Shock absorber

Abstract

A shock absorber (D) according to the present invention is provided with: a cylinder (1); a piston rod (2), which is inserted into the cylinder (1) so as to be movable in the axial direction; a piston (3), which is connected to the piston rod (2) and is inserted into the cylinder (1) so as to be movable in the axial direction; an outer cylinder (4), which houses the cylinder (1) inward and forms a reservoir (R) between the outer cylinder (4) and the cylinder (1); and a valve case (5), which is sandwiched between the cylinder (1) and a bottom part (4b) of the outer cylinder (4). The valve case (5) is provided with: a body part (5a), which is fitted to the inner periphery of the cylinder (1), and has a port (5a5) that communicates a pressure-side chamber (R2) and the reservoir (R); and a leg part (5b), which is provided at intervals in the circumferential direction on the outer peripheral part of the bottom part-side end of the body part (5a). The circumferential width of the leg part (5b) is shorter than the circumferential interval between the leg parts (5b, 5b). The circumferential width narrows as the leg part (5b) extends toward the bottom part side of the outer cylinder (4).

Description

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

[0002] A shock absorber is used, for example, by being interposed between the body and axle of a vehicle in order to improve the ride comfort of the vehicle, and suppresses vibration of the body and wheels by the damping force it exerts when expanding and contracting.

[0003] Such a shock absorber is configured, for example, with a cylinder, a piston rod inserted into the cylinder so as to be movable axially, a piston connected to the tip of the piston rod and inserted slidably into the cylinder to divide the inside of the cylinder into an extension-side chamber and a compression-side chamber, an outer cylinder that covers the cylinder and forms a reservoir between it and the cylinder, and a valve case that is fitted to the end of the cylinder to separate the compression-side chamber from the reservoir.

[0004] As disclosed in JP2022-10514A, for example, a conventional shock absorber has its interior divided into an extension-side chamber, a compression-side chamber, and a reservoir by a piston and a valve case, and a piston valve provides resistance to the flow of hydraulic oil going back and forth between the extension-side chamber and the compression-side chamber, while a base valve provides resistance to the flow of hydraulic oil from the compression-side chamber toward the reservoir, thereby generating a damping force during expansion and contraction.

[0005] JP2022-10514A

[0006] In conventional shock absorbers, the valve case separating the compression-side chamber and the reservoir is sandwiched between the lower end of the cylinder and the bottom of the outer cylinder and fixed within the shock absorber. Specifically, the valve case is disk-shaped and includes a base portion that has a step on its outer periphery that abuts against the end of the cylinder and a port that penetrates in the axial direction and that fits onto the inner periphery of the cylinder, and a plurality of legs that protrude from the lower end of the base and abut against the bottom of the outer cylinder. The step and legs are sandwiched between the cylinder and the bottom of the outer cylinder and fixed within the outer cylinder.

[0007] In a valve case configured in this manner, the legs are arranged intermittently in the circumferential direction relative to the base, and even when the legs are seated on the bottom of the outer tube, the space inside the legs is connected to the reservoir through the opening between the legs, so that the pressure side chamber and the reservoir can be connected via the port in the base.

[0008] The valve case communicates with the reservoir and the space inside the legs through the opening between the legs, but if the opening area between the legs is small, the hydraulic oil will encounter resistance as it passes between the legs, making it difficult for the hydraulic oil to move from the reservoir to the compression side chamber when the shock absorber extends, which can cause the pressure in the compression side chamber to drop excessively, creating air bubbles and disrupting the damping force.Therefore, it is desirable to make the opening area between the legs as large as possible.

[0009] To increase the opening area between the legs, the vertical length of the legs can be increased; however, because the legs are sandwiched between the cylinder and the bottom of the outer tube, increasing the length of the legs increases the distance between the cylinder and the bottom of the outer tube, which in turn increases the overall length of the outer tube or forces the stroke length of the shock absorber to be shortened, thereby compromising the mountability of the shock absorber on a vehicle.

[0010] However, if the circumferential spacing between the legs is increased, the circumferential width of the legs will be narrowed, reducing their strength, and there is a risk that the legs will deform or buckle due to the loads they receive from the ends of the cylinder and the bottom of the outer tube.

[0011] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a shock absorber that can generate a stable damping force without impairing mountability on a vehicle, while preventing deformation or buckling of the valve case.

[0012] In order to solve the above problems, the shock absorber of the present invention includes a cylinder, a piston rod inserted into the cylinder so as to be movable in the axial direction, a piston connected to the piston rod and inserted into the cylinder so as to be movable in the axial direction, and dividing the inside of the cylinder into an expansion-side chamber and a compression-side chamber, a cylindrical outer cylinder with a bottom that houses the cylinder therein and forms a reservoir between itself and the cylinder, and a valve case that is sandwiched between an end of the cylinder and a bottom of the outer cylinder and separates the compression-side chamber from the reservoir, The base is disk-shaped and has a small diameter portion and a large diameter portion separated by a step whose outer diameter abuts the end of the cylinder. The small diameter portion fits into the inner circumference of the cylinder and has a port that connects the pressure side chamber to the reservoir. The base also has a plurality of legs that are spaced apart circumferentially on the outer periphery of the bottom end of the main body facing the bottom side of the outer tube, protruding from the bottom end toward the bottom and abutting the bottom. The circumferential width of the legs is shorter than the circumferential spacing between the legs, and the circumferential width of the legs narrows as they move toward the bottom side of the outer tube.

[0013] In a shock absorber configured in this manner, the circumferential width of the legs of the valve case narrows toward the bottom of the outer cylinder, and the circumferential side surfaces of the legs are inclined, widening the spacing between the legs toward the tip, thereby ensuring a sufficient opening area between the legs without increasing the length of the legs in the axial direction of the valve case. Furthermore, since the overall length of the legs does not need to be increased, the slenderness ratio of the legs can be reduced, so even if a wide opening area between the legs is ensured, any reduction in strength of the legs can be kept to a minimum, preventing insufficient strength. Therefore, with this shock absorber, a wide opening area between the legs can be ensured without increasing the overall length of the legs, without increasing the overall length of the shock absorber or sacrificing the stroke length, and reducing resistance when liquid passes between the legs during extension.

[0014] Fig. 1 is a longitudinal cross-sectional view of a shock absorber according to an embodiment of the present invention. Fig. 2 is an enlarged cross-sectional view of a valve case portion of the shock absorber according to an embodiment of the present invention. Fig. 3 is a bottom view of the valve case of the shock absorber according to an embodiment of the present invention. Fig. 4 is a perspective view of the valve case of the shock absorber according to an embodiment of the present invention, seen from below. Fig. 5 is a perspective view of the valve case of the shock absorber according to an embodiment of the present invention, seen from above.

[0015] The present invention will be described below based on the embodiment shown in the drawings. As shown in Fig. 1, a shock absorber D in this embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1 so as to be axially movable, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movable, and dividing the interior of the cylinder 1 into an expansion-side chamber R1 and a compression-side chamber R2, a bottomed cylindrical outer cylinder 4 that houses the cylinder 1 therein and forms a reservoir R between the cylinder 1 and the outer cylinder 4, and a valve case 5 that is sandwiched between a lower end 1a of the cylinder 1 in Fig. 1 and a bottom 4b of the outer cylinder 4 and separates the compression-side chamber R2 from the reservoir R, and is used by being interposed between the body and an axle of a vehicle (not shown) to suppress vibrations of the vehicle body and wheels.

[0016] Below, we will explain in detail each part of the shock absorber D. In Fig. 1, the upper end of the cylinder 1 is closed by an annular rod guide 6 that is fitted onto the upper end of the outer cylinder 4, and the lower end is closed by fitting a valve case 5. Then, the cylinder 1, with the rod guide 6 and valve case 5 fitted together, is housed within the outer cylinder 4.

[0017] The outer tube 4 is a cylindrical member with a bottom, including a cylindrical portion 4a and a bottom portion 4b that closes the lower end of the cylindrical portion 4a in Fig. 1, and a crimped portion 4c formed by crimping the upper end of the cylindrical portion 4a from the outer periphery toward the inside to form a flange. The bottom portion 4b includes a flat portion 4b1 provided at the lowest end in Fig. 1, and a cone-shaped outer peripheral portion 4b2 that slopes upward from the outer periphery of the flat portion 4b1, and the inner peripheral surface of the outer peripheral portion 4b2 forms a bottom-side tapered surface 4b3.

[0018] 1 is fitted to the inner periphery of the upper end of the cylinder 1, and the upper, larger diameter portion in Fig. 1 is fitted to the inner periphery of the cylindrical portion 4a of the outer cylinder 4. An annular seal member 7 that is fitted to the inner periphery of the cylindrical portion 4a of the outer cylinder 4 is stacked above the rod guide 6 in Fig. 1.

[0019] Then, when the seal member 7, rod guide 6, cylinder 1, and valve case 5 are housed in the outer cylinder 4 and the upper end of the cylindrical portion 4a of the outer cylinder 4 in Figure 1 is crimped from the outer periphery, the seal member 7, rod guide 6, cylinder 1, and valve case 5 are sandwiched between the crimped portion 4c and the bottom portion 4b of the outer cylinder 4 and fixed inside the outer cylinder 4. When the cylinder 1 is inserted into the outer cylinder 4, an annular gap is formed between the cylinder 1 and the outer cylinder 4, and this annular gap forms a reservoir R that stores liquid and gas.

[0020] The piston rod 2 has a reduced outer diameter at the tip end side, and includes a small diameter portion 2a having a small outer diameter at the tip end side, a large diameter portion 2b having an outer diameter larger than that of the small diameter portion 2a and provided above the small diameter portion 2a in FIG. 1, a step portion 2c provided at the boundary between the small diameter portion 2a and the large diameter portion 2b, and a thread portion 2d provided on the outer periphery of the tip end of the small diameter portion 2a.

[0021] The piston rod 2 is inserted through the rod guide 6 and the inner periphery of the seal member 7 and is inserted into the cylinder 1 so as to be movable in the axial direction, and a piston 3 is attached to the lower end (as viewed in FIG. 1 ) which is the leading end of the piston rod 2 and is movable in the axial direction within the cylinder 1 and divides the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2. The seal member 7 seals between the piston rod 2 and the outer cylinder 4, thereby sealing off the interior of the cylinder 1 and the outer cylinder 4. The extension-side chamber R1 and the compression-side chamber R2 within the thus sealed shock absorber D are filled with a liquid, and a gas such as nitrogen gas or air is sealed in the reservoir R. The liquid filled within the shock absorber D is hydraulic oil, but may be water, an aqueous solution, or other liquids other than hydraulic oil.

[0022] 1, the upper end of the piston rod 2 protrudes outside the cylinder 1, and is provided with a bracket (not shown) at the upper end that connects the piston rod 2 to one of the vehicle body and the axle. A bracket (not shown) is also provided on the bottom 4b of the outer cylinder 4, and the outer cylinder 4 is connected to the other of the vehicle body and the axle via this bracket (not shown). The shock absorber D is used by being interposed between the vehicle body and the axle, and when the vehicle travels on an uneven road surface and the wheels vibrate up and down relative to the vehicle body, the piston rod 2 moves in and out of the cylinder 1, expanding and contracting the shock absorber D, and the piston 3 moves up and down (axially) within the cylinder 1.

[0023] 1, the piston 3 is fitted onto the outer periphery of the small diameter portion 2a of the piston rod 2 and fixed to the piston rod 2 by a piston nut 8 that is screwed onto the threaded portion 2d of the piston rod 2. The piston 3 is assembled to the piston rod 2, and the outer periphery of the piston 3 is in sliding contact with the inner periphery of the cylinder 1, dividing the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 that serve as working chambers. The piston 3 is also annular and includes an extension-side port 3a and a compression-side port 3b that communicate between the extension-side chamber R1 and the compression-side chamber R2.

[0024] Next, an extension-side leaf valve 9 is stacked below the piston 3 in Fig. 1. The extension-side leaf valve 9 is a laminated leaf valve formed by stacking a plurality of annular plates, and is stacked at the lower end of the piston 3 in Fig. 1, and is fixed to the outer periphery of the small diameter portion 2a of the piston rod 2 together with the piston 3. The extension-side leaf valve 9 is stacked at the lower end of the piston 3, and its inner periphery is fixed to the outer periphery of the small diameter portion 2a of the piston rod 2. The extension-side leaf valve 9 is allowed to bend in a direction away from the piston 3 on the outer periphery side, and can open and close an outlet end, which is the lower end in Fig. 1, of the extension-side port 3a provided in the piston 3.

[0025] When the outer circumferential side of the extension-side leaf valve 9 is seated on the piston 3, the extension-side leaf valve 9 closes the outlet end of the extension-side port 3 a. When the outer circumferential side is bent by pressure from the extension-side port 3 a side and separated from the piston 3, the extension-side leaf valve 9 opens the extension-side port 3 a and applies resistance to the flow of liquid passing through the extension-side port 3 a.

[0026] 1, an annular check valve 10 is stacked above the piston 3. The check valve 10 is a perforated check valve with an annular hole 10a in its radial center. When stacked on the piston 3, the check valve 10 closes the outlet end of the compression-side port 3b, which is the upper end in FIG. 1, of the compression-side port 3b, but communicates between the expansion-side port 3a and the expansion-side chamber R1 via the hole 10a. Also stacked above the check valve 10 in FIG. 1 are a cylindrical collar 11, a spring member 12 that biases the check valve 10 toward the piston 3, and an annular valve stopper 13. The spring member 12 is a conical coil spring that is interposed between the check valve 10 and the valve stopper 13 in a compressed state, and constantly biases the check valve 10 toward the piston 3. The spring member 12 may be an elastic body other than a conical coil spring, and although not specifically shown, may be a spring having a circular ring laminated on the upper end of the collar 11 in Fig. 1 and a plurality of arms extending radially downward from the outer periphery of the circular ring at an angle and contacting the back surface of the check valve 10, which is the side opposite the piston, to urge the check valve 10 toward the piston. The spring member 12 is provided to help the check valve 10 quickly return to a position where it closes the compression side port 3b after being deflected, but may be omitted if unnecessary.

[0027] The check valve 10 has its inner periphery fixed to the outer periphery of the small diameter portion 2 a of the piston rod 2, allowing it to flex on its outer periphery. When it is stacked on the piston 3, it closes the compression side port 3 b, and when its outer periphery flexes and compresses the spring member 12, separating it from the piston 3, it opens the compression side port 3 b, allowing liquid to flow through the compression side port 3 b from the compression side chamber R2 to the extension side chamber R1 with almost no resistance.

[0028] The valve stopper 13, spring member 12, collar 11, check valve 10, piston 3, and extension-side leaf valve 9 are assembled in this order to the outer periphery of the small diameter portion 2 a of the piston rod 2, and then fixed to the piston rod 2 by being sandwiched between the piston nut 8, which is screwed to the threaded portion 2 d of the small diameter portion 2 a, and the step portion 2 c of the piston rod 2.

[0029] Next, as shown in Figures 2 to 5, the valve case 5 has a disk-shaped main body 5a, five legs 5b protruding downward from the lower end of the main body 5a in Figure 2, and five ribs 5c protruding downward from between the legs 5b, 5b at the lower end of the main body 5a in Figure 2.

[0030] Each part of the valve case 5 will be described in detail below. The main body 5a is disk-shaped with a hole in the center, and the outer diameter thereof changes halfway in the axial direction. The main body 5a has a small-diameter portion 5a1 at the top and a large-diameter portion 5a2 at the bottom, thereby forming a step portion 5a3 on the outer periphery. The main body 5a also has six exhaust ports 5a4 axially penetrating the main body 5a, five suction ports 5a5 axially penetrating the main body 5a, an annular discharge-side seat portion 5a6 that protrudes downward in Figure 2 from the lower end of the main body 5a and surrounds the outer periphery of the exhaust port 5a4, and an annular suction-side seat portion 5a7 that protrudes upward in Figure 2 from the upper end of the main body 5a and surrounds the outer periphery of the suction port 5a5.

[0031] As shown in Fig. 3, six exhaust ports 5a4 are provided on the main body 5a at equal intervals on the same circumference of the main body 5a, and five suction ports 5a5 are provided on the main body 5a at equal intervals on the same circumference on the outer circumferential side of the exhaust ports 5a4. The number of exhaust ports 5a4 and suction ports 5a5 can be changed as desired.

[0032] 2 and 3, the discharge-side seat portion 5a6 is annular and protrudes downward from the lower end of the main body 5a between the discharge port 5a4 and the suction port 5a5 to surround the outer periphery of the discharge port 5a4. The suction-side seat portion 5a7 is annular and protrudes upward from the upper end of the main body 5a on the outer periphery of the suction port 5a5 to surround the outer periphery of the suction port 5a5.

[0033] The leg portions 5b protrude downward toward the bottom 4b side at intervals in the circumferential direction from the bottom end of the main body 5a, which is the lower end in FIG. 2 facing the bottom 4b side of the outer cylinder 4 of the main body 5a, and are located radially outward of the lower open end of the suction port 5a5. Five leg portions 5b are provided intermittently in the circumferential direction on the valve case 5. More specifically, as shown in FIGS. 3 and 4, the leg portions 5b are disposed radially outwardly of the main body 5a between the suction ports 5a5, 5a5, so as not to overlap with the suction ports 5a5. Thus, the leg portions 5b are positioned so as not to act as a barrier to the flow of liquid from the reservoir R toward the suction port 5a5 and thereby obstruct the flow.

[0034] 2 and 4, the leg 5b has a circumferential width that narrows toward the bottom of the outer cylinder 4, with the circumferential side surfaces forming inclined surfaces 5b1, 5b1. As shown in Figs. 2 and 4, the outer periphery of the bottom side surface of the leg 5b, which is the tip surface facing the bottom 4b of the outer cylinder 4, is provided with a leg-side tapered surface 5b2 that slopes so that the radial width of the leg 5b narrows toward the tip, and the bottom side surface of the leg 5b is flat and extends inward from the leg-side tapered surface 5b2 to a flat surface 5b3. When the valve case 5 is viewed axially, the leg-side tapered surface 5b2 extends toward the inner periphery of the valve case 5 beyond a circle that passes through the inner periphery of the stepped portion 5a3 of the main body 5a.

[0035] Furthermore, a curved portion 5b4 is provided at the base of the main body portion 5a on the inner peripheral side surface of the leg portion 5b facing the inside of the valve case 5 so that the thickness increases in the inward direction, and the radial width of the base portion where the leg portion 5b joins the main body portion 5a is wider in the cross section of the leg portion 5b, and the radial thickness of the base portion is thicker than that of the tip side of the leg portion 5b. Therefore, even if the leg portion 5b is sandwiched between the cylinder 1 and the bottom portion 4b of the outer tube 4 and receives an axial load, the base portion of the leg portion 5b where the leg portion 5b joins the main body portion 5a is reinforced by the curved portion 5b4, preventing deformation such as the leg portion 5b collapsing toward the inner peripheral side of the valve case 5. Note that, in order to prevent the leg portion 5b from collapsing, it is sufficient to increase the radial width of the base portion of the leg portion 5b where the leg portion 5b joins the main body portion 5a. Therefore, instead of the curved portion 5b4, an inclined portion may be provided so that the radial width of the base portion where the leg portion 5b joins the main body portion 5a is wider in the cross section of the leg portion 5b.

[0036] The rib 5c protrudes downward from between the legs 5b at the lower end of the main body 5a in Fig. 2, which is the bottom end of the main body 5a. Specifically, as shown in Fig. 3, the rib 5c is arc-shaped when viewed from the axial direction of the valve case 5, and as shown in Fig. 4, the rib 5c has a central arc-shaped horizontal surface 5c1 that is highest in the radial center and is horizontal to the axial direction, an outer peripheral tapered surface 5c2 that is continuous with the outer periphery of the horizontal surface 5c1, and an inner peripheral tapered surface 5c3 that is continuous with the inner periphery of the horizontal surface 5c1. Both circumferential ends of the rib 5c are connected to the sides of the legs 5b, which increases the strength of the legs 5b and suppresses deformation of the legs 5b when the legs 5b are subjected to an axial load.

[0037] Furthermore, if the inclination angle of the outer peripheral tapered surface 5c2 of the rib 5c relative to a plane perpendicular to the outer tube 4 is θ, and the inclination angle of the bottom side tapered surface 4b3 at the outer peripheral portion 4b2 of the bottom 4b of the outer tube 4 relative to a plane perpendicular to the outer tube 4 is α, then θ≦α.

[0038] The valve case 5 configured in this manner is housed within the outer cylinder 4, with the small-diameter portion 5a1 of the main body 5a fitted onto the inner periphery of the lower end of the cylinder 1, and the leg-side tapered surface 5b2 at the bottom end of the leg 5b abuts against the bottom-side tapered surface 4b3 at the bottom 4b of the outer cylinder 4, and is fixed within the outer cylinder 4 by being sandwiched between the crimped portion 4c of the outer cylinder 4 and the bottom 4b. Note that the leg-side tapered surface 5b2 should be in surface contact with the bottom-side tapered surface 4b3, but it may also be in partial contact with the bottom-side tapered surface 4b3. Because the outer cylinder 4 has the bottom-side tapered surface 4b3 and the valve case 5 has the leg-side tapered surface 5b2, the valve case 5 can be aligned with the outer cylinder 4 and radial displacement of the valve case 5 relative to the outer cylinder 4 can be suppressed. When the crimped portion 4c of the outer tube 4 is crimped, an axial load acts on the outer periphery of the large-diameter portion 5a2 of the main body 5a, which is sandwiched between the cylinder 1 and the bottom 4b of the valve case 5, and on the leg 5b. Because the lower end of the cylinder 1 abuts against the step 5a3, the axial load acts within the range of the step 5a3 when viewed axially of the valve case 5. Because the leg-side tapered surface 5b2 of the leg 5b extends further inward than a circle passing through the inner circumference of the step 5a3 of the main body 5a when viewed axially of the valve case 5, the line of action of the load does not pass through the flat surface 5b3 on the inner periphery of the bottom end of the leg 5b. Therefore, no moment that would open the bottom end of the leg 5b outward due to the load acts on the leg 5b, thereby suppressing bending deformation of the leg 5b due to the load.

[0039] Next, the compression-side leaf valves 14 are stacked below the valve case 5 in Figure 1. The compression-side leaf valves 14 are stacked leaf valves formed by stacking a plurality of annular plates, and are stacked at the lower end of the valve case 5 in Figure 2, and are fixed to the outer periphery of a center rod 15 that is inserted into the inner periphery of the main body 5a of the valve case 5. Because the inner periphery of the compression-side leaf valve 14 is fixed to the center rod 15, it is allowed to bend in a direction away from the valve case 5 on the outer periphery, and can be seated on and lifted from a discharge-side seat portion 5a6 provided on the valve case 5 to open and close the outlet end, which is the lower end in Figure 2 of the discharge port 5a4.

[0040] The center rod 15 includes a shaft portion 15a that is inserted into the inner periphery of the main body portion 5a of the valve case 5, a lower flange 15b that is provided at the lower end of the shaft portion 15a in FIG. 2, and an upper flange 15c that is provided at the tip of the shaft portion 15a in FIG. 2, and the lower flange 15b and the valve case 5 sandwich the inner periphery of the compression-side leaf valve 14.

[0041] When the compression side leaf valve 14 is seated on the valve case 5 on its outer periphery, it blocks the outlet end of the discharge port 5a4, and when the pressure from the discharge port 5a4 side causes the outer periphery to bend and move away from the valve case 5, it opens the discharge port 5a4 and provides resistance to the flow of liquid passing through the discharge port 5a4 from the compression side chamber R2 toward the reservoir R.

[0042] 2, an annular check valve 16 is stacked on the upper side of the valve case 5. The check valve 16 is a perforated check valve with an annular hole 16a in its radial center, and is attached to the outer periphery of the shaft portion 15a of the center rod 15. When stacked on the valve case 5, the check valve 16 seats on the suction-side seat portion 5a7 and closes the outlet end of the suction port 5a5, which is the upper end in FIG. 1, but communicates between the exhaust port 5a4 and the compression-side chamber R2 via the hole 10a.

[0043] 2, a cylindrical collar 17, a spring member 18 that urges the check valve 16 toward the valve case 5, and an annular valve stopper 20 are stacked above the check valve 16. The spring member 18 is a conical coil spring that is interposed between the check valve 16 and the valve stopper 20 in a compressed state, constantly urging the check valve 16 toward the valve case 5. The spring member 18 may be an elastic body other than a conical coil spring, or, although not specifically shown, may be a spring having a circular ring stacked on the upper end of the collar 17 in FIG. 1 and multiple arms that extend radially downward from the outer periphery of the circular ring and abut against the back surface of the check valve 16, which is the side opposite the piston, to urge the check valve 16 toward the piston. The spring member 18 is provided to help the check valve 16 quickly return to a position that closes the suction port 5a5 after deflection, but may be omitted if unnecessary.

[0044] When the outer periphery of the check valve 16 bends, compressing the spring member 18 and separating from the valve case 5, the check valve 16 separates from the suction side seat portion 5a7, opening the suction port 5a5 and allowing liquid to flow through the suction port 5a5 from the reservoir R toward the pressure side chamber R2 with almost no resistance.

[0045] The aforementioned valve stopper 20, spring member 18, collar 17, check valve 16, valve case 5, and compression side leaf valve 14 are fitted onto the outer periphery of the shaft portion 15a of the center rod 15, and are fixed to the center rod 15 by being sandwiched between the lower flange 15b and upper flange 15c of the center rod 15.

[0046] The shock absorber D is configured as described above, and its operation will be described below. First, when the shock absorber D performs an extension operation and the piston 3 moves upward in FIG. 1 relative to the cylinder 1, the upward movement of the piston 3 in FIG. 1 causes the liquid in the expansion-side chamber R1, which is compressed, to bend the expansion-side leaf valve 9 and move to the compression-side chamber R2 through the expansion-side port 3a. The expansion-side leaf valve 9 provides resistance to the flow of liquid from the expansion-side chamber R1 to the compression-side chamber R2, so the pressure in the expansion-side chamber R1 increases.

[0047] Furthermore, as the shock absorber D extends, the liquid equivalent to the volume of the piston rod 2 retracting from the cylinder 1 pushes open the check valve 16 and moves from the reservoir R to the compression-side chamber R2 via the suction port 5a5. Since the check valve 16 offers almost no resistance to the flow of liquid passing through the suction port 5a5, the pressure in the compression-side chamber R2 becomes approximately equal to the pressure in the reservoir R.

[0048] Therefore, during the extension operation of the shock absorber D, the pressure in the extension-side chamber R1 rises, and the pressure in the compression-side chamber R2 becomes substantially equal to the pressure in the reservoir R, causing a difference in pressure between the extension-side chamber R1 and the compression-side chamber R2, causing the shock absorber D to generate a damping force that hinders the extension operation. Note that, during the extension operation of the shock absorber D, as described above, the check valve 16 opens, and the liquid equivalent to the volume of the piston rod 2 withdrawn from the cylinder 1 is supplied from the reservoir R to the cylinder 1, thereby compensating for the volume of the piston rod 2 withdrawn from the cylinder 1. In this way, during the extension operation of the shock absorber D, liquid moves from the reservoir R to the compression-side chamber R2, but the liquid in the reservoir R enters the space A inside the leg 5b through the space A and reaches the compression-side chamber R2 through the suction port 5a5. The circumferential width of the legs 5b of the valve case 5 narrows as it approaches the bottom of the outer cylinder 4, and the circumferential side surfaces of the legs 5b are inclined so that the spacing between the legs 5b, 5b increases as it approaches the tip, thereby increasing the opening area between the legs 5b, 5b and allowing liquid to move smoothly between the legs 5b, 5b without resistance.

[0049] Furthermore, the rib 5c provided between the legs 5b at the lower end of the main body 5a of the valve case 5 has an outer peripheral tapered surface 5c2 that slopes outward away from the bottom 4b of the outer cylinder 4, so that even if the strength of the legs 5b is increased by providing the rib 5c, the degree of reduction in the opening area between the legs 5b can be reduced, and a sufficient opening area can be ensured.The rib 5c has an inner peripheral tapered surface 5c3 that slopes inward away from the bottom 4b of the outer cylinder 4, and a horizontal surface 5c1 formed between the outer peripheral tapered surface 5c2 and the inner peripheral tapered surface 5c3, so that liquid that has entered between the legs 5b from the reservoir R can move smoothly, without resistance, along the horizontal surface 5c1 and the inner peripheral tapered surface 5c3 to the suction port 5a5 located on the inner side of the legs 5b.

[0050] On the other hand, when the shock absorber D contracts and the piston 3 moves downward in Fig. 1 relative to the cylinder 1, the downward movement of the piston 3 causes the liquid in the compressed compression-side chamber R2 to push open the check valve 10, pass through the compression-side port 3b, and move to the expanded expansion-side chamber R1. Since the check valve 10 provides almost no resistance to the flow of liquid passing through the compression-side port 3b, the pressure in the expansion-side chamber R1 and the pressure in the compression-side chamber R2 become approximately equal.

[0051] Furthermore, as the shock absorber D contracts, an excess of liquid corresponding to the volume of the piston rod 2 penetrating into the cylinder 1 occurs in the cylinder 1, and the liquid pushes open the compression-side leaf valve 14 and moves from the compression-side chamber R2 to the reservoir R through the discharge port 5a4. The compression-side leaf valve 14 provides resistance to the flow of liquid from the compression-side chamber R2 to the reservoir R, and the check valve 10 opens, causing the pressures in the compression-side chamber R2 and the extension-side chamber R1, which are in communication with each other, to rise approximately equally. In this way, when the shock absorber D contracts, the liquid corresponding to the volume of the piston rod 2 penetrating into the cylinder 1 is discharged from the cylinder 1 to the reservoir R, thereby compensating for the volume of the piston rod 2 penetrating into the cylinder 1.

[0052] The shock absorber D of this embodiment is a single-rod type shock absorber in which the piston rod 2 is inserted only into the extension-side chamber R1, and the pressure-receiving area of ​​the piston 3 that receives the pressure in the contraction-side chamber R2 is larger than the pressure-receiving area that receives the pressure in the extension-side chamber R1 by the cross-sectional area of ​​the piston rod 2, so that when the pressures in the contraction-side chamber R2 and the extension-side chamber R1 are substantially equal, the piston 3 receives a force in a direction that pushes the piston rod 2 out of the cylinder 1. Therefore, when the shock absorber D performs a contraction operation, it generates a damping force in a direction that pushes the piston rod 2 out of the cylinder 1, thereby hindering the contraction operation.

[0053] As described above, the shock absorber D of this embodiment includes the cylinder 1, the piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, the piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be movable in the axial direction, and dividing the inside of the cylinder 1 into an expansion-side chamber R1 and a compression-side chamber R2, the outer cylinder 4 having a bottom and tubular shape and accommodating the cylinder 1 therein and forming a reservoir R between the cylinder 1 and the outer cylinder 4, and the valve case 5 sandwiched between the end of the cylinder 1 and the bottom 4b of the outer cylinder 4 and separating the compression-side chamber R2 from the reservoir R. The valve case 5 is disc-shaped and has an outer diameter of 1 / 2 mm. The main body 5a has a small diameter portion 5a1 and a large diameter portion 5a2 separated by a step 5a3 that abuts against the end 1a of the inner tube 1, and the small diameter portion 5a1 is fitted to the inner circumference of the cylinder 1 and has a suction port (port) 5a5 that communicates between the pressure-side chamber R2 and the reservoir R. The main body 5a also has a plurality of legs 5b that are spaced apart circumferentially on the outer periphery of the bottom end of the main body 5a that faces the bottom side of the outer tube 4, and protrude from the bottom end toward the bottom 4b to abut against the bottom 4b. The circumferential width of the legs 5b is shorter than the circumferential distance between the legs 5b, and the circumferential width of the legs 5b narrows toward the bottom side of the outer tube 4.

[0054] In the shock absorber D configured in this manner, the circumferential width of the legs 5b of the valve case 5 narrows toward the bottom side of the outer cylinder 4, and the circumferential side surfaces of the legs 5b are inclined so that the spacing between the legs 5b increases toward the tip, so that a sufficient opening area between the legs 5b can be secured without increasing the length of the legs 5b in the axial direction of the valve case 5. Furthermore, since the overall length of the legs 5b does not need to be increased, the slenderness ratio of the legs 5b can be reduced, so that even if a wide opening area between the legs 5b is secured, the reduction in strength of the legs 5b can be kept to a small extent, and strength does not become insufficient.

[0055] Therefore, according to the shock absorber D of this embodiment, a wide opening area between the legs 5b, 5b can be ensured without increasing the overall length of the legs 5b, so the overall length of the shock absorber D is not increased and the stroke length is not sacrificed, and resistance to the liquid passing between the legs 5b, 5b during extension can be reduced. As described above, according to the shock absorber D of this embodiment, deformation and buckling of the valve case 5 can be prevented, while a stable damping force can be generated without impairing mountability on a vehicle.

[0056] Furthermore, the above-mentioned phrase "the circumferential width of the legs 5b is shorter than the circumferential spacing between the legs 5b" means both that the circumferential width of the tips of the legs 5b is shorter than the circumferential spacing between the tips of the legs 5b and that the circumferential width of the bases of the legs 5b is shorter than the circumferential spacing between the bases of the legs 5b. Making the circumferential width of the tips of the legs 5b shorter than the circumferential spacing between the tips of the legs 5b ensures a larger opening area between the legs 5b. Furthermore, making the circumferential width of the bases of the legs 5b shorter than the circumferential spacing between the bases of the legs 5b ensures the strength of the legs 5b, thereby better preventing deformation and buckling of the valve case 5.

[0057] 2, the circumferential side surfaces of the legs 5b are inclined surfaces 5b1, 5b1 over the entire length from the top to the bottom, and the circumferential width of the legs 5b gradually narrows as they approach the bottom of the outer tube 4, but the side surfaces of the legs 5b from midway in the vertical direction to the base side toward the main body 5a in FIG. 2 may be inclined surfaces, and the side surfaces from midway in the vertical direction to the side opposite the main body in FIG. 2 may be vertical surfaces, so that the circumferential width of the tip side, which is the bottom side of the legs 5b, is narrower than the circumferential width of the base side. Conversely, the side surfaces of the legs 5b from midway in the vertical direction to the base side toward the main body 5a in FIG. 2 may be vertical surfaces, and the side surfaces from midway in the vertical direction to the side opposite the main body in FIG. 2 may be inclined surfaces, so that the circumferential width of the tip side, which is the bottom side of the legs 5b, is narrower than the circumferential width of the base side. Furthermore, the side surfaces of the legs 5b may be formed in a stepped shape so that the circumferential width of the legs 5b narrows in stages toward the bottom of the outer cylinder 4. This also ensures a wide opening area between the legs 5b while ensuring the strength of the legs 5b, thereby preventing deformation or buckling of the valve case 5 and generating a stable damping force without impairing mountability on the vehicle.

[0058] Furthermore, the valve case 5 of the shock absorber D of this embodiment includes a rib 5c that protrudes from between the legs 5b, 5b at the bottom end of the main body 5a toward the bottom and is connected to the legs 5b. According to the shock absorber D configured in this manner, the valve case 5 includes the rib 5c connected to the legs 5b. Therefore, even if the circumferential width of the legs 5b is narrowed toward the bottom side of the outer cylinder 4, the legs 5b can be reinforced by the rib 5c. Furthermore, the thickness from the step 5a3 of the main body 5a to the horizontal surface 5c1 of the rib 5c can be ensured, and the strength of the main body 5a can also be improved. Therefore, according to the shock absorber D of this embodiment, the strength of the valve case 5 can be improved and deformation of the valve case 5 can be further suppressed, making it easier to widen the gap between the legs 5b and ensure the opening area between the legs 5b.

[0059] Furthermore, the leg portions 5b of the valve case 5 of the shock absorber D of this embodiment are provided with curved portions 5b4 that widen the radial width on the inner periphery at the base of the main body portion 5a. According to the shock absorber D configured in this manner, the strength of the base portions of the leg portions 5b at the main body portion 5a is improved, so that even if the leg portions 5b are sandwiched between the cylinder 1 and the bottom portion 4b of the outer tube 4 and receive an axial load, deformation of the leg portions 5b such as collapsing toward the inner periphery of the valve case 5 is prevented. Therefore, according to the shock absorber D of this embodiment, the strength of the valve case 5 can be improved and deformation of the valve case 5 can be further suppressed, making it easier to widen the gap between the legs 5b, 5b and ensure the opening area between the legs 5b, 5b.

[0060] In addition, the rib 5c in the valve case 5 of the shock absorber D of this embodiment is arc-shaped when the valve case 5 is viewed from the axial direction, and has an outer peripheral tapered surface 5c2 provided on the outer periphery, an inner peripheral tapered surface 5c3 provided on the inner periphery, and a horizontal surface 5c1 formed between the outer peripheral tapered surface 5c2 and the inner peripheral tapered surface 5c3. In the shock absorber D configured in this manner, the ribs 5c have outer peripheral tapered surfaces 5c2 that slope outwardly away from the bottom 4b of the outer cylinder 4. Therefore, even if the strength of the legs 5b is increased by providing the ribs 5c, the degree of reduction in the opening area between the legs 5b, 5b can be reduced, and the opening area can be sufficiently secured. In addition, the ribs 5c have inner peripheral tapered surfaces 5c3 that slope inwardly away from the bottom 4b of the outer cylinder 4, and a horizontal surface 5c1 formed between the outer peripheral tapered surface 5c2 and the inner peripheral tapered surface 5c3. Therefore, liquid that has seeped into the space between the legs 5b, 5b from the reservoir R can move smoothly, without resistance, along the horizontal surface 5c1 and the inner peripheral tapered surface 5c3 to the suction port 5a5 located on the inner side of the legs 5b.

[0061] Furthermore, the bottom 4b of the outer cylinder 4 of the shock absorber D of this embodiment has a cone-shaped bottom-side tapered surface 4b3 on the inner peripheral side, and the inclination angle α of the bottom-side tapered surface 4b3 with respect to a plane perpendicular to the outer cylinder 4 is equal to or greater than the inclination angle θ of the outer peripheral tapered surface 5c2 with respect to a plane perpendicular to the outer cylinder 4. With the shock absorber D configured in this manner, the distance between the outer peripheral tapered surface 5c2 of the rib 5c and the bottom-side tapered surface 4b3 of the bottom 4b of the outer cylinder 4 does not decrease toward the outer periphery of the valve case 5, and the opening area between the legs 5b, 5b facing the reservoir R is not reduced. Therefore, with the shock absorber D, the bottom-side tapered surface 4b3 is provided on the bottom 4b of the outer cylinder 4 and abuts against the leg-side tapered surfaces 5b2 of the legs 5b of the valve case 5, improving the seating of the valve case 5 with respect to the outer cylinder 4 and ensuring the opening area between the legs 5b, 5b while aligning the valve case 5 with the outer cylinder 4.

[0062] Furthermore, the legs 5b of the valve case 5 of the shock absorber D of this embodiment have leg-side tapered surfaces 5b2 on the outer peripheral side of the bottom side surface, and the leg-side tapered surfaces 5b2 extend more inward than a circle passing through the inner circumference of the step portions 5a3 when the valve case 5 is viewed in the axial direction. With the shock absorber D configured in this manner, even if an axial load acts on the outer periphery of the large-diameter portion 5a2 of the main body 5a of the valve case 5 and the legs 5b when the valve case 5 is sandwiched between the cylinder 1 and the bottom 4b of the outer tube 4, the line of action of the load does not pass through the inner peripheral side of the leg-side tapered surfaces 5b2 of the legs 5b, so no moment that tends to open the bottom-side ends of the legs 5b outward acts, and bending deformation of the legs 5b due to the load can be suppressed.

[0063] 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.

[0064] DESCRIPTION OF SYMBOLS 1: Cylinder, 1a: End, 2: Piston rod, 3: Piston, 4: Outer cylinder, 4b: Bottom, 4b3: Bottom tapered surface, 5: Valve case, 5a: Main body, 5a1: Small diameter portion, 5a2: Large diameter portion, 5a3: Step portion, 5a5: Port (suction port), 5b: Leg, 5b2: Leg side tapered surface, 5b4: Curved portion, 5c: Rib, 5c1: Horizontal surface, 5c2: Outer peripheral tapered surface, 5c3: Inner peripheral tapered surface, D: Shock absorber, R: Reservoir, R1: Expansion side chamber, R2: Compression side chamber

Claims

1. A shock absorber comprising: a cylinder; a piston rod inserted into the cylinder so as to be axially movable; a piston connected to the piston rod, inserted into the cylinder so as to be axially movable, and dividing the interior of the cylinder into an extension-side chamber and a compression-side chamber; a bottomed cylindrical outer cylinder that houses the cylinder therein and forms a reservoir between the cylinder and the outer cylinder; and a valve case that is sandwiched between the end of the cylinder and a bottom of the outer cylinder and separates the compression-side chamber from the reservoir, wherein the valve case has a main body that is disk-shaped and has a small diameter portion and a large diameter portion separated by a step whose outer diameter abuts against the end of the cylinder, the small diameter portion fitting into the inner circumference of the cylinder and having a port that communicates between the compression-side chamber and the reservoir; and a plurality of legs that are provided at intervals in the circumferential direction on the outer periphery of a bottom-side end of the main body that faces the bottom side of the outer cylinder, the legs protruding from the bottom-side end towards the bottom and abutting against the bottom, A shock absorber, wherein a circumferential width of the legs is shorter than a circumferential distance between the legs, and the circumferential width of the legs narrows toward a bottom side of the outer cylinder.

2. A shock absorber as claimed in claim 1, wherein the valve case has a rib which protrudes from between the legs at the bottom end of the main body towards the bottom side and is connected to the legs.

3. A shock absorber as claimed in claim 1, wherein the leg portion has a curved or inclined portion on the inner circumference at the base of the main body portion, which widens the radial width.

4. A shock absorber as claimed in claim 2, wherein the rib is arc-shaped when the valve case is viewed in the axial direction, and has an outer peripheral tapered surface provided on the outer periphery, an inner peripheral tapered surface provided on the inner periphery, and a horizontal surface formed between the outer peripheral tapered surface and the inner peripheral tapered surface.

5. A shock absorber as claimed in claim 4, wherein the bottom of the outer cylinder has a cone-shaped bottom side tapered surface on the inner peripheral side, and the inclination angle of the bottom side tapered surface with respect to a plane perpendicular to the outer cylinder is equal to or greater than the inclination angle of the outer peripheral tapered surface with respect to a plane perpendicular to the outer cylinder.

6. A shock absorber as claimed in claim 5, wherein the leg has a leg-side tapered surface on the outer periphery of the bottom side, and the leg-side tapered surface extends further inward than a circle passing through the inner periphery of the step when the valve case is viewed in the axial direction.

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