JPH09196107A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the overall length by reducing a storage space of a spool and a free piston which are a frequency sensitive part. SOLUTION: In a hydraulic shock absorber, a piston rod 2 is movably inserted in a cylinder 1, the piston demarcates a rod side oil chamber A and a piston side oil chamber B in the cylinder, and a piston nut 6 to support the piston is connected to a lower part of the piston rod. A passage C to communicate the rod side oil chamber with the piston side oil chamber is formed in the piston and the piston nut, a hollow part D to be communicated with the passage is formed in the piston nut, and a spool 10 and a free piston 13 are inserted in series in the hollow part in a movable manner. In addition, the spool demarcates an upper surface side oil chamber D1 and a back side oil chamber D2 in the hollow part, the spool is provided with a disk 15 to be abutted on an upper wall of the hollow part in an attachable/detachable manner, and an orifice 10a to communicate the upper surface side oil chamber with the back side oil chamber, a port to be communicated with the passage is formed on the disk, and a damping valve 4 is provided in the middle of the port in an openable/closable manner.

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 through a piston 3, and the two oil chambers A and B are provided in the piston 3. A bypass passage R is formed which communicates with the port 3b and is opened / closed via a damping valve 4 provided in the middle of the port 3b, and further bypasses the damping valve 4 to open / close the two oil chambers A and B. Is a hydraulic shock absorber, and the bypass R
A spool 10 that opens and closes the bypass R is slidably disposed in the middle of the above, and a pressure receiving surface side oil chamber R3 formed on the pressure receiving surface side of the spool 10 and a back pressure surface formed on the back pressure surface side of the spool 10. The side oil chamber R4 is communicated with the side oil chamber R4 via the orifice 17a.
3 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 B, 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 above hydraulic shock absorber, the above-described excellent effects are obtained and there is no problem in terms of function, but the port 3b and the bypass R are provided in parallel, The damping valve 4 is provided in the middle of the free piston 1 and the free piston 1 in the middle of the bypass R is provided separately from the damping valve 4.
Since 0 is provided, an axial space for accommodating the damping valve 4 and the free piston independently is required. For this reason, it is necessary to dispose the piston nut 6 downward by the space for accommodating the damping valve 4. Therefore, the length of the cylinder 1 becomes long and the total length of the hydraulic shock absorber becomes long in order to have a sufficient stroke because the piston nut 6 is arranged below, so that the installation space of the hydraulic shock absorber may be restricted. There is a problem.

Therefore, an object of the present invention is to provide a hydraulic shock absorber in which the space for accommodating the damping valve and the free piston can be reduced and the overall length can be shortened.

[0014]

In order to achieve the above object, the structure of the present invention is such that a piston rod is movably inserted into a cylinder via a piston, and the piston is a rod-side oil chamber and a piston in the cylinder. In a hydraulic shock absorber that partitions the side oil chamber and a piston nut that supports the piston is connected to the bottom of the piston rod, a passage that connects the rod side oil chamber and the piston side oil chamber is formed between the piston and the piston nut. Then, the piston nut is formed with a hollow portion communicating with the passage, and a movable spool and a free piston are inserted in series in the hollow portion, and the spool has an upper surface side oil chamber and a rear side oil chamber in the hollow portion. And a disc that removably abuts the upper wall of the hollow portion and an orifice that connects the upper surface side oil chamber and the rear surface side oil chamber to each other. The disc forms a port communicating with the passageway and is characterized in that a damping valve in the middle of this port openably.

In this case, it is preferable that a stopper formed of an elastic material is provided between the spool and the free piston, and the stopper supports the free piston biased from below.

Similarly, the elastic member provided in the rear side oil chamber constantly urges the spool upward, and the seat portion provided at the upper end of the outer side of the disk main body abuts the upper wall of the hollow portion to bypass the damping valve. Is preferably closed.

[0017]

FIG. 1 is a block diagram showing an embodiment of the present invention.
According to the hydraulic shock absorber of the present invention, a piston rod 2 is movably inserted into a cylinder 1 via a piston 3, and the piston 3 has a rod-side oil chamber A and a piston-side oil in the cylinder 1. A chamber B is defined, and a piston nut 6 that supports the piston 1 is coupled to the lower portion of the piston rod 2. Further, a passage C that connects the rod side oil chamber A and the piston side oil chamber B is formed in the piston 3 and the piston nut 6, and the passage C is formed in the piston nut 6.
A hollow part D communicating with the hollow part D, and a movable spool 10 and a free piston 13 are inserted in series in the hollow part D. The room D2 is partitioned.

The spool 10 has a disk 15 that removably contacts the upper wall of the hollow portion D, and an orifice 10a that connects the upper surface side oil chamber D1 and the rear surface side oil chamber D2.
The disk 15 is provided with a port 5 communicating with the passage C, and a damping valve 4 is provided in the middle of the port 5 so as to be openable and closable.

A spring seat 16a, a spring 16, a check valve 17 and a piston 3 are inserted in series in the pilot portion of the piston rod 2, and a hollow piston nut 6 is fastened to these members.

A pressure port 18 is formed in the piston 3 to connect the rod side oil chamber A and the piston side oil chamber B, and a check valve 17 is openably and closably provided at the upper outlet end of the pressure port 18. .

The passage C formed in the piston 3 and the piston nut 6 includes an extension port 19 provided in the piston 3 and a vertical port 20 and a horizontal port 2 formed in the piston nut 6.
The hollow portion D in the piston nut 6 communicates with the vertical port 20 and the horizontal port 21.

An annular spring receiver 22 and a cylindrical guide 23 are inserted in the lower inner periphery of the hollow portion D, and the spring receiver 22 and the guide 23 are supported by a cap 25 fixed by caulking to the lower ends. There is.

A spring 12, which is an elastic member composed of a leaf spring, a coil spring, etc., is supported on the spring receiver 22, and the spring 12 constantly pushes up the spool 10 inserted vertically above the hollow portion D so as to be movable upward and downward. ing.

An elastic stopper 14 made of an elastic material such as rubber or a leaf spring is provided between the spring receiver 22 and the guide 23 so as to face inward. Guide 2
A free piston 13 is vertically movably inserted into the inside of 3 through a seal on the outer circumference, and the free piston 13 is pushed up by a spring 24 interposed between the free piston 13 and the cap 25. Supported on the underside of.

The free piston 13 is interlocked with the spool 10. When the spool 10 descends, the free piston 13 descends against the spring 24 due to the internal pressure of the rear oil chamber D2, and the free piston 13
The oil on the back side of the oil flows out into the piston side oil chamber B through the through hole 26 formed in the cap 25.

A large hollow 10 is formed in the center of the spool 10.
b and an orifice 10a opening to the recess 10b are formed, and the upper surface side oil chamber D1 and the rear surface side oil chamber D2 communicate with each other through the recess 10b and the orifice 10a.

A cylindrical portion 27 stands up at the center of the spool 10, and the disk 15, the damping valve 4 consisting of a leaf valve, and the spacer 28 are inserted in series on the outer periphery of the cylindrical portion 27, and these members form the cylindrical portion. It is fixed by swaging the upper end of 27.

A port 5 is formed in the main body of the disk 15, and this port 5 has a piston nut 6 through a hollow portion D.
The vertical port 20 and the horizontal port 21 of the
The damping valve 4 is openably and closably arranged at the lower outlet end of the.

An annular seat portion 15a is erected above the outside of the main body of the disk 15, and the seat portion 15a is urged upward by the spring 12 so that the spool 10 itself is urged to the upper wall of the hollow portion D at rest. Abut, passage C, ie
The communication between the vertical port 20 and the horizontal port 21 is blocked.
On the other hand, when the spool 10 descends, the seat portion 15a simultaneously descends, and the hollow portion D forms a bypass that bypasses the damping valve 4.

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. Hydraulic oil from A is port 19-vertical port 20
-Hollow part D-Port 5-Dampening valve 4-Hollow part D-Lateral port 21 to flow out to the piston side oil chamber B which is a low pressure side oil chamber. Then, when the hydraulic oil passes through the extension side valve 4, a predetermined amount of extension side damping force is generated.

By the way, during the above-mentioned extension side stroke, the hydraulic pressure from the rod side oil chamber A acts in the upper surface side oil chamber D1 formed on the pressure receiving surface side of the spool 10.

At this time, when the vibration frequency of the piston 3 is in the low frequency range, the oil pressure supplied to the upper surface side oil chamber D1 is applied to the back pressure surface side oil formed on the back pressure surface side of the spool 10 through the orifice 10a. It is also supplied to the chamber D2.
Therefore, the same pressure is applied between the upper surface side oil chamber D1 and the back pressure surface side oil chamber D2, and the hydraulic pressure difference does not appear. Therefore, the spool 12 is maintained in the neutral state by the spring 12. Together, they are kept stationary, and since the seat portion 15a is in contact with the upper wall of the hollow portion D, the bypass bypassing the damping valve 4 is kept closed.

As a result, during the expansion side stroke, the hydraulic oil from the rod side oil chamber A passes only through 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 the high frequency range during the extension side stroke, the oil pressure from the rod side oil chamber A causes the oil pressure from the rod side oil chamber A to rise.
To the back pressure surface side oil chamber D2 due to the restriction of the orifice 10a.

As a result, at this time, the upper oil chamber D1
Between the back pressure surface side oil chamber D2 and the back pressure surface side oil chamber D2, the internal pressure of the upper surface side oil chamber D1 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 D2. It slides in the backward direction, which is the downward direction in the figure, against the biasing force of the spring 12. Therefore, the seat portion 15a descends to open the bypass by the hollow portion D.

When the spool 10 slides in the backward direction, the free piston 13 urges the spring 2 to urge it.
The sliding movement of the spool 10 is ensured by retracting so as to descend in the figure against the urging force of 4.

As a result, the working oil from the rod side oil chamber A passes through the bypass opening above the seat portion 15a and flows out to the piston side oil chamber B, so that the oil passing through the expansion side damping valve 4 is discharged. The amount is reduced, and 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.

[0040]

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 range, the disk is maintained in the closed state and the bypass bypassing the damping valve is closed to generate a high damping force. On the other hand, when the vibration frequency in the piston goes out of the low frequency range, especially in the high frequency range, the spool and the disk slide and the bypass that bypasses the damping valve is opened to say low damping force. Can be generated, and the difference in damping force between the two 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 and the disk are configured to be in the neutral state and the bypass closed state by the biasing force of the spring, so that the piston speed is in the low speed range. Therefore, even when the damping force is low and the internal pressure is small, there is an advantage that the bypass can be surely closed to realize a predetermined high damping force generation state.

Similarly, even when the hydraulic shock absorber starts to expand and contract at a very low speed from the stationary state, the bypass is closed by the disk in advance, so that the hydraulic oil from the high pressure side oil chamber is bypassed. There is an advantage that a predetermined high damping force can be reliably generated without flowing out to the low pressure side oil chamber via the. 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 damping valve and the free piston are housed in the piston nut, there is no need to provide a space for disposing the damping valve between the piston and the piston nut, and this allows the axial length of the piston rod to be increased. The hydraulic shock absorber can be shortened and the cylinder can be shortened, and the total length of the hydraulic shock absorber can be shortened.

According to the second aspect of the present invention, since the free piston is supported by the elastic stopper, it is possible to prevent the generation of impact noise when the free piston returns.

[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 Damping valve 6 Piston nut 10 Spool 10a Orifice 12 Spring 13 Free piston 14 Stopper 15 Disk 15a Seat part A Rod side oil chamber B Piston side oil chamber C Passage D Hollow part D1 Top side oil chamber D2 Back pressure surface side oil chamber

Claims (3)

[Claims] 1. A piston nut in which a piston rod is movably inserted into a cylinder via a piston, the piston defines a rod-side oil chamber and a piston-side oil chamber in the cylinder, and the piston nut supports the piston at a lower portion of the piston rod. In the hydraulic shock absorber in which the piston and the piston nut are formed with a passage that communicates with the rod-side oil chamber and the piston-side oil chamber, the piston nut is formed with a hollow portion that communicates with the passage, A movable spool and a free piston are inserted in series in the hollow part, and the spool defines an upper side oil chamber and a rear side oil chamber in the hollow part, and the spool is detachably attached to the upper wall of the hollow part. A disk that abuts against
It is characterized in that an orifice that communicates the upper surface side oil chamber and the rear surface side oil chamber is provided, a port that communicates with the passage is formed in the disk, and a damping valve is provided in the middle of this port so as to be openable and closable. Hydraulic shock absorber. 2. The hydraulic shock absorber according to claim 1, wherein a stopper formed of an elastic material is provided between the spool and the free piston, and the stopper supports the free piston biased from below. 3. A bypass for urging the spool to be constantly urged upward by an elastic member provided in the rear side oil chamber, and a seat portion provided at an upper end outside the main body of the disk abuts the upper wall of the hollow portion to bypass the damping valve. The hydraulic shock absorber according to claim 1, wherein is closed.