JP4051842B2 - Oil seal for reciprocating shaft - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oil seal used for a reciprocating shaft such as a hydraulic shock absorber.
[0002]
[Prior art]
As shown in FIG. 3 , a conventional two-cylinder hydraulic shock absorber has a rod guide 32 attached to an open end of an outer cylinder 31 of the hydraulic shock absorber, and an oil seal 34 is disposed on the outer side thereof. The oil seal 34 is provided with a main lip 36 on the inner periphery of a disc-shaped metal reinforcing ring 35 and a dust lip 37 integrally formed on the outer periphery thereof. The dust strip 37 is slidable and airtight in contact with the piston rod 33 of the container, and the dust lip 37 prevents dust from entering from the outside.
[0003]
Reference numeral 39 denotes a check lip projecting obliquely downward on the lower surface of the disk-shaped metal reinforcing ring 35 of the oil seal 34. The check lip 39 is formed on the first step portion 40 of the rod guide 32. The buffer oil that abuts and passes between the rod guide 32 and the piston rod 33 by the check lip 39 and flows into the annular recess 41 of the rod guide 32 is connected to the outer cylinder 31 via the check lip 39 and the communication passage 42. The gas is recirculated to a reservoir chamber 44 formed by the inner cylinder 43 so that the gas and oil in the reservoir chamber 44 do not flow back into the annular recess 41.
[0004]
The main lip 36 of the oil seal 34 may be deformed by pressure, and the deformation changes the oil level angle and the seal angle of the main lip, thereby impairing the sealing performance. Therefore, in order to prevent the deformation of the main lip 36, a sub lip 45 that supports the main lip 36 is usually provided. The above-mentioned secondary lip 45 has a nature that the fastening margin for the piston rod 33 is the same size as that of the rod, has a slight margin, or further has a minute gap between the rod 33. It is normal to have been made.
[0005]
In the above-described oil seal for a reciprocating shaft such as a hydraulic shock absorber, the main lip 36 may be dragged by the piston rod and start to move without sliding when the reciprocating piston rod 33 is turned up and down. This is because the larger the contact area of the main lip 36 with the piston rod 33, the larger the friction, and the axial length (hereinafter referred to as dragging) in which the main lip moves without sliding in synchronism with the piston rod 33. (Referred to as the amount). When the drag amount increases, the generation of the seal stable friction is delayed. In addition, in the hydraulic shock absorber mounted on the vehicle, since friction affects the damping force, the delay in the generation of the seal stable friction delays the generation of the damping force, which causes a problem in steering stability.
[0006]
When the main lip 36 is dragged together with the rod 33 during the upper and lower dead center folding operation of the piston rod 33 described above, the rubber waist of the main lip 36 is also expanded and contracted. As shown in FIG. 4 , no special consideration is given to the distance h from the tip of the main lip 36, and the distance h is normally set large. And, in the problem at the time of the upper and lower dead center folding operation of the piston rod 33, when the distance between the main lip and the sub lip is large, the sub lip 45 has no inhibiting action on the expansion / contraction of the rubber waist 46. The drag phenomenon cannot be eliminated, and when the distance is close, it is difficult to manufacture the main lip 36 while maintaining an appropriate seal angle. Further, the present situation is that no particular consideration has been given to the fastening margin S1 of the main lip or the fastening margin S2 of the sub lip.
[0007]
[Problems to be solved by the invention]
As described above, in the problem at the time of reversing the vertical dead center of the reciprocating shaft such as a conventional piston rod of this type of hydraulic shock absorber, the secondary lip has a delay in the generation of stable friction of the main lip, so-called damping force. In order to minimize the drag of the main lip when the reciprocating shaft is turned up and down, the oil seal may not be able to obtain good maneuverability. The present invention has been completed by finding that there is a relative relationship between the main lip and the secondary lip, and by clarifying the relative relationship described above, the reciprocating shaft is turned up and down at the dead center. It is an object of the present invention to provide an oil seal for a reciprocating shaft that minimizes the drag amount of the main lip of the oil seal.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a reciprocating shaft oil seal according to the present invention includes a main lip and a reciprocating lip provided with a sub lip that supports the main lip and is formed with a smaller tightening margin with respect to the shaft than the main lip. In the dynamic shaft oil seal, when the distance between the leading end of the main lip and the leading end of the sub lip is H and the tightening margin for the shaft of the main lip is S1, the distance H and the tightening margin S1 are S1 ≦ By satisfying the relationship of H ≦ 2.5S1, expansion / contraction of the waist of the main lip during the vertical dead center folding operation of the reciprocating shaft is suppressed, and the drag amount of the main lip is suppressed. Is the feature.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
When describing the embodiments of the present invention with reference to FIG. 1, the rod guide 32 is attached to the open end of the outer tube 31 in 2 cylinder type hydraulic shock absorber as shown in FIG. 3 described above, in the outer portion The oil seal 1 according to the present invention is disposed. The oil seal 1 according to the embodiment of the present invention has a main lip 3 and an inner peripheral portion around a disc-shaped metal reinforcing ring 2. A sub lip 4 is disposed at a predetermined distance from the main lip 3, and a dust lip 5 is integrally provided on the outside thereof. The main lip 3 is slidable on a rod 6 of a hydraulic shock absorber, The secondary lip 4 is provided for preventing deformation of the main lip 3 and the dust lip 5 prevents dust from entering from the outside.
[0010]
The main lip 3 of the oil seal 1 is in sliding contact with the rod 6 with the required tightening margin S1, the sub lip 4 is in sliding contact with the rod 6 with the required tightening allowance S2, and the main lip 3 The tip and the tip of the sub lip 4 have a predetermined distance H.
[0011]
In order to avoid the main lip 3 from being dragged when the rod 6 is turned up and down, the waist of the main lip 3 can be prevented from expanding and contracting, and an appropriate seal angle of the main lip 3 can be set. It is necessary to determine the distance between the tip of the main lip 3 and the tip of the sub lip 4 that can be produced while maintaining.
[0012]
In order to satisfy the above requirements, in the present embodiment, the distance H between the front end portion of the main lip 3 and the front end portion of the sub lip 4 is larger than the tightening margin S1 of the main lip 3 and It is smaller than 2.5 times the tightening margin S1 of the main lip. That is, it has a relationship of S1 ≦ H ≦ 2.5S1.
[0013]
When the distance H between the front end portion of the main lip 3 and the front end portion of the sub lip 4 as described above is configured as described above, the front end of the main lip 3 and the sub lip 4 with respect to the reciprocating movement of the shaft as shown in FIG. While the distance H from the tip is equal to or less than 2.5 times the tightening allowance S1 of the main lip 3, the drag amount of the main lip 3 due to the reciprocating motion when the rod 6 is turned up and down is compared. Small and good maneuverability. When the distance H between the front end of the main lip 3 and the front end of the sub lip 4 exceeds 2.5 times the tightening allowance S1 of the main lip 3, the drag amount of the main lip 3 increases abruptly and good maneuverability is obtained. It becomes impossible. Further, if the H is made smaller than the tightening allowance S1 of the main lip 3, they are too close to each other, and it becomes difficult to manufacture while maintaining an appropriate seal angle of the main lip 3.
[0014]
Further, as described above, when the tightening margin of the main lip 3 with respect to the rod 6 is S1 and the tightening margin of the sub lip 4 with respect to the rod 6 is S2, the contact width of the main lip 3 with respect to the rod 6 is increased when S2 is decreased. Therefore, the friction of the main lip 3 is increased, and the drag amount of the main lip 3 when the rod 6 is turned up and down is increased. Further, if the S2 is increased, the tension of the main lip 3 against the rod 6 is weakened and the sealing performance is impaired.
[0015]
In the present embodiment, the tightening margin S2 of the sub lip 4 is larger than 0.6 times the tightening margin S1 of the main lip 3, and smaller than 0.9 times the tightening margin S1 of the main lip 3 .
[0017]
In the present embodiment, the oil seal 1 has been described as being used for sealing the rod of the hydraulic shock absorber. However, the oil seal 1 described in the present embodiment is not limited to the hydraulic shock absorber, and the shaft of the reciprocating shaft is used. Applicable for sealing.
[0018]
【The invention's effect】
The reciprocating oil seal according to the present invention has a main lip and a sub lip, and the distance between the main lip and the sub lip is set to be the same as the tightening allowance for the shaft of the main lip to 2.5 times the tightening allowance. While maintaining an appropriate seal angle of the main lip, there is almost no dragging amount of the main lip when the shaft is turned up and down .
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the distance between the tips of the main lip and the sub lip of the oil seal for a reciprocating shaft according to the present invention and the drag amount. ] Illustration of hydraulic shock absorber [Fig. 4] Conventional oil seal for reciprocal coaxial

Claims (1)

In an oil seal for a reciprocating shaft having a main lip and a sub lip that supports the main lip and has a smaller tightening margin with respect to the shaft than the main lip, the distance between the front end of the main lip and the front end of the sub lip is increased. H and when the tightening allowance with respect to the shaft of the main lip is S1, the distance H and the tightening allowance S1 satisfy the relationship of S1 ≦ H ≦ 2.5S1, thereby An oil seal for a reciprocating shaft characterized by suppressing the expansion and contraction of the waist of the main lip during the vertical dead center folding operation , thereby suppressing the drag amount of the main lip.

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