JP3131885B2 - 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 an improvement of a vibration frequency sensitive type hydraulic shock absorber which is optimally mounted on a vehicle or the like.

[0002]

2. Description of the Related Art In recent years, various types of hydraulic shock absorbers mounted on vehicles and the like have been proposed as structures having a structure in which a generated damping force is changed in response to a vibration frequency.

For example, in a hydraulic shock absorber disclosed in Japanese Patent Application Laid-Open No. 2-304229, each of an extension side and a compression side damping valve provided at a piston portion in a cylinder has a predetermined damping force at the time of its operation. While the initial load on each of the damping valves is changed in response to the vibration frequency in the cylinder.

That is, in the above-described conventional hydraulic shock absorber, the damping valve comprises an annular leaf valve having a bent outer peripheral end, and an annular leaf valve having the same outer peripheral end bent on the back side of the damping valve. It is assumed that a backup valve is provided, and the backup valve is configured to back up the damping valve by a so-called backup force acting on the pressure receiving side.

[0005] The backup force is obtained by supplying hydraulic pressure from the upstream side of the damping valve to a pressure chamber defined on the pressure receiving side of the backup valve as a first-order hydraulic pressure via an orifice. I have.

Therefore, according to the conventional hydraulic shock absorber, when the vibration frequency in the cylinder is in a low vibration frequency range of about 1 to 2 Hz, a first-order lag hydraulic pressure is supplied to the pressure chamber. The outer peripheral end of the backup valve is pressed against the outer peripheral end of the damping valve by the first-order lag hydraulic action, and the initial load on the outer peripheral end of the damping valve is changed, so that a high damping force can be generated.

When the vibration frequency in the cylinder exceeds the low vibration frequency range, the hydraulic oil cannot pass through the orifice, the first-order hydraulic action is eliminated, and the backup valve does not back up the damping valve. As a result, the initial load at the outer peripheral end of the damping valve is returned to the initial setting, and thereafter, only a low damping force is generated compared to the high damping force described above, that is, a so-called high cut phenomenon is exhibited. Will be.

Therefore, according to the above-described conventional hydraulic shock absorber, high damping force is generated near the sprung resonance point where the vibration frequency in the cylinder is in a low vibration frequency range, and vibration on the spring in the vehicle is suppressed. At the same time, when the vibration frequency in the cylinder is equal to or higher than the low vibration frequency range, a low damping force is generated and the riding comfort of the vehicle is improved.

[0009]

However, the following disadvantages have been pointed out in the conventional hydraulic shock absorber described above.

That is, in the above-described conventional hydraulic shock absorber, a piston rod for interposing a piston for guiding oil pressure from the upstream side of the damping valve to a pressure chamber formed on the pressure receiving surface side of the backup valve. Is provided with an oil passage formed by cutting out the outer periphery of the front spigot portion.

The oil passages are provided for each of the damping valves on the extension side and the compression side, and a plurality of oil passages are provided for securing a flow path area.

Therefore, the strength of the spigot portion of the piston rod is reduced by the formation of the oil passage, and the durability of the hydraulic shock absorber is reduced.

Further, the number of processing steps for the piston rod is increased in order to form the oil passage, which leads to a decrease in productivity of the hydraulic shock absorber and an increase in production cost.

In the above-mentioned conventional example, a backup valve is provided on the back side of the damping valve and a pressure chamber is formed on the pressure receiving surface side of the backup valve. Is set to be large, thereby reducing the effective stroke of the piston or increasing the overall length of the hydraulic shock absorber.

Further, in the above-mentioned conventional example, in particular, when the backup valve is formed in a form bent in advance on the pressure receiving surface side thereof and a first-order lag hydraulic pressure acts on the pressure receiving surface of the backup valve, The back surface of the backup valve is made to be adjacent to the back surface of the damping valve as the hydraulic action increases, that is, the fulcrum on which the backup force acts is gradually moved to the outer peripheral end side of the damping valve.

Therefore, when the vibration frequency in the cylinder is in an ultra-low vibration frequency range of less than 1 Hertz, a predetermined backup force cannot be expected by the backup valve. As a result, there is a disadvantage that the running stability of the vehicle at the time of undulating running at a low speed cannot be obtained.

The present invention has been made in view of the above-mentioned inconveniences, and its purpose is to generate a predetermined damping force in response to a vibration frequency. There is no danger that the durability of the piston rod will decrease due to the decrease in strength, preventing a decrease in productivity and an increase in production cost due to an increase in the number of machining steps for the piston rod, and also reducing the effective stroke of the piston and reducing the overall An object of the present invention is to provide a hydraulic shock absorber that is optimal for mounting on a vehicle without causing inconvenience such as an increase in length.

[0018]

In order to attain the above-mentioned object, the present invention is directed to a method and a method for driving a piston in a cylinder, wherein a predetermined damping force is generated by a damping valve provided on the piston portion. A hydraulic shock absorber formed so as to be able to change an initial load at a bending end of the damping valve by a first-order hydraulic action generated under the arrangement of an orifice depending on a vibration frequency in a cylinder; Is provided adjacent to a downstream end of a valve seat member having a port communicating with a port formed in the piston, and the valve seat member is formed so as to be parallel to the port formed in the valve seat member. It is assumed that the pressure chamber has a pressure chamber, and that the pressure chamber has a pressing member that slides when a first-order hydraulic pressure is supplied and changes an initial load at a bending end of the damping valve.

Further, it is assumed that the valve seat member has a communication hole communicating with a port formed in the piston and is housed in a valve case member adjacent to the end face of the piston.

[0020]

Therefore, when the vibration frequency in the cylinder is in the low vibration frequency range including the ultra-low vibration frequency range of less than 1 Hz, a predetermined first-order hydraulic pressure is supplied to the pressure chamber. Based on this, the pressing member housed in the pressure chamber slides with the seal interposed.

When the pressing member slides, the pressing member is pressed against the bending end of the damping valve, so that the initial load at the bending end of the damping valve is changed to increase, and the damping generated by the damping valve is changed. The force becomes high damping force.

The first-order lag hydraulic pressure supplied to the pressure chamber is caused by the hydraulic pressure acting on the end face of the pressing member when the piston is switched to a so-called reverse stroke, that is, the pressing member slides so as to return. It is released by doing.

On the other hand, when the vibration frequency in the cylinder exceeds the low vibration frequency range, the hydraulic oil cannot pass through the orifice, and the first-order hydraulic pressure is not supplied to the pressure chamber. The initial load is returned to the initial setting, and only a low damping force is generated compared to the high damping force described above.

Further, the pressure chamber is provided so as to be parallel to a port as an oil passage to the damping valve, and the pressing member is provided on the pressure chamber side. Becomes possible.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, a hydraulic shock absorber according to an embodiment of the present invention is inserted into a cylinder 1 under a shaft sealing structure so as to be freely protruded and retracted. A piston 3 interposed in the front spigot portion 2a of the piston rod 2 is slidably housed in the cylinder 1 and defines an extension oil chamber A and a compression oil chamber B in the cylinder 1. It becomes.

A suspension spring S is interposed between the cylinder 1 and the piston rod 2 and urges the piston rod 2 in a direction to protrude from the cylinder 1.

As shown in FIG. 2, the piston 3 is formed by diagonally piercing the piston 3, and is provided with an expansion port 3a for enabling communication between the expansion oil chamber A and the compression oil chamber B.
And the compression side port 3b.

On the other hand, an extension damping valve 4 as a damping valve is arranged on the upper end side of the piston 3, and a compression damping valve 5 as a damping valve is arranged on the lower end side of the piston 3. It is going to be.

However, the damping valves 4 and 5 on the respective sides are not provided directly adjacent to the piston 3, but in this embodiment, the respective valves provided adjacent to the upper and lower ends of the piston 3 respectively. The case member 6 is provided adjacent to a so-called downstream end.

Therefore, the structure of the valve case member 6 and the damping valves 4 and 5 on each side related thereto will be described. The structure of the valve case member 6 is the same on the so-called extension side and the compression side. Further, since the structures of the damping valves 4 and 5 on each side are the same, the structures of the valve case member 6 on the extension side and the extension side damping valve 4 will be described below. Regarding the structures of 6 and the compression side damping valve 5, only the same reference numerals are given in the drawings, and the description thereof is omitted.

First, the extension-side damping valve 4 is formed by laminating a plurality of annular leaf valves having different diameters. The inner peripheral end is a fixed end, while the outer peripheral end is a flexible end. It is arranged to be.

Next, the valve case member 6 is formed in a headed cylindrical shape having an opening at one end, and its head 6a, which is a so-called upstream side, is adjacent to the end face of the piston 3, and The front end spigot portion 2a of the piston rod 2 penetrates the center of the portion 6a.

The valve case member 6 has a communication hole 6b formed so as to penetrate the thickness of the head 6a.
And the communication hole 6b communicates with the extension side port 3a of the piston 3.

The valve case member 6 is formed in an annular shape and the center thereof is formed at the front end spigot portion 2.
The valve seat member 7 formed so as to penetrate a is accommodated therein.

The valve seat member 7 has a port 7a which is opened so as to penetrate its axial thickness, and the port 7a is communicated with the communication hole 6b.

The downstream end of the valve seat member 7 is set to be a valve seat surface at the same level as the position of the open end of the valve case member 6. The extension side damping valve 4 is adjacent to the extension damping valve.

The inner peripheral end of the extension-side damping valve 4 is formed in an annular shape with the inner peripheral end of the valve seat member 7 so that the inner peripheral end of the valve stopper 8 is interposed in the spigot end 2a of the piston rod 2. It is sandwiched between the peripheral end.

Incidentally, the valve seat member 7 has a pressure chamber R formed in parallel with the port 7a. The pressure chamber R is configured as follows.

The peripheral wall 6c of the valve case member 6 is adjacent to the outer periphery of the valve seat member 7.
Therefore, the pressure chamber R is also defined by the peripheral wall 6c of the valve case member 6.

The pressure chamber R is defined in the annular cutout by an O-ring 9 movably housed in the annular cutout on the outer peripheral side of the valve seat member 7 except for the partition wall 7b. In addition, an annular backup ring 10 movably disposed is adjacent to a downstream side of the O-ring 9 which is an upper end side in the figure, and the annular backup ring 1 is provided.
0 has an annular pressing member 11 which is also movably disposed.
Are adjacent to each other.

That is, when the O-ring 9 defining the pressure chamber R slides in the so-called retreating direction by the hydraulic action in the pressure chamber R, the annular pressing member 11 is interposed by the annular backup ring 10. It is formed to slide down.

The downstream end of the annular pressing member 11 is exposed to the pressure side oil chamber B in the cylinder 1,
The end surface position is the same level as the valve seat surface of the valve seat member 7, and the outer peripheral end of the extension-side damping valve 4 is adjacent to the valve seat surface.

On the other hand, a communication hole 7c communicating with the communication hole 6b formed in the valve case member 6 is formed in the partition wall portion 7b of the valve seat member 7.
The annular leaf valve 12 is provided so as to close the communication hole 7c from the upstream side, that is, from the communication hole 6b side.

The annular leaf valve 12 has an orifice 12a for supplying a first-order lag hydraulic pressure to the pressure chamber R.

The annular leaf valve 12 is adjacently provided with a non-return valve 13 disposed between the annular leaf valve 12 and the head 6a of the valve case member 6.

With the above arrangement, the valve case member 6 having the valve seat member 7 and the pressure chamber R is, so to speak, assembled.
In forming the piston portion according to the illustrated embodiment, it is possible to use a common part on the extension side and the compression side, which contributes to a reduction in the number of parts.

The parts interposed between the front spigot 2a of the piston rod 2 and the step 2b formed on the piston rod 2 and the piston screwed on the front thread 2c formed on the piston rod 2 are described below. With the nut 14, the piston rod 2 is held at a predetermined position, which is the tip end.

Therefore, the hydraulic shock absorber according to this embodiment formed as described above operates, for example, at the time of the extension stroke in which the piston 3 descends in the cylinder 1 as follows. .

First, the hydraulic oil in the expansion oil chamber A is supplied to the expansion port 3 a of the piston 3 and the communication hole 6 of the valve case member 6.
b flows into the valve case member 6 through the valve b.

A part of the hydraulic oil that has flowed into the valve case member 6 reaches the pressure receiving surface of the expansion damping valve 4 via the port 7a of the valve seat member, and the oil pressure at that time causes the expansion damping. It flows into the compression side oil chamber B while bending the outer peripheral end of the valve 4, and at this time, a predetermined expansion side damping force is generated by the expansion side damping valve 4.

On the other hand, when the vibration frequency in the cylinder 1 is in the low vibration frequency range of about 1 to 2 Hertz, the orifice 12a of the annular leaf valve 12 upstream of the pressure chamber R is operated by the above operation. The oil passes, and a first-order lag hydraulic pressure is generated in the pressure chamber R.

As a result, the O-ring 9 defining the pressure chamber R is retreated by the first-order oil pressure, so that the annular pressing member 11 connected to the O-ring 9 slides. Will be.

The sliding of the pressing member 11 forcibly bends the outer peripheral end of the extension side damping valve 4 to change the initial load on the extension side damping valve 4 to a rising tendency. Thus, the extension-side damping force generated by the extension-side damping valve 4 is changed to a high damping force tendency.

FIG. 3 shows the state of generation of the above-mentioned damping force. As shown in FIG. 3, the damping force generated only by the extension-side damping valve 4 has a characteristic shown by a solid line a in the figure. This is the same as in the case of the conventional example.

In FIG. 3, the vertical direction indicates the magnitude of the damping force, and the horizontal direction indicates the piston speed.

On the other hand, when the vibration frequency in the cylinder 1 is in the above low vibration frequency range, the broken line b
As shown by, even when the vibration frequency in the cylinder 1 is in an ultra-low vibration frequency region of less than 1 Hertz, the characteristic is such that a predetermined damping force increasing effect is exhibited.

That is, as long as the first-order lag hydraulic pressure acts on the pressure chamber R in the present invention, the pressing member 11 always applies a so-called external force to the outer peripheral end of the extension-side damping valve 4 to change its initial load. Cylinder 1
This is because a predetermined damping force increasing effect is also exhibited when the vibration frequency in the inside is within the ultra-low vibration frequency range.

In the case of the above-mentioned conventional example, as indicated by the imaginary line c in the figure, the initial load on the damping valve will not be changed unless the first-order lag hydraulic pressure is increased to some extent. It is on the street.

In the hydraulic shock absorber, even when the hydraulic shock absorber is compressed in the compression stroke, the same damping force is generated as in the expansion stroke.

When the vibration frequency in the cylinder 1 exceeds the low vibration frequency range, it becomes difficult for the hydraulic oil to pass through the orifice 12a, so that the first-order lag hydraulic pressure is not supplied to the pressure chamber R.

As a result, the external force for changing the initial load in the extension side damping valve 4 does not act, so that the initial load in the extension side damping valve 4 is returned to the initially set value, and the above-mentioned high damping force is generated. As a result, a lower damping force is generated, and a so-called high cut phenomenon is developed.

[0062]

As described above, according to the present invention, even when the vibration frequency in the cylinder is in an extremely low vibration frequency range, the predetermined damping force can be reliably increased in response to this. There are advantages that you can get.

Further, according to the present invention, since there is no need to perform a process for lowering the strength of the piston rod, there is no danger that the durability of the hydraulic shock absorber will be reduced based on this process. The pressure chamber, which prevents the decrease in productivity and the production cost due to the increase in the number, and which changes the initial load in the damping valve is formed on the upstream side of the damping valve, so to speak.
There is an advantage that inconveniences such as reduction of the effective stroke of the piston and increase of the overall length are not caused.

According to the present invention, it is possible to make the configuration of the damping valve the same on the extension side and the compression side, and the parts related to the damping valve can be assembled. Points can be reduced,
There is an advantage that the production cost can be further reduced and productivity can be further improved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing a hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a partially enlarged longitudinal sectional view showing a piston portion in the hydraulic shock absorber shown in FIG. 1 in an enlarged manner.

FIG. 3 is a damping force characteristic diagram of the hydraulic shock absorber according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 3 Piston part 3a Expansion side port as a port in a piston 3b Compression side port as a port in a piston 4 Expansion side damping valve as a damping valve 5 Pressure side damping valve as a damping valve 6 Valve case member 6b Communication hole 7 Valve seat member 7a port 12a orifice R pressure chamber

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16F 9/50 F16F 9/348

Claims (1)

(57) [Claims] When a piston slides in a cylinder, a predetermined damping force is generated by a damping valve disposed on the piston portion, and is generated in the presence of an orifice depending on a vibration frequency in the cylinder. In a hydraulic shock absorber formed so as to be able to change an initial load at a bending end of the damping valve by a first-order lag hydraulic action, a damping valve is provided downstream of a valve seat member having a port communicating with a port opened in a piston. A pressure chamber formed adjacent to the side end, wherein the valve seat member is formed so as to be parallel to the port formed in the valve seat member, and the pressure chamber has a first-order hydraulic pressure. A hydraulic shock absorber characterized by comprising a pressing member that changes the initial load at the bending end of the damping valve by sliding at the time of supplying oil.