JP5639882B2 - Shock absorber - Google Patents

Description

  The present invention relates to a shock absorber.

  Among the shock absorbers, there is a shock absorber whose damping force characteristics are variable according to the vibration state (see, for example, Patent Document 1).

Japanese Utility Model Publication No. 7-19642

  By the way, when changing the damping force characteristic according to the vibration state, a characteristic setting such as a smoother change is required.

  Accordingly, an object of the present invention is to provide a shock absorber capable of setting characteristics such as changing the damping force characteristics more smoothly according to the vibration state.

  In order to achieve the above object, the present invention provides a first passage and a second passage through which a working fluid flows from one chamber in a cylinder by movement of a piston, and a damping that is provided in the first passage and generates a damping force. A force generation mechanism, a housing in which at least a part of the flow path of the second passage is formed, and a free piston which is movably provided in the housing and defines the second passage in the upstream and the downstream And provided between the free piston and the housing, provided between the free piston and the housing, one elastic ring that generates an elastic force against the movement of the free piston to one side, The other elastic ring that generates an elastic force with respect to the movement of the free piston to the other and a passage for guiding the working fluid between the one elastic ring and the other elastic ring are provided. It has a configuration that.

  According to the present invention, the damping force can be changed smoothly.

It is sectional drawing which shows the buffer of 1st Embodiment which concerns on this invention. It is an expanded sectional view of an important section showing a buffer of a 1st embodiment concerning the present invention. It is an expanded sectional view of an important section showing a buffer of a 2nd embodiment concerning the present invention. It is a top view which shows the free piston of the buffer of 2nd Embodiment which concerns on this invention. It is an expanded sectional view of an important section showing a buffer of a 3rd embodiment concerning the present invention. It is a bottom view which shows the cover member of the buffer of 3rd Embodiment which concerns on this invention. It is an expanded sectional view of an important section showing a buffer of a 4th embodiment concerning the present invention. It is a bottom view which shows the free piston of the buffer of 4th Embodiment which concerns on this invention. It is an expanded sectional view of an important section showing a buffer of a 5th embodiment concerning the present invention. It is an expanded sectional view of an important section showing a buffer of a 6th embodiment concerning the present invention. It is a top view which shows the housing main body of the buffer of 6th Embodiment which concerns on this invention.

The embodiment described below solves various problems and has an effect without stopping at the contents described in the column of problems to be solved by the above-described invention and the column of effects of the invention. The main problems to be solved by the following embodiments are listed below, including the contents described in the above-mentioned column.
(Characteristic improvement)
When changing the damping force characteristic (damping force with respect to the piston speed) according to the vibration state, characteristic setting such as a smoother change is required. This is because if the characteristics that generate a small damping force and the characteristics that generate a large damping force occur suddenly, the actual damping force also switches suddenly, which deteriorates the ride comfort of the vehicle and further reduces the damping force. This is because the behavior of the vehicle becomes unstable and the driver may feel uncomfortable with respect to the steering when the changeover occurs during the steering of the vehicle. For this reason, characteristic setting that is more smoothly changed as shown in Patent Document 1 described above has been studied, but further characteristic improvement is desired.
[Suppression of enlargement]
Since the frequency sensitive mechanism requires a region in which the free piston moves up and down, it can be said that the region becomes longer in the axial direction when the region is enlarged. When the size of the cylinder device is increased, the degree of freedom of attachment to the vehicle body is reduced. Therefore, an increase in the axial length of the cylinder device is a big problem, and there is a strong demand for downsizing the frequency sensitive portion.
[Reduction of the number of parts]
Since the frequency sensitive mechanism is provided with components such as a housing and a free piston in addition to the piston, the number of components increases. As the number of parts increases, productivity, durability, reliability, etc. will be affected, so the desired characteristics, that is, the damping force characteristics corresponding to a wide range of vibration frequencies can be obtained, and the number of parts Reduction is desired.
Hereinafter, each embodiment according to the present invention will be described with reference to the drawings.

“First Embodiment”
1st Embodiment which concerns on this invention is described based on FIG. 1 and FIG. In the following description, in order to help understanding, the lower side of the figure is defined as one side and the upper side of the figure is defined as the other side.

  As shown in FIG. 1, the shock absorber according to the first embodiment is a so-called monotube hydraulic shock absorber, and includes a bottomed cylindrical cylinder 1 in which an oil liquid as a working fluid is sealed. A piston 3 is slidably fitted in the cylinder 1, and the inside of the cylinder 1 is divided into two chambers, an upper chamber 4 and a lower chamber 5, by the piston 3. The piston 3 includes a piston main body 6 and an annular sliding member 7 attached to the outer peripheral surface thereof.

  The piston body 6 is connected to one end portion of the piston rod 8, and the other end side of the piston rod 8 is inserted into a rod guide 9 and an oil seal 10 mounted on the opening side of the cylinder 1. It is extended to the outside.

  The piston rod 8 has a main shaft portion 15 and an attachment shaft portion 16 on one end side to which the piston 3 is attached with a smaller diameter. A stopper 17 is fixed to the piston rod 8 on the outer peripheral side of the main shaft portion 15 between the piston 3 and the rod guide 9. A spring receiver 18 is disposed opposite to the piston 3 of the stopper 17, and a coil spring 19 is disposed opposite to the stopper 17 of the spring receiver 18. A spring receiver 20 is disposed opposite to the spring receiver 18 of the coil spring 19, and a buffer body 21 is provided on the opposite side of the spring receiver 20 from the coil spring 19. When the piston rod 8 protrudes from the cylinder 1 by a predetermined amount, the buffer body 21 comes into contact with the rod guide 9, and when the piston rod 8 further protrudes, the buffer body 21 and the spring receiver 20 slide on the piston rod 8. However, the coil spring 19 is contracted with the spring receiver 18. As a result, the coil spring 19 generates a force that resists the protrusion of the piston rod 8.

  A partition body 26 for defining the lower chamber 5 on the piston 3 side is slidably provided in the cylinder 10 on the bottom side of the cylinder 1 with respect to the piston 3. Oil is sealed in the upper chamber 4 and the lower chamber 5 in the cylinder 1, and high-pressure (about 20 to 30 atmospheres) gas is contained in the gas chamber 27 defined by the partition body 26 from the lower chamber 5. It is enclosed.

  For example, one side of the shock absorber described above is supported by the vehicle body, and the wheel side is fixed to the other side of the shock absorber. Conversely, the other side of the shock absorber may be supported by the vehicle body and the wheel side may be fixed to one side of the shock absorber. When the wheels vibrate as the vehicle travels, the positions of the cylinder 1 and the piston rod 8 change relatively with the vibrations, but the change is suppressed by the fluid resistance of the flow path formed in the piston 3. As will be described in detail below, the fluid resistance of the flow path formed in the piston 3 is made different depending on the speed and amplitude of vibration, and the ride comfort is improved by suppressing the vibration. Between the cylinder 1 and the piston rod 8, in addition to vibration generated by the wheels, inertial force and centrifugal force generated in the vehicle body as the vehicle travels also act. For example, a centrifugal force is generated in the vehicle body when the traveling direction is changed by a steering operation, and a force based on the centrifugal force acts between the cylinder 1 and the piston rod 8. As will be described below, the shock absorber according to the present embodiment has good characteristics against vibration based on the force generated in the vehicle body as the vehicle travels, and high stability in vehicle travel is obtained.

  As shown in FIG. 2, the upper chamber 4 and the lower chamber 5 are communicated with the piston main body 6, and the piston 3 moves from the upper chamber 4 toward the lower chamber 5 in the movement toward the upper chamber 4 side, that is, in the extension stroke. A plurality of passages (first passages 30a are shown in FIG. 2 because of the cross section), and the piston 3 moves from the lower chamber 5 to the lower chamber 5 in the movement toward the lower chamber 5 side, that is, in the contraction stroke. 4, a plurality of passages (first passages) 30b from which the oil flows out (only one place is shown in FIG. 2 because of the cross-sectional view in FIG. 2) are provided. Half of these passages 30a are formed in the circumferential direction at an equal pitch with one passage 30b interposed therebetween, and one side in the axial direction of piston 3 (the upper side in FIG. 2) has a diameter. The other side in the axial direction (the lower side in FIG. 2) is open radially inward on the outer side in the direction.

  A damping force generating mechanism 32a that generates a damping force is provided in the half of the passages 30a. The damping force generation mechanism 32 a is disposed on the lower chamber 5 side in the axial direction of the piston 3 and is attached to the attachment shaft portion 16 of the piston rod 8. The passage 30a constitutes an extension-side passage through which oil liquid passes when the piston 3 moves to the extension side where the piston rod 8 extends out of the cylinder 1, and a damping force generation mechanism provided for these passages. 32a constitutes an extension-side damping force generation mechanism that generates a damping force by regulating the flow of the oil liquid in the extension-side passage 30a.

  The other half of the passages 30b are formed at an equal pitch in the circumferential direction with one passage 30a interposed therebetween, and the other side in the axial direction of the piston 3 (lower side in FIG. 2). Is open radially outward and one side in the axial direction (upper side in FIG. 2) is open radially inward.

  A damping force generation mechanism 32b that generates a damping force is provided in the remaining half of the passages 30b. The damping force generation mechanism 32 b is disposed on the upper chamber 4 side in the axial direction of the piston 3 and is attached to the attachment shaft portion 16 of the piston rod 8. The passage 30b constitutes a contraction-side passage through which oil liquid passes when the piston 3 moves to the contraction side where the piston rod 8 enters the cylinder 1, and a damping force generating mechanism 32b provided for these passages. Constitutes a contraction-side damping force generating mechanism that restricts the flow of the oil liquid in the contraction-side passage 30b and generates a damping force.

  A damping force variable mechanism 35 is attached to the piston rod 8 on the end side closer to the lower chamber 5 than the piston 3 of the attachment shaft portion 16.

  The piston main body 6 has a substantially disc shape, and an insertion hole 38 is formed in the center of the piston main body 6 so as to penetrate the mounting shaft portion 16 of the piston rod 8 through the axial direction.

  At the end of the piston body 6 on the lower chamber 5 side, an annular seat portion 41a constituting the damping force generating mechanism 32a is formed at one end opening position of the extension-side passage 30a. At the end of the piston body 6 on the upper chamber 4 side, an annular seat portion 41b constituting the damping force generating mechanism 32b is formed at the opening position of one end of the contraction side passage 30b.

  In the piston main body 6, the side opposite to the insertion hole 38 of the seat portion 41 a is an annular stepped portion 42 b whose axial direction height is lower than that of the seat portion 41 a, and a path on the contraction side at the position of the stepped portion 42 b. The other end of 30b is open. Further, in the seat portion 41a, passage grooves (orifices) 43a that are recessed in the axial direction are formed so as to extend from the passage 30a to the outside in the radial direction of the piston 3 and to escape to the stepped portion 42b. Similarly, in the piston main body 6, the side opposite to the insertion hole 38 of the seat portion 41b is an annular step portion 42a having a lower axial height than the seat portion 41b, and extends to the position of the step portion 42a. The other end of the side passage 30a is open. In addition, passage grooves (orifices) 43b that are recessed in the axial direction are also formed in the seat portion 41b so as to extend outward from the passage 30b in the radial direction of the piston 3 and to escape to the stepped portion 42a.

  The damping force generation mechanism 32a includes an annular disk valve 45a that can be seated simultaneously on the entire seat portion 41a, and an annular disk that has a smaller diameter than the disk valve 45a and is disposed on the opposite side of the piston body 6 of the disk valve 45a. The spacer 46a has an annular valve restricting member 47a that is larger in diameter than the spacer 46a and is disposed on the opposite side of the spacer 46a from the piston body 6. The disc valve 45a is configured by overlapping a plurality of annular discs, and opens the passage 30a by separating from the seat portion 41a. The valve regulating member 47a regulates deformation beyond the regulation in the opening direction of the disc valve 45a.

Similarly, the damping force generation mechanism 32b is disposed on the opposite side of the disc valve 45b from the piston main body 6 of the annular disc valve 45b that can be seated on the entire seat portion 41b and having a smaller diameter than the disc valve 45b. An annular spacer 46b, and an annular valve restricting member 47b that is larger in diameter than the spacer 46b and disposed on the opposite side of the spacer 46b from the piston body 6. The valve regulating member 47 b is in contact with the shaft step portion 48 at the end of the main shaft portion 15 of the piston rod 8 on the mounting shaft portion 16 side. The disc valve 45b is also configured by overlapping a plurality of annular discs, and the passage 30b is opened by separating from the seat portion 41b. The valve regulating member 47b regulates deformation beyond the regulation in the opening direction of the disc valve 45b.
In the present embodiment, the damping force generating mechanisms 32a and 32b are examples of the disk valve of the inner periphery clamp. However, the present invention is not limited to this, and any mechanism that generates a damping force may be used. It may be a lift type valve that is energized or may be a poppet valve.

  A male screw 49 is formed at the tip of the piston rod 8, and a damping force variable mechanism 35 is screwed to the male screw 49. The damping force variable mechanism 35 includes a lid member 51 in which a female screw 50 to be engaged with the male screw 49 of the piston rod 8 is formed, and a substantially cylindrical housing attached to the lid member 51 so that one end opening side thereof is closed. A housing 55 composed of a main body 52, a free piston 57 slidably fitted in the housing 55, and a free piston 57 interposed between the free piston 57 and the lid member 51 of the housing 55. On the other hand, the free piston is interposed between an O-ring (elastic ring) 58, which is a compression-side elastic body that compresses and deforms when moving toward the upper chamber 4 side, and the free piston 57 and the housing body 52 of the housing 55. An O-ring (elastic ring) 59 which is an elastic body on the extension side that compressively deforms when 57 moves to the lower chamber 5 side with respect to the housing 55; It is configured. In FIG. 2, the O-rings 58 and 59 in the natural state are shown for convenience. In particular, since the O-ring 59 also functions as a seal, it is desirable that the O-ring 59 is always arranged so as to be deformed (non-circular in cross section) when attached.

  The lid member 51 is formed mainly by cutting, and has a substantially cylindrical inner cylinder part 62 and a disk shape extending radially outward from the axial end of the inner cylinder part 62. The lid substrate 63, the lid outer cylinder 64 extending from the outer periphery of the lid substrate 63 in the same direction as the lid inner cylinder 62, and the lid substrate 63 in the axial direction of the lid inner cylinder 62 are opposite to each other. And a disc-like lid tip plate portion 65 extending radially inward so as to close the lid inner cylinder portion 62 from the end portion of the lid.

  On the inner peripheral portion of the lid inner cylinder portion 62, the above-described female screw 50 is formed so as to protrude radially inward at an intermediate position in the axial direction. Further, the inner peripheral surface of the lid outer cylinder portion 64 has a small diameter cylindrical surface portion 66, a tapered surface portion 67, a curved surface portion 68, and a large diameter cylindrical surface portion 69 in this order from the lid substrate portion 63 side. The small-diameter cylindrical surface portion 66 has a constant diameter, and the tapered surface portion 67 connected to the small-diameter cylindrical surface portion 66 becomes larger as the distance from the small-diameter cylindrical surface portion 66 increases. The curved surface portion 68 connected to the tapered surface portion 67 has an annular shape with a larger diameter as the distance from the tapered surface portion 67 increases. The large diameter cylindrical surface portion 69 connected to the curved surface portion 68 has a constant diameter smaller than that of the small diameter cylindrical surface portion 66. The curved surface portion 68 has an arc shape in cross section including the central axis of the lid member 51. An orifice 70 is formed in the center of the lid tip plate portion 65 in the radial direction so as to penetrate in the axial direction.

  The housing body 52 is formed mainly by cutting, and has a substantially cylindrical shape in which an inner annular protrusion 79 that protrudes radially inward is formed on one side in the axial direction. A small-diameter cylindrical surface portion 81, a tapered surface portion 82, a curved surface portion 83, a large-diameter cylindrical surface portion 84, and a large-diameter-side fitting cylindrical surface portion 85 having a larger diameter are formed on the inner peripheral surface of the housing body 52 in this order from one side in the axial direction. Is formed. The small-diameter cylindrical surface portion 81 has a constant diameter, and the tapered surface portion 82 connected to the small-diameter cylindrical surface portion 81 becomes larger as the distance from the small-diameter cylindrical surface portion 81 increases. The curved surface portion 83 connected to the tapered surface portion 82 has an annular shape with a larger diameter as the distance from the tapered surface portion 82 increases, and the large diameter cylindrical surface portion 84 connected to the curved surface portion 83 has a constant diameter larger than that of the small diameter cylindrical surface portion 81. ing. The large-diameter side fitting cylindrical surface portion 85 adjacent to the large-diameter cylindrical surface portion 84 in the axial direction has a larger diameter than the large-diameter cylindrical surface portion 84. The curved surface portion 83 has an arcuate cross section including the central axis of the housing body 52, and the small-diameter cylindrical surface portion 81, the tapered surface portion 82, and the curved surface portion 83 are formed on the inner annular protrusion 79.

  The lid outer cylinder 64 of the lid member 51 is fitted over the entire length of the large-diameter fitting cylindrical surface 85 of the housing body 52. By fitting to the large diameter side fitting cylindrical surface portion 85, the large diameter cylindrical surface portion 69 of the lid outer cylinder portion 64 is continuous with the large diameter cylindrical surface portion 84 of the housing body 52 without a step. . The tapered surface portion 67 and the curved surface portion 68 are formed on an inner annular protrusion 86 of the lid member 51 that protrudes radially inward from the large diameter cylindrical surface portion 69 and the large diameter cylindrical surface portion 84. In addition, although the housing main body 52 is described as a substantially cylindrical shape, the inner peripheral surface is preferably circular in cross section, but the outer peripheral surface may be noncircular in cross section such as a polygon.

  Here, the lid member 51 is fitted to the large-diameter fitting cylindrical surface portion 85 by the lid outer cylinder portion 64 with the lid tip plate portion 65 on the front side in the housing main body 52. In this state, a part of the large-diameter side fitting cylindrical surface portion 85 of the housing main body 52 is formed and the end protruding from the lid member 51 is crimped inward, so that the lid member 51 is fixed and integrated with the housing main body 52. Is done. As described above, the housing body 52 and the lid member 51 integrated together constitute a housing 55.

  The free piston 57 is formed mainly by cutting, and has a substantially cylindrical piston tube portion 91 and a piston closing plate portion 92 that closes the axial end portion of the piston tube portion 91. An annular outer annular protrusion 93 that protrudes radially outward is formed in the piston cylinder portion 91 at the center in the axial direction.

  A small-diameter cylindrical surface portion 97, a curved surface portion 98, a tapered surface portion 99, a large-diameter cylindrical surface portion 100, a tapered surface portion 101, a curved surface portion 102, and a small-diameter cylindrical surface portion 103 are formed on the outer peripheral surface of the piston cylinder portion 91 in this order from the lower chamber 5 side. Has been. The curved surface portion 98, the tapered surface portion 99, the large diameter cylindrical surface portion 100, the tapered surface portion 101, and the curved surface portion 102 are formed on the outer annular protrusion 93.

  The small diameter cylindrical surface portion 97 has a constant diameter, and the curved surface portion 98 connected to the small diameter cylindrical surface portion 97 has an annular shape with a larger diameter as the distance from the small diameter cylindrical surface portion 97 increases. The tapered surface portion 99 connected to the curved surface portion 98 has a larger diameter as the distance from the curved surface portion 98 increases, and the large diameter cylindrical surface portion 100 connected to the tapered surface portion 99 has a larger diameter than the small diameter cylindrical surface portion 97. The curved surface portion 98 has an arc shape in cross section including the central axis of the free piston 57.

  The tapered surface portion 101 connected to the large-diameter cylindrical surface portion 100 has a smaller diameter as the distance from the large-diameter cylindrical surface portion 100 increases, and the curved surface portion 102 connected to the tapered surface portion 101 has an annular shape with a smaller diameter as the distance from the tapered surface portion 101 increases. The small-diameter cylindrical surface portion 103 is connected to the curved surface portion 102, and the small-diameter cylindrical surface portion 103 has the same diameter as the small-diameter cylindrical surface portion 97. The curved surface portion 102 has a circular cross section including the central axis of the free piston 57. The outer annular protrusion 93 has a symmetrical shape with respect to a plane passing through the central position in the axial direction. The free piston 57 has a plurality of passage holes (passages) 105 that penetrate the outer annular protrusion 93 in the radial direction at a central position in the axial direction of the outer annular protrusion 93 at intervals in the circumferential direction of the free piston 57. Yes.

  The free piston 57 is slidably fitted into the large-diameter cylindrical surface portion 84 of the housing main body 52 and the large-diameter cylindrical surface portion 69 of the lid member 51 in the large-diameter cylindrical surface portion 100 in a state of being disposed in the housing 55. Become. The free piston 57 has a position where one small-diameter cylindrical surface portion 97 is positioned on the small-diameter cylindrical surface portion 81 of the housing body 52 and the other small-diameter cylindrical surface portion 103 is positioned on the small-diameter cylindrical surface portion 66 of the lid outer cylindrical portion 64 of the lid member 51. Can be slid. The taper surface portion 82 of the housing main body 52 and the curved surface portion 98 of the free piston 57 overlap each other in the radial direction in the state of being arranged in the housing 55, and the curved surface portion 83 of the housing main body 52 and the free piston are overlapped. 57 taper surface portions 99 overlap the positions in these radial directions. Therefore, the entire tapered surface portion 82 and curved surface portion 83 of the housing body 52 and the entire curved surface portion 98 and tapered surface portion 99 of the free piston 57 face each other in the moving direction of the free piston 57. In addition, the tapered surface portion 67 of the lid outer cylinder portion 64 of the lid member 51 and the curved surface portion 102 of the free piston 57 overlap each other in the radial direction, and the curved surface of the lid outer cylinder portion 64 of the lid member 51. The portion 68 and the tapered surface portion 101 of the free piston 57 overlap with each other in the radial direction. Therefore, the entire tapered surface portion 67 and the curved surface portion 68 of the lid member 51 and the entire curved surface portion 102 and the entire tapered surface portion 101 of the free piston 57 face each other in the moving direction of the free piston 57.

  And, between the small diameter cylindrical surface portion 97, the curved surface portion 98 and the tapered surface portion 99 of the free piston 57 and the tapered surface portion 82, the curved surface portion 83 and the large diameter cylindrical surface portion 84 of the housing main body 52, in other words, outside the free piston 57. An O-ring 59 (the natural state is shown in FIG. 2) is disposed between the annular protrusion 93 and one inner annular protrusion 79 of the housing 55. When the O-ring 59 is in a natural state, the cross section including the central axis is circular, the inner diameter is smaller than the small-diameter cylindrical surface portion 97 of the free piston 57, and the outer diameter is the large-diameter cylindrical surface portion 84 of the housing body 52. The diameter is larger than. That is, the O-ring 59 is fitted to both the free piston 57 and the housing main body 52 with an allowance in the radial direction.

  Further, between the large diameter cylindrical surface portion 69, the tapered surface portion 67 and the curved surface portion 68 of the lid member 51 and the tapered surface portion 101, the curved surface portion 102 and the small diameter cylindrical surface portion 103 of the free piston 57, in other words, outside the free piston 57. An O-ring 58 (the natural state is shown in FIG. 2) is disposed between the annular protrusion 93 and the other inner annular protrusion 86 of the housing. When the O-ring 58 is also in a natural state, the cross section including the central axis is circular, the inner diameter is smaller than the small-diameter cylindrical surface portion 103 of the free piston 57, and the outer diameter is the large-diameter cylinder of the lid member 51. The diameter is larger than that of the surface portion 69. That is, the O-ring 58 is also fitted to both the free piston 57 and the housing 55 with tightening margins in these radial directions.

  Both O-rings 58 and 59 have the same size, hold the free piston 57 in a predetermined neutral position with respect to the housing 55, and axially the upper chamber 4 side and the lower chamber of the free piston 57 with respect to the housing 55. Allow axial movement to both sides of the 5 side.

  In the free piston 57, the O-ring 58 comes into contact with the small-diameter cylindrical surface portion 103, the curved surface portion 102, and the tapered surface portion 101. Of these, the curved surface portion 102 and the tapered surface portion 101 are inclined with respect to the moving direction of the free piston 57. doing. Further, in the housing 55, the O-ring 58 comes into contact with the large-diameter cylindrical surface portion 69, the tapered surface portion 67 and the curved surface portion 68, and among these, the tapered surface portion 67 and the curved surface portion 68 are in the moving direction of the free piston 57. It is slanted.

  In other words, the outer annular protrusion 93 is provided on the outer peripheral portion of the free piston 57, and both axial surfaces of the outer annular protrusion 93 constitute a curved surface portion 98 and a tapered surface portion 99, and a curved surface portion 102 and a tapered surface portion 101, and the housing. 55, an inner annular protrusion 79 constituting the tapered surface portion 82 and the curved surface portion 83, and an inner annular protrusion 86 constituting the tapered surface portion 67 and the curved surface portion 68 are provided at positions on both sides of the outer annular protrusion 93 on the inner circumference of 55, An O-ring 59 and an O-ring 58 are provided between the outer annular protrusion 93 and the inner annular protrusion 79 and the inner annular protrusion 86, respectively.

  In the small-diameter cylindrical surface portion 97, the curved surface portion 98, and the tapered surface portion 99 of the free piston 57, the free piston contact surface that is in contact with the O-ring 59, the large-diameter cylindrical surface portion 84, the curved surface portion 83, and the In the tapered surface portion 82, the shortest distance of the portion contacting the O-ring 59 is changed by the movement of the free piston 57 from the housing contact surface that is in contact with the O-ring 59, and the portion that becomes the shortest distance is changed. The direction of the connecting line changes. In other words, the small-diameter cylindrical surface portion so that the direction of the line segment connecting the free piston contact surface of the free piston 57 and the housing contact surface of the housing 55 and the shortest distance between the portions where the O-ring 59 contacts is changed. 97, the shape of the curved surface portion 98 and the tapered surface portion 99 and the large diameter cylindrical surface portion 84, the curved surface portion 83 and the tapered surface portion 82 are set. Specifically, when the free piston 57 is positioned on the upper chamber 4 side in the axial direction with respect to the housing 55, the shortest distance between the free piston contact surface and the housing contact surface, of which the O-ring 59 is in contact with each other. Is the radius difference between the large-diameter cylindrical surface portion 84 and the small-diameter cylindrical surface portion 97 (the radius difference between the outer diameter and the inner diameter of the O-ring 59 is larger than the radius difference between the large-diameter cylindrical surface portion 84 and the small-diameter cylindrical surface portion 97. Therefore, the O-ring 59 collapses the difference, and that portion, that is, the line segment of the shortest distance has an inclination angle of 0). On the other hand, when the free piston 57 moves toward the lower chamber 5 in the axial direction with respect to the housing 55, the contact portion with the O-ring 59 becomes the curved surface portion 98 and the curved surface portion 83, and the position where the O-ring 59 is crushed most, that is, the shortest distance. The inclination angle of the line segment becomes diagonal.

  Similarly, in the small-diameter cylindrical surface portion 103, the curved surface portion 102, and the tapered surface portion 101 of the free piston 57, the free piston contact surface that is in contact with the O-ring 58, the large-diameter cylindrical surface portion 69, and the curved surface portion 68 of the housing 55. In the tapered surface portion 67, the shortest distance between the housing contact surface that is in contact with the O-ring 58 and the portion that is in contact with the O-ring 58 due to the movement of the free piston 57 is changed to the shortest distance. The direction of the line segment connecting is changed. In other words, the small diameter cylindrical surface portion so that the direction of the line segment connecting the free piston contact surface of the free piston 57 and the housing contact surface of the housing 55 and the shortest distance between the portions where the O-ring 58 contacts is changed. 103, the shape of the curved surface portion 102 and the tapered surface portion 101, the large diameter cylindrical surface portion 69, the curved surface portion 68, and the tapered surface portion 67 are set. Specifically, when the free piston 57 is positioned on the lower chamber 5 side in the axial direction with respect to the housing 55, the shortest distance between the free piston contact surface and the housing contact surface and the portion where the O-ring 58 is in contact with each other. Is the radius difference between the large-diameter cylindrical surface portion 69 and the small-diameter cylindrical surface portion 103 (the radius difference between the outer diameter and the inner diameter of the O-ring 58 is larger than the radius difference between the large-diameter cylindrical surface portion 69 and the small-diameter cylindrical surface portion 103). Because of this, the difference in the O-ring 58 is collapsed, and that portion, that is, the line segment of the shortest distance has an inclination angle of 0). On the other hand, when the free piston 57 moves toward the upper chamber 4 in the axial direction with respect to the housing 55, the contact portion with the O-ring 58 becomes the curved surface portion 68 and the curved surface portion 102, and the position where the O-ring 58 is most crushed, that is, the shortest distance The inclination angle of the line segment becomes diagonal.

  In the damping force variable mechanism 35, for example, an O-ring 59 is inserted into the housing main body 52 up to the position of the curved surface portion 83, and a free piston 57 is fitted inside the housing main body 52 and the O-ring 59. The O-ring 58 is inserted between the free piston 57 and the free piston 57 to the position of the curved surface portion 102, and the lid member 51 is crimped to the housing main body 52, thereby assembling. Then, the damping force variable mechanism 35 assembled in advance in this way is attached by screwing the female screw 50 to the male screw 49 of the mounting shaft portion 16 of the piston rod 8, and at that time, the lid substrate portion of the housing 55. 63 abuts on the valve regulating member 47a of the damping force generating mechanism 32a, and the damping force generating mechanism 32a, the piston body 6 and the damping force generating mechanism 32b are sandwiched between the shaft step portion 48 of the piston rod 8. . That is, the damping force variable mechanism 35 also serves as a fastening member that fastens the damping force generation mechanism 32 a, the piston body 6, and the damping force generation mechanism 32 b to the piston rod 8. The outer diameter of the damping force variable mechanism 35, that is, the outer diameter of the housing main body 52 is set to be smaller than the inner diameter of the cylinder 1 so as not to cause flow path resistance.

  In the piston rod 8, a passage hole 130 is formed along the radial direction at an end position of the main shaft portion 15 on the attachment shaft portion 16 side, and a passage hole 131 communicating with the passage hole 130 is formed in the attachment shaft portion 16. Are formed along the axial direction. Therefore, the upper chamber 4 communicates with the pressure chamber 132 formed in the housing 55 of the damping force variable mechanism 35 through these passage holes 130 and 131, specifically, the housing 55 of the pressure chamber 132. And an O-ring 58 and a free piston 57 communicate with the upper chamber communication chamber 133. Further, the lower chamber 5 can communicate with the inside of the housing 55 through a gap between the piston cylindrical portion 91 of the free piston 57 protruding from the housing 55 and the inner annular projection 79 of the housing 55. Specifically, The pressure chamber 132 in the housing 55 can communicate with the lower chamber communication chamber 134 defined by the housing 55, the O-ring 59 and the free piston 57.

  In the first embodiment, as described above, a plurality of passage holes 105 penetrating the outer annular protrusion 93 in the radial direction are formed at the axial center position of the outer annular protrusion 93 of the free piston 57. As a result, the upper chamber communication chamber 133 always communicates with the chamber 137 surrounded by the housing 55, the O-ring 58, the O-ring 59, and the free piston 57 via the passage hole 105. In other words, the passage hole 105 guides the oil from the upper chamber communication chamber 133 to the chamber 137 between one O-ring 58 and the other O-ring 59. Since the passage hole 105 is formed at the position of the outer annular protrusion 93 of the free piston 57, the entire O-ring 58 and the other O-ring 59 of the free piston 57 move in the entire range of movement relative to the housing 55. There is no contact with either.

  The O-ring 59 disposed between the housing main body 52 and the free piston 57 is disposed so as to always seal between the housing 55 and the free piston 57, and communicates with the upper chamber communication chamber 133 and the chamber 137, and the lower chamber communication. Communication with the chamber 134 is always blocked.

  The passage holes 130 and 131 and the upper chamber communication chamber 133 constitute a passage (second passage) 135 through which oil flows from one upper chamber 4 in the cylinder 1 by the movement of the piston 3 toward the upper chamber 4 side. The lower chamber communication chamber 134 constitutes a passage (second passage) 136 through which oil flows from one lower chamber 5 in the cylinder 1 by the movement of the piston 3 toward the lower chamber 5. Therefore, a part of the passage 135 is formed in the housing 55, and the whole passage 136 is formed in the housing 55. The free piston 57 is movably inserted into the pressure chamber 132 in the housing 55 provided in the middle of the passages 135 and 136, and defines the passages 135 and 136 which are two regions, upstream and downstream. . Here, the second passage is defined by the free piston 57, and there is no flow of replacement of the oil between the upper chamber 4 and the lower chamber 5, but the free piston 57 moves relative to the housing 55. During this time, the oil liquid in the upper chamber 4 flows into the pressure chamber 132 and the same amount of oil liquid is pushed out to the lower chamber 5 side. O-rings 58 and 59 provided between the free piston 57 and the housing 55 and disposed on both sides in the sliding direction of the free piston 57 generate a resistance force against the displacement of the free piston 57. That is, the O-ring 58 generates an elastic force when the free piston 57 moves toward the one upper chamber 4 side with respect to the housing 55, and the O-ring 59 has the other lower chamber with respect to the housing 55. When moved to the 5 side, an elastic force is generated.

  Here, in the extension stroke in which the piston rod 8 moves to the extension side, the oil liquid flows from the upper chamber 4 to the lower chamber 5 through the passage 30a. However, when the piston speed is in a very low speed range, 4 to the lower chamber 5 through a constant orifice defined by a passage groove 43a formed in the piston 3 and a disk valve 45a contacting the seat portion 41a. In the flow, a damping force having an orifice characteristic (a damping force is approximately proportional to the square of the piston speed) is generated. When the piston speed increases and reaches a low speed region, the oil introduced into the passage 30a from the upper chamber 4 basically passes between the disc valve 45a and the seat portion 41a while opening the disc valve 45a. It will flow into the lower chamber 5. For this reason, a damping force having a valve characteristic (a damping force is substantially proportional to the piston speed) is generated.

  In the contraction stroke in which the piston rod 8 moves to the contraction side, the oil liquid flows from the lower chamber 5 to the upper chamber 4 via the passage 30b. However, when the piston speed is in a very low speed region, the passage from the lower chamber 5 The oil liquid introduced into 30b basically flows into the upper chamber 4 through a constant orifice defined by a passage groove 43b formed in the piston 3 and a disk valve 45b in contact with the seat portion 41b. A damping force having an orifice characteristic (a damping force is approximately proportional to the square of the piston speed) is generated. When the piston speed increases and reaches a low speed region, the oil introduced into the passage 30b from the lower chamber 5 basically passes between the disc valve 45b and the seat portion 41b while opening the disc valve 45b. It will flow into the upper chamber 4. For this reason, a damping force having a valve characteristic (a damping force is substantially proportional to the piston speed) is generated.

  Here, when the piston speed is low, that is, the region where the frequency in the very low speed region (for example, 0.05 m / s) is relatively high (for example, 7 Hz or more) is, for example, vibration caused by unevenness on the fine surface of the road surface. In such a situation, it is preferable to reduce the damping force. Similarly, even when the piston speed is low, the region where the frequency is relatively low (for example, 2 Hz or less) is vibration such as wobbling caused by the roll of the vehicle body. In such a situation, the damping force Is preferable.

  Correspondingly, the damping force variable mechanism 35 described above makes the damping force variable according to the frequency even when the piston speed is low as well. That is, when the piston speed is low and the frequency of the reciprocating motion of the piston 3 is increased, the pressure in the upper chamber 4 is increased in the extension stroke, and the damping force variable mechanism via the passage holes 130 and 131 of the piston rod 8. While the oil liquid is introduced from the upper chamber 4 into the upper chamber communication chamber 133, the free piston 57 resists the urging force of the O-ring 59 on the lower chamber 5 side in the axial direction toward the lower chamber 5 side in the axial direction. Moving. Thus, when the free piston 57 moves to the lower chamber 5 side in the axial direction, the oil liquid is introduced into the upper chamber communication chamber 133 from the upper chamber 4, and is introduced into the passage 30a from the upper chamber 4 and the damping force. The flow rate of the oil liquid flowing through the generating mechanism 32a and flowing into the lower chamber 5 is reduced. Thereby, a damping force falls.

  In the subsequent contraction stroke, the pressure in the lower chamber 5 increases, so that the oil liquid is discharged from the upper chamber communication chamber 133 to the upper chamber 4 through the passage holes 130 and 131 of the piston rod 8, while the axially lower The free piston 57 that has moved to the chamber 5 side moves to the upper chamber 4 side in the axial direction against the urging force of the O-ring 58 on the upper chamber 4 side in the axial direction. As the free piston 57 moves to the upper chamber 4 side in the axial direction in this way, the volume of the lower chamber 5 increases, and is introduced from the lower chamber 5 into the passage 30b and passes through the damping force generating mechanism 32b. The flow rate of the oil liquid flowing into the chamber 4 is reduced. Thereby, a damping force falls.

  And in the region where the frequency of the piston 3 is high, the frequency of the movement of the free piston 57 also follows and increases. As a result, the oil liquid flows from the upper chamber 4 to the upper chamber communication chamber 133 each time the above-described extension stroke occurs. The volume of the lower chamber 5 increases with each contraction stroke, and the damping force is maintained in a reduced state as described above.

  On the other hand, when the piston speed is low and the frequency of the piston 3 is low, the frequency of the movement of the free piston 57 is also low and the oil liquid is transferred from the upper chamber 4 to the upper communication chamber 133 at the beginning of the extension stroke. However, after that, the free piston 57 compresses the O-ring 59 and stops on the lower chamber 5 side in the axial direction, and the oil liquid does not flow from the upper chamber 4 to the upper chamber communication chamber 133. The flow rate of the oil liquid introduced into 30a and passing through the damping force generating mechanism 32a and flowing into the lower chamber 5 is not reduced, and the damping force is increased.

  Even in the subsequent contraction stroke, the volume of the lower chamber communication chamber 134, that is, the lower chamber 5 is increased in the initial stage, but thereafter the free piston 57 compresses the O-ring 58 and stops on the upper chamber 4 side in the axial direction. Therefore, the flow rate of the oil liquid introduced into the passage 30b from the lower chamber 5 through the damping force generating mechanism 32b and flowing into the upper chamber 4 is not reduced, and the damping force is increased.

  In the present embodiment, as described above, the O-rings 58 and 59 made of a rubber material are used as parts for applying a biasing force to the free piston 57 so as to return to the neutral position. The O-rings 58, 59 between the free piston 57 and the housing 55 are connected to the large-diameter cylindrical surface portion 69 of the lid member 51 and the large-diameter cylindrical surface portion 84 of the housing body 52, and the small-diameter cylindrical surface portions 97, 103 of the free piston 57. Located between and.

  When the free piston 57 moves from the neutral position to the lower chamber 5 in the axial direction with respect to the housing 55 by, for example, an extension stroke, the large diameter cylindrical surface portion 84 of the housing 55 and the small diameter cylindrical surface portion 97 of the free piston 57 are connected to the O-ring 59. Are rotated so that the inner diameter side and the outer diameter side move in opposite directions, and are moved to the lower chamber 5 side in the axial direction with respect to the housing 55. The free piston 57 while the O-ring 59 rolls between the curved chamber portion 98 and the tapered surface portion 82 in the axial upper chamber 4 side and the curved surface portion 98 and the tapered surface portion 99 of the free piston 57 in the axial lower chamber 5 side. Are then compressed in the axial direction and the radial direction, and subsequently the curved chamber portion 83 and the tapered surface portion 82 of the housing 55 are axially connected to the lower chamber 5 side, and the curved surface portion 98 and the taper of the free piston 57. An upper chamber 4 of the axial section 99 compresses the O-ring 59 in the axial direction and the radial direction of the free piston 57. When the free piston 57 moves toward the lower chamber 5 in the axial direction with respect to the housing 55 in the extension stroke from the neutral position, the large-diameter cylindrical surface portion 69 of the housing 55 and the small-diameter cylindrical surface portion 103 of the free piston 57 become O-rings. 58 are caused to roll between each other and move toward the lower chamber 5 in the axial direction with respect to the housing 55.

  At this time, a region where the O-ring 59 rolls between the large-diameter cylindrical surface portion 84 of the housing 55 and the small-diameter cylindrical surface portion 97 of the free piston 57, the curved surface portion 83 and the tapered surface portion 82 of the housing 55, and the curved surface of the free piston 57. The region where the O-ring 59 rolls between the portion 98 and the tapered surface portion 99 is a rolling region where the O-ring 59 rolls at a position separated from the downstream end portion in the moving region of the free piston 57. There is a moving area where the O-ring 59 moves in a moving direction of the free piston 57 while being in contact with both the housing 55 and the free piston 57 at a position spaced from the downstream end. This movement means that at least the downstream end position (the lower end position in FIG. 2) of the O-ring 59 moves in the free piston movement direction.

  Further, the region where the O-ring 59 is compressed between the curved surface portion 83 and the tapered surface portion 82 of the housing 55 and the curved surface portion 98 and the tapered surface portion 99 of the free piston 57 is the downstream end portion side in the moving region of the free piston 57. , A moving direction deformation region in which the O-ring 59 is elastically deformed in the moving direction of the free piston 57. The elastic deformation in the movement direction deformation region is a deformation in which the upstream end position (the upper end position in FIG. 2) of the free piston movement direction of the O-ring 59 moves and the downstream end position does not move. Here, the rolling region and the moving region overlap with a part of the moving direction deformation region.

  When the free piston 57 moves to the upper chamber 4 side in the axial direction with respect to the housing 55 in the subsequent contraction stroke, the curved surface portion 83 of the housing 55 and the lower chamber 5 side in the axial direction of the tapered surface portion 82 and the curved surface portion of the free piston 57. 98 and the upper chamber 4 in the axial direction of the taper surface portion 99 release the compression of the O-ring 59, and then the upper surface 4 side in the axial direction of the curved surface portion 83 and the taper surface portion 82 of the housing 55 and the free piston 57. The curved surface portion 98 and the taper surface portion 99 of the lower chamber 5 side in the axial direction further release the compression while rolling the O-ring 59, and then the large-diameter cylindrical surface portion 84 of the housing 55 and the free piston. 57 and the small-diameter cylindrical surface portion 97 move the O-ring 59 toward the upper chamber 4 in the axial direction with respect to the housing 55 while rolling between them. At this time, also for the O-ring 58, the large-diameter cylindrical surface portion 69 of the housing 55 and the small-diameter cylindrical surface portion 103 of the free piston 57 roll between each other so as to be in the axial upper chamber 4 side with respect to the housing 55. Will be moved to. After that, the lower chamber 5 side in the axial direction of the curved surface portion 68 and the taper surface portion 67 of the housing 55 and the upper chamber 4 side in the axial direction of the curved surface portion 102 and the taper surface portion 101 of the free piston 57 form the O-ring 58. While being rolled, the free piston 57 is compressed in the axial direction and the radial direction, and subsequently the curved chamber portion 68 and the tapered surface portion 67 of the housing 55 in the axial upper chamber 4 side, and the curved surface portion 102 and the tapered surface portion 101 of the free piston 57. The lower chamber 5 side in the axial direction compresses the O-ring 58 in the axial direction and the radial direction of the free piston 57.

  At this time, a region where the O-ring 58 rolls between the large-diameter cylindrical surface portion 69 of the housing 55 and the small-diameter cylindrical surface portion 103 of the free piston 57, the curved surface portion 68 and the tapered surface portion 67 of the housing 55, and the curved surface of the free piston 57. The region where the O-ring 58 rolls between the portion 102 and the tapered surface portion 101 is a rolling region where the O-ring 58 rolls at a position away from the upstream end in the moving region of the free piston 57. There is a moving region where the O-ring 58 moves in a state in which the O-ring 58 is in contact with both the housing 55 and the free piston 57 in the moving direction of the free piston 57 at a position separated from the upstream end. This movement means that at least the upstream end position of the O-ring 58 in the free piston movement direction (the upper end position in FIG. 2) moves.

  Further, the region where the O-ring 58 is compressed between the curved surface portion 68 and the tapered surface portion 67 of the housing 55 and the curved surface portion 102 and the tapered surface portion 101 of the free piston 57 is the downstream end portion side in the moving region of the free piston 57. , A moving direction deformation region in which the O-ring 58 is elastically deformed in the moving direction of the free piston 57. The elastic deformation in the movement direction deformation region is a deformation in which the downstream end position (lower end position in FIG. 2) of the O-ring 58 in the free piston movement direction moves and the upstream end position does not move. Here, the rolling region and the moving region overlap with a part of the moving direction deformation region.

  In the extension stroke that follows, the upper chamber 4 side of the curved surface portion 68 and the tapered surface portion 67 of the housing 55 and the lower surface 5 side of the tapered surface portion 101 and the curved surface portion 102 of the free piston 57 release the compression of the O-ring 58, Subsequently, the lower chamber 5 side of the curved surface portion 68 and the tapered surface portion 67 of the housing 55 and the upper chamber 4 side of the tapered surface portion 101 and the curved surface portion 102 of the free piston 57 further release the compression while rolling the O-ring 58. Then, the large-diameter cylindrical surface portion 69 of the housing 55 and the small-diameter cylindrical surface portion 103 of the free piston 57 cause the O-ring 58 to roll between each other, so that the side of the lower chamber 5 in the axial direction with respect to the housing 55 is reached. Will be moved to. At this time, also for the O-ring 59, the large-diameter cylindrical surface portion 84 of the housing 55 and the small-diameter cylindrical surface portion 97 of the free piston 57 roll between each other and move toward the lower chamber 5 in the axial direction with respect to the housing 55. I will let you. When the free piston 57 passes through the neutral position, the O-rings 58 and 59 are operated in the same manner as described above.

  Thus, the O-rings 58 and 59 are crushed in the movement direction in the movement direction deformation region.

  Here, the load characteristic with respect to the displacement of the free piston 57 by the O-rings 58 and 59 made of a rubber material is a non-linear characteristic. That is, in a predetermined range before and after the neutral position of the free piston 57, the characteristics are close to linear, and when this range is exceeded, the rate of increase in load increases smoothly with respect to displacement. As described above, in the region where the operating frequency of the piston 3 is high, since the amplitude of the piston 3 is small, the displacement of the free piston 57 is also small, and the operation is performed in the linear characteristic range before and after the neutral position. As a result, the free piston 57 becomes easy to move and vibrates following the vibration of the piston 3 to contribute to the reduction of the damping force generated by the damping force generating mechanisms 32a and 32b.

  On the other hand, in the region where the operating frequency of the piston 3 is low, the amplitude of the piston 3 increases, so that the displacement of the free piston 57 increases, and the operation is performed in a non-linear characteristic range. As a result, the free piston 57 becomes gradually smooth and difficult to move, and it is difficult to reduce the damping force generated by the damping force generating mechanisms 32a and 32b.

  According to the first embodiment described above, a predetermined range before and after the neutral position of the free piston 57 has a characteristic close to linear, and when this range is exceeded, the rate of increase in load increases smoothly with respect to displacement. Since the rings 58 and 59 are used to restrict the movement of the free piston 57 toward the upper chamber 4 and the movement toward the lower chamber 5 with respect to the housing 55, it is smoothly changed when the damping force is changed in response to the frequency. Therefore, it is possible to set characteristics such as changing the damping force characteristics more smoothly according to the vibration state.

  Further, since the passage hole 105 for introducing the working fluid is provided in the chamber 137 between the one O-ring 58 and the other O-ring 59, the chamber 137 is removed by removing air from the chamber 137 in the shock absorber assembly process. Can be filled with working fluid. Thereby, it is possible to satisfactorily change the damping force in response to the frequency as described above. In other words, if the air in the chamber 137 does not escape, the air is compressed when the free piston 57 is operated, the internal pressure of the chamber 137 rises, the tightening force of the O-rings 58 and 59 increases, and the operation of the free piston 57 is inhibited. However, the provision of the passage hole 105 can prevent such an inhibition of the operation of the free piston 57.

  Further, since the passage hole 105 is formed at a position in the free piston 57 that does not contact one of the O-ring 58 and the other O-ring 59, the passage hole 105 contacts the O-rings 58 and 59. Therefore, it is possible to prevent the life of the O-rings 58 and 59 from being reduced. Therefore, the life of the O-rings 58 and 59 can be extended.

“Second Embodiment”
Next, the second embodiment will be described mainly based on FIGS. 3 and 4 with a focus on differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol.

  As shown in FIG. 3, in the second embodiment, the passage hole 105 of the first embodiment is not provided. Instead, the tapered surface portion 101 passes from the small diameter cylindrical surface portion 103 of the free piston 57 through the curved surface portion 102. A passage groove (passage) 140 extending in the axial direction while being recessed inward in the radial direction is formed up to a middle position. As shown in FIG. 4, the passage groove 140 is formed at a plurality of locations, specifically four locations, at equal intervals in the circumferential direction of the free piston 57. With these passage grooves 140, the O-ring 58 shown in FIG. 3 is not in close contact with the small-diameter cylindrical surface portion 103, the curved surface portion 102, and the tapered surface portion 101, so that the upper chamber communication chamber 133 is formed between the housing 55 and the O-ring 58. And a chamber 137 surrounded by the O-ring 59 and the free piston 57. In other words, the passage groove 140 guides the oil from the upper chamber communication chamber 133 to the chamber 137 between the O-ring 58 and the O-ring 59. The passage groove 140 is formed continuously with the small-diameter cylindrical surface portion 103, the curved surface portion 102, and the tapered surface portion 101 of the free piston 57, so that the free piston 57 is free at a position in contact with one O-ring 58. It is formed along the moving direction of the piston 57. The formation range of the passage groove 140 is set so that the upper chamber communication chamber 133 and the chamber 137 communicate with each other over the entire movement range of the O-ring 58.

  Also in the second embodiment, since the passage groove 140 for guiding the working fluid is provided in the chamber 137 between the O-ring 58 and the O-ring 59, air is extracted from the chamber 137 in the assembly process of the shock absorber. The chamber 137 can be filled with working fluid. Thereby, it is possible to satisfactorily change the damping force in response to the frequency.

  Further, since the passage groove 140 is formed along the moving direction of the free piston 57 at a position where the free piston 57 comes into contact with one O-ring 58, the width, depth, number, etc. of the passage groove 140 are set. By changing, the deformation characteristic of the O-ring 58 can be easily changed, and the movement characteristic of the free piston 57 can be changed.

“Third Embodiment”
Next, the third embodiment will be described mainly based on FIGS. 5 and 6 with a focus on differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol.

  As shown in FIG. 5, in the third embodiment, the passage hole 105 of the first embodiment is not provided, and instead of the tapered surface portion 67 of the lid outer cylinder portion 64 of the lid member 51 of the housing 55. A passage groove (passage) 142 extending in the axial direction while being recessed outward in the radial direction is formed from the midway position through the curved surface portion 68 to the large-diameter cylindrical surface portion 69. As shown in FIG. 6, the passage groove 142 is formed at a plurality of locations, specifically four locations, at equal intervals in the circumferential direction of the lid member 51. 5 prevents the O-ring 58 shown in FIG. 5 from coming into close contact with the large-diameter cylindrical surface portion 69, the curved surface portion 68, and the tapered surface portion 67. Therefore, the upper chamber communication chamber 133 is formed between the housing 55 and the O-ring. 58, the O-ring 59 and the free piston 57 are always in communication with a chamber 137 surrounded by the free piston 57. In other words, the passage groove 142 guides the oil from the upper chamber communication chamber 133 to the chamber 137 between the O-ring 58 and the O-ring 59. The passage groove 142 is formed continuously with the tapered surface portion 67, the curved surface portion 68, and the large-diameter cylindrical surface portion 69 of the housing 55, so that the free piston is located at a position in the housing 55 that contacts one O-ring 58. 57 along the moving direction. The formation range of the passage groove 142 is set so that the upper chamber communication chamber 133 and the chamber 137 communicate with each other over the entire movement range of the O-ring 58. Here, the passage groove 142 is not formed in the large-diameter cylindrical surface portion 84 of the housing body 52.

  Also in the third embodiment, since the passage groove 142 for guiding the working fluid is provided in the chamber 137 between the O-ring 58 and the O-ring 59, air is extracted from the chamber 137 in the assembly process of the shock absorber. The chamber 137 can be filled with working fluid. Thereby, it is possible to satisfactorily change the damping force in response to the frequency.

  Further, since the passage groove 142 is formed along the moving direction of the free piston 57 at a position in contact with the one O-ring 58 in the housing 55, the width, depth, number, etc. of the passage groove 142 are changed. As a result, the deformation characteristics of the O-ring 58 can be easily changed, and the movement characteristics of the free piston 57 can be changed.

  Any two of the passage hole 105 of the first embodiment, the passage groove 140 of the second embodiment, and the passage groove 142 of the third embodiment may be combined, or all three of these may be combined. good.

“Fourth Embodiment”
Next, the fourth embodiment will be described mainly based on FIGS. 7 and 8 with a focus on differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol.

  As shown in FIG. 7, in the fourth embodiment, the passage hole 105 of the first embodiment is not provided, and instead, from the small-diameter cylindrical surface portion 97 of the free piston 57 through the curved surface portion 98 to the tapered surface portion 99. A passage groove (passage) 144 extending in the axial direction while being recessed inward in the radial direction is formed up to an intermediate position. As shown in FIG. 8, the passage groove 144 is formed at a plurality of positions, specifically, at four positions at equal intervals in the circumferential direction of the free piston 57. 7 prevents the O-ring 59 shown in FIG. 7 from coming into close contact with the small-diameter cylindrical surface portion 97, the curved surface portion 98, and the tapered surface portion 99, so that the lower chamber communication chamber 134 is formed between the housing 55 and the O-ring 58. And an O-ring 59 and a free piston 57 are always in communication with a chamber 137 surrounded by the free piston 57. In other words, the passage groove 144 guides the oil liquid from the lower chamber communication chamber 134 to the chamber 137 between the O-ring 58 and the ring 59. The passage groove 144 is formed continuously with the small-diameter cylindrical surface portion 97, the curved surface portion 98, and the tapered surface portion 99 of the free piston 57, so that the free piston 57 is free at a position where it comes into contact with the other O-ring 59. It is formed along the moving direction of the piston 57. The formation range of the passage groove 144 is set so that the lower chamber communication chamber 134 and the chamber 137 communicate with each other over the entire movement range of the O-ring 59.

  Also in the fourth embodiment, since the passage groove 144 that guides the working fluid is provided in the chamber 137 between the O-ring 58 and the O-ring 59, air is supplied to the chamber 137 in the assembly process of the shock absorber. Can be pulled out and filled with working fluid. Thereby, it is possible to satisfactorily change the damping force in response to the frequency.

  Further, since the passage groove 144 is formed along the movement direction of the free piston 57 at a position in contact with the other O-ring 59 in the free piston 57, the width, depth, number, etc. of the passage groove 144 are set. By changing, the deformation characteristic of the O-ring 59 can be easily changed, and the movement characteristic of the free piston 57 can be changed.

“Fifth Embodiment”
Next, the fifth embodiment will be described mainly on the basis of FIG. 9 focusing on the differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol.

  As shown in FIG. 9, the fifth embodiment is not provided with the passage hole 105 of the first embodiment, and instead penetrates radially to the position of the large-diameter cylindrical surface portion 84 of the housing body 52 of the housing 55. A passage hole (passage) 146 is formed. A plurality of passage holes 146 are formed at intervals in the circumferential direction of the housing 55. Through these passage holes 146, the lower chamber 5 is always in communication with a chamber 137 surrounded by the housing 55, the O-ring 58, the O-ring 59 and the free piston 57. In other words, the passage hole 146 guides the oil from the lower chamber 5 to the chamber 137 between the O-ring 58 and the O-ring 59. The passage hole 146 matches the position of the outer annular protrusion 93 of the free piston 57 in the neutral position with the position of the free piston 57 in the axial direction. The passage hole 146 is formed at a position where the O-ring 58 and the O-ring 59 are not in contact with each other in the entire movement range.

  Also in the fifth embodiment, since the passage hole 146 for introducing the working fluid is provided in the chamber 137 between the O-ring 58 and the O-ring 59, air is extracted from the chamber 137 in the assembly process of the shock absorber. The chamber 137 can be filled with working fluid. Thereby, it is possible to satisfactorily change the damping force in response to the frequency.

  Further, the passage hole 146 is formed in the housing 55 at a position where it does not contact any of the O-ring 58 and the O-ring 59, so that the O-ring 58, It is possible to prevent the lifetime of 59 from being lowered. Therefore, the life of the O-rings 58 and 59 can be extended.

“Sixth Embodiment”
Next, the sixth embodiment will be described mainly based on FIGS. 10 and 11 with a focus on differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol.

  As shown in FIG. 10, in the sixth embodiment, the passage hole 105 of the first embodiment is not provided. Instead, the housing body 52 of the housing 55 passes from the tapered surface portion 82 through the curved surface portion 83. The large-diameter cylindrical surface portion 84 is formed with a passage groove (passage) 148 that extends in the axial direction while being recessed outward in the radial direction. As shown in FIG. 11, the passage grooves 148 are formed at a plurality of locations, specifically four locations, at equal intervals in the circumferential direction of the housing body 52. 10 prevents the O-ring 59 shown in FIG. 10 from coming into close contact with the tapered surface portion 82, the curved surface portion 83, and the large-diameter cylindrical surface portion 84, so that the lower chamber communication chamber 134 is connected to the housing 55 and the O-ring. 58, an O-ring 59, and a free piston 57 are always in communication with a chamber 137 surrounded by the free piston 57. In other words, the passage groove 148 guides the oil liquid from the lower chamber communication chamber 134 to the chamber 137 between the O-ring 58 and the O-ring 59. Since the passage groove 148 is formed continuously from the tapered surface portion 82, the curved surface portion 83, and the large diameter cylindrical surface portion 84 of the housing 55, the free piston is provided at a position in the housing 55 that contacts one O-ring 59. 57 along the moving direction. The formation range of the passage groove 148 is set so that the lower chamber communication chamber 134 and the chamber 137 communicate with each other in the entire movement range of the O-ring 59. Here, the passage groove 148 is not formed in the large-diameter cylindrical surface portion 69 of the lid member 51.

  Also in the sixth embodiment, since the passage groove 148 that guides the working fluid is provided in the chamber 137 between the O-ring 58 and the O-ring 59, air is supplied to the chamber 137 in the assembly process of the shock absorber. Can be pulled out and filled with working fluid. Thereby, it is possible to satisfactorily change the damping force in response to the frequency.

  Further, since the passage groove 148 is formed along the moving direction of the free piston 57 at a position in contact with the other O-ring 59 in the housing 55, the width, depth, number, etc. of the passage groove 148 are changed. As a result, the deformation characteristics of the O-ring 59 can be easily changed, and the movement characteristics of the free piston 57 can be changed.

  Any two of the passage groove 144 of the fourth embodiment, the passage hole 146 of the fifth embodiment, and the passage groove 148 of the third embodiment may be combined, or all three of these may be combined. good.

  In each of the above embodiments, the present invention is applied to a monotube type hydraulic shock absorber. However, the present invention is not limited to this, and an outer cylinder is provided on the outer periphery of the cylinder, and a reservoir is provided between the outer cylinder and the cylinder. It may be used for a double cylinder type hydraulic shock absorber, and can be used for any shock absorber. In the case of a double cylinder type hydraulic shock absorber, a bottom valve that communicates the lower chamber and the reservoir is provided at the bottom of the cylinder, and the housing is provided on the bottom valve, so that the present invention can be applied to the bottom valve. It is. Further, when an oil passage communicating with the inside of the cylinder is provided outside the cylinder, and the damping force generating mechanism is provided in the oil passage, the housing is provided outside the cylinder.

In the above embodiment, the hydraulic shock absorber is shown as an example, but water or air may be used as the fluid.
Further, in each of the above-described embodiments, two examples of the O-ring are shown. However, one or three or more O-rings may be used according to the same technical idea as necessary.
In each of the above embodiments, an example in which a rubber (resin) ring is used as an elastic body has been shown. However, the elastic body is not elastic in one axial direction but has elasticity in a plurality of axial directions. If so, it does not have to be rubber.

1 Cylinder 3 Piston 4 Upper chamber (chamber)
5 lower room (room)
8 Piston rod 8
30a, 30b passage (first passage)
135,136 passage (second passage)
32a, 32b Damping force generating mechanism 55 Housing 57 Free piston 58 O-ring (elastic ring)
59 O-ring (elastic ring)
105,146 passage hole (passage)
140,142,144,148 passage groove (passage)

Claims (3)

A cylinder filled with a working fluid;
A piston that is slidably fitted in the cylinder and divides the cylinder into two chambers;
A piston rod connected to the piston and extending outside the cylinder;
A first passage and a second passage through which working fluid flows from one chamber in the cylinder to the other chamber by the movement of the piston;
A damping force generating mechanism provided in the first passage for generating a damping force;
A housing in which at least a part of the flow path of the second passage is formed;
A free piston movably provided in the housing and defining the second passage upstream and downstream;
One elastic ring that is fitted to both the free piston and the housing with a tightening margin in the radial direction, and generates an elastic force against movement of the free piston to one side,
A second elastic ring that is fitted to both the free piston and the housing with a tightening margin in a radial direction and generates an elastic force with respect to the movement of the free piston to the other;
A shock absorber characterized in that a passage is provided in which the one chamber or the other chamber communicates with a chamber surrounded by the housing, the one elastic ring, the other elastic ring, and the free piston . 2. The buffer according to claim 1, wherein the passage is a passage hole formed at a position in the free piston or the housing that does not contact either the one elastic ring or the other elastic ring. vessel. Said passage comprises at least one of the one, to a position in contact with the one of the elastic ring or the other of the elastic ring, passage formed along the moving direction of the free piston of the free piston and said housing The shock absorber according to claim 1, wherein the shock absorber is a groove .

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