JP6626631B2 - Shock absorber - Google Patents

Description

  The present invention relates to a shock absorber.

  Some shock absorbers switch the damping force according to the piston position (for example, see Patent Documents 1 and 2).

JP-A-2-16838 WO 2013/081004

  It is desired to increase the degree of freedom in setting the damping force.

  An object of the present invention is to provide a shock absorber that can increase the degree of freedom in setting a damping force.

  In order to achieve the above object, the present invention has a self-leveling mechanism that adjusts the extension length of the piston rod by transferring hydraulic fluid between a cylinder and a hydraulic fluid tank by expansion and contraction of a piston rod, The cylinder has a first damping force generating mechanism provided between the upper chamber and the intermediate chamber to generate a damping force, and a second damper provided between the lower chamber and the intermediate chamber to generate a damping force. And a state in which the upper chamber and the lower chamber communicate with each other, a state in which the upper chamber and the intermediate chamber communicate with each other, and a state in which the lower chamber and the intermediate chamber communicate with each other according to the position of the piston. And a position sensitive mechanism for changing the state of the passage.

  According to the present invention, it is possible to increase the degree of freedom in setting the damping force.

It is sectional drawing which shows the shock absorber of one Embodiment concerning this invention. It is a partial expanded sectional view of the lower part showing the shock absorber of one embodiment concerning the present invention. It is a partial expanded sectional view of the upper part which shows the shock absorber of one embodiment concerning the present invention. It is a partial expanded sectional view of the middle part showing the shock absorber of one embodiment concerning the present invention. 1 shows an inner cylinder of a shock absorber according to an embodiment of the present invention, wherein (a) is a side view and (b) is a cross-sectional view. It is a fragmentary sectional view showing the position sensitive mechanism of the shock absorber of one embodiment concerning the present invention, (a) shows a state where a stroke position is in the 1st predetermined range, and (b) shows the 2nd predetermined range. (C) indicates a state within a third predetermined range, (d) indicates a state within a fourth predetermined range, and (e) indicates a state within a fifth predetermined range. , Respectively. FIG. 3 is a diagram illustrating characteristics of a damping force with respect to a stroke position of a piston of the shock absorber according to the embodiment of the present invention. It is a characteristic line figure showing the simulation result of the damping force to the piston speed of the buffer of one embodiment concerning the present invention. It is a characteristic diagram which shows the simulation result of the damping force with respect to the stroke position of the piston for every piston speed of the shock absorber of one Embodiment which concerns on this invention.

  An embodiment according to the present invention will be described with reference to the drawings. In the following description, the lower side of the figure is defined as "lower side" and the upper side of the figure is defined as "upper side" to facilitate understanding.

  The shock absorber 1 of the present embodiment shown in FIG. 1 is a position-sensitive damping force adjustment type shock absorber. The shock absorber 1 has a cylindrical inner cylinder 10, in which a working fluid such as an oil fluid as a working fluid is sealed, and a cylinder 11 having a larger diameter than the inner cylinder 10 of the cylinder 11 and coaxial with the inner cylinder 10. And a substantially cylindrical outer cylinder 12 having a bottom. The shock absorber 1 is a so-called double cylinder type hydraulic shock absorber. An upper portion between the inner cylinder 10 and the outer cylinder 12 serves as a reservoir 13.

  The outer cylinder 12 includes a stepped cylindrical body member 21 that forms an intermediate portion, a bottom member 22 that is fitted and fixed to a lower portion, which is one side of the body member 21, and closes a lower end opening of the body member 21. An annular lid member 23 which is fitted and fixed to the upper portion on the other side of the body member 21 and covers an upper end opening of the body member 21. An annular cover 24 is attached to the upper side of the outer cylinder 12 so as to cover the lid member 23.

  The trunk member 21 has its lower side bulged by bulging or the like to form a bulged portion 31, and the upper middle portion of the bulged portion 31 in the axial direction is slightly enlarged to form a spring receiving support portion 32. ing. A partition member 35 is inserted between the enlarged diameter portion 31 of the body member 21 and the inner cylinder 10 of the cylinder 11, and a flange member 36 is connected to an upper end of the partition member 35. The flange member 36 is fitted to the outer cylinder 12 to form an annular chamber between the outer cylinder 12 and the inner cylinder 10 into a lower working fluid tank 38 facing the enlarged diameter portion 31 and an upper reservoir 13. It is partitioned.

  The hydraulic fluid tank 38 is divided into a fluid chamber 43 on the inner peripheral side and a gas chamber 44 on the outer peripheral side by a bladder 41 which is a flexible film. A working fluid as a working fluid is sealed in the cylinder 11 and a liquid chamber 43 of the working fluid tank 38, and a low-pressure gas as a working fluid is sealed in a gas chamber 44 of the working fluid tank 38. A working fluid and a high-pressure gas, both of which are working fluids, are sealed in the reservoir 13.

  As shown in FIG. 2, an annular holding member 51 is interposed between the lower end of the partition member 35 and the bottom member 22. A base guide 52 is fitted to the inner peripheral portion of the holding member 51, and a liquid chamber 53 is formed between the bottom member 22 and the base guide 52. A base member 56 constituting the cylinder 11 is interposed between the base guide 52 and the lower end of the inner cylinder 10, and a liquid chamber 57 is formed between the base guide 52 and the base member 56. . An annular member 60 is fitted between the lower end of the body member 21 and the partition member 35. As shown in FIG. 1, both ends of the bladder 41 of the hydraulic fluid tank 38 are clamped by the flange member 36 and the annular member 60.

  As shown in FIG. 2, a liquid chamber 53 between the bottom member 22 and the base guide 52 stores a hydraulic fluid in a hydraulic fluid tank 38 by a liquid passage 61 provided on the inner peripheral side of the annular member 60. It is communicated with the liquid chamber 43. As shown in FIG. 1, the liquid chamber 57 between the base guide 52 and the base member 56 is connected to the reservoir 13 through an annular liquid passage 62 formed between the partition member 35 and the flange member 36 and the cylinder 11. Are in communication. Further, an orifice 63 (described later) formed inside the base member 56 communicates a lower chamber 77 (described later) in the cylinder 11 with the liquid chamber 57. Therefore, the orifice 63 communicates with the reservoir 13 via the liquid chamber 57 and the annular liquid passage 62.

  In the cylinder 11, a first piston 71 (piston) and a second piston 72 (piston) closer to the bottom member 22 than the first piston 71 are provided. The first piston 71 and the second piston 72 are slidably fitted to the inner cylinder 10. The first piston 71 and the second piston 72 provided in the cylinder 11 are provided in the cylinder 11 with an upper chamber 75 on the opposite side of the first piston 71 from the second piston 72, and the first piston 71 and the second piston 72. It defines three chambers: an intermediate chamber 76 between the piston 72 and a lower chamber 77 opposite to the first piston 71 than the second piston 72. In other words, in the cylinder 11, an upper chamber 75 is formed by the first piston 71, an intermediate chamber 76 is formed by the first piston 71 and the second piston 72, and a lower chamber 77 is formed by the second piston 72. In the cylinder 11, a working fluid as a working fluid is sealed in each of the upper chamber 75, the intermediate chamber 76, and the lower chamber 77.

  One side of a piston rod 81 is inserted into the cylinder 11, and the other side of the piston rod 81 is mounted on the upper ends of both the inner cylinder 10 and the outer cylinder 12 to form a rod guide 82 and a seal that constitute the cylinder 11. The member 83 is inserted. The other side of the piston rod 81 extends outside the cylinder 11 via a rod guide 82 and a seal member 83. The first piston 71 and the second piston 72 are connected to one end of the piston rod 81 disposed inside the cylinder 11. The first piston 71 and the second piston 72 move integrally with the piston rod 81. As a result, the intermediate chamber 76 between the first piston 71 and the second piston 72 in the cylinder 11 also moves with the piston rod 81. Move together.

  A rod guide 82 is mounted on one end opening side of the inner cylinder 10 and the outer cylinder 12, and a seal member 83 is mounted on the outer cylinder 12 on the outer end side of the cylinder 11 further than the rod guide 82. Each of the rod guide 82 and the seal member 83 has an annular shape, and the piston rod 81 is slidably inserted into each of the rod guide 82 and the seal member 83 and extends to the outside of the cylinder 11. Have been.

  Here, the rod guide 82 guides the movement of the piston rod 81 by supporting the piston rod 81 so as to be movable in the axial direction while restricting the movement in the radial direction. The seal member 83 is slidably contacted at its inner peripheral portion with the outer peripheral portion of the piston rod 81 moving in the axial direction, and at its outer peripheral portion is in close contact with the inner peripheral portion of the outer cylinder 12 so that the hydraulic fluid in the cylinder 11 is in contact with the outside. The high-pressure gas and the working fluid in the reservoir 13 in the cylinder 12 are prevented from leaking to the outside.

  As shown in FIG. 3, the rod guide 82 includes an annular outer guide member 91 that fits into the lower inner peripheral portion of the annular lid member 23 and the upper inner peripheral portion of the body member 21, and an upper outer guide member. An annular inner guide member 92 which is inserted inside the member 91 and is fitted to the inner peripheral side of the outer guide member 91 at the intermediate portion and the lower portion is fitted to the inner peripheral portion at the upper end of the inner cylinder 10; A collar 93 that is fitted and fixed to the inner peripheral portion and slidably contacts the outer peripheral portion of the piston rod 81.

  Further, the rod guide 82 is provided between the outer guide member 91 and the inner guide member 92 and seals the gap therebetween, and the rod guide 82 is provided between the outer guide member 91 and the outer peripheral portion of the piston rod 81 to reduce the gap therebetween. And a sealing member 96 for sealing. Here, the cup seal 95 is formed on the outer peripheral portion of the inner guide member 92 by opening the hydraulic fluid that has leaked upward through the gap between the collar 93 and the piston rod 81 when the pressure of the upper chamber 75 increases. The liquid is discharged to the reservoir 13 through a gap between the groove 97 and the inner peripheral portion of the outer guide member 91.

  The outer periphery of the rod guide 82 has a stepped shape in which an intermediate portion formed by the outer guide member 91 has a larger diameter than a lower portion formed by the outer periphery of the inner guide member 92. At the lower part formed by 92, it fits into the inner peripheral part at the upper end of the inner cylinder 10, and at the intermediate part formed by the outer guide member 91, fits into the inner peripheral part at the upper end of the body member 21, and The upper part formed is fitted to the inner peripheral part of the lower part of the lid member 23. A seal member 83 that seals a gap between the lid member 23 and the piston rod 81 is disposed between the outer guide member 91, the lid member 23, and the piston rod 81.

  As shown in FIG. 1, a piston rod 81 is inserted into a rod guide 82 and a seal member 83 to extend to the outside, and a threaded end of the rod body 101 disposed inside the cylinder 11. And a tip rod 102 integrally connected to the rod body 101. At the center of the rod body 101 in the radial direction, an insertion hole 105 is formed along the axial direction from the end on the tip rod 102 side to an intermediate position near the opposite end. In addition, an insertion hole 106 is formed through the distal rod 102 along the axial direction. The insertion holes 105 and 106 communicate with each other, and the insertion holes 105 and 106 are formed so that the piston rod 81 has a hollow structure.

  An annular stopper 111 is fixed on the outer peripheral side of the rod body 101 of the piston rod 81 on the distal end rod 102 side in the axial direction, and a cushion 112 is mounted on the rod guide 82 side of the stopper 111. The cushion 112 moves integrally with the stopper 111, and abuts on the inner guide member 92 of the rod guide 82 at the extended position where the piston rod 81 projects most from the cylinder 11. In this state, the stopper 111 and the cushion 112 restrict further projection of the piston rod 81 from the cylinder 11.

  The shock absorber 1 is used for a suspension device of a vehicle such as an automobile or a railway vehicle. For example, one side is supported by a vehicle body, and the other side is connected to a wheel side. Specifically, the shock absorber 1 is connected to the vehicle body side by a piston rod 81, and is connected to the wheel side by a mounting eye (not shown) fixed to the outside of the bottom member 22 of the outer cylinder 12. Conversely, the other side of the shock absorber 1 may be supported by the vehicle body, and one side of the shock absorber 1 may be connected to the wheel side. In the shock absorber 1, the piston rod 81 extends from the cylinder 11 when the vehicle body rises with respect to the wheel, and conversely, when the vehicle body descends with respect to the wheel, the piston rod 81 enters the cylinder 11. The direction in which the piston rod 81 extends from the cylinder 11 is defined as the extension side and the maximum length side, and the direction in which the piston rod 81 enters the cylinder 11 is defined as the contraction side and the minimum length side.

  As shown in FIG. 4, the end of the insertion hole 105 on the distal end rod 102 side is a screw hole 125, and on the opposite side of the axially distal end rod 102 than the screw hole 125 of the rod body 101, A passage hole 126 orthogonal to the insertion hole 105 and penetrating the rod body 101 in the radial direction is formed. The passage hole 126 is formed above the cushion 112 mounted on the rod body 101 and the distal end rod 102.

  A screw shaft 131 is formed at one end of the tip rod 102, and the tip rod 102 is integrally connected to the rod body 101 by screwing the screw shaft 131 into a screw hole 125 of the rod body 101. Have been.

  The distal rod 102 has the above-described screw shaft portion 131, a flange portion 132, and a holding shaft portion 133 in order from the rod body 101 side in the axial direction. The outer diameter of the flange portion 132 is larger than that of the screw shaft portion 131 and the rod body 101. The tip rod 102 is screwed into the screw hole 125 of the rod main body 101 at the screw shaft 131 as described above, and the flange 132 contacts the rod main body 101 at that time. The holding shaft portion 133 has a smaller diameter than the flange portion 132, and a male screw 134 is formed on the outer peripheral portion on the opposite side to the flange portion 132 in the axial direction.

  The holding shaft portion 133 of the tip rod 102 includes, in order from the flange portion 132 side, one contact disk 141, one disk 142, a disk valve 143 including a plurality of disks, and the first piston described above. 71, one disk valve 145, one disk 146, one disk valve 147, the above-mentioned second piston 72, a disk valve 148 comprising a plurality of disks, and one disk 149. , One contact disk 150 and one regulating member 151. These are sandwiched between a nut 155 screwed to the male screw 134 with a female screw 156 and the flange 132 of the distal rod 102.

  The first piston 71 includes a metal piston main body 161 supported by the distal end rod 102, and an annular synthetic resin sliding member 162 mounted on the outer peripheral surface of the piston main body 161 and sliding inside the inner cylinder 10. And is constituted by.

  The upper chamber 75 and the intermediate chamber 76 are communicated with the piston main body 161, and the first piston 71 moves toward the intermediate chamber 76, that is, the hydraulic fluid flows from the intermediate chamber 76 toward the upper chamber 75 during the contraction stroke. A plurality of passages 165 (only one portion is shown in FIG. 4 in view of the cross section) and a plurality of hydraulic fluids which flow from the upper chamber 75 toward the intermediate chamber 76 during the movement of the first piston 71 toward the upper chamber 75, that is, the extension stroke. (Only one location is shown in FIG. 4 because of the cross section). That is, the plurality of passages 165 and the plurality of passages 166 are provided in the first piston 71 so that the movement of the first piston 71 allows the working fluid as the working fluid to flow between the upper chamber 75 and the intermediate chamber 76. Communicate.

  The passages 165 constituting a half are formed at equal pitches in the circumferential direction with one passage 166 interposed therebetween, and the upper chamber 75 side in the axial direction of the piston body 161 extends in the axial direction of the piston body 161. The intermediate chamber 76 is open radially outward. A disc valve 143 is provided on the upper chamber 75 side, which is one end side of the first piston 71 in the axial direction, so as to open and close the passages 165. The passage 165 constitutes a contraction side passage through which the hydraulic fluid passes when the first piston 71 moves to the contraction side where the piston rod 81 enters the cylinder 11, and the disc valve 143 provided for these passages. Constitutes a contraction-side damping valve 168 that restricts the flow of the hydraulic fluid in the contraction-side passage 165 to generate a damping force.

  The other half of the passages 166 are formed at equal pitches in the circumferential direction with one passage 165 therebetween, and the intermediate chamber 76 side of the piston body 161 in the axial direction of the piston body 161 is formed. And the upper chamber 75 side opens radially outward. A disc valve 145 is provided on the intermediate chamber 76 side, which is the other end of the first piston 71 in the axial direction, so as to open and close the passages 166. The passage 166 constitutes a passage on the extension side through which the hydraulic fluid passes when the first piston 71 moves to the extension side where the piston rod 81 extends out of the cylinder 11. The valve 145 constitutes an extension-side damping valve 169 that restricts the flow of the hydraulic fluid in the extension-side passage 166 to generate a damping force.

  A compression damping valve 168 including the disc valve 143 and an expansion damping valve 169 including the disc valve 145 are provided between the upper chamber 75 and the intermediate chamber 76 in the cylinder 11 to generate a first damping force. Of the damping force generating mechanism 171 of FIG.

  The piston main body 161 of the first piston 71 has a substantially disk shape, and has an insertion hole 172 at the center thereof, which penetrates in the axial direction and through which the holding shaft 133 of the tip rod 102 is inserted. Is formed. A seat portion 174 is formed at an end of the piston main body 161 on the upper chamber 75 side in the axial direction, outside the one end opening position of the passage 165 on the contraction side so as to surround the passage 165 opened in the axial direction. At the end of the piston body 161 on the side of the intermediate chamber 76 in the axial direction, a seat portion 175 is formed outside the one end opening position of the passage 166 on the extension side so as to surround the passage 166 that opens in the axial direction.

  In the piston body 161, a portion between the circumferentially adjacent seat portions 174 has a stepped shape whose axial height is lower than the seat portion 174 and extends radially outward, and the stepped portion is The other end of the passage 166 on the extension side is opened. The disc valve 143 closes the passage 165 on the inner side when the outer peripheral side is seated on the seat portion 174, and opens the passage 165 when the outer peripheral side is separated from the seat portion 174. In other words, the disc valve 143 and the seat portion 174 constitute a contraction-side damping valve 168 that restricts the flow of the hydraulic fluid in the contraction-side passage 165 to generate a damping force.

  The disk valve 143 is composed of a plurality of disks made of metal and having a disc shape with a hole, and these disks have the same outer diameter. The disk 142 is made of metal and has a disc shape with a hole, and has an outer diameter smaller than that of the disk valve 143. The contact disk 141 is made of metal and has the shape of a perforated disk, and has the same outer diameter as the disk valve 143. The contact disk 141 contacts the disk valve 143 when the disk valve 143 is deformed in the opening direction, and regulates the deformation exceeding the specified amount together with the flange 132.

  Further, in the piston body 161, a portion between circumferentially adjacent seat portions 175 is formed in a stepped shape having a lower height in the axial direction than the seat portion 175 and is radially omitted. It is the other end opening of the passage 165 on the contraction side. The disc valve 145 closes a passage 166 on the inner side when the outer peripheral side is seated on the seat portion 175, and opens the passage 166 when the outer peripheral side is separated from the seat portion 175. That is, the disc valve 145 and the seat portion 175 constitute an extension-side damping valve 169 that restricts the flow of the hydraulic fluid in the extension-side passage 166 to generate a damping force.

  The disk valve 145 is formed of a single disk having a disc shape in the form of a perforated disk made of metal, and its outer diameter is substantially the same as the maximum outer diameter of the seat portion 174. The disk 146 is made of metal and has a disc shape with a hole, and has an outer diameter smaller than that of the disk valve 145. The disc valve 145 has a lower rigidity than the disc valve 143 and is easily opened.

  The second piston 72 includes a metallic piston main body 181 supported by the distal end rod 102, and an annular synthetic resin sliding member 182 mounted on the outer peripheral surface of the piston main body 181 and sliding within the inner cylinder 10. And is constituted by.

  The piston body 181 communicates the intermediate chamber 76 with the lower chamber 77, and the second piston 72 moves toward the lower chamber 77, that is, the hydraulic fluid flows from the lower chamber 77 toward the intermediate chamber 76 during the contraction stroke. The hydraulic fluid flows from the intermediate chamber 76 to the lower chamber 77 during the movement of the second piston 72 toward the intermediate chamber 76, that is, in the extension stroke, of the passage 185 (only one location is shown in FIG. 4 because of the cross section). (Only one location is shown in FIG. 4 because of the cross section). That is, the plurality of passages 185 and the plurality of passages 186 are provided in the second piston 72 so that the movement of the second piston 72 allows the working fluid as the working fluid to flow between the intermediate chamber 76 and the lower chamber 77. Communicate.

  Half of the passages 185 are formed at a constant pitch in the circumferential direction with one passage 186 therebetween, and the intermediate chamber 76 side in the axial direction of the piston main body 161 extends in the axial direction of the piston main body 161. The lower chamber 77 side is open radially outward. A disk valve 147 is provided on the intermediate chamber 76 side, which is one end side in the axial direction of the second piston 72, so as to open and close these passages 185. The passage 185 constitutes a contraction-side passage through which the hydraulic fluid passes when the second piston 72 moves to the contraction side where the piston rod 81 enters the cylinder 11, and the disk valve 147 provided for these passages. Constitutes a contraction-side damping valve 188 that restricts the flow of the hydraulic fluid in the contraction-side passage 185 to generate a damping force.

  The remaining half of the passages 186 are formed at a constant pitch in the circumferential direction with one passage 185 interposed therebetween, and the lower chamber 77 side of the piston body 161 in the axial direction is the piston body 161. , And the intermediate chamber 76 side opens radially outward. A disc valve 148 is provided on the lower chamber 77 side, which is the other end of the second piston 72 in the axial direction, so as to open and close these passages 186. The passage 186 constitutes a passage on the extension side through which the hydraulic fluid passes when the second piston 72 moves to the extension side where the piston rod 81 extends out of the cylinder 11. The valve 148 forms an extension-side damping valve 189 that restricts the flow of the hydraulic fluid in the extension-side passage 186 to generate a damping force.

  A compression damping valve 188 including a disc valve 147 and an expansion damping valve 189 including a disc valve 148 are provided between the intermediate chamber 76 and the lower chamber 77 in the cylinder 11 to generate a second damping force. Constitute the damping force generating mechanism 191.

  The piston main body 181 of the second piston 72 has a substantially disk shape, and has an insertion hole 192 in the center thereof, which penetrates in the axial direction and through which the holding shaft 133 of the tip rod 102 is inserted. Is formed. At the end of the piston body 181 on the side of the intermediate chamber 76 in the axial direction, a seat portion 194 is formed outside the one end opening position of the passage 185 on the contraction side so as to surround the passage 185 that opens in the axial direction. A seat portion 195 is formed at an end of the piston body 181 on the lower chamber 77 side in the axial direction, outside the one end opening position of the extension passage 186 so as to surround the passage 186 that opens in the axial direction.

  In the piston body 181, a portion between the circumferentially adjacent seat portions 194 is formed in a stepped shape having a lower height in the axial direction than the seat portion 194, and is radially outwardly removed. It is the other end opening of the passage 186 on the extension side. The disc valve 147 closes the inner contraction side passage 185 when the outer peripheral side is seated on the seat portion 194, and opens the passage 185 when the outer peripheral side is separated from the seat portion 194. That is, the disc valve 147 and the seat portion 194 constitute a compression-side damping valve 188 that restricts the flow of the hydraulic fluid in the compression-side passage 185 and generates a damping force. The disc valve 147 is made of a single disc made of metal and having a disc shape with a hole.

  Further, in the piston body 181, a portion between circumferentially adjacent seat portions 195 forms a step having a lower height in the axial direction than the seat portion 195, and is radially omitted. The other end of the passage 185 on the contraction side is opened. The disk valve 148 closes the passage 186 on the inner side when the outer peripheral side is seated on the seat portion 195, and opens the passage 186 when the outer peripheral side is separated from the seat portion 195. That is, the disc valve 148 and the seat portion 195 constitute an extension-side damping valve 189 that restricts the flow of the hydraulic fluid in the extension-side passage 186 to generate a damping force.

  The disc valve 148 is composed of a plurality of discs in the form of a perforated disc made of metal, and these discs have the same outer diameter. The disk 149 is made of metal and has a disc shape with a hole, and has an outer diameter smaller than that of the disk valve 148. The contact disk 150 is made of metal and has the shape of a perforated disk, and has the same outer diameter as the disk valve 148. The restricting member 151 is made of metal and has a disc shape with a hole, and has higher rigidity than the disc valve 148. The regulating member 151 has an outer diameter smaller than that of the contact disk 150. The contact disk 150 contacts the disk valve 148 when the disk valve 148 is deformed in the opening direction, and restricts the deformation exceeding the specified amount together with the restriction member 151. The disc valve 148 has higher rigidity than the disc valve 147 and is hard to open.

  The passages 165 and 166 provided in the first piston 71 communicate with the upper chamber 75 and the intermediate chamber 76 so that a working fluid as a working fluid flows, and the passages 185 and 186 provided in the second piston 72 The communication between the intermediate chamber 76 and the lower chamber 77 is performed so that the working fluid as the working fluid flows.

  The extension-side damping valves 169 and 189 are provided on the first piston 71 and the second piston 72, and generate a damping force by restricting the flow of the working fluid flowing through the passages 166 and 186 by their movement in the extension direction. In the extension stroke, the passage 166 is on the upstream side of the flow of the hydraulic fluid (ie, the upper chamber 75 side), and the passage 186 is on the downstream side (ie, the lower chamber 77 side). In the extension stroke, of the extension-side damping valves 169 and 189, the extension-side damping valve 169 is on the upstream side (ie, the upper chamber 75 side), and the extension-side damping valve 189 is on the downstream side (ie, the lower chamber 77 side). .

  As for the disc valves 145 and 148, the disc valve 145 provided on the first piston 71 has lower rigidity than the disc valve 148 provided on the second piston 72, and is easily opened. As a result, the disc valves 145 and 148 exert a damping force generated by the disc valve 145 located on the upstream side against the flow of the hydraulic fluid in the extension stroke in which the first piston 71 and the second piston 72 move in the extension direction. Is set to be softer than the damping force generated by the disk valve 148 located on the downstream side.

  The contraction-side damping valves 168, 188 are provided on the first piston 71 and the second piston 72, and restrict the flow of the hydraulic fluid flowing through the passages 165, 185 by the movement in the contracting direction to generate a damping force. In the contraction stroke, the passage 185 is on the upstream side of the flow of the hydraulic fluid (ie, the lower chamber 77 side), and the passage 165 is on the downstream side (ie, the upper chamber 75 side). In the contraction stroke, of the compression-side damping valves 168 and 188, the compression-side damping valve 188 is on the upstream side (that is, the lower chamber 77 side), and the compression-side damping valve 168 is on the downstream side (that is, the upper chamber 75 side). .

  As for the disc valves 143 and 147, the disc valve 143 provided on the first piston 71 has higher rigidity than the disc valve 147 provided on the second piston 72, and is hard to open. As a result, the contraction-side damping valves 168 and 188 cause the damping force generated by the contraction-side damping valve 188 located upstream of the flow of the hydraulic fluid in the contraction stroke in which the first piston 71 and the second piston 72 move in the contraction direction. Is set to be smaller and softer than the damping force generated by the contraction side damping valve 168 located on the downstream side.

  In a state where the nut 155 is fastened to the distal end rod 102, the inner circumference of the disc valve 143 is clamped by the disc 142 and the first piston 71, and the disc valve 145 is fixed to the disc 146 by the first piston 71. With this, the inner peripheral side is clamped. The inner circumference of the disc valve 147 is clamped by the disc 146 and the second piston 72, and the inner circumference of the disc valve 148 is clamped by the second piston 72 and the disc 149. As a result, the outer circumference of the disk valves 143, 145, 147, 148 can be deformed.

  In the inner cylinder 10 constituting the cylinder 11, a concave portion 200 extending in the axial direction is formed on an inner wall of the inner cylinder 10 over a predetermined range in the axial direction. As shown in FIG. 5B, the concave portion 200 is partially formed on the inner wall of the inner cylinder 10, and is formed at two different positions of the inner cylinder 10 by 180 degrees. The concave portion 200 is formed by plastically deforming a part of the material of the inner cylinder 10, and therefore, the inner cylinder 10 extends in the outer wall of the inner cylinder 10 in the axial direction as shown in FIG. The protrusion 201 is formed over a predetermined range in the axial direction. The inner cylinder 10 is a main body portion 202 in which a portion excluding the concave portion 200, that is, the convex portion 201 is arranged on the same cylindrical surface. The concave portion 200 is recessed radially outward from the main body portion 202, and the convex portion 201 is a main body portion. It protrudes radially outward from the portion 202.

  As shown in FIG. 4, the concave portion 200 has a length capable of passing over both the first piston 71 and the second piston 72 simultaneously in the axial direction. That is, the concave portion 200 extends longer than the axial length between the first piston 71 and the second piston 72 (the maximum distance between the sliding members 162 and 182).

  As shown in FIG. 6 (a), when both the first piston 71 and the second piston 72 are simultaneously traversed in the axial direction as shown in FIG. The chamber 76 and the lower chamber 77 are all connected. That is, the wall passage 203 can communicate the upper chamber 75, the intermediate chamber 76, and the lower chamber 77 separately from the passages 165, 166, 185, and 186 shown in FIG.

  As shown in FIG. 6B, when only the second piston 72 of the first piston 71 and the second piston 72 is traversed in the axial direction as shown in FIG. While the lower chamber 77 and the upper chamber 75 communicate with each other, the upper chamber 75 and the intermediate chamber 76 do not communicate with each other. Further, as shown in FIG. 6C, when only the first piston 71 of the first piston 71 and the second piston 72 is traversed in the axial direction, the concave portion 200 is raised by the inner wall passage 203. While the chamber 75 and the intermediate chamber 76 are in communication, the intermediate chamber 76 and the lower chamber 77 are not in communication.

  As shown in FIG. 6D, the recess 200 is entirely on the opposite side of the second piston 72 from the first piston 71, and as shown in FIG. When the piston 71 is on the opposite side of the second piston 72, neither the first piston 71 nor the second piston 72 crosses in the axial direction. Therefore, none of the upper chamber 75, the intermediate chamber 76, and the lower chamber 77 communicate with each other through the wall passage 203.

  As described above, the first piston 71 and the recess 200 are provided with respect to the wall passage 203, and adjust the flow area of the hydraulic fluid between the upper chamber 75 and the intermediate chamber 76 according to the positions of the first piston 71 and the second piston 72. The first adjusting unit 211 is configured. The second piston 72 and the concave portion 200 are provided for the wall passage 203, and adjust the flow area of the hydraulic fluid between the intermediate chamber 76 and the lower chamber 77 according to the positions of the first piston 71 and the second piston 72. The second adjustment unit 212 is configured. In other words, the flow passage area of the first adjustment unit 211 and the second adjustment unit 212 is adjusted by the concave portion 200 formed partially on the inner wall of the inner cylinder 10 of the cylinder 11. The first adjustment unit 211 and the second adjustment unit 212 are provided in the cylinder 11 and constitute a position sensitive mechanism 215 that changes the state of the wall passage 203 according to the positions of the first piston 71 and the second piston 72. .

  As shown in FIG. 1, the self-leveling mechanism 221 that transfers the hydraulic fluid between the cylinder 11 and the hydraulic fluid tank 38 by the expansion and contraction of the piston rod 81 to adjust the extension length of the piston rod 81. Is built-in. The self-leveling mechanism 221 adjusts the height of the vehicle on which the shock absorber 1 having the self-leveling mechanism 221 is mounted.

  Next, the self-leveling mechanism 221 will be described. A pump tube 224 is inserted into the hollow piston rod 81, and is held and fixed by the tip rod 102 and the spring 225. A tubular pump rod 226 is disposed in the cylinder 11 along the axis thereof, and a base end of the pump rod 226 is inserted into an opening of the base member 56 and connected to the base guide 52. A slight gap is provided between the pump rod 226 and the opening of the base member 56, and this gap serves as an orifice 63 that communicates the liquid chamber 57, the annular liquid passage 62 and the reservoir 13 with the lower chamber 77. ing. The distal end side of the pump rod 226 is inserted into the distal end rod 102 and the pump tube 224 to form a pump chamber 227 in the pump tube 224. The liquid passage 228 in the pump rod 226 communicates with the liquid chamber 53 via a liquid passage 229 provided in the base guide 52. Therefore, the liquid passage 228 in the pump rod 226 communicates with the liquid chamber 43 of the hydraulic fluid tank 38 via the liquid passage 229, the liquid chamber 53, and the liquid passage 61.

  The pump chamber 227 can communicate with a liquid passage 228 in the pump rod 226 via a check valve 233 provided at a distal end of the pump rod 226. The check valve 233 is connected to the pump chamber 227 from the liquid passage 228. Only the flow of hydraulic fluid to Further, the pump chamber 227 can communicate with an annular liquid passage 235 formed between the hollow piston rod 81 and the pump tube 224 via a check valve 234 provided at an end of the pump tube 224. Further, the liquid passage 235 communicates with the upper chamber 75 through the passage hole 126. The check valve 234 allows only the flow of the hydraulic fluid from the pump chamber 227 to the fluid passage 235.

  A passage 240 extending in the axial direction is formed between the inner peripheral surface of the distal end rod 102 and the outer peripheral surface of the pump rod 226, and the passage 240 extends in the axial direction between the inner peripheral surface of the pump tube 224 and the outer peripheral surface of the pump rod 226. Between them, a passage 241 extending along the axial direction is formed. The passage 240 has a larger passage area than the passage 241. In the shock absorber 1, the pump chamber 227 normally communicates with the lower chamber 77 via these passages 240 and 241. On the other hand, when the piston rod 81 moves to the predetermined position on the contraction side, the pump chamber 227 and the lower chamber 77 are connected to the pump chamber 227 via the passage 241 on the pump tube 224 side by the seal member 242 provided in the pump rod 226 so as not to move in the axial direction. Communication is interrupted. Further, a relief port 243 is formed in the pump rod 226 along the radial direction at a position above the seal member 242. The relief port 243 is normally closed by the pump tube 224, and the piston rod 81 is fixed to a predetermined position. When extended to the position, the lower chamber 77 is separated from the pump tube 224 and communicates with the liquid passage 228 in the pump rod 226 via the passage 240.

  When the pressure on the liquid chamber 57 side (that is, the high-pressure cylinder 11 and the reservoir 13 side) excessively increases, the base guide 52 opens the valve to reduce this pressure to the liquid chamber 53 side (that is, the low-pressure hydraulic fluid tank). 38 side), a normally-closed relief valve 244 is provided.

  An annular spring support 245 for receiving the lower end of a suspension spring (not shown) is fitted and fixed to the outer periphery of the spring support 32 of the outer cylinder 12. The shock absorber 1 connects the distal end of the piston rod 81 to the vehicle body (not shown), and connects the not-shown mounting eye attached to the lower end of the outer cylinder 12 to the wheel side (not shown). Then, the lower end portion of the suspension spring is received by the spring receiver 245 at this time.

  The upper end of the bladder 41 of the hydraulic fluid tank 38 is formed into a shape that fits into the outer peripheral groove 247 formed in the flange member 36, and is formed between the outer peripheral groove 247 and the inner peripheral surface of the trunk member 21 of the outer cylinder 12. Clamped between. An O-ring 249 is fitted in the outer peripheral groove 248 above the outer peripheral groove 247 of the flange member 36. The O-ring 249 seals between the body member 21 of the outer cylinder 12 and the flange member 36, and the upper end of the bladder 41 and the reservoir 13, the liquid chamber 43 and the gas chamber 44 of the working fluid tank 38. Is sealed between. The partition member 35 extends from the flange member 36 to a side opposite to the reservoir 13, and an annular member 60 is fitted to a lower end opposite to the flange member 36. The lower end of the bladder 41 is formed into a shape that fits into the outer peripheral groove 250 formed in the annular member 60, and is clamped between the outer peripheral groove 250 and the inner peripheral surface of the body member 21 of the outer cylinder 12. Thus, the space between the liquid chamber 43 and the gas chamber 44 is sealed.

  Hereinafter, the operation of the shock absorber 1 when the vehicle equipped with the shock absorber 1 of the present embodiment is in a standard loading state will be described.

  The solid line X1 in FIG. 7 shows the relationship between the stroke position and the damping force when the first piston 71 and the second piston 72 move in the extending direction, and the broken line X2 in FIG. 7 shows the first piston 71 and the second piston 72. The relationship between the stroke position and the damping force at the time of movement in the contraction direction 72 is shown.

  In the shock absorber 1, the stroke positions of the first piston 71 and the second piston 72 include the neutral position (the position of 1G (the position supporting the vehicle body stopped at the horizontal position in the standard loading state)) as shown in FIG. 6, the concave portion 200 simultaneously traverses both the first piston 71 and the second piston 72 in the axial direction at the same time, as shown in FIG. The upper chamber 75, the intermediate chamber 76, and the lower chamber 77 communicate with each other. In other words, the first predetermined range S4 to S5 is a range defined by the inside of the concave portion 200. In this first predetermined range S4 to S5, the flow passage area of the wall passage 203 surrounded by the first piston 71 of the first adjustment unit 211 and the recess 200, the second piston 72 of the second adjustment unit 212 and the recess The flow path area of the wall passage 203 surrounded by 200 has the same maximum value, and the upper chamber 75 and the lower chamber 77 communicate with each other with the flow path area of the wall passage 203.

  When the first piston 71 and the second piston 72 are within the first predetermined range S4 to S5, in the extension stroke in which the first piston 71 and the second piston 72 move toward the upper chamber 75, the hydraulic fluid in the upper chamber 75 is supplied to the first piston 71 and the second piston 72. 7 flows into the lower chamber 77 via the wall passage 203 between the two pistons 72 and the concave portion 200. Therefore, as shown in the first predetermined range S4 to S5 of the solid line X1 in FIG. State.

  When the first piston 71 and the second piston 72 are within the first predetermined range S4 to S5, the hydraulic fluid in the lower chamber 77 is supplied to the first piston 71 during the contraction stroke of moving to the lower chamber 77 side. 7, and flows into the upper chamber 75 via the wall passage 203 between the second piston 72 and the concave portion 200. Therefore, as shown in the first predetermined range S4 to S5 of the broken line X2 in FIG. Is in a soft state.

  In the shock absorber 1, the stroke position of the first piston 71 and the second piston 72 exceeds the above-described first predetermined range S4 to S5, and the stroke length of the shock absorber 1 on the maximum length side shown in FIG. 6, the first piston 71 of the first adjustment unit 211 cuts off the communication between the upper chamber 75 and the intermediate chamber 76 by the wall passage 203, as shown in FIG. 6B. While the flow path area is set to the minimum value, the second piston 72 of the second adjustment unit 212 communicates between the intermediate chamber 76 and the lower chamber 77 through the wall passage 203 to set the flow path area to the maximum value.

  When the first piston 71 and the second piston 72 are within the second predetermined range S6 to S7, in the extension stroke in which the first adjustment unit 211 moves toward the upper chamber 75, the first adjustment unit 211 controls the upper chamber 75 and the Since the communication between the intermediate chambers 76 is shut off, the hydraulic fluid in the upper chamber 75 is restricted from entering the wall passage 203, but passes through the passage 166 of the first piston 71 and has a soft damping force characteristic. The side damping valve 169 is opened to flow to the intermediate chamber 76. Further, since the second adjusting portion 212 allows the intermediate chamber 76 and the lower chamber 77 to communicate with each other through the wall passage 203, the hydraulic fluid in the intermediate chamber 76 flows through the wall passage 203 between the second piston 72 and the concave portion 200. It will flow to the lower chamber 77 via. Therefore, as shown in the second predetermined range S6 to S7 of the solid line X1 in FIG. 7, the soft state of the damping force is maintained.

  Further, when the first piston 71 and the second piston 72 are within the second predetermined range S6 to S7, in the contraction stroke in which the first piston 71 and the second piston 72 move toward the lower chamber 77, the second adjusting portion 212 is moved by the wall passage 203 to the intermediate chamber. The hydraulic fluid in the lower chamber 77 flows to the intermediate chamber 76 via the wall passage 203 between the second piston 72 and the recess 200 because the communication between the lower chamber 77 and the lower chamber 77 is established. Further, since the first adjusting portion 211 blocks the communication between the upper chamber 75 and the intermediate chamber 76 by the wall passage 203, the hydraulic fluid in the intermediate chamber 76 passes through the passage 165 of the first piston 71, and hard damping occurs. The compression side damping valve 168 of the force characteristic is opened to flow to the upper chamber 75. Therefore, as shown in the second predetermined range S6 to S7 of the broken line X2 in FIG. 7, the damping force is harder than the first predetermined range S4 to S5 and a third predetermined range S2 to S3 described later. Become.

  In the shock absorber 1, the stroke positions of the first piston 71 and the second piston 72 exceed the first predetermined range S <b> 4 to S <b> 5 described above, and the stroke length of the shock absorber 1 on the minimum length side shown in FIG. 6, the first adjustment unit 211 makes the upper chamber 75 and the intermediate chamber 76 communicate with each other through the wall passage 203 to increase the flow path area to the maximum value, as shown in FIG. The second adjusting unit 212 cuts off the communication between the intermediate chamber 76 and the lower chamber 77 by the wall passage 203 to minimize the flow passage area.

  When the first piston 71 and the second piston 72 are within the third predetermined range S2 to S3, during the extension stroke in which the first piston 71 and the second piston 72 move toward the upper chamber 75, the first adjustment unit 211 causes the upper chamber 75 and the Since the communication between the intermediate chambers 76 is established, the hydraulic fluid in the upper chamber 75 flows into the intermediate chamber 76 via the wall passage 203 between the first piston 71 and the recess 200. Further, since the second adjusting portion 212 blocks the communication between the intermediate chamber 76 and the lower chamber 77 by the wall passage 203, the hydraulic fluid in the intermediate chamber 76 flows from the passage 186 to the expansion-side damping valve having hard damping force characteristics. 189 is opened and flows into the lower chamber 77. Therefore, as shown in the third predetermined range S2 to S3 of the solid line X1 in FIG. 7, the damping force is harder than the first predetermined range S4 to S5 and the second predetermined range S6 to S7.

  Further, when the first piston 71 and the second piston 72 are within the third predetermined range S2 to S3, in the contraction stroke in which the first piston 71 and the second piston 72 move to the lower chamber 77 side, the second adjusting unit 212 is Since the communication between the lower chamber 77 and the lower chamber 77 is blocked, the hydraulic fluid in the lower chamber 77 passes through the passage 185 of the second piston 72 and opens the contraction-side damping valve 188 having a soft damping force characteristic to open the intermediate chamber 76. Flows to Further, since the first adjusting portion 211 allows the upper chamber 75 and the intermediate chamber 76 to communicate with each other via the wall passage 203, the hydraulic fluid in the intermediate chamber 76 flows through the wall passage 203 between the first piston 71 and the recess 200. It flows to the upper chamber 75 via the upper chamber 75. Therefore, as shown in the third predetermined range S2 to S3 of the broken line X2 in FIG. 7, the soft state of the damping force is maintained.

  The shock absorber 1 is configured such that the stroke positions of the first piston 71 and the second piston 72 exceed the second predetermined ranges S6 to S7, and extend to the fourth predetermined range S8 to the maximum longest extended position S9. At S9, as shown in FIG. 6D, the first adjustment unit 211 cuts off the communication between the upper chamber 75 and the intermediate chamber 76 by the wall passage 203 to minimize the flow passage area, and The adjusting section 212 cuts off the communication between the intermediate chamber 76 and the lower chamber 77 by the wall passage 203 to minimize the flow passage area.

  When the first piston 71 and the second piston 72 are in the fourth predetermined range S8 to S9, during the extension stroke in which the first piston 71 and the second piston 72 move toward the upper chamber 75, the first adjustment unit 211 makes the upper chamber 75 and the intermediate Since the communication between the chambers 76 is interrupted and the second adjusting portion 212 interrupts the communication between the intermediate chamber 76 and the lower chamber 77 by the wall passage 203, the hydraulic fluid in the upper chamber 75 passes through the passage 166 and is softened. The expansion-side damping valve 169 having a low damping force characteristic is opened to flow into the intermediate chamber 76, and flows through the passage 186 to the lower chamber 77 after opening the expansion-side damping valve 189 having a hard damping force characteristic. Therefore, as shown in the fourth predetermined range S8 to S9 of the solid line X1 in FIG. 7, the damping force is in a hard state similarly to the third predetermined range S2 to S3. Thereby, the damping force is in a hard state at the time of extension and extension, and it is possible to suppress abnormal noise and improve riding comfort.

  Further, when the first piston 71 and the second piston 72 are in the fourth predetermined range S8 to S9, in the contraction stroke in which the first piston 71 and the second piston 72 move toward the lower chamber 77, the first adjusting section 211 causes the upper chamber 75 by the wall passage 203 to move. Since the communication between the intermediate chamber 76 and the lower chamber 77 is interrupted by the second adjusting portion 212 and the communication between the intermediate chamber 76 and the lower chamber 77 by the wall passage 203, the hydraulic fluid in the lower chamber 77 passes through the passage 185. Then, the contraction-side damping valve 188 having soft damping force characteristics is opened to flow into the intermediate chamber 76, and flows through the passage 165 to the upper chamber 75 by opening the contraction-side damping valve 168 having hard damping force characteristics. Therefore, as shown in the fourth predetermined range S8 to S9 of the broken line X2 in FIG. 7, the damping force is in a hard state similarly to the second predetermined range S6 to S7.

  The shock absorber 1 is configured such that the stroke positions of the first piston 71 and the second piston 72 exceed the third predetermined ranges S2 to S3 and reach a fifth predetermined range S0 from the minimum length side contraction position S0. At S1, as shown in FIG. 6 (e), the first adjusting section 211 cuts off the communication between the upper chamber 75 and the intermediate chamber 76 by the wall passage 203 to minimize the flow passage area, and The adjusting section 212 cuts off the communication between the intermediate chamber 76 and the lower chamber 77 by the wall passage 203 to minimize the flow passage area.

  When the first piston 71 and the second piston 72 are in the fifth predetermined range S0 to S1, in the extension stroke in which the first piston 71 and the second piston 72 move toward the upper chamber 75, the first adjustment unit 211 controls the upper chamber 75 and the intermediate Since the communication between the chambers 76 is interrupted and the second adjusting portion 212 interrupts the communication between the intermediate chamber 76 and the lower chamber 77 by the wall passage 203, the hydraulic fluid in the upper chamber 75 passes through the passage 166 and is softened. The expansion-side damping valve 169 having a low damping force characteristic is opened to flow into the intermediate chamber 76, and flows through the passage 186 to the lower chamber 77 after opening the expansion-side damping valve 189 having a hard damping force characteristic. Therefore, as shown in the fifth predetermined range S0 to S1 of the solid line X1 in FIG. 7, the damping force is in a hard state similarly to the third predetermined range S2 to S3.

  Further, when the first piston 71 and the second piston 72 are in the fifth predetermined range S0 to S1, during the contraction stroke in which the first piston 71 and the second piston 72 move toward the lower chamber 77, the first adjustment unit 211 controls the upper chamber 75 by the wall passage 203. Since the communication between the intermediate chamber 76 and the lower chamber 77 is interrupted by the second adjusting portion 212 and the communication between the intermediate chamber 76 and the lower chamber 77 by the wall passage 203, the hydraulic fluid in the lower chamber 77 passes through the passage 185. Then, the contraction-side damping valve 188 having soft damping force characteristics is opened to flow into the intermediate chamber 76, and flows through the passage 165 to the upper chamber 75 by opening the contraction-side damping valve 168 having hard damping force characteristics. Therefore, as shown in the fifth predetermined range S0 to S1 of the broken line X2 in FIG. 7, the damping force is in a hard state as in the second predetermined range S6 to S7. As a result, the damping force is in a hard state at the time of contraction and cutoff, and it is possible to suppress abnormal noise and improve riding comfort.

  As described above, the first adjusting unit 211 and the second adjusting unit 212 constitute the position sensitive mechanism 215 that changes the state of the wall passage 203 according to the positions of the first piston 71 and the second piston 72. The position sensitive mechanism 215 is configured to communicate the upper chamber 75 and the lower chamber 77 with the maximum flow area through the intermediate chamber 76 according to the positions of the first piston 71 and the second piston 72, And a state in which the communication between the lower chamber 77 and the lower chamber 77 is interrupted, and a state in which the lower chamber 77 and the intermediate chamber 76 are connected with the maximum flow area, and The state of the wall passage 203 is changed between a state in which communication with the chamber 75 is cut off and a state in which communication with all of the upper chamber 75, the intermediate chamber 76, and the lower chamber 77 is cut off.

  As described above, when the first piston 71 and the second piston 72 are in the first predetermined range S4 to S5 including the neutral position, the damping force of the movement in the extension direction movement and the contraction direction movement is soft. In the second predetermined range S6 to S7 on the maximum length side, the damping force of the movement in the extension direction becomes a soft state, and the damping force of the movement in the contraction direction becomes a hard state. In the predetermined range S2 to S3, the damping force of the movement in the extension direction becomes a hard state and the damping force of the movement in the contraction direction becomes a soft state. Further, when the values are within the fourth predetermined range S8-S9 on the maximum length side and the fifth predetermined range S0-S1 on the minimum length side, the damping force of the movement in the extension direction and the movement in the contraction direction both become hard. That is, in the shock absorber 1, the relationship between the hardware and software of the movement in the extension direction and the movement in the contraction direction is determined by the second predetermined range S6 to S7 on the maximum length side and the third predetermined range S2 to S3 on the minimum length side. , It has a reversal type position-sensitive damping force change characteristic.

  FIG. 8 shows a simulation result of the damping force characteristic with respect to the piston speed of the shock absorber 1 described above. As is clear from FIG. 8, the damping force characteristic when the first piston 71 and the second piston 72 move in the extension direction when the first piston 71 and the second piston 72 are in the first predetermined range S4 to S5 (solid line Y1 in FIG. 8) and the second The damping force characteristic (dashed line Y2 in FIG. 8) during the movement in the elongation direction in the predetermined range S6 to S7 is in a substantially similar soft state over the entire range of the piston speed. On the other hand, the damping force characteristics during the movement in the elongation direction (solid line Y3 in FIG. 8) in the third predetermined range S2 to S3, the fourth predetermined range S8 to S9, and the fifth predetermined range S0 The damping force characteristic during the movement in the extension direction at the time of S1 (broken line Y4 in FIG. 8) is almost in the hard state in the entire region of the piston speed. In each of the damping force characteristics, the higher the piston speed, the harder the damping force.

  Further, the damping force characteristic when the first piston 71 and the second piston 72 move in the contraction direction when the first piston 71 and the second piston 72 are in the first predetermined range S4 to S5 (solid line Y5 in FIG. 8), and the third predetermined range S2 to S3 The damping force characteristic at the time of moving in the contraction direction (broken line Y6 in FIG. 8) is substantially the same in the entire region of the piston speed. On the other hand, the damping force characteristics during the movement in the contraction direction (solid line Y7 in FIG. 8) when in the second predetermined range S6 to S7, the fourth predetermined range S8 to S9, and the fifth predetermined range S0 The damping force characteristic during the movement in the contraction direction at the time of S1 (broken line Y8 in FIG. 8) is almost in the hard state in the entire region of the piston speed. In each of the damping force characteristics, the higher the piston speed, the harder the damping force.

  FIG. 9 shows a simulation result of the damping force characteristic with respect to the stroke position of the first piston 71 and the second piston 72 for each piston speed of the shock absorber 1. When the piston speed indicated by Z1 in FIG. 9 is high (specifically, 0.6 m / s) and the piston speed indicated by Z2 in FIG. 9 is an intermediate speed (specifically, 0.3 m / s). ), The piston speed indicated by Z3 in FIG. 9 is low (specifically, 0.1 m / s), and the piston speed indicated by Z4 in FIG. Specifically, the damping of the third predetermined range S2 to S3, the fourth predetermined range S8 to S9, and the fifth predetermined range S0 to S1 regardless of the movement in the extension direction at 0.05 m / s). The force becomes harder than the damping force in the first predetermined range S4 to S5 and the second predetermined range S6 to S7. Moreover, while maintaining such a relationship, the higher the piston speed, the harder the damping force.

  Also, when the piston speed indicated by Z5 in FIG. 9 is high (specifically, 0.6 m / s) and the piston speed indicated by Z6 in FIG. 9 is intermediate speed (specifically, 0.3 m / s). / S), the piston speed indicated by Z7 in FIG. 9 is low (specifically, 0.1 m / s), and the piston speed indicated by Z8 in FIG. The second predetermined range S6 to S7, the fourth predetermined range S8 to S9, and the fifth predetermined range S0 to S1 regardless of the movement in the contraction direction at low speed (specifically, 0.05 m / s). Is harder than the damping forces in the first predetermined range S4 to S5 and the third predetermined range S2 to S3. Moreover, while maintaining such a relationship, the higher the piston speed, the harder the damping force.

  By obtaining the above-described damping force change characteristics, the force for exciting the sprung can be reduced (ie, soft) and the force for damping the sprung can be increased (ie, hard), and the skyhook can be controlled without electronic control. A high-quality ride like control can be obtained.

  In the above, the operation of the shock absorber 1 when the vehicle on which the shock absorber 1 is mounted is in the standard loading state has been described. In the state where the loading load is larger or the loading load is smaller than the above, FIG. Without the self-leveling mechanism 221 shown, the axial position of the piston rod 81 of the shock absorber 1 with respect to the cylinder 11 is different from the above. Then, the characteristics will change as it is.

  On the other hand, the self-leveling mechanism 221 adjusts the axial position of the piston rod 81 with respect to the cylinder 11 of the shock absorber 1. That is, in a state where a standard load is applied, the extension length of the piston rod 81 is within a predetermined standard range. In this state, since the pump chamber 227 communicates with the lower chamber 77 through the passages 240 and 241 on the outer peripheral side of the pump rod 226, the pumping operation is not performed even if the piston rod 81 expands and contracts, and the vehicle height is maintained. Is done.

  When the vehicle height decreases due to an increase in the loading load or the like and the extension length of the piston rod 81 becomes shorter than a predetermined standard range, the passage 241 on the outer peripheral side of the pump tube 224 is shut off from the lower chamber 77 by the seal member 242. . In this state, when the piston rod 81 expands and contracts during traveling, during the extension stroke, the pump rod 226 retracts, the pump chamber 227 expands and is depressurized, the check valve 233 opens, and the liquid chamber 43 of the hydraulic fluid tank 38 opens. Is introduced into the pump chamber 227 through the liquid passage 61, the liquid chamber 53, the liquid passage 229, and the liquid passage 228. During the contraction stroke, the pump rod 226 advances, the pump chamber 227 is contracted and pressurized to open the check valve 234, and the hydraulic fluid is supplied from the pump chamber 227 to the lower chamber 77 through the liquid passage 235, and the piston rod 227 is moved. Extend 81. In this manner, the pumping operation is repeated by the expansion and contraction of the piston rod 81 during traveling, thereby extending the piston rod 81 and increasing the vehicle height. When the vehicle height reaches a predetermined standard range, the passage 241 separates from the seal member 242, and the pump chamber 227 is communicated with the lower chamber 77 via the passages 240 and 241 to release the pumping operation. .

  Further, when the vehicle height increases due to a decrease in the loading load or the like and the extension length of the piston rod 81 exceeds a predetermined standard range, the relief port 243 of the pump rod 226 separates from the pump tube 224 and the relief port 243 The lower chamber 77 and the liquid passage 228 are communicated with each other by the passage 240. Thereby, the hydraulic fluid in the lower chamber 77 is returned to the liquid chamber 43 of the hydraulic fluid tank 38, the piston rod 81 is shortened, and the vehicle height is reduced. Then, when the vehicle height decreases and the extension length of the piston rod 81 is reduced to a predetermined standard range, the relief port 243 is shut off by the pump tube 224, and the vehicle height is maintained.

  The shock absorber described in Patent Literature 1 includes two pistons each having a damping valve and a metering pin, and bypasses the damping valve of the piston located on the upstream side and downstream according to the position of the piston. A state in which damping force is generated by the damping valve of the piston on the side and a state in which hard damping force is generated by the damping valve of each of the two pistons without bypassing the damping valve of the piston located on the upstream side. It has become. On the other hand, it is desired to increase the degree of freedom in setting the damping force.

  In the shock absorber 1 according to the first embodiment, the position sensitive mechanism 215 allows the upper chamber 75 and the lower chamber 77 to communicate with each other, the upper chamber 75 and the intermediate chamber 76 communicates with each other, the lower chamber 77 In order to change the state of the wall passage 203 to a state in which the chambers 76 are communicated with each other, the upper chamber 75 and the lower chamber 77 are communicated to make the damping force soft, or the upper chamber 75 and the intermediate chamber 76 are communicated. Then, a damping force is generated by the second damping force generating mechanism 191 provided between the intermediate chamber 76 and the lower chamber 77, or the lower chamber 77 and the intermediate chamber 76 are communicated with each other to make the intermediate chamber 76 The first damping force generating mechanism 171 provided between the upper chamber 75 and the upper chamber 75 can generate a damping force. Therefore, it is possible to increase the degree of freedom in setting the damping force. Moreover, the configuration is simple and the cost is low.

  More specifically, passages 165 and 165 are provided in the first piston 71 and the second piston 72 and communicate between the upper chamber 75 and the intermediate chamber 76 and between the intermediate chamber 76 and the lower chamber 77 so that the hydraulic fluid flows. A wall passage 203 is provided separately from 166, 185, 186, and the flow passage area of the hydraulic fluid between the upper chamber 75 and the intermediate chamber 76 is adjusted in the wall passage 203 by the positions of the first piston 71 and the second piston 72. And a second adjustment unit 212 that adjusts the flow area of the working fluid between the lower chamber 77 and the intermediate chamber 76 according to the positions of the first piston 71 and the second piston 72. When the first piston 71 and the second piston 72 are within the first predetermined range S4 to S5 including the neutral position, the flow passage areas of the first adjustment unit 211 and the second adjustment unit 212 are both large, and the upper chamber is increased. The damping force is set in a soft state by communicating between the lower chamber 75 and the lower chamber 77.

  Further, when the first piston 71 and the second piston 72 are within the second predetermined range S6 to S7 on the maximum length side beyond the first predetermined range S4 to S5, the flow path area of the first adjusting unit 211 becomes smaller. The flow path area of the second adjustment unit 212 is small and large. Therefore, in the extension stroke, the hydraulic fluid in the upper chamber 75 can flow to the lower chamber 77 via the intermediate chamber 76 and the second adjusting portion 212 while passing through the extension-side damping valve 169 of the first piston 71. Further, in the contraction stroke, the hydraulic fluid in the lower chamber 77 can flow from the second adjusting portion 212 to the intermediate chamber 76 and flow to the upper chamber 75 while passing through the compression-side damping valve 168 of the first piston 71.

  When the first piston 71 and the second piston 72 are within the third predetermined range S2 to S3 on the minimum length side beyond the first predetermined range S4 to S5, the flow path area of the first adjustment unit 211 is reduced. It is large and the flow path area of the second adjustment unit 212 is small. Therefore, in the extension stroke, the hydraulic fluid in the upper chamber 75 can be introduced into the intermediate chamber 76 via the first adjusting portion 211 and flow into the lower chamber 77 while passing through the extension damping valve 189 of the second piston 72. . In the contraction stroke, the hydraulic fluid in the lower chamber 77 can flow through the compression-side damping valve 188 of the second piston 72 to the intermediate chamber 76, and can flow to the upper chamber 75 via the first adjustment unit 211. Therefore, it is possible to increase the degree of freedom in setting the damping force.

  The extension damping valve 169 of the first piston 71 and the extension damping valve 189 of the second piston 72 operate when the first piston 71 and the second piston 72 move in the extension direction. The damping force generated by the valve 169 is set smaller than the damping force generated by the extension-side damping valve 189 located on the downstream side. Therefore, the damping force due to the flow of the hydraulic fluid passing through the expansion-side damping valve 169 during the expansion stroke when it is within the second predetermined range S6 to S7 can be softened, and within the third predetermined range S2 to S3. The damping force due to the flow of the hydraulic fluid passing through the extension side damping valve 189 during a certain extension stroke can be hardened.

  When the first piston 71 and the second piston 72 move in the compression direction, the compression-side damping valve 168 of the first piston 71 and the compression-side damping valve 188 of the second piston 72 move to the compression-side damping position located on the upstream side. The damping force generated by the valve 188 is set smaller than the damping force generated by the contraction-side damping valve 168 located on the downstream side. For this reason, the damping force due to the flow of the hydraulic fluid passing through the contraction-side damping valve 188 during the contraction stroke when it is within the third predetermined range S2 to S3 can be softened, and within the second predetermined range S6 to S7. The damping force due to the flow of the hydraulic fluid passing through the contraction-side damping valve 168 during a certain contraction stroke can be hardened.

  As described above, the force for exciting the sprung mass can be reduced (that is, soft), and the force for damping the sprung mass can be increased (that is, hard). Is obtained.

  Further, when the first piston 71 and the second piston 72 are in the fourth predetermined range S8 to S9 on the maximum length side beyond the second predetermined range S6 to S7, and the third predetermined range S2 to S3 When it is in the fifth predetermined range S0 to S1 which is on the minimum length side beyond, the flow path areas of the first adjustment unit 211 and the second adjustment unit 212 are both small. Accordingly, the communication of the wall passage 203 with any of the upper chamber 75, the intermediate chamber 76, and the lower chamber 77 is restricted, so that the damping force in both the extension stroke and the contraction stroke increases. This makes it possible to increase the damping force at the time of extension and contraction, thereby suppressing abnormal noise and improving riding comfort.

  According to the above-described embodiment, the concave portion 200 that is longer than the axial length between the first adjusting portion 211 and the second adjusting portion 212 and forms the position sensitive mechanism 215 is formed in the inner cylinder 10 of the cylinder 11. Since it suffices, a simpler structure can be achieved.

  In addition, since the self-leveling mechanism 221 for adjusting the extension length of the piston rod 81 by supplying and receiving hydraulic fluid between the cylinder 11 and the hydraulic fluid tank 38 by expansion and contraction of the piston rod 81 is provided, Even if there is a difference in the loaded weight in the mounted vehicle, the force for exciting the sprung mass can be reduced (that is, soft), and the force for damping the sprung mass can be increased (that is, hard). A high-quality ride like skyhook control can be obtained. That is, if the self-leveling mechanism 221 is not provided, the 1G position will change when there is a difference in the loading weight, and in order to suppress a change in ride comfort at that time, the wall passage 203 needs to be By communicating the upper chamber 75, the intermediate chamber 76, and the lower chamber 77, the width of the dead zone in which the damping force does not switch is increased. Then, the hard area in the actual stroke range is narrowed, and the damping force is suddenly and largely changed with respect to the position change. Then, a shock due to a sudden change in the damping force is large, and even though sprung mass damping performance is improved, riding comfort is deteriorated. Therefore, the function of damping the spring must be weakened. On the other hand, according to the present embodiment, since the self-leveling mechanism 221 is provided, it is possible to automatically adjust the 1G position to be constant even if there is a difference in the loading weight, so that the width of the dead zone No longer need to be spread out. As a result, the damping force can be switched more quickly, so that the sprung mass damping property can be sufficiently improved.

  Further, since the concave portion 200 is formed in the inner wall of the inner cylinder 10 of the cylinder 11 over a predetermined range in the axial direction to form the wall passage 203, the position sensitive mechanism 215 is moved to the position of the first piston 71 and the second piston 72. Accordingly, the wall passage 203 has a state in which the upper chamber 75 communicates with the lower chamber 77, a state in which the upper chamber 75 communicates with the intermediate chamber 76, and a state in which the lower chamber 77 communicates with the intermediate chamber 76. Changing the state can be performed at low cost.

  In the present embodiment, the relationship between the length of the concave portion 200 and the length between the first piston 71 forming the first adjusting portion 211 and the second piston 72 forming the second adjusting portion 212 is changed to increase the length. Until the cutting position S9, the first adjusting section 211 may cut off the communication between the upper chamber 75 and the intermediate chamber 76 and the second adjusting section 212 may connect the intermediate chamber 76 and the lower chamber 77. That is, the second predetermined range S6 to S7 satisfying these relationships may be extended to the extended position S9. Similarly, the first adjustment unit 211 may make the upper chamber 75 communicate with the intermediate chamber 76 and the second adjustment unit 212 may cut off the communication between the intermediate chamber 76 and the lower chamber 77 until the contraction cutting position S0. That is, the third predetermined range S2 to S3 satisfying these relationships may be extended to the contraction cut position S0.

  Further, among these changes, a change on only one of the extension side and the contraction side may be adopted. Preferably, when the first piston 71 and the second piston 72 are on the maximum length side beyond the second predetermined range S6 to S7, and when the first piston 71 and the second piston 72 are in the third predetermined range S2 The flow path area of the first adjustment part 211 and the flow path area of the second adjustment part 212 are both set to be small at least on one of the minimum length sides beyond S3. The setting is made such that the flow path areas of the adjusting unit 211 and the second adjusting unit 212 are both small.

  Further, one of the first piston 71 and the second piston 72 may be provided without sliding in the cylinder 11, and the intermediate chamber 76 may be provided inside these. Further, a cylinder connecting the first piston 71 and the second piston 72 may be provided on the outer peripheral side of the first piston 71 and the second piston 72, and an intermediate chamber may be formed inside the cylinder.

  Further, the damping force characteristics of the contraction-side damping valves 168, 188 and the extension-side damping valves 169, 189 may all be different, and at least any two may have the same damping force characteristics. For example, it is possible to make a change such that two are medium characteristics between software and hardware, the other is software characteristics, and the other is hardware characteristics.

  Further, the present invention can be applied not only to the double cylinder type but also to a single cylinder type shock absorber. In this case, a free piston is provided in the cylinder on the side opposite to the side on which the piston rod of the second piston extends.

  The shock absorber according to the present embodiment includes a cylinder in which hydraulic fluid is sealed, a piston provided in the cylinder, and dividing the inside of the cylinder into an upper chamber and a lower chamber, and connected to the piston and external to the cylinder. A hydraulic fluid, a reservoir for storing hydraulic fluid and gas, a hydraulic fluid tank for storing hydraulic fluid, and transfer of hydraulic fluid between the cylinder and the hydraulic fluid tank by expansion and contraction of the piston rod. And a self-leveling mechanism for adjusting the extension length of the piston rod, wherein the cylinder has an intermediate chamber formed by the piston, and an intermediate chamber formed between the upper chamber and the intermediate chamber. A first damping force generating mechanism provided in the lower chamber to generate a damping force; a second damping force generating mechanism provided between the lower chamber and the intermediate chamber to generate a damping force; Depending on the position of the piston, a state in which the upper chamber and the lower chamber communicate with each other, a state in which the upper chamber and the intermediate chamber communicate with each other, and a state in which the lower chamber and the intermediate chamber communicate with each other, A position-sensitive mechanism for changing the state of the passage. This makes it possible to increase the degree of freedom in setting the damping force. Moreover, since the self-leveling mechanism is provided, the sprung mass damping property can be sufficiently improved even if there is a difference in the loaded weight.

  Further, since a concave portion is formed in the inner wall of the cylinder over a predetermined range in the axial direction, the position-sensitive mechanism communicates between the upper chamber and the lower chamber in accordance with the position of the piston, and the upper and lower chambers are connected to each other. The state of the passage can be changed at low cost between a state in which the chambers communicate with each other and a state in which the lower chamber and the intermediate chamber communicate with each other.

DESCRIPTION OF SYMBOLS 1 Shock absorber 11 Cylinder 13 Reservoir 38 Hydraulic fluid tank 71 First piston (piston)
72 Second piston (piston)
75 upper chamber 76 intermediate chamber 77 lower chamber 81 piston rod 221 self-leveling mechanism 171 first damping force generation mechanism 191 second damping force generation mechanism 200 recess 203 wall passage (passage)
215 Position sensitive mechanism

Claims (2)

A cylinder filled with hydraulic fluid,
A first piston and a second piston provided in the cylinder and partitioning the cylinder into an upper chamber, an intermediate chamber, and a lower chamber;
A first damping force generating mechanism provided on the first piston to generate a damping force;
A second damping force generating mechanism provided on the second piston to generate a damping force;
A piston rod connected to the first piston and the second piston and extending outside the cylinder;
A reservoir filled with hydraulic fluid and gas;
A hydraulic fluid tank for storing hydraulic fluid,
A self-leveling mechanism that transfers hydraulic fluid between the cylinder and the hydraulic fluid tank by adjusting the expansion and contraction of the piston rod to adjust the extension length of the piston rod;
A shock absorber having
In the cylinder,
(A) a state in which the upper chamber communicates with the lower chamber, and (b) a state in which the upper chamber and the intermediate chamber communicate with each other according to the positions of the first piston and the second piston. a state in which c) said lower chamber and communication between the intermediate chamber, and a state to cut off between said upper chamber and said intermediate chamber (d), and a state to cut off between (e) said lower chamber and said intermediate chamber, (F) A shock absorber provided with a position sensitive mechanism that changes the state of the passage between a state where all the passages between the upper chamber, the intermediate chamber, and the lower chamber are shut off . The position sensitive mechanism is
Said first piston;
Said second piston;
A concave portion formed on the inner wall of the cylinder in the axial direction of the cylinder, and configured to change the passage into the state of (a) to ( f ) according to the positions of the first piston and the second piston. The shock absorber according to claim 1, wherein the shock absorber is configured.

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