JP2006283924A - Hydraulic damper for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic damper for a vehicle enabling an increase in damping force characteristics during extension in the low piston speed range. <P>SOLUTION: In this hydraulic damper 1 for the vehicle, a piston 4 dividing the inside of a cylinder 2 into a compression side oil chamber A and an extension side oil chamber B is installed at the tip of a piston rod 3 inserted into the cylinder 2, and extension side and compression side main passages 42 and 41 to communicate the compression side oil chamber A with the extension side oil chamber B are formed in the piston 4. An extension main valve 6 formed of an annular plate valve and opening during the extension stroke and a compression main valve 7 opening during the compression stroke are disposed in compression chamber side openings 42a and 41b opening to the compression side oil chamber A of the extension side and compression side main passages 42 and 41 and extension chamber side openings 42b and 41a opening to the extension side oil chamber B. An extension auxiliary valve 11 communicating the compression side oil chamber A with the extension side oil chamber B at the beginning of the extension stroke of the piston 4 is installed in the hydraulic damper. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydraulic shock absorber for suppressing a change in posture during traveling of a vehicle.

  An automobile or a motorcycle is provided with a hydraulic shock absorber that suppresses a change in posture of the vehicle body due to road surface unevenness.

  FIG. 9 shows a structure of a hydraulic shock absorber conventionally used. In FIG. 9, the thick solid line arrow indicates the movement of the hydraulic oil during compression, and the thick dotted line arrow indicates the movement of the hydraulic oil during expansion.

  The cylinder 51 of the hydraulic shock absorber 50 is divided into a compression side oil chamber A and an extension side oil chamber B by a piston 53 fixed to a piston rod 52. The piston 53 is formed with a first passage 54 and a second passage 55 that allow the compression side oil chamber A and the extension side oil chamber B to communicate with each other. An extension valve 56 that opens during the extension stroke of the piston rod 52 is provided in the pressure chamber side opening 54a of the first passage 54, and a compression valve 57 that opens during the compression stroke is provided in the extension chamber side opening 55a of the second passage 55. A damping force is generated when the piston 53 relatively moves in the axial direction in the cylinder 51 due to the unevenness of the road surface.

  In such a hydraulic shock absorber, a damping force characteristic is set so that a damping force corresponding to a road surface state can be obtained in order to realize the ride comfort desired by the user. For example, it is general to set a damping force when the piston speed is 0.3 m / s, and to tune damping characteristics in a low speed region and a high speed region using this damping force as a basic damping force.

  However, the hydraulic shock absorber 50 has a problem that in the low speed region of the piston speed, the damping force characteristic becomes high both during compression and extension, and the riding comfort in the low speed region is poor.

  Therefore, Patent Document 1 discloses a hydraulic shock absorber for reducing the damping force in the low speed region to improve the riding comfort.

  FIG. 10 shows the structure of the hydraulic shock absorber disclosed in Patent Document 1. Similarly, in FIG. 10, the thick solid arrow indicates the movement of the hydraulic oil during compression, and the thick dotted arrow indicates the movement of the hydraulic oil during expansion.

  The cylinder 61 is divided into a compression side oil chamber A and an extension side oil chamber B by a piston 63 fixed to a piston rod 62. The piston 63 is formed with a compression side main passage 64 and an extension side main passage 65 that allow the compression side oil chamber A and the extension side oil chamber B to communicate with each other. An extension main valve 66 that opens during the extension stroke of the piston rod 62 is provided in the pressure chamber side opening 64a of the compression side main passage 64, and a compression main valve 67 that opens in the extension chamber side opening 65a of the extension side main passage 65 during the compression stroke. Is provided. A damping force is generated when the piston 63 relatively moves in the axial direction in the cylinder 61 due to the unevenness of the road surface.

  Further, the hydraulic shock absorber 60 is provided with a sub-valve 69 for moving the hydraulic oil in the compression side oil chamber A to the extension side oil chamber B at the initial stage of the compression stroke. That is, a second piston member 71 provided with a sub-passage 68 communicating with the compression-side oil chamber A and communicating with the extension-side oil chamber B by an in-shaft passage 70 formed in the piston rod 62 is disposed, and the compression stroke initial stage is arranged. A secondary valve 69 that opens the outlet 68 a of the secondary passage 68 is provided on the back surface of the main valve 67 during compression.

  Thereby, when the piston speed is low, that is, the auxiliary valve 69 opens at the beginning of the compression stroke, the damping force can be appropriately reduced, and the riding comfort at the low speed is improved.

However, in this hydraulic shock absorber 60, only the sub valve 69 at the time of compression that operates at the initial stage of the compression stroke of the piston 63 is provided, and the sub valve at the time of expansion that operates at the initial stage of the expansion stroke is not provided. Therefore, there is a problem that the damping force in the extension stroke at a low speed becomes high, the balance between the damping force in the compression stroke and the extension stroke is lost, and the ground contact property of the tire is lowered and the riding comfort is lowered.
JP 2001-82527 A

  The present invention has been made in view of the above prior art, and an object of the present invention is to provide a vehicle hydraulic shock absorber that improves the damping force characteristics at the time of extension in a low speed region of the piston speed.

  According to the first aspect of the present invention, a piston that divides the inside of the cylinder into a compression side oil chamber and an extension side oil chamber is attached to the tip of the piston rod inserted into the cylinder, and the compression side oil chamber and the extension side oil chamber are attached to the piston. The expansion side and compression side main passages that communicate with each other, and the pressure chamber side opening that opens to the compression side oil chambers of the extension side and compression side main passages, the extension chamber side opening that opens to the extension side oil chamber, In a hydraulic shock absorber for vehicles that consists of a plate valve and has a main valve for expansion that opens during the expansion stroke and a main valve for compression that opens during the compression stroke, the compression-side oil chamber communicates with the expansion-side oil chamber at the beginning of the piston expansion stroke. Provided is a vehicular hydraulic shock absorber provided with a secondary valve for extension.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, a sub valve at the time of compression is provided that communicates the compression side oil chamber and the extension side oil chamber at the initial stage of the compression stroke of the piston.

  According to a third aspect of the present invention, in the first aspect of the present invention, a compression main valve is provided on the back surface of the piston, and a sub-passage communicating the compression side oil chamber and the extension side oil chamber is formed on the piston rod on the back surface. The second piston member is provided, the compression side valve is provided on the back side of the second piston member, and a third passage is formed on the piston rod to communicate the compression side oil chamber and the extension side oil chamber. A piston member is provided, and an extension sub valve is provided on the opening surface of the sub passage of the third piston member.

  The invention of claim 4 is the invention of claim 3, in order from the tip side on the piston rod, the extension main valve, the piston, the compression main valve, the third piston member, the extension subvalve, the second piston member, And a secondary valve for compression is provided.

  The invention of claim 5 is characterized in that, in the invention of claim 4, the second piston member is provided by covering the outer periphery of the third piston member from the back side in an oil-tight manner.

  According to the first aspect of the present invention, since the secondary valve opens at the beginning of the extension stroke of the piston and the hydraulic fluid flows from the extension side oil chamber to the compression side oil chamber, the predetermined damping force characteristic is obtained in the middle speed range of the piston speed. It is possible to reduce the damping force when extending in the low speed range while maintaining the above.

  According to the invention of claim 2, by providing the sub valve at the time of compression in addition to the sub valve at the time of expansion, the damping force at the time of expansion and compression is lowered in the low speed region of the piston speed to balance both the damping forces. Because it can be adjusted, ride comfort is further improved.

  According to the invention of claim 3, the main valve during expansion is provided on the front side of the piston, the main valve during compression is provided on the back side of the piston, and the second piston member is disposed on the piston rod on the back side of the main valve during compression. A secondary valve is provided during compression. The extension sub-valve is provided at a position where a third piston member is provided on the piston rod on the front side or the back side of the piston and the opening surface of the sub passage of the third piston member is closed. Thereby, the sub valve at the time of extension can be efficiently arranged together with the sub valve at the time of compression using the space on the piston rod. In this case, since the compression main valve, the second piston member, and the compression sub valve are arranged in order on the back side of the piston, the deflection direction of the main valve and the sub valve during compression, that is, the main valve and the sub valve It becomes easy to make the flow direction of the hydraulic oil the same when the is opened. This reduces resistance due to interference between fluids flowing out from the main valve and the sub-valve that are placed close to each other, resulting in a smooth flow, effectively reducing the damping force particularly at high speeds. Riding comfort can be improved.

  According to the fourth aspect of the present invention, the third piston member, the extension sub-valve, the second piston member, and the compression sub-valve are arranged in this order on the back side of the compression main valve on the piston back. The side valve for compression and the side valve for expansion are arranged efficiently on the piston rod on the side, and components such as washers can be used in a compact configuration, and a highly reliable function can be obtained. If the extension sub-valve is composed of a plurality of sub-plate valves, the damping force in the low speed range can be adjusted by adjusting the number of sheets, and the riding comfort can be further improved. In this case, each sub-plate valve may have a different spring force or may have the same spring force.

  According to the invention of claim 5, since the second piston member is surrounded and disposed inside the third piston member, the axial length can be shortened and a more compact configuration can be achieved. In addition, since the second piston member is covered in an oil-tight manner, the hydraulic oil is stably prevented from being disturbed, and a highly reliable sub-valve operation is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a hydraulic shock absorber according to the present invention, FIGS. 2 and 3 are enlarged sectional views around a piston, FIG. 2 shows an operating state during expansion, and FIG. 3 shows an operating state during compression.

  The piston rod 3 is inserted into the bottomed cylindrical cylinder 2 so as to be relatively movable in the axial direction. The piston 4 is fixed to the tip of the piston rod 3, and the inside of the cylinder 2 is divided into a compression side oil chamber A on the piston tip side and an extension side oil chamber B on the piston back side. The front end of the cylinder 2 is pivotally supported by a wheel support member (not shown), and the base end of the piston rod 3 is elastically supported by the vehicle body 19 via the support plate 17 and the elastic member 18. A dust cover 16 that surrounds the piston rod 3 is provided between the support plate 17 and the base end portion of the cylinder 2, and a cushion material 15 that absorbs an impact force at the time of the most compression is provided on the distal end side of the support plate 17. Provided.

  A free piston 29 that forms a compression-side oil chamber A by the piston 4 is slidably inserted into the cylinder 2, and the space surrounded by the free piston 29 and the inside of the front end side of the cylinder 2 is high pressure. It is a gas chamber C.

  The base end side opening of the cylinder 2 is closed by press-fitting the lid plate 21, and a base member 22 is inserted inside the lid plate 21 in the cylinder 2, and the circlip 23 (FIGS. 2 and 3). Is fixed by positioning. Shaft holes 21 a and 22 a through which the piston rod 3 is inserted are formed in the shaft centers of the cover plate 21 and the base member 22, and a metal bush slidably contacting the piston rod 3 is formed on the inner peripheral surface of the shaft hole 22 a of the base member 22. 24 is inserted.

  An O-ring 25 that seals between the outer peripheral portion of the base member 22 and the inner peripheral surface of the cylinder 2 is mounted, and seal members 26a and 26b that seal between the piston rod 3 and the both end edges of the shaft hole 22a, respectively. Has been. A rubber member 27 that absorbs an impact force at the time of maximum extension is fixed to an end surface of the base member 22 facing the extension side oil chamber B.

  In the piston rod 3, an in-shaft passage 3a communicating with the compression side oil chamber A is formed extending in the axial direction. The piston rod 3 is formed with a plurality of communication holes 3b communicating with the in-shaft passage 3a and the extension side oil chamber B in a direction perpendicular to the shaft. As a result, the compression side oil chamber A and the extension side oil chamber B communicate with each other via the in-shaft passage 3a and the communication hole 3b. Further, a plurality of sub communication holes 3d are formed in the direction perpendicular to the axis at positions closer to the tip than the communication holes 3b of the piston rod 3.

  Further, the piston rod 3 has a valve insertion hole 3c that extends following the in-shaft passage 3a and has a smaller diameter than the in-shaft passage 3a. The valve insertion hole 3c has a damping force adjusting valve 30. The shaft portion 30a is inserted so as to be movable in the axial direction. The damping force adjusting valve 30 is formed by forming a conical valve portion 30b located in the in-shaft passage 3a at the tip of the shaft portion 30a located in the valve insertion hole 3c, and an outer peripheral portion of the valve portion 30b. Is mounted with an O-ring 31 that is in sliding contact with the inner peripheral surface of the in-shaft passage 3a.

  Further, a cylindrical throttle portion 32 is fixed to a position below the communication hole 3b in the in-shaft passage 3a in FIG. 2 and closer to the upper side than the sub-communication hole 3d. The valve portion 30b faces the fully closed position and the fully open position so as to be able to advance and retreat. By moving the valve portion 30b back and forth, the path area between the valve portion 30b and the throttle portion 32 changes. An adjustment member 33 (FIG. 1) is connected to the upper end portion of the shaft portion 30a. By rotating the adjustment member 33, the damping force adjustment valve 30 advances and retreats, so that during the compression stroke and the expansion stroke. Adjust the damping force especially at low speeds.

  A metal bush 5 that is in oil-tight sliding contact with the inner peripheral wall of the cylinder 2 is mounted on the outer peripheral portion of the piston 4. The piston 4 is formed with a compression-side main passage 41 and an extension-side main passage 42 penetrating the compression-side oil chamber A and the extension-side oil chamber B.

  On the end face of the piston 4 facing the compression side oil chamber A, there is provided an extension main valve 6 that opens the pressure chamber side opening 42a of the extension side main passage 42 during the extension stroke of the piston rod 3. The extension main valve 6 is formed of an annular thin leaf spring, and, for example, three plate valves 6a, 6b, and 6c are stacked in a manner that the outer shape decreases with increasing distance from the pressure chamber side opening 42a of the extension side main passage 42 in the axial direction. Configured (FIG. 2). The spring force of each plate valve 6a, 6b, 6c is gradually opened when the extension side oil chamber B becomes higher than the compression side oil chamber A during the extension stroke, and at this time, a predetermined damping force is obtained. Is set. The extension main valve 6 is always open with respect to the pressure chamber side opening 41b of the compression side main passage 41.

  A compression main valve 7 that opens the expansion chamber side opening 41a of the compression side main passage 41 during the compression stroke is provided on the end surface of the piston 4 facing the expansion side oil chamber B. The main valve 7 at the time of compression consists of an annular thin leaf spring, and the outer shape becomes smaller as it goes away from the expansion chamber side opening 41a of the compression side main passage 41 in the axial direction, for example, three plate valves 7a, 7b, 7c are laminated. Configured (FIG. 3). The spring force of each of the plate valves 7a, 7b, 7c is gradually opened when the compression side oil chamber A becomes higher in pressure than the extension side oil chamber B during the compression stroke, and a predetermined damping force is obtained at that time. Is set. The compression main valve 7 is always open with respect to the extension chamber side opening 42b of the extension side main passage 42.

  A third piston member 10, an extension sub-valve 11, and a second piston member 9 are disposed on the back surface (upper side in the drawing) of the main valve 7 during compression via a washer 8. The shapes of the second piston member 9 and the third piston member 10 and their accommodation will be described later.

  An auxiliary valve 12 is provided on the back surface of the second piston member 9 during compression. A washer seat 13 is disposed on the back surface of the auxiliary valve 12 during compression, and the washer seat 13 is fixed to the piston rod 3 by a circlip 28. The washer sheet 13 faces the rubber member 27 so as to be able to come into contact therewith.

  In order from the back side (upper side in the figure) to the washer seat 13 fixed to the piston rod 3 with a circlip 28, the secondary valve 12 during compression, the second piston member 9, the secondary valve 11 during expansion, and the third piston member 10, the washer 8, the compression main valve 7, the piston 4, the extension main valve 6, and the valve seat 38 are sequentially stacked, and each member is fixed to the piston rod 3 by screwing a nut 39 to the tip of the piston rod 3. Is done.

  4 and 5 show the shapes of the second piston member 9 and the third piston member 10. 4 (a) and FIG. 5 (a) are front views, FIG. 4 (b) and FIG. 5 (b) are rear views, and FIG. 4 (c) is a cross section viewed from the line cc of FIG. 4 (b). FIG. 5 and FIG. 5C are cross-sectional views as seen from the line dd in FIG. The detail of the 2nd piston member 9 and the 3rd piston member 10 is demonstrated based on a figure.

  The 2nd piston member 9 has the hole 9b which penetrates the piston rod 3 in the center. Two through holes 9a are formed through the hole 9b at opposite positions. As shown in FIG. 4B, a groove 9e is formed between the outer peripheral portion 9f on the back side and the four convex portions 9d arranged in the circumferential direction, and the groove 9e is formed around the central hole 9b. A recessed portion 9c that is also deeply recessed is formed. The annular groove 9e in which the through hole 9a is formed communicates with the central recess 9c through four sub-passages 9h.

  As shown in FIG. 4C, the second piston member 9 has a substantially U-shaped cross section, and forms a space 9g on the front side. The compression side sub-valve 12 is disposed on the back side. When the compression side sub-valve 12 is closed, the back surface of the outer peripheral portion 9f and the compression side sub-valve 12 are in close contact with each other.

  The third piston member 10 has a hole 10b through which the piston rod 3 is inserted in the center. Two through holes 10a are formed penetrating from the front side to the back side at opposite positions across the hole 10b. The outer diameter of the third piston member 10 is the same as the inner diameter of the space 9g formed on the front side of the second piston member 9, and the outer periphery is in close contact with the second piston member 9 as shown in FIG. And a gap 10d is provided on the back surface of the third piston member 10 for attachment. The extension sub valve 11 is disposed in the gap 10d, and the dimension of the gap 10d can be changed according to the thickness of the extension sub valve 11.

  6 is an enlarged view of part a in FIG. 2, and FIG. 7 is an enlarged view of part b in FIG. Based on FIG. 6 and FIG. 7, the detail regarding the sub valve 11 at the time of expansion | extension and the sub valve 12 at the time of compression is demonstrated.

  As shown in FIG. 6, the extension sub-valve 11 includes first and second sub-plate valves 11 a and 11 c having substantially the same diameter made of an annular thin plate spring, and a third sub-plate valve 11 b having a smaller diameter. The third sub-plate valve 11b is laminated with the sub-plate valves 11a and 11c interposed therebetween.

  The spring force of the first to third sub-plate valves 11a to 11c is set so as to open immediately when the extension side oil chamber B is slightly pressurized at the initial stage of the extension stroke, and at this time, a predetermined damping force is obtained. That is, for example, in the low speed range where the piston speed is 0.2 m / s or less, only the first sub-plate valve 11a is opened particularly at extremely low speeds, and together with the first sub-plate valve 11a at medium and low speeds slightly faster than the extremely low speed. The plate thicknesses of the sub plate valves 11a to 11c are set so that the second sub plate valve 11c opens. Thereby, while the damping force characteristic at the very low speed is secured by the first sub-plate valve 11a, the first sub-plate valve 11a is prevented from opening too much at a slightly higher speed, thereby preventing the damping force from becoming too small. Further, the spring force and dimensions are set so that the second sub-plate valve 11c is not opened too much and the inlet of the through hole 9a of the second piston member 9 is not blocked.

  When the extension side oil chamber B is slightly pressurized, the hydraulic oil in the extension side oil chamber B flows into the through hole 10a of the third piston member 10, and the auxiliary valve 11 is opened during extension. Thereby, the outlet 10c of the through hole 10a is opened, and the hydraulic oil flows into the through hole 9a of the second piston member 9. Further, it flows from the sub passage 9h through the sub communication hole 3d and the in-shaft passage 3a to the compression side oil chamber A to obtain a predetermined damping force. The second piston member 9 is attached with the piston rod 3 aligned in the axial direction so that the sub passage 9h and the sub communication hole 3d of the piston rod 3 communicate with each other.

  As shown in FIG. 7, the compression-time subvalve 12 includes first and second subplate valves 12a and 12c having substantially the same diameter made of an annular thin leaf spring, and third and fourth subplate valves having a smaller diameter. The third sub-plate valve 12b is interposed between the sub-plate valves 12a and 12c, and the fourth sub-plate valve 12d is interposed between the sub-plate valve 12c and the washer seat 13 and laminated.

  The spring force of each of the sub-plate valves 12a to 12d is set so as to open immediately when the compression side oil chamber A is slightly boosted at the beginning of the compression stroke, and at this time, a predetermined damping force is obtained. That is, as in the extension sub valve 11, for example, in the low speed range where the piston speed is 0.2 m / s or less, especially when the speed is extremely low, only the first sub plate valve 12a is opened and passes through large unevenness on the road surface. As described above, the plate thickness of each of the sub-plate valves 12a to 12d is set so that the second sub-plate valve 12c is opened together with the first sub-plate valve 12a at a medium / low speed slightly faster than the extremely low speed.

  When the pressure in the compression side oil chamber A is slightly increased, the hydraulic oil in the compression side oil chamber A flows into the sub passage 9h through the in-shaft passage 3a and the sub communication hole 3d, and the sub valve 12 is opened during compression. As a result, the sub-passage 9h is opened to the extension side oil chamber B, and the working oil flows to the extension side oil chamber B to obtain a predetermined damping force.

  In the above-described embodiment, the extension sub-valve 11 is provided on the base end side with respect to the piston 4, but may be provided on the front end side, that is, the compression side oil chamber A side.

  Next, the overall operation of the hydraulic shock absorber 1 will be described.

  When the wheel is lowered by the concave portion of the road surface or the wheel pushed up by the convex portion returns, when the hydraulic shock absorber 1 is in the extended state, the cylinder 4 moves downward, that is, in FIG. Pulled upward. At this time, the pressure in the extension side oil chamber B increases, and the main valve 6 at the time of extension opens accordingly. When the main valve 6 is opened at the time of extension, the working oil flows from the extension side oil chamber B to the compression side oil chamber A through the extension side main passage 42, and at this time, a damping force is generated. When the extension side oil chamber B is pressurized, a part of the hydraulic oil in the extension side oil chamber B flows into the compression side oil chamber A from the communication hole 3b through the throttle portion 32 and the shaft passage 3a. An adjusted damping force is generated. In FIG. 2, the flow of hydraulic oil during expansion is indicated by a thick arrow.

  Further, when the expansion side oil chamber B is slightly increased in the low speed region of the piston 4 at the initial stage of the expansion stroke, that is, the speed region before the main valve 6 is opened at the time of expansion, as in passing through small unevenness on the road surface, immediately. The secondary valve 11 is opened at the time of extension, and the hydraulic oil in the extension side oil chamber B passes through the through holes 10a and 9a and flows into the compression side oil chamber A through the sub communication hole 3d and the in-shaft passage 3a. Thereby, vibrations such as knack caused by small unevenness on the road surface are absorbed, and the riding comfort of the vehicle is improved. In such a low speed region, the main valve 6 is closed or slightly opened during expansion.

  On the other hand, when the wheel is pushed up by the convex portion of the road surface and the hydraulic shock absorber 1 is in the compressed state, the cylinder 4 moves upward in FIG. At this time, the pressure in the compression side oil chamber A increases, and the main valve 7 at the time of compression opens accordingly. When the main valve 7 is opened during compression, the hydraulic oil flows into the extension-side oil chamber B through the compression-side main passage 41, and a damping force is generated at this time. When the compression side oil chamber A is pressurized, a part of the hydraulic oil flows into the extension side oil chamber B from the communication hole 3b through the in-shaft passage 3a and the throttle portion 32, and the damping force adjusted in advance at this time appear. In FIG. 3, the flow of hydraulic oil during compression is indicated by a thick arrow.

  Further, when the compression side oil chamber A slightly increases in the low speed region of the piston 4 in the initial stage of compression, that is, the speed region before the compression main valve 7 opens, the sub valve 12 at the time of compression immediately opens and the compression side oil chamber A The hydraulic oil flows into the extension side oil chamber B through the in-shaft passage 3a and the sub-communication hole 3d through the sub-passage 9h on the back surface of the second piston member 9. Thereby, vibration is absorbed and the riding comfort of the vehicle is improved. In such a low speed range, the main valve 7 is closed or slightly opened during compression.

  Thus, according to the present invention, in the middle speed range where the piston speed exceeds the predetermined speed, the main valve 6 at the time of expansion or the main valve 7 at the time of compression is opened, and the hydraulic oil flows from the higher pressure to the lower pressure. Thereby, a predetermined damping force characteristic in the middle speed range is ensured. On the other hand, in the low speed range where the piston speed is equal to or lower than the predetermined speed, the extension sub-valve 11 or the compression sub-valve 12 is opened to allow hydraulic oil to flow, and the damping force in the low speed range can be lowered to a predetermined value.

  FIG. 8 is a graph showing test results regarding the damping force characteristics of the hydraulic shock absorber. The solid line in FIG. 8 shows the damping force characteristics of the hydraulic shock absorber 1 of the present invention provided with the extension sub-valve and the compression sub-valve as in the above-described embodiment. The dotted line shows the compression-side damping force characteristic when the compression-specific sub-valve is not provided with the same specification, and the expansion-side damping force characteristic when the expansion-side sub-valve is not provided according to Patent Document 1 described above.

  The hydraulic shock absorber according to the present invention does not provide the auxiliary valves on the expansion side and the compression side in the low speed range where the piston speed is 0.2 m / s or less while maintaining the preset damping force characteristics in the medium speed range. The damping force is reduced compared to the case. Further, even in a high speed range of 0.4 m / s or more, the damping force is reduced as compared with the case where no subvalve is provided. Thereby, it can be seen that the stroke becomes smooth in the entire speed range, and the ride comfort is improved.

  The present invention can be applied to hydraulic shock absorbers in automobiles, motorcycles, and other vehicles.

Sectional drawing which shows embodiment of this invention. The expanded sectional view at the time of the expansion stroke around the piston of FIG. The expanded sectional view at the time of the compression stroke around the piston of FIG. The figure which shows a 2nd piston member. The figure which shows a 3rd piston member. The enlarged view of the a part of FIG. The enlarged view of the b section of FIG. The damping force characteristic diagram of the hydraulic shock absorber of the present invention and the conventional product. Sectional drawing which shows the prior art example which does not provide a subvalve. Sectional drawing which shows the prior art example which provided only the subvalve at the time of compression.

Explanation of symbols

1: hydraulic shock absorber, 2: cylinder, 3: piston rod, 3a: shaft passage, 3b: communication hole, 3c: valve insertion hole, 3d: auxiliary communication hole, 4: piston, 5: metal bush, 6: extension Main valve, 6a, 6b, 6c, 7a, 7b, 7c: plate valve, 7: main valve during compression, 8: washer, 9: second piston member, 9a, 10a: through hole, 9b, 10b: hole, 9c: recessed portion, 9d: convex portion, 9e: groove portion, 9f: outer peripheral portion, 9g: space, 9h: auxiliary passage, 10: third piston member, 10c: outlet, 10d: gap,
11: Sub-valve during expansion, 11a, 11b, 11c, 12a, 12b, 12c, 12d: Sub-plate valve, 12: Sub-valve during compression, 13: Washer seat, 15: Elastic member, 16: Dust cover, 17: Support Board, 18: cushion material, 19: car body,
21: lid plate, 21a, 22a: shaft hole, 22: base member, 23, 28: circlip, 24: metal bush, 25: O-ring, 26a, 26b: seal member, 27: rubber member, 29: free piston 30: Damping force adjusting valve, 30a: Shaft portion, 30b: Valve portion,
31: O-ring, 32: throttle part, 33: adjusting member, 38: valve seat, 39: nut,
41: compression side main passage, 42: extension side main passage, 41a, 42b: extension chamber side opening, 41b, 42a: pressure chamber side opening,
50, 60: hydraulic shock absorber, 51, 61: cylinder, 52, 62: piston rod, 53, 63: piston, 54: first passage, 54a, 64a: pressure chamber side opening, 55: second passage, 55a, 65a: Extension side opening, 56: Extension valve, 57: Compression valve, 64: Compression side main passage, 65: Extension side main passage, 66: Extension main valve, 67: Compression main valve, 68: Secondary Passage, 68a: outlet, 69: auxiliary valve, 70: in-axis passage,
A: Compression side oil chamber, B: Extension side oil chamber, C: High pressure gas chamber.

Claims (5)

  A piston that divides the inside of the cylinder into a compression side oil chamber and an extension side oil chamber is attached to the tip of the piston rod inserted into the cylinder, and the extension that communicates the compression side oil chamber and the extension side oil chamber to the piston. An annular plate valve is formed on the pressure chamber side opening that opens to the compression side oil chamber of the extension side and compression side main passage, and to the extension chamber side opening that opens to the extension side oil chamber. In a vehicular hydraulic shock absorber provided with an extension main valve that opens during the extension stroke and a compression main valve that opens during the compression stroke, the compression-side oil chamber and the extension-side oil chamber communicate with each other at the initial stage of the extension stroke of the piston. A vehicular hydraulic shock absorber provided with a secondary valve during extension.   2. The vehicular hydraulic shock absorber according to claim 1, further comprising: a compression-time sub-valve that communicates the compression-side oil chamber and the expansion-side oil chamber at an initial stage of a compression stroke of the piston.   The main valve at the time of compression is provided on the back surface of the piston, and a second piston member is provided on the piston rod on the back surface, in which a secondary passage is formed to communicate the compression side oil chamber and the extension side oil chamber. A sub-valve for compression is provided on the back side of the two-piston member, and a third piston member is provided on the piston rod, in which a sub-passage that connects the compression-side oil chamber and the extension-side oil chamber is formed. 2. The vehicular hydraulic shock absorber according to claim 1, wherein the extension sub valve is provided on an opening surface of a sub passage of the three piston member.   An extension main valve, a piston, a compression main valve, a third piston member, an extension subvalve, a second piston member, and a compression subvalve are provided on the piston rod in order from the tip side. The vehicle hydraulic shock absorber according to claim 3. 4. The vehicle hydraulic shock absorber according to claim 3, wherein the second piston member is provided so as to oil-tightly cover an outer periphery of the third piston member from a back side.

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