Seal member and shock absorber

Abstract

A dust seal (10) of a seal member (S) comprises: a first inner peripheral surface (11) that reduces in diameter toward a base end side; a second inner peripheral surface (12) that expands in diameter toward the base end side; a dust lip part (14) formed at the connection portion between the first inner peripheral surface (11) and the second inner peripheral surface (12); and a rigidity reduction part provided closer to the base end side than the dust lip part (14). The rigidity reduction part is positioned closer to the tip end side of the dust seal (10) than the end surface (40a) on the dust lip part (14) side of a core metal (40) and closer to the base end side than the center between the dust lip part (14) and the end surface (40a) on the dust lip part (14) side of the core metal (40) in the axial direction.

Description

Seal members and shock absorbers

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

[0002] A seal member that seals the gap between a cylinder and a rod in a fluid pressure device such as a shock absorber is known (JPH5-38433U). In the seal member described in JPH5-38433U, a base portion (reinforcing ring) made of a metal material is held by the cylinder, and a dust lip portion made of an elastic material such as rubber is provided on the base portion (reinforcing ring) so as to be in sliding contact with the rod.

[0003] In the seal member described in JPH5-38433U, the opening at the tip end of the inner circumferential surface of the dust lip is formed in a generally edged 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, resulting in good dust resistance that prevents dust from entering.

[0004] However, with a shape like the seal member described in JPH5-38433U, 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 seal portion 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 more likely that oil will leak.

[0005] Therefore, in order to prevent oil leakage, it is possible to flatten the surface pressure gradient at the dust lip, specifically by flattening 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 high rigidity of the dust seal makes it impossible to maintain the flat surface pressure gradient, so the desired surface pressure gradient cannot be achieved and oil leakage cannot be prevented.

[0006] SUMMARY OF THE INVENTION The object of the present invention is to provide a sealing member that can achieve a desired surface pressure gradient and suppress seepage leakage.

[0007] According to one aspect of the present invention, a sealing member provided in a fluid pressure device for sealing between a cylinder and a rod comprises a core bar, and a dust seal whose base end is fixed to the core bar, extends toward the rod, and slides against the outer peripheral surface of the rod, the dust seal having a first inner surface that narrows in diameter toward the base end, a second inner surface formed on the base end side of the first inner surface and widens in diameter toward the base end, a dust lip portion formed at the connection between the first inner surface and the second inner surface, and a rigidity reduction portion provided on the base end side of the dust lip portion, the rigidity reduction portion being 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 portion.

[0008] Fig. 1 is a partial cross-sectional view of a shock absorber to which a seal member according to an embodiment of the present invention can be applied. Fig. 2 is an enlarged cross-sectional view of a seal member according to an embodiment of the present invention. Fig. 3 is an enlarged cross-sectional view of a dust seal of a seal member according to an embodiment of the present invention. Fig. 4 is an enlarged cross-sectional view of a dust seal of a seal member according to a comparative example. Fig. 5(A) is a diagram showing the distribution of surface pressure in the dust seal when the seal member according to an embodiment of the present invention is attached to a 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 a comparative example is attached to a shock absorber 100.

[0009] A sealing member S according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0010] 1 is a partial cross-sectional view of a shock absorber 100 as a fluid pressure device to which the seal member S can be applied. The shock absorber 100 is provided, for example, between the body and axle of a vehicle (not shown), and generates a damping force to suppress vibration of the vehicle body.

[0011] 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 interior 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.

[0012] 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.

[0013] The rod 2 passes through the extension-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 retracts from the cylinder 1, the shock absorber 100 extends.

[0014] When the shock absorber 100 contracts, the piston 3 moves in a direction that contracts the compression-side chamber 1a and expands 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 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 hydraulic oil by the compression-side damping valve 4a, and the shock absorber 100 exerts a damping force.

[0015] When the shock absorber 100 extends, the piston 3 moves in a direction that contracts the expansion-side chamber 1b and expands the compression-side chamber 1a. The pressure difference between the expansion-side chamber 1b and the compression-side chamber 1a causes the expansion-side damping valve 4b to open 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.

[0016] 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.

[0017] The change in volume within the cylinder 1 due to the movement of the rod 2 is compensated for by the air chamber 1 c formed within the cylinder 1 by the free piston 5 .

[0018] A rod guide 6 that slidably supports the rod 2 via a bushing 6a is provided on the inner periphery of the cylinder 1. The rod guide 6 is supported by a retaining ring 6b that is provided on the inner periphery of the cylinder 1.

[0019] The open end 1d of the cylinder 1 is bent radially inward by crimping, and a seal member S that seals 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.

[0020] As shown in FIG. 2 , the sealing member S comprises an annular dust seal 10 that is disposed at the tip side of the rod 2 and that is in sliding contact with the outer peripheral surface of the rod 2, an oil seal 30 that is provided on the opposite side of the dust seal 10 in the axial direction of the rod 2 from the dust seal 10, a cylindrical connecting portion 20 that connects the dust seal 10 and the oil seal 30, and a core bar 40 that is provided radially outside the connecting portion 20 and to which the base ends of the dust seal 10 and the oil seal 30 are fixed.

[0021] When the shock absorber 100 contracts, the dust seal 10 scrapes off foreign matter adhering to the outer peripheral surface of the rod 2. In other words, the dust seal 10 prevents foreign matter from entering the cylinder 1. Note that the dust seal 10 of this embodiment seals between itself and the rod 2 using only its own elasticity, without using a biasing member such as a garter spring.

[0022] [Correction based on Rule 91 20.08.2025] The oil seal 30 is formed so as to protrude radially inward from the connection part 20 and in the contraction direction of the rod 2, 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.

[0023] 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.

[0024] 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, preventing leakage of hydraulic oil and entry of foreign matter through this gap.

[0025] The dust seal 10, the connecting portion 20, the oil seal 30, and the outer peripheral seal portion 50 are integrally formed from a rubber material, such as nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), fluororubber (FKM), or urethane rubber (AU, EU).

[0026] The core metal 40 is an annular plate made of a metal material, and is integrated with the dust seal 10, the connecting portion 20, and the oil seal 30 by vulcanization bonding. In this embodiment, a portion of the core metal 40 is exposed from the rubber material, but the entire core metal 40 may be embedded in the rubber material.

[0027] Next, the specific shape of the dust seal 10 will be described with reference to FIG.

[0028] 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 extension 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 extension direction of the rod 2, a lip portion 10C formed so as to protrude radially inward from the covering portion 10A and in the extension 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.

[0029] 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, which are provided in this order from the tip side. Specifically, the dust seal 10 (lip portion 10C) has a first inner surface 11 that narrows in diameter from the tip surface 10a toward the base end, a second inner surface 12 that is formed closer to the base end (covered portion 10A) than the first inner surface 11 and expands in diameter toward the base end, a third inner surface 13 that is formed closer to the base end than the second inner surface 12 and expands in diameter toward the base end, a dust lip portion 14 that is formed at the connection between the first inner surface 11 and the second inner surface 12, a bent portion 15 that is formed at the connection between the second inner surface 12 and the third inner surface 13, a cylindrical fourth inner surface 16 that forms the inner surface of the covered portion 10A, and a support portion 17 that is formed at the connection between the third inner surface 13 and the fourth inner surface 16.

[0030] The fourth inner peripheral surface 16 is formed so as to be continuous with the cylindrical inner peripheral surface 20 a of the connecting portion 20 .

[0031] The first inner circumferential surface 11 is formed by a curved surface that bulges radially inward. Note that the first inner circumferential surface 11 may be formed in a flat shape (at a certain inclination angle) or may be formed by combining a flat surface and a curved surface.

[0032] The second inner peripheral surface 12 is formed as a flat surface that expands in diameter at a constant inclination angle θ2 toward the base end. The second inner peripheral surface 12 may be formed as a curved surface or a combination of a flat surface and a curved surface.

[0033] The third inner circumferential surface 13 is formed by a curved surface that is recessed radially outward. The third inner circumferential surface 13 may be formed in a flat shape (at a certain inclination angle) or may be formed by combining a flat surface and a curved surface.

[0034] 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.

[0035] The dust lip 14 has an inclination angle θ1 on the tip side set to about 1° to 10°. The inclination angle θ1 here refers to 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 also has an inclination angle θ2 on the base side set to about 10° to 20°. The inclination angle θ2 here refers to the angle between the line O1 at the dust lip 14 and the second inner circumferential surface 12.

[0036] The bent portion 15 has an inclination angle θ3 on the base end side set to approximately 30° to 90°. The inclination angle θ3 here is the angle formed between the line O1 at the bent portion 15 and the third inner circumferential surface 13.

[0037] 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.

[0038] In the sealing member S of this embodiment, the radial thickness T1 in the region of the first inner surface 11 and the second inner surface 12 of the dust seal 10 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.

[0039] The dust seal 10 further has a stiffness reducing portion R provided on the base end side of the dust lip portion 14 .

[0040] 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).

[0041] In this embodiment, 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 bend portion 15, at least in the region where the third inner surface 13 is provided.

[0042] Next, the operation and effect of the dust seal 10 configured as described above will be described with reference to a comparative example. Fig. 4 is an enlarged cross-sectional view of the dust seal 110 of the sealing member S1 according to the comparative example. Fig. 5(A) is a diagram showing the surface pressure distribution of the dust seal 10 when the sealing 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 when the sealing member S1 according to the comparative example is attached to the shock absorber 100.

[0043] The dust seal 110 of the sealing member S1 shown in Fig. 4 has an edge-shaped opening on the tip side of the inner circumferential surface (the sealing portion with the rod 2). 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 sharply (the gradient becomes steeper) as it moves from the tip to the base end of the dust seal 110.

[0044] 4, the dust seal 110 of the sealing member S1 has an edged opening on the tip end surface 110a side, which means that the oil film adhering to the outer peripheral surface of the rod 2 is scraped off when the rod 2 contracts, making it easier for oil to leak. Therefore, in order to prevent oil from leaking, it is conceivable to make the gradient of the surface pressure at the dust seal 110 gentler, specifically, to make the tip end surface 110a of the dust seal 110 inclined in the direction of contraction of the rod 2 as it moves radially inward.

[0045] 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 that the peak value P1 of the surface pressure will decrease. If 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 will decrease, and there is a risk that the dust resistance that prevents dust adhering to the rod 2 from entering the cylinder 1 will deteriorate.

[0046] Furthermore, when the tip surface 110a of the dust seal 110 is inclined as described above, the peak value P1 of the surface pressure shifts to the left in Figure 5(B), and the surface pressure distribution becomes symmetrical. If the surface pressure distribution becomes symmetrical, there is a risk of a wobbly phenomenon occurring, 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 wobbly phenomenon may destabilize the oil film thickness on the outer peripheral surface of the rod 2 and may shorten the life of the dust seal 110.

[0047] 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 decreases in diameter from the tip surface 10a of the dust seal 10 toward the base end, as shown in Fig. 5(A), it is possible to reduce (flatten) the gradient of the surface pressure from the tip to the base end of the dust seal 10 (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 near the dust lip portion 14.

[0048] Furthermore, 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 shaping the inner circumferential surface of the dust seal 10 in this manner, it is possible to make the surface pressure distribution asymmetrical about the peak value P, as shown in Fig. 5(A) , and therefore it is possible to suppress the wobbling phenomenon that occurs at the contact portion of the dust seal 10 with the rod 2 due to the reciprocating motion of the rod 2.

[0049] Furthermore, in the seal member S of this embodiment, the third inner circumferential surface 13 is located radially outward of the extension 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 of the dust seal 10 than the end face 40a of the core 40 on the dust seal 10 side. By shaping the lip portion 10C of the dust seal 10 in this manner, the thickness near the third inner circumferential surface 13 can be reduced. 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 located at a position separated from the core 40, which is a reinforcing member; more specifically, it is located closer to the base end than the midpoint in the axial direction between the end face 40a of the core 40 on the dust lip 14 side and the dust lip 14. 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 at the portion of the dust seal 10 that is pressed against the rod 2 (near the dust lip portion 14), thereby preventing a decrease in the peak value P of the surface pressure.

[0050] Therefore, the sealing member S of this embodiment can 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, preventing the hydraulic oil from spreading further.

[0051] 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 at least half the sum of the axial lengths (lengths L1, L2) of the first inner surface 11 and the second inner surface 12, it is possible to more reliably ensure the rigidity of the dust seal 10 near the dust lip portion 14 where the peak value P of the surface pressure occurs, while also more reliably ensuring the elasticity of the dust seal 10.

[0052] Furthermore, in the sealing member S, the dust seal 10 is formed so that the axial length L1 of the first inner surface 11 is approximately equal to the axial length L3 of the third inner surface 13, and the axial length L2 of the second inner surface 12 is longer than the axial lengths L1 and L3 of the first inner surface 11 and the third inner surface 13, respectively, and more preferably so that the ratio of the lengths L1, L2, and L3 is L1:L2:L3 = 1:4:1.

[0053] By forming the dust seal 10 in this shape, the distribution of surface pressure can be made asymmetric more reliably, and the dust resistance required for the dust seal 10 can be ensured more reliably.

[0054] 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; more preferably, the inclination angle θ1 of the first inner surface 11 is 1° to 10° (range), the inclination angle θ2 of the second inner surface 12 is 10° to 20° (range), and the inclination angle θ3 of the third inner surface 13 is 60° to 90° (range).

[0055] By forming the dust seal 10 in this shape, the distribution of surface pressure can be made asymmetric more reliably, and the dust resistance required for the dust seal 10 can be ensured more reliably.

[0056] Furthermore, in the sealing member S of this embodiment, the dust seal 10 is configured to seal between the cylinder 1 and the rod 2 using only its own elasticity. This eliminates the need for parts such as a garter spring, thereby reducing the number of parts.

[0057] Furthermore, for example, if the rigidity reducing portion R is provided in 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 rigidity reducing portion R from functioning sufficiently. Specifically, the dust seal 10 deforms starting from the support portion 17, but if the support portion 17 is located radially inward of the core metal 40, the core metal will prevent the lip portion 10C from deforming starting from the support portion 17, resulting in excessive rigidity. As a result, the desired surface pressure gradient cannot be maintained.

[0058] Conversely, if the rigidity reducing portion R is located closer to the tip of the dust seal 10 than the midpoint M, the rigidity will be insufficient, resulting in excessive deformation. Specifically, because the support portion 17 is located near the dust lip portion 14, the rigidity 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. Furthermore, if the rigidity reducing portion R is located closer to the tip of the dust seal 10 than the midpoint M, the area of ​​the sliding portion of the dust seal 10 may be limited, reducing the degree of design freedom.

[0059] 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.

[0060] Furthermore, in the seal member S, it is preferable that the position of the end face of the covering portion 10A on the dust lip 14 side in the axial direction be extended within the range of the rigidity reduction portion R. More preferably, the position of the end face 10b on the dust lip 14 side in the axial direction of the covering portion 10A is equal to the position of the end (support portion 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.

[0061] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0062] The sealing member S comprises a core wire 40, and a dust seal 10 whose base end is fixed to the core wire 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 that narrows in diameter toward the base end, a second inner surface 12 that is formed on the base end side of the first inner surface 11 and widens in diameter toward the base end, a dust lip portion 14 formed at the connection between the first inner surface 11 and the second inner surface 12, and a rigidity reduction portion R that is provided on the base end side of 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 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.

[0063] In this configuration, the dust lip 14 is formed at the connection between the first inner circumferential surface 11 and the second inner circumferential surface 12, so the surface pressure can be flattened by adjusting the angle between the first inner circumferential surface 11 and the second inner circumferential surface 12. Furthermore, in this configuration, the rigidity-reducing portion R is located closer to the tip of the dust seal 10 than the end face 40a of the core 40 on the dust lip 14 side, and closer to the base end than the midpoint in the axial direction between the end face 40a of the core 40 on the dust lip 14 side and the dust lip 14. Therefore, the rigidity of the dust seal 10 is neither too high nor too low, allowing the desired surface pressure gradient to be maintained. This allows the peak value P of the surface pressure of the dust seal 10 to be maintained while suppressing seepage.

[0064] 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 bending 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 bending portion 15, at least in the region where the third inner surface 13 is provided.

[0065] In this configuration, the stiffness-reduced portion R can be formed simply by changing the thickness of the dust seal 10, so that an increase in cost due to the formation of the stiffness-reduced portion R can be suppressed.

[0066] 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 14 side, and the position of the end face 10b on the dust lip 14 side in the axial direction of the covering portion 10A is equal to the position of the end (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 extension of the end face on the dust lip 14 side of the covering portion 10A in the axial direction may be within the range of the rigidity reduction portion R.

[0067] This configuration allows the desired surface pressure gradient to be maintained because the rigidity of the dust seal 10 is neither too high nor too low, thereby suppressing seepage while maintaining the peak value P of the surface pressure of the dust seal 10.

[0068] In the seal member S, the inclination angle θ2 of the second inner circumferential surface 12 is larger 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 larger than the inclination angle θ2 of the second inner circumferential surface 12.

[0069] With this configuration, the distribution of surface pressure can be made asymmetric more reliably, thereby suppressing the oscillation phenomenon that occurs at the contact portion of the dust seal 10 with the rod 2 (near the dust lip portion 14) due to the reciprocating movement of 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.

[0070] The shock absorber 100 includes a seal 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 unit) housed in the cylinder 1 and which apply resistance to the flow of the working fluid as the rod 2 moves, thereby generating a damping force.

[0071] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate 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 embodiments.

[0072] 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.

[0073] In the above embodiment, the shock absorber 100 is described as a single-cylinder shock absorber in which a compression side chamber 1a, an extension 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.

[0074] 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 seal members used in fluid pressure equipment such as fluid pressure cylinders.

[0075] In the above embodiment, the seal member S is described as including the dust seal 10 and the oil seal 30 , but the seal member S may not be configured to include the oil seal 30 .

[0076] The stiffness-reducing portion R is not limited to the embodiment, and various methods for reducing stiffness can be used. For example, the stiffness-reducing 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. Alternatively, the stiffness-reducing portion R may be formed by incorporating PTFE fibers into the sealing member S and adjusting their orientation.

[0077] This application claims priority based on Japanese Patent Application No. 2023-170266, filed with the Japan Patent Office on September 29, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A sealing member provided in a fluid pressure device for sealing between a cylinder and a rod, comprising: a core; and a dust seal whose base end is fixed to the core, extending toward the rod and making sliding contact with the outer peripheral surface of the rod, wherein the dust seal has: a first inner circumferential surface that narrows in diameter toward the base end; a second inner circumferential surface formed closer to the base end than the first inner circumferential surface and widening in diameter toward the base end; a dust lip portion formed at the connection between the first inner circumferential surface and the second inner circumferential surface; and a rigidity reduction portion provided closer to the base end than the dust lip portion, wherein the rigidity reduction portion is located closer to the tip of the dust seal than the end face of the core 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 on the dust lip side and the dust lip portion.

2. A sealing member as described in claim 1, wherein the dust seal further has a third inner circumferential surface formed closer to the base end than the second inner circumferential surface and expanding in diameter towards the base end, and a bent portion formed at the connection between the second inner circumferential surface and the third inner circumferential surface, and the rigidity reducing portion is formed by making the radial thickness of the dust seal thinner than the radial thickness of the bent portion, at least in the region where the third inner circumferential surface is provided.

3. A sealing member as described in claim 1, wherein the base end of the dust seal has a covering portion extending along the end face of the core metal on the dust lip side, and the position of the covering portion when the end face on the dust lip side in the axial direction is extended is within the range of the rigidity reduction portion.

4. A seal member according to claim 2, wherein the inclination angle of the second inner peripheral surface is larger than the inclination angle of the first inner peripheral surface, and the inclination angle of the third inner peripheral surface is larger than the inclination angle of the second inner peripheral surface.

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

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