 7b and the oil lip 7c to stabilize the oil-tight sliding contact of the dust lip 7b and the oil lip 7c with the piston rod 2 as described above. Yes.
[0009]
Reference numeral 11 denotes a vent hole formed in the seal protection case 6 to communicate the upper space Q in which the dust lip 7b is located and the outside of the seal protection case 6, and 12 is attached to the upper end of the seal protection case 6. Plate.
[0010]
An oil passage 13 communicating with the gap G between the rod guide 4 and the oil seal 7 and the reservoir R between the cylinder 1 and the outer shell 5 is formed in the flange portion 4 b of the rod guide 4.
[0011]
In such an oil seal structure of the hydraulic shock absorber, when the piston rod 2 enters / extracts (extends / contracts) in the cylinder 1 due to running of the vehicle, the hydraulic oil in the cylinder 1 is exchanged between the rod guide 4, the piston rod 2, and the bush 3. The gap between the contacting parts is sewn and leaks into the gap G above the rod guide 4.
[0012]
Further, the hydraulic oil reaching the gap G is prevented from moving upward by the oil seal 7 and is returned to the reservoir R through the oil passage 13. At this time, the oil lip 7c of the oil seal 7 is immersed in the hydraulic oil reaching the gap G, and sufficient lubrication is obtained.
[0013]
On the other hand, when the vehicle stops traveling and a certain time elapses, the hydraulic oil in the gap G drops due to its own weight, flows out from the oil passage 13 to the reservoir R, and operates in the vicinity of the oil lip 7c of the oil seal 7. Oil is also gradually depleted.
[0014]
[Problems to be solved by the invention]
However, since the oil seal structure of such a conventional hydraulic shock absorber is as described above, when there is no check seal means, the vehicle is stopped for a long time as described above, so that the hydraulic oil enters the gap G of the hydraulic oil. The oil lip of the oil seal is gradually dried and eventually a so-called oil film breakage occurs.
[0015]
As a result, the friction coefficient between the oil lip 7c and the piston rod 2 increases due to the oil film breakage, and the initial friction increases when the vehicle parked for a long time starts running, that is, when the hydraulic shock absorber starts to expand and contract. As a result, not only does the ride comfort of the vehicle worsen, but there is a problem that abnormal noise is generated.
[0016]
Further, when the oil film is cut, the nitrogen gas in the reservoir R leaks to the outside through the gap between the oil lip 7c and the dust lip 7b and the piston rod 2, and the leakage of the nitrogen gas causes a decrease in the piston rod reaction force. There was a concern that the predetermined spring force and damping force could not be obtained.
[0017]
Further, when the hydraulic shock absorber expands and contracts due to traveling of the vehicle, hydraulic oil throttle resistance is generated by the expansion side valve and the pressure side valve. Therefore, cavitation occurs due to the decrease in the nitrogen gas pressure, which causes an unpleasant difference. There was also a problem that would generate sound.
[0018]
In order to prevent the oil lip 7c from drying, a check seal may be provided integrally or separately on the oil lip 7c. However, the assembly and handling are inconvenient and costly, and a large storage space is prepared. There are disadvantages such as necessity.
[0019]
The present invention solves the above-described problems, and retains hydraulic oil between an oil lip and a piston rod that are in contact with each other even when the hydraulic shock absorber is in a non-operating state for a long time due to a stop of the vehicle. It is possible to automatically supply hydraulic oil from the top to the bottom to avoid depletion of the hydraulic oil in the oil lip. Therefore, it is possible to reduce initial friction, leakage of nitrogen gas from the reservoir, and hydraulic shock absorber. It is an object of the present invention to provide an oil seal structure for a hydraulic shock absorber that can prevent the occurrence of cavitation in the interior and thereby obtain the desired spring force and damping force at low cost.
[0020]
[Means for Solving the Problems]
"
In order to achieve the above-described object, the invention of claim 1 includes a cylinder, a piston rod that goes in and out of the cylinder, an outer shell provided on the outer peripheral side of the cylinder, and a reservoir formed between the cylinder and the outer shell. A rod guide for closing the upper ends of the cylinder and the outer shell and slidably guiding the piston rod, an oil passage formed in the rod guide and communicating with the reservoir, and a seal holding case provided above the rod guide And an oil seal provided on the inner periphery of the seal protective case, an insert metal embedded in the holding piece, and an integral connection to the holding piece to connect the piston rod to the piston rod. It consists of a dust lip and oil lip that are in sliding contact with the outer periphery, and the inner periphery of the rod guide and the outer periphery of the piston rod In the hydraulic shock absorber that returns the hydraulic oil leaking from the gap between the holding passage and the oil lip to the reservoir via the oil passage, the surface tension of the hydraulic oil is used. Thus, a plurality of oil reservoirs for holding the hydraulic oil are provided .
[0021]
According to a second aspect of the present invention, in the first aspect of the invention, the oil guide for guiding the working oil to the inner peripheral surface of the oil lip on the inner surface on the side facing the holding piece of the oil lip and the lower surface continuous therewith. It is assumed that a groove is provided.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
As in the conventional example of FIG. 5, the hydraulic shock absorber according to the present invention includes a cylinder 1, a piston rod 2 that enters and exits the cylinder 1, an outer shell 5 provided on the outer peripheral side of the cylinder 1, and a cylinder 1 and an outer shell 5. A reservoir R formed therebetween, a rod guide 4 for closing the upper ends of the cylinder 1 and the outer shell 5 and slidably guiding the piston rod 2, and an oil passage 13 formed in the rod guide 4 and communicating with the reservoir R And an oil seal 7 provided in a seal holding case 6 provided above the rod guide 4.
Further, the oil seal 7 is the sealing and retaining strip 7 a held inner periphery of the protective case 6, the holding piece and the insert metal 8 which is embedded in the 7a, holding piece 7a to be integrally connected to the piston rod 2 It comprises a dust lip 7b and an oil lip 7c that are in sliding contact with the outer periphery of the oil lip 7c.
Further, the hydraulic oil leaking from the gap between the inner periphery of the rod guide 4 and the outer periphery of the piston rod 2 is returned to the reservoir R through the oil passage 13.
According to the present invention, in the hydraulic shock absorber described above, a plurality of oil reservoirs that hold the hydraulic oil using the surface tension of the hydraulic oil at the top of the gap P between the holding piece 7a and the oil lip 7c. S is provided.
This will be described in more detail below.
1 and 2 are a front sectional view and a bottom view, partly broken, showing an oil seal structure of a hydraulic shock absorber according to the present invention.
In the figure, the oil seal 7 is attached so that the dust lip 7b and the oil lip 7c are in contact with the outer periphery of the piston rod 2 in the seal protection case 6 as shown in the figure.
[0023]
Reference numeral 7a denotes a holding piece integrally connected to the dust lip 7b and the oil lip 7c, and a ring-shaped insert metal 8 having an L-shaped cross section is embedded in the holding piece 7a.
[0024]
A plurality of partition walls 14 are integrally provided in the circumferential direction in the ring-shaped gap P having a concave cross section formed by the holding piece 7 a and the oil lip 7 c, and the plurality of oil sump portions S are formed by these partition walls 14. It is partitioned. Note that the lower end of the holding piece 7a protrudes downward sufficiently longer than the lower end of the oil lip 7c.
[0025]
Here, as shown in FIG. 1, each partition 14 is formed so as to straddle the exposed portion side lower end of the insert metal 8 in the holding piece 7a and the substantially middle portion of the outer periphery of the oil lip 7c.
[0026]
In the oil seal structure having such a configuration, when the piston rod 2 of the hydraulic shock absorber as shown in FIG. 5 enters and exits the cylinder 1 by traveling of the vehicle, the hydraulic oil in the cylinder 1 is transferred to the rod guide 4. The piston rod 2 and the bush 3 pass through the gap between adjacent portions and reach the gap G above the rod guide 4.
[0027]
In this case, the hydraulic fluid in the gap G, together with the outflow to thus upwardly in the oil seal 7 is prevented, and returned to the reservoir R through the oil passage 13 shown in FIG. At this time, a part of the hydraulic oil leaked as a jet flow into the gap G enters the oil reservoir S, and a part of the hydraulic oil adheres to the oil lip 7c of the oil seal 7 and is between the outer periphery of the piston rod 2. An oil film is formed on the surface.
[0028]
On the other hand, when the traveling of the vehicle is stopped, the movement of the piston rod in and out of the cylinder 1 is also stopped, so that hydraulic oil is not fed into the gap G from the cylinder 1.
[0029]
However, part of the hydraulic oil is retained and retained in the oil reservoir S partitioned by the partition wall 14 due to the surface tension of the hydraulic oil itself.
[0030]
For this reason, a part of the hydraulic oil held in the oil reservoir S flows to the lower part of the oil lip 7c, and prevents so-called oil film breakage.
[0031]
Therefore, the gap between the oil lip 7c and the piston rod 2 is sealed, and leakage of nitrogen gas in the reservoir R through this gap is surely prevented. Therefore, the piston rod reaction force can be prevented from being lowered, and the piston rod 2 can be extended and retracted smoothly without increasing the initial friction.
[0032]
That is, for example, when a vehicle that has been parked for a long time starts running, the expansion and contraction of the hydraulic shock absorber is started, but the friction coefficient between the oil lip 7c and the piston rod 2 increases due to the oil film running out at the start of the expansion and contraction. For this reason, the initial friction is increased, so that the situation of deteriorating the riding comfort of the vehicle is not invited, and the generation of abnormal noise at that time can be avoided.
[0033]
Further, since a decrease in gas pressure due to leakage of nitrogen gas is prevented, it is possible to prevent a deterioration in vehicle running performance due to a decrease in the piston rod reaction force, and an extension side valve or a pressure side valve during the expansion / contraction operation of the piston rod 2. The cavitation accompanying the squeezing resistance of the hydraulic oil and the generation of abnormal noise due to this can be avoided.
[0034]
Furthermore, by installing the oil reservoir S as described above, an oil seal that does not run out of oil can be obtained by a simple configuration, assembly, and handling without providing a conventional check seal integrally or separately with the oil seal. The structure can be provided at low cost.
[0035]
In the above embodiment, the description has been given of the case where the plurality of partition walls 14 are provided in the gap P between the holding piece 7a and the oil lip 7c, and the oil reservoir portion S is provided between them. A plurality of holes are provided in the top portion to be pierced, that is, in a portion where the holding piece 7a and the oil lip 7c are continuous, so that these holes penetrate into the wall thickness. The concave portion may be used as an oil sump portion as an uneven surface that undulates in the circumferential direction, and has the same operations and effects as the above embodiment.
[0036]
Moreover, the oil sump part which is the said hole can be arbitrarily engraved in a rectangular square hole, or can be round or oval. In short, it is desirable that all of these holes have a size and shape that can use the surface tension of the hydraulic oil to hold the hydraulic oil without being immediately dropped by its own weight.
[0037]
In addition, since each said partition 14 is inside the insert metal 8, when handling the oil seal 7A, there is no fear that the partition 14 touches another thing etc., and provided these partition 14 Therefore, the size of the main body of the oil seal 7A is not increased. Further, since the partition wall 14 can be formed at the same time as the oil seal 7A is molded, the manufacturing cost does not increase.
[0038]
3 and 4 are a front sectional view and a plan view of an oil seal 7B showing another embodiment of the present invention.
[0039]
This is because the hydraulic oil in the oil reservoir S is slightly applied to the lower surface of the oil lip 7c of the oil seal 7B having substantially the same structure as the oil seal 7A shown in FIGS. A plurality of oil guide grooves 15 are provided to guide the inner lip side of the oil lip.
[0040]
By providing this oil guide groove 15, even when the expansion and contraction operation of the piston rod 2 has stopped for a long time, the hydraulic oil in the oil sump portion S smoothly enters each oil guide groove 15. A part of it is guided and stays here, and the other part leaks to the inner peripheral surface side of the oil lip 7c and is held here.
[0041]
For this reason, when the vehicle resumes running and the expansion and contraction operation of the piston rod 2 starts, the hydraulic oil in each oil guide groove 15 is immediately supplied between the oil lip 7c and the piston rod 2, and these sliding contacts are made. Thus, the sealing action and the lubricating action of the part are reliably and safely performed.
[0042]
As a result, it is possible to avoid an increase in the friction coefficient and an increase in friction due to the oil film breakage, and to maintain the riding comfort of the vehicle due to the smooth operation of the piston rod 2.
[0043]
【The invention's effect】
As described above, according to the first aspect of the present invention, a plurality of oil reservoirs that hold the hydraulic oil using the surface tension of the hydraulic oil at the top of the gap between the holding piece and the oil lip in the oil seal. Even if the hydraulic shock absorber has been inactive for a long time due to vehicle stoppage, the hydraulic oil can be held in the oil sump during this time, so that it can wait for supply between the oil lip and piston rod that are in contact with each other. Therefore, when the hydraulic oil is insufficient, the hydraulic oil can be automatically flowed from the oil reservoir to the lower oil lip, thereby avoiding exhaustion of the hydraulic oil in the oil lip, Oil film breakage can be prevented.
[0044]
As a result, initial friction can be reduced, nitrogen gas leakage from the reservoir and cavitation in the hydraulic shock absorber can be prevented, and the desired spring force and damping force can be stably maintained. The effect that it can be obtained is acquired.
[0045]
According to the second aspect of the present invention, the oil guide groove for guiding the working oil to the inner peripheral surface of the oil lip is provided on the inner surface of the oil lip facing the holding piece and the lower surface continuous therewith. Therefore, even when the expansion and contraction operation of the piston rod stops for a long time, the hydraulic oil in the oil sump is guided into each oil guide groove and part of it stays, and the other part of the oil lip A small amount leaks to the inner peripheral surface side of the glass and is held here.
[0046]
As a result, when the expansion and contraction operation of the piston rod is resumed, the minute amount of oil can be immediately supplied between the oil lip and the piston rod, and the effect of being able to quickly realize the sealing action and lubrication action of these sliding contact parts is obtained, Therefore, the smooth operation of the piston rod and the riding comfort of the vehicle can be maintained well.
[Brief description of the drawings]
FIG. 1 is a front view showing a partially broken oil seal structure of a hydraulic shock absorber according to an embodiment of the present invention.
2 is a bottom view of the oil seal structure of the hydraulic shock absorber shown in FIG. 1. FIG.
FIG. 3 is a front view showing a partially broken oil seal structure of a hydraulic shock absorber according to another embodiment of the present invention.
4 is a bottom view of the oil seal structure of the hydraulic shock absorber shown in FIG. 3. FIG.
FIG. 5 is a front sectional view showing a partially broken oil seal structure of a conventional general hydraulic shock absorber.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston rod 4 Rod guide 6 Seal holding case 7 Oil seal 7a Holding piece 7c Oil lip 13 Recirculation passage 14 Partition 15 Oil guide groove S Oil reservoir P Gap

Claims (2)

A cylinder, a piston rod that goes in and out of the cylinder, an outer shell provided on the outer peripheral side of the cylinder, a reservoir formed between the cylinder and the outer shell, closes the upper ends of the cylinder and the outer shell, and allows the piston rod to slide freely A rod guide for guiding, an oil passage formed in the rod guide and communicating with the reservoir, and an oil seal provided in a seal holding case provided above the rod guide, wherein the oil seal is provided in the seal protection case. A holding piece held on the inner periphery, an insert metal embedded in the holding piece, and a dust lip and an oil lip that are integrally connected to the holding piece and slidably contact the outer periphery of the piston rod. Hydraulic fluid leaking from the gap between the outer periphery of the piston rod and the outer periphery of the piston rod through the oil passage. In a hydraulic shock absorber which is returned to the server, provided with a plurality of oil reservoir portion for holding the operating oil by utilizing the surface tension of the working fluid on the top portion of the gap between the retaining piece and the oil lip Oil seal structure of hydraulic shock absorber 2. The hydraulic shock absorber according to claim 1, wherein an oil guide groove for guiding hydraulic oil to the inner peripheral surface of the oil lip is provided on an inner surface of the oil lip facing the holding piece and a lower surface continuous therewith. Oil seal structure.

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