Shock absorber

Abstract

This shock absorber (D) is provided with: 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); an inner cylinder (10) that is accommodated in a compression-side chamber (R2) inside the cylinder (1); a fixing member (11) that has an outer circumference press-fitted into the inner circumference of the cylinder (1) to be fixed to the cylinder (1) and that holds the inner cylinder (10); and a lock piece (12) that is connected to the piston rod (2), can enter the inner cylinder (10) at the outer side, and forms a hydraulic lock chamber (L), at the outer side, in the inner cylinder (10) upon entry to the inner cylinder (10) at the outer side. The fixing member (11) is provided, on the outer circumference surface (11a1) that is press-fitted into the inner circumference of the cylinder (1), with a recess (11a2) with which the contact area of the outer circumference surface (11a1) with respect to the cylinder (1) is reduced.

Description

Shock Absorber

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

[0002] For example, a shock absorber includes a cylinder, a piston rod movably inserted into the cylinder, a piston connected to the piston rod and movably inserted into the cylinder, the piston dividing an interior of the cylinder into an extension side chamber and a compression side chamber filled with hydraulic oil, and a piston rod movably inserted into the cylinder and connected to the piston, and is used by being interposed between a vehicle body and a rear wheel of a vehicle.

[0003] A conventional shock absorber can generate a damping force when expanding and contracting in conjunction with traveling of a vehicle to suppress vibration of the vehicle body, but when a vehicle is forced to travel on a rough road such as a cobblestone road with severe unevenness or in an area where road maintenance is inadequate, when the shock absorber contracts to the vicinity of the stroke end, a large compression-side damping force is sometimes required for the shock absorber.

[0004] In order to meet such a demand, there are cases where a hydraulic lock mechanism that hinders contraction operation when vibration that causes the shock absorber to contract to the maximum extent is input is provided. A shock absorber provided with a hydraulic lock mechanism, for example, as disclosed in JP2023-505692A, includes: an inner cylinder accommodated in the compression side chamber inside the cylinder; an annular fixing member that is press-fitted and fixed to the inner circumference of the lower end of the cylinder to grip the outer circumference of the inner cylinder; and a split cylindrical lock piece with a C-shaped cross section connected to a piston, the lock piece forming a hydraulic lock chamber between the inner cylinder and the cylinder when fitted onto the outer circumference of the inner cylinder.

[0005] In this shock absorber, when the shock absorber performs a contraction operation and the lock piece is fitted onto the outer circumference of the inner cylinder, the lock piece receives the pressure of the hydraulic lock chamber from the outer circumferential side to close the split portion, restricts the movement of hydraulic oil from the hydraulic lock chamber to a chamber inside the inner cylinder, and increases the pressure in the hydraulic lock chamber, thereby exerting a large force that hinders the contraction operation.

[0006] JP2023-505692A

[0007] In conventional shock absorbers, if the inner cylinder and the lock piece are misaligned or tilted relative to each other, it becomes difficult to fit the lock piece onto the outer circumference of the inner cylinder, impairing the oil lock function. Therefore, the inner cylinder must be fixed in the correct position relative to the cylinder.

[0008] The inner cylinder is fixed to the cylinder by pressing the outer surface of the fixing member that holds the inner cylinder into the inner circumference of the cylinder. However, if the axial length of the outer surface of the fixing member is too short, there is a risk that the fixing member will be fixed at an angle to the cylinder. Therefore, the axial length of the outer surface of the fixing member is ensured as much as possible.

[0009] However, increasing the axial length of the outer surface of the fixing member in this way increases the contact area between the outer surface of the fixing member and the cylinder. This increases the resistance the fixing member receives from the cylinder during the process of pressing and fitting the fixing member into the inner circumference of the cylinder. As a result, it becomes necessary to apply an excessive pressing load to the fixing member to push it into the cylinder, which worsens assembly workability and leads to increased manufacturing costs due to the need for larger processing machines.

[0010] Therefore, the present invention aims to provide a shock absorber that can exhibit good hydraulic locking function while also improving assembly workability and reducing manufacturing costs.

[0011] To solve the aforementioned problems, the buffer of the present invention comprises 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 to divide the inside of the cylinder into an extension chamber and a compression chamber, an inner cylinder located inside the cylinder and housed in the compression chamber, a fixing member whose outer circumference is press-fitted into the inner circumference of the cylinder and fixed to the cylinder, and which also holds the inner cylinder, and a lock piece connected to the piston rod and capable of penetrating either the inside or outside of the inner cylinder, and which, upon penetrating either the inside or outside of the inner cylinder, forms a hydraulic lock chamber on either the inside or outside of the inner cylinder, wherein the fixing member has a recess on its outer surface, which is press-fitted into the inner circumference of the cylinder, that reduces the contact area of ​​the outer surface with the cylinder.

[0012] With a shock absorber configured in this way, the fixing member that holds the inner cylinder has a recess on its outer surface, which is press-fitted into the inner circumference of the cylinder, that reduces the contact area of ​​the outer surface with the cylinder. Therefore, while increasing the axial length of the fixing member to ensure that the axial length of the outer surface does not tilt relative to the cylinder, the contact area of ​​the outer surface can be reduced, thereby reducing the press-fitting load into the cylinder.

[0013] Figure 1 is a cross-sectional view of a buffer in one embodiment. Figure 2 is a partially enlarged cross-sectional view of a buffer in one embodiment. Figure 3 is a plan view of the fixing member in a buffer in one embodiment. Figure 4 is a cross-sectional view of a buffer in one embodiment in a contracted state. Figure 5 is a perspective view of a first modified example of the fixing member. Figure 6 is a perspective view of a second modified example of the fixing member. Figure 7 is a perspective view of a third modified example of the fixing member.

[0014] The present invention will be described based on the embodiment shown in the figure. As shown in Figure 1, the shock absorber D in one embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1, which divides the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, an inner cylinder 10 located inside the cylinder 1 and housed in the compression chamber R2, a fixing member 11 pressed into the cylinder 1 to hold the inner cylinder 10, and a lock piece 12 connected to the piston rod 2 via the piston 3.

[0015] Although not shown in the diagram, shock absorber D is installed, for example, between the vehicle body and the rear wheels in a vehicle, generating a damping force during expansion and contraction to suppress vibrations of the vehicle body. Note that shock absorber D may be used in vehicles other than automobiles, such as saddle-type vehicles, or in equipment other than vehicles, buildings, etc.

[0016] The following describes the various parts of the shock absorber D. The cylinder 1 is cylindrical and has a piston 3 inserted inside so as to be movable in the axial direction. The inside of the cylinder 1 is divided by the piston 3 into an extension chamber R1 above the piston 3 in Figure 1 and a compression chamber R2 below the piston 3 in Figure 1.

[0017] Furthermore, a bottomed cylindrical outer cylinder 4 is provided on the outer circumference of the cylinder 1, covering the cylinder 1. An annular gap is provided between the outer cylinder 4 and the cylinder 1, and this annular gap forms a reservoir R. Thus, the buffer D of this embodiment is configured as a double-cylinder type buffer. In addition, the extension chamber R1 and the compression chamber R2 within the cylinder 1 are filled with a liquid such as hydraulic oil, and the reservoir R is filled with the same liquid as that filled in the cylinder 1, as well as a gas. Note that in addition to hydraulic oil, water, aqueous solution, etc., may be used as the liquid. When the liquid is hydraulic oil, the gas filled in the reservoir R should preferably be an inert gas such as nitrogen to prevent deterioration of the hydraulic oil.

[0018] Next, a valve case 20 is fitted to the lower end of the cylinder 1 in Figure 1, which is placed on the bottom 4a of the outer cylinder 4 and separates the pressure chamber R2 inside the cylinder 1 from the reservoir R between the cylinder 1 and the outer cylinder 4. Furthermore, a rod guide 30 is fitted to the upper end of the cylinder 1 in Figure 1, which slidably supports the piston rod 2. This rod guide 30 is fitted to the inner circumference of the outer cylinder 4, and by crimping the upper end of the outer cylinder 4, it is fixed to the outer cylinder 4 together with a sealing member 31 which is stacked above the rod guide 30 in Figure 1 and seals the space between the outer cylinder 4, the cylinder 1, and the piston rod 2. Once the rod guide 30 is fixed to the outer cylinder 4 in this way, the cylinder 1 is held together with the sealing member 31, the rod guide 30, and the valve case 20 between the crimped upper end of the outer cylinder 4 and the bottom 4a of the outer cylinder 4 and fixed inside the outer cylinder 4.

[0019] Alternatively, instead of crimping the upper opening of the outer cylinder 4, a cap may be screwed onto the upper opening, and the sealing member 31, rod guide 30, cylinder 1, and valve case 20 may be sandwiched between this cap and the bottom 4a of the outer cylinder 4, thereby fixing these components inside the outer cylinder 4.

[0020] The piston rod 2 is cylindrical in shape, with a reduced outer diameter at the tip, and includes a piston fitting portion 2a with the smallest diameter at the tip, a larger diameter portion 2b with a larger outer diameter than the piston fitting portion 2a and located above the piston fitting portion 2a in Figure 1, a stepped portion 2c provided at the boundary between the piston fitting portion 2a and the larger diameter portion 2b, and a threaded portion 2d provided on the outer circumference of the tip of the piston fitting portion 2a.

[0021] A bracket (not shown) is provided at the base end of the piston rod 2, which is the upper end in Figure 1, and the piston rod 2 is connected to the vehicle body via this bracket (not shown). A bracket (not shown) is also provided at the bottom 4a of the outer cylinder 4, and the outer cylinder 4 is connected to the wheel via this bracket (not shown).

[0022] In this embodiment, the shock absorber D is interposed between the vehicle body and the wheel, with the piston rod 2 connected to the vehicle body and the cylinder 1 connected to the wheel. When the vehicle travels on an uneven road surface, causing the wheel to vibrate vertically relative to the vehicle body, the piston rod 2 moves in and out of the cylinder 1, causing the shock absorber D to expand and contract, and the piston 3 moves vertically (axially) within the cylinder 1.

[0023] Next, the piston 3 is annular in shape and fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2, and is fixed to the piston rod 2 by a piston nut 7 that is screwed onto the threaded portion 2d of the piston rod 2. More specifically, as shown in Figure 1, the piston 3 is composed of an annular piston body 3a, a cylindrical portion 3b provided on the outer circumference of the lower end of the piston body 3a in Figure 2, an extension port 3c that penetrates the piston body 3a in the axial direction, and a compression port 3d that penetrates the piston body 3a in the axial direction.

[0024] As described above, the piston 3 is a bottomed cylindrical shape comprising a piston body 3a and a cylindrical portion 3b, and a piston ring 3e is mounted on its outer circumference, which slides against the inner circumference of the cylinder 1, allowing it to move axially relative to the cylinder 1. The extension port 3c and compression port 3d pass through the piston body 3a in the axial direction, connecting the extension chamber R1 and the compression chamber R2.

[0025] Next, a compression damping valve 5, which opens and closes the outlet end of the compression port 3c, is stacked on the lower part of the piston body 3a of the piston 3 in Figure 1. The compression damping valve 5 is a laminated leaf valve composed of multiple annular plates stacked together, and after being mounted on the outer circumference of the piston fitting portion 2a together with the piston 3, it is fixed to the piston rod 2 by a piston nut 7. The compression damping valve 5 has its inner circumference fixed to the piston rod 2 and is allowed to flex on its outer circumference. When the outer circumference is in contact with the piston body 3a, it closes the compression port 3c, and when the outer circumference is flexed and separated from the piston body 3a, it opens the compression port 3c while providing resistance to the flow of liquid passing through the compression port 3c from the compression chamber R1 to the compression chamber R2. The outer diameter of the compression damping valve 5 is set such that even when the compression damping valve 5 is stacked on the lower end of the piston body 3a of the piston 3, the compression port 3d, which is located on the outer circumference of the compression port 3c, is not blocked.

[0026] On the other hand, a pressure-side check valve 6, which opens and closes the outlet end of the pressure-side port 3d, is stacked on the upper part of the piston body 3a in Figure 1. The pressure-side check valve 6 is constructed by stacking multiple annular plates and is mounted on the outer circumference of the piston fitting portion 2a together with the piston 3, and then fixed to the piston rod 2 by a piston nut 7. The inner circumference of the pressure-side check valve 6 is fixed to the piston rod 2 and the outer circumference is allowed to bend. When the outer circumference is in contact with the piston body 3a, it closes the pressure-side port 3d, and when the outer circumference is bent and separated from the piston body 3a, it opens the pressure-side port 3d. The pressure-side check valve 6 allows liquid to pass through the pressure-side port 3d from the pressure-side chamber R2 to the extension-side chamber R1 with almost no resistance, but conversely, when liquid attempts to pass through the pressure-side port 3d from the extension-side chamber R1 to the pressure-side chamber R2, it closes the valve and prevents the passage of the liquid. Furthermore, the inlet end of the extension port 3c is connected to the outer circumference of the piston body 3a, and care has been taken to ensure that the extension port 3c is not blocked by the compression check valve 6 even if the compression check valve 6 is stacked on the upper end of the piston body 3a in Figure 1.

[0027] The valve case 20 includes an annular fitting portion 20a fitted to the inner circumference of the lower end of the cylinder 1, with a flange 20b on its outer circumference that abuts against the lower end of the cylinder 1 in Figure 2; a plurality of legs 20c provided at equal intervals in the circumferential direction at the lower end of the fitting portion 20a in Figure 2, extending downward and seating on the bottom 4a of the outer cylinder 4; and a discharge port 20d and an intake port 20e that pass through the fitting portion 20a and connect the pressure side chamber R2 and the reservoir R.

[0028] A compression damping valve 21, which opens and closes the outlet end of the discharge port 20d, is stacked on the lower side of the fitting portion 20a in Figure 2. The compression damping valve 21 is a laminated leaf valve composed of multiple annular plates stacked together, and is mounted on the outer circumference of a center rod 23, which is inserted through the inner circumference of the fitting portion 20a together with the valve case 20. The center rod 23 is axial in shape and has a flange 23a at its base end and a threaded portion 23b at its tip to which a nut 24 is screwed. The valve case 20 and the compression damping valve 21 are sandwiched between the flange 23a and the nut 24 and fixed to the center rod 23. The compression damping valve 21 has its inner circumference fixed to the center rod 23 and is allowed to flex on its outer circumference. When the outer circumference is in contact with the fitting portion 20a, it closes the discharge port 20d. When the outer circumference is flexed and separated from the fitting portion 20a, it opens the discharge port 20d while resisting the flow of liquid passing through the discharge port 20d from the pressure chamber R2 to the reservoir R. The outer diameter of the compression damping valve 21 is set such that even when the compression damping valve 21 is stacked on the lower end of the fitting portion 20a, it does not block the inlet end of the suction port 20e, which is located on the outer circumference of the discharge port 20d.

[0029] On the other hand, an extension check valve 22, which opens and closes the outlet end of the suction port 20e, is stacked on the upper side of the fitting portion 20a in Figure 2. The extension check valve 22 is constructed by stacking multiple annular plates and, together with the valve case 20, is mounted on the outer circumference of the center rod 23, and then fixed to the center rod 23 by being sandwiched between a nut 24 and a flange 23a. The extension check valve 22 has its inner circumference fixed to the center rod 23 and is allowed to bend on its outer circumference. When the outer circumference is in contact with the fitting portion 20a, it closes the suction port 20e, and when the outer circumference is bent and separated from the fitting portion 20a, it opens the suction port 20e. The extension check valve 22 allows liquid to pass through the suction port 20e from the reservoir R to the pressure chamber R2 with almost no resistance, but conversely, if liquid attempts to pass through the suction port 20e from the pressure chamber R2 to the reservoir R, it closes to prevent the passage of that liquid. The extension check valve 22 has a hole 22a that penetrates axially and faces the discharge port 20d, and even when stacked on the upper end of the fitting portion 20a in Figure 2, it does not block the inlet end of the discharge port 20d, allowing liquid to pass through the discharge port 20d.

[0030] Furthermore, a relief valve 25 is fixed to the outer circumference of the center rod 23, on the side of the extension check valve 22 that is closer to the nut 24, and includes a valve retaining member 26 and an annular relief valve body 27 that is stacked on the valve retaining member 26.

[0031] The valve retaining member 26 is annular in shape and has a plurality of through holes 26a provided at equal intervals in the circumferential direction. The relief valve body 27 is annular in shape and has a C-shaped through hole 27a that communicates with the through holes 26a, and its outer diameter is set to be sufficiently larger than the outer diameter of the valve retaining member 26.

[0032] The fixing member 11 comprises an annular fixing member body 11a and a plurality of relief ports 11b that penetrate the fixing member body 11a. The fixing member 11 is fixed to the cylinder 1 by press-fitting the outer peripheral surface 11a1 of the annular fixing member body 11a onto the inner peripheral surface of the cylinder 1.

[0033] More specifically, the fixing member body 11a includes a plurality of recesses 11a2 provided on the outer circumference to reduce the contact area of ​​the outer circumference surface 11a1 that abuts the inner circumference surface of the cylinder 1, a valve housing portion 11a3 which is an annular recess formed by increasing the inner circumference diameter at the lower end in Figure 2, a holding portion 11a4 formed by increasing the inner circumference of the portion on the inner circumference that is spaced upward from the valve housing portion 11a3 and into which the lower end of the inner cylinder 10 in Figure 2 is press-fitted, and a rib 11a5 rising from the inner circumference of the upper end. The fixing member body 11a is also provided with a chamfered portion 11a6 on the outer circumference of the upper end in Figure 2 to enable smooth press-fitting into the cylinder 1. The axial length of the outer surface 11a1 of the fixing member body 11a, which serves as a press-fit portion that abuts the inner surface of the cylinder 1, is equal to the total axial length of the fixing member 11 minus the axial lengths of the rib 11a5 and the chamfered portion 11a6, and is approximately equal to the total axial length of the fixing member 11 from the upper end to the lower end in Figure 2. Therefore, the axial length of the press-fit portion of the fixing member 11 into the cylinder 1 is approximately equal to the total axial length which is the maximum length allowed for the fixing member 11.

[0034] As shown in Figures 2 and 3, the recesses 11a2 extend partway from the upper end in Figure 2, which is one end of the fixing member body 11a, to the lower end, which is the other end, and are provided at seven equally spaced locations in the circumferential direction on the outer circumference of the fixing member body 11a. Three or more recesses 11a2 are provided in this manner. The center point A is the circumferential center of the press-fit portion B on the outer circumference of the fixing member body 11a that is press-fitted into the cylinder 1 between the recesses 11a2, 11a2. The recesses 11a2 are arranged such that no two of the center points A do not lie on the diametrical direction of the fixing member body 11a, and there are two center points that have the same central angle of 90 degrees or more with any of the center points A. As shown in Figure 3, there are seven recesses 11a2, so there are also seven center points A between the recesses 11a2. For clarity, the symbols of the center points are shown as A1, A2, A3, A4, A5, A6, and A7. First, the recesses 11a2 are installed on the outer circumference of the fixing member 11 so that no matter which two center points A1, A2, A3, A4, A5, A6, and A7 are selected, they will not necessarily be aligned on a straight line in the diametrical direction passing through the center of the outer circumference of the fixing member body 11a. In other words, the recesses 11a2 are installed on the outer circumference of the fixing member 11 so that any two center points are not positioned with a 180-degree phase difference in the circumferential direction of the fixing member body 11a. Furthermore, if any one central point from among the central points A1, A2, A3, A4, A5, A6, and A7 is selected, for example, central point A1, then the central angle formed between central point A1 and central point A3, which is two points away clockwise from central point A1, is equal to the central angle formed between central point A1 and central point A6, which is two points away counterclockwise from central point A1. Thus, there are two central points A3 and A6 that have the same central angle of 90 degrees or more with respect to central point A1. In this embodiment, since seven recesses 11a2 are provided at equal intervals on the outer circumference of the fixing member body 11a, the central angle formed between central point A1 and central point A4, which is three points away clockwise from central point A1, is equal to the central angle formed between central point A1 and central point A5, which is three points away counterclockwise from central point A1. Thus, in addition to central points A3 and A6, there are two other central points A4 and A5 that have the same central angle of 90 degrees or more with respect to central point A1.

[0035] In this way, if the central point A is defined as the circumferential center between the recesses 11a2, 11a2 on the outer circumference of the fixing member body 11a, and at least three or more recesses 11a2 are provided such that no two of the central points A are located on the diametrical direction of the fixing member body 11a, and there are two central points A that have the same central angle of 90 degrees or more with any of the central points A, then for each central point A, two central points A that have a central angle of 90 degrees or more with this central point A are formed, and these three central points A are arranged at the vertices of an isosceles triangle. When the fixing member 11 is press-fitted into the cylinder 1, the press-fit portion B that contacts the inner circumference of the cylinder 1 between the recesses 11a2, 11a2 always includes three press-fit portions B, including a central point A that is positioned on the vertex of an isosceles triangle with an apex angle and two base angles of less than 90 degrees. Furthermore, since the press-fit portions B are not positioned in the diametrical direction of the cylinder 1, a relationship can be achieved in which the fixing member 11 is less likely to rotate around an axis perpendicular to the axis of the cylinder 1. Therefore, when the fixing member 11 is press-fitted into the cylinder 1, it is possible to effectively suppress the fixing member 11 from being fixed at an angle relative to the cylinder 1. To obtain such an effect, at least three or more recesses 11a2 should be provided and installed on the outer circumference of the fixing member 11 to satisfy the above conditions. However, if the axial length of the outer surface 11a1 of the fixing member 11 can be increased so that the fixing member 11 can be press-fitted into the cylinder 1 without tilting, the number and location of the recesses 11a2 on the outer circumference of the fixing member body 11a can be arbitrarily changed in the design, regardless of the above conditions.

[0036] By providing the recess 11a2 on the outer circumference of the fixing member body 11a in this manner, the axial length of the outer circumference surface 11a1, which is the press-fit portion of the fixing member body 11a that is press-fitted into the inner circumference of the cylinder 1, can be made approximately to its maximum length, while reducing the contact area of ​​the outer circumference surface 11a1 of the fixing member body 11a that contacts the inner circumference of the cylinder 1.

[0037] Furthermore, in this embodiment, a relief port 11b is provided that penetrates the fixing member body 11a axially in a portion of the fixing member body 11a that is on the outer circumference side of the fixing member body 11a than the rib 11a5 and where the thickness between the recesses 11a2, 11a2 is thicker in the circumferential direction of the fixing member body 11a, and opens to the lower surface of the valve housing portion 11a3 provided on the lower side of the fixing member body 11a in Figure 2.

[0038] By positioning the relief port 11b in the circumferential direction between the recesses 11a2, 11a2 relative to the fixing member body 11a, and in a position that does not overlap with the recesses 11a2 in the radial direction, the relief port 11b can be installed on the fixing member body 11a without difficulty, even if the radial depth of the recesses 11a2 is increased.

[0039] The depth of the radial recess 11a2 of the fixing member body 11a can be arbitrarily set within a range that ensures sufficient strength to hold the inner cylinder 10 fitted into the holding portion 11a4. Increasing the axial length of the recess 11a2 and increasing its radial depth is advantageous in terms of reducing the weight of the fixing member 11 and lowering material costs. In this embodiment, an annular rib 11a5 is provided on the inner circumference of the upper end of the fixing member body 11a, rising upward in Figure 2. By providing the rib 11a5, the reduction in strength of the fixing member 11 caused by providing the recess 11a2 on the outer circumference and the relief port 11b is suppressed, but the rib 11a5 can be omitted if it is not needed.

[0040] The outer diameter of the outer circumferential surface 11a1 of the fixing member 11 configured in this way is larger than the inner diameter of the cylinder 1. When the fixing member 11 is fitted into the cylinder 1, the outer circumferential surface 11a1 of the fixing member 11 and the inner circumferential surface of the cylinder 1 come into contact with each other while applying pressure, and the fixing member 11 is firmly fixed to the inner circumference of the cylinder 1.

[0041] The lower outer circumference of the inner cylinder 10 is inserted into the holding portion 11a4 formed on the inner circumference side of the fixing member 11 configured in this way. The outer diameter of the lower end of the inner cylinder 10 is larger than the inner diameter of the holding portion 11a4 of the fixing member 11, and the inner cylinder 10 inserted into the holding portion 11a4 is press-fitted into the inner circumference of the fixing member 11 and firmly fixed. In this embodiment, the inner cylinder 10 is held on the inner circumference of the fixing member 11, but for example, an annular projection may be provided on the upper end of the fixing member 11, and the inner cylinder 10 may be held on the outer circumference of the fixing member 11 by press-fitting the annular projection into the inner circumference of the lower end of the inner cylinder 10.

[0042] Thus, the inner cylinder 10 is housed within the cylinder 1 and in the pressure chamber R2, and is fixed to the cylinder 1 by the fixing member 11. The outer diameter of the inner cylinder 10 is smaller than the inner diameter of the cylinder 1, and an annular gap is formed between the outer circumference of the inner cylinder 10 and the inner circumference of the cylinder 1. When the lock piece 12 enters this annular gap, the lock piece 12 forms a hydraulic lock chamber L between the inner cylinder 10 and the cylinder 1. The annular gap between the inner cylinder 10 and the cylinder 1 is axially opposite to the relief port 11b and communicates with the reservoir R via the relief port 11b. On the other hand, the space within the pressure chamber R2 on the inner circumference side of the inner cylinder 10 is communicated with the reservoir R via the discharge port 20d and suction port 20e of the valve case 20, which is fitted to the inner circumference of the fixing member 11 and the lower end of the cylinder 1.

[0043] Press-fitting of the fixing member 11 into the cylinder 1 is performed by pressing the fixing member 11 with the valve case 20 and pushing it into the cylinder 1. When the valve case 20 is pushed into the cylinder 1 together with the fixing member 11 until the flange 20b abuts against the lower end of the cylinder 1, the fixing member 11 is press-fitted and fixed at a pre-targeted position on the inner periphery of the cylinder 1. When press-fitting the fixing member 11 as described above, the lower end of the fixing member 11 is brought into contact with the outer periphery of the fitting portion 20a of the valve case 20 to push the fixing member 11 into the cylinder 1. Since the inner diameter of the valve accommodating portion 11a3 of the fixing member 11 is larger than the outer diameter of the extension-side check valve 22, the fixing member 11 does not interfere with the extension-side check valve 22.

[0044] Furthermore, when the fixing member 11 is fixed to the inner periphery of the cylinder 1, the outer periphery of the lower end of the fixing member 11 abuts against the outer periphery of the fitting portion 20a of the valve case 20, and the flange 20b abuts against the lower end of the cylinder 1, the intermediate portion of the relief valve body 27 is clamped between the outer periphery of the upper end of the valve holding member 26 and the inner periphery of the valve accommodating portion 11a3 of the fixing member 11, and the outer periphery of the relief valve body 27 abuts against the outer peripheral portion of the lower surface of the valve accommodating portion 11a3, so that the outlet end at the lower end of the relief port 11b is closed by the relief valve body 27. The axial depth of the valve accommodating portion 11a3 is shallower at the outer peripheral portion than at the inner peripheral portion. In a state where the intermediate portion of the relief valve body 27 is clamped between the valve holding member 26 and the inner peripheral portion of the valve accommodating portion 11a3, the outer peripheral portion of the relief valve body 27 bends downward in FIG. 2 with the intermediate portion as a fulcrum, and abuts against the outer peripheral portion of the valve accommodating portion 11a3.

[0045] With the intermediate portion clamped between the valve holding member 26 and the inner peripheral portion of the valve accommodating portion 11a3 as a fulcrum, the relief valve body 27 allows bending of the outer peripheral portion downward in FIG. 2. In a state where the relief valve body 27 abuts against the outer peripheral portion of the valve accommodating portion 11a3, an initial deflection is applied thereto, so the relief valve body 27 is pressed against the valve accommodating portion 11a3 by its own elastic force. The valve opening pressure when the relief valve 25 opens the relief port 11b is set by the amount of initial deflection applied to the relief valve body 27.

[0046] The relief valve 25 opens when the pressure of the liquid trying to pass from the pressure side chamber R2 to the reservoir R by deflecting the outer peripheral portion of the relief port 11b exceeds the valve opening pressure, the outer peripheral portion of the relief valve element 27 deflects with the intermediate portion as a fulcrum to open the valve, allowing liquid to pass through the relief port 11b from the pressure side chamber R2 toward the reservoir R side. Note that the valve opening pressure of the relief valve 25 can be set not only by the initial deflection amount applied to the aforementioned relief valve element 27, but also by the flexural rigidity of the relief valve element 27.

[0047] Next, the lock piece 12 is connected to the piston rod 2 via the piston 3, and is an elastic tubular member with a C-shaped cross section that can be fitted onto the outer circumference of the inner cylinder 10. Specifically, the lock piece 12 is a cylindrical body with a C-shaped cross section formed of synthetic resin, and is provided with a split 12a extending along the axial direction at one position in the circumferential direction, and a plurality of semicircular grooves 12b formed side by side in the axial direction at opposite positions in the circumferential direction at both circumferential ends. Further, the lock piece 12 includes three annular reinforcing ribs 12c provided along the circumferential direction on the outer circumference and projecting toward the outer circumferential side, and an annular guide rib 12d that is on the outer circumference, projects outward from near the lower end in FIG. 1 below the reinforcing ribs 12c, and is in sliding contact with the inner circumferential surface of the cylinder 1, and an annular fitting rib 12e that is on the inner circumference, is provided along the circumferential direction at the upper end in FIG. 1, and projects toward the inner circumferential side.

[0048] The lock piece 12 configured as described above is connected to the piston 3 by fitting the fitting rib 12e into an annular groove 3f provided on the outer circumference of the lower end in FIG. 1 of the cylindrical portion 3b of the piston 3. In this way, the lock piece 12 is connected to the piston rod 2 via the piston 3, and by bringing the guide rib 12d into sliding contact with the inner circumferential surface of the cylinder 1, the lock piece 12 can move together with the piston rod 2 and the piston 3 in the axial direction relative to the cylinder 1 without axial runout.

[0049] In addition, the inner diameter of the lock piece 12 is slightly larger than the outer diameter of the inner cylinder 10, and the lock piece 12 allows insertion into the inner cylinder 10 when the piston rod 2 moves downward in FIG. 1.

[0050] Furthermore, when the lock piece 12 is compressed by pressure from the outer circumference, the slit 12a closes, forming a circular orifice between the opposing grooves 12b, 12b in the circumferential direction. Since numerous grooves 12b are provided at both ends of the lock piece 12 in the circumferential direction, when the slit 12a closes, numerous orifices are formed in the lock piece 12, arranged along the axial direction. The inner diameter of the orifice formed by the opposing grooves 12b, 12b in the circumferential direction is set to decrease from bottom to top in Figure 4 of the lock piece 12. In other words, the diameter of the semicircular groove 12b decreases as it goes towards the top of the lock piece 12.

[0051] As the shock absorber D contracts, the piston rod 2 moves downward relative to the cylinder 1 in Figure 1, and as shown in Figure 4, the lock piece 12 fits onto the outer circumference of the inner cylinder 10, causing the inner cylinder 10 to enter the lock piece 12. The lock piece 12 then forms a hydraulic lock chamber L in the annular gap between the inner cylinder 10 and the cylinder 1.

[0052] The relief port 11b, which connects the hydraulic lock chamber L to the reservoir R, is closed by the relief valve 25 until the pressure in the hydraulic lock chamber L reaches the opening pressure of the relief valve 25. As a result, as the shock absorber D contracts, the volume of the hydraulic lock chamber L decreases and the pressure in the hydraulic lock chamber L increases due to the intrusion of the lock piece 12 into the annular gap. Then, the pressure in the hydraulic lock chamber L acts on the lock piece 12 from the outer circumference, causing the lock piece 12 to shrink in diameter, close the split 12a, and fit onto the outer circumference of the inner cylinder 10. Therefore, the liquid that has intruded into the annular gap of the lock piece 12 passes through the orifice formed by the grooves 12b, 12b of the lock piece 12, which has shrunk in diameter and closed the split 12a, and moves into the inner cylinder 10. As the lock piece 12 moves downward in Figure 4, the orifices formed by the grooves 12b, 12b are sequentially closed on the outer circumference of the inner cylinder 10 from the lower side. As a result, the effective area of ​​the orifice connecting the hydraulic lock chamber L and the inside of the inner cylinder 10 decreases, the pressure inside the hydraulic lock chamber L becomes high, and the downward movement of the lock piece 12 relative to the inner cylinder 10 is prevented. In this way, when the lock piece 12 enters the annular gap between the inner cylinder 10 and the cylinder 1, the hydraulic lock mechanism composed of the lock piece 12 and the inner cylinder 10 exerts a force that prevents the shock absorber D from contracting.

[0053] Furthermore, when the pressure in the hydraulic lock chamber L reaches the opening pressure of the relief valve 25, the relief valve 25 opens, allowing the liquid in the hydraulic lock chamber L to move to the reservoir R through the relief port 11b and the discharge port 20d. This prevents the pressure in the hydraulic lock chamber L from becoming excessive, which would create an excessive force that hinders the contraction operation of the buffer D generated by the hydraulic lock mechanism.

[0054] When the buffer D extends from the state in which the lock piece 12 has entered the annular gap between the inner cylinder 10 and the cylinder 1, the volume inside the hydraulic lock chamber L expands, causing the pressure inside the hydraulic lock chamber L to decrease, the lock piece 12 to expand in diameter, and the split 12a to open, creating communication between the inside of the inner cylinder 10 and the hydraulic lock chamber L through the split 12a. In this state, the liquid inside the inner cylinder 10 can move through the split 12a with almost no resistance into the hydraulic lock chamber L, so the buffer D can extend with almost no resistance.

[0055] The shock absorber D is configured as described above, and the operation of the shock absorber D will be explained below. First, when the shock absorber D extends, the piston rod 2 and piston 3 move upward relative to the cylinder 1 in Figure 1, causing the extension chamber R1 to contract and the compression chamber R2 to expand. The liquid in the contracted extension chamber R1 pushes open the extension damping valve 5, passes through the extension port 3c, and moves into the expanded compression chamber R2. The extension damping valve 5 resists the flow of liquid passing through the extension port 3c, causing the pressure in the extension chamber R1 to rise and act on the piston 3, generating a damping force that hinders the extension operation of the shock absorber D. When the shock absorber D extends, the piston rod 2 retracts from the cylinder 1, resulting in a liquid shortage in the cylinder 1 equivalent to the volume of liquid lost when the piston rod 2 retracts. However, the liquid shortage is compensated for by the extension check valve 22 opening and supplying liquid from the reservoir R into the cylinder 1, thus compensating for the volume lost when the piston rod 2 retracts from the cylinder 1.

[0056] Furthermore, even when the shock absorber D is extended, and the lock piece 12 is inserted between the inner cylinder 10 and the cylinder 1 to partition the hydraulic lock chamber L, the lock piece 12 expands in diameter as described above, and communicates the hydraulic lock chamber L and the inside of the inner cylinder 10 through the split 12a. Therefore, the hydraulic lock mechanism allows the lock piece 12 to move upward relative to the cylinder 1 in Figure 1 without resistance.

[0057] On the other hand, when the shock absorber D contracts, the piston rod 2 and piston 3 move downward relative to the cylinder 1 in Figure 1, causing the compression chamber R2 to shrink and the extension chamber R1 to expand. The liquid in the shrinking compression chamber R2 pushes open the compression check valve 6, passes through the compression port 3d, and moves into the expanding extension chamber R1.

[0058] When the shock absorber D contracts, the piston rod 2 enters the cylinder 1, resulting in an excess of liquid in the cylinder 1 equivalent to the volume of liquid the piston rod 2 enters. This excess liquid, corresponding to the volume of liquid the piston rod 2 enters the cylinder 1, pushes open the pressure damping valve 21, passes through the discharge port 20d, and moves from the cylinder 1 to the reservoir R.

[0059] The compression damping valve 21 resists the flow of liquid passing through the discharge port 20d, causing the pressure inside the cylinder 1 to increase and act on the piston 3, and the shock absorber D generates a damping force that prevents the piston from contracting.

[0060] When the shock absorber D is contracting, if the lock piece 12 enters the annular gap between the inner cylinder 10 and the cylinder 1, the pressure in the hydraulic lock chamber L increases, and the shock absorber D generates a damping force as the sum of the damping force generated by the pressure-side damping valve 21 and the force generated by the hydraulic lock mechanism in response to the pressure rise in the hydraulic lock chamber L, thereby hindering the contraction operation of the shock absorber D.

[0061] As the hydraulic locking mechanism exerts a force that inhibits the contraction of the buffer D, and as the buffer D continues to contract, the number of orifices in the lock piece 12 that are blocked by the inner cylinder 10 increases, the pressure in the hydraulic locking chamber L gradually rises, and the force inhibiting the contraction of the buffer D increases. When the buffer D contracts to near the end of the stroke on the contraction side, the lock piece 12 penetrates deeply into the annular gap, greatly reducing the volume of the hydraulic locking chamber L, and almost all of the orifices in the lock piece 12 are blocked. As a result, the pressure in the hydraulic locking chamber L increases rapidly, and the force that the hydraulic locking mechanism exerts to inhibit the contraction of the buffer D increases rapidly. Furthermore, as the buffer D contracts toward the end of the stroke on the contraction side, the pressure in the hydraulic locking chamber L reaches the opening pressure of the relief valve 25, and the liquid in the hydraulic locking chamber L is discharged to the reservoir R through the relief port 11b and the discharge port 20d. Therefore, the hydraulic lock mechanism exerts a large force when the buffer D contracts near the end of its stroke, preventing the buffer D from contracting. This allows the buffer D to mitigate the impact during contraction, and prevents the pressure in the hydraulic lock chamber L from exceeding the opening pressure of the relief valve 25 and becoming excessively high.

[0062] When the shock absorber D configured in this way is applied to a vehicle, it is interposed between the vehicle body and the wheels together with the suspension spring. However, when the load on the vehicle increases, it compresses together with the suspension spring, so that even when the vehicle is stationary, the lock piece 12 is inserted between the inner cylinder 10 and the cylinder 1. In this situation, the shock absorber D increases the force that opposes compression during the compression operation, so that the damping force generated during the compression operation can be automatically increased in response to the load on the vehicle.

[0063] As described above, the buffer D of this embodiment comprises a cylinder 1, a piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 to divide the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, an inner cylinder 10 located inside the cylinder 1 and housed in the compression chamber R2, a fixing member 11 whose outer circumference is press-fitted into the inner circumference of the cylinder 1 and fixed to the cylinder 1, and a lock piece 12 connected to the piston rod 2 and capable of penetrating to the outside of the inner cylinder 10, and which, when penetrating to the outside of the inner cylinder 10, forms a hydraulic lock chamber L on the outside of the inner cylinder 10, wherein the fixing member 11 has a recess 11a2 on its outer circumferential surface 11a1 which is press-fitted into the inner circumference of the cylinder 1, which reduces the contact area of ​​the outer circumferential surface 11a1 with the cylinder 1.

[0064] With the shock absorber D configured in this way, the fixing member 11 that holds the inner cylinder 10 is provided with a recess 11a2 on its outer circumferential surface 11a1, which is press-fitted into the inner circumference of the cylinder 1, thereby reducing the contact area of ​​the outer circumferential surface 11a1 with the cylinder 1. This allows for increasing the axial length of the fixing member 11 to ensure that the axial length of the outer circumferential surface 11a1 does not tilt relative to the cylinder 1, while simultaneously reducing the contact area of ​​the outer circumferential surface 11a1 and thus reducing the press-fitting load into the cylinder 1. In this way, with the shock absorber D of this embodiment, the axial length of the outer circumferential surface 11a1 of the fixing member 11 is ensured relative to the cylinder 1, so that the fixing member 11 does not tilt relative to the cylinder 1. As a result, the inner cylinder 10 is also positioned concentrically with the cylinder 1 without tilting, and smooth insertion of the inner cylinder 10 into the lock piece 12 is also achieved. In this way, with the shock absorber D of this embodiment, there is no need to apply an excessive press-fitting load to the fixing member 11 to push it into the cylinder 1, improving assembly workability and avoiding the need for larger processing machines. Therefore, according to the buffer D of this embodiment, it is possible to achieve a good hydraulic locking function, as well as improved assembly workability and reduced manufacturing costs.

[0065] In this embodiment, the lock piece 12 penetrates the outside of the inner cylinder 10, forming a hydraulic lock chamber L on the outside of the inner cylinder 10. However, instead of the cylindrical lock piece 12 described above, a lock piece that can be inserted into the inner cylinder 10 may be installed at the tip of the piston rod 2, forming a hydraulic lock chamber that is closed inside the inner cylinder 10 when the lock piece is inserted inside the inner cylinder 10. In this case, to form a closed hydraulic lock chamber, the lower end of the inner cylinder 10 should be closed. If a relief valve is provided, the relief valve should be installed on the member that closes the lower end of the inner cylinder 10 or on the inner cylinder 10. In this case, the compression damping valve and the extension check valve should be installed on the fixing member 11.

[0066] Furthermore, in the buffer D of this embodiment, the total axial length of the fixing member 11 and the axial length of the outer circumferential surface 11a1 are approximately equal. This makes it easier to secure the axial length of the outer circumferential surface 11a1 that contacts the inner circumferential surface of the cylinder 1, effectively suppressing the fixing member 11 from being tilted relative to the cylinder 1, and enabling the hydraulic locking function to be stably performed.

[0067] Furthermore, in the buffer D of this embodiment, multiple recesses 11a2 are provided on the outer peripheral surface 11a1 in a circumferential direction, opening from the upper end in Figure 1, which is one axial end of the fixing member 11, and extending partway along the outer peripheral surface 11a1 toward the lower end in Figure 1, which is the other end. With the buffer D configured in this way, the space between the cylinder 1 and the fixing member 11 is closed by the press-fitting of the fixing member 11 into the cylinder 1, so the passage of liquid between the cylinder 1 and the fixing member 11 can be suppressed without providing a separate sealing member, the increase in the number of parts can be suppressed, and manufacturing costs can be reduced. In addition, since the recesses 11a2 open only from one axial end of the outer peripheral surface 11a1, it is easier to ensure the strength of the other end of the fixing member 11, the wall thickness of the other end can be reduced, and the cross-sectional area of ​​the relief port 11b can be increased. Therefore, by forming a hydraulic lock chamber L on the outside of the inner cylinder 10, the relief port 11b does not become a resistance, and the pressure inside the hydraulic lock chamber L becomes excessive when the buffer D is fully contracted, which can be effectively suppressed.

[0068] Furthermore, as shown in the first modified example of the fixing member 11 in Figure 5, when providing a recess on the outer circumferential surface 11a1 of the inner cylinder 10 to reduce the contact area of ​​the outer circumferential surface 11a1 with the cylinder 1, the recess has a first recess 11a7 that opens from one end of the fixing member 11 which is the upper end in Figure 5 in the axial direction and extends partway along the outer circumferential surface 11a1 toward the other end which is the lower end in Figure 5, and a second recess 11a8 that opens from the other end which is the lower end in Figure 5 in the axial direction and extends partway along the outer circumferential surface 11a1 toward the one end which is the upper end in Figure 5, and the first recess 11a7 and the second recess 11a8 may be alternately provided in the circumferential direction with respect to the outer circumferential surface 11a1.

[0069] With the buffer D configured in this way, since the first recess 11a7 and the second recess 11a8 are located at different positions in the circumferential direction, the first recess 11a7 and the second recess 11a8 are not in communication with each other, and the space between the cylinder 1 and the fixing member 11 is closed by the press-fitting of the fixing member 11 into the cylinder 1. Therefore, the passage of liquid between the cylinder 1 and the fixing member 11 can be suppressed without providing a separate sealing member, the increase in the number of parts can be suppressed, and manufacturing costs can be reduced. Furthermore, since the first recess 11a7 and the second recess 11a8 are provided to open from both sides in the axial direction relative to the outer circumferential surface 11a1 of the fixing member 11, fluctuations in the press-fitting load depending on the insertion state of the fixing member 11 into the cylinder 1 can be suppressed, and a good fixing state between the fixing member 11 and the cylinder 1 can be achieved.

[0070] Furthermore, the direction of extension, length, width, and depth of the recesses 11a2, 11a7, and 11a8 provided on the outer circumference of the fixing member 11 may change along the way, and the number of recesses 11a2, 11a7, and 11a8 provided on one fixing member 11 can also be arbitrarily changed. Moreover, the direction of extension, length, width, and depth of each of the multiple recesses 11a2, 11a7, and 11a8 provided on one fixing member 11 may differ, and the shape as seen from the outer circumference can also be arbitrarily designed and modified.

[0071] Furthermore, as shown in the second modified example of the fixing member 11 in Figure 6, the recess 11a9 provided on the outer peripheral surface 11a1 of the inner cylinder 10 may be provided along the circumferential direction midway along the axial direction of the outer peripheral surface 11a1. With the buffer D configured in this way, the space between the cylinder 1 and the fixing member 11 is closed by the press-fitting of the fixing member 11 into the cylinder 1, so the passage of liquid between the cylinder 1 and the fixing member 11 can be suppressed without providing a separate sealing member, the increase in the number of parts can be suppressed, and manufacturing costs can be reduced. Note that the recess 11a9 may be provided intermittently on the outer peripheral surface of the fixing member 11, or it may be provided in a C shape, and its axial width and depth may change midway.

[0072] Furthermore, as shown in the third modified example of the fixing member 11 in Figure 7, the recess 11a10 provided on the outer circumference of the fixing member 11 may be formed to open from one end and extend to the other end along the entire axial length of the outer circumference surface 11a1. In this case, when the fixing member 11 is press-fitted into the inner circumference of the cylinder 1, the spaces on both sides of the cylinder 1 that sandwich the fixing member 11 are connected by the recess, so it is necessary to provide a seal between the fixing member 11 and the valve case 20. However, the contact area of ​​the outer circumference surface 11a1 of the fixing member 11 with respect to the cylinder 1 is reduced, thereby reducing the press-fitting load and suppressing the tilt of the fixing member 11 with respect to the cylinder 1, so the effects of the invention are not lost. Furthermore, the direction of extension, length, width, and depth of the recess 11a10 provided on the outer circumference of the fixing member 11 may change along the way, and the number of recesses 11a10 provided on one fixing member 11 can also be arbitrarily changed. The direction in which each of the multiple recesses 11a10 provided on a single fixing member 11 extends, its length, width, and depth may differ, and the shape as viewed from the outer periphery can also be arbitrarily designed and modified.

[0073] Furthermore, in the buffer D of this embodiment, the lock piece 12 is a cylindrical shape with a C-shaped cross-section that is elastic and connected to the piston rod 2 via the piston 3 and can be fitted onto the outer circumference of the inner cylinder 10. When fitted onto the outer circumference of the inner cylinder 10, it forms a hydraulic lock chamber L between the cylinder 1 and the inner cylinder 10. The fixing member 11 has an annular fixing member body 11a having an outer surface 11a1, and a plurality of relief ports 11b that penetrate the fixing member body 11a in the axial direction and are provided between recesses 11a2 in the circumferential direction relative to the fixing member body 11a. The fixing member body 11a is equipped with a relief valve 25 which is stacked on the anti-pressure side chamber side, which is the lower end in Figure 1, and opens and closes the outlet end of the relief port 11b.

[0074] With the buffer D configured in this way, a cylindrical lock piece 12 with a C-shaped cross-section is inserted between the inner cylinder 10 and the cylinder 1 to form a hydraulic lock chamber L. During contraction, the pressure in the hydraulic lock chamber L causes the lock piece 12 to shrink in diameter and fit onto the outer circumference of the inner cylinder 10, increasing the pressure in the hydraulic lock chamber L. The relief valve 25 prevents the pressure in the hydraulic lock chamber L from becoming excessive. During extension, even if the lock piece 12 is inserted between the cylinder 1 and the inner cylinder 10, the lock piece 12 expands in diameter, allowing liquid to quickly flow from the inner cylinder 10 into the hydraulic lock chamber L without hindering the extension operation. Furthermore, since the cylindrical lock piece 12 is mounted on the piston 3, when partitioning the hydraulic lock chamber L between the inner cylinder 10 and the cylinder 1, communication between the extension port 3c and compression port 3d provided on the piston 3 and the compression chamber R2 can be ensured through the inner circumference of the lock piece 12, so the lock piece 12 does not get in the way. Furthermore, when the lock piece 12 is brought into sliding contact with the outer circumference of the cylinder 1, the cylinder 1 can be used as a guide to allow the lock piece 12 to smoothly move in and out between the inner cylinder 10, which is centered on the cylinder 1 via the fixing member 11, and the cylinder 1.

[0075] Furthermore, in the shock absorber D of this embodiment, there are three or more recesses 11a2 on the fixed member body 11a, and the circumferential center of the press-fit portion B, which is on the outer circumference of the fixed member body 11a and press-fitted into the cylinder 1 between the recesses 11a2, 11a2, is defined as the central point A. Of the central points A, no two are located on the diametrical direction of the fixed member body 11a, and there are two central points that have the same central angle of 90 degrees or more with any of the central points A.

[0076] With the shock absorber D configured in this way, the press-fit portion B always includes three press-fit portions B, including a central point A that is positioned on the vertex of an isosceles triangle where the apex angle and the two base angles are less than 90 degrees. Furthermore, since the press-fit portions B are not positioned in the diametrical direction of the cylinder 1, a relationship is achieved in which the fixing member 11 is less likely to rotate around an axis perpendicular to the axis of the cylinder 1. This effectively prevents the fixing member 11 from being fixed at an angle relative to the cylinder 1 when it is pressed into the cylinder 1. In addition, since the press-fit portions B are not positioned in the diametrical direction of the cylinder 1, the press-fit load when pressing the fixing member 11 into the cylinder 1 can also be reduced.

[0077] In this embodiment, the shock absorber D is configured as a so-called twin-cylinder type shock absorber with an outer cylinder 4 that forms a reservoir R on the outer circumference of the cylinder 1. However, it may also be configured as a single-cylinder type shock absorber by providing a free piston or diaphragm that partitions the air chamber inside the cylinder 1 and eliminating the outer cylinder 4. In the case of a single-cylinder type shock absorber, the valve case 20, compression damping valve 21, and extension check valve 22 may be eliminated.

[0078] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims.

[0079] 1...Cylinder, 2...Piston rod, 3...Piston, 10...Inner cylinder, 11...Fixing member, 11a...Fixing member body, 11a1...Outer surface, 11a2, 11a9, 11a10...Recesses, 11a7...First recess, 11a8...Second recess, 11b...Relief port, 12...Lock piece, 25...Relief valve, A...Center point, B...Press-fit portion, D...Buffer, L...Hydraulic lock chamber, R1...Extension 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 movable in the axial direction; a piston connected to the piston rod and inserted into the cylinder to divide the inside of the cylinder into an extension chamber and a compression chamber; an inner cylinder located inside the cylinder and housed in the compression chamber; a fixing member whose outer circumference is press-fitted into the inner circumference of the cylinder and fixed to the cylinder, and which holds the inner cylinder; and a locking piece connected to the piston rod and capable of penetrating either the inside or outside of the inner cylinder, which, upon penetrating either the inside or outside of the inner cylinder, forms a hydraulic locking chamber on either the inside or outside of the inner cylinder, wherein the fixing member has a recess on its outer circumference, which is press-fitted into the inner circumference of the cylinder, that reduces the contact area of ​​the outer circumference with the cylinder.

2. A shock absorber according to claim 1, wherein the total length in the axial direction of the fixing member and the axial length on the outer circumferential surface are substantially equal.

3. A shock absorber according to claim 1, wherein the recesses are provided in a plurality in the circumferential direction on the outer peripheral surface, and the recesses open from one end in the axial direction of the fixing member and extend partway to the other end on the outer peripheral surface.

4. A shock absorber according to claim 1, wherein the recess has a first recess that opens from one axial end of the fixing member and extends toward the other end to the middle of the outer peripheral surface, and a second recess that opens from the other axial end of the fixing member and extends toward the one end to the middle of the outer peripheral surface, and the first recess and the second recess are alternately provided in the circumferential direction with respect to the outer peripheral surface.

5. A shock absorber according to claim 1, wherein the recess is provided along the circumferential direction at a point in the axial direction of the outer peripheral surface.

6. A shock absorber according to claim 3, wherein three or more recesses are provided on the fixed member body, and the center of the circumferential direction of the press-fit portion that is press-fitted into the cylinder between the recesses on the outer circumference of the fixed member body is a central point, and any two of the central points do not lie on the diametrical direction of the fixed member body, and there are two central points that have the same central angle of 90 degrees or more with any of the central points.

7. A buffer according to claim 3, wherein the lock piece is a cylindrical shape with a C-shaped cross-section and elastic, connected to the piston rod via the piston and fitted onto the outer circumference of the inner cylinder, and when fitted onto the outer circumference of the inner cylinder, forms the hydraulic lock chamber between the cylinder and the inner cylinder; the fixing member has an annular fixing member body having the outer surface, and a plurality of relief ports that penetrate the fixing member body in the axial direction and are provided between the recesses in the circumferential direction relative to the fixing member body; and the buffer comprises a relief valve stacked on the anti-pressure side chamber of the fixing member body and opening and closing the outlet end of the relief port.

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