Buffer

Abstract

This shock absorber has: a cylinder in which a working fluid is sealed; a piston which is slidably fitted into the cylinder and partitions the inside of the cylinder into a first cylinder chamber and a second cylinder chamber; a first passage through which the working fluid flows out from one chamber inside the cylinder by means of a movement of the piston; a second passage provided in parallel to the first passage; valve mechanisms all of which act when the first cylinder chamber is at an upstream pressure and which are provided in the first passage and can adjust a damping force by means of the pressure of a main back pressure chamber; a frequency sensitive mechanism which is provided in the second passage and changes a volume by means of a movement of a movable member; check valves which are provided in the second passage, and all of which act when the second cylinder chamber is at the upstream pressure; and a first throttling mechanism which is provided downstream or upstream from the check valves and controls the flow of the working fluid toward the main back pressure chamber.

Description

Shock absorbers and damping force generating mechanisms

[0001] The present invention relates to a shock absorber and a damping force generating mechanism. This application claims priority to Japanese Patent Application No. 2022-189298, filed on November 28, 2022, the contents of which are incorporated herein by reference.

[0002] Some shock absorbers have a damping force generating mechanism that varies the damping force in response to frequency (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 2021-55850

[0004] In shock absorbers, it is required that the damping force generating mechanism operates smoothly.

[0005] Therefore, the present invention provides a shock absorber and a damping force generating mechanism that enable the damping force generating mechanism to operate smoothly.

[0006] A shock absorber according to a first aspect of the present invention includes a cylinder in which working fluid is sealed, a piston slidably fitted within the cylinder and dividing the interior of the cylinder into a first cylinder chamber and a second cylinder chamber, a first passage through which working fluid flows from one chamber within the cylinder as the piston moves, a second passage provided in parallel to the first passage, a valve mechanism provided in the first passage and capable of adjusting damping force according to the pressure in a main back pressure chamber, both of which act when the first cylinder chamber is at upstream pressure, a frequency sensitive mechanism provided in the second passage and which changes its volume with the movement of a movable member, a check valve provided in the second passage, both of which act when the second cylinder chamber is at upstream pressure, and a first throttle mechanism provided downstream or upstream of the check valve and which controls the flow of working fluid to the main back pressure chamber.

[0007] A damping force generating mechanism according to a second aspect of the present invention comprises a cylindrical, bottomed member that forms a back pressure chamber that generates a valve-closing force on a damping force generating member arranged on the opening side, a valve that is provided at the bottom of the member that defines a variable chamber on the opposite side to the back pressure chamber and blocks the flow of working fluid from the back pressure chamber to the variable chamber, and a regulating member that abuts the outer periphery of the valve and regulates the opening of the valve, and the valve has a first throttling portion that restricts the flow of working fluid from the variable chamber to the back pressure chamber.

[0008] According to the above-described aspect, it is possible to operate the damping force generating mechanism smoothly.

[0009] FIG. 1 is a cross-sectional view showing a shock absorber according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a damping force generating mechanism of the shock absorber according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view showing a configuration of a main part of the shock absorber according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view showing a configuration of a main part of the shock absorber according to the first embodiment of the present invention. FIG. 5 is a bottom view showing a pilot case of the shock absorber according to the first embodiment of the present invention. FIG. 6 is a hydraulic circuit diagram showing a configuration of a main part of the shock absorber according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view showing a configuration of a main part of the shock absorber according to the second embodiment of the present invention. FIG. 8 is a cross-sectional view showing a configuration of a main part of the shock absorber according to the third embodiment of the present invention. FIG. 9 is a bottom view showing a pilot case of the shock absorber according to the third embodiment of the present invention. FIG. 10 is a hydraulic circuit diagram showing a configuration of a main part of the shock absorber according to the third embodiment of the present invention. FIG. 11 is a cross-sectional view showing another application example of the configuration of the shock absorber according to the third embodiment of the present invention. FIG. 12 is a cross-sectional view showing a configuration of a main part of another application example of the configuration of the shock absorber according to the third embodiment of the present invention.

[0010] [First Embodiment] A shock absorber according to a first embodiment will be described below with reference to Figures 1 to 6. For ease of explanation, the upper side in Figures 1 to 4, 6 to 8, and 10 to 12 will be referred to as "upper," and the lower side in Figures 1 to 4, 6 to 8, and 10 to 12 will be referred to as "lower."

[0011] As shown in Figure 1, shock absorber 1 is a twin-cylinder hydraulic shock absorber. Shock absorber 1 is used in a vehicle suspension device. Shock absorber 1 has a cylinder 2 in which oil liquid L is sealed as a working fluid. Cylinder 2 has an inner cylinder 3 and an outer cylinder 4. Inner cylinder 3 is cylindrical. Outer cylinder 4 is cylindrical with a bottom. The inner diameter of outer cylinder 4 is larger than the outer diameter of inner cylinder 3. Inner cylinder 3 is disposed inside outer cylinder 4. The central axis of inner cylinder 3 and the central axis of outer cylinder 4 coincide. A reservoir chamber 6 is formed between inner cylinder 3 and outer cylinder 4.

[0012] The outer cylinder 4 has a body member 11 and a bottom member 12. The body member 11 is cylindrical. The bottom member 12 is cylindrical with a bottom. The bottom member 12 is fitted onto the lower side of the body member 11 and fixed to the body member 11 by welding. The bottom member 12 closes the lower part of the body member 11. A mounting eye 13 is fixed to the outside of the bottom member 12, opposite the body member 11 in the axial direction, by welding.

[0013] The shock absorber 1 is equipped with a piston 18. The piston 18 is slidably fitted within the inner tube 3 of the cylinder 2. The piston 18 divides the inner tube 3 into two chambers: an upper chamber 19 (first cylinder chamber) and a lower chamber 20 (second cylinder chamber). In the axial direction of the cylinder 2, the upper chamber 19 is located on the opposite side of the piston 18 from the bottom member 12. In the axial direction of the cylinder 2, the lower chamber 20 is located closer to the bottom member 12 than the piston 18. Oil L is sealed in the upper chamber 19 and the lower chamber 20 of the inner tube 3 as a working fluid. Oil L and gas G are sealed in a reservoir chamber 6 between the inner tube 3 and the outer tube 4 as a working fluid.

[0014] The shock absorber 1 is equipped with a piston rod 21. One axial end of the piston rod 21 is disposed within the inner tube 3 of the cylinder 2. This one end of the piston rod 21 is connected to the piston 18. The other axial end of the piston rod 21, opposite the one end, extends from the cylinder 2 to the outside of the cylinder 2. The piston 18 is fixed to the piston rod 21. Therefore, the piston 18 and the piston rod 21 move together. In the shock absorber 1, the stroke in which the piston rod 21 moves in a direction to increase the amount of protrusion from the cylinder 2 is the extension stroke, in which the overall length is extended. In the shock absorber 1, the stroke in which the piston rod 21 moves in a direction to decrease the amount of protrusion from the cylinder 2 is the compression stroke, in which the overall length is shortened. In the shock absorber 1, the piston 18 moves toward the upper chamber 19 during the extension stroke. In the shock absorber 1, the piston 18 moves toward the lower chamber 20 during the compression stroke.

[0015] A rod guide 22 is fitted to the upper end opening side of the inner cylinder 3, on the upper end opening side of the outer cylinder 4. A seal member 23 is fitted to the outer cylinder 4 above the rod guide 22. A disk 24 is fitted to the outer cylinder 4 above the seal member 23. Both the rod guide 22 and the seal member 23 are annular. The disk 24 is a circular flat plate with holes of a constant thickness. The disk 24 abuts against the outer peripheral portion of the seal member 23. The piston rod 21 slides axially relative to the rod guide 22 and the seal member 23. The piston rod 21 extends from inside the cylinder 2 to the outside of the cylinder 2 beyond the seal member 23.

[0016] The rod guide 22 restricts radial movement of the piston rod 21 relative to the inner cylinder 3 and outer cylinder 4 of the cylinder 2. The piston rod 21 is fitted into the rod guide 22, and the piston 18 is fitted into the inner cylinder 3. This causes the central axis of the piston rod 21 to coincide with the central axis of the cylinder 2. The rod guide 22 supports the piston rod 21 so that it can move in the axial direction of the piston rod 21. The outer periphery of the seal member 23 is in close contact with the outer periphery of the piston rod 21. The piston rod 21 moves in the axial direction of the seal member 23 relative to the seal member 23. The seal member 23 prevents the oil liquid L in the inner cylinder 3 and the high-pressure gas and oil liquid L in the reservoir chamber 6 from leaking to the outside.

[0017] The rod guide 22 has an outer periphery with a larger diameter at its upper part than at its lower part. The rod guide 22 fits into the inner periphery of the upper end of the inner cylinder 3 at its smaller diameter lower part. The rod guide 22 fits into the inner periphery of the upper part of the outer cylinder 4 at its larger diameter upper part. A base valve 25 is installed on the bottom member 12 of the outer cylinder 4. The base valve 25 is positioned radially relative to the outer cylinder 4. The base valve 25 separates the lower chamber 20 and the reservoir chamber 6. The inner periphery of the lower end of the inner cylinder 3 is fitted into the base valve 25. The upper end of the outer cylinder 4 is crimped radially inward of the outer cylinder 4. The seal member 23, together with the disk 24, is fixed to the cylinder 2 by being sandwiched between this crimped portion and the rod guide 22.

[0018] The piston rod 21 has a main shaft portion 27 and a mounting shaft portion 28. The outer diameter of the mounting shaft portion 28 is smaller than the outer diameter of the main shaft portion 27. The mounting shaft portion 28 is disposed within the cylinder 2. The piston 18 is attached to the mounting shaft portion 28 of the piston rod 21. The main shaft portion 27 of the piston rod 21 slides relative to the rod guide 22 and the seal member 23. The main shaft portion 27 has a shaft step portion 29. The shaft step portion 29 is provided at the end of the main shaft portion 27 on the mounting shaft portion 28 side. The shaft step portion 29 extends in a direction perpendicular to the central axis of the piston rod 21.

[0019] A passage groove 30 is formed on the outer periphery of the mounting shaft portion 28 of the piston rod 21. The passage groove 30 is formed by cutting out the outer periphery of the mounting shaft portion 28 along a plane parallel to the central axis of the mounting shaft portion 28. The passage groove 30 extends in the axial direction of the mounting shaft portion 28. A plurality of passage grooves 30, specifically two passage grooves 30, are formed at equal intervals in the circumferential direction of the mounting shaft portion 28. A male thread 31 is formed on the outer periphery of the mounting shaft portion 28 at an end on the opposite side of the main shaft portion 27 from the passage groove 30 in the axial direction of the mounting shaft portion 28.

[0020] The shock absorber 1 is connected to the vehicle body with, for example, the portion of the piston rod 21 that protrudes from the cylinder 2 located at the top. In this case, the shock absorber 1 is connected to the wheel side of the vehicle with the mounting eye 13 provided on the cylinder 2 side located at the bottom. If the shock absorber 1 is a single-cylinder type instead of a double-cylinder type, it may be connected to the vehicle body with the cylinder 2 side instead. In this case, the piston rod 21 of the shock absorber 1 is connected to the wheel side.

[0021] When a vehicle travels, the wheels vibrate relative to the vehicle body. This vibration causes the relative positions of the cylinder 2 and the piston rod 21 of the shock absorber 1 to change. This change is suppressed by the fluid resistance of the flow paths provided in the shock absorber 1. As will be explained below, the fluid resistance of the flow paths provided in the shock absorber 1 is designed to vary depending on the speed and amplitude of the vibration. The shock absorber 1 suppresses vibration, thereby improving the ride comfort of the vehicle.

[0022] Furthermore, in a vehicle, in addition to vibrations generated by the wheels relative to the vehicle body, inertial forces and centrifugal forces generated in the vehicle body as the vehicle travels also act between the cylinder 2 and the piston rod 21. For example, centrifugal forces are generated in the vehicle body when the direction of travel is changed by operating the steering wheel. Then, a force based on this centrifugal force acts between the cylinder 2 and the piston rod 21. As will be explained below, the shock absorber 1 has good characteristics against vibrations based on forces generated in the vehicle body as the vehicle travels. The shock absorber 1 provides the vehicle with high driving stability.

[0023] The shock absorber 1 has a damping force generating mechanism 33. The damping force generating mechanism 33 includes the piston 18 and has a configuration shown in FIG.

[0024] The piston 18 has a piston body 35 and a sliding member 36. The piston body 35 is made of metal and has an annular shape. The piston 18 has the piston body 35 fitted onto the mounting shaft portion 28 of the piston rod 21. The sliding member 36 is made of synthetic resin and has an annular shape. The sliding member 36 is integrally attached to the outer circumferential surface of the piston body 35. The piston 18 slides relative to the inner cylinder 3 with the sliding member 36 in contact with the inner cylinder 3.

[0025] The piston body 35 is provided with a passage hole 37, a passage groove 38, a passage hole 39, and a passage groove 40. The passage hole 37 penetrates the piston body 35 in the axial direction of the piston body 35. A plurality of passage holes 37 are formed in the piston body 35 at intervals in the circumferential direction of the piston body 35. The passage hole 39 penetrates the piston body 35 in the axial direction of the piston body 35. A plurality of passage holes 39 are formed in the piston body 35 at intervals in the circumferential direction of the piston body 35. The piston body 35 is formed with one passage hole 37 and one passage hole 39 alternately at equal pitches in the circumferential direction of the piston body 35.

[0026] The passage groove 38 is formed in the piston body 35 in an annular shape in the circumferential direction of the piston body 35. The passage groove 38 is formed at the end of the piston body 35 facing the lower chamber 20 in the axial direction. All of the passage holes 37 open to the passage groove 38 at their axial ends. The passage groove 40 is formed in the piston body 35 in an annular shape in the circumferential direction of the piston body 35. The passage groove 40 is formed at the end of the piston body 35 facing the upper chamber 19, opposite the passage groove 38 in the axial direction. All of the passage holes 39 open to the passage groove 40 at their axial ends opposite the passage groove 38 in the axial direction of the piston body 35. The ends of the multiple passage holes 37 opposite the passage groove 38 in the axial direction of the piston body 35 open outward from the passage groove 40 in the radial direction of the piston body 35. The ends of the plurality of passage holes 39 opposite the passage groove 40 in the axial direction of the piston body 35 open outward from the passage groove 38 in the radial direction of the piston body 35. In the piston 18, the insides of the plurality of passage holes 37 and the passage groove 38 form piston-side passages 43. In the piston 18, the insides of the plurality of passage holes 39 and the passage groove 40 form piston-side passages 44.

[0027] The damping force generating mechanism 33 has a first valve mechanism 41 (valve mechanism) provided in the piston-side passage 43. The first valve mechanism 41 opens and closes the piston-side passage 43 to generate a damping force. The first valve mechanism 41 is disposed on the lower chamber 20 side in the axial direction of the piston 18. As a result, during an extension stroke, as the piston 18 moves in one direction, toward the upper chamber 19, the piston-side passage 43 allows hydraulic fluid L to flow from one upper chamber 19 to the other lower chamber 20 via the open first valve mechanism 41. The first valve mechanism 41 suppresses the flow of hydraulic fluid L from the piston-side passage 43 to the lower chamber 20, which occurs at this time, thereby generating a damping force.

[0028] The damping force generating mechanism 33 has a first valve mechanism 42 provided in the piston-side passage 44. The first valve mechanism 42 opens and closes the piston-side passage 44 to generate a damping force. The first valve mechanism 42 is located on the upper chamber 19 side in the axial direction of the piston 18. As a result, during the compression stroke, as the piston 18 moves toward the lower chamber 20, the piston-side passage 44 allows hydraulic oil L to flow from the lower chamber 20 to the upper chamber 19 via the open first valve mechanism 42. The first valve mechanism 42 suppresses the flow of hydraulic oil L from the piston-side passage 44 to the upper chamber 19, which occurs at this time, thereby generating a damping force.

[0029] The piston body 35 is a disk-shaped body with holes, and the mounting shaft portion 28 of the piston rod 21 is fitted into the inner periphery thereof.

[0030] The piston body 35 has a body portion 50, an inner seat portion 51, a valve seat portion 53, an inner seat portion 55, and a valve seat portion 57. The body portion 50 is provided in the middle portion of the piston body 35 in the axial direction. The inner seat portion 51 and the valve seat portion 53 are provided at the end portion of the piston body 35 on the lower chamber 20 side in the axial direction. The inner seat portion 55 and the valve seat portion 57 are provided at the end portion of the piston body 35 on the upper chamber 19 side in the axial direction.

[0031] The inner seat portion 51 is annular and is provided on the inner peripheral side of the main body portion 50, and protrudes from the main body portion 50 toward the lower chamber 20 in the axial direction of the piston body 35.

[0032] The valve seat portion 53 is annular. The valve seat portion 53 is located radially outward of the inner seat portion 51 of the piston body 35. The valve seat portion 53 protrudes from the body portion 50 toward the lower chamber 20 in the axial direction of the piston body 35. The tip end surface of the protruding side of the valve seat portion 53 is higher in the protruding direction in the axial direction of the piston body 35 than the tip end surface of the protruding side of the inner seat portion 51. The valve seat portion 53 is located radially outward of the opening of the passage groove 38 on the lower chamber 20 side of the piston body 35. The valve seat portion 53 constitutes a part of the first valve mechanism 41.

[0033] The inner seat portion 55 is annular and is provided on the inner peripheral side of the main body portion 50, and protrudes from the main body portion 50 toward the upper chamber 19 in the axial direction of the piston body 35.

[0034] The valve seat portion 57 is annular. The valve seat portion 57 is located radially outward of the inner seat portion 55 of the piston body 35. The valve seat portion 57 protrudes from the body portion 50 toward the upper chamber 19 in the axial direction of the piston body 35. The tip end surface of the protruding side of the valve seat portion 57 is higher in the protruding direction in the axial direction of the piston body 35 than the tip end surface of the protruding side of the inner seat portion 55. The valve seat portion 57 is located radially outward of the opening of the passage groove 40 on the upper chamber 19 side of the piston body 35. The valve seat portion 57 constitutes a part of the first valve mechanism 42.

[0035] As shown in Figure 3, the damping force generating mechanism 33 has, on the inner seat portion 51 side in the axial direction of the piston 18, in order from the inner seat portion 51 side in the axial direction of the piston 18, one disc 70, one disc 71, one first damping valve 72 (damping force generating member), one disc 73, multiple discs, specifically four discs 74, multiple discs, specifically three discs 75, one disc 76, one disc 77, one regulating disc 78 (regulating member), one disc 79, one pilot case 81 (biasing force generating member), a second damping valve 84 consisting of multiple discs, specifically three discs 83, one disc 85, one disc 86, and one annular member 87.

[0036] The damping force generating mechanism 33 also has one disk 91 and one disk 92 between the regulating disk 78 and the pilot case 81. The disks 91 and 92 are arranged to surround the disk 79 on the radially outer side of the disk 79. Of the disks 91 and 92, the disk 91 is provided on the regulating disk 78 side, and the disk 92 is provided on the opposite side to the regulating disk 78.

[0037] The disks 70, 71, 73 to 77, 79, 83, 85, 86, 91, and 92, the regulating disk 78, the pilot case 81, and the annular member 87 are all made of metal. The disks 70, 71, 73 to 77, 79, 83, 85, 86, 91, and 92, and the annular member 87 are all circular flat plates with holes and a constant thickness. The disks 70, 71, 73 to 77, 79, 83, 85, 86, 91, and 92 are formed by press molding. The first damping valve 72, the regulating disk 78, and the pilot case 81 are all annular. The mounting shaft portion 28 of the piston rod 21 is fitted inside the disks 70, 71, 73 to 77, 79, 83, 85, and 86, the first damping valve 72, the regulating disk 78, the pilot case 81, and the annular member 87.

[0038] The piston 18 , discs 70 , 71 , 73 to 77 , 79 , 83 , first damping valve 72 , restricting disc 78 and pilot case 81 cover the passage groove 30 of the piston rod 21 , and form a pilot chamber 95 within the passage groove 30 .

[0039] The pilot case 81 is cylindrical and has a bottom. The pilot case 81 is formed seamlessly as a single piece by sintering. The pilot case 81 has a bottom portion 101 and a cylindrical portion 102.

[0040] The bottom portion 101 is a perforated disk-like plate, and the mounting shaft portion 28 of the piston rod 21 is fitted into the inner periphery of the bottom portion 101. The tubular portion 102 is cylindrical, and extends from the outer periphery of the bottom portion 101 to one side along the axial direction of the bottom portion 101. The pilot case 81 has an opening 103 on the side of the tubular portion 102 opposite the bottom portion 101 in the axial direction. In other words, the pilot case 81 is a bottomed tubular portion having the opening 103 at one end in the axial direction.

[0041] The bottom portion 101 has a bottom body portion 111 , an inner seat portion 112 , a valve seat portion 113 , an outer seat portion 114 , an inner seat portion 115 , and an outer seat portion 116 .

[0042] The bottom body 111 is a disk-shaped member with holes, and the mounting shaft 28 of the piston rod 21 is fitted to its inner circumferential side. As shown in Fig. 4, the bottom body 111 is formed with a passage hole 121 that passes through the bottom body 111 in the axial direction of the bottom body 111. As shown in Fig. 5, the bottom body 111 is provided with a plurality of passage holes 121, specifically four passage holes 121, spaced equally apart in the circumferential direction of the bottom body 111.

[0043] 3 and 4, the inner seat portion 112 is formed on the inner peripheral side of the bottom main body portion 111. The inner seat portion 112 is annular. The inner seat portion 112 protrudes from the bottom main body portion 111 on the same side as the tubular portion 102 in the axial direction of the bottom main body portion 111. A passage groove 124 is formed in the inner seat portion 112, penetrating the inner seat portion 112 in the radial direction of the inner seat portion 112.

[0044] The valve seat portion 113 is formed contiguous with the inner seat portion 112 and radially outward of the bottom main body portion 111. The valve seat portion 113 is annular. The valve seat portion 113 protrudes from the bottom main body portion 111 on the same side as the inner seat portion 112 in the axial direction of the bottom main body portion 111. In the axial direction of the pilot case 81, the height of the tip surface of the protruding side of the valve seat portion 113 is lower than the height of the tip surface of the protruding side of the inner seat portion 112 and is equal to the height of the groove bottom surface of the passage groove 124.

[0045] The outer seat portion 114 is formed contiguous with the cylindrical portion 102 and radially inward of the bottom main body portion 111. The outer seat portion 114 is formed radially outward of the valve seat portion 113 and separated from the valve seat portion 113. The outer seat portion 114 has an annular shape. The outer seat portion 114 protrudes from the bottom main body portion 111 on the same side as the inner seat portion 112 and the valve seat portion 113 in the axial direction of the bottom main body portion 111. In the axial direction of the pilot case 81, the height of the tip surface of the protruding side of the outer seat portion 114 is slightly lower than the height of the tip surface of the protruding side of the valve seat portion 113.

[0046] The bottom portion 101 is formed with an annular recess 125, which is recessed from the axial side of the cylindrical portion 102 toward the opposite side of the cylindrical portion 102, by the bottom main body portion 111, the valve seat portion 113, and the outer seat portion 114. The annular recess 125 has a circular ring shape extending in the circumferential direction of the bottom portion 101. The annular recess 125 is recessed from the protruding end surface of the valve seat portion 113 and the protruding end surface of the outer seat portion 114 toward the opposite side of the cylindrical portion 102 along the axial direction of the pilot case 81. The bottom surface of the annular recess 125 is formed by the bottom main body portion 111. The passage hole 121 is formed between the valve seat portion 113 and the outer seat portion 114 in the radial direction of the bottom main body portion 111 and opens to the bottom surface of the annular recess 125.

[0047] The inner seat portion 115 is formed on the inner circumferential side of the bottom main body portion 111. The inner seat portion 115 is annular. The inner seat portion 115 protrudes from the inner circumferential side of the bottom main body portion 111 to the opposite side from the inner seat portion 112 in the axial direction of the bottom main body portion 111. As shown in FIG. 3, the inner seat portion 115 is formed with a passage groove 132 that penetrates the inner seat portion 115 in the radial direction of the inner seat portion 115. As shown in FIG. 5, the inner seat portion 115 is provided with a plurality of passage grooves 132, specifically, four passage grooves 132, at equal intervals in the circumferential direction of the inner seat portion 115.

[0048] The outer sheet portion 116 is formed radially outward of the inner sheet portion 115 in the bottom body portion 111. As shown in FIG. 3 , the outer sheet portion 116 protrudes radially outward of the inner sheet portion 115 from the bottom body portion 111 in the axial direction of the bottom body portion 111 on the same side as the inner sheet portion 115. As shown in FIG. 5 , the outer sheet portion 116 is a non-circular, petal-shaped irregular sheet. The outer sheet portion 116 has multiple, specifically, four, sheet constituent portions 133. These sheet constituent portions 133 have the same shape and are arranged at equal intervals in the circumferential direction of the pilot case 81. The multiple sheet constituent portions 133 extend radially from the inner sheet portion 115. As shown in FIG. 3 , the position of the tip surface of the multiple sheet constituent portions 133 on the side opposite the bottom body portion 111 in the axial direction of the pilot case 81 is equivalent to the position of the tip surface of the inner sheet portion 115 on the side opposite the bottom body portion 111.

[0049] A passage recess 134 is formed inside each seat constituent portion 133. As shown in FIG. 5, the passage recess 134 is formed by being surrounded by a portion of the inner seat portion 115 and the seat constituent portion 133. As shown in FIG. 3, the passage recess 134 is recessed along the axial direction of the pilot case 81 from the tip end surface on the protruding side of the inner seat portion 115 and the tip end surface on the protruding side of the seat constituent portion 133. The bottom surface of the passage recess 134 is formed by the bottom main body portion 111. As shown in FIG. 5, the passage recess 134 is formed inside all of the seat constituent portions 133. In the circumferential direction of the pilot case 81, each of the passage recesses 134 and the passage groove 132 of the inner seat portion 115 are aligned in phase. The passage grooves 132 are provided in the inner seat portion 115 so as to open to the inside of each of the passage recesses 134.

[0050] The passage hole 121 is disposed between adjacent seat constituent portions 133 in the circumferential direction of the pilot case 81. Therefore, the passage hole 121 is disposed outside the outer seat portion 116. The pilot case 81 has four portions between adjacent seat constituent portions 133 in the circumferential direction, and a passage hole 121 is provided in each of these four portions.

[0051] The disk 70 shown in Figures 3 and 4 has a constant outer diameter around its entire circumference. The disk 70 has an outer diameter larger than the outer diameter of the inner seat portion 51 of the piston 18. A notch 141 is formed in the disk 70. The notch 141 extends radially outward from the inner peripheral edge of the disk 70 that fits onto the mounting shaft portion 28. The notch 141 penetrates the disk 70 in the axial direction of the disk 70. The notch 141 in the disk 70, together with the piston 18 and the disk 71, forms an introduction orifice 142.

[0052] The disk 71 has a constant outer diameter over its entire circumference, and a constant inner diameter over its entire circumference as well. The disk 71 has an outer diameter smaller than the outer diameter of the disk 70. The disk 71 is located inside the outer end position of the notch 141 in the radial direction of the disk 70, and the introduction orifice 142 is formed together with the notch 141.

[0053] The first damping valve 72 comprises a disc 151 and a seal member 152. The disc 151 is made of metal and is a circular flat plate with holes and a constant thickness. The disc 151 is formed by press molding. The outer diameter of the disc 151 is constant over the entire circumference, and the inner diameter is also constant over the entire circumference. The outer diameter of the disc 151 is larger than the outer diameter of the valve seat portion 53 of the piston 18. The mounting shaft portion 28 of the piston rod 21 is fitted onto the inner peripheral side of the disc 151. In the first damping valve 72, the disc 151 abuts against the valve seat portion 53.

[0054] The passage within the inlet orifice 142 of the disk 70 is in constant communication with the piston-side passage 43 and the pilot chamber 95 .

[0055] The first damping valve 72 opens and closes the opening of the piston-side passage 43 formed in the piston 18 on the side of the lower chamber 20 as the disk 151 moves away from and comes into contact with the valve seat portion 53 (see FIG. 3).

[0056] The seal member 152 is made of an elastic material with sealing properties, specifically rubber. The seal member 152 has an annular shape. The seal member 152 is fixed to the outer periphery of the disk 151. The seal member 152 is fitted over the entire circumference onto the inner circumferential surface of the cylindrical portion 102 of the pilot case 81 on the opening 103 side. The seal member 152 is axially slidable relative to the inner circumferential surface of the cylindrical portion 102. The seal member 152 constantly seals the gap between the first damping valve 72 and the cylindrical portion 102. The first damping valve 72 is arranged in the opening 103 of the pilot case 81.

[0057] The outer diameter of the disk 73 is constant over the entire circumference, and the inner diameter is also constant over the entire circumference. The outer diameter of the disk 73 is smaller than the minimum inner diameter of the seal member 152. The outer diameter of the disk 73 is equal to the outer diameter of the disk 70.

[0058] The outer diameter of the disk 74 is constant over the entire circumference, and the inner diameter is also constant over the entire circumference. The outer diameter of the disk 74 is smaller than the outer diameter of the disk 73. The outer diameter of the disk 74 is equal to the outer diameter of the disk 71.

[0059] The outer diameter of the disk 75 is constant over the entire circumference, and the inner diameter is also constant over the entire circumference. The outer diameter of the disk 75 is larger than the outer diameter of the disk 73 and larger than the outer diameter of the disk 74.

[0060] The disk 76 has a constant outer diameter over its entire circumference, and a constant inner diameter over its entire circumference. The outer diameter of the disk 76 is larger than the outer diameter of the disk 75.

[0061] The inner diameter of the disk 77 is constant around the entire circumference. The outer diameter of the disk 77 is equal to the outer diameter of the disk 76. A notch 155 is formed in the disk 77. The notch 155 extends radially inward from the outer peripheral edge of the disk 77. The notch 155 penetrates the disk 77 in the axial direction of the disk 77. The radially inner portion of the notch 155 is arc-shaped and extends long in the circumferential direction of the disk 77, and the radially inner portion of the disk 77 is longer in the circumferential direction of the disk 77 than the radially outer portion of the disk 77. A plurality of notches 155 are formed in the disk 77 at equal intervals around the circumference of the disk 77.

[0062] The regulating disk 78 has a disk 161 on the disk 77 side in the axial direction of the regulating disk 78 and a disk 162 on the opposite side to the disk 77. The disks 161 and 162 are both made of metal and are circular flat plates with holes and a fixed thickness. The disks 161 and 162 are both formed by press molding.

[0063] The disk 161 has a constant outer diameter around its entire circumference, and its inner diameter is also constant around its entire circumference. The disk 161 has an outer diameter larger than the outer diameters of the disks 76 and 77 and smaller than the inner diameter of the cylindrical portion 102 of the pilot case 81. The mounting shaft portion 28 of the piston rod 21 is fitted to the inner periphery of the disk 161. The disk 161 has a through hole 165 that penetrates the disk 161 in the axial direction of the disk 161. The through hole 165 has an arc shape that extends long in the circumferential direction of the disk 161. The through hole 165 aligns the radial position of the disks 77 and 161 with the radially inner portion of the notch 155 of the disk 77 that has an arc shape that extends long in the circumferential direction of the disk 77. The disk 161 has a plurality of through holes 165 that are equally spaced around the circumference of the disk 161. The passage in the through hole 165 communicates with the passage in the notch 155 of the disk 77. The notch 155 of the disk 77 and the through hole 165 of the disk 161 form a communication orifice 166 (second throttle mechanism).

[0064] The disk 162 has a constant outer diameter over its entire circumference, and its inner diameter is also constant over its entire circumference. The outer diameter of the disk 162 is slightly larger than the outer diameter of the disk 161 and smaller than the inner diameter of the cylindrical portion 102 of the pilot case 81. The inner diameter of the disk 162 is larger than the inner diameter of the disk 161 and is larger than the outer diameter of the valve seat portion 113 of the pilot case 81. The disk 162 is arranged coaxially with the disk 161 and is arranged radially outward of the through hole 165 of the disk 161. The disk 162 is integrated with the disk 161 by being ring-welded to the disk 161.

[0065] The disk 79 has a constant outer diameter over its entire circumference, and a constant inner diameter over its entire circumference as well. The outer diameter of the disk 79 is smaller than the inner diameter of the disk 162 of the regulating disk 78. The disk 79 is disposed radially inward of the through-hole 165 of the regulating disk 78. The disk 79 has an outer diameter equal to the outer diameter of the inner seat portion 112 of the pilot case 81.

[0066] The disk 83 has a constant outer diameter over its entire circumference, and a constant inner diameter over its entire circumference as well. The outer diameter of the disk 83 is equal to the outer diameter of the outer seat portion 116 of the pilot case 81.

[0067] The disk 85 has a constant outer diameter over its entire circumference, and a constant inner diameter over its entire circumference. The outer diameter of the disk 85 is smaller than the outer diameter of the disk 83.

[0068] The disk 86 has a constant outer diameter over its entire circumference, and a constant inner diameter over its entire circumference. The outer diameter of the disk 86 is smaller than the outer diameter of the disk 85. The outer diameter of the disk 86 is equal to the outer diameter of the inner seat portion 115 of the pilot case 81.

[0069] The outer diameter of the annular member 87 is constant over the entire circumference, and the inner diameter is also constant over the entire circumference. The outer diameter of the annular member 87 is larger than the outer diameter of the disk 85 and smaller than the outer diameter of the disk 83. The annular member 87 is thicker than the disks 83 and 85 and has higher rigidity than the disk 83.

[0070] The disk 91 has a constant outer diameter around its entire circumference. The outer diameter of the disk 91 is slightly larger than the outer diameter of the disk 162 of the regulating disk 78 and slightly smaller than the inner diameter of the tubular portion 102 of the pilot case 81. The inner diameter of the disk 91 is smaller than the outer diameter of the valve seat portion 113 of the pilot case 81 and larger than the outer diameters of the inner seat portion 112 of the valve seat portion 113 and the disk 79. A notch 171 is formed on the inner peripheral side of the disk 91. The notch 171 extends radially outward from the inner peripheral edge of the disk 91. The notch 171 penetrates the disk 91 in the axial direction of the disk 91.

[0071] The disk 92 has a constant outer diameter over its entire circumference, and a constant inner diameter over its entire circumference. The disk 92 has an outer diameter equal to that of the disk 91, and an inner diameter equal to that of the disk 91. The disk 92 has an outer diameter larger than the inner diameter of the outer seat portion 114 of the pilot case 81.

[0072] The regulating disk 78 presses the outer circumferential sides of the disks 91 and 92 against the outer seat portion 114 of the pilot case 81. At that time, the disk 162 of the regulating disk 78 abuts against the outer circumferential side of the disk 91, and causes the outer circumferential side of the disk 92 to abut against the outer seat portion 114. The regulating disk 78, together with the disks 75 to 77, restricts the outer circumferential sides of the disks 91 and 92 from moving axially away from the outer seat portion 114 of the pilot case 81, i.e., restricts the valves from opening.

[0073] As described above, in the axial direction of the pilot case 81, the outer seat portion 114 has a height in the protruding direction that is lower than that of the valve seat portion 113. Therefore, when the discs 91, 92 are pressed against the outer seat portion 114 by the regulating disc 78, the inner circumferential sides of the discs 91, 92 are elastically deformed so that their inner circumferential sides are positioned closer to the disc 161 of the regulating disc 78 than their outer circumferential sides, and the inner circumferential sides are pressed against the valve seat portion 113. At this time, the disc 92 abuts against the valve seat portion 113 over the entire circumference.

[0074] The area surrounded by the first damping valve 72, the discs 73 to 77, the regulating disc 78, and the pilot case 81 forms a main back pressure chamber 181. The area surrounded by the regulating disc 78 and the discs 91 and 92 forms a sub-back pressure chamber 182. The through hole 165 opens into the sub-back pressure chamber 182. The area surrounded by the annular recess 125 of the pilot case 81 and the disc 92 forms a variable chamber 183.

[0075] A communication orifice 166 consisting of the notch 155 of the disk 77 and the through-hole 165 of the disk 161 is provided between the main back pressure chamber 181 and the sub back pressure chamber 182. In other words, the sub back pressure chamber 182 is connected to the main back pressure chamber 181 via a passage within the communication orifice 166.

[0076] As shown in Figure 4, the variable chamber 183 is connected to the lower chamber 20 via a passage in the passage hole 121 of the pilot case 81. The volume of the variable chamber 183 is variable depending on the deformation of the discs 91, 92. That is, when the discs 91, 92 deform so as to approach the bottom surface of the annular recess 125, the volume of the variable chamber 183 decreases, thereby expanding the volume of the sub-back pressure chamber 182. When the discs 91, 92 deform from this state so as to move away from the bottom surface of the annular recess 125, the volume of the variable chamber 183 increases, thereby reducing the volume of the sub-back pressure chamber 182.

[0077] The main back pressure chamber 181, the communicating orifice 166, and the sub back pressure chamber 182 form a back pressure chamber 184. The pilot case 81, which has a cylindrical shape with a bottom, forms the back pressure chamber 184 together with the first damping valve 72 disposed on the opening 103 side.

[0078] When the pressure in the sub-back pressure chamber 182 is equal to or higher than the pressure in the variable chamber 183, the disc 92 of the discs 91, 92 abuts against the valve seat portion 113 over the entire periphery. As a result, the discs 91, 92 and the valve seat portion 113 restrict the flow of hydraulic oil L from the pilot chamber 95 and the sub-back pressure chamber 182 to the variable chamber 183. When the pressure in the variable chamber 183 is higher than the pressure in the sub-back pressure chamber 182, the discs 91, 92 are separated from the valve seat portion 113. As a result, the discs 91, 92 and the valve seat portion 113 allow the flow of hydraulic oil L from the variable chamber 183 to the pilot chamber 95 and the sub-back pressure chamber 182. Therefore, the discs 91, 92 and the valve seat portion 113 constitute a check valve 191 that restricts the flow of oil liquid L from the pilot chamber 95 and the sub-back pressure chamber 182 to the variable chamber 183, while allowing the flow of oil liquid L from the variable chamber 183 to the pilot chamber 95 and the sub-back pressure chamber 182.

[0079] The disks 91 and 92 overlap and deform and move almost integrally. The disks 91 and 92 form a movable valve 192 (movable member) of the check valve 191. The valve 192 is provided in the bottom 101 of the pilot case 81, and defines a variable chamber 183 on the opposite side to the back pressure chamber 184, blocking the flow of oil liquid L from the back pressure chamber 184 to the variable chamber 183.

[0080] When the check valve 191 opens, the inner peripheral portion of the deforming valve 192 approaches the disk 161 of the regulating disk 78, narrowing the flow path between the disk 161. The inner peripheral portion of the valve 192 and the disk 161 of the regulating disk 78 form a variable orifice 193 (first throttling mechanism, first throttling portion). The variable orifice 193 has a flow path cross-sectional area smaller than that of the communicating orifice 166. The variable orifice 193 is provided between the pilot chamber 95 and the sub-backpressure chamber 182 and changes the cross-sectional area of ​​the flow path between the pilot chamber 95 and the sub-backpressure chamber 182 in accordance with the amount of deformation of the valve 192. In other words, the variable orifice 193 narrows the flow path between the pilot chamber 95 and the sub-backpressure chamber 182 as the amount of deformation of the valve 192 increases. The variable orifice 193 includes a passage within the notch 171 of the disk 91. The passage within the notch 171 of the disk 91 sets the flow path cross-sectional area within the variable orifice 193 to a non-zero minimum value when the disk 91 of the valve 192 abuts against the disk 161 of the regulating disk 78. In this way, the valve 192 constitutes the variable orifice 193 that restricts the inflow of hydraulic fluid L from the variable chamber 183 to the sub-back pressure chamber 182. The valve 192 also functions as a check valve 191. The sub-back pressure chamber 182 is provided between the variable orifice 193 and the main back pressure chamber 181.

[0081] The disk 151 of the first damping valve 72 is seated on the valve seat portion 53 of the piston 18. When the first damping valve 72 leaves the valve seat portion 53 of the piston 18, the hydraulic oil L flows from the piston-side passage 43 shown in FIG. 3 through a passage between the disk 151 and the valve seat portion 53 from the upper chamber 19 to the lower chamber 20. The piston-side passage 43 and the passage between the disk 151 and the valve seat portion 53 form a first passage 201 that connects the upper chamber 19 and the lower chamber 20 shown in FIG. 2. The first damping valve 72 is provided in this first passage 201 and generates a damping force by suppressing the flow of hydraulic oil L caused by the sliding of the piston 18 toward the extension side. The first damping valve 72, together with the valve seat portion 53 of the piston 18, constitutes a first valve mechanism 41. The first valve mechanism 41 opens when the upper chamber 19 is at upstream pressure, thereby suppressing the flow of hydraulic oil L. The first passage 201 serves as an extension-side passage through which hydraulic fluid L flows from one upper chamber 19 to the other lower chamber 20 when the piston 18 moves toward the upper chamber 19, i.e., during the extension stroke. A first extension-side valve mechanism 41, consisting of a valve seat 53 and a first damping valve 72, is provided in the first passage 201, and generates a damping force by opening and closing the first passage 201 with the first damping valve 72 to suppress the flow of hydraulic fluid L. The first valve mechanism 41 can adjust the damping force by the pressure in the main back pressure chamber 181 of the back pressure chamber 184. The lower chamber 20 is located downstream of the first damping valve 72 in the flow direction of hydraulic fluid L in the first passage 201 during the extension stroke.

[0082] 3, the second damping valve 84, which is made up of multiple discs 83, has an outer diameter that is slightly larger than the maximum outer diameter of the tip end surface of the outer seat portion 116. The second damping valve 84 is removably seated on the outer seat portion 116.

[0083] The piston-side passage 43, the passage in the inlet orifice 142 of the disc 70, the pilot chamber 95 on the piston rod 21 side, the passage in the variable orifice 193, the back pressure chamber 184, and the passage between the second damping valve 84 and the outer seat portion 116 when the valve is open constitute a second passage 202 that connects the upper chamber 19 and the lower chamber 20 shown in Figure 2.

[0084] The second passage 202 is arranged in parallel with the first passage 201 except for the piston-side passage 43 that is common to the first passage 201, and is capable of communicating between the upper chamber 19 and the lower chamber 20. The second passage 202 is provided with the introduction orifice 142, pilot chamber 95, variable orifice 193, sub-back pressure chamber 182, communication orifice 166, and main back pressure chamber 181 shown in FIG.

[0085] The outer seat portion 116 and the second damping valve 84 constitute a second valve mechanism 205 that is provided in the second passage 202 and opens and closes the second passage 202. The second damping valve 84 of the second valve mechanism 205 is seated on the outer seat portion 116. The second damping valve 84 opens during the extension stroke to provide resistance to the flow of hydraulic fluid L from the upper chamber 19 to the lower chamber 20 via the second passage 202. In other words, the second valve mechanism 205 generates a damping force by suppressing the flow of hydraulic fluid L from the upper chamber 19 to the lower chamber 20. The second valve mechanism 205 is a damping force generating mechanism that is provided in the second passage 202 and generates a damping force by the flow of hydraulic fluid L.

[0086] The back pressure chamber 184 applies internal pressure to the first damping valve 72 in the direction of the piston 18, i.e., in the valve closing direction to seat the disc 151 on the valve seat portion 53. The pilot case 81 is cylindrical with a bottom and forms the back pressure chamber 184 that generates a biasing force in the valve closing direction on the first damping valve 72 that is arranged on the opening 103 side. In other words, the back pressure chamber 184 generates a biasing force in the valve closing direction on the first damping valve 72 that abuts against the valve seat portion 53 of the piston 18.

[0087] As shown in Figure 4, the inside of the passage hole 121 provided in the bottom 101 of the pilot case 81 constitutes a lower chamber communication passage 211 that communicates between the variable chamber 183 and the lower chamber 20. When the volume of the variable chamber 183 is reduced by the valve 192, the lower chamber communication passage 211 discharges the oil L from the variable chamber 183 to the lower chamber 20. The variable chamber 183 and the lower chamber communication passage 211 also constitute the second passage 202.

[0088] The valve 192 of the check valve 191 is provided so as to be able to open and close between the lower chamber communication passage 211 and the variable chamber 183 and the back pressure chamber 184 and the pilot chamber 95. When the valve 192 of the check valve 191 abuts against the valve seat portion 113 of the pilot case 81, it blocks the flow of oil L between the back pressure chamber 184 and the pilot chamber 95 and the variable chamber 183, the lower chamber communication passage 211, and the lower chamber 20. When the valve 192 of the check valve 191 is separated from the valve seat portion 113, it allows the flow of oil L between the lower chamber 20, the lower chamber communication passage 211, the variable chamber 183, and the back pressure chamber 184 and the pilot chamber 95.

[0089] Here, when the pressure on the variable chamber 183, lower chamber communicating passage 211, and lower chamber 20 side becomes higher than the pressure on the back pressure chamber 184 and pilot chamber 95 side by a predetermined value or more, the valve 192 of the check valve 191 allows the flow of hydraulic oil L from the lower chamber 20 to the back pressure chamber 184 and pilot chamber 95 via the lower chamber communicating passage 211 and variable chamber 183. When the pressure on the back pressure chamber 184 and pilot chamber 95 side is equal to or higher than the pressure on the variable chamber 183, lower chamber communicating passage 211, and lower chamber 20 side, the valve 192 of the check valve 191 restricts the flow of hydraulic oil L from the back pressure chamber 184 and pilot chamber 95 to the lower chamber 20 via the variable chamber 183 and lower chamber communicating passage 211. In other words, the check valve 191 restricts the flow of oil L in one direction from the back pressure chamber 184 and pilot chamber 95 side to the lower chamber 20 side between the back pressure chamber 184 and pilot chamber 95 and the lower chamber 20. On the other hand, the check valve 191 allows the flow of oil L in the other direction from the lower chamber 20 side to the back pressure chamber 184 and pilot chamber 95 side. The valve 192 of the check valve 191 is a valve member of the check valve 191.

[0090] The check valve 191 regulates the flow of hydraulic oil L from the upper chamber 19, piston-side passage 43 shown in Fig. 2, the passage in the introduction orifice 142 of the disc 70 shown in Fig. 3, the pilot chamber 95, and the back pressure chamber 184 to the variable chamber 183, lower-chamber communicating passage 211, and lower chamber 20 shown in Fig. 4. The check valve 191 allows the flow of hydraulic oil L from the lower chamber 20, the lower-chamber communicating passage 211, and the variable chamber 183 to the upper chamber 19 via the back pressure chamber 184, the pilot chamber 95, the passage in the introduction orifice 142 of the disc 70, and the piston-side passage 43 shown in Fig. 2.

[0091] The compression-side first valve mechanism 42 is provided on the inner seat portion 55 side of the piston 18 in the axial direction, and includes, in order from the inner seat portion 55 side in the axial direction of the piston 18, one disk 221, one disk 222, multiple disks (specifically, three disks 223), one disk 224, one disk 225, and one annular member 226. The disks 221 to 225 and the annular member 226 are made of metal and are circular, flat plates with holes of a constant thickness. The disks 221 to 225 are formed by press molding. The mounting shaft portion 28 of the piston rod 21 is fitted inside each of the disks 221 to 225 and the annular member 226.

[0092] The disc 221 has an outer diameter equal to the outer diameter of the inner seat portion 55 of the piston 18. The disc 222 has an outer diameter slightly larger than the outer diameter of the disc 221. A plurality of discs 223 constitute a first damping valve 231. The first damping valve 231 has an outer diameter slightly larger than the outer diameter of the valve seat portion 57 of the piston 18.

[0093] The disc 224 has an outer diameter smaller than that of the plurality of discs 223 and equal to that of the disc 221. The disc 225 has an outer diameter larger than that of the disc 224. The annular member 226 has an outer diameter larger than that of the disc 225 and smaller than that of the disc 223. The annular member 226 is thicker than the disc 223 and has high rigidity. The annular member 226 abuts against the shaft step portion 29 of the piston rod 21. The disc 225 and the annular member 226 suppress deformation of the first damping valve 231 in the opening direction beyond a specified limit.

[0094] A first damping valve 231 made up of multiple discs 223 constitutes the first valve mechanism 42 together with the valve seat portion 57 of the piston 18. The first damping valve 231 lifts off from the valve seat portion 57 and opens. When this occurs, the first damping valve 231 allows oil L from the piston-side passage 44 to flow into the upper chamber 19 via the valve seat portion 57. The piston-side passage 44 and the passage between the first damping valve 231 and the valve seat portion 57 form a compression-side first passage 232 through which oil L flows in the lower chamber 20 as the piston 18 moves toward the lower chamber 20. During the compression stroke, oil L as working fluid flows through the first passage 232 from one lower chamber 20 toward the other upper chamber 19. The compression-side first valve mechanism 42, made up of the valve seat portion 57 and the first damping valve 231, is provided in the first passage 232. The first valve mechanism 42 opens and closes the first passage 232 with the first damping valve 231 to suppress the flow of the oil L, thereby generating a damping force.

[0095] As shown in Fig. 6, the shock absorber 1 is provided with a fixed orifice 235. The fixed orifice 235 constantly communicates the upper chamber 19 and the lower chamber 20 via the piston 18 shown in Fig. 2. The fixed orifice 235 is formed, for example, by cutting out at least one of the valve seat portion 57 of the compression-side first valve mechanism 42 and the first damping valve 231. The fixed orifice 235 can also be formed by cutting out the valve seat portion 53 of the extension-side first valve mechanism 41, or a combination of both the extension and compression sides.

[0096] The pilot case 81 and valve 192 shown in FIG. 4 constitute a frequency sensitive mechanism 241 that varies the damping force in response to the frequency of the reciprocating motion of the piston 18 (hereinafter referred to as the piston frequency). The frequency sensitive mechanism 241 is composed of a portion of the sub-back pressure chamber 182 that increases when the disc 92 deforms to approach the bottom surface of the annular recess 125, the variable chamber 183, and a valve 192 that separates them. The frequency sensitive mechanism 241 is an accumulator. The frequency sensitive mechanism 241 is provided in the second passage 202 that includes the lower chamber communication passage 211. The valve 192 of the frequency sensitive mechanism 241 moves and deforms in response to the frequency of the reciprocating motion of the piston 18, changing the volume of the back pressure chamber 184 that is constantly connected to the upper chamber 19 and the volume of the variable chamber 183 that is constantly connected to the lower chamber 20. The frequency sensitive mechanism 241 has a valve 192 movably provided in the second passage 202 including the lower chamber communication passage 211. The frequency sensitive mechanism 241 varies the biasing force applied to the first damping valve 72 by the back pressure chamber 184.

[0097] During the extension stroke, the sub-back pressure chamber 182 side of the back pressure chamber 184 becomes higher in pressure than the variable chamber 183, the lower chamber communicating passage 211, and the lower chamber 20 side. Then, under pressure from the sub-back pressure chamber 182, the valve 192 deforms toward the bottom of the annular recess 125. This causes the volume of the back pressure chamber 184 to expand and the volume of the variable chamber 183 to contract. In this way, the frequency sensitive mechanism 241 operates when the upper chamber 19 is at upstream pressure, and acts to vary the damping force in response to the piston frequency. In other words, the frequency sensitive mechanism 241 changes the volume of the variable chamber 183 by moving due to the deformation of the valve 192 during the extension stroke, thereby changing the volume of the back pressure chamber 184.

[0098] During the compression stroke, the pressure in the lower chamber 20, the lower chamber communicating passage 211, and the variable chamber 183 becomes higher than the pressure in the sub-back pressure chamber 182. As a result, the valve 192 is lifted from the valve seat 113 of the pilot case 81, allowing hydraulic fluid L to flow from the lower chamber 20, the lower chamber communicating passage 211, and the variable chamber 183 to the sub-back pressure chamber 182 and the pilot chamber 95. In other words, when the lower chamber 20 is at upstream pressure, the check valve 191 provided in the second passage 202 including the lower chamber communicating passage 211 opens to allow hydraulic fluid L to flow.

[0099] During the compression stroke, when the valve 192 of the check valve 191 leaves the valve seat portion 113, the valve 192 narrows the flow path cross-sectional area of ​​the passage within the variable orifice 193 between the valve 192 and the disc 161 of the regulating disc 78. This acts to restrict the flow of hydraulic oil L from the lower chamber 20 to the sub-back pressure chamber 182 via the lower-chamber communicating passage 211, the variable chamber 183, and the open check valve 191. As a result, a pressure increase in the sub-back pressure chamber 182 is suppressed. In addition, because the communicating orifice 166 is also provided between the sub-back pressure chamber 182 and the main back pressure chamber 181, the communicating orifice 166 acts to restrict the flow of hydraulic oil L from the sub-back pressure chamber 182 to the main back pressure chamber 181. As a result, the pressure increase in the main back pressure chamber 181 is further suppressed than the pressure increase in the sub-back pressure chamber 182. In this way, when the lower chamber 20 is at upstream pressure, the variable orifice 193 located downstream of the check valve 191 operates to suppress and control the flow of oil liquid L, which is the working fluid, into the sub-back pressure chamber 182 and the main back pressure chamber 181.

[0100] 2, the annular member 226, the disk 225, the disk 224, the plurality of disks 223, the disk 222, the disk 221, the piston 18, the disk 70, the disk 71, the first damping valve 72, the disk 73, the plurality of disks 74, the plurality of disks 75, the disk 76, the disk 77, the regulating disk 78, and the disk 79 shown in FIG. 3 are stacked in this order on the shaft step 29 of the piston rod 21, with the mounting shaft portion 28 inserted into the respective insides. Also, the disks 91 and 92 are stacked in this order on the regulating disk 78. In this state, the mounting shaft portion 28 is inserted into the respective insides of the respective disks, with the pilot case 81, the plurality of disks 83, the disk 85, the disk 86, and the annular member 87 stacked in this order on the disk 79.

[0101] With the parts from the annular member 226 to the annular member 87 stacked in this manner, as shown in Fig. 2, a nut 245 is threaded onto the male threads 31 of the mounting shaft portion 28 of the piston rod 21 that protrudes beyond the annular member 87. As a result, the inner circumferential sides or all of the parts from the annular member 226 to the annular member 87, except for the disks 91 and 92 shown in Fig. 3 and Fig. 4, are sandwiched between the shank step 29 of the piston rod 21 shown in Fig. 2 and the nut 245 and clamped in the axial direction.

[0102] 3 and 4, the seal member 152 of the first damping valve 72 is fitted into the cylindrical portion 102 of the pilot case 81, and the disks 73 to 77, 79, the restricting disk 78, and the disks 91, 92 are arranged inside the pilot case 81. The restricting disk 78 presses the outer peripheral portions of the disks 91, 92 against the outer seat portion 114 of the pilot case 81 so as to prevent axial movement, and also brings the inner peripheral portions of the disks 91, 92 into contact with the valve seat portion 113 of the pilot case 81. In this state, the disks 91, 92 are slightly elastically deformed and are pressed against the valve seat portion 113.

[0103] As shown in FIG. 1 , the base valve 25 is provided between the inner tube 3 and the bottom member 12 of the outer tube 4. The base valve 25 includes a base valve member 251, a disk valve 252, a disk valve 253, and a mounting pin 254. The base valve 25 is placed on the bottom member 12 at the base valve member 251, and is fitted to the inner tube 3 at the base valve member 251. The base valve member 251 separates the lower chamber 20 from the reservoir chamber 6. The disk valve 252 is provided below the base valve member 251, i.e., on the reservoir chamber 6 side. The disk valve 253 is provided above the base valve member 251, i.e., on the lower chamber 20 side. The mounting pin 254 attaches the disk valves 252 and 253 to the base valve member 251.

[0104] The base valve member 251 has an annular shape, and a mounting pin 254 is inserted through its radial center. The base valve member 251 is formed with a plurality of passage holes 255 and a plurality of passage holes 256. The plurality of passage holes 255 allow the oil L to flow between the lower chamber 20 and the reservoir chamber 6. The plurality of passage holes 256 are arranged radially outward of the plurality of passage holes 255 of the base valve member 251. The plurality of passage holes 256 allow the oil L to flow between the lower chamber 20 and the reservoir chamber 6. The disk valve 252 on the reservoir chamber 6 side allows the oil L to flow from the lower chamber 20 to the reservoir chamber 6 via the passage hole 255. On the other hand, the disk valve 252 restricts the flow of the oil L from the reservoir chamber 6 to the lower chamber 20 via the passage hole 255. The disc valve 253 allows the oil L to flow from the reservoir chamber 6 to the lower chamber 20 via the passage hole 256. On the other hand, the disc valve 253 restricts the flow of the oil L from the lower chamber 20 to the reservoir chamber 6 via the passage hole 256.

[0105] The disc valve 252 and the base valve member 251 form a damping valve mechanism 257. The damping valve mechanism 257 opens during the compression stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the lower chamber 20 to the reservoir chamber 6 and generate a damping force. The disc valve 253 and the base valve member 251 form a suction valve mechanism 258. The suction valve mechanism 258 opens during the extension stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the reservoir chamber 6 into the lower chamber 20. The suction valve mechanism 258 mainly functions to allow hydraulic fluid to flow from the reservoir chamber 6 to the lower chamber 20 without generating any damping force, so as to compensate for a shortage of hydraulic fluid caused by the extension of the piston rod 21 from the cylinder 2.

[0106] The above-described configuration of the damping force generating mechanism 33 can be illustrated in a hydraulic circuit diagram as shown in FIG.

[0107] The damping force generating mechanism 33 has a fixed orifice 235 that constantly communicates between the upper chamber 19 and the lower chamber 20. The damping force generating mechanism 33 has a first passage 201 that communicates between the upper chamber 19 and the lower chamber 20, and a first valve mechanism 41 provided in the first passage 201. The damping force generating mechanism 33 has a second passage 202 that is parallel to the first passage 201 and communicates between the upper chamber 19 and the lower chamber 20. The damping force generating mechanism 33 has, in the second passage 202, an introduction orifice 142, a pilot chamber 95 that is closer to the lower chamber 20 than the introduction orifice 142, and a check valve 191 that is closer to the lower chamber 20 than the pilot chamber 95. The damping force generating mechanism 33 has, in the second passage 202, a second valve mechanism 205 that is provided between the pilot chamber 95 and the lower chamber 20. The damping force generating mechanism 33 has, in the second passage 202, a variable orifice 193 communicating with the pilot chamber 95, a sub-back pressure chamber 182 communicating with the variable orifice 193, a communicating orifice 166 communicating with the sub-back pressure chamber 182, and a main back pressure chamber 181 communicating with the communicating orifice 166. The damping force generating mechanism 33 has a frequency sensitive mechanism 241 between the sub-back pressure chamber 182 of the second passage 202 and the lower chamber 20. In the damping force generating mechanism 33, the pressure in the main back pressure chamber 181 is applied to the first valve mechanism 41 as back pressure. In the damping force generating mechanism 33, the check valve 191 operates in conjunction with the variable orifice 193. The damping force generating mechanism 33 has a first passage 232 communicating between the lower chamber 20 and the upper chamber 19, and a first valve mechanism 42 provided in the first passage 232.

[0108] Next, the operation of the shock absorber 1 including the damping force generating mechanism 33 will be described.

[0109] {During the extension stroke, a low-frequency, extremely low-speed region x1 in which the piston frequency is low and the piston speed is slower than the first predetermined value v1.} In this low-frequency, extremely low-speed region x1, the first valve mechanism 41 and the second valve mechanism 205 do not open. The oil L from the upper chamber 19 flows into the sub-backpressure chamber 182 of the backpressure chamber 184 via the piston-side passage 43, the passage in the inlet orifice 142 of the disc 70, and the pilot chamber 95. This causes the valve 192 of the frequency sensitive mechanism 241 to move toward the bottom of the annular recess 125. In this low-frequency, extremely low-speed region x1, the piston frequency is low and the piston 18 performs a large stroke, so a large amount of oil L is introduced from the upper chamber 19 into the backpressure chamber 184 at the beginning of the stroke. Therefore, the valve 192 of the frequency sensitive mechanism 241 moves and deforms toward the bottom of the annular recess 125 to a limit, and then becomes less likely to deform (high spring region). On the other hand, in this low-frequency, extremely low-speed region x1, the oil L from the upper chamber 19 flows into the lower chamber 20 via the fixed orifice 235. Therefore, in the low-frequency, extremely low-speed region x1, a damping force with orifice characteristics (the damping force is approximately proportional to the square of the piston speed) is generated. Therefore, in the low-frequency, extremely low-speed region x1, the rate of increase in the damping force relative to an increase in piston speed is relatively high.

[0110] {During the extension stroke, a low-frequency low-speed region x2 in which the piston frequency is low and the piston speed is equal to or greater than a first predetermined value v1 and slower than a second predetermined value v2} In this low-frequency low-speed region x2, similar to the low-frequency very-low-speed region x1, the oil L from the upper chamber 19 flows into the upper chamber 19 via the fixed orifice 235 and significantly moves and deforms the valve 192 of the frequency sensitive mechanism 241 toward the bottom surface of the annular recess 125. Thereafter, the oil L from the upper chamber 19 via the piston-side passage 43, the passage in the introduction orifice 142 of the disc 70, and the pilot chamber 95 is less likely to be introduced into the back pressure chamber 184. In the low-frequency low-speed region x2, the pressure in the back pressure chamber 184 becomes higher than in the low-frequency very-low-speed region x1. Therefore, in the low-frequency, low-speed range x2, the oil L from the upper chamber 19 flows through the piston-side passage 43, the passage in the inlet orifice 142 of the disc 70, and the pilot chamber 95, opening the second damping valve 84 of the second valve mechanism 205 and flowing into the lower chamber 20. That is, the oil L from the upper chamber 19 flows into the lower chamber 20 through the second passage 202. As a result, in the low-frequency, low-speed range x2, a damping force with valve characteristics (damping force approximately proportional to piston speed) is generated. Therefore, in the low-frequency, low-speed range x2, the rate of increase in damping force relative to an increase in piston speed is lower than in the low-frequency, very low-speed range x1. In this low-frequency, low-speed range x2, the valve 192 of the frequency sensitive mechanism 241 has moved and deformed nearly to its limit, causing the pressure in the backpressure chamber 184 to become high. Therefore, the biasing force from the backpressure chamber 184 on the first damping valve 72 of the first valve mechanism 41 is large, limiting its opening.

[0111] {A low-frequency medium-high-speed region x3 in which the piston frequency is low and the piston speed is equal to or greater than a second predetermined value v2 during the extension stroke} In this low-frequency medium-high-speed region x3, similar to the low-frequency very-low speed region x1, the oil L from the upper chamber 19 flows into the upper chamber 19 via the fixed orifice 235, and also opens the second damping valve 84 of the second valve mechanism 205, so that the oil L flows into the lower chamber 20 via the piston-side passage 43, the passage in the introduction orifice 142 of the disc 70, and the pilot chamber 95. In this way, in the low-frequency medium-high-speed region x3, the oil L flows into the lower chamber 20 via the second passage 202, and therefore a pressure increase in the back pressure chamber 184 due to the oil L introduced into the back pressure chamber 184 from the pilot chamber 95 is suppressed. In response to this, the force in the valve opening direction applied to the first valve mechanism 41 from the piston-side passage 43 increases, and the oil L from the upper chamber 19 passes through the piston-side passage 43, opens the first damping valve 72 of the first valve mechanism 41, and flows into the lower chamber 20. That is, the oil L from the upper chamber 19 flows into the lower chamber 20 via the first passage 201. As a result, in the low-frequency medium-to-high speed range x3, the rate of increase in damping force relative to an increase in piston speed is lower than in the low-frequency low-speed range x2.

[0112] {During the extension stroke, a high-frequency, very-low-speed region x4 in which the piston frequency is higher than the low frequency and the piston speed is slower than the third predetermined value v3.} In this high-frequency, very-low-speed region x4, the first valve mechanism 41 and the second valve mechanism 205 do not open. Similarly to the low-frequency, very-low-speed region x1, the oil L from the upper chamber 19 flows into the upper chamber 19 via the fixed orifice 235, and also flows into the sub-backpressure chamber 182 of the backpressure chamber 184 via the piston-side passage 43, the passage in the inlet orifice 142 of the disc 70, and the pilot chamber 95. This causes the valve 192 of the frequency sensitive mechanism 241 to move and deform toward the bottom of the annular recess 125. In this high-frequency, very-low-speed region x4, the piston frequency is high and the stroke of the piston 18 is small. Therefore, the amount of oil L introduced from the upper chamber 19 into the backpressure chamber 184 is less than in the low-frequency, very-low-speed region x1. Therefore, the valve 192 of the frequency sensitive mechanism 241 does not deform to near its limit and is easily deformed (low spring region). As a result, the oil L introduced from the upper chamber 19 to the back pressure chamber 184 can be absorbed by the movement and deformation of the valve 192. Therefore, in the high frequency very low speed region x4, although the rate of increase in damping force relative to an increase in piston speed is high, the damping force at the same piston speed is lower than in the low frequency very low speed region x1, resulting in a softer characteristic.

[0113] {A high-frequency, low-medium-high-speed region x5 in which the piston frequency is higher than the low frequency and the piston speed is equal to or greater than the third predetermined value v3 during the extension stroke.} In this high-frequency, low-medium-high-speed region x5, similar to the high-frequency, very low-speed region x4, the oil L from the upper chamber 19 flows into the upper chamber 19 via the fixed orifice 235 and moves and deforms the valve 192 of the frequency sensitive mechanism 241 toward the bottom surface of the annular recess 125. In the high-frequency, low-medium-high-speed region x5, the amount of oil L introduced into the back pressure chamber 184 is small, so the deformation of the valve 192 suppresses a pressure increase in the back pressure chamber 184. As a result, the biasing force from the back pressure chamber 184 on the first damping valve 72 of the first valve mechanism 41 is reduced, making it easier for the first damping valve 72 to open. Therefore, the oil L from the upper chamber 19 passes through the piston-side passage 43, opens the first damping valve 72 of the first valve mechanism 41, and flows into the lower chamber 20. That is, the oil liquid L from the upper chamber 19 flows into the lower chamber 20 via the first passage 201. As a result, in the high-frequency, low-medium-high-speed range x5, the rate of increase in damping force relative to an increase in piston speed is lower than in the high-frequency, very low-speed range x4. Furthermore, in the high-frequency, low-medium-high-speed range x5, the damping force at the same piston speed is lower than in the low-frequency, low-speed range x2 and the low-frequency, medium-high-speed range x3, resulting in a softer characteristic. In this high-frequency, low-medium-high-speed range x5, the pressure increase in the back pressure chamber 184 is suppressed, so the second valve mechanism 205 remains in a closed state.

[0114] {Extra-low speed region y1 in which the piston speed is slower than the fourth predetermined value v4 during the compression stroke} In this extremely low speed region y1, the first valve mechanism 42 and the check valve 191 do not open. The oil L from the lower chamber 20 flows into the upper chamber via the fixed orifice 235. Therefore, in the extremely low speed region y1, a damping force with orifice characteristics (the damping force is approximately proportional to the square of the piston speed) is generated. Therefore, in the extremely low speed region y1, the rate of increase of the damping force relative to an increase in piston speed is relatively high.

[0115] {Low-speed region y2 in which the piston speed is equal to or greater than the fourth predetermined value v4 and slower than the fifth predetermined value v5 during the compression stroke} In this low-speed region y2, hydraulic fluid L from the lower chamber 20 flows into the upper chamber 19 via the fixed orifice 235, as in the very-low-speed region y1. In addition, in the low-speed region y2, hydraulic fluid L from the lower chamber 20 is introduced into the variable chamber 183 from the lower-chamber communicating passage 211, opens the check valve 191, is introduced into the pilot chamber 95, and flows into the upper chamber 19 via the introduction orifice 142 of the disc 70 and the piston-side passage 43. In the low-speed region y2, the rate of increase in damping force relative to an increase in piston speed is lower than in the very-low-speed region y1. At this time, the valve 192 of the open check valve 191 narrows the passage within the variable orifice 193, suppressing a pressure increase in the sub-backpressure chamber 182, and the communicating orifice 166 further suppresses a pressure increase in the main backpressure chamber 181.

[0116] {Medium-high speed range y3 in which the piston speed is equal to or greater than the fifth predetermined value v5 during the compression stroke} In this medium-high speed range y3, similar to the low speed range y2, the oil L from the lower chamber 20 flows into the upper chamber 19 via the fixed orifice 235, and also flows from the lower chamber communicating passage 211 to the upper chamber 19 via the pilot chamber 95, the introduction orifice 142, and the piston-side passage 43, opening the check valve 191. In the medium-high speed range y3, in addition to the above, the oil L from the lower chamber 20 passes through the piston-side passage 44, opens the first damping valve 231 of the first valve mechanism 42, and flows into the upper chamber 19. As a result, in the medium-high speed range y3, the rate of increase in damping force relative to an increase in piston speed is lower than in the low speed range y2. At this time, the valve 192 of the open check valve 191 narrows the passage in the variable orifice 193 to suppress the pressure increase in the sub back pressure chamber 182 , and the communicating orifice 166 further suppresses the pressure increase in the main back pressure chamber 181 .

[0117] Here, the diameter of the back pressure chamber 184 is larger than the diameter of the valve seat portion 53 of the piston 18. Therefore, the extension-side first damping valve 72 receives the pressure of the lower chamber 20 during the compression stroke.

[0118] When the pressure in the lower chamber 20 rises during the compression stroke and reaches a predetermined pressure, a valve 192 of a check valve 191 provided in the pilot case 81 opens to introduce pressure into the back pressure chamber 184. As a result, a valve closing force due to the back pressure acts on the first damping valve 72, and this force exceeds the valve opening force due to the pressure in the lower chamber 20 acting on the outer circumferential side of the first damping valve 72, preventing the first damping valve 72 from opening during the compression stroke.

[0119] During the compression stroke, the shock absorber 1 also exhibits a damping force characteristic that is achieved by the damping valve mechanism 257.

[0120] The aforementioned Patent Document 1 discloses a shock absorber having a damping force generating mechanism that varies damping force in response to frequency. Smooth operation of the damping force generating mechanism is required for shock absorbers. For example, the shock absorber described in Patent Document 1 is provided with a free valve that functions as a check valve during the compression stroke and as a backpressure introduction valve during the extension stroke. In this case, if the backpressure chamber is high-pressure due to the check valve opening during the compression stroke, when the check valve closes during stroke reversal from the compression stroke to the extension stroke, the high backpressure in the backpressure chamber may prevent the extension-side damping force generating mechanism from opening smoothly, resulting in high damping force. As a result, it becomes difficult to generate soft damping force during stroke reversal from the compression stroke to the extension stroke.

[0121] The shock absorber 1 of the first embodiment has a first passage 201 through which hydraulic fluid L flows from one upper chamber 19 in the cylinder 2 as the piston 18 moves, and a second passage 202 provided in parallel to the first passage 201. The shock absorber 1 also has a first valve mechanism 41 provided in the first passage 201, which acts when the upper chamber 19 is under upstream pressure during an extension stroke to adjust the damping force according to the pressure in the main back pressure chamber 181, and a frequency sensitive mechanism 241 provided in the second passage 202, which acts when the upper chamber 19 is under upstream pressure and changes its volume by moving a valve 192. The shock absorber 1 also has a check valve 191 provided in the second passage 202, which acts when the lower chamber 20 is under upstream pressure to allow hydraulic fluid L to flow. The shock absorber 1 also has a variable orifice 193 downstream of the check valve 191, which acts when the lower chamber 20 is under upstream pressure during a compression stroke to control the flow of hydraulic fluid L to the main back pressure chamber 181. As a result, even if the check valve 191 is opened during the compression stroke, the variable orifice 193 can suppress the flow of hydraulic fluid L into the main back pressure chamber 181, preventing the main back pressure chamber 181 from becoming high pressure. This prevents the back pressure in the main back pressure chamber 181 from interfering with the smooth opening of the first valve mechanism 41 during stroke reversal from the compression stroke to the extension stroke. This allows the damping force generating mechanism 33, including the first valve mechanism 41, to operate smoothly. As a result, in a situation where a soft damping force is required during stroke reversal from the compression stroke to the extension stroke, a soft damping force can be generated satisfactorily.

[0122] Furthermore, in the shock absorber 1, the valve 192 also serves as the check valve 191, so the number of parts in the damping force generating mechanism 33 can be reduced, thereby making it possible to make the shock absorber 1 more compact. Since the number of parts in the damping force generating mechanism 33 can be reduced, the cost and weight of the shock absorber 1 can be reduced.

[0123] Furthermore, the shock absorber 1 is provided with a sub-back pressure chamber 182 between the variable orifice 193 and the main back pressure chamber 181. Therefore, even if the check valve 191 is opened during the compression stroke, hydraulic fluid L flows from the variable orifice 193 to the sub-back pressure chamber 182, and hydraulic fluid L flows from the sub-back pressure chamber 182 to the main back pressure chamber 181. This further restricts the flow of hydraulic fluid L into the main back pressure chamber 181, thereby further preventing the main back pressure chamber 181 from becoming high pressure. As a result, it is possible to further prevent the back pressure in the main back pressure chamber 181 from interfering with the smooth opening of the first valve mechanism 41 during the stroke reversal from the compression stroke to the extension stroke. This therefore enables the damping force generating mechanism 33, including the first valve mechanism 41, to operate more smoothly.

[0124] Furthermore, in the shock absorber 1, the sub-back pressure chamber 182 is connected to the main back pressure chamber 181 via the communication orifice 166. Therefore, even if the check valve 191 is opened during the compression stroke, the variable orifice 193 can suppress the flow of hydraulic fluid L into the sub-back pressure chamber 182, and the communication orifice 166 can suppress the flow of hydraulic fluid L from the sub-back pressure chamber 182 to the main back pressure chamber 181. This further prevents the main back pressure chamber 181 from becoming high pressure. As a result, it is further prevented that the back pressure in the main back pressure chamber 181 will hinder the smooth opening of the first valve mechanism 41 during the stroke reversal from the compression stroke to the extension stroke. This therefore enables the damping force generating mechanism 33, including the first valve mechanism 41, to operate more smoothly.

[0125] The damping force generating mechanism 33 of the first embodiment includes a pilot case 81, a valve 192, and a regulating disk 78. The pilot case 81 is cylindrical and has a bottom, and defines a back pressure chamber 184 that generates a biasing force in a valve closing direction on the first damping valve 72 disposed on the opening 103 side. The valve 192 is provided in the bottom 101 of the pilot case 81, and defines a variable chamber 183 on the opposite side from the back pressure chamber 184, blocking the flow of hydraulic fluid L from the back pressure chamber 184 to the variable chamber 183. The regulating disk 78 abuts the outer periphery of the valve 192, regulating the opening of the valve 192. The valve 192 has a variable orifice 193 that restricts the flow of hydraulic fluid L from the variable chamber 183 to the back pressure chamber 184. As a result, even if the valve 192 is opened, the variable orifice 193 can restrict the inflow of hydraulic fluid L from the variable chamber 183 to the back pressure chamber 184, preventing the back pressure chamber 184 from becoming high pressure. This prevents the back pressure in the back pressure chamber 184 from interfering with the smooth opening of the first valve mechanism 41 during stroke reversal. This allows the damping force generating mechanism 33 to operate smoothly.

[0126] The shock absorber 1 and the damping force generating mechanism 33 of the first embodiment can be modified as in the following modified examples 1 and 2.

[0127] <Modification 1> In the shock absorber 1 and the damping force generating mechanism 33 of the first embodiment, the regulating disc 78 is formed by welding the disc 162 to the disc 161 to form an integrated unit. However, the disc 162 may be integrated with the valve 192 by welding to the outer periphery of the disc 91 on the side opposite to the disc 92, without being welded to the disc 161. In this case, the disc 161 (regulating member) abuts against the disc 162 integrated with the disc 91, and presses the valve 192 including the disc 162 against the outer seat portion 114 of the pilot case 81. That is, in this case, the outer periphery of the valve 192 including the disc 162 abuts against the disc 161 to regulate the opening of the valve 192.

[0128] <Variation 2> The disk 162 is not welded to either the disk 161 or the disk 91, but is positioned radially by the cylindrical portion 102 of the pilot case 81. In this case, the disk 162 is sandwiched between the disks 161 and 91 in the axial direction, and the disk 162 (restricting member) abuts against the disk 91, pressing the valve 192 against the outer seat portion 114 of the pilot case 81. That is, in this case, the outer peripheral side of the valve 192 abuts against the disk 162, restricting the opening of the valve 192.

[0129] Second Embodiment Next, a second embodiment will be described, focusing on differences from the first embodiment, mainly with reference to Fig. 7. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0130] 7, the shock absorber 1A of the second embodiment has a damping force generating mechanism 33A that is partially different from the damping force generating mechanism 33, instead of the damping force generating mechanism 33. The damping force generating mechanism 33A has a regulating disk 78A that is partially different from the regulating disk 78, instead of the regulating disk 78. The regulating disk 78A has a disk 161A that is partially different from the disk 161, instead of the disk 161.

[0131] A slit 171A is formed in the disk 161A radially inward of the through-hole 165. The slit 171A penetrates the disk 161A in the axial direction of the disk 161A. The slit 171A is linear and extends radially of the disk 161A. A plurality of slits 171A are formed in the disk 161A at equal intervals in the circumferential direction of the disk 161A. The slits 171A open to the sub-back pressure chamber 182.

[0132] The damping force generating mechanism 33A has a valve 192A (movable member) that is partially different from the valve 192, instead of the valve 192. The valve 192A has a disk 91A that is partially different from the disk 91, instead of the disk 91.

[0133] The disk 91A does not have the notch 171 formed in the disk 91. The disk 91A has a constant outer diameter over the entire circumference, and a constant inner diameter over the entire circumference. The disk 91A is a common part having the same shape as the disk 92.

[0134] The damping force generating mechanism 33A has a check valve 191A that is partially different from the check valve 191, instead of the check valve 191. The check valve 191A differs from the check valve 191 in that it has a valve 192A instead of the valve 192. In the check valve 191A, the valve 192A operates in the same manner as the valve 192. Therefore, the check valve 191A operates in the same manner as the check valve 191.

[0135] The damping force generating mechanism 33A has a frequency sensitive mechanism 241A that is partially different from the frequency sensitive mechanism 241 in place of the frequency sensitive mechanism 241. The frequency sensitive mechanism 241A differs from the frequency sensitive mechanism 241 in that it has a valve 192A instead of the valve 192. In the frequency sensitive mechanism 241A, the valve 192A operates in the same way as the valve 192. Therefore, the frequency sensitive mechanism 241A operates in the same way as the frequency sensitive mechanism 241.

[0136] The damping force generating mechanism 33A has a variable orifice 193A (first throttling mechanism, first throttling portion) that is partially different from the variable orifice 193, instead of the variable orifice 193. When the check valve 191A is open, the inner peripheral portion of the variable orifice 193A approaches the disk 161A of the regulating disk 78A, narrowing the flow path between the disk 161A. The inner peripheral portion of the valve 192A and the disk 161A of the regulating disk 78A constitute the variable orifice 193A. The flow path cross-sectional area of ​​the variable orifice 193A is smaller than the flow path cross-sectional area of ​​the communicating orifice 166. The variable orifice 193A is provided between the pilot chamber 95 and the sub-backpressure chamber 182, and changes the flow path between the pilot chamber 95 and the sub-backpressure chamber 182 in accordance with the amount of deformation of the valve 192A. The variable orifice 193A includes the slit 171A of the disk 161A. The passage within the slit 171A of the disk 161A sets the flow path cross-sectional area within the variable orifice 193A to a non-zero minimum value when the disk 91A of the valve 192A abuts against the disk 161A of the regulating disk 78A. In other words, the slit 171A of the disk 161A performs the same function as the notch 171 of the disk 91A. In this way, the valve 192A constitutes the variable orifice 193A that limits the inflow of hydraulic fluid L from the variable chamber 183 to the sub-back pressure chamber 182. The valve 192A also functions as the check valve 191A. The sub-back pressure chamber 182 is provided between the variable orifice 193A and the main back pressure chamber 181.

[0137] The damping force generating mechanism 33A has a second passage 202A that is partially different from the second passage 202 instead of the second passage 202. The second passage 202A differs from the second passage 202 in that it has a variable orifice 193A instead of the variable orifice 193.

[0138] In the shock absorber 1A, when the valve 192A of the check valve 191A leaves the valve seat portion 113, the valve 192A narrows the flow path cross-sectional area of ​​the passage within the variable orifice 193A between the valve 192A and the disc 161A of the regulating disc 78A. This restricts the flow of hydraulic fluid L from the lower chamber 20 to the sub-back pressure chamber 182 via the lower-chamber communicating passage 211, the variable chamber 183, and the open check valve 191A. As a result, a pressure increase in the sub-back pressure chamber 182 is suppressed. In this way, when the lower chamber 20 is at upstream pressure, the variable orifice 193A provided downstream of the check valve 191A acts to restrict and control the flow of hydraulic fluid L, which is the working fluid, to the sub-back pressure chamber 182 and the main back pressure chamber 181.

[0139] The hydraulic circuit diagram of the configuration of the damping force generating mechanism 33A described above is similar to that of the damping force generating mechanism 33 of the first embodiment. That is, in Fig. 6, the second passage 202 becomes a second passage 202A, the check valve 191 becomes a check valve 191A, the variable orifice 193 becomes a variable orifice 193A, and the frequency sensitive mechanism 241 becomes a frequency sensitive mechanism 241A.

[0140] The shock absorber 1A and damping force generating mechanism 33A of the second embodiment also have a variable orifice 193A that functions in the same manner as the variable orifice 193, and therefore have the same effects as the shock absorber 1 and damping force generating mechanism 33 of the first embodiment.

[0141] The shock absorber 1A and the damping force generating mechanism 33A of the second embodiment can be modified as in Modification 1 and Modification 2 of the first embodiment. That is, the disk 162 may not be welded to the disk 161A, but may be integrated by welding to the outer periphery of the disk 91A of the valve 192A on the side opposite to the disk 92. Alternatively, the disk 162 may be positioned radially by the cylindrical portion 102 of the pilot case 81, and may be sandwiched axially between the disk 161 and the disk 91A, without being welded to either the disk 161 or the disk 91A.

[0142] [Third Embodiment] Next, a third embodiment will be described, focusing on differences from the first embodiment, mainly with reference to Figures 8 to 10. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0143] 8, the shock absorber 1B of the third embodiment has a damping force generating mechanism 33B that is partially different from the damping force generating mechanism 33, instead of the damping force generating mechanism 33. The damping force generating mechanism 33B has a regulating disk 78B that is partially different from the regulating disk 78, instead of the regulating disk 78. The regulating disk 78B has a disk 161B that is partially different from the disk 161, instead of the disk 161.

[0144] The disk 161B has a through hole 165B that is partially different from the through hole 165, instead of the through hole 165. The through hole 165B penetrates the disk 161B in the axial direction of the disk 161B. In the radial direction of the disk 161B, the through hole 165B extends more inward than the through hole 165. The through hole 165B opens to the sub back pressure chamber 182. The disk 161B has a plurality of through holes 165B that are equally spaced apart in the circumferential direction of the disk 161B. The through hole 165B, together with the notch 155 of the disk 77, constitutes a communication orifice 166 similar to that in the first embodiment.

[0145] The damping force generating mechanism 33B has a valve 192B (movable member) that is partially different from the valve 192, instead of the valve 192. The valve 192B has a disk 91B that is partially different from the disk 91, instead of the disk 91.

[0146] The disk 91B does not have the notch 171 formed in the disk 91. The disk 91B has a constant outer diameter over the entire circumference, and a constant inner diameter over the entire circumference. The disk 91B is a common part having the same shape as the disk 92.

[0147] The damping force generating mechanism 33B has a check valve 191B that is partially different from the check valve 191, instead of the check valve 191. The check valve 191B differs from the check valve 191 in that it has a valve 192B instead of the valve 192. In the check valve 191B, the valve 192B operates in the same manner as the valve 192. Therefore, the check valve 191B operates in the same manner as the check valve 191.

[0148] The damping force generating mechanism 33B has a frequency sensitive mechanism 241B that is partially different from the frequency sensitive mechanism 241, instead of the frequency sensitive mechanism 241. The frequency sensitive mechanism 241B differs from the frequency sensitive mechanism 241 in that it has a valve 192B instead of the valve 192. In the frequency sensitive mechanism 241B, the valve 192B operates in the same way as the valve 192. Therefore, the frequency sensitive mechanism 241B operates in the same way as the frequency sensitive mechanism 241.

[0149] The damping force generating mechanism 33B is not provided with a variable orifice 193. The passage in the through hole 165B of the disk 161B communicates the variable chamber 183 and the pilot chamber 95 with the sub-back pressure chamber 182 even when the disk 91B of the valve 192B abuts against the disk 161B of the regulating disk 78B.

[0150] The damping force generating mechanism 33B has a pilot case 81B that is partially different from the pilot case 81, instead of the pilot case 81. The pilot case 81B has a bottom 101B that is partially different from the bottom 101, instead of the bottom 101. The bottom 101B has a bottom main body 111B that is partially different from the bottom main body 111, instead of the bottom main body 111. As shown in FIG. 9 , the bottom main body 111B has a passage hole 121 at only one location.

[0151] The bottom portion 101B has an outer seat portion 116B that is partially different from the outer seat portion 116. A connecting seat portion 311B is formed in the outer seat portion 116B, connecting the seat constituent portions 133, each having a passage hole 121 disposed between them in the circumferential direction of the pilot case 81B. The connecting seat portion 311B is disposed outward of the passage hole 121 in the radial direction of the pilot case 81B. As shown in FIG. 8 , in the axial direction of the pilot case 81B, the leading end surface of the connecting seat portion 311B opposite the bottom main body portion 111B is aligned with the leading end surface of the inner seat portion 115 opposite the bottom main body portion 111B and the leading end surface of the seat constituent portion 133 opposite the bottom main body portion 111B.

[0152] The connecting seat portion 311B has a notch 312B formed therein, penetrating the connecting seat portion 311B in the radial direction of the pilot case 81B. The notch 312B is recessed toward the bottom body portion 111B from the tip surface of the connecting seat portion 311B on the side opposite the bottom body portion 111B. The notch 312B is formed in the pilot case 81B by coining. The notch 312B, together with the disk 83 that abuts against the outer seat portion 116B, forms an orifice 313B.

[0153] As shown in Fig. 9, a passage recess 315B is formed by two seat constituent portions 133 arranged on both sides of the passage hole 121 in the circumferential direction of the pilot case 81B, a portion of the inner seat portion 115 between these seat constituent portions 133, and the connecting seat portion 311B. As shown in Fig. 8, the passage recess 315B is recessed along the axial direction of the pilot case 81 from the leading end surface on the protruding side of the inner seat portion 115, the leading end surface on the protruding side of the seat constituent portion 133, and the leading end surface of the connecting seat portion 311B. The bottom surface of the passage recess 315B is formed by the bottom main body portion 111. The orifice 313B opens to the inside of the passage recess 315B and to the lower chamber 20.

[0154] The damping force generating mechanism 33B has a lower chamber communication passage 211B that is partially different from the lower chamber communication passage 211 instead of the lower chamber communication passage 211. The lower chamber communication passage 211B is made up of a passage in the passage recess 315B and a passage in the passage hole 121. The lower chamber communication passage 211B communicates with the lower chamber 20 via an orifice 313B.

[0155] The damping force generating mechanism 33B has a second passage 202B that is partially different from the second passage 202 instead of the second passage 202. The second passage 202B differs from the second passage 202 in that it has a lower chamber communicating passage 211B instead of the lower chamber communicating passage 211, that it has an orifice 313B, and that it does not have a variable orifice 193.

[0156] In shock absorber 1B, during the compression stroke, orifice 313B of pilot case 81B acts to suppress the flow of hydraulic oil L from the lower chamber 20 to the lower chamber communicating passage 211B and variable chamber 183. This suppresses the flow of hydraulic oil L from the lower chamber 20 to the sub-back pressure chamber 182 via orifice 313B, lower chamber communicating passage 211B, and open check valve 191B. As a result, a pressure increase in the sub-back pressure chamber 182 is suppressed. In this way, when the lower chamber 20 is at upstream pressure, orifice 313B provided upstream of check valve 191B acts to suppress and control the flow of hydraulic oil L, which is the working fluid, to the sub-back pressure chamber 182 and main back pressure chamber 181.

[0157] A hydraulic circuit diagram of the configuration of the damping force generating mechanism 33B described above is as shown in Figure 10. That is, the check valve 191 becomes a check valve 191B, the frequency sensitive mechanism 241 becomes a frequency sensitive mechanism 241B, and an orifice 313B is provided between the lower chamber communication passage 211B and the lower chamber 20. Also, in the damping force generating mechanism 33B, the second passage 202 becomes a second passage 202B, and the variable orifice 193 is not provided in this second passage 202B.

[0158] The shock absorber 1B of the third embodiment is provided with an orifice 313B upstream of the check valve 191B. The orifice 313B acts to control the flow of hydraulic fluid L to the main back pressure chamber 181 during the compression stroke when the lower chamber 20 has upstream pressure. As a result, even when the check valve 191 is opened during the compression stroke, the orifice 313B can restrict the flow of hydraulic fluid L to the main back pressure chamber 181, preventing the main back pressure chamber 181 from becoming high pressure. This prevents the back pressure in the main back pressure chamber 181 from interfering with the smooth opening of the first valve mechanism 41 during stroke reversal from the compression stroke to the extension stroke. This allows the damping force generating mechanism 33B, including the first valve mechanism 41, to operate smoothly. As a result, a soft damping force can be generated effectively during stroke reversal from the compression stroke to the extension stroke.

[0159] Furthermore, the shock absorber 1B is provided with a sub-back pressure chamber 182 between the orifice 313B and the main back pressure chamber 181. Therefore, even if the check valve 191 is opened during the compression stroke, hydraulic fluid L flows from the orifice 313B to the sub-back pressure chamber 182, and hydraulic fluid L flows from the sub-back pressure chamber 182 to the main back pressure chamber 181. This further restricts the flow of hydraulic fluid L into the main back pressure chamber 181, thereby further preventing the main back pressure chamber 181 from becoming high pressure. As a result, it is further possible to prevent the back pressure in the main back pressure chamber 181 from interfering with the smooth opening of the first valve mechanism 41 during the stroke reversal from the compression stroke to the extension stroke. This therefore enables the damping force generating mechanism 33B, including the first valve mechanism 41, to operate more smoothly.

[0160] The shock absorber 1B and the damping force generating mechanism 33B of the third embodiment can be modified as in the first and second modifications of the first embodiment. That is, the disk 162 may be integrated by welding to the outer periphery of the disk 91B of the valve 192B on the side opposite to the disk 92, without being welded to the disk 161B. Alternatively, the disk 162 may be positioned radially by the cylindrical portion 102 of the pilot case 81, and sandwiched axially between the disk 161 and the disk 91B, without being welded to either the disk 161 or the disk 91B.

[0161] [Other Application Examples of the First to Third Embodiments] The configurations of the first to third embodiments can all be applied to a built-in control valve type damping force generating mechanism.

[0162] 11 and 12 show a shock absorber 1C having a built-in control valve type damping force generating mechanism 33C, in which the main components of the damping force generating mechanism 33B of the third embodiment are applied to the extension side of the damping force generating mechanism 33C. Note that, here too, the same names and symbols are used for parts that are common to the third embodiment.

[0163] As shown in Figure 11, the damping force generating mechanism 33C separates the inner tube 3 of the cylinder 2 into an upper chamber 19 and a lower chamber 20 by a piston 18C. The damping force generating mechanism 33C has a case 401C, a solenoid 402C covered by the case 401C, and a piston bolt portion 403C which serves as a shaft member. In the damping force generating mechanism 33C, the case 401C is connected to a connecting rod 404C. This connecting rod 404C extends from the cylinder 2 to the outside through the rod guide 22 (see Figure 1) and the seal member 23 (see Figure 1).

[0164] An extension-side damping force generating mechanism 411C is provided on the lower chamber 20 side of the piston 18C, and a compression-side damping force generating mechanism 412C is provided on the upper chamber 19 side of the piston 18C.

[0165] The extension-side damping force generating mechanism 411C will be described with reference to Figure 12. Oil L passes from the upper chamber 19 through the extension-side piston-side passage 43C, passes through the extension-side inlet orifice 142 provided in the disc 70, passes through the extension-side inlet port 416C provided in the piston bolt 415C, and enters the extension-side pilot chamber 95C.

[0166] The extension-side pilot chamber 95C is connected to the back pressure chamber 184 for the extension-side first damping valve 72 via a pilot communication passage 418C provided in the piston bolt 415C and a passage in the passage groove 124 provided in the pilot case 81B.

[0167] Pilot valve 421C installed in piston bolt 415C receives a closing force from the thrust of solenoid 402C, and opens when the valve opening force produced by the biasing force of spring 422C and the pressure in pilot chamber 95C exceeds the thrust of solenoid 402C. When pilot valve 421C opens, oil L in pilot chamber 95C passes through compression-side inlet port 424C, opens disc valve 426C provided with compression-side inlet orifice 425C, passes through compression-side piston-side passage 44C, and flows into lower chamber 20.

[0168] The oil L that passes through the extension-side piston-side passage 43C from the upper chamber 19 passes through the extension-side inlet orifice 142 provided in the disc 70, passes through the extension-side inlet port 416C provided in the piston bolt 415C, and enters the extension-side pilot chamber 95C. After that, the oil L that passes through the passage in the passage groove 30C provided in the piston bolt 415C is introduced into the sub-back pressure chamber 182 of the back pressure chamber 184 via the passage in the passage groove 124 provided in the pilot case 81B, passes through the regulating disc 78B and the communicating orifice 166 provided in the disc 77, and enters the main back pressure chamber 181 of the back pressure chamber 184.

[0169] A valve 192B provided in the sub-back pressure chamber 182 separates the sub-back pressure chamber 182 from a variable chamber 183 into which hydraulic oil L is introduced from the lower chamber 20 via an orifice 313B provided in the pilot case 81B and a lower-chamber communicating passage 211B. The valve 192B also constitutes a check valve 191B that only allows hydraulic oil L to flow from the lower chamber 20 to the back pressure chamber 184 via the orifice 313B and the lower-chamber communicating passage 211B. During the extension stroke, the check valve 191B is normally closed to maintain the pilot pressure in the back pressure chamber 184. When the axial movement of the piston 18C is high-frequency, the deflection amount of the valve 192B is small, and the internal pressure of the back pressure chamber 184 is low. When the axial movement of the piston 18C is low-frequency, the deflection amount of the valve 192B is large, and the internal pressure of the back pressure chamber 184 is high. Therefore, the valve opening pressure of the first damping valve 72 can be changed according to the frequency. This frequency can be adjusted by the introduction orifice 142 provided in the disk 70. Furthermore, the valve opening pressure of the first damping valve 72 can be adjusted by the disk rigidity of the first damping valve 72 at high frequencies, and by the disk rigidity of the second damping valve 84 at low frequencies. Volume compensation for the moving volume of the valve 192B is performed by the lower chamber communicating passage 211B and orifice 313B provided in the pilot case 81B.

[0170] When the hydraulic fluid L in the back pressure chamber 184 reaches a predetermined pressure, it passes through the passage in the passage groove 30C, opens the second damping valve 84, and flows into the lower chamber 20. When the first damping valve 72 opens during the extension stroke, the second damping valve 84 is open in this manner, and the back pressure chamber 184 communicates with the lower chamber 20. This makes it possible to compensate for the volume of hydraulic fluid L that corresponds to the volume of movement of the first damping valve 72.

[0171] The diameter of the back pressure chamber 184 is larger than the diameter of the valve seat portion 53 of the piston 18C. Therefore, the first damping valve 72 on the extension side receives the pressure of the lower chamber 20 during the compression stroke.

[0172] When the pressure in the lower chamber 20 rises during the compression stroke and reaches a predetermined pressure, the valve 192B of the check valve 191B provided in the pilot case 81B opens to introduce pressure into the back pressure chamber 184, causing a valve closing force due to the back pressure to act on the first damping valve 72. This valve closing force exceeds the valve opening force due to the pressure in the lower chamber 20 acting on the outer circumferential side of the first damping valve 72, thereby preventing the first damping valve 72 from opening during the compression stroke.

[0173] The compression-side damping force generating mechanism 412C will now be described. Oil L passes from the lower chamber 20 through the compression-side piston-side passage 44C, passes through the compression-side inlet orifice 425C provided in the disc valve 426C, and enters the passage in the compression-side passage groove 431C.

[0174] The passage in the compression side passage groove 431C is connected to a back pressure chamber 442C for the compression side first damping valve 441C via an orifice 455C of a check valve 451C provided in a pilot case 432C.

[0175] Pilot valve 421C installed in piston bolt 415C receives a closing force from the thrust of solenoid 402C, and opens when the valve-opening force due to the pressure of spring 422C and pilot chamber 95C exceeds the thrust of solenoid 402C. When pilot valve 421C opens, oil L that has entered the passage in passage groove 431C flows from compression-side inlet port 424C through extension-side pilot chamber 95C, opens disc 70 provided with extension-side inlet orifice 142, and flows through extension-side piston-side passage 43C to upper chamber 19.

[0176] A check valve 451C that allows only the flow of hydraulic oil L from the upper chamber 19 to the back pressure chamber 442C and an upper chamber communication passage 452C are provided inside the pilot case 432C, and an orifice 455C is provided on the inner periphery of the check valve 451C. During the compression stroke, the check valve 451C is normally closed to maintain the pilot pressure in the back pressure chamber 442C.

[0177] When the first damping valve 441C opens during the compression stroke, the back pressure chamber 442C is connected to the upper chamber 19 via the orifice 455C and the passage in the passage groove 431C, making it possible to compensate for the volume of oil L moving through the first damping valve 441C.

[0178] At the bottom of the pilot case 432C, where the compression side first damping valve 441C is installed, there are provided a second damping valve 461C, an inner circumferential groove 462C, and a relief communication passage 463C for relieving the pressure in the back pressure chamber 442C that has reached a predetermined pressure to the upper chamber 19.

[0179] The seat of the second damping valve 461C is an irregularly shaped seat, which separates a relief communication passage 463C from an upper chamber communication passage 452C. The amount of back pressure introduced can be adjusted by a notch 465C provided in the seat.

[0180] Here, since the diameter of the back pressure chamber 442C of the first damping valve 441C is larger than the diameter of the valve seat portion 57 of the piston 18C, the compression side first damping valve 441C receives the pressure of the upper chamber 19 during the extension stroke.

[0181] When the pressure in the upper chamber 19 rises during the extension stroke and reaches a predetermined pressure, the check valve 451C opens to introduce pressure into the back pressure chamber 442C, causing a valve closing force due to the back pressure to act on the first damping valve 441C. This valve closing force exceeds the valve opening force due to the pressure in the upper chamber 19 acting on the outer periphery of the first damping valve 441C, preventing the first damping valve 441C from opening during the extension stroke.

[0182] According to the above-described embodiment of the present invention, it is possible to provide a shock absorber and a damping force generating mechanism that can smoothly operate the damping force generating mechanism, and thus the present invention has great industrial applicability.

[0183] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C... shock absorber, 2... cylinder, 18... piston, 19... upper chamber (first cylinder chamber), 20... lower chamber (second cylinder chamber), 41... first valve mechanism (valve mechanism), 72... first damping valve (damping force generating member), 78, 78A, 78B... regulating disc (regulating member), 81... pilot case (biasing force generating member), 101... bottom, 166... ​​communicating orifice (second throttle mechanism), 181 ...Main back pressure chamber, 182...Sub back pressure chamber, 183...Variable chamber, 184...Back pressure chamber, 191, 191A, 191B...Check valve, 192, 192A, 192B...Valve (movable member), 193, 193A...Variable orifice (first throttling mechanism, first throttling portion), 201...First passage, 202...Second passage, 241, 241, 241B...Frequency sensitive mechanism, 313B...Orifice (first throttling mechanism, first throttling portion).

Claims

1. A cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder and dividing the interior of the cylinder into a first cylinder chamber and a second cylinder chamber; a first passage through which working fluid flows from one chamber in the cylinder as the piston moves; a second passage provided in parallel with the first passage; Both act when the first cylinder chamber is at upstream pressure. a valve mechanism provided in the first passage and capable of adjusting a damping force according to a pressure in a main back pressure chamber; a frequency response mechanism that is provided in the second passage and changes a volume by movement of a movable member; Both act when the second cylinder chamber is at upstream pressure. A check valve provided in the second passage; a first throttling mechanism provided downstream or upstream of the check valve and configured to control the flow of working fluid to the main back pressure chamber; having A sub-back pressure chamber is provided between the first throttling mechanism and the main back pressure chamber. buffer.

2. The shock absorber according to claim 1 , wherein the movable member also serves as the check valve.

3. 3. The shock absorber according to claim 1, wherein the sub back pressure chamber is connected to the main back pressure chamber via a second throttle mechanism.

4. A cylinder in which a working fluid is sealed, a piston slidably fitted in the cylinder and dividing the interior of the cylinder into a first cylinder chamber and a second cylinder chamber; a first passage through which working fluid flows from one chamber in the cylinder as the piston moves; a second passage provided in parallel with the first passage; Both act when the first cylinder chamber is at upstream pressure. a valve mechanism provided in the first passage and capable of adjusting a damping force according to a pressure in a main back pressure chamber; a frequency response mechanism that is provided in the second passage and changes a volume by movement of a movable member; Both act when the second cylinder chamber is at upstream pressure. A check valve provided in the second passage; a variable orifice that operates to narrow a portion of a flow path of the second passage when the check valve is opened, thereby controlling the flow of the working fluid to the main back pressure chamber; A shock absorber having a shock absorber.