Buffer

Abstract

To provide a buffer which can improve durability.SOLUTION: A buffer includes: an attenuation force generation mechanism 40 provided on first passages 101, 132; and a frequency sensing unit provided in a lower chamber 20, which is on a second passage 107 parallel with the first passages 101, 132 and is a one-side chamber in a cylinder 2. The attenuation force generation mechanism 40 includes: a main valve 231 provided in the one-side chamber 20 in the cylinder 2 for generating an attenuation force by suppressing flow of an oil liquid L caused by sliding of a piston 18; and a main valve 129 provided in the other side chamber 19 in the cylinder 2 for generating an attenuation force by suppressing the flow of the oil liquid L caused by sliding of the piston 18. A sub valve 130 forming a normal communication path 127, which is a normal communication path which can communicate between the lower chamber 20 and an upper chamber 19 in the cylinder 2, is disposed on the side of a main valve 129 provided in the upper chamber 19 among the main valves 129, 231.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Some shock absorbers have a variable damping force that is sensitive to frequency (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7038613 Summary of the Invention [Problem to be solved by the invention]

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

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

[0006] In order to achieve the above object, a shock absorber according to one aspect of the present invention includes a cylinder in which a working fluid is sealed, a piston slidably fitted within the cylinder and dividing the interior of the cylinder into two chambers, a piston rod having one end connected to the piston and the other end extending to the outside of the cylinder, a first passage through which the working fluid flows from one of the chambers as the piston moves, a second passage provided in parallel with the first passage, a damping force generating mechanism provided in the first passage and generating a damping force, and a frequency sensitive portion provided in the second passage in one side chamber of the cylinder. The damping force generating mechanism has a first main valve provided in one side chamber of the cylinder, which generates a damping force by suppressing the flow of working fluid caused by the sliding of the piston, and a second main valve provided in the other side chamber of the cylinder, which generates a damping force by suppressing the flow of working fluid caused by the sliding of the piston, and a sub-valve forming a constant communication passage that can communicate between the one side chamber of the cylinder and the other side chamber of the cylinder is arranged on the second main valve side of the first main valve and the second main valve. [Effects of the Invention]

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

[0008] [Figure 1] 1 is a partially cross-sectional front view showing a shock absorber according to an embodiment of the present invention. [Figure 2] 1 is a partial cross-sectional view showing the periphery of a piston of a shock absorber according to an embodiment of the present invention. [Figure 3] 1 is a partial cross-sectional view showing the periphery of a damping force generating portion on an extension side of a shock absorber according to an embodiment of the present invention. [Figure 4] 1 is a partial cross-sectional view showing the periphery of a frequency sensitive portion of a shock absorber according to an embodiment of the present invention. [Figure 5] FIG. 2 is a plan view showing one of the disks that form a fixed orifice of the shock absorber according to the embodiment of the present invention. [Figure 6] FIG. 10 is a plan view showing the other disk that forms the fixed orifice of the shock absorber according to the embodiment of the present invention. [Figure 7] 4 is a characteristic diagram showing the damping force characteristics of the shock absorber according to the embodiment of the present invention when the piston speed is in a very low speed range and a low speed range. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described with reference to the drawings. For ease of explanation, the upper side in Figures 1 to 4 will be referred to as "top" and the lower side in Figures 1 to 4 will be referred to as "bottom."

[0010] As shown in Fig. 1, the shock absorber 1 of this embodiment is a so-called twin-cylinder hydraulic shock absorber, and includes a cylinder 2 in which hydraulic fluids, such as oil L and gas G, are sealed. The cylinder 2 includes a cylindrical inner cylinder 3 and a bottomed cylindrical outer cylinder 4 that is larger in diameter than the inner cylinder 3 and is concentrically arranged to cover the inner cylinder 3, and a reservoir chamber 6 is formed between the inner cylinder 3 and the outer cylinder 4. The cylinder 2 has oil L sealed within the inner cylinder 3, and oil L and gas G sealed in the reservoir chamber 6. The shock absorber 1 includes a cover 7 that covers the upper opening side of the outer cylinder 4, and a main bracket 8 and a spring seat 9, both of which are fixed to the outer periphery of the outer cylinder 4.

[0011] The outer cylinder 4 is composed of a cylindrical body 11 and a cylinder bottom 12 that is integrally formed with the lower side of the body 11 and closes the lower part of the body 11.

[0012] The shock absorber 1 is provided with a piston 18 slidably fitted in the inner tube 3 of the cylinder 2. This piston 18 divides the inner tube 3 into two chambers: an upper chamber 19 (chamber, other side chamber) on one side, and a lower chamber 20 (chamber, one side chamber) on the other side. Oil liquid L is sealed in the upper chamber 19 and the lower chamber 20 of the inner tube 3 as a working fluid.

[0013] The shock absorber 1 is equipped with a piston rod 21, one end of which is disposed within the inner tube 3 of the cylinder 2 and connected to the piston 18, and the other end of which extends out of the cylinder 2. The piston 18 and the piston rod 21 move together. During the extension stroke, in which the piston rod 21 increases the amount of protrusion from the cylinder 2, the piston 18 moves toward the upper chamber 19, and during the compression stroke, in which the piston rod 21 decreases the amount of protrusion from the cylinder 2, the piston 18 moves toward the lower chamber 20.

[0014] Rod guides 22 are fitted to the upper end openings of the inner cylinder 3 and the outer cylinder 4, and a seal member 23 is attached to the outer cylinder 4 above the rod guide 22, closer to the exterior of the cylinder 2. A friction member 24 is provided between the rod guide 22 and the seal member 23. The rod guide 22, the seal member 23, and the friction member 24 are all annular, and the piston rod 21 is slidably inserted through the rod guide 22, the friction member 24, and the seal member 23, and extends from the interior of the cylinder 2 to the exterior.

[0015] The rod guide 22 supports the piston rod 21 so that it can move axially while restricting its radial movement, thereby guiding the movement of the piston rod 21. The seal member 23 has its outer periphery in close contact with the outer tube 4 and its inner periphery in sliding contact with the outer periphery of the piston rod 21 moving in the axial direction, preventing leakage of the oil L in the inner tube 3 and the high-pressure gas G and oil L in the reservoir chamber 6 in the outer tube 4 to the outside. The friction member 24 has its inner periphery in sliding contact with the outer periphery of the piston rod 21, generating frictional resistance in the piston rod 21. Note that the friction member 24 is not intended as a seal.

[0016] The rod guide 22 has a stepped outer periphery with a larger diameter at the top than at the bottom, with the smaller-diameter lower part fitting into the inner periphery of the upper end of the inner cylinder 3 and the larger-diameter upper part fitting into the inner periphery of the upper part of the outer cylinder 4. A base valve 25 that separates the lower chamber 20 and the reservoir chamber 6 is installed on the cylinder bottom 12 of the outer cylinder 4, and the inner periphery of the lower end of the inner cylinder 3 is fitted into this base valve 25. The upper end of the outer cylinder 4 is crimped radially inward, and this crimped portion and the rod guide 22 hold a seal member 23 in place.

[0017] The piston rod 21 has a main shaft portion 27 and a mounting shaft portion 28 (shaft portion) having a smaller diameter than the main shaft portion 27. The mounting shaft portion 28 is disposed inside the cylinder 2, and the piston 18 and the like are attached to the mounting shaft portion 28. The end of the main shaft portion 27 on the mounting shaft portion 28 side forms a shaft step portion 29 that widens in a direction perpendicular to the axis. A passage groove 30 that is cut out and extends axially at a midpoint in the axial direction is formed on the outer periphery of the mounting shaft portion 28, and a male thread 31 is formed on the axial opposite side from the main shaft portion 27. The passage groove 30 is formed so that the cross section of the plane perpendicular to the central axis of the piston rod 21 has a rectangular, square, or D-shaped shape.

[0018] The piston rod 21 is provided with a stopper member 32, a pair of buffer bodies 33, and a coil spring 34, all of which are annular, in a portion of the main shaft portion 27 between the piston 18 and the rod guide 22. The piston rod 21 is inserted into the inner peripheral side of the stopper member 32, and the stopper member 32 is fixed to the main shaft portion 27 by crimping. Arranged in this order from the stopper member 32 side are one buffer body 33, a coil spring 34, and the other buffer body 33. The piston rod 21 is inserted into the inside of this pair of buffer bodies 33 and coil spring 34, and they are arranged between the stopper member 32 and the rod guide 22. Note that, although an example in which the stopper member 32, buffer body 33, and coil spring 34 are provided has been shown, other stopper mechanisms, such as a hydraulic locking mechanism or only a cushion, may also be used.

[0019] In shock absorber 1, for example, the portion of piston rod 21 protruding from cylinder 2 is positioned at the top and supported by the vehicle body, and the main bracket 8 on the cylinder 2 side is positioned at the bottom and connected to the wheel. In the case of a mono-tube shock absorber, the cylinder 2 may be supported by the vehicle body and the piston rod 21 may be connected to the wheel. When the wheel vibrates as the vehicle moves, the relative positions of cylinder 2 and piston rod 21 change with the vibration. However, this change is suppressed by the fluid resistance of the flow passages formed in at least one of piston 18 and piston rod 21. As described in detail below, the fluid resistance of the flow passages formed in at least one of piston 18 and piston rod 21 is designed to vary depending on the speed and amplitude of the vibration. By suppressing the vibration, ride comfort is improved. In addition to the vibration generated by the wheel, inertial force and centrifugal force generated in the vehicle body as the vehicle moves also act between cylinder 2 and piston rod 21. For example, when the driving direction is changed by operating the steering wheel, centrifugal force is generated in the vehicle body, and 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 the force generated in the vehicle body as the vehicle travels, and high stability during vehicle travel is obtained.

[0020] As shown in FIG. 2, the piston 18 is composed of a metal piston body 35 supported by the mounting shaft portion 28 of the piston rod 21, and an annular sliding member 36 made of synthetic resin that is integrally attached to the outer peripheral surface of the piston body 35 and slides inside the inner cylinder 3.

[0021] The piston body 35 is provided with a plurality of passage holes 37 (only one is shown in FIG. 2 because it is a cross-section) that communicate between the upper chamber 19 and the lower chamber 20, and a plurality of passage holes 39 (only one is shown in FIG. 2 because it is a cross-section) that communicate between the upper chamber 19 and the lower chamber 20. The plurality of passage holes 37 are formed at equal intervals in the circumferential direction, with one passage hole 39 sandwiched between each of them, and constitute half of the passage holes 37, 39. The plurality of passage holes 37 open radially outward on one axial side of the piston 18 (upper side in FIG. 2) and radially inward on the other axial side (lower side in FIG. 2).

[0022] These passage holes 37 are provided with damping force generating units 41 of a damping force generating mechanism 40 that opens and closes the passages in these passage holes 37 to generate a damping force. The damping force generating unit 41 is arranged on the lower chamber 20 side in the axial direction, which is one axial end side of the piston 18, and is attached to the piston rod 21. By arranging the damping force generating unit 41 on the lower chamber 20 side, the passages formed inside each of the multiple passage holes 37 become passages through which oil L as a working fluid 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. The damping force generating units 41 provided for the passages in these passage holes 37 serve as extension-side damping force generating units that suppress the flow of oil L in the passages in the extension-side passage holes 37 to generate a damping force.

[0023] The remaining half of the passage holes 37, 39, the passage holes 39, are formed at equal intervals in the circumferential direction with one passage hole 37 sandwiched between each other, and the other axial side of the piston 18 (the lower side in Figure 2) opens radially outward, and one axial side (the upper side in Figure 2) opens radially inward.

[0024] These passage holes 39 are provided with damping force generating units 42 of a damping force generating mechanism 40 that opens and closes the passages in these passage holes 39 to generate a damping force. The damping force generating unit 42 is arranged on the upper chamber 19 side in the axial direction, which is the other axial end side of the piston 18, and is attached to the piston rod 21. By arranging the damping force generating unit 42 on the upper chamber 19 side, the passages formed inside each of the multiple passage holes 39 become passages through which the oil L flows from the lower chamber 20 to the upper chamber 19 when the piston 18 moves toward the lower chamber 20, that is, during the compression stroke. The damping force generating units 42 provided for the passages in these passage holes 39 serve as compression-side damping force generating units that suppress the flow of oil L in the passages in the compression-side passage holes 39 to generate a damping force.

[0025] As described above, the piston 18 is provided with a damping force generating mechanism 40 having a damping force generating portion 41 on the lower chamber 20 side and a damping force generating portion 42 on the upper chamber 19 side.

[0026] In the shock absorber 1, the passage portions within the multiple passage holes 37 and the passage portions within the multiple passage holes 39 are connected so that oil liquid L, which is a working fluid, flows between the upper chamber 19 and the lower chamber 20 as the piston 18 moves. The oil liquid L passes through the passage portion within the passage hole 37 when the piston rod 21 and the piston 18 move to the extension side (upper side in Figure 2), and the oil liquid L passes through the passage portion within the passage hole 39 when the piston rod 21 and the piston 18 move to the compression side (lower side in Figure 2).

[0027] The piston body 35 has a generally circular disk shape, and a fitting hole 45 is formed in its radial center, penetrating in the axial direction, for fitting with the mounting shaft portion 28 of the piston rod 21. At the end of the piston body 35 on the lower chamber 20 side in the axial direction, the portion between the fitting hole 45 and the passage hole 37 supports the inner peripheral side of a main valve 231 (described later) of the damping force generating section 41, and at the end of the piston body 35 on the upper chamber 19 side in the axial direction, the portion between the fitting hole 45 and the passage hole 39 supports the inner peripheral side of a main valve 129 (described later) of the damping force generating section 42.

[0028] An annular valve seat portion 47, which is part of the damping force generating portion 41, is formed at the axial end of the piston body 35 facing the lower chamber 20, radially outward of the opening of the passage hole 37 facing the lower chamber 20. Furthermore, an annular valve seat portion 49, which is part of the damping force generating portion 42, is formed at the axial end of the piston body 35 facing the upper chamber 19, radially outward of the opening of the passage hole 39 facing the upper chamber 19. The fitting hole 45 of the piston body 35 has a small diameter hole portion 201 on the axial side of the valve seat portion 49, into which the mounting shaft portion 28 of the piston rod 21 is fitted, and a large diameter hole portion 202 which has a larger diameter than the small diameter hole portion 201 and is formed on the axial side of the valve seat portion 47 than the small diameter hole portion 201.

[0029] In the piston body 35, an opening on the lower chamber 20 side of the compression-side passage hole 39 is located on the opposite side of the fitting hole 45 of the valve seat portion 47, and an opening on the upper chamber 19 side of the extension-side passage hole 37 is located on the opposite side of the fitting hole 45 of the valve seat portion 49.

[0030] As shown in FIG. 3, on the lower chamber 20 side of the piston 18, in order from the piston 18 side in the axial direction, one disk 51, one disk 210, one disk 216, one pilot valve 52, one disk 53, and one pilot case member 55 are stacked.

[0031] On the opposite side of the pilot case member 55 from the disk 53, stacked in order from the pilot case member 55 side in the axial direction are one disk 56, a plurality of (specifically, five) disks 57, and as shown in Figure 4, a plurality of (specifically, two) disks 58, a plurality of (specifically, two) disks 59, a plurality of (specifically, two) disks 60, one disk 61, and one disk 62.

[0032] The discs 51, 53, 56-62, 210, 216 and the pilot case member 55 are made of metal. The discs 51, 53, 56-62, 210, 216 are each a flat plate with holes of a constant thickness, into which the mounting shaft portion 28 of the piston rod 21 can be fitted. The discs 51, 56-60, 62, 216 are provided to be flexible. The pilot valve 52 and the pilot case member 55 are each annular, into which the mounting shaft portion 28 of the piston rod 21 can be fitted. The discs 51, 53, 56-62, 210, 216 are each a circular plate.

[0033] As shown in FIG. 3 , the pilot case member 55 is a cylindrical member with a bottom, including a perforated disk-shaped bottom 71, a cylindrical inner cylindrical portion 72 that protrudes from the inner periphery of the bottom 71 to one side along the axial direction of the bottom 71, and a cylindrical outer cylindrical portion 73 that protrudes from the outer periphery of the bottom 71 to the same side as the inner cylindrical portion 72 along the axial direction of the bottom 71. A through-hole 74 is formed in the bottom 71, penetrating in the axial direction, between the inner cylindrical portion 72 and the outer cylindrical portion 73. A small-diameter hole 75 is formed in the inner periphery of the pilot case member 55 on the axial side facing the inner cylindrical portion 72, into which the mounting shaft portion 28 of the piston rod 21 is fitted, and a large-diameter hole 76, having a diameter larger than the small-diameter hole 75, is formed on the axial opposite side of the inner cylindrical portion 72. An opening 77 is formed on the side of the outer cylindrical portion 73 opposite the bottom 71. The pilot case member 55 comprises an outer cylindrical portion 73 having an opening 77 at one end, an inner cylindrical portion 72 and a bottom portion 71 .

[0034] The bottom 71 of the pilot case member 55 has a perforated, disk-shaped bottom body portion 70, an annular protruding portion 78 protruding from the inner periphery of the bottom body portion 70 toward the opposite side of the inner tubular portion 72, and an annular valve seat portion 79 protruding from the outer periphery of the bottom body portion 70 toward the opposite side of the outer tubular portion 73. In other words, the bottom 71 is formed with the protruding portion 78 protruding from the inner periphery toward the opposite side of the inner tubular portion 72, and the valve seat portion 79 protruding from the outer periphery toward the opposite side of the outer tubular portion 73. The through hole 74 is formed in the portion of the bottom body portion 70 between the protruding portion 78 and the valve seat portion 79. The protruding portion 78 is partially formed in the circumferential direction, with a flow path groove 81 extending radially across the protruding portion 78. The flow path groove 81 opens into the large-diameter hole portion 76.

[0035] The end of the inner cylindrical portion 72 of the pilot case member 55 opposite the axial protrusion 78 abuts against the disk 53, and the end of the protrusion 78 opposite the axial end of the inner cylindrical portion 72 abuts against the inner circumferential side of the disk 56. A flow path groove 81 extends radially across the portion of the protrusion 78 that contacts the disk 56. The pilot valve 52 is disposed on the opening 77 side of the pilot case member 55. A back pressure chamber 80 is formed between the inner cylindrical portion 72 and the outer cylindrical portion 73 of the pilot case member 55, and pressure is applied to the pilot valve 52 in the direction of the piston 18. A pressure receiving chamber 82 is formed between the protrusion 78 and the valve seat portion 79 of the pilot case member 55, and is constantly in communication with the back pressure chamber 80 via a passage in the through hole 74.

[0036] The disk 51 has an outer diameter smaller than the inner diameter of the valve seat portion 47. The disk 51 is formed with a notch 87 extending radially outward from its inner peripheral edge, which fits onto the mounting shaft portion 28 of the piston rod 21. The passage within the notch 87 is constantly in communication with the passage within the passage hole 37 of the piston 18, and the passage within the passage hole 37 is constantly in communication with the passage between the large diameter hole portion 202 of the piston 18 and the mounting shaft portion 28, and with the passage within the passage groove 30 of the piston rod 21, via the passage within the notch 87.

[0037] The disk 210 has an outer diameter smaller than the outer diameter of the disk 51. The disk 210 has an outer diameter that does not close the passage portion in the notch 87 of the disk 51.

[0038] The disk 216 has an outer diameter equal to the outer diameter of the valve seat portion 47 of the piston 18. The disk 216 abuts against the valve seat portion 47, and opens and closes the opening of the passage portion in the passage hole 37 formed in the piston 18 by moving away from and abutting against the valve seat portion 47.

[0039] The pilot valve 52 comprises a metal disc 85 and a rubber seal member 86 fixed to the disc 85. The disc 85 is a flexible, circular plate with holes and a constant thickness into which the mounting shaft portion 28 of the piston rod 21 can be fitted, and has an outer diameter slightly larger than that of the disc 216. The seal member 86 is fixed to the outer periphery of the disc 85, opposite the piston 18, and is annular in shape. In other words, the pilot valve 52 has an annular seal member 86 on its outer periphery.

[0040] The seal member 86 is slidably and liquid-tightly fitted around the entire inner circumferential surface of the outer cylindrical portion 73 of the pilot case member 55, and constantly seals the gap between the pilot valve 52 and the outer cylindrical portion 73. In other words, the pilot valve 52 has the seal member 86 slidably and tightly fitted into the outer cylindrical portion 73 of the pilot case member 55. As a result, the pilot valve 52 and the pilot case member 55 form a back pressure chamber 80 between them.

[0041] As described above, the disc 216 can be seated on the valve seat portion 47 of the piston 18. The disc 216 and the pilot valve 52 constitute an extension-side main valve 231 (first main valve) provided in the lower chamber 20 of the cylinder 2, which is provided in a passage portion within the passage hole 37 formed in the piston 18 and which suppresses the flow of hydraulic fluid L caused by the piston 18 sliding toward the extension side (upper side in FIG. 3 ) to generate a damping force. Therefore, the main valve 231 is disposed in the opening 77 of the pilot case member 55, and forms a back pressure chamber 80 inside the pilot case member 55. The back pressure chamber 80 between the pilot valve 52 and the pilot case member 55 applies internal pressure to the main valve 231 in the direction of the piston 18, i.e., in the valve-closing direction to seat the disc 216 on the valve seat portion 47.

[0042] The main valve 231 is a pilot-type damping valve having a back pressure chamber 80, and the main valve 231 and the back pressure chamber 80 constitute a part of the damping force generating section 41. In other words, the damping force generating section 41 includes the main valve 231 and the back pressure chamber 80, and is a pressure-controlled valve mechanism.

[0043] The disk 53 has an outer diameter that is approximately the same as the outer diameter of the end of the inner cylindrical portion 72 of the pilot case member 55 that faces the disk 53. The outer cylindrical portion 73 of the pilot case member 55 abuts against the disk 85 of the pilot valve 52, suppressing deformation of the main valve 231 in the opening direction beyond a specified limit.

[0044] The passage in the flow passage groove 81 formed in the bottom portion 71 of the pilot case member 55 is constantly in communication with the back pressure chamber 80 via the pressure receiving chamber 82 and the passage in the through hole 74. The back pressure chamber 80 is constantly in communication with the passage between the large diameter hole 76 of the pilot case member 55 and the mounting shaft portion 28, and the passage in the passage groove 30 of the piston rod 21, via the passage in the through hole 74, the pressure receiving chamber 82, and the passage in the flow passage groove 81.

[0045] The passage portion within the notch 87 of the disk 51, the passage portion between the large-diameter hole portion 202 of the piston 18 and the mounting shaft portion 28, the passage portion within the passage groove 30 of the piston rod 21, the passage portion between the large-diameter hole portion 76 of the pilot case member 55 and the mounting shaft portion 28, the passage portion within the flow path groove 81 formed in the bottom portion 71 of the pilot case member 55, the pressure-receiving chamber 82, and the passage portion within the through hole 74 constitute a back pressure introduction passage 235 that constantly connects the passage portion within the passage hole 37 of the piston 18 with the back pressure chamber 80 and introduces oil L from the upper chamber 19 to the back pressure chamber 80 via the passage portion within the passage hole 37. Thus, the back pressure introduction passage 235 includes the passage portion within the flow path groove 81 formed in the bottom portion 71 of the pilot case member 55 and the passage portion within the through hole 74. In other words, a portion of the back pressure introduction passage 235 is provided in the bottom portion 71 of the pilot case member 55.

[0046] When the disc 216 of the main valve 231 is lifted off the valve seat 47 of the piston 18 and opens, the oil L from the passage portion within the passage hole 37 flows into the lower chamber 20 via the passage portion between the valve seat 47 and the passage portion between the piston 18 and the outer tubular portion 73 of the pilot case member 55. The passage portions formed inside each of the plurality of passage holes 37, the passage between the main valve 231 and the valve seat 47, and the passage portion between the piston 18 and the outer tubular portion 73 of the pilot case member 55 form a passage 101 (first passage). This passage 101 serves as an extension-side passage through which the oil L as working fluid 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. The extension-side damping force generating unit 41, which includes the valve seat portion 47 and the main valve 231, is provided in this passage 101, and generates a damping force by opening and closing this passage 101 with the main valve 231 to suppress the flow of hydraulic fluid L. The extension-side damping force generating unit 41 introduces a portion of the hydraulic fluid L flowing in the passage 101 into the back pressure chamber 80 via a back pressure introducing passage 235, and controls the opening of the main valve 231 using the pressure in the back pressure chamber 80.

[0047] The damping force generating mechanism 40 has its main valve 231 provided in the passage 101 to generate a damping force. The damping force generating section 41 including the main valve 231 of the damping force generating mechanism 40 does not have a fixed orifice, which is a constant communication passage that constantly connects the upper chamber 19 and the lower chamber 20. Therefore, the passage 101 is not a passage that constantly connects the upper chamber 19 and the lower chamber 20.

[0048] The disk 56 has an outer diameter that is smaller than the inner diameter of the valve seat portion 79 of the pilot case member 55 and larger than the outer diameter of the protrusion 78. No grooves or the like for forming a flow path are formed in the disk 56. The multiple disks 57 have an outer diameter that is slightly larger than the outer diameter of the valve seat portion 79 and can be seated on the valve seat portion 79.

[0049] As shown in FIG. 4, disk 58 has an outer diameter smaller than that of disk 57. Disk 59 has an outer diameter smaller than that of disk 58. Disk 60 has an outer diameter smaller than that of disk 59. Disk 61 has an outer diameter smaller than that of disk 60. Disk 62 has an outer diameter equal to that of disk 59.

[0050] The discs 56-60 form a valve 99 that can be seated on and removed from the valve seat portion 79. The valve 99 is seated on the valve seat portion 79 of the disc 57, defining a pressure-receiving chamber 82 inside the valve seat portion 79. When the valve 99 is released from the valve seat portion 79, the back pressure chamber 80 shown in FIG. 3 communicates with the lower chamber 20 via the pressure-receiving chamber 82 and the passage portion in the through-hole 74, and the valve 99 suppresses the flow of oil L between them. The pressure-receiving chamber 82 between the protrusion 78 of the pilot case member 55 and the valve seat portion 79 applies pressure to the valve 99, which is in contact with the valve seat portion 79, in a direction away from the valve seat portion 79. The passage portions formed inside each of the multiple passage holes 37, the back pressure introduction passage 235, the pressure-receiving chamber 82, and the space between the valve 99 and the valve seat portion 79 are arranged partially in parallel with the passage 101 to form a passage 103 that communicates the upper chamber 19 and the lower chamber 20.

[0051] When the pressure in the back pressure chamber 80 reaches a predetermined pressure, the valve 99 lifts off the valve seat portion 79 to open the passage 103. The valve 99, together with the valve seat portion 79, constitutes a damping force generating portion 105 that opens when the pressure in the back pressure chamber 80 reaches a predetermined pressure, opening the passage 103 and generating a damping force. The valve 99 opens due to the pressure in the back pressure chamber 80, allowing the hydraulic fluid L to flow from the passage 103 to the lower chamber 20, and at that time, applies resistance to the flow of the hydraulic fluid L.

[0052] The damping force generating section 105 including the valve 99 does not have a fixed orifice, which is a constant communication passage that constantly connects the upper chamber 19 and the lower chamber 20. Therefore, the passage 103 is not a passage that constantly connects the upper chamber 19 and the lower chamber 20.

[0053] The disk 62 shown in FIG. 4 comes into contact with the valve 99 when the valve 99 is deformed in the opening direction, and together with a case member 131 (described later), prevents the valve 99 from deforming beyond a specified level.

[0054] 2, on the upper chamber 19 side of the piston 18, there are stacked, in order from the piston 18 side in the axial direction, one disk 110, one disk 111, one disk 112, one disk 113, one disk 114, a plurality of (specifically, two) disks 115, one disk 116, a plurality of (specifically, two) disks 117, one disk 118, one disk 119, and one annular member 120. The disks 110 to 119 and the annular member 120 are made of metal, and each has the shape of a perforated circular flat plate of a certain thickness into which the mounting shaft portion 28 of the piston rod 21 can be fitted. The disks 111 to 117 and 119 are provided to be flexible.

[0055] The disk 110 has an outer diameter that is smaller than the inner diameter of the valve seat portion 49 of the piston 18 .

[0056] The disk 111 has an outer diameter equal to the outer diameter of the valve seat portion 49 of the piston 18. The disk 111 abuts against the valve seat portion 49, and opens and closes the opening of the passage portion in the passage hole 39 formed in the piston 18 by moving away from and abutting against the valve seat portion 49.

[0057] As shown in Fig. 5, the disk 111 has a plurality of arc-shaped passage holes 121 (specifically, two locations) formed at intervals in the circumferential direction of the disk 111. These passage holes 121 are of the same shape, arc-shaped with the same diameter and centered at the center of the disk 111, and penetrate the disk 111 in the axial direction. The maximum radius of these passage holes 121 measured from the center of the disk 111 is smaller than the radius of the inner circumferential surface of the valve seat portion 49 shown in Fig. 2, and the minimum radius of these passage holes 121 measured from the center of the disk 111 is larger than the radius of the outer circumferential surface of the disk 110. Thus, these passage holes 121 are disposed between the valve seat portion 49 and the disk 110.

[0058] The disk 112 has the same outer diameter as the disk 111. As shown in FIG. 6, the disk 112 has a plurality of notches 124 (specifically, five notches) formed on the outer periphery at equal intervals in the circumferential direction of the disk 112. These notches 124 have the same shape and are composed of outer notches 125 on the outer side in the radial direction of the disk 112 and inner notches 126 on the inner side in the radial direction of the disk 112. The outer notches 125 have a constant width in the circumferential direction of the disk 112, and the inner notches 126 are wider than the outer notches 125 in the circumferential direction of the disk 112. The length of the inner notches 126 in the circumferential direction of the disk 112 is shorter than the length of the passage holes 121 in the circumferential direction of the disk 111. When the disks 111 and 112 are stacked with their centers aligned, the passage holes 121 and the inner notches 126 communicate with each other by overlapping the radial positions of the disks 111 and 112. At this time, the disk 111 closes the outer notch 125 of the disk 112 on the side opposite to the disk 113 shown in FIG.

[0059] Disk 113 has the same outer diameter as disk 112. Disk 113 is centered and overlaps disk 112, completely closing the sides of the multiple cutouts 124 opposite to disk 111. Disk 114 has the same outer diameter as disk 113.

[0060] The passage portion within the passage hole 121 of the disc 111 and the passage portions within the plurality of notches 124 of the disc 112 form a fixed orifice 127, which is a constantly communicating passage that constantly communicates the upper chamber 19 and the lower chamber 20 via the passage portion within the passage hole 39. That is, in this fixed orifice 127, the oil liquid L introduced from the lower chamber 20 into the passage hole 39 flows from the passage portion within the passage hole 121 through the passage portions within the inner notches 126 of the notches 124 and the passage portions within the outer notches 125 to the upper chamber 19, the flow path area is narrowed from the passage portions within the inner notches 126 to the passage portions within the outer notches 125, and the oil liquid L flows into the upper chamber 19 from the passage portions within the outer notches 125. Furthermore, in this fixed orifice 127, oil L from the upper chamber 19 flows through a passage portion in an outer notch 125 of the notch 124 and a passage portion in an inner notch 126, then through a passage portion in the passage hole 121 and a passage portion in the passage hole 39, to the lower chamber 20, where the flow path area is narrowed in the passage portion of the outer notch 125, before flowing into the lower chamber 20. The fixed orifice 127 includes a choke passage 128. Specifically, the choke passage 128 is a portion of the flow path formed by the outer notch 125 of the disc 113, the disc 111, and the disc 112. The discs 111 to 113 constitute a choke valve 130 (sub-valve).

[0061] The disk 111 has a circular shape with a continuous outer periphery, and the disk 111 abuts against the valve seat portion 49 of the piston 18, opening and closing the opening of the passage portion in the passage hole 39 formed in the piston 18 by moving away from and abutting against the valve seat portion 49.

[0062] The plurality of discs 115 have an outer diameter smaller than that of disc 114. Disc 116 has an outer diameter smaller than that of disc 115. The plurality of discs 117 have an outer diameter smaller than that of disc 116. Disc 118 has an outer diameter smaller than that of disc 117. Disc 119 has an outer diameter equal to that of disc 116. The annular member 120 has an outer diameter smaller than that of disc 119, and is thicker and more rigid than discs 110 to 119. This annular member 120 abuts against the shaft step portion 29 of the piston rod 21.

[0063] The discs 111-117 are capable of being seated on and removed from the valve seat 49. When the discs 111-117 are seated on and removed from the valve seat 49, the passage portion in the passage hole 39 can be opened to the upper chamber 19. This constitutes a main valve 129 (second main valve) provided on the upper chamber 19 side of the cylinder 2, which generates a damping force by suppressing the flow of hydraulic fluid L between the upper chamber 19 and the lower chamber 20 caused by the piston 18 sliding toward the compression side, i.e., the lower chamber 20. The main valve 129 and the valve seat 49 constitute the compression-side damping force generating unit 42. The passage portions formed inside each of the plurality of passage holes 39 and the space between the main valve 129 and the valve seat 49 constitute a compression-side passage 132 (first passage) through which hydraulic fluid L flows from one of the lower chambers 20 when the piston 18 moves toward the compression side. The passage 103 shown in FIG. 3 is also provided in parallel with the passage 132 shown in FIG. 2. The damping force generating mechanism 40 has a main valve 129 disposed in a passage 132 to generate a damping force.

[0064] The main valve 129 is formed with a fixed orifice 127 including a choke passage 128 that constantly communicates between the upper chamber 19 and the lower chamber 20 even when the main valve 129 is in contact with the valve seat portion 49. The disc 119 and the annular member 120 abut against the main valve 129 to prevent the main valve 129 from deforming beyond a specified level in the opening direction. The fixed orifice 127 including the choke passage 128 and the choke valve 130 are provided in the main valve 129. In other words, the damping force generating unit 42 including the main valve 129 is provided with the fixed orifice 127, which is a constantly communicating passage that constantly communicates between the upper chamber 19 and the lower chamber 20. As described above, the damping force generating unit 41 including the main valve 231 is not provided with a fixed orifice, which is a constantly communicating passage that constantly communicates between the upper chamber 19 and the lower chamber 20. Therefore, in the damping force generating mechanism 40, the fixed orifice 127, which is a constant communication passage that can connect the upper chamber 19 and the lower chamber 20 in the cylinder 2, and the choke valve 130 that forms the fixed orifice 127 are arranged only on the main valve 129 side of the main valves 129, 231.

[0065] As shown in Fig. 4, a frequency sensitive unit 43 that varies the damping force in response to the frequency of the axial reciprocating motion of the piston 18 (hereinafter referred to as the piston frequency) is attached to the mounting shaft portion 28 of the piston rod 21 on the opposite side of the damping force generating unit 105 from the pilot case member 55. The frequency sensitive unit 43 is provided in the lower chamber 20. The frequency sensitive unit 43 has, in order from the axial damping force generating unit 105 side, one case member 131 (first case member) that abuts against the disk 62, multiple disks 133 (specifically, two disks), one partition disk 134, one disk 135, one disk 136, and a cover member 139. The case member 131, the disks 133, 135, 136, and the cover member 139 are made of metal. The disks 133, 135, and 136 are each a circular flat plate with holes of a constant thickness, into which the mounting shaft 28 of the piston rod 21 can be fitted. The case member 131 and the cover member 139 are each annular, into which the mounting shaft 28 of the piston rod 21 can be fitted. The case member 131 and the cover member 139 form a box-shaped frequency sensitive unit case 140. The mounting shaft 28 of the piston rod 21 is partially disposed inside the case member 131.

[0066] The case member 131 is a cylindrical member with a bottom, having a perforated disk-shaped bottom 141 and a cylindrical outer tube portion 144 that protrudes from the outer peripheral side of the bottom 141 along the axial direction of the bottom 141. The bottom 141 has a perforated disk-shaped bottom main body portion 147, an annular protruding portion 142 that protrudes from the inner peripheral side of the bottom main body portion 147 toward the outer tube portion 144 in the axial direction beyond the bottom main body portion 147, and an annular support portion 143 that protrudes from between the protruding portion 142 on the bottom main body portion 147 and the outer tube portion 144 toward the outer tube portion 144 in the axial direction beyond the bottom main body portion 147. In other words, the bottom 141 is formed with the protruding portion 142 that protrudes from the inner peripheral side toward the outer tube portion 144 beyond the bottom main body portion 147 toward the outer tube portion 144, and the support portion 143 that protrudes from the radially intermediate position toward the outer tube portion 144 beyond the bottom main body portion 147.

[0067] The protruding portion 142 has a flow path groove 148 formed in a portion of its circumferential direction, traversing it in the radial direction. The support portion 143 has a flow path groove 203 formed in a portion of its circumferential direction, traversing it in the radial direction. A small-diameter hole 145 into which the mounting shaft portion 28 of the piston rod 21 is fitted is formed on the inner peripheral side of the bottom portion 141, on the side opposite the protruding portion 142 in the axial direction, and a large-diameter hole 146 larger in diameter than the small-diameter hole 145 is formed on the side facing the protruding portion 142 in the axial direction. The flow path groove 148 opens into the large-diameter hole 146. The outer cylindrical portion 144 has an opening 149 on the side opposite the bottom portion 141. Therefore, the case member 131 is composed of the outer cylindrical portion 144 having the opening 149 at one end and the bottom portion 141. The cover member 139 is provided at an opening 149 of the outer cylindrical portion 144 of the case member 131 , and together with the cylindrical case member 131 , a box-shaped frequency sensitive part case 140 is formed.

[0068] The mounting shaft portion 28 passes through the radial center of the case member 131 in the axial direction, and multiple disks 133, partition disks 134, disks 135 and disks 136 are arranged within the case member 131 with the mounting shaft portion 28 passing through the inside of each.

[0069] The bottom 141 of the case member 131 supports the inner peripheral side of the disk 62 at its outer end on the axial side of the small diameter hole 145, and supports the outer peripheral side of the disk 133 at its inner end on the axial side of the large diameter hole 146. The support portion 143 of the case member 131 supports the radially intermediate position of the annular partition disk 134 at its end on the protruding tip side. The support portion 143 constantly communicates the radially inner side and the radially outer side of the support portion 143 of the case member 131 by means of the flow path groove 203.

[0070] The plurality of disks 133 have an outer diameter smaller than the outer diameter of the protruding portion 142 of the case member 131. The flow path groove 148 traverses the contact portion of the protruding portion 142 with the disks 133 in the radial direction.

[0071] The partition disk 134 is composed of a flexible, circular, flat disk 155 with holes and a constant thickness made of a metal material, and an elastic seal member 156 made of a rubber material fixed to the outer periphery of the disk 155. The partition disk 134 is generally circular and elastically deformable, i.e., flexible. The annular disk 155 has an inner diameter larger than the outer diameter of the disk 133, allowing the disk 133 to be placed inside with a radial gap. The disk 155 is thinner than the thickness of the number of disks 133 (two disks). The disk 155 has an outer diameter larger than the outer diameter of the support portion 143 of the case member 131 and smaller than the inner diameter of the outer cylindrical portion 144. The disk 155 is disposed within the case member 131 with the mounting shaft portion 28 penetrating into the interior. The disk 155 is attached to the bottom portion 141 within the case member 131.

[0072] Elastic seal member 156 is fixed in an annular shape to the outer periphery of disk 155. The entire surface of elastic seal member 156 that faces disk 155 is fixed to disk 155. Elastic seal member 156 has a seal portion 158 that protrudes from disk 155 in the axial direction away from cover member 139, and a stopper portion 159 that protrudes from disk 155 toward cover member 139 in the axial direction. In other words, elastic seal member 156 is provided with seal portion 158 on the outer periphery of one surface 181 in the axial direction (thickness direction) of disk 155, and stopper portion 159 on the outer periphery of the other surface 182 in the axial direction (thickness direction) of disk 155.

[0073] Seal portion 158, provided on the outer peripheral side of surface 181, is formed in a continuous annular cylindrical shape around the entire circumference of disk 155, and is fixed to surface 181 of disk 155 along the entire circumference. Seal portion 158 is slidably and liquid-tightly fitted to the inner peripheral surface of outer cylindrical portion 144 of case member 131 along the entire circumference, and constantly seals between itself and outer cylindrical portion 144. Therefore, elastic seal member 156 is fixed to surface 181 of disk 155 continuously along the entire circumference.

[0074] The stopper portions 159 provided on the outer periphery of the surface 182 are formed intermittently in the circumferential direction of the disk 155. The stopper portions 159 are composed of a plurality of arc-shaped stopper components 160 shaped to fit along the outer periphery of the disk 155, and these stopper components 160 are fixed to the surface 182 of the disk 155 at intervals in the circumferential direction of the disk 155. As a result, on the outer periphery of the surface 182 on which the stopper portions 159 of the disk 155 are provided, disk exposed portions 161 are provided, where the disk 155 is exposed, between adjacent stopper components 160 in the circumferential direction of the disk 155. A plurality of disk exposed portions 161 are also provided at intervals in the circumferential direction of the disk 155. The disk exposed portions 161 cross the stopper portions 159 in the radial direction. Therefore, an elastic seal member 156 is fixed to part of the surface 182 of the disk 155 in the circumferential direction. When the partition disk 134 is deformed toward the cover member 139, the stopper portion 159 comes into contact with the cover member 139 and is elastically deformed, and as a result, the partition disk 134 is prevented from further deformation.

[0075] An annular gap is provided between the disk 155 and the outer cylindrical portion 144 of the case member 131, and the elastic seal member 156 has a seal portion 158 and a stopper portion 159 fixed to both surfaces 181, 182 of the disk 155 through this gap. In other words, the elastic seal member 156 is fixed to both surfaces 181, 182 of the disk 155 through the gap between the disk 155 and the outer cylindrical portion 144. Therefore, the elastic seal member 156 has an annular connecting portion 162 that covers the outer peripheral surface 183 of the disk 155 and connects the seal portion 158 and the multiple stopper components 160. The outer peripheral surface 183 of the disk 155 has a continuous circular shape around the entire circumference, and is fixed to the outer peripheral surface 183 around the entire circumference. This connecting portion 162 is disposed between the disk 155 and the outer cylindrical portion 144.

[0076] The elastic seal member 156 has a seal portion 158, a stopper portion 159, and a connecting portion 162 that are vulcanization-bonded to the disk 155. The mold used for this vulcanization bonding has a seal portion-forming cavity that forms the seal portion 158 and bonds it to the surface 181 of the disk 155, a connecting portion-forming cavity that forms the connecting portion 162 and bonds it to the outer peripheral surface 183 of the disk 155, and a plurality of stopper component-forming cavities that form the plurality of stopper component portions 160 and bonds them to the surface 182 of the disk 155. The portions of the mold between adjacent stopper component-forming cavities become disk abutting portions that abut against the disk 155 to form the disk exposed portion 161. Therefore, when the elastic seal member 156 is formed on the disk 155, the mold supports the outer peripheral side of the disk 155 at a plurality of equally spaced positions in the circumferential direction at a plurality of equally spaced disk abutting portions.

[0077] The rubber material is introduced into the mold in a molten state so that it flows from the seal portion-forming cavity that forms the seal portion 158 to the connecting portion-forming cavity that forms the connecting portion 162, and then to the stopper component-forming cavity that forms the stopper portion 159, relative to the disk 155 placed in the mold. At this time, the flow path is narrowed in the connecting portion-forming cavity, causing a pressure difference in the disk 155 between the seal portion-forming cavity side and the stopper component-forming cavity side. However, because the mold supports the surface of the disk 155 facing the stopper component-forming cavity, which is the low-pressure side, with multiple disk abutment portions, deformation of the disk 155 is suppressed even when such a pressure difference occurs. Therefore, the elastic seal member 156 can be molded onto the disk 155 with high precision.

[0078] The partition disc 134 is centered relative to the case member 131 with the elastic seal member 156 in contact with the outer cylindrical portion 144 of the case member 131. The partition disc 134 is supported with its disc 155 in contact with the support portion 143 of the case member 131.

[0079] The protrusion 142 of the case member 131 and the disk 135 have outer diameters larger than the inner diameter of the disk 155 of the partition disk 134. As a result, the inner peripheral side of the disk 155 of the partition disk 134 is disposed between the protrusion 142 of the case member 131 and the disk 135. When there is no pressure difference between the front and back sides of the partition disk 134, the disk 155 is supported by abutting against the support portion 143 and the disk 135. The disk 135 is a seat portion on which the partition disk 134 is seated.

[0080] The inner circumferential side of the partition disc 134 is movable between the protrusion 142 of the case member 131 and the disc 135 within the range of the axial length of the multiple discs 133. In addition, the partition disc 134 is provided with an annular elastic seal member 156 on the outer circumferential side of the disc 135, which is the non-supported side opposite to the side supported by the disc 135, to seal the space between the disc 135 and the case member 131. The partition disc 134 has a simply supported structure in which its inner circumferential side is not clamped from both sides but is supported by the disc 135 on only one side. The disc 136 has an outer diameter larger than the outer diameter of the disc 135.

[0081] Here, the stopper portion 159 is made up of a plurality of stopper constituent portions 160 arranged at intervals in the circumferential direction, and a flow path groove 203 is provided in the support portion 143. Therefore, whether the partition disk 134 abuts against the cover member 139 at the stopper portion 159 or abuts against the support portion 143 of the case member 131 at the disk 155, the pressure-receiving area on the side where the seal portion 158 of the disk 155 is provided and the pressure-receiving area on the side where the stopper portion 159 is provided are approximately the same.

[0082] The lid member 139 has a cylindrical tubular portion 261 and a disk-shaped flange portion 262 that extends radially outward from the axial center position of the outer periphery of the tubular portion 261. The tubular portion 261 is thicker in the axial direction than the flange portion 262. The lid member 139 has the mounting shaft portion 28 of the piston rod 21 fitted inside the tubular portion 261. The lid member 139 is fitted into the outer periphery of the flange portion 262 in the outer tubular portion 144 of the case member 131 to form the frequency sensitive unit case 140.

[0083] In cover member 139, grooves 264 are formed on the outer periphery of flange portion 262, the grooves being recessed radially inward from the outer periphery, which is a cylindrical surface, and traverse flange portion 262 in the axial direction. Grooves 264 have an arc-shaped cross section, and a plurality of grooves 264 are arranged at equal intervals in the circumferential direction of cover member 139. As shown in FIG. 4 , when cover member 139 is fitted to outer cylindrical portion 144 of case member 131 at flange portion 262, grooves 264 form communication passages 265 between outer cylindrical portion 144 and cover member 139, which communicate the inside of frequency sensitive unit case 140 with lower chamber 20.

[0084] Here, cover member 139 has a mirror-symmetrical shape with respect to a plane that passes through the axial center and is perpendicular to the axial direction. In other words, cover member 139 has no front or back and is shaped to prevent incorrect assembly due to incorrect front and back placement. Also, by locating groove 264 for forming communication passage 265 on the outer periphery of cover member 139, cover member 139 can be formed, including groove 264, by sintering, and is sintered.

[0085] As described above, the seal portion 158 of the partition disk 134 contacts the inner circumferential surface of the outer cylindrical portion 144 of the case member 131 over the entire circumference, thereby sealing the gap between the partition disk 134 and the outer cylindrical portion 144. In other words, the partition disk 134 is a packing valve. The seal portion 158 constantly seals the gap between the partition disk 134 and the outer cylindrical portion 144, even if the partition disk 134 is displaced and deformed within an allowable range within the frequency sensitive unit case 140. The seal portion 158 contacts the outer cylindrical portion 144 over the entire circumference, so that the partition disk 134 is centered with respect to the frequency sensitive unit case 140 as described above. With the partition disk 134 centered in this way, the inner circumferential portion of the disk 155 contacts the disk 135 over the entire circumference, thereby sealing the gap between the disk 135.

[0086] Partition disk 134 divides the interior of frequency sensitive unit case 140 into two chambers: a variable-volume case chamber 171 on the bottom 141 side, and a variable-volume case chamber 172 on the cover member 139 side. In other words, the two case chambers 171, 172 are defined by partition disk 134, which is made up of disk 155 and elastic seal member 156, and are provided inside case member 131 of frequency sensitive unit case 140. Case chamber 171 is constantly in communication with the passage between large-diameter hole 146 of case member 131 and mounting shaft 28 via a passage in flow channel 148 of case member 131, and case chamber 172 is constantly in communication with lower chamber 20 via a communication passage 265 in groove 264 of cover member 139.

[0087] The passage groove 30 of the piston rod 21 faces the large diameter hole portion 202 of the piston 18 shown in FIG. 2, the notch 87 of the disk 51, the large diameter hole portion 76 of the pilot case member 55 shown in FIG. 3, the flow passage groove 81 of the pilot case member 55, and the large diameter hole portion 146 of the case member 131 and the flow passage groove 148 of the case member 131 shown in FIG. 4 in the radial direction of the piston rod 21, with the axial position of the piston rod 21 overlapping these. 3, the passage between the large diameter hole 202 of the piston 18 and the mounting shaft 28, the passage in the passage groove 30 of the piston rod 21, the passage between the large diameter hole 76 of the pilot case member 55 of the extension-side damping force generating unit 41 and the mounting shaft 28, the passage in the flow groove 81 of the pilot case member 55, the passage between the large diameter hole 146 of the case member 131 of the frequency sensitive unit 43 and the mounting shaft 28, and the passage in the flow groove 148 of the case member 131. A communication passage 265 formed between the cover member 139 and the outer cylindrical portion 144 of the case member 131 is always in communication with the case chamber 172 and also always in communication with the lower chamber 20. That is, the communication passage 265 always communicates the case chamber 172 with the lower chamber 20 .

[0088] 2, the passage portion within passage hole 37 of piston 18, the passage portion within notch 87 of disc 51, the passage portion between large diameter hole portion 202 of piston 18 and mounting shaft portion 28, the passage portion within passage groove 30 of piston rod 21, the passage portion between large diameter hole portion 146 of case member 131 and mounting shaft portion 28 shown in FIG. 4, the passage portion within flow path groove 148 of case member 131, case chambers 171, 172 within case member 131, and a communication passage 265 within groove 264 of cover member 139 constitute passage 107 (second passage) that extends and connects upper chamber 19 and lower chamber 20. Thus, case chambers 171, 172, which are at least a part of passage 107, are formed within cylindrical case member 131 having case chambers 171, 172 therein. The passage 107 connects the upper chamber 19 and the lower chamber 20 via a route that is partially different from the passages 101 and 103. The frequency sensitive part 43 is provided in the passage 107 on the lower chamber 20 side.

[0089] 2 , the passage 107 shares a passage portion within the passage hole 37 on the upper chamber 19 side with the passage 101, and the portion of the passage 107 excluding the passage portion within the passage hole 37 is arranged in parallel to the passage 101. That is, in the passage 107, the passage portion within the notch 87 of the disc 51, the passage portion between the large diameter hole 202 of the piston 18 and the mounting shaft portion 28, the passage portion within the passage groove 30 of the piston rod 21, the passage portion between the large diameter hole 146 of the case member 131 and the mounting shaft portion 28 shown in FIG. 4 , the passage portion within the flow channel groove 148 of the case member 131, the case chambers 171 and 172 within the case member 131, and the communicating passage 265 within the groove 264 of the cover member 139 form a parallel passage 109 that is parallel to the passage that connects the passage portion of the passage 101 between the valve seat portion 47 and the main valve 231 and the passage portion between the piston 18 and the outer cylindrical portion 73 of the pilot case member 55.

[0090] The frequency sensitive unit 43 has a frequency sensitive unit case 140 disposed in a parallel passage 109 of the passage 107. Therefore, the frequency sensitive unit case 140 has two case chambers 171 and 172, which are part of the parallel passage 109, defined by a partition disk 134.

[0091] The partition disc 134 is displaceable and deformable within a range in which its inner circumferential side moves between the protrusion 142 of the case member 131 and the disc 135, and its outer circumferential side moves between the support portion 143 and the flange portion 262 of the cover member 139. Here, the shortest axial distance between the support portion 143, which supports the axially intermediate portion of the disc 155 of the partition disc 134 from one axial side, and the disc 135, which supports the inner circumferential side of the disc 155 from the other axial side, is smaller than the axial thickness of the disc 155. Therefore, when the case chambers 171 and 172 are at the same pressure, the disc 155 presses against the support portion 143 and the disc 135 by its own elastic force in a slightly deformed state.

[0092] When the inner circumferential side of the partition disc 134 is in contact with the disc 135 along the entire circumference, it blocks the flow of oil liquid L between the case chambers 171 and 172 in the parallel passage 109. When the inner circumferential side of the disc 155 is separated from the disc 135, the partition disc 134 allows the flow of oil liquid L between the case chamber 171 and the case chamber 172, i.e., the lower chamber 20. Therefore, the inner circumferential side of the disc 155 of the partition disc 134 and the disc 135 as a seat portion constitute a check valve 245 in the parallel passage 109 that restricts the flow of oil liquid L from the case chamber 171 to the case chamber 172 and the lower chamber 20, while allowing the flow of oil liquid L from the lower chamber 20 and the case chamber 172 to the case chamber 171.

[0093] During the extension stroke, when the pressure on the upper chamber 19 side becomes higher than the pressure on the lower chamber 20, the check valve 245 blocks communication with the parallel passage 109 that can communicate between the upper chamber 19 and the lower chamber 20 via the passage portion in the passage hole 37 of the piston 18, while during the compression stroke, when the pressure on the upper chamber 19 side becomes lower than the pressure on the lower chamber 20, the check valve 245 opens the parallel passage 109.

[0094] The check valve 245 is a free valve in which the entire partition disc 134, which is its valve element, is movable in the axial direction. Note that the partition disc 134 may be configured so that the entire inner periphery of the disc 155 is always in contact with the disc 135 regardless of the pressure states of the case chambers 171 and 172, thereby constantly blocking the flow of oil liquid L between the case chambers 171 and 172 of the parallel passage 109. In other words, the disc 155 of the partition disc 134 only needs to block the flow of oil liquid L in at least one direction, including the flow in both directions between the case chambers 171 and 172 of the passage 107.

[0095] 2, the piston rod 21 is provided with the following components stacked in this order on the piston rod 21: annular member 120, disc 119, disc 118, a plurality of discs 117, disc 116, a plurality of discs 115, disc 114, disc 113, disc 112, disc 111, disc 110, piston 18, disc 51, disc 210, disc 216 shown in Fig. 3, pilot valve 52, disc 53, pilot case member 55, disc 56 shown in Fig. 4, a plurality of discs 57, a plurality of discs 58, a plurality of discs 59, a plurality of discs 60, disc 61, disc 62, case member 131, and a plurality of discs 133. At this time, the pilot case member 55 shown in Fig. 3 fits the seal member 86 of the pilot valve 52 into the outer cylindrical portion 73.

[0096] 4 is inserted inside, the partition disk 134 is placed on the support portion 143 of the case member 131. At this time, the elastic seal member 156 of the partition disk 134 is fitted into the outer cylindrical portion 144 of the case member 131. Furthermore, with the mounting shaft portion 28 inserted inside each, the disk 135 is placed on the disks 133 and 155 of the partition disk 134. Furthermore, with the mounting shaft portion 28 inserted inside, the disk 136 is placed on the disk 135, and the cover member 139 is placed on the disk 136. At this time, the cover member 139 is inserted inside the outer cylindrical portion 144 of the case member 131.

[0097] With the parts arranged in this manner, a nut 176 is threaded onto the male thread 31 of the mounting shaft portion 28 that protrudes beyond the cover member 139. As a result, the inner circumferential side or the entirety of the annular member 120, disc 119, disc 118, the plurality of discs 117, disc 116, the plurality of discs 115, disc 114, disc 113, disc 112, disc 111, disc 110, piston 18 shown in Fig. 2, disc 51, disc 210, disc 216, pilot valve 52, disc 53, pilot case member 55 shown in Fig. 3, disc 56, the plurality of discs 57, the plurality of discs 58, the plurality of discs 59, the plurality of discs 60, disc 61, disc 62, case member 131, the plurality of discs 133, disc 135, disc 136, and cover member 139 shown in Fig. 4 are sandwiched between the shaft step portion 29 of the piston rod 21 and the nut 176 and clamped in the axial direction. At this time, the inner peripheral side of the partition disk 134 is not clamped in the axial direction, but is supported by the support portion 143 and the disk 135. The nut 176 is a general-purpose hexagonal crimping nut, which is tightened to the piston rod 21 with a predetermined torque and then crimped to prevent rotation.

[0098] As described above, the compression-side damping force generating unit 42 shown in Fig. 2, the piston 18, the extension-side damping force generating unit 41 shown in Fig. 3, the extension-side damping force generating unit 105 shown in Fig. 4, and the extension-side frequency sensitive unit 43 are fastened to the piston rod 21 with the nut 176, with the piston rod 21 inserted into their respective inner peripheries. Furthermore, the frequency sensitive unit 43, consisting of the case member 131, the plurality of discs 133, 135, 136, and the cover member 139, is fastened to the piston rod 21 with the nut 176, with the piston rod 21 inserted into their inner peripheries.

[0099] It is also possible to assemble frequency sensitive part 43 to piston rod 21 in a pre-assembled state. In this case, a dummy rod is inserted in place of piston rod 21, and while removing this rod, mounting shaft portion 28 of piston rod 21 is inserted into the inner peripheral side of frequency sensitive part 43. When frequency sensitive part 43 is in a pre-assembled state, it becomes possible to press-fit and fix cover member 139 into outer cylindrical portion 144 of case member 131.

[0100] It is also possible to assemble the pilot valve 52, the disc 53, and the pilot case member 55 in advance and then attach them to the piston rod 21. In this case, too, a dummy rod is inserted in place of the piston rod 21, and while removing this rod, the mounting shaft portion 28 of the piston rod 21 is inserted into the inner peripheral side of these components.

[0101] 1, the above-mentioned base valve 25 is provided between the cylinder bottom 12 of the outer cylinder 4 and the inner cylinder 3. This base valve 25 has a base valve member 191 that separates the lower chamber 20 and the reservoir chamber 6, a disk 192 provided on the lower side of this base valve member 191, i.e., on the reservoir chamber 6 side, a disk 193 provided on the upper side of the base valve member 191, i.e., on the lower chamber 20 side, and a mounting pin 194 that attaches the disk 192 and the disk 193 to the base valve member 191.

[0102] The base valve member 191 has an annular shape through which a mounting pin 194 is inserted at its radial center. The base valve member 191 has a plurality of passage holes 195 for circulating the oil L between the lower chamber 20 and the reservoir chamber 6, and a plurality of passage holes 196 for circulating the oil L between the lower chamber 20 and the reservoir chamber 6, formed radially outward of these passage holes 195. The disk 192 on the reservoir chamber 6 side allows the oil L to flow from the lower chamber 20 to the reservoir chamber 6 via the passage holes 195, while suppressing the flow of the oil L from the reservoir chamber 6 to the lower chamber 20 via the passage hole 195. The disk 193 allows the oil L to flow from the reservoir chamber 6 to the lower chamber 20 via the passage hole 196, while suppressing the flow of the oil L from the lower chamber 20 to the reservoir chamber 6 via the passage hole 196.

[0103] The disc 192, together with the base valve member 191, constitutes a compression-side damping valve 197 that opens during the compression stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the lower chamber 20 to the reservoir chamber 6 and generate a damping force. The disc 193, together with the base valve member 191, constitutes a suction valve 198 that opens during the extension stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the reservoir chamber 6 into the lower chamber 20. The suction valve 198 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 make up for a shortage of hydraulic fluid caused by the extension of the piston rod 21 from the cylinder 2.

[0104] Assuming that there is no frequency sensitive section 43 during the extension stroke in which the piston rod 21 moves to the extension side, in the extremely slow speed range where the axial movement speed of the piston 18 (hereinafter referred to as the piston speed) is slow as shown by 0 to v1 in Fig. 7, the oil L from the upper chamber 19 flows into the lower chamber 20 via the fixed orifice 127 including the choke passage 128 of the damping force generating section 42 and the passage section inside the passage hole 39, generating a damping force with choke characteristics (the damping force is approximately proportional to the piston speed) as shown by the solid line X1 in Fig. 7. At this time, the characteristic of the damping force relative to the piston speed is such that the rate of increase of the damping force becomes relatively high as the piston speed increases.

[0105] If the fixed orifice 127 did not include the choke passage 128, a damping force with an orifice characteristic (where the damping force is approximately proportional to the square of the piston speed) would be generated, as shown by the dashed line X2 in FIG. 7. In contrast, in this embodiment, the oil L flows through the fixed orifice 127, which includes the choke passage 128, so the damping force has a linear characteristic where the damping force is approximately proportional to the piston speed, as shown by the solid line X1 in FIG. 7. This allows sufficient damping force to be generated even during the extension stroke when the piston speed is very low, suppressing the dizzy feeling that occurs in the vehicle due to insufficient damping force and improving ride comfort. Note that if an ordinary fixed orifice that does not include the choke passage 128 is used to increase the damping force at very low piston speeds, the damping force at low piston speeds would also increase, resulting in a worsening of ride comfort.

[0106] When the piston speed increases and enters the low speed range (v1~), oil L from the upper chamber 19 flows from the passage portion within the passage hole 37 to the lower chamber 20 via a passage 101 that includes the gap between the main valve 231 and the valve seat portion 47 of the piston 18 and the passage portion between the piston 18 and the outer cylindrical portion 73 of the pilot case member 55 while opening the main valve 231 of the damping force generating unit 41 shown in Fig. 3, generating a damping force with valve characteristics (damping force is approximately proportional to piston speed). At this time, the characteristic of the damping force relative to the piston speed is such that the rate of increase of the damping force relative to an increase in piston speed is lower than in the extremely low speed range (0~v1), as shown by the solid line X3 in Fig. 7.

[0107] When the piston speed becomes even faster, the oil L from the upper chamber 19 flows into the lower chamber 20 via passage 101, which includes the gap between the main valve 231 and valve seat 47, which are separated from each other in the damping force generating section 41, and into the lower chamber 20. In addition, the oil L also flows from the back pressure introducing passage 235 shown in Fig. 4 to the lower chamber 20, through passage 103, which includes the gap between the valve 99 and valve seat 79, while opening valve 99, which is a hard valve, in the damping force generating section 105, further suppressing the increase in damping force. Therefore, the characteristic of the damping force relative to the piston speed is such that the rate of increase in the damping force decreases further as the piston speed increases.

[0108] As the piston speed increases further, the relationship of the forces (hydraulic pressure) acting on the pilot valve 52 shown in FIG. 3 changes such that the opening force applied from the passage in the passage hole 37 becomes greater than the closing force applied from the back pressure chamber 80. Therefore, in this region, as the piston speed increases, the main valve 231 of the damping force generating unit 41 opens farther away from the valve seat 47 of the piston 18 than described above. This causes more hydraulic fluid L to flow to the lower chamber 20 through passage 103, which includes the passage in the passage hole 37, the back pressure introduction passage 235, and the gap between the valve 99 and the valve seat 79 of the damping force generating unit 105, as well as through passage 101, which includes the passage between the piston 18 and the outer cylindrical portion 73 of the pilot case member 55. This further suppresses the increase in damping force. Therefore, the damping force vs. piston speed characteristic shows a further decrease in the rate of increase in damping force as the piston speed increases.

[0109] During the compression stroke in which the piston rod 21 moves toward the compression side, when the piston speed is slow, the oil L from the lower chamber 20 flows into the upper chamber 19 via the passage in the compression-side passage hole 39 shown in Figure 2 and the fixed orifice 127 including the choke passage 128 of the main valve 129 of the damping force generating section 42, generating a damping force with choke characteristics (damping force is approximately proportional to piston speed). At this time, the damping force characteristic relative to piston speed is such that the rate of increase in damping force becomes relatively high as the piston speed increases.

[0110] Again, if fixed orifice 127 does not include choke passage 128, a damping force with orifice characteristics (damping force approximately proportional to the square of the piston speed) will be generated. In contrast, in this embodiment, oil L is caused to flow through fixed orifice 127 including choke passage 128, so the damping force has linear characteristics that are approximately proportional to the piston speed. As a result, sufficient damping force can be generated even during the compression stroke when the piston speed is extremely low, and the dizzy feeling that occurs in the vehicle due to insufficient damping force can be suppressed.

[0111] Furthermore, when the piston speed increases, oil L introduced from the lower chamber 20 into the passage portion inside the compression-side passage hole 39 flows into the upper chamber 19 through between the main valve 129 and the valve seat portion 49 while basically opening the main valve 129 of the damping force generating portion 42, generating a damping force with valve characteristics (damping force is approximately proportional to piston speed).For this reason, the damping force characteristic relative to piston speed is such that the rate of increase in damping force decreases as the piston speed increases.

[0112] The above is the operation when it is assumed that there is no frequency sensitive section 43, but in this embodiment, the frequency sensitive section 43 makes the damping force variable depending on the piston frequency even when the piston speed is the same.

[0113] In other words, when the piston frequency is high, the amplitude of the piston 18 is small, and during the extension stroke when the piston frequency is thus high, the pressure in the upper chamber 19 increases, causing oil liquid L to be introduced from the upper chamber 19 into the case chamber 171 in the frequency sensing unit case 140 via the passage portion within the passage hole 37 of the passage 107 shown in FIG. 2, the passage portion within the notch 87 of the disc 51, the passage portion between the large diameter hole portion 202 of the piston 18 and the mounting shaft portion 28, the passage portion within the passage groove 30 of the piston rod 21, the passage portion between the large diameter hole portion 146 of the case member 131 and the mounting shaft portion 28 shown in FIG. 4, and the passage portion within the flow path groove 148 of the case member 131. In response to this, the partition disk 134, which had previously been abutting the support portion 143 and the disk 135 at the disk 155, deforms in a direction that brings the stopper portion 159 closer to the flange portion 262 of the cover member 139, expanding the volume of the case chamber 171, and discharging the oil liquid L from the case chamber 172, which is the portion of the passage 107 on the lower chamber 20 side, to the lower chamber 20 through the connecting passage 265 in the groove 264 of the cover member 139.

[0114] This deformation of the partition disc 134 during each extension stroke introduces hydraulic fluid L from the upper chamber 19 into the case chamber 171. As a result, the flow rate of hydraulic fluid L from the upper chamber 19 to the lower chamber 20 via the passage 101 is reduced while opening the damping force generating unit 41. Additionally, introducing hydraulic fluid L from the upper chamber 19 into the case chamber 171 suppresses the pressure increase in the back pressure chamber 80 compared to when the case chamber 171 is not present, making it easier for the main valve 231 of the damping force generating unit 41 to open. These factors result in a softer damping force on the extension stroke. At this time, the damping force generating unit 105, which is a hard valve, does not open. Because the inner circumferential side of the partition disc 134 is spaced from the protruding portion 142 of the case member 131 and supported by the disc 135 from only one side, the inner circumferential end of the partition disc 134 is easily deformed toward the protruding portion 142, and therefore the stopper portion 159 on the outer circumferential side is easily deformed toward the cover member 139.

[0115] On the other hand, when the piston frequency is low, the amplitude of the piston 18 is large, and during the extension stroke when the piston frequency is thus low, the frequency of deformation of the partition disc 134 also decreases accordingly, so that at the beginning of the extension stroke, similarly to the above, oil lubricant L flows from the upper chamber 19 to the case chamber 171 via the passage 107, but thereafter the partition disc 134 abuts against the lid member 139 at the stopper portion 159 and stops, and oil lubricant L no longer flows from the upper chamber 19 to the case chamber 171. Since oil lubricant L no longer flows from the upper chamber 19 to the case chamber 171, the pressure in the case chamber 171 increases, and the pressure in the back pressure chamber 80, which is always in communication with the case chamber 171, also increases, resulting in a state in which the opening of the main valve 231 of the damping force generating unit 41 is inhibited. That is, the damping force generating section 41 is in a state where the main valve 231 does not open and the oil L flows from the upper chamber 19 to the lower chamber 20 via the fixed orifice 127, and the damping force on the extension side becomes hard.

[0116] When the pressure in the back pressure chamber 80 further increases, the oil L opens the valve 99 of the damping force generating unit 105, which is a hard valve, and flows into the lower chamber 20 through a passage 103 that includes the gap between the valve 99 and the valve seat 79. When the pressure in the back pressure chamber 80 further increases, the oil L not only flows through the passage 103, but also opens the main valve 231 of the damping force generating unit 41, causing the oil L to flow from the passage 101 into the lower chamber 20.

[0117] As a result, when the piston frequency is low, the damping force on the extension side becomes hard.

[0118] Here, during the compression stroke, the pressure in the lower chamber 20 increases, and the pressure in the case chamber 172 becomes higher than the pressure in the case chamber 171. As a result, the disc 155 of the partition disc 134 serving as the valve body of the check valve 245 deforms with the support portion 143 of the case member 131 as a fulcrum, and disengages from the disc 135 serving as the valve seat of the check valve 245. This causes the check valve 245 to open the passage 107 including the communication passage 265 in the groove 264, allowing the oil liquid L to flow from the lower chamber 20 toward the upper chamber 19. At this time, the disc 155 moves away from the disc 135, eliminating the pressure difference and suppressing further movement.

[0119] The shock absorber of the above-mentioned Patent Document 1 is provided with a frequency sensitive part that varies the damping force in response to frequency. In this shock absorber, a flow path is formed between the piston and the frequency sensitive part to allow oil L from the upper chamber to flow to the frequency sensitive part. In addition, a choke valve that forms a choke passage is provided in the main valve on the same side as the frequency sensitive part, on the lower chamber side. Therefore, the structure between the piston and the frequency sensitive part is complex. As a result, there is room for improvement in terms of durability.

[0120] The shock absorber 1 of this embodiment has a damping force generating mechanism 40 that is provided in the passages 101, 132 and generates a damping force, and a frequency sensitive unit 43 that is provided in a passage 107 that is parallel to the passages 101, 132 and in the lower chamber 20 that is one side chamber in the cylinder 2. The damping force generating mechanism 40 has a main valve 231 that is provided in the lower chamber 20 in the cylinder 2 and that generates a damping force by suppressing the flow of oil liquid L generated by the sliding of the piston 18, and a main valve 129 that is provided in the upper chamber 19 in the cylinder 2 and that generates a damping force by suppressing the flow of oil liquid L generated by the sliding of the piston 18. The shock absorber 1 has a choke valve 130 that forms a fixed orifice 127 that includes a choke passage 128 that is a constantly communicating passage that can communicate between the lower chamber 20 and the upper chamber 19 in the cylinder 2, and that is arranged on the side of the main valve 129, 231, that is provided in the upper chamber 19. Therefore, in shock absorber 1, the configuration between piston 18 and frequency sensitive portion 43 is simpler than when the choke valve forming the choke passage is provided in main valve 231 on the same side of lower chamber 20 as frequency sensitive portion 43. As a result, durability can be improved.

[0121] That is, shock absorber 1 is provided with disc 51 between piston 18 and frequency sensitive portion 43, which forms a flow path for flowing oil liquid L from upper chamber 19 to frequency sensitive portion 43. If a choke valve were also provided between piston 18 and frequency sensitive portion 43, the flow path configuration between piston 18 and frequency sensitive portion 43 would become complicated, which could affect the durability of the parts between piston 18 and frequency sensitive portion 43. For example, disc 51 would be more susceptible to the flow of oil liquid L through the fixed orifice, which could result in a decrease in durability. In shock absorber 1, choke valve 130 is located on the main valve 129 side, opposite disc 51 from piston 18, so a decrease in the durability of disc 51 can be suppressed.

[0122] In the shock absorber 1, the choke valve 130 is arranged on the side of the main valve 129 provided in the upper chamber 19 of the main valves 129, 231, so it is easy to secure space when assembling the choke valve 130, and assembling can be improved. [Explanation of symbols]

[0123] 1... shock absorber, 2... cylinder, 18... piston, 19... upper chamber (chamber, other side chamber), 20... lower chamber (chamber, one side chamber), 21... piston rod, 40... damping force generating mechanism, 43... frequency sensitive part, 101, 132... passage (first passage), 107... passage (second passage), 127... fixed orifice (constantly communicating passage), 129... main valve (second main valve), 130... choke valve (sub-valve), 231... main valve (first main valve).

Claims

[Claim 1] a cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder to divide the interior of the cylinder into two chambers; a piston rod having one end connected to the piston and the other end extending to the outside of the cylinder; a first passage through which working fluid flows from one of the chambers in response to movement of the piston; a second passage provided in parallel with the first passage; a damping force generating mechanism provided in the first passage and configured to generate a damping force; a frequency sensitive portion provided in the second passage and in one side chamber of the cylinder; and The damping force generating mechanism includes: a first main valve provided in the one side chamber of the cylinder, the first main valve suppressing a flow of working fluid caused by sliding of the piston to generate a damping force; a second main valve provided in the other side chamber of the cylinder, the second main valve suppressing the flow of working fluid caused by the sliding of the piston to generate a damping force; and a sub-valve that forms a constantly communicating passage that can communicate the one side chamber in the cylinder with the other side chamber in the cylinder, and that is disposed on the second main valve side of the first main valve and the second main valve.

Images