JP3182922B2 - Hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spring for automatically keeping the extension damping force low and keeping the extension damping force low when the unsprung vibration frequency of the traveling vehicle enters a high frequency range above a set value. The present invention relates to an improvement in a dependent frequency variable type hydraulic shock absorber capable of improving the riding comfort of a vehicle by appropriately adjusting a setting high frequency range of a lower vibration frequency.

[0002]

2. Description of the Related Art When a vibration frequency enters a high-frequency range higher than a set value, a phase difference is given to a hydraulic pressure transmitted from an upper hydraulic oil chamber to a primary lag pressure chamber for adjusting an extension-side damping force to lower the extension-side damping force. An example of a variable-frequency-variable type hydraulic shock absorber that can appropriately adjust a set high-frequency range for maintaining the extension side damping force low while maintaining the extension side damping force is, for example, Hei 4
Patent Application No. 35707 discloses an example.

In this type, as shown in FIG. 6, an expansion damping force generating valve C is provided at an outlet of a main oil passage A extending from an upper hydraulic oil chamber U to a lower hydraulic oil chamber L, and An oil passage E branching from the main oil passage A, passing through the lower end spigot portion I of the piston rod R, and leading to a first-order lag pressure chamber D formed at the back of the extension-side damping force generating valve C; A variable orifice F that can be adjusted externally is interposed in the middle of the road E.

When the vibration frequency of the hydraulic shock absorber enters a high frequency range equal to or higher than a set value by means of the variable orifice F, a phase difference is given to the hydraulic pressure transmitted from the upper hydraulic oil chamber U to the first-order lag pressure chamber D to give a primary phase difference. The increase in the hydraulic pressure in the lagging pressure chamber D is suppressed, thereby keeping the damping force generated by the expansion-side damping force generation valve C low, and adjusting the opening diameter of the variable orifice F from the outside to reduce the expansion-side damping force. The set high frequency range to be kept low can be appropriately adjusted.

As described above, the above-mentioned hydraulic shock absorber has a structure in which the frequency dependence of the damping force is controlled by selecting the opening diameter of the variable orifice F, so that the extension side damping force can be controlled from hard to soft. Therefore, the opening diameter of the variable orifice F for controlling the pressure gain in the first-order lag pressure chamber D is generally considerably small.

Therefore, when there is a leakage of pressure hydraulic oil from the upper hydraulic oil chamber U to the primary delay pressure chamber D without passing through the variable orifice F during the extension stroke of the hydraulic shock absorber, the primary delay pressure by the variable orifice F is increased. The pressure gain control in the chamber D will be seriously disrupted.

Therefore, in order to prevent this leakage, in the above-mentioned conventional hydraulic shock absorber, the seal member S1 is provided between the spigot portion I of the piston rod R and the piston nut N.
With the seal member S1, the primary lagging pressure chamber D is passed from the joint surface between the piston P and the piston rod spigot portion I and between the piston P and the piston nut N through the joint surface between the piston rod spigot portion I and the piston nut N. The leakage of the pressure hydraulic oil in the upper hydraulic oil chamber U that is about to enter is prevented.

At the same time, a seal member S2 is interposed also at the joint surface between the piston nut N and the block member B, and the leakage of pressure hydraulic oil which tries to flow into the first-order lag pressure chamber D from this portion is also performed. Is also blocking.

[0009]

However, if the leakage of the pressure hydraulic oil to the first-order lag pressure chamber D is prevented by using the sealing members S1 and S2, the piston rod spigot portion I and the variable orifice Leakage of the pressure hydraulic oil which tries to enter the first-order lag pressure chamber D through the joint surface of the control valve V provided with F becomes a problem, and unless this is also prevented, the inside of the first-order lag pressure chamber D The pressure gain control is out of order.

However, this piston rod spigot part I
In the same manner as described above, a seal member is interposed between the control valve V and the control valve V. In order to prevent leakage of hydraulic oil into the first-order lag pressure chamber D by this seal member, the piston rod spigot portion I and the control valve The friction between Vs increases, causing a response delay in the control operation of the control valve V, resulting in a defect that accurate control cannot be performed.

[0011] Therefore, with respect to the gap leakage of this part,
Until now, measures have been taken to reduce the gap as much as possible by making the component tolerances as tight as possible, or to prevent leakage by increasing the total length of the control valve V. However, the former requires a lot of trouble in processing the components. In addition to the increase in cost, an increase in the operating torque of the control valve V is inevitable to some extent, and the latter has a problem that the basic length of the piston assembly is lengthened and the effective stroke as a hydraulic shock absorber is correspondingly reduced. was there.

Accordingly, an object of the present invention is to control the pressure gain in the first-order lag pressure chamber even if there is a certain degree of leakage of pressure oil from the upper working oil chamber to the first-order lag pressure chamber during the extension stroke. It is an object of the present invention to provide an improved hydraulic shock absorber of this kind which is dependent on a variable frequency without causing any deviation.

[0013]

Means for Solving the Problems To achieve the above object, a means of the present invention is to movably insert a piston rod into a cylinder via a piston, and the piston is provided in the cylinder with an upper hydraulic oil chamber and a lower hydraulic oil chamber. A hydraulic oil chamber is defined, a main passage connecting the upper hydraulic oil chamber and the lower hydraulic oil chamber is formed between the piston and the piston rod, and a leaf valve for generating the extension side damping force is opened and closed in the middle of this main passage. A first-order lag pressure chamber facing the back of the leaf valve via a push member is provided in the piston rod, and a passage branched from the main passage and communicating with the first-order lag pressure chamber is provided between the piston and the piston. A variable orifice is provided in the rod and in this passage so that the high-frequency range that reduces the extension-side damping force with the variable adjustment operation of the variable orifice can be appropriately adjusted. And the dependent variable frequency of the hydraulic shock absorber, between the first-order lag pressure chamber and a lower hydraulic oil chamber,
A control orifice having a smaller diameter than the variable orifice is provided.

[0014]

Thus, according to the present invention, during the extension stroke of the hydraulic shock absorber, the pressure hydraulic oil flowing into the first-order lag pressure chamber from the upper hydraulic oil chamber flows therefrom to the lower hydraulic oil chamber through the control orifice. Therefore, the pressure applied to the first-order lag pressure chamber at this time appears as a differential pressure due to the ratio of the variable orifice diameter to the control orifice diameter.

Accordingly, even if the hydraulic oil leaking into the primary delay pressure chamber through the joint surface between the piston rod spigot portion and the control valve is added to the hydraulic oil flowing into the primary delay pressure chamber through the variable orifice, the primary oil does not There is no significant perturbation in the pressure gain control in the lagging pressure chamber.

[0016]

An embodiment will be described below with reference to the drawings. As shown in FIG. 1, the hydraulic shock absorber of the present invention movably inserts a piston rod 3 into a cylinder 1 via a piston 2, and the piston 2 has an upper hydraulic oil chamber A and a lower hydraulic oil chamber inside the cylinder 1. B and the piston 2 and the piston rod 3
And a piston nut 5, which is a part of the main passage, and forms a main passage composed of an expansion port 2a and a passage 5a for communicating the upper hydraulic oil chamber A and the lower hydraulic oil chamber B. A leaf valve 12 for generating force is provided so as to be openable and closable. In the piston rod 3, the leaf valve 12 is provided.
A first-order lagging pressure chamber D is provided at the back of the piston 2 via a push member 13, and a passage composed of a plurality of through-holes branching from the main passage and communicating with the first-order lagging pressure chamber D is formed by the piston 2 and the piston rod 3. And a variable orifice provided by the control valve 17 in this passage. A high frequency range in which the extension-side damping force is reduced can be appropriately adjusted in accordance with the variable orifice variable adjustment operation. Further, the present invention is characterized in that a control orifice 14c having a smaller diameter than the variable orifice is provided between the primary delay pressure chamber D and the lower hydraulic oil chamber B.
This will be described in more detail below.

As shown in FIG. 1, a hydraulic shock absorber according to one embodiment of the present invention includes a cylinder 1 having a closed cylinder, a piston 2 slidably inserted into the cylinder 1, and a cylinder 1 and a piston rod 3 extending outward through the upper end sealing portion.

The piston 2 is fitted in a lower end spigot portion 3a of a piston rod 3, and a gasket 4 made of a sealing member such as metal rubber is applied to the lower surface. The piston 3 is fixed to the piston rod 3 with the piston nut 5 screwed from below into the lower spiral portion 3b of the piston rod 3 while sealing the joint surface of the piston 3 and the joint surface of the piston 2 and the piston nut 5.

Thus, the piston 2 moves the cylinder 1 into the upper hydraulic oil chamber U on the rod side and the lower hydraulic oil chamber L on the head side.
When the hydraulic oil in the upper hydraulic oil chamber U flows from the piston 2 to the lower hydraulic oil chamber L through the expansion-side damping force generating mechanism during the extension stroke of the hydraulic shock absorber, the expansion-side damping force generation is performed. The mechanism generates damping force during the extension stroke.

During the compression stroke, the hydraulic oil in the lower hydraulic oil chamber L flows from the piston 2 to the upper hydraulic oil chamber through the compression-side damping force control mechanism. Through the reservoir chamber (not shown), a damping force during the compression stroke is generated by the compression side damping force control and generation mechanism.

For this purpose, the piston 2 is provided with two sets of port groups, a diagonal hole-shaped expansion port 2a and a compression port 2b, which communicate the upper hydraulic oil chamber U and the lower hydraulic oil chamber L. .

The extension port 2a group has an upper end directly opened to the upper hydraulic oil chamber U and a lower end formed with a hole 4 formed in the gasket 4 from an annular groove 2d formed on the lower surface of the piston 2.
a, an annular groove 5d formed on the upper surface of the piston nut 5, a passage 5a formed in the piston nut 5, and an extension side damping force generating mechanism, which communicates with the lower hydraulic oil chamber L side.

The lower end of the pressure side port 2b group is directly opened to the lower hydraulic oil chamber L, and the upper end is
The upper working oil chamber U passes through a check valve 7 pressed by the pressure sensor 2 to a concave portion 2e formed on the upper surface of the piston 2, and further passes from the concave portion 2e through a hole 8b of a valve seat member 8 provided over the concave portion 2e and a rear valve 9. Leads to.

On the other hand, the extension side damping force generation mechanism extending from the piston rod 3 to the inside of the piston nut 5, an extension side damping force control mechanism for controlling the frequency-dependent characteristics of the extension side damping force generation mechanism, and the back valve 9 A compression damping force control mechanism that also controls the compression damping force characteristic in cooperation with the above is provided.

The extension side damping force generating mechanism includes a piston nut 5
An outer periphery fixed leaf whose outer periphery is sandwiched between an annular rib 10d of a ring-shaped support member 10 which is crimped inward at a lower end of the ring member and an annular rib 11d of a valve seat member 11 arranged opposite to the upper surface of the support member 10. It is configured as a valve 12.

The extension-side damping force control mechanism for controlling the frequency-dependent characteristics of the extension-side damping force generation mechanism includes a push member 13 which is vertically movably fitted on the inner peripheral surface of the valve seat member 11.
A leaf spring 15 crimped to the push member 13 with a pin 14, a block member 16 disposed above the push spring 13, and a control valve rotatably housed in a vertical hole 3d penetrating the piston rod 3. 17

The valve seat member 11 has a plurality of through holes 11a formed in concentric circles and an annular groove 11e formed on the lower surface so as to communicate with the through holes 11a. A seal member 18 is provided on the outer periphery of the portion 16d, and a through hole 16c and a divergent concave portion 16e following the through hole 16c are provided at the center.

The valve seat member 11 and the block member 16 hold the upper end of the cap-like member 19 having the opening 19a together with the push member 13 with the outer periphery of the leaf spring 15 sandwiched therebetween. , The lower end of the cap-shaped member 19 is connected to the valve seat member 11.
Into a sub-assembly by press fitting.

Then, the sub-assembly is combined with the step 16 e of the block member 16 and the piston nut 5.
The guide 16 d of the block member 16 is inserted into the through hole 5 c of the piston nut 5 and assembled with the spring 20 interposed between the shoulder 5 e and the shoulder 5 e.

In this case, the seal member 18 is fitted on the outer peripheral surface of the guide portion 16d of the block member 16, so that the piston nut 5 and the block member 16
Are sealed oil-tight by a seal member 18, and
The entire component subassembled by the spring 20 is constantly pressed downward.

As a result, the leaf valve 12, which is the extension side damping force generating mechanism, has its outer peripheral portion formed by the annular rib 10d of the support member 10 and the annular rib 11d of the valve seat member 11 by the restoring force of the spring 20, as described above. It is pinched from above and below.

In this state, the leaf valve 1
2 is pressed against the seat portion 11f of the inner circumferential lower surface of the valve seat member 11 to close the annular groove 11e formed between the annular rib 11d and the seat portion 11f of the normal valve seat member 11. To keep.

Accordingly, during the extension stroke of the hydraulic shock absorber, the pressure hydraulic oil in the upper hydraulic oil chamber U flows from the expansion port 2a of the piston 2 to the annular groove 2d, the hole 4a of the gasket 4,
Annular groove 5d of piston nut 5, passage 5a, opening 19a of cap-like member 19, through hole 1 of valve seat member 11
1a, it flows into the lower hydraulic oil chamber L while pushing and opening the leaf valve 12, which is the extension side damping force generating mechanism, through the annular groove 11e.

The leaf valve 12 is clamped by utilizing the restoring force of the spring 20 because the supporting member 10, the valve seat member 11, and the cap-like member 19 are used.
This is to prevent rattling of the leaf valve 12 due to dimensional errors such as those described above.

The leaf spring 15 which has been crimped to the push member 13 with the pin 14 has its outer peripheral portion sandwiched between the valve seat member 11 and the block member 16 at the time of sub-assembly, and its restoring force is used. Usually, the push member 13 is kept at the upper position.

In this state, the lower seat portion 13d of the push member 13 formed to have the same thickness as the valve seat member 11 is in close proximity to or in contact with the inner peripheral upper surface of the leaf valve 12. It is in.

The recess 16e of the block member 16
The lower end faces the upper surface of the leaf spring 15 and forms a first-order lag pressure chamber D there.

The first-order lag pressure chamber D is provided with a pin 14 for connecting the push member 13 and the leaf spring 15 on the one hand.
Communicates with the lower hydraulic oil chamber L through a control orifice 14c machined at the center of the piston, on the other hand, from the through hole 16c of the block member 16 to the through hole 5c of the piston nut 5, the vertical hole 3d of the piston rod 3, and into the vertical hole 3d. It passes through an internal passage 17c of the control valve 17 which is rotatably fitted, and the expansion side variable orifice 17d formed in the control valve 17, and a compression side variable orifice 17e and a check port 17 described later.
f.

On the other hand, the inner peripheral surface of the piston 2 is located on the same plane as the extension-side variable orifice 17d and has an annular recess 2f.
On the one hand, this annular concave portion 2f communicates with the extension side variable orifice 17d of the control valve 17 through a through hole 3c formed in the lower end spigot portion 3a of the piston rod 3, and on the other hand, penetrates the piston 2. It communicates with the annular groove 2d on the lower surface through the through hole 2c.

Thus, during the extension stroke of the hydraulic shock absorber, the pressure hydraulic oil in the upper hydraulic oil chamber U pushes the leaf valve 12 from the expansion port 2a of the piston 2 while opening the lower hydraulic oil chamber L as described above. In parallel with the flow toward, the through hole 2c, the annular concave portion 2e, the through hole 3c of the piston rod inlay portion 3a, the extension side variable orifice 17d of the control valve 17, the internal passage 17c, the through hole 2c of the piston rod inlay portion 3a. Vertical hole 3d, through hole 16 of block member 16
c, the first-order lag pressure chamber D, and the control hydraulic orifice 14a are guided to the lower hydraulic oil chamber L.

The compression side damping force control mechanism for controlling the damping force characteristic of the rear valve 9 includes the compression side variable orifice 17 formed in the control valve 17 alongside the extension side variable orifice 17d.
e and a check port 17f. The pressure side variable orifice 17e and the check port 17f are connected to the internal passage 17 of the control valve 17 together with the expansion side variable orifice 17d.
c communicate with each other.

The pressure side variable orifice 17e communicates with the upper concave portion 2e of the piston 2 through a through hole 3e formed in the lower end spigot portion 3a of the piston rod 3, and from there through the pressure side port 2b of the piston 2 to the lower hydraulic oil chamber L. ,Also,
It communicates with the upper hydraulic oil chamber U through the hole 8b of the valve seat member 8 and the rear valve 9 respectively.

A disk 21 is provided on the outer peripheral surface of the piston rod spigot portion 3a on the same plane as the check port 17f, and an annular concave portion 21f is formed on the inner peripheral surface of the disk 21.

On the one hand, the annular recess 21f communicates with the check port 17f from the through hole 3f formed in the piston rod spigot portion 3a through an annular groove 17g formed on the outer peripheral surface of the control valve 17, and on the other hand, the disc 21. Through the through hole 21g to the upper hydraulic oil chamber A side.

A check valve 22 which opens toward the upper hydraulic oil chamber A is provided at the upper end opening of the through hole 21g. A check spring 24 and a valve are provided above the check valve 22 with a spacer 23 interposed therebetween. A stopper 25 is provided.

Then, the valve stopper 25, the check spring 24, the spacer 23, the check valve 22, the disk 8, the spacer 26, the rear valve 9 of the pressure-side damping force control mechanism,
The piston 2 and the gasket 4 are sequentially stacked, inserted into the piston rod spigot portion 3a, and the piston nut 5 is screwed into the helical portion 3b at the lower end of the spigot portion 3a and tightened from underneath. Fixed.

Thus, the lower hydraulic oil chamber L is
From the pressure side port 2b through the back valve 9 to the upper hydraulic oil chamber U, and the front side of the back valve 9
e, through hole 3e, pressure side variable orifice 17e, internal passage 17c, check port 17f, annular groove 17g, through hole 3
f, annular concave portion 21f, through hole 21g, check valve 22
And is connected to the upper hydraulic oil chamber U by a bypass passage passing through.

In addition, at the same time, the first-order lag pressure chamber D also communicates with the upper hydraulic oil chamber U through the through hole 16c, the vertical hole 3d, the internal passage 17c, the check port 17f, and the check valve 22.

From the control valve 17, the piston rod 3
A control rod 27 extends to the outside through the vertical hole 3d, and the control valve 17 is rotated from the outside through the control rod 27 to thereby control the extension side variable orifice 17d.
And the opening area of the pressure side variable orifice 17e can be controlled simultaneously.

At this time, the check port 17f is always kept in communication with the through hole 3f by the action of the annular groove 17g regardless of the rotation operation of the control valve 17.

The control rod 27 and the piston rod 3
Between the vertical hole 3d is kept oil-tight by a seal 28,
A cylindrical stopper 29 is provided below the control valve 17 to prevent the control valve 17 from slipping out of the control rod 27 and dropping off.
d.

At the lower end of the cylinder 1, there is provided a base valve 30 which is a pressure-side damping force generating mechanism. In this embodiment, the base valve 30 is also shown as a frequency-dependent type, but it is not necessarily The base valve is not limited and may be a normal type base valve.

That is, the base valve 30 serving as a compression-side damping force generating mechanism includes an annular rib 31 d of a support member 31 fitted to the lower end of the cylinder 1, and a valve seat member 32 disposed opposite to the upper surface of the support member 31. Annular rib 32d
Fixed leaf valve 3 with upper and lower outer peripheral surfaces sandwiched between
The leaf valve 33 generates a pressure-side damping force at the base valve 30.

The leaf valve 3 for generating the compression side damping force
In order to give the frequency-dependent characteristic to the base member 3, the base valve 30 further includes a push member 34 housed on the inner peripheral surface of the valve seat 32 so as to be vertically movable.
A leaf spring 36 secured with a pin 35, a disk 37 disposed above the leaf spring 36, and an orifice plate 38 provided on the disk 37.

The valve seat member 32 is provided with a plurality of through holes 32a drilled concentrically and an annular groove 32e formed on the lower surface so as to communicate with the through holes 32a. Together with the disk 37 and the orifice plate 38, the upper end of the cap member 39 having the opening 39a is hooked on the orifice plate 38,
The lower end of the cap member 39 is pre-assembled as a sub-assembly by press-fitting the lower end into the valve seat member 32.

The leaf spring 36 and the disc 3
7 is a first-order lag pressure chamber D1. The first-order lag pressure chamber D1 communicates with a lower hydraulic oil chamber L in the cylinder 1 through an orifice hole 38c of an orifice plate 38 from a hole 37c formed in the disk 37. I have.

Each of the sub-assembled members is vertically movably housed in a case member 40 having an opening 40a, the lower end of which is press-fitted into the support member 31. The orifice plate 38 and the case member 40 The base valve 30 is configured by pressing the seat portion 32f of the sub-assembled valve seat member 32 against the leaf valve 33 with a spring 41 interposed therebetween.

Thus, the outer periphery of the leaf valve 33 of the base valve 30 is sandwiched between the annular rib 31d of the support member 31 and the annular rib 32d of the valve seat member 32 from above and below by the restoring force of the spring 41. Is pressed against a seat portion 32f on the inner peripheral lower surface of the valve seat member 32 to close the annular groove 32e of the normal valve seat member 32.

Next, in order to explain the operation of the hydraulic shock absorber constructed as described above, FIG. 2 shows a hydraulic circuit diagram, and FIG. FIG. 4 shows the frequency characteristic of the extension damping force, and FIG. 4 shows the relationship between the generated damping force and the damping force characteristics obtained by switching the control valve 17. The description will be made separately for each of the three-stage modes that are “soft”. [Hard mode] During the extension stroke: As shown in FIG. 3, the extension-side variable orifice 17d has a large diameter, so the extension port 2c of the piston 2
From the annular groove 2d, the through hole 2c, the annular concave portion 2f, the through hole 3c,
Extension side variable orifice 17d, internal passage 17c, through hole 1
The pressure in the primary lag pressure chamber D communicating with the upper hydraulic oil chamber U through 6c is always the pressure of the upper hydraulic oil chamber U even if the primary lag pressure chamber D communicates with the lower hydraulic oil chamber L through the control orifice 14c. Becomes equal to

Therefore, the push member 13 is always pushed down against the leaf spring 15 by the pressure in the first-order lag pressure chamber D irrespective of the vibration frequency, and the inner circumference of the leaf valve 12 which is the extension-side damping force generating mechanism. The end side is deflected downward to keep the initial load increased.

As a result, the upper port 2a, the annular groove 2d, the hole 4a of the gasket 4, the annular groove 5d, the annular groove 5d, and the upper hydraulic oil chamber U do not exhibit high cut characteristics (characteristics of switching to a low damping force at high frequency input). Hydraulic oil flowing to the lower hydraulic oil chamber L while pushing and opening the leaf valve 12 through the passage 5a, the opening 19a of the cap-shaped member 19, the through hole 11a, and the annular groove 11e receives a large flow resistance by the leaf valve 12, and FIG. A high damping force is maintained as indicated by X in FIG.

On the other hand, at this time, an amount of hydraulic oil corresponding to the rejected volume integral of the piston rod 5 is supplied from the reservoir chamber to the lower hydraulic oil chamber L together with the leaf valve 33 which is a pressure-side damping force generating mechanism. Each sub-assembled member of the valve valve 30 is supplied to the lower hydraulic oil chamber L while being pushed up against the spring 41.

At the time of the extension stroke in the hard mode, the hydraulic oil flowing into the primary delay pressure chamber D through the extension variable orifice 17d is subjected to the primary delay pressure through the joint surface between the piston rod spigot portion 3a and the control valve 17. Even if the leaked hydraulic oil is added to the chamber D, it originally acts in the direction of increasing the pushing amount of the push member 13, so that there is no problem in characteristics, and the primary lag pressure chamber D
There is no significant perturbation in the internal pressure gain control.

During the compression stroke: As shown in FIG. 3, since the pressure-side variable orifice 17e is closed, the lower hydraulic oil chamber L
From the pressure side port 2 b of the piston 2 to the concave portion 2 e and the valve seat member 8.
It flows while pushing and opening the rear valve 9 through the hole 8b.

In parallel with this, the piston rod 3
Hydraulic fluid in the lower hydraulic oil chamber L
Through the opening 40a of the case member 40, the opening 39a of the cap member 39, the through hole 32a of the valve seat member 32, and the annular groove 32e, the water flows into the reservoir chamber while pushing and opening the leaf valve 33 which is a pressure-side damping force generating mechanism.

On the other hand, the pressure in the lower hydraulic oil chamber L, which has risen due to the flow resistance of the rear valve 9 and the leaf valve 33, is increased from the orifice hole 38c to the hole 37c of the disk 37.
To the first-order lag pressure chamber D1.

As a result, when the input frequency is
In the range below the set frequency determined by the diameter of 8c, the pressure in the first-order lag pressure chamber D1 becomes equal to the pressure in the lower hydraulic oil chamber L, and pushes down the push member 34 against the leaf spring 36. Accompanying leaf valve 33
Is bent downward to increase the initial load.

On the other hand, when the input frequency exceeds the set frequency, the hydraulic shock absorber shifts to the extension stroke before the pressure of the lower hydraulic oil chamber U is transmitted to the first-order lag pressure chamber D1, and therefore, the first-order lag pressure chamber D1 Is maintained at a low pressure, and the initial load of the leaf valve 33 remains low.

Thus, the pressure-side damping force in this case exhibits a high-cut characteristic at the set frequency and generates a high damping force in which the flow resistance of the back valve 9 is added to the flow resistance of the leaf valve 33. [Medium Mode] At the time of the extension stroke: As shown in FIG. 3, the extension-side variable orifice 17d has a small diameter, so that the extension-side variable orifice 17d is frequency-dependent similarly to the orifice hole 38c during the compression stroke in the hard mode. To have sex.

Therefore, when the input frequency exceeds the set frequency corresponding to the diameter of the extension-side variable orifice 17d, the pressure in the first-order lag pressure chamber D does not increase and the push member 13
Does not fall, the initial load of the leaf valve 12 is kept low, and the damping force characteristic shows a high-cut characteristic like Y in FIG.

However, in this case, if hydraulic oil leaks from the joint surface between the piston rod spigot portion 3a and the control valve 17 to the first-order lagging pressure chamber D without passing through the expansion-side variable orifice 17d, the first-order lag is reduced accordingly. The pressure in the pressure chamber D rises, and the pressure gain control is deviated, resulting in a damping force characteristic in which the break frequency shifts to the higher frequency side as indicated by Y1 in FIG.

However, in this embodiment, the pins 14
Is provided with a control orifice 14c having a diameter smaller than that of the expansion side variable orifice 17d, and the primary delay pressure chamber D is communicated with the lower hydraulic oil chamber L. Therefore, the pressure in the primary delay pressure chamber D is controlled by the expansion side variable orifice 17d. Diameter and control orifice 14
The pressure difference is based on the difference in the diameter of c, and the pressure control gain in the primary delay pressure chamber D is performed by this differential pressure. Therefore, even if the hydraulic oil leaks into the primary delay pressure chamber D, By appropriately selecting the difference between the diameter of the expansion-side variable orifice 17d and the diameter of the control orifice 14c, a high-cut characteristic such as Y in FIG. 4 can be obtained.

At the time of the compression stroke: As shown in FIG. 3, the diameter of the pressure-side variable orifice 17e is small, so that the pressure-side port 2b, the recess 2e, the through-hole 3e, the pressure-side variable Orifice 17e, internal passage 17c, check port 17f, annular groove 17g, through hole 3
f, the annular concave portion 21f, and the check valve 22 are opened through the through hole 21g, and the flow rate of the hydraulic oil passing through the rear valve 9 is reduced by the amount of bypass to the upper hydraulic oil chamber U.

Accordingly, the hydraulic oil pressure generated in the lower hydraulic oil chamber L is reduced by that amount, so that the damping force characteristic is lower than that having the same high cut characteristic as in the previous hard mode. . [Soft Mode] During the extension stroke: As shown in FIG. 3, since the extension-side variable orifice 17d is closed, there is no inflow of hydraulic oil from the upper hydraulic oil chamber U into the first-order lag pressure chamber D, and therefore, the first-order lag. Since there is no pressure increase in the pressure chamber D, the push member 1
3, the damping force characteristic is a low damping force having no high-cut characteristic as shown by Z in FIG. .

However, even in this case, if there is leakage of hydraulic oil from the joint surface between the piston rod spigot portion 3a and the control valve 17 to the first-order lag pressure chamber D without passing through the extension-side variable orifice 17d, the leakage will occur. The pressure in the first-order lag pressure chamber D rises, and as shown by Z1 in FIG. 4, a high cut characteristic in which the breakpoint frequency is shifted to a lower frequency side than in the previous medium mode is exhibited.

However, as described in the medium mode, since the pin 14 is provided with the control orifice 14c having a diameter smaller than that of the expansion-side variable orifice 17d, the pressure gain control in the first-order lag pressure chamber D is controlled by these expansion orifices. This is performed by a differential pressure based on the difference between the diameter of the side variable orifice 17d and the diameter of the control orifice 14c.

Therefore, even if the hydraulic oil leaks into the first-order lag pressure chamber D, the expansion-side variable orifice 1
By appropriately selecting the difference between the diameter of 7d and the diameter of the control orifice 14c, a low damping force characteristic having no high-cut characteristic as shown by Z in FIG. 4 is obtained.

During the compression stroke: As shown in FIG. 3, since the pressure-side variable orifice 17e has a large diameter, the lower hydraulic oil chamber L
From the pressure side variable orifice 17e to open the check valve 22, and the flow rate of the hydraulic oil passing through the back valve 9 becomes zero, which is the same as in the previous medium mode. And the damping force characteristic is lower than in the medium mode.

In the above embodiment, as shown in FIG. 3, the extension side variable orifice 17d of the control valve 17 is switched from a large diameter to a small diameter and closed (the compression side variable orifice 17).
e is also switched from closed to small diameter and large diameter), thereby bringing the input frequency range where the extension side damping force switches to low damping force at the time of large diameter and closing, out of the practical frequency range, and the mode of generated damping force Although the switching is performed, this is not always the case. For example, by controlling the degree of restriction of the expansion-side variable orifice 17d (of course, the compression-side variable orifice 17e may be included), the expansion-side damping force is controlled. The mode switching may be performed by adjusting the input frequency range in which the switching to the low damping force is performed in multiple stages.

Further, in the embodiment of FIG. 1 described so far, the control orifice 14c is formed directly on the pin 14. However, as in the embodiment of FIG.
4d, and an orifice plate 42 having a control orifice 42c is fitted to the push member 13 from below, and is held by a locking plate 43 having a through hole 43c. And control orifice 42c
The same applies to the case where the temporarily delayed pressure chamber D and the lower hydraulic oil chamber L are connected through the through hole 43c.

[0081]

As described above, according to the present invention, in the hydraulic shock absorber of the damping force frequency dependent variable type, the pressure in the first-order lag pressure chamber due to the hydraulic oil leakage at the joint surface between the piston rod and the control valve is obtained. Deviations in gain control can be reliably eliminated by a simple configuration in which the primary delay pressure chamber and the lower hydraulic oil chamber are connected by a control orifice smaller in diameter than the variable orifice on the extension side of the control valve.

Further, this eliminates the necessity of reducing the gap between the joint surface between the piston rod and the control valve and increasing the total length of the control valve, thereby increasing the processing cost and the basic length as a hydraulic shock absorber. Can be minimized.

[Brief description of the drawings]

FIG. 1 is a cutaway view of a main part of a hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of FIG.

FIG. 3 is a diagram showing a relationship between an opening degree of a control valve and a generated damping force mode.

FIG. 4 is a graph showing frequency characteristics of the extension damping force.

FIG. 5 is a cutaway view of a main part of a hydraulic shock absorber according to another embodiment of the present invention.

FIG. 6 is a cutaway view of a main part of a conventional hydraulic shock absorber.

[Explanation of symbols]

 D Primary delay pressure chamber L Lower hydraulic oil chamber U Upper hydraulic oil chamber 1 Cylinder 2 Piston 2a Expansion port 2b Pressure port 2c Through hole 2d Annular groove 2e Depression 2f Annular recess 3 Piston rod 3c Through hole 3e Through hole 3f Through hole 4 Gasket 5 Piston nut 5a Passage 9 Rear valve 11 which is a compression side damping force adjustment mechanism 11 Valve seat member 11a Through hole 12 Leaf valve which is an extension side damping force generation mechanism 13 Push member 14 Pin 14c Control orifice 15 Leaf spring 16 Block member 16c Through hole 17 Control valve 17c Internal passage 17d Extension side variable orifice 17e Pressure side variable orifice 17f Check port 17g Annular groove 18 Seal member 21 Disk 21f Annular recess 21g Through hole 22 Check valve 27 Control rod 42 Orifice plate 42c control orifice

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-168435 (JP, A) JP-A-5-202972 (JP, A) Jikai Sho 62-34238 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) F16F 9/50 B60G 17/08

Claims (1)

(57) [Claims] A piston rod is movably inserted into a cylinder via a piston, the piston partitions an upper hydraulic oil chamber and a lower hydraulic oil chamber in the cylinder, and an upper hydraulic oil chamber is formed between the piston and the piston rod. And a lower hydraulic oil chamber.A main passage communicating with the lower hydraulic oil chamber is formed.A leaf valve for generating an extension-side damping force is provided in the middle of the main passage so as to be openable and closable, and a push member is provided in the piston rod at the back of the leaf valve. A first-order lag pressure chamber opposed to the first-order lag pressure chamber is provided, and a passage branching from the main passage and communicating with the first-order lag pressure chamber is provided in the piston and the piston rod, and a variable orifice is provided in this passage. In the dependent frequency variable type hydraulic shock absorber which is capable of appropriately adjusting a high frequency range in which the extension side damping force is reduced along with the variable adjustment operation, the first-order lag pressure A hydraulic shock absorber characterized in that a control orifice smaller in diameter than the variable orifice is provided between the chamber and the lower hydraulic oil chamber.