Shock absorber

Abstract

To provide a shock absorber which enables improvement of durability of a damping valve.SOLUTION: A shock absorber 1 includes: in a first passage 172 where working fluid L flows from a chamber 19 at the upstream side to a chamber 20 at the downstream side by movement of a piston 18, a first damping force generation mechanism 41 which is operated by the movement of the piston 18 relative to a cylinder 2 to generate damping force; an orifice part 92 which is provided in a manner that enables the working fluid L to circulate separately from the first damping force generation mechanism 41 and allows the upstream side and the downstream side of the first damping force generation mechanism 41 to communicate with each other; a second damping force generation mechanism 145 which is operated prior to the first damping force generation mechanism 41 to generate the damping force when the moving speed of the piston 18 relative to the cylinder 2 is low; and a valve mechanism 151 which is provided in a manner that enables the working fluid L to circulate separately from the second damping force generation mechanism 145 and operated when the second damping force generation mechanism 145 generates the predetermined damping force.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Some shock absorbers have a very low speed damping force generating valve that generates a damping force when the moving speed of the piston relative to the cylinder is very low and close to zero (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-173140 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for improved durability in shock absorbers.

[0005] Therefore, an object of the present invention is to provide a shock absorber that can improve durability. [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of the present invention is a configuration including a cylinder in which a working fluid is sealed, a piston slidably provided within the cylinder and dividing the interior of the cylinder into two chambers, a piston rod connected to the piston and extending to the outside of the cylinder, a first passage through which working fluid flows from the upstream chamber to the downstream chamber as the piston moves, a first damping force generating mechanism provided in the first passage and operated by movement of the piston relative to the cylinder to generate a damping force, an orifice portion provided in the first passage to allow working fluid to flow separately from the first damping force generating mechanism and communicating between the upstream and downstream sides of the first damping force generating mechanism, a second damping force generating mechanism provided in the first passage and operating before the first damping force generating mechanism when the moving speed of the piston relative to the cylinder is low to generate a damping force, and a valve mechanism provided in the first passage to allow working fluid to flow separately from the second damping force generating mechanism and operating when the second damping force generating mechanism generates a predetermined damping force. Effect of the Invention

[0007] According to the present invention, it is possible to improve durability. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a shock absorber according to an embodiment of the present invention. [Diagram 2] 1 is a partial cross-sectional view showing a main portion of a shock absorber according to an embodiment of the present invention. [Diagram 3] 2 is a partial cross-sectional view showing an open valve state of a main part of a shock absorber according to an embodiment of the present invention. FIG. [Figure 4] 1 is a hydraulic circuit diagram showing a main part of a shock absorber according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the upper side in Fig. 1 and Fig. 2 will be referred to as "upper", and the lower side in Fig. 1 and Fig. 2 will be referred to as "lower".

[0010] 1, the shock absorber 1 of the embodiment is a so-called twin-cylinder hydraulic shock absorber, and includes a cylinder 2 in which oil liquid L is sealed as a working fluid. The cylinder 2 includes a cylindrical inner cylinder 3 and a bottomed cylindrical outer cylinder 4 that is larger in diameter than the inner cylinder 3 and is concentrically provided to cover the inner cylinder 3. A reservoir chamber 6 is formed between the inner cylinder 3 and the outer cylinder 4.

[0011] The outer cylinder 4 consists of a stepped cylindrical body member 11 whose axial ends are smaller in diameter than the axial middle part, and a bottom member 12 which is fitted into the lower side of the body member 11 and fixed by welding to close the lower part of the body member 11.

[0012] The shock absorber 1 includes a piston 18 slidably disposed inside the inner tube 3 of the cylinder 2. The piston 18 divides the inner tube 3 into two chambers, an upper chamber 19 which is one chamber, and a lower chamber 20 which is the other chamber. In other words, the piston 18 is slidably disposed inside the cylinder 2 and divides the inner tube 2 into an upper chamber 19 on one side and a lower chamber 20 on the other side. An oil liquid L is sealed in the upper chamber 19 and the lower chamber 20 in the inner tube 3 as a working fluid, and the oil liquid L and gas G are sealed in the reservoir chamber 6 between the inner tube 3 and the outer tube 4 as a working fluid.

[0013] The shock absorber 1 is equipped with a rod-shaped piston rod 21. One axial end of the piston rod 21 is disposed inside the inner tube 3 of the cylinder 2 and connected to the piston 18, and the other axial end portion extends to the outside of the cylinder 2. The piston rod 21 passes through the upper chamber 19, but does not pass through the lower chamber 20. Thus, the upper chamber 19 is a rod side chamber through which the piston rod 21 passes, and the lower chamber 20 is a bottom side chamber on the bottom side of the cylinder 2.

[0014] The piston 18 and the piston rod 21 move together. During the extension stroke of the shock absorber 1, in which the piston rod 21 increases its protruding amount from the cylinder 2, the piston 18 moves toward the upper chamber 19, and during the compression stroke of the shock absorber 1, in which the piston rod 21 decreases its protruding amount from the cylinder 2, the piston 18 moves toward the lower chamber 20.

[0015] A rod guide 22 is fitted to the upper end openings of the inner cylinder 3 and the outer cylinder 4, and a seal member 23 is fitted to the outer cylinder 4 above the rod guide 22, which is on the outer side of the cylinder 2. The rod guide 22 and the seal member 23 are both annular, and the piston rod 21 is slidably inserted through the rod guide 22 and the seal member 23, respectively, and extends from the inside of the cylinder 2 to the outside.

[0016] The rod guide 22 supports the piston rod 21 so as to be movable in the axial direction while restricting its radial movement, and guides the movement of the piston rod 21. The seal member 23 has its outer periphery in close contact with the outer tube 4, and its inner periphery in sliding contact with the outer periphery of the piston rod 21 moving in the axial direction. In this way, the seal member 23 prevents the oil liquid L in the inner tube 3 and the gas G and oil liquid L in the reservoir chamber 6 in the outer tube 4 from leaking to the outside.

[0017] The outer periphery of the rod guide 22 is stepped, with the upper part being larger in diameter than the lower part, and the smaller-diameter lower part fits into the inner periphery of the upper end of the inner cylinder 3, while the larger-diameter upper part fits into the inner periphery of the upper part of the outer cylinder 4. A base valve 25 that separates the lower chamber 20 and the reservoir chamber 6 is installed on the bottom member 12 of the outer cylinder 4, and the inner periphery of the lower end of the inner cylinder 3 is fitted into this base valve 25. The upper end of the outer cylinder 4 is crimped radially inward to form an engagement portion 26, and this engagement portion 26 and the rod guide 22 hold the seal member 23 in between.

[0018] The piston rod 21 has a main shaft portion 27, a mounting shaft portion 28 whose outer diameter is smaller than that of the main shaft portion 27, and a threaded shaft portion 31 provided on the mounting shaft portion 28 opposite to the main shaft portion 27. The main shaft portion 27 has a cylindrical outer circumferential surface. The main shaft portion 27 of the piston rod 21 is slidably fitted into the rod guide 22 and the seal member 23, and the mounting shaft portion 28 and the threaded shaft portion 31 are disposed in the cylinder 2 and connected to the piston 18. The end of the main shaft portion 27 on the mounting shaft portion 28 side is a shaft step portion 29 that expands in the direction perpendicular to the axis. The mounting shaft portion 28 has a cylindrical outer circumferential surface. The threaded shaft portion 31 is provided at the tip position inside the cylinder 2 in the piston rod 21, and a male thread 32 is formed on the outer circumferential surface.

[0019] For example, the portion of the piston rod 21 protruding from the cylinder 2 of the shock absorber 1 is disposed at the top and supported by the vehicle body, and the cylinder 2 is disposed at the bottom and connected to the wheel side. This allows the shock absorber 1 to expand and contract due to the relative movement between the wheel and the vehicle body. If the shock absorber 1 is a single-cylinder type, the cylinder 2 may be supported by the vehicle body and the piston rod 21 may be connected to the wheel side.

[0020] As shown in FIG. 2, the piston 18 is composed of a metal piston body 33 connected to the piston rod 21, a metal case member 34 connected to the piston rod 21, and a circular synthetic resin sliding member 35 that is integrally attached to the outer circumferential surface of the piston body 33 and slides inside the inner cylinder 3.

[0021] The piston body 33 has a disk-shaped main body 36 that forms its main portion, and this main body 36 is formed with a plurality of passage holes 37 that penetrate in the axial direction (only one is shown in Figures 1 and 2 because the views are cross-sectional views) and a plurality of passage holes 39 that penetrate in the axial direction (only one is shown in Figures 1 and 2 because the views are cross-sectional views).

[0022] The multiple passage holes 37 extend linearly along the axial direction of the piston body 33, and are formed at equal pitches in the circumferential direction of the piston body 33. An annular groove 40 that connects the multiple passage holes 37 is formed in the piston body 33 on the side opposite the upper chamber 19 in the axial direction. A first damping force generating mechanism 41 that opens and closes the passages in the annular groove 40 and the multiple passage holes 37 to generate a damping force is provided on the side opposite the upper chamber 19 to the annular groove 40. The multiple passage holes 37 are constantly connected to the upper chamber 19, as will be described later.

[0023] By arranging the first damping force generating mechanism 41 on the opposite side of the piston 18 from the upper chamber 19, the passages in the multiple passage holes 37 and the annular groove 40 become extension-side passages through which the oil liquid L flows from the upper chamber 19, which is the upstream side, to the lower chamber 20, which is the downstream side, when the piston 18 moves toward the upper chamber 19, i.e., during the extension stroke. The first damping force generating mechanism 41 provided for the passages in the multiple passage holes 37 and the annular groove 40 serves as an extension-side damping force generating mechanism that generates a damping force by suppressing the flow of the oil liquid L from the passages in the multiple passage holes 37 and the annular groove 40 on the extension side to the lower chamber 20.

[0024] The multiple passage holes 39 extend linearly along the axial direction of the piston body 33, and are formed at a predetermined pitch in the circumferential direction of the piston body 33. All of the passage holes 39 are formed further outward in the radial direction of the piston body 33 than all of the passage holes 37. A first damping force generating mechanism 42 that opens and closes passages in the multiple passage holes 39 to generate a damping force is provided on the upper chamber 19 side of the multiple passage holes 39.

[0025] By arranging the first damping force generating mechanism 42 on the upper chamber 19 side with respect to the piston 18, the passages in the multiple passage holes 39 become compression-side passages through which the oil L flows from the lower chamber 20, which is the upstream side, to the upper chamber 19, which is the downstream side, when the piston 18 moves toward the lower chamber 20, i.e., during the compression stroke. The first damping force generating mechanism 42 provided for the passages in the multiple passage holes 39 serves as a compression-side damping force generating mechanism that generates a damping force by suppressing the flow of the oil L from the passages in the multiple compression-side passage holes 39 to the upper chamber 19.

[0026] A fitting hole 44 for fitting the mounting shaft portion 28 of the piston rod 21 therein is formed axially through the main body portion 36 of the piston body 33 at its radial center.

[0027] A portion of the main body 36 of the piston body 33 opposite the upper chamber 19 in the axial direction is an annular inner seat portion 46 located radially inward of the opening of the annular groove 40 opposite the upper chamber 19. A portion of the main body 36 of the piston body 33 opposite the upper chamber 19 is an annular valve seat portion 47 constituting a part of the first damping force generating mechanism 41 located radially outward of the opening of the annular groove 40 opposite the upper chamber 19. The annular groove 40 is located between the inner seat portion 46 and the valve seat portion 47. A plurality of passage holes 39 are provided in the main body 36 radially outward of the valve seat portion 47.

[0028] The piston body 33 is formed with a cylindrical fitting tube portion 48 that protrudes from the main body portion 36 toward the opposite side of the upper chamber 19 beyond the valve seat portion 47, outside the multiple passage holes 39 in the radial direction of the piston body 33. The fitting tube portion 48 has an inner circumferential surface that is a cylindrical surface coaxial with the fitting hole 44. The passage hole 39 is provided between the fitting tube portion 48 and the valve seat portion 47 in the radial direction of the main body portion 36.

[0029] At the end of the main body 36 of the piston body 33 on the upper chamber 19 side in the axial direction, an annular inner seat portion 49 is provided radially inside the piston body 33 from the openings of the passage holes 37 on the upper chamber 19 side. At the end of the main body 36 of the piston body 33 on the upper chamber 19 side in the axial direction, a plurality of valve seat portions 50 are provided at intervals in the circumferential direction so as to surround one or more openings on the upper chamber 19 side of the passage holes 39. The inner seat portion 49 and the plurality of valve seat portions 50 protrude toward the upper chamber 19 side in the axial direction from the main body 36. The plurality of valve seat portions 50 are shaped like a petal as a whole. Each of the plurality of passage holes 37 is constantly in communication with the upper chamber 19 via a gap (not shown) between the valve seat portions 50 adjacent to each other in the circumferential direction of the piston body 33. The first damping force generating mechanism 42 includes the plurality of valve seat portions 50 of the piston body 33.

[0030] Between the shaft step 29 of the piston rod 21 and the piston body 33, in order from the piston body 33 side in the axial direction, a plurality of (specifically, two) disks 63 having the same inner diameter and the same outer diameter, a disk 64, a disk 65, and an annular member 67 are stacked, and the mounting shaft portion 28 is fitted to the inside of each of them. The annular member 67 abuts against the shaft step 29 of the piston rod 21. The disks 63 to 65 are all made of metal, and each is a perforated circular flat plate with a constant thickness and a constant radial width. The annular member 67 is made of metal, and is a perforated circular plate with a constant radial width.

[0031] The outer diameter of the disc 63 is approximately the same as the diameter of the circumscribing circle of the multiple valve seat portions 50. The disc 64 has an outer diameter smaller than the outer diameter of the disc 63 and larger than the outer diameter of the inner seat portion 49 of the piston body 33. The disc 65 has an outer diameter smaller than the outer diameter of the disc 64 and smaller than the outer diameter of the inner seat portion 49 of the piston body 33.

[0032] The annular member 67 has a stepped shape with a radially outer portion offset in the axial direction from the remaining portion. The annular member 67 is thicker and more rigid than the disks 63 to 65. The annular member 67 has a base plate portion 68 and a stepped plate portion 69, both of which are annular. The base plate portion 68 is a circular flat plate with a hole of a constant thickness, and the mounting shaft portion 28 can be fitted thereto. The stepped plate portion 69 is located outside the base plate portion 68 in the radial direction of the base plate portion 68 and is offset in the axial direction of the base plate portion 68 from the base plate portion 68. The annular member 67 is attached to the mounting shaft portion 28 in a direction in which the stepped plate portion 69 protrudes from the base plate portion 68 toward the opposite side to the piston 18 in the axial direction, and the base plate portion 68 abuts against the shaft stepped portion 29.

[0033] An annular rubber buffer 70 is disposed on the axially opposite side of the annular member 67 from the piston body 33. The buffer 70 has the main shaft portion 27 of the piston rod 21 fitted inside. The buffer 70 comes into contact with the rod guide 22 (see FIG. 1) when the piston rod 21 is fully extended, thereby absorbing impact.

[0034] Of the multiple discs 63, the disc 63 on the inner seat portion 49 side is constantly in contact with the inner seat portion 49 and can be seated on the multiple valve seat portions 50 to block all of the valve seat portions 50. The multiple discs 63 and one disc 64, both made of thin metal plates, constitute a compression-side main valve 71 of the first damping force generating mechanism 42 that is flexible and can be seated on and removed from the multiple valve seat portions 50. By being lifted from the valve seat portions 50, the main valve 71 communicates the passages in the multiple passage holes 39 with the upper chamber 19 and generates a damping force by suppressing the flow of oil L between the valve seat portions 50. The annular member 67 suppresses deformation of the main valve 71 in the opening direction beyond a specified value.

[0035] Here, in the shock absorber 1, in the passages in the multiple passage holes 39, no orifice portion is provided that is provided to allow the flow of oil liquid L separately from the flow of oil liquid L when the compression side first damping force generating mechanism 42 is opened and that communicates between the upstream and downstream sides of the first damping force generating mechanism 42. In other words, in the shock absorber 1, when the main valve 71 constituting the first damping force generating mechanism 42 is in abutting state against the multiple valve seat portions 50 also constituting the first damping force generating mechanism 42, the passages in the multiple passage holes 39 do not communicate with the upper chamber 19. In other words, in the shock absorber 1, when the main valve 71 is in a closed state, the passages in the multiple passage holes 39 do not communicate with the upper chamber 19.

[0036] On the mounting shaft portion 28 of the piston rod 21, on the opposite side of the shaft step portion 29 in the axial direction of the main body portion 36 of the piston body 33, in order from the main body portion 36 side, one disk 81, one disk 82, one disk 83, one disk 84, and a plurality of disks (specifically, two disks) 85 having the same inner and outer diameters are stacked, with the mounting shaft portion 28 fitted inside each of them. All of the disks 81 to 85 are made of metal, and each is a perforated circular flat plate of a uniform thickness.

[0037] The disk 81 has an outer diameter substantially equal to the outer diameter of the inner seat portion 46 of the piston body 33 and abuts against the inner seat portion 46 .

[0038] The disc 82 has an outer diameter substantially equal to the outer diameter of the valve seat portion 47 of the piston body 33, and is capable of being seated on the valve seat portion 47. The disc 82 is formed with a notch 87 that allows communication between the radial inside and outside of the valve seat portion 47 even when the disc 82 is seated on the valve seat portion 47. The disc 83 has an outer diameter substantially equal to the outer diameter of the disc 82. The disc 84 has an outer diameter smaller than the outer diameter of the disc 83. The disc 85 has an outer diameter smaller than the outer diameter of the disc 84 and smaller than the outer diameter of the inner seat portion 46 of the piston body 33.

[0039] The disk 82 is always in contact with the disk 81 and can be seated on the valve seat portion 47 to close the valve seat portion 47. The disks 82 to 84, all made of thin metal plates, constitute an extension-side main valve 91 of the first damping force generating mechanism 41 that is flexible and can be seated on and removed from the valve seat portion 47. By lifting the main valve 91 from the valve seat portion 47, the upper chamber 19 communicates with the lower chamber 20 via gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33 and the passages in the multiple passage holes 37 and the annular groove 40, and generates a damping force by suppressing the flow of oil L between the valve seat portion 47.

[0040] The passage in the cutout portion 87 of the disk 82 is an orifice portion 92 that is provided to allow the oil liquid L to flow through it separately from the flow of the oil liquid L generated when the first damping force generating mechanism 41 is opened in the passage in the annular groove 40, and communicates between the upstream side and the downstream side of the first damping force generating mechanism 41. In other words, even when the main valve 91 constituting the first damping force generating mechanism 41 is in a closed state in which it abuts against the valve seat portion 47 also constituting the first damping force generating mechanism 41, the orifice portion 92 communicates the upper chamber 19 with the side of the first damping force generating mechanism 41 opposite to the upper chamber 19 through the gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33, the passages in the multiple passage holes 37, and the passage in the annular groove 40.

[0041] On the mounting shaft portion 28 of the piston rod 21, on the opposite side of the upper chamber 19 in the axial direction of the multiple disks 85, there are stacked, in order from the disk 85 side, one case member 34, one disk 100, one disk valve 101 which is a sub-valve, one opening / closing disk 102, one disk 103, one disk 104, and one annular member 105, with the mounting shaft portion 28 of the piston rod 21 fitted inside each of them. The disks 100, 103, 104, the disk valve 101, the opening / closing disk 102, and the annular member 105 are all made of metal, and each is in the form of a perforated circular flat plate of a constant thickness.

[0042] The case member 34 is made of metal and is a one-piece molded product in the shape of a cylinder with a bottom. The case member 34 has a bottom 111 in the shape of a perforated disk, a cylindrical outer tubular part 112 protruding from the outer peripheral edge of the bottom 111 to the opposite side to the disk 85 along the axial direction of the bottom 111, an annular inner flange part 113 protruding inward in the radial direction of the outer tubular part 112 from the end of the outer tubular part 112 opposite the bottom 111 in the axial direction, and an annular inner seat part 114 protruding from the inner peripheral edge of the bottom 111 to the same side as the outer tubular part 112 along the axial direction of the bottom 111. The case member 34 is fitted into the fitting tubular part 48 of the piston body 33 at the bottom 111 and abuts against the disk 85.

[0043] An intermediate chamber 115 is defined by the main body 36 and fitting cylindrical portion 48 of the piston body 33, the bottom portion 111 of the case member 34, and the discs 81 to 85.

[0044] When the main valve 91 is opened, the first damping force generating mechanism 41 communicates the upper chamber 19 with the intermediate chamber 115 via gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33, the passages in the multiple passage holes 37, the passage in the annular groove 40, and a gap between the main valve 91 and the valve seat portion 47. Even when the main valve 91 of the first damping force generating mechanism 41 is in a closed state in which it abuts against the valve seat portion 47, the orifice portion 92 communicates the upper chamber 19 with the intermediate chamber 115 via gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33, the passages in the multiple passage holes 37, and the passage in the annular groove 40.

[0045] The case member 34 has a through hole 120 formed in its radial center, axially penetrating the bottom portion 111 and the inner seat portion 114, into which the mounting shaft portion 28 of the piston rod 21 is fitted.

[0046] In the case member 34, a passage hole 121 penetrating the bottom portion 111 in the axial direction is formed between the outer cylindrical portion 112 and the inner seat portion 114 in the radial direction of the bottom portion 111. In the case member 34, at least one passage hole 121 is provided, in other words, one in the bottom portion 111, and a plurality of passage holes 121 are provided at intervals in the circumferential direction of the bottom portion 111.

[0047] The outer diameter of the disk 100 is smaller than the outer diameter of the inner seat portion 114 of the case member . The disk 100 abuts against the inner seat portion 114 of the case member .

[0048] The disk valve 101 has an inner circumferential side, which is one radial end, fixed to the piston rod 21, and an outer circumferential side, which is the other radial end, formed as a free end. The disk valve 101 is flexible. The disk valve 101 has an outer diameter larger than the outer diameter of the disk 100 and smaller than the inner diameter of the inner circumferential end 113a of the inner flange portion 113 of the case member 34. The disk valve 101 is formed with a communication hole 131 penetrating the disk valve 101 in the axial direction. The thickness of the disk valve 101 is approximately equal to the axial length of the inner circumferential end 113a of the inner flange portion 113 of the case member 34.

[0049] The open-close disc 102 is flexible. The open-close disc 102 has an outer diameter smaller than that of the disc valve 101. The open-close disc 102 has an outer diameter portion located outside an outer end of the communication hole 131 of the disc valve 101 in the radial direction of the disc valve 101. The open-close disc 102 has an inner diameter portion located inside an inner end of the communication hole 131 in the radial direction of the disc valve 101. Thus, the open-close disc 102 overlaps with the entire communication hole 131 of the disc valve 101 in the radial direction. As a result, when the open-close disc 102 is in full contact with the disc valve 101, the open-close disc 102 covers the entire communication hole 131 and closes the communication hole 131. The disc valve 101 is formed to have a lower rigidity than the open-close disc 102.

[0050] The outer diameter of the disk 103 is smaller than the outer diameter of the open / close disk 102, and the outer diameter portion is located inside the inner end of the communication hole 131 of the disk valve 101 in the radial direction of the disk valve 101. Therefore, the disk 103 does not overlap with the communication hole 131 of the disk valve 101 in the radial direction.

[0051] The disk 104 has an outer diameter larger than that of the disk 103 and smaller than that of the opening / closing disk 102 .

[0052] The outer diameter of the annular member 105 is larger than the outer diameter of the disk 104 and smaller than the outer diameter of the open-close disk 102. The annular member 105 is thicker and more rigid than the disk valve 101 and the open-close disk 102. The annular member 105 comes into contact with the open-close disk 102 when the open-close disk 102 deforms, thereby suppressing further deformation of the open-close disk 102.

[0053] A threaded shaft portion 31 is disposed on the piston rod 21 on the axial opposite side of the mounting shaft portion 28 from the main shaft portion 27, and on a portion that protrudes beyond the annular member 105 on the opposite side from the main shaft portion 27. A nut 135 is screwed onto the male thread 32 of the threaded shaft portion 31 of the piston rod 21. The nut 135 abuts against the annular member 105, and together with the shaft step portion 29 of the piston rod 21, clamps at least the inner peripheral side of the parts from the annular member 67 to the annular member 105 in the axial direction.

[0054] When the disc valve 101 is in an undeformed state, it is aligned with the inner peripheral end portion 113a of the inner flange portion 113 of the case member 34 in the axial direction of the piston rod 21 and faces this inner peripheral end portion 113a in the radial direction.

[0055] The open / close disk 102 is located on the opposite side of the inner flange portion 113 of the case member 34 from the bottom portion 111 in the axial direction of the piston rod 21 .

[0056] The area surrounded by the bottom 111, outer cylindrical portion 112, inner flange portion 113, inner seat portion 114 of the case member 34, the disk 100, the disk valve 101, and the open-close disk 102 forms a case chamber 141. The case chamber 141 communicates with the intermediate chamber 115 via the passage hole 121 of the case member 34.

[0057] When the disc valve 101 is in a non-deformed state and aligned axially with the inner peripheral end 113a of the inner flange portion 113 of the case member 34, the gap between the disc valve 101 and the inner peripheral end 113a of the inner flange portion 113 is narrowest. This gap serves as a communication passage 142 that connects the case chamber 141 with the lower chamber 20. The communication passage 142 is annular. The communication passage 142 is formed between the disc valve 101 and the case member 34 that is provided on the radial outer periphery of the disc valve 101.

[0058] When the outer circumferential side of the disc valve 101 moves away from the inner circumferential end 113a of the inner flange portion 113 of the case member 34 in the axial direction, the gap between the inner circumferential end 113a of the inner flange portion 113 increases.

[0059] When the pressure on the case chamber 141 side becomes higher than the pressure on the lower chamber 20 side by a predetermined value or more, the disc valve 101 elastically deforms so that the outer circumferential side moves away from the inner circumferential end 113a of the inner flange portion 113 of the case member 34 to the side opposite the bottom 111, and oil liquid L flows from the case chamber 141 to the lower chamber 20 through the gap with the inner circumferential end 113a of the inner flange portion 113. The deforming disc valve 101 and the inner flange portion 113 of the case member 34 at this time form a second damping force generating mechanism 145.

[0060] When the pressure on the lower chamber 20 side becomes higher than the pressure on the case chamber 141 side by a predetermined value or more, the disc valve 101 elastically deforms so that the outer circumferential side approaches the bottom 111 from the inner circumferential end 113a of the inner flange portion 113 of the case member 34, and oil liquid L flows from the lower chamber 20 to the case chamber 141 through the gap with the inner circumferential end 113a of the inner flange portion 113. The deforming disc valve 101 and the inner flange portion 113 of the case member 34 at this time form a second damping force generating mechanism 146.

[0061] Therefore, when the disc valve 101 deforms away from the bottom 111, it constitutes a second damping force generating mechanism 145, and when it deforms toward the bottom 111, it constitutes a second damping force generating mechanism 146.

[0062] The communication passage 142 is a passage that communicates between the case chamber 141 and the lower chamber 20, and is provided to allow the flow of oil liquid L separately from the flow of oil liquid L generated when the second damping force generating mechanism 145 is open, and communicates between the case chamber 141 on the upstream side of the second damping force generating mechanism 145 and the lower chamber 20 on the downstream side. In other words, the shock absorber 1 communicates between the case chamber 141 and the lower chamber 20 via the communication passage 142 even when the disc valve 101 constituting the second damping force generating mechanism 145 is in a closed state in which it is closest to the inner flange portion 113 also constituting the second damping force generating mechanism 145.

[0063] The communication passage 142 is a passage that communicates between the lower chamber 20 and the case chamber 141, and is provided to allow the oil liquid L to flow therethrough separately from the oil liquid L generated when the second damping force generating mechanism 146 is open, thereby communicating the lower chamber 20 on the upstream side of the second damping force generating mechanism 146 with the case chamber 141 on the downstream side. That is, the shock absorber 1 communicates between the lower chamber 20 and the case chamber 141 via the communication passage 142 even when the disc valve 101 constituting the second damping force generating mechanism 146 is in a closed state in which it is closest to the inner flange portion 113 also constituting the second damping force generating mechanism 146.

[0064] The communication hole 131 of the disk valve 101 and its surroundings, and the open-close disk 102 constitute a valve mechanism 151. When the open-close disk 102 is in full contact with the disk valve 101, the valve mechanism 151 closes the communication hole 131 provided in the disk valve 101, blocking communication between the upstream case chamber 141 and the downstream lower chamber 20. When the open-close disk 102 deforms so as to move away from the disk valve 101, the valve mechanism 151 opens the communication hole 131 provided in the disk valve 101, connecting the upstream case chamber 141 and the downstream lower chamber 20. In other words, the valve mechanism 151 opens and closes the communication hole 131 provided in the disk valve 101, which connects the upstream case chamber 141 and the downstream lower chamber 20.

[0065] In a state where the pressure in the case chamber 141 does not exceed the pressure in the lower chamber 20 by a predetermined value or more, including when the disc valve 101 is deformed, the open-close disc 102 comes into full contact with the disc valve 101 to close the communication hole 131. In this state, the valve mechanism 151 does not allow the oil L to flow between the case chamber 141 and the lower chamber 20 through the communication hole 131.

[0066] When the pressure in the case chamber 141 becomes higher than the pressure in the lower chamber 20 by a predetermined value or more, the valve mechanism 151 deforms so that the opening / closing disc 102 moves away from the disc valve 101, thereby opening the communication hole 131. In this state, the valve mechanism 151 allows the oil L to flow from the case chamber 141 to the lower chamber 20 through the communication hole 131.

[0067] In order to operate as described above, the valve mechanism 151 is formed so that the opening area of ​​the communication hole 131 is larger than the pressure-receiving area (the area of ​​the portion excluding the communication hole 131 at the portion radially outward of the disk 100 of the disk valve 101) where the disk valve 101 receives pressure from the oil liquid L from the upstream case chamber 141. In other words, the valve mechanism 151 is formed so that the pressure-receiving area where the disk valve 101 receives pressure from the oil liquid L from the upstream case chamber 141 is larger than the pressure-receiving area where the disk valve 101 receives pressure from the oil liquid L from the case chamber 141. In other words, the valve mechanism 151 is formed so that the pressure-receiving area where the opening / closing disk 102 receives pressure from the oil liquid L from the upstream case chamber 141 is larger than the pressure-receiving area where the disk valve 101 receives pressure from the oil liquid L from the case chamber 141.

[0068] Here, when the pressure in the lower chamber 20 becomes higher than the pressure in the case chamber 141 and the disc valve 101 deforms toward the bottom 111, if the pressure difference between the lower chamber 20 and the case chamber 141 is less than a predetermined value, the valve mechanism 151 maintains a state in which the open-close disc 102 deforms together with the disc valve 101 and is in full contact with the disc valve 101. In this state, the valve mechanism 151 does not allow the oil liquid L to flow from the lower chamber 20 to the case chamber 141 through the communication hole 131. When the pressure in the lower chamber 20 becomes higher than the pressure in the case chamber 141 by a predetermined value or more, the rigidity of the disc valve 101 is set lower than that of the open-close disc 102, so that the amount of bending of the disc valve 101 becomes larger than the amount of bending of the open-close disc 102, as shown in FIG. When the amount of deflection of the disk valve 101 becomes larger than the amount of deflection of the open-close disk 102, a portion of the disk valve 101 that is on the outer diameter side of the communication hole 131 separates from the contact portion 201 on the outer diameter side of the open-close disk 102 that had been in contact with the disk valve 101 until then, and the pressure-receiving area of ​​the disk valve 101 increases, while the pressure-receiving area of ​​the open-close disk 102 decreases by the amount of separation from the disk valve 101, and the amount of deflection is suppressed. In this way, the contact portion 201 of the open-close disk 102 separates from the portion on the outer diameter side of the communication hole 131 of the disk valve 101, and the communication hole 131 of the disk valve 101 communicates with the lower chamber 20 and the case chamber 141. That is, as shown by the arrows in FIG. 3, the oil L flows from the lower chamber 20 to the case chamber 141 through the communication hole 131 in addition to the flow between the inner flange portion 113 of the second damping force generating mechanism 146 and the disk valve 101. The disk valve 101 and the opening / closing disk 102 also constitute a valve mechanism 151b that opens during the compression stroke.

[0069] The valve mechanism 151 is provided in a passage that communicates the case chamber 141 and the lower chamber 20 so as to allow the oil liquid L to flow therethrough separately from the flow of the oil liquid L generated when the second damping force generating mechanism 145 is open, and communicates the case chamber 141 on the upstream side of the second damping force generating mechanism 145 with the lower chamber 20 on the downstream side. That is, when the disc valve 101 constituting the second damping force generating mechanism 145 is in an open state separated from the inner flange portion 113 also constituting the second damping force generating mechanism 145, the valve mechanism 151 allows the oil liquid L to flow between the case chamber 141 and the lower chamber 20 via a passage in the communication hole 131 provided in the disc valve 101 separately from the flow of the oil liquid L generated between the disc valve 101 and the inner flange portion 113.

[0070] The passage between the disc valve 101 and the inner flange portion 113 that appears when the compression side second damping force generating mechanism 146 is opened, the case chamber 141, and the passage inside the passage hole 121 of the case member 34 constitute a passage portion 161. In addition, the orifice portion 92 in the cutout portion 87 of the disc 82, the passage inside the annular groove 40 of the piston body 33 and the passages inside the plurality of passage holes 37, and gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33 constitute a passage portion 162. The passage portion 161 and the passage portion 162 communicate with each other via the intermediate chamber 115.

[0071] The passage portion 161, the intermediate chamber 115, and the passage portion 162 are connected in series. The passage portion 161, the intermediate chamber 115, and the passage portion 162 form a compression-side passage 163 through which the oil L flows from the lower chamber 20, which is the upstream side within the cylinder 2, to the upper chamber 19, which is the downstream side, as the piston 18 moves toward the lower chamber 20 during the compression stroke. When constituting the second damping force generating mechanism 146, the disc valve 101 has an outer circumferential edge portion that approaches or moves away from the inner circumferential end portion 113a of the inner flange portion 113 of the case member 34 to open and close the passage portion 161 of the passage 163.

[0072] The disc valve 101 and the inner flange portion 113 that constitute the second damping force generating mechanism 146 are provided in a passage portion 161 of a compression-side passage 163, and open and close this passage portion 161 to suppress the flow of oil L from this passage portion 161 to the upper chamber 19 side, thereby generating a damping force. Therefore, the second damping force generating mechanism 146 is a compression-side damping force generating mechanism.

[0073] The passage between the main valve 71 and the valve seat portion 50 that appears when the compression side first damping force generating mechanism 42 is opened, and the passages within the multiple passage holes 39 of the piston body 33 form a passage portion 164 that can connect the passage portion 161 to the upper chamber 19 via the intermediate chamber 115.

[0074] The passage 161, the intermediate chamber 115, and the passage 164 are connected in series. The passage 161, the intermediate chamber 115, and the passage 164 form a compression-side passage 165 through which the oil L flows from the lower chamber 20, which is the upstream side in the cylinder 2, to the upper chamber 19, which is the downstream side, as the piston 18 moves toward the lower chamber 20 during the compression stroke. The first damping force generating mechanism 42 on the compression side opens and closes the passage 164 of the passage 165, suppressing the flow of the oil L from the passage 164 to the upper chamber 19, thereby generating a damping force. The first damping force generating mechanism 42 and the second damping force generating mechanism 146 on the compression side are both arranged in series in the passage 165 consisting of the passages 161, 164, and the intermediate chamber 115, so that the second damping force generating mechanism 146 is on the upstream side and the first damping force generating mechanism 42 is on the downstream side.

[0075] When the first damping force generating mechanism 42 is in a closed state and the second damping force generating mechanism 146 is in an open state, in a passage 163 consisting of the passages 161, 162 and the intermediate chamber 115, the orifice portion 92 in the cutout portion 87 of the disk 82 has a flow path cross-sectional area narrowed down more than in the front and rear. The orifice portion 92 is disposed downstream of the second damping force generating mechanism 146 in the flow of the oil liquid L when the disk valve 101 of the second damping force generating mechanism 146 is opened and the oil liquid L flows in the passage 163. In other words, the orifice portion 92 is disposed closer to the upper chamber 19 than the second damping force generating mechanism 146 in the passage 163 when the first damping force generating mechanism 42 is in a closed state and the second damping force generating mechanism 146 is in an open state.

[0076] When the first damping force generating mechanism 42 is in a closed state and the second damping force generating mechanism 146 is also in a closed state, the cross-sectional area of ​​the communication passage 142 between the disc valve 101 of the second damping force generating mechanism 146 and the inner flange portion 113 is narrowed more than in the front and rear in a passage 163 consisting of the passage portions 161, 162 and the intermediate chamber 115. The communication passage 142 is disposed upstream of the orifice portion 92 of the flow of the oil liquid L when the oil liquid L is caused to flow in the passage 163 with the disc valve 101 of the second damping force generating mechanism 146 in a closed state. In other words, the communication passage 142 is disposed closer to the lower chamber 20 than the orifice portion 92 in the passage 163 when the first damping force generating mechanism 42 is in a closed state and the second damping force generating mechanism 146 is also in a closed state.

[0077] When configuring the second damping force generating mechanism 145, the disc valve 101 has its outer circumferential side separated from the inner flange portion 113, thereby connecting the upper chamber 19 to the lower chamber 20 via gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33, the passages in the multiple passage holes 37, the passage in the annular groove 40, the orifice portion 92 in the cutout portion 87 of the disc 82, the intermediate chamber 115, the passage in the passage hole 121 of the case member 34, and the case chamber 141. At this time, the disc valve 101 of the second damping force generating mechanism 145 generates a damping force by suppressing the flow of oil L between it and the inner flange portion 113.

[0078] The gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33, the passages in the multiple passage holes 37, the passages in the annular groove 40, and the orifice portion 92 in the cutout portion 87 form the above-mentioned passage portion 162. The passage in the passage hole 121 of the case member 34, the case chamber 141, and the passage between the disc valve 101 and the inner flange portion 113 of the second damping force generating mechanism 145 that appears when the valve is open form a passage portion 171.

[0079] The passage portion 162, the intermediate chamber 115, and the passage portion 171 are connected in series. The passage portion 162, the intermediate chamber 115, and the passage portion 171 form a first passage 172 on the extension side through which the oil L flows from the upper chamber 19, which is the upstream side within the cylinder 2, to the lower chamber 20, which is the downstream side, as the piston 18 moves toward the upper chamber 19 during the extension stroke. The disc valve 101 of the second damping force generating mechanism 145 opens and closes the first passage 172 by moving its outer circumferential edge toward or away from the inner flange portion 113.

[0080] A second damping force generating mechanism 145 consisting of the disc valve 101 and the inner flange portion 113 is provided in a first passage 172 consisting of the extension-side passage portions 162, 171 and the intermediate chamber 115, and opens and closes the passage portion 171 to suppress the flow of oil L from the first passage 172 to the lower chamber 20, thereby generating a damping force. The second damping force generating mechanism 145 is an extension-side damping force generating mechanism.

[0081] A first passage 172 consisting of the passage portions 162, 171 and the intermediate chamber 115 includes a passage between the main valve 91 and the valve seat portion 47 that appears when the first damping force generating mechanism 41 is open. The first damping force generating mechanism 41 opens and closes the first passage 172 to suppress the flow of oil L from the upper chamber 19 to the lower chamber 20 via the first passage 172, thereby generating a damping force. The first damping force generating mechanism 41 and the second damping force generating mechanism 145, both of which are on the extension side, are arranged in series in the first passage 172 such that the first damping force generating mechanism 41 is on the upstream side and the second damping force generating mechanism 145 is on the downstream side.

[0082] In the first passage 172 consisting of the passage portions 162, 171 and the intermediate chamber 115, when the first damping force generating mechanism 41 is in a closed state and the second damping force generating mechanism 145 is in an open state, the orifice portion 92 in the cutout portion 87 of the disk 82 has a flow path cross-sectional area narrowed more than in the front and rear. The orifice portion 92 is disposed upstream of the second damping force generating mechanism 145 in the flow of the oil liquid L when the second damping force generating mechanism 145 is open and the oil liquid L flows in the first passage 172. In other words, the orifice portion 92 is disposed on the upper chamber 19 side of the second damping force generating mechanism 145 in the first passage 172.

[0083] In the first passage 172 consisting of the passages 162, 171 and the intermediate chamber 115 when the first damping force generating mechanism 41 is in a closed state and the second damping force generating mechanism 145 is also in a closed state, the flow path cross-sectional area of ​​the communication passage 142 between the disc valve 101 and the inner flange portion 113 is narrowed more than in the front and rear. The communication passage 142 is disposed downstream of the orifice portion 92 of the flow of the oil liquid L when the oil liquid L flows in the first passage 172 with the disc valve 101 of the second damping force generating mechanism 145 in a closed state. In other words, the communication passage 142 is disposed closer to the lower chamber 20 than the orifice portion 92 in the first passage 172 when the first damping force generating mechanism 41 is in a closed state and the second damping force generating mechanism 145 is also in a closed state.

[0084] In the valve mechanism 151, a passage in the communication hole 131, which is generated when the open-close disc 102 is separated from the disc valve 101, and a passage between the open-close disc 102 and the disc valve 101 constitute a passage portion 171 of a first passage 172. Therefore, the valve mechanism 151 opens and closes the passage portion 171 of the first passage 172.

[0085] In the first passage 172, oil L flows from the upper chamber 19 on the upstream side to the lower chamber 20 on the downstream side due to the movement of the piston 18. The first damping force generating mechanism 41 is provided in the first passage 172, and is operated by the movement of the piston 18 relative to the cylinder 2 to generate a damping force. The orifice portion 92 is provided in the first passage 172 to allow the oil L to flow separately from the first damping force generating mechanism 41, and connects the upper chamber 19 on the upstream side of the first damping force generating mechanism 41 to the intermediate chamber 115 on the downstream side.

[0086] The valve mechanism 151 is provided in the first passage 172 to allow oil L to flow separately from the second damping force generating mechanism 145, and operates when the second damping force generating mechanism 145 generates a predetermined damping force. The valve mechanism 151 operates to open at a predetermined pressure during the extension stroke of the piston 18 relative to the cylinder 2, and operates to close at a predetermined pressure during the compression stroke of the piston 18 relative to the cylinder 2.

[0087] In the shock absorber 1, the damping force characteristics when the second damping force generating mechanisms 145, 146 are operated change depending on the shape of the case member 34. That is, for example, by lengthening or shortening the axial length of the inner peripheral end 113a of the inner flange portion 113 in the direction away from the bottom portion 111 relative to the thickness of the disc valve 101, the damping force characteristics when the second damping force generating mechanism 145 is operated change. Also, for example, by lengthening or shortening the axial length of the inner peripheral end 113a of the inner flange portion 113 in the direction toward the bottom portion 111 relative to the thickness of the disc valve 101, the damping force characteristics when the second damping force generating mechanism 146 is operated change.

[0088] A hydraulic circuit diagram of a configuration in which oil L flows between an upper chamber 19 and a lower chamber 20 provided in a piston rod 21 is as shown in FIG.

[0089] As shown in Fig. 4, the first damping force generating mechanism 41 is provided in a passage portion 162 connecting the upper chamber 19 and the intermediate chamber 115. In addition, an orifice portion 92 is provided in the passage portion 162 separately from the first damping force generating mechanism 41 and in parallel with the first damping force generating mechanism 41. The second damping force generating mechanism 145 is provided in a passage portion 171 connecting the intermediate chamber 115 and the lower chamber 20. In addition, a communication passage 142 is provided in the passage portion 171 separately from the second damping force generating mechanism 145 and in parallel with the second damping force generating mechanism 145. In addition, a valve mechanism 151 that opens during the expansion stroke and a valve mechanism 151b that opens during the compression stroke are provided in the passage portion 171 separately from the second damping force generating mechanism 145 and the communication passage 142 and in parallel with the second damping force generating mechanism 145.

[0090] Moreover, a second damping force generating mechanism 146 is provided in parallel to the second damping force generating mechanism 145, the communication passage 142, and the valve mechanism 151 in a passage portion 161 connecting the lower chamber 20 and the intermediate chamber 115. Moreover, a first damping force generating mechanism 42 is provided in parallel to the first damping force generating mechanism 41 and the orifice portion 92 in a passage portion 164 connecting the intermediate chamber 115 and the upper chamber 19.

[0091] 1, the above-mentioned base valve 25 is provided between the bottom member 12 of the outer cylinder 4 and the inner cylinder 3. This base valve 25 has a base valve member 191 that separates the lower chamber 20 and the reservoir chamber 6, a disk 192 provided on the lower side of this base valve member 191, i.e., on the reservoir chamber 6 side, a disk 193 provided on the upper side of the base valve member 191, i.e., on the lower chamber 20 side, and a mounting pin 194 for mounting the disk 192 and the disk 193 to the base valve member 191.

[0092] The base valve member 191 has an annular shape, and a mounting pin 194 is inserted through the center in the radial direction. The base valve member 191 is formed with a plurality of passage holes 195 through which the oil L can flow between the lower chamber 20 and the reservoir chamber 6, and a plurality of passage holes 196 through which the oil L can flow between the lower chamber 20 and the reservoir chamber 6, which are formed radially outward of the base valve member 191 from the passage holes 195. The disk 192 on the reservoir chamber 6 side allows the oil L to flow from the lower chamber 20 to the reservoir chamber 6 via the passage hole (not shown) of the disk 193 and the passage hole 195 of the base valve member 191, while suppressing the flow of the oil L from the reservoir chamber 6 to the lower chamber 20 via the passage hole 195 and the passage hole (not shown) of the disk 193. The disk 193 allows the flow of oil L from the reservoir chamber 6 to the lower chamber 20 via the passage hole 196, while restricting the flow of oil L from the lower chamber 20 to the reservoir chamber 6 via the passage hole 196.

[0093] The disk 192, together with the base valve member 191, constitutes a compression-side damping valve mechanism 197 that opens during the compression stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the lower chamber 20 to the reservoir chamber 6 and generate a damping force. The disk 193, together with the base valve member 191, constitutes a suction valve mechanism 198 that opens during the extension stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the reservoir chamber 6 into the lower chamber 20. The suction valve mechanism 198 mainly functions to allow hydraulic fluid L to flow from the reservoir chamber 6 to the lower chamber 20 without generating any damping force, so as to make up for a shortage of hydraulic fluid caused by the extension of the piston rod 21 from the cylinder 2.

[0094] 2, the first damping force generating mechanism 41 and the second damping force generating mechanism 145, both of which are on the extension side, are provided in a first passage 172 consisting of passages 162, 171 and an intermediate chamber 115. The main valve 91 of the first damping force generating mechanism 41 has higher rigidity and a higher valve opening pressure than the disc valve 101 of the second damping force generating mechanism 145. Therefore, in the extension stroke, in a region where the moving speed of the piston (hereinafter referred to as piston speed) is slower than a predetermined value, the first damping force generating mechanism 41 is closed and the second damping force generating mechanism 145 is open.

[0095] In addition, in a normal speed region where the piston speed is equal to or higher than this predetermined value, both the first damping force generating mechanism 41 and the second damping force generating mechanism 145 open. In other words, the first damping force generating mechanism 41 is provided in a first passage 172 consisting of the passages 162, 171 and the intermediate chamber 115, and closes in a region where the piston speed is low, and opens in a region where the piston speed is higher than low. The second damping force generating mechanism 145 is provided in the first passage 172 consisting of the passages 162, 171 and the intermediate chamber 115, and opens from the region where the piston speed is low. The disc valve 101 of the second damping force generating mechanism 145 is an extremely low speed valve that opens in a region where the piston speed is extremely low to generate a damping force. The second damping force generating mechanism 145 is provided in a first passage 172 consisting of passage portions 162, 171 and the intermediate chamber 115, and operates before the first damping force generating mechanism 41 when the moving speed of the piston 18 relative to the cylinder 2 is low, thereby generating a damping force.

[0096] During the extension stroke, the piston 18 moves toward the upper chamber 19, so that the pressure in the upper chamber 19 increases and the pressure in the lower chamber 20 decreases. During the extension stroke when the piston speed is less than the first predetermined value, neither the first damping force generating mechanism 41 nor the second damping force generating mechanism 145 provided in the first passage 172 consisting of the passages 162, 171 and the intermediate chamber 115 opens. Therefore, the oil L from the upper chamber 19 flows through the first passage 172 consisting of the passages 162, 171 and the intermediate chamber 115, is throttled by the communication passage 142 provided in the passage 171, and flows to the lower chamber 20. Therefore, during the extension stroke when the piston speed is less than the first predetermined value, a damping force with orifice characteristics (where the damping force is approximately proportional to the square of the piston speed) is obtained, and the damping force rises up rapidly.

[0097] In a region where the piston speed is equal to or higher than a first predetermined value where the second damping force generating mechanism 145 opens, and in a very low speed region where the piston speed is faster than the first predetermined value and slower than a second predetermined value, the first damping force generating mechanism 41 is closed and the second damping force generating mechanism 145 opens. In other words, the disc valve 101 of the second damping force generating mechanism 145 deforms toward the lower chamber 20 together with the opening / closing disc 102 and moves away from the inner flange portion 113, and communicates between the upper chamber 19 and the lower chamber 20 through a first passage 172 consisting of the passage portions 162, 171 and the intermediate chamber 115. Therefore, the oil liquid L in the upper chamber 19 flows into the lower chamber 20 through gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33, the passages in the multiple passage holes 37, the passages in the annular groove 40, the orifice portion 92, the intermediate chamber 115, the passages in the multiple passage holes 121 in the case member 34, the case chamber 141, and the passage between the open disc valve 101 and the inner flange portion 113 of the second damping force generating mechanism 145. As a result, a damping force with valve characteristics (a characteristic in which the damping force is approximately proportional to the piston speed) can be obtained even in an extremely low speed region where the piston speed is slower than the second predetermined value.

[0098] In addition, during the extension stroke, in the region where the piston speed is equal to or greater than the second predetermined value and in the normal speed region which is faster than the second predetermined value and slower than a third predetermined value, the first damping force generating mechanism 41 opens while the second damping force generating mechanism 145 remains open. In other words, the disc valve 101 of the second damping force generating mechanism 145 moves away from the inner flange portion 113, and the oil liquid L flows from the upper chamber 19 to the lower chamber 20 through a first passage 172 consisting of the passage portions 162, 171 and the intermediate chamber 115. At this time, the flow of the oil liquid L is narrowed by the orifice portion 92 located upstream of the second damping force generating mechanism 145 in the first passage 172, so that the pressure applied to the main valve 91 of the first damping force generating mechanism 41 increases and the pressure difference increases. As a result, the main valve 91 moves away from the valve seat portion 47, and the oil liquid L flows from the upper chamber 19 to the lower chamber 20 through the first passage 172, which is wider than the orifice portion 92. Therefore, the oil liquid L in the upper chamber 19 flows into the lower chamber 20 through gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33, the passages in the multiple passage holes 37, the passage in the annular groove 40, the passage between the main valve 91 in the open state and the valve seat portion 47, the intermediate chamber 115, the passage in the passage hole 121 of the case member 34, the case chamber 141, and the passage between the disc valve 101 in the open state and the inner flange portion 113 of the second damping force generating mechanism 145. As a result, a damping force with valve characteristics (damping force approximately proportional to piston speed) can be obtained even in a normal speed range where the piston speed is equal to or higher than the second predetermined value.

[0099] The rate of increase in the extension damping force with respect to an increase in the piston speed in the normal speed region is lower than the rate of increase in the extension damping force with respect to an increase in the piston speed in the extremely low speed region. In other words, the slope of the rate of increase in the extension damping force with respect to an increase in the piston speed in the normal speed region can be made gentler than in the extremely low speed region.

[0100] Here, during the extension stroke, when the piston speed reaches or exceeds a third predetermined value and the second damping force generating mechanism 145 generates a predetermined damping force, the valve mechanism 151 provided in the first passage 172 consisting of the passage portions 162, 171 and the intermediate chamber 115 opens while the second damping force generating mechanism 145 and the first damping force generating mechanism 41 remain open. That is, the disc valve 101 of the second damping force generating mechanism 145 moves away from the inner flange portion 113, and the main valve 91 of the first damping force generating mechanism 41 moves away from the valve seat portion 47 to cause the oil liquid L to flow from the upper chamber 19 to the lower chamber 20 through the first passage 172 consisting of the passage portions 162, 171 and the intermediate chamber 115, and in addition, the valve mechanism 151 provided in the first passage 172 opens to cause the oil liquid L to flow from the upper chamber 19 to the lower chamber 20 through the passage in the communication hole 131 of the disc valve 101. That is, the open-close disc 102 moves away from the disc valve 101 to open the communication hole 131 of the disc valve 101, and a passage is provided in the first passage 172 via the communication hole 131. As a result, the oil L flowing from the upper chamber 19 through the first passage 172 to the lower chamber flows through the passage in the communication hole 131 of the disc valve 101 to the lower chamber 20.

[0101] When the communication hole 131 opens, the disc valve 101 eliminates the pressure difference between the case chamber 141 side and the lower chamber 20 side, and the outer circumferential edge returns from the elastically deformed state to align with the inner flange portion 113 of the case member 34 in the axial direction. As a result, most of the oil L flowing from the upper chamber 19 through the first passage 172 to the lower chamber 20 flows through the passage in the communication hole 131 of the disc valve 101 to the lower chamber 20. In this way, by eliminating the pressure difference between the case chamber 141 side and the lower chamber 20 side of the disc valve 101, excessive deformation of the disc valve 101 can be suppressed.

[0102] Of the first damping force generating mechanism 42 and the second damping force generating mechanism 146, both of which are on the compression side, the main valve 71 of the first damping force generating mechanism 42 has higher rigidity and a higher valve opening pressure than the disc valve 101 of the second damping force generating mechanism 146. Therefore, during the compression stroke, in a region where the piston speed is slower than a predetermined value, the first damping force generating mechanism 42 is closed and the second damping force generating mechanism 146 is open, and in a normal speed region where the piston speed is equal to or higher than the predetermined value, both the second damping force generating mechanism 146 and the first damping force generating mechanism 42 are open. In other words, the first damping force generating mechanism 42 is provided in a passage 165 consisting of the passages 161, 164 and the intermediate chamber 115, and is closed in a region where the piston speed is low, and is open in a region where the piston speed is higher than low. The second damping force generating mechanism 146 is provided in a passage 165 consisting of the passages 162, 164 and the intermediate chamber 115, and opens when the piston speed is in a low speed range. The disc valve 101 of the second damping force generating mechanism 146 is an extremely low speed valve that opens when the piston speed is in an extremely low speed range to generate a damping force. The second damping force generating mechanism 146 is provided in a passage 165 consisting of the passages 161, 164 and the intermediate chamber 115, and operates before the first damping force generating mechanism 42 when the moving speed of the piston 18 relative to the cylinder 2 is low, thereby generating a damping force.

[0103] During the compression stroke, the piston 18 moves toward the lower chamber 20, so that the pressure in the lower chamber 20 increases and the pressure in the upper chamber 19 decreases. During the compression stroke when the piston speed is less than the fourth predetermined value, neither the first damping force generating mechanism 42 nor the second damping force generating mechanism 146 provided in the passage 165 consisting of the passages 161, 164 and the intermediate chamber 115 opens. Therefore, the oil L from the lower chamber 20 flows through the passage 161, the passage 162 including the orifice 92, and the passage 163 consisting of the intermediate chamber 115 to the upper chamber 19, and is throttled by the communication passage 142 provided in the passage 161. Therefore, during the compression stroke when the piston speed is less than the fourth predetermined value, a damping force with orifice characteristics (wherein the damping force is approximately proportional to the square of the piston speed) is obtained, and the damping force rises sharply.

[0104] In a high-speed region where the piston speed is equal to or higher than a fourth predetermined value at which the second damping force generating mechanism 146 opens, and in an extremely low-speed region where the piston speed is higher than the fourth predetermined value and lower than a fifth predetermined value, the second damping force generating mechanism 146 opens while the first damping force generating mechanism 42 is in a closed state. In other words, the disc valve 101, together with the opening / closing disc 102, deforms toward the opposite side to the lower chamber 20, and moves away from the inner flange portion 113, and the lower chamber 20 and the upper chamber 19 communicate with each other through a passage 163 consisting of the passages 161, 162 and the intermediate chamber 115. Therefore, the oil liquid L in the lower chamber 20 flows into the upper chamber 19 through the passage between the disc valve 101 and the inner flange portion 113, the case chamber 141, the passage in the passage hole 121, the intermediate chamber 115, the orifice portion 92, the passage in the annular groove 40, the passages in the multiple passage holes 37, and the gaps (not shown) between the valve seat portions 50 in the circumferential direction of the piston body 33. As a result, a damping force with valve characteristics (a characteristic in which the damping force is approximately proportional to the piston speed) can be obtained even in an extremely low speed region where the piston speed is slower than the fifth predetermined value.

[0105] During the compression stroke, in a normal speed region where the piston speed is equal to or higher than the fifth predetermined value, the first damping force generating mechanism 42 opens while the second damping force generating mechanism 146 remains open. That is, the disc valve 101 moves away from the inner flange portion 113, and the oil L flows from the lower chamber 20 to the upper chamber 19 through a passage 163 consisting of the passages 161, 162 and the intermediate chamber 115. At this time, since the flow rate of the oil L in the passage 163 is restricted by the orifice portion 92, the pressure difference generated in the main valve 71 of the first damping force generating mechanism 42 increases, and the main valve 71 moves away from the valve seat portion 50, and the oil L flows from the lower chamber 20 to the upper chamber 19 through a passage 165 consisting of the passages 161, 164 and the intermediate chamber 115. Therefore, oil liquid L in the lower chamber 20 flows through the passage between the disc valve 101 and the inner flange portion 113, the case chamber 141, the passage in the passage hole 121, the intermediate chamber 115, the passages in the multiple passage holes 39, and the passage between the main valve 71 and the valve seat portion 50. As a result, even in a normal speed region where the piston speed is equal to or higher than the fifth predetermined value, a damping force with valve characteristics (the damping force is approximately proportional to the piston speed) can be obtained.

[0106] The rate of increase in the compression damping force with respect to an increase in the piston speed in the normal speed region is lower than the rate of increase in the compression damping force with respect to an increase in the piston speed in the extremely low speed region. In other words, the slope of the rate of increase in the compression damping force with respect to an increase in the piston speed in the normal speed region can be made gentler than in the extremely low speed region.

[0107] The above-mentioned Patent Document 1 discloses a shock absorber having a very low speed damping force generating valve that generates a damping force when the moving speed of the piston relative to the cylinder is very low speed close to 0. However, there is a demand for improving the durability of shock absorbers.

[0108] In the shock absorber 1 of the embodiment, a first damping force generating mechanism 41 that operates by the movement of the piston 18 relative to the cylinder 2 to generate a damping force is provided in a first passage 172 through which the oil L flows from the upper chamber 19 on the upstream side to the lower chamber 20 on the downstream side by the movement of the piston 18, an orifice portion 92 that is provided so that the oil L can flow separately from the first damping force generating mechanism 41 and communicates between the upstream side and the downstream side of the first damping force generating mechanism 41, and a second damping force generating mechanism 145 that operates before the first damping force generating mechanism 41 to generate a damping force when the moving speed of the piston 18 relative to the cylinder 2 is low. The shock absorber 1 further includes a valve mechanism 151 that is provided in the first passage 172 so that the oil L can flow separately from the second damping force generating mechanism 145 and that operates when the second damping force generating mechanism 145 generates a predetermined damping force. Therefore, in the shock absorber 1, when the oil L flows from the upper chamber 19 to the lower chamber 20 through the first passage 172, the valve mechanism 151 opens to suppress excessive pressure load from being applied to the second damping force generating mechanism 145. Therefore, the durability of the shock absorber 1 can be improved.

[0109] In addition, in the shock absorber 1 of the embodiment, the second damping force generating mechanism 145 has a disk valve 101 having one radial end fixed and the other radial end formed as a free end, and the valve mechanism 151 opens and closes the communication hole 131 that is provided in the disk valve 101 and communicates between the upstream side and the downstream side. Therefore, even if the valve mechanism 151 is provided, the shock absorber 1 can suppress an increase in the axial length.

[0110] Moreover, in the shock absorber 1 of the embodiment, the communication hole 131 is formed to have an area larger than a pressure receiving area where the disc valve 101 receives pressure from the upstream side by the oil liquid L. Therefore, by providing the open-close disc 102, which is a member that closes the communication hole 131, on the downstream side of the disc valve 101, the shock absorber 1 can open the open-close disc 102 when the differential pressure between the disc valve 101 and the open-close disc 102 increases to a certain level during the extension stroke. Note that, when the open-close disc 102 is in an open state, the differential pressure of the disc valve 101 disappears, and the shock absorber 1 starts moving in the compression stroke when the open-close disc 102 closes.

[0111] Moreover, in the shock absorber 1 of the embodiment, the valve mechanism 151 is formed so that the pressure receiving area thereof that receives pressure from the oil liquid L from the upstream side is larger than the pressure receiving area thereof that receives pressure from the oil liquid L from the upstream side of the disc valve 101. Therefore, the shock absorber 1 can prevent the valve mechanism 151 from opening before the second damping force generating mechanism 145 opens.

[0112] Moreover, the shock absorber 1 of the embodiment has a communication passage 142 that is provided so that the oil L can flow separately from the second damping force generating mechanism 145 and always communicates the upstream side and the downstream side of the second damping force generating mechanism 145, and the communication passage 142 is formed between the case member 34 provided on the radial outer periphery of the disc valve 101. Therefore, the shock absorber 1 can change the damping force characteristics when the second damping force generating mechanism 145 operates depending on the shape of the case member 34. Therefore, for example, even if the disc valve 101 is bent in the second damping force generating mechanism 145, the shock absorber 1 can adjust the valve opening amount of the second damping force generating mechanism 145 by forming the case member 34 so that the flow path area of ​​the communication passage 142 does not change, and the degree of freedom of tuning can be increased.

[0113] Furthermore, in the shock absorber 1 of the embodiment, the valve mechanism 151 operates to open at a predetermined pressure during the extension stroke of the piston 18 relative to the cylinder 2, and operates to close at a predetermined pressure during the compression stroke of the piston 18 relative to the cylinder 2. Thus, in the shock absorber 1, the valve mechanism 151 operates differently during the extension stroke and the compression stroke, and it is possible to change the damping force characteristics between the extension stroke and the compression stroke. Therefore, the shock absorber 1 has a high degree of freedom in tuning characteristics.

[0114] In the shock absorber 1 of the embodiment, the disc valve 101 has an inner circumferential side, which is one radial end, fixed to the piston rod 21, and an outer circumferential side, which is the other radial end, formed as a free end, but the disc valve 101 may have an outer circumferential side, which is one radial end, fixed to the piston rod 21, and an inner circumferential side, which is the other radial end, formed as a free end. In this case, a member is disposed at a position facing the inner circumferential end of the disc valve 101 so as to form a communication passage 142 between the inner circumferential end of the disc valve 101 and the member. [Explanation of symbols]

[0115] Reference Signs List: 1...shock absorber, 2...cylinder, 19...upper chamber, 20...lower chamber, 18...piston, 21...piston rod, 34...case member, 41...first damping force generating mechanism, 92...orifice portion, 101...disc valve, 131...communicating hole, 142...communicating passage, 145...second damping force generating mechanism, 151...valve mechanism, 172...first passage, L...oil (working fluid).

Claims

1. A cylinder in which a working fluid is sealed; a piston slidably disposed within the cylinder and dividing the interior of the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder; a first passage through which the working fluid flows from the upstream chamber to the downstream chamber as the piston moves; a first damping force generating mechanism that is provided in the first passage and operates in response to movement of the piston relative to the cylinder to generate a damping force; an orifice portion provided in the first passage so as to allow a working fluid to flow therethrough separately from the first damping force generating mechanism, the orifice portion communicating an upstream side with a downstream side of the first damping force generating mechanism; a second damping force generating mechanism that is provided in the first passage and operates prior to the first damping force generating mechanism when the moving speed of the piston relative to the cylinder is low to generate a damping force; a valve mechanism that is provided in the first passage so as to allow a working fluid to flow therethrough separately from the second damping force generating mechanism and that operates when the second damping force generating mechanism generates a predetermined damping force; A shock absorber comprising:

2. 2. The shock absorber according to claim 1, the second damping force generating mechanism has a disk valve having one radial end fixed and the other radial end formed as a free end, The valve mechanism is a shock absorber that opens and closes a communication hole that is provided in the disk valve and connects the upstream side and downstream side of the disk valve.

3. 3. The shock absorber according to claim 2, The communication hole is formed to have an area larger than a pressure-receiving area where the disk valve receives pressure from the upstream side of the working fluid.

4. 3. The shock absorber according to claim 2, a shock absorber in which the valve mechanism is formed so that a pressure receiving area thereof that receives pressure from the working fluid from the upstream side is larger than a pressure receiving area of ​​the disc valve that receives pressure from the working fluid from the upstream side.

5. 3. The shock absorber according to claim 2, a communication passage that is provided so that a working fluid can flow therethrough separately from the second damping force generating mechanism and that constantly communicates between an upstream side and a downstream side of the second damping force generating mechanism, The communication passage is formed between the disk valve and a case member provided on the radial outer periphery of the disk valve.

6. A shock absorber according to any one of claims 1 to 5, The valve mechanism operates to open at a predetermined pressure during the extension stroke of the piston relative to the cylinder, and to close at a predetermined pressure during the compression stroke of the piston relative to the cylinder.

7. 3. The shock absorber according to claim 2, The disk valve is a shock absorber formed to have a lower rigidity than the valve mechanism.

Images