Shock absorber

Abstract

A shock absorber (D) according to the present embodiment comprises: an outer shell (1); a rod (2) that goes in and out of the outer shell (1); a bump cap (3) which has a topped cylindrical shape and an annular top part (3a), which is attached to the outer periphery of an upper end serving as a rod-side end of the outer shell (1), and through which the rod (2) is inserted on the inner peripheral side of the top part (3a); bump rubber (4) that is attached to the rod (2) and that faces the bump cap (3) in the axial direction of the rod (2); and a cylindrical dust boot (5) that covers the outer periphery of the rod (2), and that has an upper end attached to the rod (2) and a lower end which abuts a cylindrical part (3b) of the bump cap (3) over the entire circumference. The shape of an upper end inner peripheral part of the inner periphery of the top part (3a) of the bump cap (3) is a non-cylindrical shape, and the clearance between the rod (2) and the inner periphery of the top part (3a) is 5mm or less.

Description

buffer

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

[0002] Conventionally, vehicle shock absorbers have been equipped with a bump stop rubber attached to the outer periphery of the tip of the piston rod, and a cylindrical bump cap with a top that is attached to the upper end of the outer shell and faces the bump stop rubber in the axial direction.When the shock absorber is fully compressed, the bump stop rubber and the bump cap collide with each other, and the elastic force exerted by the compressed bump stop rubber prevents bottoming out and reduces impact when the shock absorber is fully compressed.

[0003] The shock absorber also includes a cylindrical dust cover with bellows that covers the piston rod to protect the outer periphery of the piston rod, as shown in JP2015-190555A, for example. The dust boot has an upper end attached to a suspension spring attached to the tip of the piston rod, and a lower end abutting against a flange-shaped skirt provided on the outer periphery of the lower end of the cylindrical part of the bump cap, so that when the shock absorber expands or contracts, the dust boot can expand or contract without causing axial wobble relative to the piston rod.

[0004] JP2015-190555A

[0005] In conventional shock absorbers, the outer periphery of the piston rod is protected by a dust boot, but in recent years there has been a demand for improving the airtightness inside the dust boot by not only abutting the lower end of the dust boot against the skirt of the bump cap but also by fixing it in close contact with the skirt, so as to more effectively prevent raindrops and dust from adhering to the outer periphery of the piston rod.

[0006] Fixing the lower end of the dust boot to the skirt of the bump cap increases the airtightness inside the dust boot and more effectively protects the piston rod, but because the space between the dust cover and the bump cap is blocked, air inside the dust boot will leak out through the gap between the bump cap and the outer shell when the shock absorber contracts.

[0007] On the other hand, the bump cap is composed of an annular top portion, through whose inner periphery the piston rod is inserted and which faces the bump rubber, and a tubular portion having a plurality of ribs on its inner periphery that abut against the outer periphery of the outer shell, and when the bump rubber collides with the bump cap and is compressed, the bump rubber becomes pinched between the inner periphery of the top portion and the rod, causing the bump rubber to deteriorate. Therefore, in order to prevent deterioration of the bump rubber, it is preferable to narrow the clearance between the inner periphery of the top portion and the outer periphery of the piston rod.

[0008] However, if the clearance between the inner circumference of the top and the outer circumference of the piston rod is narrowed, the flow rate of the air passing through the clearance increases when the shock absorber contracts, causing the air to hit the upper edge of the inner circumference of the top of the bump cap hard, causing the air to swirl and vibrate, resulting in a whistling noise.

[0009] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a shock absorber that can prevent deterioration of the bump rubber while suppressing the generation of whistling noise from the bump cap.

[0010] In order to solve the above problems, the shock absorber of the present invention comprises an outer shell, a rod that enters and exits the outer shell, a bump cap that is cylindrical with a top and has a ring-shaped top and is attached to the outer periphery of the upper end, which is the rod side end of the outer shell, and through which the rod is inserted on the inner periphery of the top, a bump rubber that is attached to the rod and faces the bump cap in the axial direction of the rod, and a cylindrical dust boot that covers the outer periphery of the rod, has its upper end attached to the rod, and its lower end abuts against the cylindrical portion of the bump cap around its entire circumference, and the shape of the upper inner periphery of the inner periphery of the top of the bump cap is non-cylindrical, and the clearance between the rod and the inner periphery of the top is 5 mm or less.

[0011] With this shock absorber configured in this manner, the clearance between the rod and the inner circumference of the top is 5 mm or less, preventing the bump rubber, which is compressed at the time of maximum contraction, from getting caught between the bump cap and the rod. However, since the shape of the upper inner periphery of the inner circumference of the top of the bump cap is non-cylindrical, the generation of whistling noise can be suppressed even when the shock absorber contracts at high speed and the air inside the dust boot passes between the bump cap and the rod.

[0012] Fig. 1 is a side view showing a shock absorber according to an embodiment of the present invention, with a portion cut away. Fig. 2 is a cross-sectional view of a bump cap of the shock absorber according to an embodiment of the present invention, taken along the line XX. Fig. 3 is a plan view of the bump cap of the shock absorber according to an embodiment of the present invention. Fig. 4 is a bottom view of the bump cap of the shock absorber according to an embodiment of the present invention. Fig. 5 is a plan view of a first modified bump cap of the shock absorber according to an embodiment of the present invention. Fig. 6 is a cross-sectional view of a second modified bump cap of the shock absorber according to an embodiment of the present invention.

[0013] The present invention will be described below based on the embodiments shown in the drawings. As shown in Fig. 1, a shock absorber D in one embodiment is configured to include an outer shell 1, a rod 2 that enters and exits the outer shell 1, a bump cap 3 attached to the outer periphery of the upper end of the outer shell 1, which is the end on the rod side, a bump rubber 4 attached to the rod 2 and facing the bump cap 3 in the axial direction of the rod 2, and a cylindrical dust boot 5 that covers the outer periphery of the rod 2, has an upper end attached to the rod 2, and a lower end that abuts against the bump cap 3 over the entire circumference. The embodiments of the present invention will be described below with reference to the drawings. The same reference numerals used throughout the drawings indicate the same parts.

[0014] Below, we will explain each part that makes up the shock absorber D. The shock absorber D has a cylindrical outer shell 1 and a rod 2 that is movably inserted into the outer shell 1, and when the rod 2 moves axially relative to the outer shell 1 in an expansion / contraction operation, a damping force is generated that prevents the rod 2 from moving relative to the outer shell 1, thereby damping vibrations of the vehicle body and wheels.

[0015] The shock absorber D includes, for example, a cylindrical outer shell 1 whose lower end is closed, a cylinder (not shown) housed in the outer shell 1, a rod 2 movably inserted into the cylinder, a piston connected to the rod 2 and inserted into the cylinder to divide the interior of the cylinder into an extension-side chamber and a compression-side chamber, a reservoir formed between the cylinder and the outer shell 1, and a valve case provided at the lower end of the cylinder to separate the compression-side chamber from the reservoir. The extension-side chamber and the compression-side chamber are filled with a liquid such as hydraulic oil, and the reservoir is filled with a liquid and a gas. The liquid used in the shock absorber D may be a liquid other than hydraulic oil, such as water or an aqueous solution.

[0016] The piston is provided with a passage connecting the expansion-side chamber and the compression-side chamber and a damping valve that resists the flow of fluid passing through the passage. The valve case is provided with a discharge passage and a suction passage connecting the expansion-side chamber and the reservoir, a compression-side damping valve that resists the flow of fluid from the expansion-side chamber to the reservoir through the discharge passage, and a check valve that allows only the flow of fluid from the reservoir to the expansion-side chamber through the suction passage. The shock absorber D configured in this manner generates a damping force that hinders expansion and contraction by resisting the flow of fluid through the damping valve or the compression-side damping valve during expansion and contraction. Furthermore, since the shock absorber D is a single-rod shock absorber in which the rod 2 is inserted only into the expansion-side chamber, the volume of the rod 2 moving in and out of the cylinder during expansion and contraction is compensated for by the exchange of fluid between the reservoir and the cylinder. The upper open end of the outer shell 1 in FIG. 1 is crimped from the outer periphery and folded inward, forming a flat shoulder 1a at the upper end of the outer shell 1.

[0017] The internal configuration of the shock absorber D described above is merely an example, and the design can be modified as desired as long as a damping force can be generated when the rod 2 extends and retracts relative to the outer shell 1. For example, the reservoir may be formed as a separate tank provided laterally outside the outer shell 1, or a movable partition such as a free piston, bladder, or bellows that forms an expandable air chamber within the outer shell 1 may be provided to compensate for changes in the cylinder volume due to the volume of the rod extending and retracting and changes in the liquid volume due to temperature changes. In such a case, the shock absorber D may be a single-cylinder shock absorber D in which the piston divides the interior of the outer shell 1 into an extension-side chamber and a compression-side chamber, and the outer shell 1 is used as a cylinder. Furthermore, the shock absorber D is a single-rod type in which the rod 2 extends from one side of the piston to the outside of the cylinder, but may also be a double-rod type in which the rod 2 extends from both sides of the piston to the outside of the cylinder. Furthermore, the shock absorber D is a hydraulic shock absorber that utilizes fluid force, but it may also be a pneumatic shock absorber or other shock absorbers.

[0018] The bump rubber 4 is made of an elastic material such as rubber, synthetic resin, or urethane foam, and is cylindrical and attached to the outer periphery of the upper end of the rod 2. Specifically, the upper end of the bump rubber 4 is held by a cylindrical cup 6 attached to the upper end of the rod 2, and the bump rubber 4 is fixedly attached to the rod 2 via the cup 6. Note that the means for fixing the bump rubber 4 to the rod 2 can be designed differently as needed.

[0019] Next, the bump cap 3 attached to the outer periphery of the upper end of the outer shell 1 is cylindrical with a top, as shown in Figures 2 and 3, and has an annular top portion 3a and a cylindrical portion 3b connected to the outer periphery of the top portion 3a.

[0020] In this embodiment, the top portion 3a is annular, and the rod 2 is inserted into the inner periphery when the bump cap 3 is attached to the outer periphery at the upper end of the outer shell 1. The side of the top portion 3a facing inward of the bump cap 3 is the inner side, and the side facing outward of the bump cap 3 (the upper side in FIG. 2) is the outer side.

[0021] 2 and 3, the top portion 3a has three ribs 3c extending radially outward along the diameter of the top portion 3a. The ribs 3c protrude in the axial direction from the upper end, which is the outer end of the top portion 3a, and face the bump rubber 4 in the axial direction.

[0022] When the shock absorber D is contracted with the rod 2 entering the outer shell 1, the bump rubber 4 collides with the outer surface of the top 3a when the shock absorber is fully contracted, but the underside of the bump rubber 4 comes into contact with the rib 3c first and deforms, preventing the entire underside of the bump rubber 4 from coming into flat contact with the outer surface of the top 3a, thereby reducing the impact noise when the bump rubber 4 collides with the bump cap 3. The number and shape of the ribs 3c can be changed depending on the shape, material, etc. of the bump rubber 4 used.

[0023] The top portion 3a has a curved surface 3a1 formed by chamfering the inner periphery with an R-shape at the upper end in FIG. 2 . Thus, the shape of the inner periphery of the top portion 3a of the bump cap 3 is not cylindrical, but rather has a trumpet shape with an inner diameter that increases upward due to the curved surface 3a1. An annular gap is formed between the inner periphery of the top portion 3a and the rod 2 inserted through the inner periphery of the top portion 3a, and the radial width of the annular gap, i.e., the clearance, is set to 5 mm or less at its narrowest point. Furthermore, as shown in FIG. 4 , six protrusions 3f are arranged circumferentially on the inside of the top portion 3a, extending radially and abutting against the upper end of the outer shell 1. The number of protrusions 3f can be arbitrarily changed as long as the top portion 3a is stably supported by the upper end of the outer shell 1.

[0024] The cylindrical portion 3b is connected to the outer periphery of the top portion 3a and has six fitting protrusions 3d that protrude inward from the inner periphery and extend along the axial direction. The fitting protrusions 3d protrude inward from the inner periphery of the cylindrical portion 3b and are provided along the axial direction. In this embodiment, as shown in FIG. 4 , the fitting protrusions 3d are provided between the convex portions 3f, 3f on the inner side of the top portion 3a. When the bump cap 3 is attached to the outer periphery of the upper end of the outer shell 1, the inner surface of the fitting protrusions 3d abuts against the outer periphery of the outer shell 1. The inscribed circle passing through the inner surface of the fitting protrusions 3d is slightly smaller than the outer diameter of the outer shell 1. Therefore, when the bump cap 3 is fitted to the outer periphery of the upper end of the outer shell 1, the cylindrical portion 3b expands in diameter and tightens the outer periphery of the outer shell 1 via the fitting protrusions 3d, firmly fixing the bump cap 3 to the outer periphery of the outer shell 1. The number and shape of the fitting protrusions 3d provided on the cylindrical portion 3b are not limited to those described above, and can be arbitrarily modified in design as long as the bump cap 3 can be fixed to the outer periphery of the outer shell 1.

[0025] Furthermore, when the bump cap 3 is attached to the outer periphery of the upper end of the outer shell 1, the convex portion 3f of the top 3a abuts against the shoulder 1a of the outer shell 1, and the inner surface of the top 3a moves away from the shoulder 1a. Therefore, an air passage P is formed between the bump cap 3 and the outer shell 1, consisting of a top-side gap A surrounded by the shoulder 1a, the top 3a, and the convex portions 3f, 3f, and a cylindrical-side gap B surrounded by the outer periphery of the outer shell 1, the cylindrical portion 3b, and the fitting protrusions 3d, 3d.

[0026] Furthermore, as long as the top-side gap A between the protrusions 3f, 3f and the tubular-side gap B between the engaging protrusions 3d, 3d are connected to form a passage P, the protrusions 3f and the engaging protrusions 3d may be formed in a position that coincides circumferentially with respect to the bump cap 3.

[0027] The cylindrical portion 3b also has a skirt 3e at its lower end, which protrudes at an angle from the lower end of the cylindrical portion 3b toward the outer periphery and has a tapered surface on its outer periphery.

[0028] The dust boot 5 is made of synthetic resin or the like and is cylindrical with bellows. The inner periphery of the lower end portion 5a, where the diameter of the bellows increases downward, is provided with a barb 5b that hooks onto the lower end of the skirt 3e. The upper end is attached to the lower end of the cup 6. The dust boot 5 is thus attached to the rod 2 via the cup 6, and the bump cap 3 attached to the outer periphery of the upper end of the outer shell 1 is inserted into the inner periphery of the lower end. When the barb 5b at the lower end of the dust boot 5 hooks onto the lower end of the skirt 3e of the bump cap 3, the inner periphery of the lower end portion 5a of the dust boot 5 comes into close contact with the outer periphery of the skirt 3e, preventing air from passing between the lower end portion 5a of the dust boot 5 and the skirt 3e. In this way, the lower end of the dust boot 5 abuts against the skirt 3e of the tubular portion 3b of the bump cap 3 over the entire circumference, preventing air from passing between the lower end portion 5a of the dust boot 5 and the skirt 3e. The dust boot 5 is attached to the tubular portion 3b of the bump cap 3 by a barb 5b at its lower end, but the barb 5b may not be provided as long as the lower end abuts against the tubular portion 3b around the entire circumference.

[0029] When the dust boot 5 is fixed to the rod 2 and the bump cap 3 in this way, the dust boot 5 has a bellows, so that when the rod 2 moves in and out of the outer shell 1, the bellows portion can be expanded and contracted in the axial direction. The dust boot 5 covers the outer periphery of the rod 2 to prevent adhesion of dust, dirt, or rainwater to the outer periphery of the rod 2, and also protects the outer periphery of the rod 2 from flying stones.

[0030] When the shock absorber D expands or contracts, the dust boot 5 expands or contracts, changing the volume of the space inside the dust boot 5. When the volume decreases, air is expelled from inside the dust boot 5 to outside the dust boot 5, and when the volume increases, air is sucked into the dust boot 5 from outside the dust boot 5. The lower end portion 5a of the dust boot 5 tightly contacts the skirt 3e of the tubular portion 3b of the bump cap 3 all around, making it difficult for air to pass between the dust boot 5 and the bump cap 3, and the upper end of the dust boot 5 is also fitted into the cup 6, making it difficult for air to pass between the dust boot 5 and the cup 6.

[0031] Therefore, when the shock absorber D expands or contracts, the air exchanged between the inside and outside of the dust boot 5 passes through the passage P between the bump cap 3 and the outer shell 1.

[0032] The inventor's research has revealed that in conventional shock absorbers, when the clearance between the inner circumference of the top of the bump cap and the rod is 5 mm or less at its narrowest point, when the air inside the dust boot passes between the rod and the inner circumference of the top of the bump cap toward the outside of the dust boot, the shock absorber contracts at high speed, increasing the air flow rate, causing the air to hit the corner of the upper edge of the upper inner circumference of the top of the bump cap hard, creating a vortex in the air flow, causing vibration and producing a whistling sound.

[0033] Furthermore, when the clearance between the inner periphery of the top of the bump cap and the rod is 3 mm or less at its narrowest point, the whistling sound becomes louder and higher-pitched than when the clearance is 5 mm, causing discomfort to vehicle occupants to which shock absorber D is applied, and when the clearance between the inner periphery of the top of the bump cap and the rod is 2 mm or less at its narrowest point, the whistling sound becomes louder and higher-pitched than when the clearance is 3 mm, causing greater discomfort to vehicle occupants. Note that when the clearance between the inner periphery of the top of the bump cap and the rod is 5 mm or less at its widest point, a whistling sound will also occur because the narrowest point of the clearance is 5 mm or less. Similarly, when the clearance is 3 mm or less, or even 2 mm or less at its widest point, the whistling sound becomes louder and higher-pitched.

[0034] Therefore, in the shock absorber D of this embodiment, the shape of the upper inner periphery of the top 3a of the bump cap 3 is non-cylindrical. Specifically, in the shock absorber D of this embodiment, the upper inner periphery of the top 3a is trumpet-shaped with a curved surface 3a1, so that even if the air flow velocity increases, the air passes smoothly through the annular gap between the inner periphery of the top 3a of the bump cap 3 and the rod 2, making it less likely that a vortex will occur in the air flow. Therefore, in the shock absorber D of this embodiment, even if the clearance between the inner periphery of the top 3a of the bump cap 3 and the rod 2 is set to 5 mm or less, air vibrations can be reduced and the generation of a whistling sound can be suppressed.

[0035] In addition, since the clearance between the inner circumference of the top 3a of the bump cap 3 and the rod 2 is set to 5 mm or less, the annular gap between the top 3a of the bump cap 3 and the rod 2 is narrowed, and even if the bump rubber 4 abuts against the top 3a of the bump cap 3 and is compressed and deformed when the shock absorber D is fully contracted, the inner circumference of the lower end of the bump rubber 4 is prevented from entering the annular gap between the inner circumference of the top 3a of the bump cap 3 and the outer circumference of the rod 2, and the bump rubber 4 is prevented from being pinched between the bump cap 3 and the rod 2 when compressed and being deteriorated.

[0036] As described above, the shock absorber D of this embodiment comprises the outer shell 1, the rod 2 that enters and exits the outer shell 1, the bump cap 3 that is cylindrical with a top and has a ring-shaped top 3a that is attached to the outer periphery of the upper end of the outer shell 1, which is the rod side end, and through which the rod 2 is inserted on the inner periphery of the top 3a, the bump rubber 4 that is attached to the rod 2 and faces the bump cap 3 in the axial direction of the rod 2, and the cylindrical dust boot 5 that covers the outer periphery of the rod 2, has its upper end attached to the rod 2, and its lower end abuts against the cylindrical portion 3b of the bump cap 3 around its entire circumference, and the shape of the upper inner periphery of the inner periphery of the top 3a of the bump cap 3 is non-cylindrical, and the clearance between the rod 2 and the inner periphery of the top 3a is 5 mm or less.

[0037] In the shock absorber D configured as described above, the clearance between the rod 2 and the inner periphery of the top portion 3a is 5 mm or less, preventing the bump rubber 4 from being pinched between the bump cap 3 and the rod 2 when fully compressed. Furthermore, since the upper end inner periphery of the inner periphery of the top portion 3a of the bump cap 3 has a non-cylindrical shape, whistling noise can be suppressed even when the shock absorber D rapidly contracts and air in the dust boot 5 passes between the bump cap 3 and the rod 2. As described above, the shock absorber D of this embodiment can suppress the generation of whistling noise from the bump cap 3 while preventing deterioration of the bump rubber 4. Incidentally, when the clearance is 3 mm or less, deterioration of the bump rubber 4 can be further prevented and the generation of whistling noise can be suppressed, thereby preventing discomfort to vehicle occupants. Furthermore, when the clearance is 2 mm or less, deterioration of the bump rubber 4 can be more effectively prevented and the generation of whistling noise can be suppressed, thereby preventing discomfort to vehicle occupants.

[0038] Furthermore, in the shock absorber D of this embodiment, the bump cap 3 has a curved surface 3a1 on the upper edge of the inner circumference of the top portion 3a. With the shock absorber D configured in this manner, the upper inner periphery of the top portion 3a is curved surface 3a1, giving it a trumpet shape. Therefore, even if the air flow velocity increases, the air passes smoothly through the annular gap between the inner circumference of the top portion 3a of the bump cap 3 and the rod 2, making it less likely to generate vortexes in the air flow and effectively suppressing the generation of whistling noise. Furthermore, since the bump cap 3 can suppress the generation of whistling noise simply by providing the curved surface 3a1 on the upper edge of the inner circumference of the top portion 3a, the bump cap 3 is easy to manufacture, and the shape of the upper inner periphery is simple, so that manufacturing costs do not increase.

[0039] 5, a groove 3a2 opening from the inner periphery may be provided in at least one location on the upper edge of the inner periphery of the top 3a of the bump cap 3. When the groove 3a2 is provided in this manner, the shape of the upper inner periphery of the top 3a becomes a non-cylindrical shape by cutting out the shape of the groove 3a2 at one or more locations on the upper end of the cylindrical shape.

[0040] By providing grooves 3a2 opening from the inner periphery at at least one location on the upper edge of the inner periphery of the top portion 3a of the bump cap 3, the air flow becomes uneven in the circumferential direction when passing between the inner periphery of the top portion 3a of the bump cap 3 and the rod 2, thereby suppressing the generation of whistling noise. Furthermore, since the generation of whistling noise can be suppressed simply by providing grooves 3a2 on the upper edge of the inner periphery of the top portion 3a, the bump cap 3 is easy to manufacture, and the shape of the upper inner periphery is simple, so manufacturing costs are not increased. Although the grooves 3a2 are provided only on the upper edge of the inner periphery of the top portion 3a, they may be provided so as to open from the inner periphery at the upper end of the top portion 3a and connect to the outer periphery, or so as to connect the inner periphery of the top portion 3a along the axial direction from the upper end to the lower end of the top portion 3a. The cross-sectional shape of the grooves 3a2 is semicircular, but is not limited thereto and may be triangular, rectangular, or other shapes.

[0041] 6, a plurality of ribs 3c may be provided that extend radially from the inner periphery of the top 3a of the bump cap 3 and are capable of contacting the bump rubber 4, with the end faces 3c1 of the ribs 3c facing the inner periphery continuing to the inner periphery of the top 3a. When the ribs 3c are provided on the top 3a in this way, the shape of the inner periphery of the upper end of the top 3a becomes a non-cylindrical shape with the end faces 3c1 of the ribs 3c facing the inner periphery projecting at multiple points from the upper end of the cylindrical shape.

[0042] By providing multiple ribs 3c on the top 3a of the bump cap 3 in this way, the air flow becomes uneven in the circumferential direction when it passes between the inner periphery of the top 3a of the bump cap 3 and the rod 2, thereby suppressing the generation of whistling noise. Also, since the bump cap 3 can suppress the generation of whistling noise simply by providing ribs 3c on the upper edge of the inner periphery of the top 3a, the bump cap 3 is easy to manufacture, and the shape of the upper inner periphery is simple, so there is no increase in manufacturing costs, and the impact noise when hitting the bump rubber 4 can also be reduced.

[0043] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims.

[0044] DESCRIPTION OF SYMBOLS 1: outer shell, 2: rod, 3: bump cap, 3a: top, 3a1: curved surface, 3a2: groove, 3b: cylindrical portion, 3c: rib, 3c1: end surface of rib, 4: bump rubber, 5: dust boot, D: shock absorber

Claims

1. A shock absorber comprising: an outer shell; a rod that enters and exits the outer shell; a bump cap that is cylindrical with a top and has a ring-shaped top, and is attached to the outer periphery of the upper end of the outer shell that is the rod side end, and through which the rod is inserted on the inner periphery of the top; a bump rubber that is attached to the rod and faces the bump cap in the axial direction of the rod; and a cylindrical dust boot that covers the outer periphery of the rod, has its upper end attached to the rod, and its lower end abuts against the tubular portion of the bump cap all around, wherein the shape of the upper inner periphery of the inner periphery of the top of the bump cap is non-cylindrical, and the clearance between the rod and the inner periphery of the top is 5 mm or less.

2. A shock absorber according to claim 1, wherein the bump cap has a curved surface at the upper edge of the inner periphery of the top portion.

3. A shock absorber according to claim 1, wherein the bump cap has a groove opening from the inner periphery at at least one location on the upper edge of the inner periphery of the top portion.

4. A shock absorber as claimed in claim 1, wherein the bump cap has a plurality of ribs extending radially from the inner periphery at the top and capable of abutting against the bump rubber, and the end faces of the ribs facing the inner periphery are continuous with the inner periphery of the top.

Images