Buffer

Abstract

To provide a buffer which can redress insufficient damping force at an extremely low piston speed.SOLUTION: A buffer 1 includes: a piston 21 which partitions the inside of a cylinder 4 into two chambers 22, 23; a piston rod 25 connected to the piston 21 and extending outside of the cylinder 4; a first passage 102 and a second passage 172(b) into which work fluid flows out with movement of the piston 21; a first damping force generation mechanism 41 provided in the first passage 102 and generating a damping force; a first orifice 91a provided in parallel with the first damping force generating mechanism 41; a capacity varying mechanism 186 provided in the second passage 172(b) and changing the capacity of the capacity chamber 147; and a second orifice 139a provided upstream of the capacity chamber 147. A flow passage cross section area of the second orifice 139a is larger than a flow passage cross section area of the first orifice 91a.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Some shock absorbers have two damping force generating mechanisms that open in the same stroke (see, for example, Patent Document 1). In addition, some shock absorbers have an extremely low-speed valve that opens at an extremely low piston speed, which is the axial movement speed of the piston, to generate damping force, and an accumulator that can store pressure (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 1-149037 [Patent Document 2] Japanese Patent Publication No. 2022-186977 Summary of the Invention [Problem to be solved by the invention]

[0004] In the shock absorber, it is desired to improve the lack of damping force when the piston speed is extremely low.

[0005] An object of the present invention is to provide a shock absorber that can improve the insufficient damping force when the piston speed is extremely low. [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of the present invention includes 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 and a second passage through which the working fluid flows as the piston moves, a first damping force generating mechanism disposed in the first passage and generating a damping force, a first orifice disposed in parallel with the first damping force generating mechanism, a volume variable mechanism disposed in the second passage and changing the volume of a volume chamber, and a second orifice disposed upstream of the volume chamber, wherein the flow path cross-sectional area of ​​the second orifice is larger than the flow path cross-sectional area of ​​the first orifice. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve the lack of damping force when the piston speed is extremely low. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a shock absorber according to a first embodiment of the present invention. [Figure 2] 1 is a partial cross-sectional view showing a main part of a shock absorber according to a first embodiment of the present invention. [Figure 3] 1 is a hydraulic circuit diagram showing a main part of a shock absorber according to a first embodiment of the present invention. [Figure 4] 4 is a characteristic diagram of damping force versus piston speed in the extension stroke of the shock absorber of the first embodiment according to the present invention. FIG. [Figure 5] FIG. 4 is a partial cross-sectional view showing a main part of a shock absorber according to a second embodiment of the present invention. [Figure 6] FIG. 5 is a hydraulic circuit diagram showing a main part of a shock absorber according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a partial cross-sectional view showing a main part of a shock absorber according to a third embodiment of the present invention. [Figure 8] FIG. 10 is a hydraulic circuit diagram showing a main part of a shock absorber according to a third embodiment of the present invention. [Figure 9]FIG. 11 is a characteristic diagram of damping force versus piston speed in the extension stroke of a shock absorber according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a partial cross-sectional view showing a main part of a shock absorber according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments will be described with reference to the drawings. For convenience of explanation, the upper side in Figures 1, 2, 5, 7, and 10 will be referred to as "upper" and the lower side in the drawings will be referred to as "lower."

[0010] [First embodiment] <Configuration> The shock absorber 1 of the first embodiment is a shock absorber used in suspension systems for railway vehicles and automobiles such as two-wheeled and four-wheeled vehicles, and more specifically, a shock absorber used in suspension systems for four-wheeled automobiles. As shown in Fig. 1, the shock absorber 1 is a double-tube shock absorber equipped with a cylinder 4 having a cylindrical inner tube 2 and a cylindrical outer tube 3 with a bottom that is larger in diameter than the inner tube 2 and is provided radially outward of the inner tube 2. A reservoir chamber 5 is formed between the outer tube 3 and the inner tube 2.

[0011] The outer tube 3 has a stepped cylindrical body member 8 whose axial ends have a smaller diameter than the axial middle portion, and a bottom member 9 that closes the lower end, which is one axial end of the body member 8, and the upper end of the body member 8 opposite the bottom member 9 is an opening.

[0012] The shock absorber 1 has an annular valve body 10 provided at the lower end, which is one axial end of the inner cylinder 2, and an annular rod guide 11 provided at the upper ends, which are the other axial ends of the inner cylinder 2 and the outer cylinder 3. The valve body 10 constitutes a base valve 12, and has a stepped outer periphery. The rod guide 11 also has a stepped outer periphery, and its large diameter part is fitted into the body member 8.

[0013] The inner cylinder 2 has its lower end, which is one axial end, fitted into a small-diameter portion on the outer periphery of a valve body 10, and engages with the bottom member 9 of the outer cylinder 3 via this valve body 10. The inner cylinder 2 has its upper end, which is the other axial end, fitted into a small-diameter portion on the outer periphery of a rod guide 11, and engages with the body member 8 of the outer cylinder 3 via this rod guide 11. In this state, the inner cylinder 2 is positioned radially relative to the outer cylinder 3. The space between the valve body 10 and the bottom member 9 is in communication with the inner cylinder 2 and outer cylinder 3, and constitutes a reservoir chamber 5, just like the space between the inner cylinder 2 and outer cylinder 3.

[0014] The shock absorber 1 has an annular seal member 13 on the side of the rod guide 11 opposite the bottom member 9. This seal member 13 is also fitted into the inner peripheral portion of the body member 8, similar to the rod guide 11. An engaging portion (not shown) is formed at the end of the body member 8 opposite the bottom member 9 by plastically deforming the body member 8 radially inward by crimping, such as curling. The radially outer portion of the seal member 13 is sandwiched between this engaging portion (not shown) and the rod guide 11. The seal member 13 closes the opening of the outer cylinder 3, and is specifically an oil seal.

[0015] The shock absorber 1 has a resistance force generating mechanism 20 between the rod guide 11 and the seal member 13. The resistance force generating mechanism 20 is annular.

[0016] The shock absorber 1 has a piston 21 provided in a cylinder 4. The piston 21 is slidably provided in an inner tube 2 of the cylinder 4. The piston 21 divides the inner tube 2 into two chambers: an upper chamber 22 and a lower chamber 23. The upper chamber 22 is provided between the piston 21 and a rod guide 11 in the inner tube 2, and the lower chamber 23 is provided between the piston 21 and a valve body 10 in the inner tube 2. The lower chamber 23 is defined as a reservoir chamber 5 by the valve body 10. Within the cylinder 4, oil liquid L as a working fluid is sealed in the upper chamber 22 and the lower chamber 23, and gas G and oil liquid L as working fluids are sealed in the reservoir chamber 5.

[0017] The shock absorber 1 is provided with a piston rod 25, one axial side of which is disposed inside the cylinder 4 and connected and fixed to the piston 21, and the other axial side of which extends outside the cylinder 4. The piston rod 25 is made of metal, and passes through the upper chamber 22 but does not pass through the lower chamber 23. Therefore, the upper chamber 22 is a rod-side chamber through which the piston rod 25 passes, and the lower chamber 23 is a bottom-side chamber on the bottom member 9 side of the cylinder 4.

[0018] The piston 21 and the piston rod 25 move together. During the extension stroke of the shock absorber 1, in which the piston rod 25 increases the amount of protrusion from the cylinder 4, the piston 21 moves toward the upper chamber 22, and during the compression stroke of the shock absorber 1, in which the piston rod 25 decreases the amount of protrusion from the cylinder 4, the piston 21 moves toward the lower chamber 23.

[0019] The rod guide 11, resistance force generating mechanism 20, and seal member 13 are all annular, and the piston rod 25 is slidably inserted through the rod guide 11, resistance force generating mechanism 20, and seal member 13, respectively, and extends from the inside to the outside of the cylinder 4. One axial end of the piston rod 25 is fixed to the piston 21 inside the cylinder 4, and the other axial end protrudes to the outside of the cylinder 4 via the rod guide 11, resistance force generating mechanism 20, and seal member 13.

[0020] The rod guide 11 supports the piston rod 25 relative to the cylinder 4 so as to be movable in the axial direction while restricting the movement of the piston rod 25 in the radial direction, thereby guiding the movement of the piston rod 25.

[0021] The outer periphery of the seal member 13 is in close contact with the outer tube 3 of the cylinder 4, and the inner periphery is in sliding contact with the outer periphery of the piston rod 25 that moves in the axial direction. In this way, the seal member 13 prevents the oil L and gas G in the cylinder 4 from leaking to the outside.

[0022] The resistance force generating mechanism 20 is not intended to seal between the piston rod 25 and the rod guide 11, but rather to apply frictional resistance force by sliding against the piston rod 25.

[0023] Piston rod 25 has a cylindrical main shaft portion 30 and a cylindrical mounting shaft portion 31 whose outer diameter is smaller than that of main shaft portion 30. In piston rod 25, main shaft portion 30 is slidably fitted into rod guide 11, resistance force generating mechanism 20, and seal member 13, and mounting shaft portion 31 is disposed in cylinder 4 and connected to piston 21, etc. The end of main shaft portion 30 on the mounting shaft portion 31 side widens in the direction perpendicular to the axis.

[0024] An axially extending passage cutout 33 is formed in the outer periphery of the mounting shaft portion 31 at an axially intermediate position, and a male thread 34 is formed at a tip position on the opposite side of the axial passage cutout 33 from the main shaft portion 30. As shown in Fig. 2, the passage cutout 33 has an axial cutout 33a formed by cutting out the outer periphery of the mounting shaft portion 31 in a plane parallel to the central axis of the mounting shaft portion 31 in a flat shape and extending in the axial direction of the mounting shaft portion 31, an annular groove 33b provided at the end of the axial cutout 33a on the main shaft portion 30 side of the mounting shaft portion 31 in the axial direction, and an annular groove 33c provided at the end of the axial cutout 33a on the opposite side of the main shaft portion 30 in the axial direction of the mounting shaft portion 31.

[0025] In shock absorber 1, for example, the portion of piston rod 25 protruding from cylinder 4 is positioned at the top and supported by the vehicle body, and the bottom member 9 of cylinder 4 is positioned at the bottom and connected to the wheel side. In the case of a mono-tube type, it is possible to reverse this and have cylinder 4 supported by the vehicle body and piston rod 25 connected to the wheel side.

[0026] The piston 21 is composed of a metal piston body 36 that is connected to the piston rod 25 and a ring-shaped sliding member 37 made of synthetic resin that is integrally attached to the outer surface of the piston body 36 and slides inside the inner tube 2 of the cylinder 4.

[0027] The piston body 36 is provided with a plurality of passage holes 38 (only one of which is shown in Figure 2 because it is a cross-section) that can connect the upper chamber 22 and the lower chamber 23, and a plurality of passage holes 39 (only one of which is shown in Figure 2 because it is a cross-section) that can connect the upper chamber 22 and the lower chamber 23.

[0028] The plurality of passage holes 38 are formed at equal intervals in the circumferential direction of the piston body 36, with one passage hole 39 sandwiched between each adjacent passage hole, and constitute half of the total number of passage holes 38, 39. The plurality of passage holes 38, on the lower chamber 23 side in the axial direction of the piston 21, open radially inward of the piston 21 relative to the upper chamber 22 side. An annular groove 52 that connects the plurality of passage holes 38 is formed in the piston body 36 on the lower chamber 23 side in the axial direction, and an annular groove 53 that is also annular is formed radially outward and axially outward (lower) of the annular groove 52 so as to surround the annular groove 52 on the radially outer side.

[0029] A damping force generating mechanism 41 is provided on the lower chamber 23 side of the annular groove 52, which generates a damping force by opening and closing the passages in the annular groove 52 and the plurality of passage holes 38. By disposing the damping force generating mechanism 41 on the lower chamber 23 side, the passages in the plurality of passage holes 38 and the annular groove 52 serve as extension-side passages through which oil L flows from the upper chamber 22, which is the upstream side, to the lower chamber 23, which is the downstream side, when the piston 21 moves toward the upper chamber 22, i.e., during the extension stroke. The damping force generating mechanism 41 provided for the passages in the plurality of passage holes 38 and the annular groove 52 serves as an extension-side damping force generating mechanism that generates a damping force by suppressing the flow of oil L from the passages in the extension-side plurality of passage holes 38 and the annular groove 52 toward the lower chamber 23.

[0030] A damping force generating mechanism 42 is provided on the lower chamber 23 side of the damping force generating mechanism 41 and on the lower chamber 23 side of the annular groove 53. When the damping force generating mechanism 41 is in an open state, the damping force generating mechanism 42 opens and closes the passages in the plurality of passage holes 38, the annular groove 52, and the annular groove 53 to generate a damping force. By disposing the damping force generating mechanism 42 on the lower chamber 23 side, the passages in the plurality of passage holes 38, the annular groove 52, and the annular groove 53 serve as extension-side passages through which oil L flows from the upper chamber 22, which is upstream, to the lower chamber 23, which is downstream, during the movement of the piston 21 toward the upper chamber 22, i.e., during the extension stroke. The damping force generating mechanism 42 provided for the passages in the plurality of passage holes 38, the annular groove 52, and the annular groove 53 serves as an extension-side damping force generating mechanism that generates a damping force by suppressing the flow of oil L from the passages in the plurality of extension-side passage holes 38, the annular groove 52, and the annular groove 53 to the lower chamber 23. The damping force generating mechanism 42 has a valve opening pressure higher than that of the damping force generating mechanism 41, and opens after the damping force generating mechanism 41 opens.

[0031] The passage holes 39, which constitute the remaining half of the total number of passage holes 38, 39, are formed at equal intervals in the circumferential direction of the piston body 36, with one passage hole 38 sandwiched between each other. The plurality of passage holes 39, on the upper chamber 22 side in the axial direction of the piston 21, open radially inward of the piston 21 relative to the lower chamber 23 side. An annular groove 54 is formed in the piston body 36 to connect the plurality of passage holes 39 to the upper chamber 22 side in the axial direction, and an annular groove 55 is formed radially outward and axially outer (upper) of the annular groove 54 so as to surround the annular groove 54 on the radially outer side.

[0032] A damping force generating mechanism 43 is provided on the upper chamber 22 side of the annular groove 54, which generates a damping force by opening and closing the passages in the plurality of passage holes 39 and the annular groove 54. By disposing the damping force generating mechanism 43 on the upper chamber 22 side, the passages in the plurality of passage holes 39 and the annular groove 54 become compression-side passages through which oil L flows from the lower chamber 23, which is the upstream side, to the upper chamber 22, which is the downstream side, when the piston 21 moves toward the lower chamber 23, that is, during the compression stroke. The damping force generating mechanism 43 provided for the passages in the plurality of passage holes 39 and the annular groove 54 serves as a compression-side damping force generating mechanism that generates a damping force by suppressing the flow of oil L from the passages in the plurality of compression-side passage holes 39 and the annular groove 54 toward the upper chamber 22.

[0033] A damping force generating mechanism 44 is provided on the upper chamber 22 side of the damping force generating mechanism 43 and on the upper chamber 22 side of the annular groove 55. When the damping force generating mechanism 43 is in an open state, the damping force generating mechanism 44 opens and closes the passages in the plurality of passage holes 39, the passages in the annular groove 54, and the passages in the annular groove 55 to generate a damping force. By disposing the damping force generating mechanism 44 on the upper chamber 22 side, the passages in the plurality of passage holes 39, the annular groove 54, and the annular groove 55 serve as compression-side passages through which oil L flows from the lower chamber 23, which is upstream, to the upper chamber 22, which is downstream, when the piston 21 moves toward the lower chamber 23, i.e., during the compression stroke. The damping force generating mechanism 44 provided for the passages in the plurality of passage holes 39, the annular groove 54, and the annular groove 55 serves as a compression-side damping force generating mechanism that generates a damping force by suppressing the flow of oil L from the passages in the plurality of compression-side passage holes 39, the annular groove 54, and the annular groove 55 to the upper chamber 22. The damping force generating mechanism 44 has a valve opening pressure higher than that of the damping force generating mechanism 43, and opens after the damping force generating mechanism 43 opens.

[0034] The piston body 36 is made up of two members: a first constituent body 57 and a second constituent body 58. Both the first constituent body 57 and the second constituent body 58 are formed by sintering. The first constituent body 57 constitutes the portion of the piston body 36 on the lower chamber 23 side in the axial direction, and the second constituent body 58 constitutes the portion of the piston body 36 on the upper chamber 22 side in the axial direction.

[0035] The first component 57 has a substantially circular disk shape. A through-hole 59 is formed in the center of the first component 57 in the radial direction, penetrating the first component 57 in the axial direction of the first component 57. The through-hole 59 is a portion of the first component 57 into which the mounting shaft portion 31 of the piston rod 25 is fitted.

[0036] An engagement recess 60 is formed at the end of the first component 57 on the second component 58 side in the axial direction, recessed in the axial direction from the end face on the second component 58 side. The engagement recess 60 has a shape in which the through hole 59 is expanded radially outward, and is provided partially in the circumferential direction of the first component 57.

[0037] The above-mentioned annular groove 53 is formed at the lower end of the first component 57. An annular outer valve seat portion 48 that constitutes a part of the damping force generating mechanism 42 is formed at the radially outer end side of the lower end of the first component 57, radially outward from the opening of the annular groove 53 on the lower chamber 23 side. The above-mentioned annular groove 52 is formed at the lower end of the first component 57, radially inward from the annular groove 53. An annular inner valve seat portion 46 that constitutes a part of the damping force generating mechanism 41 is formed between the annular groove 53 and the annular groove 52 in the radial direction of the first component 57. The inner valve seat portion 46 is located closer to the second component 58 in the axial direction of the first component 57 than the outer valve seat portion 48. An inner seat portion 47 is formed at the lower end of the first component 57, radially inward from the opening of the annular groove 52 on the lower chamber 23 side. The inner seat portion 47 is located slightly closer to the second component 58 in the axial direction of the first component 57 than the inner valve seat portion 46.

[0038] The second component 58 has a substantially circular plate shape. A circular through-hole 61 is formed in the radial center of the second component 58, penetrating the second component 58 in the axial direction of the second component 58. The through-hole 61 is a portion of the second component 58 into which the mounting shaft portion 31 of the piston rod 25 is fitted.

[0039] An engaging protrusion 62 that protrudes in the axial direction from the end face on the first component 57 side of the second component 58 is formed on the first component 57 side in the axial direction. A through hole 61 is formed inside the engaging protrusion 62 in the radial direction of the second component 58, and the engaging protrusion 62 is provided partially in the circumferential direction of the second component 58. A passage groove 63 that extends from the passage hole 38 radially inward of the second component 58 is formed in the engaging protrusion 62 and inside the passage hole 38 in the radial direction of the end face of the second component 58 on the first component 57 side. The passage groove 63 opens into the passage hole 38 and the through hole 61.

[0040] The above-mentioned annular groove 55 is formed at the upper end of the second component 58. An annular outer valve seat portion 50 that constitutes a part of the damping force generating mechanism 44 is formed at the radially outer end side of the upper end of the second component 58, radially outward from the opening of the annular groove 55 on the upper chamber 22 side. The above-mentioned annular groove 54 is formed at the upper end of the second component 58, radially inward from the annular groove 55. An annular inner valve seat portion 51 that constitutes a part of the damping force generating mechanism 43 is formed between the annular grooves 55 and 54 in the radial direction of the second component 58. The inner valve seat portion 51 is located closer to the first component 57 than the outer valve seat portion 50 in the axial direction of the second component 58. An inner seat portion 49 is formed at the upper end of the second component 58, radially inward from the opening of the annular groove 54 on the upper chamber 22 side. The inner seat portion 49 is located slightly closer to the first component 57 in the axial direction of the second component 58 than the inner valve seat portion 51.

[0041] The first component 57 and the second component 58 are connected by engaging the engaging protrusion 62 of the second component 58 with the engaging recess 60 of the first component 57. As a result, the first component 57 and the second component 58 are connected in a state where they are positioned in the circumferential direction so as to form the passage holes 38 and 39. In this state, the sliding member 37 is placed over the radially outside of the first component 57 and the second component 58. As a result, the first component 57 and the second component 58 are integrated to form the piston main body 36, and the first component 57, the second component 58, and the sliding member 37 are integrated to form the piston 21.

[0042] In the first component 57, the opening of the compression-side passage hole 39 on the lower chamber 23 side is disposed radially outward of the outer valve seat portion 48. In the second component 58, the opening of the extension-side passage hole 38 on the upper chamber 22 side is disposed radially outward of the outer valve seat portion 50.

[0043] In the piston 21, the passage in the passage groove 63 of the second component 58 is positioned to overlap with the annular groove 33b of the piston rod 25 in the axial direction of the piston rod 25. This allows the passage in the passage groove 63 of the second component 58, which communicates with the upper chamber 22 via the passage in the passage hole 38, to communicate with the passages in the annular groove 33b, axial cutout 33a and annular groove 33c of the piston rod 25, i.e., the passage in the passage cutout 33, without circumferentially aligning the phase of the piston 21 with the piston rod 25.

[0044] The inner valve seat portion 51 of the piston 21 is provided with one disk 71, one disk 72, and one disk 73 in this order from the piston 21 side in the axial direction.

[0045] On outer valve seat portion 50 of piston 21, there are provided, in axial order from the piston 21 side, one disk 74, multiple disks 75, one disk 76, one disk 77, one disk 78, and one washer 79. Disk 74 abuts against disk 73.

[0046] The disks 71 to 78 and the washer 79 are all made of metal and are circular flat plates with holes of a uniform thickness. The disks 71 to 78 and the washer 79 are all positioned radially relative to the piston rod 25 by fitting the mounting shaft portion 31 inside. The disks 71 to 78 are all press-formed.

[0047] The disc 71 has an outer diameter equal to that of the inner valve seat portion 51 of the piston 21, and is constantly in contact with the inner seat portion 49, being able to seat on and separate from the inner valve seat portion 51. The disc 71, together with the inner valve seat portion 51, constitutes the damping force generating mechanism 43, which opens and closes the upper chamber 22 side of the passage in the annular groove 54 of the piston 21. The disc 71 is cut out on its outer periphery, and this cutout portion serves as an orifice 71a that connects the passage in the annular groove 54 of the piston 21 to the annular groove 55 on the upper chamber 22 side, even when the disc 71 is in contact with the inner valve seat portion 51, i.e., when the damping force generating mechanism 43 is closed. The orifice 71a ceases to function after the damping force generating mechanism 43 is opened, and therefore the damping force generating mechanism 43 and the orifice 71a are arranged in parallel in the flow path of the oil L, as shown in FIG. 3.

[0048] As shown in FIG. 2, the disk 72 has an outer diameter smaller than the outer diameter of the disk 71, and abuts on the disk 71 radially inward of the orifice 71a. The disc 73 has an outer diameter that is larger than the outer diameter of the disc 72 and smaller than the inner diameter of the outer valve seat portion 50 of the piston 21.

[0049] The disc 74 has an outer diameter larger than that of the disc 73 and equal to that of the outer valve seat portion 50 of the piston 21, and is capable of being seated on and removed from the outer valve seat portion 50. The disc 74 opens and closes the passage in the annular groove 55 of the piston 21 and the upper chamber 22 by being seated on and removed from the outer valve seat portion 50. The disc 74 is cut out on its outer periphery, and this cutout portion serves as an orifice 74a that connects the passage in the annular groove 55 of the piston 21 with the upper chamber 22 even when the disc 74 is in contact with the outer valve seat portion 50.

[0050] The outer diameters of the plurality of discs 75 on the disc 74 side are the same as the outer diameter of disc 74, and the outer diameters of the plurality of discs 75 on the opposite side of disc 74 are smaller than the outer diameter of disc 74. Disc 74 and the plurality of discs 75, together with outer valve seat portion 50, constitute damping force generating mechanism 44 that opens and closes between the passage in annular groove 55 of piston 21 and upper chamber 22. Since orifice 74a ceases to function after damping force generating mechanism 44 opens, orifice 74a of disc 74 and damping force generating mechanism 44 are arranged in parallel on the flow path of oil L, as shown in FIG. 3.

[0051] As shown in FIG. 2, the disk 76 has an outer diameter smaller than the outer diameter of the smallest disk 75 among the plurality of disks 75. The disc 77 has an outer diameter larger than the outer diameter of the disc 77. The disk 78 has an outer diameter larger than that of the disk 77 .

[0052] The washer 79 has an outer diameter smaller than that of the disc 78 and larger than that of the main shaft portion 30 of the piston rod 25. The washer 79 is thicker and more rigid than the discs 71 to 78, and abuts against the end of the main shaft portion 30 on the mounting shaft portion 31 side in the axial direction.

[0053] The disc 71 constitutes a compression-side sub-valve that is releasable from the inner valve seat portion 51. When the disc 71 is releasable from the inner valve seat portion 51, the disc 71 connects the passages in the multiple passage holes 39 and the annular groove 54 with the passage in the annular groove 55 on the upper chamber 22 side, and suppresses the flow of oil L between the disc 71 and the inner valve seat portion 51, thereby generating a damping force.

[0054] The disc 74 and the multiple discs 75 constitute a compression-side main valve 81 that is releasable from the outer valve seat portion 50. When the sub-valve disc 71 is in an open state, the main valve 81 releasable from the outer valve seat portion 50. By releasable from the outer valve seat portion 50, the passages in the multiple passage holes 39, the passage in the annular groove 54, the passage between the disc 71 and the inner valve seat portion 51, and the passage in the annular groove 55 communicate with the upper chamber 22, and the flow of oil L between the disc 71 and the outer valve seat portion 50 is suppressed, thereby generating a damping force. The washer 79, together with the disc 78, abuts against the main valve 81 to suppress deformation of the main valve 81 in the opening direction beyond a specified limit.

[0055] The passages in the multiple passage holes 39 and the annular groove 54, the passage between the orifice 71a or the disc 71 that appears when the valve is open and the inner valve seat portion 51, the passage in the annular groove 55, and the passage between the orifice 74a or the main valve 81 that appears when the valve is open and the outer valve seat portion 50 are formed in the piston 21, and constitute a first compression passage 82 through which oil L flows from the lower chamber 23, which is the upstream side within the cylinder 4, to the upper chamber 22, which is the downstream side, as the piston 21 moves toward the lower chamber 23.

[0056] The compression-side damping force generating mechanism 43, which generates a damping force, includes the disc 71, which is a sub-valve, and the inner valve seat portion 51, and is therefore provided in the first passage 82. The compression-side damping force generating mechanism 44, which generates a damping force, includes the main valve 81 and the outer valve seat portion 50, and is therefore provided in the first passage 82. The damping force generating mechanism 43 and the damping force generating mechanism 44 are provided in series in the first passage 82. The orifice 71a and the orifice 74a are provided in series in the first passage 82. The damping force generating mechanism 43 and the orifice 71a are provided in parallel in the first passage 82. The damping force generating mechanism 44 and the orifice 74a are provided in parallel in the first passage 82. The first passage 82 is formed in the piston 21, which includes the inner valve seat portion 51 and the outer valve seat portion 50, and oil L passes through it when the piston rod 25 and the piston 21 move toward the compression side.

[0057] The inner valve seat portion 46 of the piston 21 is provided with, in axial order from the piston 21 side, one disc 91, one disc 92, and one disc 93. The outer valve seat portion 48 of the piston 21 is provided with, in axial order from the piston 21 side, one disc 94, multiple discs 95, one disc 96, and one disc 97. The discs 93 and 94 are in contact with each other.

[0058] The disks 91 to 97 are all made of metal and are circular flat plates with holes of a uniform thickness. The disks 91 to 97 are all press-formed. The disks 91 to 97 are all positioned radially relative to the piston rod 25 by fitting the mounting shaft portion 31 inside.

[0059] The disc 91 has an outer diameter equal to the outer diameter of the inner valve seat portion 46 of the piston 21, and is constantly in contact with the inner seat portion 47, being able to seat on and separate from the inner valve seat portion 46. The disc 91 is cut out on its outer periphery, and this cutout portion serves as an orifice 91a that connects the passage in the annular groove 52 of the piston 21 to the lower chamber 23, even when the disc 91 is in contact with the inner valve seat portion 46.

[0060] The disc 92 has an outer diameter equal to that of the disc 91. The discs 91, 92, together with the inner valve seat portion 46, constitute the damping force generating mechanism 41 that opens and closes the lower chamber 23 side of the passage in the annular groove 52 of the piston 21. Since the orifice 91a ceases to function after the damping force generating mechanism 41 is opened, the damping force generating mechanism 41 and the orifice 91a are arranged in parallel on the flow path of the oil L as shown in FIG. As shown in FIG. 2, the disk 93 has an outer diameter smaller than the outer diameter of the disk 92.

[0061] The disc 94 has an outer diameter larger than that of the disc 93 and equal to that of the outer valve seat portion 48 of the piston 21, and is capable of being seated on and removed from the outer valve seat portion 48. The disc 94 opens and closes the passage in the annular groove 53 of the piston 21 and the lower chamber 23 by being seated on and removed from the outer valve seat portion 48. The disc 94 is cut out on its outer periphery, and this cutout portion forms an orifice 94a that connects the passage in the annular groove 53 of the piston 21 to the lower chamber 23 even when the disc 94 is in contact with the outer valve seat portion 48.

[0062] The outer diameters of the plurality of discs 95 on the disc 94 side are the same as the outer diameter of disc 94, and the outer diameters of the plurality of discs 95 on the opposite side of disc 94 are smaller than the outer diameter of disc 94. The disc 94 and the plurality of discs 95, together with the outer valve seat portion 48, constitute the damping force generating mechanism 42 that opens and closes between the passage in the annular groove 53 of the piston 21 and the lower chamber 23. Since the orifice 94a ceases to function after the damping force generating mechanism 42 is opened, the orifice 94a of the disc 94 and the damping force generating mechanism 42 are arranged in parallel on the flow path of the oil L as shown in FIG.

[0063] As shown in FIG. 2, the disk 96 has an outer diameter smaller than the outer diameter of the smallest disk 95 among the plurality of disks 95. The disk 97 has an outer diameter larger than that of the disk 96 .

[0064] The discs 91, 92 constitute an extension-side sub-valve 100 that is releasable from the inner valve seat portion 46. When the sub-valve 100 is releasable from the inner valve seat portion 46, it connects the passages in the multiple passage holes 38 and the annular groove 52 to the passage in the annular groove 53 on the lower chamber 23 side, and suppresses the flow of oil L between the sub-valve 100 and the inner valve seat portion 46, thereby generating a damping force.

[0065] The disc 94 and the multiple discs 95 constitute an extension-side main valve 101 that is releasable from the outer valve seat 48. When the sub-valve 100 is in an open state, the main valve 101 releasable from the outer valve seat 48. By releasable from the outer valve seat 48, the passages in the multiple passage holes 38, the passage in the annular groove 52, the passage between the sub-valve 100 and the inner valve seat 46, and the passage in the annular groove 53 are connected to the lower chamber 23, and the flow of oil L between the sub-valve 100 and the outer valve seat 48 is suppressed, thereby generating a damping force.

[0066] The passages in the multiple passage holes 38 and the annular groove 52, the passage between the orifice 91a or the sub-valve 100 that appears when the valve is open and the inner valve seat portion 46, the passage in the annular groove 53, and the passage between the orifice 94a or the main valve 101 that appears when the valve is open and the outer valve seat portion 48 are formed in the piston 21, and constitute a first extension passage 102 through which oil L flows from the upper chamber 22, which is the upstream side within the cylinder 4, to the lower chamber 23, which is the downstream side, as the piston 21 moves toward the upper chamber 22.

[0067] The extension-side damping force generating mechanism 41, which generates a damping force, includes a sub-valve 100 and an inner valve seat portion 46, and is therefore provided in this first passage 102. The extension-side damping force generating mechanism 42, which generates a damping force, includes a main valve 101 and an outer valve seat portion 48, and is therefore provided in this first passage 102. The damping force generating mechanism 41 and the damping force generating mechanism 42 are provided in series in the first passage 102. The orifice 91a and the orifice 94a are provided in series in the first passage 102. The damping force generating mechanism 41 and the orifice 91a are provided in parallel in the first passage 102. The damping force generating mechanism 42 and the orifice 94a are provided in parallel in the first passage 102. The first passage 102 is formed in the piston 21 including the inner valve seat portion 46 and the outer valve seat portion 48, and oil L passes through the first passage 102 when the piston rod 25 and the piston 21 move in the extension direction.

[0068] An accumulator portion 104 is provided on the axially opposite side of the disc 97 from the disc 96. The accumulator portion 104 has a cylindrical case member 105 with a bottom that opens toward the disc 97 in the axial direction. The accumulator portion 104 is provided within this case member 105 with, in order from the axially opposite side of the disc 97, one valve member 106, one disc 107, one flexible disc 110, one disc 111, one disc 112, one disc 113, and one blocking member 116 with an O-ring 115 provided on the outer periphery thereof, with the mounting shaft portion 31 of the piston rod 25 fitted inside each of them.

[0069] On the axial side of the accumulator portion 104 opposite to the disk 97, in order from the accumulator portion 104 side, one disk 117, one disk 118, and one washer 119 are provided, with the mounting shaft portion 31 of the piston rod 25 fitted inside each of them.

[0070] A male thread 34 is formed on the mounting shaft portion 31 of the piston rod 25 at a portion that protrudes beyond the washer 119, and a nut 120 is screwed onto this male thread 34.

[0071] At least the radially inner circumferential sides of the washer 79, discs 71-78, piston 21, discs 91-97, closure member 116, discs 111-113, flexible disc 110, disc 107, valve member 106, case member 105, discs 117, 118, and washer 119 are clamped in the axial direction by the nut 120 and the end of main shaft portion 30 of piston rod 25 on the axial side of mounting shaft portion 31, and are thus fixed to piston rod 25. In this state, the outer circumferential side of disc 71, which serves as the sub-valve, abuts against inner valve seat portion 51 of piston 21, the outer circumferential side of main valve 81 abuts against outer valve seat portion 50 of piston 21, the outer circumferential side of sub-valve 100 abuts against inner valve seat portion 46 of piston 21, and the outer circumferential side of main valve 101 abuts against outer valve seat portion 48 of piston 21. In this state, the valve member 106, the disk 107, the flexible disk 110, the disks 111 to 113, and the closing member 116 are disposed within the case member 105.

[0072] The case member 105, valve member 106, discs 107, 111 to 113, 117, and 118, flexible disc 110, closing member 116, and washer 119 are all made of metal. The discs 107, 111 to 113, 117, and 118, flexible disc 110, and washer 119 are all perforated circular flat plates of a uniform thickness. The valve member 106, case member 105, and closing member 116 are all annular. The discs 107, 111 to 113, 117, and 118, valve member 106, and flexible disc 110 are all press-molded.

[0073] The case member 105 is a cylindrical, bottomed, integrally molded product formed, for example, by plastic processing or cutting a metal plate. The case member 105 has a perforated, disk-shaped bottom portion 122 and a cylindrical portion 124 extending axially from the outer peripheral edge of the bottom portion 122.

[0074] The bottom portion 122 is a circular flat plate with holes, into whose inner periphery the mounting shaft portion 31 of the piston rod 25 is fitted. By fitting the mounting shaft portion 31 into the inner periphery of the bottom portion 122, the case member 105 is positioned radially relative to the piston rod 25 and arranged coaxially. A plurality of passage holes 126 are formed in the bottom portion 122 between the inner periphery and the outer periphery, penetrating the bottom portion 122 in the axial direction of the bottom portion 122. The plurality of passage holes 126 are arranged at equal intervals in the circumferential direction of the bottom portion 122, at positions equidistant from the center of the bottom portion 122. The cylindrical portion 124 is coaxial with the bottom portion 122 .

[0075] The disk 117 abuts against the axial side of the bottom 122 of the case member 105 opposite to the cylindrical portion 124. The outer diameter of the disk 117 is smaller than twice the shortest distance connecting the radial center of the case member 105 and the passage hole 126. Disk 118 has an outer diameter that is larger than the outer diameter of disk 117 . The washer 119 has an outer diameter smaller than the outer diameter of the disk 118 .

[0076] The valve member 106 is a flexible, perforated, circular metal plate. The valve member 106 has an inner annular portion 127 on the radially inner side and an outer conical portion 128 on the radially outer side. The inner annular portion 127 is a perforated circular flat plate. The outer conical portion 128 is a conical cylinder that extends radially outward and axially to one side from the outer peripheral edge of the inner annular portion 127. The valve member 106 is a disc spring. The valve member 106 is formed by stamping and bending a single sheet of plate material using a press molding method.

[0077] The outer diameter of the outer conical portion 128 of the valve member 106, i.e., the outer diameter of the valve member 106, is smaller than the inner diameter of the cylindrical portion 124 of the case member 105. The valve member 106 is in a state where the inner annular portion 127 abuts against the bottom portion 122 of the case member 105 and the outer conical portion 128 extends away from the bottom portion 122 in the axial direction. In this state, the valve member 106 is positioned radially relative to the piston rod 25 by fitting the mounting shaft portion 31 into the inner peripheral side of the inner annular portion 127. The cylindrical portion 124 of the case member 105 is disposed radially outward of the valve member 106.

[0078] The valve member 106 has a hole 129 formed between the inner periphery and the outer periphery of the inner annular portion 127. The hole 129 penetrates the valve member 106 in the thickness direction (axial direction). The inner annular portion 127 has a plurality of holes 129 formed at intervals in the circumferential direction thereof. The hole 129 has an arc shape that is long in the circumferential direction of the inner annular portion 127. When the inner annular portion 127 of the valve member 106 abuts against the bottom portion 122 of the case member 105, the hole 129 aligns with the passage hole 126 of the bottom portion 122 in the radial direction of the case member 105 and the valve member 106. Therefore, the passages in the plurality of holes 129 communicate with the passages in the plurality of passage holes 126.

[0079] The outer diameter of the disk 107 is smaller than twice the distance from the radial center of the valve member 106 to the inner end of the hole 129. Therefore, the disk 107 does not block or narrow the passages within the multiple hole portions 129. The disk 107 is thicker than the thickness of the inner annular portion 127 of the valve member 106, i.e., the plate thickness of the valve member 106.

[0080] The flexible disk 110 is flexible and has an outer diameter larger than the outer diameter of the valve member 106 and smaller than the inner diameter of the cylindrical portion 124 of the case member 105.

[0081] The flexible disk 110 is formed by punching out a single plate material using a press molding method. The flexible disk 110 has a flat plate shape in its natural state before being assembled to the piston rod 25. The flexible disk 110 has a passage hole 130 formed between its inner and outer peripheries, penetrating the flexible disk 110 in the thickness direction (axial direction) of the flexible disk 110. The flexible disk 110 has a plurality of passage holes 130 formed at equal intervals in the circumferential direction of the flexible disk 110. The diameter of the flexible disk 110 is twice the distance from the center to the inner end position of the passage hole 130 in the radial direction, which is larger than the outer diameter of the disk 107. Therefore, the passage hole 130 of the flexible disk 110 is not blocked or narrowed by the disk 107.

[0082] The valve member 106 has a circular outer peripheral edge of the outer conical portion 128, and this circular outer peripheral edge abuts over the entire circumference on the outer peripheral edge side of the flexible disk 110 outside the passage hole 130 in the radial direction.

[0083] The valve member 106 is disposed between the bottom 122 of the case member 105 and the flexible disk 110, with the disk 107 sandwiched between the valve member 106 and the flexible disk 110. Here, the axial length of the outer conical portion 128 of the valve member 106 in its natural state before being assembled to the piston rod 25 is longer than the thickness of the disk 107. Therefore, when the valve member 106 is assembled to the piston rod 25, the outer conical portion 128 abuts against the flexible disk 110 while bending to shorten its axial length. As a result, the valve member 106 is assembled so as to apply an axial load to the bottom 122 of the case member 105 and the flexible disk 110.

[0084] The disc 111 is flexible. The disc 111 has a flat plate shape in its natural state before being assembled to the piston rod 25. The disc 111 has an outer diameter smaller than that of the flexible disc 110 and larger than twice the distance from the center of the flexible disc 110 in the radial direction to the outer ends of the passage holes 130. When the disc 111 comes into surface contact with the flexible disc 110 over the entire periphery, it closes all of the passage holes 130.

[0085] The disk 112 has an outer diameter smaller than that of the disk 111 . The outer diameter of the disk 113 is larger than the outer diameter of the disk 111 and is equal to the outer diameter of the flexible disk 110. The disk 113 is thicker and more rigid than the flexible disk 110 and the disk 111. When the flexible disk 110 deforms, the disk 113 comes into contact with the flexible disk 110 to prevent further deformation of the flexible disk 110.

[0086] The closing member 116 is formed by sintering and has a perforated disk shape with a through hole 131 formed in the radial center thereof, which penetrates the closing member 116 in the axial direction. The through hole 131 has a small diameter hole portion 132 on one axial side into which the mounting shaft portion 31 of the piston rod 25 is fitted, and a large diameter hole portion 133 on the other axial side, which has a larger diameter than the small diameter hole portion 132.

[0087] The closing member 116 is thicker than one of the discs 94, 95 and has higher rigidity than the discs 94, 95. Therefore, the closing member 116, together with the disc 97, abuts against the main valve 101, which is made up of multiple discs 94, 95, to suppress deformation of the main valve 101 in the opening direction beyond a specified level.

[0088] A passage groove 139 that penetrates radially is formed in the end of the blocking member 116 on the axial side of the large diameter hole portion 133. The passage in the passage groove 139 forms an orifice 139a, which communicates with the passage in the large diameter hole portion 133. Therefore, the orifice 139a is provided in the accumulator portion 104.

[0089] The closing member 116 is disposed so that the passage in the large diameter hole portion 133 overlaps the position of the annular groove 33c of the piston rod 25 in the axial direction of the piston rod 25. This allows the orifice 139a of the closing member 116 to communicate with the passages in the annular groove 33c, axial cutout 33a, and annular groove 33b of the piston rod 25 via the passage in the large diameter hole portion 133, without circumferentially aligning the phase of the closing member 116 with the piston rod 25.

[0090] The closing member 116 has an O-ring 115 disposed in a circular groove-shaped portion recessed radially inward and formed at the axially intermediate position of the outer periphery. The closing member 116 is fitted into the cylindrical portion 124 at its outer periphery with the axial passage groove 139 facing the bottom portion 122. By being provided in the case member 105 in this manner, the closing member 116 closes the open side of the case member 105. In this state, the O-ring 115 seals the gap between the cylindrical portion 124 of the case member 105 and the closing member 116.

[0091] When assembled to the piston rod 25, the flexible disc 110 has its inner peripheral side fixed to the piston rod 25 and its outer peripheral side abutting against the outer conical portion 128 of the valve member 106. At this time, the flexible disc 110 elastically deforms in a slightly tapered shape such that the portion radially outward of the disc 107 moves away from the bottom 122 in the axial direction as it moves radially outward. At this time, the valve member 106 abuts against the flexible disc 110 over its entire circumference while elastically deforming at its outer conical portion 128. In this state, the disc 111 also elastically deforms in a slightly tapered shape, following the shape of the flexible disc 110, such that the portion radially outward of the disc 112 moves away from the bottom 122 in the axial direction as it moves radially outward.

[0092] A first communication volume chamber 149 is formed surrounded by the valve member 106, the disk 107, the flexible disk 110, and the disk 111. This first communication volume chamber 149 is constantly in communication with the passages in the multiple holes 129 in the valve member 106 and the passages in the multiple passage holes 126 in the bottom 122 of the case member 105.

[0093] A second communicating volume chamber 147 is formed surrounded by the case member 105, the valve member 106, the flexible disc 110, the discs 111 to 113, and the closing member 116. This second communicating volume chamber 147 communicates with the orifice 139a of the closing member 116.

[0094] The first communicating volume chamber 149 and the second communicating volume chamber 147 are blocked from communication by the bottom 122 of the case member 105, the valve member 106, the flexible disk 110, and the disk 111.

[0095] The accumulator unit 104, which includes an annular closing member 116 and a bottomed cylindrical case member 105, is disposed in the lower chamber 23, which is one of the upper chamber 22 and the lower chamber 23. In this case, the closing member 116 of the accumulator unit 104 is disposed closer to the piston 21 in the axial direction than the bottom 122 of the case member 105. The passage within the passage hole 126 in the bottom 122 of the case member 105 is constantly in communication with the lower chamber 23. Therefore, the first communication volume chamber 149 is constantly in communication with the lower chamber 23 via the passage within the hole 129 of the valve member 106 and the passage within the passage hole 126 in the bottom 122 of the case member 105.

[0096] The second communication volume chamber 147 is constantly in communication with the upper chamber 22 via the orifice 139a of the closing member 116 and the passage within the large diameter hole portion 133, the annular groove 33c of the piston rod 25, the passage within the axial cutout portion 33a and the annular groove 33b, the passage within the passage groove 63 of the piston 21, and the passage within the passage hole 38 of the piston 21.

[0097] As the flexible disc 110 bends in the axial direction, the volumes of the first communicating volume chamber 149 and the second communicating volume chamber 147 change. That is, as the flexible disc 110 bends, the first communicating volume chamber 149 and the second communicating volume chamber 147 function as accumulators. The first communicating volume chamber 149 decreases in volume to absorb the increase in the volume of the second communicating volume chamber 147, thereby discharging the oil liquid L to the lower chamber 23, and increases in volume to absorb the decrease in the volume of the second communicating volume chamber 147, thereby allowing the oil liquid L to flow in from the lower chamber 23. Conversely, the second communicating volume chamber 147 decreases in volume to absorb the increase in the volume of the first communicating volume chamber 149, thereby discharging the oil liquid L to the upper chamber 22, and increases in volume to absorb the decrease in the volume of the first communicating volume chamber 149, thereby allowing the oil liquid L to flow in from the upper chamber 22. In this way, the deformation of the flexible disc 110 is prevented from being hindered by the oil liquid L in the second communication volume chamber 147 and the first communication volume chamber 149.

[0098] The passage in the passage hole 38 of the piston 21, the passage in the passage groove 63 of the piston 21, the passage in the passage cutout 33 of the piston rod 25, the passage in the large diameter hole 133 of the closing member 116, the orifice 139a of the closing member 116, the second communicating volume chamber 147, the first communicating volume chamber 149, the passage in the hole 129 of the valve member 106, and the passage in the passage hole 126 of the case member 105 constitute a second passage 172 that can communicate between the upper chamber 22 and the lower chamber 23. In the second passage 172, the flow path of the oil liquid L is narrowed by the orifice 139a. The second passage 172 is provided in parallel with the first passage 82 and the first passage 102, and can communicate between the upper chamber 22 and the lower chamber 23. When the outer circumferential side of the flexible disk 110 abuts against the outer circumferential edge of the valve member 106 and the outer circumferential side of the inner annular portion 127 of the valve member 106 abuts against the bottom 122 of the case member 105, the second passage 172 is blocked at the intermediate position.

[0099] During the compression stroke, when the pressure in the first communicating volume chamber 149 communicating with the lower chamber 23 becomes higher by a predetermined value or more than the pressure in the second communicating volume chamber 147 communicating with the upper chamber 22, the outer periphery of the flexible disc 110 deforms so as to move axially away from the outer periphery of the valve member 106, thereby connecting the first communicating volume chamber 149 and the second communicating volume chamber 147 and connecting the lower chamber 23 and the upper chamber 22 via the second passage 172. When the second passage 172 becomes the compression-side second passage 172(a) in this way, it includes a passage between the outer periphery of the flexible disc 110 and the outer periphery of the valve member 106.

[0100] The valve member 106, flexible disc 110, and disc 111 are provided in the second passage 172(a) and form a compression-side damping force generating mechanism 173 that opens and closes the second passage 172(a) to suppress the flow of hydraulic fluid L from the lower chamber 23 to the upper chamber 22 through the second passage 172(a) and generates a damping force. In the damping force generating mechanism 173, the outer periphery of the opening and closing flexible disc 110 and the outer periphery of the valve member 106 control communication between the first communicating volume chamber 149 and the second communicating volume chamber 147. The damping force generating mechanism 173 is disposed separately from the damping force generating mechanisms 43 and 44 that generate damping forces during the same compression stroke. The damping force of the damping force generating mechanism 173 can be adjusted by changing and adjusting the thickness of the disc 107. The damping force generating mechanism 173 and the orifice 139a are disposed in series in the compression-side second passage 172(a).

[0101] During the extension stroke, when the pressure in the second communicating volume chamber 147 communicating with the upper chamber 22 becomes higher than the pressure in the first communicating volume chamber 149 communicating with the lower chamber 23 by a predetermined value or more, the outer circumferential side of the inner annular portion 127 of the valve member 106 deforms so as to move axially away from the bottom 122 of the case member 105, thereby connecting the second communicating volume chamber 147 and the first communicating volume chamber 149 and connecting the upper chamber 22 and the lower chamber 23 via the second passage 172. When the second passage 172 becomes the extension-side second passage 172(b) in this manner, it includes a passage between the outer circumferential side of the inner annular portion 127 of the valve member 106 and the bottom 122 of the case member 105.

[0102] The valve member 106 and the bottom 122 of the case member 105 are provided in the second passage 172(b) and open and close the second passage 172(b), thereby constituting an extension-side damping force generating mechanism 183 that generates a damping force by suppressing the flow of oil L from the upper chamber 22 to the lower chamber 23 through the second passage 172(b). The damping force generating mechanism 183 controls communication between the second communicating volume chamber 147 and the first communicating volume chamber 149 using the outer circumferential side of the inner annular portion 127 of the valve member 106 that opens and closes and the bottom 122 of the case member 105. The damping force generating mechanism 183 is arranged separately from the damping force generating mechanisms 41 and 42 that generate damping forces during the same extension stroke. The damping force of the damping force generating mechanism 183 can be adjusted by changing and adjusting the thickness of the disc 107. The damping force generating mechanism 183 and the orifice 139a are provided in series in the extension-side second passage 172(b).

[0103] In the compression-side second passage 172(a), when the damping force generating mechanism 173 is in an open state, the orifice 139a of the closing member 116 has the narrowest flow path cross-sectional area among the portions with fixed flow path cross-sectional areas, and the flow path cross-sectional area is narrower than that on the upstream and downstream sides thereof. The orifice 139a is disposed downstream of the damping force generating mechanism 173 in the flow of the oil liquid L when the damping force generating mechanism 173 is open and the oil liquid L flows from the lower chamber 23 to the upper chamber 22 in the second passage 172(a). Note that the orifice 139a may also be disposed upstream of the damping force generating mechanism 173 in the flow of the oil liquid L when the damping force generating mechanism 173 is open and the oil liquid L flows from the lower chamber 23 to the upper chamber 22 in the second passage 172(a).

[0104] In the extension-side second passage 172(b), when the damping force generating mechanism 183 is in an open state, the orifice 139a of the closing member 116 has the narrowest flow path cross-sectional area among the portions with fixed flow path cross-sectional areas, and the flow path cross-sectional area is narrower than that on its upstream and downstream sides. The orifice 139a is disposed upstream of the damping force generating mechanism 183 in the flow of the oil liquid L when the damping force generating mechanism 183 is open and the oil liquid L flows from the upper chamber 22 to the lower chamber 23 in the second passage 172(b). Note that the orifice 139a may also be disposed downstream of the damping force generating mechanism 183 in the flow of the oil liquid L when the damping force generating mechanism 183 is open and the oil liquid L flows from the upper chamber 22 to the lower chamber 23 in the second passage 172(b).

[0105] In the second passage 172, when the outer periphery of the flexible disc 110 abuts against the outer periphery of the valve member 106 and the outer periphery of the inner annular portion 127 of the valve member 106 abuts against the bottom portion 122 of the case member 105, that is, when both the damping force generating mechanisms 173, 183 are closed, no orifice is formed that connects the upper chamber 22 and the lower chamber 23. In other words, when the outer periphery of the flexible disc 110 abuts against the outer periphery of the valve member 106 over the entire periphery, that is, when the damping force generating mechanism 173 is closed, the compression-side damping force generating mechanism 173 does not connect the lower chamber 23 and the upper chamber 22. Furthermore, when the outer periphery of the inner annular portion 127 of the valve member 106 is in contact with the bottom portion 122 of the case member 105 over the entire circumference, i.e., when the damping force generating mechanism 183 is in a closed state, the extension-side damping force generating mechanism 183 does not provide communication between the upper chamber 22 and the lower chamber 23. In other words, the second passage 172 does not have an orifice that constantly provides communication between the upper chamber 22 and the lower chamber 23, and is not a passage that constantly provides communication between the upper chamber 22 and the lower chamber 23.

[0106] The second compression passage 172(a), which can communicate between the lower chamber 23 and the upper chamber 22, is parallel to the first passage 82, which is also a compression passage which can communicate between the lower chamber 23 and the upper chamber 22. The damping force generating mechanisms 43, 44 are provided in the first passage 82, and the damping force generating mechanism 173 is provided in the second passage 172(a). Therefore, the damping force generating mechanisms 43, 44 on the compression side and the damping force generating mechanism 173 are arranged in parallel.

[0107] The second extension passage 172(b), which can communicate between the upper chamber 22 and the lower chamber 23, is parallel to the first passage 102, which is also an extension passage which can communicate between the upper chamber 22 and the lower chamber 23. The damping force generating mechanisms 41, 42 are provided in the first passage 102, and the damping force generating mechanism 183 is provided in the second passage 172(b). Therefore, the damping force generating mechanisms 41, 42 on the extension side and the damping force generating mechanism 183 are arranged in parallel.

[0108] The bottom 122 of the case member 105, the valve member 106, the disk 107, the flexible disk 110, the disk 111, and the first communicating volume chamber 149 constitute a first volume variable mechanism 185 that can change the volume of the first communicating volume chamber 149. The first volume variable mechanism 185 is provided in the second passage 172 that includes the first communicating volume chamber 149, and changes the volume of this first communicating volume chamber 149.

[0109] The first volume variable mechanism 185 is operated by the movement of the piston 21 during the compression stroke causing hydraulic fluid L to flow from the lower chamber 23 located upstream within the inner tube 2 of the cylinder 4 into the second passage 172(a), and is provided with a first communicating volume chamber 149 that stores the hydraulic fluid L from the lower chamber 23 located upstream. The damping force generating mechanism 173 is provided in the first volume variable mechanism 185, and when the first volume variable mechanism 185 is deformed by a predetermined amount or more, communicates between the first communicating volume chamber 149 and the upper chamber 22 located downstream of the cylinder 4. The first volume variable mechanism 185 has a case member 105 that covers the first volume variable mechanism 185, a valve member 106 that has one radial end fixed and the other radial end formed as a free end and that abuts against the case member 105, and a flexible disk 110 that is formed to abut against the valve member 106. In the damping force generating mechanism 173, the valve member 106 is separated from the flexible disc 110, thereby communicating the first communication volume chamber 149 with the upper chamber 22 located downstream of the cylinder 4.

[0110] The first volume varying mechanism 185 changes the volume of the first communicating volume chamber 149 so as to increase it by deforming and moving the flexible disc 110 and the disc 111 together away from the bottom 122. At this time, if the flexible disc 110 is kept in contact with the valve member 106 over the entire circumference, i.e., if the damping force generating mechanism 173 is kept in a closed state, the flexible disc 110 closes the gap with the outer conical portion 128 of the valve member 106. In other words, if the flexible disc 110 is kept in contact with the valve member 106 over the entire circumference when it deforms away from the bottom 122, the volume of the first communicating volume chamber 149 increases and the volume of the second communicating volume chamber 147 decreases while maintaining a blocked state between the first communicating volume chamber 149 and the second communicating volume chamber 147.

[0111] Furthermore, the first volume varying mechanism 185 changes the volume of the first communicating volume chamber 149 by deforming and moving the flexible disc 110 and disc 111 together so that they approach the bottom 122. Even at this time, the flexible disc 110 remains in contact with the valve member 106 as a whole, and the space between the flexible disc 110 and the outer conical portion 128 of the valve member 106 is closed.

[0112] The first communicating volume chamber 149 and the orifice 139a of the first volume variable mechanism 185 are arranged in series in the second passage 172(a), and the orifice 139a is arranged downstream of the first communicating volume chamber 149 in the second passage 172(a). When the damping force generation mechanism 173 opens, the first communicating volume chamber 149 no longer functions as a volume chamber but becomes a passage, so the first communicating volume chamber 149 and the damping force generation mechanism 173 are arranged in parallel in the flow path of the oil liquid L.

[0113] The case member 105, the valve member 106, the flexible disc 110, the disc 111, the discs 112 and 113, the closing member 116, and the second communicating volume chamber 147 constitute a second volume variable mechanism 186 that can change the volume of the second communicating volume chamber 147. The second volume variable mechanism 186 is provided in the second passage 172 that includes the second communicating volume chamber 147. The second volume variable mechanism 186 changes the volume of the second communicating volume chamber 147.

[0114] The second volume variable mechanism 186 is operated by the movement of the piston 21 during the extension stroke, causing hydraulic fluid L to flow from the upper chamber 22 on the upstream side within the inner tube 2 of the cylinder 4 into the second passage 172, and is provided with a second communication volume chamber 147 that stores the hydraulic fluid L in the upper chamber 22 on the upstream side. The damping force generation mechanism 183 is provided in the second volume variable mechanism 186, and when the second volume variable mechanism 186 is deformed by a predetermined amount or more, the second communication volume chamber 147 communicates with the lower chamber 23 on the downstream side of the cylinder 4. The second volume variable mechanism 186 has a case member 105 that covers the second volume variable mechanism 186, a valve member 106 that has one radial end fixed and the other radial end formed as a free end and that abuts against the case member 105, and a flexible disk 110 that is formed to abut against the valve member 106. In the damping force generating mechanism 183, the valve member 106 is separated from the case member 105, thereby communicating the second communication volume chamber 147 with the lower chamber 23 located downstream of the cylinder 4.

[0115] As the piston 21 moves toward the compression side, the valve member 106 communicates between the upper chamber 22, which is on the downstream side of the cylinder 4, and a first communicating volume chamber 149 that communicates with the lower chamber 23, which is one of the upper chamber 22 and the lower chamber 23 in the cylinder 4. As the piston 21 moves in the extension direction, the valve member 106 communicates between the lower chamber 23, which is on the downstream side of the cylinder 4, and a second communicating volume chamber 147 that communicates with the upper chamber 22, which is the other of the upper chamber 22 and the lower chamber 23 in the cylinder 4. Thus, the valve member 106 communicates between the upper chamber 22 or the lower chamber 23, which is on the downstream side of the cylinder 4 depending on the movement direction of the piston 21, and either the first communicating volume chamber 149 that communicates with the lower chamber 23, which is one of the upper chamber 22 and the lower chamber 23 in the cylinder 4, or the second communicating volume chamber 147 that communicates with the upper chamber 22, which is the other of the upper chamber 22 and the lower chamber 23 in the cylinder 4.

[0116] The second volume variable mechanism 186 changes the volume of the second communicating volume chamber 147 by deforming and moving the flexible disc 110 and the disc 111 together so that they move away from the disc 113. At that time, if the outer periphery of the inner annular portion 127 of the valve member 106 is kept in contact with the bottom portion 122 of the case member 105, i.e., if the damping force generating mechanism 183 is kept in the closed state, the second volume variable mechanism 186 increases the volume of the second communicating volume chamber 147 and decreases the volume of the first communicating volume chamber 149 while maintaining the isolation state between the second communicating volume chamber 147 and the first communicating volume chamber 149.

[0117] Furthermore, the second volume variable mechanism 186 changes the volume of the second communicating volume chamber 147 by deforming and moving the flexible disc 110 and the disc 111 so that they approach the disc 113, thereby reducing the volume of the second communicating volume chamber 147. Even at this time, the valve member 106 maintains a state in which the outer circumferential side of the inner annular portion 127 abuts against the bottom 122 of the case member 105, and the space between the valve member 106 and the bottom 122 of the case member 105 is blocked.

[0118] The second communicating volume chamber 147 and the orifice 139a of the second volume variable mechanism 186 are arranged in series in the second passage 172(b), and the orifice 139a is arranged upstream of the second communicating volume chamber 147 in the second passage 172(b). When the damping force generation mechanism 183 opens, the second communicating volume chamber 147 no longer functions as a volume chamber but becomes a passage, so the second communicating volume chamber 147 and the damping force generation mechanism 183 are arranged in parallel in the flow path of the oil liquid L.

[0119] The flexible disc 110, disc 111, and valve member 106 are shared by the first volume variable mechanism 185 and the second volume variable mechanism 186. The first volume variable mechanism 185, which includes the first communicating volume chamber 149, and the second volume variable mechanism 186, which includes the second communicating volume chamber 147, store hydraulic fluid L as a working fluid, and constitute an accumulator unit 104. The accumulator unit 104 is provided on the piston rod 25. In the accumulator unit 104, the second volume variable mechanism 186 changes the volume of the second communicating volume chamber 147 before the damping force generation mechanism 183 opens during the extension stroke, and the first volume variable mechanism 185 changes the volume of the first communicating volume chamber 149 before the damping force generation mechanism 173 opens during the compression stroke.

[0120] The first volume variable mechanism 185 and the second volume variable mechanism 186 are provided in series on the flow path of the oil liquid L in the second passage 172, as shown in Figure 3. The damping force generating mechanism 173 and the damping force generating mechanism 183 are provided in parallel on the flow path of the oil liquid L in the second passage 172.

[0121] The above configuration is shown in a hydraulic circuit diagram as shown in Figure 3. As shown in Figure 3, a compression-side damping force generating mechanism 43 and an orifice 71a are provided in parallel in a first passage 82 connecting the lower chamber 23 and the upper chamber 22. A compression-side damping force generating mechanism 44 and an orifice 74a are provided in parallel on the upper chamber 22 side of the damping force generating mechanism 43 and the orifice 71a in the first passage 82. An extension-side damping force generating mechanism 41 and an orifice 91a are provided in parallel in a first passage 102 connecting the upper chamber 22 and the lower chamber 23. An extension-side damping force generating mechanism 42 and an orifice 94a are provided in parallel on the lower chamber 23 side of the damping force generating mechanism 41 and the orifice 91a in the first passage 102. An accumulator unit 104 is provided in a second passage 172 connecting the upper chamber 22 and the lower chamber 23. In the accumulator portion 104, an orifice 139a is provided in the second passage 172, and a damping force generating mechanism 173, a damping force generating mechanism 184, a first volume variable mechanism 185, and a second volume variable mechanism 186 are provided closer to the lower chamber 23 than the orifice 139a. The damping force generating mechanism 173 allows the flow of oil L from the lower chamber 23 to the upper chamber 22, and the damping force generating mechanism 183 allows the flow of oil L from the upper chamber 22 to the lower chamber 23. In the first volume variable mechanism 185, the first communicating volume chamber 149 communicates between the damping force generating mechanisms 173, 183 of the second passage 172 and the lower chamber 23, and in the second volume variable mechanism 186, the second communicating volume chamber 147 communicates between the orifice 139a of the second passage 172 and the damping force generating mechanisms 173, 183.

[0122] Here, the relationship between the flow path cross-sectional area S1 of the orifice 91a, the flow path cross-sectional area S2 of the orifice 94a, and the flow path cross-sectional area S5 of the orifice 139a is such that the flow path cross-sectional area S1 is smaller than the flow path cross-sectional area S2 and smaller than the flow path cross-sectional area S5. <S2,S1<S5となっている。 The relationship between the flow path cross-sectional area S3 of the orifice 71a, the flow path cross-sectional area S4 of the orifice 74a, and the flow path cross-sectional area S5 of the orifice 139a is such that the flow path cross-sectional area S3 is smaller than the flow path cross-sectional area S4, and is smaller than the flow path cross-sectional area S5. <S4,S3<S5となっている。

[0123] In addition, the relationship between the valve opening pressure V1 of the damping force generating mechanism 41, the valve opening pressure V2 of the damping force generating mechanism 42, and the valve opening pressure V5 of the damping force generating mechanism 183, all of which are on the extension side, is such that the valve opening pressure V5 is greater than the valve opening pressure V1, and the valve opening pressure V2 is greater than the valve opening pressure V5. <V5<V2となっている。 In addition, the relationship between the valve opening pressure V3 of the damping force generating mechanism 43, the valve opening pressure V4 of the damping force generating mechanism 44, and the valve opening pressure V6 of the damping force generating mechanism 173 on the compression side is such that the valve opening pressure V6 is greater than the valve opening pressure V3, and the valve opening pressure V4 is greater than the valve opening pressure V6. <V6<V4となっている。

[0124] Therefore, the shock absorber 1 has a damping force generating mechanism 41 (first damping force generating mechanism) that generates a damping force, and an orifice 91a (first orifice) that is arranged in parallel with the damping force generating mechanism 41, all of which are arranged in the first passage 102 (first passage) on the extension side, a second volume variable mechanism 186 (volume variable mechanism) that changes the volume of the second communicating volume chamber 147 (volume chamber), all of which are arranged in the second passage 172(b) (second passage) on the extension side, and an orifice 139a (second orifice) that is arranged upstream of the second communicating volume chamber 147, and the flow path cross-sectional area of ​​the orifice 139a is larger than the flow path cross-sectional area of ​​the orifice 91a. Furthermore, the shock absorber 1 is provided with a damping force generating mechanism 42 (third damping force generating mechanism) in series with the damping force generating mechanism 41.

[0125] The shock absorber 1 also has a damping force generating mechanism 43 that generates a damping force, an orifice 71a that is arranged in parallel with the damping force generating mechanism 43, and a first volume variable mechanism 185 that changes the volume of the first communicating volume chamber 149, all of which are arranged in the second passage 172(a) on the compression side, and an orifice 139a that is arranged downstream of the first communicating volume chamber 149, and the flow path cross-sectional area of ​​the orifice 139a is larger than the flow path cross-sectional area of ​​the orifice 71a. In addition, the shock absorber 1 is provided with a damping force generating mechanism 44 in series with the damping force generating mechanism 43.

[0126] 1, the valve body 10 is formed with fluid passages 251 and 252 that penetrate in the axial direction. The fluid passages 251, 252 are capable of communicating between the lower chamber 23 and the reservoir chamber 5. The base valve 12 has a compression-side damping force generating mechanism 255 that can open and close the fluid passage 251 on the axial side of the bottom member 9 of the valve body 10. The base valve 12 also has an extension-side damping force generating mechanism 256 that can open and close the fluid passage 252 on the axial side of the valve body 10 opposite the bottom member 9.

[0127] When the piston rod 25 moves toward the compression side and the piston 21 moves in a direction that narrows the lower chamber 23, causing the pressure in the lower chamber 23 to become higher than the pressure in the reservoir chamber 5 by a predetermined value or more, the damping force generating mechanism 255 opens the fluid passage 251 to allow the oil L in the lower chamber 23 to flow into the reservoir chamber 5, generating a damping force. In other words, when the piston rod 25 moves toward the compression side and moves the piston 21, the oil L flows out of the fluid passage 251 into the reservoir chamber 5. The damping force generating mechanism 255 is a compression-side damping force generating mechanism. This damping force generating mechanism 255 does not obstruct the flow of the oil L in the fluid passage 252.

[0128] When the piston rod 25 moves toward the extension side and the piston 21 moves toward the upper chamber 22, causing the pressure in the lower chamber 23 to drop below the pressure in the reservoir chamber 5, the damping force generating mechanism 256 opens the fluid passage 252 to allow the hydraulic fluid L in the reservoir chamber 5 to flow into the lower chamber 23, generating a damping force. In other words, when the piston rod 25 moves toward the extension side and moves the piston 21, the hydraulic fluid L flows out of the fluid passage 252 into the lower chamber 23. The damping force generating mechanism 256 is an extension-side damping force generating mechanism. This damping force generating mechanism 256 does not obstruct the flow of the hydraulic fluid L in the fluid passage 251. The damping force generating mechanism 256 may also be a suction valve that allows the hydraulic fluid L to flow from the reservoir chamber 5 into the lower chamber 23 without generating any substantial damping force.

[0129] <Activation> During the extension stroke, piston 21 moves toward upper chamber 22 shown in Fig. 2, increasing the pressure in upper chamber 22 and decreasing the pressure in lower chamber 23. During the extension stroke in the extremely low-speed region where the piston speed is equal to or less than first predetermined value X1, damping force generating mechanism 41, damping force generating mechanism 42, and damping force generating mechanism 183 are all in a closed valve state, and oil L in upper chamber 22 flows to lower chamber 23 via the passages in multiple passage holes 38 and annular groove 52 of piston 21, orifice 91a provided in disc 91 of sub-valve 100, a passage in annular groove 53 of piston 21, and orifice 94a provided in disc 94 of main valve 101. This generates a damping force with orifice characteristics (damping force is approximately proportional to the square of the piston speed). Therefore, as shown by the solid line Y1 in Figure 4, during the extension stroke in the extremely low speed region where the piston speed is less than the first predetermined value X1, the damping force characteristics relative to the piston speed become hard, with the damping force increasing at a relatively high rate as the piston speed increases.

[0130] At this time, a portion of the oil L in the upper chamber 22 shown in FIG. 2 flows into the second communicating volume chamber 147 via the passage hole 38 and the passage groove 63 of the piston 21, the passage in the passage cutout 33 of the piston rod 25, and the passage in the large-diameter hole 133 of the closing member 116 and the orifice 139a. This increases the pressure in the second communicating volume chamber 147. Therefore, before any of the damping force generating mechanisms 41, 42, and 183 open, the second volume variable mechanism 186 bends the portion of the flexible disc 110 radially inward from the position where it abuts against the outer conical portion 128 of the valve member 106 toward the bottom 122 of the case member 105, thereby increasing the capacity of the second communicating volume chamber 147. This allows the second volume variable mechanism 186 to suppress an increase in pressure in the second communicating volume chamber 147. At this time, the flexible disk 110 bends and moves toward the bottom portion 122, so that the first volume variable mechanism 185 reduces the volume of the first communicating volume chamber 149.

[0131] Here, during the extension stroke in the extremely low-speed region when a low-frequency input (large-amplitude vibration) occurs, which is the piston frequency of the axial movement of the piston 21, the amount of oil L flowing from the upper chamber 22 into the second communicating volume chamber 147 increases, as described above, causing the flexible disc 110 to deform significantly. As the amount of deformation of the flexible disc 110 increases, the reaction force due to the support rigidity of the clamped inner periphery increases, limiting the amount of deformation. This causes the pressure in the second communicating volume chamber 147 to rise. As a result, the pressure in the first passage 102 rises to a state where the damping force generating mechanism 41 opens, with the damping force generating mechanism 42 and the damping force generating mechanism 183 closed.

[0132] During the extension stroke in the extremely low speed region where the piston speed is greater than the first predetermined value X1 and less than a second predetermined value X2 that is greater than the first predetermined value X1, the pressure rise in the first passage 102 becomes high, and the damping force generating mechanism 42 and the damping force generating mechanism 183 remain in a closed state, while the oil L in the upper chamber 22 opens the damping force generating mechanism 41. Therefore, the oil L in the upper chamber 22 flows into the lower chamber 23 via the passage holes 38 and the passage in the annular groove 52 of the piston 21, the passage between the opened sub-valve 100 and the inner valve seat portion 46, the passage in the annular groove 53 of the piston 21, and the orifice 94a provided in the disc 94 of the main valve 101. As a result, the oil L flows through the orifice 94a, which has a larger flow path cross-sectional area than the orifice 91a. Therefore, as shown by the solid line Y1 in Figure 4, during the extension stroke in the extremely low speed region where the piston speed is less than the second predetermined value X2, the rate of increase in damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the extremely low speed region where the piston speed is equal to or less than the first predetermined value X1.

[0133] During the extension stroke in the low-speed region where the piston speed is equal to or greater than the second predetermined value X2 and less than a third predetermined value X3 that is greater than the second predetermined value X2, the damping force generating mechanism 42 shown in Fig. 2 closes, the damping force generating mechanism 41 remains open, and the pressure in the second passage 172(b) rises until the damping force generating mechanism 183 opens. In other words, the outer circumferential side of the inner annular portion 127 of the valve member 106 moves away from the bottom 122 of the case member 105 in the axial direction, opening the damping force generating mechanism 183 and connecting the upper chamber 22 and the lower chamber 23 through the extension-side second passage 172(b). Therefore, oil L in the upper chamber 22 flows into the lower chamber 23 via the passages in the passage hole 38 and passage groove 63 of the piston 21, the passage in the passage cutout 33 of the piston rod 25, the passage and orifice 139a in the large diameter hole portion 133 of the closing member 116, the second communicating volume chamber 147, the damping force generating mechanism 183 in the open state, and the passage in the passage hole 126 in the bottom 122 of the case member 105. As a result, during the extension stroke in the low speed range where the piston speed is less than the third predetermined value X3, a damping force with a valve characteristic (a characteristic in which the damping force is approximately proportional to the piston speed) is obtained, and as shown by the solid line Y1 in Figure 4, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the very low speed range where the piston speed is less than the second predetermined value X2.

[0134] During the extension stroke in the normal speed range where the piston speed is equal to or greater than the third predetermined value X3, the damping force generating mechanism 42 opens while the damping force generating mechanism 41 and the damping force generating mechanism 183 remain open. That is, as described above, the outer peripheral side of the inner annular portion 127 of the valve member 106 moves axially away from the bottom portion 122 of the case member 105, allowing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 in the extension-side second passage 172(b). At this time, the flow of the hydraulic fluid L is throttled by the orifice 139a provided upstream of the damping force generating mechanism 183 in the second passage 172(b), increasing the pressure applied to the main valve 101 in the first passage 102 and increasing the pressure difference. As a result, the main valve 101 lifts off the outer valve seat portion 48, allowing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 in the extension-side first passage 102. Therefore, oil L in the upper chamber 22 flows into the lower chamber 23 via the passages in the multiple passage holes 38 and annular groove 52 of the piston 21, the passage between the open sub-valve 100 and the inner valve seat portion 46, the passage in the annular groove 53 of the piston 21, and the passage between the open main valve 101 and the outer valve seat portion 48. As a result, as shown by the solid line Y1 in Fig. 4, during the extension stroke in the normal speed range where the piston speed is equal to or greater than the third predetermined value X3, the rate of increase in damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the low speed range where the piston speed is less than the third predetermined value X3.

[0135] During the extension stroke in the extremely low speed region when a high frequency input (small amplitude vibration) is applied to the shock absorber 1 at a piston frequency higher than that at the time of the low frequency input described above, the amount of oil L flowing from the upper chamber 22 into the second communicating volume chamber 147 is small. Therefore, the deformation of the flexible disc 110 is small, and the second volume variable mechanism 186 can absorb the volume of oil L flowing into the second communicating volume chamber 147 with the amount of deflection of the flexible disc 110, and the pressure increase in the second communicating volume chamber 147 is small. Therefore, when the damping force rises in the extremely low speed region where the piston speed is equal to or lower than the first predetermined value X1, it is possible to achieve a state as if the flexible disc 110 were not present and the second communicating volume chamber 147 were connected to the lower chamber 23 via the first communicating volume chamber 149, the passage in the hole 129 of the valve member 106, and the passage in the passage hole 126 in the bottom 122 of the case member 105, i.e., a state identical to a structure without the damping force generating mechanism 183. Therefore, during the extension stroke in the extremely low speed region when a high frequency input is performed, the rise of the damping force is gradual compared to when a low frequency input is performed.

[0136] Here, during the extension stroke, the damping force characteristics due to the damping force generating mechanism 256 shown in FIG. 1 are also taken into account.

[0137] During the compression stroke, piston 21 moves toward lower chamber 23 (shown in FIG. 2), increasing the pressure in lower chamber 23 and decreasing the pressure in upper chamber 22. During the compression stroke, in the extremely low-speed region where the piston speed is equal to or less than fifth predetermined value X5, damping force generating mechanism 43, damping force generating mechanism 44, and damping force generating mechanism 173 are all in a closed valve state, and oil L in lower chamber 23 flows to upper chamber 22 via the passage holes 39 and the annular groove 54 in piston 21, the orifice 71a in disc 71 (sub-valve), the passage in annular groove 55 in piston 21, and the orifice 74a in disc 74 of main valve 81. This generates a damping force with orifice characteristics. Therefore, during the compression stroke, in the extremely low-speed region where the piston speed is equal to or less than fifth predetermined value X5, the damping force characteristic relative to piston speed is relatively high and hard as the piston speed increases.

[0138] At this time, a portion of the oil liquid L in the lower chamber 23 flows into the first communicating volume chamber 149 through the passage in the passage hole 126 of the case member 105 and the passage in the hole 129 of the valve member 106. This causes the pressure in the first communicating volume chamber 149 to increase. Therefore, the first volume variable mechanism 185 causes the flexible disc 110 to bend toward the disc 113, increasing the capacity of the first communicating volume chamber 149, before any of the damping force generating mechanisms 43, 44, and 173 open. This causes the first volume variable mechanism 185 to suppress an increase in pressure in the first communicating volume chamber 149. At this time, the disc 111 deforms following the flexible disc 110. Also, at this time, because the flexible disc 110 bends and moves toward the disc 113, the second volume variable mechanism 186 reduces the volume of the second communicating volume chamber 147.

[0139] Here, during the compression stroke in the extremely low speed region when a low-frequency input (large-amplitude vibration) occurs with a low piston frequency, the amount of oil L flowing from the lower chamber 23 into the first communication volume chamber 149 increases, causing the flexible disc 110 to deform significantly. As the amount of deformation of the flexible disc 110 increases, the reaction force due to the support rigidity of the clamped inner periphery increases, limiting the amount of deformation. This causes the pressure in the first communication volume chamber 149 to rise. As a result, the pressure in the first passage 82 rises to a state where the damping force generating mechanism 43 opens, with the damping force generating mechanism 44 and the damping force generating mechanism 173 closed.

[0140] During the compression stroke in the extremely low speed region where the piston speed is greater than the first predetermined value X5 and less than a sixth predetermined value X6 that is greater than the first predetermined value X5, the pressure rise in the first passage 82 becomes high, and the damping force generating mechanism 44 and the damping force generating mechanism 173 remain in a closed state, while the oil L in the lower chamber 23 opens the damping force generating mechanism 43. Therefore, the oil L in the lower chamber 23 flows into the upper chamber 22 via the passage holes 39 and the passage in the annular groove 54 of the piston 21, the passage between the disc 71, which is the open sub-valve, and the inner valve seat portion 51, the passage in the annular groove 55 of the piston 21, and the orifice 74a provided in the disc 74 of the main valve 81. As a result, the oil L flows through the orifice 74a, which has a larger flow path cross-sectional area than the orifice 71a. Therefore, during the compression stroke in the extremely slow speed region where the piston speed is less than the sixth predetermined value X6, the rate of increase in damping force relative to an increase in piston speed is lower and softer than during the compression stroke in the extremely slow speed region where the piston speed is equal to or less than the fifth predetermined value X5.

[0141] During the compression stroke in the low-speed region where the piston speed is equal to or greater than the sixth predetermined value X6 and less than a seventh predetermined value X7 that is greater than the sixth predetermined value X6, the damping force generating mechanism 44 closes, the damping force generating mechanism 43 remains open, and the pressure in the second passage 172(a) rises until the damping force generating mechanism 173 opens. Then, the flexible disc 110 moves away from the outer conical portion 128 of the valve member 106, the damping force generating mechanism 173 opens, and the lower chamber 23 and the upper chamber 22 communicate with each other through the second passage 172(a) on the compression side. Therefore, oil liquid L in the lower chamber 23 flows into the upper chamber 22 via the passage inside the passage hole 126 in the bottom portion 122 of the case member 105, the passage inside the hole portion 129 of the valve member 106, the first communicating volume chamber 149, the passage between the flexible disc 110 in the open state and the outer conical portion 128 of the valve member 106, the second communicating volume chamber 147, the passage inside the orifice 139a and large diameter hole portion 133 of the closing member 116, the passage inside the passage cutout portion 33 of the piston rod 25, the passage inside the passage groove 63 of the piston 21, and the passage inside the passage hole 38. As a result, during the compression stroke in the low speed range where the piston speed is less than the seventh predetermined value X7, a damping force with valve characteristics is obtained, and the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the compression stroke in the extremely low speed range where the piston speed is less than the sixth predetermined value X6.

[0142] During the compression stroke in the normal speed range where the piston speed is equal to or higher than the seventh predetermined value X7, the damping force generating mechanism 44 opens while the damping force generating mechanism 43 and the damping force generating mechanism 173 remain open. That is, as described above, the flexible disc 110 separates from the outer conical portion 128 of the valve member 106, causing the hydraulic oil L to flow from the lower chamber 23 to the upper chamber 22 in the compression-side second passage 172(a). At this time, the flow of the hydraulic oil L is throttled by the orifice 139a provided in the second passage 172(a) downstream of the damping force generating mechanism 173, so that the pressure applied to the main valve 81 in the first passage 82 increases, increasing the pressure difference. As a result, the main valve 81 separates from the outer valve seat portion 50, causing the hydraulic oil L to flow from the lower chamber 23 to the upper chamber 22 in the compression-side first passage 82. Therefore, oil L in the lower chamber 23 flows into the upper chamber 22 via the passages in the multiple passage holes 39 and annular groove 54 of the piston 21, the passage between the disc 71, which is the sub-valve in an open state, and the inner valve seat portion 51, the passage in the annular groove 55 of the piston 21, and the passage between the main valve 81 in an open state and the outer valve seat portion 50. As a result, during the compression stroke in the normal speed range where the piston speed is equal to or greater than the seventh predetermined value X7, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the low speed range where the piston speed is less than the seventh predetermined value X7.

[0143] During the compression stroke in the extremely low speed region when a high frequency input (small amplitude vibration) is applied to the shock absorber 1 at a piston frequency higher than that during the low frequency input described above, the amount of oil L flowing from the lower chamber 23 into the first communicating volume chamber 149 is small. Therefore, the deformation of the flexible disc 110 is small, and the first volume variable mechanism 185 can absorb the volume of oil L flowing into the first communicating volume chamber 149 by the amount of deflection of the flexible disc 110, thereby reducing the pressure increase in the first communicating volume chamber 149. Therefore, during the compression stroke in the extremely low speed region when the piston speed is equal to or lower than the fifth predetermined value X5, it is possible to achieve a state in which the flexible disc 110 is not present and the first communicating volume chamber 149 is connected to the second communicating volume chamber 147, i.e., a state identical to that in the structure in which the damping force generating mechanism 173 is not present. Therefore, during the compression stroke in the extremely low speed region when a high frequency input is applied, the damping force rises more gradually than during a low frequency input.

[0144] Here, during the compression stroke, the damping force characteristics due to the damping force generating mechanism 255 shown in FIG. 1 are also taken into account.

[0145] The reference example shown in the above-mentioned Patent Document 1 describes a shock absorber having two damping force generating mechanisms that open in the same stroke. Furthermore, the reference example shown in Patent Document 2 describes a shock absorber having an extremely low speed valve that opens at an extremely low piston speed, which is the axial movement speed of the piston, to generate damping force, and an accumulator that can store pressure. However, it is desired to improve the insufficient damping force when the piston speed is extremely low in a shock absorber.

[0146] The shock absorber 1 of the first embodiment has a damping force generating mechanism 41 that is provided in the first extension passage 102 and generates a damping force, an orifice 91a that is provided in parallel with the damping force generating mechanism 41, a second volume variable mechanism 186 that is provided in the second extension passage 172(b) and changes the volume of the second communication volume chamber 147, and an orifice 139a that is provided upstream of the second communication volume chamber 147, the flow path cross-sectional area of ​​the orifice 139a being larger than the flow path cross-sectional area of ​​the orifice 91a. This makes it possible to improve the insufficient damping force when the piston speed is extremely low during the extension stroke.

[0147] Furthermore, since the shock absorber 1 has the damping force generating mechanism 42 provided in series with the damping force generating mechanism 41, the structure can be simplified.

[0148] For example, if the shock absorber 1 is configured without the second passage 172 and the accumulator portion 104 and an attempt is made to suppress changes in the damping force, during the extension stroke, the damping force will be low in the extremely low speed region where both the damping force generating mechanism 42 and the damping force generating mechanism 41 are closed, and in the extremely low speed region and low speed region where the damping force generating mechanism 42 is closed and the damping force generating mechanism 41 is open, as shown by the dashed line Y2 in Fig. 4. For this reason, in the case of a configuration without the second passage 172 and the accumulator portion 104, if an attempt is made to increase the damping force in the extremely low speed region where both the damping force generating mechanism 42 and the damping force generating mechanism 41 are closed, the flow path cross-sectional area of ​​the orifice 91a will need to be reduced. As a result, as shown by the dashed line Y3 in Figure 4, the insufficient damping force in the extremely low speed region where the piston speed is equal to or less than the first predetermined value X1 is improved, but the damping force in the extremely low speed region and the low speed region where the piston speed after the damping force generating mechanism 41 opens is greater than the first predetermined value X1 and less than the third predetermined value X3 remains insufficient. This may result in a deterioration in the ride comfort of the vehicle. Furthermore, the change in damping force from the extremely low speed region to the extremely low speed region at the first predetermined value X1 becomes large, which also reduces the ride comfort of the vehicle and increases the possibility of generating abnormal noise. In particular, in heavy vehicles such as electric vehicles, the insufficient initial damping force can affect the vehicle's behavior, potentially resulting in a deterioration in ride comfort.

[0149] In contrast, as shown by the solid line Y1 in Fig. 4, the shock absorber 1 improves the insufficient damping force in the extremely low speed region where the piston speed is equal to or less than the first predetermined value X1, and also improves the insufficient damping force in the extremely low speed region and low speed region where the piston speed after the damping force generation mechanism 41 opens is greater than the first predetermined value X1 and less than the third predetermined value X3, thereby suppressing a deterioration in the ride comfort of the vehicle. Furthermore, the valve opening function of the damping force generation mechanism 183 of the accumulator unit 104 serves as a multi-valve opening mechanism in which the damping force generation mechanism 41, the damping force generation mechanism 183, and the damping force generation mechanism 42 open in this order, thereby suppressing the change in damping force from the extremely low speed region to the extremely low speed region that switches at the first predetermined value X1, thereby suppressing a deterioration in the ride comfort of the vehicle and the generation of abnormal noise.

[0150] Furthermore, in the shock absorber 1, the accumulator portion 104 has the second volume variable mechanism 186 that changes the volume of the upper chamber 22, so that the flow path cross-sectional area of ​​the orifice 91a can be narrowed to an extremely small value or set to zero. In addition, the shock absorber 1 can increase the flow path cross-sectional area between the first passage 102 and the second passage 172(b) when the damping force generating mechanism 41, the damping force generating mechanism 42, and the damping force generating mechanism 183 are open, thereby suppressing the increase in damping force in response to an increase in piston speed in the normal speed range above the third predetermined value X3. Furthermore, by opening the valve of the damping force generating mechanism 183, the pressure difference acting on the second volume variable mechanism 186 is suppressed, and the durability of the accumulator portion 104 can be improved.

[0151] Furthermore, in the shock absorber 1, even during the compression stroke, the insufficient damping force in the extremely low speed region where the piston speed is equal to or less than the fifth predetermined value X5 is improved, and the insufficient damping force in the extremely low speed region and low speed region where the piston speed after the damping force generation mechanism 43 opens is also improved, thereby suppressing a deterioration in the ride comfort of the vehicle. Furthermore, the valve opening function of the damping force generation mechanism 173 of the accumulator unit 104 forms a multi-valve opening system in which the damping force generation mechanism 43, the damping force generation mechanism 173, and the damping force generation mechanism 44 open in this order, suppressing the change in damping force from the extremely low speed region to the extremely low speed region that switches at the fifth predetermined value X5, thereby suppressing a deterioration in the ride comfort of the vehicle and the generation of abnormal noise.

[0152] Furthermore, in the shock absorber 1, the accumulator portion 104 has the first volume variable mechanism 185 that changes the volume of the lower chamber 23, so that the flow path cross-sectional area of ​​the orifice 71a can be narrowed to an extremely small value or set to zero. In addition, the shock absorber 1 can increase the flow path cross-sectional area between the first passage 82 and the second passage 172(a) when the damping force generating mechanism 43, the damping force generating mechanism 44, and the damping force generating mechanism 173 are open, thereby suppressing the increase in damping force in response to an increase in piston speed in the normal speed range above the seventh predetermined value X7. Furthermore, by opening the valve of the damping force generating mechanism 173, the pressure difference acting on the first volume variable mechanism 185 is suppressed, and the durability of the accumulator portion 104 can be improved.

[0153] [Second embodiment] Next, the second embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Figures 5 and 6. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0154] <Configuration> As shown in Fig. 5, the shock absorber 1A of the second embodiment has a piston rod 25A that is partially different from the piston rod 25 instead of the piston rod 25. The piston rod 25A has a mounting shaft portion 31A that is partially different from the mounting shaft portion 31 instead of the mounting shaft portion 31. The mounting shaft portion 31A is provided with a passage cutout 33A that is located in an axial position and has a length different from that of the passage cutout 33. The passage cutout 33A has an axial cutout 33Aa that has a shape similar to that of the axial cutout 33a but is located in an axial position and has a length different from that of the passage cutout 33, an annular groove 33Ab that has a shape similar to that of the annular groove 33b but is located in an axial position different from that of the annular groove 33b, and an annular groove 33Ac that has a shape similar to that of the annular groove 33c but is located in an axial position different from that of the annular groove 33c.

[0155] Shock absorber 1A has a piston 21A that is partially different from piston 21 in place of piston 21. Piston 21A has a piston main body 36A that is partially different from piston main body 36 in place of piston main body 36A. Piston main body 36A has a second component 58A that is partially different from second component 58 in place of second component 58.

[0156] In the second component 58A, instead of the passage groove 63, a passage groove 63A extending from the passage hole 39 radially inward of the second component 58A is formed on the end face on the first component 57 side, inside the passage hole 39 in the radial direction, and on the engaging protrusion 62. The passage groove 63A opens into the passage hole 39 and the through-hole 61.

[0157] In shock absorber 1A, disc 96, disc 97, and accumulator portion 104, which were located between disc 95 and disc 117 in shock absorber 1, are arranged upside down between disc 76 and disc 75 and are provided on mounting shaft portion 31A. Therefore, bottom portion 122 of case member 105 of accumulator portion 104 abuts against disc 76, and disc 97 and disc 96 are stacked in order on closing member 116 of accumulator portion 104, with disc 75 abutting against disc 96. Furthermore, disc 96, disc 97, and accumulator portion 104 are no longer located between disc 95 and disc 117, and disc 95 abuts against disc 117. Disc 76 abuts on the bottom portion 122 of case member 105 radially inward of passage hole 126.

[0158] In the shock absorber 1A, the upper annular groove 33Ab of the passage cutout 33A is overlapped in the axial direction and communicates with the large-diameter hole 133 of the closing member 116 of the accumulator portion 104. This allows the orifice 139a of the closing member 116 to communicate with the annular groove 33Ab, the axial cutout 33Aa, and the passage in the annular groove 33Ac of the piston rod 25A via the passage in the large-diameter hole 133, without circumferentially aligning the phase of the closing member 116 with the piston rod 25A. The lower annular groove 33Ac of the passage cutout 33A is overlapped in the axial direction and communicates with the passage groove 63A of the piston 21A. As a result, even without circumferentially aligning the phase of the piston 21A with the piston rod 25A, the passage in the passage groove 63A of the second component 58A, which communicates with the lower chamber 23 via the passage in the passage hole 39, can be connected to the passages in the annular groove 33Ac, the axial cutout 33Aa, and the annular groove 33Ab of the piston rod 25A.

[0159] The accumulator portion 104 is disposed in the upper chamber 22, which is one of the upper chamber 22 and the lower chamber 23. The passage in the passage hole 126 in the bottom portion 122 of the case member 105 is constantly connected to the upper chamber 22. Therefore, the first communication volume chamber 149 is constantly connected to the upper chamber 22 via the passage in the hole portion 129 of the valve member 106 and the passage in the passage hole 126 in the bottom portion 122 of the case member 105.

[0160] The second communication volume chamber 147 is constantly connected to the lower chamber 23 via the orifice 139a of the closing member 116 and a passage in the large diameter hole portion 133, the annular groove 33Ab, the axial cutout portion 33Aa and the annular groove 33Ac of the piston rod 25A, the passage in the passage groove 63A of the piston 21A, and the passage in the passage hole 39 of the piston 21A.

[0161] In the accumulator portion 104, the volumes of the first communicating volume chamber 149 and the second communicating volume chamber 147 change as the flexible disk 110 bends in the axial direction. The first communicating volume chamber 149 decreases in volume to absorb the increase in the volume of the second communicating volume chamber 147, thereby discharging the oil liquid L to the upper chamber 22, or increases in volume to absorb the decrease in the volume of the second communicating volume chamber 147, thereby allowing the oil liquid L to flow in from the upper chamber 22. Conversely, the second communicating volume chamber 147 decreases in volume to absorb the increase in the volume of the first communicating volume chamber 149, thereby discharging the oil liquid L toward the lower chamber 23, or increases in volume to absorb the decrease in the volume of the first communicating volume chamber 149, thereby allowing the oil liquid L to flow in from the lower chamber 23.

[0162] The passage within passage hole 39 of piston 21A, the passage within passage groove 63A of piston 21A, the passage within passage cutout 33A of piston rod 25A, the passage within large diameter hole portion 133 of closing member 116, orifice 139a of closing member 116, second communicating volume chamber 147, first communicating volume chamber 149, the passage within hole portion 129 of valve member 106, and the passage within passage hole 126 of case member 105 constitute a second passage 172A that can communicate between lower chamber 23 and upper chamber 22. Second passage 172A is provided in parallel with first passage 82 and first passage 102, and can communicate between lower chamber 23 and upper chamber 22. When the outer circumferential side of the flexible disk 110 abuts against the outer circumferential edge of the valve member 106 and the outer circumferential side of the inner annular portion 127 of the valve member 106 abuts against the bottom 122 of the case member 105, the second passage 172A blocks the intermediate position of the second passage 172A.

[0163] During the extension stroke, when the pressure in the first communicating volume chamber 149 communicating with the upper chamber 22 becomes higher than the pressure in the second communicating volume chamber 147 communicating with the lower chamber 23 by a predetermined value or more, the outer periphery of the flexible disc 110 deforms so as to move axially away from the outer periphery of the valve member 106, thereby connecting the first communicating volume chamber 149 and the second communicating volume chamber 147 and connecting the upper chamber 22 and the lower chamber 23 via the second passage 172A. When the second passage 172A becomes the extension-side second passage 172A(b) in this way, it includes a passage between the outer periphery of the flexible disc 110 and the outer periphery of the valve member 106.

[0164] A damping force generating mechanism 173 having a valve member 106, a flexible disc 110, and a disc 111 is provided in the second passage 172A(b) and serves as an extension-side damping force generating mechanism that opens and closes this second passage 172A(b) to suppress the flow of oil L from the upper chamber 22 to the lower chamber 23 through this second passage 172A(b) and generates a damping force. The damping force generating mechanism 173 is arranged separately from the damping force generating mechanisms 41, 42 that generate damping forces in the same extension stroke. The damping force generating mechanism 173 and the orifice 139a are provided in series in the extension-side second passage 172A(b).

[0165] During the compression stroke, when the pressure in the second communicating volume chamber 147 communicating with the lower chamber 23 becomes higher by a predetermined value or more than the pressure in the first communicating volume chamber 149 communicating with the upper chamber 22, the outer circumferential side of the inner annular portion 127 of the valve member 106 deforms so as to move axially away from the bottom 122 of the case member 105, thereby connecting the second communicating volume chamber 147 and the first communicating volume chamber 149 and connecting the lower chamber 23 and the upper chamber 22 via the second passage 172A. When the second passage 172A becomes the compression-side second passage 172A(a) in this way, it includes a passage between the outer circumferential side of the inner annular portion 127 of the valve member 106 and the bottom 122 of the case member 105.

[0166] A damping force generating mechanism 183 having the valve member 106 and the bottom 122 of the case member 105 is provided in the second passage 172A(a) and serves as a compression-side damping force generating mechanism that opens and closes this second passage 172A(a) and generates damping force by suppressing the flow of oil L from the lower chamber 23 to the upper chamber 22 through this second passage 172A(a). The damping force generating mechanism 183 is arranged separately from the damping force generating mechanisms 43, 44 that generate damping force during the same compression stroke. The damping force generating mechanism 183 and the orifice 139a are provided in series in the compression-side second passage 172A(a).

[0167] In the extension-side second passage 172A(b), when the damping force generation mechanism 173 is in an open state, the orifice 139a of the closing member 116 has the narrowest flow path cross-sectional area among the portions with fixed flow path cross-sectional areas, and the flow path cross-sectional area is narrower than that on its upstream and downstream sides. The orifice 139a is located downstream of the damping force generation mechanism 173 in the flow of oil liquid L when the damping force generation mechanism 173 opens and oil liquid L flows from the upper chamber 22 to the lower chamber 23 in the second passage 172A(b).

[0168] In the compression-side second passage 172A(a), when the damping force generation mechanism 183 is in the open state, the orifice 139a of the closing member 116 has the narrowest flow path cross-sectional area among the fixed portions, and the flow path cross-sectional area is narrower than that on its upstream and downstream sides. The orifice 139a is located upstream of the damping force generation mechanism 183 in the flow of oil liquid L when the damping force generation mechanism 183 opens and oil liquid L flows from the lower chamber 23 to the upper chamber 22 in the second passage 172A(a).

[0169] In the second passage 172A, when the outer circumferential side of the flexible disc 110 abuts against the outer circumferential edge portion of the valve member 106 and the outer circumferential side of the inner annular portion 127 of the valve member 106 abuts against the bottom portion 122 of the case member 105, that is, when both of the damping force generating mechanisms 173, 183 are closed, no orifice that communicates between the lower chamber 23 and the upper chamber 22 is formed. In other words, when the outer circumferential side of the flexible disc 110 abuts against the outer circumferential edge portion of the valve member 106 over the entire circumference, that is, when the damping force generating mechanism 173 is closed, the extension-side damping force generating mechanism 173 does not communicate between the upper chamber 22 and the lower chamber 23. Furthermore, when the outer periphery of the inner annular portion 127 of the valve member 106 is in contact with the bottom portion 122 of the case member 105 over the entire circumference, i.e., when the damping force generating mechanism 183 is in a closed state, the compression side damping force generating mechanism 183 does not provide communication between the lower chamber 23 and the upper chamber 22. In other words, the second passage 172A does not have an orifice that constantly provides communication between the upper chamber 22 and the lower chamber 23, and is not a passage that constantly provides communication between the upper chamber 22 and the lower chamber 23.

[0170] The second compression passage 172A(a), which allows communication between the lower chamber 23 and the upper chamber 22, is arranged in parallel with the first passage 82, which is also a compression passage which allows communication between the lower chamber 23 and the upper chamber 22. The damping force generating mechanisms 43, 44 are provided in the first passage 82, and the damping force generating mechanism 183 is provided in the second passage 172A(a). Therefore, the damping force generating mechanisms 43, 44 on the compression side and the damping force generating mechanism 183 are arranged in parallel.

[0171] The second extension passage 172A(b), which can communicate between the upper chamber 22 and the lower chamber 23, is parallel to the first passage 102, which is also an extension passage which can communicate between the upper chamber 22 and the lower chamber 23. The damping force generating mechanisms 41, 42 are provided in the first passage 102, and the damping force generating mechanism 173 is provided in the second passage 172A(b). Therefore, the damping force generating mechanisms 41, 42 on the extension side and the damping force generating mechanism 173 are arranged in parallel.

[0172] The first volume variable mechanism 185 is operated by the movement of the piston 21A during the extension stroke causing hydraulic fluid L to flow from the upper chamber 22 located upstream within the inner tube 2 of the cylinder 4 into the second passage 172A(b), and is provided with a first communicating volume chamber 149 that stores the hydraulic fluid L from the upper chamber 22 located upstream. The damping force generating mechanism 173 is provided in the first volume variable mechanism 185, and when the first volume variable mechanism 185 is displaced by a predetermined amount or more, communicates between the first communicating volume chamber 149 and the lower chamber 23 located downstream of the cylinder 4. The damping force generating mechanism 173 communicates between the first communicating volume chamber 149 and the lower chamber 23 located downstream of the cylinder 4 when the valve member 106 is separated from the flexible disc 110.

[0173] The first communicating volume chamber 149 and the orifice 139a of the first volume variable mechanism 185 are arranged in series in the extension-side second passage 172A(b), and the orifice 139a is arranged downstream of the first communicating volume chamber 149 in the second passage 172A(b). When the damping force generation mechanism 173 opens, the first communicating volume chamber 149 no longer functions as a volume chamber but becomes a passage, so the first communicating volume chamber 149 and the damping force generation mechanism 173 are arranged in parallel in the flow path of the oil liquid L.

[0174] The second volume variable mechanism 186 is operated by the movement of the piston 21A during the compression stroke causing hydraulic fluid L to flow from the lower chamber 23 located upstream within the inner tube 2 of the cylinder 4 into the second passage 172A(a), and is provided with a second communicating volume chamber 147 that stores the hydraulic fluid L from the lower chamber 23 located upstream. The damping force generating mechanism 183 is provided in the second volume variable mechanism 186, and when the second volume variable mechanism 186 is displaced by a predetermined amount or more, communicates between the second communicating volume chamber 147 and the upper chamber 22 located downstream of the cylinder 4. The damping force generating mechanism 183 communicates between the second communicating volume chamber 147 and the upper chamber 22 located downstream of the cylinder 4 when the valve member 106 is separated from the case member 105.

[0175] The second communicating volume chamber 147 and the orifice 139a of the second volume variable mechanism 186 are arranged in series in the second passage 172A(a), and the orifice 139a is arranged upstream of the second communicating volume chamber 147 in the second passage 172A(a). When the damping force generation mechanism 183 opens, the second communicating volume chamber 147 no longer functions as a volume chamber but becomes a passage, so the second communicating volume chamber 147 and the damping force generation mechanism 183 are arranged in parallel in the flow path of the oil liquid L.

[0176] As the piston 21A moves in the extension direction, the valve member 106 communicates between the lower chamber 23, which is downstream of the cylinder 4, and a first communicating volume chamber 149, which communicates with the upper chamber 22. As the piston 21A moves in the contraction direction, the valve member 106 communicates between the upper chamber 22, which is downstream of the cylinder 4, and a second communicating volume chamber 147, which communicates with the lower chamber 23.

[0177] In the accumulator portion 104, the first volume variable mechanism 185 changes the volume of the first communicating volume chamber 149 before the damping force generating mechanism 173 opens during the extension stroke, and the second volume variable mechanism 186 changes the volume of the second communicating volume chamber 147 before the damping force generating mechanism 183 opens during the compression stroke.

[0178] The first volume variable mechanism 185 and the second volume variable mechanism 186 are provided in series in the second passage 172A on the flow path of the oil liquid L. The damping force generating mechanism 173 and the damping force generating mechanism 183 are provided in parallel in the flow path of the oil liquid L in the second passage 172A.

[0179] The above configuration is shown in a hydraulic circuit diagram as shown in Fig. 6. As shown in Fig. 6, the configuration on the side of the first passages 82, 102 is the same as in the first embodiment, and an accumulator unit 104 is provided in a second passage 172A connecting the upper chamber 22 and the lower chamber 23. In the accumulator unit 104, an orifice 139a is provided in the second passage 172A, and a damping force generating mechanism 173, a damping force generating mechanism 183, a first volume variable mechanism 185, and a second volume variable mechanism 186 are provided on the upper chamber 22 side of the orifice 139a. The damping force generating mechanism 173 allows the flow of oil liquid L from the upper chamber 22 to the lower chamber 23, and the damping force generating mechanism 183 allows the flow of oil liquid L from the lower chamber 23 to the upper chamber 22. In the first volume variable mechanism 185, the first communicating volume chamber 149 is connected between the damping force generating mechanisms 173, 183 of the second passage 172A and the upper chamber 22, and in the second volume variable mechanism 186, the second communicating volume chamber 147 is connected between the orifice 139a of the second passage 172A and the damping force generating mechanisms 173, 183.

[0180] Here, similarly to shock absorber 1, the relationship between the flow path cross-sectional area S1 of orifice 91a, the flow path cross-sectional area S2 of orifice 94a, and the flow path cross-sectional area S5 of orifice 139a is such that the flow path cross-sectional area S1 is smaller than the flow path cross-sectional area S2 and smaller than the flow path cross-sectional area S5, and the relationship between the flow path cross-sectional area S3 of orifice 71a, the flow path cross-sectional area S4 of orifice 74a, and the flow path cross-sectional area S5 of orifice 139a is such that the flow path cross-sectional area S3 is smaller than the flow path cross-sectional area S4 and smaller than the flow path cross-sectional area S5.

[0181] The relationship between the valve opening pressure V1 of the damping force generating mechanism 41, the valve opening pressure V2 of the damping force generating mechanism 42, and the valve opening pressure V5 of the damping force generating mechanism 173 on the extension side is such that the valve opening pressure V5 is greater than the valve opening pressure V1, and the valve opening pressure V2 is greater than the valve opening pressure V5. Furthermore, the relationship between the valve opening pressure V3 of the damping force generating mechanism 43, the valve opening pressure V4 of the damping force generating mechanism 44, and the valve opening pressure V6 of the damping force generating mechanism 183, all on the compression side, is such that the valve opening pressure V6 is greater than the valve opening pressure V3, and the valve opening pressure V4 is greater than the valve opening pressure V6.

[0182] Therefore, the shock absorber 1A has a damping force generating mechanism 43 (first damping force generating mechanism) that generates a damping force, and an orifice 71a (first orifice) that is provided in parallel with the damping force generating mechanism 43, all of which are provided in the first passage 82 (first passage) on the compression side, a second volume variable mechanism 186 (volume variable mechanism) that changes the volume of the second communicating volume chamber 147 (volume chamber), all of which are provided in the second passage 172A(a) (second passage) on the compression side, and an orifice 139a (second orifice) that is provided upstream of the second communicating volume chamber 147, and the flow path cross-sectional area of ​​the orifice 139a is larger than the flow path cross-sectional area of ​​the orifice 71a. In addition, the shock absorber 1A is provided with a damping force generating mechanism 44 (third damping force generating mechanism) in series with the damping force generating mechanism 43.

[0183] The shock absorber 1A also has a damping force generating mechanism 41 that generates a damping force, an orifice 91a that is arranged in parallel with the damping force generating mechanism 41, and a first volume variable mechanism 185 that changes the volume of the first communicating volume chamber 149, all of which are arranged in the second passage 172A(b) on the extension side, and an orifice 139a that is arranged downstream of the first communicating volume chamber 149, and the flow path cross-sectional area of ​​the orifice 139a is larger than the flow path cross-sectional area of ​​the orifice 91a. In addition, the shock absorber 1A is provided with a damping force generating mechanism 42 in series with the damping force generating mechanism 41.

[0184] <Activation> During the extension stroke, piston 21A moves toward upper chamber 22 shown in Figure 5, increasing the pressure in upper chamber 22 and decreasing the pressure in lower chamber 23. During the extension stroke in the extremely low speed range where the piston speed is equal to or less than first predetermined value X1, damping force generating mechanism 41, damping force generating mechanism 42, and damping force generating mechanism 173 are all in a closed valve state, and oil L in upper chamber 22 flows to lower chamber 23 via the passage holes 38 and the passage in annular groove 52 of piston 21A, orifice 91a provided in disc 91 of sub-valve 100, a passage in annular groove 53 of piston 21A, and orifice 94a provided in disc 94 of main valve 101. For this reason, during the extension stroke in the extremely low speed range where the piston speed is equal to or less than first predetermined value X1, the damping force characteristic with respect to piston speed is relatively high and hard as the piston speed increases.

[0185] At this time, a portion of the oil liquid L in the upper chamber 22 flows into the first communicating volume chamber 149 through the passage in the passage hole 126 of the case member 105 and the passage in the hole 129 of the valve member 106. This causes the pressure in the first communicating volume chamber 149 to increase. Therefore, the first volume variable mechanism 185 causes the flexible disc 110 to bend toward the disc 113, increasing the capacity of the first communicating volume chamber 149, before any of the damping force generating mechanisms 41, 42, and 173 open. This causes the first volume variable mechanism 185 to suppress an increase in pressure in the first communicating volume chamber 149. At this time, the disc 111 deforms following the flexible disc 110. Also, at this time, because the flexible disc 110 bends and moves toward the disc 113, the second volume variable mechanism 186 reduces the volume of the second communicating volume chamber 147.

[0186] Here, during the extension stroke in the extremely low speed region when a low frequency input (large amplitude vibration) is applied to the piston 21A, which is the frequency of the axial movement of the piston 21A, the amount of oil L flowing from the upper chamber 22 into the first communicating volume chamber 149 increases, causing the flexible disc 110 to deform significantly. As the amount of deformation of the flexible disc 110 increases, the reaction force due to the support rigidity of the clamped inner periphery increases, limiting the amount of deformation. This causes the pressure in the first communicating volume chamber 149 to rise. As a result, the pressure in the first passage 102 rises to a state where the damping force generating mechanism 41 opens, with the damping force generating mechanism 42 and the damping force generating mechanism 173 closed.

[0187] During the extension stroke in the extremely low speed region where the piston speed is greater than the first predetermined value X1 and less than a second predetermined value X2 that is greater than the first predetermined value X1, the pressure rise in the first passage 102 becomes high, and the damping force generating mechanism 42 and the damping force generating mechanism 173 remain closed, while the oil L in the upper chamber 22 opens the damping force generating mechanism 41. Therefore, the oil L in the upper chamber 22 flows into the lower chamber 23 via the passage holes 38 and the passage in the annular groove 52 of the piston 21A, the passage between the opened sub-valve 100 and the inner valve seat portion 46, the passage in the annular groove 53 of the piston 21A, and the orifice 94a provided in the disk 94 of the main valve 101. As a result, the oil L flows through the orifice 94a, which has a larger flow path cross-sectional area than the orifice 91a. Therefore, in the extension stroke in the extremely low speed region where the piston speed is less than the second predetermined value X2, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than in the extension stroke in the extremely low speed region where the piston speed is equal to or less than the first predetermined value X1.

[0188] During the extension stroke in the low-speed region where the piston speed is equal to or greater than the second predetermined value X2 and less than a third predetermined value X3 that is greater than the second predetermined value X2, the damping force generating mechanism 42 closes, and the damping force generating mechanism 41 remains open, and the pressure in the second passage 172A(b) increases until the damping force generating mechanism 173 opens. Then, the flexible disc 110 moves away from the outer conical portion 128 of the valve member 106, opening the damping force generating mechanism 173 and connecting the upper chamber 22 and the lower chamber 23 through the extension-side second passage 172A(b). Therefore, oil liquid L in the upper chamber 22 flows to the lower chamber 23 via the passage inside the passage hole 126 in the bottom portion 122 of the case member 105, the passage inside the hole portion 129 of the valve member 106, the first communicating volume chamber 149, the passage between the flexible disc 110 in the open state and the outer conical portion 128 of the valve member 106, the second communicating volume chamber 147, the passage inside the orifice 139a and large diameter hole portion 133 of the closing member 116, the passage inside the passage cutout portion 33A of the piston rod 25A, the passage inside the passage groove 63A of the piston 21A and the passage inside the passage hole 39. As a result, during the extension stroke in the low speed region where the piston speed is less than the third predetermined value X3, the increase rate of the damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the extremely low speed region where the piston speed is less than the second predetermined value X2.

[0189] During the extension stroke in the normal speed range where the piston speed is equal to or greater than the third predetermined value X3, the damping force generating mechanism 42 opens while the damping force generating mechanism 41 and the damping force generating mechanism 173 remain open. That is, as described above, the flexible disc 110 moves away from the outer conical portion 128 of the valve member 106, opening the damping force generating mechanism 173 and allowing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 in the extension-side second passage 172A(b). At this time, the flow of the hydraulic fluid L is throttled by the orifice 139a, which is provided downstream of the damping force generating mechanism 173 in the second passage 172A(b), increasing the pressure applied to the main valve 101 in the first passage 102 and increasing the pressure difference. As a result, the main valve 101 moves away from the outer valve seat portion 48, allowing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 in the extension-side first passage 102. Therefore, oil L in the upper chamber 22 flows into the lower chamber 23 via the passages in the multiple passage holes 38 and annular groove 52 of the piston 21A, the passage between the open sub-valve 100 and the inner valve seat portion 46, the passage in the annular groove 53 of the piston 21A, and the passage between the open main valve 101 and the outer valve seat portion 48. As a result, during the extension stroke in the normal speed range where the piston speed is equal to or greater than the third predetermined value X3, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the low speed range where the piston speed is less than the third predetermined value X3.

[0190] During the extension stroke in the extremely low speed region when a high frequency input (small amplitude vibration) is input to the shock absorber 1A at a piston frequency higher than that during the low frequency input described above, the amount of oil L flowing from the upper chamber 22 into the first communicating volume chamber 149 is small. Therefore, deformation of the flexible disc 110 is small, and the first volume variable mechanism 185 can absorb the volume of oil L flowing into the first communicating volume chamber 149 by the amount of deflection of the flexible disc 110, thereby reducing the pressure increase in the first communicating volume chamber 149. Therefore, during the extension stroke in the extremely low speed region when the piston speed is equal to or less than the fifth predetermined value X1, it is possible to achieve a state in which the flexible disc 110 is not present and the first communicating volume chamber 149 is connected to the second communicating volume chamber 147, i.e., a state identical to that in the structure in which the damping force generating mechanism 173 is not present. Therefore, during the extension stroke in the extremely low speed region when a high frequency input is input, the damping force rises more gradually than during a low frequency input.

[0191] During the compression stroke, piston 21A moves toward lower chamber 23, increasing the pressure in lower chamber 23 and decreasing the pressure in upper chamber 22. During the compression stroke in the extremely low speed range where the piston speed is equal to or less than fifth predetermined value X5, damping force generating mechanism 43, damping force generating mechanism 44, and damping force generating mechanism 183 are all in a closed valve state, and oil L in lower chamber 23 flows to upper chamber 22 via the passage holes 39 and the passage in annular groove 54 of piston 21A, orifice 71a provided in disc 71 serving as a sub-valve, a passage in annular groove 55 of piston 21A, and orifice 74a provided in disc 74 of main valve 81. For this reason, during the compression stroke in the extremely low speed range where the piston speed is equal to or less than fifth predetermined value X5, the damping force characteristic relative to piston speed is relatively high and hard as the piston speed increases.

[0192] At this time, some of the oil L in the lower chamber 23 flows into the second communicating volume chamber 147 via the passage hole 39 and the passage groove 63A of the piston 21A, the passage in the passage cutout 33A of the piston rod 25A, and the passage in the large diameter hole 133 of the closing member 116 and the orifice 139a. This increases the pressure in the second communicating volume chamber 147. Therefore, before any of the damping force generating mechanisms 43, 44, and 183 open, the second volume variable mechanism 186 bends the portion of the flexible disc 110 radially inward from the position where it abuts against the outer conical portion 128 of the valve member 106 toward the bottom portion 122, thereby increasing the capacity of the second communicating volume chamber 147. This allows the second volume variable mechanism 186 to suppress an increase in pressure in the second communicating volume chamber 147. At this time, the flexible disk 110 bends and moves toward the bottom portion 122, so that the first volume variable mechanism 185 reduces the volume of the first communicating volume chamber 149.

[0193] Here, during the compression stroke in the extremely low speed range when a low-frequency input (large-amplitude vibration) occurs, which is the piston frequency of the axial movement of the piston 21A, the amount of oil L flowing from the lower chamber 23 into the second communication volume chamber 147 increases, as described above, causing the flexible disc 110 to deform significantly. As the amount of deformation of the flexible disc 110 increases, the reaction force due to the support rigidity of the clamped inner periphery increases, limiting the amount of deformation. This causes the pressure in the second communication volume chamber 147 to rise. As a result, the pressure in the first passage 82 rises to a state where the damping force generating mechanism 43 opens, with the damping force generating mechanism 44 and the damping force generating mechanism 183 closed.

[0194] During the compression stroke in the extremely low speed region where the piston speed is greater than the first predetermined value X5 and less than a sixth predetermined value X6 that is greater than the first predetermined value X5, the pressure rise in the first passage 82 becomes high, and the damping force generating mechanism 44 and the damping force generating mechanism 183 remain in a closed state, while the oil L in the lower chamber 23 opens the damping force generating mechanism 43. Therefore, the oil L in the lower chamber 23 flows into the upper chamber 22 via the passage holes 39 and the passage in the annular groove 54 of the piston 21A, the passage between the disc 71, which is the open sub-valve, and the inner valve seat portion 51, the passage in the annular groove 55 of the piston 21A, and the orifice 74a provided in the disc 74 of the main valve 81. As a result, the oil L flows through the orifice 74a, which has a larger flow path cross-sectional area than the orifice 71a. Therefore, during the compression stroke in the extremely slow speed region where the piston speed is less than the sixth predetermined value X6, the rate of increase in damping force relative to an increase in piston speed is lower and softer than during the compression stroke in the extremely slow speed region where the piston speed is equal to or less than the fifth predetermined value X5.

[0195] During the compression stroke in the low-speed region where the piston speed is equal to or greater than the sixth predetermined value X6 and less than a seventh predetermined value X7 that is greater than the sixth predetermined value X6, the damping force generating mechanism 44 closes, the damping force generating mechanism 43 remains open, and the pressure in the second passage 172A(a) rises until the damping force generating mechanism 183 opens. Then, the outer periphery of the inner annular portion 127 of the valve member 106 moves away from the bottom 122 of the case member 105 in the axial direction, opening the damping force generating mechanism 183 and connecting the lower chamber 23 and the upper chamber 22 through the compression-side second passage 172A(a). Therefore, oil L in the lower chamber 23 flows into the upper chamber 22 via the passages in the passage hole 39 and passage groove 63A of the piston 21A, the passage in the passage cutout 33A of the piston rod 25A, the passage and orifice 139a in the large diameter hole 133 of the closing member 116, the second communicating volume chamber 147, the damping force generating mechanism 183 in the open state, the passage in the hole 129 of the valve member 106, and the passage in the passage hole 126 in the bottom 122 of the case member 105. As a result, during the compression stroke in the low speed range where the piston speed is less than the seventh predetermined value X7, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the compression stroke in the extremely low speed range where the piston speed is less than the sixth predetermined value X6.

[0196] During the compression stroke in the normal speed range where the piston speed is equal to or higher than the seventh predetermined value X7, the damping force generating mechanism 44 opens while the damping force generating mechanism 43 and the damping force generating mechanism 183 remain open. That is, as described above, the outer peripheral side of the inner annular portion 127 of the valve member 106 moves axially away from the bottom portion 122 of the case member 105, and causes the hydraulic oil L to flow from the lower chamber 23 to the upper chamber 22 in the compression-side second passage 172A(a). At this time, the flow of the hydraulic oil L is throttled by the orifice 139a provided in the second passage 172A(a) upstream of the damping force generating mechanism 183, so that the pressure applied to the main valve 81 in the first passage 82 increases, increasing the pressure difference. As a result, the main valve 81 lifts off the outer valve seat portion 50, and the hydraulic oil L flows from the lower chamber 23 to the upper chamber 22 in the compression-side first passage 82. Therefore, oil L in the lower chamber 23 flows into the upper chamber 22 through the passages in the multiple passage holes 39 and annular groove 54 of the piston 21A, the passage between the disc 71, which is the sub-valve in the open state, and the inner valve seat portion 51, the passage in the annular groove 55 of the piston 21A, and the passage between the main valve 81 in the open state and the outer valve seat portion 50. As a result, during the compression stroke in the normal speed range where the piston speed is equal to or greater than the seventh predetermined value X7, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the compression stroke in the low speed range where the piston speed is less than the seventh predetermined value X7.

[0197] During the compression stroke in the extremely low speed region when a high frequency input (small amplitude vibration) occurs in which a piston frequency higher than that during the low frequency input described above is input to the shock absorber 1A, the amount of oil L that flows from the lower chamber 23 to the second communicating volume chamber 147 is small. Therefore, the deformation of the flexible disc 110 is small, and the second volume variable mechanism 186 can absorb the volume of oil L that flows into the second communicating volume chamber 147 with the amount of deflection of the flexible disc 110, and the pressure increase in the second communicating volume chamber 147 is small. Therefore, when the damping force rises in the extremely low speed region where the piston speed is equal to or lower than the fifth predetermined value X5, it is possible to achieve a state as if the flexible disc 110 were not present and the second communicating volume chamber 147 were connected to the upper chamber 22 via the first communicating volume chamber 149, the passage in the hole 129 of the valve member 106, and the passage in the passage hole 126 in the bottom 122 of the case member 105, i.e., a state identical to a structure without the damping force generating mechanism 183. Therefore, during the compression stroke in the extremely low speed region when a high frequency is input, the rise of the damping force is gradual compared to when a low frequency is input.

[0198] The shock absorber 1A of the second embodiment has a damping force generating mechanism 43 that is provided in the compression-side first passage 82 and generates a damping force, an orifice 71a that is provided in parallel with the damping force generating mechanism 43, a second volume variable mechanism 186 that is provided in the compression-side second passage 172A(a) and changes the volume of the second communicating volume chamber 147, and an orifice 139a that is provided upstream of the second communicating volume chamber 147, the flow path cross-sectional area of ​​the orifice 139a being larger than the flow path cross-sectional area of ​​the orifice 71a. This makes it possible to improve the insufficient damping force when the piston speed is extremely slow during the compression stroke.

[0199] Furthermore, since the shock absorber 1A has the damping force generating mechanism 44 provided in series with the damping force generating mechanism 43, the structure can be simplified.

[0200] [Third embodiment] Next, the third embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Figures 7 to 9. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0201] <Configuration> As shown in FIG. 7 , a shock absorber 1B of the third embodiment is provided with a disc 72 instead of the disc 71 of the shock absorber 1, and therefore, multiple discs 72 are provided. The shock absorber 1B does not include the disc 71, which is a sub-valve, and does not include the orifice 71a or the damping force generating mechanism 43. The passages within the multiple passage holes 39 of the piston 21, the annular groove 54, and the annular groove 55 are always in communication. The shock absorber 1B has a first passage 82B that differs from the first passage 82 in that the orifice 71a and the damping force generating mechanism 43 are not provided. The first passage 82B is made up of the passages within the multiple passage holes 39, the annular groove 54, and the annular groove 55, and the orifice 74a or a passage between the main valve 81 and the outer valve seat portion 50 that appears when the valve is open. The first passage 82B is also formed in the piston 21, and is a compression-side passage through which oil L flows from the lower chamber 23, which is the upstream side within the cylinder 4, to the upper chamber 22, which is the downstream side, as the piston 21 moves toward the lower chamber 23. The damping force generating mechanism 44 and the orifice 74a are provided in parallel in the first passage 82B.

[0202] Furthermore, shock absorber 1B is provided with a disc 93 instead of discs 91 and 92 of shock absorber 1, and therefore has a plurality of discs 93. Therefore, shock absorber 1B does not have a sub-valve 100, and therefore does not have an orifice 91a or a damping force generating mechanism 41. The passages within the plurality of passage holes 38 of piston 21, and within the annular groove 52 and the annular groove 53 are always in communication. Shock absorber 1B has a first passage 102B that differs from first passage 102 in that it does not have an orifice 91a or a damping force generating mechanism 41. First passage 102B is made up of the passages within the plurality of passage holes 38, the annular groove 52 and the annular groove 53, and the orifice 94a or a passage between main valve 101 and outer valve seat portion 48 that appears when the valve is open. The first passage 102B is also formed in the piston 21, and is an extension-side passage through which oil L flows from the upper chamber 22, which is the upstream side within the cylinder 4, to the lower chamber 23, which is the downstream side, as the piston 21 moves toward the upper chamber 22. The damping force generating mechanism 42 and the orifice 94a are provided in parallel in the first passage 102B.

[0203] The above configuration is shown in a hydraulic circuit diagram as shown in Figure 8. As shown in Figure 8, the compression-side damping force generating mechanism 44 and the orifice 74a are provided in parallel in the first passage 82B connecting the lower chamber 23 and the upper chamber 22. Furthermore, the extension-side damping force generating mechanism 42 and the orifice 94a are provided in parallel in the first passage 102B connecting the upper chamber 22 and the lower chamber 23. Furthermore, as in the first embodiment, an accumulator unit 104 is provided in the second passage 172 connecting the upper chamber 22 and the lower chamber 23.

[0204] Here, the relationship between the flow path cross-sectional area S11 of the orifice 94a and the flow path cross-sectional area S13 of the orifice 139a is such that the flow path cross-sectional area S11 is smaller than the flow path cross-sectional area S13. <S13となっている。 The relationship between the flow passage cross-sectional area S12 of the orifice 74a and the flow passage cross-sectional area S13 of the orifice 139a is such that the flow passage cross-sectional area S12 is smaller than the flow passage cross-sectional area S13. <S13となっている。

[0205] In addition, the relationship between the valve opening pressure V11 of the damping force generating mechanism 42 and the valve opening pressure V13 of the damping force generating mechanism 183 on the extension side is such that the valve opening pressure V11 is greater than the valve opening pressure V13. <V11となっている。 In addition, the relationship between the valve opening pressure V12 of the damping force generating mechanism 44 and the valve opening pressure V14 of the damping force generating mechanism 173 on the compression side is such that the valve opening pressure V12 is greater than the valve opening pressure V14. <V12となっている。

[0206] Therefore, the shock absorber 1B has a damping force generating mechanism 42 (first damping force generating mechanism) that generates a damping force, and an orifice 94a (first orifice) that is arranged in parallel with the damping force generating mechanism 42, all of which are arranged in the first passage 102B (first passage) on the extension side, a second volume variable mechanism 186 (volume variable mechanism) that changes the volume of the second communicating volume chamber 147 (volume chamber), all of which are arranged in the second passage 172(b) (second passage) on the extension side, and an orifice 139a (second orifice) that is arranged upstream of the second communicating volume chamber 147, and the flow path cross-sectional area of ​​the orifice 139a is larger than the flow path cross-sectional area of ​​the orifice 94a.

[0207] The shock absorber 1B also has a damping force generating mechanism 44 that generates a damping force, an orifice 74a that is arranged in parallel with the damping force generating mechanism 44, and a first volume variable mechanism 185 that changes the volume of the first communicating volume chamber 149, all of which are arranged in the second passage 172(a) on the compression side, and an orifice 139a that is arranged downstream of the first communicating volume chamber 149, and the flow path cross-sectional area of ​​the orifice 139a is larger than the flow path cross-sectional area of ​​the orifice 74a.

[0208] In addition, the shock absorber 1B has a damping force generating mechanism 183 (second damping force generating mechanism) provided in parallel with the second communicating volume chamber 147, and the valve opening pressure of the first damping force generating mechanism 42 is greater than the valve opening pressure of the damping force generating mechanism 183.

[0209] Furthermore, the shock absorber 1B is provided with a damping force generating mechanism 173 in parallel with the first communication volume chamber 149, and the valve opening pressure of the damping force generating mechanism 173 is greater than the valve opening pressure of the damping force generating mechanism 44.

[0210] <Activation> During the extension stroke, the piston 21 moves toward the upper chamber 22 shown in FIG. 7, increasing the pressure in the upper chamber 22 and decreasing the pressure in the lower chamber 23. During the extension stroke, when the piston speed is in the extremely low speed range below the eleventh predetermined value X11, the damping force generating mechanism 42 and the damping force generating mechanism 183 are both in a closed state, and the oil L in the upper chamber 22 flows to the lower chamber 23 via the passage holes 38 of the piston 21, the annular grooves 52 and 53, and the orifice 94a in the disk 94 of the main valve 101. This generates a damping force with orifice characteristics. Therefore, as shown by the solid line Y11 in FIG. 9, during the extension stroke when the piston speed is in the extremely low speed range below the eleventh predetermined value X11, the damping force characteristic with respect to the piston speed becomes hard, with a relatively high rate of increase in the damping force as the piston speed increases.

[0211] At this time, a portion of the oil L in the upper chamber 22 shown in FIG. 7 flows into the second communicating volume chamber 147 via the passage hole 38 and the passage groove 63 of the piston 21, the passage in the passage cutout 33 of the piston rod 25, and the passage in the large diameter hole 133 of the closing member 116 and the orifice 139a. This increases the pressure in the second communicating volume chamber 147. Therefore, before both of the damping force generating mechanisms 42 and 183 open, the second volume variable mechanism 186 bends the portion of the flexible disc 110 radially inward from the position where it abuts against the outer conical portion 128 of the valve member 106 toward the bottom portion 122, thereby increasing the capacity of the second communicating volume chamber 147. This allows the second volume variable mechanism 186 to suppress an increase in pressure in the second communicating volume chamber 147. At this time, the flexible disk 110 bends and moves toward the bottom portion 122, so that the first volume variable mechanism 185 reduces the volume of the first communicating volume chamber 149.

[0212] Here, during the extension stroke in the extremely low-speed region when a low-frequency input (large-amplitude vibration) occurs, which is the piston frequency of the axial movement of the piston 21, the amount of oil L flowing from the upper chamber 22 into the second communicating volume chamber 147 increases, as described above, causing the flexible disc 110 to deform significantly. As the amount of deformation of the flexible disc 110 increases, the reaction force due to the support rigidity of the clamped inner periphery increases, limiting the amount of deformation. This causes the pressure in the second communicating volume chamber 147 to rise. As a result, while the damping force generating mechanism 42 remains closed, the pressure in the second passage 172(b) rises to a state where the damping force generating mechanism 183 opens.

[0213] During the extension stroke in the low-speed region where the piston speed is greater than an eleventh predetermined value X11 and less than a twelfth predetermined value X12 that is greater than the eleventh predetermined value X11, the damping force generating mechanism 42 remains closed, and the pressure in the second passage 172(b) increases until the damping force generating mechanism 183 opens. In other words, the outer circumferential side of the inner annular portion 127 of the valve member 106 moves axially away from the bottom 122 of the case member 105, opening the damping force generating mechanism 183 and connecting the upper chamber 22 and the lower chamber 23 through the extension-side second passage 172(b). Therefore, oil L in the upper chamber 22 flows into the lower chamber 23 via the passages in the passage hole 38 and passage groove 63 of the piston 21, the passage in the passage cutout 33 of the piston rod 25, the passage and orifice 139a in the large diameter hole portion 133 of the closing member 116, the second communicating volume chamber 147, the damping force generating mechanism 183 in the open state, the passage in the hole 129 of the valve member 106, and the passage in the passage hole 126 in the bottom 122 of the case member 105. As a result, during the extension stroke in the low speed region where the piston speed is less than the twelfth predetermined value X12, a damping force with valve characteristics is obtained, and as shown by the solid line Y11 in FIG. 9, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the very low speed region where the piston speed is less than the first predetermined value X11.

[0214] During the extension stroke in the normal speed range where the piston speed is equal to or greater than the twelfth predetermined value X12, the damping force generating mechanism 42 opens while the damping force generating mechanism 183 shown in Fig. 7 remains open. That is, as described above, the outer circumferential side of the inner annular portion 127 of the valve member 106 moves axially away from the bottom portion 122 of the case member 105, causing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 in the extension-side second passage 172(b). At this time, the flow of the hydraulic fluid L is throttled by the orifice 139a provided in the second passage 172(b) upstream of the damping force generating mechanism 183, so that the pressure applied to the main valve 101 in the first passage 102B increases, increasing the pressure difference. As a result, the main valve 101 lifts off the outer valve seat portion 48, causing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 in the extension-side first passage 102B. Therefore, the oil L in the upper chamber 22 flows into the lower chamber 23 through the passages in the multiple passage holes 38 of the piston 21, the annular grooves 52 and 53, and the passage between the open main valve 101 and the outer valve seat portion 48. As a result, as shown by the solid line Y11 in Fig. 9, during the extension stroke in the normal speed range where the piston speed is equal to or greater than the twelfth predetermined value X12, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the low speed range where the piston speed is less than the twelfth predetermined value X12.

[0215] During the extension stroke in the extremely low speed region when a high frequency input (small amplitude vibration) is applied to the shock absorber 1B, in which a piston frequency higher than that during the low frequency input described above is applied, the amount of oil L flowing from the upper chamber 22 into the second communicating volume chamber 147 shown in FIG. 7 is small. Therefore, the deformation of the flexible disc 110 is small, and the second volume variable mechanism 186 can absorb the volume of oil L flowing into the second communicating volume chamber 147 using the amount of deflection of the flexible disc 110, thereby reducing the pressure increase in the second communicating volume chamber 147. Therefore, during the rise of the damping force in the extremely low speed region where the piston speed is equal to or lower than the eleventh predetermined value X11, it is possible to achieve the same state as if the damping force generation mechanism 183 were not present. Therefore, during the extension stroke in the extremely low speed region when a high frequency input is applied, the rise of the damping force is gentler than when a low frequency input is applied.

[0216] During the compression stroke, as the piston 21 moves toward the lower chamber 23, the pressure in the lower chamber 23 increases and the pressure in the upper chamber 22 decreases. During the compression stroke, in the extremely low speed range where the piston speed is equal to or less than the fifteenth predetermined value X15, the damping force generating mechanism 44 and the damping force generating mechanism 173 are both in a closed state, and the oil L in the lower chamber 23 flows into the upper chamber 22 through the passages in the multiple passage holes 39 of the piston 21, the annular grooves 54 and 55, and the orifice 74a provided in the disk 74 of the main valve 81. This generates a damping force with orifice characteristics. Therefore, during the compression stroke, in the extremely low speed range where the piston speed is equal to or less than the fifteenth predetermined value X15, the damping force characteristic with respect to the piston speed is relatively high and hard as the piston speed increases.

[0217] At this time, a portion of the oil L in the lower chamber 23 flows into the first communicating volume chamber 149 through the passage in the passage hole 126 of the case member 105 and the passage in the hole 129 of the valve member 106. This causes the pressure in the first communicating volume chamber 149 to increase. Therefore, the first volume variable mechanism 185 causes the flexible disc 110 to bend toward the disc 113, increasing the capacity of the first communicating volume chamber 149, before both of the damping force generating mechanisms 44, 173 open. This causes the first volume variable mechanism 185 to suppress an increase in pressure in the first communicating volume chamber 149. At this time, the disc 111 deforms following the flexible disc 110. Also, at this time, because the flexible disc 110 bends and moves toward the disc 113, the second volume variable mechanism 186 reduces the volume of the second communicating volume chamber 147.

[0218] Here, during the compression stroke in the extremely low speed range when a low-frequency input (large-amplitude vibration) occurs, which is the piston frequency of the axial movement of the piston 21, the amount of oil L flowing from the lower chamber 23 into the first communicating volume chamber 149 increases, as described above, causing the flexible disc 110 to deform significantly. As the amount of deformation of the flexible disc 110 increases, the reaction force due to the support rigidity of the clamped inner periphery increases, limiting the amount of deformation. This causes the pressure in the first communicating volume chamber 149 to rise. As a result, while the damping force generating mechanism 44 remains closed, the pressure in the second passage 172(a) rises to a state where the damping force generating mechanism 173 opens.

[0219] During the compression stroke in the low-speed region where the piston speed is greater than a fifteenth predetermined value X15 and less than a sixteenth predetermined value X16 that is greater than the fifteenth predetermined value X15, the damping force generating mechanism 44 remains closed, and the pressure in the second passage 172(a) increases until the damping force generating mechanism 173 opens. Then, the flexible disc 110 moves away from the outer conical portion 128 of the valve member 106, opening the damping force generating mechanism 173 and connecting the lower chamber 23 and the upper chamber 22 through the compression-side second passage 172(a). Therefore, oil liquid L in the lower chamber 23 flows into the upper chamber 22 via the passage inside the passage hole 126 in the bottom portion 122 of the case member 105, the passage inside the hole portion 129 of the valve member 106, the first communicating volume chamber 149, the passage between the flexible disc 110 in the open state and the outer conical portion 128 of the valve member 106, the second communicating volume chamber 147, the passage inside the orifice 139a and large diameter hole portion 133 of the closing member 116, the passage inside the passage cutout portion 33 of the piston rod 25, the passage inside the passage groove 63 of the piston 21, and the passage inside the passage hole 38. As a result, during the compression stroke in the low speed range where the piston speed is less than the 16th predetermined value X16, a damping force with valve characteristics is obtained, and the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the compression stroke in the extremely low speed range where the piston speed is equal to or less than the 15th predetermined value X15.

[0220] During the extension stroke in the normal speed range where the piston speed is equal to or greater than the 16th predetermined value X16, the damping force generating mechanism 44 opens while the damping force generating mechanism 173 remains open. That is, as described above, the flexible disc 110 separates from the outer conical portion 128 of the valve member 106, causing the hydraulic oil L to flow from the lower chamber 23 to the upper chamber 22 in the compression-side second passage 172(a). At this time, the flow of the hydraulic oil L is throttled by the orifice 139a provided in the second passage 172(a) downstream of the damping force generating mechanism 173, so that the pressure applied to the main valve 81 in the first passage 82B increases, increasing the pressure difference. As a result, the main valve 81 separates from the outer valve seat portion 50, causing the hydraulic oil L to flow from the lower chamber 23 to the upper chamber 22 in the compression-side first passage 82B. Therefore, oil L in the lower chamber 23 flows into the upper chamber 22 through the passages in the multiple passage holes 39 of the piston 21, the annular groove 54, and the annular groove 55, and the passage between the open main valve 81 and the outer valve seat portion 50. As a result, during the compression stroke in the normal speed range where the piston speed is equal to or greater than the 16th predetermined value X16, the rate of increase in the damping force relative to an increase in piston speed is lower and softer than during the extension stroke in the low speed range where the piston speed is less than the 16th predetermined value X16.

[0221] During the compression stroke in the extremely low speed region when a high frequency input (small amplitude vibration) is applied to the shock absorber 1B, in which a piston frequency higher than that during the low frequency input described above is applied, the amount of oil L flowing from the lower chamber 23 into the first communicating volume chamber 149 is small. Therefore, deformation of the flexible disc 110 is small, and the first volume variable mechanism 185 can absorb the volume of oil L flowing into the first communicating volume chamber 149 with the amount of deflection of the flexible disc 110, thereby reducing the pressure increase in the first communicating volume chamber 149. Therefore, during the rise of the damping force in the extremely low speed region where the piston speed is equal to or lower than the 15th predetermined value X15, it is possible to achieve the same state as if the damping force generation mechanism 173 were not present. Therefore, during the compression stroke in the extremely low speed region when a high frequency input is applied, the rise of the damping force is gentler than when a low frequency input is applied.

[0222] The shock absorber 1B of the third embodiment has a damping force generating mechanism 42 that is provided in the first extension passage 102B and generates a damping force, an orifice 94a that is provided in parallel with the damping force generating mechanism 42, a second volume variable mechanism 186 that is provided in the second extension passage 172(b) and changes the volume of the second communication volume chamber 147, and an orifice 139a that is provided upstream of the second communication volume chamber 147, the flow path cross-sectional area of ​​the orifice 139a being larger than the flow path cross-sectional area of ​​the orifice 94a. This makes it possible to improve the insufficient damping force when the piston speed is extremely low during the extension stroke.

[0223] Furthermore, the shock absorber 1B is provided with a damping force generating mechanism 183 in parallel with the second communicating volume chamber 147, and the valve opening pressure of the first damping force generating mechanism 42 is greater than the valve opening pressure of the damping force generating mechanism 183. This makes it possible to reduce the rate of increase in damping force relative to an increase in piston speed when the piston speed is normal during the extension stroke.

[0224] Furthermore, the shock absorber 1B does not have the damping force generating mechanisms 41 and 43 and the orifices 71a and 91a that are provided in the shock absorber 1, and therefore the number of parts can be reduced. As a result, it is possible to suppress increases in costs and variations in product performance.

[0225] In the shock absorber 1B, either the orifice 74a or the orifice 94a may not be provided, that is, either the first passage 82B or the first passage 102B may be orifice-less.

[0226] [Fourth embodiment] Next, the fourth embodiment will be described, focusing on the differences from the third embodiment, mainly with reference to Fig. 10. Note that parts common to the third embodiment will be designated by the same names and symbols.

[0227] <Configuration> As shown in Fig. 10, a shock absorber 1C of the fourth embodiment has a piston rod 25C that is partially different from the piston rod 25 instead of the piston rod 25. The piston rod 25C has a mounting shaft portion 31C that is partially different from the mounting shaft portion 31, including its axial length, instead of the mounting shaft portion 31. The mounting shaft portion 31C is provided with a passage cutout 33C that is located in a different position and has a different axial length from the passage cutout 33. The passage cutout 33C has an axial cutout 33Ca that has a similar shape to the axial cutout 33a but is located in a different axial position and has a different length, an annular groove 33Cb that has a similar shape to the annular groove 33b but is located in a different axial position, and an annular groove 33Cc that has a similar shape to the annular groove 33c but is located in a different axial position.

[0228] The shock absorber 1C has a piston 21C that is partially different from the piston 21, instead of the piston 21. The piston 21C has a piston main body 36C that is partially different from the piston main body 36, instead of the piston 21. The piston main body 36C has a second component 58C that is partially different from the second component 58, instead of the second component 58. The second component 58C differs from the second component 58 in that the passage groove 63 is not provided.

[0229] The shock absorber 1C has, between the disk 78 and the washer 79, in order from the disk 78 side, a flow path forming member 201, a disk 202, a disk 203, a disk 204, and a disk 205. The flow path forming member 201 and the disks 202 to 205 are all made of metal. The flow path forming member 201 is in the shape of a perforated circular plate. The disks 202 to 205 are all in the shape of perforated circular flat plates of a uniform thickness, and are all press-formed. The flow path forming member 201 and the disks 202 to 205 are all positioned radially with respect to the piston rod 25C by fitting the mounting shaft portion 31C inside them.

[0230] The flow path forming member 201 is formed by sintering and has a through hole 211 penetrating axially in the radial center. One axial side of the through hole 211 is a large-diameter hole portion 212, and the other axial side is a small-diameter hole portion 213 having a diameter smaller than the large-diameter hole portion 212 and adapted to fit the mounting shaft portion 31C. The flow path forming member 201 has an annular recessed portion 215 recessed from the end face of the axially large-diameter hole portion 212 side formed radially outward of the large-diameter hole portion 212 at the end axially on the large-diameter hole portion 212 side. The flow path forming member 201 has an inner seat portion 216 radially inside the recessed portion 215 and an outer seat portion 217 radially outside the recessed portion 215. The inner seat portion 216 has a passage groove 218 formed radially. The passage groove 218 opens to the large-diameter hole portion 212 and the recessed portion 215. The large diameter hole portion 212 of the flow passage forming member 201 is aligned in the axial direction with the annular groove 33Cb of the passage cutout portion 33C of the piston rod 25C and communicates with it.

[0231] The outer diameter of the disk 202 is slightly larger than the outer diameter of the outer seat portion 217 of the flow path forming member 201. A notched orifice 139Ca is formed on the outer periphery of the disk 202. The orifice 139Ca connects the flow path in the recessed portion 215 to the upper chamber 22 even when the disk 202 is in contact with the outer seat portion 217.

[0232] The disk 203 has an outer diameter equal to that of the disk 202 . The disk 204 has an outer diameter smaller than that of the disk 203 . The disk 205 has an outer diameter larger than that of the disk 204 .

[0233] In the shock absorber 1C, the orifice 139Ca of the disk 202, the passages in the recessed portion 215, the passage groove 218, and the large diameter hole portion 212 of the passage forming member 201, the passage in the passage cutout portion 33C of the piston rod 25C, the passage in the large diameter hole portion 133 of the closing member 116, the passage in the passage groove 139 of the closing member 116, the second communicating volume chamber 147, the first communicating volume chamber 149, the passage in the hole portion 129 of the valve member 106, and the passage in the passage hole 126 of the case member 105 constitute a second passage 172C that can communicate between the upper chamber 22 and the lower chamber 23. In the second passage 172C, the flow path of the oil liquid L is narrowed by the orifice 139Ca formed in the disk 202. The second passage 172C is provided in parallel with the first passage 82B and the first passage 102B, and is capable of connecting the upper chamber 22 and the lower chamber 23 to each other.

[0234] The second passage 172C becomes a compression-side second passage 172C(a) when the oil L flows from the lower chamber 23 to the upper chamber 22 during the compression stroke, and becomes a compression-side second passage 172C(b) when the oil L flows from the upper chamber 22 to the lower chamber 23 during the extension stroke. The damping force generating mechanism 173 and the orifice 139Ca are provided in series in the second passage 172(a), with the damping force generating mechanism 173 provided upstream of the orifice 139Ca. The damping force generating mechanism 183 and the orifice 139Ca are provided in series in the second passage 172(b), with the damping force generating mechanism 183 provided downstream of the orifice 139Ca. The shock absorber 1C has an accumulator section 104C that differs from the accumulator section 104 in that an orifice 139Ca is provided instead of the orifice 139a.

[0235] The above configuration is shown in a hydraulic circuit diagram in FIG. 8, where an accumulator section 104C is provided instead of the accumulator section 104, and the accumulator section 104C is provided with an orifice 139Ca instead of the orifice 139a.

[0236] Here, the relationship between the flow path cross-sectional area S11 of the orifice 94a and the flow path cross-sectional area S13c of the orifice 139Ca shown in FIG. 10 is such that the flow path cross-sectional area S11 is smaller than the flow path cross-sectional area S13c. <S13cとなっている。 The relationship between the flow passage cross-sectional area S12 of the orifice 74a and the flow passage cross-sectional area S13c of the orifice 139Ca is such that the flow passage cross-sectional area S12 is smaller than the flow passage cross-sectional area S13c. <S13cとなっている。

[0237] Therefore, the shock absorber 1C has a damping force generating mechanism 42 (first damping force generating mechanism) that generates a damping force, and an orifice 94a (first orifice) that is arranged in parallel with the damping force generating mechanism 42, all of which are arranged in the first passage 102B (first passage) on the extension side, a second volume variable mechanism 186 (volume variable mechanism) that changes the volume of the second communicating volume chamber 147 (volume chamber), all of which are arranged in the second passage 172C(b) (second passage) on the extension side, and an orifice 139Ca (second orifice) that is arranged upstream of the second communicating volume chamber 147, and the flow path cross-sectional area of ​​the orifice 139Ca is larger than the flow path cross-sectional area of ​​the orifice 94a.

[0238] The shock absorber 1C also has a damping force generating mechanism 44 that generates a damping force, an orifice 74a that is arranged in parallel with the damping force generating mechanism 44, all of which are arranged in the first passage 82B on the compression side, a first volume variable mechanism 185 that changes the volume of the first communicating volume chamber 149, all of which are arranged in the second passage 172C(a) on the compression side, and an orifice 139Ca that is arranged downstream of the first communicating volume chamber 149, and the flow path cross-sectional area of ​​the orifice 139Ca is larger than the flow path cross-sectional area of ​​the orifice 74a.

[0239] In addition, the shock absorber 1C has a damping force generating mechanism 183 (second damping force generating mechanism) provided in parallel with the second communicating volume chamber 147, and the valve opening pressure of the first damping force generating mechanism 42 is greater than the valve opening pressure of the damping force generating mechanism 183.

[0240] Furthermore, the shock absorber 1C is provided with a damping force generating mechanism 173 in parallel with the first communication volume chamber 149, and the valve opening pressure of the damping force generating mechanism 173 is greater than the valve opening pressure of the damping force generating mechanism 44.

[0241] <Activation> The operation of shock absorber 1C is the same as that of shock absorber 1B, except that in second passage 172C, which is provided in place of second passage 172, oil L is throttled by orifice 139Ca, which is provided in place of orifice 139a, and flows therethrough.

[0242] The shock absorber 1C of the fourth embodiment has the same effects as the shock absorber 1B of the third embodiment. Additionally, in shock absorber 1C, orifice 139Ca of second passage 172C is formed in disc 202, so when the flow path cross-sectional area of ​​orifice 139Ca is changed, it is sufficient to replace only disc 202. Therefore, the cost required for changing the flow path cross-sectional area of ​​orifice 139Ca can be reduced. That is, when the flow path cross-sectional area of ​​orifice 139Ca is changed in shock absorber 1B, it is necessary to change closing member 116, which is a sintered part, and this requires costs such as changing the sintering mold. However, when the flow path cross-sectional area of ​​orifice 139Ca is changed in shock absorber 1C, it is sufficient to replace disc 202, which is a pressed part, and there is no need to change the sintering mold, so it is possible to suppress an increase in costs. [Explanation of symbols]

[0243] 1, 1A to 1C... shock absorber, 4... cylinder, 21, 21A, 21C... piston, 22... upper chamber (chamber), 23... lower chamber (chamber), 25, 25A, 25C... piston rod, 41, 42, 43... damping force generating mechanism (first damping force generating mechanism), 42, 44... damping force generating mechanism (third damping force generating mechanism), 71a, 91a, 94a... orifice (first orifice), 82, 102, 102B... first passage, 139a, 139Ca... orifice (second orifice), 147... second communicating volume chamber (volume chamber), 172(b), 172A(b), 172C(b)... second passage, 183... damping force generating mechanism (second damping force generating mechanism), 186... second volume variable mechanism (volume variable mechanism).

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 and a second passage through which the working fluid flows in response to movement of the piston; a first damping force generating mechanism provided in the first passage and configured to generate a damping force; a first orifice provided in parallel with the first damping force generating mechanism; a volume variable mechanism provided in the second passage for changing the volume of the volume chamber; a second orifice provided upstream of the volume chamber; and a flow path cross-sectional area of ​​the second orifice is larger than a flow path cross-sectional area of ​​the first orifice; buffer.

2. a second damping force generating mechanism is provided in parallel with the volume chamber; the valve opening pressure of the first damping force generating mechanism is greater than the valve opening pressure of the second damping force generating mechanism; The shock absorber according to claim 1 .

3. a third damping force generating mechanism is provided in series with the first damping force generating mechanism; The shock absorber according to claim 1 .

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