shock absorbers

Abstract

Shock absorber (1), with: a cylinder (2) which contains a sealed hydraulic fluid; a piston (5) which is slidably fitted to the cylinder (2); a piston rod (6) which is coupled to the piston (5) and extended to an outside of the cylinder (2); and a damping force generation mechanism (26) configured to generate a damping force by controlling a flow of the hydraulic fluid caused by sliding of the piston (5) in the cylinder (2), wherein the damping force generation mechanism (26) comprises: a valve body (35) which has a connecting passage (38) formed therein, and an inner seat section (91) and an outer seat section (39) which are formed accordingly on a central side and an outer circumferential side of the valve body (35) over the connecting passage (38); a pilot-type main valve (27) which is designed to be able to be separated from and placed on the outer seat section (39), and is opened by receiving pressure from the hydraulic fluid in order to generate a damping force, wherein the opening pressure of the main valve (27) is adjusted by an internal pressure in a pilot chamber (49) which is formed on one side opposite the outer seat section (39); a control valve (28), which is a pressure control valve designed to control the internal pressure in the pilot chamber (49) into which the hydraulic fluid is directed; and an auxiliary valve (111) which is provided on an upstream side of the main valve (27) in series with the main valve (27), wherein the main valve (27) is an annular disc valve which is opened and closed such that an outer circumferential side (27A) of it is separated from and placed on the outer seat section (39), and wherein an inner circumferential side (27B) of the main valve (27) is prevented from being clamped from both surface sides thereof, and the main valve (27) is supported only from one surface side on the inner circumferential side (27B) by a first holding device (92), wherein the shock absorber (1) further comprises a recessed valve (101) which is provided between the main valve (27) and the seat sections (39, 91) of the valve body (35), and is formed from an annular disc valve with a recess (104) on an outer circumferential side (102) thereof, wherein an inner circumferential side (103) of the recess valve (101) is clamped by both surface sides thereof, wherein the recess valve (101) comprises a coupling section (105) formed between the outer circumferential side (102) and the inner circumferential side (103), and wherein the coupling section (105) comprises a pair of coupling pieces (106, 107) formed by removing part of the recess valve (101) between the outer circumferential side (102) and the inner circumferential side (103).

Description

TECHNICAL FIELD

[0001] The present invention relates to a shock absorber configured to generate a damping force by controlling a flow of hydraulic fluid according to a stroke of a piston rod, according to claims 1 and 6. STATE OF THE ART

[0002] For example, Patent Literature 1 discloses a damping force adjustable type hydraulic shock absorber having an auxiliary disc valve provided on an upstream side of a main disc valve in series with the main disc valve. The shock absorber gradually opens a main valve (in two steps), thereby smoothly changing the damping force.

[0003] US 7,896,311 B2 relates to a solenoid valve mounted on a shock absorber of a vehicle for adjusting the damping force. The solenoid valve comprises a backpressure chamber for generating a backpressure against a disc valve by a fluid introduced through a backpressure adjusting flow channel; and a spool moved in a spool guide by actuation of an electromagnet to control the opening / closing or opening rate of the backpressure adjusting flow channel. The backpressure adjusting flow channel comprises a variable orifice whose opening rate is adjusted by the spool and spool guide, the backpressure chamber, and a fixed orifice formed on the disc valve.The disc valve includes first and second discs stacked on an annular valve plate of a valve holder; first and second valve springs spaced apart from the first and second discs by a spacer; and a disc ring disposed between an outer periphery of the first and second discs and an outer periphery of the first and second valve springs.The first disc, which is in close contact with the valve holder, has a slit open to an inner circumference, the second disc, which is stacked on the first disc and in close contact with the disc ring, has a slit open to an outer circumference, the first valve spring, which is in close contact with the disc ring, has a slit open to the outer circumference, the second valve spring stacked on the first valve spring has no slit, and the slits formed on the second disc and the first valve spring form the fixed opening. BIBLIOGRAPHYPATENT LITERATURE

[0004] PTL 1: JP 11- 287 281 A SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[0005] In such a damping force adjustable type hydraulic shock absorber, an auxiliary valve is arranged on an upstream side of the main valve in series with the main valve. Thus, a total differential pressure generated by the main valve and the auxiliary valve is higher than a differential pressure generated by a main valve without an auxiliary valve, that is, a differential pressure generated by a main valve that is not opened stepwise. As a result, a damping force is relatively large in a low speed range of a piston speed. Therefore, an improvement in ride comfort with a soft-side damping force characteristic has been demanded.

[0006] It is an object of the present invention to provide a shock absorber capable of smoothly changing a damping force in a low speed range of a piston speed and opening a main valve with a smaller differential pressure. SOLUTION TO THE PROBLEM

[0007] The problem is solved by a shock absorber having the features of patent claims 1 and 6.

[0008] According to one embodiment of the present invention, a shock absorber as defined in claim 1 is provided, comprising: a cylinder in which hydraulic fluid is sealingly contained; a piston slidably fitted to the cylinder; a piston rod coupled to the piston and extended to an outside of the cylinder; and a damping force generating mechanism configured to generate a damping force by controlling a flow of the hydraulic fluid caused by sliding of the piston in the cylinder, wherein the damping force generating mechanism comprises: a valve body having a communication passage formed therein and including an inner seat portion and an outer seat portion,which are formed respectively on a central side and an outer peripheral side of the valve body via the communication passage; a pilot-type main valve which is provided to be capable of being separated from and placed on the outer seat portion, and is opened by receiving a pressure of the hydraulic fluid to thereby generate a damping force, wherein a pressure of opening of the main valve is adjusted by an internal pressure in a pilot chamber formed on a side opposite to the outer seat portion; a control valve which is a pressure control valve configured to control the internal pressure in the pilot chamber into which the hydraulic fluid is supplied; and an auxiliary valve which is provided on an upstream side of the main valve in series with the main valve, in which the main valve is an annular disc valve which is opened and closed in such a way,that an outer peripheral side thereof is separated from and placed on the outer seat portion, and in which an inner peripheral side of the main valve is prevented from being clamped by both surface sides thereof, and the main valve is supported only from one surface side on the inner peripheral side by a first holding device. The shock absorber further includes a recess valve provided between the main valve and the seat portions of the valve body and formed of an annular disc valve with a recess on an outer peripheral side thereof. An inner peripheral side of the recess valve is clamped by both surface sides thereof. The recess valve includes a coupling portion formed between the outer peripheral side and the inner peripheral side, and the coupling portion includes a pair of coupling pieces,which are formed by cutting out a part of the recess valve between the outer peripheral side and the inner peripheral side.,

[0009] The shock absorber according to embodiments of the present invention is capable of smoothly changing the damping force in the low speed range of the piston speed and opening the main valve with the smaller differential pressure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view illustrating a shock absorber according to a first embodiment of the present invention when taken along an axial plane. Fig. 2 is an enlarged view showing a damping force generating mechanism of Fig. 1. Fig. 3 is an enlarged view showing main components of Fig. 2. Fig. 4 is a plan view showing a recess valve used in the first embodiment and a fourth embodiment of the present invention. Fig. 5 is an explanatory graph of the first embodiment for showing relationships (analysis results) between a differential pressure and a flow rate in three types of valve structures, in which a curve (A) shows the relationship between the differential pressure and the flow rate in the valve structure of the first embodiment, in which a curve (B) shows the relationship between the differential pressure and the flow rate in the existing single-step structure, and in which a curve (C) shows the relationship between the differential pressure and the flow rate in the existing two-step structure. Fig. 6 is a view that Fig. 3, to illustrate a second embodiment of the present invention. Fig. 7 is a view that Fig. 3, to illustrate a third embodiment of the present invention. Fig. 8 is a view that Fig. 3, to illustrate the fourth embodiment. DESCRIPTION OF THE EMBODIMENTS (First Embodiment)

[0010] A first embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, an up-and-down direction is Fig. 1 is defined as an up-and-down direction as it is.

[0011] As in Fig. 1, a damping force adjustable type shock absorber 1, which is a shock absorber according to the first embodiment, has a multi-cylinder structure in which an outer tube 3 is provided on an outer side of a cylinder 2, and a reservoir 4 is formed between the cylinder 2 and the outer tube 3. A piston 5 is slidably fitted to the cylinder 2, and the piston 5 divides an inner side of the cylinder 2 into two chambers, that is, an upper cylinder chamber 2A and a lower cylinder chamber 2B. One end of a piston rod 6 is coupled to the piston 5 with a nut 7. Another end side of the piston rod 6 passes through the upper cylinder chamber 2A and is inserted through a rod guide 8 and an oil seal 9, which are mounted on upper end portions of the cylinder 2 and the outer tube 3 to extend to an outer side of the cylinder 2.

[0012] A bottom valve 10 configured to partition the lower cylinder chamber 2B and the reservoir 4 is provided at a lower end portion of the cylinder 2. Passages 11 and 12 configured to allow communication between the upper cylinder chamber 2A and the lower cylinder chamber 2B are formed in the piston 5. A check valve 13 is provided in the passage 12. The check valve 13 allows oil fluid (hydraulic fluid) to flow only from the lower cylinder chamber 2B side to the upper cylinder chamber 2A side. Further, a disc valve 14 is provided in the passage 11. The disc valve 14 is opened when a pressure of the oil fluid on the upper cylinder chamber 2A side reaches a predetermined pressure, and relieves the pressure to the lower cylinder chamber 2B side.

[0013] Passages 15 and 16, which are configured to allow communication between the lower cylinder chamber 2B and the reservoir 4, are formed in the bottom valve 10. A check valve 17 is provided in the passage 15. The check valve 17 allows the oil fluid to flow only from the reservoir 4 side to the lower cylinder chamber 2B side. Further, a disc valve 18 is provided in the passage 16. The disc valve 18 is opened when the pressure of the oil fluid on the lower cylinder chamber 2B side reaches a predetermined pressure, and relieves the pressure to the reservoir 4 side. As the hydraulic fluid, the oil fluid is sealed in the cylinder 2, and the oil fluid and gas are sealed in the reservoir 4.

[0014] A separating pipe 20 is externally fitted to both upper and lower end portions of the cylinder 2 by means of sealing members 19, and an annular passage 21 is formed between the cylinder 2 and the separating pipe 20. The annular passage 21 communicates with the upper cylinder chamber 2A through a passage 22 formed in a side wall of the cylinder 2 in a vicinity of the upper end portion of the cylinder 2. A cylindrical branch pipe 23 is formed at a lower portion of the separating pipe 20 to extend laterally (rightward in Fig. 1). An opening 24 having a larger diameter than that of the branch pipe 23 is formed in a side wall of the outer pipe 3 coaxially with the branch pipe 23, and a cylindrical housing 25 is coupled to the side wall of the outer pipe 3 by welding or the like to surround the opening 24. A damping force generating mechanism 26 is housed in the housing 25. (Damping force generation mechanism)

[0015] As in Fig. 2, the damping force generating mechanism 26 includes a valve block 30 and a solenoid block 31. A main valve 27 of a pilot type (back pressure type), a pilot valve 28 (control valve), which is a solenoid-driven pressure control valve configured to control a pressure of opening the main valve 27, a fail-safe valve 29 provided on a downstream side of the pilot valve 28 and operated in the event of a failure, and an auxiliary valve 111 are integrally incorporated into the valve block 30. The solenoid block 31 is configured to actuate the pilot valve 28. A passage member 32 is inserted into the housing 25, and the valve block 30 and the solenoid assembly 31 are coupled and integrated with each other.Further, both the valve block 30 and the solenoid assembly 31 are inserted into the housing 25, and a nut 34 threadedly engaged with the housing 25 is tightened. In this way, the valve block 30, the solenoid assembly 31, and the passage member 32 are fixed in the housing 25.

[0016] A plurality of recesses 25C extending in a radial direction are formed on an inner surface side of an inner flange portion 25A formed at one end portion of the housing 25, and the recesses 25C and the opening 24 of the outer tube 3 allow communication between the reservoir 4 and a chamber 25B formed in the housing 25. The passage member 32 is fixed such that a flange portion 32B is formed on an outer periphery of one end of a cylindrical portion 32A having a substantially cylindrical shape, that the cylindrical portion 32A protrudes from an opening 25E of the inner flange portion 25A of the housing 25 to be fitted into the branch pipe 23, and that the flange portion 32B is held in abutment against the inner flange portion 25A of the housing 25.Further, a part of a surface of the passage member 32 is covered with a sealing material 33, and a joint portion between the branch pipe 23 and a main body 35 to be described later is sealed by the sealing material 33.

[0017] The valve block 30 includes the main body 35 (valve body), a pilot or guide pin 36, and a pilot body 37. The main body 35 has a substantially annular shape, and one end of the main body 35 is brought into abutment with the flange portion 32B of the passage member 32. Further, a plurality of passages 38 are formed along a circumferential direction of the main body 35 to pass through the main body 35 in a direction along an axis of the main body 35 (in a right-and-left direction in Fig. 2). Each of the passages 38 communicates with a passage (axial hole) in the passage member 32 through an annular recessed portion 90 formed in one end of the main body 35. An annular outer seat portion 39 protrudes on an outer peripheral side of another end of the main body 35, and an annular inner seat portion 91 protrudes between the outer seat portion 39 and the passages 38 of the main body 35. Further, an annular clamp portion 40 protrudes on an inner peripheral side of the main body 35.

[0018] As in Fig. As shown in Figure 2, the guide pin 36 has a stepped cylindrical shape to have a larger diameter portion 36A at a central portion thereof, and an opening 46 is formed in one end of the guide pin 36. One end portion of the guide pin 36 is press-fitted into the main body 35. As shown in Fig. 3, the larger diameter portion 36A and the clamping portion 40 clamp a disc valve 115, the auxiliary valve 111, a washer 94, a cutout valve 101, a washer 95, a first retainer 92, and a second retainer 93 in the specified order from an upstream side. Another end portion of the guide pin 36 is press-fitted into a passage 50, which is an axial hole of the pilot body 37. As a result, a plurality of passages 47 extending along the direction of the axis (right-and-left direction in Fig. 2) are formed between another end portion of the guide pin 36 and the passage 50 of the pilot body 37.

[0019] The pilot body 37 has a substantially cylindrical shape with a bottom to have a bottom 37A at a central portion thereof. The pilot body 37 is fixed such that the bottom 37A is held in abutment with the larger diameter portion 36A of the guide pin 36 by means of a flexible disk 48. A sealing member 45 adhered to the main valve 27 is slidably and fluid-tightly fitted to an inner peripheral surface of a cylindrical portion 37B on one end side of the pilot body 37. Thus, a pilot chamber 49 is formed behind the main valve 27. An internal pressure in the pilot chamber 49 is applied to the main valve 27 in a direction of opening the main valve 27. The auxiliary valve 111 is separated from the inner seat portion 91 by receiving a pressure on one side of the passages 38, and is thus opened.In this way, the main valve 27 is separated from the outer seat portion 39 by receiving the pressure on the side of the passages 38, and is thus opened. As a result, the passages 38 communicate with the chamber 25B in the housing 25 on a downstream side.

[0020] A passage 51 passes through the bottom 37A of the pilot body 37 in the direction along the axis, and the flexible disk 48 is fitted onto an annular seat portion projecting around an opening of the passage 51. Further, the flexible disk 48 is bent by the internal pressure in the pilot chamber 49. As a result, the pilot chamber 49 is imparted with volume elasticity. During a valve opening operation of the main valve 27, the internal pressure in the pilot chamber 49 is thus prevented from increasing excessively and causing an unstable valve opening operation. An elongated recess 52 extending in the radial direction (up-and-down direction in Fig. 2) is formed in an inner peripheral edge portion of the flexible disc 48, which is to be brought into contact with the guide pin 36. The recess 52 and the passages 47 allow communication between the pilot chamber 49 and the passage 50.

[0021] A valve chamber 54 is formed in a cylindrical portion 37C at another end side of the pilot body 37. An annular seat portion 55 is formed on the bottom 37A of the pilot body 37 so as to protrude along a peripheral edge portion of the opening of the passage 50. A pilot valve element 56 is provided in the valve chamber 54. The pilot valve element 56 is a valve body constituting the pilot valve 28 and is configured to open and close the passage 50 by being separated from and fitted onto the seat portion 55. The pilot valve element 56 has a substantially cylindrical shape, and a distal end portion of the pilot valve element 56, which is to be separated from and fitted onto the seat portion 55, has a tapered shape.A large-diameter spring receiving portion 57 and a flange portion are formed on an outer peripheral portion on a proximal end side of the pilot valve member 56. A small-diameter rod receiving portion 58 is formed on an inner peripheral portion on a distal end side of the pilot valve member 56. A tapered portion 56A is formed on an inner peripheral edge portion of an opening of a rear portion of the pilot valve member 56, so that the opening becomes wider.

[0022] The pilot valve element 56 is elastically retained by a pilot spring 59, a fail-safe spring 60, and a fail-safe disc valve 61, which are urging elements, to be opposite to the seat portion 55 and movable in the direction along the axis. An inner diameter of the cylindrical portion 37C on another end side of the pilot body 37 is gradually increased toward the opening side, and two stepped portions 62 and 63 are formed on an inner peripheral portion of the cylindrical portion 37C. The stepped portion 62 supports a radially outer end portion of the pilot spring 59. The fail-safe spring 60, an annular retainer 64, the fail-safe disc valve 61, a retainer 65, a spacer 66, and a retainer plate 67 are superimposed on the stepped portion 63, and are fixed by a cap 68 fitted to one end portion of the cylindrical portion 37C.

[0023] The solenoid assembly 31 is obtained such that a coil 72, cores 73 and 74 inserted into the coil 72, a plunger 75 guided through the cores 73 and 74, and a hollow actuating rod 76 coupled to the plunger 75 are combined and housed in a solenoid housing 71. These components are fixed by an annular spacer 77 and a cup-shaped cover 78 that are swaged to a rear end portion of the solenoid housing 71. A solenoid actuator includes the coil 72, the cores 73 and 74, the plunger 75, and the actuating rod 76. When the coil 72 is energized through a lead wire (not shown), the plunger 75 generates a thrust force according to an electric current in the direction along the axis.

[0024] A distal end portion of the operating rod 76 is tapered to include a tapered portion 76A at an outer peripheral edge portion thereof. A return chamber of the operating rod 76, the passage 50, and the valve chamber 54 communicate with each other through a communication passage 76B formed in the hollow operating rod 76. Further, a communication passage 75A is formed in the plunger 75, allowing chambers formed on both end sides of the piston 75 to communicate with each other. The communication passages 76B and 75A balance fluid forces acting on the operating rod 76 and the plunger 75 and apply appropriate damping forces to a movement of the operating rod 76 and the piston 75.

[0025] The solenoid housing 71 includes a cylindrical portion 71A formed at one end thereof. The cylindrical portion 71A is to be fitted into the housing 25. A protruding portion of an outer periphery of the cap 68 mounted on the pilot body 37 is fitted into the cylindrical portion 71A. A space between the cylindrical portion 71A and the housing 25 is sealed by an O-ring 80. The solenoid housing 71 is coupled to the valve block 30 such that the distal end portion of the operating rod 76 projecting into the cylindrical portion 71A is inserted into the pilot valve element 56 accommodated in the valve block 30, and further brought into abutment with the rod receiving portion 58, and that the projecting portion of the outer periphery of the cap 68 mounted on the pilot body 37 is fitted into the cylindrical portion 71A.Then, the solenoid housing 71 is fixed to the housing 25 by tightening, with the nut 34, a retaining ring 81 which is mounted in an outer circumferential groove of the solenoid housing 71.

[0026] In a state in which the valve block 30 and the solenoid block 31 are coupled to each other and the operating rod 76 is inserted into the pilot valve element 56 while no energy is supplied to the coil 72, as shown in Fig. Further, as shown in Fig. 2, the pilot valve element 56 is retracted together with the actuating rod 76 by a spring force of the fail-safe spring 60, so that the spring receiving portion 57 is brought into abutment against the fail-safe disc valve 61. At this time, the pilot spring 59 does not apply a spring force to the pilot valve element 56. When the coil 72 is energized, the actuating rod 76 drives the pilot valve element 56 toward the seat portion 55. Thus, the pilot valve element 56 is seated on the seat portion 55 against the spring forces of the fail-safe spring 60 and the pilot spring 59, and the valve opening pressure is controlled by an electric excitation current. (main valve)

[0027] As in Fig. 3, the main valve 27 is an annular disc valve that is opened and closed by separating / setting an outer peripheral portion 27A (outer peripheral side) thereof from / onto the outer seat portion 39 (valve seat). An inner peripheral portion 27B (inner peripheral side) of the main valve 27 is prevented from being pushed from both surface sides (both right and left sides in Fig. 3) thereof, and the first holding device 92 mounted on the guide pin 36 only supports the side (right side in Fig. 3) of the inner peripheral portion 27B opposite the seat portions. The second retainer 93 (large diameter retainer) is arranged between the first retainer 92 and the larger diameter portion 36A of the guide pin 36. The first retainer 92 is arranged with respect to the main body 35 in the direction along the axis (in the right-and-left direction in Fig. 3) by fitting an end portion of the guide pin 36 to an axial hole 35A of the main body 35. Further, the main valve 27 is fitted onto the outer seat portion 39 through the intermediary of the recess valve 101 to be described later.

[0028] As described above, the annular sealing member 45, formed of an elastic body such as rubber, adheres to the side (pilot chamber 49 side) of the main valve 27 opposite the seat portions. The main valve 27 is centered, that is, positioned with respect to the main body 35 in the radial direction, by fitting the outer peripheral portion of the sealing member 45 to the inner peripheral surface of the cylindrical portion 37B of the pilot body 37. Between the main valve 27 and both the outer seat portion 39 and the inner seat portion 91 of the main body 35 (valve body), the recess valve 101 is provided. The recess valve 101 is an annular disc valve having an outer peripheral portion 102 (outer peripheral side) in which four recesses 104 (slits) are formed at equal intervals.An outer diameter of the main valve 27 is set to be larger than an outer diameter of the annular seal member 45 and an inner diameter of the cylindrical portion 37B of the pilot body 37. (recess valve)

[0029] An inner peripheral portion 103 (inner peripheral side) of the recess valve 101 is formed from both surface sides (both right and left sides in Fig. 3) thereof is clamped by the washers 94 and 95 mounted on the guide pin 36, and a coupling portion 105 with a low rigidity is formed between the outer peripheral portion 102 and the inner peripheral portion 103. As shown in Fig. 4, the coupling portion 105 includes a pair of coupling pieces 106 and 107 formed by cutting out a part of a portion between the outer peripheral portion 102 and the inner peripheral portion 103. The pair of coupling pieces 106 and 107 each has a substantially S-shape and are formed to be symmetrical with respect to a center line of the recess valve 101. In other words, a pair of recess portions 108 and 109 are formed between the outer peripheral portion 102 and the inner peripheral portion 103 to be symmetrical with respect to the center line of the recess valve 101. As described above, the recess portions 108 and 109 are formed to be symmetrical with respect to the center line of the recess valve 101. Consequently, when the relief valve 101 is actuated, there is no imbalance in the circumferential direction.

[0030] The coupling piece 106 includes an outer end portion 106A connected to the outer peripheral portion 102, an inner end 106B connected to the inner peripheral portion 103, and a spring portion 106C formed between the outer end portion 106A and the inner end 106B to extend in the circumferential direction. The coupling piece 107 includes an outer end portion 107A connected to the outer peripheral portion 102, an inner end 107B connected to the inner peripheral portion 103, and a spring portion 107C formed between the outer end portion 107A and the inner end 107B to extend in the circumferential direction. As shown in Fig. 3, an outer diameter of the relief valve 101 is smaller than the outer diameter of the main valve 27, and a surface of an outer peripheral edge of the outer peripheral portion 102 on the seat portion side (left side in Fig. 3) is fixed to be brought into contact with (seated on) the outer seat portion 39 of the main body 35. The outer peripheral portion 102 of the recess valve 101 is formed on the seat portion side (left side in Fig. 3) brought into close contact with the surface of the main valve 27 by spring forces of the spring portions 106C and 107C of the coupling pieces 106 and 107, so that the corresponding recesses 104 form fastening openings between the main valve 27 and the outer seat portion 39. (auxiliary valve)

[0031] As in Fig. 3, the auxiliary valve 111 is an annular disc valve which is opened and closed by separating / setting an outer peripheral portion 112 (outer peripheral side) from / onto the inner seat portion 91, and the auxiliary valve 111 is provided on an upstream side (left side in Fig. 3) of the main valve 27 is provided in series with the main valve 27. Further, the auxiliary valve 111 is positioned in the radial direction by fitting an axial hole thereof to the guide pin 36, and an inner peripheral portion 113 (inner peripheral side) of the auxiliary valve 111 is contacted from both surface sides (both right and left sides in Fig. 3) It is clamped by the washer 94 and the clamp portion 40. The annular disc valve 115, which has an outer peripheral portion (outer peripheral side) in which a plurality of recesses 114 (slits) are formed at equal intervals, is provided between the auxiliary valve 111 and the inner seat portion 91 of the main body 35 (valve body). The disc valve 115 is formed to have an outer diameter equal to the outer diameter of the auxiliary valve 111. The disc valve 115 is superimposed on the auxiliary valve 111, and an inner peripheral portion (inner peripheral side) of the disc valve 115 is clamped from both surface sides thereof by the washer 95 and the clamp 40. With this configuration, the corresponding recesses 114 form fastening holes between the auxiliary valve 111 and the inner seat portion 91.The auxiliary valve 111 and the disc valve 115 are each formed to have the outer diameter smaller than the outer diameter of the main valve 27.

[0032] Next, operations of the above-mentioned adjustable damping force type shock absorber 1 will be described.

[0033] The adjustable damping force type shock absorber 1 is mounted between a sprung side and an unsprung side of a vehicle suspension device. In a normal operating state, by energizing the coil 72 by an on-board control device, the pilot valve element 56 is seated on the seat portion 55 of the pilot body 37, thereby causing the pilot valve 28 to perform pressure control.

[0034] During an extension stroke of the piston rod 6, the check valve 13 of the piston 5 is closed along with a movement of the piston 5 in the cylinder 2. Before the disc valve 14 is opened, the oil fluid (hydraulic fluid) on the upper cylinder chamber 2A side is pressurized. The pressurized oil fluid flows from the branch pipe 23 of the partition pipe 20 into the passage member 32 of the damping force generating mechanism 26 through a flow passage 22 and the annular passage 21. At this time, a volume of oil fluid corresponding to a movement amount of the piston 5 flows from the reservoir 4 into the lower cylinder chamber 2B while opening the check valve 17 of the bottom valve 10.When the pressure in the upper cylinder chamber 2A reaches a pressure of opening the disc valve 14 of the piston 5, the disc valve 14 is opened, and relieves the pressure in the upper cylinder chamber 2A to the lower cylinder chamber 2B, thereby preventing an excessive increase in the pressure in the upper cylinder chamber 2A.

[0035] Meanwhile, during a compression stroke of the piston rod 6, along with a movement of the piston 5 in the cylinder 2, the check valve 13 of the piston 5 is opened, and the check valve 17 in the passage 15 of the bottom valve 10 is closed. Before the disc valve 18 is opened, the oil fluid in the lower piston chamber 2B flows into the upper cylinder chamber 2A, and a volume of oil fluid corresponding to an entry amount of the piston rod 6 into the cylinder 2 flows from the upper cylinder chamber 2A into the reservoir 4 in the same manner as during the above-mentioned extension stroke. When the pressure in the lower cylinder chamber 2B reaches the opening pressure of the disc valve 18 of the bottom valve 10, the disc valve 18 is opened, relieving the pressure in the lower cylinder chamber 2B to the reservoir 4, thereby preventing an excessive increase in the pressure in the lower cylinder chamber 2B.

[0036] In a state before the main valve 27 is opened (in a low-speed range of piston speed), the oil fluid that has flowed from the passage member 32 into the damping force generating mechanism 26 flows through the opening 46 of the guide pin 36 and the passage 50 of the pilot body 37, and then pushes and opens the pilot valve member 56 of the pilot valve 28 to flow into the valve chamber 54. Then, the oil fluid flows from the valve chamber 54 into the reservoir 4 via the opening of the fail-safe disc valve 61, the opening of the retainer plate 67, a recess of the cap 68, and the chamber 25B in the housing 25.

[0037] When the piston speed is increased, and then the pressure of the oil fluid flowing from the passage member 32 reaches the opening pressure of the main valve 27 and further reaches the opening pressure of the auxiliary valve 111, the oil fluid flows through the annular recessed portion 90 and the passages 38, and opens the main valve 27 and the auxiliary valve 111, flowing into the reservoir 4 through the chamber 25B in the housing 25. In an extremely low speed range of the piston speed, the oil fluid flowing from the passage member 32 flows into the reservoir 4 through the annular recessed portion 90, the passages 38, the recesses 114 of the disc valve 115, the recesses 104 of the recess valve 101, and the chamber 25B in the housing 25.

[0038] Therefore, during both the extension stroke and the compression stroke of the piston rod 6 before the main valve 27 is opened (in the low speed range of the piston speed), the damping force generating mechanism 26 generates the damping force through the orifice 46 and the pressure of opening the pilot valve element 56 of the pilot valve 28. After the main valve 27 is opened (in a middle speed range of the piston speed), the damping force generating mechanism 26 generates the damping force according to a degree of opening of the main valve 27. After the auxiliary valve 111 is opened (in a high speed range of the piston speed), the damping force generating mechanism 26 also generates the damping force according to a degree of opening of the auxiliary valve 111.By adjusting the opening pressure of the pilot valve 28 through the electric current applied to the coil 72, the damping force can be directly controlled regardless of the piston speed. At this time, the opening pressure of the pilot valve 28 changes the internal pressure in the pilot chamber 49, which communicates with the upstream passage 50. Here, the internal pressure in the pilot chamber 49 is applied in a direction of closing the main valve 27. Consequently, by controlling the opening pressure of the pilot valve 28, the opening pressure of the main valve 27 can be adjusted at the same time. Thus, damping force characteristics can be adjusted within a wide range.

[0039] Further, when the electric current applied to the coil 72 is reduced and then the thrust of the piston 75 is reduced, the opening pressure of the pilot valve 28 is reduced, so that a soft-side damping force is generated. Conversely, when the electric excitation current is increased and then the thrust of the piston 75 is increased, the opening pressure of the pilot valve 28 is increased, so that a hard-side damping force is generated. In this way, the soft-side damping force, which is often used, can be generated by a low electric current, thereby reducing energy consumption.

[0040] Furthermore, when the thrust of the plunger 75 is lost at the time of occurrence of a failure such as breakage of the spool 72 or failure of the on-board control device, the pilot valve element 56 is retracted by a spring force of the fail-safe spring 60 to open the passage 50, and the spring receiving portion 57 of the pilot valve element 56 is brought into abutment with the fail-safe disc valve 61 to close the flow passage between the valve chamber 54 and the chamber 25B in the housing 25. In this state, a flow of the oil fluid in the valve chamber 54 from the passage 50 into the chamber 25 in the housing 25 is controlled by the fail-safe valve 29.Consequently, a desired damping force can be obtained by setting the opening pressure of the fail-safe disc valve 61, and the internal pressure in the pilot chamber 49, namely the opening pressure of the main valve 27, can be adjusted. As a result, an appropriate damping force can be obtained even in the event of a failure.

[0041] Here shows Fig. 5 Relationships between differential pressure and flow rate of the oil fluid (hereinafter referred to simply as “flow rate”) for three types of valve structures. Fig. 5, a curve (A) shows the relationship between the differential pressure and the flow rate in the valve structure of the first embodiment, that is, the valve structure in which the auxiliary valve 111 is provided on the upstream side of the main valve 27 in series with the main valve 27, and in which the inner peripheral portion 27B (inner peripheral side) of the main valve 27 is prevented from being clamped by both of the surface sides thereof, and the first retainer 92 supports only the side of the inner peripheral portion 27B opposite the seat portions. A curve (B) shows the relationship between the differential pressure and the flow rate in the existing valve structure in which the auxiliary valve 111 is not provided, and the inner peripheral portion 27B (inner peripheral side) of the main valve 27 is clamped by both of the surface sides thereof (such a structure is hereinafter referred to as a "single-step structure").A curve (C) shows the relationship between the differential pressure and the flow rate in the existing valve structure in which the auxiliary valve 111 is provided on the upstream side of the main valve 27 in series with the main valve 27, and the inner peripheral portion 27B (inner peripheral side) of the main valve 27 is clamped from both of the surface sides thereof (such a structure is hereinafter referred to as a "two-step structure").

[0042] Furthermore, the curve (A) of Fig. 5, the pilot valve 28 is opened at a point A1, the main valve 27 is opened at a point A2, and the auxiliary valve 111 is opened at a point A3. Meanwhile, at the curve (B) of Fig. 5, the pilot valve 28 is opened at a point B1, and the main valve 27 is opened at a point B2. Furthermore, in the curve (C) of Fig. 5 the pilot valve 28 is opened at a point C1, the main valve 27 is opened at a point C2, and the auxiliary valve 111 is opened at a point C3.

[0043] As Fig. 5, the valve structure of the first embodiment can achieve a predetermined flow rate (for example, 3.5 L / min.) with a smaller differential pressure than the single-step structure and the two-step structure, particularly in an initial stage of valve opening under a soft-side damping force characteristic. In other words, the valve structure of the first embodiment requires a relatively small differential pressure to achieve the same valve lift amount in the initial stage of valve opening under the soft-side damping force characteristic. Further, in the valve structure of the first embodiment, the auxiliary valve 111 and the main valve 27 are smoothly lifted and actuated in two steps. Consequently, the flow rate is gently increased from the start of the differential pressure action in the initial stage of valve opening under the soft-side damping force characteristic.

[0044] As described above, according to the valve structure of the first embodiment, a more stable damping force can be generated in the low-speed range of the piston speed. Furthermore, in the valve structure of the first embodiment, the inner peripheral side of the main valve 27 is prevented from being clamped and is simply supported in a cantilever state. Thus, compared with the existing valve structures (the single-step structure and the two-step structure), rigidity can be set to be lower, and consequently, the main valve 27 can be opened with a smaller differential pressure.As a result, the damping force in the low speed range of the piston speed in the soft-side damping force characteristic can be set to be lower compared with the existing valve structures, thereby being able to contribute to an improvement in the ride comfort of the vehicle in the soft-side damping force characteristic.

[0045] Furthermore, in the valve structure of the first embodiment, the auxiliary valve 111 on the upstream (first-step) side has a small diameter and is supported in a clamped state. Meanwhile, the main valve 27 on the downstream (second-step) side has a large diameter and is simply supported. With this structure, a large difference in rigidity is established between the main valve 27 and the auxiliary valve 111, thereby preventing the damping force from becoming unstable due to coupled oscillation between the two valves 27 and 111. Furthermore, in the valve structure of the first embodiment, the main valve 27 is simply supported, so a lift amount is increased along with a decrease in the rigidity of the main valve 27, and breakage of the main valve 27 due to lift is easy to occur.However, the outer diameter of the main valve 27 is set to be larger than a sliding diameter of the seat member 45 (inner diameter of the cylindrical portion 37B of the pilot body 37). Consequently, when the lift amount of the main valve 27 reaches a fixed amount, the main valve 27 is brought into abutment with an opening end of the cylindrical portion 37B of the pilot body 37. Thus, the main valve 27 can be prevented from excessive lift, and breakage of the main valve 27 due to lift can be prevented.

[0046] Furthermore, in the main valve 27 having the inner peripheral side clamped by both of the surface sides thereof and having the annular seal member 45 adhered thereto, in order to keep the soft-side damping force characteristic low, a fixed load (preload) is set to a vicinity of zero. This causes a fluctuation in the damping force. However, in the valve structure of the first embodiment, the inner peripheral portion 27B (inner peripheral side) is simply supported, and the recess valve 101, which has low rigidity and the inner peripheral portion 103 (inner peripheral side) clamped by both of the surface sides thereof, is superimposed and provided on the seat portion 39 side of the main valve 27.With this structure, the set load can be set to be larger, and the sensitivity of the damping force characteristics to the set load is low because the rigidity is sufficiently low. Therefore, easy control of the damping force and reduction of the damping force can be achieved, and a problem with existing valve structures, such as a late start of the damping force due to an insufficient set load, can be prevented. Furthermore, the recess valve 101 is formed by coupling the outer peripheral portion 102 and the inner peripheral portion 103 through the two coupling pieces 106 and 107, each with a low rigidity, and the outer peripheral portion 102 of the recess valve 101 is brought into close contact with the main valve 27 by the spring forces of the coupling pieces 106 and 107.Thus, the oil fluid can be prevented from leaking between the main valve 27 and the relief valve 101, thereby being able to obtain a stable damping force. (Second embodiment)

[0047] A second embodiment of the present invention will be described with reference to the accompanying drawings. The same components as those of the above-mentioned shock absorber 1 according to the first embodiment, or corresponding components, are denoted by the same terms and the same reference numerals, and a detailed description thereof will be omitted.

[0048] A valve structure of the second embodiment (see Fig. 6) differs from the valve structure of the first embodiment in that instead of the recess valve 101 in the valve structure of the first embodiment (see Fig. 3), a disc valve 121 without the recess sections 108 and 109 is used.

[0049] As in Fig. 6, an inner peripheral portion 123 (inner peripheral side) of the disc valve 121 (leakage prevention valve) is sealed from both surface sides (both right and left sides in Fig. 6) is clamped by the washers 94 and 95, and an annular spring portion 124 is formed between the inner peripheral portion 123 and an outer peripheral portion 122 (outer peripheral side). The spring portion 124 is configured to bring the outer peripheral portion 122 into close contact with the surface of the main valve 27 on the seat portion 39 side. A plurality of recesses 125 (slits) are formed in an edge portion of the main valve 27 on the inner peripheral side. With this configuration, a chamber 126 defined by the main valve 27, the disc valve 121, the washer 95, and the first retainer 92 is allowed to communicate with the pilot chamber 49.

[0050] According to the valve structure of the second embodiment, operations and effects equivalent to those of the valve structure of the first embodiment can be obtained. Furthermore, compared with the valve structure of the first embodiment using the low-rigidity recess valve 101, the soft-side damping force characteristic is slightly higher in the valve structure of the second embodiment. However, the oil fluid (hydraulic fluid) can be more reliably prevented from leaking into the pilot chamber 49 between the inner peripheral portion 27B (inner peripheral side) of the main valve 27 and the first retainer 92, thereby being able to obtain a more stable damping force. In addition, the chamber 126 and the pilot chamber 49 are allowed to communicate with each other through the recesses 125 formed in the main valve 27.Thus, the chamber 126 and the pilot chamber 49 can be maintained at the same pressure, thereby being able to prevent a problem (pressure abnormality) caused when pressure equalization between the chamber 126 and the pilot chamber 49 fails.

[0051] Furthermore, compared to the valve structure of the first embodiment using the recess valve 101, the valve structure of the second embodiment allows the disc valve 121 to be manufactured easily. Consequently, manufacturing costs can be reduced and assembly efficiency can be increased. Furthermore, a plurality of disc valves 121 can be used in a superimposed state. By selecting the number of disc valves 121, the damping force can be adjusted. (Third embodiment)

[0052] A third embodiment of the present invention will be described with reference to the accompanying drawings. The same components as those of the above-mentioned shock absorber 1 according to the first and second embodiments, or corresponding components, are denoted by the same terms and the same reference numerals, and a detailed description thereof will be omitted.

[0053] In the valve structure of the second embodiment (see Fig. 6), the recesses 125 (slits) designed to allow communication between the chamber 126 and the pilot chamber 49 are formed in an inner peripheral side edge portion of the main valve 27. In contrast, in a valve structure of the third embodiment (see Fig. 7), recesses 128 (slots) configured to allow communication between the chamber 126 and the pilot chamber 49 are formed in an outer peripheral side edge portion of the first holder 92.

[0054] According to the valve structure of the third embodiment, operations and effects equivalent to those of the valve structure of the second embodiment can be obtained. (Fourth embodiment)

[0055] A fourth embodiment of the present invention will be described with reference to the accompanying drawings. The same components as those of the above-mentioned shock absorber 1 according to the first embodiment, or corresponding components, are denoted by the same terms and the same reference numerals, and a detailed description thereof will be omitted.

[0056] In the valve structure of the first embodiment (see Fig. 3), the first holding device 92, which is designed to simply support the inner peripheral portion 27B (inner peripheral side) of the main valve 27 (support in a cantilever state), is formed to have an outer diameter equal to an outer diameter of the second holding device 93, which is superimposed on the first holding device 92 for use. In contrast, in a valve structure of the fourth embodiment (see Fig. 8) the second holding device 93 is designed to have the outer diameter larger than the outer diameter of the first holding device 92. Along with this configuration, a flange-shaped support portion 131 is formed on the side of the main valve 27 (left side in Fig. 8) of the larger diameter portion 36A of the guide pin 36, and the support portion 131 is configured to support the outer peripheral side of the second holder 93 which is enlarged in diameter.

[0057] In the valve structure of the fourth embodiment, in the low-speed piston speed range (at a low flow rate), the main valve 27 with the simply supported structure is opened at the outer peripheral side edge portion of the first support device 92, which is a support point P1 (support line) at which the main valve 27 is supported. In the high-speed piston speed range (at a high flow rate), the main valve 27 is opened at an outer peripheral side edge portion of the second support device 93, which is a support point P2 (support line) at which the main valve 27 is supported. As shown in Fig. 8, in a state before the main valve 27 is opened, a distance between the main valve 27 and the second holding device 93 in the direction along the axis (in the right-and-left direction in Fig.8), in other words, a thickness of the first holder 92, is set to be shorter (smaller) than a distance H between the main valve 27 and the cylindrical portion 37B of the pilot body 37 in the direction along the axis.

[0058] According to the valve structure of the fourth embodiment, operations and effects equivalent to those of the valve structure of the first embodiment can be obtained. Further, in the valve structure of the fourth embodiment, along with an increase in piston speed (flow rate), the support point (support line) at which the main valve 27 is supported is shifted from the inner peripheral side (P1) to the outer peripheral side (P2). With this configuration, compared with the valve structure of the first embodiment, a substantial valve rigidity can be increased. Thus, the lift amount of the main valve 27 can be prevented from increasing excessively and causing breakage of the main valve 27 due to lift.

[0059] As the shock absorber according to the above-described embodiments, for example, the following modes are conceivable. As a first mode of the shock absorber, a shock absorber is provided including: a cylinder in which hydraulic fluid is sealed; a piston slidably fitted to the cylinder; a piston rod coupled to the piston and extended to an outside of the cylinder; and a damping force generating mechanism configured to generate a damping force by controlling a flow of hydraulic fluid caused by sliding of the piston in the cylinder. The damping force generating mechanism includes: a valve body having a communication passage formed therein and including an inner seat portion and an outer seat portion.which are formed respectively on a central side and an outer peripheral side of the valve body via the communication passage; a pilot-type main valve which is provided to be capable of being separated from and placed on the outer seat portion, and is opened by receiving a pressure of the hydraulic fluid to thereby generate a damping force, wherein a pressure of opening of the main valve is adjusted by an internal pressure in a pilot chamber formed on a side opposite to the outer seat portion; a control valve which is a pressure control valve configured to control the internal pressure in the pilot chamber into which the hydraulic fluid is supplied; and an auxiliary valve which is provided on an upstream side of the main valve in series with the main valve, in which the main valve is an annular disc valve which is opened and closed in such a way,that an outer peripheral side thereof is separated from and placed on the outer seat portion, and in which an inner peripheral side of the main valve is prevented from being clamped from both surface sides thereof, and the main valve is supported only from one surface side on the inner peripheral side by a first holding device, wherein the shock absorber further comprises a recess valve provided between the main valve and the seat portions of the valve body and formed of an annular disc valve having a recess on an outer peripheral side thereof, wherein an inner peripheral side of the recess valve is clamped from both surface sides thereof, and wherein the recess valve includes a coupling portion with low rigidity,which is formed between the outer peripheral side and the inner peripheral side by cutting out a part of the recess valve between the outer peripheral side and the inner peripheral side.,

[0060] According to a second mode of the above-mentioned shock absorber, in the first mode, the shock absorber further comprises an annular sealing member provided on a side of the main valve opposite to the seat portions and slidably and fluid-tightly fitted to an inner tube portion of the pilot chamber.

[0061] According to a third mode of the above-mentioned shock absorber, in the first or the second mode, the coupling portion is formed to be symmetrical with respect to a center of the recess valve.

[0062] According to a fourth mode of the above-mentioned shock absorber, in any one of the first to third modes, the shock absorber further comprises a retainer provided on a side of the main valve opposite to the outer seat portion and having a larger diameter than a diameter of the first retainer, the retainer having the larger diameter regulating a valve opening amount of the main valve.

[0063] As a fifth mode of the shock absorber, a shock absorber is provided, comprising: a cylinder sealingly containing a hydraulic fluid; a piston slidably fitted to the cylinder; a piston rod coupled to the piston and extended to an outside of the cylinder; and a damping force generating mechanism configured to generate a damping force by controlling a flow of the hydraulic fluid caused by sliding of the piston in the cylinder, wherein the damping force generating mechanism includes: a valve body having a communication passage formed therein, and an inner seat portion and an outer seat portion formed respectively on a central side and an outer peripheral side of the valve body across the communication passage; a pilot-type main valve provided to be capable ofto be separated from and placed on the outer seat portion, and is opened by receiving a pressure of the hydraulic fluid to thereby generate a damping force, wherein a pressure of opening of the main valve is adjusted by an internal pressure in a pilot chamber formed on a side opposite to the outer seat portion; a control valve, which is a pressure control valve configured to control the internal pressure in the pilot chamber into which the hydraulic fluid is supplied; and an auxiliary valve provided on an upstream side of the main valve in series with the main valve, wherein the main valve is an annular disc valve that is opened and closed such that an outer peripheral side thereof is separated from and placed on the outer seat portion, and wherein an inner peripheral side of the main valve is prevented fromto be clamped from both surface sides thereof, and the main valve is supported only from one surface side on the inner peripheral side by the first holding device, wherein the shock absorber further comprises a leakage prevention valve configured to prevent the hydraulic fluid from leaking through between the inner peripheral side of the main valve and the first holding device to the pilot chamber side. The leakage prevention valve has an outer peripheral side to be brought into contact with the outer seat portion side of the main valve and has an inner peripheral side clamped by both surface sides of the leakage prevention valve.

[0064] According to a sixth mode of the above-mentioned shock absorber, in the fifth mode, the shock absorber further comprises an annular sealing member provided on a side of the main valve opposite to the seat portions, and slidably and fluid-tightly fitted to an inner tube portion of the pilot chamber.

[0065] According to a seventh mode of the above-mentioned shock absorber, in the fifth or sixth mode, the shock absorber further comprises a retainer provided on a side of the main valve opposite the outer seat portion and having a larger diameter than a diameter of the first retainer. The retainer with the larger diameter regulates a valve opening amount of the main valve.

[0066] A description of only a few embodiments of the present invention has been given, but it will be readily understood by one skilled in the art that various modifications and improvements can be made to the exemplary embodiment within the scope of the appended claims. Thus, forms in which such modifications and improvements are made are also intended to be included within the technical scope of the present invention. The above-mentioned embodiments can be arbitrarily combined within the scope of the appended claims. LIST OF REFERENCE SYMBOLS

[0067] 1 Shock absorber, 2 Cylinder, 5 Piston, 6 Piston rod, 26 Damping force generating mechanism, 27 Main valve, 28 Pilot valve (control valve), 35 Main body (valve body), 38 Passage (connecting passage), 39 Outer seat portion, 49 Pilot chamber, 91 Inner seat portion, 92 First retainer, 111 Auxiliary valve

Claims

[1] Shock absorber (1), with: a cylinder (2) which contains a sealed hydraulic fluid; a piston (5) slidably fitted to the cylinder (2); a piston rod (6) coupled to the piston (5) and extended to an outer side of the cylinder (2); and a damping force generating mechanism (26) configured to generate a damping force by controlling a flow of the hydraulic fluid caused by sliding of the piston (5) in the cylinder (2), the damping force generating mechanism (26) comprising: a valve body (35) having a communication passage (38) formed therein, and comprising an inner seat portion (91) and an outer seat portion (39) formed respectively on a central side and an outer peripheral side of the valve body (35) across the communication passage (38); a main valve (27) of a pilot type which is provided to be able to be separated from and placed on the outer seat portion (39), and is opened by receiving a pressure of the hydraulic fluid to thereby generate a damping force, wherein a pressure of opening of the main valve (27) is adjusted by an internal pressure in a pilot chamber (49) formed on a side opposite to the outer seat portion (39); a control valve (28) which is a pressure control valve designed to control the internal pressure in the pilot chamber (49) into which the hydraulic fluid is fed; and an auxiliary valve (111) provided on an upstream side of the main valve (27) in series with the main valve (27), wherein the main valve (27) is an annular disc valve which is opened and closed such that an outer peripheral side (27A) thereof is separated from and placed on the outer seat portion (39), and wherein an inner peripheral side (27B) of the main valve (27) is prevented from being clamped from both surface sides thereof, and the main valve (27) is supported only from one surface side on the inner peripheral side (27B) by a first holding device (92), wherein the shock absorber (1) further comprises a recess valve (101) which is provided between the main valve (27) and the seat portions (39, 91) of the valve body (35), and is formed from an annular disc valve having a recess (104) on an outer peripheral side (102) thereof, wherein an inner peripheral side (103) of the recess valve (101) is clamped from both surface sides thereof, the recess valve (101) comprising a coupling portion (105) formed between the outer peripheral side (102) and the inner peripheral side (103), and wherein the coupling portion (105) comprises a pair of coupling pieces (106, 107) formed by cutting out a part of the recess valve (101) between the outer peripheral side (102) and the inner peripheral side (103). [2] The shock absorber (1) according to claim 1, further comprising an annular sealing member (45) provided on a side of the main valve (27) opposite to the seat portions (39, 91) and slidably and fluid-tightly fitted to an inner tube portion (37B) of the pilot chamber (49). [3] The shock absorber (1) according to claim 1 or 2, wherein the coupling portion (105) is formed to be symmetrical with respect to a center of the relief valve (101). [4] Shock absorber (1) according to one of claims 1 to 3, further comprising a retainer (93) provided on a side of the main valve (27) opposite to the outer seat portion (39) and having a larger diameter than a diameter of the first retainer (92), the retainer (93) having the larger diameter regulating a valve opening amount of the main valve (27). [5] The shock absorber (1) according to any one of claims 1 to 4, wherein each coupling piece (106, 107) comprises an outer end portion (106A, 107A) connected to the outer peripheral side (102), an inner end (106B, 107B) connected to the inner peripheral side (103), and a spring portion (106C, 107C) formed between the outer end portion (106A, 107A) and the inner end (106B, 107B) to extend in the circumferential direction. [6] Shock absorber (1), with: a cylinder (2) which contains a sealed hydraulic fluid; a piston (5) slidably fitted to the cylinder (2); a piston rod (6) coupled to the piston (5) and extended to an outer side of the cylinder (2); and a damping force generating mechanism (26) configured to generate a damping force by controlling a flow of the hydraulic fluid caused by sliding of the piston (5) in the cylinder (2), the damping force generating mechanism (26) comprising: a valve body (35) having a communication passage (38) formed therein, and comprising an inner seat portion (91) and an outer seat portion (39) formed respectively on a central side and an outer peripheral side of the valve body (35) across the communication passage (38); a main valve (27) of a pilot type which is provided to be able to be separated from and placed on the outer seat portion (39), and is opened by receiving a pressure of the hydraulic fluid to thereby generate a damping force, wherein a pressure of opening of the main valve (27) is adjusted by an internal pressure in a pilot chamber (49) formed on a side opposite to the outer seat portion (39); a control valve (28) which is a pressure control valve designed to control the internal pressure in the pilot chamber (49) into which the hydraulic fluid is fed; and an auxiliary valve (111) provided on an upstream side of the main valve (27) in series with the main valve (27), wherein the main valve (27) is an annular disc valve which is opened and closed such that an outer peripheral side (27A) thereof is separated from and placed on the outer seat portion (39), and wherein an inner peripheral side (27B) of the main valve (27) is prevented from being clamped from both surface sides thereof, and the main valve (27) is supported only from one surface side on the inner peripheral side (27B) by a first holding device (92), wherein the shock absorber (1) further comprises a leakage prevention valve (121) configured to prevent the hydraulic fluid from leaking through between the inner peripheral side (27B) of the main valve (27) and the first retainer (92) to the pilot chamber (49) side, wherein the leakage prevention valve (121) has an outer peripheral side (122) to be brought into abutment against the outer seat portion (39) side of the main valve (27) and an inner peripheral side (123) clamped by both surface sides of the leakage prevention valve (121). [7] Shock absorber (1) according to claim 6, further comprising an annular sealing member (45) provided on a side of the main valve (27) opposite the seat portions (39, 91) and slidably and fluid-tightly fitted to an inner tube portion (37B) of the pilot chamber (49). [8] The shock absorber (1) according to claim 6 or 7, further comprising a retainer (93) provided on a side of the main valve (27) opposite to the outer seat portion (39) and having a larger diameter than a diameter of the first retainer (92), the retainer (93) having the larger diameter regulating a valve opening amount of the main valve (27).

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