JPH0430438Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a damping force adjustment device for a hydraulic shock absorber for two-wheeled vehicles, four-wheeled vehicles, etc., which absorbs and alleviates impact energy from the road surface.

[Conventional technology]

As a conventional hydraulic shock absorber, one having a structure shown in FIG. 7 is known.

In this case, a piston rod 3 is movably inserted into the cylinder 1 via a piston 2, and the piston 2
divides the cylinder into two upper and lower oil chambers A and B,
A reservoir chamber C is defined on the outer periphery of the cylinder 1.

The piston 2 is provided with an expansion port 4 and a pressure port 5 that communicate the two oil chambers A and B, and an expansion valve 6 that is biased by a spring is provided at the outlet end of the expansion port 4 so as to be openable and closable. Similarly, a pressure valve 7 is provided at the mouth end of the pressure port 5.

A communication hole 13 and a passage 14 are formed in the piston rod 3 to communicate the oil chambers A and B, and a variable orifice 10 is formed in the rotary valve rotatably inserted into the piston rod 3. Rotation operation is performed via the door 15.

A piston nut 16 is provided at the lower end of the piston rod 3 for tightening and holding a piston, etc., and this piston nut has an expansion orifice facing the passage 14 and a check valve incorporated therein.

A base valve is provided at the bottom of the cylinder 1. In the above hydraulic shock absorber, variable orifice 1
0 is closed, and when it is extended, piston 2
moves to the left, and the oil in oil chamber A bends expansion valve 6 from expansion port 4 and flows into oil chamber B. Due to the resistance at that time, a differential pressure is generated between oil chambers A and B, and the expansion valve 6 A high damping force on the rebound side is generated. At this time, an amount of oil corresponding to the discharge volume of the piston rod 3 is supplied from the reservoir chamber C to the oil chamber B via the base valve.

On the other hand, during compression, piston 2 moves to the right and oil chamber B
The oil flows from the pressure port 5 into the oil chamber A by deflecting the pressure valve 7, and at this time, a pressure difference is generated between the oil chambers A and B, resulting in a high damping force on the pressure side. At this time, the oil corresponding to the volume of the intrusion of the piston rod 3 returns the oil in the oil chamber B to the reservoir C from the base valve, but the pressure in the oil chamber B increases due to the resistance of the base valve, and a damping force is also generated by the base valve.

When the control rod is further rotated and the variable orifice 10 is opened to the communication hole 13, in addition to the flow path through the expansion valve 4 during expansion, the flow from the variable orifice 10 passes through the passage 14 and from the expansion orifice in the piston nut 16. Oil flows into oil chamber B.
Therefore, the resistance is smaller than in the above case,
The differential pressure between oil chambers A and B also becomes smaller, and a lower damping force is generated. In this case, the extension orifice in the piston nut is usually set smaller than the variable orifice, and the low damping force during the extension stroke is controlled by this extension orifice.

Next, during the compression stroke, in addition to the flow path passing through the pressure valve 7, a flow is generated through the passage 14 and the variable orifice 13, and as a result, the resistance becomes smaller than the high damping force described above, and the oil chambers A, B The differential pressure between them also becomes smaller, and a lower damping force is generated. The damping force at this time is mainly controlled by the variable orifice 13.

[Problem that the invention attempts to solve]

The damping force characteristics of the above hydraulic shock absorber are shown in FIG. 8, the high damping force characteristics when the variable orifice 13 is closed are shown in graphs a ₁ and a ₂ , and the low damping force characteristics when the variable orifice 13 is open are shown in graphs a 1 and a 2. The force characteristics are shown in graphs b ₁ and b ₂
It is indicated by. That is, when the damping force is low, the expansion valve 4,
The area of the orifice that bypasses the pressure valve 7 is
Since it is constant regardless of pressure and flow rate, expansion valve 4,
Until the pressure valve 7 opens, the damping force (or differential pressure between oil chambers A and B) is proportional to the piston speed (or oil flow rate).
has a square characteristic, and as a result, the low damping force characteristics are graphs b ₁ and b ₂ , and when the piston speed is medium or high speed, there is not that much difference compared to the high damping force characteristics a ₁ and a ₂ . . Therefore, even on the riding surface of a car,
There is a problem that a desired low damping force cannot be obtained in situations where a high piston speed occurs, such as on a rough road surface or rough road.

Therefore, an object of the present invention is to provide a damping force adjustment device for a hydraulic shock absorber that allows a large change in damping force to be obtained from a low piston speed range to a high speed range, and that also allows a large difference in high damping force to be obtained. That's true.

[Means for solving problems]

In order to achieve the above purpose, the configuration of the present invention is as follows:
A valve consisting of a leaf valve and a main valve is provided opposite the port of the piston so that it can be opened and closed freely, and a pressure chamber is provided at the back of the leaf valve, and this pressure chamber opens to the upstream oil chamber through a small hole provided in the leaf valve. At the same time, it is characterized in that it is communicated with the other downstream oil chamber via a variable orifice that can be opened and closed.

[Effect]

When oil is bypassed by adjusting the opening area of the variable orifice, it is firstly throttled by the small hole, then secondarily by the variable orifice, and as a result, not only the variable orifice but also the leaf valve opens. The pressure and leaf valve spring constant are adjusted.

〔Example〕

An example of implementing the present invention will be described below with reference to FIGS. 1 to 6.

A piston rod 22 is movably inserted into the cylinder 20 via a piston 21.
1 partitions the cylinder 20 into two upper and lower first oil chambers 23 and second oil chambers 24.

An outer cylinder 25 is provided outside the cylinder 20, and the cylinder 20 and the outer cylinder 25
A reservoir chamber 26 is defined therebetween, and this reservoir chamber 26 communicates with the second lower oil chamber 24 via a base valve provided at the lower part of the cylinder 20.

An eye 28 is provided on the cylinder bottom 27 and connected to the wheel side of the automobile, and the piston rod 22
The piston rod 22 passes through a bearing provided at the upper end of the cylinder 20, and the upper end of the piston rod 22 is connected to the vehicle body.
are connected.

A second lower oil chamber 24 is located inside the piston rod 22.
A hollow part 30 is formed which is open to the inside, and a rotary valve 31 is rotatably inserted into this hollow part 30, and the rotary valve 31 can be rotated from the outside via a control rod 32. .

The rotary valve 31 can also be used as a valve that moves in the axial direction.

Three through holes 33, 34, 35 are bored in the piston rod 22 in the radial direction, and the upper through hole 3
3 opens directly into the first upper oil chamber 23.

The rotary valve 31 has upper and lower passages 36, 3.
7 is formed, and the upper passage 36 communicates with the through hole 33 and the upper oil chamber 23 through the through hole 38, and is opened and closed with the middle through hole 34 through the variable orifice 39.

Further, the lower passage 37 is opened and closed to the lower passage hole 35 via the variable orifice 40 at the upper side, and is always open to the passage 30 and the lower oil chamber 24.

The piston rod 22 is provided with a step, and up to this step, in order from below, an upper valve guide 41, an upper spring 42, an upper spacer 43, a pressure main valve 44, a pressure leaf valve A ₂ , a piston 21,
The extension leaf valve A ₁ , the extension main valve 45, the lower spring 46, the lower spacer 47, and the lower valve guide 48 are inserted, and these members are attached to the piston nut 4 screwed to the lower end of the piston rod 22.
9 is tightened.

Since each member is sequentially inserted into the piston rod 22 in this way, a pair of expansion/compression valve mechanisms are provided symmetrically above and below the piston 21, so that the expansion and compression damping forces are respectively effective. It's summery.

However, for example, it is also possible to provide only a valve mechanism for generating damping force on the expansion side at the lower part of the piston 21.

A pair of extension ports 5 are provided in the piston 21 in a diagonal direction.
0 and a pressure port 51 are bored, and a leaf valve _A1 as a valve and an extension main valve 45 are provided at the lower outlet of the extension port 50 so as to be openable and closable.
Leaf valve A ₂ , which is also a valve at the upper outlet of
A pressure main valve 44 is provided so as to be openable and closable.

The extension main valve 45 is composed of a valve body consisting of a cylindrical body part and a flange part, and is pushed upward by a lower spring 46 interposed between the flange part and the seat of the valve guide 48. The expansion leaf valve _A2 is always biased in the direction of closing the outlet of the expansion port 50. The expansion leaf valve _A2 is provided with a small hole _B1 .

A growth-side pressure chamber 52 is defined by the cylindrical body of the expansion valve 45, the spacer 47, and the body of the valve guide 48, and this growth-side pressure chamber 52 is located at the back of the expansion leaf valve _A2 on the downstream side. .

An annular passage 53 is defined in the axial direction between the expansion main valve 45 and the spacer 47.
3 communicates the expansion side pressure chamber 52 with the expansion port 50 and the upper oil chamber 23 through a small hole _B1 , which is a fixed orifice, bored in the expansion leaf valve _A2 .

A through hole 54 is provided in the spacer 47, and this through hole 54 allows the pressure chamber 52 to communicate with the variable orifice 40 via the through hole 35.

A valve mechanism of the same structure is provided above the piston.

That is, a pressure leaf valve _A2 and a pressure main valve 44, which are valves, are provided at the upper outlet of the pressure port 51 so as to be openable and closable, and are always urged in the closing direction by an upper spring 42.

A pressure side pressure chamber 55 is defined at the back of the pressure leaf valve A ₂ on the downstream side, and this pressure chamber 55 receives pressure through a fixed passage 57 and a small hole B ₂ which is a pressure fixing orifice bored in the pressure leaf valve A ₂ . The port 51 communicates with the lower oil chamber 24, and also communicates with the through hole 34 and the variable orifice 39 through the through hole 56 provided in the spacer 43.
It is familiar to

When the piston 21 expands and contracts, when the variable orifices 39 and 40 are closed, the only flow path is to push open the expansion/compression leaf valves A ₁ and A ₂ , but when the variable orifices 39 and 40 are open, When the expansion/compression leaf valves A ₁ and A ₂ are opened, the flow passages, passages 53 and 57, and pressure chambers 52 and 5 are opened.
5 and flow paths passing through variable orifices 39 and 40, respectively, are formed.

For example, the oil flow circuit during the extension stroke is shown in FIG.

Next, we will discuss the operation.

Now, when trying to generate a high damping force, the variable orifice 39, 4 is used via the rotary valve 32.
0 to the through holes 34 and 35 in advance.

In this state, when the extension stroke begins, the oil in the first upper oil chamber 23 passes through the extension port 50 and the leaf valve
A ₁ and expansion main valve 45 are pushed open to flow into the second lower oil chamber 24 . At this time, variable orifice 4
0 is closed, so it is a small hole that is an expansion and fixed orifice.
If oil does not flow into _B1 and the expansion port 50 is large, the pressure in the upper oil chamber 23 and the pressure in the expansion side pressure chamber 52 are the same pressure. Therefore, the pressure difference between the upper oil chamber 23 on the upstream side and the lower oil chamber 24 on the downstream side is
P ₁ , the pressing force of the lower spring 46 is F _s , the cross-sectional area of the seat of the expansion port 50 is D ₁ , the outer diameter cross-sectional area of the cylindrical body of the expansion main valve 45 is D ₂ , the inner diameter cross-sectional area is D ₄ , The outer diameter cross-sectional area of the spacer 47 is D ₃
As shown in Figure 5, pressure P ₁ acts between diameters D ₁ and D ₄ , and in the opposite direction F = F _s + π/4 (D ² ₂ − D ² ₄ ) of P ₁ . Force is at work.

When π/4 (D ² ₁ − D ² ₄ ) P ₁ becomes larger than F, the expansion leaf valve A ₁ opens and oil flows into the lower oil chamber 24.
This resistance generates a damping force.

This high damping force characteristic is shown by characteristic C ₁ in FIG.

Also in the compression stroke, when the variable orifice 39 is fully closed, the lower oil chamber 2
4 oil flows into the upper oil chamber 23, and the pressure leaf valve
A high damping force on the compression side is generated by A ₂ , and its characteristics are shown by graph c ₂ in FIG.

On the other hand, when the rotary valve 31 is rotated from the outside via the control valve 32 to open the variable orifices 39, 40, an intermediate or soft damping force corresponding to the opening degree of the variable orifices 39, 40 can be obtained.

Now, if variable orifices 39 and 40 are fully opened, expansion/compression valves A ₁ and A ₂ and main valve 4
A flow path flowing from 4, 45 and a fixed orifice 5
A flow path is formed through small holes B ₁ and B ₂ of 3 and 57, pressure chambers 52 and 55, and variable orifices 39 and 40. During the extension stroke, oil is flowing through the small hole B ₁ , so the pressure in the pressure chamber 52 is reduced by P ₂ compared to the pressure in the upper oil chamber 23, and this reduced pressure P ₂ is transferred to the small hole B ₁ . It is determined by the area of the expandable orifice 40.

Therefore, as shown in Fig. 6, pressure P ₁ acts on the expansion leaf valve _A 1 between the diameters D ₁ and D ₄ , and pressure P ₂ acts between the diameters D ₄ and D ₃ . A force of F=F _s + π/4 (D ² ₂ −D ² ₄ )×(P ₁ −P ₂ ) is acting on.

When π/4(D ² ₁ −D ² ₄ )P ₁ +π/4(D ² ₄ −D ² ₃ )P ₂ becomes larger than F′, the extension leaf valve A ₁ opens and oil can pass to the lower oil chamber 24 . Extension leaf valve A ₁
Since the pressing force F' is π/4 (D ² ₂ − D ² ₄ )P ₂ smaller than when the damping force is high, the extension leaf valve A ₁ opens at a low pressure P ₁ .

The damping force characteristic when the variable orifices 39, 40 are fully opened is the softest characteristic _d1 , and an arbitrary characteristic shown by the dotted line occurs depending on the opening degree of the variable orifices 39, 40.

In the pressure stroke, a soft characteristic d ₂ can be obtained using exactly the same principle. Also, considering the deflection of the expansion leaf valve A ₁ with respect to the pressure _{P 1} after _the expansion leaf valve A 1 opens, P ₂ is proportional to the change in P ₁ and changes together, so the , the extension leaf valve A ₁ is easier to sag than when the damping force is high,
The spring constant of the expansion leaf valve _A1 will also change. In addition, not only the opening pressure and spring constant of the expansion leaf valve _A1 change, but also the orifice flow that bypasses the expansion leaf valve _A1 , so the orifice characteristics in the low speed range also change. Therefore, as shown by the solid line in FIG. 3, the damping force characteristic exhibits a large difference from a low speed range to a high speed range, and the difference becomes larger as the speed increases.

That is, when the variable orifices 39 and 40 are opened, the expansion/compression leaf valves A ₁ ,
Not only does the opening pressure of A ₂ decrease, but there is also orifice flow that bypasses the expansion/compression leaf valves A ₁ and A _2. As a result, the damping force characteristics are shown in Figure 3, resulting in a high damping force. There is a large difference between the characteristics c ₁ , c ₂ and the low damping force characteristics d ₁ , d ₂ , and a large difference is obtained not only in the low speed range but also in the medium and high speed ranges.
In addition, if the expansion/compression variable orifices 39, 40 are opened and closed continuously, the orifice flow, the pressure at which the expansion/compression leaf valves A ₁ and A ₂ open, and the expansion/compression leaf valves will change.
The spring constants of A ₁ and A ₂ also change continuously, and the characteristics at that time change as shown by the dotted line in FIG.

[Effect of idea]

According to the present invention, compared to the conventional orifice adjustable type, not only the orifice but also the opening pressure and spring constant of the leaf valve can be adjusted, and a large change in damping force can be obtained from the low speed range to the high speed range of the piston. , the higher the speed, the greater the difference in damping force can be obtained.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional front view of a hydraulic shock absorber according to an embodiment of the present invention, Fig. 2 is a circuit diagram showing the flow path, Fig. 3 is a graph showing damping force characteristics, and Fig. 4 is the same as Fig. 1. A partially enlarged sectional view, FIGS. 5 and 6 are schematic diagrams showing the relationship of forces applied to the leaf valve, FIG. 7 is a partially longitudinal front view of a conventional hydraulic shock absorber, and FIG. 8 is a conventional damping It is a graph showing characteristics. 20...Cylinder, 21...Piston, 22...
...Piston rod, 23, 24...Oil chamber, 39,
40...Variable orifice, 44,45...Main valve, 50,51...Port, 52,55...
Pressure chamber, A ₁ , A ₂ ... Leaf valve, B ₁ , B ₂ ...
Small hole.

Claims (1)

[Scope of utility model registration request] A piston rod is movably inserted into the cylinder via the piston, and the piston defines two oil chambers, a first and a second oil chamber, within the cylinder. In a hydraulic shock absorber that communicates through two ports and is provided with an expansion/compression valve that opens and closes each port on both end faces of the piston, the expansion/compression valve contacts the end face of the piston. Consisting of a leaf valve and a main valve that contacts the back of the leaf valve, each has a pressure chamber on the back of the leaf valve, and this pressure chamber opens to the upstream oil chamber through a fixed orifice provided on each leaf valve. At the same time, the damping force adjustment device of the hydraulic shock absorber is connected to the other downstream oil chamber through variable orifices on the expansion side and compression side that can be changed simultaneously by a single valve provided in the piston rod. .