JP5632301B2 - Hydraulic shock absorber for vehicles - Google Patents

Description

  The present invention relates to a hydraulic shock absorber for a vehicle.

  As a conventional hydraulic shock absorber, as described in Patent Document 1, an inner tube is slidably inserted into an outer tube, and an annular oil chamber is provided between the inner periphery of the outer tube and the outer periphery of the inner tube. The partition wall is provided on the inner periphery of the inner tube, the hydraulic oil chamber is partitioned in the lower part, the reservoir is partitioned in the upper part, and the piston rod attached to the outer tube passes through the partition part and passes through the partition part. A piston rod side oil chamber in which the piston rod is inserted into the hydraulic oil chamber, the piston slidingly contacting the inner periphery of the inner tube is fixed to the tip of the piston rod inserted into the inner tube, and the piston rod is accommodated in the hydraulic oil chamber And the piston rod-side oil chamber through an oil hole provided in the inner tube. Is communicated with the piston-side oil chamber, the cross-sectional area of the annular oil chamber is formed to be larger than the cross-sectional area of the piston rod, and the partition wall portion extends from the hydraulic oil chamber to the oil reservoir chamber of the reservoir during the extension side stroke. In some cases, a check valve is provided to prevent the flow to the flow path, and a fine flow path is provided in the partition wall portion to communicate the hydraulic oil chamber and the oil reservoir chamber of the reservoir.

  According to this conventional hydraulic shock absorber, the number of parts can be reduced as compared with a case in which a damper cylinder is provided inside the outer tube and the inner tube and a piston is slidably contacted with the inner periphery of the damper cylinder.

  Further, according to this conventional hydraulic shock absorber, the hydraulic oil corresponding to the volume of the piston rod entering into the inner tube in the compression side stroke and the hydraulic oil corresponding to the withdrawal volume of the piston rod exiting from the inner tube in the expansion side stroke are supplied. The compensation is made by supplying and discharging between the outer tube and the annular oil chamber between the inner tube.

  At this time, in this conventional hydraulic shock absorber, the outer tube and the inner tube are formed by making the cross-sectional area S1 of the annular oil chamber larger than the cross-sectional area S2 of the piston rod and providing a check valve and a minute flow path in the partition wall. No delicate setting is required for setting the annular gap. That is, in each of the compression side stroke and the extension side stroke, the hydraulic oil corresponding to the volume of the piston rod entering / exiting the inner tube is compensated by the presence of the annular oil chamber, and the volume change ΔS1 of the annular oil chamber is compensated for by the piston. The shortage / surplus for the volume change ΔS2 of the rod is replenished / discharged between the hydraulic oil chamber and the oil reservoir chamber via the check valve / microchannel.

JP2003-269515

  In the hydraulic shock absorber described in Patent Document 1, the oil in the oil reservoir chamber of the reservoir is agitated by the vibration of the vehicle and entrains air, and the air entrained in the oil is provided on the partition wall in the pressure side stroke. There is a risk of being introduced into the hydraulic oil chamber. The air thus introduced into the hydraulic oil chamber impairs the response of the damping force generated by the damping force generator provided on the piston.

  Further, in the hydraulic shock absorber described in Patent Document 1, when the air chamber of the reservoir is compressed and the air spring effect is obtained in the pressure side stroke, the pressurized air pressure is operated through a check valve provided in the partition wall. Pressurizes the oil chamber. When the compression ratio of the air chamber is increased, the damper becomes harder on the most compression stroke side due to the difference in air pressure between the extended stroke and the most compressed state, and the ride comfort is deteriorated.

  An object of the present invention is to prevent agitation of oil in a reservoir, avoid introduction of air into a hydraulic oil chamber, and improve the response of damping force.

  Another object of the present invention is to suppress the pressurization of the hydraulic oil chamber due to the air pressure compressed in the reservoir, and to improve the ride comfort by avoiding a hard damper on the most compression stroke side. is there.

According to the first aspect of the present invention, an inner tube is slidably inserted into the outer tube, an annular oil chamber is defined between the inner periphery of the outer tube and the outer periphery of the inner tube, and the inner tube A partition wall is provided on the inner periphery of the cylinder, a hydraulic oil chamber is defined in the lower part, a reservoir is defined in the upper part, and a piston rod attached to the outer tube is inserted into the hydraulic oil chamber through the partition part, A piston slidingly contacting the inner periphery of the inner tube is fixed to the tip of the piston rod inserted into the inner tube, and the hydraulic oil chamber is not accommodated in the piston rod side oil chamber in which the piston rod is accommodated and the piston rod is not accommodated. A piston-side oil chamber is partitioned, and the annular oil chamber communicates with the piston rod-side oil chamber or the piston-side oil chamber through an oil hole provided in the inner tube. A check valve for forming a cross-sectional area of the annular oil chamber larger than a cross-sectional area of the piston rod, and preventing flow from the hydraulic oil chamber to the oil reservoir chamber of the reservoir during the extension side stroke in the partition wall portion; In the hydraulic shock absorber for a vehicle, wherein the partition wall is provided with a micro flow path that communicates the hydraulic oil chamber and the oil reservoir chamber of the reservoir, the inner periphery of the inner tube and above the partition wall A free piston is provided in the portion, the free piston is slidably in close contact with the inner periphery of the inner tube and the outer periphery of the piston rod, and the reservoir is provided between the free piston and the partition wall portion. an oil reservoir chamber is partitioned into an air chamber in an upper portion of the free piston, also the free piston and to be provided with a biasing means for urging the side of the air chamber of the reservoir It is.

  The invention according to claim 2 is the invention according to claim 1, wherein the free piston further includes an outer free piston that is in close contact with the inner periphery of the inner tube, and an inner free piston that is in close contact with the outer periphery of the piston rod. The outer free piston and the inner free piston are in close contact with each other without any gap in the axial direction, and through a gap that can be relatively moved in the radial direction.

  The invention according to claim 3 is the invention according to claim 1 or 2, further provided a seal escape portion near the partition wall portion on the inner periphery of the inner tube or the outer periphery of the piston rod on which the free piston slides, When the free piston reaches the seal escape portion, the air chamber of the reservoir can communicate with the oil reservoir chamber.

The invention according to claim 4 is the invention according to any one of claims 1 to 3 , wherein the partition wall portion is formed by a bottom portion of a bottomed cylindrical partition wall case, and the cylinder portion of the partition wall case is formed of the inner tube. It is inserted into the upper end opening to form the inner circumference of the inner tube, and the free piston is slidably fitted to the inner circumference of the cylindrical portion of the partition wall case.

(Claim 1)
(a) The oil level of the reservoir oil reservoir decreases when the oil in the oil reservoir chamber is replenished to the hydraulic oil chamber in the compression stroke, and the oil in the hydraulic oil chamber is discharged to the oil reservoir chamber in the extension stroke. When you rise. At this time, the free piston provided on the inner periphery of the inner tube and on the upper side of the partition wall always moves up and down following the oil level of the oil reservoir, and always separates the oil reservoir and the air chamber. Therefore, even if the vehicle vibrates, the free piston can prevent the oil in the oil reservoir chamber from being stirred, and air can be prevented from being caught in the oil in the oil reservoir chamber. Therefore, when the oil in the oil reservoir chamber is replenished to the hydraulic oil chamber through the check valve of the partition wall, air is prevented from being introduced into the hydraulic oil chamber, and the response of the damping force is improved.
(b) A biasing means for biasing the free piston toward the air chamber side of the reservoir is provided. Therefore, the air pressure generated by compressing the air chamber of the reservoir in the pressure side stroke can be relatively reduced by the biasing means. This prevents the air pressure pressurized in the air chamber from pressing the hydraulic oil chamber via the check valve on the partition wall, avoiding a hard damper on the most compressed stroke side and improving riding comfort To do.

(Claim 2)
(c) The free piston is divided into an outer free piston that is in close contact with the inner periphery of the inner tube and an inner free piston that is in close contact with the outer periphery of the piston rod, and there is no gap between the outer free piston and the inner free piston in the axial direction. It is in close contact with each other via a gap that can be relatively moved in the radial direction. Therefore, when the inner tube that supports the piston rod and the partition wall is bent due to the external force of the lateral load and the inner tube and the piston rod are misaligned, the outer free piston that is in close contact with the inner periphery of the inner tube and the outer periphery of the piston rod The inner free piston that is in close contact with the inner member moves relatively in the radial direction so as to follow the axial deviation. As a result, the free piston does not become a resistance against the axial displacement between the inner tube and the piston rod, and as a result, an increase in the sliding resistance of expansion and contraction of the inner tube is suppressed.

(Claim 3)
(d) A seal relief portion is provided near the partition wall on the inner circumference of the inner tube on which the free piston slides or the outer circumference of the piston rod, and when the free piston reaches the seal relief portion, the air chamber of the reservoir is stored in the oil reservoir. Allow communication to the room. When the oil in the annular oil chamber between the outer tube and the inner tube passes through a seal such as a bush on the upper end side of the inner tube and is discharged to the air chamber of the reservoir, the oil in the hydraulic oil chamber and the reservoir oil reservoir chamber The amount will decrease accordingly. On the other hand, when the free piston moves downward as shown in (a) in the compression side stroke, the free piston is greatly lowered by the amount of oil decrease in the oil reservoir chamber and reaches the seal escape portion. The oil discharged to the air chamber passes through the seal escape portion and is returned to the oil reservoir chamber and the hydraulic oil chamber. This eliminates the inconvenience caused by the circulation prevention of the air chamber to the oil reservoir chamber due to the provision of the free piston.

(Claim 4 )
(e) The partition wall portion is formed by the bottom portion of the bottomed cylindrical partition wall case, and the cylindrical portion of the partition wall case is inserted into the upper end opening of the inner tube to form the inner periphery of the inner tube, A free piston is slidably fitted on the inner periphery of the slab. By providing the partition wall portion integrally with the partition wall case and the free piston also being fitted, the assembly can be improved by inserting them into the upper end opening of the inner tube as a single unit.

FIG. 1 is an overall cross-sectional view showing an extended state of the hydraulic shock absorber. FIG. 2 is a lower cross-sectional view of FIG. FIG. 3 is a cross-sectional view of the middle lower part of FIG. 4 is a cross-sectional view of the upper middle portion of FIG. FIG. 5 is a top sectional view of FIG. FIG. 6 is a cross-sectional view showing the most compressed state of the hydraulic shock absorber. FIG. 7 is a sectional view showing a modification of the hydraulic shock absorber.

  The front fork (hydraulic shock absorber) 10 is an inverted front fork in which the outer tube 11 is disposed on the vehicle body side and the inner tube 12 is disposed on the wheel side. As shown in FIGS. The inner tube 12 is slidably inserted into the outer tube 11 through a guide bush 11A fixed to the inner periphery of the inner tube 12 and a guide bush 12A fixed to the outer periphery of the upper end opening of the inner tube 12. 11B is an oil seal, and 11C is a dust seal. A cap 13 is screwed and sealed to the upper end opening of the outer tube 11 in a liquid-tight manner, and a vehicle body side mounting member is provided on the outer periphery of the outer tube 11. An axle bracket 15 is liquid-tightly inserted and screwed into the lower end opening of the inner tube 12 to form the bottom of the inner tube 12, and the axle bracket 15 is provided with an axle mounting hole 15A.

  The front fork 10 defines an annular oil chamber 17 defined by the inner periphery of the outer tube 11, the outer periphery of the inner tube 12, and the two guide bushes 11A and 12A.

  The front fork 10 is provided with a bottomed cylindrical partition case 19 on the inner periphery of the upper end side of the inner tube 12 via an O-ring or the like, and a hydraulic oil chamber is provided below the partition portion 19A at the bottom of the partition case 19. 21 and a reservoir 22 at the top. In the reservoir 22, the lower region is an oil reservoir chamber 22A, and the upper region is an air chamber 22B. The cylindrical portion 19B of the partition wall case 19 is inserted into the upper end opening of the inner tube 12 to form the inner periphery of the inner tube 12, and a free piston 200 described later slides on the inner periphery of the cylindrical portion 19B of the partition wall case 19. Fits freely.

  The front fork 10 slidably inserts the piston rod 23 attached to the outer tube 11 into the partition wall portion 19 </ b> A of the partition wall case 19. Specifically, the hollow piston rod 23 is screwed to the mounting collar 24 screwed to the lower end portion of the center portion of the cap 13, and this is fixed by the lock nut 24A.

  The front fork 10 fixes a piston 26 slidably in contact with the inner periphery of the inner tube 12 to a piston bolt 25 screwed to the tip of a piston rod 23 inserted into the inner tube 12 from the partition wall portion 19A of the partition wall case 19, The oil chamber 21 is partitioned into a piston rod side oil chamber 21A in which the piston rod 23 is accommodated and a piston side oil chamber 21B in which the piston rod 23 is not accommodated. The piston 26 is fixed by a piston nut 27.

  The front fork 10 always communicates the annular oil chamber 17 with the piston rod side oil chamber 21 </ b> A through an oil hole 28 provided in the inner tube 12.

The front fork 10 has an upper spring receiver 31 attached to the lower end surface of the piston 26 facing the piston-side oil chamber 21B, and a lower spring receiver 32 disposed at the bottom of the inner tube 12 formed by the axle bracket 15. A main suspension spring 33 is interposed between the spring receiver 31 and the lower spring receiver 32. The entire suspension spring 33 is immersed in the piston-side oil chamber 21B. The front fork 10 absorbs the impact force received from the road surface when the vehicle travels by the expansion and contraction vibration of the suspension spring 33. At this time, a spring load adjusting device 100, which will be described later, raises and lowers the lower spring receiver 32 so that the spring load of the suspension spring 33 can be adjusted.
The front fork 10 includes a damping force generator 40 on the piston 26 (FIG. 3).

  The damping force generator 40 includes a compression side channel 41 and an extension side channel 42. The pressure side channel 41 is opened and closed by a pressure side disk valve 41A (pressure side damping valve) backed up by a valve stopper 41B. The extension side flow path 42 is opened and closed by an extension side disk valve 42A (extension side damping valve) backed up by a valve stopper 42B. The valve stopper 41B, the valve 41A, the piston 26, the valve 42A, and the valve stopper 42B constitute a valve assembly that is inserted into the piston bolt 25, and are sandwiched between piston nuts 27 that are screwed into the piston bolt 25. Fixed.

  The damping force generating device 40 is provided with a damping force adjusting device 40A, which will be described in detail later, at the center of the cap 13, and the needle valve 44 of the damping force adjusting device 40A is inserted into the hollow portion of the piston rod 23 and provided on the piston rod 23. The opening degree of the bypass passage 45 is adjusted by the vertical movement of the needle valve 44. The bypass passage 45 bypasses the piston 26 and connects the piston rod side oil chamber 21A and the piston side oil chamber 21B.

  In the compression side stroke, the damping force generator 40 generates a compression side damping force by the passage resistance of the bypass passage 45 whose opening degree is adjusted by the needle valve 44 in the low speed region, and the bending deformation of the compression side disk valve 41A in the medium to high speed region. Generates a compression damping force. Further, in the extension side stroke, an extension side damping force is generated by the passage resistance of the bypass passage 45 whose opening degree is adjusted by the needle valve 44 in the low speed range, and in the middle and high speed range, the extension side disc valve 42A is extended by the bending deformation. Generates side damping force. The above-described expansion and contraction vibration of the suspension spring 33 is suppressed by the compression side damping force and the extension side damping force.

  The front fork 10 is provided with a stopper rubber 13A and a stopper plate 13B in which the upper end portion of the partition wall case 19 provided in the inner tube 12 abuts with the most compression stroke on the lower end surface of the cap 13, and the stopper rubber 13A Regulate the compression stroke.

  The front fork 10 has a spring seat 46 fixed to the lower end surface of the partition case 19 on the upper end side of the inner tube 12 facing the piston rod side oil chamber 21A using a stopper ring 46A, and a stopper ring 47A provided on the piston rod 23. A rebound spring 48 is interposed between the spring seat 47 and the latched spring seat 47. When the front fork 10 is fully extended, the spring seat 46 on the partition wall case 19 side presses the rebound spring 48 against the spring seat 47 to restrict the maximum extension stroke.

  However, in the front fork 10, the sectional area S1 of the annular oil chamber 17 formed by the annular gap between the outer tube 11 and the inner tube 12 is larger than the sectional area (area surrounded by the outer diameter) S2 of the piston rod 23. (S1> S2).

  Further, the partition wall 19A of the partition wall case 19 and the spring seat 46 are allowed to flow oil from the oil reservoir chamber 22A of the reservoir 22 to the piston rod side oil chamber 21A in the compression side stroke, and in the piston rod side oil chamber in the extension side stroke. A check valve 50 is provided to block the flow of oil from 21A to the oil reservoir chamber 22A of the reservoir 22.

  Further, since the partition wall portion 19 </ b> A of the partition wall case 19 does not seal an oil seal around the piston rod 23, the bush pressed into the inner periphery of the check valve 50 is formed by a minute gap formed around the piston rod 23. A fine flow path (orifice) 51 that communicates the piston rod side oil chamber 21A and the reservoir 22 is formed. The minute channel 51 may be formed by an orifice 52 that is formed in the partition wall portion 19 </ b> A of the partition case 19 and communicates the piston rod side oil chamber 21 </ b> A and the reservoir 22.

The operation of the front fork 10 is as follows.
(Pressure side stroke)
The hydraulic oil corresponding to the volume of the piston rod 23 entering the inner tube 12 in the compression side stroke is transferred from the inner oil chamber 21 </ b> A of the inner tube 12 to the annular oil chamber 17 through the oil hole 28 of the inner tube 12. At this time, since the volume increase ΔS1 (replenishment amount) of the annular oil chamber 17 is larger than the volume increase ΔS2 of the piston rod 23, the required amount of oil supplied to the annular oil chamber 17 is insufficient (ΔS1−ΔS2). Minutes are replenished from the oil reservoir chamber 22 </ b> A of the reservoir 22 through the check valve 50.

  In the compression side stroke, as described above, a compression side damping force is generated by the passage resistance of the bypass passage 45 whose opening degree is adjusted by the needle valve 44 in the low speed region, and in the middle and high speed region, the compression side is deformed by the deformation of the compression side disk valve 41A. Generates a damping force.

(Extension process)
The hydraulic oil corresponding to the retraction volume of the piston rod 23 that retreats from the inner tube 12 in the extension stroke is transferred from the annular oil chamber 17 to the oil chamber 21 </ b> A on the inner periphery of the inner tube 12 through the oil hole 28 of the inner tube 12. . At this time, since the volume decrease ΔS1 (discharge amount) of the annular oil chamber 17 is larger than the volume decrease ΔS2 of the piston rod 23, the excess of (ΔS1−ΔS2) of the oil discharge amount from the annular oil chamber 17 Is discharged to the oil reservoir chamber 22A of the reservoir 22 through the orifices 51 and 52.

  In this extension side stroke, as described above, the extension side damping force is generated by the passage resistance of the bypass passage 45 whose opening degree is adjusted by the needle valve 44 in the low speed region, and the extension side disk valve 42A is bent in the middle and high speed region. The expansion side damping force is generated by the deformation. Further, the extension side damping force due to the passage resistance of the micro flow path 51 is also generated.

Hereinafter, the damping force adjusting device 40A will be described.
As shown in FIG. 3, the damping force adjusting device 40 </ b> A inserts two push rods 61, 62 inserted concentrically into the hollow portion of the piston rod 23 (the push rod 62 is pushed into the hollow portion of the piston rod 23. The push rod 61 is inserted into the hollow portion of the rod 62), the first adjustment portion 70 for moving the push rod 61 in the axial direction, and the second adjustment portion 80 for moving the push rod 62 in the axial direction. It is provided on the cap 13 which is the upper part.

  The first adjustment unit 70 adjusts the damping force due to the passage resistance of the bypass passage 45 by moving the needle valve 44. The second adjustment unit 80 adjusts the damping force due to the bending deformation of the pressure side disk valve 41A by adjusting the set load of the spring 87 that urges the pressure side disk valve 41A in the closing direction. Hereinafter, the structure of the first adjusting unit 70 and the second adjusting unit 80, the damping force adjusting structure using the needle valve 44, and the damping force adjusting structure using the spring 87 will be described.

(Structure of the 1st adjustment part 70 and the 2nd adjustment part 80) (FIG. 3)
A mounting collar 24 is screwed to the lower end opening side of the cap 13 to form a cap assembly 90A. The cap 13 of the cap assembly 90A is screwed in a liquid-tight manner to the upper end opening of the outer tube 11 via the O-ring 91, and the upper end of the piston rod 23 is screwed to the lower end of the mounting collar 24. It is fixed with. A stopper rubber 13A is loaded into an annular recess formed by the cap 13 and the mounting collar 24 of the cap assembly 90A, and a stopper plate 13B is inserted into the outer periphery of the mounting collar 24, and the stopper plate 13B is locked. A stopper ring 13C is engaged.

  An adjustment assembly 90B is loaded on the cap 13 and the mounting collar 24 of the cap assembly 90A. In the adjustment assembly 90B, the first adjustment portion 70 is configured by the first adjustment bolt 71, the second adjustment portion 80 is configured by the second adjustment bolt 81, and the first and second adjustment bolts 71 and 81 correspond to each of the first and second adjustment bolts 71 and 81. Second adjustment nuts 72 and 82 are provided. The first adjustment nut 72 includes a screw hole 72A into which the screw portion 71A of the corresponding first adjustment bolt 71 is screwed, and a guide hole 72B into which the guide portion 81B of another adjustment bolt 81 is inserted. The second adjustment nut 82 includes a screw hole 82A into which the screw portion 81A of the corresponding second adjustment bolt 81 is screwed, and a guide hole 82B into which the other adjustment bolt 71 is inserted. Accordingly, the first adjusting nut 72 into which the adjusting bolt 71 is screwed by the rotation operation of the first adjusting bolt 71 is related to the guide hole 72B of the adjusting nut 72 and the guide portion 81B of the other adjusting bolt 81. Through rotation, it is prevented from rotating and is guided to move in the axial direction, and moves up and down in the axial direction. On the other hand, when the second adjusting bolt 81 is rotated, the second adjusting nut 82 into which the adjusting bolt 81 is screwed is engaged with the guide hole 82B of the adjusting nut 82 and the guide collar 71B of the other adjusting bolt 71. Through rotation, it is prevented from rotating and is guided to move in the axial direction, and moves up and down in the axial direction.

  The first adjustment bolt 71 of the first adjustment portion 70 constituting the adjustment assembly 90B and the second adjustment bolt 81 of the second adjustment portion 80 are the center of the cap 13 in plan view of the cap 13 constituting the cap assembly 90A. From the back surface side of the cap 13, the two loading holes juxtaposed at positions away from each other are inserted liquid-tightly through O-rings 73 and 83. The first adjustment bolt 71 and the second adjustment bolt 81 are housed in the central recess 92 of the cap assembly 90A formed by screwing the mounting collar 24 onto the cap 13 together with the adjustment nuts 72 and 82, and the adjustment bolt 71, The flange portions 71C and 81C of 81 are applied to the lower surface of the cap 13, and the lower end surfaces of the adjusting bolts 71 and 81 are brought close to the bottom surface of the central recess 92 formed by the mounting collar 24. The adjusting nuts 72 and 82 are accommodated in the inner periphery of the central recess 92 formed by the mounting collar 24 so as to be slidable. The push rod 61 protruding from the hollow portions of the piston rod 23 and the push rod 62 passes through the center hole 82C of the second adjustment nut 82 and is abutted against the lower end surface of the first adjustment nut 72, so that the hollow portion of the piston rod 23 The push rod 62 protruding from the center of the second adjustment nut 82 is abutted against the lower end surface of the second adjustment nut 82 around the center hole 82C.

  Thereby, the upper end operation part 70A of the first adjustment bolt 71 of the first adjustment part 70 and the upper end operation part 80A of the second adjustment bolt 81 of the second adjustment part 80 are the plane of the cap 13 constituting the cap assembly 90A. They are juxtaposed with each other at a level that is flush with the upper surface of the cap 13 at a position deviating from the center of the cap 13. The first adjusting bolt 71 of the first adjusting unit 70 is pivotally supported by the cap 13 so as not to rotate but move in the axial direction, and the second adjusting bolt 81 of the second adjusting unit 80 is also only rotated by the cap 13. Thus, it is pivotally supported so as not to move in the axial direction. Accordingly, when the first adjustment bolt 71 of the first adjustment unit 70 is rotated, the first adjustment nut 72 to which the first adjustment bolt 71 is screwed moves up and down in the axial direction, and the first adjustment nut 72 is moved. It is possible to move the push rod 61 abutted against the shaft in the axial direction. On the other hand, when the second adjustment bolt 81 of the second adjustment unit 80 is rotated, the second adjustment nut 82 with which the second adjustment bolt 81 is screwed moves up and down in the axial direction, and the second adjustment nut 82 is moved. It is possible to move the push rod 62 abutted against the shaft in the axial direction.

(Damping force adjustment structure using needle valve 44) (FIG. 3)
An inner base 74 is attached to the lower end portion of the hollow portion of the piston rod 23, and the lower end surface of the piston rod 23 and the inner diameter step portion of the piston bolt 25 clamp and fix the inner base 74. The inner base 74 may be press-fitted into the hollow portion of the piston rod 23. In this way, the needle valve 44 is liquid-tightly inserted into the inner periphery of the inner base 74 fixed to the piston rod 23, and is interposed between the intermediate flange portion 75 </ b> A of the needle valve 44 and the upper end surface of the inner base 74. The spring 76 biases the needle valve 44 upward (in the valve opening direction) in the axial direction, and the upper end surface of the needle valve 44 abuts against the lower end surface of the push rod 61.

  As described above, when the first adjusting bolt 71 of the first adjusting unit 70 moves the push rod 61 up and down in the axial direction, the needle valve 44 that is abutted in the axial direction with the push rod 61 moves against the piston bolt 25. The valve moves up and down with respect to the valve seat at the upper end of the vertical hole of the bypass passage 45 provided in the piston bolt 25, adjusts the opening degree of the bypass passage 45, and as a result, expands and contracts due to the passage resistance of the bypass passage 45. The damping force on the side can be adjusted.

(Damping force adjustment structure using spring 87) (FIG. 3)
On both sides in the diameter direction on the lower end side of the piston rod 23, long hole-shaped guide holes 23A extending in the axial direction are provided, and both side protrusions of the pushing piece 84 slide in the guide hole 23A in the axial direction with almost no play. It is possible to be engaged. The lower end surface of the push rod 62 inserted into the hollow portion of the piston rod 23 directly contacts the upper surface of the push piece 84, and the cross section of the needle valve 44 inserted loosely into the lower end portion of the push rod 62 is pushed. It is loosely inserted into a circular hole provided at the center of the moving piece 84 so as to be movable in the axial direction.

  Around the lower end portion (piston bolt 25) of the piston rod 23, there are a spring receiver 85 that abuts against the protrusions on both ends of the pushing piece 84 from below, and a valve retainer 86 that abuts on the upper surface (rear surface) of the compression side disk valve 41A. The valve retainer spring 87 is interposed between the spring receiver 85 and the valve retainer 86. The spring receiver 85 has a cup shape and abuts with both side protrusions of the pushing piece 84 at the lower end of the inner periphery of the cup, and the spring 87 is seated on the upper peripheral flange of the cup. The valve presser 86 includes an annular presser portion 86A that continuously and continuously (or intermittently) contacts with an appropriate outer diameter position on the upper surface of the compression-side disc valve 41A, and a slide that is slidably guided on the outer periphery of the upper end of the piston bolt 25. An oil passage 86C that connects the portion 86B and the piston rod side oil chamber 21A to the pressure side passage 41, the extension side passage 42, and the bypass passage 45 is provided, and a spring 87 is seated on the outer circumferential step portion.

  As described above, when the adjusting bolt 81 of the second adjusting unit 80 moves the push rod 62 in the axial direction, the pushing piece 84 with which the lower end surface of the push rod 62 abuts moves the spring receiver 85 up and down. The valve presser spring 87 is expanded and contracted to adjust the set load of the spring 87. As a result, the set load of the spring 87 urges the pressure side disc valve 41A in the closing direction via the valve presser 86, and the pressure side damping force due to the bending deformation of the pressure side disc valve 41A can be adjusted. The valve presser 86 can be replaced with one having a different diameter of the presser part 86A. The valve presser 86 provided with the large-diameter presser part 86A presses the outer peripheral side of the pressure side disc valve 41A, so that the piston speed can be reduced. Increase the damping force. The valve presser 86 provided with the small-diameter presser part 86A presses the inner peripheral side of the pressure side disc valve 41A, and increases the damping force in the middle to high speed range of the piston speed.

  Hereinafter, the spring load adjustment device 100 that raises and lowers the spring receiver 32 and adjusts the spring load of the suspension spring 33 will be described.

  As shown in FIGS. 2 and 4, the spring load adjusting device 100 is built in a small-diameter closing hole 16 </ b> B following the large-diameter opening hole 16 </ b> A into which the lower end portion of the inner tube 12 in the axle bracket 15 is screwed. The spring load adjusting device 100 inserts an adjusting bolt 101 facing the outside at a position where the axle mounting hole 15A of the axle bracket 15 is removed from the outside of the axle bracket 15 into the small diameter blocking hole 16B, and the bottom surface 16C ( The slider 102 provided on the slide surface (the surface that faces the lower end of the spring support 32) is linear in the direction intersecting the central axis of the inner tube 12 (the axial direction of the adjustment bolt 101) by the rotational force of the adjustment bolt 101. Make it movable. A lower inclined surface A1 of a spring receiver 32 (spring receiving base portion 111 described later) is placed on an upper inclined surface A2 of the slider 102, and the spring receiver 32 is supported on the axle bracket 15 via the adjusting bolt 101, the slider 102, and the holder 103. The spring receiver 32 (a spring receiving base portion 111 and a spring receiving tube portion 112 described later) is moved up and down by the rotation of the adjusting bolt 101 to adjust the spring load of the suspension spring 33.

  (1) Arranged orthogonally to the central axis passing through the axle mounting hole 15A of the axle bracket 15 (same as the central axis passing through the axle mounting hole 15A of the inner tube 12 when the axle bracket 15 is attached to the inner tube 12). The holder 103 of the adjusting bolt 101 is screwed and fixed in a liquid-tight manner to the mounting hole 15B penetrating from the outside of the axle bracket 15 to the small-diameter blocking hole 16B. In the adjusting bolt 101, a rotary operation shaft 101A having a hexagonal hole on its outer end face is liquid-tightly inserted into the holder 103, and a screw shaft 101B is inserted into the small-diameter closing hole 16B. The adjusting bolt 101 abuts the intermediate step surface of the rotation operation shaft 101A with the intermediate step surface of the holder 103 in the axial direction, and the end surface of the screw shaft 101B abuts with the vertical wall surface of the small-diameter closing hole 16B. Free movement is restrained. Further, the adjustment bolt 101 has engaging grooves 103A in which balls 101D that are repelled by springs 101C loaded in holes formed on the diameter of the rotation operation shaft 101A are provided at a plurality of circumferential positions on the inner periphery of the holder 103. Are engaged with each other in turn, and are locked with a sense of moderation at an arbitrary rotational operation position corresponding to each engagement groove 103A.

  (2) When the rotary operation shaft 101A of the adjusting bolt 101 is pivotally attached to the axle bracket 15 as described in (1) above, the washer 104, slider 102, and nut 105 are inserted into the screw shaft 101B of the adjusting bolt 101. . That is, the washer 104 is abutted against the step surface at the boundary between the rotation operation shaft 101A of the adjustment bolt 101 and the screw shaft 101B. The washer 104 has a quadrilateral shape, and the lower side of the washer 104 is prevented from rotating by contacting the bottom surface 16C of the small-diameter closing hole 16B of the axle bracket 15. A slider 102 is inserted into the screw shaft 101B of the adjusting bolt 101, and an accompanying nut 105 attached to the slider 102 is screwed into the threaded portion.

  (3) The spring receiver 32 is divided into a spring receiving base portion 111 and a spring receiving tube portion 112. When the spring receiving base 111 is inserted into the large-diameter opening hole 16A and the small-diameter closing hole 16B of the axle bracket 15 and engages with the slider 102 and the washer 104 of the spring load adjusting device 100, the spring receiving base 111 does not rotate relative to the axle bracket 15. The outer diameter of the inner tube 12 is smaller than that of the inner tube 12. The spring receiving cylinder portion 112 has a bottomed cylindrical shape, and is inserted into the inner circumference of the inner tube 12 through a slight gap so that the suspension spring 33 can be seated (via the flange of the spring collar 113 in this embodiment). To be. The cylindrical outer peripheral surface of the downward convex (or concave) lower end engaging portion 112A provided at the lower end (cylinder bottom) of the cylindrical portion 131 of the spring receiving cylindrical portion 112 is used as the annular head of the spring receiving base portion 111. The upper end engaging portion 111A provided at the upper end portion of 121 is loaded in a self-aligning manner on the inner peripheral surface of the round hole-like inner peripheral surface of the upper end engaging portion 111A, and the lower end engaging portion 112A of the spring receiving tube portion 112 is spring-loaded. The spring receiving tube portion 112 is seated on the upper end engaging portion 111 </ b> A of the receiving base portion 111 so that it can be coaxially set on the inner tube 12. In this embodiment, a cup-shaped spring collar 113 is liquid-tightly fitted to the upper end opening of the spring receiving tube portion 112 via an O-ring 113A, and the flange of the spring collar 113 is placed over the spring receiving tube portion 112. Place on the end face. The spring receiving cylinder portion 112 and the spring collar 113 keep the internal space sealed and integrated in a cavity, reducing the amount of oil to be injected into the oil chamber 21 of the inner tube 12 and reducing the weight.

  The spring support base 111 protrudes a downward projection 122 at the lower portion of the annular head 121, and in a side view, one end surface of the downward projection 122 is a lower slope A1, and the other end surface is a lower vertical surface B. A1 and the lower vertical surface B intersect at an acute angle. The spring receiving base 111 includes an upper end engaging portion 111 </ b> A on the inner peripheral side of the annular head 121. The spring receiving base portion 111 extends from the lower slope A1 to the lower vertical surface B at the center portion of the downward projection 122 in the front view and opens below the downward projection 122 to be outside the screw shaft 101B of the adjustment bolt 101. A detent U-shaped groove 123 that loosely fits in the diameter portion is provided. The spring receiving base 111 is prevented from rotating with respect to the central axis of the axle bracket 15 by loosely fitting a U-shaped groove 123 to the outer diameter portion of the screw shaft 101B of the adjusting bolt 101. That is, the spring receiving base portion 111 is supported so as not to rotate relative to the axle bracket 15 through engagement with the components of the spring load adjusting device 100, in this embodiment, engagement with the outer diameter portion of the adjusting bolt 101. It will be done.

  The downward protrusion 122 of the spring support base 111 is sandwiched between the slider 102 and the washer 104 when inserted into the small-diameter closing hole 16B of the axle bracket 15, and the lower slope A1 is placed on the upper slope A2 of the slider 102. At the same time, the lower vertical surface B is brought into contact with the end surface of the washer 104. The rotation of the adjusting bolt 101 causes the nut 105 and thus the slider 102 to move linearly, and the spring receiving base portion 111 and the spring receiving tube portion 112 are moved up and down. At this time, the spring receiving base portion 111 is in sliding contact with the circular inner peripheral surface of the small-diameter blocking hole 16B on the arc-shaped outer peripheral surface of the projecting guide portion provided at two locations facing each other in the diameter direction on the outer periphery of the lower end of the downward projecting portion 122. The spring receiving tube portion 112 is guided by sliding on the inner peripheral surface of the inner tube 12 and moved up and down without play.

  (4) Insert the axle bracket 15 into the lower end of the inner tube 12 and screw it. At this time, the adjustment bolt 101, the slider 102, the holder 103, the washer 104, and the nut 105 are assembled in the axle bracket 15 as described above, and the spring receiving base portion 111 of the spring receiver 32 is inserted.

  The lower end portion of the inner tube 12 is inserted into the inner periphery of the large-diameter opening hole 16 </ b> A via an O-ring 106 that is loaded in the inner circumferential annular groove near the lower end of the large-diameter opening hole 16 </ b> A of the axle bracket 15. By clamping one of the inner tube 12 and the axle bracket 15 and rotating the other, the lower end of the inner tube 12 is a screw portion provided above the O-ring 106 of the large-diameter opening hole 16A in the axle bracket 15. Screw on. At this time, the washer 107 loaded in the large-diameter opening hole 16A of the axle bracket 15 is seated on the stepped portion at the boundary between the large-diameter opening hole 16A and the small-diameter closing hole 16B and screwed into the large-diameter opening hole 16A of the axle bracket 15. The tip of the lower end portion of the inner tube 12 is brought into contact with the washer 107, and the washer 107 is sandwiched between the step portion of the large diameter opening hole 16A and the small diameter closing hole 16B.

  (5) The inner tube 12 screwed to the axle bracket 15 is brought into an upright state, and the spring receiving tube portion 112 of the spring receiver 32 is inserted into the inner tube 12 from the upper end opening of the inner tube 12, and the spring receiving tube portion The lower end engaging portion 112A of 112 is seated on the upper end engaging portion 111A of the spring receiving base portion 111, and the spring receiving base portion 111 and the spring receiving tube portion 112 are coaxially set on the central axis of the inner tube 12 without falling down. The above-described (3) spring collar 113 is fitted into the upper end opening of the spring receiving cylinder portion 112, and then the suspension spring 33 to be inserted into the inner tube 12 is moved through the flange of the spring collar 113 to the spring receiving 32 (spring receiving). The base part 111 and the spring receiving cylinder part 112) are supported.

  When the adjustment bolt 101 is screwed in a state where the front fork 10 is assembled, the spring support is received via the lower slope A1 of the downward projection 122 provided on the spring support base 111 of the spring receiver 32 and the upper slope A2 of the slider 102. The protruding guide portions of the 32 spring receiving base portions 111 are guided by the inner peripheral surface of the small-diameter blocking hole 16B of the axle bracket 15, and as a result, the spring receiving tube portion 112 is guided by the inner peripheral surface of the inner tube 12. Go up and down. The spring receiver 32 adjusts the initial length of the suspension spring 33 between the spring receiver 31 on the piston rod 23 side and adjusts the spring load of the suspension spring 33.

  However, in the front fork 10, the oil in the oil reservoir chamber 22A of the reservoir 22 is agitated by the vibration of the vehicle and entrains air, and the air entrained in the oil is provided in the partition wall portion 19A in the pressure side stroke. In order to prevent the air introduced into the hydraulic oil chamber 21 through the valve 50 and the air introduced into the hydraulic oil chamber 21 from damaging the responsiveness of the damping force generated by the damping force generator 40 provided in the piston 26, As shown in FIG. 4, a free piston 200 is provided on the inner periphery of the inner tube 12, that is, the inner periphery of the cylindrical portion 19B of the partition case 19 in this embodiment, and on the upper portion of the partition portion 19A. The free piston 200 is slidable in close contact with the inner periphery of the cylindrical portion 19 </ b> B as the inner periphery of the inner tube 12 and the outer periphery of the piston rod 23. The reservoir 22 is divided into an oil reservoir chamber 22 </ b> A between the free piston 200 and the partition wall portion 19 </ b> A and an air chamber 22 </ b> B above the free piston 200. The free piston 200 closes the oil reservoir chamber 22A with respect to the air chamber 22B.

  In the lower part of the air chamber 22B in contact with the upper surface of the free piston 200, a certain amount of oil stays in order to lubricate the sliding portions (O-rings 201A, 201B, 201C) of the free piston 200 (see FIG. 4 L indicates the oil level).

  Here, the free piston 200 includes an outer free piston 201 that is in close contact with the inner periphery of the cylindrical portion 19B of the partition wall case 19 as the inner periphery of the inner tube 12 via an O-ring 201A, and an O-ring on the outer periphery of the piston rod 23. It is divided into an inner free piston 202 that is in close contact with each other via 202A. The inner free piston 202 is provided with a bush 203 that is slidably contacted with the piston rod 23 and press-fitted.

  The outer free piston 201 includes an inner peripheral flange F1 that protrudes toward the inner diameter side of the inner periphery of the bottom of the cylindrical body. The outer free piston 201 includes an O-ring 201A in an outer circumferential annular groove and an O-ring 201B in an annular groove on the upper surface of the inner circumferential flange F1. The inner free piston 202 includes an outer peripheral flange F2 projecting to the outer diameter side of the outer periphery of the intermediate portion of the cylindrical body. The inner free piston 202 includes an O-ring 202A and a bush 203 in an inner circumferential annular groove. The inner free piston 202 is loaded on the inner periphery of the outer free piston 201, and the lower surface of the outer peripheral flange F2 of the inner free piston 202 is axially spaced from the upper surface of the inner peripheral flange F1 of the outer free piston 201 via the O-ring 201B. Close contact. In the free piston 200, a washer 204 is placed on the outer peripheral flange F2 of the inner free piston 202 loaded on the inner periphery of the outer free piston 201. The outer peripheral flange F2 of the inner free piston 202 is sandwiched between the inner peripheral flange F1 of the free piston 201 and assembled. When the free piston 200 is assembled in the annular space between the inner periphery of the cylindrical portion 19B of the partition wall case 19 as the inner periphery of the inner tube 12 and the outer periphery of the piston rod 23 as described above, the outer free piston 201 The inner free piston 202 has a radially movable gap G (a radial gap G1 between the inner periphery of the outer free piston 201 and the outer peripheral flange F2 of the inner free piston 202, an inner flange F1 of the outer free piston 201 and an inner Through a radial gap G2) with the outer periphery of the free piston 202.

  Further, the inner periphery of the cylinder portion 19B is located closer to the partition wall portion 19A in the inner periphery of the tube portion 19B of the partition wall case 19 (the outer periphery of the piston rod 23 is acceptable) as the inner periphery of the inner tube 12 on which the free piston 200 slides. An expanded seal escape portion 206 (a seal escape portion having a reduced diameter on the outer periphery of the piston rod 23 is also possible) is provided. As will be described later, when the free piston 200 moves downward along the inner periphery of the cylindrical portion 19B and reaches the seal escape portion 206, the seal escape portion 206 oils the air chamber 22B of the reservoir 22 in the compression side stroke. This enables communication with the reservoir 22A.

  Further, in the front fork 10, the hydraulic oil chamber 21 is suppressed from being pressurized by the air pressure compressed in the reservoir 22, and a rider is prevented from becoming a hard damper on the most compression stroke side. In order to improve, an urging means 210 for urging the free piston 200 toward the air chamber 22B of the reservoir 22 is provided. In this embodiment, the urging means 210 is formed of a coil spring and is loaded between the upper surface of the partition wall portion 19A of the partition wall case 19 and the lower surface of the free piston 200 (outer free piston 201). The biasing means 210 may be of any other structure as long as it biases the free piston 200 toward the air chamber 22B of the reservoir 22.

  When the cylindrical portion 19B of the partition wall case 19 is inserted into the upper end opening of the inner tube 12 to form the inner periphery of the inner tube 12, a free piston 200 and a biasing means 210 are formed on the inner periphery of the cylindrical portion 19B of the partition wall case 19. Is preassembled.

  The front fork 10 expands and contracts between the extended state shown in FIG. 1 and the most compressed state shown in FIG. 6, and as described above, the piston rod 23 enters and leaves the inner tube 12 in each of the compression side stroke and the extension side stroke. The volume of hydraulic oil is compensated for by the presence of the annular oil chamber 17, and the check valve 50 / orifices 51, 52 indicate that the volume change ΔS1 of the annular oil chamber 17 is deficient / surplus with respect to the volume change ΔS2 of the piston rod 23. Is supplied / discharged between the hydraulic oil chamber 21 and the oil reservoir chamber 22A.

Therefore, according to the present Example, there exist the following effects.
(a) The oil level in the oil reservoir chamber 22A of the reservoir 22 is lowered when the oil in the oil reservoir chamber 22A is supplied to the hydraulic oil chamber 21 in the compression stroke, and the oil in the hydraulic oil chamber 21 is oiled in the extension stroke. It rises when discharged into the reservoir 22A. At this time, the free piston 200 provided on the inner circumference of the inner tube 12 and on the upper side of the partition wall portion 19A always moves up and down following the oil level of the oil reservoir chamber 22A, and the oil reservoir chamber 22A and the air chamber 22B are moved. Always partition. Therefore, even if the vehicle vibrates, the free piston 200 can prevent the oil in the oil reservoir chamber 22A from being stirred, and air can be prevented from being caught in the oil in the oil reservoir chamber 22A. Therefore, when oil in the oil reservoir 22A is supplied to the hydraulic oil chamber 21 through the check valve 50 of the partition wall portion 19A, air is prevented from being introduced into the hydraulic oil chamber 21 and the response of the damping force is avoided. To improve.

  (b) The free piston 200 is divided into an outer free piston 201 that is in close contact with the inner periphery of the inner tube 12 and an inner free piston 202 that is in close contact with the outer periphery of the piston rod. Are in close contact with each other without any gap in the axial direction, and through a gap that is relatively movable in the radial direction. Therefore, when the inner tube 12 that supports the piston rod and the partition wall portion 19A is bent by receiving an external force of a lateral load, and the inner tube 12 and the piston rod are displaced from each other, the outer free piston 201 that is in close contact with the inner periphery of the inner tube 12 The inner free piston 202 closely contacting the outer periphery of the piston rod relatively moves in the radial direction so as to follow the axial deviation. Thereby, the free piston 200 does not become a resistance against the axial displacement between the inner tube 12 and the piston rod, and as a result, an increase in the sliding resistance of the expansion and contraction of the inner tube 12 is suppressed.

  (c) A seal escape portion 206 is provided near the partition wall portion 19A on the inner periphery of the inner tube 12 on which the free piston 200 slides or on the outer periphery of the piston rod, and the reservoir when the free piston 200 reaches the seal escape portion 206. The 22 air chambers 22B can communicate with the oil reservoir 22A. When the oil in the annular oil chamber 17 between the outer tube 11 and the inner tube 12 passes through a seal such as a bush 12A on the upper end side of the inner tube 12 and is discharged to the air chamber 22B of the reservoir 22, The amount of oil in the oil reservoir chamber 22A of the reservoir 22 is reduced accordingly. On the other hand, when the free piston 200 moves downward as shown in (a) in the compression side stroke, the free piston 200 greatly decreases by the amount of oil decrease in the oil reservoir 22A and reaches the seal escape portion 206. The oil discharged into the air chamber 22B above the free piston 200 passes through the seal escape portion 206 and is returned to the oil reservoir chamber 22A and the hydraulic oil chamber 21 side. This eliminates the inconvenience due to the circulation prevention of the air chamber 22B to the oil reservoir chamber 22A due to the provision of the free piston 200.

  (d) A biasing means 210 for biasing the free piston 200 toward the air chamber 22B of the reservoir 22 is provided. Therefore, the air pressure generated by the compression of the air chamber 22B of the free piston 200 in the compression stroke can be relatively reduced by the biasing means 210. As a result, the air pressure pressurized in the air chamber 22B is suppressed from pressurizing the hydraulic oil chamber 21 via the check valve 50 of the partition wall 19A, and it is avoided that it becomes a hard damper on the most compression stroke side. Improve riding comfort.

  (e) The partition wall portion 19A is formed by the bottom of the bottomed cylindrical partition wall case 19, and the tube portion 19B of the partition wall case 19 is inserted into the upper end opening of the inner tube 12 to form the inner periphery of the inner tube 12. The free piston 200 is slidably fitted on the inner periphery of the cylindrical portion 19B of the partition wall case 19. The partition wall case 19 is integrally provided with the partition wall portion 19A, and the free piston 200 is also fitted and provided, so that they can be assembled as a single unit and inserted into the upper end opening of the inner tube 12. it can.

  FIG. 7 shows a modified example of the front fork 10, in which a support spring 220 for supporting the free piston 200 as a backup is loaded in the cylindrical portion 19 </ b> B of the partition wall case 19 as the inner periphery of the inner tube 12. The support spring 220 is positioned at a position where the free piston 200 always closes the oil reservoir 22A of the reservoir 22 with respect to the air chamber 22B. The support spring 220 is pre-compressed between a spring bearing 222 supported by a retaining ring 221 engaged with the inner diameter of the upper end side of the cylindrical portion 19B and the upper end surface of the free piston 200 (outer free piston 201). Be dressed.

  However, in the front fork 10, the air chamber 22 </ b> B of the reservoir 22 always maintains a positive pressure state in a use state after the inner tube 12 is inserted and assembled in the outer tube 11. The free piston 200 is positioned at a position where the oil reservoir chamber 22A is always closed by the positive pressure of the air chamber 22B, and it is not essential to provide the support spring 220.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention.

  In the present invention, an inner tube is slidably inserted into an outer tube, and an annular oil chamber is defined between the inner periphery of the outer tube and the outer periphery of the inner tube, and the inner tube has an inner periphery. A partition wall is provided, a hydraulic oil chamber is defined in the lower part, a reservoir is defined in the upper part, and a piston rod attached to the outer tube passes through the partition part and is inserted into the hydraulic oil chamber. A piston slidingly contacting the inner periphery of the inner tube is fixed to the tip of the inserted piston rod, and the hydraulic oil chamber is divided into a piston rod side oil chamber in which the piston rod is accommodated and a piston side oil chamber in which the piston rod is not accommodated. The annular oil chamber communicates with the piston rod side oil chamber or the piston side oil chamber via an oil hole provided in the inner tube, and the annular oil chamber is communicated with the annular oil chamber. A cross-sectional area of the chamber is formed larger than the cross-sectional area of the piston rod, and a check valve is provided in the partition wall portion to prevent a flow from the hydraulic oil chamber to the oil reservoir chamber of the reservoir during the extension side stroke. In a hydraulic shock absorber for a vehicle in which a partition wall is provided with a minute flow path communicating the hydraulic oil chamber and an oil reservoir chamber of the reservoir, a free piston is provided at an inner periphery of the inner tube and above the partition wall. The free piston is slidably in close contact with the inner periphery of the inner tube and the outer periphery of the piston rod, and the reservoir is an oil reservoir chamber between the free piston and the partition wall. And an air chamber above the free piston. This prevents oil from agitating in the reservoir, avoids introduction of air into the hydraulic oil chamber, and improves the response of the damping force.

  Further, according to the present invention, a biasing means for biasing the free piston toward the air chamber side of the reservoir is provided. As a result, it is possible to prevent the hydraulic oil chamber from being pressurized by the air pressure compressed by the reservoir, and to avoid a hard damper on the most compression stroke side, thereby improving riding comfort.

10 Front fork (hydraulic shock absorber)
11 Outer tube 12 Inner tube 17 Annular oil chamber (annular oil chamber)
19 partition wall case 19A partition wall portion 19B cylinder portion 21 hydraulic oil chamber 21A piston rod side oil chamber 21B piston side oil chamber 22 reservoir 22A oil reservoir chamber 22B air chamber 23 piston rod 26 piston 28 oil hole 50 check valve 51, 52 orifice (small) Flow path)
200 free piston 201 outer free piston 202 inner free piston 206 seal escape portion 210 biasing means

Claims (4)

Insert the inner tube slidably into the outer tube,
An annular oil chamber is defined between the inner periphery of the outer tube and the outer periphery of the inner tube,
A partition wall is provided on the inner periphery of the inner tube, a hydraulic oil chamber is defined in the lower part, and a reservoir is defined in the upper part,
A piston rod attached to the outer tube passes through the partition wall and is inserted into the hydraulic oil chamber;
A piston slidingly contacting the inner periphery of the inner tube is fixed to the tip of the piston rod inserted into the inner tube, and the hydraulic oil chamber is not accommodated in the piston rod side oil chamber in which the piston rod is accommodated and the piston rod is not accommodated. Partition into the oil chamber on the piston side,
The annular oil chamber communicates with the piston rod side oil chamber or the piston side oil chamber through an oil hole provided in the inner tube,
A check valve for forming a cross-sectional area of the annular oil chamber larger than a cross-sectional area of the piston rod, and preventing flow from the hydraulic oil chamber to the oil reservoir chamber of the reservoir during the extension side stroke in the partition wall portion; In the vehicle hydraulic shock absorber, wherein the partition wall is provided with a micro flow path communicating the hydraulic oil chamber and the oil reservoir chamber of the reservoir.
A free piston is provided on the inner circumference of the inner tube and above the partition wall, and the free piston is slidably in close contact with the inner circumference of the inner tube and the outer circumference of the piston rod,
The reservoir is partitioned into an oil reservoir chamber between the free piston and the partition wall, and an air chamber above the free piston ,
A hydraulic shock absorber for a vehicle , comprising urging means for urging the free piston toward the air chamber side of the reservoir .   The free piston is divided into an outer free piston that is in close contact with the inner periphery of the inner tube and an inner free piston that is in close contact with the outer periphery of the piston rod, and the outer free piston and the inner free piston are axially spaced. The hydraulic shock absorber for a vehicle according to claim 1, wherein the hydraulic shock absorber is in close contact with and through a gap that is relatively movable in the radial direction.   A seal escape portion is provided near the partition wall on the inner periphery of the inner tube or the outer periphery of the piston rod on which the free piston slides, and when the free piston reaches the seal escape portion, the air chamber of the reservoir is provided. The hydraulic shock absorber for a vehicle according to claim 1 or 2, which enables communication with an oil reservoir chamber. The partition is formed by the bottom of a bottomed cylindrical partition case,
The cylindrical portion of the partition case is inserted into the upper end opening of the inner tube to form the inner periphery of the inner tube, and the free piston is slidably fitted to the inner periphery of the cylindrical portion of the partition case. The vehicle hydraulic shock absorber according to any one of claims 1 to 3 .

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