Seal member and shock absorber

Abstract

To provide a seal member which can realize a desired surface pressure gradient and inhibit seeping.SOLUTION: A dust seal 10 of a seal member S has: a first inner peripheral surface 11 whose diameter reduces toward a base end side; a second inner peripheral surface 12 whose diameter expands toward the base end side; a dust lip part 14 formed in a connection portion between the first inner peripheral surface 11 and the second inner peripheral surface 12; and a rigidity reduction part which is provided closer to the base end side than the dust lip part 14. The rigidity reduction part is located closer to the tip side of the dust seal 10 than the end surface 40a at the dust lip part 14 side of a core grid 40 and closer to the base end side than the middle portion between the end surface 40a at the dust lip part 14 side of the core grid 40 and the dust lip part 14 in an axial direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a seal member and a shock absorber. [Background technology]

[0002] In fluid pressure equipment such as shock absorbers, a seal member that seals the gap between a cylinder and a rod is known (Patent Document 1). In the seal member described in Patent Document 1, a base portion (reinforcement ring) made of a metal material is held by the cylinder, and a dust lip portion made of an elastic body such as a rubber material is provided on the base portion (reinforcement ring) so as to be in sliding contact with the rod. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 5-38433 Summary of the Invention [Problem to be solved by the invention]

[0004] In the seal member described in Patent Document 1, the opening at the tip side of the inner circumferential surface of the dust lip is formed into a substantially edge shape. When a seal member of this shape is attached to a shock absorber, dust adhering to the outer circumferential surface of the rod can be effectively removed when the rod contracts, and therefore the seal member has good dust resistance to prevent dust from entering.

[0005] However, with a shape such as that of the sealing member described in Patent Document 1, the surface pressure at the dust lip portion rises sharply from the tip side; specifically, the opening at the tip side (the tip side of the sealing part with the rod) has an edge shape, so when the rod contracts, the oil film adhering to the outer surface of the rod is scraped off, making it easy for oil to leak.

[0006] In order to prevent the oil from seeping out, it is possible to flatten the gradient of the surface pressure at the dust lip, specifically, to flatten the angle of the tip face of the dust lip. However, even if the tip face of the dust lip is flattened in this way, the rigidity of the dust seal is high, so the surface pressure gradient cannot be maintained in a flat state, and the desired surface pressure gradient cannot be achieved, and the oil cannot be prevented from seeping out.

[0007] The present invention has been made in consideration of the above problems, and has an object to provide a sealing member that can achieve a desired surface pressure gradient and suppress seepage leakage. [Means for solving the problem]

[0008] The present invention is a sealing member provided in a fluid pressure device to seal between a cylinder and a rod, and comprises a core bar, and a dust seal having a base end fixed to the core bar, extending toward the rod, and in sliding contact with the outer peripheral surface of the rod, the dust seal having a first inner circumferential surface that narrows in diameter toward the base end, a second inner circumferential surface formed on the base end side of the first inner circumferential surface and expanding in diameter toward the base end side, a dust lip portion formed at the connection portion between the first inner circumferential surface and the second inner circumferential surface, and a rigidity reduction portion provided on the base end side of the dust lip portion, the rigidity reduction portion being located on the tip side of the dust seal relative to the end face of the core bar on the dust lip side, and on the base end side relative to the midpoint in the axial direction between the end face of the core bar on the dust lip side and the dust lip portion.

[0009] In this invention, the dust lip is formed at the connection between the first inner circumferential surface and the second inner circumferential surface, so that the surface pressure can be made flat by adjusting the angle between the first inner circumferential surface and the second inner circumferential surface. Also, in this invention, the rigidity reducing portion is located closer to the tip of the dust seal than the end face of the core bar on the dust lip side, and closer to the base end than the midpoint in the axial direction between the end face of the core bar on the dust lip side and the dust lip, so that the rigidity of the dust seal is neither too high nor too low, so that a desired surface pressure gradient can be maintained. This makes it possible to suppress seepage while maintaining the peak value of the surface pressure of the dust seal.

[0010] The present invention is characterized in that the dust seal further has a third inner circumferential surface formed on the base end side from the second inner circumferential surface and expanding in diameter toward the base end side, and a bent portion formed at the connection portion between the second inner circumferential surface and the third inner circumferential surface, and the rigidity reduction portion is formed by making the radial thickness of the dust seal thinner than the radial thickness at the bent portion, at least in the region where the third inner circumferential surface is provided.

[0011] In the present invention, since the rigidity reducing portion can be formed simply by changing the thickness of the dust seal, an increase in cost due to the formation of the rigidity reducing portion can be suppressed.

[0012] The present invention is characterized in that the base end of the dust seal has a covering portion extending along the end face of the core wire on the dust lip side, and the position where the end face on the dust lip side in the axial direction of the covering portion is extended is within the range of the rigidity reduction portion.

[0013] In the present invention, the stiffness of the dust seal is neither too high nor too low, so a desired surface pressure gradient can be maintained, thereby suppressing seepage while maintaining the peak value of the surface pressure of the dust seal.

[0014] The present invention is characterized in that the inclination angle of the second inner circumferential surface is larger than the inclination angle of the first inner circumferential surface, and the inclination angle of the third inner circumferential surface is larger than the inclination angle of the second inner circumferential surface.

[0015] In this invention, the distribution of the surface pressure can be made asymmetrical more reliably, so that the oscillation phenomenon caused by the reciprocating movement of the rod can be suppressed at the contact portion between the dust lip and the rod. Furthermore, by making the dust seal in this shape, the dust resistance required for the dust seal can be reliably secured.

[0016] The present invention is characterized by comprising the above-mentioned sealing member, a cylinder in which a working fluid is sealed, a rod inserted into the cylinder so as to be freely movable in the axial direction, and a damping force generating section housed in the cylinder that applies resistance to the flow of the working fluid as the rod moves, thereby generating a damping force. Effect of the Invention

[0017] According to the present invention, it is possible to provide a sealing member capable of realizing a desired surface pressure gradient and suppressing seepage. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a partial cross-sectional view of a shock absorber to which a sealing member according to an embodiment of the present invention can be applied. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a seal member according to an embodiment of the present invention. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a dust seal of the seal member according to the embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a dust seal of a sealing member according to a comparative example. [Diagram 5] Fig. 5(A) is a diagram showing the distribution of surface pressure in the dust seal when the seal member according to the embodiment of the present invention is attached to the shock absorber 100. Fig. 5(B) is a diagram showing the distribution of surface pressure in the dust seal when the seal member according to the comparative example is attached to the shock absorber 100. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a sealing member S according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0020] 1 is a partial cross-sectional view of a shock absorber 100 as a fluid pressure device to which a seal member S can be applied. The shock absorber 100 is provided, for example, between a body and an axle of a vehicle (not shown), and generates a damping force to suppress vibration of the vehicle body.

[0021] The shock absorber 100 includes a cylinder 1, a rod 2 movably inserted into the cylinder 1, and a piston 3 connected to the rod 2. The piston 3 is slidably housed in the cylinder 1, and divides the inside of the cylinder 1 into a compression-side chamber 1a and an extension-side chamber 1b. Hydraulic oil is sealed in the compression-side chamber 1a and the extension-side chamber 1b as a working fluid.

[0022] A compression side passage 3a and an extension side passage 3b that communicate between the compression side chamber 1a and the extension side chamber 1b are formed in the piston 3. The compression side passage 3a and the extension side passage 3b are opened and closed by a compression side damping valve 4a and an extension side damping valve 4b, respectively, that serve as damping force generating units provided in the piston 3.

[0023] The rod 2 passes through the expansion-side chamber 1b and extends from the cylinder 1. When the rod 2 enters the cylinder 1, the shock absorber 100 contracts, and when the rod 2 retreats from the cylinder 1, the shock absorber 100 extends.

[0024] When the shock absorber 100 contracts, the piston 3 moves in a direction to reduce the compression side chamber 1a and expand the expansion side chamber 1b. The pressure difference between the compression side chamber 1a and the expansion side chamber 1b causes the compression side damping valve 4a to open the compression side passage 3a, and the hydraulic oil flows from the compression side chamber 1a through the compression side passage 3a into the expansion side chamber 1b. At this time, resistance is applied to the flow of the hydraulic oil by the compression side damping valve 4a, and the shock absorber 100 exerts a damping force.

[0025] When the shock absorber 100 expands, the piston 3 moves in a direction to reduce the expansion-side chamber 1b and expand the compression-side chamber 1a. The expansion-side damping valve 4b opens due to the pressure difference between the expansion-side chamber 1b and the compression-side chamber 1a, opening the expansion-side passage 3b, and hydraulic oil flows from the expansion-side chamber 1b through the expansion-side passage 3b into the compression-side chamber 1a. At this time, resistance is applied to the flow of hydraulic oil by the expansion-side damping valve 4b, and the shock absorber 100 exerts a damping force.

[0026] In this way, the compression side damping valve 4a and the extension side damping valve 4b apply resistance to the flow of hydraulic oil as the rod 2 moves, thereby generating a damping force.

[0027] The change in volume within the cylinder 1 accompanying the movement of the rod 2 is compensated for by an air chamber 1 c formed within the cylinder 1 by a free piston 5 .

[0028] A rod guide 6 that slidably supports the rod 2 via a bush 6a is provided on the inner periphery of the cylinder 1. The rod guide 6 is supported by a retaining ring 6b provided on the inner periphery of the cylinder 1.

[0029] The open end 1d of the cylinder 1 is bent radially inward by crimping, and a seal member S that closes the gap between the cylinder 1 and the rod 2 is provided between the open end 1d and the rod guide 6. In other words, the seal member S and the rod guide 6 are fixed to the cylinder 1 by being sandwiched between the open end 1d of the cylinder 1 and a retaining ring 6b.

[0030] As shown in FIG. 2, the sealing member S comprises an annular dust seal 10 arranged at the tip side of the rod 2 and in sliding contact with the outer peripheral surface of the rod 2, an oil seal 30 provided on the opposite side of the dust seal 10 in the axial direction of the rod 2, a cylindrical connecting part 20 connecting the dust seal 10 and the oil seal 30, and a core bar 40 provided radially outside the connecting part 20 and to which the base ends of the dust seal 10 and the oil seal 30 are fixed.

[0031] When the shock absorber 100 contracts, the dust seal 10 scrapes off foreign matter adhering to the outer circumferential surface of the rod 2. In other words, the dust seal 10 prevents foreign matter from entering the cylinder 1. The dust seal 10 of this embodiment seals between the rod 2 and the dust seal 10 using only its own elasticity, without using a biasing member such as a garter spring.

[0032] The oil seal 30 is formed so as to protrude radially inward from the connection part 20 and in the direction in which the rod 2 contracts into the cylinder 1, and is in sliding contact with the outer circumferential surface of the rod 2. When the shock absorber 100 extends, the hydraulic oil adhering to the outer periphery of the rod 2 is scraped off by the oil seal 30 and returned to the inside of the cylinder 1. In other words, the oil seal 30 prevents the hydraulic oil from leaking from the cylinder 1.

[0033] An annular groove 31 is formed on the outer periphery of the oil seal 30, and an annular garter spring 32 is fitted in the groove 31. The garter spring 32 ensures the sealing performance of the oil seal 30 against the rod 2.

[0034] The seal member S further includes an outer circumferential seal portion 50 that extends annularly in the axial direction from the outer edge of the oil seal 30 along the inner periphery of the cylinder 1. The outer circumferential seal portion 50 closes the gap between the outer periphery of the core metal 40 and the inner periphery of the cylinder 1, and prevents leakage of hydraulic oil and entry of foreign matter in this gap.

[0035] The dust seal 10, the connection portion 20, the oil seal 30, and the outer circumferential seal portion 50 are integrally formed from a rubber material. Examples of the rubber material that can be used include nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), fluororubber (FKM), and urethane rubber (AU, EU).

[0036] The core metal 40 is an annular plate made of a metal material, and is integrated with the dust seal 10, the connection portion 20, and the oil seal 30 by vulcanization adhesion. In this embodiment, a part of the core metal 40 is exposed from the rubber material, but the entire core metal 40 may be embedded in the rubber material.

[0037] Next, a specific shape of the dust seal 10 will be described with reference to FIG.

[0038] The dust seal 10 has a covering portion 10A as a base end extending along the end face 40a of the core wire 40 on the side of the elongation direction of the rod 2, a circular protrusion portion 10B (see Figure 2) formed at the outer edge of the covering portion 10A so as to protrude in the elongation direction of the rod 2, a lip portion 10C formed so as to protrude radially inward from the covering portion 10A and in the elongation direction of the rod 2 and in sliding contact with the outer periphery of the rod 2, and a recess 10D formed between the protrusion portion 10B and the lip portion 10C.

[0039] The inner circumferential surface of the dust seal 10 is constituted by a first inner circumferential surface 11, a second inner circumferential surface 12, a third inner circumferential surface 13, and a fourth inner circumferential surface 16 provided in this order from the tip side. Specifically, the dust seal 10 (lip portion 10C) has a first inner surface 11 which reduces in diameter from the tip surface 10a toward the base end, a second inner surface 12 which is formed on the base end (covered portion 10A) side of the first inner surface 11 and which expands in diameter toward the base end, a third inner surface 13 which is formed on the base end side of the second inner surface 12 and which expands in diameter toward the base end, a dust lip portion 14 formed at the connection portion between the first inner surface 11 and the second inner surface 12, a bent portion 15 formed at the connection portion between the second inner surface 12 and the third inner surface 13, a cylindrical fourth inner surface 16 which forms the inner surface of the covered portion 10A, and a support portion 17 formed at the connection portion between the third inner surface 13 and the fourth inner surface 16.

[0040] The fourth inner circumferential surface 16 is formed so as to be continuous with the cylindrical inner circumferential surface 20 a of the connection portion 20 .

[0041] The first inner circumferential surface 11 is formed by a curved surface that bulges radially inward. The first inner circumferential surface 11 may be formed in a flat shape (at a constant inclination angle) or may be formed by combining a flat surface and a curved surface.

[0042] The second inner peripheral surface 12 is formed in a flat surface that expands in diameter at a constant inclination angle θ2 toward the base end side. The second inner peripheral surface 12 may be formed in a curved surface or may be formed in a combination of a flat surface and a curved surface.

[0043] The third inner circumferential surface 13 is formed by a curved surface recessed radially outward. The third inner circumferential surface 13 may be formed in a flat shape (at a constant inclination angle) or may be formed by combining a flat surface and a curved surface.

[0044] The axial length L1 of the first inner circumferential surface 11 is approximately equal to the axial length L3 of the third inner circumferential surface 13, and the axial length L2 of the second inner circumferential surface 12 is longer than the axial length L1 of the first inner circumferential surface 11 and the axial length L3 of the third inner circumferential surface 13. Preferably, the first inner circumferential surface 11, the second inner circumferential surface 12, and the third inner circumferential surface 13 are formed so that the ratio of the length L1, the length L2, and the length L3 is 1:4:1.

[0045] The dust lip 14 has an inclination angle θ1 at the tip end set to about 1° to 10°. The inclination angle θ1 here is the angle between a line O1 parallel to the central axis O of the rod 2 (see Figs. 1 and 2) at the dust lip 14 and the first inner circumferential surface 11. The dust lip 14 has an inclination angle θ2 at the base end set to about 10° to 20°. The inclination angle θ2 here is the angle between the line O1 at the dust lip 14 and the second inner circumferential surface 12.

[0046] The bent portion 15 has an inclination angle θ3 on the base end side set to about 30° to 90°. The inclination angle θ3 here is the angle between the line O1 at the bent portion 15 and the third inner circumferential surface 13.

[0047] In the following, the inclination angle θ1 will be referred to as the inclination angle of the first inner circumferential surface 11, the inclination angle θ2 will be referred to as the inclination angle of the second inner circumferential surface 12, and the inclination angle θ3 will be referred to as the inclination angle of the third inner circumferential surface 13.

[0048] In the sealing member S of this embodiment, the radial thickness T1 of the dust seal 10 in the region of the first inner surface 11 and the second inner surface 12 is set to a total of more than half the sum of the length L1 of the first inner surface 11 and the axial length L2 of the second inner surface 12.

[0049] The dust seal 10 further has a stiffness reducing portion R provided on the base end side of the dust lip portion 14 .

[0050] The rigidity reduction portion R is located closer to the tip of the dust seal 10 than the end face 40a of the core wire 40 on the dust lip portion 14 side, and closer to the base end than the midpoint in the axial direction between the end face 40a of the core wire 40 on the dust lip portion 14 side and the dust lip portion 14 (see midpoint M in Figure 3).

[0051] In this embodiment, the rigidity reduced portion R is formed by making the radial thickness T3 of the dust seal 10 thinner than the radial thickness T2 at the bent portion 15 at least in the region where the third inner circumferential surface 13 is provided.

[0052] Next, the function and effect of the dust seal 10 thus configured will be described with reference to a comparative example. Fig. 4 is an enlarged cross-sectional view of the dust seal 110 of the seal member S1 according to the comparative example. Fig. 5(A) is a diagram showing the surface pressure distribution of the dust seal 10 in a state in which the seal member S according to this embodiment is attached to the shock absorber 100, and Fig. 5(B) is a diagram showing the surface pressure distribution of the dust seal 110 in a state in which the seal member S1 according to the comparative example is attached to the shock absorber 100.

[0053] The dust seal 110 of the sealing member S1 shown in Fig. 4 has an edge-shaped opening (sealing portion with the rod 2) on the tip side of the inner circumferential surface. When the sealing member S1 having such a shape is attached to the shock absorber 100, the distribution of surface pressure in the dust seal 110 is as shown in Fig. 5(B). As is clear from Fig. 5(B), in the sealing member S1, the surface pressure rises abruptly (the gradient becomes steeper) from the tip of the dust seal 110 toward the base end side.

[0054] 4, the dust seal 110 of the sealing member S1 has an edged opening on the side of the tip surface 110a, so that when the rod 2 contracts, the oil film adhering to the outer peripheral surface of the rod 2 is scraped off, making it easy for oil to leak out. In order to prevent oil from leaking out, it is therefore conceivable to make the gradient of the surface pressure in the dust seal 110 gentler, specifically, to make the tip surface 110a of the dust seal 110 inclined in the direction of contraction of the rod 2 as it moves radially inward.

[0055] However, when the tip surface 110a of the dust seal 110 is inclined in this manner, although the gradient of the surface pressure from the tip to the base end of the dust seal 110 becomes smaller, there is a risk of the peak value P1 of the surface pressure decreasing. And when the peak value P1 of the surface pressure decreases, the maximum value of the pressing force of the dust seal 110 against the rod 2 decreases, so there is a risk of the dust resistance, which prevents dust adhering to the rod 2 from entering the cylinder 1, deteriorating.

[0056] Furthermore, when the tip surface 110a of the dust seal 110 is inclined as described above, the peak value P1 of the surface pressure moves to the left in Fig. 5(B), and the distribution of the surface pressure becomes symmetrical. When the distribution of the surface pressure becomes symmetrical, a swinging phenomenon may occur in which the contact portion of the dust seal 110 with the rod 2 is deformed by the reciprocating motion of the rod 2. The occurrence of such a swinging phenomenon may destabilize the oil film thickness on the outer circumferential surface of the rod 2 and may shorten the life of the dust seal 110.

[0057] Therefore, the seal member S of this embodiment is provided with the first inner circumferential surface 11, the second inner circumferential surface 12, and the third inner circumferential surface 13 as described above. By providing the first inner circumferential surface 11, which narrows in diameter from the tip surface 10a of the dust seal 10 toward the base end side as described above, the gradient of the surface pressure from the tip to the base end side of the dust seal 10 can be made smaller (flattened) as shown in Fig. 5(A) (see the portion indicated by CL in Fig. 5(A)). Note that in the seal member S of this embodiment, a peak value P of the surface pressure occurs in the vicinity of the dust lip portion 14.

[0058] In the seal member S of this embodiment, the inclination angle θ2 of the second inner circumferential surface 12 and the inclination angle θ3 of the third inner circumferential surface 13 are formed to be different, in other words, the inner circumferential surface of the dust seal 10 is formed to bend at the bend portion 15. By forming the inner circumferential surface of the dust seal 10 in this shape, it is possible to make the surface pressure distribution asymmetric about the peak value P as shown in Fig. 5(A), and therefore it is possible to suppress the swinging phenomenon that accompanies the reciprocating motion of the rod 2 at the contact portion of the dust seal 10 with the rod 2.

[0059] Furthermore, in the seal member S of this embodiment, the third inner circumferential surface 13 is located radially outward from the extended surface 12a of the second inner circumferential surface 12, and the connection portion (support portion 17) between the third inner circumferential surface 13 and the fourth inner circumferential surface 16 is located closer to the tip end of the dust seal 10 than the end face 40a of the core metal 40 on the dust seal 10 side. By forming the lip portion 10C of the dust seal 10 in such a shape, the thickness in the vicinity of the third inner circumferential surface 13 can be made thinner. In other words, the seal member S of this embodiment includes a rigidity reducing portion R formed by making the radial thickness T3 of the dust seal 10 thinner than the thickness T2 at the bent portion 15 in the region where the third inner circumferential surface 13 is provided. Furthermore, in the seal member S of this embodiment, the rigidity reducing portion R is provided at a position separated from the core metal 40, which is a reinforcing member, more specifically, on the base end side of the midpoint between the end face 40a of the core metal 40 on the dust lip portion 14 side and the dust lip portion 14 in the axial direction. Therefore, in the seal member S of this embodiment, the rigidity of the base end side of the lip portion 10C of the dust seal 10 can be reduced compared to the shape of the dust seal 110 of the comparative example shown in Fig. 4. This increases the stress of the portion of the dust seal 10 pressed against the rod 2 (near the dust lip portion 14), thereby suppressing a decrease in the peak value P of the surface pressure.

[0060] Therefore, according to the seal member S of the present embodiment, it is possible to suppress leakage while maintaining the peak value P of the surface pressure of the dust seal 10. In addition, the hydraulic oil that has leaked is captured in the recess 10D, and the hydraulic oil can be prevented from spreading further.

[0061] Furthermore, in the sealing member S, by setting the radial thickness T1 of the first inner surface 11 and the second inner surface 12 of the dust seal 10 to a total of more than half the sum of the axial lengths (lengths L1, L2) of the first inner surface 11 and the second inner surface 12, the rigidity of the dust seal 10 in the vicinity of the dust lip portion 14 where the peak value P of the surface pressure occurs can be more reliably ensured while also ensuring the elasticity of the dust seal 10.

[0062] Furthermore, in the sealing member S, the dust seal 10 is formed so that the axial length L1 of the first inner circumferential surface 11 is approximately equal to the axial length L3 of the third inner circumferential surface 13, and the axial length L2 of the second inner circumferential surface 12 is longer than the axial lengths L1, L3 of the first inner circumferential surface 11 and the third inner circumferential surface 13, respectively, and more preferably so that the ratio of lengths L1, L2, L3 is L1:L2:L3 = 1:4:1.

[0063] By forming the dust seal 10 in this shape, the distribution of surface pressure can be made asymmetrical more reliably, and the dust resistance required for the dust seal 10 can be ensured more reliably.

[0064] Furthermore, in the sealing member S, the dust seal 10 is formed so that the inclination angle θ2 of the second inner surface 12 is larger than the inclination angle θ1 of the first inner surface 11 and the inclination angle θ3 of the third inner surface 13 is larger than the inclination angle θ2 of the second inner surface 12, and more preferably so that the inclination angle θ1 of the first inner surface 11 is in the range of 1° to 10°, the inclination angle θ2 of the second inner surface 12 is in the range of 10° to 20°, and the inclination angle θ3 of the third inner surface 13 is in the range of 60° to 90°.

[0065] By forming the dust seal 10 in this shape, the distribution of surface pressure can be made asymmetrical more reliably, and the dust resistance required for the dust seal 10 can be ensured more reliably.

[0066] Furthermore, in the seal member S of this embodiment, the dust seal 10 is configured to seal between the cylinder 1 and the rod 2 by its own elasticity alone. This eliminates the need for parts such as a garter spring, allowing the number of parts to be reduced.

[0067] Furthermore, for example, if the stiffness reducing portion R is provided at a position close to the core metal 40 in the axial direction (for example, near the connection portion 20), the core metal 40 will prevent the stiffness reducing portion R from functioning sufficiently. Specifically, the dust seal 10 deforms with the support portion 17 as the starting point, but if the support portion 17 is located radially inside the core metal 40, the core metal will prevent the lip portion 10C from deforming with the support portion 17 as the starting point, resulting in excessive stiffness. As a result, the desired surface pressure gradient cannot be maintained.

[0068] Conversely, if the stiffness reducing portion R is provided on the tip side of the dust seal 10 from the midpoint M, the stiffness will be insufficient and deformation will be excessive. Specifically, since the support portion 17 is located near the dust lip portion 14, the stiffness will be insufficient and the lip portion 10C will be prone to excessive deformation. As a result, the desired surface pressure gradient cannot be maintained. In addition, if the stiffness reducing portion R is provided on the tip side of the dust seal 10 from the midpoint M, the area of ​​the sliding portion of the dust seal 10 may be limited, reducing the design freedom.

[0069] Therefore, as in this embodiment, by positioning the rigidity reduction portion R closer to the tip of the dust seal 10 than the end face 40a of the core wire 40 on the dust lip portion 14 side, and closer to the base end than the midpoint in the axial direction between the end face 40a of the core wire 40 on the dust lip portion 14 side and the dust lip portion 14, the desired surface pressure gradient can be maintained.

[0070] Furthermore, in the seal member S, it is preferable that the position of the end face of the covering part 10A on the dust lip part 14 side in the axial direction is extended within the range of the rigidity reducing part R. More preferably, the position of the end face 10b on the dust lip part 14 side in the axial direction of the covering part 10A is equal to the position of the end part (support part 17) on the base end side in the axial direction of the third inner circumferential surface 13. This makes it possible to more reliably maintain the desired surface pressure gradient.

[0071] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0072] The sealing member S comprises a core bar 40 and a dust seal 10 whose base end is fixed to the core bar 40, extends toward the rod 2, and slides against the outer peripheral surface of the rod 2. The dust seal 10 has a first inner surface 11 which narrows in diameter toward the base end, a second inner surface 12 which is formed toward the base end from the first inner surface 11 and widens in diameter toward the base end, a dust lip portion 14 which is formed at the connection between the first inner surface 11 and the second inner surface 12, and a rigidity reduction portion R which is provided on the base end side from the dust lip portion 14. The rigidity reduction portion R is located closer to the tip of the dust seal 10 than the end face 40a of the core bar 40 on the dust lip portion 14 side, and closer to the base end than the midpoint between the end face 40a of the core bar 40 on the dust lip portion 14 side and the dust lip portion 14 in the axial direction.

[0073] In this configuration, the dust lip portion 14 is formed at the connection portion between the first inner peripheral surface 11 and the second inner peripheral surface 12, so that the surface pressure can be made flat by adjusting the angle between the first inner peripheral surface 11 and the second inner peripheral surface 12. Also, in this configuration, the rigidity reduction portion R is located closer to the tip of the dust seal 10 than the end face 40a of the core metal 40 on the dust lip portion 14 side, and closer to the base end than the midpoint between the end face 40a of the core metal 40 on the dust lip portion 14 side and the dust lip portion 14 in the axial direction. Therefore, the rigidity of the dust seal 10 is not too high and not too low, so that the desired surface pressure gradient can be maintained. This allows the peak value P of the surface pressure of the dust seal 10 to be maintained while suppressing the seepage leakage.

[0074] In the sealing member S, the dust seal 10 further has a third inner surface 13 formed on the base end side from the second inner surface 12 and expanding in diameter toward the base end side, and a bent portion 15 formed at the connection portion between the second inner surface 12 and the third inner surface 13, and the rigidity reduction portion R is formed by making the radial thickness T3 of the dust seal 10 thinner than the radial thickness T2 at the bent portion 15, at least in the region where the third inner surface 13 is provided.

[0075] In this configuration, since the rigidity reduced portion R can be formed simply by changing the thickness of the dust seal 10, an increase in cost due to the formation of the rigidity reduced portion R can be suppressed.

[0076] In the seal member S, the base end of the dust seal 10 has a covering portion 10A extending along the end face of the core metal 40 on the dust lip portion 14 side, and the position of the end face 10b on the dust lip portion 14 side in the axial direction of the covering portion 10A is equal to the position of the end portion (support portion 17) on the base end side in the axial direction of the third inner circumferential surface 13. Note that the position of the end face of the covering portion 10A on the dust lip portion 14 side in the axial direction extended therefrom may be within the range of the rigidity reducing portion R.

[0077] In this configuration, the rigidity of the dust seal 10 is neither too high nor too low, so that a desired surface pressure gradient can be maintained. This makes it possible to suppress seepage while maintaining the peak value P of the surface pressure of the dust seal 10.

[0078] In the seal member S, the inclination angle θ2 of the second inner circumferential surface 12 is greater than the inclination angle θ1 of the first inner circumferential surface 11, and the inclination angle θ3 of the third inner circumferential surface 13 is greater than the inclination angle θ2 of the second inner circumferential surface 12.

[0079] In this configuration, the distribution of surface pressure can be made asymmetrical more reliably, so that the oscillation phenomenon caused by the reciprocating movement of the rod 2 can be suppressed at the contact portion (near the dust lip portion 14) of the dust seal 10 with the rod 2. Furthermore, by forming the dust seal 10 in this manner, the dust resistance required for the dust seal 10 can be reliably ensured.

[0080] The shock absorber 100 includes a sealing member S, a cylinder 1 in which a working fluid is sealed, a rod 2 inserted into the cylinder 1 so as to be freely movable in the axial direction, and a compression side damping valve 4a and an extension side damping valve 4b (damping force generating section) that are housed in the cylinder 1 and generate a damping force by applying resistance to the flow of the working fluid as the rod 2 moves.

[0081] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments.

[0082] In the above embodiment, hydraulic oil is used as the working fluid, but a non-compressible fluid such as water or an aqueous solution may be used instead of hydraulic oil.

[0083] In the above embodiment, the shock absorber 100 is described as a single-cylinder shock absorber in which a compression side chamber 1a, an expansion side chamber 1b, and an air chamber 1c are formed within the cylinder 1. However, the shock absorber 100 may also be a double-cylinder shock absorber in which an outer tube is provided on the outer periphery of an inner tube serving as a cylinder, and a reservoir is formed between the inner tube and the outer tube.

[0084] Furthermore, in the above embodiment, the seal member S used in the shock absorber 100 has been described, but the present invention is also applicable to a seal member used in a fluid pressure device such as a fluid pressure cylinder.

[0085] In the above embodiment, the seal member S is described as including the dust seal 10 and the oil seal 30. However, the seal member S may not include the oil seal 30.

[0086] The stiffness-reduced portion R is not limited to the embodiment, and various methods for reducing stiffness can be used. For example, the stiffness-reduced portion R may be formed by extending the second inner circumferential surface 12 and connecting it to the connecting portion 20 or the fourth inner circumferential surface 16, and providing a groove in the extended portion of the second inner circumferential surface 12, or by forming the extended portion of the second inner circumferential surface 12 from a different material that is easily elastically deformed. The stiffness-reduced portion R may also be formed by including PTFE fibers in the seal member S and adjusting the orientation of the fibers. [Explanation of symbols]

[0087] 100 shock absorber, S seal member, 1 cylinder, 2 rod, 4a compression side damping valve (damping force generating portion), 4b rebound side damping valve (damping force generating portion), 10 dust seal, 10A covering portion (base end), 10C dust lip portion, 10a tip surface, 11 first inner peripheral surface, 12 second inner peripheral surface Circumferential surface, 12a...extension surface, 13...third inner circumferential surface, 13a...end portion, 14...first boundary portion, 15...second boundary portion, 20...connection portion, 20a...inner circumferential surface, 30...oil seal, 40...core metal, 40a...end face, 50...outer circumferential seal portion, 110...dust seal, S1...sealing member, R...rigidity reduction portion

Claims

1. A seal member that is provided in a fluid pressure device and seals between a cylinder and a rod, A core metal and a dust seal having a base end fixed to the core metal, extending toward the rod, and in sliding contact with an outer circumferential surface of the rod; The dust seal is A first inner circumferential surface that decreases in diameter toward the base end side; a second inner circumferential surface formed closer to the base end than the first inner circumferential surface and expanding in diameter toward the base end; a dust lip portion formed at a connection portion between the first inner circumferential surface and the second inner circumferential surface; a stiffness reducing portion provided on the base end side of the dust lip portion, A sealing member characterized in that the rigidity reduction portion is located closer to the tip of the dust seal than the end face of the core bar on the dust lip portion side, and closer to the base end than the midpoint in the axial direction between the end face of the core bar on the dust lip portion side and the dust lip portion.

2. The seal member according to claim 1 , The dust seal is a third inner circumferential surface that is formed closer to the base end than the second inner circumferential surface and that expands in diameter toward the base end; a bent portion formed at a connection portion between the second inner circumferential surface and the third inner circumferential surface, The rigidity reduction portion is A sealing member characterized in that the dust seal is formed such that the radial thickness thereof is thinner at least in the region where the third inner circumferential surface is provided than the radial thickness thereof at the bent portion.

3. The seal member according to claim 1 , The base end of the dust seal has a covering portion extending along an end surface of the core metal on the dust lip portion side, A sealing member, characterized in that a position when an end face of the covering portion on the dust lip portion side in the axial direction is extended is within the range of the rigidity reducing portion.

4. The seal member according to claim 2, The inclination angle of the second inner circumferential surface is larger than the inclination angle of the first inner circumferential surface, A seal member, wherein an inclination angle of the third inner circumferential surface is greater than an inclination angle of the second inner circumferential surface.

5. A seal member according to any one of claims 1 to 4; The cylinder in which a working fluid is sealed; The rod is inserted into the cylinder so as to be movable in the axial direction; a damping force generating section that is housed in the cylinder and generates a damping force by applying resistance to the flow of working fluid as the rod moves.

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