JP2016173140A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber which has a very low speed attenuation force generating valve which generates attenuation force when the moving speed of a piton to a cylinder is at a very low speed close to 0.SOLUTION: An attenuation force generating valve 24 has a leaf valve element 50 cantilever-supported by a piston 18; and an opposite portion 54 oppositely spaced at a free end of the leaf valve element. The lead valve element 50 is configured so as to displace the free end in an arc-shape around a predetermined center when elastically deformed. The leaf valve element 50 and the opposite portion 54 are offset from each other in a displacing direction of the free end when the leaf valve element 50 starts elastic deformation, and at least one of surfaces opposite to each other of the free end and the opposite portion of the leaf element 50 is extended in the arc-shape around the center.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a shock absorber.

  In vehicles such as automobiles, shock absorbers are provided corresponding to the respective wheels for the purpose of damping unsprung vibrations. The shock absorber includes a cylinder and a piston that is fitted in the cylinder so as to be reciprocable and forms a cylinder upper chamber and a cylinder lower chamber in cooperation with the cylinder. The piston is provided with a damping force generation valve for an extension stroke and a damping force generation valve for a contraction stroke.

  Generally, the damping force generation valve for the extension stroke and the damping force generation valve for the contraction stroke are provided as independent valves. However, the damping force generation valve for the extension stroke and the damping force generation valve for the contraction stroke are provided. Shock absorbers configured as one valve are already known. For example, Patent Literature 1 below describes a shock absorber having a common damping force generation valve that achieves the functions of both a damping force generation valve for an extension stroke and a damping force generation valve for a contraction stroke.

  The common damping force generating valve is provided in common with the communication path provided in the piston and connecting the cylinder upper chamber and the cylinder lower chamber, the elastically deformable leaf valve element cantilevered by the piston, and the free end of the leaf valve element. And an opposing portion that forms an orifice that is part of the communication path. The free end has an end face perpendicular to the plate face of the leaf valve element. In the present specification, the damping force generating valve having this structure is referred to as an “opposing damping force generating valve”.

  In particular, FIG. 3 of Patent Document 1 describes an opposing type damping force generating valve configured so that the damping force in the expansion stroke is higher than the damping force in the contraction stroke. That is, when the leaf valve elements are viewed in a cross section perpendicular to the plate surface of the leaf valve element when not elastically deformed, they are in addition to each other along the displacement direction of the free end when the leaf valve element starts elastic deformation. It is offset with respect to it.

JP 2009-299768 A

[Problems to be Solved by the Invention]
When the opposing damping force generating valve is opened, the leaf valve element is bent by elastic deformation, and the free end of the leaf valve element is around a center near the cantilevered portion of the leaf valve element. It is displaced in a substantially arc shape. Therefore, when the leaf valve element is elastically deformed, the end face of the free end and the opposing member when the leaf valve element is not elastically deformed so that the upper and lower corners of the end face of the free end of the leaf valve element do not interfere with the opposing member. There is no choice but to increase the distance between them. Therefore, it is inevitable that the damping force in the very low speed region where the relative speed of the piston and the cylinder is very low is insufficient. Also, with the elastic deformation of the leaf valve element, the minimum distance between the end face of the free end and the opposing member, and thus the effective passage area of the orifice, changes unnecessarily. It is inevitable that the damping force unnecessarily increases or decreases with the increase of.

  The present invention has been made in view of the above-described problems in a conventional shock absorber having an opposing damping force generation valve. And the main subject of this invention is providing the shock absorber which has the opposing type damping force generation valve improved so that it can generate | occur | produce a required damping force, without increasing / decreasing unnecessarily in a very low speed range. It is.

[Means for Solving the Problems and Effects of the Invention]
According to the present invention, there is provided a cylinder and a piston that is reciprocally fitted to the cylinder and that cooperates with the cylinder to form first and second cylinder chambers. A shock absorber having a communication path connecting the first and second cylinder chambers, and a low-speed damping force generation valve that generates a damping force when the moving speed of the piston relative to the cylinder is a very low speed close to 0 The damping force generating valve for very low speed is cantilevered by the piston and elastically deformed by a differential pressure between the first and second cylinder chambers, and a free end of the leaf valve element A shock absorber is provided having a facing portion that is opposed to the free end and forms an orifice that is part of the communication path in cooperation with the free end.

  The leaf valve element is configured so that when viewed in a cross section perpendicular to the plate surface of the leaf valve element when not elastically deformed, the free end is displaced in an arc around a preset center when elastically deformed. Has been. The leaf valve element and the facing portion are offset from each other along the direction of displacement of the free end when the leaf valve element starts elastic deformation when viewed in the cross section. At least one of the free end of the leaf valve element and the mutually opposing surfaces of the facing portion has a region extending in an arc around the center as seen in the cross section.

  According to the above configuration, when viewed in a cross section perpendicular to the plate surface of the leaf valve element when the leaf valve element is not elastically deformed, the leaf valve element and the opposing portion are at the free end when the leaf valve element starts elastic deformation. They are offset from each other along the displacement direction. Therefore, it is possible to vary the damping force in the expansion stroke and the damping force in the contraction stroke when the elastic deformation amount of the leaf valve element is small, in other words, when the moving speed of the piston with respect to the cylinder is very low.

  Moreover, at least one of the mutually opposing surfaces of the free end and the opposing portion of the leaf valve element has a region extending in an arc around the center as seen in the cross section. Therefore, in the region where the amount of elastic deformation of the leaf valve element is small, the minimum distance between the free end of the leaf valve element and the opposing member when the leaf valve element is elastically deformed does not substantially change. Therefore, the distance between the free end and the opposing member when the leaf valve element is not elastically deformed can be made smaller than in the prior art, and the necessary damping force can be secured in the very low speed region. Further, in the very low speed region, that is, in the region where the amount of elastic deformation of the leaf valve element is small, the effective passage sectional area of the orifice determined by the minimum distance between the free end and the opposing member does not substantially change. Therefore, it can be avoided that the damping force is unnecessarily increased or decreased as the relative speed of the cylinder and the piston increases in the very low speed range.

It is sectional drawing which shows 1st embodiment of the shock absorber by this invention. It is an expanded fragmentary sectional view which shows the principal part of 1st embodiment. It is an expanded partial sectional view which shows the front-end | tip and opposing part of the leaf valve element of 1st embodiment. It is a graph which shows the damping-force characteristic of 1st embodiment. It is an expanded partial sectional view which shows the principal part of 2nd embodiment of the shock absorber by this invention. It is an expanded partial sectional view which shows the front-end | tip and opposing part of the leaf valve element of 2nd embodiment. It is an expanded partial sectional view which shows the principal part of the modification example of the shock absorber by this invention. It is a graph which shows the damping force characteristic of the correction example shown by FIG.

  Several preferred embodiments will now be described in detail with reference to the accompanying drawings.

[First embodiment]
1 to 3 are sectional views showing a shock absorber 10 according to the first embodiment of the present invention.

  In these drawings, a shock absorber 10 is fitted into a cylinder 12 extending along an axis 11 and a cylinder 12 so as to be reciprocable along the axis 11. And a piston 18 that forms a cylinder lower chamber 16. The cylinder upper chamber 14 and the cylinder lower chamber 16 are filled with oil 19 as a working liquid. The piston 18 includes a rod portion 18R extending along the axis 11 and a piston body 18M attached to the lower end portion of the rod portion 18R.

  Although not shown in the drawing, the upper end and the lower end of the cylinder 12 are closed by an end cap, and the rod portion 18R extends outside the cylinder 12 through the end cap at the upper end. The upper end of the rod portion 18R is connected to the vehicle body, and the lower end of the cylinder 12 is connected to the unsprung member of the vehicle. Further, a free piston is disposed in the cylinder 12 between the main body portion 18M of the piston 18 and the end cap at the lower end. The free piston cooperates with the end cap at the lower end to form a gas chamber, and separates the gas chamber from the cylinder lower chamber 16. As the volume of the rod portion 18R existing in the cylinder 12 changes as the shock absorber 10 expands and contracts, the gas chamber absorbs the change in the volume.

  As shown in FIG. 1, the piston body 18M is provided with a damping force generation valve 20 for an expansion stroke, a damping force generation valve 22 for a contraction stroke, and a damping force generation valve 24 for a very low speed. ing. The piston body 18M includes a main body 18MM and a sub body 18MS. The damping force generation valves 20, 22 and 24, the main body 18MM, and the sub body 18MS are sandwiched between the support ring 30 by a nut 28 that is screwed into a male screw 26 provided at the lower end of the rod portion 18R. Are attached to the lower end of the rod portion 18R.

  In the illustrated embodiment, a resin seal member 32 is attached to the outer periphery of the main body 18MM, and the seal member 32 is in sliding contact with the inner surface of the cylinder 12. The sub main body 18MS has an outer diameter smaller than the inner surface of the cylinder 12, and is fixed by press-fitting in a state of being fitted to the lower end portion of the main main body 18MM. Is forming. The main body 18MM is formed with an extension stroke passage 36 and a contraction stroke passage 38, and the sub body 18MS is formed with a plurality of passages 40 common to the extension stroke and the contraction stroke.

  The passage 36 is always in communication with an arc groove 42 and an annular groove 44 formed on the upper surface and the lower surface of the main body 18MM, respectively, and the arc groove 42 and the annular groove 44 extend around the axis 11. The arc groove 42 is always in communication with the cylinder upper chamber 14 through a notch 46 formed in the radially outer land portion regardless of whether or not the damping force generating valve 22 is in a closed state. . Even when the damping force generating valve 20 is in the closed state, the annular groove 44 is always in communication with the intermediate chamber 34 through the notch 45 formed in the land portion on the radially outer side.

  The passage 38 always communicates with an arc groove 48 formed on the upper surface of the main body 18MM so as to extend around the axis 11 at the upper end, and always communicates with the intermediate chamber 34 at the lower end. Even when the damping force generating valve 22 is in the closed state, the arc groove 48 is always in communication with the cylinder upper chamber 14 via the notch 49 formed in the land portion on the radially outer side. The passage 40 is always in communication with the intermediate chamber 34 at the upper end, and is always in communication with the annular groove 41 at the lower end. As will be described in detail later, the annular groove 41 is always in communication with the cylinder lower chamber 16 via the low speed damping force generating valve 24. In FIG. 1, only one passage 36 and 38 is shown, but a plurality of passages 36 and 38 may be provided in a state of being separated from each other around the axis 11.

  The damping force generation valve 20 for the extension stroke is formed by a laminated body of a plurality of reed valve elements 21 having an annular shape that can be elastically deformed, and is disposed in the intermediate chamber 34. The damping force generation valve 20 is cantilevered in a state of being sandwiched between the main body 18MM and the sub body 18MS together with the spacer 42 at the inner periphery. The damping force generation valve 22 for the contraction stroke is also formed of a laminated body of a plurality of reed valve elements 23 having an annular shape that can be elastically deformed, and is disposed in the cylinder upper chamber 14. The damping force generation valve 22 is cantilevered in a state of being sandwiched between the support ring 30 and the main body 18MM together with the spacer 43 at the inner peripheral portion.

  In addition, instead of the notch 45, a notch is provided in the outer edge portion of the reed valve element 21 of the damping force generating valve 20, and the annular groove 44 and the intermediate chamber 34 are always connected via the notch. Also good. Similarly, in place of the notch 49, a notch is provided in the outer edge portion of the reed valve element 23 having the largest outer diameter of the damping force generating valve 22, and the arc groove 48 and the cylinder upper chamber 14 are provided through these notches. May be always connected.

  As shown in FIGS. 1 and 2, the very low speed damping force generating valve 24 includes two reed valve elements 50 and two centering valve elements 52 that are elastically deformable and have an annular plate shape. Contains. The two reed valve elements 50 and the two centering valve elements 52 are stacked on each other, and the thicknesses of the four elements are all the same. The reed valve element 50 is cantilevered between the sub main body 18MS and the nut 28 together with the centering valve element 52 and the spacers 51 and 53 at the inner peripheral portion. On the radially outer side of the reed valve element 50, an annular plate-like facing member 54 formed of a substantially rigid material is disposed.

  A support member 56 is fixed to the outer periphery of the lower end portion of the sub-main body 18MS by, for example, press fitting, and the support member 56 has an annular plate-like support portion 56S at the lower end. The opposing member 54 is supported in a state of being sandwiched between the sub main body 18MS and the supporting portion 56S at the outer peripheral portion together with the spacer 57 disposed above the opposing member 54. In the first embodiment, the opposing member 54 has substantially the same thickness as the single reed valve element 50, and is in the radial direction with the lower reed valve element 50 when not elastically deformed. It is arranged at a matching position. The outer edge of the lower reed valve element 50 and the inner edge of the opposing member 54 are slightly spaced in the radial direction even when the two reed valve elements 50 are not elastically deformed to form a minute orifice 58. .

  As can be understood from the above description, the notch 46, the arc groove 42, the passage 36, the annular groove 44, the notch 45, the intermediate chamber 34, the passage 40 and the annular groove 41 connect the cylinder upper chamber 14 and the cylinder lower chamber 16. The communication path for the extending stroke is formed. The annular groove 41, the passage 40, the intermediate chamber 34, the passage 38, the circular arc groove 48, and the notch 49 form a communication path for a contraction stroke that connects the cylinder upper chamber 14 and the cylinder lower chamber 16. The orifice 58 is a part of the communication path for the extension stroke and the communication path for the contraction stroke.

  In the extension stroke of the shock absorber 10, the pressure in the cylinder upper chamber 14 becomes higher than the pressure in the cylinder lower chamber 16. Therefore, the oil 19 in the cylinder upper chamber 14 tends to flow to the cylinder lower chamber 16 through the communication path for the extension stroke. Accordingly, the two reed valve elements 50 of the very low speed damping force generating valve 24 are elastically deformed downward as indicated by a two-dot chain line in FIG. 2, for example. On the other hand, in the contraction stroke of the shock absorber 10, the pressure in the cylinder lower chamber 16 becomes higher than the pressure in the cylinder upper chamber 14. Therefore, the oil 19 in the cylinder lower chamber 16 tends to flow to the cylinder upper chamber 14 through the communication path for the contraction stroke. Accordingly, the two reed valve elements 50 are elastically deformed upward as indicated by a two-dot chain line in FIG. 2, for example.

  Accordingly, as shown in FIGS. 2 and 3, the locus drawn by the center of the outer edge when the two reed valve elements 50 are elastically deformed is a single point as seen in the radial section passing through the axis 11. This is a substantially arc-shaped locus 60 indicated by a chain line. The center O of the arc-shaped locus 60 is considered to be located on the free end side of the cantilever-supported portion and at the center in the thickness direction of the inner peripheral portions of the two reed valve elements 50.

  In the first embodiment, as shown in detail in FIG. 3, the inner surface 54 </ b> SI of the facing member 54 that faces the low speed damping force generating valve 24 has a cylindrical shape that extends along the axis 11. There is no. Therefore, the inner surface 54 </ b> SI forms a straight line extending in parallel to the axis 11 when viewed in a radial section passing through the axis 11. On the other hand, the outer edges of the two reed valve elements 50 are substantially arcuate along the locus 60 when viewed in the radial cross section passing through the axis 11, and thus arcuate around the center O. It is extended.

  In the situation where the two reed valve elements 50 are not elastically deformed, the shortest distance between the outer edge of the low speed damping force generating valve 24 and the inner surface 54SI of the opposing member 54 is defined as D. The upper end of the outer edge of the upper reed valve element 50 is the same as or above the lower end of the inner surface 54SI, and the lower end of the outer edge of the lower reed valve element 50 is the same or lower than the upper end of the inner surface 54SI. The range is set as a predetermined elastic deformation range of the damping force generation valve 24. When the amount of elastic deformation of the damping force generating valve 24 is a value within a predetermined elastic deformation range, the shortest distance D is substantially constant regardless of the amount of elastic deformation. The shortest distance D may be about 10 to several tens of μm, for example.

  Therefore, the effective passage cross-sectional area of the orifice 58 is substantially independent of the amount of elastic deformation of the damping force generating valve 24 when the amount of elastic deformation of the damping force generating valve 24 is a value within a predetermined elastic deformation range. Is constant. The effective passage sectional area of the orifice 58 is smaller than the effective passage sectional area of the notch 45 when the expansion stroke damping force generation valve 20 is in the closed state, and the damping stroke generation force generation valve 22 for the contraction stroke is It is smaller than the effective passage cross-sectional area of the notch 49 when the valve is closed.

  As described above, the facing member 54 has a thickness substantially the same as that of the single reed valve element 50, and is in a radial alignment with the lower reed valve element 50 when not elastically deformed. Is arranged. In other words, the thickness of the damping force generating valve 24 is twice the thickness of the opposing member 54, and the center of the damping force generating valve 24 in the thickness direction is higher than the center of the opposing member 54 in the thickness direction. And is aligned with the upper surface of the opposing member 54.

  Although not shown in the drawing, the elastic deformation of the damping force generating valve 24 when the upper end of the outer edge of the upper reed valve element 50 is aligned with the lower end of the inner surface 54SI due to the downward elastic deformation of the damping force generating valve 24. Let the amount be Le1. Conversely, the amount of elastic deformation of the damping force generation valve 24 when the lower end of the outer edge of the lower reed valve element 50 is aligned with the upper end of the inner surface 54SI due to the upward elastic deformation of the damping force generation valve 24 is Lc1. . Since the damping force generation valve 24 is offset upward with respect to the opposing member 54, the elastic deformation amount Le1 is larger than the elastic deformation amount Lc1.

  FIG. 4 shows the damping force characteristics of the first embodiment. In a very low speed range where the relative speed Vr of the piston 18, that is, the moving speed of the piston 18 with respect to the cylinder 12 is very low, the elastic deformation amount of the damping force generation valve 24 is a value within a predetermined elastic deformation range. Therefore, since the oil 19 passes through the orifice 58 having an extremely small effective passage cross-sectional area, the damping force Fd increases rapidly as the relative speed Vr increases. The relative speeds Vr when the elastic deformation amounts of the damping force generating valve 24 are Le1 and Lc1, respectively, are Vre1 and Vrc1, respectively, and the damping forces are Fe1 and Fc1, respectively. Since the elastic deformation amount Le is larger than the elastic deformation amount Lc, the relative velocity Vre1 is larger than the relative velocity Vrc1 and the damping force Fe1 is higher than the damping force Fc1 as shown in FIG.

  When the amount of elastic deformation of the damping force generating valve 24 is a value within a predetermined elastic deformation range, the effective passage area of the orifice 58 is very small. Therefore, the flow rate of the oil 19 passing through the orifice 58 is very small. Therefore, although the damping force characteristic is exaggerated in FIG. 4, the relative speeds Vre1 and Vrc1 are actually values close to zero.

  When the outer edge of the damping force generating valve 24 has a cylindrical shape extending along the axis 11, the corner of the outer edge does not interfere with the opposing member 54 when the damping force generating valve 24 is elastically deformed. The space between the outer edge and the inner surface 54SI of the opposing member 54 must be increased. In addition, it is inevitable that the distance between the outer edge of the reed valve element 50 and the inner surface 54SI of the facing member 54 changes unnecessarily with the elastic deformation of the damping force generation valve 24. For this reason, it is inevitable that the damping force in the very low speed range is insufficient, or that the damping force Fd increases or decreases unnecessarily as the relative speed Vr increases.

  On the other hand, according to the first embodiment, in the very low speed range, the orifice 58 functions as a fixed orifice having a substantially constant effective passage cross-sectional area in both the expansion stroke and the contraction stroke. Therefore, in the very low speed range, the damping force Fd can be increased monotonously without increasing or decreasing unnecessarily as the relative speed Vr increases, thereby ensuring the necessary damping force. Since the damping force Fd in the very low speed region of the extension stroke can be made higher than the damping force Fd in the very low speed region of the contracting stroke, the damping force against the unsprung push-up is excessively increased in the very low speed region. In addition, the unsprung vibration can be effectively damped by the damping force of the extension stroke.

  In the extension stroke, when the relative speed Vr increases from Vre1 to Vre2, the flow rate of the oil 19 passing through the notch 45 increases in the state where the damping force generation valve 20 for the extension stroke is closed. The damping force Fd increases from Fe1 to Fe2 (orifice region). When the relative speed Vr further increases from Vre2, the damping force generation valve 20 for the extension stroke is opened, and the oil 19 passes through the opened damping force generation valve 20, so that the damping force Fd is higher than that from Fe1 to Fe2. Increase at a small rate of increase (valve area).

  Similarly, when the relative speed Vr increases from Vrc1 to Vrc2 in the contraction stroke, the flow rate of the oil 19 passing through the notch 49 increases with the damping force generation valve 22 for the contraction stroke closed. The damping force Fd increases from Fc1 to Fc2 (orifice region). When the relative speed Vr further increases from Vrc2, the damping force generating valve 22 for the contraction stroke is opened, and the oil 19 passes through the opened damping force generating valve 22. Therefore, the damping force Fd is higher than that from Fc1 to Fc2. Increase at a small rate of increase (valve area)

[Second Embodiment]
FIG.5 and FIG.6 is sectional drawing which shows the shock absorber 10 concerning 2nd embodiment of this invention. 5 and 6, members corresponding to those shown in FIGS. 1 to 3 are denoted by the same reference numerals as those in FIGS. 1 to 3. The same applies to FIG. 7 showing a modification example described later.

  In the second embodiment, there is one reed valve element 50 and a centering valve element 52 of the damping force generating valve 24 for very low speed, and two spacers are provided below the reed valve element 50 and the centering valve element 52. 53 is arranged. The center O of the locus 60 at the corner of the outer edge accompanying the elastic deformation of the reed valve element 50 is located on the free end side of the cantilevered portion and at the center of the plate thickness of the inner peripheral portion of the reed valve element 50. ing. The outer edge of the reed valve element 50 is a cylindrical surface perpendicular to the plate surface of the reed valve element 50 when not elastically deformed (a cylindrical surface parallel to the shock absorber axis 11 not shown in FIGS. 5 and 6). However, it may have an arc shape extending around the center O.

  The opposing member 54 disposed so as to surround the reed valve element 50 on the radially outer side of the reed valve element 50 includes two annular plate-like bodies 54A and 54B formed of a substantially rigid material. ing. The two annular plates 54A and 54B have the same thickness, which is the same as the thickness of the reed valve element 50. The upper annular plate-like body 54A is aligned with the reed valve element 50 in the radial direction. The inner surface 54SI of the opposing member 54 extends along an arc 61 centered on the center O of the locus 60 when viewed in a radial cross section passing through the axis 11 of the shock absorber 10, and therefore around the center O. It extends in an arc shape. Even when the reed valve element 50 is not elastically deformed, the outer edge of the reed valve element 50 and the inner edge of the opposing member 54 are slightly spaced apart in the radial direction to form a minute orifice 58.

  Let D be the shortest distance between the outer edge of the slow speed damping force generating valve 24 and the inner surface 54SI of the opposing member 54 when the reed valve element 50 is not elastically deformed. The upper end of the outer edge of the upper reed valve element 50 is the same as or above the lower end of the inner surface 54SI, and the lower end of the outer edge of the lower reed valve element 50 is the same or lower than the upper end of the inner surface 54SI. The range is set as a predetermined elastic deformation range of the damping force generation valve 24. When the amount of elastic deformation of the damping force generating valve 24 is a value within a predetermined elastic deformation range, the shortest distance D is substantially constant regardless of the amount of elastic deformation.

  Therefore, the effective passage cross-sectional area of the orifice 58 is substantially independent of the amount of elastic deformation of the damping force generating valve 24 when the amount of elastic deformation of the damping force generating valve 24 is a value within a predetermined elastic deformation range. Is constant. Also in this embodiment, the effective passage sectional area of the orifice 58 is smaller than the effective passage sectional area of the notch 45 when the damping force generating valve 20 for the expansion stroke is in the closed state, and is used for the contraction stroke. It is smaller than the effective passage sectional area of the notch 49 when the damping force generating valve 22 is in the closed state.

  As can be understood from the above description, according to the second embodiment, similarly to the first embodiment, the damping force Fd is not increased or decreased unnecessarily in the very low speed range as the relative speed Vr increases. Necessary damping force can be secured. Further, in the very low speed range, the unsprung vibration can be effectively damped by the damping force of the extension stroke without excessively increasing the damping force against the unsprung thrust.

[Modification example]
FIG. 7 is an enlarged partial cross-sectional view showing a main part of the shock absorber 10 configured as a modification of the first embodiment.

  In this modified example, the very low speed damping force generating valve 24 is configured in the same manner as in the first embodiment. Therefore, the outer edges of the two reed valve elements 50 are circles extending around the center O of the outer edge locus 60 due to the elastic deformation of the reed valve elements 50 when viewed in a radial section passing through the axis of the shock absorber. It has an arc shape and extends along the locus 60.

  The facing member 54 is located above the spacer 57 and is arranged radially in alignment with the upper reed valve element 50 on the radially outer side of the upper reed valve element 50. The inner surface 54SI of the opposing member 54 has a cylindrical shape extending along the axis 11 and forms a straight line extending in parallel to the axis 11 when viewed in a radial section passing through the axis 11 of the shock absorber 10. ing.

  Similar to the first embodiment, the shortest distance D between the outer edge of the very low speed damping force generating valve 24 and the inner surface 54SI of the opposing member 54 in a situation where the two reed valve elements 50 are not elastically deformed. It is substantially constant regardless of the amount of elastic deformation. However, since the damping force generation valve 24 is offset downward with respect to the opposing member 54, the elastic deformation amount Le1 of the damping force generation valve 24 is smaller than the elastic deformation amount Lc1, and the magnitude relationship between the elastic deformation amounts Le1 and Lc1 is This is the reverse of the case of the first embodiment.

  Therefore, according to this modified example, as in the first and second embodiments, in the very low speed range, the orifice 58 substantially has an effective passage cross-sectional area in both the expansion stroke and the contraction stroke. Acts as a fixed orifice. Therefore, as the relative speed Vr increases, the damping force Fd can be monotonously increased without unnecessarily increasing or decreasing. Therefore, according to the modified example, as in the first and second embodiments, the necessary damping force is secured in the very low speed range without unnecessarily increasing or decreasing the damping force Fd as the relative speed Vr increases. can do.

  Since the elastic deformation amount Le1 of the damping force generating valve 24 is smaller than the elastic deformation amount Lc1, the damping force characteristic is as shown in FIG. That is, the damping force Fd in the contraction stroke is higher than the damping force Fd in the expansion stroke. Therefore, this modified example is suitable for an application in which the damping force in the contraction stroke is preferably higher than the damping force in the expansion stroke.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. This will be apparent to those skilled in the art.

  For example, in each of the above-described embodiments, the damping force characteristic of the shock absorber 10 has an orifice region, but the orifice region may not exist. That is, when the relative speed Vr becomes equal to or higher than Vre1Vrc1, the extension stroke damping force generation valve 20 and the contraction stroke damping force generation valve 22 may be modified to close.

  In the first embodiment described above, the outer edges of the two reed valve elements 50 have an arc shape extending around the center O, but the inner surface 54SI of the opposing member 54 has a cylindrical shape. There is no. In the second embodiment described above, the inner surface 54SI of the facing member 54 has an arc shape extending around the center O, but the outer edge of the reed valve element 50 has a cylindrical surface. However, both the reed valve element 50 of the damping force generating valve 24 for very low speed and the inner surface 54SI of the opposing member 54 facing this may have an arc shape extending around the center O.

  Further, in the above-described modification, the low speed damping force generating valve 24 is offset downward with respect to the opposing member 54, but the damping force generating valve 24 may be offset upward with respect to the opposing member 54. Even in this case, it is preferable that the inner surface 54SI of the facing member 54 extends in an arc shape around the center O.

  In each of the above-described embodiments and modifications, the outer edge of the reed valve element 50 or the inner surface 54SI of the opposing member 54 extends in the shape of an arc around the center O over the entire width in the thickness direction. However, the portion extending in an arc shape does not have to be the full width in the thickness direction of the outer edge of the reed valve element 50 or the inner surface 54SI of the opposing member 54. For example, the central portion in the thickness direction is cylindrical. Further, an arc shape other than the arc shape may be formed around the center O.

  Furthermore, in the first and second embodiments described above, the shock absorber 10 is a single-cylinder shock absorber, but the present invention may be applied to a multi-cylinder shock absorber.

DESCRIPTION OF SYMBOLS 10 ... Shock absorber, 12 ... Cylinder, 14 ... Cylinder upper chamber, 16 ... Cylinder lower chamber, 18 ... Piston, 20 ... Damping force generating valve for expansion stroke, 22 ... Damping force generating valve for contraction stroke, 24 ... Fine Low-speed damping force generation valve, 36: passage for expansion stroke, 38: passage for contraction stroke, 50: reed valve element, 54 ... opposing member

Claims (1)

A cylinder and a piston that is reciprocally fitted to the cylinder and that cooperates with the cylinder to form first and second cylinder chambers, the piston being the first and second cylinders; A shock absorber having a communication path connecting chambers and a damping force generating valve for very low speed that generates damping force when the moving speed of the piston relative to the cylinder is very low speed close to 0,
The low-speed damping force generating valve is opposed to the leaf valve element that is cantilevered by the piston and elastically deformed by the differential pressure between the first and second cylinder chambers, and the free end of the leaf valve element. A shock absorber having an opposing portion that cooperates with the free end to form an orifice that is part of the communication path,
The leaf valve element is configured so that when viewed in a cross section perpendicular to the plate surface of the leaf valve element when not elastically deformed, the free end is displaced in an arc around a preset center when elastically deformed. The leaf valve element and the facing portion are offset from each other along the direction of displacement of the free end when the leaf valve element starts elastic deformation when seen in the cross section, and the leaf valve element At least one of the free end and the opposing surface of the opposing portion has a region extending in an arc around the center as seen in the cross section,
shock absorber.

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