JP5639879B2 - 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, in the shock absorber, it is required to make the damping force characteristic smooth.

  Accordingly, an object of the present invention is to provide a shock absorber capable of smoothing damping force characteristics.

  To achieve the above object, the present invention provides a first passage and a second passage communicating between two chambers, a damping force generating mechanism that is provided in the first passage and generates a damping force, and the second passage. A pressure chamber provided in the middle of the pressure chamber, a free piston movably provided in the pressure chamber and defining the second passage in two regions, and a damping valve provided at the inner and outer passage ports of the pressure chamber, It was set as the structure provided with.

  According to the present invention, the damping force characteristic can be made smooth.

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 a top view which shows the base member of the buffer of 1st Embodiment which concerns on this invention. It is a characteristic diagram which shows the relationship between the stroke of 1st Embodiment which concerns on this invention, and damping force. It is sectional drawing which shows 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 2nd embodiment concerning the present 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”
A first embodiment according to the present invention will be described with reference to FIGS. 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 double cylinder type hydraulic shock absorber, and has a bottomed cylindrical cylinder 1 in which an oil liquid as a working fluid is sealed, and a larger diameter than the cylinder 1. And the outer cylinder 2 which is arranged coaxially with the cylinder 1 and covers the cylinder 1. 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 end of the outer cylinder 2 opposite to the protruding side of the piston rod 8 is closed with a base cap 11, and a base valve 12 is attached between the base cap 11 and the cylinder 1. An oil liquid is sealed in the upper chamber 4 and the lower chamber 5 in the cylinder 1, and a reservoir chamber 13 is provided between the cylinder 1 and the outer cylinder 2. The reservoir chamber 13 is filled with oil and high-pressure gas.

  The base valve 12 controls communication and blocking between the lower chamber 5 and the reservoir chamber 13, and the lower chamber 5 side has a higher pressure than the reservoir chamber 13 side. The flow of the oil liquid from the reservoir chamber 13 to the lower chamber 5 side is allowed in a state where the damping force is generated by allowing the oil liquid flow to the lower chamber 5 and the pressure on the lower chamber 5 side is lower than the pressure on the reservoir chamber 13 side. Allow. When the amount of protrusion of the piston rod 8 from the cylinder 1 changes, the volume in the cylinder 1 increases or decreases. Correspondingly, the oil liquid flows between the lower chamber 5 and the reservoir chamber 13 via the base valve 12. It is supplied and discharged at.

  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.

  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 controlling 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 generation mechanism that generates a damping force by controlling the flow of oil in the contraction-side passage 30b.

  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 disc 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 including a main body 52 and a disk-like base member 54 of a damping valve mechanism 53 attached so as to close the other end opening side of the housing main body 52, and is slidably fitted into the housing 55. A free piston 57, an O-ring 58 that is interposed between the free piston 57 and the lid member 51 of the housing 55, and is a compression-side elastic body that compresses and deforms when the free piston 57 moves in one direction; Elongation that is interposed between the piston 57 and the housing body 52 of the housing 55 and compresses and deforms when the free piston 57 moves in the other direction. Is composed of the O-ring 59 is an elastic body. 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. And a lid outer cylinder portion 64 extending from the outer peripheral side of the lid plate portion 63 in the same direction as the lid inner cylinder portion 62.

  On the inner peripheral portion of the lid inner cylinder portion 62, the above-described female screw 50 is formed so as to project radially inward from an intermediate position in the axial direction to an end position opposite to the lid plate portion 63. 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, and a curved surface portion 68 in this order from the lid plate 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 curved surface portion 68 has an arc shape in cross section including the central axis of the lid member 51.

  The housing body 52 is formed mainly by cutting, and has a substantially cylindrical shape in which one side in the axial direction is narrowed. On the inner peripheral portion of the housing main body 52, an annular inner annular projection 79 protruding radially inward is formed at the constricted portion. On the inner peripheral surface of the housing main body 52, in order from one side in the axial direction, a small-diameter side fitting cylindrical surface portion 80, a smaller-diameter small-diameter cylindrical surface portion 81, a tapered surface portion 82, a curved surface portion 83, a large-diameter cylindrical surface portion 84, and so on. A large-diameter large-diameter fitting cylindrical surface portion 85 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 portion 64 of the lid member 51 is fitted to the large-diameter fitting cylindrical surface portion 85 of the housing main body 52. By fitting the large-diameter side fitting cylindrical surface portion 85, the curved surface portion 68 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 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, in the housing main body 52, the lid member 51 has a large-diameter side fitting at the lid outer cylinder part 64 with the lid inner cylinder part 62 and the lid outer cylinder part 64 on the front side and the lid plate part 63 on the rear side. It will be fitted to the combined cylindrical surface portion 85. 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. Further, the disc-shaped base member 54 of the damping valve mechanism 53 is fitted into the small diameter side fitting cylindrical surface portion 80, and in this state, a part of the small diameter side fitting cylindrical surface portion 80 of the housing body 52 is formed. The base member 54 is fixed and integrated with the housing main body 52 by crimping the end portion protruding from the base member 54 inward. Thus, the housing body 52, the lid member 51, and the base member 54 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 an axial intermediate portion of the piston tube portion 91. In addition, an annular outer annular projection 93 projecting radially outward is formed in the piston cylinder portion 91 at an intermediate position in the axial direction.

  A small-diameter cylindrical surface portion 97 is formed on the outer peripheral surface of the piston cylinder portion 91 on the lower chamber 5 side with respect to the outer annular projection 93. The curved surface portion 98 and the tapered surface portion are formed on the outer annular projection 93 in order from the lower chamber 5. 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.

  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. A 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 through-holes 105 penetrating the outer annular protrusion 93 in the radial direction at the axial center position of the outer annular protrusion 93.

  The free piston 57 is slidably inserted into the large-diameter cylindrical surface portion 84 of the housing main body 52 in the large-diameter cylindrical surface portion 100 in a state of being disposed in the housing 55. 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.

  In addition, between the large-diameter cylindrical surface portion 84 of the housing body 52, 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, Between the outer annular protrusion 93 of the free piston 57 and the other inner annular protrusion 86 of the housing, an O-ring 58 (the natural state is shown in FIG. 2) is arranged. 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 housing body 52. The diameter is larger than that of the surface portion 84. 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 84, 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 84, 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 curved surface portion 102 and the tapered surface portion 101, and the large diameter cylindrical surface portion 84, 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 84 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 84 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.

  The disc-shaped base member 54 of the damping valve mechanism 53 is formed with a fitting hole 110 penetrating in the center in the axial direction. As shown in FIG. 3, the base member 54 has inflow holes (inner and outer passage ports) 111 as two orifices penetrating in the axial direction at positions different from each other by 180 degrees around the fitting hole 110. Outflow holes (inner and outer passage openings) 112 as two orifices are formed penetratingly along the axial direction at positions different from these inflow holes 111 by 90 degrees. The two outflow holes 112 are also 180 degrees apart from each other around the fitting hole 110. The base member 54 is formed with an inflow side sheet portion 113 protruding in the axial direction so as to surround the inflow holes 111 on one side in the axial direction, and these inflow side sheet portions 113 are arranged around the fitting hole 110. It is connected to each other so as to surround. The two inflow-side sheet portions 113 as a whole are not circular with the fitting hole 110 as the center, but are irregularly shaped sheets. On the other side in the axial direction of the base member 54, an outflow side sheet portion 114 protruding in the axial direction is formed so as to surround the outflow holes 112, and these outflow side sheet portions 114 are also formed in the fitting holes 110. They are connected to each other so as to surround them. The outflow side sheet portion 114 is also a deformed sheet. The base member 54 has the same shape on both sides, and the inflow hole 111, the outflow hole 112, the inflow side seat part 113, and the outflow side sheet part 114 are defined by the direction of attachment to the housing body 52.

  As shown in FIG. 2, the damping valve mechanism 53 includes an annular inflow side disk valve (attenuation valve) 117 that can be seated simultaneously on the entire inflow side seat portion 113 surrounding the inflow hole 111 of the base member 54, and an inflow side. An annular spacer 118 having a smaller diameter than the disk valve 117 and disposed on the opposite side of the base member 54 of the inflow side disk valve 117, and a base member 54 having a larger diameter than the spacer 118 and the spacer 118 And an annular valve regulating member 119 disposed on the opposite side. The inflow side disk valve 117, the spacer 118, and the valve restricting member 119 are disposed inside the housing 55.

  The inflow side disc valve 117 is configured by stacking a plurality of annular disks, and closes the inflow hole 111 by being seated on the inflow side seat portion 113 and is separated from the inflow side seat portion 113. As a result, the inflow hole 111 is opened, and the open passage area of the inflow hole 111 is changed according to the amount of deformation at the time of separation. The valve restricting member 119 restricts deformation of the inflow side disc valve 117 beyond the regulation in the opening direction.

  The damping valve mechanism 53 has an annular outflow side disk valve (damping valve) 121 that can be simultaneously seated on the entire outflow side seat portion 114 surrounding the outflow hole 112 of the base member 54, and a smaller diameter than the outflow side disk valve 121. In addition, an annular spacer 122 disposed on the opposite side to the base member 54 of the outflow side disk valve 121 and a main shaft member 123 are provided. The main shaft member 123 has a larger diameter than the spacer 122 and is disposed on the opposite side of the spacer 122 from the base member 54, the spacer 122, the outflow side disk valve 121, the base member 54, and the inflow side disk valve. 117, a spacer 118, and a shaft restricting portion 119 that penetrates the valve restricting member 119 and engages with the valve restricting member 119. The outflow side disk valve 121 and the spacer 122 are disposed outside the housing 55.

  The outflow side disc valve 121 is also configured by stacking a plurality of annular discs. The outflow hole 112 is closed by being seated on the outflow side seat portion 114 and is separated from the outflow side seat portion 114. As a result, the outflow hole 112 is opened, and the open passage area of the outflow hole 112 is changed according to the amount of deformation at the time of separation. Further, the flange portion 124 of the main shaft member 123 restricts deformation beyond the regulation in the opening direction of the outflow side disk valve 121.

  The main shaft member 123 has a caulking portion 126 formed by the distal end portion of the shaft portion 125 being caulked and spread in the radial direction to lock the valve restricting member 119. In this manner, the main shaft member 123, the spacer 122, the outflow side disk valve 121, the base member 54, the inflow side disk valve 117, the spacer 118, and the valve restricting member 119 are integrally assembled to form the damping valve mechanism 53. Here, the inner diameter of the piston cylinder portion 91 of the free piston 57 is larger than the outer diameter of the inflow side disk valve 117, and a caulking portion 126, a valve regulating member 119, a spacer is provided inside the piston cylinder portion 91. 122, the inflow side disc valve 117 and the inflow side seat portion 113 can enter. Instead of caulking the shaft portion 125, the valve regulating member 119 may be locked to the main shaft member 123 by screw fastening.

  The damping force variable mechanism 35 includes, for example, an O-ring 59 inserted up to the position of the curved surface portion 83 in the housing body 52 to which the damping valve mechanism 53 is attached in advance, and the inside of the housing body 52 and the O-ring 59. The free piston 57 is fitted to the housing body 52, the O-ring 58 is inserted between the housing main body 52 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. become. 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 this time, the lid plate 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. In addition, the lower chamber 5 can communicate with the housing 55 through either the inflow hole 111 or the outflow hole 112 of the damping valve mechanism 53 of the housing 55. The housing 55, the O-ring 59, and the free piston 57 can communicate with each other in a lower chamber communication chamber 134.

  The O-ring 59 disposed between the housing body 52 and the free piston 57 is disposed so as to always seal between the housing 55 and the free piston 57, and the upper chamber communication chamber 133 and the lower chamber communication chamber 134. Always block communication with. The damping valve mechanism 53 is disposed at a boundary position between the lower chamber communication chamber 134 and the lower chamber 5 of the pressure chamber 132 and generates a damping force with respect to the bidirectional flow of inflow and outflow to the lower chamber 5. Let Further, the inflow hole 111 of the damping valve mechanism 53 constitutes an inner and outer passage opening at the boundary with the lower chamber 5 of the pressure chamber 132 formed in the housing 55 when the oil liquid flows from the lower chamber 5. An inflow side disc valve 117 as a damping valve is provided in the inflow hole 111. The outflow hole 112 of the damping valve mechanism 53 constitutes an inner and outer passage opening at the boundary with the lower chamber 5 of the pressure chamber 132 formed in the housing 55 when the oil liquid flows into the lower chamber 5. An outflow side disk valve 121 as a damping valve is provided in the hole 112.

  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 inflow hole 111 and the lower chamber communication chamber 134 of the damping valve mechanism 53 pass through 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 side. It is composed. Therefore, a part of the passage 135 is formed in the housing 55, and a part of the 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. The O-rings 58 and 59 arranged on both sides in the sliding direction of the free piston 57 generate a resistance force against the displacement of the free piston 57.

  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. In addition, the oil liquid is introduced into the upper chamber communication chamber 133 from the upper chamber 4, and the outflow side disk valve 121 of the damping valve mechanism 53 is opened from the lower chamber communication chamber 134 of the damping force variable mechanism 35, and the downstream in the passage 136. The free piston 57 resists the urging force of the O-ring 59 on the axial lower chamber 5 side while discharging the oil liquid to the lower chamber 5 through the side outflow hole 112. 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. This means that while the free piston 57 is moving, the oil liquid apparently flows separately from the piston portion, thereby decreasing the damping force.

  In the subsequent contraction stroke, the pressure in the lower chamber 5 increases, so the inflow side disk valve 117 of the damping valve mechanism 53 is opened, and the lower chamber communication of the damping force variable mechanism 35 is established via the upstream inflow hole 111 in the passage 136. The oil liquid is introduced into the chamber 134 from the lower chamber 5 and 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 lower chamber 5 in the axial direction until then. The free piston 57 that has moved to the 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 oil liquid is introduced from the lower chamber 5 into the lower chamber communication chamber 134 and is introduced from the lower chamber 5 into the passage 30b and the damping force. The flow rate of the oil liquid flowing through the generating mechanism 32b and flowing into the upper chamber 4 is reduced. As a result, the damping force decreases in the same manner as the extension stroke.

  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 outflow side disk valve of the damping valve mechanism 53 from the lower chamber communication chamber 134 at each expansion stroke described above. The oil liquid flows from the upper chamber 4 to the upper chamber communication chamber 133 while opening 121 and discharging the oil liquid to the lower chamber 5 through the outflow hole 112, and a passage hole is formed from the upper chamber communication chamber 133 in each contraction stroke. The oil liquid flows from the lower chamber 5 to the lower chamber communication chamber 134 through the inflow hole 111 by opening the inflow side disk valve 117 of the damping valve mechanism 53 while discharging the oil liquid to the upper chamber 4 through 130, 131. Thus, as described above, the damping force is maintained in a lowered state.

  On the other hand, when the piston speed is low, if the frequency of the piston 3 is low, the frequency of movement of the free piston 57 is also low, so the outflow of the damping valve mechanism 53 from the lower chamber communication chamber 134 at the beginning of the extension stroke. Although the oil liquid flows from the upper chamber 4 to the upper chamber communication chamber 133 while opening the side disk valve 121 and discharging the oil liquid to the lower chamber 5 through the outflow hole 112, the free piston 57 then compresses the O-ring 59. Therefore, the oil liquid stops flowing from the upper chamber 4 to the upper chamber communication chamber 133, and is introduced into the passage 30a from the upper chamber 4 and passes through the damping force generating mechanism 32a. Therefore, the flow rate of the oil flowing through the cylinder does not decrease, and the damping force increases.

  Even in the subsequent contraction stroke, at the initial stage, the inflow side disk valve 117 of the damping valve mechanism 53 is opened from the lower chamber 5 while the oil liquid is discharged from the upper chamber communication chamber 133 to the upper chamber 4 through the passage holes 130 and 131. Although the oil liquid flows into the lower chamber communication chamber 134 through the hole 111, the free piston 57 then compresses the O-ring 58 and stops on the upper chamber 4 side in the axial direction, and from the lower chamber 5 to the lower chamber communication chamber 134. Therefore, the flow rate of the oil liquid introduced into the passage 30b from the lower chamber 5 through the damping force generation 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 and 59 between the free piston 57 and the housing 55 are located between the large-diameter cylindrical surface portion 84 of the housing main body 52 and the small-diameter cylindrical surface portions 97 and 103 of the free piston 57.

  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 process from the neutral position, the large-diameter cylindrical surface portion 84 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 84 of the housing 55 and the small-diameter cylindrical surface portion 103 of the free piston 57 roll between each other so that the axially 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 84 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 84 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 lower chamber 5 side in the axial direction relative 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.

  When switching from the contraction stroke to the extension stroke, the inflow side disk valve 117 of the damping valve mechanism 53 temporarily closes the inflow hole 111 and the outflow side disk valve 121 closes the outflow hole 112. 4, the pressure of the upper chamber communication chamber 133 increases, and the pressure of the lower chamber communication chamber 134 does not become higher than the pressure of the lower chamber 5 by a predetermined value via the free piston 57. Then, the outflow side disk valve 121 does not open the outflow hole 112. When the pressure in the lower chamber communication chamber 134 becomes higher than the pressure in the lower chamber 5 by a predetermined value, the outflow side disk valve 121 opens the outflow hole 112 and allows oil to flow from the lower chamber communication chamber 134 to the lower chamber 5. (During this time, the inflow disc valve 117 keeps closing the inflow hole 111). As described above, when the outflow side disk valve 121 opens the outflow hole 112 and discharges the oil from the lower chamber communication chamber 134 to the lower chamber 5, the outflow side disk valve 121 gradually moves into the outflow hole 112 as an orifice. The opening area will be expanded. As described above, the damping force can be generated smoothly immediately after switching from the contraction stroke to the extension stroke, and the damping force transient characteristic of switching from the contraction stroke to the extension stroke can be smoothed.

  In addition, when switching from the above-described expansion stroke to the contraction stroke, a state in which the outflow side disk valve 121 of the damping valve mechanism 53 temporarily closes the outflow hole 112 and the inflow side disk valve 117 closes the inflow hole 111 occurs. Even if oil liquid flows from the chamber 5 to the lower chamber communication chamber 134, the pressure in the lower chamber 5 increases and does not become a predetermined value higher than the pressure in the lower chamber communication chamber 134, the inflow side disk valve 117 opens the inflow hole 111. Absent. When the pressure in the lower chamber 5 becomes higher than the pressure in the lower chamber communication chamber 134 by a predetermined value, the inflow side disk valve 117 opens the inflow hole 111 and allows oil to flow from the lower chamber 5 to the lower chamber communication chamber 134 ( During this time, the outflow disc valve 121 keeps closing the outflow hole 112). Thus, even when the inflow side disc valve 117 opens the inflow hole 111 and the oil liquid flows into the lower chamber communication chamber 134 from the lower chamber 5, the inflow side disc valve 117 gradually becomes the inflow hole 111 as an orifice. This increases the opening area. As described above, the damping force can be generated smoothly immediately after switching from the extension stroke to the contraction stroke, and the damping force transient characteristic of switching from the extension stroke to the contraction stroke can be smoothed.

  That is, when the outflow side disk valve 121 and the inflow side disk valve 117 of the damping valve mechanism 53 are not provided, as shown by a broken line in FIG. 4, immediately after the stroke is switched from the contraction side to the expansion side, and from the expansion side. Immediately after switching to the contraction side, regions Y1 ′ and Y2 ′ in which the damping force is insufficient are generated. On the other hand, by providing the outflow side disk valve 121 and the inflow side disk valve 117, as shown by the solid line in FIG. 4, the shortage of damping force is suppressed as in the areas Y1 and Y2 with respect to the areas Y1 ′ and Y2 ′. The delay of the damping force can be reduced. That is, immediately after the stroke of the shock absorber is switched from the contraction side to the extension side, the outflow hole 112 is temporarily closed by the outflow side disk valve 121, so that the oil liquid from the upper chamber 4 to the upper chamber communication chamber 133 is obtained. And a flow of oil from the lower chamber communication chamber 134 to the lower chamber 5 are temporarily blocked to generate a damping force (region Y1). Further, immediately after the stroke of the shock absorber is switched from the expansion side to the contraction side, the inflow hole 111 is temporarily closed by the inflow side disk valve 117, so that the oil liquid from the lower chamber 5 to the lower chamber communication chamber 134 is obtained. And a flow of oil from the upper chamber communication chamber 133 to the upper chamber 4 are temporarily blocked to generate a damping force (solid line region Y2).

  According to the first embodiment described above, the outflow as a damping valve that generates a damping force in the outflow hole 112 and the inflow hole 111 that are the inner and outer passage ports on the lower chamber 5 side formed in the housing 55. Since the side disc valve 121 and the inflow side disc valve 117 are provided, the damping force characteristic can be made smooth, and in particular, the damping force transient characteristic at the time of reversing the expansion / contraction stroke can be made smooth. Thereby, in a vehicle equipped with this shock absorber, it is possible to generate a sense of responsiveness to the operation at the time of reversal of steering, and it is possible to improve the operational feeling. In this way, when the expansion / contraction stroke is reversed, the delay of the damping force is alleviated and the damping force transient characteristic is smoothed. As a result, the piston rod 8 is vibrated to generate noise and vibration due to pressure fluctuations at once. Can be reduced.

  Further, in the damping valve mechanism 53, since the inflow side disk valve 117 and the outflow side disk valve 121 are used as the damping valves, the configuration of the damping valve mechanism 53 can be simplified and the overall length can be suppressed.

  Further, since the inflow side disk valve 117 and the outflow side disk valve 121 generate a damping force with respect to the bidirectional flow between the lower chamber 5 and the pressure chamber 132, the damping is performed when the expansion stroke is switched to the contraction stroke. Both the force transient characteristic and the damping force transient characteristic when switching from the contraction stroke to the extension stroke can be made smooth.

  Further, by making the inflow side seat portion 113 and the outflow side seat portion 114 differently shaped sheets, the outflow side disk valve 121 side can always be opened as the straight inflow hole 111, and the inflow side as the straight outflow hole 112 is also provided. Since the disk valve 117 side can always be opened, the thickness of the base member 54 can be suppressed, and as a result, the entire thickness of the damping valve mechanism 53 can be suppressed.

  Further, the inner diameter of the piston cylinder portion 91 of the free piston 57 of the damping force variable mechanism 35 is larger than the outer diameter of the inflow side disk valve 117. Since the restricting member 119, the spacer 118, the inflow side disk valve 117, and the inflow side seat portion 113 can enter, the entire length of the damping force variable mechanism 35 can be suppressed.

  The valve opening characteristic of the damping valve mechanism 53 that affects the damping force frequency characteristic of the shock absorber according to the first embodiment includes the pressure receiving area of the inflow side seat portion 113, the passage diameter of the inflow hole 111, and the valve of the inflow side disk valve 117. This is determined by the rigidity, the pressure receiving area of the outflow side seat portion 114, the passage diameter of the outflow hole 112, and the valve rigidity of the outflow side disk valve 121.

“Second Embodiment”
Next, the second 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, the second embodiment is a so-called monotube type hydraulic shock absorber that does not have the outer cylinder 2 and the base valve 12 of the first embodiment. For this reason, a partition body 141 for partitioning the lower chamber 5 and the chamber 140 is slidably provided in the cylinder 1 on the bottom side of the cylinder 1 with respect to the piston 3. The chamber 140 is filled with high-pressure (about 20 to 30 atmospheres) gas.

  Furthermore, the second embodiment is partially different from the first embodiment in the damping force variable mechanism 35. Specifically, as shown in FIG. 6, in the damping force variable mechanism 35, the damping valve mechanism 53 is attached to the lid member 51 instead of the housing body 52 of the housing 55. That is, the in-lid cylinder part 62 of the lid member 51 is formed with a threaded cylinder part 144 in which a female screw 50 to be screwed into the male screw 49 of the piston rod 8 is formed, and the lid plate part 63 with respect to the screwed cylinder part 144. Has a fixed cylinder portion 145 protruding to the opposite side. On the inner peripheral surface of the fixed cylindrical portion 145, the cylindrical surface portion 146 in order from the screwed cylindrical portion 144 side, the tapered surface portion 147 that increases in diameter as the distance from the cylindrical surface portion 146 increases, and the fitting cylinder having a larger diameter than the large diameter side of the tapered surface portion 147. A surface portion 148 is provided.

  Then, the disc-shaped base member 54 of the damping valve mechanism 53 similar to that of the first embodiment is fitted to the fitting cylindrical surface portion 148, and in this state, the fitting cylindrical surface portion 148 of the housing body 52 is fitted. The base member 54 is fixed to and integrated with the housing main body 52 by forming a part and projecting the end portion protruding from the base member 54 inward.

  In the second embodiment, the damping valve mechanism 53 is disposed at the boundary position between the upper chamber communication chamber 133 of the pressure chamber 132 and the passage holes 130 and 131 connected to the upper chamber 4. A damping force is generated for the bidirectional flow of the outflow. Further, when the inflow hole 111 of the damping valve mechanism 53 flows in from the upper chamber 4, the inside and outside of the boundary between the pressure chamber 132 formed in the housing 55 and the passage holes 130, 131 on the upper chamber 4 side. The inflow hole 111 is provided with an inflow side disk valve 117 as a damping valve. The outflow hole 112 of the damping valve mechanism 53 is an internal / external passage opening at the boundary between the pressure chamber 132 formed in the housing 55 and the passage holes 130 and 131 on the upper chamber 4 side when the oil liquid flows into the upper chamber 4. The outflow hole 112 is provided with an outflow side disk valve 121 as a damping valve. In the second embodiment, a caulking portion 126, a spacer 118, and an annular valve regulating member 119 are provided on the outflow side disk valve 121 side. In addition to the flange portion 124 of the main shaft member 123, a valve restricting member 150 is provided between the flange portion 124 disposed on the inflow side disk valve 117 side and the spacer 122.

  Further, with the above arrangement of the damping valve mechanism 53, the piston closing plate portion 92 is formed to be shifted toward the lower chamber 5 side of the piston cylinder portion 91, and the inner diameter of the piston cylinder portion 91 is larger than the outer diameter of the fixed cylinder portion 145. The large-diameter free piston 57 is held by the housing 55 in a state where the damping valve mechanism 53 and the fixed cylinder part 145 have entered the piston cylinder part 91.

  When switching from the contraction stroke to the extension stroke, the outflow side disk valve 121 of the damping valve mechanism 53 temporarily closes the outflow hole 112, and the inflow side disk valve 117 closes the inflow hole 111. Even if the oil liquid flows into the upper chamber communication chamber 133 through the passage holes 130 and 131, the pressure on the upper chamber 4 increases and does not become a predetermined value higher than the pressure of the upper chamber communication chamber 133. The inflow hole 111 is not opened. When the pressure in the upper chamber 4 becomes higher than the pressure in the upper chamber communication chamber 133 by a predetermined value, the inflow side disk valve 117 opens the inflow hole 111 and allows oil to flow from the upper chamber 4 to the upper chamber communication chamber 133. (During this time, the outflow disc valve 121 keeps closing the inflow hole 112). As described above, when the inflow side disk valve 117 opens the inflow hole 111 and allows the oil liquid to flow into the upper chamber communication chamber 133 from the upper chamber 4 through the passage holes 130 and 131, the inflow side disk valve 117 is The opening area of the inflow hole 111 as an orifice is gradually expanded. As described above, the damping force can be generated smoothly immediately after switching from the contraction stroke to the extension stroke, and the damping force transient characteristic of switching from the contraction stroke to the extension stroke can be smoothed.

  In addition, when switching from the above-described expansion stroke to the contraction stroke, a state in which the inflow side disk valve 117 of the damping valve mechanism 53 temporarily closes the inflow hole 111 and the outflow side disk valve 121 closes the outflow hole 112 occurs. Even if oil liquid flows from the chamber communication chamber 133 to the upper chamber 4 through the passage holes 130 and 131, the pressure in the lower chamber 5 increases, and the pressure in the upper chamber communication chamber 133 is higher than the pressure in the upper chamber 4 by a predetermined value. Otherwise, the outflow disc valve 121 will not open the outflow hole 112. When the pressure in the upper chamber communication chamber 133 becomes higher than the pressure in the upper chamber 4 by a predetermined value, the outflow side disk valve 121 opens the outflow hole 112 and allows oil to flow from the upper chamber communication chamber 133 to the upper chamber 4. (During this time, the inflow disc valve 117 keeps closing the inflow hole 111). As described above, when the outflow side disc valve 121 opens the outflow hole 112 and allows the oil solution to flow out from the upper chamber communication chamber 133 through the passage holes 130 and 131 to the upper chamber 4, the outflow side disc valve 121 is The opening area of the outflow hole 112 as an orifice is gradually expanded. As described above, the damping force can be generated smoothly immediately after switching from the extension stroke to the contraction stroke, and the damping force transient characteristic of switching from the extension stroke to the contraction stroke can be smoothed.

  The first embodiment shows an example using the present invention for a double cylinder type hydraulic shock absorber, and the second embodiment shows a monotube type hydraulic shock absorber, but the damping valve mechanism 53 of the first embodiment is used. The damping force variable mechanism 35 including the damping tube mechanism 53 including the damping valve mechanism 53 according to the second embodiment may be applied to the monotube hydraulic shock absorber. . Furthermore, the present invention can be applied to the base valve 12 by providing the housing 55 in the base valve 12 of the double cylinder type hydraulic shock absorber. 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 55 is provided outside the cylinder. In addition, depending on the layout of the vehicle body, there are cases where there is a degree of freedom in the axial length and a degree of freedom in the radial direction when mounting the shock absorber. Although the shock absorber according to the first embodiment has a long axial length, the shock absorber according to the second embodiment can suppress the radial length, and the shock absorber according to the second embodiment can shorten the axial length, but the radial direction. The length increases. Therefore, the degree of freedom of attachment to the vehicle body can be improved by selecting as appropriate according to the layout of the vehicle body.

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, a plurality of rubber balls may be provided at intervals in the circumferential direction, and used in the present invention. The elastic body that can be used is not necessarily elastic in one axial direction, and may not be rubber as long as it has elasticity in a plurality of axial directions.

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 57 Free piston 111 Inflow hole (inside / outside passage port)
112 Outflow hole (inside / outside passageway)
117 Inflow side disk valve (damping valve)
121 Outflow disk valve (Damping valve)
132 Pressure chamber

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 communicating between the two chambers;
A damping force generating mechanism provided in the first passage for generating a damping force;
A pressure chamber provided in the middle of the second passage;
A free piston provided movably in the pressure chamber and defining the second passage in two regions;
A damping valve provided at the inner and outer passage opening of the pressure chamber and having a disk valve for generating a damping force ;
The free piston has a substantially cylindrical piston cylinder part and a piston closing plate part that closes the piston cylinder part, and the piston cylinder part has an inner diameter larger than an outer diameter of the disk valve, and the piston cylinder A shock absorber characterized in that the disk valve can enter into the section . The damping valve has an inflow side disk valve that opens and closes an inflow hole into the pressure chamber and an outflow side disk valve that opens and closes an outflow hole from the pressure chamber, and the inflow side disk valve is located in the piston cylinder portion. The shock absorber according to claim 1, wherein the shock absorber can be entered . The damping valve has an inflow side disk valve that opens and closes an inflow hole into the pressure chamber and an outflow side disk valve that opens and closes an outflow hole from the pressure chamber, and the inflow side disk valve and The shock absorber according to claim 1 , wherein the outflow side disk valve is in an approached state .

Images