JP2009047298A - Shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock absorber improved in vibration damping performance. <P>SOLUTION: This shock absorber comprises a cylinder 1, a piston 2 partitioning the inside of the cylinder into one chamber R1 and the other chamber R2, passages 4 and 5 communicating the one chamber R1 with the other chamber R2, and damping force generating elements 6 and 7 provided on the way of the passages 4 and 5. A bypass passage 8 for communicating the one chamber R1 with the other chamber R2, bypassing the passages 4 and 5, is provided, and a valve 9 for opening the bypass passage 8 when a change of the movement direction of the piston 2 relative to the cylinder 1 is sensed is provided on the way of the bypass passage 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a shock absorber.

  2. Description of the Related Art Conventionally, a shock absorber having a cylinder, a piston that is slidably inserted into the cylinder, and a rod that is movably inserted into the cylinder via the piston is known.

Even in the case of a shock absorber that uses the working fluid filled in the cylinder as a gas, the rod side chamber and the piston side chamber communicate with each other through the passage of the piston portion, and an outer cylinder is provided outside the cylinder. The rod side chamber and the piston side chamber communicate with each other through a gap between the cylinder and the outer cylinder, and a small amount of lubricating oil enclosed with gas in the cylinder is moved to the piston side chamber and the rod side chamber in the manner of a pump by the vibration of the shock absorber. It is made to circulate so as to ensure the slidability of the sliding portion which is the contact portion between the piston and the cylinder and the contact portion between the rod and the sealing member provided at the lower end of the cylinder. The other structure is substantially the same as the structure of the hydraulic shock absorber, and the conventional damping force generating valve of the shock absorber is also the same structure as the hydraulic shock absorber (see, for example, Patent Documents 1 and 2).
JP 2004-132429 A JP 2004-132428 A

  As described above, in the conventional shock absorber, the function as a shock absorber can be exhibited regardless of the type of the working fluid by ensuring slidability, but it is pointed out that there are the following problems. there is a possibility.

  That is, in the shock absorber, if the cylinder pressure changes substantially linearly with respect to the vibration speed change, the generated damping force is preferably linear with respect to the vibration speed. Therefore, the change in the cylinder pressure is delayed with respect to the change in the expansion / contraction speed due to the compressibility of the hydraulic oil, and the generated damping force with respect to the speed has a characteristic having hysteresis. In particular, in a shock absorber that makes the working fluid a gas rich in compressibility, this tendency becomes remarkable, and as shown in FIG. 17, the hysteresis in the speed damping force characteristic that is the relationship between the speed and the generated damping force, that is, the above-described Hysteresis increases.

  Thus, the conventional shock absorber has a large hysteresis in the generated damping force with respect to the speed regardless of the working fluid for high-frequency vibration, and thus functions as a spring in addition to exhibiting the damping force. In other words, there is a possibility that the damping property is deteriorated due to the influence of the spring component.

  Accordingly, the present invention has been developed to improve the above-described problems, and an object of the present invention is to provide a shock absorber capable of improving vibration damping.

  In order to solve the above-described object, the problem solving means in the present invention includes a cylinder, a piston that divides the cylinder into one chamber and the other chamber, a passage that communicates the one chamber and the other chamber, In the shock absorber provided with the damping force generating element provided in the above, a bypass path that bypasses the passage and communicates the one chamber with the other chamber is provided, and the direction of movement of the piston relative to the cylinder is switched in the middle of the bypass path. A valve that opens the bypass when it senses is provided.

  According to the shock absorber of the present invention, when the direction of movement of the piston with respect to the cylinder is switched, the pressure in the one of the chambers or the other chamber that has been compressed so far is released into the chamber that has been expanded, and is then compressed. Since it is possible to prompt a rapid pressure increase in the expansion chamber and a rapid pressure decrease in the compression chamber to be expanded, it is possible to respond to a change in the vibration speed of the differential pressure change between the one chamber and the other chamber. The reaction is accelerated.

  That is, in this shock absorber, the phase delay of the pressure change in the one chamber and the other chamber with respect to the vibration speed change in the shock absorber can be alleviated, so that the vibration damping property of the shock absorber can be improved, and the vehicle It is possible to drastically improve the ride comfort in the vehicle, and in particular, it is possible to reduce the hysteresis of the generated damping force with respect to the speed during high-frequency vibration. That is, according to the shock absorber of the present embodiment, it is possible to solve the problem that the vibration damping property is deteriorated because the velocity damping force characteristic has a large hysteresis like the conventional shock absorber.

  The valve structure of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of a shock absorber according to an embodiment. FIG. 2 is a schematic longitudinal sectional view of a piston portion of the shock absorber according to the embodiment. FIG. 3 is a schematic longitudinal sectional view of the piston portion in a state where the piston in the shock absorber according to the embodiment moves downward with respect to the cylinder. FIG. 4 is a schematic longitudinal sectional view of the piston portion in a state where the piston in the shock absorber according to the embodiment has moved upward with respect to the cylinder. FIG. 5 is a diagram showing the velocity damping force characteristics of the shock absorber according to the embodiment. FIG. 6 is a schematic longitudinal sectional view of the piston portion of the shock absorber according to a modification of the embodiment. FIG. 7 is a schematic longitudinal sectional view of a piston portion of a shock absorber according to another embodiment. FIG. 8 is a schematic longitudinal sectional view of the piston portion in a state where the piston in the shock absorber according to another embodiment is moved upward with respect to the cylinder. FIG. 9 is a schematic longitudinal sectional view of the piston portion immediately after the movement direction of the piston relative to the cylinder in the shock absorber according to another embodiment is switched from the upper side to the lower side. FIG. 10 is a schematic longitudinal sectional view of the piston portion in a state where the moving direction of the piston with respect to the cylinder in the shock absorber according to another embodiment is switched from the upper side to the lower side and the other side pressure-dependent release element is in the cut-off state. . FIG. 11 is a schematic longitudinal sectional view of the piston portion in a state in which the moving direction of the piston with respect to the cylinder in the shock absorber according to another embodiment has moved downward. 12 is a schematic longitudinal sectional view of a piston portion showing a state in the middle of a process in which a shock absorber according to another embodiment shifts from the state of FIG. 10 to the state of FIG. 11. FIG. 13 is a schematic longitudinal sectional view of the piston portion immediately after the moving direction of the piston relative to the cylinder in the shock absorber according to another embodiment is switched from the lower side to the upper side. FIG. 14 is a schematic longitudinal sectional view of a piston portion in a state where the moving direction of the piston with respect to the cylinder in the shock absorber according to another embodiment is switched from the lower side to the upper side and the one-side pressure-dependent release element is in the cut-off state. . FIG. 15 is a list of operation modes of the direction switching sensing release element, the one-side pressure-dependent release element, the other-side pressure-dependent release element, and the shutter in the shock absorber according to another embodiment. FIG. 16 is a diagram illustrating a change characteristic of the damping force with respect to a change in vibration speed of the shock absorber according to another embodiment.

  As shown in FIGS. 1 and 2, the shock absorber D <b> 1 in the embodiment is inserted into the cylinder 1, the piston 2 that partitions the cylinder 1 into one chamber R <b> 1 and the other chamber R <b> 2, and the cylinder 1. In addition, the rod 3 connected to the piston 2, the passages 4 and 5 communicating with the one chamber R1 and the other chamber R2, the leaf valves 6 and 7 as damping force generating elements for opening and closing the passages 4 and 5, A bypass path 8 that bypasses 5 and communicates one chamber R1 and the other chamber R2, and a valve 9 that opens the bypass path 8 when a change in the direction of movement of the piston 2 with respect to the cylinder 1 is detected in the middle of the bypass path 8. And is configured.

  In addition, the one chamber R1 and the other chamber R2 in the cylinder 1 are filled with gas, and the buffer D1 is configured as an air pressure buffer that uses a working fluid as a gas. In the shock absorber D1, the piston 1 basically moves in the vertical direction in FIG. 1 with respect to the cylinder 1, and the gas as the working fluid passes through the passages 4 and 5 in one chamber R1 and the other chamber R2. When the gas flows back and forth, the corresponding leaf valves 6 and 7 give resistance to the gas flow to generate a predetermined pressure loss, thereby generating a predetermined damping force and exhibiting a vibration damping function It is.

  Hereinafter, the cylinder 1 will be described in detail. The upper and lower ends of the cylinder 1 are closed by the head member 15 and the bottom member 16 and filled with gas, respectively, and are disposed outside the cylinder 1. It is accommodated in a bottomed cylindrical outer cylinder 12 that covers the cylinder 1. A small amount of lubricating oil is contained in the cylinder 1 to lubricate the sliding portion of the shock absorber D1, that is, the contact portion between the cylinder 1 and the piston 2 and the contact portion between the head member 15 and the seal 24 and the rod 3. Filled with gas.

  The cylinder 1 is partitioned into a first chamber R1 and a second chamber R2 by a piston 2 that is slidably inserted. A rod 3 is connected to the upper end of the piston 2 in FIG. 1. The rod 3 is inserted into the inner peripheral side of the annular head member 15 and protrudes out of the cylinder 1. That is, the shock absorber D1 is configured as a so-called single rod type shock absorber, but may be configured as a double rod type shock absorber, and is not intended to prevent this.

  Further, the piston 2 is provided with passages 4 and 5 communicating the one chamber R1 and the other chamber R2, and the passages 4 and 5 are stacked on the upper and lower sides of the piston 2 in FIG. 1 and FIG. It is opened and closed by annular leaf valves 6 and 7 that function as a damping force generating element.

  Specifically, the lower end of the passage 4 in FIG. 2 which is the outlet end of the passage 4 is opened and closed by a leaf valve 6 and allows only a gas flow from the one chamber R1 to the other chamber R2. 2 and the upper end in FIG. 2 which is the outlet end of the passage 5 is opened and closed by a leaf valve 7, and a one-way passage allowing only gas flow from the other chamber R2 toward the one chamber R1. It is said that.

  Therefore, in this shock absorber D1, when the piston 2 exhibits vibrations that move upward in FIG. 2 with respect to the cylinder 1, the gas moves from the one chamber R1 to the other chamber R2 via the passage 4, A resistance is applied to the gas flow by the leaf valve 6 to cause a difference in pressure between the one chamber R1 and the other chamber R2, and the buffer D1 exerts a damping force that suppresses the upward movement of the piston 2 relative to the cylinder 1, When the piston 2 vibrates downward in FIG. 2 with respect to the cylinder 1, the gas moves from the other chamber R 2 to the one chamber R 1 through the passage 5, and a resistance is given to this gas flow by the leaf valve 7. Thus, a difference is generated in the pressure between the other chamber R2 and the one chamber R1, and the damping force that suppresses the downward movement of the piston 2 relative to the cylinder 1 is exerted on the shock absorber D1.

  Further, the piston 2 includes a bypass path 8 that bypasses the passages 4 and 5 and communicates the one chamber R1 and the other chamber R2, and a valve 9 is provided in the middle of the bypass path 8.

  The valve 9 is slidable into a base portion 9 a that is in sliding contact with the inner periphery of the cylinder 1, and a valve hole 10 that rises from the base portion 9 a and opens from the lower end in FIG. 2 that is one end of the piston 2 and intersects the middle of the bypass path 8. A shaft portion 9b accommodated in the shaft portion 9 and a through hole 9c provided in the shaft portion 9b. Further, the bottom of the valve hole 10 is communicated with the other chamber R2 by a branch passage 14 that branches from the middle of the bypass passage 8, and the pressure receiving areas in the upper and lower portions in FIG. Thus, the valve 9 is prevented from being moved by the pressure in the other chamber R2.

  The vertical length in FIG. 2, which is the axial length of the shaft portion 9 b, is fixed so that the leaf valve 6 and the leaf valve 6 are fixed to the piston 2 even when the upper end abuts against the bottom portion of the valve hole 10. The length is set so as not to interfere with the portion, the bending of the leaf valve 6 is not hindered, and the passages 4 and 5 are not blocked by the base portion 9a.

  Further, the base portion 9a is provided with a through hole 9d that communicates the space A partitioned by the base portion 9a and the piston 2 to the other chamber R2, and hinders the movement of gas to the one chamber R1 and the other chamber R2. There is no such thing. Instead of the through hole 9d, a cutout may be provided on the outer periphery of the base 9a to form a gap with the cylinder 1 so that the space A communicates with the other chamber R2.

  Further, a small diameter portion 9e is provided below the shaft portion 9b and a small diameter portion 9e is provided. The small diameter portion 9e is slidable on the inner periphery of the cylinder 13 fitted in the vicinity of the outlet of the valve hole 10 in FIG. The valve 9 is prevented from falling off from the valve hole 10, and the valve 9 is moved downward in FIG. 2 by the abutment between the tube 13 and the step portion 9f provided by forming the small diameter portion 9e. Is restricted, and the lower limit of movement of the valve 9 is set. In this case, although not shown, it is considered that the gap formed between the tube 13 and the step 9f is not sealed so as not to hinder the movement of the valve 9 relative to the piston 2. Specifically, a notch groove is provided in one or both of the inner periphery of the cylinder part 13 and the outer periphery of the small diameter part 9e, or a gap formed between the cylinder 13 and the step part 9f is provided in the piston 2 to the other chamber R2. What is necessary is just to provide the channel | path which connects. Further, a flow path of a notch groove provided in one or both of a passage communicating the gap formed between the tube 13 and the step portion 9f to the other chamber R2 or the inner periphery of the tube portion 13 and the outer periphery of the small diameter portion 9e. The ease of movement of the valve 9 relative to the piston 2 can be controlled by adjusting the road area. In this case, if the flow path area is increased, the resistance of the gas in and out of the air gap is reduced, so that the valve 9 is easy to move with respect to the piston 2.

  As described above, the valve 9 can be moved upward in FIG. 2 until the upper end of the shaft portion 9b contacts the upper surface in FIG. 2 which is the bottom of the valve hole 10, and the upper movement limit of the valve 9 is limited. Is set.

  The outer diameter of the shaft portion 9b above the small diameter portion 9e is set to a diameter that allows sliding contact with the inner periphery of the valve hole 10, and the valve 9 is centered with respect to the upper and lower movement limits described above. 2, that is, when in the neutral position shown in FIG. 2, the through hole 9 c faces the opening of the bypass path 8 to the valve hole 10, and the bypass path 8 is in a communicating state.

  On the other hand, the valve 9 is displaced upward from the neutral position shown in FIG. 2 to be in the state shown in FIG. 3 or displaced downward to be in the state shown in FIG. If it becomes impossible to oppose, the bypass 8 is made into the interruption | blocking state.

  Further, the outer periphery of the base portion 9a is in sliding contact with the inner periphery of the cylinder 1 as described above, but the frictional force generated between the base portion 9a and the cylinder 1 is caused by the shaft portion 9b of the valve 9, the valve hole 10, and the cylinder 13. When the piston 2 in FIG. 2 moves upward with respect to the cylinder 1, the valve 9 does not move until the cylinder 13 abuts against the step 9 f. If the piston 2 does not follow the upward movement of the piston 2 with respect to the cylinder 1 and the piston 2 continues to move upward with respect to the cylinder 1, it finally protrudes from the piston 2 to the state shown in FIG. On the other hand, when the piston 2 in FIG. 2 moves downward with respect to the cylinder 1, the valve 9 does not follow the downward movement of the piston 2 with respect to the cylinder 1 until it abuts against the bottom of the valve hole 10. When the piston 2 continues to move downward with respect to the cylinder 1, it finally enters the valve hole 10 until it abuts against the bottom of the valve hole 10 and the state shown in FIG.

  Therefore, when the piston 2 moves downward with respect to the cylinder 1 and becomes in the state shown in FIG. 3, when the moving direction is reversed and the piston 2 moves upward with respect to the cylinder 1, the valve 9 is moved to FIG. 2. When the piston 2 returns to the neutral position shown and continues to move upward relative to the cylinder 1, the valve 9 is in the state shown in FIG. Subsequently, when the moving direction of the piston 2 relative to the cylinder 1 is reversed from this state and this time moves downward, the valve 9 returns to the neutral position shown in FIG. If it continues to move, the valve 9 will be in the state shown in FIG.

  If this is continued, each time the movement direction of the piston 2 relative to the cylinder 1 is switched, the valve 9 returns to the neutral position at one end to bring the bypass passage 8 into a communicating state, and the movement direction of the piston 2 relative to the cylinder 1 changes. If there is no valve, the valve 9 is positioned at the position shown in FIG. 3 or FIG. That is, when the movement direction of the piston 2 with respect to the cylinder 1 is switched, that is, when the vibration direction of the shock absorber D1 is switched, the valve 9 communicates with the one-way bypass path 8, and the movement of the piston 2 continues and changes in that direction. If there is no, it functions to block the bypass 8.

  In addition, in the above place, in order to make the valve 9 follow the movement of the piston 2 when the movement of the piston 2 continues, the valve 9 is directly brought into contact with the bottom of the tube 13 and the valve hole 10. In order to mitigate the impact at the time of the collision, a cushion may be provided at one of the collision parts between the cylinder 13 and the valve 9 and one of the collision parts between the valve hole 10 and the valve 9, as described above. By doing so, deterioration of each part can be suppressed.

  As can be understood from the above description, the valve 9 opens the bypass path 8 when it senses a change in the direction of movement of the piston 2 relative to the cylinder 1 in the shock absorber D1, and in this embodiment, Specifically, a part of the valve 9 is slidably contacted with the inner periphery of the cylinder 1 and a range in which the valve 9 can move with respect to the piston 2 is set, thereby switching the moving direction of the piston 2 relative to the cylinder 1. In this case, the valve 9 is delayed to follow the movement of the piston 2 so as to detect the change of the moving direction of the piston 2 relative to the cylinder 1 and to open the bypass path 8.

  In this embodiment, the valve 9 can detect the switching of the moving direction of the piston 2 with respect to the cylinder 1 and the operation of opening the bypass 8 without applying any energy from the outside, and drives the valve 9. Since there is no need to connect to an external device, energy saving and space saving are achieved, and the practicality and versatility of the shock absorber D1 are improved. However, the movement direction of the piston 2 relative to the cylinder 1 can be switched, for example, by a stroke sensor or an acceleration sensor. It is also possible to use a valve configured to operate the proportional electromagnetic on-off valve driven by a solenoid as described above.

  In addition, in the above description, the through hole 9c is used for communication with the bypass passage 8, but a small diameter portion is provided with a part of the outer diameter of the shaft portion 9b as a small diameter, and this small diameter portion is connected to the bypass passage 8 at a neutral position. You may make it ensure communication of the bypass path 8 by making it oppose. By doing in this way, there exists an advantage which can ensure the communication of the bypass path 8 reliably, without positioning the valve 9 in the circumferential direction.

  Subsequently, as shown in FIG. 1, the outer cylinder 12 is formed in a bottomed cylinder shape, and lubricating oil is supplied to the one chamber R1 and the other chamber R2 through an annular gap formed between the outer cylinder 12 and the cylinder 1. Is circulated, and the circulation passage 17 is filled with lubricating oil.

 In turn, the head member 15 has an annular shape as described above and is fitted to the upper end of the cylinder 1 in FIG. 1, and has a bearing 18 that pivotally supports the rod 3 on its inner peripheral side, and the upper end side. The recessed part 19 opened from is provided. Further, the head member 15 includes a flow path 20 that communicates the outer periphery and the recess 19 and a flow path 21 that communicates the lower end and the recess 19, and the opening end on the outer periphery side of the flow path 20 is the above-described circulation path. 17 and the open end on the lower end side of the flow path 21 is opposed to the one chamber R1. That is, one end of the circulation passage 17 is communicated with the one chamber R <b> 1 through the flow path 20, the recess 19, and the flow path 21.

 On the other hand, the bottom member 16 that closes the lower end in FIG. 1 of the cylinder 1 is formed in a disc shape and is fitted to the lower end in FIG. 1 of the cylinder 1, and includes a flow path 22 that communicates the upper end with the outer periphery. Configured. The opening end on the upper end side of the flow path 22 faces the other chamber R <b> 2, and the opening end on the outer peripheral side faces the circulation passage 17. That is, the other end of the circulation passage 17 is communicated with the other chamber R <b> 2 via the flow path 22. In addition, a check valve 23 that allows only a flow from the other chamber R2 to the one chamber R1 via the circulation passage 17 is provided in the middle of the flow path 22.

 Then, the cylinder 1 closed at both ends by the head member 15 and the bottom member 16 configured as described above is inserted and accommodated in the outer cylinder 12, and the upper surface of the head member 15 in FIG. An annular sealing member 25 that holds an annular seal 24 that is in sliding contact is laminated, and the opening end that is the upper end of the outer cylinder 12 in the figure is crimped. These sealing member 25, head member 15, cylinder 1, and bottom member 16. Is housed and fixed in the outer cylinder 12 and integrated.

  In addition, in FIG. 1 in the sealing member 25 described above, the axial length that is the vertical length is set shorter than the axial length that is the vertical length of the seal 24 described above, and the seal 24 is The sealing member 25 is held by the sealing member 25 so as to protrude from the lower end of the sealing member 25 toward the inside of the cylinder 1. In the above description, the sealing member 25 holds the seal 24. However, the seal 24 may be welded to the sealing member 25 so that it cannot be separated.

  And the lower end in FIG. 1 of the seal 24 protruding from the sealing member 25 is disposed in the recess 19 of the head member 15, and the oil storage chamber 26 is separated by the recess 19 and the sealing member 25, The oil storage chamber 26 is filled with lubricating oil. Therefore, the circulation passage 17 is connected to the oil storage chamber 26 by the above-described flow path 20, whereby the circulation passage 17 communicates the one chamber R 1 and the other chamber R 2 via the oil storage chamber 26.

  Further, as described above, the rod 3 that protrudes from the cylinder 1 and is slidably inserted into the bearing 18 of the head member 15 is inserted on the inner peripheral side of the seal 24. The outer periphery of the rod 3 is pressed against the outer periphery of the rod 3 to seal the outer periphery of the rod 3. A seal (not shown) that seals between the outer periphery of the sealing member 25 and the outer cylinder 12 is provided on the outer peripheral side of the sealing member 25. The cylinder 12 is maintained in an airtight state.

  As is apparent from the above description, the rod 3 penetrates the oil storage chamber 26, and the oil storage chamber 26 faces the sliding portion 27 between the rod 3 and the seal 24.

  Here, the opening end 21 a on the oil storage chamber 26 side of the flow path 21 opens from the side wall 19 a of the recess 19, and the opening end 21 a is positioned at least above the lowermost end of the seal 24 in FIG. The oil level 28 of the lubricating oil filled in the oil storage chamber 26 is always maintained in contact with the lower end of the seal 24.

  Therefore, in the shock absorber D1, the working gas is sealed in the cylinder 1, and the lubricating oil is filled in the oil storage chamber 26 and the circulation passage 17, but in this embodiment, In order to ensure lubrication between the rod 3 and the seal 24, the oil level 28 of the oil in the oil storage chamber 26 is not lowered below the lowermost end of the seal 24 depending on the position of the opening end 21a. In addition, the excess lubricating oil beyond that is discharged to the one chamber R1, and the opening end of the flow path 20 is provided even on the oil surface 29 of the lubricating oil in the circulation passage 17. It is set to be positioned above 20a.

  The one chamber R1 and the other chamber R2 are also filled with a small amount of lubricating oil. However, the lubricating oil filled in the one chamber R1 is used when the shock absorber D1 performs a vibration operation for the first time. The lubricating oil in the other chamber R2 is supplied before the gas into the circulation passage 17 when the shock absorber D1 is contracted to supply the lubricating oil in the oil storage chamber 26. Filled to prevent the oil level 28 from descending.

  When the shock absorber D1 is contracted, that is, when the piston 2 in FIG. 1 moves downward relative to the cylinder 1, the working gas in the other chamber R2 is caused to flow through the check valve 23 by the pressure increase in the other chamber R2. It pushes open and flows into the circulation passage 17 via the flow path 22. At this time, since the lubricating oil in the other chamber R2 is heavier than the working gas and is accumulated in the opening of the flow path 22, the lubricating oil also moves to the circulation passage 17 together with the working gas. Then, the inside of the circulation passage 17 and the oil storage chamber 26 are pressurized in the same manner as the other chamber R2, so that the lubricating oil in the circulation passage 17 flows into the oil storage chamber 26 and further into the oil storage chamber 26. Therefore, the oil level 28 of the lubricating oil rises.

  Then, due to the rise of the oil level 28 and the pressure rise in the oil storage chamber 26, the lubricating oil in the oil storage chamber 26 passes through the flow path 21 and flows into the one chamber R1 together with the working gas. Here, since the opening position of the opening 21a of the flow path 21 is located above the lowermost end of the seal 24, even if the lubricating oil moves from the oil storage chamber 26 into the one chamber R1 as described above, the oil storage chamber. The oil surface 28 of the lubricating oil in the oil 26 is always located above the lowermost end of the seal 24, and the lubricating oil in the oil storage chamber 26 maintains the lubrication of the sliding portion 27 between the rod 3 and the seal 24. In addition, the sliding portion between the rod 3 and the bearing 18 is continuously lubricated in the same manner. Note that a check valve 23 is provided in the middle of the flow path 22 of the bottom member 16, and this check valve 23 can prevent backflow of gas to the oil storage chamber 26 side. A check valve that allows only the flow from 19 to the one chamber R1 is not provided.

  Thus, even if the shock absorber D1 repeats vibration, the lubricating oil in the oil storage chamber 26 lubricates the sliding portion 27 between the rod 3 and the seal 24 and the sliding portion between the rod 3 and the bearing 18. Since the lubricating oil circulates through the one chamber R1 and the other chamber R2 due to vibration and continues to lubricate the sliding portion 30 between the cylinder 1 and the piston 2, it is formed upright. The smooth vibration operation of the shock absorber D1 is ensured, and the reliability of the shock absorber D1 is improved.

  Further, in the shock absorber D1 in the present embodiment, the oil storage chamber 26 facing the sliding portion of the rod 3 is provided, and the oil surface 28 is positioned above the lowermost end of the sliding portion 27, whereby the sliding portion 27 and the sliding part between the rod 3 and the bearing 19 can be surely lubricated, so that the structure is not complicated and the shock absorber is made upright without significant cost increase. Can do.

  Further, as described above, since the sliding portion 27 of the rod 3 and the sliding portion between the rod 3 and the bearing 18 are reliably lubricated, the smooth vibration operation of the shock absorber D is also guaranteed in this respect. The reliability of the shock absorber D1 is improved, and the wear resistance of the seal 24 is improved, so that the sealing performance of the shock absorber D1 is also improved.

  Next, the operation of the shock absorber D1 configured as described above will be described. First, the piston 2 in the shock absorber D1 moves upward with respect to the cylinder 1, the piston 2 continues to move upward sufficiently with respect to the cylinder 1, and the valve 9 protrudes from the piston 2 to the maximum in FIG. In the state shown, the one chamber R1 is compressed and the other chamber R2 is expanded, so that the pressure in the one chamber R1 increases, and the working gas in the one chamber R1 passes through the passage 4 and enters the other chamber R2. Try to move on.

  Since the one chamber R1 is compressed and the pressure rises in the one chamber R1, the gas moves to the other chamber R2 by pushing the leaf valve 6 closing the passage 4, and the shock absorber D1 is predetermined. Generates a damping force. Subsequently, when the moving direction of the piston 2 with respect to the cylinder 1 is reversed and the piston 2 moves downward with respect to the cylinder 1, this time the one chamber R1 is expanded and the other chamber R2 is compressed. The pressure inside the chamber increases, and the working gas in the other chamber R2 passes through the passage 5 and tends to move into the one chamber R1. In addition to this, since the moving direction of the piston 2 relative to the cylinder 1 is switched, the valve 9 returns from the state shown in FIG. 4 to the neutral position shown in FIG. When 2 continues to move sufficiently without changing the moving direction with respect to the cylinder 1, it finally shifts to the state shown in FIG. 3 and closes the bypass path 8.

  Here, immediately after the moving direction of the piston 2 with respect to the cylinder 1 is switched from the upper side to the lower side in the figure, the pressure in the one chamber R1 is still higher than the pressure in the other chamber R2, and the bypass path bypasses the passage 4. 8 is opened, so that while the bypass passage 8 is open, the gas passes from the one chamber R1 to the other chamber R2 preferentially through the bypass passage 8 which does not give resistance to the gas flow compared to the passage 4. The pressure in the one chamber R1 is quickly released to the other chamber R2, realizing a rapid decrease in the pressure in the one chamber R1 and a rapid increase in the pressure in the other chamber R2, The pressure change in the one chamber R1 and the other chamber R2 is prevented from being delayed in phase with respect to the vibration speed change.

  Then, the piston 2 continues to move downward sufficiently with respect to the cylinder 1, and the valve 9 enters the state shown in FIG. 3 and closes the bypass passage 8. The movement to the chamber R1 is performed only through the passage 5, and the gas moves to the chamber R1 by pushing the leaf valve 7 closing the passage 5, and the buffer D1 A predetermined damping force is generated.

  On the other hand, from this state, the moving direction of the piston 2 relative to the cylinder 1 is reversed again, and immediately after the switching of the moving direction, the pressure in the other chamber R2 is still higher than the pressure in the one chamber R1. Since the bypass passage 8 that bypasses the passage 5 is opened, the bypass passage 8 that gives no resistance to the gas flow as compared with the passage 5 preferentially passes the gas while the bypass passage 8 is open. Is moved from the other chamber R2 to the one chamber R1, and the accumulated pressure in the other chamber R2 is quickly released to the one chamber R1, and the pressure in the other chamber R2 is quickly reduced and the pressure in the one chamber R1 is released. Of the pressure in the one chamber R1 and the other chamber R2 is prevented from being delayed in phase with respect to the vibration speed change.

  Therefore, according to the shock absorber D1, as shown in FIG. 5, when the movement direction of the piston 2 with respect to the cylinder 1 is switched, the pressure in the one of the chambers R1 or the other chamber R2 that has been compressed is expanded. One chamber R1 can be urged to escape to the room that has been done, and to promptly increase the pressure in the expansion side chamber to be compressed and to quickly decrease the pressure in the compression side chamber to be expanded. And the reaction to the change of the vibration speed of the differential pressure change of the other chamber R2 is accelerated.

  That is, in the shock absorber D1, the phase delay of the pressure change in the one chamber R1 and the other chamber R2 with respect to the vibration speed change in the shock absorber D1 can be alleviated, so that the vibration damping property of the shock absorber D1 is improved. It is possible to dramatically improve the riding comfort in the vehicle, and in particular, it is possible to reduce the hysteresis of the generated damping force with respect to the speed during high-frequency vibration. That is, according to the shock absorber D1 of the present embodiment, it is possible to solve the problem that the vibration damping property is deteriorated because the speed damping force characteristic has a large hysteresis as in the conventional shock absorber.

  Note that in the contraction stroke of the shock absorber D1, the gas enclosed in the other chamber R2 passes through the passage 5 provided in the piston 2 and flows into the one chamber R1, so that the flow path 22 and the circulation path are clear. 17, at least one of the flow path 20 and the flow path 21 gives a larger resistance to the flow of gas and oil than the leaf valve 7, and this resistance is from the other chamber R2 to the flow path 22, the circulation path 17, and the flow path 20. Alternatively, a valve may be provided between the other chamber R2 and the one chamber R1 via the flow path 21, the circulation passage 17, the flow path 20, and the flow path 21. For example, the check valve 23 may be a leaf valve or the flow passage area of the circulation passage 17 may be minimized.

  Next, a shock absorber D2 in a modification of the embodiment shown in FIG. 6 will be described. This shock absorber D2 has the same structure as the above-described shock absorber D1, but a pressure-dependent opening element 32 that opens the bypass passage 8 only when the absolute value of the difference between the pressure in the one chamber R1 and the pressure in the other chamber R2 exceeds a predetermined pressure. Is added.

  That is, the valve 31 in the shock absorber D2 includes the pressure-dependent opening element 32 in addition to the direction switching sensing opening element 33 that adopts the same structure as that of the valve 9 of the embodiment. Yes.

  Since the other configuration of the shock absorber D2 is the same as that of the above-described shock absorber D1, the description of the same components as those of the shock absorber D1 in the shock absorber D2 is repeated, and therefore only the same reference numerals are given. Detailed description thereof will be omitted.

  The direction switching sensing opening element 33 includes a base portion 33a that is in sliding contact with the inner periphery of the cylinder 1, and a valve hole that rises from the base portion 33a and opens from the lower end in FIG. 10 includes a shaft portion 33b slidably accommodated in the shaft 10 and a through hole 33c provided in the shaft portion 33b, and exhibits the same operation as the valve 9 in the above-described embodiment. That is, since the direction switching sensing opening element 33 makes the through hole 33c face the bypass path 8 in the neutral position, each time the movement direction of the piston 2 relative to the cylinder 1 is switched, the one end bypass path 8 is opened, and thereafter Until the moving direction is switched, the bypass path 8 is kept blocked.

  On the other hand, the pressure-dependent release element 32 includes a spool 35 provided in the piston 2 and slidably received in a valve hole 34 that intersects the middle of the bypass path 8, and a pair of biasing the spool 35 from both ends. Spring elements 36 and 37 are provided.

  Further, the spool 35 includes small-diameter portions 35a and 35b arranged in two positions in the axial direction, and the outer periphery between the small-diameter portions 35a and 35b is bypassed in a state where the spool 35 is biased by the spring elements 36 and 37 and is positioned at the neutral position. The bypass path 8 is blocked against the path 8.

  Further, the upper part of the valve hole 34 in FIG. 6 communicates with the one chamber R1 to apply the pressure in the one chamber R1 to the upper end of the spool 35 in FIG. 6, and the lower part of the valve hole 34 in FIG. It communicates with the other chamber R2 so that the pressure in the other chamber R2 acts on the middle and lower ends.

  When the pressure in the one chamber R1 exceeds the pressure in the other chamber R2 by a predetermined pressure, the spool 35 moves downward in FIG. 6 so that the small-diameter portion 35a faces the bypass path 8 and communicates with the bypass path 8. On the other hand, when the pressure in the other chamber R2 exceeds the pressure in the one chamber R1 by a predetermined pressure, it moves upward in FIG. 6 so that the small diameter portion 35b faces the bypass path 8 and communicates with the bypass path 8. .

  Therefore, the pressure-dependent release element 32 is configured to bring the bypass path 8 into communication when the absolute value of the difference between the pressure in the one chamber R1 and the pressure in the other chamber R2 exceeds a predetermined pressure. The predetermined pressure, which is a condition for releasing the pressure, can be set by the spring constant of the spring elements 36, 37 and the distance between the small diameter portions 35a, 35b. By setting this predetermined pressure as low as possible, This is preferable because the effect of reducing the delay in the pressure change with respect to the vibration speed change is enhanced.

  Now, in the shock absorber D2 of this embodiment, in addition to the direction switching sensing open element 33 having the same configuration as the valve 9 in the shock absorber D1, the pressure-dependent open element 32 has the pressure in the one chamber R1. Only when the absolute value of the difference from the pressure in the other chamber R2 exceeds a predetermined pressure, the bypass path 8 is brought into a communication state.

  Therefore, when the vibration speed of the shock absorber D2, that is, the moving speed of the piston 2 relative to the cylinder 1 is relatively low, it takes time until the direction switching sensing opening element 33 opens the bypass path 8 and closes it. Even so, when the pressure-dependent release element 32 eliminates the difference between the pressure in the one chamber R1 and the pressure in the other chamber R2, the bypass passage 8 is shut off, so that either the one chamber R1 or the other chamber R2 has been compressed to that point. After the internal pressure of the room is released into the expanded room, the bypass path 8 is immediately shut off, and the pressure is expanded with a rapid pressure increase in the expansion side room that is subsequently compressed. Thus, it is possible to promptly reduce the pressure in the compression side chamber.

  In other words, in the shock absorber D2, the vibration speed of the shock absorber D2 is relatively low, and it takes time until the direction switching sensing opening element 33 opens the bypass path 8 until it closes. However, the reaction to the change in the vibration speed of the differential pressure change between the one chamber R1 and the other chamber R2 can be accelerated. Even in such a case, the one chamber R1 and the other chamber to the vibration speed change in the shock absorber D2 can be accelerated. Since the phase lag of the pressure change of R2 can be relaxed, the vibration damping property of the shock absorber D2 can be improved, and the riding comfort in the vehicle can be dramatically improved. The hysteresis of the generated damping force with respect to the speed at the time can be reduced. That is, according to the shock absorber D2 of the present embodiment, it is possible to further eliminate the problem that the vibration damping property is deteriorated because the speed damping force characteristic has a large hysteresis like the conventional shock absorber. .

  Furthermore, in this shock absorber D2, the vibration state of small amplitude is continued, the direction switching sensing release element 33 vibrates little by little in the vicinity of the neutral position with respect to the piston 2, and the through hole 33c does not face the bypass path 8. Even in a state where it cannot be displaced to the position, that is, a state where the bypass path 8 cannot be closed, the pressure-dependent release element 32 has a predetermined absolute value of the difference between the pressure in the one chamber R1 and the pressure in the other chamber R2. Since the bypass path 8 is blocked until the pressure is exceeded, it is possible to avoid a situation in which the damping force cannot be exhibited at all even in such a case.

  Finally, the shock absorber D3 of another embodiment shown in FIG. 7 will be described. In the shock absorber D3 of this other embodiment, the bypass path is composed of the one-side bypass path 40 and the other-side bypass path 41, and the valve 50 in the other embodiments has these one-side bypass paths. One of the path 40 and the other side bypass path 41 is selectively opened.

  Specifically, the bypass path includes a one-side bypass path 40 that allows only a flow from one chamber R1 to the other chamber R2, and an other-side bypass path 41 that allows only a flow from the other chamber R2 to the one chamber R1. The piston 2 is provided.

  And the valve 50 in this buffer D3 is in the middle of the direction switching sensing opening element 51 that adopts a configuration substantially similar to the configuration of the valve 9 of one embodiment, and the one side bypass path 40 and the other side bypass path 41. The one-side pressure-dependent release element 52 and the other-side pressure-dependent release element 53, and the shutter 54 that selectively communicates only one of the one-side bypass path 40 and the other-side bypass path 41, respectively. .

  The direction switching sensing release element 51 includes a base 51a that is in sliding contact with the inner periphery of the cylinder 1, and a valve that rises from the base 51a and opens from one end of the piston 2 and intersects the middle of the one-side bypass path 40 and the other-side bypass path 41. A shaft portion 51b that is slidably accommodated in the hole 55, two through holes 51c and 51d provided in the shaft portion 51b, and a pair of abutting pieces 51e and 51f provided above and below the shaft portion 51b in FIG. It is configured with.

  In addition, the bottom of the valve hole 55 is in the middle of the one-side bypass passage 40 and to the other chamber R2 by the branch passage 14 that branches from the one-side pressure-dependent opening element 52 and the direction switching sensing opening element 51 from the other chamber R2 side. The upper and lower pressure receiving areas that communicate with each other and receive the pressure in the other chamber R2 of the direction switching sensing opening element 51 are the same area, and the direction switching sensing opening element 51 is prevented from being moved by the pressure in the other chamber R2. . In the case of this embodiment, the branch passage may be branched from the other chamber R2 side in the middle of the other side bypass passage 41 and from the other side pressure-dependent opening element 53 and the direction switching sensing opening element 51. Further, in order to communicate the bottom portion of the valve hole 55 to the other chamber R2, an independent passage communicating directly with the other chamber R2 is used without using the one side bypass passage 40 or the other side bypass passage 41. Also good.

  Further, the piston 2 is provided with passages 42 and 43 corresponding to the damping force generation passages 4 and 5 of the embodiment, and allows passage of gas from the other chamber R2 toward the one chamber R1. 43 is common to a part of the other side bypass passage 41, and is branched from the other chamber R 2 side from the intersection with the valve hole 55 in the middle of the other side bypass passage 41 and becomes an outlet end by the leaf valve 7. The middle upper end is opened and closed. In the case of this embodiment, the passage 43 is not branched from the other-side bypass passage 41, but is branched from the other chamber R2 side from the intersection with the valve hole 55 in the middle of the one-side bypass passage 40. Alternatively, the first bypass passage 40 and the second bypass passage 41 may be independent from each other.

  Returning, the vertical length in FIG. 7 which is the axial length of the shaft portion 51 b of the direction switching sensing release element 51 is the same as that of the leaf valve 6 or the leaf valve 6, even if its upper end abuts against the bottom portion of the valve hole 55. The length is set so as not to interfere with the fixed portion fixed to the piston 2, so that the leaf valve 6 is not hindered from being bent, and the passages 42 and 43 are not blocked by the base 51a.

  Furthermore, the base 51a is provided with a through hole 51g that communicates the space B partitioned by the base 51a and the piston 2 to the other chamber R2, and hinders the movement of gas to the one chamber R1 and the other chamber R2. There is no such thing.

  Further, the shaft 51b is slidable on the inner periphery of the tube 56 in which the outlet side of the valve hole 55, which is the lower side in FIG. 7 from the installation position of the abutting piece 51f, is fitted in the vicinity of the outlet of the valve hole 55 in FIG. The direction switching sensing opening element 51 is prevented from falling off the valve hole 55, and the direction switching sensing opening element 51 is moved downward in FIG. The movement is restricted, and a downward movement limit of the direction switching sensing release element 51 is set.

  As described above, the upper end of the shaft portion 51b of the direction switching sensing release element 51 is movable upward in FIG. 7 until the upper end of the shaft portion 51b comes into contact with the upper surface as the bottom of the valve hole 55. The movement limit to is set.

  When the direction switching sensing release element 51 is located at the center with respect to the upper and lower movement limits described above, that is, when it is in the neutral position shown in FIG. 7, the through hole 51 c is the valve of the one-side bypass passage 40. The one-side bypass passage 40 is in communication with the opening to the hole 55, and the through-hole 51 d is in communication with the opening to the valve hole 55 in the other-side bypass passage 41. It is supposed to be.

  On the other hand, the direction-switching sensing opening element 51 is displaced upward or downward from the neutral position shown in FIG. 7, so that the one-side bypass passage 40 and the other-side bypass passage corresponding to the through holes 51c and 51d. If it cannot oppose the opening of 41, the one side bypass path 40 and the other side bypass path 41 will be in the interruption | blocking state.

  Further, the outer periphery of the base portion 51a is in sliding contact with the inner periphery of the cylinder 1 as described above, but the frictional force generated between the base portion 51a and the cylinder 1 is caused by the shaft portion 51b of the direction switching sensing release element 51 and the cylinder 56. When the piston 2 in FIG. 7 moves upward with respect to the cylinder 1 in FIG. 7, the direction switching sensing release element 51 causes the cylinder 56 to move to the abutting piece 51f. Until the collision, the piston 2 does not follow the upward movement with respect to the cylinder 1, and when the piston 2 continues to move upward with respect to the cylinder 1, the piston 2 finally protrudes to the maximum. On the other hand, when the piston 2 moves downward with respect to the cylinder 1 in FIG. 7, the piston 2 moves downward with respect to the cylinder 1 until the direction switching sensing release element 51 hits the bottom of the valve hole 55. If the piston 2 continues to move downward with respect to the cylinder 1 without following, the valve 2 will eventually enter the valve hole 55 until it contacts the bottom of the valve hole 55.

  Accordingly, when the piston 2 moves downward with respect to the cylinder 1 and the direction switching sensing release element 51 enters the valve hole 55 most, the movement direction of the piston 2 with respect to the cylinder 1 is reversed and moved upward. When the direction switching sensing opening element 51 returns to the neutral position shown in FIG. 7 and the piston 2 continues to move upward with respect to the cylinder 1 thereafter, the direction switching sensing opening element 51 is in the most projecting state. Subsequently, when the moving direction of the piston 2 relative to the cylinder 1 is reversed from this state and this time it moves downward, the direction switching sensing release element 51 returns to the neutral position shown in FIG. If the movement continues downward, the direction switching sensing release element 51 enters the most intrusion state.

  If this is continued, every time the moving direction of the piston 2 relative to the cylinder 1 is switched, the direction switching sensing release element 51 returns to the neutral position at one end and the one side bypass path 40 and the other side bypass path 41 are in communication. When there is no change in the moving direction of the piston 2 relative to the cylinder 1, the direction switching sensing release element 51 is positioned at the most protruding or most intruding position from the valve hole 55 to block the one side bypass path 40 and the other side bypass path 41. Will do. That is, when the moving direction of the piston 2 with respect to the cylinder 1 is switched, that is, when the expansion / contraction direction of the shock absorber D3 is switched, the direction switching sensing release element 51 communicates with the one-side bypass path 40 and the other-side bypass path 41. When the movement of the piston 2 with respect to the cylinder 1 continues and there is no change in the direction, the one-side bypass passage 40 and the other-side bypass passage 41 function to be shut off. As can be understood from the above description, the direction switching detection opening element 51 opens the one-side bypass path 40 and the other-side bypass path 41 when detecting the switching of the movement direction of the piston 2 with respect to the cylinder 1. .

  Subsequently, the one-side pressure-dependent opening element 52 is provided in the middle of the one-side bypass passage 40, and only opens the one-side bypass passage 40 when the pressure in the one chamber R1 exceeds the pressure in the other chamber R2. It is like that.

  Specifically, the one-side pressure-dependent release element 52 is provided in the piston 2 independently of the passages 42, 43, the one-side bypass passage 40 and the other-side bypass passage 41 and intersects the middle of the one-side bypass passage 40. The spool 58 is slidably accommodated in the 57, a pair of spring elements 59 and 60 for biasing the spool 58 from both ends, and a stopper 61 for setting the upper and lower movement limits of the spool 58 in FIG. , 62.

  The spool 58 is provided with a small diameter portion 58a in the middle, and is urged by the spring elements 59 and 60 to be positioned at a position where the upper end abuts against the upper stopper 61. At this position, the spool 58 is located below the small diameter portion 58a. The outer periphery of this is opposed to the one-side bypass passage 40 and blocks the one-side bypass passage 40.

  Further, the upper part of the valve hole 57 in FIG. 7 communicates with the one chamber R1 to apply the pressure in the one chamber R1 to the upper end of the spool 58 in FIG. 7, and the lower part of the valve hole 57 in FIG. It communicates with the other chamber R2 so that the pressure in the other chamber R2 acts on the middle and lower ends.

  When the pressure in the one chamber R1 exceeds the pressure in the other chamber R2 by a predetermined pressure, the spool 58 moves downward in FIG. 7 so that the small-diameter portion 58a faces the one-side bypass passage 40 and the one-side bypass In other situations, the passage 40 is communicated, and the one-side bypass passage 40 is blocked by being positioned upward in FIG. If the pressure in the one chamber R1 exceeds the pressure in the other chamber R2 by a predetermined pressure, the stopper 62 comes into contact with the spool 58 and restricts further downward movement of the spool 58. Below, the one side bypass path 40 can be reliably maintained in a communicating state.

  Accordingly, the one-side pressure-dependent opening element 52 is configured to bring the one-side bypass passage 40 into communication only when the pressure in the one chamber R1 exceeds the pressure in the other chamber R2 by a predetermined pressure. The predetermined pressure, which is a condition for releasing the pressure, can be set by the spring constant of the spring elements 59, 60 and the position of the small diameter portion 58a with respect to the spool 58, and by setting this predetermined pressure as low as possible. This is preferable because the effect of reducing the delay in the pressure change with respect to the vibration speed change is enhanced.

  The other-side pressure-dependent opening element 53 is provided in the middle of the other-side bypass passage 41 so that the other-side bypass passage 41 is opened only when the pressure in the other chamber R2 exceeds the pressure in the one chamber R1. It has become.

  Specifically, even in the other-side pressure-dependent release element 53, the piston 2 is provided independently of the passages 42 and 43, the one-side bypass passage 40 and the other-side bypass passage 41 and intersects the middle of the other-side bypass passage 41. A spool 64 slidably accommodated in the valve hole 63, a pair of spring elements 65 and 66 for urging the spool 64 from both ends, and a limit for moving the spool 64 upward and downward in FIG. The stoppers 67 and 68 are configured.

  The spool 64 is provided with a small diameter portion 64a in the middle, and is positioned at a position where the lower end is in contact with the lower stopper 68 by being urged by the spring elements 65, 66. The outer periphery of this is opposed to the other side bypass path 41 so as to block the other side bypass path 41.

  Further, the upper part of the valve hole 63 in FIG. 7 communicates with the one chamber R1 to apply the pressure in the one chamber R1 to the upper end of the spool 64 in FIG. 7, and the lower part of the valve hole 63 in FIG. It communicates with the other chamber R2 so that the pressure in the other chamber R2 acts on the middle and lower ends.

  Then, when the pressure in the other chamber R2 exceeds the pressure in the one chamber R1 by a predetermined pressure, the spool 64 moves upward in FIG. 7 so that the small diameter portion 64a faces the other side bypass passage 41 and the other side bypass. In other situations, the path 41 is communicated, and the other side bypass path 41 is blocked by being positioned downward in FIG. If the pressure in the other chamber R2 exceeds the pressure in the one chamber R1 by a predetermined pressure, the stopper 67 comes into contact with the spool 64 and restricts further upward movement of the spool 64. Below, the other side bypass path 41 can be reliably maintained in a communicating state.

  Therefore, the other-side pressure-dependent opening element 53 is configured to bring the other-side bypass passage 41 into communication only when the pressure in the other chamber R2 exceeds the pressure in the one chamber R1 by a predetermined pressure. The predetermined pressure, which is a condition for releasing the pressure, can be set by the spring constants of the spring elements 65 and 66 and the position of the small diameter portion 64a with respect to the spool 64. The predetermined pressure is preferably set as low as possible. This is preferable because the effect of reducing the delay in the pressure change with respect to the vibration speed change is enhanced.

  Furthermore, the shutter 54 is provided with holes 70 a, 70 b, 71 a, 71 b that are tubular and communicate with the inside and outside, and are slidably mounted on the outer periphery of the shaft portion 51 b of the direction switching sensing release element 51, so that the inside of the valve hole 55. Is inserted together with the shaft portion 51b.

  Further, the shutter 54 can be slid in the vertical direction in FIG. 7 on the shaft 51b, and the abutting pieces 51e provided at positions sandwiching the shutter 54 with an interval from the shaft 51b. The upper and lower movement limits with respect to the shaft portion 51b are set by 51f.

  When the shutter 54 comes into contact with the abutting piece 51e provided above the shaft 51b, that is, when the shutter 54 reaches the upper movement limit with respect to the shaft 51b, the holes 71a and 71b provided on the lower side are provided. Is opposed to the through hole 51d provided in the shaft portion 51b, and the shutter 54 is in contact with the abutting piece 51f provided below the shaft portion 51b, that is, the shutter 54 is in contact with the shaft portion 51b. On the other hand, when the lower movement limit is reached, the holes 70a and 70b provided on the upper side are opposed to the through holes 51c provided on the shaft portion 51b.

  Further, in a state where the holes 70a and 70b of the shutter 54 face the one-side bypass path 40, the holes 71a and 71b do not face the other-side bypass path 41, and the shutter 54 blocks the other-side bypass path 41 and is opposite. In addition, in a state where the holes 71a and 71b of the shutter 54 face the other side bypass path 41, the holes 70a and 70b do not face the one side bypass path 40 and the shutter 54 blocks the one side bypass path 40. It has become. Therefore, the shutter 54 selectively communicates only one of the one side bypass path 40 and the other side bypass path 41.

  Further, the frictional force generated between the outer periphery of the shutter 54 and the valve hole 55 is set to be larger than the frictional force generated between the outer periphery of the shaft portion 51 b of the direction switching sensing release element 51 and the inner periphery of the shutter 54. The shutter 54 is displaced with respect to the valve hole 55 without following the displacement of the direction switching sensing release element 51 in a state where it does not collide with any of the abutting pieces 51e and 51f provided on the shaft portion 51b. Instead, only the direction switching sensing opening element 51 is displaced. On the other hand, in a state where the shutter 54 collides with the upper abutting piece 51e provided in the shaft portion 51b, the direction switching sensing release element 51 follows the downward displacement and moves downward along with the direction switching sensing release element 51. In the state where the shutter 54 abuts on the lower abutting piece 51f provided on the shaft portion 51b, the direction switching sensing release element 51 is followed along with the upward movement of the direction switching sensing release element 51. It is designed to be displaced upward.

  Next, the operation of the shock absorber D3 of another embodiment configured as described above will be described. First, when the shock absorber D3 vibrates in the extending direction from the state shown in FIG. 7 and the piston 2 continues to move sufficiently upward with respect to the cylinder 1, as shown in FIG. Is displaced downward with respect to the piston 2 and protrudes most from the valve hole 55 to block the one-side bypass passage 40 and the other-side bypass passage 41, and the shutter 54 has an upper end above the shaft portion 51b. It collides with the side abutting piece 51e and moves downward with respect to the piston 2 together with the direction switching sensing release element 51, and the one side bypass path 40 with the upper holes 70a and 70b facing the one side bypass path 40. Is opened and the other bypass path 41 is shut off.

  On the other hand, since the pressure in the one chamber R1 increases and the pressure in the other chamber R2 decreases, the pressure in the one chamber R1 exceeds the pressure in the other chamber R2 by a predetermined pressure. And the other side pressure-dependent opening element 53 puts the other side bypass passage 41 in a blocked state.

  As a result, when the moving direction of the piston 2 with respect to the cylinder 1 is not switched and the piston 2 simply moves upward with respect to the cylinder 1, as shown in the table of FIG. 15, the one-side bypass path 40 and the other-side bypass path 41 is cut off and gas is moved from one chamber R1 to the other chamber R2 only through the passage 42. That is, in the state transitioning from FIG. 7 to FIG. 8, the damping characteristic of the shock absorber D3 (representing the relationship between speed and damping force) is as shown by the line a in FIG.

  Further, when the moving direction of the piston 2 relative to the cylinder 1 is switched from the state shown in FIG. 8 and the shock absorber D3 is contracted, the direction switching sensing release element 51 is displaced upward with respect to the piston 2 as shown in FIG. The one side bypass path 40 and the other side bypass path 41 communicate with each other. When the direction switching sensing release element 51 shifts from the state shown in FIG. 8 to the state shown in FIG. 9, the shutter 54 does not collide with any of the abutting pieces 51e and 51f of the shaft portion 51b, so that the direction is switched. Without following the displacement of the sensing opening element 51, the one-side bypass path 40 is opened and the other-side bypass path 41 is maintained in the cut-off state.

  On the other hand, even if the movement direction of the piston 2 with respect to the cylinder 1 is switched, there is a delay in the pressure change in the one chamber R1 and the other chamber R2, so that the pressure in the one chamber R1 is high and the other chamber R2 The one side bypass path 40 is in a communicating state, and the other side pressure dependent opening element 53 conversely puts the other side bypass path 41 in a blocked state.

  As a result, immediately after the movement direction of the piston 2 with respect to the cylinder 1 is switched from the upper side to the lower side, as shown in the table of FIG. 15, the one-side bypass path 40 is opened, and the other-side bypass path 41 is in a cut-off state. When the high-pressure gas in the one chamber R1 escapes to the other chamber R2 by opening the one-side bypass passage 40, and the pressure in the one chamber R1 does not exceed the pressure in the other chamber R2, as shown in FIG. The one-side pressure-dependent release element 52 is cut off, and the communication between the one chamber R1 and the other chamber R2 by the one-side bypass passage 40 is cut off. Then, for the subsequent downward movement of the piston 2 relative to the cylinder 1, the gas is moved from the other chamber R2 to the one chamber R1 only through the passage 43.

  That is, when the moving direction of the piston 2 with respect to the cylinder 1 is switched from the upper side to the lower side, the pressure in the one chamber R1 is quickly decreased and the pressure in the other chamber R2 is rapidly increased. When the pressure in the one chamber R1 does not exceed the pressure in the other chamber R2 by a predetermined pressure, the one-side pressure-dependent release element 52 is cut off, and the other chamber is compressed by switching the moving direction of the piston 2 relative to the cylinder 1. Since the pressure of R2 can be quickly increased, the rising of the damping force after switching of the moving direction of the piston 2 with respect to the cylinder 1 can be sharpened, and the damping force is generated in the buffer D3 with high responsiveness. Can be made.

  That is, in the state transitioning from FIG. 8 to FIG. 9 and FIG. 10, the pressure in the one chamber R1 is quickly decreased and the pressure in the other chamber R2 is rapidly increased. The damping characteristic of the shock absorber D3 (showing the relationship between speed and damping force) is as shown by the line b in FIG.

  Therefore, the phase delay of the pressure change in the one chamber R1 and the other chamber R2 with respect to the vibration speed change in the shock absorber D3 can be alleviated, the vibration damping property of the shock absorber D3 can be improved, and the riding comfort in the vehicle can be improved. In particular, the hysteresis of the generated damping force with respect to the speed during high-frequency vibration can be reduced.

  Subsequently, when the downward movement of the piston 2 with respect to the cylinder 1 is continued without switching the movement direction of the piston 2 with respect to the cylinder 1 from the state shown in FIG. 10, as shown in FIG. Is displaced upward with respect to the piston 2 and enters the valve hole 55 to block the one-side bypass passage 40 and the other-side bypass passage 41. The lower end of the shutter 54 collides with the abutting piece 51f on the lower side of the shaft portion 51b and moves upward with respect to the piston 2 together with the direction switching sensing release element 51, and the lower holes 71a and 71b are moved to the other side. The other side bypass path 41 is opened while being opposed to the side bypass path 41, and the one side bypass path 40 is set in a cut-off state.

  On the other hand, the one-side pressure-dependent release element 52 is in a state where the pressure in the other chamber R2 is increased and the pressure in the one chamber R1 is lowered. The pressure in the other chamber R2 exceeds the pressure in the one chamber R1 by a predetermined pressure to bring the other side bypass passage 41 into a communicating state.

  As a result, when the moving direction of the piston 2 with respect to the cylinder 1 is not switched and the piston 2 simply moves downward with respect to the cylinder 1, as shown in the table of FIG. The passage 41 is cut off, and gas is moved from the other chamber R2 to the one chamber R1 only through the passage 43. That is, in the state transitioning from FIG. 10 to FIG. 11, the damping characteristic of the shock absorber D3 (showing the relationship between speed and damping force) is as shown by the line c in FIG.

  When the transition from FIG. 10 to FIG. 11 is performed, if there is no shutter 54, the other-side bypass passage 41 is kept open until the through hole 51d in the direction switching sensing opening element 51 shifts to the state of FIG. In addition, the other-side pressure-dependent release element 53 may cause the other-side bypass passage 41 to communicate, and the other chamber R2 and one chamber R1 communicate with each other through the other-side bypass passage 41 to increase the pressure in the other chamber R2. And the damping force cannot be generated immediately after the movement direction of the piston 2 with respect to the cylinder 1 is switched. However, due to the presence of the shutter 54, the state shown in FIGS. In the state of FIG. 12 during the transition, the communication between the through hole 51d and the other bypass path 41 is prevented, and the other bypass path 41 is cut off. No trouble, the moving direction is to be able to generate a rapidly damping force after Tsu switching with respect to the cylinder 1 of the piston 2.

  Further, when the moving direction of the piston 2 with respect to the cylinder 1 is switched from the state shown in FIG. 11 and the piston 2 moves upward with respect to the cylinder 1, the direction switching sensing release element 51 is moved to the piston 2 as shown in FIG. On the other hand, it is displaced downward to allow the one-side bypass path 40 and the other-side bypass path 41 to communicate with each other. When the direction switching sensing release element 51 shifts from the state shown in FIG. 11 to the state shown in FIG. 13, the shutter 54 does not collide with any of the abutting pieces 51e and 51f of the shaft portion 51b, so that the direction is switched. Without following the displacement of the sensing opening element 51, the other side bypass path 41 is opened and the one side bypass path 40 is maintained in the cut-off state.

  On the other hand, even if the movement direction of the piston 2 relative to the cylinder 1 is switched, the one-side pressure-dependent release element 52 is delayed in the pressure change in the one chamber R1 and the other chamber R2, so that the pressure in the one chamber R1 is low and the other chamber R2 The one side bypass path 40 is shut off, and the other side pressure dependent opening element 53 conversely places the other side bypass path 41 in a communicating state.

  As a result, immediately after the moving direction of the piston 2 relative to the cylinder 1 is switched from the lower side to the upper side, as shown in the table of FIG. 15, the other side bypass path 41 is opened and the one side bypass path 40 is cut off. When the high-pressure gas in the other chamber R2 escapes to the one chamber R1 due to the opening of the other-side bypass passage 41 and the pressure in the other chamber R2 does not exceed the pressure in the one chamber R1 by a predetermined pressure, as shown in FIG. The other-side pressure-dependent release element 53 is cut off, and the communication between the one chamber R1 and the other chamber R2 through the other-side bypass passage 41 is cut off. Then, for subsequent upward vibration of the shock absorber D3, the gas is moved from the one chamber R1 to the other chamber R2 only through the passage 42.

  That is, when the moving direction of the piston 2 with respect to the cylinder 1 is switched from the lower side to the upper side, the pressure in the other chamber R2 is quickly decreased and the pressure in the one chamber R1 is rapidly increased. When the pressure in the other chamber R2 does not exceed the pressure in the one chamber R1 by a predetermined pressure, the other-side pressure-dependent release element 53 enters a shut-off state and is compressed by switching the moving direction of the piston 2 relative to the cylinder 1. Since the pressure of R1 can be quickly increased, the rising of the damping force after switching of the moving direction of the piston 2 with respect to the cylinder 1 can be sharpened, and the damping force is generated in the buffer D3 with high responsiveness. Can be made.

  That is, in the state transitioning from FIG. 11 to FIG. 13 and FIG. 14, the pressure in the other chamber R2 is quickly reduced and the pressure in the one chamber R1 is rapidly increased. The damping characteristic of the shock absorber D3 (representing the relationship between speed and damping force) is as shown by the line d in FIG.

  Therefore, the phase delay of the pressure change in the one chamber R1 and the other chamber R2 with respect to the vibration speed change in the shock absorber D3 can be alleviated, the vibration damping property of the shock absorber D3 can be improved, and the riding comfort in the vehicle can be improved. In particular, the hysteresis of the generated damping force with respect to the speed during high-frequency vibration can be reduced.

  Next, when the upward movement of the piston 2 relative to the cylinder 1 continues without switching the movement direction of the piston 2 relative to the cylinder 1 from the state illustrated in FIG. 14, the state illustrated in FIG. During one cycle of vibration, a series of states from FIG. 8 to FIG. 14 are taken.

  In the transition from the state shown in FIG. 14 to the state shown in FIG. 8, the shutter 54 prevents communication between the through hole 51c and the one-side bypass path 40, and the one-side bypass path 41 is cut off. Therefore, a damping force can be generated promptly after the moving direction of the piston 2 with respect to the cylinder 1 is switched from the lower side to the upper side.

  As described above, even in the shock absorber D3 of this other embodiment, when the movement direction of the piston 2 with respect to the cylinder 1 is switched, the one chamber R1 or the other chamber R2 has been compressed to that point. The pressure in the room is released into the room that has been inflated, and a rapid pressure increase in the room on the expansion side that will be compressed this time and a rapid pressure decrease in the room on the compression side that is to be expanded can be promoted. Therefore, the reaction to the change in the vibration speed of the differential pressure change between the one chamber R1 and the other chamber R2 is accelerated.

  That is, in the shock absorber D3, the phase delay of the pressure change in the one chamber R1 and the other chamber R2 with respect to the vibration speed change in the shock absorber D3 can be alleviated, so that the vibration damping property of the shock absorber D3 is improved. It is possible to dramatically improve the riding comfort in the vehicle, and in particular, it is possible to reduce the hysteresis of the generated damping force with respect to the speed during high-frequency vibration. That is, according to the shock absorber D3 of the present embodiment, it is possible to solve the problem that the vibration damping property is deteriorated because the speed damping force characteristic has a large hysteresis like the conventional shock absorber.

  Further, the vibration speed of the shock absorber D3, that is, the moving speed of the piston 2 relative to the cylinder 1 is relatively low, and the direction switching sensing release element 51 opens the one side bypass path 40 or the other side bypass path 41. Even if it takes time to close, one side pressure-dependent release element 52 or the other side pressure-dependent release element 53 corresponds to the difference between the pressure in one chamber R1 and the pressure in the other chamber R2, respectively. Since the side bypass path 40 or the other side bypass path 41 is blocked, the pressure in the one chamber R1 or the other chamber R2 that has been compressed up to that time is released into the expanded chamber and then compressed. It is possible to promote a rapid pressure increase in the expansion side chamber to be accelerated and a rapid pressure decrease in the compression side chamber to be expanded. It made.

  That is, even in the shock absorber D3, the vibration speed is relatively low, and the one-side pressure-dependent release element 52 or the other-side pressure-dependent release element 53 opens the one-side bypass path 40 or the other-side bypass path 41. Even if it takes a long time to close, the reaction to the change in the vibration speed of the differential pressure change between the one chamber R1 and the other chamber R2 can be accelerated. The phase delay of the pressure change in the one chamber R1 and the other chamber R2 with respect to the vibration speed change in D3 can be alleviated, and the vibration damping property of the shock absorber D3 can be improved.

  Further, even in this shock absorber D3, the vibration state with a small amplitude is continued, and the direction switching sensing release element 51 vibrates little by little in the vicinity of the neutral position with respect to the piston 2, and the through holes 51c and 51d are moved to one side. Even if it cannot be displaced to a position where it does not oppose the side bypass path 40 or the other side bypass path 41, the one-side pressure-dependent release element 52 and the other-side pressure-dependent release element 53 have the pressure in the one chamber R1 and the other chamber R2. The one-side bypass passage 40 and the other-side bypass passage 41 are shut off until the difference from the pressure exceeds the predetermined pressure, so that it is possible to avoid a situation where the damping force cannot be exhibited at all even in such a case. Is possible.

  In the above description, the shock absorber is described as a pneumatic shock absorber. However, even if the working fluid is oil or other liquid, it has hysteresis in the speed damping force characteristic against high frequency vibration. Since the hysteresis can be reduced by applying the present invention, the operational effects of the present invention are not lost.

  Further, in each of the above-described embodiments, the bypass path is provided in the piston, and the direction switching sensing release element is moved with respect to the valve hole provided in the piston so as to switch between bypass communication and blocking. Therefore, there is an advantage that it is easy to ensure the stroke length of the shock absorber, but the above-mentioned bypass path and valve hole are provided in the connecting member connected to the piston, and the direction is switched to the valve hole provided in the connecting member. The sensing release element may be configured to be movably inserted.

 It should be noted that the scope of the present invention is not limited to the details shown or described.

It is a schematic longitudinal cross-sectional view of the shock absorber in one embodiment. It is a schematic longitudinal cross-sectional view of the piston part of the shock absorber of one embodiment. It is a schematic longitudinal cross-sectional view of the piston part in the state which the piston in the buffer in one Embodiment moved below with respect to the cylinder. It is a schematic longitudinal cross-sectional view of the piston part in the state which the piston in the buffer in one Embodiment moved upwards with respect to the cylinder. It is the figure which showed the speed damping force characteristic of the buffer in one Embodiment. It is a schematic longitudinal cross-sectional view of the piston part of the shock absorber in one modification of one embodiment. It is a schematic longitudinal cross-sectional view of the piston part of the buffer of other embodiment. It is a schematic longitudinal cross-sectional view of the piston part in the state which the piston in the buffer of other embodiment moved upwards with respect to the cylinder. It is a schematic longitudinal cross-sectional view of the piston part immediately after the moving direction with respect to the cylinder of the piston in the shock absorber of other embodiment switched from upper direction to the downward direction. It is a schematic longitudinal cross-sectional view of the piston part in the state which the movement direction with respect to the cylinder of the piston in the shock absorber of other embodiment switches from the upper direction to the downward direction, and the other side pressure dependence open | release element will be in the interruption | blocking state. It is a schematic longitudinal cross-sectional view of the piston part in the state which the moving direction with respect to the cylinder of the piston in the buffer of other embodiment moved below. It is a schematic longitudinal cross-sectional view of the piston part which shows the state in the middle of the process in which the buffer of other embodiment transfers from the state of FIG. 10 to the state of FIG. It is a schematic longitudinal cross-sectional view of the piston part immediately after the moving direction with respect to the cylinder of the piston in the buffer of other embodiment switched from the downward direction to the upward direction. It is a schematic longitudinal cross-sectional view of the piston part in the state which the moving direction with respect to the cylinder of the piston in the shock absorber of other embodiment switches from the downward direction to the upper direction, and the one side pressure dependence open | release element will be in the interruption | blocking state. It is a table | surface of the operation mode of the direction change sensing open element in the buffer of other embodiment, the one side pressure dependent open element, the other side pressure dependent open element, and a shutter. It is the figure which showed the change characteristic of the damping force with respect to the vibration speed change of the buffer in other embodiment. It is the figure which showed the speed damping force characteristic of the conventional shock absorber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Rod 4,5,42,43 Passage 6,7 Leaf valve 8 which is damping force generation element Bypass path 9,31,50 Valve 9a Base 9b in valve Shaft 9c in valve Through-hole 9d in valve Through hole 9e Small diameter portion 9f in valve Step portions 10, 34, 55, 57, 63 in valve Valve hole 12 Outer cylinder 15 Head member 16 Bottom member 13 Tube 14 Branch passage 17 Circulation passage 18 Bearing 19 Recess 20, 20, 22 Flow Paths 20a, 21a Open end 23 Check valve 24 Seal 25 Sealing member 26 Oil storage chamber 27 Sliding portion 28, 29 between rod and seal Oil level 30 Sliding portion 32 between cylinder and piston Pressure dependent release element 33, 51 Direction switching sensing opening element 33a, 51a Base 33b in direction switching sensing opening element 51b Shaft portion 33 in direction switching sensing opening element , 51c, 51d Through holes 35, 58, 64 in the direction switching sensing opening element 36, 37, 59, 60, 65, 66 Spring element 35a, 36a, 58a, 64a Small diameter portion 40 in the spool One side bypass path 41 The other side Bypass path 51 Direction switching sensing opening element 51e, 51f Abutting piece 51g in direction switching sensing opening element Through hole 52 in direction switching sensing opening element One side pressure dependent opening element 53 The other side pressure dependent opening element 54 Shutter 56 Tube 61, 62 , 67, 68 Stoppers 70a, 70b, 71a, 71b Holes A, B in shutters D1, D2, D3 Buffer R1 One chamber R2 The other chamber

Claims (9)

A shock absorber comprising a cylinder, a piston that divides the inside of the cylinder into one chamber and the other chamber, a passage that connects the one chamber and the other chamber, and a damping force generation element provided in the middle of the passage. A buffer having a bypass path that bypasses and communicates between the one chamber and the other chamber, and a valve that opens the bypass path when a change in the direction of movement of the piston with respect to the cylinder is detected in the middle of the bypass path. vessel. 2. The shock absorber according to claim 1, wherein the valve closes the bypass when the absolute value of the difference between the pressure in the one chamber and the pressure in the other chamber is equal to or lower than a predetermined pressure. The bypass passage is provided in the piston, and the valve is slidably accommodated in a base portion that is in sliding contact with the inner periphery of the cylinder, and a valve hole that rises from the base portion and opens from one end of the piston and intersects the bypass passage. A direction switching sensing opening element having a shaft portion and a through hole or a small diameter portion provided in the shaft portion is provided, and the direction switching sensing opening element is in the neutral position with the through hole or the small diameter portion facing the bypass path. 2. The shock absorber according to claim 1, wherein the shock absorber connects the passage and closes the bypass passage with the side portion of the shaft portion facing the bypass passage when displaced from the neutral position in the axial direction. 4. The shock absorber according to claim 3, wherein the valve includes a pressure-dependent opening element that opens the bypass passage only when the absolute value of the difference between the pressure in the one chamber and the pressure in the other chamber exceeds a predetermined pressure. The bypass path is provided in the piston with a one-side bypass path that allows only a flow from one chamber to the other chamber and an other-side bypass path that allows only a flow from the other chamber to the one chamber. A base that slides in contact with the inner periphery of the cylinder, a shaft that rises from the base, opens from one end of the piston, and is slidably received in a valve hole that intersects the middle of the one-side bypass passage and the other-side bypass passage; A direction switching sensing opening element provided with two through holes or a small diameter portion provided in the section, wherein the direction switching sensing opening element is in a neutral position to connect each through hole or each small diameter portion to the one side bypass path and the other. The one side bypass path and the other side bypass path are communicated with each other so as to face the side bypass path, and when the shaft is displaced from the neutral position in the axial direction, the side portion of the shaft portion is moved to the one side bypass path and the other side bypass path. The shock absorber according to claim 1, characterized in that for closing the one side bypass passage and the other side bypass passage to face the scan path. The bypass passage includes a one-side bypass passage that allows only a flow from one chamber to the other chamber and a second bypass passage that allows only a flow from the other chamber to the one chamber, and is a connecting member that is connected to the piston. The valve is provided in a slidable manner in a base portion that is in sliding contact with the inner periphery of the cylinder and a valve hole that rises from the base portion and opens from one end of the connecting member and intersects the middle of the one-side bypass passage and the other-side bypass passage. And a direction switching sensing opening element having two through holes or a small diameter portion provided in the shaft section, and the direction switching sensing opening element has the through holes or the small diameter portions in a neutral position. The one side bypass path and the other side bypass path are communicated with each other so as to oppose the one side bypass path and the other side bypass path, respectively, and when the shaft is displaced from the neutral position in the axial direction, the side portion of the shaft portion is shifted to the one side bypass. The shock absorber according to claim 1, characterized in that to close the to face the road and the other side bypass passage one side bypass passage and the other side bypass passage. The valve includes a one-side pressure-dependent opening element that opens the one-side bypass passage only when the pressure in one chamber exceeds the pressure in the other chamber, and the other side only when the pressure in the other chamber exceeds the pressure in one chamber. The shock absorber according to claim 5 or 6, comprising a pressure-dependent opening element on the other side for opening the bypass passage. The valve includes a shutter that selectively communicates only one of the one-side bypass path and the other-side bypass path, and the shutter is moved when the moving direction of the piston relative to the cylinder changes from one chamber side to the other chamber side. The shock absorber according to claim 7, wherein the side bypass path is opened, and the other side bypass path is opened when the moving direction of the piston relative to the cylinder changes from the other chamber side to the one chamber side. The shutter is cylindrical and is slidably mounted on the outer periphery of the shaft portion of the direction switching sensing release element and is slidably inserted into the valve hole so as to sandwich the shutter with a space in the shaft portion. A pair of abutting pieces that displace the shutter by colliding with the end of the shutter is provided at the position, and when the direction switching sensing release element is displaced from the neutral position to the one chamber side, the shutter is opened on the one side bypass path. When the direction switching sensing release element is displaced from the neutral position to the other chamber side, the shutter is moved from the state where the other side bypass path is opened to the one side. The shock absorber according to claim 8, wherein the shock absorber is displaced so as to open the bypass path.

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