Shock absorber

Abstract

The shock absorber is provided with a first passage through which a working fluid flows out from a chamber on an upstream side to a chamber on a downstream side due to movement of a piston, a first damping force generation mechanism that is provided in the first passage and that generates damping force, a second passage that is provided separately from the first passage, a second damping force generation mechanism that is provided in the second passage and that generates damping force, and a volume variable mechanism that changes the volume of a volume chamber provided in parallel with the second passage. The second damping force generation mechanism generates a first resistance force from a frequency at which the piston frequency is lower than a first frequency. The variable volume mechanism is provided with a resistance force generation mechanism that limits the flow rate of the working fluid to the second damping force generating mechanism when the piston frequency becomes equal to or higher than the first frequency, and generates a second resistance force when the piston frequency becomes equal to or higher than the first frequency.

Description

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[0001] This application claims priority to Japanese Patent Application No. 2023-195227, filed on November 16, 2023, the contents of which are incorporated herein by reference.

[0002] Some shock absorbers have two damping force generating mechanisms that open in the same stroke (see, for example, Patent Document 1).

[0003] International Publication No. 2022 / 024766

[0004] Incidentally, there is a demand for shock absorbers that improve the ride comfort of vehicles.

[0005] An object of the present invention is to provide a shock absorber that can improve ride comfort.

[0006] In order to achieve the above object, a shock absorber according to one aspect of the present invention comprises: a cylinder in which a working fluid is sealed; a piston slidably provided within the cylinder and dividing the interior of the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder; a first passage through which the working fluid flows from the upstream chamber to the downstream chamber as the piston moves; a first damping force generating mechanism provided in the first passage and generating a damping force; a second passage provided separately from the first passage; a second damping force generating mechanism provided in the second passage and generating a damping force; and a volume variable mechanism that changes the volume of a volumetric chamber provided in parallel to the second passage; wherein the second damping force generating mechanism generates a first resistance force when the piston frequency is lower than a first frequency; and the volume variable mechanism limits the flow rate of the working fluid to the second damping force generating mechanism when the piston frequency is equal to or higher than the first frequency, and generates a second resistance force when the piston frequency is equal to or higher than the first frequency. configuration was adopted.

[0007] According to the above aspect of the present invention, it is possible to provide a shock absorber that can improve ride comfort.

[0008] 1 is a cross-sectional view showing a shock absorber according to an embodiment of the present invention. Here, the symbol CL indicates a central axis of the shock absorber. It is a view showing the periphery of a piston of the shock absorber of the same embodiment, and is a partially enlarged cross-sectional view showing part A of FIG. 1. It is a view showing a main part of the shock absorber of the same embodiment, and is a partially enlarged cross-sectional view showing part B of FIG. 2. It is a view showing an operating state of a relief mechanism in an extension stroke of the shock absorber of the same embodiment, and is a partially enlarged cross-sectional view showing part B of FIG. 2. It is a view showing an operating state of a relief mechanism in a compression stroke of the shock absorber of the same embodiment, and is a partially enlarged cross-sectional view showing part B of FIG. 2. It is a characteristic diagram showing the rod axial force versus piston frequency in each of the shock absorber of the same embodiment and a shock absorber of a reference example.

[0009] An embodiment of a shock absorber according to the present invention will be described with reference to the drawings. For ease of explanation, the upper side in Figures 1 to 3 will be referred to as "top" and the lower side in Figures 1 to 3 will be referred to as "bottom." In addition, in the drawings, the central axis of the shock absorber 1 may be indicated by the symbol CL.

[0010] <Configuration> The shock absorber 1 of this embodiment is used in suspension devices for railway vehicles and automobiles such as two-wheeled and four-wheeled vehicles, and more specifically, in suspension devices 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 bottomed cylindrical outer tube 3 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 one axial end of the body member 8, with the side of the body member 8 opposite the bottom member 9 being an opening.

[0012] The shock absorber 1 has an annular valve body 10 provided at one axial end of the inner cylinder 2, and an annular rod guide 11 provided at the other axial end 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 portion is fitted into the body member 8.

[0013] One axial end of the inner cylinder 2 is fitted into a small-diameter portion on the outer periphery of the valve body 10, and engages with the bottom member 9 of the outer cylinder 3 via this valve body 10. The other axial end of the inner cylinder 2 is 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 space between the inner cylinder 2 and the outer cylinder 3, and constitutes a reservoir chamber 5, just like the space between the inner cylinder 2 and the 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. The seal member 13 has an annular seal portion 15 made of rubber, which is a friction material and a sealing material, and a perforated disk-shaped metal reinforcing portion 16 embedded in the seal portion 15. The entire inner circumferential side and the entire outer circumferential side of the seal member 13 are made up of the seal portion 15, and the reinforcing portion 16 is embedded in the middle position of the seal member 13 in the radial direction.

[0015] Like the rod guide 11, the seal member 13 is fitted into the inner peripheral portion of the body member 8. 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. A portion of the seal member 13 where a reinforcing portion 16 is provided in the radial direction is sandwiched between the engaging portion (not shown) and the rod guide 11. The seal member 13 has a seal portion 15 that closes the opening of the outer tube 3, and is specifically an oil seal.

[0016] 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.

[0017] 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.

[0018] The shock absorber 1 is provided with a piston rod 25, one axial end of which is disposed inside the cylinder 4 and fixedly connected to the piston 21, and the other axial end of which extends outside the cylinder 4. The piston rod 25 is made of metal, and passes through the upper chamber 22 but not the lower chamber 23. Thus, 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.

[0019] 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.

[0020] 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 outside the cylinder 4 via the rod guide 11, resistance force generating mechanism 20, and seal member 13.

[0021] The rod guide 11 supports the piston rod 25 relative to the cylinder 4 so as to allow axial movement while restricting radial movement of the piston rod 25, thereby guiding the movement of the piston rod 25.

[0022] The outer periphery of the seal portion 15 of the seal member 13 is in close contact with the outer tube 3 of the cylinder 4, and the inner periphery of the seal portion 15 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.

[0023] The resistance generating mechanism 20 has an annular friction portion 27 made of rubber, which is a friction material, and an annular support portion 28 made of metal, which has higher rigidity than the friction portion 27. The friction portion 27 is bonded to the radially inner side of the support portion 28. The resistance generating mechanism 20 is fixed by fitting the support portion 28 on its outer periphery to the rod guide 11. The friction portion 27 on its inner periphery comes into sliding contact with the outer periphery of the piston rod 25, which moves axially. The friction portion 27 of the resistance generating mechanism 20 generates frictional resistance against the axial movement of the piston rod 25. Note that a passage groove 29 is formed in the rod guide 11 between the fitting support portion 28 and the resistance generating mechanism 20, connecting both axial ends of the resistance generating mechanism 20. Therefore, the resistance generating mechanism 20 is not intended to seal between the piston rod 25 and the rod guide 11, but rather to impart frictional resistance to the piston rod 25.

[0024] 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. Main shaft portion 30 of piston rod 25 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 forms a shaft step portion 32 that widens in the direction perpendicular to the axis.

[0025] A passage cutout 33 extending in the axial direction 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 main shaft portion 30 from the axial passage cutout 33. The passage cutout 33 is formed, for example, by cutting out a flat portion of the outer periphery of the mounting shaft portion 31 in a plane parallel to the central axis of the mounting shaft portion 31. The passage cutout 33 can be formed in a so-called two-flat shape at two positions 180 degrees apart in the circumferential direction of the mounting shaft portion 31.

[0026] In shock absorber 1, for example, the portion of piston rod 25 protruding from cylinder 4 is arranged at the top and supported by the vehicle body, and the bottom member 9 of cylinder 4 is arranged at the bottom and connected to the wheel side. In the case of a single-cylinder type, the opposite may be true, with cylinder 4 supported by the vehicle body and piston rod 25 connected to the wheel side.

[0027] As shown in FIG. 2, 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 that is integrally attached to the outer circumferential surface of the piston body 36 and that slides within the inner tube 2 of the cylinder 4.

[0028] 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.

[0029] 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 are crank-shaped with two bending points, and the side facing the lower chamber 23 in the axial direction of the piston 21 opens more inward in the radial direction of the piston 21 than the side facing the upper chamber 22. An annular groove 55 that connects the plurality of passage holes 38 is formed in the piston body 36 on the side facing the lower chamber 23 in the axial direction.

[0030] A first damping force generating mechanism 41 is provided on the lower chamber 23 side of the annular groove 55, and generates a damping force by opening and closing the passages in the annular groove 55 and the plurality of passage holes 38. By disposing the first damping force generating mechanism 41 on the lower chamber 23 side, the passages in the plurality of passage holes 38 and the annular groove 55 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, when the piston 21 moves toward the upper chamber 22, i.e., during the extension stroke. The first damping force generating mechanism 41 provided for the passages in the plurality of passage holes 38 and the annular groove 55 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 55 to the lower chamber 23.

[0031] The remaining half of the total number of passage holes 38, 39, the passage holes 39, are arranged 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 are crank-shaped with two bending points, and the upper chamber 22 side in the axial direction of the piston 21 opens more inward in the radial direction of the piston 21 than the lower chamber 23 side. The piston body 36 is formed with an annular groove 56 that connects the plurality of passage holes 39 to the upper chamber 22 side in the axial direction.

[0032] A first damping force generating mechanism 42 is provided on the upper chamber 22 side of the annular groove 56, and generates a damping force by opening and closing the passages in the plurality of passage holes 39 and the annular groove 56. By disposing the first damping force generating mechanism 42 on the upper chamber 22 side, the passages in the plurality of passage holes 39 and the annular groove 56 become 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 first damping force generating mechanism 42 provided for the passages in the plurality of passage holes 39 and the annular groove 56 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 56 to the upper chamber 22.

[0033] The piston body 36 has a generally circular disk shape, and an insertion hole 44 is formed axially through its radial center, into which the mounting shaft portion 31 of the piston rod 25 is inserted. The insertion hole 44 has a small-diameter hole portion 45 on one axial side into which the mounting shaft portion 31 of the piston rod 25 is fitted, and a large-diameter hole portion 46 on the other axial side, which has a larger diameter than the small-diameter hole portion 45. The small-diameter hole portion 45 is provided on the axial side of the upper chamber 22, and the large-diameter hole portion 46 is provided on the axial side of the lower chamber 23. The piston 21 is positioned radially with respect to the piston rod 25 by fitting the mounting shaft portion 31 into the small-diameter hole portion 45.

[0034] An annular inner seat portion 47 is formed at the end of the piston body 36 on the axial side of the lower chamber 23, radially inward of the opening of the annular groove 55 on the lower chamber 23 side. Also, an annular valve seat portion 48 that constitutes part of the first damping force generating mechanism 41 is formed at the end of the piston body 36 on the axial side of the lower chamber 23, radially outward of the opening of the annular groove 55 on the lower chamber 23 side.

[0035] An annular inner seat portion 49 is formed at the end of the piston body 36 on the axial side of the upper chamber 22, radially inward of the opening of the annular groove 56 on the upper chamber 22 side. Furthermore, an annular valve seat portion 50 that constitutes part of the first damping force generating mechanism 42 is formed at the end of the piston body 36 on the axial side of the upper chamber 22, radially outward of the opening of the annular groove 56 on the upper chamber 22 side.

[0036] The insertion hole 44 of the piston body 36 has a large diameter hole portion 46 that is located closer to the inner seat portion 47 in the axial direction than the small diameter hole portion 45. The passage in the large diameter hole portion 46 of the piston body 36 is always in communication with a piston rod passage portion 51 in the passage cutout portion 33 of the piston rod 25, with the passage portions overlapping in the axial direction.

[0037] The piston body 36 has a stepped portion radially outward of the valve seat portion 48 that is lower in axial height than the valve seat portion 48, and the opening of the compression-side passage hole 39 on the lower chamber 23 side is located in this stepped portion. Similarly, the piston body 36 has a stepped portion radially outward of the valve seat portion 50 that is lower in axial height than the valve seat portion 50, and the opening of the extension-side passage hole 38 on the upper chamber 22 side is located in this stepped portion.

[0038] The compression-side first damping force generating mechanism 42 includes the valve seat portion 50 of the piston 21 and includes, in order from the piston 21 side in the axial direction, one disk 63, multiple (specifically, two) disks 64 having the same inner and outer diameters, multiple (specifically, three) disks 65 having the same inner and outer diameters, multiple (specifically, two) disks 66 having the same inner and outer diameters, one disk 67, one disk 68, and one annular member 69. The disks 63 to 68 and the annular member 69 are made of metal and each has a perforated circular flat plate shape with a constant thickness. The disks 63 to 68 and the annular member 69 are radially positioned relative to the piston rod 25 by fitting the mounting shaft portion 31 to the inside thereof. The disks 63 to 68 are plain disks (flat disks without any protrusions protruding in the axial direction).

[0039] The disc 63 has an outer diameter larger than the outer diameter of the inner seat portion 49 of the piston 21 but smaller than the inner diameter of the valve seat portion 50, and is constantly in contact with the inner seat portion 49. The multiple discs 64 have an outer diameter equal to the outer diameter of the valve seat portion 50 of the piston 21 and are able to seat on the valve seat portion 50. The multiple discs 65 have an outer diameter smaller than the outer diameter of the disc 64. The multiple discs 66 have an outer diameter smaller than the outer diameter of the disc 65. The disc 67 has an outer diameter smaller than the outer diameter of the disc 66 but equal to the outer diameter of the inner seat portion 49 of the piston 21. The disc 68 has an outer diameter equal to the outer diameter of the disc 65. The annular member 69 has an outer diameter smaller than the outer diameter of the disc 68 but larger than the outer diameter of the shaft step portion 32 of the piston rod 25. The annular member 69 is thicker and more rigid than the discs 63 to 68, and is in contact with the shaft step portion 32.

[0040] A plurality of discs 64, a plurality of discs 65, and a plurality of discs 66 constitute a compression-side main valve 71 that is releasable from the valve seat portion 50. When the main valve 71 is releasable from the valve seat portion 50, the main valve 71 connects the passages in the plurality of passage holes 39 and the annular groove 56 with the upper chamber 22, and generates a damping force by suppressing the flow of oil L between the valve seat portion 50 and the main valve 71. The annular member 69, together with the disc 68, abuts against the main valve 71 to restrict deformation of the main valve 71 in the opening direction beyond a specified limit.

[0041] The passages within the multiple passage holes 39 and the annular groove 56, and the passage between the main valve 71 and the valve seat 50 that appears when the valve is open, are formed in the piston 21, and constitute a compression-side first passage 72 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 compression-side first damping force generating mechanism 42 that generates a damping force includes the main valve 71 and the valve seat 50, and is therefore provided in this first passage 72. The first passage 72 is formed in the piston 21 including the valve seat 50, and oil L passes through it when the piston rod 25 and piston 21 move toward the compression side.

[0042] Here, in the compression-side first damping force generating mechanism 42, no fixed orifice is formed in either the valve seat portion 50 or the main valve 71 abutting thereon, which communicates between the upper chamber 22 and the lower chamber 23, even when these are in an abutting state. In other words, when the valve seat portion 50 and the main valve 71 are in abutting state over the entire circumference, the compression-side first damping force generating mechanism 42 does not communicate between the upper chamber 22 and the lower chamber 23. In other words, the first passage 72 does not have a fixed orifice formed therein, which constantly communicates between the upper chamber 22 and the lower chamber 23, and is not a passage that constantly communicates between the upper chamber 22 and the lower chamber 23.

[0043] The extension-side first damping force generating mechanism 41 includes the valve seat portion 48 of the piston 21 and includes, in axial order from the piston 21 side, one disk 82, one disk 83, a plurality of disks 84 (specifically, four) having the same inner and outer diameters, one disk 85, a plurality of disks 86 (specifically, three) having the same inner and outer diameters, and one disk 87. The disks 82 to 87 are made of metal and are all plain disks in the shape of circular flat plates with holes and a constant thickness. The disks 82 to 87 are all positioned radially relative to the piston rod 25 by fitting the mounting shaft portion 31 inside them.

[0044] The disk 82 has an outer diameter larger than the outer diameter of the inner seat portion 47 of the piston 21 but smaller than the inner diameter of the valve seat portion 48, and is constantly in contact with the inner seat portion 47. As shown in FIG. 3 , the disk 82 has a notch 90 extending from a midpoint radially outward of the inner seat portion 47 to its inner periphery. The notch 90 constantly connects the passages in the annular groove 55 and the passage holes 38 with the passages in the large-diameter hole portion 46 of the piston 21 and the piston rod passage portion 51 in the passage notch 33 of the piston rod 25. The notch 90 is formed during press molding of the disk 82. The notch 90 faces adjacent to the large-diameter hole 46 of the piston 21. The disk 83 has the same outer diameter as the disk 82 and does not have a notch like the disk 82. The multiple disks 84 have an outer diameter equal to the outer diameter of the valve seat portion 48 of the piston 21 and are capable of seating on the valve seat portion 48. The disc 85 has an outer diameter smaller than the outer diameter of the disc 84. The plurality of discs 86 also have an outer diameter smaller than the outer diameter of the disc 85. The disc 87 has an outer diameter smaller than the outer diameter of the disc 86 and slightly larger than the outer diameter of the inner seat portion 47 of the piston 21.

[0045] The plurality of discs 84, one disc 85, and the plurality of discs 86 constitute an extension-side main valve 91 that can be seated on and removed from the valve seat portion 48. When the main valve 91 is lifted from the valve seat portion 48, the main valve 91 connects the passages in the annular groove 55 and the passage holes 38 with the lower chamber 23, and suppresses the flow of oil L between the main valve 91 and the valve seat portion 48, thereby generating a damping force.

[0046] 2 , the passages within the plurality of passage holes 38 and the annular groove 55, and the passage between the main valve 91 and the valve seat 48 that appears when the valve is open, are formed in the piston 21, constituting a first extension passage 92 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 first extension damping force generating mechanism 41 that generates a damping force includes the main valve 91 and the valve seat 48, and is therefore provided in this first passage 92. The first passage 92 is formed in the piston 21 including the valve seat 48, and oil L passes through the first passage 92 when the piston rod 25 and piston 21 move toward the extension side.

[0047] In the extension-side first damping force generating mechanism 41, no fixed orifice is formed in either the valve seat portion 48 or the main valve 91 abutting thereon, which communicates between the upper chamber 22 and the lower chamber 23, even when these are in an abutting state. In other words, when the valve seat portion 48 and the main valve 91 are in an abutting state over the entire circumference, the extension-side first damping force generating mechanism 41 does not communicate between the upper chamber 22 and the lower chamber 23. In other words, the first passage 92 does not have a fixed orifice formed therein, which constantly communicates between the upper chamber 22 and the lower chamber 23, and is not a passage that constantly communicates between the upper chamber 22 and the lower chamber 23.

[0048] As shown in FIG. 3 , on the opposite side of the first damping force generating mechanism 41 on the extension side from the piston 21, there are provided, in order from the first damping force generating mechanism 41 side, one cap member 95, one disc spring 116, one disc 97, one flexible disc 100, one valve seat disc 101, one disc 102, one disc 103, one disc 104, one spring member 105, one disc 106, one sub-valve 107, one valve seat member 109 with an O-ring 108 provided on the outer periphery thereof, one sub-valve 110, one disc 111, one spring member 112, one disc 113, and one annular member 114, with the mounting shaft portion 31 of the piston rod 25 fitted inside each of them. By fitting the mounting shaft portion 31 into the inside of each of them, the cap member 95, the disc spring 116, the disc 97, the flexible disc 100, the valve seat disc 101, the discs 102 to 104, the spring member 105, the disc 106, the sub-valve 107, the valve seat member 109, the sub-valve 110, the disc 111, the spring member 112, the disc 113 and the annular member 114 are positioned radially relative to the piston rod 25.

[0049] 2, a male thread 34 is formed on the mounting shaft portion 31 of the piston rod 25 in a portion that protrudes beyond the annular member 114, and a nut 119 is threaded onto this male thread 34. The nut 119 abuts against the annular member 114.

[0050] As shown in FIG. 2, at least the radially inner circumferential sides of the annular member 69, discs 63 to 68, piston 21, discs 82 to 87, cap member 95, disc spring 116 shown in FIG. 3, disc 97, flexible disc 100, valve seat disc 101, discs 102 to 104, spring member 105, disc 106, sub-valve 107, valve seat member 109, sub-valve 110, disc 111, spring member 112, disc 113, and annular member 114 are clamped in the axial direction by the shaft step portion 32 of piston rod 25 and nut 119, and are fixed to the piston rod 25. In this state, as shown in FIG. 3, the disc spring 116, the disc 97, the flexible disc 100, the valve seat disc 101, the discs 102 to 104, the spring member 105, the disc 106, the sub-valve 107, the valve seat member 109, the sub-valve 110, the disc 111, the spring member 112, and the disc 113 are arranged within the cap member 95.

[0051] The cap member 95, disks 97, 102 to 104, 106, 111, and 113, flexible disk 100, valve seat disk 101, spring members 105 and 112, sub-valves 107 and 110, valve seat member 109, annular member 114, and disc spring 116 are all made of metal. The disks 97, 102 to 104, 106, 111, and 113, flexible disk 100, valve seat disk 101, sub-valves 107 and 110, and annular member 114 are all plain disks having a constant thickness and a perforated circular flat plate shape. The cap member 95, valve seat member 109, and disc spring 116 are annular. The spring members 105 and 112 are annular.

[0052] The cap member 95 is a cylindrical, bottomed, one-piece molded product formed, for example, by plastic processing or cutting a metal plate. The cap member 95 has a perforated, disk-shaped bottom portion 122 of a constant thickness, a curved middle portion 123 that extends from the outer peripheral edge of the bottom portion 122 toward one axial direction of the bottom portion 122 while expanding in diameter, and a cylindrical portion 124 that extends in the opposite direction from the edge of the curved middle portion 123 opposite the bottom portion 122.

[0053] The bottom portion 122 has a constant radial width around its entire circumference and is a perforated circular flat plate with an inner periphery into which the mounting shaft portion 31 of the piston rod 25 fits. By fitting the mounting shaft portion 31 into the inner periphery of the bottom portion 122, the cap member 95 is positioned radially relative to the piston rod 25 and arranged coaxially. The bottom portion 122 has a plurality of passage holes 126 formed between the inner and outer peripheries that penetrate the bottom portion 122 in the axial direction of the bottom portion 122. The plurality of passage holes 126 are arranged equidistant from the center of the bottom portion 122 and equidistantly spaced circumferentially around the bottom portion 122. The cap member 95 is oriented such that the bottom portion 122 is closer to the piston 21 than the cylindrical portion 124 and abuts against the disk 87, and the mounting shaft portion 31 fits into the inner periphery of the bottom portion 122. The outer diameter of the disk 87 is smaller than twice the shortest distance connecting the radial center of the cap member 95 and the passage hole 126 .

[0054] The intermediate curved portion 123 is annular and coaxial with the bottom portion 122, and a cross section of the plane including the central axis thereof has a curved shape that is convex radially outward and axially toward the bottom portion 122. The cylindrical portion 124 is also coaxial with the bottom portion 122 and the intermediate curved portion 123.

[0055] The cap member 95 is thicker than one of the discs 84 to 86, and is cylindrical with a bottom, making it more rigid than the discs 84 to 86. Therefore, the cap member 95 abuts against the main valve 91, which is made up of the multiple discs 84 to 86, and prevents the main valve 91 from deforming beyond a specified limit in the opening direction.

[0056] The disc spring 116 is a flexible, perforated, circular metal plate. The disc spring 116 is formed by stamping and bending a single sheet of plate material using a press. As shown in FIG. 4 , the disc spring 116 has an inner annular portion 401, an intermediate annular portion 402, an outer conical portion 403, and multiple support portions, specifically two support portions 404, connecting the inner annular portion 401 and the intermediate annular portion 402. The inner annular portion 401 is a perforated circular flat plate, and the intermediate annular portion 402 is a perforated circular flat plate having an inner diameter larger than the outer diameter of the inner annular portion 401. The two support portions 404 are provided between the inner annular portion 401 and the intermediate annular portion 402. The inner annular portion 401, the intermediate annular portion 402, and the two support portions 404 are flat and arranged on the same plane. The outer conical portion 403 has a conical cylindrical shape that spreads radially outward and axially to one side from the outer peripheral edge of the intermediate annular portion 402. The disc spring 116 has the outer conical portion 403 on its outer diameter side and an inner flat portion 414 on its inner diameter side, which has the inner annular portion 401, the intermediate annular portion 402, and two support portions 404. The inner flat portion 414 is closer to a flat surface than the outer conical portion 403.

[0057] As shown in FIG. 3 , the outer diameter of the outer conical portion 403 of the disc spring 116, i.e., the outer diameter of the disc spring 116, is slightly smaller than the inner diameter of the cylindrical portion 124 of the cap member 95. The disc spring 116 is configured such that the inner annular portion 401, the intermediate annular portion 402, and the two support portions 404 abut against the bottom portion 122 of the cap member 95, and the outer conical portion 403 extends axially on the same side as the cylindrical portion 124. In this state, the disc spring 116 is radially positioned relative to the piston rod 25 by fitting the mounting shaft portion 31 into the inner peripheral side of the inner annular portion 401. The disc spring 116 is configured so that its inner peripheral end abuts against the piston rod 25. The cylindrical portion 124 of the cap member 95 is disposed radially outward of the disc spring 116.

[0058] As shown in FIG. 4 , the inner annular portion 401, the intermediate annular portion 402, and the outer conical portion 403 all have a constant radial width around the entire circumference. The radial width of the outer conical portion 403 is wider than the radial width of the inner annular portion 401. The radial width of the inner annular portion 401 is wider than the radial width of the intermediate annular portion 402. The inner annular portion 401, the intermediate annular portion 402, and the outer conical portion 403 are arranged coaxially, and two support portions 404 connect the inner annular portion 401 to the intermediate annular portion 402 and the outer conical portion 403 in a coaxial state. The two support portions 404 connect the outer peripheral edge of the inner annular portion 401 and the inner peripheral edge of the intermediate annular portion 402.

[0059] The two support portions 404 have two outer connection portions 411 that are arranged on the same line passing through the centers of the inner annular portion 401, the intermediate annular portion 402, and the outer conical portion 403, in other words, the center of the disc spring 116, and these outer connection portions 411 are connected to the intermediate annular portion 402. The two outer connection portions 411 are arranged 180 degrees out of phase with each other in the circumferential direction of the intermediate annular portion 402, and both protrude from the inner peripheral edge of the intermediate annular portion 402 radially inward of the intermediate annular portion 402.

[0060] Furthermore, the two support portions 404 have two inner connection portions 412 arranged on the same straight line passing through the center of the disc spring 116, and these inner connection portions 412 are connected to the inner annular portion 401. The two inner connection portions 412 are arranged 180 degrees out of phase with each other in the circumferential direction of the inner annular portion 401, and both protrude radially outward from the outer circumferential edge of the inner annular portion 401. Each of the two outer connection portions 411 is closer to one of the two inner connection portions 412 in the circumferential direction of the disc spring 116 than to the other. In other words, each of the two inner connection portions 412 is closer to one of the two outer connection portions 411 in the circumferential direction of the disc spring 116 than to the other.

[0061] On the other hand, the distance between the outer connection portion 411 and the inner connection portion 412 that are farther away in the circumferential direction of the disc spring 116 is equal to the distance between the outer connection portion 411 and the inner connection portion 412 that are farther away in the circumferential direction of the disc spring 116.

[0062] Furthermore, the two support portions 404 are provided with two connecting arms 413 so as to connect the outer connection portion 411 and the inner connection portion 412 that are farther away in the circumferential direction of the disc spring 116. That is, the disc spring 116 is provided with one connecting arm 413 that connects one outer connection portion 411 and one inner connection portion 412 that are farther away in the circumferential direction of the disc spring 116, and these outer connection portion 411, inner connection portion 412, and connecting arm 413 constitute one support portion 404. The disc spring 116 is also provided with the other connecting arm 413 that connects the other outer connection portion 411 and the other inner connection portion 412 that are farther away in the circumferential direction of the disc spring 116, and these outer connection portion 411, inner connection portion 412, and connecting arm 413 constitute the other support portion 404.

[0063] The two connecting arms 413 extend in an arc shape along the outer circumferential surface of the inner annular portion 401 and the inner circumferential surface of the intermediate annular portion 402, and are arranged on the same circle concentric with the inner annular portion 401, the intermediate annular portion 402, and the outer conical portion 403. The two connecting arms 413 each extend within an angular range slightly smaller than 180° in the circumferential direction of the disc spring 116. The radial distance of the two connecting arms 413 from the inner circumferential surface of the intermediate annular portion 402 is greater than the radial distance from the outer circumferential surface of the inner annular portion 401.

[0064] The disc spring 116 has the above-described shape, and thus has two stepped arc-shaped holes 415 surrounded by the inner annular portion 401, the intermediate annular portion 402, and the two support portions 404. The two holes 415 penetrate the disc spring 116 in the thickness direction (axial direction). The two holes 415 are provided between the inner annular portion 401 and the intermediate annular portion 402. Therefore, the disc spring 116 has two stepped arc-shaped holes 415 between the inner peripheral end and the outer peripheral end. The two stepped arc-shaped holes 415 are provided in the inner flat portion 414.

[0065] The two holes 415 have the same shape and each include an arc-shaped small-diameter hole 421 formed between the inner annular portion 401 and the connecting arm portion 413, an arc-shaped large-diameter hole 422 formed between the intermediate annular portion 402 and the connecting arm portion 413, and a connecting hole 423 connecting the small-diameter hole 421 and the large-diameter hole 422. The small-diameter hole 421 and the large-diameter hole 422 are both arc-shaped and coaxial with the inner annular portion 401 and the intermediate annular portion 402, and the large-diameter hole 422 has an arc-shaped diameter larger than that of the small-diameter hole 421. The holes 415 are arranged such that the large-diameter hole 422 and the small-diameter hole 421 are adjacent to each other in the circumferential direction, and the sides of the large-diameter hole 422 and the small-diameter hole 421 that are close to each other are connected by a connecting hole 423 that runs along the radial direction of the disc spring 116.

[0066] As shown in FIG. 3 , the inner diameter of the intermediate annular portion 402 of the disc spring 116 is smaller than twice the longest distance connecting the radial center of the cap member 95 and the passage hole 126, and is larger than twice the shortest distance connecting the radial center of the cap member 95 and the passage hole 126. Therefore, in the disc spring 116, the communication passage 425 in the hole 415 is always in communication with the communication passage 148 in the passage hole 126 of the bottom portion 122. In the disc spring 116, the portion of the communication passage 425 in the hole 415 within the large-diameter hole portion 422 shown in FIG. 4 is always in communication with the communication passage 148 in the passage hole 126. Also, as shown in FIG. 3 , the outer diameter of the intermediate annular portion 402 of the disc spring 116, i.e., the inner diameter of the outer conical portion 403, is larger than twice the longest distance connecting the radial center of the cap member 95 and the passage hole 126. The intermediate annular portion 402 of the disc spring 116 abuts over the entire circumference at a position radially outward of all of the passage holes 126 in the bottom portion 122 of the cap member 95 .

[0067] The disk 97 has a constant radial width around its entire circumference, and its outer diameter is smaller than the outer diameter of the inner annular portion 401 of the disk spring 116. The disk 97 is thicker than the thickness of the inner annular portion 401 of the disk spring 116, i.e., the plate thickness of the disk spring 116.

[0068] The inner annular portion 401 of the disc spring 116 is clamped in the axial direction by the bottom portion 122 of the cap member 95 and the disc 97 shown in Fig. 3, and is thereby fixed to the piston rod 25. The two support portions 404 and the intermediate annular portion 402 shown in Fig. 4 abut against the bottom portion 122 of the cap member 95 shown in Fig. 3, but do not abut against the disc 97, and are therefore not clamped in the axial direction.

[0069] The flexible disk 100 is flexible. The inner peripheral end of the flexible disk 100 abuts against the piston rod 25. The outer diameter of the flexible disk 100 is larger than the outer diameter of the disc spring 116 and slightly smaller than the inner diameter of the cylindrical portion 124 of the cap member 95. The flexible disk 100 has a thickness equal to the thickness of the disc spring 116.

[0070] The flexible disk 100 is formed by punching out a single sheet of plate material using a press molding method. The flexible disk 100 has a flat plate shape in its natural state before being attached to the piston rod 25. As shown in FIG. 5 , the flexible disk 100 has a constant radial width around its entire circumference, and multiple, specifically 15, communication holes 501 are formed at intermediate positions in the radial direction. All of the communication holes 501 are circular holes of the same diameter, and penetrate the flexible disk 100 in the thickness direction (axial direction). All of the communication holes 501 are formed at equal distances from the center of the flexible disk 100. All of the communication holes 501 are formed at equal intervals around the circumference of the flexible disk 100.

[0071] The flexible disk 100 has a plurality of communication holes 501 formed therein, and thus has an inner annular portion 502 extending from the inner peripheral edge to the communication holes 501, an outer annular portion 503 extending from the outer peripheral edge to the communication holes 501, and a connecting portion 504 extending radially of the flexible disk 100 to connect the inner annular portion 502 and the outer annular portion 503. The inner annular portion 502 has a constant radial width over the entire circumference, and the outer annular portion 503 also has a constant radial width over the entire circumference. The outer annular portion 503 has a larger radial width than the inner annular portion 502.

[0072] The connecting portions 504 are located between adjacent communication holes 501 in the circumferential direction of the flexible disk 100, and therefore a plurality of connecting portions 504 are formed at radially intermediate positions of the flexible disk 100, specifically 15 connecting portions, the same number as the number of communication holes 501. All connecting portions 504 have the same shape and are formed at positions equidistant from the center of the flexible disk 100. All connecting portions 504 are formed at equal intervals in the circumferential direction of the flexible disk 100. As shown in FIG. 3 , the outer diameter of the inner annular portion 502 of the flexible disk 100 is larger than the outer diameter of the disk 97. Therefore, the communication holes 501 of the flexible disk 100 are not blocked by the disk 97.

[0073] The disc spring 116 has a circular edge on the opposite side of the outer conical portion 403 from the intermediate annular portion 402 , and this circular edge abuts against the outer peripheral edge of the outer annular portion 503 of the flexible disk 100 over its entire circumference.

[0074] The valve seat disk 101 has a constant radial width over its entire circumference and is flat in its natural state before being assembled to the piston rod 25. The valve seat disk 101 is slightly thinner than the flexible disk 100. The outer diameter of the valve seat disk 101 is larger than the inner diameter of the outer annular portion 503 of the flexible disk 100 and smaller than the outer diameter of the outer annular portion 503. When the valve seat disk 101 abuts in surface contact over its entire circumference against the outer annular portion 503 of the flexible disk 100, it closes all of the communication holes 501.

[0075] The disk 102 is a common part having the same shape as the disk 97. The disk 102, together with the disk 97, clamps the inner peripheral sides of the flexible disk 100 and the valve seat disk 101 in the axial direction.

[0076] The disk 103 has a constant radial width around its entire circumference. The disk 103 has an outer diameter that is larger than the outer diameter of the disk 102 and smaller than the outer diameter of the valve seat disk 101. The disk 103 has a thickness equal to that of the flexible disk 100.

[0077] The disk 104 has a constant radial width around its entire circumference. The disk 104 has an outer diameter that is larger than the outer diameter of the valve seat disk 101 and smaller than the outer diameter of the flexible disk 100. The disk 104 has a thickness equal to that of the disks 97 and 102. The disk 104 is thicker and more rigid than the flexible disk 100 and the valve seat disk 101.

[0078] The spring member 105 has a base plate portion 331 in the shape of a circular plate with holes that fits onto the mounting shaft portion 31, and a plurality of spring plate portions 332 that extend radially outward from the base plate portion 331 at equally spaced positions around the circumferential direction of the base plate portion 331. The spring plate portions 332 are inclined relative to the base plate portion 331 so that the spring plate portions 332 move away from the base plate portion 331 in the axial direction of the base plate portion 331 as they extend toward their extending tips. The spring member 105 abuts against the disk 104 at the base plate portion 331. The spring member 105 is attached to the mounting shaft portion 31 so that the spring plate portions 332 extend from the base plate portion 331 toward the sub-valve 107 in the axial direction of the base plate portion 331.

[0079] The disk 106 has an outer diameter smaller than that of the base plate portion 331 of the spring member 105 and larger than that of the disk 102. The base plate portion 331 of the spring member 105 abuts against the disk 106, and the plurality of spring plate portions 332 abut against the sub-valve 107.

[0080] 2, the valve seat member 109 is in the form of a perforated disk extending axially and penetrating in the thickness direction, with a through hole 131 formed in the radial center for inserting the mounting shaft portion 31. 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.

[0081] The valve seat member 109 has an annular inner seat portion 134 at its axial end facing the large-diameter hole portion 133 and surrounding the large-diameter hole portion 133, and a valve seat portion 135 extending radially outward from this inner seat portion 134. The valve seat member 109 also has an annular inner seat portion 138 at its axial end facing the small-diameter hole portion 132 and surrounding the small-diameter hole portion 132, and a valve seat portion 139 extending radially outward from this inner seat portion 138. The valve seat member 109 has a perforated, disk-shaped main body portion 140 between the inner seat portion 134 and valve seat portion 135 and the inner seat portion 138 and valve seat portion 139 in the axial direction.

[0082] The inner seat portion 134 protrudes to one side along the axial direction of the main body portion 140 from the inner peripheral edge portion of the main body portion 140 on the large-diameter hole portion 133 side in the axial direction, and the valve seat portion 135 also protrudes from the main body portion 140 radially outside the inner seat portion 134 along the axial direction of the main body portion 140 to the same side as the inner seat portion 134. The inner seat portion 134 and the valve seat portion 135 have flat tip surfaces on the protruding side, i.e., the tip surfaces on the opposite side to the main body portion 140, which extend in a direction perpendicular to the axis of the valve seat member 109 and are arranged on the same plane.

[0083] The inner seat portion 138 protrudes from the inner peripheral edge of the main body portion 140 on the axial side of the small-diameter hole portion 132 toward the opposite side of the inner seat portion 134 along the axial direction of the main body portion 140, and the valve seat portion 139 also protrudes radially outward of the inner seat portion 138 and along the axial direction of the main body portion 140 toward the same side as the inner seat portion 138. The inner seat portion 138 and the valve seat portion 139 have flat tip surfaces on the protruding side, i.e., the tip surfaces opposite the main body portion 140, which extend in a direction perpendicular to the axis of the valve seat member 109 and are arranged on the same plane. The inner seat portions 134, 138 have the same outer diameter.

[0084] The valve seat portion 135 is a petal-shaped irregular seat and has multiple valve seat constituent portions 201 (only one is shown in FIG. 2 because it is a cross-section). These valve seat constituent portions 201 have the same shape and are arranged at equal intervals around the circumferential direction of the valve seat member 109. The inner seat portion 134 is annular and has its center on the central axis of the valve seat member 109.

[0085] A passage recess 205 is formed inside each valve seat constituent portion 201, surrounded by a part of the inner seat portion 134, and recessed from the tip end surface on the protruding side in the axial direction of the valve seat member 109. The bottom surface of the passage recess 205 is formed by the main body portion 140. A passage recess 205 is formed inside all of the valve seat constituent portions 201.

[0086] A passage hole 206 is formed at the center of the passage recess 205 in the circumferential direction of the valve seat member 109, penetrating the main body 140 in the axial direction and thereby penetrating the valve seat member 109 in the axial direction. The passage hole 206 is a linear hole parallel to the central axis of the valve seat member 109. The passage hole 206 is formed in the bottom surface of all of the passage recesses 205.

[0087] The valve seat portion 139 is also a petal-shaped irregular seat and has multiple valve seat constituent portions 211 (only one is shown in FIG. 2 because it is a cross-section). These valve seat constituent portions 211 have the same shape and are arranged at equal intervals around the circumferential direction of the valve seat member 109. The valve seat constituent portions 211 have the same shape as the valve seat constituent portions 201. The inner seat portion 138 is annular and has its center on the central axis of the valve seat member 109.

[0088] A passage recess 215 is formed inside each valve seat constituent portion 211, surrounded by a part of the inner seat portion 138, and recessed from the tip surface on the protruding side in the axial direction of the valve seat member 109. The bottom surface of the passage recess 215 is formed by the main body portion 140. The passage recess 215 is formed inside all of the valve seat constituent portions 211.

[0089] A passage hole 216 is formed at the center of the passage recess 215 in the circumferential direction of the valve seat member 109, penetrating the main body 140 in the axial direction and thereby penetrating the valve seat member 109 in the axial direction. The passage hole 216 is a linear hole parallel to the central axis of the valve seat member 109. The passage hole 216 is formed in the bottom surface of all of the passage recesses 215.

[0090] The arrangement pitch of the multiple valve seat components 201 in the circumferential direction of the valve seat member 109 is the same as the arrangement pitch of the multiple valve seat components 211 in the circumferential direction of the valve seat member 109, and the valve seat components 201 and 211 are offset from each other by half a pitch. The passage hole 206 is arranged between two valve seat components 211 that are adjacent to each other in the circumferential direction of the valve seat member 109, and is therefore arranged outside the range of the valve seat portion 139. The passage hole 216 is arranged between two valve seat components 201 that are adjacent to each other in the circumferential direction of the valve seat member 109, and is therefore arranged outside the range of the valve seat portion 135.

[0091] A passage groove 221 that radially crosses the inner seat portion 134 is formed in the valve seat member 109 on the axial side of the large diameter hole portion 133. The passage groove 221 is recessed in the axial direction of the valve seat member 109 from the tip surface of the inner seat portion 134 on the side opposite to the main body portion 140. The passage groove 221 also extends between adjacent valve seat constituent portions 201 in the circumferential direction of the valve seat member 109. The passage hole 216 opens to the bottom surface of the passage groove 221. The passage groove 221 connects the passage hole 216 and the large diameter hole portion 133.

[0092] The passage hole 216 and the passage recess 215 into which this passage hole 216 opens form a first passage portion 161 provided in the valve seat member 109. A plurality of first passage portions 161 are provided in the valve seat member 109 at equal intervals in the circumferential direction of the valve seat member 109. The passage groove 221 forms a radial passage 222 extending radially toward the first passage portion 161. A plurality of radial passages 222 are provided in the valve seat member 109 at equal intervals in the circumferential direction of the valve seat member 109.

[0093] The valve seat member 109 has a passage groove 225 between adjacent valve seat constituent portions 211 in the circumferential direction of the valve seat member 109. The passage hole 206 opens to the bottom surface of the passage groove 225. Therefore, the passage groove 225 communicates with the passage hole 206.

[0094] The passage hole 206 and the passage recess 205 into which the passage hole 206 opens form a second passage portion 162 provided in the valve seat member 109. The valve seat member 109 is provided with a plurality of second passage portions 162 at equal intervals in the circumferential direction of the valve seat member 109.

[0095] A plurality of first passage portions 161 and a plurality of second passage portions 162 are provided in the valve seat member 109 to form a valve seat member passage portion 160 through which the oil liquid L flows.

[0096] The valve seat member 109 has an annular seal groove 141 recessed radially inward at the axially intermediate position of the outer periphery of the main body 140. An O-ring 108 is disposed in this seal groove 141. The outer periphery of the valve seat member 109 is fitted onto the cylindrical portion 124 of the cap member 95, with the inner seat portion 138 and the valve seat portion 139 facing away from the bottom 122. In this state, the O-ring 108 seals the gap between the cylindrical portion 124 of the cap member 95 and the valve seat member 109.

[0097] The cap member 95, the O-ring 108, and the valve seat member 109 form a cap chamber 146 inside the cap member 95. The cap chamber 146 is provided between the bottom 122 of the cap member 95 and the valve seat member 109. As shown in FIG. 3 , the disks 97, 102 to 104, and 106, the flexible disk 100, the valve seat disk 101, the spring member 105, the sub-valve 107, and the disc spring 116 are provided within this cap chamber 146.

[0098] Within the cap chamber 146, a lower-chamber communicating volume chamber 149 (volume chamber) is formed, surrounded by the flexible disk 100, the valve seat disk 101, the disc spring 116, the disk 97, and the bottom 122 of the cap member 95. This lower-chamber communicating volume chamber 149 is constantly in communication with the communication passages 425 within the multiple holes 415 of the disc spring 116 and the communication passages 148 within the multiple passage holes 126 in the bottom 122 of the cap member 95.

[0099] An upper-chamber communicating volume chamber 147 (volume chamber) is formed within the cap chamber 146, surrounded by the cap member 95, the disc spring 116, the flexible disc 100, the valve seat disc 101, the discs 102 to 104 and 106, the spring member 105, and the sub-valve 107. Communication between the lower-chamber communicating volume chamber 149 and the upper-chamber communicating volume chamber 147 is blocked by the disc spring 116, the flexible disc 100, and the valve seat disc 101.

[0100] As shown in Fig. 2, the annular valve seat member 109 and the bottomed cylindrical cap member 95 are disposed in the lower chamber 23, which is one of the upper chamber 22 and the lower chamber 23. In this case, the valve seat portion 135 of the valve seat member 109 is disposed on the cap chamber 146 side, and the valve seat portion 139 is disposed on the lower chamber 23 side. As shown in Fig. 3, the communication passage 148 in the bottom portion 122 of the cap member 95 is constantly in communication with the lower chamber 23.

[0101] The upper chamber-communicating volume chamber 147 is constantly in communication with the upper chamber 22 shown in FIG. 2 via a passage between the cylindrical portion 124 of the cap member 95 and the sub-valve 107, a radial passage 222 in the passage groove 221 of the valve seat member 109, a passage in the large diameter hole portion 133 of the valve seat member 109, a piston rod passage portion 51 in the passage cutout portion 33 of the piston rod 25 and a passage in the large diameter hole portion 46 of the piston 21, a passage in the cutout portion 90 of the disk 82, and passages in the annular groove 55 of the piston 21 and the plurality of passage holes 38.

[0102] As the flexible disk 100 flexes in the axial direction, the volumes of the lower-chamber communicating volume chamber 149 and the upper-chamber communicating volume chamber 147 change. That is, as the flexible disk 100 flexes, the lower-chamber communicating volume chamber 149 and the upper-chamber communicating volume chamber 147 function as accumulators. The lower-chamber communicating volume chamber 149 decreases in volume to absorb the increase in the volume of the upper-chamber 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 upper-chamber communicating volume chamber 147, thereby allowing the oil liquid L to flow in from the lower chamber 23. Conversely, the upper-chamber communicating volume chamber 147 decreases in volume to absorb the increase in the volume of the lower-chamber 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 lower-chamber 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 disk 100 is prevented from being hindered by the oil liquid L in the upper chamber communication volume chamber 147 and the lower chamber communication volume chamber 149 .

[0103] The plurality of passage grooves 225 of the valve seat member 109 are provided facing the lower chamber 23, and the plurality of second passage portions 162 are constantly in communication with the lower chamber 23 via the passages in the plurality of passage grooves 225. As shown in Figure 3, the communication passage 425 formed in the disc spring 116 and the communication passage 148 formed in the bottom portion 122 of the cap member 95 are constantly in communication with the lower chamber 23, which is one of the upper chamber 22 and the lower chamber 23.

[0104] The radial passage 222 in the passage groove 221 that opens into the first passage portion 161 of the valve seat member 109 is constantly connected to the upper chamber communicating volume chamber 147, and constantly connects the upper chamber communicating volume chamber 147 with the passage in the large diameter hole portion 133 of the valve seat member 109 and the piston rod passage portion 51 in the passage cutout portion 33 of the piston rod 25.

[0105] As shown in FIG. 2 , the sub-valve 107 is disk-shaped and has an outer diameter equal to the outer diameter of the valve seat portion 135 of the valve seat member 109. The sub-valve 107 is constantly in contact with the inner seat portion 134 and is releasable from the valve seat portion 135. The sub-valve 107 seats on the entire valve seat portion 135 to close all of the second passage portions 162. The sub-valve 107 seats on the entire valve seat component 201 of one of the valve seat portions 135 to close the second passage portion 162 inside that valve seat component 201. The spring member 105 causes the sub-valve 107 to abut against the valve seat portion 135 of the valve seat member 109. The biasing force of the spring member 105 causes the sub-valve 107 to seat on the valve seat portion 135 and close the second passage portion 162.

[0106] The sub-valve 107, which is releasable from the valve seat 135, is provided in the cap chamber 146. When the sub-valve 107 is releasable from the valve seat 135 within the cap chamber 146, it connects the plurality of second passage portions 162 with the upper chamber communication chamber 147, thereby connecting the lower chamber 23 with the upper chamber 22. At this time, the sub-valve 107 suppresses the flow of hydraulic fluid L between the valve seat 135 and the sub-valve 107, generating a damping force. The sub-valve 107 is an inflow valve that opens when hydraulic fluid L flows from the lower chamber 23 to the upper chamber communication chamber 147 via the plurality of second passage portions 162, and is a check valve that restricts the outflow of hydraulic fluid L from the upper chamber communication chamber 147 to the lower chamber 23 via the second passage portions 162. Here, the passage hole 216 constituting the first passage portion 161 opens outside the range of the valve seat portion 135 in the valve seat member 109, and therefore is always in communication with the upper chamber communication volume chamber 147 regardless of the sub-valve 107 seated on the valve seat portion 135.

[0107] The passages in the plurality of passage grooves 225, the plurality of second passage portions 162, the passage between the sub-valve 107 and the valve seat portion 135 that appears when the valve is opened, the upper-chamber-communicating volume chamber 147, the radial passage 222 in the passage groove 221 of the valve seat member 109, the passage in the large-diameter hole portion 133 of the valve seat member 109, the piston rod passage portion 51 in the passage cutout portion 33 of the piston rod 25 and the passage in the large-diameter hole portion 46 of the piston 21, the passage in the cutout portion 90 of the disc 82, and the passages in the annular groove 55 of the piston 21 and the plurality of passage holes 38 constitute a second passage 172 through which oil liquid L flows from the lower chamber 23, which is on the upstream side within the cylinder 4, to the upper chamber 22, which is on the downstream side, as the piston 21 moves toward the lower chamber 23. The second passage 172 serves as a compression-side passage through which the oil L flows from the lower chamber 23, which is the upstream side, to the upper chamber 22, which is the downstream side, during the movement of the piston 21 toward the lower chamber 23, i.e., the compression stroke. The second compression-side passage 172 is provided separately from the first compression-side passage 72.

[0108] The communication passages 148, 425 and the lower-chamber-communicating volume chamber 149 constitute a third compression passage 511, which is always in communication with the lower chamber 23. The third compression passage 511 is provided separately from the second compression passage 172 and is arranged in parallel to the second compression passage 172.

[0109] The disk 104 is thicker and more rigid than the sub-valve 107. When the sub-valve 107 deforms, the disk 104 comes into contact with the sub-valve 107, suppressing further deformation of the sub-valve 107. When the flexible disk 100 deforms, the disk 104 comes into contact with the flexible disk 100, suppressing further deformation of the flexible disk 100. The sub-valve 107, the valve seat member 109 including the valve seat portion 135, the cap member 95, the communicating passage 148 formed in the cap member 95, the disc spring 116, the discs 97, 102 to 104, and 106 shown in FIG. 3, the flexible disc 100, the valve seat disc 101, and the spring member 105, all of which are provided on the piston rod 25, are provided in the second compression passage 172 shown in FIG. 2 and constitute a second compression damping force generating mechanism 173 that opens and closes the second passage 172, suppresses the flow of oil liquid L from the second passage 172 to the upper chamber 22, and generates a damping force.

[0110] The second damping force generating mechanism 173 is provided on the piston rod 25, and its valve seat portion 135 is provided on the valve seat member 109. The second damping force generating mechanism 173 is arranged separately from the first damping force generating mechanism 42, which generates damping force during the same compression stroke. The sub-valve 107 that constitutes the compression-side second damping force generating mechanism 173 is the compression-side sub-valve. The cap member 95 covers one end face of the second damping force generating mechanism 173 and the outer peripheral surface of the valve seat member 109. It is sufficient that the cap member 95 covers one end face of the second damping force generating mechanism 173 and at least a portion of the outer peripheral surface of the valve seat member 109.

[0111] 3, a communication passage 148 that connects the inside and outside of the cap member 95 is formed in the bottom portion 122 at one axial end of the cap member 95. The disc spring 116 is provided so that one axial end face thereof abuts on the outer circumferential side of the cap member 95 relative to the communication passage 148. The flexible disc 100 is provided so as to abut on the other axial end face of the disc spring 116.

[0112] 2 , in the second passage 172, when the second damping force generating mechanism 173 is in an open state, the passage within the cutout portion 90 of the disk 82 has the narrowest flow path cross-sectional area among the portions with fixed flow path cross-sectional area, and the flow path cross-sectional area is narrower than the upstream and downstream sides thereof, forming an orifice 175 in the second passage 172. The orifice 175 is disposed downstream of the sub-valve 107 in the flow of the oil liquid L when the sub-valve 107 is open and the oil liquid L flows in the second passage 172. Note that the orifice 175 may also be disposed upstream of the sub-valve 107 in the flow of the oil liquid L when the sub-valve 107 is open and the oil liquid L flows in the second passage 172. The orifice 175 is formed by cutting out a portion of the disk 82 that abuts against the piston 21 in the first damping force generating mechanism 41.

[0113] In the compression-side second damping force generating mechanism 173, no fixed orifice is formed in either the valve seat portion 135 or the sub-valve 107 abutting thereon, which communicates between the upper chamber 22 and the lower chamber 23, even when these are in an abutting state. In other words, when the valve seat portion 135 and the sub-valve 107 are in abutting state over the entire circumference, the compression-side second damping force generating mechanism 173 does not communicate between the upper chamber 22 and the lower chamber 23. In other words, the second passage 172 does not have a fixed orifice formed therein, which constantly communicates between the upper chamber 22 and the lower chamber 23, and is not a passage that constantly communicates between the upper chamber 22 and the lower chamber 23.

[0114] The second compression passage 172, which allows communication between the upper chamber 22 and the lower chamber 23, is arranged in parallel with the first passage 72, which is also a compression passage that allows communication between the upper chamber 22 and the lower chamber 23. The first damping force generating mechanism 42 is provided in the first passage 72, and the second damping force generating mechanism 173 is provided in the second passage 172. Therefore, the first damping force generating mechanism 42 and the second damping force generating mechanism 173, both of which are on the compression side, are arranged in parallel.

[0115] As shown in Figure 3, the sub-valve 110 is disk-shaped and has an outer diameter equal to the outer diameter of the valve seat portion 139 of the valve seat member 109. It is constantly in contact with the inner seat portion 138 and is able to seat on and separate from the valve seat portion 139. The sub-valve 110 seats on the entire valve seat portion 139, thereby closing all of the first passage portions 161. The sub-valve 110 also seats on the entire valve seat component 211 of one of the valve seat portions 139, thereby closing the first passage portion 161 inside that valve seat component 211. The sub-valve 110 can be a common component having the same shape as the sub-valve 107.

[0116] The disk 111 is a common part having the same shape as the disk 106. The outer diameter of the disk 111 is smaller than the outer diameter of the sub-valve 110 and smaller than the outer diameter of the inner seat portion 138.

[0117] The spring member 112 has a perforated circular flat plate-shaped base plate 341 that fits onto the mounting shaft 31, and multiple spring plate portions 342 that extend radially outward from the base plate portion 341 at equally spaced positions around the circumferential direction of the base plate portion 341. The outer diameter of the base plate portion 341 is larger than the outer diameter of the disk 111. The spring plate portions 342 are inclined relative to the base plate portion 341 so that they move away from the base plate portion 341 in the axial direction of the base plate portion 341 toward the extending tip end. The spring member 112 is attached to the mounting shaft 31 so that the spring plate portions 342 extend from the base plate portion 341 toward the sub-valve 110 in the axial direction of the base plate portion 341. The base plate portion 341 of the spring member 112 abuts against the disk 111, and the multiple spring plate portions 342 abut against the sub-valve 110. The spring member 112 causes the sub-valve 110 to abut against the valve seat portion 139 of the valve seat member 109. The sub-valve 110 is seated on the valve seat portion 139 by the biasing force of the spring member 112, and closes the first passage portion 161.

[0118] The sub-valve 110 is provided in the lower chamber 23, and when it leaves the valve seat 139, it connects the upper chamber 22 and the upper-chamber-communicating volume chamber 147 with the lower chamber 23. At this time, the sub-valve 110 suppresses the flow of hydraulic fluid L between the valve seat 139 and the sub-valve 110, generating a damping force. The sub-valve 110 is a discharge valve that opens when discharging hydraulic fluid L from the upper chamber 22 and the upper-chamber-communicating volume chamber 147 to the lower chamber 23 via the multiple first passage portions 161 of the valve seat member 109, and is a check valve that restricts the inflow of hydraulic fluid L from the lower chamber 23 into the upper chamber 22 and the upper-chamber-communicating volume chamber 147 via the first passage portions 161. As shown in FIG. 2, the passage hole 206 constituting the second passage portion 162 opens outside the range of the valve seat portion 139 of the valve seat member 109, and is therefore always in communication with the lower chamber 23 regardless of the sub-valve 110 seated on the valve seat portion 139.

[0119] The passages in the multiple passage holes 38 of the piston 21 and the annular groove 55, the passage in the cutout 90 of the disk 82, the piston rod passage portion 51 in the passage cutout 33 of the piston rod 25, the passage in the large diameter hole portion 46 of the piston 21 and the passage in the large diameter hole portion 133 of the valve seat member 109, the radial passage 222 in the passage groove 221 of the valve seat member 109, the multiple first passage portions 161 of the valve seat member 109, and the passage between the sub-valve 110 and the valve seat portion 139 that appears when the valve is opened constitute a second passage 182 through which the 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, when the piston 21 moves toward the upper chamber 22. The second passage 182 serves as an extension-side passage through which the 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.

[0120] The second extension passage 182, which can connect the upper chamber 22 and the lower chamber 23, is parallel to the first passage 92, which is also an extension passage which can connect the upper chamber 22 and the lower chamber 23, except for the passages within the annular groove 55 on the upper chamber 22 side and the multiple passage holes 38, and the parallel portions of the first passage 92 and the second passage 182 are provided separately from each other.

[0121] The upper chamber communication volume chamber 147, together with the passage between the cylindrical portion 124 of the cap member 95 and the sub-valve 107, constitutes a third extension passage 512. The third extension passage 512 branches off from the second extension passage 182 and is provided separately from the second extension passage 182.

[0122] The disk 113 has an outer diameter equal to that of the sub-valve 110. The disk 113 is thicker and more rigid than the sub-valve 110. The disk 113 abuts against the sub-valve 110 when the sub-valve 110 deforms, preventing further deformation of the sub-valve 110. The annular member 114 has an outer diameter smaller than that of the disk 113. The annular member 114 is a common part having the same shape as the annular member 69.

[0123] The sub-valve 110, the valve seat member 109 including the valve seat portion 139, the discs 111, 113, and the spring member 112, all of which are provided on the piston rod 25, are provided in the extension-side second passage 182 and constitute an extension-side second damping force generating mechanism 183 that opens and closes the second passage 182 to suppress the flow of hydraulic fluid L from the second passage 182 to the lower chamber 23 and generates a damping force. In other words, the second damping force generating mechanism 183 is provided on the piston rod 25, and its valve seat portion 139 is provided on the valve seat member 109. The second damping force generating mechanism 183 is arranged separately from the first damping force generating mechanism 41, which generates a damping force during the same extension stroke. The sub-valve 110 that constitutes the extension-side second damping force generating mechanism 183 is the extension-side sub-valve.

[0124] 3 , the flexible disk 100, the valve seat disk 101, the disc spring 116, the disk 97, the bottom portion 122 of the cap member 95, and the lower-chamber communicating volume chamber 149 constitute a lower-chamber volume variable mechanism 185 (volume variable mechanism) that can change the volume of the lower-chamber communicating volume chamber 149. The lower-chamber volume variable mechanism 185 is provided in the compression-side third passage 511 that includes the lower-chamber communicating volume chamber 149. The lower-chamber communicating volume chamber 149 is provided in parallel with the compression-side second passage 172, and the lower-chamber volume variable mechanism 185 changes the volume of this lower-chamber communicating volume chamber 149. The lower-chamber communicating volume chamber 149 is provided in the flow path between the flexible disk 100 and the sub-valve 110, via the lower chamber 23 and the communicating passages 148 and 425.

[0125] The lower chamber volume variable mechanism 185 changes the volume of the lower chamber communication volume chamber 149 so as to increase it by deforming and moving the flexible disk 100 and the valve seat disk 101 together so as to move away from the bottom 122. At that time, if the flexible disk 100 remains in contact with the disc spring 116 over the entire circumference, the space between the flexible disk 100 and the outer conical portion 403 of the disc spring 116 is blocked. In other words, if the flexible disk 100 remains in contact with the disc spring 116 over the entire circumference when deforming so as to move away from the bottom 122, the lower chamber communication volume chamber 149 and the upper chamber communication volume chamber 147 are kept blocked.

[0126] Furthermore, the lower chamber volume variable mechanism 185 changes the volume of the lower chamber communication volume chamber 149 by deforming and moving the flexible disk 100 and the valve seat disk 101 together so as to approach the bottom 122. At this time, the flexible disk 100 is maintained in a state in which the entire flexible disk 100 abuts against the disc spring 116, and the space between the flexible disk 100 and the outer conical portion 403 of the disc spring 116 is closed.

[0127] As shown in FIG. 2 , the third extension passage 512, which includes the upper-chamber communicating volume chamber 147 that communicates with the upper chamber 22, branches off from the second extension passage 182 and is provided separately from the second extension passage 182. As shown in FIG. 3 , the flexible disk 100, the valve seat disk 101, the disc spring 116, the disks 102 to 104, the spring member 105, the disk 106, the sub-valve 107, the cap member 95, and the upper-chamber communicating volume chamber 147 constitute an upper-chamber volume variable mechanism 186 (volume variable mechanism) that can change the volume of the upper-chamber communicating volume chamber 147. The upper-chamber volume variable mechanism 186 is provided in the third extension passage 512 that includes the upper-chamber communicating volume chamber 147. The upper-chamber communicating volume chamber 147 is provided in parallel with the second extension passage 182, and the upper-chamber volume variable mechanism 186 changes the volume of this upper-chamber communicating volume chamber 147. An upper chamber communicating volume chamber 147 is provided in the flow path between the flexible disk 100 and the sub-valve 107 .

[0128] The upper chamber volume variable mechanism 186 changes the volume of the upper chamber communicating volume chamber 147 so as to increase it by deforming and moving the flexible disk 100 and the valve seat disk 101 together so as to move away from the disk 104. At this time, if the valve seat disk 101 remains in contact with the flexible disk 100 as a whole, it closes the communication passage 505 in the communication hole 501 of the flexible disk 100. In other words, the lower chamber communicating volume chamber 149 and the upper chamber communicating volume chamber 147 are kept blocked.

[0129] Furthermore, the upper chamber volume variable mechanism 186 changes the volume of the upper chamber communication volume chamber 147 so as to reduce the volume thereof by deforming and moving the flexible disk 100 and the valve seat disk 101 so as to approach the disk 104. At this time, the valve seat disk 101 is maintained in a state in which the entirety of the disk 101 abuts against the flexible disk 100, and closes the communication passage 505 in the communication hole 501 of the flexible disk 100.

[0130] The flexible disk 100, valve seat disk 101, and disc spring 116 are shared by the lower chamber volume variable mechanism 185 and the upper chamber volume variable mechanism 186. The lower chamber volume variable mechanism 185, which includes the lower chamber communication volume chamber 149, and the upper chamber volume variable mechanism 186, which includes the upper chamber communication volume chamber 147, form an accumulator 190 that stores hydraulic oil as a working fluid. The accumulator 190 is provided on the piston rod 25. The accumulator 190 is disposed within the shock absorber 1 separately from the extension-side second damping force generating mechanism 183. The flexible disk 100 of the accumulator 190 deforms before the second damping force generating mechanism 183 opens during the extension stroke, and deforms before the second damping force generating mechanism 173 opens during the compression stroke.

[0131] In the second passage 182, when the second damping force generating mechanism 183 is in an open state, the passage within the notch 90 of the disk 82 has the narrowest flow path cross-sectional area among the portions with fixed flow path cross-sectional area, and the flow path cross-sectional area is narrower than that on the upstream and downstream sides, forming an orifice 175 in the second passage 182 as well. The orifice 175 is common to the second passages 172, 182. The orifice 175 is located upstream of the sub-valve 110 in the flow of the oil liquid L when the sub-valve 110 is open and the oil liquid L flows in the second passage 182. Note that the orifice 175 may also be located downstream of the sub-valve 110 in the flow of the oil liquid L when the sub-valve 110 is open and the oil liquid L flows in the second passage 182. The sub-valve 110 and the above-described sub-valve 107 open and close independently of each other.

[0132] In the extension-side second damping force generating mechanism 183, no fixed orifice is formed in either the valve seat portion 139 or the sub-valve 110 abutting thereon, which communicates between the upper chamber 22 and the lower chamber 23, even when these are in contact. In other words, the extension-side second damping force generating mechanism 183 does not communicate between the upper chamber 22 and the lower chamber 23 when the valve seat portion 139 and the sub-valve 110 are in contact over the entire circumference. In other words, the second passage 182 does not have a fixed orifice that constantly communicates between the upper chamber 22 and the lower chamber 23, and is not a passage that constantly communicates between the upper chamber 22 and the lower chamber 23. The annular member 114, together with the disc 113, abuts against the sub-valve 110 to restrict deformation of the sub-valve 110 in the opening direction beyond a specified limit.

[0133] In the shock absorber 1, the flow of oil liquid L passing in the axial direction at least within the range of the piston 21 allows communication between the upper chamber 22 and the lower chamber 23 only via the first damping force generating mechanisms 41, 42 and the second damping force generating mechanisms 173, 183. In the shock absorber 1, no fixed orifice that constantly communicates between the upper chamber 22 and the lower chamber 23 is provided in the passage for the oil liquid L.

[0134] As described above, the second passage 182 and the first passage 92 are parallel to each other except for the passages inside the annular groove 55 and the plurality of passage holes 38, and in the parallel portion, the first damping force generating mechanism 41 is provided in the first passage 92, and the second damping force generating mechanism 183 is provided in the second passage 182. Therefore, the first damping force generating mechanism 41 and the second damping force generating mechanism 183, both of which are on the extension side, are arranged in parallel to each other.

[0135] The second damping force generating mechanisms 173, 183 include a valve seat member 109, a sub-valve 110 provided on one side of a valve seat member passage portion 160, which is a portion of the second passages 172, 182 provided in the valve seat member 109, a sub-valve 107 provided on the other side of the valve seat member passage portion 160, and a bottomed, cylindrical cap member 95 provided between the piston 21 and the valve seat member 109 in the second passages 172, 182. The valve seat member 109 is provided within the cap member 95, the sub-valve 110 is provided on the lower chamber 23 side of the valve seat member 109, and the sub-valve 107 is provided within a cap chamber 146 between the bottom 122 of the cap member 95 and the valve seat member 109.

[0136] As described above, the upper chamber volume variable mechanism 186 changes the volume of the upper chamber communication volume chamber 147 so as to increase it by deforming and moving the flexible disc 100 away from the disc 104, but when the pressure difference between the upper chamber communication volume chamber 147 and the lower chamber communication volume chamber 149 exceeds a predetermined value with the second damping force generation mechanism 183 in an open state, the flexible disc 100 deforms at its outer periphery toward the bottom 122 while elastically deforming the outer conical portion 403 of the disc spring 116 toward the bottom 122, as shown in Figure 4. Then, the flexible disc 100 moves away from the valve seat disc 101 in the axial direction, connecting the upper chamber communication volume chamber 147 and the lower chamber communication volume chamber 149 via the communication passage 505 in the communication hole 501. The communication passage 505 in the communication hole 501 and the passage between the flexible disk 100 and the valve seat disk 101 constitute a fourth extension passage 521 that connects the upper-chamber communicating volume chamber 147 and the lower-chamber communicating volume chamber 149 during the extension stroke. The fourth passage 521 is provided separately from the third passage 512 that includes the upper-chamber communicating volume chamber 147, and is provided to communicate in series with the third passage 512 when open.

[0137] The flexible disc 100 and the valve seat disc 101 constitute an extension-side relief mechanism 522 that allows oil L to flow from the upper-chamber communication volume chamber 147 to the lower-chamber communication volume chamber 149 via the fourth passage 521, in other words, from the upper chamber 22 to the lower chamber 23. The relief mechanism 522 is provided in the upper-chamber volume variable mechanism 186, and is provided in the extension-side fourth passage 521. The relief mechanism 522 is set to open after the extension-side second damping force generation mechanism 183 opens.

[0138] The upper chamber volume variable mechanism 186 includes a flexible disk 100 that deforms before the second damping force generating mechanism 183 opens and has a communication hole 501 formed between the inner peripheral end and the outer peripheral end, which connects the upstream side and the downstream side, and a disc spring 116 that abuts against the end face of the flexible disk 100 and biases the flexible disk 100. The relief mechanism 522 is arranged to be able to open and close the communication hole 501 of the flexible disk 100 depending on the amount of deflection of the flexible disk 100.

[0139] The lower chamber volume variable mechanism 185 changes the volume of the lower chamber communication chamber 149 so as to increase it by deforming and moving the flexible disc 100 so as to approach the disc 104. However, when the pressure difference between the upper chamber communication chamber 147 and the lower chamber communication chamber 149 exceeds a predetermined value with the second damping force generating mechanism 173 open, the amount of deformation on the outer circumferential side of the flexible disc 100 increases, as shown in FIG. 5 . Then, the flexible disc 100 moves away from the disc spring 116 in the axial direction, thereby connecting the lower chamber communication chamber 149 and the upper chamber communication chamber 147 through the disc spring 116. In other words, the portion of the disc spring 116 that abuts against the end face of the flexible disc 100 moves at least partially away from the end face of the flexible disc 100 depending on the amount of deflection of the flexible disc 100. The passage between the flexible disk 100 and the disc spring 116 is a fourth passage 531 on the compression side that connects the lower chamber communicating volume chamber 149 and the upper chamber communicating volume chamber 147 during the compression stroke. The fourth passage 531 is provided separately from the third passage 511 that includes the lower chamber communicating volume chamber 149, and is provided to communicate in series with the third passage 511 when open.

[0140] The flexible disc 100 and the disc spring 116 constitute a compression-side relief mechanism 532 that allows oil L to flow from the lower-chamber communication volume chamber 149 to the upper-chamber communication volume chamber 147 via the fourth passage 531, in other words, from the lower chamber 23 to the upper chamber 22. The relief mechanism 532 is provided in the lower-chamber volume variable mechanism 185, and is provided in the compression-side fourth passage 531. The relief mechanism 532 is set to open after the compression-side second damping force generation mechanism 173 opens.

[0141] When assembled to the piston rod 25, the inner periphery of the main valve 71 is clamped between the discs 63 and 67, and the entire outer periphery of the main valve 71 abuts against the valve seat 50 of the piston 21. In this state, the inner periphery of the main valve 91 is clamped between the discs 83 and 87, and the entire outer periphery of the main valve 91 abuts against the valve seat 48 of the piston 21.

[0142] In this state, the inner circumferential side of the sub-valve 107 is clamped between the inner seat portion 134 of the valve seat member 109 and the disc 106, and the entire periphery of the sub-valve 107 abuts against the valve seat portion 135 of the valve seat member 109. In this state, the inner circumferential side of the sub-valve 110 is clamped between the inner seat portion 138 of the valve seat member 109 and the disc 111, and the entire periphery of the sub-valve 110 abuts against the valve seat portion 139 of the valve seat member 109.

[0143] 3, the inner circumferential side of the flexible disk 100 is clamped to the disks 97 and 102 together with the valve seat disk 101, and the outer circumferential side abuts against the outer conical portion 403 of the disc spring 116 along the entire circumference. At this time, the flexible disk 100 elastically deforms in a tapered manner so that the portion radially outward from the disk 97 moves away from the bottom 122 in the axial direction as it moves radially outward. At this time, the disc spring 116 abuts against the flexible disk 100 along the entire circumference while its outer conical portion 403 elastically deforms. In this state, the valve seat disk 101 also elastically deforms in a tapered manner, following the shape of the flexible disk 100, so that the portion radially outward from the disk 102 moves away from the bottom 122 in the axial direction as it moves radially outward.

[0144] 1, the valve body 10 is formed with fluid passages 251 and 252 that penetrate in the axial direction. The fluid passages 251, 252 allow communication 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.

[0145] When the piston rod 25 moves toward the compression side and the piston 21 moves in a direction narrowing the lower chamber 23, causing the pressure in the lower chamber 23 to exceed 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.

[0146] 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.

[0147] 2 , of the first damping force generating mechanism 41 and the second damping force generating mechanism 183, both of which are on the extension side, the main valve 91 of the first damping force generating mechanism 41 has greater rigidity and a higher valve opening pressure than the sub-valve 110 of the second damping force generating mechanism 183. Therefore, during the extension stroke, in the extremely low speed region where the piston speed, which is the axial movement speed of the piston 21, is slower than a predetermined value, the first damping force generating mechanism 41 remains closed while the second damping force generating mechanism 183 opens. Furthermore, in the normal speed region where the piston speed is equal to or greater than this predetermined value, both the first damping force generating mechanism 41 and the second damping force generating mechanism 183 open. The sub-valve 110 is an extremely low speed valve that opens and generates damping force in the extremely low piston speed region.

[0148] That is, during the extension stroke, as the piston 21 moves toward the upper chamber 22, the pressure in the upper chamber 22 increases and the pressure in the lower chamber 23 decreases. Then, although neither the first damping force generating mechanisms 41, 42 nor the second damping force generating mechanisms 173, 183 have a fixed orifice that constantly connects the upper chamber 22 and the lower chamber 23, the oil L in the upper chamber 22 flows into the upper-chamber-communicating volume chamber 147 via the passages in the multiple passage holes 38 and the annular groove 55 of the piston 21, the orifice 175, the passage in the large-diameter hole portion 46 of the piston 21, the piston rod passage portion 51 in the passage cutout portion 33 of the piston rod 25 and the passage in the large-diameter hole portion 133 of the valve seat member 109, the radial passage 222 in the passage groove 221 of the valve seat member 109, and the third passage 512. As a result, the pressure in the upper-chamber-communicating volume chamber 147 increases. Therefore, before the second damping force generating mechanism 183 opens, the portion of the flexible disc 100 that is radially inward of the position where the disc spring 116 abuts against the outer conical portion 403 bends toward the bottom portion 122, increasing the capacity of the upper chamber communication volume chamber 147. As a result, the upper chamber volume variable mechanism 186 suppresses an increase in pressure in the upper chamber communication volume chamber 147. At this time, the valve seat disc 101 deforms following the flexible disc 100, maintaining the fourth passage 521 in a closed state. Also, at this time, because the flexible disc 100 bends and moves toward the bottom portion 122, the lower chamber volume variable mechanism 185 reduces the volume of the lower chamber communication volume chamber 149.

[0149] During the extension stroke when the piston is subjected to low-frequency input (large-amplitude vibration), the amount of oil L flowing from the upper chamber 22 to the upper-chamber communication volume chamber 147 increases, causing the flexible disc 100 to deform significantly. As the amount of deformation of the flexible disc 100 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 upper-chamber communication volume chamber 147 to rise. As a result, the pressure in the second passage 182 rises to a state where the second damping force generating mechanism 183 opens.

[0150] At this time, because neither the first damping force generating mechanisms 41, 42 nor the second damping force generating mechanisms 173, 183 have a fixed orifice that constantly connects the upper chamber 22 and the lower chamber 23, the damping force rises abruptly during the extension stroke when the piston speed is less than the first predetermined value at which the second damping force generating mechanism 183 opens. Furthermore, in a region where the piston speed is higher than the first predetermined value and in an extremely low speed region that is higher than the first predetermined value but lower than a second predetermined value, the first damping force generating mechanism 41 remains closed and the second damping force generating mechanism 183 opens.

[0151] In other words, the sub-valve 110 is lifted off the valve seat 139, and the upper chamber 22 and the lower chamber 23 are connected via the extension-side second passage 182. As a result, the oil L in the upper chamber 22 flows into the lower chamber 23 via the passages in the multiple passage holes 38 and the annular groove 55 of the piston 21, the orifice 175, the passage in the large-diameter hole 46 of the piston 21, the piston rod passage 51 in the passage cutout 33 of the piston rod 25 and the passage in the large-diameter hole 133 of the valve seat member 109, the radial passage 222 in the passage groove 221 of the valve seat member 109, the first passage 161 in the valve seat member 109, and the passage between the sub-valve 110 and the valve seat 139. As a result, a damping force with a valve characteristic (a characteristic in which the damping force is approximately proportional to the piston speed) can be obtained even in an extremely low-speed region where the piston speed is lower than the second predetermined value.

[0152] Furthermore, during the extension stroke, in a normal speed range where the piston speed is equal to or greater than a second predetermined value and the frequency of the axial reciprocating movement of the piston rod 25, i.e., the piston frequency, which is the frequency of the axial reciprocating movement of the piston 21, is equal to or greater than a first frequency (first frequency), the relief mechanism 522 is provided, which opens after the second damping force generating mechanism 183 opens. Therefore, when the pressure in the upper chamber communication volume chamber 147 increases, the relief mechanism 522 of the upper chamber volume variable mechanism 186 opens the fourth passage 521 while the second damping force generating mechanism 183 remains open, as shown in FIG. 4 , to allow the hydraulic fluid L from the upper chamber communication volume chamber 147 to flow into the lower chamber 23. This limits the flow rate of hydraulic fluid L to the second damping force generating mechanism 183. In other words, the upper chamber volume variable mechanism 186 limits the flow rate of hydraulic fluid L to the second damping force generating mechanism 183 when the piston frequency is equal to or greater than the first frequency. Therefore, excessive load on the sub-valve 110 that constitutes the second damping force generating mechanism 183 is suppressed.

[0153] Thereafter, the first damping force generating mechanism 41 opens while the second damping force generating mechanism 183 and the relief mechanism 522 remain open. That is, as described above, the sub-valve 110 leaves the valve seat 139, causing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 through the second extension passage 182. Thereafter, while the second damping force generating mechanism 183 remains open, the relief mechanism 522 opens the fourth passage 521, causing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 through the fourth passage 521. At this time, the flow of the hydraulic fluid L is throttled by the orifice 175, which is provided downstream of the main valve 91 in the second passage 182, so that the pressure applied to the main valve 91 increases, increasing the pressure difference. As a result, the main valve 91 leaves the valve seat 48, causing the hydraulic fluid L to flow from the upper chamber 22 to the lower chamber 23 through the first extension passage 92. Therefore, the oil L in the upper chamber 22 flows into the lower chamber 23 through the passages in the plurality of passage holes 38 and the annular groove 55 and the passage between the main valve 91 and the valve seat portion 48 .

[0154] This allows the damping force to have valve characteristics (the damping force is approximately proportional to the piston speed) even in the normal speed region where the piston speed is equal to or greater than the second predetermined value. The rate of increase in the extension damping force relative to an increase in piston speed in the normal speed region is lower than the rate of increase in the extension damping force relative to an increase in piston speed in the extremely low speed region. In other words, the slope of the increase rate of the extension damping force relative to an increase in piston speed in the normal speed region can be made flatter than in the extremely low speed region.

[0155] As a result of the above, the second damping force generating mechanism 183 on the extension side generates a first axial resistance force (first resistance force) on the piston rod 25 from a piston frequency lower than the first frequency, and the upper chamber volume variable mechanism 186 limits the flow rate of oil liquid L to the second damping force generating mechanism 183 when the piston frequency becomes higher than this first frequency.

[0156] Then, during the extension stroke, when the piston frequency becomes equal to or higher than the first frequency and the upper chamber volume variable mechanism 186 restricts the flow rate of oil L to the second damping force generating mechanism 183, the resistance force generating mechanism 20 generates a second axial resistance force (second resistance force) on the piston rod 25.

[0157] Here, during the extension stroke, in a normal speed region where the piston speed is equal to or greater than the second predetermined value, the pressure difference between the upper chamber 22 and the lower chamber 23 is larger than in a low speed region where the piston speed is equal to or greater than the first predetermined value and less than the second predetermined value, but because the first passage 92 is not restricted by an orifice, opening the main valve 91 allows the oil L to flow at a large flow rate through the first passage 92. This, together with the fact that the second passage 182 is restricted by the orifice 175 and that the relief mechanism 522 opens the fourth passage 521 to allow the oil L in the upper-chamber-communicating volume chamber 147 to flow to the lower chamber 23, makes it possible to suppress deformation of the sub-valve 110.

[0158] Also, at this time, pressures in opposite directions are applied to the closed sub-valve 107 from the lower chamber 23 and the upper chamber communication volume chamber 147. Even if the pressure difference between the upper chamber 22 and the lower chamber 23 increases, the orifice 175 is formed upstream of the sub-valve 107 in the second passage 182, so the pressure increase in the upper chamber communication volume chamber 147 is gradual compared to the pressure increase in the upper chamber 22. This, together with the relief mechanism 522 opening the fourth passage 521 to allow the oil L in the upper chamber communication volume chamber 147 to flow to the lower chamber 23, prevents the pressure difference between the upper chamber communication volume chamber 147 and the lower chamber 23 from increasing. This prevents the pressure difference between the upper chamber communication volume chamber 147 and the lower chamber 23 that the closed sub-valve 107 receives from increasing, and prevents a large back pressure from being applied to the sub-valve 107 from the upper chamber communication volume chamber 147 toward the lower chamber 23.

[0159] In the shock absorber 1, a first passage 92 and a second passage 182 are provided in parallel to form a flow path for flowing the oil L from the upper chamber 22 to the lower chamber 23 during the extension stroke, and a main valve 91 and a sub-valve 110 are provided in parallel. In addition, an orifice 175 is connected in series with the sub-valve 110.

[0160] As described above, during the extension stroke, in the normal speed region where the piston speed is equal to or greater than the second predetermined value, the main valve 91 opens, allowing the hydraulic fluid L to flow at a large flow rate through the first passage 92. This reduces the flow rate through the passage between the sub-valve 110 and the valve seat 139. Therefore, for example, it is possible to lower the rate of increase in damping force with respect to an increase in piston speed in the normal speed region (equal to or greater than the second predetermined value). In other words, the slope of the rate of increase in the extension-side damping force with respect to an increase in piston speed in the normal speed region (equal to or greater than the second predetermined value) can be made flatter than in the extremely low speed region (less than the second predetermined value). This allows for greater design flexibility.

[0161] During the extension stroke when a high frequency input (small amplitude vibration) occurs in which a higher frequency than that during the low frequency input described above is input to the shock absorber 1, the amount of oil L flowing from the upper chamber 22 into the upper chamber communication volume chamber 147 is small. Therefore, deformation of the flexible disc 100 is small, and the upper chamber volume variable mechanism 186 can absorb the volume of oil L flowing into the upper chamber communication volume chamber 147 by the amount of deflection of the flexible disc 100, thereby reducing the pressure increase in the upper chamber communication volume chamber 147. Therefore, during the rise of the extremely low speed damping force, it is possible to achieve a state as if the flexible disc 100 were not present and the upper chamber communication volume chamber 147 were constantly in communication with the lower chamber 23 via the communication passage 425 of the disc spring 116 and the communication passage 148 of the cap member 95, i.e., a state identical to that of a structure without the second damping force generating mechanism 183.

[0162] Therefore, during the extension stroke when a high frequency is input, the rise of the extremely low-speed damping force is gradual compared to when a low frequency is input or compared to conventional damping force characteristics. In other words, when the frequency of the piston 21 exceeds a predetermined frequency during the extension stroke, the upper chamber volume variable mechanism 186 including the flexible disk 100 limits the flow rate of the oil L to the sub-valve 110 of the second damping force generating mechanism 183. Note that the change in damping force (the slope of the damping force relative to the piston speed) until the second damping force generating mechanism 183 opens can be adjusted by varying the rigidity (plate thickness, etc.) of the flexible disk 100.

[0163] Of the first damping force generating mechanism 42 and second damping force generating mechanism 173, both of which are on the compression side, the main valve 71 of the first damping force generating mechanism 42 has greater rigidity and a higher valve opening pressure than the sub-valve 107 of the second damping force generating mechanism 173. Therefore, during the compression stroke, when the piston speed is in the extremely low speed range where it is slower than a predetermined value, the first damping force generating mechanism 42 remains closed and the second damping force generating mechanism 173 opens, and when the piston speed is in the normal speed range where it is equal to or greater than this predetermined value, both the first damping force generating mechanism 42 and the second damping force generating mechanism 173 open. The sub-valve 107 is an extremely low speed valve that opens in the extremely low piston speed range to generate damping force.

[0164] That is, during the compression stroke, the piston 21 moves toward the lower chamber 23, increasing the pressure in the lower chamber 23 and decreasing the pressure in the upper chamber 22. Although neither the first damping force generating mechanisms 41, 42 nor the second damping force generating mechanisms 173, 183 have a fixed orifice that constantly connects the lower chamber 23 and the upper chamber 22, the oil L in the lower chamber 23 flows into the lower-chamber communicating volume chamber 149 via the communicating passage 148 in the cap member 95 and the communicating passage 425 in the disc spring 116. This increases the pressure in the lower-chamber communicating volume chamber 149. Therefore, before the second damping force generating mechanism 173 opens, the lower-chamber volume variable mechanism 185 bends the flexible disc 100 toward the disc 104, thereby increasing the capacity of the lower-chamber communicating volume chamber 149. This allows the lower-chamber volume variable mechanism 185 to suppress an increase in pressure in the lower-chamber communicating volume chamber 149. At this time, the valve seat disk 101 deforms following the flexible disk 100, maintaining the closed state of the fourth passage 521. Also, at this time, the flexible disk 100 bends and moves toward the disk 104, causing the upper chamber volume variable mechanism 186 to reduce the volume of the upper chamber communication volume chamber 147.

[0165] During the compression stroke of the shock absorber 1 when a low-frequency input (large-amplitude vibration) is applied, the amount of oil L flowing from the lower chamber 23 to the lower-chamber communication chamber 149 increases, causing the flexible disc 100 to deform significantly. As the amount of deformation of the flexible disc 100 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 lower-chamber communication chamber 149 to increase. As a result, the pressure in the second passage 172 increases to the point where the second damping force generating mechanism 173 opens.

[0166] At this time, because neither the first damping force generating mechanisms 41, 42 nor the second damping force generating mechanisms 173, 183 have a fixed orifice that constantly connects the lower chamber 23 and the upper chamber 22, the damping force rises abruptly during the compression stroke when the piston speed is less than the third predetermined value at which the second damping force generating mechanism 173 opens. Furthermore, in a region where the piston speed is higher than the third predetermined value but in an extremely low speed region that is higher than the third predetermined value but lower than a fourth predetermined value, the first damping force generating mechanism 42 remains closed and the second damping force generating mechanism 173 opens.

[0167] That is, the sub-valve 107 is lifted from the valve seat 135, and the lower chamber 23 and the upper chamber 22 are connected via the compression-side second passage 172. As a result, the oil L in the lower chamber 23 flows to the upper chamber 22 via the second passage portion 162 in the valve seat member 109, the passage between the sub-valve 107 and the valve seat 135, the upper-chamber communicating volume chamber 147, the radial passage 222 in the passage groove 221 in the valve seat member 109, the passage in the large-diameter hole portion 133 in the valve seat member 109, the piston rod passage portion 51 in the passage cutout 33 in the piston rod 25, the passage in the large-diameter hole 46 of the piston 21, the orifice 175, and the passages in the multiple passage holes 38 and the annular groove 55 in the piston 21. As a result, a damping force with a valve characteristic (a characteristic in which the damping force is approximately proportional to the piston speed) can be obtained even in an extremely low-speed region where the piston speed is lower than the fourth predetermined value.

[0168] Furthermore, during the compression stroke, in the normal speed region where the piston speed is equal to or greater than the fourth predetermined value and the piston frequency is equal to or greater than the second frequency (first frequency), the relief mechanism 532 is provided, which opens after the second damping force generating mechanism 173 opens. Therefore, when the pressure in the lower chamber communication volume chamber 149 increases, the relief mechanism 532 opens the fourth passage 531 while the second damping force generating mechanism 173 remains open, as shown in FIG. 5 , allowing the hydraulic fluid L from the lower chamber 23 and the lower chamber communication volume chamber 149 to flow to the upper chamber 22 via the upper chamber communication volume chamber 147. This limits the flow rate of hydraulic fluid L to the second damping force generating mechanism 173. In other words, the lower chamber volume variable mechanism 185 limits the flow rate of hydraulic fluid L to the second damping force generating mechanism 173 when the piston frequency is equal to or greater than the second frequency. This suppresses excessive load on the sub-valve 107 constituting the second damping force generating mechanism 173.

[0169] Thereafter, the first damping force generating mechanism 42 opens while the second damping force generating mechanism 173 and the relief mechanism 532 remain open. That is, as described above, the sub-valve 107 leaves the valve seat 135, causing the hydraulic oil L to flow from the lower chamber 23 to the upper chamber 22 through the compression-side second passage 172. Thereafter, while the second damping force generating mechanism 173 remains open, the relief mechanism 532 opens the fourth passage 531, causing the hydraulic oil L to flow from the lower chamber 23 to the upper chamber 22 through the fourth passage 531. At this time, the flow of the hydraulic oil L is throttled by the orifice 175, which is provided downstream of the sub-valve 107 and the relief mechanism 532 in the second passage 172, so that the pressure applied to the main valve 71 increases, increasing the pressure difference. As a result, the main valve 71 leaves the valve seat 50, causing the hydraulic oil L to flow from the lower chamber 23 to the upper chamber 22 through the compression-side first passage 72. Therefore, the oil L in the lower chamber 23 flows into the upper chamber 22 through the passages in the multiple passage holes 39 and the annular groove 56 and the passage between the main valve 71 and the valve seat portion 50 .

[0170] As a result, even in the normal speed region where the piston speed is equal to or greater than the fourth predetermined value, a damping force with valve characteristics (damping force being approximately proportional to piston speed) can be obtained. The rate of increase in compression damping force with respect to an increase in piston speed in the normal speed region is lower than the rate of increase in compression damping force with respect to an increase in piston speed in the extremely low speed region. In other words, the slope of the rate of increase in extension damping force with respect to an increase in piston speed in the normal speed region can be made flatter than in the extremely low speed region.

[0171] As a result of the above, the second damping force generating mechanism 173 on the compression side generates a third axial resistance force (first resistance force) on the piston rod 25 from a piston frequency lower than the second frequency, and the lower chamber volume variable mechanism 185 limits the flow rate of oil L to the second damping force generating mechanism 173 when the piston frequency becomes higher than this second frequency.

[0172] Then, during the compression stroke, when the piston frequency becomes equal to or higher than the second frequency and the lower chamber volume variable mechanism 185 restricts the flow rate of oil L to the second damping force generating mechanism 173, the resistance force generating mechanism 20 generates a fourth axial resistance force (second resistance force) on the piston rod 25.

[0173] During the compression stroke, in a normal speed region where the piston speed is equal to or greater than the fourth predetermined value, the pressure difference between the lower chamber 23 and the upper chamber 22 becomes larger than in a low speed region where the piston speed is equal to or greater than the third predetermined value and less than the fourth predetermined value, but because the first passage 72 is not restricted by an orifice, opening the main valve 71 allows the oil L to flow at a large flow rate through the first passage 72. This, combined with the fact that the second passage 172 is restricted by the orifice 175 and the relief mechanism 532 opens the fourth passage 531 to allow the oil L in the lower chamber 23 and the lower-chamber-communicating volume chamber 149 to flow to the upper-chamber-communicating volume chamber 147, makes it possible to suppress deformation of the sub-valve 107.

[0174] At this time, pressures in opposite directions are applied to the closed sub-valve 110 from the lower chamber 23 and the upper chamber communicating volume chamber 147. Even if the pressure difference between the lower chamber 23 and the upper chamber 22 increases, the pressure difference between the lower chamber 23 and the upper chamber communicating volume chamber 147 is prevented from increasing because the orifice 175 is formed in the second passage 172 downstream of the sub-valve 110, and the relief mechanism 532 opens the fourth passage 531 to allow the oil L in the lower chamber 23 and the lower chamber communicating volume chamber 149 to flow into the upper chamber communicating volume chamber 147. This prevents the pressure difference between the lower chamber 23 and the upper chamber communicating volume chamber 147 that the closed sub-valve 110 receives from increasing, and prevents a large back pressure from being applied to the sub-valve 110 from the lower chamber 23 toward the upper chamber communicating volume chamber 147.

[0175] In the shock absorber 1, a first passage 72 and a second passage 172 are provided in parallel to form a flow path for flowing oil L from the lower chamber 23 to the upper chamber 22 during the compression stroke, and the main valve 71 and the sub-valve 107 are provided in parallel. In addition, the orifice 175 is connected in series with the sub-valve 107.

[0176] As described above, during the compression stroke, when the piston speed is in the normal speed range equal to or greater than the fourth predetermined value, the main valve 71 opens, allowing the hydraulic fluid L to flow at a large flow rate through the first passage 72. This reduces the flow rate through the passage between the sub-valve 107 and the valve seat 135. Therefore, for example, it is possible to lower the rate of increase in the damping force relative to an increase in piston speed in the normal speed range (equal to or greater than the fourth predetermined value). In other words, the slope of the rate of increase in the compression damping force relative to an increase in piston speed in the normal speed range (equal to or greater than the fourth predetermined value) can be made flatter than in the extremely low speed range (less than the fourth predetermined value). This allows for greater design flexibility.

[0177] During the compression stroke when a high frequency input (small amplitude vibration) is input to the shock absorber 1 at a frequency higher than that during the low frequency input described above, the amount of oil L flowing from the lower chamber 23 into the lower chamber communication volume chamber 149 is small. Therefore, deformation of the flexible disc 100 is small. Therefore, deformation of the flexible disc 100 is small, and the lower chamber volume variable mechanism 185 can absorb the volume of oil L flowing into the lower chamber communication volume chamber 149 by the amount of deflection of the flexible disc 100, thereby reducing the pressure rise in the lower chamber communication volume chamber 149. Therefore, during the rise of the extremely low speed damping force, it is possible to achieve a state as if the flexible disc 100 were not present and the lower chamber communication volume chamber 149 were constantly connected to the upper chamber communication volume chamber 147, i.e., a state identical to that of a structure without the second damping force generating mechanism 173.

[0178] Therefore, during the compression stroke when a high frequency is input, the rise of the extremely low-speed damping force is gradual compared to when a low frequency is input or compared to conventional damping force characteristics. In other words, when the frequency of the piston 21 exceeds a predetermined frequency, the lower chamber volume variable mechanism 185 including the flexible disc 100 limits the flow rate of the oil L to the sub-valve 107 of the second damping force generating mechanism 173. Note that the change in damping force (the slope of the damping force relative to the piston speed) until the second damping force generating mechanism 173 opens can be adjusted by varying the rigidity (plate thickness, etc.) of the flexible disc 100.

[0179] Here, during the compression stroke, the damping force characteristics of the damping force generating mechanism 255 are also taken into account.

[0180] The reference example shown in the aforementioned Patent Document 1 discloses a shock absorber having two damping force generating mechanisms that open in the same stroke. These damping force generating mechanisms are configured so that one low-speed damping force generating mechanism generates a damping force with valve characteristics when the piston speed is slow and the piston frequency is low, while the other high-speed damping force generating mechanism generates a damping force with valve characteristics when the piston speed is faster and the piston frequency is higher than that of the low-speed damping force generating mechanism. This shock absorber has a variable volume mechanism that changes the damping force in response to the piston frequency, and the variable volume mechanism has a relief mechanism that limits the flow of air to the low-speed damping force generating mechanism to prevent excessive load on the low-speed damping force generating mechanism.

[0181] There is a demand for shock absorbers that improve the ride comfort of vehicles. For example, in the shock absorber of the reference example, as shown by the dashed line X in FIG. 6 , at the beginning of the start of movement when the piston frequency is low and the piston speed is low, the low-speed damping force generating mechanism generates a high damping force and generates a high rod axial force on the piston rod. This gives the vehicle a flat feeling when the shock absorber starts moving. Then, in the shock absorber of the reference example, as the piston frequency increases, the variable volume mechanism reduces the damping force generated by the low-speed damping force generating mechanism, thereby reducing the rod axial force of the piston rod and absorbing vibration. In the shock absorber of the reference example, as the piston frequency increases further, the relief mechanism provided in the variable volume mechanism opens, suppressing excessive load on the low-speed damping force generating mechanism. At this time, the rod axial force generated in the piston rod remains reduced.

[0182] The shock absorber 1 of this embodiment has a first passage 92 through which oil L flows from the upper chamber 22 on the upstream side to the lower chamber 23 on the downstream side as the piston 21 moves during the extension stroke, a first damping force generating mechanism 41 that is provided in the first passage 92 and generates a damping force, a second passage 182 that is provided separately from the first passage 92, and a second damping force generating mechanism 183 that is provided in the second passage 182 and generates a damping force. The shock absorber 1 also has an upper chamber volume variable mechanism 186 that changes the volume of the upper chamber communication volume chamber 147 that is provided in parallel with the second passage 182.

[0183] Then, in the shock absorber 1, during the extension stroke, when the piston frequency is lower than the first frequency, such as during an initial roll at the beginning of steering, a large amount of oil liquid L flows from the upper chamber 22 into the upper chamber communicating volume chamber 147 of the upper chamber volume variable mechanism 186 provided in parallel to the second passage 182, causing the upper chamber communicating volume chamber 147 to immediately expand. After that, the reaction force due to the support rigidity of the clamped inner peripheral side of the flexible disc 100 that forms the upper chamber communicating volume chamber 147 becomes large, restricting the amount of deformation and restricting the expansion of the volume of the upper chamber communicating volume chamber 147. As a result, the second damping force generating mechanism 183 provided in the second passage 182 opens and generates a damping force, i.e., a first resistance force. As a result, as shown by the solid line Y in Figure 6, at the beginning of the extension stroke, such as during an initial roll at the beginning of steering when the piston speed is low and the piston frequency is low, the second damping force generating mechanism 183 generates a high rod axial force in the piston rod 25, and similar to the shock absorber of the reference example shown by the dashed line X in Figure 6, the shock absorber 1 gives the vehicle a flat feeling when it starts to move.

[0184] Furthermore, in the shock absorber 1, when the piston frequency increases during the extension stroke, the upper chamber volume variable mechanism 186 introduces oil L from the upper chamber 22 into the upper chamber communication volume chamber 147 provided in parallel with the second passage 182, but the upper chamber communication volume chamber 147 does not expand until the volume expansion is limited, so it absorbs oil L from the upper chamber 22, thereby reducing the flow rate of oil L flowing through the second damping force generation mechanism 183 provided in the second passage 182, lowering the damping force by the second damping force generation mechanism 183 and reducing the rod axial force of the piston rod 25. As a result, similar to the shock absorber of the reference example, vibrations with a high piston frequency are absorbed.

[0185] In the shock absorber 1, when the piston frequency increases further during the extension stroke, the relief mechanism 522 provided in the upper chamber volume variable mechanism 186 opens. This allows the oil L to flow from the second passage 182 to the lower chamber 23 via the third passage 512, the fourth passage 521, and the upper chamber communication volume chamber 147, suppressing excessive load on the second damping force generating mechanism 183. At this time, without the resistance force generating mechanism 20, the rod axial force generated in the piston rod 25 would remain reduced, similar to the shock absorber of the reference example indicated by the dashed line X in Figure 6.

[0186] However, since the shock absorber 1 is provided with the resistance force generating mechanism 20, when the piston frequency becomes equal to or higher than the first frequency during the extension stroke, the resistance force generating mechanism 20 generates a second resistance force on the piston rod 25. In other words, when the piston frequency becomes equal to or higher than the first frequency, the resistance force generating mechanism 20 increases the rod axial force of the piston rod 25 as shown by the solid line Y in FIG. 6 due to the effect of a rubber dynamic spring. As a result, the ride comfort of the vehicle during the extension stroke improves. That is, if the piston frequency increases due to, for example, unevenness in the pavement while the rod axial force generated in the piston rod 25 remains low as shown by the dashed line X in FIG. 6, the ride comfort of the vehicle and the quality of the vehicle deteriorate. However, by having the resistance force generating mechanism 20 increase the rod axial force of the piston rod 25, it is possible to prevent the ride comfort and the quality of the vehicle from being reduced due to unevenness in the pavement.

[0187] The shock absorber 1 of this embodiment has a first passage 72 through which oil L flows from the lower chamber 23 on the upstream side to the upper chamber 22 on the downstream side as the piston 21 moves during the compression stroke, a first damping force generating mechanism 42 that is provided in the first passage 72 and generates a damping force, a second passage 172 that is provided separately from the first passage 72, and a second damping force generating mechanism 173 that is provided in the second passage 172 and generates a damping force. The shock absorber 1 also has a lower chamber volume variable mechanism 185 that changes the volume of a lower chamber communication volume chamber 149 that is provided in parallel with the second passage 172.

[0188] Then, in the shock absorber 1, during the compression stroke, when the piston frequency is lower than the second frequency, such as during an initial roll at the beginning of steering, a large amount of oil L flows from the lower chamber 23 into the lower chamber communication volume chamber 149 of the lower chamber volume variable mechanism 185 provided in parallel with the second passage 172, causing the lower chamber communication volume chamber 149 to immediately expand, and then the reaction force due to the support rigidity of the clamped inner peripheral side of the flexible disc 100 forming the lower chamber communication volume chamber 149 becomes large, restricting the amount of deformation and restricting the volume expansion of the lower chamber communication volume chamber 149, causing the second damping force generating mechanism 173 provided in the second passage 172 to open and generate a damping force, i.e., a third resistance force. As a result, in the shock absorber 1, during the initial start of movement of the compression stroke, such as during an initial roll at the beginning of steering when the piston speed is low and the piston frequency is low, the second damping force generating mechanism 173 generates a high rod axial force on the piston rod 25, and similar to the shock absorber of the reference example, a flat feeling is created when the shock absorber 1 starts moving.

[0189] Furthermore, in the shock absorber 1, when the piston frequency becomes high during the compression stroke, the lower chamber volume variable mechanism 185 introduces oil L from the lower chamber 23 into the lower chamber communication volume chamber 149 provided in parallel with the second passage 172, but the lower chamber communication volume chamber 149 does not expand until the volume expansion is limited, so it absorbs oil L from the lower chamber 23, thereby reducing the flow rate of oil L flowing through the second damping force generation mechanism 173 provided in the second passage 172, lowering the damping force by the second damping force generation mechanism 173 and reducing the rod axial force of the piston rod 25. As a result, similar to the shock absorber of the reference example, vibrations with a high piston frequency are absorbed.

[0190] In the shock absorber 1, when the piston frequency becomes higher during the compression stroke, the relief mechanism 532 provided in the lower chamber volume variable mechanism 185 opens. This causes oil L to flow from the third passage 511, the lower chamber communication volume chamber 149, and the fourth passage 531 to the upper chamber 22 via the second passage 172, thereby suppressing excessive load on the second damping force generation mechanism 173. At this time, without the resistance force generation mechanism 20, the rod axial force generated in the piston rod 25 would remain reduced, as in the shock absorber of the reference example.

[0191] However, since the shock absorber 1 is provided with the resistance force generating mechanism 20, when the piston frequency becomes equal to or higher than the second frequency during the compression stroke, the resistance force generating mechanism 20 generates a fourth resistance force on the piston rod 25. In other words, when the piston frequency becomes equal to or higher than the second frequency, the resistance force generating mechanism 20 increases the rod axial force of the piston rod 25 by using the effect of a rubber dynamic spring. As a result, the ride comfort of the vehicle during the compression stroke is improved. In other words, if the piston frequency increases due to, for example, unevenness in the pavement while the rod axial force generated in the piston rod 25 remains low, the ride comfort of the vehicle and the quality of the vehicle will decrease. However, by using the resistance force generating mechanism 20 to increase the rod axial force of the piston rod 25, it is possible to prevent the ride comfort and the quality of the vehicle from decreasing due to unevenness in the pavement.

[0192] According to the above aspects of the present invention, it is possible to provide a shock absorber that can improve ride comfort, and therefore the industrial applicability is great.

[0193] 1... shock absorber, 4... cylinder, 20... resistance force generating mechanism, 21... piston, 22... upper chamber (chamber), 23... lower chamber (chamber), 25... piston rod, 41, 42... first damping force generating mechanism, 72, 92... first passage, 147... upper chamber communicating volume chamber (volume chamber), 149... lower chamber communicating volume chamber (volume chamber), 172, 182... second passage, 173, 183... second damping force generating mechanism, 185... lower chamber volume variable mechanism (volume variable mechanism), 186... upper chamber volume variable mechanism (volume variable mechanism), L... oil (working fluid).

Claims

1. A cylinder in which a working fluid is sealed; a piston slidably provided within the cylinder and dividing the interior of the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder; a first passage through which the working fluid flows from the upstream chamber to the downstream chamber as the piston moves; a first damping force generating mechanism provided in the first passage and configured to generate a damping force; a second passage provided separately from the first passage; A shock absorber comprising: a second damping force generating mechanism provided in the second passage and generating a damping force; and a volume variable mechanism that changes the volume of a volumetric chamber provided in parallel with the second passage; wherein the second damping force generating mechanism generates a first resistance force from a piston frequency that is lower than a first frequency; and the volume variable mechanism limits the flow rate of the working fluid to the second damping force generating mechanism when the piston frequency becomes equal to or higher than the first frequency, and generates a second resistance force when the piston frequency becomes equal to or higher than the first frequency.

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