Shock absorber

Abstract

A shock absorber (D) of the present invention comprises: a cylinder (1); a piston rod (2) that is inserted into the cylinder (1) so as to be movable in the axial direction; a piston (3) that is connected to the piston rod (2) and partitions the inside of the cylinder (1) into an extension-side chamber (R1) and a pressure-side chamber (R2); a cap (10) that has a cylindrical shape with a bottom, has a small inner diameter portion (insertion portion) (10a2) on the inner periphery of a cylinder portion (10a) into which the other end of the cylinder (1) is inserted, and closes the other end of the cylinder (1); an outer tube (4) that covers the outer peripheral side of the cylinder (1), forms, between the outer tube (4) and the cylinder (1), an annular passage (C) communicating with the extension-side chamber (R1), and is screw-coupled to the inner periphery of the cylindrical portion (10a) of the cap (10) on the tip-end side relative to the small inner diameter portion (insertion portion) (10a2); and a stopper (S) that is attached to the outer tube (4) to face one end of the cylinder (1), and prevents the cylinder (1) from falling off the cap (10).

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 wheels of a saddle-type vehicle, and suppresses vibrations between the body and wheels by the damping force generated when the shock absorber expands or contracts.

[0003] As shown in JP2020-143682A, for example, such a shock absorber is configured to include a cylinder, a piston that is movably inserted into the cylinder and divides the interior of the cylinder into an extension-side chamber and a compression-side chamber filled with hydraulic oil, a piston rod that is movably inserted into the cylinder and connected to the piston, a tank that stores hydraulic oil, a hard-side damping element that is provided on the piston and communicates between the extension-side chamber and the compression-side chamber and provides resistance to the flow of hydraulic oil passing through it, a bypass path that bypasses the hard-side damping element and communicates between the extension-side chamber and the compression-side chamber, and a soft-side damping element that is provided in the bypass path in series with a solenoid valve.

[0004] In a shock absorber configured in this manner, the opening area of ​​the bypass passage is adjusted using an electromagnetic valve, thereby adjusting the distribution ratio of the flow rate of hydraulic oil passing through the hard damping element and the soft damping element, thereby providing a wide range of damping force adjustment and outputting a damping force that is optimal for suppressing vehicle vibrations.

[0005] JP2020-143682A

[0006] In conventional shock absorbers, the outer periphery of the cylinder is covered with an outer tube, and the outer periphery of the cylinder is cut or ground to form an annular groove between the upper and lower ends of the cylinder. This annular groove forms an annular passage between the outer tube and the cylinder that is connected to the extension-side chamber, and a bypass path is formed by the annular passage and an external passage in which a solenoid valve and a soft-side damping element are installed.

[0007] The external passage is provided in a cap that is screwed to the outer periphery of the outer tube, and the cylinder and outer tube are fixed to the cap by clamping a flange provided on the outer periphery of the lower end of the cylinder between the end of the outer tube and the bottom of the cap.

[0008] As described above, in conventional shock absorbers, forming a bypass passage requires groove processing to form an annular groove on the outer periphery of the cylinder, which results in an increase in manufacturing costs.

[0009] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a shock absorber that can reduce manufacturing costs even if it has an annular passage inside.

[0010] In order to solve the above problem, the shock absorber of the present invention includes a cylinder, a piston rod that is inserted into the cylinder so as to be axially movable and that protrudes outward from one end of the cylinder, a piston that is connected to the piston rod and inserted into the cylinder so as to be axially movable and that divides the inside of the cylinder into an extension-side chamber and a compression-side chamber, a cylindrical cap with a bottom that has an insertion portion into the inner periphery of the cylindrical portion into which the other end of the cylinder is inserted and that closes the other end of the cylinder, an outer tube that covers the outer periphery of the cylinder and forms an annular passage between it and the cylinder that is connected to the extension-side chamber, and is screw-connected to the inner periphery of the cylindrical portion of the cap closer to the tip than the fitting portion, and a stopper that is attached to the outer tube and faces one end of the cylinder to prevent the cylinder from falling off the cap.

[0011] With a shock absorber configured in this manner, the other end of the cylinder is inserted into the cylindrical portion of the cap, the outer tube is screwed into the cylindrical portion of the cap, and the outer tube is provided with a stopper facing one end of the cylinder to prevent the cylinder from falling off the cap.This means that there is no need to adopt a structure in which a flange is provided at the other end of the cylinder and the outer tube clamps the flange together with the cap, and therefore there is no need to perform groove processing to form an annular groove on the outer periphery of the cylinder.

[0012] Fig. 1 is a cross-sectional view of a shock absorber according to an embodiment. Fig. 2 is a partially enlarged cross-sectional view of the shock absorber according to an embodiment. Fig. 3 is a diagram showing damping force characteristics of the shock absorber according to an embodiment. Fig. 4 is a partially enlarged cross-sectional view of a shock absorber according to a first modified example of the embodiment. Fig. 5 is a cross-sectional view of a shock absorber according to a second modified example of the embodiment. Fig. 6 is a cross-sectional view of a shock absorber according to a third modified example of the embodiment.

[0013] 1, a shock absorber D in one embodiment includes a cylinder 1, a piston rod 2 movably inserted into the cylinder 1 in the axial direction and protruding outward from an upper end (in FIG. 1) of the cylinder 1, a piston 3 connected to the piston rod 2 and movably inserted into the cylinder 1 in the axial direction, the piston 3 dividing the cylinder 1 into an expansion-side chamber R1 and a compression-side chamber R2, a cylindrical cap 10 with a bottom that closes the lower end (in FIG. 1) of the cylinder 1, an outer tube 4 that covers the outer periphery of the cylinder 1 to form an annular passage C between the cylinder 1 and the cap 10, and a stopper S that is attached to the outer tube 4 and faces the upper end of the cylinder 1 to prevent the cylinder 1 from falling off the cap 10.

[0014] Although not shown, this shock absorber D is installed between the body and rear wheel of a saddle-ride type vehicle such as a motorcycle to suppress vibrations of the body and rear wheel. Note that the shock absorber D may also be used to suppress vibrations of vehicles other than saddle-ride type vehicles.

[0015] Each part of the shock absorber D will now be described in detail. As shown in Fig. 1, the cylinder 1 is cylindrical, and its other end, the lower end in Fig. 1, is closed by a cap 10. A through-hole 1a that communicates between the inside and outside of the cylinder 1 is provided on a side near the upper end in Fig. 1, which is one end of the cylinder 1. A piston rod 2 is inserted into the cylinder 1 so as to be movable in the axial direction, and its tip, the upper end in Fig. 1, which is the tip of the piston rod 2, protrudes outward from the upper end of the cylinder 1 in Fig. 1.

[0016] The piston rod 2 has a small diameter portion 2a at its lower end in Fig. 1, the outer diameter of which is smaller than that of the upper portion, and the piston 3 is attached to its outer periphery. A bracket 6 that can be connected to the body of a saddle-type vehicle is attached to the upper end of the piston rod 2 in Fig. 1.

[0017] A piston 3 attached to a piston rod 2 is inserted into the cylinder 1 so as to be axially movable, and the interior of the cylinder 1 is divided by the piston 3 into an expansion-side chamber R1 above the piston 3 and a compression-side chamber R2 below the piston 3. The expansion-side chamber R1 and the compression-side chamber R2 are filled with a liquid such as hydraulic oil. Note that, although the liquid is hydraulic oil in this embodiment, it may be liquid other than hydraulic oil, such as water or an aqueous solution.

[0018] Next, the piston 3 is annular and attached to the outer periphery of the small diameter portion 2a of the piston rod 2, and is provided with an expansion-side port 3a and a compression-side port 3b that respectively communicate in parallel with the expansion-side chamber R1 and the compression-side chamber R2. An expansion-side main damping valve 13 is annular and attached to the outer periphery of the small diameter portion 2a and opens and closes the expansion-side port 3a, and is stacked at the lower end of the piston 3 in FIG. 1. Also, an expansion-side main damping valve 14 is annular and attached to the outer periphery of the small diameter portion 2a and opens and closes the compression-side port 3b, and is stacked at the upper end of the piston 3 in FIG. 1. The piston 3, the expansion-side main damping valve 13, and the compression-side main damping valve 14 are fitted onto the outer periphery of the small diameter portion 2a of the piston rod 2, and are fixed to the piston rod 2 by a piston nut 15 that is threaded onto the lower end of the small diameter portion 2a.

[0019] In the shock absorber D of this embodiment, the expansion-side main damping valve 13 is a laminated leaf valve that is configured by stacking a plurality of annular plates on the lower end of the piston 3 in FIG. 1 , has an inner circumferential side fixed, and opens the expansion-side port 3a when the outer circumferential side is deflected by the pressure in the expansion-side chamber R1. The expansion-side main damping valve 13 is capable of opening and closing the expansion-side port 3a, and opens the valve to provide resistance to the flow of fluid passing through the expansion-side port 3a from the expansion-side chamber R1 to the compression-side chamber R2 when the shock absorber D expands, and closes the valve to block the expansion-side port 3a when the shock absorber D contracts. Note that the expansion-side main damping valve 13 may be a damping valve other than a laminated leaf valve as long as it is a damping valve that provides resistance to the flow of fluid from the expansion-side chamber R1 to the compression-side chamber R2 and can exert a damping force that prevents the expansion of the shock absorber D when the shock absorber D expands.

[0020] In contrast, in the shock absorber D of this embodiment, the compression side main damping valve 14 is a laminated leaf valve configured by stacking multiple annular plates on the upper end of the piston 3 in FIG. 1 , with the inner circumferential side fixed and the outer circumferential side deflected by the pressure in the compression side chamber R2, opening the compression side port 3b. The compression side main damping valve 14 is capable of opening and closing the compression side port 3b, and opens the valve to provide resistance to the flow of fluid passing through the compression side port 3b from the compression side chamber R2 to the expansion side chamber R1 when the shock absorber D contracts, and closes the valve to block the compression side port 3b when the shock absorber D expands. Note that the compression side main damping valve 14 may be a damping valve other than a laminated leaf valve as long as it provides resistance to the flow of fluid from the compression side chamber R2 to the expansion side chamber R1 and is capable of exerting a damping force that prevents the shock absorber D from contracting when the shock absorber D contracts. Also, although not shown, an orifice is provided in parallel with the expansion side main damping valve 13 and the compression side main damping valve 14. The orifice is formed, for example, by a notch provided in the annular plate that constitutes the extension side main damping valve 13 and the compression side main damping valve 14, or by a stamping provided in the valve seat of the piston 3 on which the annular plate is seated and released.

[0021] In this way, the expansion-side port 3a and the compression-side port 3b of the piston 3 communicate with the expansion-side chamber R1 and the compression-side chamber R2. Furthermore, when the expansion-side main damping valve 13 and the compression-side main damping valve 14 are closed, the orifice provides resistance to the flow of fluid passing through the expansion-side port 3a and the compression-side port 3b and moving back and forth between the expansion-side chamber R1 and the compression-side chamber R2. When the expansion-side main damping valve 13 and the compression-side main damping valve 14 are open, the expansion-side main damping valve 13 provides resistance to the flow of fluid passing through the expansion-side port 3a, and the compression-side main damping valve 14 provides resistance to the flow of fluid passing through the compression-side port 3b. In this embodiment, the expansion-side port 3a, the compression-side port 3b, the orifice, the expansion-side main damping valve 13, and the compression-side main damping valve 14 configure a main damping passage M that provides resistance to the flow of fluid moving between the expansion-side chamber R1 and the compression-side chamber R2. The main damping passage M may be configured to include only a single passage and a bidirectional valve such as an orifice or a choke that is provided in the passage and provides resistance to the flow of fluid reciprocating between the expansion-side chamber R1 and the compression-side chamber R2.

[0022] As shown in Figure 1, the outer tube 4 is cylindrical and covers the outer periphery of the cylinder 1, forming an annular passage C with the annular gap between it and the cylinder 1. The outer tube 4 has a threaded portion 4a slightly above the lower end of its outer periphery, an annular groove 4b provided on its inner periphery near its upper end, and an annular groove 4c provided on its inner periphery at a position spaced below the annular groove 4b. The lower end of the outer tube 4 in Figure 1 is closed by a cap 10 that is screwed together using the threaded portion 4a on the outer periphery.

[0023] Furthermore, a stopper S is provided inside the outer tube 4, which is composed of an annular collar 11 and a snap ring 12 that is fitted into the annular groove 4c and prevents the collar 11 from slipping out upward in FIG. 1.

[0024] The collar 11 is fitted onto the inner periphery of the outer tube 4 and includes a cylindrical fitting portion 11a that fits onto the outer periphery of the upper end (in FIG. 1 ), which is one end of the cylinder 1, and an opposing portion 11b that is provided on the inner periphery of the fitting portion 11a and faces the upper end of the cylinder 1, and is restricted from moving upward in FIG. 1 by a snap ring 12. Since the collar 11 is restricted from moving upward in FIG. 1 relative to the outer tube 4 by the snap ring 12 fixed to the inner periphery of the outer tube 4, a stopper S formed by the collar 11 and snap ring 12 restricts upward movement of the cylinder 1 in FIG. 1 and prevents it from coming off the cap 10. The collar 11 also positions the cylinder 1 concentrically with the outer tube 4 in the radial direction and closes the upper end (in FIG. 1 ) of the annular passage C between the cylinder 1 and the outer tube 4.

[0025] A snap ring 16 is also fitted in the annular groove 4b on the upper end side of the outer tube 4. This snap ring 16 abuts against the outer periphery at the upper end (in Figure 1) of a rod guide 17 that is fitted onto the inner periphery at the upper end of the outer tube 4, and restricts the rod guide 17 from moving upward (in Figure 1) from the outer tube 4.

[0026] The rod guide 17 is annular and has an annular seal member 17a on its inner periphery that slides against the outer periphery of the piston rod 2, and an annular bush 17b. The seal member 17a seals the outer periphery of the piston rod 2 to airtightly seal the inside of the cylinder 1, and the bush 17b guides the axial movement of the piston rod 2.

[0027] In addition, a gap is provided between the lower end of the rod guide 17 in Figure 1 and the snap ring 12 at the stopper S, so that when disassembling the shock absorber D, the rod guide 17 can be pushed into the gap to remove the snap ring 16 that restricts the rod guide 17 from moving upward in Figure 1.

[0028] The cap 10 is cylindrical with a bottom, and has a cylindrical portion 10a and a bottom portion 10b that closes the lower end of the cylindrical portion 10a. The lower end of the cylinder 1 is inserted into the cylindrical portion 10a, and the cylindrical portion 10a is screwed to the outer periphery of the outer tube 4.

[0029] More specifically, as shown in FIG. 2, the inner diameter of the cylindrical portion 10a increases in four stages from the bottom portion 10b toward the tip, and the cylindrical portion 10a includes a minimum inner diameter portion 10a1 having the smallest inner diameter at its deepest portion, a small inner diameter portion 10a2 adjacent to and above the minimum inner diameter portion 10a1 in FIG. 2 and having an inner diameter larger than that of the minimum inner diameter portion 10a1, a medium inner diameter portion 10a3 adjacent to and above the small inner diameter portion 10a2 in FIG. 2 and having an inner diameter larger than that of the small inner diameter portion 10a2, and a large inner diameter portion 10a4 adjacent to and above the medium inner diameter portion 10a3 in FIG. 2 and having the largest inner diameter. The cylindrical portion 10a also includes a small diameter step 10a5 as a second step formed between the minimum inner diameter portion 10a1 and the small inner diameter portion 10a2, a medium diameter step 10a6 formed between the small inner diameter portion 10a2 and the medium inner diameter portion 10a3, and a large diameter step 10a7 as a first step formed between the medium inner diameter portion 10a3 and the large inner diameter portion 10a4. The cylindrical portion 10a also includes an annular groove 10a8 on the inner periphery of the large inner diameter portion 10a4 and a threaded portion 10a9 on the inner periphery of the large inner diameter portion 10a4 and above the annular groove 10a8 in Fig. 1. The cap 10 also includes a bracket 10c at the lower end of the bottom portion 10b that can be connected to a swing arm that holds a rear wheel of a saddle-ride type vehicle (not shown). In this embodiment, the piston rod 2 is connected to the body of the saddle-riding type vehicle, and the cap 10 is connected to the rear wheel of the saddle-riding type vehicle. However, the piston rod 2 may be connected to the rear wheel of the saddle-riding type vehicle, and the cap 10 may be connected to the body of the saddle-riding type vehicle.

[0030] 1, in this embodiment, the cap 10 is provided with a tank 18 integrally at the tip of a tank connecting portion 10d extending from the side of the cylindrical portion 10a. The tank 18 is cylindrical and contains a bladder 19 therein. The tank 18 is divided by the bladder 19 into a liquid chamber L filled with liquid and an air chamber G filled with gas. Note that gas is sealed in the air chamber G so that the pressure in the air chamber G is at least equal to or greater than atmospheric pressure when the shock absorber D is fully extended. Note that the liquid chamber L and the air chamber G in the tank 18 can be separated by a free piston in addition to using an elastic partition such as the bladder 19 or a diaphragm.

[0031] Next, the outer periphery of the lower end of the cylinder 1 is press-fitted into the inner periphery of the small inner diameter portion 10a2 of the tubular portion 10a of the cap 10, thereby fixing the cylinder 1 to the cap 10. In this manner, the small inner diameter portion 10a2 functions as an insertion portion into which the cylinder 1 is inserted. The other end of the cylinder 1, which is the lower end in FIG. 2, is inserted into the small inner diameter portion 10a2 until it abuts against the small diameter step 10a5, which is the second step portion of the tubular portion 10a.

[0032] The outer tube 4 is inserted into the large inner diameter portion 10a4 of the cylindrical portion 10a of the cap 10, and the threaded portion 4a on the outer periphery is threadedly coupled to a threaded portion 10a9 provided on the inner periphery of the large inner diameter portion 10a4, thereby fixing the outer tube 4 to the cap 10. The lower end of the outer tube 4 in FIG. 2 abuts against a large diameter step 10a7, which serves as a first step, of the cylindrical portion 10a, and an axial force acting downward from the threaded portion 4a generates a frictional force between the threads of the threaded portions 4a, 10a9, thereby firmly fixing the outer tube 4 to the cap 10. A seal ring 20 that fits tightly against the outer periphery of the outer tube 4 is housed in an annular groove 10a8 provided on the inner periphery of the large inner diameter portion 10a4 of the cylindrical portion 10a, thereby sealing the gap between the outer tube 4 and the cap 10.

[0033] When the cylinder 1 and outer tube 4 are attached to the cap 10 in this manner, the fitting portion 11a of the collar 11 of the stopper S attached to the inner periphery of the outer tube 4 fits onto the outer periphery of the upper end of the cylinder 1 in FIG. 1, and the opposing portion 11b abuts against the upper end of the cylinder 1 or faces it with a small gap between them. As a result, the upper end of the cylinder 1 is aligned with the cap 10 and the outer tube 4 by the stopper S, and the cylinder 1 is prevented from falling off from the small inner diameter portion 10a2, which serves as the insertion portion for the cap 10.

[0034] Furthermore, when the cylinder 1 and the outer tube 4 are attached to the cap 10, the outer tube 4 covers the outer periphery of the cylinder 1 and forms an annular passage C between the cylinder 1 and the outer tube 4, as described above. A through hole 1a is provided near the upper end of the cylinder 1, and the annular passage C communicates with the expansion-side chamber R1 inside the cylinder 1 through the through hole 1a.

[0035] The cap 10 also includes an external passage P that is connected to the expansion-side chamber R1 and the compression-side chamber R2 via the annular passage C. Specifically, the external passage P includes a first port P1 that opens to the inner periphery of the medium-inner-diameter portion 10a3, which is located closer to the bottom than the tip of the outer tube 4 of the tubular portion 10a, and is connected to the annular passage C; a second port P2 that opens to the inner periphery of the minimum-inner-diameter portion 10a1, which is located closer to the bottom than the cylinder 1, and is connected to the compression-side chamber R2; and a connecting passage P3 that connects the first port P1 and the second port P2. Thus, the annular passage C and the external passage P communicate with the expansion-side chamber R1 and the compression-side chamber R2, bypassing the main damping passage M, and thus form a bypass path B. Because the lower end of the outer tube 4 abuts against the large-diameter step 10a7, there is no risk of the outer tube 4 blocking the first port P1. Furthermore, because the outer periphery of the lower end of the cylinder 1 is press-fitted into the inner periphery of the small inner diameter portion 10a2 of the cap 10, the compression-side chamber R2 is not communicated with the annular passage C through the gap between the cylinder 1 and the cap 10. Furthermore, because the second port P2 opens to the inner periphery of the minimum inner diameter portion 10a1, the second port P2 can be opened linearly from the lateral direction relative to the cap 10, making it possible to form the second port P2 easily and at low cost. Note that if the minimum inner diameter portion 10a1 is not provided in the tubular portion 10a, the second port P2 may be provided to open from the bottom portion 10b, and the other end face of the cylinder 1 may be abutted against the bottom portion 10b.

[0036] Furthermore, the tank connecting portion 10d of the cap 10 is provided with: a variable damping valve 21 that is arranged in the external passage P and is capable of adjusting the flow path area of ​​the bypass passage B; an extension side auxiliary damping valve 22 that is arranged in series with the variable damping valve 21 in the external passage P and provides resistance to the flow of fluid from the extension side chamber R1 to the compression side chamber R2; and a compression side auxiliary damping valve 23 that is arranged in series with the variable damping valve 21 in the external passage P and in parallel with the extension side auxiliary damping valve 22 and provides resistance to the flow of fluid from the compression side chamber R2 to the expansion side chamber R1. Furthermore, a part of the external passage P that is closer to the compression side chamber than the locations of the variable damping valve 21, the extension side auxiliary damping valve 22, and the compression side auxiliary damping valve 23 is connected to the fluid chamber L in the tank 18.

[0037] In this embodiment, the variable damping valve 21 includes a valve element 21a that can open and close the bypass path B, a spring 21b that biases the valve element 21a to close it, and a solenoid 21c that can generate a thrust that pushes the valve element 21a in the valve opening direction against the biasing force of the spring 21b, and is an electromagnetic valve that can adjust the degree of valve opening in accordance with the amount of current supplied to the solenoid 21c and closes when the current to the solenoid 21c is cut off. Note that the variable damping valve 21 is an electromagnetic valve that can adjust the degree of valve opening in this way, but it may also be an electromagnetic valve that can adjust the valve opening pressure, or it may be a variable valve that manually adjusts the valve opening degree or the valve opening pressure.

[0038] The expansion-side auxiliary damping valve 22 is a damping valve that opens to provide resistance to the flow of liquid from the expansion-side chamber R1 to the compression-side chamber R2, and closes to block the passage of liquid from the compression-side chamber R2 to the expansion-side chamber R1, and is a damping valve that provides smaller resistance to the flow of liquid than the expansion-side main damping valve 13 when the flow rate through the valve is the same.

[0039] The compression side auxiliary damping valve 23 is a damping valve that opens to provide resistance to the flow of liquid from the compression side chamber R2 to the expansion side chamber R1, and closes to block the passage of liquid from the expansion side chamber R1 to the compression side chamber R2, and when the flow rate of liquid passing through is the same, the resistance that it provides to the flow of liquid is smaller than that of the compression side main damping valve 14. Note that an orifice may be provided in parallel with the expansion side auxiliary damping valve 22 and the compression side auxiliary damping valve 23.

[0040] The shock absorber D of this embodiment is configured as described above, and operation of the shock absorber D will be described below. When the shock absorber D extends, the piston rod 2 retracts from the cylinder 1, causing the piston 3 to compress the extension-side chamber R1. As a result, fluid in the extension-side chamber R1 flows through an orifice (not shown) in the main damping passage M, the extension-side main damping valve 13 in the main damping passage M, or the extension-side auxiliary damping valve 22 in the bypass path B, and into the compression-side chamber R2. At the same time, fluid equivalent to the volume of the piston rod 2 retracted from the cylinder 1 is supplied from the tank 18 into the cylinder 1. Resistance is applied to the flow of fluid from the extension-side chamber R1 to the compression-side chamber R2 by the orifice (not shown), the main damping passage M, or the extension-side auxiliary damping valve 22, and an extension-side damping force is generated due to this resistance. During extension of the shock absorber D, the distribution ratio of fluid passing through the main damping passage M and the extension-side auxiliary damping valve 22 changes depending on the amount of current supplied to the variable damping valve 21. With regard to the resistance provided when the liquid passes through the main damping passage M, when the extension speed of the shock absorber D is in the low-speed range, the extension side main damping valve 13 does not open and an orifice (not shown) provides resistance to the flow of the liquid, whereas when the extension speed of the shock absorber D is in the high-speed range, the extension side main damping valve 13 opens and provides resistance to the flow of the liquid by the extension side main damping valve 13.

[0041] Specifically, during an extension operation of the shock absorber D, when the variable damping valve 21 is open, the fluid passes through the main damping passage M and the extension side auxiliary damping valve 22, but when the variable damping valve 21 is closed, the bypass path B is blocked and the fluid cannot pass through the extension side auxiliary damping valve 22, but passes only through the main damping passage M and moves from the extension side chamber R1 to the compression side chamber R2. Furthermore, when a current is supplied to the variable damping valve 21 to open it and the amount of current supplied is increased, the degree of opening of the variable damping valve 21 increases and the flow rate of fluid passing through the bypass path B increases, so that the proportion of fluid passing through the extension side auxiliary damping valve 22 increases and the proportion of fluid passing through the main damping passage M decreases. Therefore, as shown in FIG. 3 , the damping force characteristics generated by the shock absorber D during an extension operation can be changed within a range from soft characteristics generated mainly by the extension side auxiliary damping valve 22 to hard characteristics generated mainly by the main damping passage M by adjusting the amount of current supplied to the variable damping valve 21.

[0042] Conversely, when the shock absorber D is contracting, the piston rod 2 enters the cylinder 1 and the piston 3 compresses the compression-side chamber R2. Then, the fluid in the compression-side chamber R2 passes through an orifice (not shown) in the main damping passage M, the compression-side main damping valve 14 in the main damping passage M, or the compression-side auxiliary damping valve 23 in the bypass path B and moves to the expansion-side chamber R1, and an amount of fluid equivalent to the volume of the piston rod 2 that entered the cylinder 1 is discharged from the compression-side chamber R2 to the tank 18. Resistance is applied to the flow of fluid from the compression-side chamber R2 to the expansion-side chamber R1 by the main damping passage M or the compression-side auxiliary damping valve 23, and a compression-side damping force is generated due to this resistance. Then, when the shock absorber D is contracting, the distribution ratio of the fluid passing through the main damping passage M and the compression-side auxiliary damping valve 23 changes depending on the amount of current supplied to the variable damping valve 21. Regarding the resistance provided when the liquid passes through the main damping passage M, when the contraction speed of the shock absorber D is in the low-speed range, the compression side main damping valve 14 does not open and resistance is provided to the flow of the liquid by an orifice not shown, and when the contraction speed of the shock absorber D is in the high-speed range, the compression side main damping valve 14 opens and resistance is provided to the flow of the liquid by the compression side main damping valve 14.

[0043] Specifically, when the shock absorber D is contracting, the fluid passes through the main damping passage M and the compression side secondary damping valve 23 when the variable damping valve 21 is open, but when the variable damping valve 21 is closed, the bypass path B is blocked and the fluid cannot pass through the compression side secondary damping valve 23, so that the fluid passes only through the main damping passage M and moves from the compression side chamber R2 to the expansion side chamber R1. Furthermore, when a current is supplied to the variable damping valve 21 to open it and the amount of current supplied is increased, the degree of opening of the variable damping valve 21 increases and the flow rate of fluid passing through the bypass path B increases, so that the proportion of fluid passing through the compression side secondary damping valve 23 increases and the proportion of fluid passing through the main damping passage M decreases. Therefore, the damping force characteristics generated by the shock absorber D during contraction can be changed within a range from soft characteristics generated mainly by the compression side secondary damping valve 23 to hard characteristics generated mainly by the main damping passage M by adjusting the amount of current supplied to the variable damping valve 21, as shown in FIG. 3 .

[0044] As described above, the shock absorber D of this embodiment includes the cylinder 1, the piston rod 2 that is inserted into the cylinder 1 so as to be axially movable and that protrudes outward from one end of the cylinder 1, the piston 3 that is connected to the piston rod 2, inserted into the cylinder 1 so as to be axially movable, and that divides the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2, the cap 10 that is cylindrical and has a bottom and a small inner diameter portion (insertion portion) 10a2 into which the other end of the cylinder 1 is inserted on the inner periphery of the cylindrical portion 10a, thereby closing the other end of the cylinder 1, the cylindrical outer tube 4 that covers the outer peripheral side of the cylinder 1 and forms, between the cylinder 1 and the outer periphery, an annular passage C that is connected to the extension-side chamber R1, and is screw-coupled to the inner periphery of the cylindrical portion 10a of the cap 10 on the tip side of the small inner diameter portion (insertion portion) 10a2, and the stopper S that is attached to the outer tube 4 and faces one end of the cylinder 1 to prevent the cylinder 1 from falling off the cap 10.

[0045] With shock absorber D configured in this manner, the other end of the cylinder 1 is inserted into the tubular portion 10a of the cap 10, the outer tube 4 is screwed to the tubular portion 10a of the cap 10, and the outer tube 4 is provided with a stopper S facing one end of the cylinder 1 to prevent the cylinder 1 from falling off the cap 10, so there is no need to employ a structure in which a flange is provided at the other end of the cylinder 1 and the outer tube 4 sandwiches the flange together with the cap 10, eliminating the need to perform groove machining to form an annular groove on the outer periphery of the cylinder 1. Therefore, with shock absorber D of this embodiment, it is not necessary to perform groove machining on the cylinder 1 to form the annular passage C between the cylinder 1 and the outer tube 4, and therefore manufacturing costs can be reduced even if the shock absorber has an annular passage C inside.

[0046] Furthermore, in the shock absorber D of this embodiment, the cap 10 has a large-diameter step (first step) 10a7 on the inner periphery of the cylindrical portion 10a that abuts against the end of the outer tube 4, and the cylinder 1 is press-fitted into the small-diameter portion (insertion portion) 10a2 of the cap 10. According to the shock absorber D configured in this manner, the end of the outer tube 4 can abut against the first step (large-diameter step) 10a7, so that an axial force can be applied to the outer tube 4 to firmly fix the outer tube 4 to the cap 10, and the cylinder 1 is press-fitted into the small-diameter portion (insertion portion) 10a2 of the cap 10, so that the annular passage C is prevented from communicating with the compression-side chamber R2 through the gap between the cylinder 1 and the cap 10, and therefore it is not necessary to install a seal member between the cylinder 1 and the cap 10, thereby further reducing manufacturing costs. Furthermore, since the outer tube 4 abuts against the large diameter step (first step) 10a7, by locating the first port P1 of the bypass passage B closer to the bottom than the large diameter step (first step) 10a7 of the cylindrical portion 10a, it is possible to prevent the outer tube 4 from closing the first port P1. Furthermore, since the stopper S only needs to prevent the cylinder 1 from falling off the cap 10, there is no need to apply axial force to the cylinder 1, so high strength is not required and an inexpensive configuration can be adopted.

[0047] The stopper S in the shock absorber D of this embodiment includes a snap ring 12 attached to the inner periphery of the outer tube 4, and a collar 11 having a fitting portion 11a fitted to the inner periphery of the outer tube 4 and fitted to the outer periphery of one end of the cylinder 1, and a facing portion 11b provided on the inner periphery of the fitting portion 11a and facing the one end of the cylinder 1. With the shock absorber D configured in this manner, the collar 11 fitted to the inner periphery of the outer tube 4 allows the one end of the cylinder 1 to be aligned concentrically with the outer tube 4, the use of the snap ring 12 makes it easy to fix the collar 11, and the inner periphery of the outer tube 4 can be machined inexpensively. Note that it is also possible to configure the stopper S using only the collar 11 by screwing the collar 11 to the inner periphery of the outer tube 4, but this requires machining to provide threaded portions on the inner periphery of the outer tube 4 and the outer periphery of the collar 11, making it more advantageous in terms of cost to configure the stopper S using the snap ring 12 and collar 11.

[0048] 1, a fitting portion that fits onto the outer periphery of the cylinder 1 can be provided on the outer periphery of the rod guide 17. In this case, the rod guide 17 approaches one end of the cylinder 1 and faces or abuts against it, making it impossible to push the rod guide 17 into the outer tube 4. If a structure is adopted in which the rod guide 17 is fixed with a snap ring 16, it will be impossible to disassemble the shock absorber D. Therefore, it is possible to do away with the snap ring 16 and provide threaded portions on the outer periphery of the rod guide 17 and the inner periphery of the outer tube 4, and to threadably connect the rod guide 17 to the outer tube 4.

[0049] Furthermore, the shock absorber D of this embodiment includes a main damping passage M that provides resistance to the flow of liquid traveling between the expansion-side chamber R1 and the compression-side chamber R2, a bypass passage B that bypasses the main damping passage M and connects the expansion-side chamber R1 and the compression-side chamber R2, and a variable damping valve 21 that provides resistance to the flow of liquid passing through the bypass passage B. The cap 10 has a first port P1 that opens closer to the bottom than the tip of the outer tube 4 of the cylindrical portion 10a and is connected to the annular passage C, and a second port P2 that opens closer to the bottom than the cylinder 1 and is connected to the compression-side chamber R2. The bypass passage B connects the first port P1 and the second port P2 and is formed by an external passage P in which the variable damping valve 21 is provided, and the annular passage C.

[0050] With the shock absorber D configured in this manner, the damping characteristics can be adjusted by the variable damping valve 21 provided in the bypass path B, and even when the cylinder 1 is inserted into the cylindrical portion 10a of the cap 10 and the outer tube 4 is screwed together, the external passage P that constitutes the bypass path B is not blocked by the cylinder 1 and the outer tube 4, and there is no need to provide holes in the cylinder 1 and the outer tube 4 to ensure communication between the bypass path B and the external passage P, which further reduces manufacturing costs and improves assembly ease.

[0051] 2 , which is the other end of the cylinder 1, is press-fitted into the small inner diameter portion 10a2 of the cap 10 as an insertion portion, but as in the shock absorber D1 of a first modified example of an embodiment shown in FIG. 4 , a thread groove may be formed on the inner periphery of the small inner diameter portion 10a2 and a threaded portion 1b may be formed on the outer periphery of the other end of the cylinder 1, and the other end of the cylinder 1 may be screwed to the small inner diameter portion 10a2 of the cap 10 to fix the cylinder 1 to the cap 10. In this case, if a small diameter step portion (second step portion) 10a5 that abuts on the other end surface of the cylinder 1 is formed on the tubular portion 10a of the cap 10, when the cylinder 1 is screwed to the cap 10, the cylinder 1 is pressed against the small diameter step portion (second step portion) 10a5, and the gap between the cylinder 1 and the cap 10 is sealed. This eliminates the need for a sealing member, and the manufacturing cost of the shock absorber D can be further reduced.

[0052] Furthermore, as described above, the other end of the cylinder 1 is press-fitted into the small inner diameter portion 10a2 that serves as the insertion portion of the tubular portion 10a of the cap 10. However, if the cylinder 1 is not fixed to the cap 30 simply by inserting the other end of the cylinder 1 into the small inner diameter portion 10a2, the inner diameter of the tubular portion 30a may be expanded in three stages from the bottom 30b side toward the tip, as in shock absorber D2 of the second modified embodiment of the embodiment shown in Figure 5, thereby eliminating the steps where the end face of the outer tube 4 abuts against the tubular portion 30a, and threading the outer tube 4 to the tubular portion 10a of the cap 10, thereby clamping the cylinder 1 between the stopper S and the cap 30 and fixing the cylinder 1. In this case, the cylindrical portion 30a of the cap 30 includes a small diameter portion 30a1 having the smallest inner diameter at its deepest portion, a medium diameter portion 30a2 adjacent to the small diameter portion 30a1 above in FIG. 2 and having an inner diameter larger than that of the small diameter portion 30a1, a large diameter portion 30a3 adjacent to the medium diameter portion 30a2 above in FIG. 5 and having an inner diameter larger than that of the medium diameter portion 30a2, a small step portion 30a4 as a second step portion formed between the small diameter portion 30a1 and the medium diameter portion 30a2, and a large step portion 30a5 formed between the medium diameter portion 30a2 and the large diameter portion 30a3. In addition, the cylindrical portion 30a includes an annular groove 30a6 on the inner circumference of the large diameter portion 30a3 and a thread portion 30a7 on the inner circumference of the large diameter portion 30a3 above the annular groove 30a6 in FIG. 5.

[0053] The outer periphery of the lower end of the cylinder 1 is inserted into the inner periphery of the medium diameter portion 30a2 of the tubular portion 10a of the cap 10. In this manner, the medium diameter portion 30a2 functions as an insertion portion into which the cylinder 1 is inserted. The other end of the cylinder 1, which is the lower end in FIG. 5, is inserted into the medium diameter portion 30a2 until it abuts against the small step portion 30a4, which is the second step portion of the tubular portion 30a.

[0054] The outer tube 4 is inserted into the large diameter portion 30a3 of the cylindrical portion 30a of the cap 30, and the threaded portion 4a on the outer periphery is screwed to a threaded portion 30a7 provided on the inner periphery of the large diameter portion 30a3, thereby fixing the outer tube 4 to the cap 10. When the outer tube 4 is screwed to the threaded portion 30a7, the cylinder 1 is sandwiched between a stopper S attached to the inner periphery of the outer tube 4 and a small step portion 30a4 serving as a first step portion of the cap 30, and the cylinder 1 is fixed to the cap 30.

[0055] A seal ring 20 that fits tightly against the outer periphery of the outer tube 4 is housed in an annular groove 30a6 provided on the inner periphery of the large diameter portion 30a3 of the cylindrical portion 30a, thereby sealing the gap between the outer tube 4 and the cap 30.

[0056] Furthermore, when the cylinder 1 and the outer tube 4 are attached to the cap 10, the outer tube 4 covers the outer periphery of the cylinder 1 and forms an annular passage C between the cylinder 1 and the outer tube 4, as described above. A through hole 1a is provided near the upper end of the cylinder 1, and the annular passage C communicates with the expansion-side chamber R1 inside the cylinder 1 through the through hole 1a. Like the cap 10, the cap 30 is equipped with a bracket 30c and a tank connecting portion 30d that is connected to the tank 18. Furthermore, an external passage P that communicates with the annular passage C, a variable damping valve 21, an expansion-side auxiliary damping valve 22, and a compression-side auxiliary damping valve 23 are provided within the tank connecting portion 30d. In the shock absorber D2 of the second modification, the cylinder 1 is sandwiched between a small step 30a4 serving as a second step formed on the inner periphery of the tubular portion 30a of the cap 30 and the stopper S of the outer tube 4, so that the other end face of the cylinder 1 and the small step 30a4 are not in close contact with each other, and the compression-side chamber R2 is not connected to the annular passage C through the gap between the cylinder 1 and the cap 10. Furthermore, even when the outer tube 4 is threadedly coupled to the tubular portion 30a, a sufficient distance is provided between the first port P1 and the threaded portion 30a7 so that the lower end of the outer tube 4 does not face the first port P1 that opens into the large-diameter portion 30a3.

[0057] As described above, in the shock absorber D2 of the second modified example, the cap 30 is provided with a small step portion (second step portion) 30a4 on the inner periphery of the tubular portion 30a that abuts against the other end of the cylinder 1, and the cylinder 1 is sandwiched between the small step portion (second step portion) 30a4 and the stopper S. According to the shock absorber D2 configured in this manner, the cylinder 1 can be sandwiched and firmly fixed between the outer tube 4 and the cap 30, and the cylinder 1 is in close contact with the small step portion (second step portion) 30a4 of the cap 30. Therefore, the annular passage C can be prevented from communicating with the compression-side chamber R2 via the gap between the cylinder 1 and the cap 10, and there is no need to install a seal member between the cylinder 1 and the cap 10, thereby further reducing manufacturing costs.

[0058] In the shock absorbers D, D1, and D2 of the present embodiment, in addition to the variable damping valve 21, the bypass path B is provided with the extension side auxiliary damping valve 22 and the compression side auxiliary damping valve 23. However, since the variable damping valve 21 can adjust the opening area of ​​the bypass path B to provide resistance to the flow of fluid passing through and adjust the damping force, the damping force can be adjusted even if the extension side auxiliary damping valve 22 and the compression side auxiliary damping valve 23 are eliminated.

[0059] Furthermore, as in shock absorber D3 of a third modified example of the embodiment shown in Fig. 6, stopper S1 may be configured with bump stopper 40 that is screwed to outer tube 4 and rod guide 17 to prevent cylinder 1 from falling off cap 10. Specifically, in shock absorber D3 of the third modified example, as shown in Fig. 6, cylinder 1 is fixed by sandwiching it between small diameter step portion 10a5 of cap 10 that is screwed to the outer periphery of the lower end of outer tube 4 in Fig. 6 and stopper S1 that is made up of bump stopper 40 and rod guide 17, thereby preventing cylinder 1 from falling off cap 10.

[0060] More specifically, the bump stopper 40 has an annular top portion 40a and a tubular portion 40b that extends from the outer periphery of the top portion 40a toward the cylinder side and has a threaded portion 40b1 on its outer periphery, and is screwed to the inner periphery of the upper end of the outer tube 4 in Figure 6. The bump stopper 40 axially faces a tubular bump cushion 41 that is attached to the outer periphery of the upper end of the piston rod 2 in Figure 6, and abuts against the bump cushion 41 when the shock absorber D3 is fully compressed. When the bump cushion 41 abuts against the bump stopper 40 and is compressed by the contraction of the shock absorber D3, it exerts a resilient force that prevents further contraction of the shock absorber D3 and absorbs the impact when the shock absorber D3 is fully compressed.

[0061] In the third modified example, the collar 11 is eliminated and the rod guide 17 is fitted to the outer periphery of the cylinder 1. Therefore, the rod guide 17 has an annular fitting portion 17c on the outer periphery of the lower end in Fig. 6 that fits to the outer periphery of the cylinder 1. Also, the upper end of the cylinder 1 in Fig. 6 abuts against the inner circumferential surface of the fitting portion 17c at the lower end in Fig. 6 of the rod guide 17, and the cylinder 1 is aligned by the fitting portion 17c of the rod guide 17, thereby restricting radial movement and upward movement.

[0062] In the shock absorber D3 of the third modification, a valve case 43 to which the extension side auxiliary damping valve 22 and the compression side auxiliary damping valve 23 are assembled is fitted onto the inner periphery of the lower end of the cylinder 1 in Fig. 6. The valve case 43 is annular and includes an annular case main body 43a that fits onto the inner periphery of the lower end of the cylinder 1, a flange 43b that is provided on the outer periphery of the lower end of the case main body 43a in Fig. 6 and abuts against the lower end of the cylinder 1, and an extension side port 43c and a compression side port 43d that axially pass through the case main body 43a.

[0063] When the bump stopper 40 is screwed onto the inner periphery of the upper end of the outer tube 4, the cylinder 1 with the valve case 43 fitted onto the inner periphery at the lower end thereof causes the cylindrical portion 40b of the bump stopper 40 to come into contact with the outer periphery at the upper end of the rod guide 17 in FIG. 6 and is tightened so that the rod guide 17 moves downward, and therefore the cylinder 1 and the flange 43b of the valve case 43 receive an axial load and are firmly fixed between the rod guide 17 and the cap 10. In this way, by adopting a structure in which the stopper S1 is composed of the bump stopper 40 and the rod guide 17 and the bump stopper 40 is screwed to the outer tube 4, the cylinder 1 can be pressed against the cap 10 while applying a desired axial force to the cylinder 1, preventing the cylinder 1 from falling off the cap 10.

[0064] 6, the expansion side auxiliary damping valve 22, which is an annular leaf valve that opens and closes the upper end opening of the expansion side port 43c, is stacked above the valve case 43, and the compression side auxiliary damping valve 23, which is an annular leaf valve that opens and closes the lower end opening of the compression side port 43d, is stacked below the valve case 43. The expansion side auxiliary damping valve 22 and the compression side auxiliary damping valve 23 are fixed to the valve case 43 by being sandwiched between a center rod 44 that is inserted into the inner periphery of the case main body 43a and has a threaded portion 44a at its tip and a flange 44b at its base end, and a nut 45 that is threadedly coupled to the threaded portion 44a of the center rod 44.

[0065] As described above, in the shock absorber D3 of the third modification, the cap 10 is provided with a small-diameter step (second step) 10a5 on the inner periphery of the cylindrical portion 10a that abuts against the valve case 43 that is fitted to the lower end of the cylinder 1, and the cylinder 1 is sandwiched between the small-diameter step (second step) 10a5 and the stopper S1. With the shock absorber D3 configured in this manner, the cylinder 1 can be sandwiched and firmly fixed between the outer tube 4 and the cap 10, and the cylinder 1 is in close contact with the small-diameter step (second step) 10a5 of the cap 10. This prevents the annular passage C from communicating with the compression-side chamber R2 through the gap between the cylinder 1 and the cap 10, eliminating the need to install a seal member between the cylinder 1 and the cap 10 and further reducing manufacturing costs. In addition, the valve case 43 to which the extension-side damping valve 22 and the compression-side damping valve 23 are assembled can be fixed to the cap 10 together with the cylinder 1, making it easy to assemble the extension-side damping valve 22 and the compression-side damping valve 23. If the extension side auxiliary damping valve 22 and the compression side auxiliary damping valve 23 are not required, the valve case 43 can be eliminated, and the cylinder 1 can be fixed to the cap 10 by directly abutting the small diameter step portion (second step portion) 10a5.

[0066] 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.

[0067] DESCRIPTION OF SYMBOLS 1: Cylinder, 2: Piston rod, 3: Piston, 4: Outer tube, 10, 30: Cap, 10a, 30a: Cylindrical portion, 10a2: Small inner diameter portion (insertion portion), 10a5: Small diameter step portion (second step portion), 10a7: Large diameter step portion (first step portion), 11: Collar, 11a: Fitting portion, 11b: Opposing portion, 21: Variable damping valve, 30a2: Medium diameter portion, 30a4: Small step portion (second step portion), B: Bypass path, C: Annular passage, D, D1, D2, D3: Shock absorber, M: Main damping passage, P: External passage, P1: First port, P2: Second port, R1: Expansion side chamber, R2: Compression side chamber, S, S1: Stopper

Claims

1. A shock absorber, comprising: a cylinder; a piston rod axially movably inserted into the cylinder and protruding outward from one end of the cylinder; a piston connected to the piston rod and axially movably inserted into the cylinder to partition the inside of the cylinder into an extension chamber and a compression chamber; a cap having a bottomed cylindrical shape and having an insertion portion into which the other end of the cylinder is inserted on the inner periphery of the cylindrical portion to close the other end of the cylinder; an outer tube covering the outer peripheral side of the cylinder and forming an annular passage communicating with the extension chamber between the outer tube and the cylinder, and being screwed to the inner periphery of the cylindrical portion of the cap on the tip side of the insertion portion; and a stopper attached to the outer tube and facing one end of the cylinder to prevent the cylinder from falling off the cap.

2. The shock absorber according to claim 1, wherein the cap has a first step portion that abuts against an end portion of the outer tube on the inner periphery of the cylindrical portion, and the cylinder is press-fitted into the insertion portion of the cap.

3. The shock absorber according to claim 1, wherein the cap has a second step portion that abuts against the other end of the cylinder on the inner periphery of the cylindrical portion, and the cylinder is sandwiched between the second step portion and the stopper.

4. The shock absorber according to any one of claims 1 to 3, wherein the stopper includes a snap ring attached to the inner periphery of the outer tube, a cylindrical fitting portion fitted to the inner periphery of the outer tube and fitted to the outer periphery of one end of the cylinder, and a collar having an opposing portion provided on the inner periphery of the fitting portion and facing one end of the cylinder.

5. A shock absorber according to any one of claims 1 to 3, comprising: a main damping passage that provides resistance to the flow of liquid flowing between the extension chamber and the compression chamber; a bypass passage that bypasses the main damping passage and communicates the extension chamber and the compression chamber; and a variable damping valve that provides resistance to the flow of liquid passing through the bypass passage, wherein the cap has a first port that opens on the bottom side rather than the tip of the outer tube of the cylindrical portion and communicates with the annular passage, and a second port that opens on the bottom side rather than the cylinder and communicates with the compression chamber, and the bypass passage is formed by an external passage that connects the first port and the second port and is provided with the variable damping valve, and the annular passage. Shock absorber.

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