Dust seal and shock absorber provided with same

Abstract

This dust seal (20) is an annular member capable of sealing a gap between a cylindrical member (11) and a shaft member (12) inserted through the cylindrical member (11) so as to be capable of reciprocating relative thereto. The dust seal (20) includes: an annular attachment part (30) that is attached to an opening end (11a) of the cylindrical member (11); and an annular lip (40) that is integrally formed with the attachment part (30) and that is in slidable contact with the entire periphery of the outer peripheral surface (12a) of the shaft member (12). The lip (40) includes: a plurality of low-rigidity lip parts (70) having rigidity the same as or smaller than a reference rigidity of the lip (40); and a plurality of high-rigidity lip parts (60) having higher rigidity than the reference rigidity. The low-rigidity lip parts (70) and the plurality of high-rigidity lip parts (60) are alternately arranged in the circumferential direction (Rd) of the lip (40).

Description

Dust seal and shock absorber equipped with this dust seal

[0001] The present invention relates to an improved dust seal and a shock absorber equipped with the dust seal.

[0002] Some types of equipment, such as shock absorbers, are equipped with dust seals to prevent dust from entering the equipment from the outside. This dust seal is an annular member that can seal between a cylindrical member and a shaft member that is inserted into the cylindrical member and is capable of reciprocating relative to the cylindrical member. The lip of the dust seal must ensure sealing performance while also scraping off foreign matter adhering to the outer surface of the shaft member, so it has been required to have uniform rigidity in the circumferential direction.

[0003] Furthermore, dust seals are required to prevent stick-slip caused by the relative reciprocating motion between the shaft member and the sliding surface of the lip. Stick-slip is a self-excited vibration that occurs when the lip repeatedly adheres to and slides against the outer circumferential surface of the shaft member, and is also known as the stick-slip phenomenon or slip-stick phenomenon. Patent Document 1, for example, is known as a conventional technique for preventing stick-slip.

[0004] The technology disclosed in Patent Document 1 is to prevent stick-slip from occurring at the lip by applying a surface treatment to the sliding surface of the lip of the dust seal to improve its self-lubrication. Examples of surface treatments include forming a coating film using a coating agent, applying wax, and applying grease.

[0005] Japanese Patent Application Laid-Open No. 2002-022026

[0006] The technology disclosed in Patent Document 1 only prevents stick-slip of the lip during the initial use of the dust seal. As the dust seal continues to be used, the surface treatment will wear off and disappear from the sliding surface of the lip. Furthermore, stick-slip occurs when there is no lubrication between the outer circumferential surface of the shaft member and the sliding surface of the lip, so there is room for improvement.

[0007] Furthermore, the occurrence of stick-slip of the lip is easily affected by the surface texture (surface roughness) of the outer peripheral surface of the shaft member. Generally, when the surface texture of the outer peripheral surface of the shaft member is rough, the contact pressure (surface pressure) of the sliding surface of the lip against the outer peripheral surface of the shaft member is locally greater than when the surface texture is fine. As a result, stick-slip tends to be less likely to occur. However, when processing the outer peripheral surface of the shaft member, it is extremely difficult to make the surface texture of this outer peripheral surface completely uniform.

[0008] An object of the present invention is to provide a technique that can suppress the occurrence of stick-slip even when there is no lubrication between the outer peripheral surface of the shaft member and the sliding surface of the lip.

[0009] After extensive research, the inventors of the present invention found that rather than striving to achieve uniformity in the roughness of the surface texture of the outer peripheral surface of the shaft member, it would be possible to make the contact pressure (surface pressure) of the lip with the outer peripheral surface of the shaft member non-uniform. They then discovered that stick-slip can be suppressed by actively making the rigidity of the lip non-uniform, rather than making it completely uniform in the circumferential direction. The present invention was completed based on this finding.

[0010] According to the present disclosure, there is provided an annular dust seal capable of sealing between a cylindrical member and an axial member inserted therethrough so as to be able to reciprocate relatively to the cylindrical member, the dust seal including: an annular mounting portion that can be mounted to the open end of the cylindrical member; and an annular lip that is formed integrally with the mounting portion and can slide over the entire circumference against the outer surface of the axial member, the lip including a plurality of low-rigidity lip portions that have the same or lower rigidity than a preset reference rigidity of the lip, and a plurality of high-rigidity lip portions that have higher rigidity than the reference rigidity, the plurality of low-rigidity lip portions and the plurality of high-rigidity lip portions being arranged alternately in the circumferential direction of the lip.

[0011] The present disclosure can provide a technique that can suppress the occurrence of stick-slip even when there is no lubrication between the outer peripheral surface of the shaft member and the sliding surface of the lip.

[0012] FIG. 6A is a schematic diagram of a shock absorber according to Example 1. FIG. 6B is a perspective view of the periphery of the dust seal shown in FIG. 1. FIG. 6C is a cross-sectional view taken along line 3-3 in FIG. 2. FIG. 6D is a cross-sectional view taken along line 4-4 in FIG. 2. FIG. 6E is a cross-sectional view taken along arrow 5 in FIG. 2. FIG. 6A is a first modified view of the high-rigidity lip portion shown in FIG. 4, and FIG. 6B is a second modified view of the high-rigidity lip portion shown in FIG. 4. FIG. 6F is a third modified view of the high-rigidity lip portion shown in FIG. 4. FIG. 6G is a fourth modified view of the high-rigidity lip portion shown in FIG. 4. FIG. 6H is a fifth modified view of the high-rigidity lip portion shown in FIG. 4. FIG. 6I is a plan view of a main portion of the dust seal of a shock absorber according to Example 2. FIG. 6J is a plan view of a dust seal of a shock absorber according to Example 3.

[0013] An embodiment of the present invention will be described below with reference to the accompanying drawings. Note that the embodiment shown in the accompanying drawings is an example of the present invention, and the present invention is not limited to this embodiment. In the description, "up" and "down" refer to the state in which the shock absorber is mounted on a saddle-ride type vehicle. In addition, "Up" in the drawings refers to the top, and "Dn" refers to the bottom.

[0014] First Embodiment A dust seal 20 according to a first embodiment and a shock absorber 10 including the dust seal 20 will be described with reference to FIGS. 1 to 9. FIG.

[0015] 1, a shock absorber 10 is used, for example, as a rear cushion in a saddle-ride vehicle such as a motorcycle or a three-wheeled motor vehicle. The shock absorber 10 includes a cylindrical outer tube 11 (first tube 11) and a cylindrical inner tube 12 (second tube 12) inserted therethrough so as to be able to reciprocate relative to the outer tube 11. The outer tube 11 and the inner tube 12 are biased by a compression coil spring 13 in directions that separate them from each other in the axial direction.

[0016] The inner tube 12 has a cylinder 14 extending from its closed end to its open end. The outer tube 11 has a piston rod 15 extending from its closed end into the cylinder 14. A piston 16 is provided at the tip of the piston rod 15. The piston 16 is capable of reciprocating within the cylinder 14.

[0017] Here, the center line CL of the shock absorber 10 may be referred to as the "center line CL of the outer tube 11" or the "center line CL of the inner tube 12" as appropriate. Furthermore, the axial direction of the shock absorber 10 may be referred to as the "axial direction of the outer tube 11" or the "axial direction of the inner tube 12" as appropriate.

[0018] Furthermore, the shock absorber 10 is provided with an annular dust seal 20 that can seal between the outer tube 11 and the inner tube 12. The outer tube 11 may be referred to as the "cylindrical member 11," and the inner tube 12 may be referred to as the "shaft member 12."

[0019] 2 and 3, the dust seal 20 is formed integrally into an annular shape from an elastic material, preferably various types of rubber, urethane, or a synthetic resin material such as PTFE. The dust seal 20 includes an annular mounting portion 30 that can be mounted to the open end 11a of the outer tube 11, and an annular lip 40 that is formed integrally with the mounting portion 30. The mounting portion 30 is fitted to the outer peripheral surface 11b of the outer tube 11 on the open end 11a side, for example, by fitting a recess and a protrusion to the outer peripheral surface 11b.

[0020] The lip 40 (also referred to as the sealing lip 40) is capable of sliding contact over the entire circumference of the portion 12b (exposed portion 12b) of the outer peripheral surface 12a of the inner tube 12 that is exposed from the open end 11a of the outer tube 11. More specifically, the lip 40 extends in a tapered shape from the tip 31 of the mounting portion 30 toward the exposed portion 12b of the outer peripheral surface 12a of the inner tube 12. The sliding surface 41a of the tip 41 of the lip 40 elastically contacts the outer peripheral surface 12a of the inner tube 12. As a result, a dust seal (sealing) is achieved between the open end 11a of the outer tube 11 and the outer peripheral surface 12a of the inner tube 12. The thickness t1 of the lip 40 is constant.

[0021] 2 and 4, a plurality of protrusions 50 (ribs 50) that protrude radially outward from the outer peripheral surface 42 of the lip 40 are integrally formed on the outer peripheral surface 42 of the lip 40. These protrusions 50 extend at least from the tip 41 of the lip 40 to the base end 43 of the lip 40 (corresponding to the tip 31 of the mounting portion 30).

[0022] The multiple protrusions 50 will be described in more detail. FIG. 5 shows a cross section of the inner tube 12, lip 40, and multiple protrusions 50 shown in FIG. 2, taken along the tip 41 of the lip 40. As shown in FIGS. 2 and 5, the multiple protrusions 50 are radially arranged around the entire outer surface 42 of the lip 40, with the center line CL of the dust seal 20 (the center line CL of the outer tube 11) as the reference. The arrangement angle θ1 of all of the protrusions 50 is constant. In other words, the arrangement spacing of all of the protrusions 50 is constant in the circumferential direction Rd of the outer surface 42. When the dust seal 20 is viewed axially, each of the protrusions 50 has a rectangular cross section.

[0023] The widths W1 of the multiple protrusions 50 are set to be different from one another in the circumferential direction Rd of the lip 40. As a result, the widths W2 between adjacent protrusions 50, 50 on the outer peripheral surface 42 of the lip 40 are also set to be different from one another in the circumferential direction Rd of the lip 40. Note that the widths W2 between adjacent protrusions 50, 50 may be set to be the same in the circumferential direction Rd of the lip 40. The width W1 of each protrusion 50 is constant, for example, from the tip 41 to the base end 43 of the lip 40 (see FIG. 2 ). Here, the width W1 of the protrusion 50 and the width W2 between the protrusions 50, 50 are the dimensions of the outer peripheral surface 42 at the tip 41 of the lip 40 in the circumferential direction Rd.

[0024] 4, the thickness t2 (thickness t2 in the radial direction from the outer circumferential surface 42 of the lip 40) of all the protrusions 50 is constant. Moreover, the thickness t2 of each protrusion 50 is uniform from the base end 43 to the tip end 41 of the lip 40.

[0025] The portion 44 of the lip 40 having the protrusion 50 is reinforced by the protrusion 50 and is therefore configured to have high rigidity in the radial direction of the lip 40. In this way, the portion 44 of the lip 40 having the protrusion 50 and the protrusion 50 are collectively referred to as the "high-rigidity lip portion 60." On the other hand, the portion 70 of the lip 40 not having the protrusion 50 is referred to as the "low-rigidity lip portion 70."

[0026] The plurality of low-rigidity lip portions 70 have rigidity equal to or smaller than a preset reference rigidity of the lip 40. The plurality of high-rigidity lip portions 60 have rigidity greater than the reference rigidity. The plurality of low-rigidity lip portions 70 and the plurality of high-rigidity lip portions 60 are alternately arranged in the circumferential direction Rd of the lip 40.

[0027] Here, the "predetermined reference rigidity of the lip 40" refers to a rigidity that ensures the sealing performance of the lip 40 against the outer peripheral surface 12a of the inner tube 12 (shaft member 12) and is capable of scraping off foreign matter adhered to the outer peripheral surface 12a of the inner tube 12. In other words, the "reference rigidity" refers to a rigidity that is capable of maintaining the contact pressure (surface pressure) of the lip 40 against the outer peripheral surface 12a of the inner tube 12 at a predetermined reference value.

[0028] As is clear from the above description, the lip 40 of the dust seal 20 has a plurality of low-rigidity lip portions 70 and a plurality of high-rigidity lip portions 60 integrally formed around the entire periphery.

[0029] As described above, the widths W1 of the multiple protrusions 50 are set to different sizes in the circumferential direction Rd of the lip 40, and therefore the widths W1 of the multiple high-rigidity lip portions 60 are set to different sizes in the circumferential direction Rd of the lip 40. As a result, the multiple high-rigidity lip portions 60 have non-uniform widths in the circumferential direction Rd of the lip 40.

[0030] Because the widths W1 of the multiple protrusions 50 are set to different sizes in the circumferential direction Rd of the lip 40, the widths W2 of the multiple low-rigidity lip portions 70 are also set to different sizes in the circumferential direction Rd of the lip 40. As a result, the multiple low-rigidity lip portions 70 are non-uniform in the circumferential direction Rd of the lip 40. Note that the widths W2 of the low-rigidity lip portions 70 may be set to the same size in the circumferential direction Rd of the lip 40.

[0031] As shown in Figure 4, the thickness t3 of each high-rigidity lip portion 60 is the sum of the thickness t1 of the lip 40 and the thickness t2 of the protrusion 50, and is greater than the thickness t1 of each low-rigidity lip portion 70 (which is the same as the thickness t1 of the lip 40).

[0032] The thickness t2 of the protrusion 50 shown in Fig. 4 (thickness t2 in the radial direction from the outer circumferential surface 42 of the lip 40) can be changed as shown in Fig. 6A and Fig. 6B. Fig. 6A shows that the thickness t22 of the portion 52 (base end portion 52) of the protrusion 50 on the base end 43 side is set larger than the thickness t21 of the portion 51 (tip end portion 51) on the tip 41 side of the lip 40. By doing so, the base end portion 52 is thick and therefore stable, and the tip end portion 51 is thin and therefore makes it easier to repel the tip 41 of the lip 40.

[0033] 6B shows that the thickness t21 of the portion 51 (tip portion 51) of the protrusion 50 on the tip 41 side is set larger than the thickness t22 of the portion 52 (base end portion 52) on the base end 43 side of the lip 40. By doing so, the tip portion 51 is thick, which increases the rigidity of the tip 41 of the lip 40, making it possible to make the tip 41 of the lip 40 less prone to vibration.

[0034] 4 can be provided on the inner circumferential surface 45 of the lip 40 as shown in FIG.

[0035] 5 can be formed to have an arc-shaped cross section when the dust seal 20 is viewed in the axial direction, as shown in FIG.

[0036] 5 can be configured such that a protrusion 50A made of a separate member is fixed (for example, by adhesion or welding) to the lip 40, as shown in FIG. 9. The multiple high-rigidity lip portions 60 are configured to have high rigidity by fixing the separate members 50A (protrusions 50A) to the lip 40. The portion 44 of the lip 40 having the protrusion 50 and the protrusion 50A are collectively referred to as the "high-rigidity lip portion 60."

[0037] <Embodiment 2> A dust seal 120 of embodiment 2 and a shock absorber 100 including this dust seal 120 will be described with reference to FIG. 10. FIG. 10 is a cross-sectional view illustrating the dust seal 120 included in the shock absorber 100 of embodiment 2, and corresponds to FIG. 5 illustrating the dust seal 20 of embodiment 1. The dust seal 120 of embodiment 2 is characterized in that the multiple low-rigidity lip portions 70 and multiple high-rigidity lip portions 60 of the dust seal 20 of embodiment 1 shown in FIG. 5 are replaced with multiple low-rigidity lip portions 70 and multiple high-rigidity lip portions 160 shown in FIG. 10. The rest of the basic configuration is common to the dust seal 20 of embodiment 1 and the shock absorber 10 including this dust seal 20. The same reference numerals will be used for parts common to the dust seal 20 of embodiment 1 and the shock absorber 10 including this dust seal 20, and detailed description thereof will be omitted.

[0038] The lip 40 of Example 2 does not have multiple protrusions 50 and includes multiple high-rigidity lip portions 160 having rigidity equivalent to that of the high-rigidity lip portion 60 of Example 1. The dust seal 120 does not have any members protruding radially outward from the outer peripheral surface 42 of the lip 40. In other words, the multiple high-rigidity lip portions 160 are made of a different material than the multiple low-rigidity lip portions 70 (lip 40), thereby being configured to have higher rigidity than the multiple low-rigidity lip portions 70. For example, the hardness of the multiple high-rigidity lip portions 160 is set to be greater than the hardness of the multiple low-rigidity lip portions 70. Like the high-rigidity lip portion 60 of Example 1, the multiple high-rigidity lip portions 160 of Example 2 have rigidity greater than the reference rigidity. The multiple low-rigidity lip portions 70 and the multiple high-rigidity lip portions 160 are alternately arranged in the circumferential direction Rd of the lip 40. Therefore, the rigidity of the lip 40 in the circumferential direction Rd can be set to be non-uniform without changing the appearance of the dust seal 20.

[0039] <Embodiment 3> A dust seal 220 of embodiment 3 and a shock absorber 200 including this dust seal 220 will be described with reference to FIG. 11 . FIG. 11 is a cross-sectional view illustrating the dust seal 220 included in the shock absorber 200 of embodiment 3, and corresponds to FIG. 5 illustrating the dust seal 20 of embodiment 1. The dust seal 220 of embodiment 3 is characterized in that the arrangement of the plurality of low-rigidity lip portions 70 and the plurality of high-rigidity lip portions 60 of the dust seal 20 of embodiment 1 shown in FIG. 5 is changed to an arrangement of the plurality of low-rigidity lip portions 70 and the plurality of high-rigidity lip portions 60 shown in FIG. 11 . The other basic configuration is common to the dust seal 20 of embodiment 1 and the shock absorber 10 including this dust seal 20. The same reference numerals will be used for parts common to the dust seal 20 of embodiment 1 and the shock absorber 10 including this dust seal 20, and detailed description thereof will be omitted.

[0040] In Example 3, the widths W1 of the multiple protrusions 50 are set to the same size (constant) in the circumferential direction Rd of the lip 40. Meanwhile, the arrangement angles θ1 of the multiple protrusions 50 are set to different sizes. As a result, the widths W2 between adjacent protrusions 50, 50 on the outer peripheral surface 42 of the lip 40 are set to different sizes in the circumferential direction Rd of the lip 40.

[0041] As described above, because the width W1 of the multiple protrusions 50 is constant in the circumferential direction Rd of the lip 40, the width W1 of the multiple high-rigidity lip portions 60 is set to a constant size in the circumferential direction Rd of the lip 40. However, the arrangement angles θ1 of the multiple protrusions 50 are set to different sizes. As a result, the multiple high-rigidity lip portions 60 are unevenly spaced in the circumferential direction Rd of the lip 40 (the arrangement intervals are different). Furthermore, because the widths W2 between adjacent protrusions 50, 50 are different sizes in the circumferential direction Rd of the lip 40, the multiple low-rigidity lip portions 70 are unevenly spaced in the circumferential direction Rd of the lip 40.

[0042] The dust seal 20 and the shock absorber 10 equipped with this dust seal 20 described above can be summarized as follows.

[0043] 1 to 11. According to this embodiment, first, the dust seal 20, 120, 220 (see FIGS. 1, 10, and 11) is an annular member capable of sealing between the cylindrical member 11 and the shaft member 12 inserted therethrough so as to be capable of reciprocating relative to the cylindrical member 11. The dust seal 20, 120, 220 includes an annular mounting portion 30 that can be mounted to the open end 11a of the cylindrical member 11, and an annular lip 40 that is integrally formed with the mounting portion 30 and can be in sliding contact with the outer circumferential surface 12a of the shaft member 12 over the entire circumference. The lip 40 includes a plurality of low-rigidity lip portions 70 (see FIGS. 5 and 10) that have rigidity equal to or lower than a preset reference rigidity of the lip 40, and a plurality of high-rigidity lip portions 60, 160 (see FIGS. 5 and 10) that have rigidity higher than the reference rigidity. The plurality of low-rigidity lip portions 70 and the plurality of high-rigidity lip portions 60, 160 are arranged alternately in the circumferential direction Rd of the lip 40.

[0044] Here, the "predetermined reference rigidity of the lip 40" refers to a rigidity that ensures the sealing performance of the lip 40 against the outer peripheral surface 12a of the shaft member 12 and is capable of scraping off foreign matter adhered to the outer peripheral surface 12a of the shaft member 12. In other words, the "reference rigidity" refers to a rigidity that is capable of maintaining the contact pressure (surface pressure) of the lip 40 against the outer peripheral surface 12a of the shaft member 12 at a predetermined reference value.

[0045] In this embodiment, by arranging multiple low-rigidity lip portions 70 and multiple high-rigidity lip portions 60, 160 alternately in the circumferential direction Rd of the lip 40, the contact pressure (surface pressure) of the lip 40 against the outer peripheral surface 12a of the shaft member 12 is non-uniform (varies) in the circumferential direction. In this manner, the rigidity of the annular lip 40 is not made completely uniform in the circumferential direction Rd, but is instead intentionally made non-uniform. When the shaft member 12 and the dust seal 20, 120, 220 reciprocate relative to each other, the magnitude of the frictional resistance between the outer peripheral surface 12a of the shaft member 12 and the annular lip 40 is non-uniform between the low-rigidity lip portions 70 and the high-rigidity lip portions 60, 160. When the shaft member 12 and the dust seal 20, 120, 220 reciprocate relative to each other, only the tip of the low-rigidity lip portion 70 is curled radially inward due to frictional resistance. In other words, if only a portion of the annular lip 40 (the low-rigidity lip portion 70) is turned up due to frictional resistance, stick-slip is unlikely to occur in the entire lip 40.

[0046] As described above, even when no lubrication is applied between the outer peripheral surface 12 a of the shaft member 12 and the sliding surface 41 a of the tip 41 of the lip 40, the occurrence of stick-slip can be suppressed extremely effectively by actively setting (controlling) the low-rigidity portion (low-rigidity lip portion 70) and the high-rigidity portion (high-rigidity lip portions 60, 160). Furthermore, the surface texture (surface roughness) of the outer peripheral surface 12 a of the shaft member 12 due to processing is less likely to have an effect on the suppression of stick-slip. For example, when the shaft member 12 and the dust seal 20, 120, 220 reciprocate relative to each other, it is possible to set (control) the low-rigidity portion and the high-rigidity portion so as to optimize the frequency of abnormal noises, such as chatter vibration noise, that occur between the outer peripheral surface 12 a of the shaft member 12 and the sliding surface 41 a of the tip 41 of the lip 40 (for example, so as to be in a range that is difficult for humans to hear).

[0047] See Figures 5 and 8 to 11. Secondly, preferably, in the dust seal 20, 120, 220 described above, the plurality of high-rigidity lip portions 60, 160 are distributed non-uniformly in the circumferential direction Rd of the lip 40. Therefore, the plurality of low-rigidity lip portions 70 are also distributed non-uniformly in the circumferential direction Rd of the lip 40. For this reason, the rigidity of the lip 40 in the circumferential direction Rd can be set to be non-uniform.

[0048] See Figures 5 and 8 to 10. Thirdly, preferably, in the dust seal 20, 120 described in the second aspect, the multiple high-rigidity lip portions 60, 160 are set to widths W1 that differ from one another in the circumferential direction Rd of the lip 40. Therefore, the multiple low-rigidity lip portions 70 are also set to widths W2 that differ from one another in the circumferential direction Rd of the lip 40. Therefore, the rigidity of the lip 40 in the circumferential direction Rd can be set to be non-uniform.

[0049] See Figures 3, 4, and 11. Fourth, preferably, in the dust seal 20, 220 described in the second aspect, the thickness t3 of the plurality of high-rigidity lip portions 60 is greater than the thickness t1 of the plurality of low-rigidity lip portions 70. Therefore, the rigidity of the lip 40 in the circumferential direction Rd can be set to be non-uniform.

[0050] See Fig. 9. Fifth, preferably, in the dust seal 20 described in any one of the first to fourth aspects, the plurality of high-rigidity lip portions 60 are portions configured to have high rigidity by fixing a separate member 50A (protrusion 50A) to the lip 40. This allows the rigidity of the lip 40 in the circumferential direction Rd to be easily set to be non-uniform, resulting in good productivity. Moreover, by appropriately changing the material of the separate member 50A relative to the material of the lip 40, the rigidity characteristics can be set to be optimal.

[0051] See Fig. 10. Sixth, preferably, in the dust seal 120 described in the second aspect, the plurality of high-rigidity lip portions 160 are configured to have high rigidity by being made of a material that is different from the material of the plurality of low-rigidity lip portions 70. Therefore, the rigidity of the lip 40 in the circumferential direction Rd can be set to be non-uniform without changing the appearance of the dust seal 120.

[0052] See Figures 1, 10 and 11. Seventh, the shock absorbers 10, 100, 200 preferably include the dust seals 20, 120, 220 described in any of the first to sixth aspects, the cylindrical member 11, and the shaft member 12. Therefore, it is possible to provide the shock absorbers 10, 100, 200 that include the dust seals 20, 120, 220 that can extremely effectively suppress the occurrence of stick-slip.

[0053] The dust seals 20, 120, 220 according to the present invention and the shock absorbers 10, 100, 200 equipped with these dust seals 20, 120, 220 are not limited to the above-described embodiments, as long as they achieve the functions and effects of the present invention. For example, any two or more of the embodiments and modified examples shown in Figures 1 to 11 may be combined.

[0054] The dust seals 20, 120, 220 of the present invention and the shock absorbers 10, 100, 200 equipped with these dust seals 20, 120, 220 are suitable for use in rear dampers mounted on saddle-ride type vehicles.

[0055] DESCRIPTION OF SYMBOLS 10... shock absorber, 11... cylindrical member, 11a... opening end, 12... shaft member, 20... dust seal, 30... mounting portion, 31... tip, 40... lip, 41... tip, 41a... sliding surface, 42... outer circumferential surface, 43... base end, 44... portion having protrusion, 50... protrusion, 50A... separate member (protrusion), 60... high-rigidity lip portion, 70... low-rigidity lip portion, 100... shock absorber, 120... dust seal, 160... high-rigidity lip portion, 200... shock absorber, 220... dust seal, Rd... circumferential direction of outer circumferential surface of lip, t1... thickness of lip (thickness of low-rigidity lip portion), t2... thickness of protrusion, t3... thickness of high-rigidity lip portion, W1... width of protrusion, W2... width between adjacent protrusions (width of low-rigidity lip portion).

Claims

1. An annular dust seal capable of sealing between a cylindrical member and a shaft member inserted therethrough so as to be able to reciprocate relatively to the cylindrical member, comprising: an annular mounting portion that can be mounted to the open end of the cylindrical member; and an annular lip that is formed integrally with the mounting portion and can slide over the entire circumference against the outer surface of the shaft member, wherein the lip comprises a plurality of low-rigidity lip portions that have the same or lower rigidity than a preset reference rigidity of the lip, and a plurality of high-rigidity lip portions that have higher rigidity than the reference rigidity, and the low-rigidity lip portions and the high-rigidity lip portions are arranged alternately in the circumferential direction of the lip.

2. A dust seal according to claim 1, wherein the plurality of high-rigidity lip portions are distributed unevenly in the circumferential direction of the lip.

3. A dust seal according to claim 2, wherein the plurality of high-rigidity lip portions are set to different widths in the circumferential direction of the lip.

4. A dust seal according to claim 2, wherein the thickness of said plurality of high-rigidity lip portions is greater than the thickness of said plurality of low-rigidity lip portions.

5. A dust seal according to claim 2, wherein the plurality of high-rigidity lip portions are portions that are made highly rigid by fixing a separate member to the lip.

6. A dust seal as described in claim 2, wherein the plurality of high-rigidity lip portions are made of a material different from that of the plurality of low-rigidity lip portions, thereby achieving high rigidity.

7. A shock absorber comprising the dust seal according to claim 1, the cylindrical member, and the shaft member.

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