JPH11108101A - Seal for hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a stable seal for a hydraulic shock absorber that a valve is opened at a low pressure against the pressure in an inner cylinder side of the hydraulic shock absorber and also an inverted pressure is not reduced against the pressure in an outer cylinder side. SOLUTION: This oil seal applied for a hydraulic shock absorber is provided by installing a check lip 14 having a required thickness and a step 16 cut at right angles to the inside direction at the tip of the check lip 14, and by forming a thin sub-lip 17 of the check lip 14, connected with the cut step 16, and also by installing many ribs 15, which reach the cut step 16 in the direction of the tip of the lip 14, on the whole inner circumferential surface contacting with a circular step of a rod guide of the check lip 14 at required intervals.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a seal used for a hydraulic shock absorber. 2. Description of the Related Art A conventional hydraulic shock absorbing seal of this type is shown in FIG.
As shown in FIG. 4, a rod guide 32 is attached to the open end side of the outer cylinder 31 of the hydraulic shock absorber, and an oil seal 34 is provided on the outer side of the rod guide 32. An annular recess 35 surrounding the piston rod 33 is formed in the guide 32, and an inner wall 35 of the annular recess 35 is formed.
In addition to providing an annular step 36 on the outer peripheral side of the upper end of a,
An annular cylindrical portion 3 7 for supporting the oil seal 3 4 is integrally formed outside the step portion 3 6, and a small-diameter communication hole 3 8 for oil recirculation for buffering is formed in the rod guide 32. I have. [0003] The above-described oil seal 34 has a main lip 41 inside a disk-shaped metal reinforcing ring 40.
And a dust lip 42 is integrally provided on the outside thereof,
The main lip 4 1 is a piston rod 3 3 of a hydraulic shock absorber.
Slidably and airtightly in sliding contact with the dust lip 4 2
Is provided to prevent intrusion of dust from the outside, and an outer peripheral seal 4 3 is provided at the peripheral portion of the lower surface of the disk-shaped metal reinforcing ring 40, which is in contact with the outer cylinder 3 1. Further, the metal reinforcing ring 40 of the oil seal 34 described above is used.
A check lip 44 is provided diagonally on the lower side of the lower side. When the above-mentioned hydraulic shock absorber operates, the guide bush
The buffer oil that has passed between 39 and the piston rod 33 flows into the annular recess 35 of the rod guide 32, and the inflow buffer oil is removed through the check lip 44 and the communication hole 38. It is recirculated to the reservoir chamber 49 formed by the cylinder 31 and the inner cylinder 48, and the gas and the like in the reservoir 49 flow back into the annular recess 35 by the action of the check lip 44. Not to be. [0005] As described above, the passage of the buffer oil is allowed, and the gas and the like in the reservoir chamber 49 are formed in the annular recess.
3 5 Check lip that acts to prevent backflow into the inside 4
In order for the above operation to work smoothly, the lip of the check lip 4 4 opens the valve even at low pressure while maintaining good sealing (low valve opening pressure), There is a demand to maintain the same pressure as before, and in order to cope with this, if the lip of the check lip is formed thin, the valve opening pressure can be lowered, but the reversal pressure is reduced and the tip of the lip is rolled up etc. This will induce backflow, and if the lip stiffness is increased or the crushing margin is increased, the reversal pressure will rise and prevent backflow, but the valve opening pressure will increase and hinder the smooth flow of buffer oil. become. Accordingly, the present invention meets the above-mentioned demands in the prior art, and in order to improve the reliability of the hydraulic shock absorber and operate the hydraulic shock absorber smoothly, the pressure at the inner cylinder side must be low. The seal for the hydraulic shock absorber that opens the valve and obtains an effective check lip even at high pressure against the pressure on the outer cylinder side, that is, a stable low valve opening pressure without lowering the reversing pressure Its purpose is to provide. [0007] In order to achieve the above object, a seal for a hydraulic shock absorber according to the present invention is arranged such that the seal is provided on the piston rod outside a rod guide in which the piston rod is slidable. An oil seal is provided for sliding contact, and the check lip of the oil seal is brought into contact with the annular step of the rod guide. The thin check lip is attached to the tip of the check lip via a notch step. A lip is formed, and a large number of ribs are formed on the inner peripheral surface of the check lip abutting on the annular step of the rod guide from the base of the check lip to the cutting step at a required interval. Is what you do. 1 and 2 show an embodiment of the present invention.
Referring to FIG. 3 and FIG. 3, the hydraulic shock absorber seal according to the present invention has a rod guide 2 attached to the open end side of the outer cylinder 1 of the hydraulic shock absorber, and an oil seal 4 on the outer side of the rod guide 2. It is arranged. The rod guide 2 has an annular recess 5 surrounding the piston rod 3.
An annular step 6 is formed so that the upper end of the inner wall 5 a of the annular recess 5 is cut into the outer peripheral side, and an annular cylindrical section 7 supporting the oil seal 4 is integrally formed outside the annular step 6. The rod guide 2 is formed with a small-diameter communication hole 8 for oil recirculation for buffering. The above-mentioned oil seal 4 is provided with a main lip 11 on the inside of a disk-shaped metal reinforcing ring 10 and a dust lip 12 on the outside thereof, and is integrally provided with the main lip 11. The lip 11 is slidably and airtightly slidably in contact with the piston rod 3 of the hydraulic shock absorber, and the dust lip 12 is for preventing dust from entering from outside. An outer peripheral seal 13 is provided on the peripheral edge of the lower surface of the ring 10 so as to abut the outer cylinder 1, and a check lip is provided on the lower surface of the metal reinforcing ring 10 of the oil seal 4 in an oblique outer direction. 1 4 are provided. The check lip 14 is an annular step provided on the outer peripheral side of the upper end of the annular recess 5 of the rod guide 2.
6 has its lip portion in contact with the upper surface thereof, and the buffer oil flowing in from the side of the annular recess 5 is supplied to the reservoir chamber 19 through the small-diameter communication hole 8 for buffer oil recirculation drilled in the rod guide 2. The gas and the like in the reservoir chamber 19 are returned to the annular recess.
5 to prevent backflow. The check lip 14 according to the embodiment of the present invention will be described in more detail with reference to FIGS. 2 and 3.
The check lip 14 has a required thickness, and has a notch step 16 provided at a front end thereof at a substantially right angle inward in the inward direction.
A thin check lip sub-lip 17 is formed in series with the check lip 14 and the rod guide 2 of the check lip 14 is formed.
The check lip 14 is attached to the inner peripheral surface of the
The ribs 15, 15, 15,..., Which reach the cutting step 16 from the base toward the distal end, are required along the entire circumference of the inner peripheral surface. Many are provided at intervals. The check lip 14 is connected to an annular step provided on the outer peripheral side of the upper end of the annular recess 5 of the rod guide 2.
When the check lip 14 is brought into contact with the upper surface of the check lip 14 along with the sub-lip 17 of the check lip, ribs 15, 15, 15, 15 ...
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The buffer oil flowing in from the side 5
, A plurality of ribs 15, 15, 15,..., Are formed between adjacent ribs 15 and ribs 15. , 1 8,..., And reaches the sub-lip 17 of the thin check lip from the cutting step 16, and acts on the sub lip 17 of the thin check lip. The auxiliary lip 17 of the check lip is opened, and the buffer oil is returned to the reservoir chamber 19 through the small-diameter communication hole 8 for buffer oil return drilled in the rod guide 2 described above. Since the auxiliary lip 17 of the check lip is formed to be thin, the valve opening pressure can be reduced. Further, the gas or the like from the reservoir chamber 19 is received by the entire check lip 14 and the sub lip 17 of the check lip, and the sub lip 17 of the check lip is formed thin. The check lip 14 described above is also applied to the pressure of gas or the like from the reservoir chamber 19.
Becomes a backup, the reversal pressure depends on the rigidity of the entire check lip 14 including the auxiliary lip 17 of the check lip, and despite the fact that the valve opening pressure described above could be reduced, The reverse pressure can be maintained as in the prior art, and gas or the like can be prevented from flowing back into the annular recess 5. An experiment was conducted on the valve opening property of the check lip according to the above-described embodiment of the present invention. As a result, the valve opening pressure of the conventional check lip tended to increase in proportion to the squeeze allowance of the check lip. However, the check lip of this embodiment was able to obtain a substantially constant valve opening pressure regardless of the size of the crushing allowance. When the check lip of the present embodiment is compared with the conventional check lip, when the squeeze allowance of the check lip is the same, the valve opening pressure of the check lip of the present embodiment is 1/2 to 1 / 3, especially the larger the crushing allowance, the greater the difference in valve opening pressure compared to the conventional product.
As described above, in the check lip according to the present embodiment, the dependence of the crushing allowance on the valve opening pressure of the check lip is reduced, and a stable valve opening pressure can be obtained even with a change in the crushing allowance during assembly or the like. Was. Further, it was confirmed that the reversal pressure for the same crushing allowance of the check lip was not different from the conventional one. According to the seal for a hydraulic shock absorber according to the present invention, the check lip of the oil seal to be brought into contact with the annular step of the rod guide has a thin check at the tip of the check lip through the notch step. Since the auxiliary lip of the lip was formed, and a large number of ribs were formed on the inner peripheral surface of the check lip abutting on the annular step of the rod guide from the base of the check lip to the notch step at required intervals, When the check lip and the sub lip of the check lip are brought into contact with the upper surface of the annular step portion of the rod guide, the buffer oil flowing in from the annular recess side when the hydraulic shock absorber is operated is reduced by the rib formed on the check lip. The small diameter of the ribs which flows between the ribs and acts on the sub-lip of the check lip which is thinner than the cutting step, opens the sub-lip of the check lip and forms buffer oil on the rod guide. Is recirculated to the reservoir chamber through the communication hole, but since the auxiliary lip of the check lip is formed thin, the valve opening pressure can be reduced. In addition, since the check lip serves as a backup for the pressure of gas or the like from the reservoir chamber, the reverse pressure depends on the rigidity of the entire check lip including the sub lip of the check lip. Thus, despite the fact that the valve opening pressure can be reduced, the reversal pressure can be maintained in the same manner as in the prior art, and gas and the like can be prevented from flowing back into the annular recess.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an essential part of a hydraulic shock absorber to which an oil seal according to the present invention is applied. FIG. 2 is an explanatory view of an oil seal of the present invention. FIG. Enlarged explanatory view of the check lip [Fig. 4] Cross-sectional view of main parts of a conventional hydraulic shock absorber [Description of symbols] 1 External cylinder 2 Rod guide 3 Piston rod 4 Oil seal 6 Annular step 1 0 Metal reinforcement ring 1 4 Check Lip 1 5 Rib 1 6 Notch step 1 7 Secondary lip of check lip 1 8 Groove

Claims (1)

Claims 1. An oil seal slidably contacting a piston rod is provided outside a rod guide on which a piston rod is slidable, and a check lip of the oil seal is attached to the rod guide. A check lip is formed at the tip of the check lip through a notch step to form an auxiliary lip of the thin check lip, and the check lip contacts the annular step of the rod guide. A seal for a hydraulic shock absorber, wherein a large number of ribs are formed on a peripheral surface from a base of the check lip to the cutting step at required intervals.