JPH09170641A - Hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a storing space of a spool and free piston which are frequency sensing parts and shorten an entire length. SOLUTION: In this hydraulic buffer, two oil rooms partitioned in a cylinder 1 are opened/closed through a damping valve and further a bypass passage for communicating two oil rooms is formed by turning around the damping valve and a spool 10 for opening/closing the bypass passage and a free piston for communicating with the spool are inserted movably in this bypass passage and the upper surface side oil room 6a of the spool in the bypass passage is connected to its back side oil room R4 through an orifice 10a installed on the spool. The free piston 13 is formed cylindrically and the spool is inserted in this free piston movably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber mounted on a vehicle, and more particularly to an improvement of a hydraulic shock absorber in which a damping force generated is so-called high cut adjusted in response to a vibration frequency.

[0002]

2. Description of the Related Art In recent years, hydraulic shock absorbers mounted on vehicles have been
In many cases, the generated damping force is adjusted in response to the vibration frequency.

For example, the applicant of the present invention has developed a hydraulic shock absorber which can generate a predetermined damping force in response to a vibration frequency and is optimal for mounting on a vehicle (Japanese Patent Application No. 7- 2467
41).

In this hydraulic shock absorber, as shown in FIG. 2, two oil chambers A and B are defined in a cylinder 1 via a piston 3, and the two oil chambers A and B are interposed via a damping valve 4. Is a hydraulic shock absorber in which a bypass path R for bypassing the damping valve 4 and opening and closing the two oil chambers A and B is formed, and the bypass path R is opened and closed in the middle of the bypass path R. Spool 10 is slidably arranged, and spool 1
The pressure receiving surface side oil chamber R3 formed on the pressure receiving surface side of 0 and the back pressure surface side oil chamber R4 formed on the back pressure surface side of the spool 10 are communicated with each other through the orifice 17a.
4, a free piston 13 is slidably inserted, and a spring 12 for urging the spool 10 in the closing direction is interposed between the free piston 13 and the spool 10.

In the above case, the bypass passage R is formed in the piston rod 2 and the piston nut 6 connected to the lower end of the piston rod 2, and the spool 10 and the free piston 13 are connected in series in the hollow portion of the piston nut. It is located in. According to the above hydraulic shock absorber, when the vibration frequency in the cylinder 1 is in the low frequency range, for example, the hydraulic pressure from the high pressure side oil chamber A is formed on the pressure receiving surface side of the spool 10 on the pressure receiving surface side. The oil is supplied to the oil chamber R3 and is also supplied to the back pressure surface side oil chamber R4 formed on the back pressure surface side of the spool 10 through the orifice 17a. At this time, no hydraulic pressure difference appears between the pressure receiving surface side oil chamber R3 and the back pressure surface side oil chamber R4, and the bypass passage R is maintained in a closed state by being kept stationary.

As a result, the hydraulic oil from the high pressure side oil chamber A passes through only the damping valve 4 and flows out to the low pressure side oil chamber R4, and the predetermined damping force set by the damping valve 4 can be generated. .

On the other hand, when the vibration frequency in the cylinder 1 is out of the low frequency range, and particularly in the high frequency range,
The oil pressure from the high pressure side oil chamber A is supplied to the pressure receiving surface side oil chamber R3, but the oil pressure via the orifice 17a is not supplied to the back pressure surface side oil chamber R4.

At this time, a hydraulic pressure difference appears between the pressure receiving surface side oil chamber R3 and the back pressure surface side oil chamber R4, and the spool 10 is arranged in the back pressure surface side oil chamber R4. 12
The bypass R is opened by sliding in the backward direction against the biasing force of the bypass passage R.

In this case, when the spool 10 slides in the backward direction, the free piston 13 provided in the back pressure surface side oil chamber R4 retracts to ensure the sliding of the spool 10.

As a result, the hydraulic oil from the high pressure side oil chamber A passes through the bypass passage R and flows out to the low pressure side oil chamber B, the amount of oil passing through the damping valve 4 is reduced, and the damping force is small. Become.

When the vibration frequency in the cylinder 1 changes from the low frequency region to the high frequency region, the damping force generation state that has been generated until then is adjusted to a lower damping force generation state, and the damping force is so-called high cut adjustment. To be done.

[0012]

According to the hydraulic shock absorber described above, the spool 10 and the free piston 13 are provided in the piston nut 6 although they have the above-mentioned excellent effects and have no problem in function. Since they are arranged in series along the axial direction, it is necessary to increase the axial space for accommodating the spool 10 and the free piston 13, and for this reason, it is necessary to shape the piston nut 6 long. Therefore, the length of the cylinder 1 is increased in order to obtain a sufficient stroke corresponding to the lengthening of the piston nut 6, the total length of the hydraulic shock absorber is increased, and the installation space of the hydraulic shock absorber may be restricted. There is. Therefore,
An object of the present invention is to provide a hydraulic shock absorber capable of reducing the accommodation space between the spool, which is the frequency sensitive portion, and the free piston, and shortening the overall length.

[0013]

In order to achieve the above object, the structure of the present invention is such that two oil chambers are defined in a cylinder, and the two oil chambers are opened and closed via a damping valve.
A bypass passage that bypasses the damping valve and connects the two oil chambers is formed, and a spool that opens and closes the bypass passage and a free piston that is interlocked with the spool are movably inserted in the bypass passage. In the hydraulic shock absorber in which the oil chamber on the upper surface side and the oil chamber on the back surface side of the spool in the passage are connected via an orifice provided in the spool, the free piston is formed in a tubular shape, and the spool is arranged in the free piston. It is characterized by being inserted movably.

In this case, the damping valve is provided in the piston, the bypass passage is formed in the piston rod and the hollow piston nut provided at the lower end of the piston rod, and the hollow portion in the piston nut is provided with a seal to the downward direction. A urged cylindrical free piston is inserted so that it can move up and down,
Further, a bottomed cylindrical spool urged upward through a seal is inserted inside the free piston so as to be vertically movable, and the internal pressure of the rear side oil chamber of the spool acts on the lower end of the free piston. Preferably.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention in which a piston rod 2 is movably inserted into a cylinder 1 via a piston 3, and the piston 3 is a rod in the cylinder 1. The side oil chamber A and the piston side oil chamber B are partitioned, and the two oil chambers A and B communicate with each other through the expansion side port 3b and the compression side port 3c provided in the piston 3, and the expansion side port 3
An expansion-side damping valve 4 is openably and closably provided on the outlet side of a, and a check valve 7 is similarly openably and closably provided on the outlet side of the pressure side port 3c. Further, in the hydraulic shock absorber according to this embodiment, a bypass path R3 that bypasses the extension side damping valve 4 is formed, and the bypass path R3 is
A spool 10 that is formed on the piston rod 2 and a piston nut 6 that is a housing coupled to the lower portion of the piston rod 2 and that opens and closes the bypass passage R3 is movably inserted into the bypass passage R3. Further, the upper surface side oil chamber 6a of the spool 10 in the bypass passage R3 and the back pressure surface side oil chamber R4 which is a primary lag pressure chamber are connected via an orifice 10a formed in the center of the spool 10, and the outer peripheral side of the spool 10 is connected. A free piston 13 is movably arranged in the.

The bypass passage R3 includes a passage 3b formed in the piston 3, a lateral passage 2a and a vertical passage 2b formed in the piston rod 2, a hollow portion C in the piston nut 6, and a lateral passage formed in the piston nut 6. 6c, the passage 3b opens to the rod-side oil chamber A, and the lateral passage 6c opens to the piston-side oil chamber B.

The hollow portion C in the piston nut 6 is sealed with a cap 14 made of metal, rubber or the like fixed to the lower end by caulking, screws, pins or the like.

A cylindrical free piston 13 is provided in the hollow portion C.
Is vertically movably inserted through a seal on the outer circumference, and inside the free piston 13, a cylindrical spool 10 with a bottom is installed.
Is vertically movably inserted through a seal on the outer periphery. A spring 13a is interposed between the upper end of the free piston 13 and the upper wall of the hollow portion C to constantly urge the free piston 13 downward. The lower end of the free piston 13 is normally in contact with the upper surface of the cap 14, but a cushion material may be interposed on the upper surface of the cap 14 to prevent the generation of impact noise when the free piston 13 suddenly descends. . However, if the cap 14 is made of an elastic material, it is not necessary to insert the cushion material as described above.

An annular taper surface is formed at the lower end of the free piston 13 so that the hydraulic pressure in the rear side oil chamber R4 acts.

The spool 10 is biased upward, that is, in the closing direction by a spring 12 provided in the rear side oil chamber R4, and an orifice 10a is formed at the center of the spool 10.

An annular protrusion 10b is provided on the upper end of the spool 10.
Is formed, and the upper surface side oil chamber 6b is defined above the spool 10. However, the protrusion 10b can be used without it.

In the hydraulic shock absorber according to this embodiment formed as described above, the rod side oil chamber, which basically becomes the high pressure side oil chamber, during the extension side stroke in which the piston 3 rises in the cylinder 1. The hydraulic oil from A is the expansion side valve 4 of the piston 3.
Is discharged to the piston side oil chamber B which is a low pressure side oil chamber. When the hydraulic oil passes through the extension side valve 4,
An extension side damping force of a predetermined magnitude is generated.

By the way, during the above expansion side stroke, the hydraulic pressure from the rod side oil chamber A is applied to the pressure receiving surface side of the spool 10 through the passage 3a provided in the piston 3 and the passages 2a and 2b for opening the piston rod 2. It acts in the formed upper surface side oil chamber 6a.

At this time, when the vibration frequency of the piston 3 is in the low frequency range, the hydraulic pressure supplied to the upper surface side oil chamber 6a causes the oil pressure on the back pressure surface side formed on the back pressure surface side of the spool 10 via the orifice 10a. It is also supplied to the chamber R4.
For this reason, the upper surface side oil chamber 6a and the back pressure surface side oil chamber R4 have the same pressure, and the hydraulic pressure difference does not appear. Therefore, the spool 10 is maintained in the neutral state by the spring 12. For this reason, the stationary state is maintained, and the bypass R3 is maintained in the closed state.

As a result, during the expansion side stroke, the hydraulic oil from the rod side oil chamber A passes through only the damping valve 4 and flows out to the piston side oil chamber B which is the low pressure side oil chamber.
It is possible to generate a predetermined high damping force set by the damping valve 4.

When the vibration frequency of the piston 3 deviates from the low frequency range and reaches a high frequency range during the extension side stroke, the oil pressure from the rod side oil chamber A is applied to the upper surface side oil chamber 6a.
To the back pressure surface side oil chamber R4 due to the restriction of the orifice 10a.

As a result, at this time, the upper surface side oil chamber 6a
Between the back pressure surface side oil chamber R4 and the back pressure surface side oil chamber R4, the internal pressure of the upper surface side oil chamber 6a becomes higher, and as a result, a hydraulic pressure difference appears, and the spool 10 is distributed in the back pressure surface side oil chamber R4. The bypass passage R3 is opened by sliding in the backward direction which is the downward direction in the figure against the biasing force of the spring 12.

When the spool 10 slides in the backward direction, the free piston 13 urges the spring 1 to urge it.
The spool 10 is retracted so as to rise in the figure against the urging force of the spool 3a to ensure sliding of the spool 10.

As a result, the hydraulic oil from the rod side oil chamber A passes through the bypass passage R3 and flows out to the piston side oil chamber B, so that the amount of oil passing through the extension side damping valve 4 decreases.
A predetermined low damping force set by the extension side damping valve 4 is generated.

That is, when the vibration frequency in the cylinder 1 changes from the low frequency region to the high frequency region, the damping force generation state that has been generated until then is changed and adjusted to a lower damping force generation state. That is, the damping force is so-called high cut adjustment.

Needless to say, the so-called high cut adjustment described above can be applied to the base valve portion of the hydraulic shock absorber by using the same structure.

[0033]

According to the present invention, the following effects can be obtained.

According to the invention of each claim, when the vibration frequency in the piston is in the low frequency region, the spool is maintained in the closed state and the bypass passage is closed to enable generation of a high damping force. On the other hand, when the vibration frequency in the piston is out of the low frequency range, and especially in the high frequency range, the spool slides to open the bypass passage, so that a low damping force can be generated. The difference can be increased. Even when the input vibration is a superposed wave vibration in which both low frequency and high frequency are mixed, the adjustment for reducing the generated damping force in response to the high frequency element, that is, the so-called high cut adjustment is surely realized. There are advantages.

Similarly, when the vibration frequency is in the low frequency range, the spool is constructed so that it is kept in the neutral state by the biasing force of the spring and is kept in the closed state. Even when the damping force is low and the internal pressure is small, there is an advantage that the bypass passage can be surely closed to realize a predetermined high damping force generation state.

Similarly, even when the hydraulic shock absorber starts expanding and contracting at a very low speed from the stationary state, the bypass passage is closed in advance by the spool, so that the hydraulic oil from the high pressure side oil chamber is discharged. There is an advantage that a predetermined high damping force can be reliably expected to be generated without flowing out to the low pressure side oil chamber via the bypass passage. Therefore, the hydraulic shock absorber according to the present invention can generate a predetermined damping force by appropriately sensing the vibration frequency, and is optimal for mounting on a vehicle.

Since the free piston is formed in a tubular shape and the spool is movably inserted in the free piston, the space for accommodating the spool and the free piston in the vertical direction may be any space required for the stroke of the spool. As a result, the bypass path for inserting the spool and the free piston can be shortened. In other words, for example, the axial length of the piston rod and the piston nut that form the bypass passage can be shortened, which allows the cylinder to be shortened and the total length of the hydraulic shock absorber to be shortened.

[Brief description of the drawings]

FIG. 1 is a partial vertical cross-sectional view showing a hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a partial vertical cross-sectional view showing a conventional hydraulic shock absorber.

[Explanation of symbols]

 1 Cylinder 2 Piston rod 3 Piston 4 Expansion side damping valve as a damping valve 6 Piston nut 6a Top side oil chamber 10 Spool 10a Orifice 12 Spring 13 Free piston A Rod side oil chamber B Piston side oil chamber R3 Bypass passage R4 Back pressure side Oil chamber

Claims (2)

[Claims] 1. A cylinder is divided into two oil chambers, the two oil chambers are opened and closed via a damping valve, and a bypass path is formed to bypass the damping valve and communicate the two oil chambers. A spool that opens and closes the bypass passage and a free piston that interlocks with the spool are movably inserted into the bypass passage, and the upper oil chamber and the rear oil chamber of the spool in the bypass passage are provided on the spool. In the hydraulic shock absorber connected via the orifice, the free piston is formed in a tubular shape, and the spool is movably inserted in the free piston. 2. A damping valve is provided in a piston, a bypass path is formed in a piston rod and a hollow piston nut provided at a lower end of the piston rod, and is attached to a hollow portion in the piston nut downward through a seal. A urged cylindrical free piston is vertically movably inserted, and a bottomed cylindrical spool urged upward through a seal is vertically movably inserted inside the free piston. The hydraulic shock absorber according to claim 1, wherein the internal pressure of the side oil chamber acts on the lower end of the free piston.