JP2002195335A - Valve structure of hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic shock absorber capable of smoothly increasing a pressure side rear surface damping force generated on the check valve side of a piston from a very low piston speed range when the hydraulic shock absorber is switched from an extending stroke to a retracting stroke. SOLUTION: Check valves comprising leaf valves 3 are opposed to the upper side opening windows 105D to 105G of a piston 105, and the check valves are energized from the rear surface thereof by a leaf spring 102 having a plurality of support pieces 102D to 102A capable of increasing an energizing force in order according to the opening windows at the upper side opening window 105D with the maximum opening area toward the upper side opening window 105G with the minimum opening area. The upper opening windows are allowed to communicate with a lower chamber through outer peripheral ports 105d to 105g formed in the piston and, when a piston rod is lowered, the check valves are opened in order as a piston speed is increased at a portion corresponding to the upper side opening window 105D with a large opening area and a small opening pressure toward a portion corresponding to the upper side opening window 105G with a small opening area and a large opening pressure. The pressure side rear surface damping force based on a passage resistance from the lower chamber to an upper chamber is increased as the piston speed is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber for suppressing vibration of a vehicle body such as a suspension system of an automobile, and more particularly to an improvement in a damping force generating structure.

[0001]

2. Description of the Related Art As this type of hydraulic shock absorber, for example,
FIG. 4 shows an example in which the technique disclosed in JP-A-3-163234 is applied to the upper surface of a piston. First, an outline of the structure will be described with reference to the drawings. When the hydraulic shock absorber is attached to the vehicle, the vertical relationship is the same as that in FIG. 4. Therefore, the position or position of the member of the hydraulic shock absorber will be described below with reference to the vertical relationship in FIG. 4.

2. Description of the Related Art A hydraulic shock absorber mounted between a vehicle body and a wheel via a connecting member is provided with a piston 5 and a piston valve for controlling an extension-side damping force mounted on a lower end portion of a piston rod 1 mounted on the vehicle body side. A cylinder 21, which is slidably housed and has a base valve for controlling a compression damping force at the lower end, is housed in an outer cylinder 22 attached to the wheel side, and a seal 24 and a rod guide 23 for shutting off outside air are formed. After the accommodated packing case 25 is fitted and inserted from above the outer cylinder 22, the upper end of the outer cylinder 22 is hermetically sealed by welding all around. A tank chamber D is formed between the cylinder 21 and the outer cylinder 22.

[0003] When the piston rod 1 rises in the cylinder 21 filled with hydraulic oil, the hydraulic oil in the closed upper chamber A is supplied to the lower chamber via a piston valve attached to the lower end of the piston rod 1. B, and the passage resistance at this time becomes the extension-side damping force. Hydraulic oil corresponding to the piston rod withdrawal volume that is insufficient due to the rise of the piston rod 1 is supplied to the lower chamber B from the bottom chamber C connected to the tank chamber D via a base valve attached to the lower end of the cylinder 21.

Next, a piston valve for controlling the extension-side damping force will be described. The lower end of the piston rod 1 is provided with a spigot portion 1A having a smaller diameter than the upper portion, in which a valve stopper 2 for regulating the maximum deflection of the check valve CV composed of the leaf valve 3 and an outer peripheral edge of the check valve CV are bent. Ring 7, leaf valve 3, supporting surface of leaf valve 3
Are sequentially inserted.

[0005] A piston 5 having a cylinder 21 partitioned into an upper chamber A and a lower chamber B and having a guide 5S wound around the outer periphery thereof has a structure shown in FIG.
As shown in FIG. 5, a plurality of upper opening windows 5D to 5G whose opening areas are sequentially reduced are provided on the upper surface side. Each upper opening window communicates with the lower chamber B via the outer peripheral port 5A, and a concave portion 5K formed between the upper opening windows.
Communicates with the annular lower opening window 5C via the inner peripheral port 5B.

[0006] Subsequently, a notch leaf valve 4 having a notch 4A on the outer peripheral side facing the lower opening window 5C, and an extension damping valve PV comprising a leaf valve 6 superimposed on the back surface of the notch leaf valve. And a ring seat 7 whose outer peripheral edge is the supporting diameter of the bending of the extension side damping valve PV, and a valve stopper 8 for regulating the maximum deflection of the extension side damping valve PV, and finally the piston nut 9 is screwed into the threaded portion of the spigot portion 1A. And a piston valve is formed by fastening with a tightening tool.

In a so-called extension stroke in which the piston rod 1 rises in the cylinder 21 filled with hydraulic oil, the piston speed is small, and in a so-called low-speed range where the pressure difference between the lower opening window 5C of the piston 5 and the lower chamber B is small. , Extension damping valve P
V covers the lower opening window 5C. Therefore, upper chamber A
Is guided to the lower opening window 5C through the recess 5K on the upper surface of the piston and the inner peripheral port 5B, and through the notch 4A of the notch leaf valve 4 facing the lower opening window 5C. Then, due to the passage resistance at this time, an extension-side damping force in a low-speed range that is approximately proportional to the square of the piston speed is generated.

[0008] As the piston speed increases, the flow rate passing through the notch 4A increases, and the pressure difference between the lower opening window 5C and the lower chamber B also increases. As the piston speed approaches the middle speed range, the outer peripheral side of the extension damping valve PV disposed opposite to the lower opening window 5C overcomes the combined flexural rigidity, and becomes outside the lower opening window 5C. The hydraulic fluid is pushed open from the seat portion, and the hydraulic oil flows into the lower chamber B. At this time, the passage resistance of the inner peripheral port 5B and the passage resistance of the inner peripheral port 5B generate an extension-side damping force in a middle speed region and thereafter. Notched leaf valve 4 and leaf valve 6
By appropriately selecting the flexural rigidity of the expansion-side damping valve PV and the passage area of the inner peripheral port 5B, required damping force characteristics can be obtained.

Next, a base valve for controlling the compression side damping force will be described. First, on the shaft 11A of the guide 11,
A valve stopper 12 for restricting the maximum deflection of the suction valve DV, which comprises a leaf valve 13 and a notched leaf valve 14 provided with a notch 14A on the outer peripheral side; a ring seat 17, the outer peripheral edge of which serves as a support for the deflection of the suction valve DV; The leaf valve 13, a notched leaf valve 14 superimposed below the leaf valve 13, and a valve case 15 whose upper surface faces the notched leaf valve 14 are sequentially fitted.

The lower chamber B is fitted to the lower end of the cylinder 21 and
An inner peripheral port 15B communicating with an annular upper opening window 15D and an annular lower opening window 15C communicating with the lower chamber B is drilled in the valve case 15 that defines the lower chamber C and the bottom case C. An outer peripheral port 15A that communicates the bottom chamber C with the annular outer opening window 15E is drilled.

Subsequently, on the shaft portion 11A of the guide 11, a compression damping valve BV comprising a leaf valve 16 facing the lower opening window 15C of the valve case 15, and further, the outer peripheral edge of the compression damping valve BV is supported. A ring seat 17 having a diameter and a valve stopper 18 for restricting the maximum deflection of the pressure-side damping valve BV are sequentially assembled, and finally, a lower end of the shaft 11A of the guide 11 is swaged with a tool to form a base valve.

In a so-called contraction stroke in which the piston rod 1 descends in the cylinder 21 filled with hydraulic oil, in a so-called low-speed range where the piston speed is small and the pressure difference between the lower opening window 15C of the valve case 15 and the bottom chamber C is small. , The compression side damping valve BV covers the lower opening window 15C. For this reason, the pressure oil in the lower chamber B corresponding to the intrusion volume of the piston rod 1 excluding the amount replenished to the upper chamber A whose volume increases via the piston 5 is reduced by the notch 4 of the notch leaf valve 4.
A, flows out to the bottom chamber C through the outer opening window 15E of the valve case 15 and the outer peripheral port 15A, and generates a pressure-side base damping force in a low speed range proportional to the square of the piston speed due to the passage resistance at this time. .

Here, the piston speed is low and the piston 5
In a so-called low-speed range where the pressure difference between the outer opening windows 5D to 5G and the upper chamber A is small, the check valve CV including the leaf valve 3 covers the outer opening windows 5D to 5G. For this reason, the pressure oil in the lower chamber B, which is replenished to the upper chamber A whose volume increases through the piston 5, is supplied to the outer peripheral port 5A of the piston 5.
Through the notch 4A of the notch leaf valve 4, the upper chamber A is replenished. At this time, the passage resistance generates a pressure-side back-side damping force in a low-speed region proportional to the square of the piston speed. The compression-side damping force obtained by adding the compression-side back surface damping force to the compression-side base damping force is a compression-side damping force in a low-speed range.

As the piston speed increases, the flow rate passing through the notch 14A increases, the pressure difference before and after the notch increases, and the through hole 12A of the valve stopper 12, the through hole 13A of the leaf valve 13, and the like. The opening 14B of the notched leaf valve 14 communicating with the hole 13A, the upper opening 15D of the valve case 15, and the lower opening 15C of the valve case 15 communicating with the lower chamber B via the inner peripheral port 15B.
And the pressure difference between the bottom chambers C also increases.

For this reason, as the piston speed approaches the middle speed range, the outer peripheral side of the compression side damping valve BV composed of the leaf valve 16 disposed opposite to the lower opening window 15C has its combined flexural rigidity. It overcomes and is pushed open from the outer seat portion of the lower opening window 15C, and the hydraulic oil flows out to the bottom chamber C, and the passage resistance at this time and the passage resistance of the inner peripheral port 15B cause the compression-side base damping force after the middle speed range. Occurs. By appropriately selecting the bending rigidity of the compression side damping valve BV including the leaf valve 16 and the passage area of the inner peripheral port 15B,
The required damping force characteristics can be obtained.

Here, the upper chamber A, whose volume is increased, passes through the outer peripheral port 5A of the piston 5 and overcomes the combined flexural rigidity of the check valve CV composed of the leaf valve 3, so that the check valve CV is moved outward. It is pushed open from the outer sheet portion of the opening window 5E, and the operating oil is replenished from the lower chamber B, and the passage resistance at this time generates a pressure-side rear damping force in the middle speed range and thereafter. The compression-side damping force obtained by adding the compression-side rear damping force to the compression-side base damping force is the compression-side damping force in the middle speed range and thereafter.

Conversely, when the piston rod 1 rises, the outer peripheral port 15A of the valve case 15
, Overcoming the bending rigidity of the suction valve DV composed of the leaf valve 13 and the notch leaf valve 14, the suction valve DV is pushed open from the outer seat portion of the outer opening window 15 </ b> E, and the operation corresponding to the retreated volume of the piston rod 1 is performed. Oil in lower chamber B
Will be replenished.

[0018]

When the hydraulic shock absorber switches from the expansion stroke to the contraction stroke, the suction valve DV closes promptly due to the differential pressure between the lower chamber B and the bottom chamber C whose pressure increases. The pressure oil in the lower chamber B flows out to the bottom chamber C via the compression damping valve BV, and generates a compression damping force due to the passage resistance at this time. On the other hand, the lower chamber B communicates with the upper opening windows 5D to 5G of the piston via the outer peripheral port 5A. However, since the check valve CV faces the upper opening window, the pressure oil in the lower chamber B is increased. First, it is attempted to flow through the notch 4A of the notch leaf valve 4 and into the upper chamber A whose volume increases through the lower opening window 5C.

In a very low piston speed region where the pressure difference between the lower chamber B and the upper chamber A is small, the check valve CV cannot overcome the bending rigidity and push it open. Moreover, the passage area S of the notch 4A is, for example, S = 2 × 4 when the width = 2 mm, the number of orifices = 4, and the plate thickness = 0.15 mm.
× 0.15 = approximately 1.2 m ■. For this reason, the working oil cannot be sufficiently replenished to the upper chamber A, so that the compression-side back surface damping force cannot be increased smoothly.

The present invention has been made in view of the above circumstances, and an object of the present invention is to occur on the check valve side of a piston when a hydraulic shock absorber switches from an extension stroke to a contraction stroke. An object of the present invention is to provide a hydraulic shock absorber capable of smoothly increasing the compression-side back surface damping force from a very low piston speed range.

[0021]

SUMMARY OF THE INVENTION According to the present invention, an upper chamber and a lower chamber are formed in a cylinder through a piston having a plurality of upper opening windows which are fastened to a piston rod and whose opening area gradually decreases on the upper surface side. And a lower chamber and a bottom chamber communicating with the tank chamber via a valve case provided at the lower part of the cylinder, and a piston rod is arranged by a check valve and an extension damping valve arranged on the piston. While controlling the compression-side rear damping force when descending and the extension-side damping force when the piston rod extends, the compression-side damping valve arranged in the valve case generates a compression-side base damping force when the piston rod descends, It is assumed that a hydraulic shock absorber controls the compression-side damping force by adding the compression-side back surface damping force to the compression-side base damping force.

Means taken by the present invention to solve the problem is that a check valve composed of a leaf valve is opposed to each upper opening window of the piston, and the check valve is opened from the upper opening window having the largest opening area. The leaf spring is provided with a plurality of support pieces whose biasing force increases in order to correspond to the smallest upper opening window. It is urged from the back by a leaf spring, and each upper opening window communicates with the lower chamber through an outer peripheral port formed in the piston. When the piston rod descends, from the portion corresponding to the upper opening window having a large opening area and a small valve opening pressure to the portion corresponding to the upper opening window having a small opening area and a large valve opening pressure,
The check valve is sequentially opened as the piston speed increases, and the compression-side back surface damping force based on the passage resistance from the lower chamber to the upper chamber increases as the piston speed increases.

The leaf spring sets the urging force by changing the width of the base end of each support piece, the height in the axial direction from the base end to the outer end of each support piece, or both. Can be. Further, in order to smoothly increase the compression-side rear damping force as the piston speed increases, the hole diameter of the outer peripheral port formed in each of the upper opening windows is such that the opening area is from the largest upper opening window to the smallest upper opening window. It is desirable to increase in order.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a hydraulic shock absorber according to the present invention has the same basic structure as that of the prior art shown in FIG. 4, and a piston rod 101 is provided via a piston 105 mounted at a lower end thereof. Thus, the upper chamber A and the lower chamber B are partitioned while being movably inserted into the cylinder 21. A valve case 15 is fitted to the lower end of the cylinder 21, and a bottom chamber C communicating with the lower chamber B and the tank chamber D is also provided.
Is partitioned.

The hydraulic shock absorber according to the present invention has a plurality of upper opening windows 105D to 105G having different opening areas connected to the lower chamber on the upper surface side of the piston, and the upper opening window 105D having the largest opening area has a leaf. The upper portion of the upper opening window 105G having the smallest opening area corresponds to the portion of the leaf spring 102 that biases the valve 3 from the rear surface.
Is assembled so as to correspond to the largest part of the urging force of the leaf spring 102, and the check valve CV
Is smoothly opened from a very low speed region of the piston speed where the differential pressure is small, so that the compression-side back surface damping force can be smoothly increased.

At the lower end of the piston rod 101, FIG.
(A) As shown in FIG.
2A, a leaf spring 102 shown in FIG. 2A for urging the leaf valve 3 from the back, and a ring seat 103 having an outer peripheral edge corresponding to the supporting diameter of the deflection of the leaf valve 3 shown in FIG. 2B. A check valve CV composed of a leaf valve 3 superimposed on the lower side of the ring seat 103, and a piston 105 whose upper surface faces the leaf valve 3 shown in FIG.
As shown in (B), the positioning straight portion W on the inner diameter side of each component is aligned and inserted into the flat portion 101B in which a part of the spigot portion 101A is cut out in a D shape.

The leaf spring 102 has a plurality of support pieces 102A, 102B, 102C, 1
02D, the urging force of the support piece 102D opposed to the upper opening window 105D having the largest opening area of the piston 105 is minimized, and the supporting area is gradually reduced as the opening areas of the upper opening windows 105E, 105F, and 105G decrease. Piece 102C,
The urging force is increased in the order of 102B and 102A.

The leaf spring 102 is, for example, as shown in FIG.
As shown in (A), the width of the base end of each of the support pieces 102A to 102D or the height in the axial direction from the base end to the outer end of each of the support pieces 102A to 102D is manufactured differently. The biasing force can be set. Alternatively, the urging force may be set by changing both of them.

As shown in FIG. 2 (C), on the upper surface side of the piston 105 having the inside of the cylinder 21 divided into an upper chamber A and a lower chamber B and having a guide 5S wound around the outer periphery, a plurality of openings having a smaller opening area are formed. Upper opening windows 105D to 105G are provided, and the respective upper opening windows are provided with outer peripheral ports 105d to 105g.
The recess 105K formed between the upper opening windows communicates with the annular lower opening window 105C via the inner peripheral port 105B.

Subsequently, a notch leaf valve 4 having a notch 4A provided on the outer peripheral side facing the lower opening window 105C and a leaf damping valve PV comprising a leaf valve 6 superimposed on the back surface of the notch leaf valve. And a ring seat 7 whose outer peripheral edge is the supporting diameter of the bending of the extension side damping valve PV, and a valve stopper 8 for regulating the maximum deflection of the extension side damping valve PV. And a piston valve is formed by fastening with a tightening tool. Depending on the required damping force, a plurality of leaf valves 3 on the check valve CV side are used in an overlapping manner.

Next, the base valve side will be described. First, like the conventional structure, the shaft 11A of the guide 11
A valve stopper 12 for regulating the maximum deflection of the suction valve DV comprising a leaf valve 13, a ring seat 17 whose outer peripheral edge serves as a support for the deflection of the suction valve DV, a leaf valve 13, and a valve case 15 whose upper surface faces the leaf valve 13. Are sequentially inserted. A plurality of leaf valves 13 are used as needed.

Subsequently, a leaf valve 16, 106, 1 having a shaft portion 11A of the guide 11 opposed to the lower opening window 15C of the valve case 15 and having an outer diameter sequentially decreasing.
07 are sequentially superimposed, a ring seat 17 whose outer peripheral edge is a supporting diameter of the bending of the compression-side damping valve BV, and a valve stopper 18 that regulates the maximum bending of the compression-side damping valve BV are sequentially assembled. A base valve is formed by caulking the lower end of the shaft 11A of the guide 11 with a tool.

When switching from the so-called extension stroke in which the piston rod 1 rises in the cylinder 21 filled with hydraulic oil to the so-called contraction stroke in which the piston rod 1 descends, the compression-side damping valve BV composed of the leaf valves 16, 106 and 107 is used.
Covers the lower opening window 15C. In addition, the suction valve DV comprising the leaf valve 13 is also
05E is covered.

Here, the pressure oil in the lower chamber B excluding the replenishment of the upper chamber A is supplied to the through holes 12A,
It is led to a lower opening window 15C communicating with the lower chamber B via a through hole 13A of the leaf valve 13, an upper opening window 15D of the valve case 15, and an inner peripheral port 15B. Therefore, the outer peripheral side of the leaf valve 16 disposed opposite to the lower opening window 15C is connected to the lower leaf valves 106 and 10.
7 and the lower opening window 1
It is pushed open from the outer sheet portion of 5C and flows out to the bottom chamber C, and the passage-side resistance at this time generates a compression-side base damping force.

By the way, the compression side damping valve composed of the leaf valves 16, 106 and 107 whose outer diameters become smaller in order starts to open from the leaf valve 16 having the larger outer diameter, and the leaf valve 16 is moved with increasing deflection.
Are pushed down one after another, and the flexural rigidity gradually increases. For this reason, the leaf valve 16 opens from the very low speed range of the piston speed, and the passage resistance determined by the flexural rigidity of the leaf valves 16, 106, 107 causes the piston speed of FIG. As shown by Fa, a pressure-side base damping force that rises linearly substantially in proportion to the piston speed is generated.

As a result, the pressure in the lower chamber B is smoothly increased from a very low speed range of the piston speed, so that the pressure difference between the lower chamber B and the upper chamber A whose volume is increased also increases smoothly. Upper opening windows 105D, 105E, 105F, 1 of the piston
05G are outer peripheral ports 105d, 105e, 1 respectively.
Since the lower chamber B communicates with the lower chamber B through the air passages 05f and 105g, the opening area has a maximum pushing force (open area × lower chamber B and upper chamber A) when the piston speed is very low.
The check valve CV at the portion facing the upper opening window 105D where the pressure difference between the two becomes largest is the portion corresponding to this portion of the support piece of the leaf spring 102 which biases the check valve CV from the back. The biasing force of the supporting piece 102D having the smallest force is overcome to be pushed open, and the pressure oil in the lower chamber B flows out to the upper chamber A, and the resistance of the passage at this time generates a compression-side back surface damping force in a very low speed range.

As the piston speed increases, the flow rate passing through the outer peripheral port 105d having the smallest hole diameter corresponding to the upper opening window 105D increases, and the lower chamber B due to the passage resistance at this time.
The pressure difference between the upper chamber A and the upper chamber A also increases. For this reason, the check valve C at a portion opposed to the upper opening window 105E having the second largest opening area via the outer peripheral port 105e having the second smallest hole diameter.
V is pushed open by the biasing force corresponding to this portion overcoming the biasing force of the support piece 102C of the second smallest leaf spring, and the pressure oil in the lower chamber B flows out to the upper chamber A.

The opening area of the upper opening window 105E is set smaller than that of the upper opening window 105D, and the urging force of the supporting piece 102C of the leaf spring corresponding to this area is larger. Since the pressure difference between B and the upper chamber A also increases, the pressure-side back surface damping force due to the passage resistance at this time also increases.

When the piston speed further increases, the flow rate passing through the outer peripheral port 105e of the upper opening window 105E increases, and the differential pressure between the lower chamber B and the upper chamber A due to the passage resistance at this time further increases. The pressurized oil of B sequentially pushes and opens the upper opening windows 105F and 105G whose opening areas become smaller in order, pushes and opens the check valve CV of the opposing portion, and flows out to the upper chamber A.

The opening areas of the upper opening windows 105D to 105G are set so as to decrease in the order of 105D, 105E, 105F, and 105G.
Outer peripheral ports 105d-105 for communicating 5G with lower chamber B
g is set so as to become smaller sequentially, and the biasing force of the leaf spring support pieces 102D to 102A corresponding to the respective upper opening windows 105D to 105G is 10 g.
2D, 102C, 102B, and 102A, the lower chamber B and the upper chamber A
Since the pressure difference between them also increases, the compression side damping force due to the passage resistance at this time smoothly increases with respect to the piston speed as shown by Fb in FIG.

The compression side damping force obtained by adding the compression side backing damping force to the compression side base damping force is the compression side damping force indicated by Fc in FIG. In the contraction stroke in which the piston rod 1 descends in the cylinder 21 filled with the hydraulic oil, the differential pressure between the lower chamber B and the upper chamber A that generates the compression-side back-side damping force causes the lower chamber B that generates the compression-side base damping force. If the pressure difference is smaller than the pressure difference between the upper chamber A and the lower chamber C, the hydraulic oil is smoothly replenished to the upper chamber A.
The compression-side rear damping force can be increased to near the limit as long as the above condition is satisfied.

For this reason, the compression damping force increases smoothly as shown by Fc in FIG. 3 over the entire range of the piston speed from the very low speed region to the high speed region of the piston speed, and the compression side damping force is reduced to the very low speed region of the piston speed. Will be able to be larger. As a result, for example, when the vehicle runs on a good road, a sufficient vibration damping force can be obtained even with a gentle posture change such as a roll caused by undulation of the road surface.

In the above-described embodiment, the outer peripheral ports 105d, 105e, and 105 are formed in the upper opening windows.
f and 105g have described the case where the hole diameter is sequentially increased from the upper opening window having the largest opening area to the smallest upper opening window, but the opening areas of the upper opening windows 105D to 105G are as follows.
105D, 105E, 105F, and 105G are set so as to become smaller in this order.
Supporting piece 102D of leaf spring corresponding to 5G
Since the biasing force of -102 A is set so as to increase in order, if the hole diameter of the outer peripheral port is selected so as to generate a predetermined passage resistance, substantially similar performance can be realized even if the hole diameter is the same. it can.

The extension damping force in the extension stroke in which the piston rod 1 rises in the cylinder 21 filled with the hydraulic oil is the same as the extension damping valve PV of the conventional structure, and the detailed explanation is omitted. .

[0045]

As described above in detail, in the piston valve according to the present invention, the differential pressure between the lower chamber and the upper chamber, which generates the compression-side rear damping force via the check valve, is reduced via the compression-side damping valve. If the pressure difference is smaller than the pressure difference between the lower chamber and the bottom chamber that generates the base damping force, the upper chamber will be replenished with hydraulic oil smoothly. Can be. For this reason, in the entire range of the piston speed from the very low speed range to the high speed range of the piston speed, the compression side damping force smoothly increases, and the compression side damping force obtained by adding the compression side backing damping force to the compression side base damping force is applied to the piston. The speed can be increased from a very low speed range. As a result, for example, when the vehicle runs on a good road, a sufficient vibration damping force can be obtained even with a gentle posture change such as a roll caused by undulation of the road surface.

[Brief description of the drawings]

FIG. 1A is a sectional view of a main part of a hydraulic shock absorber according to the present invention. (B) It is sectional drawing of the spigot part of a piston rod.

FIG. 2A is a plan view of a leaf spring according to the present invention. (B) It is a top view of a leaf valve similarly. (C) It is a top view of the piston concerning this invention.

FIG. 3 is an example of a damping force characteristic according to the present invention.

FIG. 4 is a longitudinal sectional view of a hydraulic shock absorber according to the related art.

FIG. 5 is a top view of a piston according to the related art.

[Explanation of symbols]

 A upper chamber B lower chamber C bottom chamber D tank chamber BV compression side damping valve CV check valve PV extension side damping valve 3 leaf valve 15 valve case 21 cylinder 101 piston rod 105 piston 105D to 105G upper opening window 105d to 105g outer peripheral port

Claims (3)

[Claims] A cylinder is divided into an upper chamber and a lower chamber via a piston having a plurality of upper opening windows which are fastened to a piston rod and whose opening area decreases in order on the upper surface side. The lower chamber and the bottom chamber communicating with the tank chamber are separated via the valve case provided in the piston, and the check-side back-side damping force when the piston rod descends by the check valve and the extension-side damping valve arranged on the piston While controlling the extension damping force when the piston rod extends, the compression damping valve arranged in the valve case generates a compression base damping force when the piston rod descends, and the compression base damping force is applied to the compression side damping force. In the hydraulic shock absorber that controls the compression-side damping force by adding the back-side damping force, a check valve including a leaf valve is opposed to each upper opening window of the piston, and the check valve has a maximum opening area. The upper opening window is urged from the back by a leaf spring having a plurality of support pieces whose urging force sequentially increases in correspondence with the smallest upper opening window from the upper opening window, and each upper opening window is connected to an outer peripheral port formed in a piston. When the piston rod descends, from the portion corresponding to the upper opening window having a large opening area and a small valve opening pressure to the portion corresponding to the upper opening window having a small opening area and a large valve opening pressure, The check valve is sequentially opened as the piston speed increases, and the compression-side back surface damping force based on the passage resistance from the lower chamber to the upper chamber is configured to increase as the piston speed increases. Hydraulic shock absorber valve structure. 2. The leaf spring sets an urging force by changing a width of a base end of each support piece, or a height in an axial direction from a base end to an outer end of each support piece, or both. The valve structure of the hydraulic shock absorber according to claim 1, wherein 3. The opening diameter of each outer peripheral port corresponding to each upper opening window is gradually increased from the upper opening window having the largest opening area to the smallest upper opening window.
The valve structure of the hydraulic shock absorber according to the above.