JP2001059539A - Damping force generating structure of hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate upper zone damping force higher than a normal zone of stroke by fixing an auxiliary seal to an inner surface of a cylinder, and discharging a flow quantity which raising speed is multiplied by a pressure receiving area of a bush to an upper chamber since the bush is connected to a piston rod, and generating auxiliary damping force. SOLUTION: In association with raising of a piston rod 100, a bush 102 is entered to an upper zone Su of stroke, and communication between an upper chamber A and an auxiliary chamber E is shut out when the bush 102 is fitted to an inner circumferential lip 101A of an auxiliary seal 101. When the piston rod 100 is further raised, operating oil having a flow quantity which piston speed is multiplied by a pressure receiving area of the bush 102 is discharged from the auxiliary chamber E to the upper chamber A since the bush 102 is connected to the piston rod 100, and auxiliary damping force is generated by a passage resistance. In an upper zone of stroke, auxiliary damping force is applied to normal expanding side damping force, and upper zone damping force which is larger than the normal zone of stroke is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force generating structure for a hydraulic shock absorber which suppresses vibration of a vehicle body such as a suspension system of a motor vehicle, and more particularly to an extension damping when a piston enters a region above or below a stroke. The present invention relates to a structure for increasing a force or a compression damping force.

[0002]

2. Description of the Related Art As this type of hydraulic shock absorber, for example, the one shown in FIG. 4 is known. First, an outline of the structure will be described with reference to the drawings. The hydraulic shock absorber mounted between the vehicle body and the wheels via a coupling member includes a piston rod 1
The expansion side damping valve PV is mounted on the outer cylinder 22, and the cylinder 21 having the lower end mounted with the compression side damping valve BV is housed in the outer cylinder 22, and the seal 23 and the rod guide 24 for shutting off the outside air are assembled. After the accommodated packing case 25 is inserted from above the outer cylinder 22, the upper end of the outer cylinder 22 is sealed by welding all around. A tank chamber D storing hydraulic oil is formed between the cylinder 21 and the outer cylinder 22 at a lower portion.

In the so-called extension stroke in which the piston rod 1 rises in the cylinder 21 filled with hydraulic oil, the hydraulic oil in the closed upper chamber A flows out to the lower chamber B via the extension damping valve PV. At this time, the extension side damping force is generated by the passage resistance. Hydraulic oil corresponding to the piston rod withdrawal volume that is insufficient due to the rise of the piston rod 1 is transferred from the bottom chamber C connected to the tank chamber D to the lower chamber B via a pressure-side damping valve BV disposed at the lower end of the cylinder 21. Inhaled.

Next, the extension damping valve PV of the hydraulic shock absorber will be described. A base end of a cap 3 having several support legs, each of which has an outer cylinder portion cut out as passages for hydraulic oil, is fitted into the outer surface of the valve stopper 2. The supporting leg of the cap 3 has a disk 5 which is urged from the back by a valve spring 4 to fit on the outer surface of the valve stopper 2 so as to be vertically movable, and a lower end surface of an inner cylindrical portion of an opening window 5B on the lower surface of the disk 5. A leaf valve 6 on the disc 5 side and a notched leaf valve 7 on the seat surface 8C are provided between the annular seat surface 8C of the piston 8 around which the guide 8D is wound around the outer surface 5C.
Are superimposed and housed in an openable and closable manner.

[0005] With the support legs of the cap 3 containing these parts fitted on the outside of the annular seat surface 8C provided on the upper surface of the piston 8, the support legs are inserted into the spigot portion 1A of the piston rod, Finally, the piston nut 9 is screwed onto the thread portion of the spigot portion 1A of the piston rod, and tightened with a specified tightening torque, so that the extension-side damping valve PV
Is configured.

In the so-called low-speed range in which the piston speed is small and the pressure difference between the upper chamber A and the opening 8B at the top of the piston is small during the extension stroke in which the piston rod 1 rises,
There is a seat surface 8 between the upper chamber A and the opening 8B at the top of the piston.
4 (C), which communicates via the notch 7A of the notch leaf valve 7 shown in FIG. 4 (C), the pressure oil passing through the notch 7A passes through the port 8A formed in the piston 8. Then, it is released to the lower chamber B, and the extension side damping force in the low speed region is generated by the passage resistance at this time.

[0007] As the piston speed increases and approaches the medium speed range, the pressure difference between the upper chamber A and the opening 8B at the upper part of the piston increases. As a result, the inner peripheral side of the notched leaf valve 7 and the leaf valve 6 shown in FIG. 4B, which is disposed on the upper surface of the notch, overcomes the combined flexural rigidity of these leaf valves and the lower surface of the disk. Is opened from the lower end surface 5C of the inner cylindrical portion of the opening window 5B, and the hydraulic oil in the upper chamber A is released to the opening 8B through the through hole 5A of the disk 5. The released hydraulic oil flows out into the lower chamber B through the port 8A of the piston, and generates an extension damping force as shown by a solid line in FIG. 3 due to the passage resistance at this time.

The above description is based on the cylinder 2 filled with hydraulic oil.
In the so-called compression stroke in which the piston rod 1 rises in the piston rod 1, a part of the hydraulic oil in the sealed lower chamber B is partially removed by the port 8 A of the piston 8 in the so-called compression stroke in which the piston rod 1 descends. Through the notch leaf valve 7 and the outer peripheral side of the leaf valve 6 with the seat surface 8C of the piston 8
And is replenished to the upper chamber A which becomes a negative pressure. The hydraulic oil in the lower chamber B excluding this portion flows out to the bottom chamber C via a pressure-side damping valve BV mounted on the lower end of the cylinder 21, and generates a pressure-side damping force due to the passage resistance at this time.

Next, the compression side damping valve BV mounted on the lower end of the cylinder 21 will be described. A disk 13, which is urged from the back by a valve spring 12 and is guided in a vertically movable manner, is provided on the support leg of the cap 11 in which the outer cylinder portion is cut out at several places as passages for hydraulic oil. As shown in FIG. 4, the disk side is located between the inner peripheral seat surface 13C of the opening window 13B connected to the through hole 13A and the annular seat surface 16A formed on the upper surface of the valve case 16.
FIG. 4 shows a leaf valve 14 similar to FIG.
A notched leaf valve 15 similar to that shown in FIG. 3C is overlapped and held so as to be openable and closable, and several support legs of the cap 11 containing these components are pressed into the lower end of the cylinder 21. The compression side damping valve BV is formed by being fitted to the outer peripheral side of the seat surface 16A of the valve case 16.

In the low-speed range of the piston speed in the pressure-side stroke in which the piston rod 1 descends, the pressure oil in the lower chamber B excluding the portion replenished to the upper chamber A is a notched leaf partially cut off on the outer peripheral side. The fluid flows out to the bottom chamber C through the notch 15A of the valve 15, and a pressure-side damping force in a low-speed region is generated by the passage resistance at this time.

In the middle speed range and thereafter, where the piston speed increases, the pressure oil guided from the lower chamber B to the opening window 13B through the through hole 13A of the disc 13 is superimposed on the notched leaf valve 15 and the cut valve. The opened inner circumference of the leaf valve 14 is pushed open to discharge the working oil corresponding to the volume entered by the piston rod 1 from the lower chamber B to the bottom chamber C, and due to the passage resistance at that time, as shown by the solid line in FIG. Generates compression-side damping force.

Conversely, during the extension stroke in which the piston rod 1 rises, the leaf valve 14 is guided by the support leg of the cap 11 so as to be able to move up and down, and is urged by the valve spring 12 via the disc 13. Leaf valve 15
Of the piston rod 1 is sucked into the lower chamber B, which has a negative pressure, from the bottom chamber C connected to the tank chamber D.

[0013]

As described above, in the low-speed range of the piston speed, the hydraulic oil on the upstream side passes through the notch of the cut-out leaf valve, which is partially cut off on the outer peripheral side, and also in the middle-speed range. Thereafter, in addition to this passage, the notched leaf valve and the inner peripheral side of the leaf valve superposed thereon are pushed open to flow downstream, and a damping force is generated by the passage resistance at this time. This damping force is substantially constant over the entire stroke as shown by the solid line in FIG. If the damping force is reduced in order to improve the riding comfort of the vehicle, the damping of the large amplitude vertical vibration when passing through the undulation of the road is insufficient, so that the piston approaches the upper or lower limit of the stroke, so-called. Excessive stretching or bottoming occurs, which degrades the riding comfort of the vehicle.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the damping force when the piston enters the upper region or the lower region of the stroke as compared with the normal region of the stroke. To provide a hydraulic shock absorber that can be made even higher.

[0015]

According to the present invention, there is provided an apparatus for dividing a cylinder into an upper chamber and a lower chamber, and using a piston nut to extend a damping valve provided on a piston slidably guided in the cylinder. A compression damping valve that couples to the lower end of the piston rod to control the extension damping force when the piston rod is extended and that partitions the inside of the cylinder into a lower chamber and a bottom chamber that communicates with the tank chamber at the lower end of the cylinder And a hydraulic shock absorber that controls the compression side damping force when the piston rod contracts.

A first means adopted by the present invention to solve the problem is that a bush having a larger outer diameter than the piston rod is connected to the piston rod side above the expansion damping valve, An auxiliary seal having an auxiliary orifice penetrating up and down is fixed, and an upper chamber and an auxiliary chamber formed corresponding to an upper region of the stroke are partitioned, and a normal stroke of the auxiliary chamber is opened. In the region, the flow rate obtained by multiplying the pressure receiving area of the upper chamber by the rising speed of the piston rod is supplied to the expansion damping valve to generate a normal expansion damping force, while the bush connected to the piston rod has a stroke of the stroke. When the bush enters the upper region, the bush fits into the inner peripheral lip of the auxiliary seal to shut off between the upper chamber and the auxiliary chamber, and the flow rate obtained by multiplying the pressure receiving area of the bush by the ascending speed is used. And discharged into the upper chamber from the auxiliary chamber through the secondary orifice to generate an auxiliary damping force, by adding the auxiliary damping force extension damping force of the normal,
Generating an upper band damping force that is greater than the normal region of the stroke. "

Next, the second means is that "a bush having an outer orifice penetrating vertically above the expansion damping valve and having a larger outer diameter than the piston rod is connected to the piston rod side, and The auxiliary seal is fixed to the upper chamber, and an upper chamber and an auxiliary chamber formed corresponding to the upper area of the stroke are partitioned, and in a normal area of the stroke in which the auxiliary chamber is open, the upper chamber has a pressure receiving area. While supplying the flow rate multiplied by the rising speed of the piston rod to the extension damping valve to generate a normal extension damping force, when the bush connected to the piston rod enters the upper region of the stroke, The bush is fitted to the inner peripheral lip of the auxiliary seal to shut off the space between the upper chamber and the auxiliary chamber, and the flow rate obtained by multiplying the pressure receiving area of the bush by the ascending speed is passed through the auxiliary orifice. By generating an auxiliary damping force by discharging from the auxiliary chamber to the upper chamber and adding the auxiliary damping force to the normal extension side damping force, generating an upper region damping force larger than a normal region of the stroke. ".

Subsequently, a third means is that "an auxiliary seal is fixed to the inner surface of the cylinder above the compression side damping valve, and the lower chamber and an auxiliary chamber formed corresponding to a lower region of the stroke are formed. In the normal region of the stroke where the auxiliary chamber is open, the flow rate obtained by multiplying the cross-sectional area of the piston rod by the descending speed of the piston rod is supplied to the compression damping valve to generate a normal compression damping force. On the other hand, when the piston rod enters the lower part of the stroke, the expanded portion of the piston nut, which is connected to the lower end of the piston rod and has a larger outer diameter than the piston rod, is attached to the inner peripheral lip of the auxiliary seal. By fitting and shutting off the lower chamber and the auxiliary chamber, and supplying the flow rate obtained by multiplying the cross-sectional area of the enlarged diameter portion of the piston nut by the lowering speed to the pressure-side damping valve, the normal range of the stroke is achieved. Base and is larger for generating lower band attenuation force. "

On the upper side of the auxiliary seal of the cylinder, a side hole communicating the lower chamber and the tank chamber is provided, and in a normal region of a stroke in which the auxiliary chamber is opened, the side hole of the cylinder is connected to the auxiliary hole. While the check band fitted over the seal covers the inside of the cylinder from the inside, when the piston rod descends in the lower part of the stroke, the check band is pushed inward through this side hole to open the lower part from the tank chamber. Refill the chamber directly with hydraulic oil. This effect can be achieved even if the check band is integral with the auxiliary seal.

A fourth means is that a bush having a larger outer diameter than the piston rod is connected to the piston rod side above the extension-side damping valve, and an outer peripheral groove penetrating vertically is formed on the inner surface of the cylinder. A collar having an auxiliary orifice communicating with the outer peripheral groove is fixed, and an upper chamber and an auxiliary chamber formed on the inner peripheral side of the collar corresponding to the upper region of the stroke are partitioned, and the auxiliary chamber is opened. In the normal range of the stroke, the flow rate obtained by multiplying the pressure receiving area of the upper chamber by the rising speed of the piston rod is supplied to the expansion damping valve to generate a normal expansion damping force, while being coupled to the piston rod. When the bush enters the upper region of the stroke, the bush fits on the inner peripheral side of the collar to shut off the space between the upper chamber and the auxiliary chamber, and multiplies the pressure receiving area of the auxiliary chamber by the ascending speed. Flow Is discharged from the auxiliary chamber to the upper chamber through the auxiliary orifice to generate an auxiliary damping force, and the auxiliary damping force is added to the normal extension-side damping force, so that the stroke is larger than the normal stroke. To generate an upper damping force ”.

Finally, the fifth means is that “a cylinder is provided with a side hole above the compression side damping valve, which communicates the lower chamber with the tank chamber, and the cylinder inner surface covers the side hole from the inside. A collar in which a check band to be perforated is loosely fitted in an outer peripheral groove is fixed, and a lower chamber and an auxiliary chamber formed on the inner peripheral side of the collar corresponding to a lower region of the stroke are partitioned, and the auxiliary chamber is opened. In the normal range of the stroke, the flow rate obtained by multiplying the cross-sectional area of the piston rod by the descending speed of the piston rod is supplied to the compression-side damping valve to generate a normal compression-side damping force. When entering the region, the expanded portion of the piston nut, which is connected to the lower end portion of the piston rod and has a larger outer diameter than the piston rod, fits on the inner peripheral side of the collar and is between the lower chamber and the auxiliary chamber. Blocking the passage, by supplying the flow obtained by multiplying the descent velocity to the pressure receiving area of the auxiliary chamber to the compression side damping valve is possible to generate a normal large downward band attenuation force than the region of the stroke. "

A side hole of the cylinder communicating the lower chamber and the tank chamber is covered from the inside of the cylinder by a check band loosely fitted to the collar in a normal region of the stroke, while a piston rod is formed by a piston rod in a lower region of the stroke. When descending, the check band is pushed inward through the side holes to open and replenish the hydraulic oil directly from the tank chamber to the lower chamber. If a seal is attached to the expanded portion of the bush and the piston nut, the damping force in the upper region and the lower region of the stroke can be stabilized.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic shock absorber according to the present invention has the same basic structure as the prior art shown in FIG.
00 is movably inserted into the cylinder 121 via the extension-side damping valve PV mounted on the lower end thereof, and defines an upper chamber A and a lower chamber B. Also, cylinder 1
A pressure-side damping valve BV is provided at the lower end of the lower chamber 21, and also partitions a lower chamber B and a bottom chamber C.

In order to solve the problem of the prior art, the damping force when the hydraulic shock absorber expands and contracts in the upper region Su or the lower region Sd of the stroke, as shown by the broken line in FIG. Higher than the damping force shown by the solid line
The piston speed may be reduced in the upper region Su or the lower region Sd of the stroke. Hereinafter, the first embodiment of the present invention will be described with reference to the main part sectional view of FIG. 1A shown in the left half section of FIG.

First, a description will be given from the upper side Su side of the stroke. The difference from the hydraulic shock absorber described in the prior art is that an auxiliary seal 101 in which a bush 102 having a larger outer diameter than the piston rod 100 is coupled to the upper side of the extension damping valve PV and an auxiliary orifice 101C penetrating vertically is provided.
Is fixed to the inner surface of the cylinder 121 above the extension-side damping valve PV by press-fitting, punching, or caulking, thereby partitioning the upper chamber A and the auxiliary chamber E corresponding to the upper region Su of the stroke. . In the normal range Sn of the stroke,
Since the bush 102 and the auxiliary seal 101 do not fit, the inner peripheral lip 101A of the auxiliary seal 101 is open.

In the first embodiment, the auxiliary seal 101 is provided with the auxiliary orifice 101C.
1B shown in the right half section of FIG.
Instead of using the auxiliary seal 201 without the auxiliary orifice, a bush 202 having a larger outer diameter than the piston rod 100 is fixed above the extension-side damping valve PV, and an auxiliary orifice 202A is provided on the bush 202 side to provide an inner peripheral passage. The upper and lower sides of the bush 202 may be communicated via the 202B. The function of the auxiliary orifice 202A is the same as that of the auxiliary orifice 101C of the first embodiment.

In the following, items common to the upper side Su of the stroke in the first and second embodiments will be described in the form of the first (second) embodiment by appropriately dividing numbers. 1st (2nd)
In any of the embodiments, when the piston 8 moves up and down in the normal range Sn of the stroke, the upper chamber A and the auxiliary chamber E on the upper side of the extension damping valve PV and the lower chamber B and the auxiliary chamber F on the lower side are Since both are in communication, similar to the prior art,
A normal damping force is generated as shown by the solid line in FIG.

As the piston rod 100 rises, the bush 102 (202) enters the upper region Su of the stroke, and the inner peripheral lip 101A of the auxiliary seal 101 (201).
When fitted to (201A), the space between the upper chamber A and the auxiliary chamber E is shut off. When the piston rod 100 is further raised, the bush 102 (202) is connected to the piston rod 100, so that the pressure receiving area of the bush 102 (202) (= the outer diameter cross-sectional area of the bush-the cross-sectional area of the piston rod).
Is multiplied by the piston speed, and is discharged from the auxiliary chamber E to the upper chamber A via the auxiliary orifice 101C (202A) of the auxiliary seal (bush), and an auxiliary damping force is generated by the passage resistance at this time. . That is, in the upper region Su of the stroke, the auxiliary damping force is added to the normal extension side damping force to generate an upper region damping force larger than the normal region Sn of the stroke as shown by the broken line in FIG.

Hydraulic oil is replenished from the bottom chamber C to the lower chamber B and the auxiliary chamber F, which become negative pressures as the piston rod 100 rises, via the pressure-side damping valve BV. Conversely, when the piston rod 100 descends from the upper region Su of the stroke, the bush 1 connected to the piston rod 100
02 (202) descends at the same elongation speed, so that the auxiliary chamber E, which becomes negative pressure, pushes open the inner peripheral lip 101A (201A) of the auxiliary seal 101 (201) and replenishes hydraulic oil from the upper chamber A. Is done.

In any of the embodiments, the auxiliary seal 101 (201) is fixed to a predetermined height on the inner surface of the cylinder 121 by press-fitting, punching or caulking with a roll. If a thin rubber film is formed on the outer peripheral side, the cylinder 121 can be firmly fixed without damaging the inner surface.

Next, the lower side Sd side of the stroke will be described. The difference from the hydraulic shock absorber described in the prior art is that the inner surface of the cylinder 121 above the compression side damping valve BV
Lower chamber B and auxiliary chamber F corresponding to lower area Sd of stroke
And a check band 104 is fitted over the auxiliary seal 103. In the normal range Sn of the stroke, the inner peripheral lip 103A of the auxiliary seal 103 fixed to the inner surface of the cylinder 121 by press-fitting, punching or roll-tightening is opened, and the cylinder 12
Side hole 121A drilled near the lower region of one stroke
Are covered with a check band 104 from the inside.

In the first embodiment, the case where the auxiliary seal 103 and the check band 104 are separate parts has been described. However, the auxiliary seal 103 and the check band 104 are separate parts as shown in FIG. As shown in the seal 203, the auxiliary seal body and the check lip 203C may be integrally formed. The function of the check lip 203C is the same as that of the check band 104 of the first embodiment, which is a separate and separate component.

Hereinafter, matters common to the lower region Sd side of the stroke in the first and second embodiments will be described by appropriately dividing numbers in the form of the first (second) embodiment. 1st (2nd)
In any of the embodiments, when the piston 8 moves up and down in the normal range Sn of the stroke, the upper chamber A and the auxiliary chamber E on the upper side of the extension damping valve PV and the lower chamber B and the auxiliary chamber F on the lower side are Since both are in communication, similar to the prior art,
A normal damping force is generated as shown by the solid line in FIG.

When the enlarged diameter portion 109A of the piston nut 109 having a diameter larger than that of the piston rod 100 enters the lower region Sd of the stroke and is fitted to the inner peripheral lip 103A (203A) of the auxiliary seal 103 (203), the lower chamber is lowered. The connection between B and the auxiliary chamber F is shut off. When the piston rod 100 further descends, the piston nut 109 moves to the piston rod 1
00, the enlarged diameter portion 1 of the piston nut
Hydraulic oil of a flow rate obtained by multiplying the pressure receiving area of 09A by the piston speed is supplied to the compression side damping valve BV. At this time, the lower region damping force larger than the normal region Sn of the stroke as shown by the broken line in FIG. Occurs.

The lower chamber B, which communicates with the upper chamber A whose volume decreases with the lowering of the piston rod 100 via the extension damping valve PV, has a check band covering the side hole 121A of the cylinder from the inside. 104 (check lip 203
C) is pushed inward and hydraulic oil is replenished from the tank chamber D.

Assuming that the outer diameter of the piston rod 100 is Dr and the outer diameter of the expanded portion 109A of the piston nut is Dp, the flow rate Qd passing through the compression side damping valve BV in the lower stroke area Sd is the flow rate in the normal stroke Sn area of the stroke. Qd = Qn (Dp / Dr) ² = Qn × k That is, k ｛= (Dp / Dr) ² ｝ times Qn. The size of the hydraulic shock absorber is, for example, Dr = 12.5 mm, Dp = 18 mm
In the case of, k = 2.1.

The fact that the flow rate Qd in the lower stroke area becomes k times the flow rate Qn in the normal area corresponds to the fact that the piston speed has increased k times. The area damping force is equal to the damping force at a piston speed of V × k times the normal damping force curve shown by the solid line in FIG. 3, and becomes larger than the normal damping force as shown by the broken line in FIG.

On the other hand, when the piston rod 100 reverses and extends from the lower region Sd of the stroke, the hydraulic oil in the upper chamber A whose volume decreases is discharged to the lower chamber B through the expansion damping valve PV, The extension side damping force is generated by the passage resistance at this time. At this time, in the section where the auxiliary seal 103 (203) and the enlarged diameter portion 109A of the piston nut are fitted, the pressure of the sealed lower chamber B increases, so that the check band covering the side hole 121A of the cylinder 121 is formed. 104 (check lip 203C) is pushed inward to open the tank chamber D
Hydraulic fluid is replenished without delay.

In any of the embodiments, the auxiliary seal 103 (203) is fixed at a predetermined height in a lower portion of the stroke of the inner surface of the cylinder by press-fitting, punching, or caulking with a roll. 203
If a thin rubber film is formed on the outer peripheral side of B), the cylinder 12
1 can be firmly fixed without damaging the inner surface.

In the first (second) embodiment, the case where the auxiliary seal 103 (203) is fixed to the inner surface of the cylinder has been described. However, as shown in the third embodiment in FIG.
Similar actions and effects can be obtained by using the collar 301 fixed to the inner surface of the cylinder 121 instead of the auxiliary seal. Next, a third embodiment of the present invention will be described with reference to the main part sectional view of FIG.

First, a description will be made from the upper side Su of the stroke. The difference from the hydraulic shock absorber described in the prior art is that a bush 30 is provided above the extension damping valve PV on the piston rod side.
2 and a seal 301 is mounted in an annular groove 302B provided in the enlarged diameter portion 302A of the bush, and a collar 301 is provided with an outer peripheral groove 301B penetrating vertically and an auxiliary orifice 301A communicating with the outer peripheral groove 301B. Is brought into contact with the lower end of the rod guide 124 and is fixed to the inner surface of the cylinder 321 by press-fitting, punching or roll caulking or the like, thereby dividing the upper chamber A and the auxiliary chamber E corresponding to the upper region Su of the stroke. is there. In the normal region Sn of the stroke where the bush 302 and the collar 301 do not fit,
The inner peripheral side (auxiliary chamber E) of the collar 301 is open.

In the third embodiment, the bush 3
Although the seal 303 is mounted on the side 02,
Is for reducing leakage of a gap in a section where the enlarged diameter portion 302A of the bush and the inner peripheral side of the collar 301 are fitted. If the fitting gap is reduced, the seal 303 can be omitted.

Hereinafter, matters relating to the upper side Su of the stroke in the third embodiment will be described. When the piston 8 moves up and down in the normal range Sn of the stroke, the upper chamber A and the auxiliary chamber E on the upper side of the extension-side damping valve PV and the lower chamber B and the auxiliary chamber F on the lower side are both in communication with each other. As with the prior art,
A normal damping force is generated as shown by the solid line in FIG.

The bush 302 fixed to the piston rod 100 penetrates into the upper region Su of the stroke, and the seal 303 fitted in the annular groove 302B provided in the expanded portion 302A of the bush fits on the inner peripheral side of the collar 301. Then, the space between the upper chamber A and the auxiliary chamber E is shut off. Piston rod 10
When 0 further increases, the hydraulic oil at a flow rate obtained by multiplying the pressure receiving area of the bush 302 (= the inner peripheral cross-sectional area of the collar-the cross-sectional area of the piston rod) by the piston speed passes through the auxiliary orifice 301A and the outer peripheral groove 301B of the collar. As a result, the air is discharged from the auxiliary chamber E to the upper chamber A, and an auxiliary damping force is generated by the passage resistance at this time.

As a result, in the upper region Su of the stroke,
As shown by the broken line in FIG. 3, the auxiliary damping force is added to the normal extension-side damping force to generate an upper-range damping force larger than the normal region Sn of the stroke.

The lower chamber B and the auxiliary chamber F, each of which has a negative pressure as the piston rod 100 rises, are replenished with hydraulic oil from the bottom chamber C via a pressure-side damping valve BV. Conversely, when the piston rod 100, to which the bush 302 is connected, descends from the upper region Su of the stroke, the auxiliary chamber E, which is under negative pressure, has the outer peripheral groove 301B of the collar and the auxiliary orifice 301A.
, Hydraulic oil is replenished from the upper chamber A.

Next, the lower region Sd side of the stroke will be described. The difference from the hydraulic shock absorber described in the related art is that the inner surface of the cylinder 321 above the compression side damping valve BV has
The collar 304 in which the check band 305 is loosely fitted is fixed by press-fitting, punching, or caulking with a roll, or the like, to partition the auxiliary chamber F corresponding to the lower stroke area Sd. On the side of the cylinder 321 facing the check band 305, a side hole 321A communicating with the tank chamber D is formed, and the side hole 321A is formed by the check band 305.
Is covered from the inside. The groove into which the check band 305 is loosely fitted is designed to be slightly larger than the cross-sectional area of the check band to allow the check band 305 to be deformed inward.

The piston rod 100 enters the lower region Sd of the stroke, and the expanded portion 309 of the piston nut 309
When the seal 303 made of a resin or rubber material and housed in the annular groove 309C provided in A is fitted on the inner peripheral side of the collar 304, as illustrated in FIG.
The seal 303 is located on the lower chamber B side (annular groove 309C) where negative pressure
309B from the auxiliary chamber F to the communication hole 309B.
Is closed to the lower chamber B through the lower chamber B
And the auxiliary chamber F is shut off.

When the piston rod 100 further descends,
Hydraulic oil at a flow rate obtained by multiplying the pressure receiving area of the auxiliary chamber F by the piston speed is supplied to the pressure-side damping valve BV. At this time, a lower region larger than the normal region Sn of the stroke as shown by the broken line in FIG. Generates damping force.

A check band which covers the side hole 321A of the cylinder from the inside is provided in the lower chamber B which communicates with the upper chamber A whose volume increases with the lowering of the piston rod 100 via the extension damping valve PV. 305 is pushed inward and hydraulic oil is replenished from the tank chamber D via the passage 304A above the collar.

Conversely, when the piston rod 100 extends in the reverse direction from the lower region Sd of the stroke, the hydraulic oil in the upper chamber A whose volume decreases is discharged to the lower chamber B through the expansion damping valve PV, The extension side damping force is generated by the passage resistance at this time. At this time, in the section where the collar 304 and the seal 303 are fitted, the pressure of the sealed lower chamber B increases, so that
As illustrated in the right half section of FIG.
3 is pushed down below the annular groove 309C (on the auxiliary chamber F side), and the hydraulic oil is discharged from the lower chamber B to the auxiliary chamber F via the annular groove 309C and the communication hole 309B. Hydraulic oil is replenished from the bottom chamber C to the auxiliary chamber F, which becomes a negative pressure, via the pressure-side damping valve BV.

[0052]

As described in detail above, the first (second) embodiment of the present invention.
According to the embodiment, the auxiliary seal is fixed to the cylinder side above the extension-side damping valve (compression-side damping valve), and when the piston rod enters the upper region (lower region) of the stroke,
The bush (expanded portion of the piston nut) fits into the inner peripheral lip of the auxiliary seal, and the piston rod further moves up (down)
Then, the hydraulic oil having a flow rate obtained by multiplying the pressure receiving area of the bush (the enlarged diameter portion of the piston nut) by the piston speed flows from the auxiliary chamber to the upper chamber via the auxiliary orifice (from the auxiliary chamber to the bottom chamber via the pressure-side damping valve). It is discharged, and an upper region (lower region) damping force larger than the normal region of the stroke is generated by the passage resistance at this time. Next, according to the third embodiment of the present invention, when the piston rod enters the upper region (lower region) of the stroke, the enlarged diameter portion of the bush (piston nut) fits on the inner peripheral side of the collar. When the piston rod further rises (falls), the hydraulic oil of a flow rate obtained by multiplying the pressure receiving area of the enlarged diameter portion of the bush (piston nut) by the piston speed flows from the auxiliary chamber through the auxiliary orifice to the upper chamber (the pressure side damping from the auxiliary chamber). It is discharged to the bottom chamber through a valve, and the passage resistance at this time generates a lower region damping force larger than the normal region of the stroke. In any of the above embodiments, the upper region (lower region) of the stroke generated in the upper region (lower region) of the stroke is applied as a reaction force to the piston rod as a reaction force. The ascending (falling) speed of the piston rod, which has risen (falled) to (lower region), is quickly reduced, preventing the hydraulic shock absorber from being fully extended (bottom striking) and improving the riding comfort of the vehicle. .

[Brief description of the drawings]

FIG. 1A is a left half sectional view of a hydraulic shock absorber according to a first embodiment of the present invention. (B) It is a right half sectional view of the hydraulic shock absorber concerning a 2nd embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a hydraulic shock absorber according to a third embodiment of the present invention. (A) is a state diagram when the seal enters the upper region (lower region) of the stroke. (B) A state diagram when the seal exits from the upper region (lower region) of the stroke.

FIG. 3 shows damping force characteristics of a normal region, an upper region, and a lower region of the hydraulic shock absorber according to the present invention.

FIG. 4A is a longitudinal sectional view of a hydraulic shock absorber according to the related art. (B) It is a top view of the notch leaf valve based on a prior art. (C) It is a top view of the lower leaf valve concerning a prior art.

[Explanation of symbols]

 Reference Signs List A Upper chamber B Lower chamber C Bottom chamber D Tank chamber E, F Auxiliary chamber PV Extension damping valve BV Pressure damping valve Sd Lower range of stroke Sn Normal range of stroke Su Upper range of stroke 100 Piston rods 101, 201, 103, 203 Auxiliary seal 101A, 201A, 103A, 203A Inner peripheral lip 104 Check band 101C, 202A Auxiliary orifice 102, 202, 302 Bush 109, 309 Piston nut 109A, 309A Expanded portion of piston nut 121, 321 Cylinder 121A, 321A Cylinder Side hole 301, 304 Collar 301A Auxiliary orifice 303 Seal

Claims (8)

[Claims] 1. The interior of a cylinder is partitioned into an upper chamber and a lower chamber.
The extension damping valve provided on the piston slidably guided in the cylinder is connected to the lower end of the piston rod by a piston nut to control the extension damping force when the piston rod extends, A hydraulic shock absorber that fits a pressure-side damping valve that partitions the inside into a lower chamber and a bottom chamber that communicates with the tank chamber at the lower end of the cylinder, and controls a compression-side damping force when the piston rod contracts; Above the damping valve, a bush having a larger outer diameter than the piston rod is connected to the piston rod side, and an auxiliary seal with an auxiliary orifice penetrating vertically is fixed to the inner surface of the cylinder, and the upper chamber and the stroke are fixed. An auxiliary chamber formed corresponding to the upper area is partitioned, and in a normal area of a stroke in which the auxiliary chamber is open, the piston lock is applied to the pressure receiving area of the upper chamber. While the flow rate multiplied by the rising speed of the piston rod is supplied to the extension damping valve to generate a normal extension damping force, when the bush connected to the piston rod enters the upper region of the stroke, Is fitted into the inner peripheral lip of the auxiliary seal to shut off the space between the upper chamber and the auxiliary chamber, and discharges the flow rate obtained by multiplying the pressure receiving area of the bush by the rising speed from the auxiliary chamber to the upper chamber via the auxiliary orifice. Generating an auxiliary damping force, and adding the auxiliary damping force to the normal extension-side damping force, thereby generating an upper region damping force larger than a normal region of a stroke. Damping force generating structure. 2. The interior of the cylinder is partitioned into an upper chamber and a lower chamber.
The extension damping valve provided on the piston slidably guided in the cylinder is connected to the lower end of the piston rod by a piston nut to control the extension damping force when the piston rod extends, A hydraulic shock absorber that fits a pressure-side damping valve that partitions the inside into a lower chamber and a bottom chamber that communicates with the tank chamber at the lower end of the cylinder, and controls a compression-side damping force when the piston rod contracts; Above the damping valve, an auxiliary orifice penetrating vertically is provided. A bush whose outer diameter is larger than that of the piston rod is connected to the piston rod side, and an auxiliary seal is fixed to the inner surface of the cylinder. And an auxiliary chamber formed corresponding to the area, and in a normal area of the stroke in which the auxiliary chamber is open, the piston rod is provided in the pressure receiving area of the upper chamber. The flow rate multiplied by the rising speed is supplied to the extension damping valve to generate a normal extension damping force, and when the bush connected to the piston rod enters the upper region of the stroke, the bush is By fitting the inner peripheral lip of the auxiliary seal to shut off the space between the upper chamber and the auxiliary chamber, the flow rate obtained by multiplying the pressure receiving area of the bush by the rising speed is discharged from the auxiliary chamber to the upper chamber via the auxiliary orifice. Generating an auxiliary damping force, and adding the auxiliary damping force to the normal extension-side damping force, thereby generating an upper region damping force larger than a normal region of the stroke. Damping force generation structure. 3. The interior of the cylinder is partitioned into an upper chamber and a lower chamber.
The extension damping valve provided on the piston slidably guided in the cylinder is connected to the lower end of the piston rod by a piston nut to control the extension damping force when the piston rod extends, A hydraulic shock absorber that fits a pressure-side damping valve that partitions the inside into a lower chamber and a bottom chamber that communicates with the tank chamber at the lower end of the cylinder to control a compression-side damping force when the piston rod contracts. Above the valve, an auxiliary seal is fixed to the inner surface of the cylinder to partition the lower chamber and an auxiliary chamber formed corresponding to a lower area of the stroke, and a normal area of a stroke in which the auxiliary chamber is open. Then, a flow rate obtained by multiplying the cross-sectional area of the piston rod by the descending speed of the piston rod is supplied to the compression damping valve to generate a normal compression damping force, while the piston rod is struck. When the piston enters the lower region of the roak, the enlarged diameter portion of the piston nut, which is connected to the lower end portion of the piston rod and has a larger outer diameter than the piston rod, fits into the inner peripheral lip of the auxiliary seal and engages in the lower chamber. By supplying the flow rate obtained by multiplying the cross-sectional area of the enlarged diameter portion of the piston nut by the lowering speed to the compression damping valve, a lower damping force greater than the normal stroke area is generated. A damping force generating structure for a hydraulic shock absorber. 4. A side hole communicating the lower chamber and the tank chamber is provided above the auxiliary seal of the cylinder, and the side hole of the cylinder is provided in a normal region of a stroke in which the auxiliary chamber is open. The damping force generating structure for a hydraulic shock absorber according to claim 3, wherein a hole is formed from the inside of the cylinder by a check band fitted on the upper side of the auxiliary seal. 5. The damping force generating structure for a hydraulic shock absorber according to claim 3, wherein the check band is integrated with the auxiliary seal. 6. The interior of the cylinder is partitioned into an upper chamber and a lower chamber.
The extension damping valve provided on the piston slidably guided in the cylinder is connected to the lower end of the piston rod by a piston nut to control the extension damping force when the piston rod extends, A hydraulic shock absorber that fits a pressure-side damping valve that partitions the inside into a lower chamber and a bottom chamber that communicates with the tank chamber at the lower end of the cylinder, and controls a compression-side damping force when the piston rod contracts; Above the damping valve, a bush having a larger outer diameter than the piston rod is connected to the piston rod side, and a collar provided with an outer peripheral groove penetrating vertically and an auxiliary orifice communicating with the outer peripheral groove on the inner surface of the cylinder. The upper chamber and the auxiliary chamber formed on the inner peripheral side of the collar corresponding to the upper region of the stroke are fixed, and the normal stroke of the stroke in which the auxiliary chamber is open is defined. In the region, a flow obtained by multiplying the pressure receiving area of the upper chamber by the rising speed of the piston rod is supplied to the extension damping valve to generate a normal extension damping force,
When the bush connected to the piston rod enters the upper region of the stroke, the bush fits on the inner peripheral side of the collar to shut off the space between the upper chamber and the auxiliary chamber, and the pressure receiving area of the auxiliary chamber Is discharged from the auxiliary chamber to the upper chamber via the auxiliary orifice to generate an auxiliary damping force, and the auxiliary damping force is added to the normal extension side damping force. A damping force generating structure for a hydraulic shock absorber, wherein the damping force generating structure generates a larger damping force in an upper region than in a normal region. 7. The interior of the cylinder is partitioned into an upper chamber and a lower chamber.
The extension damping valve provided on the piston slidably guided in the cylinder is connected to the lower end of the piston rod by a piston nut to control the extension damping force when the piston rod extends, A hydraulic shock absorber that fits a pressure-side damping valve that partitions the inside into a lower chamber and a bottom chamber that communicates with the tank chamber at the lower end of the cylinder to control a compression-side damping force when the piston rod contracts. Above the valve, a cylinder is provided with a side hole communicating with the lower chamber and the tank chamber, and a collar in which a check band that covers the side hole from the inside is loosely fitted in the outer circumferential groove is fixed to the inner surface of the cylinder. A lower chamber and an auxiliary chamber formed on the inner peripheral side of the collar corresponding to the lower area of the stroke, and in the normal area of the stroke where the auxiliary chamber is open, the piston lock is formed. While the flow rate obtained by multiplying the cross-sectional area of the piston rod by the descending speed of the piston rod is supplied to the compression damping valve to generate a normal compression damping force, when the piston rod enters the lower region of the stroke, the piston The enlarged diameter portion of the piston nut, which is connected to the lower end of the rod and has a larger outer diameter than the piston rod, fits on the inner peripheral side of the collar to block the passage between the lower chamber and the auxiliary chamber, and A damping force generating structure for a hydraulic shock absorber, wherein a flow rate obtained by multiplying the pressure receiving area by the lowering speed is supplied to a compression damping valve to generate a lower damping force greater than a normal stroke area. 8. The damping force generating structure for a hydraulic shock absorber according to claim 6, wherein a seal is attached to a bulging portion of the bush and the piston nut.