shock absorbers

Abstract

Shock absorber (1) which has: a cylinder (2) in which a working fluid is enclosed; a piston (18) which is fitted into the cylinder (2) and is designed to be moved within the cylinder (2); a piston rod (21) whose first end side is coupled to the piston (18) and whose second end side extends outwards relative to the cylinder (2); a damping valve (147, 197) that suppresses a flow of the working fluid due to the displacement of the piston (18) and generates a damping force; a tubular pilot housing (118, 168) closed at the bottom, which together with the damping valve (147, 197) forms a pilot chamber (140, 190) that causes pressure to act on the damping valve (147, 197) in a valve closing direction; and an annular sealing element (146, 196) which is fixed to the outer circumferential side of a rear surface of the damping valve (147, 197), is fitted into a tube of the pilot chamber (118, 168) and is designed to be displaced in a liquid-tight manner, wherein the damping valve (147, 197) is constructed such that the inner circumferential side of the damping valve (147, 197) is clamped and the outer circumferential side of the damping valve (147, 197) is open, a portion of the working fluid flow is directed to the pilot chamber (140, 190) and the pressure of the pilot chamber (147, 197) suppresses the opening of the damping valve (147, 197). characterized by the fact that an outer circumferential surface of the sealing element (146, 196) is formed with: a convex section (381) on the damping valve side, which is formed on a mounting section to which the sealing element (146, 196) is attached to the damping valve (147, 197) and which has a vertex that projects furthest outwards in a radial direction of the sealing element (146, 196), an annular concave section (380) which is formed at a position further away from the damping valve (147, 197) than the convex section (381) on the damping valve side and which is recessed inwards in the radial direction, and a convex section (382) on the side of the pilot chamber, which is formed at a position that is further away from the damping valve (147, 197) than the annular concave section (380), with a smaller diameter than a diameter of the convex section (381) on the damping valve side and a larger diameter than a diameter of the annular concave section (380) and which projects radially outwards from the outer circumferential surface of the sealing element (146, 196).

Description

Technical field

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

[0002] Priority is claimed for Japanese patent application No. 2013-248367, filed on November 29, 2013, the contents of which are incorporated herein by reference. background

[0003] A shock absorber is known in which a sealing element is provided on the outer circumferential side of a rear surface of a valve that opens and closes a flow path, wherein a pilot chamber is constructed from the sealing element and a pilot housing and wherein the pressure of the pilot chamber is caused to act on the valve in a valve closing direction (see, for example, PTL 1). List of citations from patent literature

[0004] [PTL 1] JP 2006- 38 097 A.

[0005] DE 10 2011 004 962 A1 discloses features that fall under the preamble of claim 1. DE 10 2011 081 792 A1 is further prior art. Summary of the invention: Technical problem

[0006] It is desirable to improve the durability of the sealing element.

[0007] The present invention provides a shock absorber that is capable of improving the durability of a sealing element. Solution to the problem

[0008] The invention is defined by claim 1.

[0009] According to a first aspect of the invention, a shock absorber comprises: a cylinder in which a working fluid is enclosed; a piston slidably fitted into the cylinder; a piston rod, the first end of which is coupled to the piston and the second end of which extends outwards with respect to the cylinder; a damping valve which suppresses a flow of the working fluid due to the displacement of the piston in order to generate a damping force; a tubular pilot housing closed at the bottom, which together with the damping valve forms a pilot chamber that causes a pressure in a valve closing direction to act on the damping valve; and an annular sealing element which is provided to be attached or fixed to the outer circumferential side of a rear surface of the damping valve and which is fitted into a tube of the pilot housing so that the latter is slidably enclosed and is fluid-tight.The damping valve is designed such that the inner circumferential side of the damping valve is clamped and the outer circumferential side of the damping valve is open, whereby a portion of the working fluid flow is directed to the pilot chamber and opening of the damping valve is suppressed by the pressure of the pilot chamber. An annular concave section is formed on the outer circumferential side of the sealing element, and an annular convex section is formed on the inner circumferential side of the sealing element.

[0010] According to a second aspect of the invention, a shock absorber comprises: a cylinder in which a working fluid is enclosed; a piston slidably fitted into the cylinder; a piston rod, the first end of which is coupled to the piston and the second end of which extends outwards with respect to the cylinder; a damping valve which suppresses a flow of the working fluid due to the displacement of the piston in order to generate a damping force; a pilot housing closed at the bottom which, together with the damping valve, forms a pilot chamber which causes pressure to act on the damping valve in a valve closing direction; and an annular sealing element which is provided to be fixed to the outer circumferential side of a rear surface of the damping valve and which is fitted into a tube of the pilot housing in such a way as to be slidable and to be fluid-tight.The damping valve is designed such that its inner circumferential side is clamped and its outer circumferential side is open, directing a portion of the working fluid flow to the pilot chamber and suppressing opening of the damping valve by the pilot chamber pressure. An annular concave section is formed on an outer circumferential section of the sealing element, and the height of a section of the minimum diameter of the concave section of the damping valve is greater than one-third of the height of a section of the maximum diameter of the damping valve. The section of the maximum diameter has its largest diameter on a side further away from the damping valve on the outer circumferential section of the sealing element than the section of the minimum diameter.

[0011] According to a third aspect of the invention, with respect to the first or second aspect, the section of maximum diameter having the largest diameter can be formed on the outer circumferential side of the sealing element further away or further separated from the damping valve on one side than the annular concave section, and a damping valve-side convex section that projects further outwards in a radial direction than the section of maximum diameter can be provided on the damping valve side of the sealing element.

[0012] According to a fourth aspect of the invention, with respect to one of the first to third aspects, the distance of a vertex of the convex section from the damping valve can be greater than the distance of the section of the minimum diameter of the concave section from the damping valve. Advantageous effects of the invention

[0013] According to the shock absorber described above, it is possible to improve the durability of the sealing element. Brief description of the drawings Fig. Figure 1 is a sectional view showing a shock absorber according to one embodiment of the invention. Fig. Figure 2 is a partially enlarged sectional view showing the environment of a passage cross-section adjustment mechanism of the shock absorber according to the embodiment of the invention. Fig. Figure 3 is a partially enlarged sectional view showing the environment of a piston of the shock absorber according to the embodiment of the invention. Fig. Figure 4 is a partially enlarged sectional view showing the environment of a rod guide of the shock absorber according to the embodiment of the invention. Fig. Figure 5 is a sectional view showing a sealing element of the shock absorber according to the embodiment of the invention. Fig. Figure 6 is a partially enlarged sectional view showing the sealing element of the shock absorber according to the embodiment of the invention. Fig. Figure 7A is a partially enlarged sectional view showing a natural state and a modified state of the sealing element, and provides a comparative example of the natural state and the modified state. Fig. Figure 7B is a partially enlarged sectional view showing a natural state and a modified state of the sealing element and provides a comparative example of the natural state and the modified state. Fig. Figure 7C is a partially enlarged sectional view showing a natural state and a modified state of the sealing element and represents an example of the invention. Description of embodiments

[0014] An embodiment of the invention is described below with reference to the drawings. For ease of understanding, in the following description, the lower side of the drawing is defined as a first side and a bottom side, and the upper side of the drawing is defined as a second side and a top side.

[0015] A shock absorber 1 of the embodiment is a position-sensitive shock absorber with controllable damping force. As described in Fig. As shown in Figure 1, the shock absorber 1 of this embodiment is a so-called hydraulic twin-cylinder shock absorber and has a cylinder 2 in which oil is enclosed as the working fluid. The cylinder 2 has a cylindrical inner tube 3, a cylindrical outer tube 4 closed at its bottom, the diameter of which is larger than that of the inner tube 3 and which is arranged concentrically to cover the inner tube 3, and a cover 5 that covers an upper opening of the outer tube 4. A reservoir chamber 6 is formed between the inner tube 3 and the outer tube 4.

[0016] The outer tube 4 is composed of an approximately cylindrical barrel member 7, a bottom element 8 which is fitted into and attached to the side of the lower section of the barrel member 7 and blocks the barrel member 7, and an approximately cylindrical mouthpiece element 9 which is fitted into and attached to the side of the upper section of the barrel member 7.

[0017] The mouthpiece element 9 is pressed into the drum element 7, such that the latter is fitted into and attached to a small-diameter section 10 formed on an outer circumferential section of a deeper section of the mouthpiece element 9. The upper side of the small-diameter section 10 of the mouthpiece element 9 is a large-diameter section 11, having a diameter larger than that of the small-diameter section 10. An external thread 12 is formed on an outer circumferential section of the large-diameter section 11. Furthermore, an inner circumferential section of the deeper section of the mouthpiece 9 forms a small-diameter section 13, and an inner circumferential section of an upper section of the mouthpiece 9 forms a large-diameter section 14, having a diameter larger than that of the small-diameter section 13.

[0018] The cover 5 has a tubular section 15 and an internal flange section 16 extending radially inwards from an upper end face of the tubular section 15, and an internal thread 17 is formed on an inner circumferential section of the tubular section 15. The cover 5 covers an opening section of the upper end of the mouthpiece 9 and is fastened by screwing the internal thread 17 formed on the tubular section 15 to the external thread 12 of the mouthpiece element 9.

[0019] A piston 18 is slidably fitted into the inner tube 3. The piston 18 divides the inside of the inner tube 3 into two chambers, an upper chamber 19 and a lower chamber 20. Oil, as the working fluid, is enclosed in the upper chamber 19 and the lower chamber 20 within the inner tube 3. Oil and gas, as the working fluid, are enclosed in the reservoir chamber 6 between the inner tube 3 and the outer tube 4.

[0020] A first end of a piston rod 21 is inserted into the cylinder 2. A second end of the piston rod 21 extends outwards relative to the cylinder 2. The piston 18 is coupled to the first end of the piston rod 21 in the cylinder 2. A rod guide 22 is fitted into the nozzle element 9 at an opening side of the first end of the inner tube 3 and the outer tube 4. A sealing element 23 is located further outwards in the nozzle element 9 than the rod guide 22. A friction element 24 is provided on the rod guide 22 at a position further inwards in the cylinder 2 than the sealing element 23. The rod guide 22, the sealing element 23, and the friction element 24 are all annular in shape. The piston rod 21 is slidably inserted into the inside of the rod guide 22, the friction element 24 and the sealing element 23 and extends outwards with respect to the cylinder 2.

[0021] Here, the rod guide 22 directs the movement of the piston rod 21 by supporting or bearing the piston rod 21 in such a way that the piston rod 21 can move in an axial direction, while its movement in the radial direction is prevented. An inner circumferential section of the sealing element 23 is in sliding contact with an outer circumferential section of the piston rod 21, which moves in the axial direction, in such a way that oil in the inner tube 3 and high-pressure gas and oil in the reservoir chamber 6 in the outer tube 4 are prevented from escaping to the outside.

[0022] An inner circumferential section of the friction element 24 is in sliding contact with the outer circumferential section of the piston rod 21, thus generating frictional resistance with respect to the piston rod 21. The friction element 24 is not intended to act as a seal.

[0023] The rod guide 22 is stepped, with the outer circumferential section of an upper section of the rod guide 22 having a larger diameter than the outer circumferential section of a lower section of the rod guide 22. The lower section of the rod guide 22 is fitted into an inner circumferential section of an upper end of the inner tube 3, and the upper section of the same is fitted into the inner circumferential section of the large diameter 14 of the nozzle element 9 of the outer tube 4. A base valve 25, which separates the lower chamber 20 in the inner tube 3 and the reservoir chamber 6, is provided on the bottom element 8 of the outer tube 4. The inner circumferential section of a lower end of the inner tube 3 is fitted into the base valve 25. An annular pressure element 33 is arranged between the inner flange section 16 of the cover 5 and the sealing element 23.When the internal thread 17 of the cover 5 is screwed to the external thread 12 of the outer tube 4, the pressure element 33 and the sealing element 23 are arranged between the inner flange section 16 and the rod guide 22, which is fitted into the inner tube 3.

[0024] The piston rod 21 is composed of a main rod body 26, which is inserted into the rod guide 22, the friction element 24, and the sealing element 23 and extends outwards; a front rod 27, which is screwed to be integrally coupled to an end section of the main rod body 26 in the cylinder 2; and a nut 210, which is screwed to the front rod 27. An insertion opening 28 is formed in the axial direction at the center of the main rod body 26 and extends radially from the side of the front rod 27 to an intermediate position in the vicinity of the end section on the opposite side. Furthermore, a through-opening 29 is formed in the axial direction at the center of the front rod 27 and radially. The insertion opening 28 and the through-opening 29 form an insertion opening 30, which is formed in the center of the piston rod 21 and radially.In this way, the piston rod 21 is designed with a hollow structure. A metering pin 31 is inserted into the insertion opening 30 of the piston rod 21. A first end face of the metering pin 31 is attached to the base valve 25, which is provided on the first side of the cylinder 2, and a second end face of the same is inserted into the insertion opening 30 of the piston rod 21. An inner rod passage 32, through which oil can flow into the piston rod 21, is formed between the insertion opening 30 and the metering pin 31.

[0025] An annular spring bearing 35 is provided on the piston-side side of the piston 18 in the axial direction of the outer circumferential side of the main rod body 26 of the piston rod 21. An annular spring bearing 36 is provided on the side of the piston-side spring bearing 35 opposite the piston 18 in the axial direction of the outer circumferential side of the main rod body 26 of the piston rod 21. The piston-side spring bearing 35 and the main rod body spring bearing 36 are slidably mounted along the main rod body 26, the main rod body 26 being inserted through them. A return spring 38, which is constructed from a coil spring, is arranged between the piston-side spring bearing 35 and the main rod body spring bearing 36, the main rod body 26 being inserted through it.An annular buffer 39, made of an elastic material, is provided on one side of the rod guide-side spring bearing 36 opposite the return spring 38 in the axial direction. The buffer 39 is also slidably provided along the main rod body 26, the main rod body 26 being inserted through it.

[0026] In the shock absorber 1 described above, the first side of the shock absorber is supported by a vehicle body, and a second side of the shock absorber is coupled to, for example, a vehicle wheel. Specifically, the piston rod 21 is coupled to the vehicle body, and the side of the cylinder 2 opposite the projecting side of the piston rod 21 is coupled to the vehicle wheel. It should be noted that, in contrast to the description above, the second side of the shock absorber 1 can also be supported by the vehicle body, and the first side of the shock absorber 1 can be fixed to the vehicle wheel.

[0027] When the vehicle wheel vibrates during travel, the positions of cylinder 2 and piston rod 21 relative to each other change according to the vibrations. However, this change is suppressed by the fluid resistance of the inner rod passage 32 formed in the piston rod 21. As described in detail below, the fluid resistance of the inner rod passage 32, formed in the piston rod 21, is set such that it changes depending on the frequency or amplitude of the vibration, thereby improving ride quality by suppressing the vibrations. In addition to the vibrations generated by the vehicle wheel, the inertial force or centrifugal force, which is caused in the vehicle body by the vehicle's movement, also acts on a space between cylinder 2 and piston rod 21.For example, the centrifugal force in the vehicle body is caused by a change in the direction of travel, by turning the steering wheel, and a force based on the centrifugal force acts on the space between the cylinder 2 and the piston rod 21. As described below, the shock absorber 1 of the embodiment has advantageous characteristics with respect to the force that is generated in the vehicle body according to the vehicle's movement, and thus high stability can be maintained during the vehicle's movement.

[0028] As it is in Fig. As shown in Figure 2, a screw opening 43, which has a larger diameter than the insertion opening 28 and communicates with the insertion opening 28, is formed on the end section of the main rod body 26 on the side of the front rod 27. The through-opening 29, which forms the inner rod passage 32 of the front rod 27, is formed from a main opening section 47, which essentially forms the entire through-opening 29, and a small-diameter opening section 48, which is only located at a deeper end section, as shown in Figure 2. Fig. 3 shown, is formed and has a smaller diameter than the main opening section 47. From the side of the main rod body 26, shown in Fig. 2, are in this order a through opening 49 and a through opening 50 and the through opening 51, which are in Fig. Figure 3 shows the openings formed in the front bar 27 to pass through the front bar 27 in the radial direction. All through-openings 49 to 51 are formed at a position of the main opening section 47 of the front bar 27 in the axial direction and are perpendicular to the through-opening 29.

[0029] As it is in Fig. As shown in Figure 2, the front rod 27, from the side of the main rod body 26 in the axial direction, has, in this order, a threaded shank section 55, in which an external thread 54 is formed on an outer circumferential section, a flange section 56, and a retaining shank section 57. The threaded shank section 55 is screwed into the threaded opening 43 of the main rod body 26, using the external thread 54, when the front rod 27 is integrated with the main rod body 26. Since the flange section 56 comes into contact with the main rod body 26 when the front rod 27 is integrated with the main rod body 26, the main rod body 26 is designed such that its outer diameter is larger than that of the threaded shank section 55 and the main rod body 26. The retaining shank section 57 is designed such that it has a smaller diameter than the flange section 56. An external thread 61, shown in Figure 2, is formed in the threaded shank section 55. Fig. 3, is formed on a section of the retaining shaft section 57 on one side opposite the flange section 56 in the axial direction. The through-openings 49 to 51 described above are located further or closer to the side of the flange section 56, as shown in Fig. 2, as the external thread 61 of the retaining shaft section 57 is formed.

[0030] As it is in Fig. As shown in Figure 2, the piston-side spring bearing 35 comprises: a cylindrical section 65; an intermediate body section 66 extending axially outward in the radial direction from the first end face of the cylindrical section 65; and a cylindrical pressure section 67 extending axially from the outer circumferential section of the intermediate body section 66 to the side opposite the cylindrical section 65. In the piston-side spring bearing 35, an end face of the intermediate body section 66 on the cylindrical section 65 in the axial direction comes into contact with an end section of the return spring 38 in the axial direction in a state in which the cylindrical section 65 is arranged inside the return spring 38.In the piston-side spring bearing 35, an end face of the intermediate body section 66 on the side of the pressure section 67 can come into axial contact with the flange section 56 of the front rod 27. The inner circumferential section of the intermediate body section 66 on the side of the cylindrical section 65 is designed such that it has a diameter equal to the inner diameter of the cylindrical section 65 in the axial direction, and the inner circumferential section of the intermediate body section 66 on the side of the pressure section 67 has a stepped section 68 in the axial direction, which has a diameter larger than the inner diameter of the cylindrical section 65. A sliding element 69 is fitted and fastened in the stepped section 68, and the sliding element 69 slides on the outer circumferential surface of the main rod body 26.Several through-openings 70, which pass through the pressure section 67 in the radial direction, are formed in the pressure section 67.

[0031] From the side of the flange section 56, several discs 73, a single disc 74, several preload discs 75, a single opening and closing disc 76, a single intermediate disc 77, a single intermediate disc 78, a single contact disc 79 and a through-formation element 80 are provided in this order on the retaining shaft section 57 of the front rod 27.

[0032] Each of the multiple discs 73 is designed in a perforated or perforated disc shape and has an outer diameter that is smaller than the inner diameter of the pressure section 67 of the piston-side spring bearing 35. The disc 74 is designed in a perforated disc shape that has an outer diameter that is smaller than that of the disc 73. Each of the multiple preload discs 75 is designed in a perforated disc shape and has an outer diameter that is substantially equal to the outer diameter of a front section of the pressure section 67 of the piston-side spring bearing 35.

[0033] The opening / closing disc 76 is designed in a perforated disc shape and has an outer diameter that is essentially equal to the outer diameter of the preload discs 75. An annular opening and closing section 83, which is recessed from a first surface in the axial direction to the second side in the axial direction and projects from a second surface in the axial direction to the second side in the axial direction, is provided on the outer circumferential side of the opening and closing disc 76.

[0034] The intermediate disk 77 is formed in a perforated disk shape and has an outer diameter that is smaller than that of the opening and closing disk 76. The intermediate disk 78 is formed in a perforated disk shape and has the same outer diameter as the intermediate disk 77. Furthermore, several notches 78A are formed on the outer circumferential side of the intermediate disk 78. The contact disk 79 is formed in a perforated disk shape and has the same outer diameter as the opening and closing disk 76. A C-shaped through-hole 79A is formed in an intermediate section of the contact disk 79 in the radial direction.

[0035] The through-flow element 80 is formed in a perforated disc shape and has an outer diameter that is smaller than that of the contact disc 79. Several notches 80A are formed on the inner circumferential side of the through-flow element 80. A through-flow 86 is formed by the notches 78A, which are formed on the outer circumferential section of the intermediate disc 78, the through-flow opening 79A, which is formed in an intermediate position of the contact disc 79 in the radial direction, and the notches 80A, which are formed on the inner circumferential section of the through-flow element 80. The through-flow 86 causes the outer side of the intermediate disc 78, i.e., the upper chamber 19, to communicate with the through-flow opening 49 in the radial direction.

[0036] In a state where the multiple preload discs 75 are not pressed through the piston-side spring bearing 35, they are flat and cause the opening and closing section 83 of the opening and closing disc 76 to be separated from the contact disc 79.

[0037] Here, a gap between the opening and closing section 83 of the opening and closing disc 76 and the contact disc 79, and the passage 86 formed by the intermediate disc 78, the contact disc 79, and the passage element 80, create an opening 88. The opening 88 and the passage opening 49 of the front rod 27 form a passage 89 that allows the upper chamber 19 to communicate with the inner rod passage 32.

[0038] The intermediate body section 66 of the piston-side spring bearing 35 is separated from the flange section 56 of the front rod 27 in the axial direction by a preload force primarily exerted by the several preload washers 75. In this state, the piston rod 21 is moved towards the expansion side, with the piston rod 21 projecting from the cylinder 2, i.e., towards the upper side, with the piston-side spring bearing 35, the return spring 38, the rod guide-side spring bearing 36, and the buffer 39, which are located in Fig. 1 are shown, move to the side of the rod guide 22, together with the piston rod 21, and the buffer 39 comes into contact with the rod guide 22 at a certain position.

[0039] When the piston rod 21 is moved further in a forward direction, the buffer 39 and the rod guide-side spring bearing 36 are stopped relative to the cylinder 2 after the buffer 39 is compressed (crushed). As a consequence, the piston-side spring bearing 35, which has moved together with the piston rod 21, shortens the length of the return spring 38, and the preload force of the return spring 38 at this point becomes a resistance to the movement of the piston rod 21. In this way, the return spring 38, which is provided in the cylinder 2, acts elastically on the piston rod 21 to control the extension or retraction of the piston rod 21.It should be noted that the return spring 38 provides resistance to the extension of the piston rod 21, so that a stroke of the vehicle wheels on the inner circumferential side of a vehicle in which the shock absorber is installed is suppressed at the time of turning, and thus the rolling amount of the vehicle body is suppressed or reduced.

[0040] When the piston rod 21 moves in the projection direction and the buffer 39 comes into contact with the rod guide 22, the piston-side spring bearing 35 moves slightly to the side of the flange section 56 in the axial direction, causing the intermediate body section 66 to come into contact with the flange section 56, while the several preload discs 75 and the opening and closing disc 76, with which the pressure section 67, shown in Fig. 2, which comes into contact, are deformed by the preload force of the return spring 38, before the piston-side spring bearing 35 shortens the length of the return spring 38 between the piston-side spring bearing 35 and the rod guide-side spring bearing 36. When, in this way, the piston-side spring bearing 35, using the pressure section 67, deforms the preload discs 75 and the opening and closing disc 76 by the preload force of the return spring 38, the opening and closing section 83 of the opening and closing disc 76 comes into contact with the contact disc 79. Then the opening 88 is closed, so that the communication between the upper chamber 19 and the inner rod passage 32 via the passage 89 is blocked.

[0041] The piston-side spring bearing 35, the return spring 38, the rod guide-side spring bearing 36, and the buffer 39, which are in Fig. The components shown in Figure 1 form a spring mechanism 90. The spring mechanism 90 is provided in the cylinder 2, wherein a first end of the same is able to actuate the opening and closing disc 76 via the preload discs 75, shown in Figure 1. Fig. 2, to press or squeeze, and a second end of the same is able to engage with the rod guide 22, which is in Fig. Figure 1 shows the mechanism 90 coming into contact at the end section side of the cylinder 2. The spring mechanism 90 deforms the preload discs 75 and the opening and closing disc 76 in a valve closing direction, against the spring force of the preload discs 75 and the opening and closing disc 76, as shown in Figure 1. Fig. 2. The spring mechanism 90, the opening and closing disc 76, and the contact disc 79, which open and close the opening 88, form a passage cross-section adjustment mechanism 91. This mechanism adjusts the passage cross-section of the opening 88, i.e., the passage cross-section of the passage 89, according to the preload force of the return spring 38, which changes according to the position of the piston rod 21. In other words, the opening 88 is a variable opening whose passage cross-section varies in response to the position of the piston rod 21.

[0042] The cross-sectional area of ​​the opening 88 relative to the stroke position of the shock absorber 1, which is modified by the cross-sectional area adjustment mechanism 91, has a constant maximum value from the total stroke range on the compression side to a specific first position on the extension side, including the neutral position (position 1G (position at which the vehicle body is supported when held in a horizontal position)). When the spring mechanism 90 begins to close the opening and closing disc 76 against the preload force of the preload discs 75 at the first position, the cross-sectional area decreases proportionally as it moves towards the extension side.The through-cross-sectional area becomes minimal at a specific second position where the opening and closing section 83 of the opening and closing disc 76 comes into contact with the contact disc 79, and the through-cross-sectional area has a constant minimum value on the extension side of the second position.

[0043] As it is in Fig. As shown in Figure 3, the piston 18 consists of a piston main body 95, which is supported by the front rod 27 and is made of metal, and an annular sliding element 96, which is attached to the outer circumferential surface of the piston main body 95, performs a displacement in the inner tube 3 and is made of a synthetic resin.

[0044] The piston main body 95 is provided with several passages 101 (only one of these is in Fig. 3 shown, since the Fig. 3 shows a cross-section), through which oil passes from the upper chamber 19 to the lower chamber 20 during the movement of the piston 18 to the upper chamber 19, that is, during the expansion stroke; and several passages 102 (only one of these is in Fig. 3 shown, since the Fig. Figure 3 shows a cross-section), through which oil passes from the lower chamber 20 to the upper chamber 19 during the movement of the piston 18 to the lower chamber 20, that is, during the compression stroke, with passages 101 and 102 causing the upper chamber 19 to communicate with the lower chamber 20. In other words, the multiple passages 101 and 102 communicate with the upper chamber 19 and the lower chamber 20 through the movement of the piston 18, causing the oil to flow through them as a working fluid.

[0045] The passages 101 are arranged at uniform intervals in the circumferential direction, with a passage 102 provided between them, and open so that a first side (upper side of the Fig. 3) the same in the axial direction of the piston 18 extends radially to the outside and has a second side (lower side in Fig. 3) the same in the axial direction towards the inside and in the radial direction. A damping force generation mechanism 104, which generates a damping force, is provided for half of all passages 101. The damping force generation mechanism 104 is arranged on the side of the lower chamber 20, which is the first end face of the piston 18 in the axial direction. The passage 101 forms an expansion-side passage through which oil flows when the piston 18 moves towards the expansion side, where the piston rod 21 extends outwards with respect to the cylinder 2. The damping force generation mechanism 104 provided for such a passage is an expansion-side damping force generation mechanism that regulates the flow of oil through the expansion-side passage 101 to generate a damping force.

[0046] Furthermore, the passages 102, the other half of all passages, are formed at regular intervals in the circumferential direction, with a passage 101 provided between each one. The passages 102 are designed such that a second side (a lower side in the Fig. 3) the same in the axial direction of the piston 18 towards the outside in the radial direction and a first side (upper side in the Fig. 3) the same in the axial direction towards the inside in the radial direction. A damping force generation mechanism 105, which generates a damping force, is provided for the other half of all passages 102. The damping force generation mechanism 105 is arranged on the side of the upper chamber 19 in an axial direction which is the second end face of the piston 18 in the axial direction. The passage 102 forms a compression-side passage through which oil passes when the piston 18 moves to the compression side, with the piston rod 21 entering the cylinder 2. The damping force generation mechanism 105, which is provided for such a passage, is a compression-side damping force generation mechanism that regulates the flow of oil in the compression-side passage 102 to generate a damping force.

[0047] The piston body 95 is approximately disc-shaped, and its center is provided with an insertion opening 106 that extends axially through the piston body 95 and into which the retaining shaft section 57 of the front rod 27 is inserted. An annular seat section 107, forming the damping force generation mechanism 104, is formed on the outside of an opening position of the first end of the expansion-side passage 101 at an end section of the piston body 95 on the side of the lower chamber 20. An annular seat section 108, forming the damping force generation mechanism 105, is formed on the outside of an opening position of the first end of the compression-side passage 102 at an end section of the piston body 95 on the side of the upper chamber 19.

[0048] In the piston main body 95, a stepped section, the height of which is lower in the axial direction than the seat section 107, is formed on one side of the seat section 107 opposite the insertion opening 106. The second end of the compression-side passage 102 opens in the stepped section. Similarly, in the piston main body 95, a stepped section, the height of which is lower in the axial direction than the seat section 108, is formed on one side of the seat section 108 opposite the insertion opening 106. The second end of the expansion-side passage 101 opens in the stepped section.

[0049] The extension-side damping force generation mechanism 104 is a pressure-controlled valve mechanism. The damping force generation mechanism 104 comprises, from the side of the piston 18 in the axial direction in the following order: several disks 111, a single contact disk 112, a single valve element 113, a single disk 114, several disks 115, a single disk 116, a single disk 117, a pilot housing 118, a single disk 119, a single disk 120, a single disk 121, several disks 122, a single disk 123, a single disk 124, and a regulating element 125.

[0050] The pilot housing 118 is made of metal. The pilot housing 118 is formed in a tubular shape, closed at the bottom, and has a perforated disc-shaped base 131 perpendicular to the axis, a cylindrical inner tube 132 extending axially along the inner circumferential side of the base 131, and a cylindrical outer tube 133 extending axially along the outer circumferential side of the base 131. The base 131 deviates axially on the first side relative to the inner tube 132 and the outer tube 133. Several through-openings 134, extending axially through the base 131, are formed in the base 131.On the inside of the inner tube 132, a small-diameter opening section 135, into which the retaining shaft section 57 of the front rod 27 is fitted, is formed on the side of the base 131 in the axial direction. A large-diameter opening section 136, which has a larger diameter than the small-diameter opening section 135, is formed on one side opposite the base 131 in the axial direction. An annular seat section 137 is formed on an end section of the outer tube 133 of the pilot housing 118 on the side of the base 131 in the axial direction. The disk 119 sits on the seat section 137.

[0051] A space surrounded by the bottom 131, the inner tube 132 and the outer tube 133 of the pilot housing 118 and located on one side opposite the bottom 131 in the axial direction, and the through-opening 134 of the pilot housing 118 form a pilot chamber or pilot control chamber 140, which applies a pressure against the valve element 113 in one direction of the piston 18. The through-hole 51 of the front rod 27, the large diameter opening section 136 of the pilot housing 118 and an opening 151, described below, formed on the disks 116 and 117, form a pilot chamber inlet passage 141, which is connected to the inner rod passage 32 and the pilot chamber 140, in order to direct part of the oil flow from the upper chamber 19 and the lower chamber 20 via the inner rod passage 32 to the pilot chamber 140.

[0052] The multiple discs 111 are made of metal and are designed in a perforated disc shape, having an outer diameter smaller than that of the seat section 107 of the piston 18. The contact disc 112 is made of metal and is designed in a perforated disc shape, having an outer diameter larger than that of the seat section 107 of the piston 18 and being able to sit on the seat section 107.

[0053] The valve element 113 is composed of a metal disc 145 in a perforated disc shape, having an outer diameter substantially equal to the outer diameter of the contact disc 112; and an annular sealing element 146, made of a rubber material, designed to be fixed to the outer circumferential section of the disc 145 by baking, firing, or the like, on one side of the rear surface opposite the seat section 107. The contact disc 112 and the disc 145 of the valve element 113 form an expansion-side damping valve 147, which, in a closed state, comes into contact with the seat section 107 of the piston 18 and, in an open state, is separated from the seat section 107 of the piston 18. The damping valve 147, together with the pilot housing 118, forms the pilot chamber 140.The damping valve 147 is located between the passage 101 provided in the piston 18 and the pilot chamber 140 provided in the pilot housing 118. It suppresses the oil flow through the passage 101 by displacing the piston 18 towards the expansion side, thereby generating a damping force. Thus, the damping valve 147 is a disc valve. The opening of the damping valve 147 is suppressed or prevented by the pressure of the pilot chamber 140. It should be noted that no axially extending section is formed in the contact disc 112 and the disc 145, with the exception of the central opening into which the retaining shaft section 57 of the piston rod 21 is inserted.

[0054] The sealing element 146 of the valve element 113 is slidably fitted into the inner circumferential surface of the outer tube 133 of the pilot housing 118 in a liquid-tight manner and seals a gap between the valve element 113 and the outer tube 133. Thus, the pilot chamber 140 between the valve element 113 and the pilot housing 118 causes the internal pressure to act on the damping valve 147, which is formed from the contact disc 112 and the disc 145 of the valve element 113, in the direction of the piston 18, i.e., the valve closing direction in which the contact disc 112 comes into contact with the seat section 107. The damping valve 147 is a pilot-type or pre-operated damping valve that incorporates the pilot chamber 140.When the contact disc 112 is separated from the seat section 107 of the piston 18, causing the damping valve to open, oil flows via a passage 148 from the passage 101 to the lower chamber 20 along the radial direction between the piston 18 and the pilot housing 118.

[0055] The disk 114 is made of metal and is formed in a perforated disk shape with an outer diameter smaller than that of disk 145. The multiple disks 115 are made of metal and are formed in a perforated disk shape with an outer diameter substantially equal to that of disk 111. The disk 116 is made of metal and is formed in a perforated disk shape with an outer diameter substantially equal to that of disk 115. Several notches 116A are formed on the outer circumferential side of disk 116. The disk 117 is made of metal and is formed in a perforated disk shape with an outer diameter substantially equal to that of disk 115. Several notches 117A are formed on the inner circumferential side of disk 117.The notches 116A of disk 116 and the notches 117A of disk 117 communicate with each other to form the opening 151. As described above, the inner area of ​​the large-diameter opening section 136 of pilot housing 118 and the pilot chamber 140 communicate with each other via the opening 151.

[0056] The disk 119 is made of metal. The disk 119 is formed in a perforated disk shape with an outer diameter larger than that of the seat section 137 of the pilot housing 118, and it is capable of sitting on the seat section 137. Several notches 119A are formed on the outer circumferential side of the disk 119, and a through-hole 119B, connected to the notches 119A, is formed radially in the intermediate section. The disk 120 is made of metal and has an outer diameter substantially equal to that of the disk 119. A through-hole 120A is formed radially in the intermediate section of the disk 120. The disk 121 has an outer diameter substantially equal to that of the disk 119. Several notches 121A are formed on the outer circumferential side of the disk 121.Each of the several disks 122 has an outer diameter that is essentially the same as that of disk 119.

[0057] The discs 119 to 122 and the seat section 137 form a disc valve 153 that suppresses the oil flow between the pilot chamber 140, provided in the pilot housing 113, and the lower chamber 20. The notches 119A and the through-hole 119B of disc 119, the through-hole 120A of disc 120, and the notches 121A of disc 121 form an opening that allows the pilot chamber 140 to communicate with the lower chamber 20, even when disc 119 is in contact with the seat section 137. The disc valve 153 causes the pilot chamber 140 to communicate with the lower chamber 20, with a passage cross-sectional area larger than that of the opening 154 when the disc 122 is separated from the disc 121 or when the disc 119 is separated from the seat section 137.The disc 124 is in contact with the regulating element 125, which has high strength, and comes into contact with the disc 122 when the disc valve 153 is deformed in a valve opening direction, regulating the deformation of the disc valve 153 beyond a certain amount.

[0058] As with the expansion side, the compression-side damping force generation mechanism 105 is a pressure-controlled valve mechanism. The damping force generation mechanism 105 comprises, from the side of the piston 18 in the axial direction, in the following order: several disks 161, a single contact disk 162, a single valve element 163, a single disk 164, several disks 165, a single disk 166, a single disk 167, a pilot housing 168, a single disk 169, a single disk 170, a single disk 171, several disks 172, a single disk 173, and several disks 174.

[0059] The pilot housing 168 is the same component as the pilot housing 118 described above. The pilot housing 168 is formed in a tubular shape, closed at the bottom, and has a perforated disc-shaped bottom 181 along a direction perpendicular to the axis, a cylindrical inner tube 182 formed along the axial direction on the inner circumferential side of the bottom 181, and a cylindrical outer tube 183 formed along the axial direction on the outer circumferential side of the bottom 181. The bottom 181 deviates on the second side in the axial direction relative to the inner tube 182 and the outer tube 183. Several through-openings 184, extending axially through the bottom 181, are formed in the bottom 181.On the inside of the inner tube 182, a small-diameter opening section 185, into which the retaining shaft section 57 of the front rod 27 is fitted, is formed on the side of the base 181 in the axial direction, and a large-diameter opening section 186, which has a larger diameter than that of the small-diameter opening section 185, is formed on one side opposite the base 181 in the axial direction. An annular seat section 187 is formed on an end section of the outer tube 183 of the pilot housing 168, on the side of the base 181 in the axial direction, and the disk 169 sits on the seat section 187.

[0060] A space enclosed by the base 181, the inner tube 182, and the outer tube 183 of the pilot housing 168, located on one side opposite the base 181 in the axial direction, and the through-opening 184 of the pilot housing 168 form a pilot chamber 190, which exerts a pressure against the valve element 163 in one direction of the piston 18. The through-opening 50 of the front rod 27, the large-diameter opening section 186 of the pilot housing 168, and an opening 201, described below, formed on the disks 166 and 167, form a pilot chamber inlet passage 191, which is connected to the inner rod passage 32 and the pilot chamber 190 to direct a portion of the oil flow from the upper chamber 19 and the lower chamber 20 via the inner rod passage 32 to the pilot chamber 190.

[0061] The multiple discs 161 are made of metal and are formed in a perforated disc shape, having an outer diameter smaller than that of the seat section 108 of the piston 18. The contact disc 162 is the same component as the contact disc 112. The contact disc 162 is formed in a perforated disc shape, having an outer diameter larger than that of the seat section 108 of the piston 18, and it is able to sit on the seat section 108.

[0062] The valve element 163 is the same component as the valve element 113 described above. The valve element 163 consists of a disc 195, which is formed in a perforated disc shape and has an outer diameter substantially equal to the outer diameter of the contact disc 162; and an annular sealing element 196, which is formed from a rubber material and is designed to be fixed to the outer circumferential section of the disc 195 on one side of the rear surface, which is opposite the seat section 108. The contact disc 162 and the disc 195 of the valve element 163 form a compression-side damping valve 197, which, in a closed state, comes into contact with the seat section 108 of the piston 18 and, in an open state, is separated from the seat section 108 of the piston 18. The damping valve 197, together with the pilot housing 168, forms the pilot chamber 190.The damping valve 197 is arranged between the passage 102 provided in the piston 18 and the pilot chamber 190 provided in the pilot housing 168. It suppresses the oil flow through the passage 102 due to the displacement of the piston 18 towards the compression side, thereby generating a damping force. Thus, the damping valve 197 is a disc valve. The opening of the damping valve 197 is suppressed by the pressure of the pilot chamber 190. It should be noted that no section extending in the axial direction is formed in the contact disc 162 and the disc 195, with the exception of the central opening into which the retaining shaft section 57 of the piston rod 21 is inserted.

[0063] The sealing element 196 of the valve element 163 is slidably fitted into the inner circumferential surface of the outer tube 183 of the pilot housing 168 in a liquid-tight manner and seals a gap between the valve element 163 and the outer tube 183. Thus, the pilot chamber 190 between the valve element 163 and the pilot housing 168 causes the internal pressure to act on the damping valve 197, which is constructed from the contact disc 162 and the disc 195 of the valve element 163, in the direction of the piston 18, i.e., the valve closing direction in which the contact disc 162 comes into contact with the seat section 108. The damping valve 197 is a pilot-type or pre-operated damping valve that incorporates the pilot chamber 190.When the contact disc 162 is separated from the seat section 108 of the piston 18, causing the damping valve to open, the damping valve 197 causes a flow of oil from the passage 102 to the upper chamber 19, via a passage 198 along the radial direction between the piston 18 and the pilot housing 168.

[0064] The disk 164 is made of metal and is formed in a perforated disk shape with an outer diameter smaller than that of disk 195. The multiple disks 195 are made of metal and are formed in a perforated disk shape with an outer diameter substantially equal to that of disk 161. The disk 166 is made of metal and is formed in a perforated disk shape with an outer diameter substantially equal to that of disk 165. Several notches 166A are formed on the outer circumferential side of disk 166. The disk 167 is formed in a perforated disk shape with an outer diameter substantially equal to that of disk 166, and several notches 167A are formed on the inner circumferential side of disk 167. The notches 166A of disk 166 and the notches 167A of disk 167 communicate with each other to form the opening 201.As described above, the inner area of ​​the large diameter opening section 186 of the pilot housing 168 and the pilot chamber 190 communicate with each other via the opening 201.

[0065] The disk 169 is made of metal and is formed in a perforated disk shape with an outer diameter larger than that of the seat section 187 of the pilot housing 168, and it is capable of sitting on the seat section 187. Several notches 169A are formed on the outer circumferential side of the disk 169, and a through-hole 169B, connected to the notches 169A, is formed in the intermediate section in the radial direction. The disk 170 is made of metal and has an outer diameter substantially equal to that of the disk 169. A through-hole 170A is formed in the intermediate section of the disk 170 in the radial direction. The disk 171 is made of metal and has an outer diameter substantially equal to that of the disk 169. Several notches 171A are formed on the outer circumferential side of the disk 171.Each of the several discs 172 is made of metal and has an outer diameter that is essentially the same as that of disc 169.

[0066] The discs 169 to 172 and the seat section 187 form a disc valve 203 that suppresses the oil flow between the pilot chamber 190, provided in the pilot housing 168, and the upper chamber 19. The notches 169A and the through-hole 169B of disc 169, the through-hole 170A of disc 170, and the notches 171A of disc 171 form an opening 204 that allows the pilot chamber 190 to communicate with the upper chamber 19, even when disc 169 is in contact with the seat section 187. The disc valve 203 causes the pilot chamber 190 to communicate with the upper chamber 119, with a passage cross-sectional area larger than that of the opening 204 when the disc 172 is separated from the disc 171 or when the disc 169 is separated from the seat section 187.The multiple discs 174 come into contact with the disc 172 when the discs 169 to 172 are deformed in the valve opening direction, whereby the deformation of the discs 169 to 172 is regulated beyond a certain amount.

[0067] The nut 210 is screwed to the external thread 61 on the front of the front rod 27. The nut 210 is secured by means of the external thread 61, so that there is a gap between the nut 210 and the flange section 56 of the front rod 27, as shown in Fig. 2, arranged in a sandwich-like manner are: the several discs 73, the disc 74, the several preload discs 75, the opening and closing disc 76, the intermediate disc 77, the intermediate disc 78, the contact disc 79, the through-formation element 80, the several discs 174, the disc 173, the several discs 172, the disc 171, the disc 170 and the disc 169, shown in Fig. 2; the pilot housing 168, the disc 167, the disc 166, the multiple discs 165, the disc 164, the valve element 163, the contact disc 162, the multiple discs 161, the piston 18, the multiple discs 111, the contact disc 112, the valve element 113, the disc 114, the multiple discs 115, the disc 116, the disc 117, the pilot housing 118, the disc 119, the disc 120, the disc 121, the multiple discs 122, the disc 123, the disc 124 and the regulating element 125, shown in Fig. 3.

[0068] In this state, the inner circumferential side of the damping valve 147, which consists of the disc 145 and the contact disc 112, is clamped by the disc 114 and the discs 111. Consequently, when the outer circumferential side of the damping valve 147 rests on the seat section 107, the passage 101 is closed, and when the outer circumferential side of the damping valve 147 is separated from the seat section 107, the passage 101 is open. Similarly, the inner circumferential side of the damping valve 197, which consists of the disc 195 and the contact disc 162, is clamped by the disc 164 and the discs 161. Consequently, when the outer circumferential side of the damping valve 167 is seated on the seat section 108, the passage 102 is closed, and when the outer circumferential side of the damping valve 197 is separated from the seat section 108, the passage 102 is open.

[0069] As it is in Fig. As shown in Figure 1, the metering pin 31 has: a support flange section 220, which is supported by the base valve 25; a large-diameter axial section 222, which has a smaller diameter than the support flange section 220 and extends axially from the support flange section 220; a tapered or conical axial section 223, which extends axially from one side of the large-diameter axial section 222 opposite the support flange section 220; and a small-diameter axial section 224, which extends axially from one side of the tapered axial section 223 opposite the large-diameter axial section 222.The axial section of the large diameter 222 has a constant diameter, and the axial section of the small diameter 224 has a constant diameter that is smaller than that of the axial section of the large diameter 222.

[0070] The metering pin 31 is inserted into the insertion opening 30 of the piston rod 21. The metering pin 31 forms the inner rod passage 32 between the metering pin 31 and the insertion opening 30 of the piston rod 21. As shown in Fig. As shown in Figure 3, the gap between the metering pin 31 and the small diameter opening section 48, which is positioned at the first end of the piston rod 21 in the cylinder 2, forms an opening 225 that puts the inner rod passage 32 in communication with the lower chamber 20.

[0071] Passage 89, which leads to opening 88, is shown in Fig. 2, and the inner bar passage 32, which forms the opening 225, shown in Fig. 3, communicate with each other to cause the working fluid to flow between the upper chamber 19 and the lower chamber 20 through the movement of the piston 18.

[0072] The cross-sectional area of ​​the opening 225 is minimized when the large-diameter axial section 222 of the metering pin 31 and the small-diameter opening section 48 are positioned such that they are aligned in the axial direction. Furthermore, the cross-sectional area of ​​the opening 225 is maximized when the small-diameter axial section 224 of the metering pin 31 and the small-diameter opening section 48 are positioned such that they are aligned in the axial direction. Additionally, the opening 225 is designed such that the cross-sectional area towards the small-diameter axial section 224 of the tapered axial section 223 gradually increases when the tapered axial section 223 of the metering pin 31 and the small-diameter opening section 48 are positioned such that they are aligned in the axial direction.In other words, the opening 225 is a variable opening whose cross-sectional area changes in response to the position of the piston rod 21.

[0073] The small-diameter opening section 48, located at the first end of the piston rod 21 in the cylinder 2, and the metering pin 31 form the opening 225 and constitute a flow area adjustment mechanism 227, which adjusts the flow area of ​​the opening 225 using the position of the piston rod 21 relative to the cylinder 2. In other words, the flow area adjustment mechanism 227 adjusts the flow area of ​​the opening 225 using the metering pin 31.

[0074] Due to the cross-sectional area adjustment mechanism 227, the cross-sectional area of ​​the opening 225, relative to the stroke position of the shock absorber 1, exhibits a constant minimum value further on the compression side than at a specific third position on the compression side. This is achieved by positioning the small-diameter opening section 48 and the large-diameter axial section 220 so that they are aligned in the axial direction. From the third position up to a fourth position on the extension side, which includes position 1G, the cross-sectional area of ​​the opening 225 increases along the opening towards the extension side. This is achieved by positioning the small-diameter opening section 48 and the tapered axial section 223 so that they are aligned in the axial direction.From the fourth position to the extension side, the passage cross-sectional area of ​​the opening 225 has a constant maximum value by positioning the opening section of the small diameter 48 and the axial section of the small diameter 224 so that they are aligned in the axial direction.

[0075] As it is in Fig. As shown in Figure 1, the base valve 25 is provided between the bottom element 8 of the outer tube 4 and the inner tube 3. The base valve 25 comprises: a base valve element 231 that separates the lower chamber 20 and the reservoir chamber 6; a disc 232 that is provided on the lower side of the base valve element 231, i.e., on the side of the reservoir chamber 6; a disc 233 that is provided on the upper side of the base valve element 231, i.e., on the side of the lower chamber 20; an attachment pin 234 that attaches the disc 232 and the disc 233 to the base valve element 231; a locking element 235 that is attached to the outer circumferential side of the base valve element 231; and a support plate 236 that supports the support flange section 220 of the metering pin 31. The mounting pin 234 arranges the center side of the disc 232 and the disc 233 in a sandwich-like manner in the radial direction between the mounting pin and the base valve element 231.

[0076] The base valve element 231 is annular in shape, such that the mounting pin 234 is inserted radially into the center of the base valve element 231. The base valve element 231 is formed with several through-openings 239, which allow oil to flow between the lower chamber and the reservoir chamber 6; and several through-openings 240, which are located on the outside of the through-openings 239 in the radial direction and allow oil to flow between the lower chamber 20 and the reservoir chamber 6. The disk 232 on the side of the reservoir chamber 6 allows oil to flow from the lower chamber 20 to the reservoir chamber 6 via the through-openings 239 on the inside and further regulates the oil flow from the reservoir chamber 6 to the lower chamber 20 via the through-openings 239 on the inside.The disc 233 allows oil flow from the reservoir chamber 6 to the lower chamber 20 via the through-openings 240 on the outside and further regulates the oil flow from the lower chamber 20 to the reservoir chamber 6 via the through-openings 240 on the outside.

[0077] The disc 232 and the base valve element 231 form a compression-side damping valve 242, which is open during the compression stroke of the shock absorber 1 to cause oil to flow from the lower chamber 20 to the reservoir chamber 6, thereby generating a damping force. The disc 233 and the base valve element 231 form a suction valve 243, which is open during the extension stroke of the shock absorber 1 to cause oil to flow from the reservoir chamber 6 to the lower chamber 20. The suction valve 243 primarily functions to allow fluid to flow from the reservoir chamber 6 to the lower chamber 20, essentially without generating a damping force, to compensate for a fluid deficit (supplement) that occurs when the piston rod 21 extends from the cylinder 2.

[0078] The locking element 235 is tubular, and the base valve element 231 is fitted into its inner surface. The base valve element 231 is fitted into the inner circumferential section of the lower end of the inner tube 3 via the locking element 235. A locking flange section 245, extending radially towards the inner surface, is formed in an end section of the locking element 235 on the side of the piston 18. With respect to the support plate 236, the outer circumferential section of the locking flange section 245 is locked against the piston 18 on one side, and the inner circumferential section is locked against the support flange section 220 of the metering pin 31 on the side of the piston 18. In this way, the locking element 235 and the support plate 236 keep the support flange section 220 of the metering pin 31 in a state in which the support flange section 220 is in contact with the mounting pin 234.

[0079] As it is in Fig. As shown in Figure 4, the rod guide 22 has an outer shape in which a section of the large outer diameter 252 is formed on the first side in the axial direction, and a section of the small outer diameter 253, which has a smaller diameter than the section of the large outer diameter 252, is formed on the second side in the axial direction. The rod guide 22 is a sintered component, wherein the section of the large outer diameter 252 of the rod guide 22 is fitted into the inner circumferential section of the large diameter 14 of the mouthpiece element 9 of the outer tube 4, and the section of the small outer diameter 253 thereof is fitted into the inner circumferential section of the inner tube 3.

[0080] A large-diameter opening section 254, an intermediate opening section 255, and a small-diameter section 256 are formed in the center of the rod guide 22 in the radial direction. The large-diameter opening section 254 is formed on the side of the large-diameter section 252 of the rod guide 22 in the axial direction. The intermediate opening section 255 has a smaller diameter than the large-diameter opening section 254 and is formed in the axial direction closer to the small-diameter section 253 than to the large-diameter opening section 254 of the rod guide 22.The small diameter section 256 has a diameter that is smaller than that of the large diameter opening section 254 and slightly larger than the intermediate opening section 255, and is formed in the axial direction on one side of the intermediate opening section 255 opposite the large diameter opening section 254 of the rod guide 22.

[0081] A communication groove 257 is formed on the opening section of the large diameter 254 to be continuous from the inner circumferential surface of the base surface. The communication groove 257 extends axially over the entire length of the inner circumferential surface of the opening section of the large diameter 254 and radially over the entire length of the base surface of the opening section of the large diameter 254.

[0082] An annular convex section 258 is formed in an end face of the rod guide 22 on the side of the section with the large outer diameter 252 in the axial direction. The annular convex section 258 is designed to project outwards in the axial direction from the end face of the rod guide 22 on the side of the section with the large outer diameter 252. A communication opening 261 is formed in the rod guide 22 on the inside of the annular convex section 258. The communication opening 261 extends through the section with the large outer diameter 252 of the rod guide 22 in the axial direction and communicates with the reservoir chamber 6 between the outer tube 4 and the inner tube 3.

[0083] The sealing element 23 is arranged in the first end section of the cylinder 2 in the axial direction, and its inner circumferential section is in press contact or pressure contact with the outer circumferential section of the main rod body 26 of the piston rod 21. The inner circumferential section of the sealing element 23 is in sliding contact with the outer circumferential section of the piston rod 21, which moves in the axial direction, in order to prevent oil in the inner tube 3 and the high-pressure gas and oil in the reservoir chamber 6 in the outer tube 4 from escaping to the outside through a gap between the rod guide 22 and the piston rod 21 and a gap between the rod guide 22 and the outer tube 4. Fig. 4 the piston rod 21 is represented by an imaginary line (two-dot dashed line), and the sealing element 23 is shown in a natural state before the piston rod 21 is inserted (meaning that the sealing element 23 does not engage with the piston rod 21).

[0084] The sealing element 23 is composed of a sealing element main body 267, which is an integrally formed product consisting of a sealing element 265 and an annular element 266, which has an annular shape; and an annular spring 268; and an annular spring 269. The sealing section 265 is made of an elastic rubber material exhibiting advantageous sliding properties, such as nitrile rubber or fluorocarbon rubber. The annular element 266 serves to maintain the shape of the sealing element 23 by concealing or providing it within the sealing section 265, and to provide rigidity for fixation; it is made of metal.

[0085] The sealing section 265 has an annular tubular dirt lip 272 and an annular tubular oil lip 273 on its inner side in the radial direction. The dirt lip 272 extends from the outside of the cylinder's inner / outer direction along the inner circumferential side of the annular element 266 in a direction that separates it from the annular element 266 along the axial direction. The oil lip 273 extends from the inside of the cylinder's inner / outer direction along the inner circumferential side of the annular element 266 in a direction that separates it from the annular element 266 along the axial direction. The spring 268 is fitted into the outer circumferential section of the dirt lip 272, and the spring 269 is fitted into the outer circumferential section of the oil lip 273.

[0086] Furthermore, the sealing section 265 has an outer circumferential seal 274 and an annular sealing lip 275 on its outer surface in the radial direction. The outer circumferential seal 274 covers the outer circumferential surface of the annular element 266.

[0087] The sealing lip 275 extends from the outer circumferential seal 274 to the inner side with respect to the cylinder's inner / outer direction. Furthermore, the sealing section 265 has an annular locking lip 276. The locking lip 276 extends from the inner side with respect to the cylinder's inner / outer direction of the intermediate section of the sealing section 265 in the radial direction to the inner side with respect to the cylinder's inner / outer direction, while its diameter increases.

[0088] In its natural state, the dirt lip 272 is formed in a tapered or conical tubular shape, in which the inner diameter decreases with increasing distance of the dirt lip from the annular element 266 outwards in the cylinder's inner / outer direction. The outer circumferential section of the dirt lip 272 has a shape that is recessed inwards in the radial direction, and the spring 268 is fitted into the recessed section.

[0089] In its natural state, the oil lip 273 is formed in a tapered tubular shape, in which the inner diameter of the oil lip decreases with increasing distance inwards from the annular element 266 in the cylinder's inner / outer direction. The outer circumferential section of the oil lip 273 has a recessed shape in the radial direction, and the spring 269 is fitted into this recessed section. The inner circumferential section of the oil lip 273 is stepped.

[0090] In a state where the dirt lip 272 is arranged on the outside with respect to the cylinder's inner / outside direction and the oil lip 273 is arranged on the inside with respect to the cylinder's inner / outside direction, the outer circumferential seal 274 of the sealing element 23 is in sealing contact with the inner circumferential section of the large diameter 14 of the nozzle element 9 of the outer tube 4. In this state, the position of the annular element 266 of the sealing section 256 in the sealing element 23 is sandwiched between the annular convex section 258 of the rod guide 22 and the inner flange section 16 of the cover 5. Simultaneously, the sealing lip 275 in the sealing element 23 is arranged between the annular convex section 258 of the rod guide 22 and the inner circumferential section of the large diameter 14 of the nozzle element 9 of the outer tube 4 and is thus in sealing contact.Furthermore, the oil lip 273 is arranged in the opening section of the large diameter 254 of the rod guide 22.

[0091] The main body 26 of the piston rod 21 is inserted into the inner surface of the dirt lip 272 and the oil lip 273 of the sealing element 23 in a state in which the sealing element 23 is attached to the cylinder 2. In this state, the first end of the piston rod 21 protrudes from the first end of the cylinder 2. Furthermore, in this state, the dirt lip 272 is provided on the first end face of the cylinder 2, where the piston rod 21 protrudes, and the oil lip 273 is provided on the inner surface with respect to the dirt lip 272 in the cylinder-inside / outside direction.

[0092] The spring 268, which is fitted into the dirt lip 272, is an element for maintaining the clamping force in a constant state in the direction of the tight contact between the dirt lip 272 and the piston rod 21. Furthermore, the spring 268 is also used to adjust the clamping force to meet a design specification. The spring 269, which is fitted into the oil lip 273, adjusts the clamping force in the direction of the tight contact between the oil lip 273 and the piston rod 21.

[0093] The locking lip 276 of the sealing section 265 on the side of the rod guide 22 is designed to be in sealing contact with a section located further inward than the annular convex section 258 of the rod guide 22, over its entire circumference, with a specific fixing dimension. Here, oil escaping from the gap between the rod guide 22 and the piston rod 21 is collected in a chamber 280, which is formed primarily by the large-diameter opening section 254 located further inward than the locking lip 276 of the sealing element 23. The locking lip 276 opens when the pressure of the chamber 280 is a certain amount greater than the pressure of the reservoir chamber 6, causing the oil collected in the chamber 280 to flow to the reservoir chamber 6 via the communication opening 261.This means that the sealing lip 276 acts as a shut-off valve to allow the oil and gas flow to take place only in one direction from chamber 280 to reservoir chamber 6, and to regulate the flow in the opposite direction.

[0094] The sealing element 23 maintains sealing properties by ensuring that the dirt lip 272 is in close contact with the piston rod 21 through its interaction and the radial load of the spring 268. The sealing element 23 regulates the ingress of foreign substances that adhere to the piston rod 21 when the piston rod 21 is exposed to the outside, primarily using the dirt lip 272. The sealing element 23 maintains sealing properties by ensuring that the oil lip 273 is in close contact with the piston rod 21 through its interaction and the radial load of the spring 269. The sealing element 23 regulates the outward escape of oil that adheres to the piston rod 21 when the piston rod 21 penetrates the inner tube 3, primarily using the oil lip 273.

[0095] The friction element 24 is fitted into the opening section of the large diameter 254 of the rod guide 22 at its base. Consequently, the friction element 24 is positioned further inside the cylinder 2 than the sealing element 23. The inner circumferential section of the friction element 24 is in contact with the outer circumferential section of the main rod body 26 of the piston rod 21 and generates a frictional force against the piston rod 21. Fig. In Figure 4, the piston rod 21 is represented by an imaginary line (two-dot dashed line), and the friction element 24 is shown in a natural state before the piston rod 21 is inserted (meaning that the friction element 24 does not engage with the piston rod 21).

[0096] The friction element 24 is an integrally formed product consisting of an annular elastic rubber section 291 and an annular base section 292. The elastic rubber section 291 is made of an elastic rubber material, such as nitrile rubber or fluorocarbon rubber, and is fixed to the base section 292. The base section 292 is made of metal and serves to maintain the shape of the elastic rubber section 291 and to provide the necessary strength for fixing it to the rod guide 22.

[0097] The base section 292 of the friction element 24 is composed of a base 301 and a tube 302. The base 301 is formed in a perforated disc shape. The tube 302 is formed in a cylindrical shape, extending axially from the outer circumferential side of the base 301. The central axes of the base 301 and the tube 302 coincide. In other words, the tube 302 extends vertically relative to the base 301.

[0098] The elastic rubber section 291 is annular in shape, with its central axis coinciding with that of the base section 292. The elastic rubber section 291 covers the inner circumferential surface of the base 301 of the base section 292 and the base 301 on the side of the tube 302 in the axial direction and is designed to extend from the base 301 to the side of the tube 302 in the axial direction. In its natural state, the elastic rubber section 291 is separated from the tube 302 in the radial direction and has a tapered surface 305 whose diameter increases with the extension of the outer circumferential side facing the tube 302 towards the side of the base 301 in the axial direction. In its natural state, the elastic rubber section 291 has a section of minimum inner diameter 307, a diameter increase section 308, and a diameter increase section 309 on its inner circumferential surface.The section with the minimum inner diameter 307 is designed to have the minimum inner diameter at the friction element 24. The diameter increase section 308 is located on one side of the section with the minimum inner diameter 307 opposite the base 301 in the axial direction and is formed in a tapered shape, the diameter of which increases with increasing distance of the diameter increase section 308 from the section with the minimum inner diameter 307. The diameter increase section 309 is located on the side of the base 301 of the section with the minimum inner diameter 307 in the axial direction and is formed in a tapered shape, the diameter of which increases with increasing distance of the diameter increase section 309 from the section with the minimum inner diameter 307.In other words, the elastic rubber section 291 is provided with the section of minimum inner diameter 307 and the diameter-increasing sections 308 and 309, which are located on both sides of the section of minimum inner diameter 307 in the axial direction, on the inner circumferential side. The boundary between the diameter-increasing sections 308 and 309 is the section of minimum inner diameter 307. In its natural state, the axial length of the diameter-increasing section 309 between the section of minimum inner diameter 307 and the base 301 is greater than the axial length of the diameter-increasing section 308.

[0099] In a state where the side of the tube 302 of the base section 292 is arranged externally in the axial direction with respect to the cylinder's inner / outer direction, and the bottom 301 of the base section 292 is arranged internally in the axial direction with respect to the cylinder's inner / outer direction, the friction element 24, which has the structure described above, is press-fitted into the large-diameter opening section 254 of the rod guide 22. Simultaneously, the bottom 301 of the base section 292 of the friction element 24 is in contact with the bottom surface of the large-diameter opening section 254.

[0100] With the friction element 24 attached to the cylinder 2, the main body 26 of the piston rod 21 is inserted into the elastic rubber section 291 with a specific fit. In this way, the elastic rubber section 291 of the friction element 24 is in close contact with the main body 26 of the piston rod 21, while the latter is elastically deformed radially outwards. When the piston rod 21 is then moved in the cylinder-inward / outward direction, the elastic rubber section 291 is in sliding contact with the main body 26. Simultaneously, the friction element 24 establishes the friction characteristic.

[0101] In a state where the friction element 24 is fitted, a communication passage 311 is formed by the communication groove 257, which is formed on the large-diameter opening section 254, between the large-diameter opening section 254 of the rod guide 22 and the friction element 24. The communication passage 311 causes the side of the small-diameter section 256 of the rod guide 22 to communicate with the side of the large-diameter opening section 254, i.e., the side of the chamber 280. The side of the small-diameter section 256 of the rod guide 22 communicates with the upper chamber 19 via the piston rod 21. In this way, the communication passage 311 causes the chamber 280 to communicate with the upper chamber 19, thereby reducing the differential pressure between them.In other words, the communication passage 311 causes the opposite sides of the friction element 24 to communicate with each other in the axial direction, thereby reducing the differential pressure between the opposite sides of the friction element 24 in the axial direction. Thus, the friction element 24 is not an element that plays an active role in sealing. The friction element 24 and the communication passage 311 form a damping force generation mechanism 312, which generates a damping force with respect to the shock absorber 1 by making the friction element 24 a displacement resistance of the piston rod 21.

[0102] Instead of or in addition to the communication passage 311, a communication passage for reducing the differential pressure on the opposite side of the friction element 24 in the axial direction can be provided on the inner circumference of the friction element 24. The communication passage 311 does not have to provide communication at all times; for example, a shut-off valve from the inside of the cylinder 2 to the outside can be provided. The point is that the friction element 24 is preferably a friction element that does not act as a perfect seal.

[0103] The operation of the shock absorber 1 of the embodiment is described. The shock absorber 1 of the embodiment has a position-sensitive function in which the damping force changes according to the stroke position by being provided with the cross-sectional area adjustment mechanisms 91 and 227.

[0104] In a specific maximum-length region, where the piston rod 21 extends further outwards relative to the cylinder 2 than a specific maximum-length position, the buffer 39 is located, as shown in Fig. 1, with the rod guide 22 in contact, and the length of the spring mechanism 90, which includes the return spring 38, is shortened. Consequently, the cross-sectional area adjustment mechanism 91 elastically deforms the preload discs 75 and the opening and closing disc 76 through the piston-side spring bearing 35 of the spring mechanism 90, as shown in Fig. 2, so that the opening and closing disc 76 comes into contact with the contact disc 79 and the passage 89 is thus closed. Furthermore, the passage cross-section adjustment mechanism 227, shown in [reference], is positioned within the defined maximum length area. Fig. 3, the opening section of the small diameter 48, so that it is aligned with the axial section of the small diameter 224 of the metering pin 31 in the axial direction, thereby maximizing the passage cross-sectional area of ​​the opening 225. In the specified maximum length-side region, the inner rod passage 32 communicates with the lower chamber 20 in the passage cross-sectional area of ​​the opening 225, and the pilot chamber 140 of the expansion-side damping force generation mechanism 104 and the pilot chamber 190 of the compression-side

[0105] Damping force generation mechanism 105 communicates with the lower chamber 20 via the inner rod passage 32, which has the opening 225 and the pilot chamber inflow passages 141 and 191.

[0106] Within the defined maximum length-side region, during the expansion stroke, in which the piston rod 21 extends outwards relative to the cylinder 2, the piston 18 is moved towards the side of the upper chamber 19, increasing the pressure in the upper chamber 19 and decreasing the pressure in the lower chamber 20. Subsequently, the pressure of the upper chamber 19 acts on the disk 145 and the contact disk 112 of the damping valve 147 of the expansion-side damping force generation mechanism 104 via the expansion-side passage 101 formed in the piston 18. Since the pilot chamber 140, which applies the pilot pressure in one direction of the seat section 107 against the damping valve 147, communicates with the lower chamber 20 via the inner rod passage 32, which has the opening 225, and the pilot chamber inlet passage 141, there is simultaneously a pressure in the pilot chamber 140 in the range or near that of the lower chamber 20, and the pilot pressure is reduced.Consequently, the differential pressure acting on the damping valve 147 increases, and thus the damping valve 147 opens relatively easily to separate from the seat section 107, causing oil to flow radially through the passage 148 between the piston 18 and the pilot housing 118 to the side of the lower chamber 20. In this way, the damping force increases. That is, the expansion-side damping force is in a soft state.

[0107] Furthermore, within the defined maximum length-side range, during the compression stroke, when the piston rod 21 enters the interior of the cylinder 2, the piston moves towards the side of the lower chamber 20, increasing the pressure of the lower chamber 20 and decreasing the pressure of the upper chamber 19. Subsequently, the hydraulic pressure of the lower chamber 20 acts on the disc 195 and the contact disc 162 of the damping valve 197 of the compression-side damping force generation mechanism 105 via the compression-side passage 102 formed in the piston 18.Since the pilot chamber 190, which applies the pilot pressure in one direction of the seat section 108 against the damping valve 197, communicates with the lower chamber 20 via the inner rod passage 32, which has the opening 225, and the pilot chamber inlet passage 191, the pilot chamber 190 simultaneously has a pressure close to that of the lower chamber 20, and thus the pressure of the lower chamber 20 and the pilot pressure are increased.

[0108] Since, in this state, the pressure increase in the pilot chamber 190 can follow the pressure increase in the lower chamber 20 when the piston speed is low, the differential pressure acting on the damping valve 197 decreases, and thus it is hardly possible for the damping valve 197 to separate from the seat section 108. Therefore, the oil from the lower chamber 20 passes through the inner rod passage 32, which has the opening 225, the pilot chamber 190, and the pilot chamber inlet passage 191, and flows through the opening 204 of the disc valve 203 to the upper chamber 19, thereby generating a damping force with opening characteristics (the damping force is approximately proportional to the square of the piston speed). Consequently, the characteristics of the damping force relative to the piston speed are designed such that the rate of increase of the damping force becomes large relative to the increase in piston speed.

[0109] Even at high piston speeds, it is highly unlikely that the damping valve 197 will separate from the seat section 108. Consequently, oil from the lower chamber 20 passes through the inner rod passage 32, which has the opening 225, the pilot chamber 190, and the pilot chamber inlet passage 191, and flows over the seat section 187 and the discs 169 to 172 to the upper chamber 19 as the disc valve 203 opens. A damping force is thus generated, exhibiting valve characteristics (the damping force is approximately proportional to the piston speed). Therefore, the characteristics of the damping force relative to the piston speed are designed such that the rate of increase of the damping force is somewhat reduced relative to the increase in piston speed.

[0110] In this way, the damping force during the compression stroke becomes greater than the damping force during the extension stroke, and the compression-side damping force is in a hard state.

[0111] Even during the compression stroke within the specified maximum length range, in a case where a shock is generated due to a difference in the level of the road surface or the like, the pressure increase in the pilot chamber 190 may not follow the pressure increase in the lower chamber 20 if the piston speed continues to increase. Consequently, the relationship of the force due to the differential pressure of the damping valve 197 of the compression-side damping force generation mechanism 105, which acts on the disk 195 and the contact disk 162, is designed such that the force in the opening direction, applied by the passage 102 formed in the piston 18, becomes greater than the force in the closing direction, applied by the pilot chamber 190. Thus, in this range, the damping valve 197 opens according to the increase in piston speed, causing it to separate from the seat section 108.In this way, in addition to the flow to the upper chamber 19 via the discs 169 and 172 and the seat section 187, oil flows through the passage 198 along the radial direction between the piston 18 and the pilot housing 168 to the upper chamber 19, thus preventing an increase in the damping force. At the same time, the characteristics of the damping force relative to the piston speed are designed such that the rate of increase of the damping force relative to the increase in piston speed is almost zero. Therefore, in a case where a shock is generated due to a difference in the level of the road surface or the like, where the piston speed is high and the frequency is relatively high, it is possible to adequately absorb the shock by suppressing the increase in the damping force relative to the increase in piston speed.

[0112] In the specified maximum length-side region, in which the piston rod 21 extends further outwards with respect to the cylinder 2 than the specified maximum length-side position, maximum length-side characteristics are obtained in which the extension-side damping force is in a soft state and the compression-side damping force is in a hard state.

[0113] Furthermore, in a specific minimum-length region where the piston rod 21 enters the cylinder 2 further than a specific minimum-length position, the length of the return spring 38 is not shortened. Consequently, the cross-sectional area adjustment mechanism 91, shown in Fig. 2, by means of the spring mechanism 90, which includes the return spring 38, is not pressed, and the opening and closing disc 76 separates from the contact disc 79, so that the passage cross-sectional area of ​​the opening 88 of the passage 89 is maximized. In the specific minimum length-side area, the passage cross-sectional area adjustment mechanism 227, shown in Fig. 3, the opening section of the small diameter 48, so that it is aligned in the axial direction with the axial section of the large diameter 222 of the metering pin 31, causing the opening 225 to close. In the defined minimum length-side region, the inner rod passage 32 communicates with the upper chamber 19 via the passage 89, shown in Fig. 2. In this way, the pilot chamber 140 of the expansion-side damping force generation mechanism 104 and the pilot chamber 190 of the compression-side damping force generation mechanism 105 communicate, as shown in Fig. 3, via the inner bar passage 32 with the upper chamber 19.

[0114] In the defined minimum-length region, during the extension stroke, when the piston rod 21 extends outwards with respect to the cylinder 23, the piston 18 is moved towards the side of the upper chamber 19, increasing the pressure in the upper chamber 19 and decreasing the pressure in the lower chamber 20. Subsequently, the pressure of the upper chamber 19 acts on the disk 145 and the contact disk 112 of the damping valve 147 of the extension-side damping force generation mechanism 104 via the extension-side passage 101 formed in the piston 18. Since the pilot chamber 140, which applies the pilot pressure in one direction of the seat section 106 against the valve element 113 and the contact disk 112, is connected to the upper chamber 19 via the passage 89 and the inner rod passage 32, as shown in Fig. 2, and the pilot chamber inlet passage 141, shown in Fig. 3, communicated, the pilot chamber 140 simultaneously has a pressure close to that of the upper chamber 19, and thus the pressure in the upper chamber 19 and the pilot pressure are increased.

[0115] Since, in this state, the pressure increase in the pilot chamber 140 can follow the pressure increase in the upper chamber 19 when the piston speed is low, the differential pressure acting on the valve element 113 and the contact disc 112 decreases, and thus it is hardly possible for the valve element 113 and the contact disc 112 to separate from the seat section 107. Therefore, the oil from the upper chamber 19 passes through the passage 89 and the inner rod passage 32, as shown in Fig. 2, and the pilot chamber inlet passage 141 and the pilot chamber 140, shown in Fig. 3, and flows through the opening 154 of the disc valve 153 to the lower chamber 20, thereby generating a damping force that exhibits opening characteristics (the damping force is approximately proportional to the square of the piston speed). Consequently, the characteristics of the damping force relative to the piston speed are designed such that the rate of increase of the damping force becomes large relative to the increase in piston speed.

[0116] Even at high piston speeds, the valve element 113 and contact disc 112 do not separate from the seat section 107. Consequently, oil passes from the upper chamber 19 through passage 89 and inner rod passage 32, as shown in Fig. 2, and the pilot chamber inlet passage 141 and the pilot chamber 140, shown in Fig. 3, and flows via the seat section 137 and the discs 119 to 122 to the lower chamber 20 as the disc valve 153 opens. Consequently, a damping force is generated that exhibits valve characteristics (the damping force is approximately proportional to the piston speed). Therefore, the characteristics of the damping force relative to the piston speed are designed such that the rate of increase of the damping force relative to the increase in piston speed is somewhat reduced.

[0117] In this way, the damping force becomes large during the extension stroke, and the extension-side damping force is in a hard state.

[0118] In the defined minimum length-side region, the pressure of the lower chamber 20 increases during the compression stroke, when the piston rod 21 enters the inner region of the cylinder 2, and the pressure of the upper chamber 19 decreases. Subsequently, the hydraulic pressure of the lower chamber 20 acts on the disc 195 and the contact disc 162 of the damping valve 197 of the compression-side damping force generation mechanism 105 via the compression-side passage 102 formed in the piston 18. Simultaneously, the pilot chamber 190, which applies the pilot pressure in one direction of the seat section 108 against the damping valve 197, communicates with the upper chamber 19 via the passage 89 and the inner rod passage 32, as shown in Fig. 2, and the pilot chamber inlet passage 191, shown in Fig. 3.

[0119] Consequently, the pilot chamber 190 has a pressure close to that of the upper chamber 19, and the pilot pressure is reduced. As a result, the differential pressure acting on the valve element 163 and the contact disc 162 increases, and thus the valve element 163 and the contact disc 162 open relatively easily to separate from the seat section 108, causing oil to flow through the passage 198 along the radial direction between the piston 18 and the pilot housing 168 to the side of the upper chamber 19.

[0120] In this way, the damping force during the compression stroke becomes smaller than the damping force during the extension stroke, and the compression-side damping force is in a soft state.

[0121] In the specified minimum length-side region, where the piston rod 21 enters the cylinder 2 further than the specified minimum length-side position, the minimum length-side characteristics are obtained, in which the expansion-side damping force is in a hard state and the compression-side damping force is in a soft state.

[0122] The shock absorber 1 according to the embodiment achieves inverted change characteristics of the position-sensitive damping force, in which the relationship of the hard state and the soft state between the determined maximum length-side area and the determined minimum length-side area is inverted by including the passage cross-section area adjustment mechanisms 91 and 227.

[0123] In addition to the structure for maintaining the position-sensitive damping force characteristics, the shock absorber 1 of the embodiment is equipped with the damping force generation mechanism 312, as shown in Fig. 4, provided, which operates independently of the setup to obtain the position-sensitive damping force characteristics. The friction element 24 of the damping force generation mechanism 312 provides an acting force on the piston rod 21 when the piston velocity is very low and a small amplitude is applied. That is, when the friction element 24 is used, if the piston velocity is very low and a small amplitude is applied, in a friction range where the piston velocity starts at 0, the friction element 24 generates a spring force through elastic deformation of the elastic rubber section 291 without causing a displacement of the piston rod 21, and the spring force becomes the acting force (dynamic spring range).If the piston rod 21 then moves by a certain amount (0.1 mm) or more, a displacement occurs between the friction element 24 and the piston rod 21, and a dynamic frictional force is generated (dynamic friction range). In this embodiment, a dynamic spring constant is improved when the piston speed is very low and a small amplitude is applied, and a dynamic coefficient of friction is increased by the friction element 24. Thus, it is possible to further increase the damping force compared to the damping force generated by the damping force generation mechanisms 104 and 105 of the shock absorber 1, which have the cross-sectional area adjustment mechanisms 91 and 227, without including the friction element 24.

[0124] Next, details of valve elements 113 and 163, which are designed as the same component, will be given with reference mainly to the Fig. 5, Fig. 6 to Fig. 7 described, with the valve element 113 being taken as an example.

[0125] As described above, the valve element 113 comprises the perforated disc-shaped disk 145 and the sealing element 146, which are designed to be attached to the outer circumferential section of the disk 145. The disk 145 is made of a steel plate, and the sealing element 146 is made of an elastic rubber material, such as nitrile rubber or fluorocarbon rubber.

[0126] In the Fig. 5 and Fig. Figure 6 shows the valve element 113 in its natural state, before it is installed in the shock absorber 1. The natural state is described. As it appears in Fig. As shown in Figure 5, the central axes of the disk 145 and the sealing element 146 coincide. These central axes are the central axis of the valve element 113. The disk 145 is formed in a flat plate shape, the position of which is constant in the axial direction. With respect to the disk 145, a cylindrical surface 341 is formed in the outer circumferential section, a cylindrical surface 342 is formed in the inner circumferential section, and the cylindrical surfaces 341 and 342 are arranged concentrically. With respect to the disk 145, a surface on the first side in the axial direction is a mounting surface 343, to which the sealing element 146 is attached or fixed, and the mounting surface 343 is the rear surface, which is located on one side opposite the seat section 107, as shown in Figure 5. Fig. 3, is arranged.

[0127] As it is in Fig. As shown in Figure 6, the outer circumferential surface of the sealing element 146 is composed in the radial direction of a cylindrical base end surface section 351, a flat surface section 352, a curved surface section 353, a tapered surface section 354, a curved surface section 355, a tapered surface section 356, a curved surface section 357, a tapered surface section 358, a curved surface section 359, a tapered surface section 360 and a cylindrical surface section of the remote end 361.

[0128] The cylindrical base end surface section 351 is located on the side closest to the disk 145 with respect to the outer circumferential surface of the sealing element 146 and extends from the mounting surface 343 of the disk 145 to have a cylindrical shape with the central axis of the valve element 113 as its center. The flat surface section 352 extends radially inward with a certain width from an edge section of the cylindrical base end surface section 351 on the side opposite the disk 145. The flat surface section 352 is annular in shape, with the central axis of the valve element 113 as its center, and is arranged on the same plane perpendicular to the central axis of the valve element 113.

[0129] The curved surface section 353 is annular in shape, with the central axis of the valve element 113 as its center. The curved surface section 353 extends from the inner circumferential edge section of the flat surface section 352, which is slightly inclined to separate itself radially from the disk 145 in the axial direction along the course of the curved surface section 353. The cross-sectional shape of the curved surface section 353, which has its central axis, is arc-shaped, with its center on the outside of the sealing element 146.The tapered surface section 354 extends from the inner circumferential edge section of the curved surface section 353 by being inclined in such a way that, in the course of the tapered surface section 354, it separates from the disk 145 in the axial direction towards the inside in the radial direction, and is formed in a tapered shape with the central axis of the valve element 113 as a center.

[0130] The curved surface section 355 is annular in shape, with the central axis of the valve element 113 as its center. The curved surface section 355 extends from the inner circumferential edge section of the tapered surface section 354, separating from the disk 145 in the radial direction along its length towards the inside. The cross-sectional shape of the curved surface section 355, which has its central axis, is arc-shaped, with its center on the outside of the sealing element 146. The tapered surface section 356 extends from the inner circumferential edge section of the curved surface section 355, separating from the disk 145 in the radial direction along its length towards the inside, and is tapered, with the central axis of the valve element 113 as its center.Here, the degree of inclination of the tapered surface section 356, which is obtained by dividing the difference between a diameter at a certain position of the large diameter side and a diameter at a certain position of the small diameter side by the length in the axial direction between these positions, is smaller than that of the tapered surface section 354.

[0131] The curved surface section 357 is annular in shape, with the central axis of the valve element 113 as its center. The curved surface section 357 extends from the inner circumferential edge section of the tapered surface section 356, such that the latter has a smaller or decreasing diameter in the axial direction with increasing distance of the curved surface section 357 from the disk 145, thus becoming a section of the minimum diameter 357A. Conversely, the curved surface section 357 extends from the section of the minimum diameter 357A, such that the latter has a larger or increasing diameter in the axial direction with increasing distance of the curved surface section 357 from the disk 145. The cross-sectional shape of the curved surface section 357, which has its central axis, is arc-shaped, with its center on the outside of the sealing element 146.The tapered surface section 358 extends from an edge section of the curved surface section 357 on one side opposite the tapered surface section 356, such that its diameter increases in the axial direction with increasing distance of the tapered surface section 358 from the disk 145, and is formed in a tapered shape with the central axis of the valve element 113 as one center. The degree of inclination of the tapered surface section 358 is less than that of the tapered surface section 356.

[0132] The curved surface section 359 is annular in shape, with the central axis of the valve element 113 as its center. The curved surface section 359 extends from an edge section of the tapered surface section 358 on one side opposite the curved surface section 357, such that it has an increasing diameter in the axial direction with increasing distance of the curved surface section 359 from the disk 145, forming a section with a maximum diameter 359A. The curved surface section 359 extends from the section with a maximum diameter 359A, such that it has a decreasing diameter in the axial direction with increasing distance of the curved surface section 359 from the disk 145. The cross-sectional shape of the curved surface section 359, which has its central axis, is arc-shaped, with its center on the inside of the sealing element 146.The tapered surface section 360 extends from an edge section of the curved surface section 359 on one side opposite the tapered surface section 358, such that it has a decreasing diameter in the axial direction with increasing distance of the tapered surface section 360 from the disk 145, and is formed in a tapered shape with the central axis of the valve element 113 as one center. The degree of inclination of the tapered surface section 360 is smaller than that of the tapered surface section 354 and is greater than that of the tapered surface section 356. The cylindrical surface section of the far end 361 extends from an edge section of the tapered surface section 360 on one side opposite the curved surface section 359 in a direction opposite to the disk 145 and is formed in a cylindrical shape with the central axis of the valve element 113 as one center.The cylindrical surface section of the remote end 361 is located largely on one side opposite the disk 145 with respect to the outer circumferential surface of the sealing element 146. The diameter of the cylindrical surface section of the remote end 361 is equivalent to that of the minimum diameter section 357A of the curved surface section 357.

[0133] A front surface section 365, positioned largely on one side opposite the disk 145 in the sealing element 146, is formed on one side of the cylindrical surface section of the remote end 361 opposite the disk 145. The front surface section 365 extends radially inwards with a certain width from an edge section of the cylindrical surface section of the remote end 361 on one side opposite the disk 145. The front surface section 365 is annular in shape, with the central axis of the valve element 113 as its center, and is arranged on the same plane perpendicular to the central axis of the valve element 113.

[0134] The inner circumferential surface of the sealing element 146 is composed of a curved surface section 371, a tapered surface section 372, a curved surface section 373, a tapered surface section 374 and a curved surface section 375.

[0135] The curved surface section 371 is located on the inner circumferential surface of the sealing element 146 on the side closest to the disk 145 and is annular in shape, with the central axis of the valve element 113 as its center. The curved surface section 371 extends from the mounting surface 343 of the disk 145, such that its diameter increases axially with increasing distance from the disk 145. The cross-sectional shape of the curved surface section 371, which has its central axis, is arc-shaped, with its center on the outside of the sealing element 146.The tapered surface section 172 extends from an edge section of the curved surface section 371 on one side opposite the disk 145, so that it has an increasing diameter with increasing distance of the tapered surface section 372 from the disk 145 in the axial direction, and is formed in a tapered shape, with the central axis of the valve element 113 as a center.

[0136] The curved surface section 373 is annular in shape, with the central axis of the valve element 113 as its center. The curved surface section 373 extends from an edge section of the tapered surface section 372 on one side opposite the disk 145, such that its diameter increases axially with increasing distance between the curved surface section 373 and the disk 145. The cross-sectional shape of the curved surface section 373, which has its central axis, is arc-shaped, with its center on the inside of the sealing element 146.The tapered surface section 374 extends from an edge section of the curved surface section 373 on one side opposite the tapered surface section 372, such that it has an increasing diameter in the axial direction with increasing distance of the tapered surface section 374 from the disk 145, and is formed in a tapered shape with the central axis of the valve element 113 as one center. The degree of inclination of the tapered surface section 374 is greater than that of the tapered surface section 372. The curved surface section 375 is annular in shape with the central axis of the valve element 113 as one center.The curved surface section 375 extends from an edge section of the tapered surface section 374 on one side opposite the disk 145, such that it has an increasing diameter in the axial direction with increasing distance of the curved surface section 375 from the disk 145, and is connected to the inner circumferential edge section of the front surface section 365. The cross-sectional shape of the curved surface section 375, which has its central axis, is arc-shaped, with its center on the inside of the sealing element 146.

[0137] A concave section 380, recessed radially inwards, is formed on the outer circumferential side of the sealing element 146 by the flat surface section 352, the curved surface section 353, the tapered surface section 354, the curved surface section 355, the tapered surface section 356, the curved surface section 357, the tapered surface section 358, and a section of the curved surface section 359 that lies closer to the side of the tapered surface section 358 than to the side of the section of maximum diameter 359A. The deepest section of the concave section 380 forms the section of minimum diameter 357A of the curved surface section 357. The cross-sectional shape of the concave section 380, which has its central axis, is overall a curved surface shape.

[0138] Furthermore, a convex section 381, projecting outwards in the radial direction, is formed on the outer circumferential side of the sealing element 146, by a bonding surface 377, which is bonded to the mounting surface 343, the cylindrical base end surface section 351, the flat surface section 352, the curved surface section 353, the tapered surface section 354, the curved surface section 355, the tapered surface section 356 and a section of the curved surface section 357, which lies more on the side of the tapered surface section 356 than on the side of the section of the minimum diameter 357A.

[0139] Furthermore, a convex section 382, ​​projecting radially outwards, is formed on the outer circumferential side of the sealing element 146 and is composed of a section of the curved surface section 357, closer on one side to the tapered surface section 358 than to the section of the minimum diameter 357A, a tapered surface section 358, the curved surface section 359 and the tapered surface section 360. The highest section of the convex section 382 forms the section of the maximum diameter 359A of the curved surface section 359.

[0140] Furthermore, a notched section 383, which is cut out on the outer circumferential side and on one side opposite the disk 145 in the axial direction, is formed on the outer circumferential side of the sealing element 146 and is composed of a section of the curved surface section 359, on one side closer to the tapered surface section 360 than to the section of the maximum diameter 359A, the tapered surface section 360 and the cylindrical surface section of the far end 361. The concave section 380, the convex section 381, the convex section 382 and the notched section 383 are all annular in shape, with the central axis of the valve element 113 as a center.

[0141] A convex section 385, projecting radially outwards, is formed on the inner circumferential side of the sealing element 146 and is composed of the tapered surface section 372, the curved surface section 373, and the tapered surface section 374. The convex section 385 is also annular, with the central axis of the valve element 113 as its center. The projection direction of the convex section 385 is oblique, with the convex section 385 lying close to the central axis of the valve element 113, and separating from the disk 145 in the axial direction towards the front of the projection.A position on the curved surface section 373, to which bisectors of the extended plane of the converging surface section 372 and the extended plane of the converging surface section 374 extend, from the line of intersection between the extended planes, and intersect, is a vertex 385A of the convex section 385.

[0142] With respect to the sealing element 146, the apex 385A of the convex section 385 is formed within a region of the concave section 380 in the axial direction of the sealing element 146. The distance of the apex 385A of the convex section 385 from the disk 145 is greater than the distance of the section of minimum diameter 357A of the concave section 380 from the disk 145. Furthermore, with respect to the sealing element 146, a concave section 380 is formed in a region of 50% or more of the length of the sealing element 146 in the axial direction, preferably 70% or more.

[0143] With regard to the sealing element 146, the height H2 of the minimum diameter section 357A of the concave section 380 from the disk 145 is greater than 1 / 3 of the height H1 of the maximum diameter section 359A from the disk 145, wherein the maximum diameter section 359A has the largest diameter on a side that is farther away from the disk 145 at the outer circumferential section of the sealing element 146 than the minimum diameter section 357A.

[0144] The sealing element 145 of the valve element 113 is inserted into the outer tube 133 of the pilot housing 118, as shown in Fig. 3, fitted as a tight fit or press fit. The sealing element 146 is fitted by means of the tight fit in such a way that it is displaceable with respect to the outer tube 133 and is always in a liquid-tight state.

[0145] In the shock absorber described in PTL 1, a sealing disc forms a pilot chamber between the sealing disc and a pilot housing by fitting a sealing element into the pilot housing. The pressure of the pilot chamber prevents the valve from opening.

[0146] With such a structure, the durability of the sealing element may be reduced, especially if the pilot chamber pressure becomes high. Furthermore, if the pilot chamber pressure becomes high, the sealing element may become trapped within the pilot chamber, causing unstable displacement, and consequently, the damping force characteristics may become unstable.

[0147] In contrast, in the shock absorber 1 of the embodiment, the convex section 381, which projects radially outwards, is formed on the side of the disc 145 of the concave section 380, since the annular concave section 380 is formed on the outer circumferential side of the sealing element 146. Thus, the volume of the sealing element 146 on the side fixed to the disc 145 can be increased by the convex section 381. Consequently, it is possible to improve the strength of the sealing element 146 on the side fixed to the disc 145. Furthermore, since the annular concave section 380 is formed on the outer circumferential side of the sealing element 146, it is possible to prevent abnormal deformation of the outer circumferential side of the sealing element 146 when the sealing element 146 is in close contact with the outer tube 133.Furthermore, since the annular convex section 385 is formed on the inner circumferential side and the volume reduction due to the concave section 380 is compensated for (supplemented) by the convex section 385 to ensure strength, it is possible to prevent abnormal deformation of the inner circumferential side of the sealing element 146. Thus, it is possible to improve the durability of the sealing element 146. With regard to the sealing element 196, which is the same component as the sealing element 146, it is possible to improve its durability in the same way.

[0148] Furthermore, in the shock absorber 1 according to the embodiment, the height H2 of the minimum diameter section 357A of the annular concave section 380 of the outer circumferential section of the sealing element 146 is greater than 1 / 3 of the height H1 of the maximum diameter section 359A of the disc 145, wherein the maximum diameter section 359A has its largest diameter on a side that is further away from the disc 145 on the outer circumferential section of the sealing element 146 than the minimum diameter section 357A. Consequently, it is possible to improve the durability of the sealing element 146. That is, if the height H2 is much smaller than 1 / 3 of the height H1, as is the case in the upper section of the Fig. As shown in Figure 7A, the concave section on the outer circumferential side of the sealing element is deformed so that it has an abnormal shape by curving at an acute angle when fitted into the outer tube 133, circled with a dashed line Xa in the lower section of the Fig. 7A.

[0149] Even if the height H2 is in the range of 1 / 3 of the height H1, as in the upper section of the Fig. As shown in Figure 7B, if the height H2 is less than 1 / 3 of the height H1, the concave section on the outer circumferential side of the sealing element deforms, giving it an abnormal shape in which it curves at an acute angle when fitted into the outer tube 133, circled with a dashed line Xb in the lower section of the Fig. 7B. If, on the other hand, the height H2 is greater than 1 / 3 of the height H1, as in the upper section of the Fig. As shown in Figure 7C, the concave section 380 of the sealing element 146 deforms at an obtuse angle when it is fitted into the outer tube 133, encircled by a dashed line Xc in the lower section of the Fig. 7C, which is not abnormal. Consequently, it is possible to improve the durability of sealing element 146. Similarly, it is possible to improve the durability of sealing element 196, which is the same component as sealing element 146.

[0150] With regard to the sealing element 146, the apex 385A of the convex section 385 is formed within the area of ​​the concave section 380 in the axial direction of the sealing element 146, and the distance of the apex 385A of the convex section 385 from the disk 145 is greater than that of the section of minimum diameter 357A of the concave section 380 from the disk 145. With such a shape as is found in the lower section of the Fig. As shown in Figure 7C, it is possible to obtain a shape in which the inner circumferential surface of the sealing element 146 becomes flat or soft during use. Thus, if the pressure in the pilot chamber 140 increases, the inner circumferential surface can bear the entire pressure.

[0151] Even if the pressure in pilot chambers 140 and 190 becomes high according to the configuration described above, it is possible to prevent abnormal deformation of the sealing elements 146 and 196 and to improve their durability. Consequently, it is possible to introduce a higher pressure into pilot chambers 140 and 190. In this way, it is possible to prevent or suppress the opening of the damping valves 147 and 197 and to set the damping force so that it is in a hard state. Furthermore, since abnormal deformation of the sealing elements 146 and 196 can be prevented even if the pressure of the pilot chambers 140 and 190 is set high, resulting in a hard condition, it is possible to achieve a smooth displacement of the sealing elements 146 and 196 relative to the pilot housings 118 and 168.Thus, it is possible to stabilize the damping force characteristic by suppressing the fluctuation of the damping force characteristics.

[0152] Furthermore, the rigidity of the sealing elements 146 and 196 is increased on one side, which is fixed to the disc 145. This results in a shape that prevents deformation, thus enabling the sealing elements 146 and 196 to extend axially and improving their spring properties. Since a design is used in which the volume of the convex section 385 is increased compared to the prior art, and the interference fit of the pilot housing 118 with respect to the outer tube 133 is improved, it is possible to increase the frictional force with respect to the pilot housing 118. In this way, it is possible to improve the response behavior when a valve closing operation is performed after the valve element 113 has been opened.

[0153] Furthermore, the convex section 381, which projects radially outwards and is formed on the side of the disc 145 of the concave section 380, has a larger diameter than the section with the maximum diameter 359A; that is, the convex section 381 extends to a position separated from the central axis of the valve element 113. In this way, the volume of the sealing element 146 can be increased on the side fixed to the disc 145 by the convex section 381.

[0154] The shock absorber of this embodiment comprises: a cylinder in which a working fluid is enclosed; a piston slidably fitted into the cylinder; a piston rod whose first end is coupled to the piston and whose second end extends outwards with respect to the cylinder; a damping valve that suppresses the flow of the working fluid due to the displacement of the piston in order to generate a damping force; a tubular pilot housing closed at the bottom, which together with the damping valve forms a pilot chamber that causes pressure to act on the damping valve in a valve closing direction; and an annular sealing element provided to be fixed or attached to the outer circumferential side of a rear surface of the damping valve and fitted into a tube of the pilot housing in such a way as to be slidable and to be fluid-tight.The damping valve is designed such that the inner circumferential side is clamped and the outer circumferential side is open. A portion of the working fluid flow is directed to the pilot chamber, and the pressure of the pilot chamber suppresses the opening of the damping valve. An annular concave section is formed on the outer circumferential side of the sealing element, and an annular convex section is formed on the inner circumferential side. In this way, the sealing element has the convex section projecting outwards in the radial direction on the damping valve side of the concave section. Thus, the volume of the sealing element on the side fixed to the damping valve is increased by the convex section. Consequently, it is possible to improve the strength of the sealing element on the side fixed to the damping valve.Furthermore, since the annular concave section is formed on the outer circumferential side of the sealing element, abnormal deformation of the outer circumferential side of the sealing element is prevented when the sealing element is in close contact with the pipe. Since the annular convex section is formed on the inner circumferential side of the sealing element, the volume reduction due to the concave section is compensated for (supplemented) by the convex section, thus ensuring strength and preventing abnormal deformation of the inner circumferential side of the sealing element. This improves the durability of the sealing element.

[0155] Furthermore, the shock absorber according to the embodiment comprises: a cylinder in which working fluid is enclosed; a piston which is slidably fitted into the cylinder; a piston rod whose first end is coupled to the piston and whose second end extends outwards with respect to the cylinder; a damping valve which suppresses or prevents the flow of working fluid due to the displacement of the piston in order to generate a damping force; a tubular pilot housing closed at the bottom which, together with the damping valve, forms a pilot chamber which causes pressure to act on the damping valve in a valve closing direction; and an annular sealing element which is provided to be attached or fixed to the outer circumferential side of a rear surface of the damping valve and which is fitted into a tube of the pilot housing in such a way as to be slidable and to be fluid-tight.The damping valve is designed such that the inner circumferential side is clamped and the outer circumferential side is open. A portion of the working fluid flow is directed to the pilot chamber, and the pressure of the pilot chamber suppresses the damping valve from opening. An annular concave section is formed on an outer circumferential section of the sealing element. The height of the minimum diameter section of the concave section is greater than one-third of the height of the maximum diameter section of the damping valve. The maximum diameter section has its largest diameter on the side that is farther from the damping valve on the outer circumferential section of the sealing element than the minimum diameter section. Consequently, the durability of the sealing element is improved.

[0156] Furthermore, the section of maximum diameter, which has the largest diameter, can be formed on the outer circumferential side of the sealing element on a side that is further away from the damping valve than the annular concave section, and the damping valve-side convex section, which projects further outwards in a radial direction than the section of maximum diameter, can be provided on the damping valve side of the sealing element.

[0157] Furthermore, the distance of a vertex of the convex section from the damping valve can be greater than the distance of the section with the minimum diameter of the concave section from the damping valve.

[0158] The embodiment shown illustrates a case in which the invention is applied in a hydraulic twin-cylinder shock absorber, but the invention is not limited thereto. The invention can be applied in a hydraulic monotube shock absorber in which no outer tube is provided, and wherein a gas chamber in the cylinder 2 is formed on one side of the lower chamber 20 opposite the upper chamber 19 by a movable separating element, and wherein this can be applied in any shock absorber.

[0159] The invention can, of course, be applied to the base valve 25. Furthermore, the invention can be applied in a case where an oil passage communicating with the inside of the cylinder 2 is provided on the outside of the cylinder 2 and a damping force generation mechanism is provided in the oil passage.

[0160] The embodiment describes, by way of example, a hydraulic shock absorber, but water or air can also be used as the fluid.

[0161] In the embodiment, an exemplary setup is described which includes the friction element 24, but the friction element 24 need not be provided even if the damping force is reduced in a range of very low speeds. Industrial applicability

[0162] According to the shock absorber described above, it is possible to improve the durability of the sealing element. Reference symbol list 1 shock absorber 2 cylinders 18 pistons 21 Piston rod 118, 168 Pilot housing 140, 190 Pilot chamber 146, 196 Sealing element 147, 197 Damping valve 357A Section of minimum diameter 359A Section of maximum diameter 380 Concave Section 385 Convex section

Claims

[1] Shock absorber (1) which has: a cylinder (2) in which a working fluid is enclosed; a piston (18) which is fitted into the cylinder (2) and is designed to be moved within the cylinder (2); a piston rod (21) whose first end side is coupled to the piston (18) and whose second end side extends outwards relative to the cylinder (2); a damping valve (147, 197) that suppresses a flow of the working fluid due to the displacement of the piston (18) and generates a damping force; a tubular pilot housing (118, 168) closed at the bottom, which together with the damping valve (147, 197) forms a pilot chamber (140, 190) that causes pressure to act on the damping valve (147, 197) in a valve closing direction; and an annular sealing element (146, 196) which is fixed to the outer circumferential side of a rear surface of the damping valve (147, 197), is fitted into a tube of the pilot chamber (118, 168) and is designed to be displaced in a liquid-tight manner, wherein the damping valve (147, 197) is constructed such that the inner circumferential side of the damping valve (147, 197) is clamped and the outer circumferential side of the damping valve (147, 197) is open, a portion of the working fluid flow is directed to the pilot chamber (140, 190) and the pressure of the pilot chamber (147, 197) suppresses the opening of the damping valve (147, 197). characterized by , that an outer circumferential surface of the sealing element (146, 196) is formed with: a convex section (381) on the damping valve side, which is formed on a mounting section to which the sealing element (146, 196) is attached to the damping valve (147, 197) and which has a vertex that projects furthest outwards in a radial direction of the sealing element (146, 196), an annular concave section (380) which is formed at a position further away from the damping valve (147, 197) than the convex section (381) on the damping valve side and which is recessed inwards in the radial direction, and a convex section (382) on the side of the pilot chamber, which is formed at a position that is further away from the damping valve (147, 197) than the annular concave section (380), with a smaller diameter than a diameter of the convex section (381) on the damping valve side and a larger diameter than a diameter of the annular concave section (380) and which projects radially outwards from the outer circumferential surface of the sealing element (146, 196). [2] Shock absorber (1) according to claim 1 wherein a height (H2) of a section (357A) of the minimum diameter of the concave section (380) of the damping valve (147, 197) is greater than 1 / 3 of a height (H1) of a section (359A) of the maximum diameter of the convex section (382) on the side of the pilot chamber of the damping valve (147, 197). [3] Shock absorber (1) according to one of claims 1 to 2, wherein an inner surface of the sealing element (146, 196) is designed with a convex surface (373) opposite the concave section (380), and wherein a distance of a vertex of the convex surface (373) from the damping valve (147, 197) is greater than a distance of the section (357A) of the minimum diameter of the concave section (380) from the damping valve (147, 197). [4] Shock absorber (1) according to claim 3, wherein an inner surface of the sealing element (146, 196) is formed with a concave surface (371) on the fastening section to which the sealing element (146, 196) is attached to the damping valve (147, 197), wherein the concave surface (371) is designed to connect the convex surface (373) and the fastening section of the damping valve (147, 197).

Images