JP2015028353A - Attenuation force adjustment type shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain suitable attenuation force even in a failure without depending on a stroke of a valve body of a pilot control valve in a pilot type attenuation force adjustment type shock absorber.SOLUTION: A piston 5 to which a piston rod 6 is joined is inserted into a cylinder 2 in which oil liquid is enclosed and an oil liquid flow generated due to movement of the piston 5 is controlled by an attenuation force generation mechanism 26 to generate attenuation force. In the attenuation force generation mechanism 26, attenuation force is generated by a pilot type main valve 27 and a solenoid-driven normally open pilot valve 28. A fail switching valve 30 by-passes a fail valve 29 in a normal state, and in a failure state, the fail switching valve 30 is switched by pressure difference between the upstream side and the downstream side of the pilot valve 28 and suitable attenuation force is generated by a fail valve 29 instead of the pilot valve 28.

Description

  The present invention relates to a damping force adjusting type shock absorber capable of generating a damping force and controlling the damping force by controlling a fluid flow with respect to a stroke of a piston rod.

  A shock absorber attached to a suspension device of a vehicle such as an automobile generally has a piston in which a piston rod is coupled in a cylinder filled with a fluid so as to be slidable. The fluid flow generated by the sliding of the piston in the cylinder is controlled by a damping force generating mechanism including an orifice, a disk valve, and the like to generate a damping force.

  For example, in a pilot-type hydraulic shock absorber described in Patent Document 1, a back pressure chamber (pilot chamber) is formed at the back of a main disk valve that is a damping force generation mechanism, and fluid is introduced into the back pressure chamber to The internal pressure of the back pressure chamber acts on the disc valve in the valve closing direction, and the valve pressure of the main disc valve is controlled by adjusting the internal pressure of the back pressure chamber with a solenoid valve (pilot valve). . Thereby, the freedom degree of adjustment of a damping force characteristic can be raised.

  Also, in the case described in Patent Document 1, in the unlikely event that energization to the solenoid valve becomes impossible, the valve spring of the valve spring moves to the fail position by the spring force of the valve spring and hits the fail valve. The flow path area is mechanically adjusted by a fail valve instead of the solenoid valve. Thereby, an appropriate damping force can be obtained even at the time of failure.

JP 2011-75060 A

  In the case of opening / closing the fail valve by moving the valve body of the solenoid valve, such as that described in Patent Document 1, it is necessary to lengthen the stroke of the valve body of the solenoid valve to some extent. large.

  The present invention has been made in view of the above points, and is a pilot type in which an appropriate damping force can be obtained even during a failure without depending on the stroke of the valve body of a solenoid valve that is a pilot control valve. An object of the present invention is to provide a damping force adjusting type shock absorber.

In order to solve the above problems, a damping force adjusting type shock absorber according to the present invention includes a cylinder in which a working fluid is sealed, a piston slidably fitted in the cylinder, and a piston connected to the piston. A piston rod extending to the outside of the cylinder, and a damping force generating mechanism for generating a damping force by controlling the flow of the working fluid generated by the sliding of the piston in the cylinder,
The damping force generation mechanism opens a valve upon receiving the pressure of the working fluid to generate a damping force, introduces the working fluid into the pilot chamber, and adjusts the valve opening pressure by the internal pressure of the pilot chamber. A normally open solenoid valve that controls the internal pressure of the pilot chamber, a fail valve that is disposed downstream of the solenoid valve and generates a damping force, and a differential pressure between the upstream side and the downstream side of the solenoid valve. A fail that switches the flow path of the working fluid so that the upstream side pressure bypasses the fail valve when the pressure is higher than the downstream pressure by a normal value and is normal, and when the pressure is not higher than a predetermined value, the flow is passed to the fail valve. And a switching valve.

  According to the damping force adjusting type shock absorber according to the present invention, it is possible to obtain an appropriate damping force even at the time of failure without depending on the stroke of the solenoid valve body that is a pilot control valve.

It is a longitudinal cross-sectional view of the damping force adjustment type shock absorber according to one embodiment of the present invention. FIG. 2 is an enlarged longitudinal sectional view showing a damping force generation mechanism that is a main part of the damping force adjusting shock absorber shown in FIG. FIG. 3 is an enlarged longitudinal sectional view showing a fail switching valve of the damping force generation mechanism shown in FIG. 2. FIG. 3 is a hydraulic circuit diagram of the damping force generation mechanism shown in FIG. 2.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the damping force adjustment type shock absorber 1 according to the present embodiment has a multi-cylinder structure in which an outer cylinder 3 is provided on the outer side of a cylinder 2, and between the cylinder 2 and the outer cylinder 3. A reservoir 4 is formed. A piston 5 is slidably fitted in the cylinder 2, and the inside of the cylinder 2 is defined by the piston 5 as two chambers, a cylinder upper chamber 2A and a cylinder lower chamber 2B. One end of a piston rod 6 is connected to the piston 5 by a nut 7, and the other end side of the piston rod 6 passes through the cylinder upper chamber 2 </ b> A and is a rod guide attached to the upper ends of the cylinder 2 and the outer cylinder 3. 8 and the oil seal 9 are extended to the outside of the cylinder 2. A base valve 10 that partitions the cylinder lower chamber 2 </ b> B and the reservoir 4 is provided at the lower end of the cylinder 2.

  The piston 5 is provided with passages 11 and 12 for communicating between the cylinder upper and lower chambers 2A and 2B. The passage 12 allows only fluid flow from the cylinder lower chamber 2B side to the cylinder upper chamber 2A side, and has a small set load that opens at the moment when the piston rod 6 switches from the expansion stroke to the contraction stroke. A check valve 13 is provided. The passage 11 is provided with a disk valve 14 that opens when the pressure of the fluid on the cylinder upper chamber 2A side reaches a predetermined pressure during the extension stroke and relieves the pressure to the cylinder lower chamber 2B side. The valve opening pressure of the disk valve 14 is considerably high and is set to such an extent that it does not open during normal road running. The disc valve 14 is provided with an orifice (not shown) that always connects the cylinder upper and lower chambers 2A, 2B.

  The base valve 10 is provided with passages 15 and 16 that allow the cylinder lower chamber 2B and the reservoir 4 to communicate with each other. The passage 15 allows only fluid flow from the reservoir 4 side to the cylinder lower chamber 2B side, and is a check with a small set load that opens at the moment when the piston rod 6 switches from the contraction stroke to the expansion stroke. A valve 17 is provided. The passage 16 is provided with a disk valve 18 that opens when the pressure of the fluid on the cylinder lower chamber 2B side reaches a predetermined pressure and relieves it to the reservoir 4 side. The valve opening pressure of the disk valve 18 is considerably high, and is set to such an extent that it does not open during normal road running. The disc valve 18 is provided with an orifice (not shown) that always connects the cylinder lower chamber 2 </ b> B and the reservoir 4. In the cylinder 2, oil liquid is sealed as a working fluid, and in the reservoir 4, oil liquid and gas are sealed.

  A separator tube 20 is externally fitted to the upper and lower ends of the cylinder 2 via seal members 19, and an annular passage 21 is formed between the cylinder 2 and the separator tube 20. The annular passage 21 communicates with the cylinder upper chamber 2 </ b> A through a passage 22 provided on a side wall near the upper end of the cylinder 2. A plurality of passages 22 may be provided in the circumferential direction according to specifications. A cylindrical connection port 23 is formed in the lower part of the separator tube 20 so as to protrude sideways and open. An opening 24 that is concentric with the connection port 23 and larger in diameter than the connection port is provided on the side wall of the outer cylinder 3, and a cylindrical case 25 is joined by welding or the like so as to surround the opening 24. A damping force generation mechanism 26 is attached to the case 25.

Next, the damping force generation mechanism 26 will be described with reference to FIGS.
The damping force generation mechanism 26 includes a pilot-type main valve 27, a pilot valve 28 that is a normally open solenoid valve, a fail valve 29, and a fail switching valve 30 that switches a flow path of oil to the fail valve 29. I have.

  The main valve 27 is opened by receiving the pressure of the oil liquid on the cylinder upper chamber 2A side, and distributes the oil liquid to the reservoir 4 side, and in the valve closing direction with respect to the disk valve 31. A pilot chamber 32 for applying an internal pressure is provided. The pilot chamber 32 is connected to the cylinder upper chamber 2 </ b> A side through a fixed orifice 33, and is connected to the reservoir 4 side through a pilot valve 28. The downstream side of the pilot valve 28 is connected to the reservoir 4 via a fail valve 29 and a fail switching valve 30 arranged in parallel. The disc valve 31 is provided with an orifice 31A that always connects the cylinder upper chamber 2A side and the reservoir 4 side.

  The pilot valve 28 is a normally open pressure control valve. The flow path is narrowed by a small-diameter port 34, and the port 34 is opened and closed by a valve body 36 driven by a solenoid 35, whereby the pilot chamber 32 of the main valve 27 is opened. Adjust the internal pressure. By reducing the diameter of the port 34 and reducing the pressure receiving area of the valve body 36, it is possible to reduce the load on the solenoid 35 and to save power and reduce the size of the pilot valve 28.

  The fail switching valve 30 opens and closes due to the differential pressure between the upstream and downstream of the pilot valve 28. When the differential pressure is equal to or higher than a predetermined pressure, the fail valve 29 is bypassed and the downstream side of the pilot valve 28 is connected to the reservoir. The bypass passage 37 connected to the fourth side is opened, and when the differential pressure is less than the predetermined pressure, the bypass passage 37 is closed and the downstream side of the pilot valve 28 is connected to the reservoir 4 side via the fail valve 29.

Next, the specific structure of the damping force generation mechanism 26 will be described in more detail with reference mainly to FIGS.
The cylindrical portion of the substantially bottomed cylindrical rear case 38 is screwed into the cylindrical portion of the substantially cylindrical case 25 attached to the outer cylinder 3, and the main valve 27, A pilot valve 28, a fail valve 29, and a fail switching valve 30 are incorporated. In the case 25 and the rear case 38, a passage member 39, a main body 40, a pilot chamber member 41, a holding member 42, a fail valve member 43, and a guide member 44 are disposed concentrically along the axial direction. . These members abut against each other in the axial direction, and are pressed and fixed in the axial direction by the screw connection between the case 25 and the rear case 38.

  The passage member 39 has a cylindrical shape having a flange portion 39A on the outer periphery of one end portion, the flange portion 39A abuts on the inner flange portion 25A of the case 25, and the cylindrical portion is liquid-tightly fitted to the connection port 23 of the separator tube 20. These are connected to the annular passage 21. A flange groove 39A of the passage member 39 is formed with a passage groove 39B extending in the radial direction, and the reservoir 4, the chamber 25A in the case 25 and the rear case 38 are formed by the passage groove 39B and the opening 24 of the outer cylinder 3. Communicate.

  The main body 40 and the pilot chamber member 41 are substantially annular, and the holding member 42 is a stepped substantially cylindrical shape having a small diameter portion 42A and a large diameter portion 42B, and the small diameter portion 42A of the holding member 42 is the main body 40. And the pilot chamber member 41 is inserted and these are positioned concentrically.

  The main body 40 is provided with a plurality of passages 45 penetrating in the axial direction along the circumferential direction. The outer peripheral portion of the flange portion 39A of the passage member 39 is in liquid-tight contact with one end portion of the main body 40, and the passage 45 is connected to the passage member 39 via a radially extending groove 39C formed in the flange portion 39A. Communicating with At the other end of the main body 40, an annular seat portion 46 projects from the outer peripheral side of the openings of the plurality of passages 45, and an annular clamp portion 47 projects from the inner peripheral side. The outer periphery of the disc valve 31 is seated on the seat portion 46. The inner peripheral portion of the disk valve 31 is clamped between the clamp portion 47 and the large diameter portion 42B of the holding member 42 together with the washer 50 and the pilot chamber member 41. The disc valve 31 is provided with a notch that forms an orifice 31A that allows the passage 45 side and the chamber 25C side to always communicate with each other on the outer peripheral portion. The disk valve 31 may be appropriately laminated with a disk-shaped valve body so as to obtain a desired bending characteristic. An annular elastic seal member 48 made of an elastic material such as rubber is fixed to the outer peripheral portion on the back side of the disk valve 31 by fixing means such as vulcanization adhesion.

  The pilot chamber member 41 is formed by press-molding a plate material. An annular recess 49 is formed on one end facing the disc valve 31, and an outer periphery of an elastic seal member 48 fixed to the disc valve 31 in the recess 49. The portions are slidably and fluid-tightly fitted, and a pilot chamber 32 is formed in the recess 49. The disk valve 31 receives the pressure on the passage 45 side and lifts and opens from the seat portion 46 to connect the passage 45 to the chamber 25 </ b> A in the case 25 and the rear case 38. The internal pressure of the pilot chamber 32 acts on the disc valve 31 in the valve closing direction. The pilot chamber 32 communicates with the inside of the holding member 42 through the side wall of the small-diameter portion 42 </ b> A of the holding member 42 and the passage 51 provided in the washer 50, and further through a fixed orifice 33 provided at the tip of the holding member 42. It communicates with the passage member 39.

  The fail valve member 43 has a substantially bottomed cylindrical shape and is fitted to the bore 52 on the bottom side of the rear case 38. The guide member 44 is formed in a stepped cylindrical shape having a small-diameter port press-fit portion 44A on one end side, a small-diameter plunger guide portion 44B on the other end side, and a large-diameter portion 44C on an intermediate portion. Yes. The plunger guide portion 44 </ b> B is inserted through the opening 53 at the bottom of the rear case 38, and the large diameter portion 44 </ b> C is fitted into a recess 54 formed around the opening 53 at the bottom of the rear case 38. The large-diameter portion 42 </ b> B of the holding member 42 is fitted to the opening end portion of the fail valve member 43. The large-diameter bore 55 in the fail valve member 43 and the small-diameter bore 56 formed in the large-diameter portion 42B of the holding member 42 are connected to the large-diameter portion 57A and the small-diameter of the stepped cylindrical valve member 57 constituting the fail switching valve 30. The parts 57B are fitted in a liquid-tight and slidable manner.

  A substantially cylindrical port member 58 is press-fitted and fixed in the port press-fit portion 44 </ b> A of the guide member 44. An end of the port member 58 protruding from the port press-fit portion 44A is slidably and liquid-tightly inserted into the valve member 57, and is further inserted into the holding member 42 with a gap. At the end of the port member 58 that is press-fitted into the guide member 65, a port 34 is formed by reducing the inner diameter of the passage 58 </ b> A in the port member 58, and the port 34 is a valve chamber 59 formed in the guide member 44. Open in. The valve chamber 59 is communicated with the large-diameter bore 55 of the fail valve member 43 by an axial groove 60 formed in the port press-fit portion 44A of the guide member 44, and the fail valve 29 and the fail switching valve 30, which will be described in detail later, are provided. And connected to the chamber 38A.

  A plunger 62 is inserted into the plunger guide portion 44B of the guide member 44 and is guided so as to be slidable along the axial direction. A tapered valve element 36 is provided at the distal end of the plunger 62, and the valve element 36 is inserted into the valve chamber 59 in the guide member 44, and is seated on the seat 34 </ b> A at the end of the port member 58. Port 34 is opened and closed. A large-diameter armature 63 is provided at the proximal end portion of the plunger 62, and the armature 63 is disposed outside the plunger guide portion 44B. A substantially bottomed cylindrical cover 64 that covers the armature 63 is attached to the plunger guide portion 44B, and the cover 64 guides the armature 63 so as to be movable in the axial direction.

  A solenoid cover 65 is attached to the rear end portion of the rear case 38. The solenoid cover 65 is provided so as to cover the plunger guide portion 44B of the guide member 44 protruding from the rear case 38, the cover 64, and the solenoid 35 disposed around these. A lead wire 66 for energizing the solenoid 35 extends from the solenoid cover 65. The plunger 62 is biased in the valve opening direction in which the valve body 36 is separated from the seat portion 34 </ b> A and opens the port 36 by the spring force of the return spring 67 provided between the plunger 62 and the solenoid member 35. By energizing, the thrust is generated, and the valve body 36 is seated on the seat portion 34A and moves in the valve closing direction to close the port 34 against the spring force of the return spring 67.

Next, the structure of the fail valve 29 will be described.
The fail valve member 43 is provided with a plurality of fail passages 68 extending along the circumferential direction and penetrating along the axial direction and communicating with the large-diameter bore 55. On the end face of the bottom side of the rear case 38 of the fail valve member 43, an annular seat portion 69 protrudes on the outer peripheral side of the openings of the plurality of fail passages 68, and an annular clamp portion 70 protrudes on the inner peripheral side. The inner peripheral portion of the fail disc 71 and the retainer 72 are clamped between the clamp portion 70 and the large diameter portion 44C of the guide member 44, and the valve chamber 73 is formed by a gap between the fail valve member 43 and the bottom portion of the rear case 38. Is formed. The fail disc 71 receives the pressure on the fail passage 68 side, bends and lifts from the seat portion 69 to connect the fail passage 68 to the valve chamber 73, and generates a damping force according to the opening degree. The valve chamber 73 communicates with the chamber 38A through a passage 52A formed between the bore 52 of the rear case 38 and the fail valve member 43.

Next, the structure of the fail switching valve 30 will be described mainly with reference to FIG.
The large-diameter portion 57A of the valve member 57 is provided with a plurality of switching passages 74 penetrating in the axial direction along the circumferential direction. The chamber 55 </ b> A and the chamber 55 </ b> B defined by the large-diameter portion 57 </ b> A of the valve member 57 are communicated with each other through the switching passage 74. An annular seat portion 75 projects on the outer peripheral side of the openings of the plurality of switching passages 74 of the valve member 57 on the surface of the large diameter portion 42 </ b> B of the holding member 42 facing the large diameter portion 57 </ b> A of the valve member 57. A plate-like valve spring 76 is provided between the annular protrusion 43 </ b> A formed at the center of the bottom of the fail valve member 43 and the valve member 57.

  As shown in FIG. 3A, the valve member 57 is urged by the spring force of the valve spring 76, the end surface of the large diameter portion 57A abuts against the seat portion 75, and the passage groove 61 and the switching passage 74 are separated from each other. Block the gap. As shown in FIG. 3B, the valve member 57 moves against the spring force of the valve spring 76, so that the end surface of the large diameter portion 57A is separated from the seat portion 75 and the passage groove 61. The switch passage 74 is communicated. The chamber 55B in the large-diameter bore 55 communicates with the fail passage 68, and a bore 57C formed at the end of the valve member 57 on the large-diameter portion 57A side and a port press-fitting of the guide member 44 inserted into the bore 57C. It communicates with the axial groove 60 via an axial and radial gap 77 between the portion 44 </ b> A and a notch 76 </ b> A on the inner peripheral portion of the valve spring 76.

  The valve member 57 moves due to a differential pressure between the upstream side of the pilot valve 28, that is, the pressure in the holding member 42, and the downstream side, that is, the pressure in the large-diameter bore 55 of the fail valve member 43. The valve member 57 moves against the spring force of the valve spring 76 when the pressure on the upstream side of the pilot valve 28 is higher than the pressure on the downstream side by a predetermined amount or more, and is separated from the seat portion 75 ( 3A), when not higher than a predetermined level, the spring force of the valve spring 76 makes contact with the seat portion 75.

Next, the operation of the damping force adjusting shock absorber 1 configured as described above will be described.
The damping force adjustment type shock absorber 1 is mounted between a spring and an unsprung part of a vehicle suspension device, and energizes the solenoid 35 via a lead wire 66 in a normal operation state in response to a command from an in-vehicle controller or the like. Then, thrust is generated in the plunger 62, the valve body 36 is seated on the seat portion 34A, and pressure control by the pilot valve 28 is executed to adjust the damping force.

  During the extension stroke of the piston rod 6, the check valve 13 of the piston 5 is closed by the movement of the piston 5 in the cylinder 2, and the fluid on the cylinder upper chamber 2A side is pressurized before the disc valve 14 is opened. , Through the passage 22 and the annular passage 21, flows into the passage member 39 of the damping force generation mechanism 26 from the connection port 23 of the separator tube 20, flows through the damping force generation mechanism 26, and passes from the opening 23 of the outer cylinder 3 to the reservoir 4. Flow into.

  At this time, the oil corresponding to the movement of the piston 5 opens the check valve 17 of the base valve 10 from the reservoir 4 and flows into the cylinder lower chamber 2B. When the pressure in the cylinder upper chamber 2A reaches the valve opening pressure of the disk valve 14 of the piston 5, the disk valve 14 is opened, and the pressure in the cylinder upper chamber 2A is relieved to the cylinder lower chamber 2B. Prevent excessive pressure rise of 2A.

  During the contraction stroke of the piston rod 6, the check valve 13 of the piston 5 is opened by the movement of the piston 5 in the cylinder 2, the check valve 17 of the passage 15 of the base valve 10 is closed, and before the disk valve 18 is opened. The fluid in the piston lower chamber 2B flows into the cylinder upper chamber 2A, and the fluid corresponding to the piston rod 6 that has entered the cylinder 2 flows from the cylinder upper chamber 2A through the same path as in the extension stroke to the reservoir. It flows to 4. When the pressure in the cylinder lower chamber 2B reaches the valve opening pressure of the disk valve 18 of the base valve 10, the disk valve 18 is opened, and the pressure in the cylinder lower chamber 2B is relieved to the reservoir 4, thereby Prevent excessive pressure rise of 2B.

  In the damping force generation mechanism 26, the oil liquid flowing in from the passage member 39 is fixed orifice 33 provided at the tip of the holding member 42 before the disk valve 31 of the main valve 27 is opened (piston speed low speed region). , The inside of the holding member 42 and the passage 58A of the port member 58, the valve body 36 of the pilot valve 28 is pushed open from the port 34 and flows into the valve chamber 59, and further, the axial groove 60, the gap 77 and It flows into the chamber 55B through the notch 76A.

  At this time, the pressure on the upstream side of the pilot valve 28 acts on the end surface of the small diameter portion 57B of the valve member 57 fitted into the small diameter bore 56 from the inside of the holding member 42. On the other hand, the pressure on the downstream side of the pilot valve 28 acts on both end surfaces of the large-diameter portion 57A of the valve member 57 from the valve chamber 59 through the axial groove 60, the gap 77, the notch 76A, and the fail passage 68. When normal, that is, when the pilot valve 28 is in a normal operating state due to energization of the solenoid 35, due to the differential pressure between the upstream side and the downstream side of the pilot valve 28 due to the control pressure (pressure loss) of the pilot valve 28, As shown in FIG. 3A, the valve member 57 moves against the spring force of the valve spring 76, moves away from the seat portion 75, and connects the switching passage 74 to the passage groove 61. In this state, the oil liquid flows from the chamber 55B to the reservoir 4 through the switching passage 74, the chamber 55A, the passage groove 61, the chamber 38A, the passage groove 39B, and the opening 23 of the outer cylinder 3. Therefore, the oil liquid bypasses the fail valve 29.

  When the piston speed increases and the pressure on the cylinder upper chamber 2A side reaches the valve opening pressure of the disc valve 31 of the main valve 27 (piston speed high speed region), the oil liquid that has flowed into the passage member 39 flows into the groove 39C and the passage. 45, the disc valve 31 is pushed open and flows directly to the chamber 38A in the case 25 and the rear case 38.

  As a result, during the expansion / contraction stroke of the piston rod 6, the opening force of the fixed orifice 33 and the pilot valve 28 before the opening of the disk valve 31 of the main valve 27 (piston speed low speed region) in the damping force generation mechanism 26. Therefore, after the disc valve 31 of the main valve 27 is opened (piston speed high speed region), the damping force is generated according to the opening degree. The damping force can be directly controlled by adjusting the valve opening pressure of the pilot valve 28 with the energization current of the solenoid 35. At this time, the valve opening pressure of the pilot valve 28 changes the internal pressure of the pilot chamber 32 upstream, that is, in the pilot chamber 32 communicating with the holding member 42 via the passage 51. The valve opening pressure of the disk valve 31 of the valve 27 can be adjusted simultaneously.

  When the energization current to the solenoid 35 is reduced and the thrust of the plunger 62 is reduced, the valve opening pressure of the pilot valve 28 is reduced, a soft-side damping force is generated, the energization current is increased, and the plunger is increased. When the thrust of 62 is increased, the valve opening pressure of the pilot valve 28 increases, and a hard-side damping force is generated. Accordingly, it is possible to generate a soft-side damping force that is generally used frequently with a low current, and to reduce power consumption.

  In the unlikely event that energization of the solenoid 35 becomes impossible due to a failure of the controller, disconnection, etc. (during failure), the thrust of the plunger 62 disappears, and the valve body 36 moves backward due to the spring force of the return spring 67. The port 34 of the pilot valve 28 is fully opened. In this state, the pressure in the holding member 42 on the upstream side of the pilot valve 28 decreases, and the differential pressure between the upstream side and the downstream side of the pilot valve 28 decreases, as shown in FIG. The valve member 57 abuts against the seat portion 74 by the spring force of the valve spring 76 and blocks the switching passage 74 and the passage groove 61. As a result, the oil in the chamber 55 passes through the fail passage 68, pushes the fail valve 29 open to flow to the valve chamber 73, and further flows to the chamber 38A through the passage 52A. As a result, a damping force can be generated by the fail valve 29 in place of the pilot valve 28 that has become inoperable, and the valve opening pressure of the main valve 27 can be controlled by adjusting the internal pressure of the pilot chamber 32. In this way, it is possible to generate an appropriate damping force even during a failure.

  DESCRIPTION OF SYMBOLS 1 ... Damping force adjustment type buffer, 2 ... Cylinder, 5 ... Piston, 6 ... Piston rod, 26 ... Damping force generating mechanism, 27 ... Main valve, 28 ... Pilot valve (solenoid valve), 32 ... Pilot chamber, 29 ... Fail valve, 30 ... Fail switching valve

Claims (1)

A cylinder filled with a working fluid; a piston slidably fitted in the cylinder; a piston rod connected to the piston and extending to the outside of the cylinder; and a slide of the piston in the cylinder. A damping force generation mechanism that generates a damping force by controlling the flow of the working fluid generated by the movement,
The damping force generation mechanism opens a valve upon receiving the pressure of the working fluid to generate a damping force, introduces the working fluid into the pilot chamber, and adjusts the valve opening pressure by the internal pressure of the pilot chamber. A normally open solenoid valve that controls the internal pressure of the pilot chamber, a fail valve that is disposed downstream of the solenoid valve and generates a damping force, and a differential pressure between the upstream side and the downstream side of the solenoid valve. A fail that switches the flow path of the working fluid so that the upstream side pressure bypasses the fail valve when the pressure is higher than the downstream pressure by a normal value and is normal, and when the pressure is not higher than a predetermined value, the flow is passed to the fail valve. A damping force adjusting type shock absorber having a switching valve.

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