JP4187091B2 - Hydraulic shock absorber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic shock absorber such as a front fork of a motorcycle.
[0002]
[Prior art]
In a front fork of a motorcycle, as described in Patent Document 1, a vehicle body side tube and an axle side tube are slidably fitted, and a damper cylinder is disposed inside the vehicle body side tube and the axle side tube. A damper including a piston rod that slides through a piston provided at a tip portion inside the cylinder is accommodated, and a piston rod side oil chamber that accommodates the piston rod and a piston that does not accommodate the piston rod are accommodated in the damper cylinder. A side oil chamber is formed, the damper cylinder is fixed to one of the vehicle body side tube and the axle side tube, and the piston rod is fixed to the other.
[0003]
[Patent Document 1]
Japanese Patent No. 2666895 (2 pages, Fig. 2)
[0004]
In the front fork of Patent Document 1, a seal member that seals the piston rod side oil chamber of the damper cylinder is provided on one end side of the damper cylinder, and an annular free piston is provided on the outer periphery of the damper cylinder. An annular oil chamber communicating with the piston-side oil chamber is hermetically sealed on the outer periphery of the damper cylinder, and a compression-side damping force generator is provided between the piston-side oil chamber and the free piston. Thus, when the front fork is compressed, the compression side damping force is generated by the compression side damping force generator. At the same time, the oil chamber in the damper cylinder is hermetically sealed to prevent bubbles from entering the oil chamber in the damper cylinder so as to stabilize the damping force, and the hydraulic oil corresponding to the volume of the piston rod entering or leaving the damper cylinder. Can be compensated by the displacement of the free piston.
[0005]
Further, in the front fork of Patent Document 1, a suspension spring is interposed between the vehicle body side tube and the axle side tube, and when the front fork is compressed, the spring of the front fork is generated by a spring force generated by bending the suspension spring toward the contraction side. The reaction force has been increased to prevent the front fork from sinking during braking.
[0006]
[Problems to be solved by the invention]
In the prior art, the compression-side damping force generator can always generate the compression-side damping force even when the front fork is subjected to a compression stroke more than a certain amount, such as during cornering after braking (during steady turning). For this reason, when the front fork goes over a fine disturbance such as a gap on the far side of the compression stroke, the generated damping force makes it difficult for the front fork to expand and contract, thereby deteriorating riding comfort and operability.
[0007]
The subject of this invention is improving the absorptivity of fine disturbances, such as a gap, in the back | inner side of a compression stroke in a hydraulic shock absorber.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, the vehicle body side tube and the axle side tube are slidably fitted, and a damper cylinder is provided inside the vehicle body side tube and the axle side tube. A damper including a piston rod that slides through a piston is accommodated, and a piston rod side oil chamber that accommodates the piston rod and a piston side oil chamber that does not accommodate the piston rod are formed in the damper cylinder, In a hydraulic shock absorber in which a damper cylinder is fixed to one of the vehicle body side tube and the axle side tube and the piston rod is fixed to the other, the damper cylinder is disposed on one end side of the damper cylinder through which the piston rod is inserted. A seal member for sealing the piston rod side oil chamber is provided, and an annular free piston is provided on the outer periphery of the damper cylinder. At the annular free piston, sealed compartment the annular oil chamber communicating with the piston side oil chamber on the outer periphery of the damper cylinder, The amount of piston rod volume that enters the damper cylinder by the amount of the compression stroke of the vehicle body side tube relative to the axle side tube flows into the annular oil chamber from the piston side oil chamber to cause the free piston to perform the compression stroke. Composed of A compression-side damping force generator is provided between the piston-side oil chamber and the annular oil chamber, and the damper cylinder is provided with the pressure ~ side Bypassing the damping force generator, a bypass oil passage is provided that communicates the piston-side oil chamber and the annular oil chamber. The amount corresponding to the compression stroke of the vehicle body side tube relative to the axle side tube The piston-side oil chamber communicates with the annular oil chamber when the free piston has a compression stroke of a certain level or more.
[0009]
In the invention of claim 2, the axle side tube is slidably fitted in the vehicle body side tube, a damper cylinder is erected in the axle side tube, and a piston is provided at the tip of the damper cylinder. A piston rod is slidably inserted, and a piston rod side oil chamber for accommodating the piston rod and a piston side oil chamber for not accommodating the piston rod are formed in the damper cylinder, and an upper portion is formed on the outer periphery of the damper cylinder. In the hydraulic shock absorber provided with an oil reservoir chamber as a gas chamber, a seal member that seals the piston rod side oil chamber in the damper cylinder is provided on one end side of the damper cylinder through which the piston rod is inserted, and the damper cylinder An annular free piston urged by a spring is slidably provided on the outer periphery of the damper cylinder. The piston-side oil chamber and an annular oil chamber which communicates sealingly partitioned circumferentially, The amount of piston rod volume that enters the damper cylinder by the amount of the compression stroke of the vehicle body side tube relative to the axle side tube flows into the annular oil chamber from the piston side oil chamber to cause the free piston to perform the compression stroke. Composed of A compression-side damping force generator is provided between the piston-side oil chamber and the annular oil chamber, and the piston-side oil chamber and the annular oil chamber are bypassed in the damper cylinder. Providing a bypass oil passage, the bypass oil passage, The amount corresponding to the compression stroke of the vehicle body side tube relative to the axle side tube The piston-side oil chamber communicates with the annular oil chamber when the free piston has a compression stroke of a certain level or more.
[0010]
According to a third aspect of the present invention, in the first or second aspect of the present invention, an intermediate cylinder is further provided between the outer periphery of the damper cylinder and the inner periphery of the axle side tube via an annular gap. The annular free piston is provided between the damper cylinders.
[0011]
According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the bypass oil passage is a long hole along the axial direction of the damper cylinder.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
1 is a cross-sectional view showing the entire hydraulic shock absorber, FIG. 2 is a lower cross-sectional view of FIG. 1, and FIG. 3 is an enlarged view of a main part of FIG.
[0013]
The front fork 10 (hydraulic shock absorber) is used as a front fork of a motorcycle, and as shown in FIGS. 1 and 2, the vehicle body side tube 11 and the axle side tube 12 are slidably fitted in a fluid-tight manner. Configured. A bush 13 is provided on the inner periphery of the lower end of the vehicle body side tube 11, and a bush 14 is provided on the inner periphery of the upper end side of the vehicle body side tube 11.
[0014]
The vehicle body side tube 11 is provided with a cap 16 detachably and liquid-tightly at the opening 15 at the upper end, and the vehicle body side tube 11 is provided with a vehicle body side mounting portion. The axle-side tube 12 has a bottom bracket 18 fixed in a liquid-tight manner at the lower end, and an axle-side mounting portion 19 is provided on the bottom bracket 18.
[0015]
The front fork 10 accommodates a damper cylinder 21 and a piston rod 24 constituting the damper 20 inside the vehicle body side tube 11 and the axle side tube 12. That is, the front fork 10 has a damper cylinder 21 fixed inside the bottom bracket 18 erected inside the axle side tube 12. The damper cylinder 21 is fixed by a center bolt 22 inserted into the bottom of the bottom bracket 18. In the front fork 10, a spring load adjusting sleeve 23 is screwed in a liquid-tight manner at the center of the cap 16, and a hollow piston rod 24 is fixedly fixed to a lower end portion of the spring load adjusting sleeve 23 inserted into the vehicle body side tube 11. To support. The piston rod 24 slidably passes through a rod guide 25 provided at the upper end of the damper cylinder 21 and is inserted into an oil chamber 27 inside the damper cylinder 21, and is connected to a piston bolt 24 </ b> A provided at the insertion tip of the piston rod 24. 26. The piston 26 slides up and down on the inner surface of the damper cylinder 21. The oil chamber 27 is partitioned by the piston 26 into a piston rod side oil chamber 27A on the side where the piston rod 24 is inserted and a piston side oil chamber 27B on the side where the piston rod 24 is not inserted.
[0016]
In the front fork 10, a seal member 25 </ b> A made of an oil seal that is in close contact with the outer periphery of the piston rod 24 is provided on a rod guide 25 provided at the upper end of the damper cylinder 21 to seal the piston rod side oil chamber 27 </ b> A of the damper cylinder 21. .
[0017]
In the front fork 10, between the vehicle body side tube 11 and the axle side tube 12, the outer peripheral space of the damper cylinder 21 is an oil reservoir chamber 28, and the upper portion of the oil reservoir chamber 28 is a gas chamber (air chamber) 29. Reference numeral 29A denotes an air valve provided on a damping force adjusting rod 54 described later.
[0018]
In the front fork 10, an intermediate cylinder 31 is erected around the other end side of the damper cylinder 21 through a gap that forms an annular shape with the inner periphery of the axle-side tube 12. The intermediate cylinder 31 has a base end flange portion 31 </ b> A seated on a stepped seat provided on the bottom bracket 18, and is sandwiched between the bottom bracket 18 by the other end surface of the axle side tube 12 screwed to the bottom bracket 18. An O-ring 32 is provided between the axle side tube 12 and the bottom bracket 18, and an O-ring 33 is provided between the axle side tube 12 and the intermediate cylinder 31.
[0019]
An annular free piston 34 is slidably provided between the inner periphery of the intermediate cylinder 31 and the outer periphery of the damper cylinder 21 (101 is a bush), and oil passages 44A and 45A of the bottom bracket 18 and a sub tank are provided below the free piston 34. An annular oil chamber 35 communicating with the piston-side oil chamber 27 </ b> B is defined through 43 oil chambers 44 and 45.
[0020]
The free piston 34 is fitted with an O-ring 36 in the outer ring groove and an O-ring 37 in the inner ring groove. The free piston 34 is attached to the intermediate cylinder 31 from the lowest end position indicated by a broken line in the right half of FIGS. 1 to 3 attached to the stopper portion 38 formed of a retaining ring or the like engaged with the inner periphery of the lower end side of the intermediate cylinder 31. 3 and the damper cylinder 21 are moved upward as indicated by the solid lines in the left half and the right half of FIGS. 1 to 3, and the O-ring 36 is moved over the entire range of the intermediate cylinder 31. The O-ring 37 is slid on the outer periphery of the damper cylinder 21 in the normal movement range (the movement range of the free piston 34 corresponding to the maximum compression stroke of the front fork 10) excluding the upper end of the entire movement range. Touch. The free piston 34 seals the piston-side oil chamber 27B with respect to the oil reservoir chamber 28 via the annular oil chamber 35 in the normal movement range described above.
[0021]
The free piston 34 is an upper end portion (sliding end) that exceeds the above-described normal movement range, and when the O-ring 37 reaches the reduced-diameter communication portion 39 provided on the outer periphery of the damper cylinder 21, the communication portion with the O-ring 37 is provided. 39, an oil escape passage from the annular oil chamber 35 to the oil reservoir chamber 28 is formed. Seal member 25A at the upper end of damper cylinder 21 (seal member 25A completely prevents oil leakage from piston rod side oil chamber 27A to oil reservoir chamber 28, but from oil reservoir chamber 28 to piston rod side oil chamber 27. When the hydraulic oil that has entered the damper cylinder 21 from a unidirectional seal member that does not completely prevent the intrusion of the oil increases to a certain amount or more, the free piston 34 moves up to the sliding end described above, and the damper The oil in the cylinder 21 is released to the oil reservoir chamber 28 outside the damper cylinder 21.
[0022]
The front fork 10 urges the free piston 34 toward the annular oil chamber 35 between a spring seat 41 screwed to the outer periphery of the damper cylinder 21 and a spring seat 34A provided at the upper end of the free piston 34. In addition, a coil spring 42 that pressurizes the oil chamber 27 of the damper cylinder 21 is interposed. The spring seat 41 includes an annular portion 41 </ b> A, and the annular portion 41 </ b> A is fitted to the inner periphery of the upper end of the intermediate cylinder 31. A space for accommodating the spring 42 between the damper cylinder 21 and the intermediate cylinder 31 is provided via an oil hole 31B provided in the intermediate cylinder 31 and an oil hole 41B provided in the spring seat 41. Oil reservoir A part of 28 is comprised.
[0023]
In the front fork 10, the sub tank 43 is connected to the aforementioned bottom bracket 18 fixed to the lower end portion of the axle side tube 12, and the piston side oil chamber 27 </ b> B of the damper cylinder 21 and the lower oil chamber 44 of the sub tank 43 are connected to the center bolt 22. The provided oil passage 22A communicates with an oil passage 44A provided on the bottom bracket 18, and the annular oil chamber 35 below the free piston 34 and the upper oil chamber 45 of the sub tank 43 communicate with each other via an oil passage 45A provided on the bottom bracket 18. ing.
[0024]
The front fork 10 includes a spring collar 47 formed by combining a plurality of members that are supported by the above-described spring load adjusting sleeve 23 provided on the cap 16 and moved up and down, and an upper spring seat 48A that is backed up by the spring collar 47; A suspension spring 49 is interposed between the lower spring seat 48B fixed to the outer periphery of the rod guide 25.
[0025]
The front fork 10 buffers the impact force received from the road surface when the vehicle travels by the spring reaction force of the suspension spring 49 and the spring reaction force of the air spring of the air chamber 29.
[0026]
The front fork 10 suppresses the expansion and contraction vibrations of the suspension spring 49 and the air spring of the air chamber 29, so that a piston valve device (extension-side damping force generation device) 50 and a bottom valve device (pressure-side damping force generation device) 60 are used. have.
[0027]
The piston valve device 50 includes an extension side channel 51 (not shown) and a pressure side channel 52 that allow the piston rod side oil chamber 27A and the piston side oil chamber 27B to communicate with the piston 26 that is in sliding contact with the inner surface of the damper cylinder 21. The extension side channel 51 can be opened and closed by the extension side damping valve 51A, and the pressure side channel 52 can be opened and closed by the compression side damping valve 52A. The compression side damping valve 52A is backed up and supported by a valve spring 52C locked to the piston rod 24 via a spring receiver 52B. The piston valve device 50 has a bypass passage 53 that bypasses the piston 26 and allows the piston rod side oil chamber 27A and the piston side oil chamber 27B to communicate with each other. The bypass passage 53 can be opened and closed by the needle valve 53A. And At this time, the damping force adjusting rod 54 is screwed into the center of the spring load adjusting sleeve 23 provided on the cap 16, the damping force adjusting rod 54 is inserted into the hollow portion of the piston rod 24, and the needle valve 53A is inserted into the insertion end. Is provided.
[0028]
The bottom valve device 60 is built in the sub tank 43 installed between the piston side oil chamber 27B of the damper cylinder 21 and the annular oil chamber 35 below the free piston 34 as described above. In the bottom valve device 60, a cap 62 is screwed into the opening 61 of the sub tank 43, and a support bolt 63 is screwed to the upper end surface of the cap 62 facing the lower oil chamber 44 of the sub tank 43. A bypass bolt 64 is screwed and a bottom piece 65 is fixed to an intermediate portion of the bypass bolt 64. The bottom piece 65 partitions the lower oil chamber 44 and the upper oil chamber 45. The bottom piece 65 includes a pressure side channel 66 and an extension side channel 67 that allow the lower oil chamber 44 and the upper oil chamber 45 to communicate with each other. The pressure side channel 66 can be opened and closed by a pressure side damping valve 66A. The path 67 can be opened and closed by a check valve 67A. Further, the bottom valve device 60 has a bypass oil passage 68 in the bolts 63 and 64 that bypasses the bottom piece 65 and allows the lower oil chamber 44 and the upper oil chamber 45 to communicate with each other, and the bypass oil passage 68 is connected to the needle valve 68A. The plate valve 68B can be opened and closed. At this time, the damping force adjusting rod 69 is screwed into the cap 62, the damping force adjusting rod 69 is inserted into the center of the cap 62, and the needle valve 68A is provided at the insertion end.
[0029]
The sub tank 43 has a hydraulic oil supply / discharge port 71 that opens into the upper oil chamber 45, and the supply / discharge port 71 can be opened and closed by a plug 72 screwed into a screw hole of the sub tank 43. plug 72 Is opened and the supply / discharge port 71 is opened to supply / discharge hydraulic oil through the supply / discharge hole 72A of the plug 72. Reference numeral 73 denotes a cap for the supply / discharge hole 72 </ b> A attached to the plug 72.
[0030]
Note that the front fork 10 is removably attached to the inside of the damper cylinder 21 by a rebound spring 55 interposed between the rod guide 25 and the piston bolt 24A. Stretch Make a buffer of time.
[0031]
Further, the front fork 10 provides a buffer at the time of maximum compression by abutting a stopper rubber 56 fixed to the outer periphery of the piston rod 24 with the rod guide 25 outside the damper cylinder 21.
[0032]
Further, the front fork 10 has the following configuration in order to improve the absorbability of fine disturbances such as a gap entering the wheel on the back side (maximum compression stroke side) of the compression stroke.
[0033]
The front fork 10 bypasses the compression side damping force generator 60 built in the sub tank 43 on the lower end side of the damper cylinder 21 so that the piston side oil chamber 27B and the annular oil chamber 35 below the free piston 34 communicate with each other. A hole-shaped bypass oil passage 80 is formed. The bypass oil passage 80 communicates the piston-side oil chamber 27B and the annular oil chamber 35 when the free piston 34 is compressed more than a certain distance within the normal movement range described above on the far side of the compression stroke of the front fork 10; As a result, the generation of the compression side damping force by the compression side damping force generating device 60 is stopped, and only a lower compression side damping force based on the passage resistance of the bypass oil passage 80 is generated, and the generated damping force of the front fork 10 is reduced. Improves the absorption of fine disturbances such as gaps entering the wheels.
[0034]
The free piston 34 is a skirt portion 81 that extends downward on the inner periphery that is in sliding contact with the outer periphery of the damper cylinder 21, and the bypass oil passage 80 is closed by the skirt portion 81 in a range excluding the back side of the compression stroke of the front fork 10. 1 to 3 (a free piston 34 indicated by a solid line in the left half portion and a free piston 34 indicated by a broken line in the right half portion), and bypass oil is provided by a skirt portion 81 at the back of the compression stroke of the front fork 10. The path 80 is opened (free piston 34 shown by a solid line in the right half of FIGS. 1 to 3).
[0035]
Accordingly, the front fork 10 operates as follows.
(Compression process)
When the front fork 10 is compressed, one of the vehicle body side tube 11 and the axle side tube 12 is compressed relative to the other, and the suspension spring 49 is compressed. Further, the piston rod 24 enters the damper cylinder 21, and the hydraulic oil in the piston side oil chamber 27B passes through the bypass flow path 53 of the piston 26 at low speed, and the pressure side damping valve of the pressure side flow path 52 of the piston 26 at medium and high speed. It flows through the piston rod side oil chamber 27A through 52A. In addition, the hydraulic oil corresponding to the volume of the piston rod 24 entering flows through the bypass flow path 68 that bypasses the bottom piece 65 at a low speed and flows into the lower oil chamber 35 of the free piston 34, and at the medium and high speed, the pressure side flow path of the bottom piece 65. It flows through the compression side damping valve 66A of 66 and flows into the lower oil chamber 35 of the free piston.
[0036]
During this compression, the free piston 34 moves upward and compresses the spring 42. Thus, at low speed, the oil in the piston-side oil chamber 27B flows through the bypass passage 53 of the piston 26 to the piston rod-side oil chamber 27A, and a compression-side damping force is obtained by the throttle resistance of the needle valve 53A during this time. At the same time, the oil corresponding to the volume of the piston rod 24 entering the damper cylinder 21 enters the lower oil chamber 44 of the sub tank 43 from the piston side oil chamber 27B, and further passes through the bypass passage 68 of the bottom piece 65 to the upper oil chamber 45. In the flow process, the compression side damping force is obtained by the throttle resistance of the needle valve 68A and the bending resistance of the plate valve 68B. Further, the oil in the piston side oil chamber 27B passes through the pressure side flow path 52 of the piston 26 and flows from the micro flow path formed by lifting up the pressure side damping valve 52A to the piston rod side oil chamber 27A. Get damping force. At medium and high speeds, the oil corresponding to the volume of the piston rod 24 entering the damper cylinder 21 enters the lower oil chamber 44 of the sub tank 43 from the piston side oil chamber 27B, and further passes through the pressure side flow channel 66 of the bottom piece 65 to the upper oil chamber. The pressure side damping force is obtained by the bending resistance of the pressure side damping valve 66A during this period. Further, the oil in the piston side oil chamber 27B passes through the pressure side flow path 52 of the piston 26 and flows into the piston rod side oil chamber 27A in a state in which the pressure side damping valve 52A is bent and deformed. Get damping force. The suspension spring 49 and the spring 42 buffer an impact during compression, and the compression side damping force controls the compression speed of the suspension spring 49 and the spring 42.
[0037]
(a) By the way, during the compression stroke of the front fork 10, the suspension spring 49 is compressed by an amount corresponding to the compression stroke of the vehicle body side tube 11 relative to the axle side tube 12. Further, since the piston rod 24 enters the damper cylinder 21, the hydraulic oil corresponding to the volume of the piston rod 24 that has entered flows into the lower oil chamber 35 of the free piston 34, causing the free piston 34 to move upward and the spring 42. Compress.
[0038]
That is, at the time of compression, in addition to the suspension spring 49 being deflected to the contraction side, the spring 42 urging the free piston 34 is equivalent to the amount that the piston rod 24 enters the damper cylinder 21 and the free piston 34 moves upward. Bends to the shrink side. Thereby, the spring reaction force of the front fork 10 increases, and the sinking of the front fork 10 can be suppressed by a large spring reaction force during braking.
[0039]
(b) Then, when the compression stroke of the front fork 10 reaches a certain value (back side of the compression stroke) as in cornering after breaking, the piston rod 24 enters the damper cylinder 21 for a certain length or more. As a result, the free piston 34 moves upward by a certain length, and the skirt portion 81 of the free piston 34 opens the bypass oil passage 80 provided in the damper cylinder 21, and the compression side damping force generator 60 (pressure side damping valve 66 A, needle) described above. Generation of the compression side damping force by the valve 68A and the plate valve 68B) is stopped as described above. The front fork 10 only generates a lower compression side damping force based on the passage resistance of the bypass oil passage 80, reduces the generated damping force and can absorb fine disturbances such as a gap entering the wheel, and the stable running state of the vehicle Can be secured.
[0040]
( Stretch Process)
Front fork 10 Stretch Sometimes one of the vehicle body side tube 11 and the axle side tube 12 is relative to the other. Stretch Then, the suspension spring 49 extends. Further, the piston rod 24 retreats from the damper cylinder 21, and the hydraulic oil in the piston rod side oil chamber 27A passes through the bypass flow path 53 of the piston 26 at low speed, and passes through the expansion side flow path 51 of the piston 26 at medium speed. It flows into the piston-side oil chamber 27B through the expansion-side damping valve 51A. Further, the hydraulic oil corresponding to the volume that the piston rod 24 has retreated enters from the lower oil chamber 35 of the free piston 34 into the upper oil chamber 45 of the sub tank 43, and passes through the check valve 67 </ b> A of the extension side channel 67 of the bottom piece 65. Return to the piston side oil chamber 27B.
[0041]
The free piston 34 is moved downward by the urging force of the spring 42, and the spring 42 extends.
[0042]
Thereby, at low speed, the oil in the piston rod side oil chamber 27A flows into the piston side oil chamber 27B through the bypass flow path 53 of the piston 26, and the expansion side damping force is obtained by the throttle resistance of the needle valve 53A during this time. At medium and high speeds, the oil in the piston rod side oil chamber 27A flows into the piston side oil chamber 27B through the extension side flow passage 51 of the piston 26, and the extension side damping force is obtained by the bending resistance of the extension side damping valve 51A during this time. The extension side damping force prevents the suspension spring 49 and the spring 42 from resonating.
[0043]
by the way, From the compression process Stretch If it moves to a stroke, the suspension spring 49 is only the part which the vehicle body side tube 11 strokes with respect to the axle side tube 12. Stretch To do. Further, since the piston rod 24 retracts from the damper cylinder 21, the lower oil chamber 35 of the free piston 34 is depressurized, and the free piston 34 is moved downward by the biasing force of the spring 42.
[0044]
That is, from the compression stroke Stretch When moving to the stroke, in addition to the suspension spring 49 being bent to the extension side, the piston 42 is retracted from the damper cylinder 21 and the free piston 34 is moved downward. Deflection to the extension side. As a result, the spring reaction force of the front fork 10 is reduced, and it is possible to prevent the front fork 10 from extending during cornering to prevent the front fork 10 from being understeered.
[0046]
According to this embodiment, there are the following operations.
(Operation corresponding to claim 1)
(1) When the front fork 10 is compressed, the suspension spring 49 is compressed, the piston rod 24 enters the damper cylinder 21, and the oil in the piston side oil chamber 27B passes through the compression side damping force generator 60 and the free piston 34. The pressure-side damping force generated by the pressure-side damping force generator 60 during this period is obtained. The compression side damping force controls the compression speed of the suspension spring 49.
[0047]
(2) When the compression stroke of the front fork 10 advances and reaches a compression stroke above a certain level, the annular oil chamber below the free piston 34 is bypassed by the bypass oil passage 80 where the piston-side oil chamber 27B bypasses the compression-side damping force generator 60. Communicate with 35. Thereby, the generation of the compression side damping force by the compression side damping force generator 60 is stopped at a compression stroke of a certain level or more.
[0048]
(3) At the time of braking, the suspension spring 49 is greatly contracted by the large compression stroke of the front fork 10, and the sinking of the front fork 10 is suppressed by the spring reaction force.
[0049]
(4) During cornering after braking (during steady turning), the front fork 10 still has a compression stroke even if it is further compressed by the above-mentioned (3) or slightly extended from the above-mentioned (3) by canceling the brake. The bypass oil passage 80 is set to be in an open state as described in (2) above, and the generation of the compression side damping force by the compression side damping force generator 60 is stopped. As a result, the front fork 10 absorbs fine disturbances such as a gap entering the wheel well on the back side of the compression stroke, facilitates expansion and contraction, and improves riding comfort and operability.
[0050]
(Operation corresponding to claim 2)
(5) Since the spring 42 is attached to the free piston 34, when the front fork 10 is compressed, when the hydraulic oil corresponding to the volume of the piston rod 24 entering the damper cylinder 21 moves the free piston 34 upward, the spring 42 is It will be compressed. Accordingly, the spring reaction force of the front fork 10 is obtained by adding the compression amount of the spring 42 to the compression amount of the suspension spring 49, and the sinking of the front fork 10 is suppressed by a large spring reaction force during braking.
[0051]
(6) Since the free piston 34 pressurizes the oil chamber 27 in the damper cylinder 21 by the spring force of the spring 42, the generation of bubbles (cavitation) in the hydraulic oil in the damper cylinder 21 is prevented, and the damping force is stabilized. Secure.
[0052]
(Operation corresponding to claim 3)
(7) Since the front fork 10 is provided with the intermediate cylinder 31 through the annular gap inside the axle tube 12 and the free piston 34 between the intermediate cylinder 31 and the damper cylinder 21, the axle tube 12 is traversed. Even if it is bent elliptically on the surface, it is not affected by the bending. Therefore, the smooth slidability of the free piston 34 can be ensured.
[0053]
FIG. 4 shows a modification of the front fork 10 shown in FIGS. 1 to 3, in which the hole-like bypass oil passage 80 shown in FIGS. The bypass oil passage 90 is perforated along the axial direction on the lower end side of the damper cylinder 21, bypasses the compression side damping force generator 60 built in the sub tank 43, and is provided below the piston side oil chamber 27 </ b> B and the free piston 34. The annular oil chamber 35 is communicated.
[0054]
According to the long hole-like bypass oil passage 90, when the hole area of the bypass oil passage 90 is the same as the hole area of the bypass oil passage 80, the free piston 34 performs a compression stroke at the back of the compression stroke of the front fork 10. The bypass oil passage 90 gradually opens from one end side of the long hole as it goes, in other words, gradually connects the piston-side oil chamber 27B and the annular oil chamber 35, and as a result, the compression-side damping force generated by the compression-side damping force generator 60 is reduced. While the generation is gradually stopped, the state shifts to a state in which the generated damping force of the front fork 10 is gradually reduced to generate a lower compression side damping force based on the passage resistance of the bypass oil passage 90. Therefore, a state in which a sudden change in the compression side damping force of the front fork 10 due to the opening of the bypass oil passage 90 on the back side of the compression stroke of the front fork 10 can be alleviated, and fine disturbances such as a gap entering the wheel can be well absorbed Thus, the running state of the vehicle can be further stabilized.
[0055]
In the front fork 10, the spring 42 attached to the free piston 34 is separated from the suspension spring 49. However, in the front fork 10 of the present invention, the free piston 34 may be urged by the suspension spring 49 without using the spring 42.
[0056]
Further, the front fork 10 is an inverted type in which the vehicle body side tube 11 is an outer tube and the axle side tube 12 is an inner tube inserted into the vehicle body side tube 11. However, in the front fork 10 of the present invention, it may be an upright type in which the vehicle body side tube 11 is an inner tube and the axle side tube is an outer tube.
[0057]
Further, in the front fork 10, the damper cylinder 21 is fixed to the axle side tube 12 side, and the piston rod 24 is fixed to the vehicle body side tube 11 side. However, in the front fork 10 of the present invention, the damper cylinder 21 may be fixed to the vehicle body side tube 11 side, and the piston rod 24 may be fixed to the axle side tube 12 side.
[0058]
In the front fork 10, the outer peripheral space of the damper cylinder 21 is an oil reservoir chamber 28. However, in the front fork 10 of the present invention, the outer periphery of the damper cylinder 21 may be a gas chamber (air chamber).
[0059]
Although the embodiment of the present invention has been described with reference to the drawings, the specific configuration of the present invention is not limited to this embodiment, and there are design changes and the like without departing from the scope of the present invention. Are also included in the present invention.
[0060]
【The invention's effect】
As described above, according to the present invention, in the hydraulic shock absorber, it is possible to improve the absorbability of fine disturbances such as a gap on the back side of the compression stroke.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an entire hydraulic shock absorber.
FIG. 2 is a lower cross-sectional view of FIG.
FIG. 3 is an enlarged view of a main part of FIG. 2;
FIG. 4 is an enlarged view of a main part showing a modification of the hydraulic shock absorber.
[Explanation of symbols]
10 Front fork (hydraulic shock absorber)
11 Car body side tube
12 Axle side tube
20 damper
21 Damper cylinder
24 piston rod
25A Seal member
26 Piston
27 Oil chamber
27A Piston rod side oil chamber
27B Piston side oil chamber
28 Oil reservoir
29 Gas chamber
31 Intermediate cylinder
34 Free piston
35 Annular oil chamber
42 Spring
60 Pressure-side damping force generator
80, 90 Bypass oil passage

Claims (4)

Fit the body side tube and axle side tube slidably,
Inside the vehicle body side tube and the axle side tube is housed a damper having a damper cylinder and a piston rod that slides through a piston provided in the tip of the damper cylinder,
In the damper cylinder, a piston rod side oil chamber that accommodates the piston rod and a piston side oil chamber that does not accommodate the piston rod are formed,
In the hydraulic shock absorber in which the damper cylinder is fixed to one of the vehicle body side tube and the axle side tube, and the piston rod is fixed to the other.
On one end side of the damper cylinder through which the piston rod is inserted, a seal member for sealing the piston rod side oil chamber of the damper cylinder is provided,
An annular free piston is provided on the outer periphery of the damper cylinder, and an annular oil chamber communicating with the piston-side oil chamber is sealed on the outer periphery of the damper cylinder by the annular free piston, and the vehicle body side tube is the axle side tube. With respect to the compression stroke, hydraulic oil corresponding to the volume of the piston rod that enters the damper cylinder is caused to flow from the piston-side oil chamber into the annular oil chamber to cause the free piston to perform the compression stroke,
Between the oil chamber of the annular and the piston side oil chamber, the compression side damping force generating device is provided, the damper cylinder, said bypass the pressure side damping force generating device, the oil of the annular and the piston side oil chamber A bypass oil passage that connects the chambers
The bypass oil passage communicates the piston-side oil chamber and the annular oil chamber when the free piston is compressed more than a certain amount by a compression stroke of the vehicle body-side tube relative to the axle-side tube. Features a hydraulic shock absorber. The axle side tube is slidably fitted in the body side tube,
A damper cylinder is erected in the axle side tube, and a piston rod provided with a piston at its tip is slidably inserted into the damper cylinder.
In the damper cylinder, a piston rod side oil chamber that accommodates the piston rod and a piston side oil chamber that does not accommodate the piston rod are formed,
In the hydraulic shock absorber provided with an oil reservoir chamber whose upper part is a gas chamber on the outer periphery of the damper cylinder,
On one end side of the damper cylinder through which the piston rod is inserted, a seal member for sealing the piston rod side oil chamber in the damper cylinder is provided,
An annular free piston urged by a spring is slidably provided on the outer periphery of the damper cylinder,
With the annular free piston, an annular oil chamber communicating with the piston-side oil chamber is hermetically sealed on the outer periphery of the damper cylinder, and the vehicle body side tube enters the damper cylinder by the amount of the compression stroke relative to the axle side tube. Is configured to cause the free piston to perform a compression stroke by flowing hydraulic oil corresponding to the volume of the piston rod from the piston side oil chamber into the annular oil chamber,
A compression-side damping force generator is provided between the piston-side oil chamber and the annular oil chamber, and the piston-side oil chamber and the annular oil chamber are bypassed in the damper cylinder. Establish a bypass oil passage that communicates
The bypass oil passage communicates the piston-side oil chamber and the annular oil chamber when the free piston is compressed more than a certain amount by a compression stroke of the vehicle body-side tube relative to the axle-side tube. Features a hydraulic shock absorber. An intermediate cylinder is provided via an annular gap between the outer periphery of the damper cylinder and the inner periphery of the axle tube.
The hydraulic shock absorber according to claim 1 or 2, wherein the annular free piston is provided between the intermediate cylinder and the damper cylinder.   The hydraulic shock absorber according to any one of claims 1 to 3, wherein the bypass oil passage includes a long hole along an axial direction of the damper cylinder.

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