JP2004044670A - Hydraulic shock absorber for vehicles - Google Patents

Abstract

A hydraulic shock absorber in which a piston slides on the inner periphery of an inner tube has a pressure-side damping force having a position dependency.
In a vehicle hydraulic shock absorber having an annular oil chamber surrounded by an inner circumference of an outer tube, an outer circumference of an inner tube, and two upper and lower bushes, the annular oil chamber is provided with an inner oil chamber. The oil chamber 21A is always in communication with the piston rod side oil chamber 21A through an oil hole 28 provided in the tube 12, the cross-sectional area of the annular oil chamber 17 is formed larger than the cross-sectional area of the piston rod 23, and the two oil passages 51 , 52, a check valve 60 for preventing flow from the piston rod side oil chamber 21A to the oil reservoir chamber 22 during the extension stroke in one oil path 51, and a piston rod side oil chamber 21A in the other oil path 52. A resistance valve 70 for providing resistance to the flow from the oil reservoir 22 to the oil reservoir 22 is provided, and the resistance valve 70 is urged at the lower end of the suspension spring 33.
[Selection] Fig. 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydraulic shock absorber for a vehicle.
[0002]
[Prior art]
The front fork described in Japanese Utility Model Laid-Open Publication No. 63-75493 communicates between the damper cylinders 5, 47 and the inner tubes 2, 44 via passages 33, 34 provided in the lower oil chamber 13 in the damper cylinder and the spacer 32. A reservoir 16 is provided, and the reservoir 16 performs volume compensation accompanying the piston rods 6 and 49 entering and exiting the damper cylinder. A passage 36 connecting the passage 33 and the reservoir 16 is provided in the bracket 11, and a pressure-side base valve device 35 that generates a damping force when compressed is incorporated in the passage 36. The front fork of this structure requires a damper cylinder for partitioning the oil reservoir between the front fork and the inner periphery of the inner tube, and requires a pressure-side base valve device, resulting in high cost.
[0003]
Japanese Patent Publication No. 63-23957 discloses a front fork in which a damper is not provided and a piston 17 slides directly on the inner periphery of the inner tube 11 to generate a damping force. In this front fork, an oil chamber C is formed between the outer circumference of the inner tube and the inner circumference of the outer tube and between the annular bearing portion 18 and the bearing portion 13, and this oil chamber C is used as a volume compensation chamber for the piston rod.
[0004]
[Problems to be solved by the invention]
However, in the front fork of Japanese Patent Publication No. 63-23957, the annular bearing portion 18 is provided with the seal 18a for the piston rod and the seal 18b for the outer tube, so that the upper air chamber E and the lower oil chambers B and C are completely oiled. Tightly separated. Therefore, the number of parts increases and the cost increases due to the provision of the seals 18a and 18b. Further, it is necessary to separately provide a volume compensation chamber D for compensating for the volume expansion of the oil accompanying the temperature rise, which increases the cost. That is, the structure of the front fork becomes complicated as a whole, resulting in high cost.
[0005]
The present applicant has filed a Japanese Patent Application No. 2002-71008 for a hydraulic shock absorber that does not include a damper cylinder and has a simplified structure while sliding a piston on the inner circumference of an inner tube.
[0006]
It is an object of the present invention to provide a hydraulic shock absorber in which a piston slides on the inner periphery of an inner tube, and has a pressure-dependent damping force having a position dependency.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, the inner tube is slidably inserted into the outer tube through bushes fixed to the inner peripheral opening of the outer tube and the outer peripheral end of the inner tube, respectively. An annular oil chamber surrounded by the inner circumference of the tube, the outer circumference of the inner tube, and the two bushes is partitioned, a partition member is provided on the inner circumference of the inner tube, and the oil chamber is partitioned at a lower portion, and an upper portion is formed. A piston that slidably inserts a piston rod attached to the outer tube into the partition member and slidably contacts an inner periphery of the inner tube with a tip end of the piston rod inserted into the inner tube. And the oil chamber is partitioned into a piston rod-side oil chamber in which the piston rod is housed and a piston-side oil chamber in which the piston rod is not housed. A hydraulic damper for a vehicle provided with a compression-side damping force generating means, wherein the annular oil chamber is always in communication with the piston rod-side oil chamber via an oil hole provided in the inner tube, Is formed larger than the cross-sectional area of the piston rod, two oil passages are provided in the partition member, and the flow from the piston rod-side oil chamber to the oil sump chamber in one of the oil paths during the extension stroke. A check valve for preventing the flow, a resistance valve for providing resistance to the flow from the piston rod side oil chamber to the oil reservoir chamber is provided in the other oil path, and the resistance valve is urged at a lower end portion of the suspension spring. It is.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
1 is a cross-sectional view showing the entire hydraulic shock absorber, FIG. 2 is a cross-sectional view showing a main part of FIG. 1, FIG. 3 is a cross-sectional view showing an enlarged main part of FIG. 2, and FIG. FIG. 5 is a perspective view showing the check valve.
[0009]
As shown in FIGS. 1 to 3, the hydraulic shock absorber 10 includes a bush 11 </ b> A fixed to the inner periphery of the lower opening of the outer tube 11 and a bush 12 </ b> A fixed to the outer periphery of the upper opening of the inner tube 12. The inner tube 12 is slidably inserted into the outer tube 11. 11B is an oil seal, and 11C is a dust seal. A cap 13 is screwed to the upper end opening of the outer tube 11 in a liquid-tight manner, and vehicle body side mounting members 14A and 14B are provided on the outer periphery of the outer tube 11. A bottom bracket 15 is screwed to the lower end opening of the inner tube 12 in a liquid-tight manner, and the bottom bracket 15 is provided with a wheel-side mounting portion 16.
[0010]
The hydraulic shock absorber 10 defines an inner periphery of the outer tube 11, an outer periphery of the inner tube 12, and an annular oil chamber 17 surrounded by the two bushes 11A, 12A.
[0011]
The hydraulic shock absorber 10 is provided with a partition member 19 on the inner periphery on the upper end side of the inner tube 12, and partitions the hydraulic oil chamber 21 below the rod guide portion 19 </ b> A of the partition member 19 and partitions the oil reservoir 22 above. . The lower area of the oil reservoir 22 is an oil chamber 22A, and the upper area is an air chamber 22B.
[0012]
The partition member 19 has the rod guide portion 19A crimped and held at the lower end of the cylindrical body 19B, and the upper end of the cylindrical body 19B is screwed onto the inner periphery of the inner tube 12 (19C is the upper end surface of the cylindrical body 19B). The rod guide portion 19 </ b> A is positioned below the upper end of the inner tube 12. Thereby, while ensuring the fitting length of the outer tube 11 and the inner tube 12 at the time of extension, the volume of the oil reservoir 22 is secured, and the volume of the air chamber 22B for generating an air spring (air reaction force). Can be secured. In addition, a seal ring 19 </ b> D which is in sliding contact with the inner periphery of the outer tube 11 to secure the hermeticity of the annular oil chamber 17 is fitted on the outer peripheral portion on the upper end side of the cylindrical body 19 </ b> B.
[0013]
The hydraulic shock absorber 10 slidably inserts the piston rod 23 attached to the outer tube 11 into the rod guide 19 </ b> A of the partition member 19. Specifically, a rod connecting portion 24 provided at the center of the cap 13 is inserted into the oil reservoir 22, a hollow piston rod 23 is screwed into the rod connecting portion 24, and this is fixed with a lock nut 25.
[0014]
The hydraulic shock absorber 10 fixes a piston 26 slidably in contact with the inner periphery of the inner tube 12 at the tip of a piston rod 23 inserted into the inner tube 12 from the rod guide portion 19A of the partition member 19, and The piston rod-side oil chamber 21A in which the rod 23 is accommodated and the piston-side oil chamber 21B in which the piston rod 23 is not accommodated are partitioned. The piston 26 is fixed by a nut 27.
[0015]
The hydraulic shock absorber 10 always communicates the annular oil chamber 17 with the piston rod side oil chamber 21 </ b> A via an oil hole 28 provided in the inner tube 12. At this time, the annular oil chamber 17 is provided with the lower guide bush 11A on the inner periphery of the outer tube 11 and the upper guide bush 12A on the outer periphery of the inner tube 12 among the upper and lower guide bushes as described above. The volume changes with the operation of the vessel 10. The annular oil chamber 17 expands during compression to absorb the discharge of hydraulic oil from the hydraulic oil chamber 21 accompanying the entry of the piston rod 23, and contracts during expansion to return hydraulic oil to the hydraulic oil chamber 21. Then, a part of the volume compensation chamber is formed. Therefore, the fluctuation of the oil level in the oil reservoir 22 is reduced, and the entrainment of air is reduced.
[0016]
In the hydraulic shock absorber 10, a spring load adjusting sleeve 29 is screwed onto the cap 13, a pushing rod 29A pushed by the spring load adjusting sleeve 29 is inserted through the cap 13 into the oil reservoir 22, A suspension spring 33 is interposed between the spring seat 31 backed up by the pushing rod 29A and the spring seat 32 supported by the rod guide 19A of the partition wall member 19. The hydraulic shock absorber 10 vertically moves the pushing rod 29A by screwing the spring load adjusting sleeve 29, and adjusts the spring load of the suspension spring 33 by this vertical movement. The hydraulic shock absorber 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. A spring guide 34 for supporting the inner periphery of the suspension spring 33 at a substantially intermediate portion of the suspension spring 33 to prevent the suspension spring 33 from bending at the outer periphery of the piston rod 23 is provided with a lock nut 25 and a stopper ring 35. It is sandwiched between and fixed.
[0017]
The hydraulic shock absorber 10 includes a damping force generator 40 on the piston 26.
The damping force generator 40 includes a pressure-side flow path 41 and an extension-side flow path 42. The compression-side flow path 41 is opened and closed by a compression-side disk valve 41A (compression-side damping force generating means) 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 force generating means) backed up by a valve stopper 42B. The piston 26, the compression-side disc valve 41A, the valve stopper 41B, the extension-side disc valve 42A, and the valve stopper 42B are a valve assembly, and are fixed by being sandwiched between a nut 27 and a stopper ring 23A fixed to the outer periphery of the piston rod 23. You.
[0018]
The damping force generator 40 has an adjusting rod 43 screwed into the hollow portion of the cap 13 in a liquid-tight manner, and a needle valve 44 (damping force adjusting means) fixed to the adjusting rod 43 is inserted into the hollow portion of the piston rod 23. The opening degree of the bypass 45 provided in the piston rod 23 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.
[0019]
The damping force generator 40 generates a compression damping force in the compression stroke by a passage resistance of the bypass passage 45 whose opening degree is adjusted by the needle valve 44 in a low speed region, and a bending deformation of the compression disk valve 41A in a middle and high speed region. As a result, a compression damping force is generated. In the extension side stroke, the extension side damping force is generated by the passage resistance of the bypass passage 45 whose opening is adjusted by the needle valve 44 in the low speed range, and the extension side is caused by the bending deformation of the extension side disk valve 42A in the middle and high speed range. Generates side damping force. By the compression side damping force and the extension side damping force, the above-described expansion and contraction vibration of the suspension spring 33 is damped.
[0020]
The hydraulic shock absorber 10 includes a spring seat 48 which is swaged and fixed to a lower end surface of the partition member 19 on the upper end side of the inner tube 12 facing the piston rod side oil chamber 21A, and a valve stopper 41B provided on the upper end surface side of the piston 26. And a rebound spring 49 is interposed therebetween. When the hydraulic shock absorber 10 is fully extended, the partition member 19 presses the rebound spring 49 to regulate the maximum extension stroke.
[0021]
However, in the hydraulic shock absorber 10, as shown in FIG. 4, 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 changed to the sectional area of the piston rod 23 (to the outer diameter). (Enclosed area) S2.
[0022]
Further, as shown in FIG. 3, in the oil passage 51 formed by the inner periphery of the rod guide portion 19A of the partition member 19, the oil flow from the oil storage chamber 22 to the piston rod-side oil chamber 21A is allowed in the pressure side stroke, In the extension stroke, a check valve 60 for preventing the flow of oil from the piston rod side oil chamber 21A to the oil reservoir 22 is provided. A valve chamber 61 is provided on the inner periphery of the rod guide portion 19A of the partition member 19, and between the stepped portion 61A on the upper end side of the valve chamber 61 and the above-described spring seat 48 provided on the lower end side of the valve chamber 61. The check valve 60 is housed. As shown in FIG. 5, the check valve 60 is shorter than the gap between the step portion 61A and the spring seat 48, and has a lateral groove 62 formed on the lower end surface. The check valve 60 is slidably contacted with the inner periphery of a valve chamber 61 provided in the rod guide portion 19A of the partition wall member 19 and is vertically displaceable, and slidably supports the piston rod 23. A flow path that allows the flow of oil from the oil reservoir chamber 22 to the piston rod side oil chamber 21A between the outer circumference of the check valve 60 and the inner circumference of the valve chamber 61 provided in the rod guide portion 19A of the partition member 19. 63 is formed. In the compression side stroke, the check valve 60 moves along with the piston rod 23 entering the inner tube 12 and moves downward in FIG. 3 to abut the spring seat 48 and form a gap with the stepped portion 61A. The oil in the piston rod-side oil chamber 21A can be discharged from the lateral groove 62 to the oil reservoir 22 through the gap between the lateral groove 62 and the stepped portion 61A. In the extension side stroke, the check valve 60 moves along with the piston rod 23 retreating from the inner tube 12 and moves upward in FIG. 3, and abuts the step 61A to close the gap between the step 61A. This prevents the oil in the piston rod side oil chamber 21 </ b> A from being discharged to the oil reservoir 22.
[0023]
As shown in FIG. 3, an oil passage 52 is formed in the rod guide portion 19A of the partition wall member 19 to communicate the piston rod side oil chamber 21A and the oil storage chamber 22. A resistance valve that provides resistance to the flow to the oil passage, in this embodiment, a resistance valve 70 composed of a disk valve is provided in the oil passage 52. The resistance valve 70 is urged via the spring seat 32 at the lower end of the suspension spring 33 described above, and is pressed and seated on a seat surface 71 formed on the upper end surface of the rod guide 19A where the oil passage 52 opens. .
In the extension side stroke, when hydraulic oil corresponding to the retreat volume of the piston rod 23 retreating from the inner tube 12 is transferred from the annular oil chamber 17 to the piston rod side oil chamber 21A of the inner tube 12 via the oil hole 28, When a surplus (ΔS1−ΔS2), which will be described in detail later, of the volume decrease ΔS1 of the oil chamber 17 is discharged from the oil passage 52 to the oil reservoir 22 by opening the resistance valve 70, the opening degree of the resistance valve 70 A correspondingly formed microchannel 72 provides a throttle resistance to this discharged oil.
[0024]
The suspension spring 33 changes the urging force applied to the resistance valve 70 according to the stroke of the hydraulic shock absorber 10, and is small on the entire extension side and large on the contraction side. As a result, on the entire extension side, the minute flow path 72 opened by the resistance valve 70 becomes larger, the hydraulic pressure in the oil chambers (21A, 21B) of the inner tube 12 is low, and the hydraulic oil is likely to produce cavitation. On the other hand, the compression side damping force generated in the compression stroke from around the full elongation (around the 1G ride) is reduced. Further, on the contraction side, the minute flow path 72 opened by the resistance valve 70 becomes smaller, the oil pressure in the oil chambers (21A, 21B) of the inner tube 12 is high, and the cavitation of the working oil is suppressed, so that it becomes large. The compression side damping force generated on the most compression side after the stroke is increased. Accordingly, the compression-side damping force generated by the compression-side disc valve 41A provided in the piston 26 can have stroke position dependency as described later.
[0025]
The operation of the hydraulic shock absorber 10 is as follows.
(Pressure side stroke)
Hydraulic oil corresponding to the volume of the piston rod 23 that enters the inner tube 12 in the compression stroke is transferred from the oil chamber 21 </ b> A on the inner periphery of the inner tube 12 to the annular oil chamber 17 via 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 shortage of (ΔS1−ΔS2) in the required oil supply amount to the annular oil chamber 17 is obtained. The oil is supplied from the oil reservoir 22 via the check valve 60.
[0026]
In the compression side stroke, as described above, the compression side damping force is generated by the passage resistance of the bypass passage 45 whose opening is adjusted by the needle valve 44 in the low speed range, and the compression side damping force is generated by the bending deformation of the compression side disc valve 41A in the middle and high speed range. Generates damping force.
[0027]
(Extension stroke)
Hydraulic oil corresponding to the retreat volume of the piston rod 23 retreating from the inner tube 12 in the extension side 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 via 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 amount of (ΔS1−ΔS2) in the oil discharge amount from the annular oil chamber 17 Is discharged to the oil reservoir 22 through the minute flow path 70.
[0028]
In the extension side stroke, as described above, the extension side damping force is generated by the passage resistance of the bypass passage 45 whose opening is adjusted by the needle valve 44 in the low speed range, and the bending of the extension side disc valve 42A in the middle and high speed range. Deformation generates an extension-side damping force. In addition, the extension-side damping force due to the passage resistance of the minute flow channel 72 is also generated.
[0029]
According to the present embodiment, the following operations are provided.
(Action corresponding to claim 1)
(1) The cross-sectional area S1 of the annular oil chamber 17 is made larger than the cross-sectional area S2 of the piston rod 23, and the annular gap between the outer tube 11 and the inner tube 12 is smaller than that of S1 and S2. Does not require delicate settings. Therefore, the pressure condition inside the inner tube 12 does not change due to the processing dimensional tolerance of the outer tube 11 and the inner tube 12.
[0030]
(2) According to the above (1), when the piston rods 23 having the same outer diameter are used, even if the inner tube 12 has a large diameter, the annular gap between the outer tube 11 and the inner tube 12 does not necessarily need to be narrowed. No constraints on the design.
[0031]
(3) According to the above (1), when the annular gap between the outer tube 11 and the inner tube 12 is made constant, the outer diameter of the piston rod 23 does not necessarily need to be increased even if the inner tube 12 has a larger diameter. The components of the rod 23 can be shared.
[0032]
{Circle around (4)} In the compression-side stroke, when oil corresponding to the volume of the piston rod 23 entering the inner tube 12 is transferred from the piston rod-side oil chamber 21A of the inner tube 12 to the annular oil chamber 17 via the oil hole 28, The shortage (ΔS1−ΔS2) of the volume increase ΔS1 (required supply amount) of the annular oil chamber 17 is supplied from the oil reservoir 22 via the check valve 60 (the flow path 63).
[0033]
In the extension side stroke, when oil corresponding to the retreat volume of the piston rod 23 retreating from the inner tube 12 is transferred from the annular oil chamber 17 to the piston rod-side oil chamber 21A of the inner tube 12 via the oil hole 28, the annular oil The surplus (ΔS1−ΔS2) of the volume decrease ΔS1 (total discharge amount) of the chamber 17 is discharged to the oil reservoir 22 via the minute flow path 72 opened by the resistance valve 70.
[0034]
{Circle around (5)} The urging force applied by the suspension spring 33 to the resistance valve 70 is small on the whole extension side and large on the contraction side. Therefore, on the full extension side, the micro flow path 72 opened by the resistance valve 70 becomes larger, the hydraulic pressure in the oil chambers (21A, 21B) of the inner tube 12 is low, and the hydraulic oil is liable to generate cavitation. In the compression stroke from near full elongation (near ride 1G), the compression damping force generated by the compression disc valve 41A is reduced, and a soft ride feeling can be obtained. On the other hand, on the contraction side, the minute flow path opened by the resistance valve 70 becomes smaller, the hydraulic pressure in the oil chambers (21A, 21B) of the inner tube 12 becomes high, and the cavitation of the hydraulic oil is suppressed, so that the stroke becomes large. On the most compression side, the compression-side damping force generated by the compression-side disc valve 41A is increased, so that a large input is buffered, and a feeling of flatness (prevention of bottoming) can be obtained. That is, the compression damping force depending on the stroke position can be generated stably and reliably by a simple mechanism.
[0035]
{Circle around (6)} The volume change due to the temperature change of the oil inside the inner tube 12 is also discharged to the oil reservoir 22 through the flow path 63 formed by the check valve 60 and the minute flow path 72 formed by the resistance valve 70. Alternatively, compensation can be made by supplying oil from the oil reservoir 22.
[0036]
As described above, the embodiment of the present invention has been described with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, Are also included in the present invention.
[0037]
【The invention's effect】
As described above, according to the present invention, in the hydraulic shock absorber in which the piston slides on the inner circumference of the inner tube, the pressure-side damping force can have position dependency.
[Brief description of the drawings]
FIG. 1 is a sectional view showing the entire hydraulic shock absorber.
FIG. 2 is a sectional view showing a main part of FIG. 1;
FIG. 3 is an enlarged sectional view showing a main part of FIG. 2;
FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2;
FIG. 5 is a perspective view showing a check valve.
[Explanation of symbols]
Reference Signs List 10 hydraulic shock absorber 11 outer tube 11A bush 12 inner tube 12A bush 17 annular oil chamber 19 partition member 21 oil chamber 21A piston rod side oil chamber 21B piston side oil chamber 22 oil storage chamber 23 piston rod 26 piston 28 oil hole 33 suspension spring 41A compression side disc valve (compression side damping force generating means)
51, 52 Oil passage 60 Check valve 70 Resistance valve

Claims (1)

The inner tube is slidably inserted into the outer tube via bushes fixed to the inner tube opening and the outer tube distal end, respectively,
Defining an annular oil chamber surrounded by the inner periphery of the outer tube, the outer periphery of the inner tube, and the two bushes;
A partition member is provided on the inner periphery of the inner tube, and an oil chamber is defined at a lower portion, and an oil reservoir is defined at an upper portion,
A piston rod attached to the outer tube is slidably inserted into the partition member,
A piston that slides in contact with the inner periphery of the inner tube is fixed to a distal end of a piston rod inserted into the inner tube, and the oil chamber is a piston rod-side oil chamber in which the piston rod is housed and a piston in which the piston rod is not housed. Partitioned into the side oil chamber,
In a vehicle hydraulic shock absorber provided with a compression-side damping force generating means on the piston,
The annular oil chamber is always in communication with the piston rod-side oil chamber via an oil hole provided in the inner tube,
Forming a cross-sectional area of the annular oil chamber larger than a cross-sectional area of the piston rod;
The partition member is provided with two oil passages, one of the oil passages is provided with a check valve for preventing a flow from the piston rod-side oil chamber to the oil storage chamber during the extension stroke, and the other oil passage is provided with the piston rod. A hydraulic shock absorber for a vehicle, comprising: a resistance valve for providing resistance to the flow from the side oil chamber to the oil reservoir, wherein the resistance valve is biased at a lower end of a suspension spring.

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