JP4707119B2 - Hydraulic shock absorber - Google Patents

Description

  The present invention relates to a hydraulic shock absorber comprising a reciprocating shaft and an oil seal having a main lip and a sub lip used for the shaft.

  As shown in FIG. 4, in the two-cylinder hydraulic shock absorber, a rod guide 32 is attached to the open end of the outer cylinder 31 of the hydraulic shock absorber, and an oil seal 34 is disposed on the outer side. 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.

  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 flow 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.

  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 36, 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.

  In the oil seal for the reciprocating shaft of the hydraulic shock absorber described above, the main lip 36 may start to move together without being slid by being dragged by the piston rod 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 dragged) that the main lip moves without sliding in synchronism with the piston rod 33. Volume). When the drag amount increases, the generation of the seal stable friction is delayed. In addition, in a hydraulic shock absorber mounted on a vehicle, since friction affects the damping force, the delay in the generation of the seal stable friction delays the generation of the damping force and causes a problem in the stability of operation.

  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. 5, 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.

  As described above, in the problem when the top and bottom dead center folding operation of the reciprocating shaft such as the piston rod of this type of conventional hydraulic shock absorber is turned on, the secondary lip generates a delay in the generation of stable friction of the main lip, so-called generation of damping force. In order to suppress the drag of the main lip as much as possible when the reciprocating shaft is turned up and down, the oil seal of the oil seal can be used as much as possible. The present invention has been completed by finding that there is a relative relationship between the main lip and the sub lip, and by clarifying the relative relationship described above, the reciprocating shaft can be turned up and down at the time of turning back and forth. It is an object of the present invention to provide a hydraulic shock absorber provided with an oil seal for a reciprocating shaft that minimizes the drag amount of the main lip of the oil seal.

The hydraulic shock absorber according to the present invention is a hydraulic shock absorber comprising a reciprocating shaft and a reciprocating shaft oil seal provided with a main lip and a sub lip used for the shaft. When the distance between the lip and the tip of the sub lip is H and the tightening allowance with respect to the axis of the main lip is S1, the distance H and the tightening allowance S1 satisfy the relationship S1 ≦ H ≦ 2.5S1. By comprising, the expansion / contraction of the waist part of the main lip at the time of the vertical dead center folding operation of the reciprocating shaft is suppressed, and the drag amount of the main lip is suppressed .

  A hydraulic shock absorber provided with a reciprocating shaft according to the present invention and a reciprocating shaft oil seal provided with a main lip and a sub lip used for the reciprocating shaft mainly uses the distance between the main lip and the sub lip. Since it is set between the same tightening allowance as the shaft of the lip and 2.5 times the tightening allowance, it can be manufactured while maintaining the proper seal angle of the main lip, and the main lip when the shaft is turned up and down There is almost no dragging amount, and the main lip becomes difficult to be dragged when the shaft is turned up and down, so that good maneuverability can be obtained.

  The embodiment of the present invention will be described with reference to the drawings. A rod guide 32 is attached to the open end of the outer cylinder 31 in the above-described two-cylinder hydraulic shock absorber shown in FIG. Instead of the oil seal 34, the oil seal 1 shown in FIG. The oil seal 1 used in the hydraulic shock absorber according to the present embodiment has a main lip 3 and a sub lip 4 arranged at a predetermined distance from the main lip 3 around the disc-shaped metal reinforcing ring 2. A dust lip 5 is integrally provided on the outside of the main lip 3 so that the main lip 3 is slidable and airtightly contacted with a rod 6 of a hydraulic shock absorber, and the sub lip 4 is provided with the main lip 4. The dust strip 5 is provided to prevent the lip 3 from being deformed, and the dust strip 5 prevents dust from entering from the outside.

  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.

  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 maintained and manufactured.

  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 allowance S1 of the main lip 3. That is, it has a relationship of S1 ≦ H ≦ 2.5S1.

  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.

  As described above, when the tightening allowance of the main lip 3 to the rod 6 is S1 and the tightening allowance of the sub lip 4 to the rod 6 is S2, if the S2 is reduced, the contact width of the main lip 3 to the rod 6 is increased. 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.

  Therefore, in the present embodiment, the construction is such that the fastening margin S2 of the sub lip 4 is larger than 0.6 times the fastening margin S1 of the main lip 3 and smaller than 0.9 times the fastening margin S1 of the main lip 3. That is, the above-described problem is solved by adopting a configuration satisfying the relationship of 0.6S1 ≦ S2 ≦ 0.9S1.

  When configured as described above, as shown in FIG. 3, as long as S2 is not less than 0.6 times or not more than 0.9 times S1, the main lip due to reciprocation during the vertical dead center folding operation of the rod 6 The drag amount of 3 is substantially constant and relatively small. When S2 is smaller than 0.6 times S1, the amount of dragging of the main lip 3 when the rod 6 is turned up and down is suddenly increased. Further, when S2 exceeds 0.9 times S1, the sealing performance is impaired.

Oil seal for reciprocating shaft of hydraulic shock absorber of the present invention The figure which shows the relationship between the tip distance of the main lip of the oil seal for reciprocating shafts of the hydraulic shock absorber of this invention, the front-end | tip distance of a sub lip, and the drag amount. The figure which shows the relationship between the ratio of the interference amount of the sub lip with respect to the interference amount of the main lip of the oil seal for reciprocating shafts of the hydraulic shock absorber of this invention, and the drag amount. Illustration of hydraulic shock absorber Oil seal for reciprocating shaft of conventional hydraulic shock absorber

Explanation of symbols

1 Oil seal 3 Main lip 4 Sub lip 6 Axis H Distance between the tip of the main lip and the tip of the sub lip S1 Tightening allowance for the main lip shaft S2 Tightening allowance for the sub lip shaft

Claims (1)

In a hydraulic shock absorber comprising a reciprocating shaft and a reciprocating shaft oil seal having a main lip and a sub lip used for the shaft, the distance between the front end of the main lip and the front end of the sub lip is determined. H and when the tightening allowance for the shaft of the main lip is S1, the distance H and the allowance S1 satisfy the relationship of S1 ≦ H ≦ 2.5S1 , whereby the reciprocating shaft A hydraulic shock absorber characterized by suppressing the expansion and contraction of the waist of the main lip when the upper and lower dead centers are turned back, thereby reducing the drag amount of the main lip .

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