JP2993667B2 - Hydraulic shock absorber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in damping force characteristics of a hydraulic shock absorber.

(Prior Art) As a conventional hydraulic shock absorber, for example, Japanese Utility Model Laid-Open No.
What is described in the issue is known.

The hydraulic buffer has a cylinder tube whose interior is divided into an upper liquid chamber and a lower liquid chamber by a piston provided at a lower end of a piston rod, and a base which divides a lower liquid chamber and a reservoir chamber of the cylinder tube. A guide member provided at the end of the cylinder tube to guide the piston rod into and out of the cylinder tube, and a disc valve that opens to generate a damping force on the piston. Was.

The disc valve is provided to open and close an orifice hole formed in the piston body.
A constant orifice is provided between the disc valve and the seat surface so that the hydraulic fluid can flow in a low speed range.

In the hydraulic shock absorber having such a structure, the damping force of the disc valve is such that a characteristic as shown in FIG. 12 (a) is obtained, that is, in a low speed region, the velocity squared by the constant orifice. When the disc valve opens, the characteristic becomes the speed 2/3 power characteristic. Further, as the damping force of the orifice hole, a velocity square characteristic as shown in FIG. 12 (b) is obtained.

Therefore, as the damping force of the hydraulic shock absorber, a characteristic as shown in FIG. 13 which combines the characteristics of FIGS.
That is, a characteristic is obtained in which the rise in the low-speed range is gentle, the slope becomes steeper as the speed becomes higher in the middle-speed range, and the slope falls at the inflection point thereafter.

(Problems to be Solved by the Invention) However, in the conventional hydraulic shock absorber having the above-described damping force characteristics, since the damping force in a low-speed range is low, low-frequency vibration of the vehicle body is reduced. As it happens
For example, when turning the steering wheel or driving at high speed,
There is a problem that the steering stability is poor.

Therefore, in order to increase the damping force in the low-speed range, it is conceivable to obtain a speed 2/3 power characteristic from the low-speed range by not providing a constant orifice in the disk valve that opens in the low-speed range. (For example, German Patent 833574
issue).

However, simply eliminating the constant orifice in this way causes a small amount of hydraulic fluid to leak between the piston and the cylinder tube or between the piston rod and the guide member. , As if a constant orifice was provided, and the rise of the damping force at the time of operation was poor, resulting in a new problem. By the way, those with a constant orifice have the same characteristics as a constant orifice due to such leakage,
It was not a problem.

The present invention has been made by paying attention to the above-described conventional problems, and has excellent damping force rising characteristics in a low-speed range.
In particular, it is an object of the present invention to provide a technique suitable for applying to a hydraulic shock absorber that obtains a linear damping force characteristic.

(Means for Solving the Problems) In order to achieve such an object, in the hydraulic shock absorber of the present invention, one end is sealed by a guide member, and the other end is sealed to a reservoir chamber by a base. A stationary cylinder tube, a piston provided at the end of a piston rod guided by the guide member, and communicating the upper liquid chamber and the lower liquid chamber with a piston that divides the inside of the cylinder into an upper liquid chamber and a lower liquid chamber. At least one of a communication passage formed in the piston and a communication passage formed in the base so as to communicate the lower liquid chamber with the reservoir chamber, and the working fluid flows through the communication passage along with the stroke of the piston. And a disc valve structure that opens to generate a damping force when the hydraulic fluid flows in the communication passage in the first stage from the upstream in the communication direction of the working fluid in the communication passage. The disk valve and the second stage disk valve are arranged in series,
The first-stage disc valve is formed to have a relatively low rigidity relative to the second-stage disc valve, and the first-stage disc valve has a structure that does not have a constant orifice that covers the communication path over the entire circumference. On the other hand, the second-stage disc valve is provided with a constant orifice that secures a flow path having a constant cross-sectional area in a closed state, and seals between the liquid chambers between the piston and the cylinder tube on the outer periphery of the piston. And a seamless seal ring for sealing the upper liquid chamber and the outside of the cylinder tube is provided on the guide member.

Further, the seal ring is in close contact with the piston rod, has an interval capable of following the eccentricity of the piston rod with respect to the guide member, and has a piston provided by a position regulating member provided on the guide member. A structure in which the axial movement of the rod is restricted may be adopted.

(Operation) When the piston slides in the cylinder tube, a hydraulic pressure difference occurs in any of the upper liquid chamber, the lower liquid chamber, and the reservoir chamber, and a disc is formed in the communication passage formed in the piston or the communication passage formed in the base. The valve structure opens,
Hydraulic fluid flows and damping force is generated.

At this time, due to the difference in rigidity between the two disc valves according to the sliding speed of the piston, the first disc valve is opened while the second disc valve is kept closed, and the two disc valves are kept closed. The speed range forming the former condition is referred to as a low speed range, and the speed range forming the latter condition is referred to as a middle / high speed range.

In the low-speed range described above, sufficient opening characteristics can be obtained when the first-stage disc valve is opened. In addition,
In the high-speed range, the high-rigidity second-stage disc valve opens, so the decrease in the rate of increase in the damping force in the middle and high-speed ranges of the first-stage disc valve is compensated for by the second-stage disc valve. Damping force characteristics can be obtained.

In the low-speed range described above, the outer periphery of the piston and the cylinder tube are sealed by a seamless piston ring, so that no leak occurs in this portion, and the outer periphery of the piston rod and the guide member also have a joint. Since there is no seal ring, no leakage occurs in this area. Therefore, when a leak occurs in such a place, the start-up is not delayed as if there is a constant orifice, and a linear damping force characteristic is obtained in the entire speed range from the low speed range to the middle and high speed ranges. Can be.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

 First, the configuration of the embodiment will be described.

FIG. 1 is a sectional view showing a hydraulic shock absorber according to a first embodiment of the present invention, in which 1 indicates a cylinder tube.
The cylinder tube 1 has an upper end closed by a guide member 2 and a seal member 3, and a lower end closed by a base 4 to be filled with a working fluid. 5 is slidably loaded,
It is partitioned into an upper liquid chamber 1a and a lower liquid chamber 1b.

An outer cylinder 6 having a bottomed cylindrical shape is provided outside the cylinder tube 1, and the liquid chambers 1a, 1
A reservoir chamber 7 is formed which is separated from the b by the guide member 2 and the base 4 and is filled with a desired amount of hydraulic fluid under the pressure of the sealed gas.

The piston 5 is attached to a lower end of a piston rod 8. That is, a mounting portion 8b having a smaller diameter than the upper portion and having a screw 8a formed on the outer periphery is provided at a lower end portion of the piston rod 8, and a retainer 5a, a check plate 5b, a piston body 5c, 1st stage disc valve 5d,
Washer 5e, stopper plate 5f, 2nd stage disc valve 5
g, a washer 5h, a collar 5j, a spring seat 5k, and an assist spring 5m are sequentially inserted, and finally fastened with a tightening nut 5n.

In addition, a large-diameter mounting hole 501 is formed in the center of the piston body 5c in the axial direction, and a first communication passage 502 having a large cross-sectional area and a small-sized A second communication passage 503 having an area is formed.

Then, the first communication path 502 is connected to the check plate 5.
The opening at the upper end is closed by b to allow only the flow of the hydraulic fluid from the lower liquid chamber 1b to the upper liquid chamber 1a.

On the other hand, as shown in FIG. 2, which is a detailed view of the portion A in FIG. 1, a boss portion seat surface 504 is formed on the lower surface side of the piston body 5c on the center side of the second communication passage 503,
A first sheet surface 505 is formed outside the second communication path 503,
Further, a second sheet surface 506 is formed on the outside.

The second seat surface 506 is formed with a step at a position lower than the first seat surface 505, and is annular between the two seat surfaces 506, and has a semicircular cross-section. Groove 507 is formed.

The first-stage disc valve 5d abuts on the boss portion seat surface 504 and the first seat surface 505, and the second-stage communication passage 503 can be opened and closed by the first-stage disc valve 5d.

The first-stage disc valve 5d is provided with a support point for bending by an outer peripheral portion of a washer 5e having a diameter smaller than that of the valve 5d. , The valve opening force changes.

The second-stage disc valve 5g is in contact with the second seat surface 506 by being biased by an assist spring 5m. The piston body 5c at the position of the second seat surface 506 is provided with a constant orifice 508 that connects the inside and outside of the contact surface between the second-stage disc valve 5g and the second seat surface 506.

The first-stage disc valve 5d is formed to be resilient so as to open even if the piston speed is extremely low. This can be realized by a two-stage valve structure.

Next, the base 4 is also provided with a valve structure, and the structure will be described.

As shown in FIG. 1, the base 4 is provided with a washer 4b, a second-stage disc valve 4c, and a washer 4d, 1 with respect to a bolt 4a.
The stage disc valve 4e, the base body 4f, the check plate 4g, the retainer 4h, and the collar 4j are sequentially inserted, and finally fastened with a tightening nut 4k.

In the base body 4f, a through hole 401 through which the bolt 4a penetrates is formed at the center, and a first communication path 402 having a large cross-sectional area and a second communication path 403 having a small cross-sectional area are formed. .

And check plate 4g on top of base body 4f
The first communication passage 402 allows only the hydraulic fluid to flow from the reservoir chamber 7 to the lower liquid chamber 1b.

FIG. 3 is a detailed view of a part B of FIG. 1 showing a main part of the base 4, and a lower end surface of the base 4 is provided with a second communication passage 40.
(3) A boss portion sheet surface 404 is formed at the center side of the base, a first sheet surface 405 is formed outside the second communication passage 403, and a second sheet surface 406 is formed outside the boss portion sheet surface 404. Have been.

The second seat surface 406 is formed with a step at a position lower than the first seat surface 405, and is annular between the two seat surfaces 405 and 406 and has a semicircular cross section. Groove 407 is formed. Also, the second sheet surface 406
Are formed with a constant orifice 408 in several places.

The first-stage disc valve 4e abuts on the boss-side seat surface 404 and the first seat surface 405, and the first-stage disc valve 4e allows the second communication passage 403 to be opened and closed.

The first-stage disc valve 4e is provided with a support point for bending by the outer peripheral portion of a washer plate 4d having a smaller diameter than the valve 4e. When the first-stage disc valve 4e bends by the thickness of the washer plate 4d, the second-stage disc valve 4e Abut on 4c,
The valve opening force changes.

A second-stage disc valve is in contact with the second seat surface.

Next, a description will be given of an upper end portion of the hydraulic pressure absorber according to the embodiment with reference to FIG. 1. The guide member 2 has a through hole through which the piston rod 8 enters and exits the cylinder tube 1.
2a is formed. A guide bush 9 is provided on the inner periphery of the through hole 2a.

The seal member 3 provided above the guide member 2 is provided with a lip 3a for contacting and sealing the piston rod 8, and a through hole 9 is provided between the seal member 3 and the guide member 2. And a liquid storage chamber 10 for storing hydraulic fluid leaking from between the piston rod 8 and
The liquid chamber 10 communicates with the reservoir chamber 7 through a communication groove 2c formed in the guide member 2.

The lip 3a of the seal member 3 is in contact with the piston rod 8 to seal the liquid chamber 10 with the outside, and the liquid chamber is provided between the liquid chamber 10 and the communication groove 2c. Ten
A check section 3c is formed to allow only the flow of the hydraulic fluid from the reservoir chamber 7 to the reservoir chamber 7 and to regulate the flow of the sealed gas and the hydraulic fluid in the reservoir chamber 7 in the opposite direction.

As described above, the upper liquid chamber 1a and the lower liquid chamber 1b
The lower liquid chamber 1b and the reservoir chamber 7 are divided by a base 4
Further, the reservoir chamber 7 and the upper liquid chamber 1a are
The guide member 2 and the check portion 3c of the lip 3a of the seal member 3 are separated from each other. In the present embodiment, the piston body 5 is provided to enhance the sealing between the chambers 1a, 1b, and 7.
A piston ring 11 is provided on the outer circumference of c, and a seal ring 12 is provided between the guide member 2 and the piston rod 8.

The piston ring 11 is made of polychloro trifluoro
It is formed by ethylene (commonly known as Teflon) and has a seamless annular shape in the middle. As shown in FIG. 4 which is a detailed view of a portion C in FIG. 1, a fitting formed on the outer periphery of the piston body 5c The groove 5p is provided in a fitted state in which the movement of the piston body 5c in the sliding direction is restricted, and a convex ridge 5q formed at the center of the fitting groove 5p allows the upper end portion as shown in the drawing. The outer periphery is in contact with the inner surface of the cylinder tube 1, and the inner periphery at the lower end is in contact with the piston body 5c to obtain a sealing property.

Polychloro trifluoroethylene, which is a material of the piston ring 11, has excellent lubricity, low sliding resistance, and excellent operability.

Further, the seal ring 12 is
In the same way as with polychlorotrifluoroethylene,
It is formed into a seamless ring shape on the way, and its inner periphery is in contact with the piston rod 8. As shown in FIG. 5, which is a detailed view of a portion D in FIG. 1, the seal ring 12 is tightly attached to the outer periphery of the mounting groove 2c and the guide member 2 formed at the lower end of the through hole 2a of the guide member 2. The piston rod 8 is accommodated in the accommodating groove 13a formed by the fitted cover 13, and the movement of the piston rod 8 in the reciprocating direction is restricted. In the radial direction, the diameter of the accommodating groove 2c is larger than the outer diameter of the seal ring. A moving allowance 13b that can follow the eccentricity of the piston rod 8 by being formed large is provided.

 Next, the operation of the embodiment will be described.

(I) At the time of extension stroke When the piston 5 slides in the extension direction (the direction to narrow the upper liquid chamber 1a), the piston 5 passes through the second communication passage 503 of the piston 5 based on the liquid pressure difference between the upper and lower liquid chambers 1a and 1b. The working fluid flows from the upper fluid chamber 1a to the lower fluid chamber 1b, and the amount of working fluid corresponding to the volume of the piston rod 8 withdrawn from the cylinder tube 1 is passed through the first communication passage 402 of the base 4. From the reservoir chamber 7 into the lower liquid chamber 1b.

At this time, the piston 5 receives 1 according to the piston speed.
Second stage disc valve 5d, second stage disc valve 5g and second
A damping force is generated in the communication passage 503.

The respective damping force characteristics will be described with reference to FIG.

FIG. 6 (a) shows the damping force characteristics of the first-stage disc valve 5d. The first-stage disc valve 5d normally comes into contact with the first seat surface 505 to completely close the second communication passage 503. It is in a closed state. Therefore, in the first-stage disc valve 5d, after the valve is opened, it first has a characteristic of a speed of 2/3 power, and as shown in this figure, even at an extremely low speed, compared with a valve having a constant orifice, A large damping force can be obtained.

When the amount of deflection of the first-stage disc valve 5d increases and comes into contact with the stopper plate 5f, the elastic force is increased, and the inclination of the characteristic becomes steep. still,
In this figure, the inflection point a is the first-stage disc valve 5d.
Shows a state in which it comes into contact with the stopper plate 5f.

In addition, the explanation at the time of low speed is added.
Indicates the hydraulic fluid flow rate immediately after switching the stroke at low speed.
The dotted line shows the case with a constant orifice. In this case, the flow rate Q is proportional to the square of the pressure change ΔP. The solid line indicates the case of the present embodiment, and the flow rate Q is proportional to the 2/3 power of the pressure change ΔP. As shown in this figure, the flow rate at the rise immediately after the stroke switching is greatly different, that is, in the embodiment, the response of the damping force is high.

Next, FIG. 6 (b) shows the damping force characteristics of the second-stage disc valve 5g, which is closed while the piston speed is low, and the hydraulic fluid is constantly in a closed state. Passes through orifice 508. Therefore, as shown in the figure, the characteristic of the constant orifice 508 is as follows.
It has a velocity squared characteristic, and the damping force is low at low speeds.

Then, when the piston speed becomes high and this second-stage disc valve 5g is opened, the speed 2/3 power characteristic is obtained. The inflection point b indicates the time when the second-stage disc valve 5g is opened.

Next, FIG. 6 (c) shows a damping force characteristic of the second communication passage 503. The second communication passage 503 has almost no damping force while the piston speed is low. Has become.

As described above, in the extension stroke, the above-described characteristics are obtained in each part, and particularly, in the first-stage disc valve 5d,
Since a 2/3 power characteristic with a good rise is obtained from a very low speed, the characteristic obtained by combining them is a substantially linear damping force characteristic as shown in FIG.

When such characteristics are obtained, when applied to the suspension of an automobile, for example, when turning the steering wheel, it is possible to respond to a change in the body posture with a low piston speed with good responsiveness and improve the handling. Also, it is excellent in damping effect for a bounce with a low piston speed, such as during high-speed running. Furthermore, the characteristics are almost linear as described above,
Since there is a characteristic that does not have an inflection point on the way as shown in FIG. 7), the characteristic does not suddenly change at the piston speed near the inflection point, and there is no problem that the steering stability is reduced.

Further, in the present embodiment, the piston 5 and the guide member 2
In addition, a seamless piston ring 11 and seal ring 12
Is provided. For this reason, when the piston 2 slides in the extension direction, the working fluid in the upper liquid chamber 1a flows between the piston 2 and the cylinder tube 1 into the lower liquid chamber 1b, It is difficult for the liquid to flow into the liquid reservoir 10 through the space between the piston rod 8 and the liquid, so that almost all of the moving hydraulic fluid from the upper liquid chamber 1a moves through the second communication passage 503.

That is, FIG. 9 shows a case where such a piston ring 11 and a seal ring 12 are provided (shown by solid lines: this embodiment).
And the one not provided (indicated by the dotted line)
If there is a leak in the piston 5 and the guide member 2 as shown in this figure, the leak causes an effect as if a constant orifice was provided in parallel, and the rise is delayed as shown in the figure. On the other hand, in this embodiment, since no leakage occurs, the responsiveness is excellent as shown in the figure.

(II) During the pressure stroke When the piston 5 slides in the pressure direction (direction in which the lower liquid chamber 1b is narrowed), the first communication passage 502 of the piston 5 is used to equalize the liquid pressure difference between the upper and lower liquid chambers 1a and 1b. The hydraulic fluid flows through the lower fluid chamber 1b through the second communication passage 403 of the base 4 in an amount corresponding to the volume of the piston rod 8 entering the cylinder tube 1. It flows into the reservoir chamber 7.

At this time, in the base 4, a damping force is generated in the first-stage disc valve 4e, the second-stage disc valve 4c, and the second communication passage 403 according to the piston speed.

This damping force is generated by opening the first-stage disc valve 4e in the low-speed range, as in the case described above.
A 2/3 power damping characteristic is obtained, and when the first-stage disc valve 4e contacts the second-stage disc valve 4c, the generated damping force increases and the slope of the characteristic becomes steep.

On the other hand, the second-stage disc valve 4c does not open in the low-speed range, and the speed square characteristic by the constant orifice 408 is obtained, and changes from the valve opening time to the speed 2/3 characteristic.

Further, in the second communication passage 403, in a low speed region, a speed square characteristic in which damping force hardly occurs is obtained.

Even during this pressure stroke, leakage is prevented by the seal ring 12, so that high responsiveness is obtained.

Next, a second embodiment shown in FIGS. 10 and 11 will be described.

In this embodiment, a plurality of annular grooves 1515a, 25a are formed in parallel on the inner surface of the piston ring 15 and the outer surface of the piston body 25, and irregularities formed by the grooves 15a, 25a are fitted.

Further, in the guide member 22, the liquid reservoir chamber 10 and the reservoir chamber 7 are communicated with each other through a communication hole 22a.

The other configuration is the same as that of the first embodiment, and the description is omitted. The same reference numerals indicate the same objects.

The embodiments of the present invention have been described in detail with reference to the drawings.
The specific configuration is not limited to this embodiment, and any change in design without departing from the spirit of the present invention is also included in the present invention.

For example, in the embodiment, the present invention is applied to both the disc valve that generates the damping force in the extension stroke and the disc valve that generates the damping force in the compression stroke (the structure is not provided with the constant orifice). Alternatively, only one of them may be applied.

Further, in the embodiment, the example in which the piston ring and the seal ring are formed of polychloro-trifluoro-ethylene is shown, but the piston ring and the seal ring may be formed of another material such as another resin or a metal, or both materials may be different. Good.

(Effects of the Invention) As described above, in the hydraulic shock absorber of the present invention, the disc valve structure provided in at least one of the communication passages provided in the piston and the base includes:
A first-stage disc valve having no constant orifice, a second-stage disc valve provided in series with the first-stage disc valve and having a constant orifice, and further provided with a cylinder tube provided on the outer periphery of the piston. The piston ring that seals between the piston ring and the seal ring that is provided on the outer periphery of the piston rod and seals between the piston member and the guide member has no seam, so that the rising characteristics of the damping force in a low-speed range can be improved. And a linear damping force characteristic can be obtained in the entire speed range from the low speed range to the high speed range, and the effect that the damping force characteristics of the hydraulic shock absorber can be made ideal can be obtained. Can be

[Brief description of the drawings]

FIG. 1 is a sectional view showing a hydraulic shock absorber according to a first embodiment of the present invention,
2 is a detailed view of part A of FIG. 1, FIG. 3 is a detailed view of part B of FIG. 1, FIG. 4 is a detailed view of part C of FIG. 1, FIG. 5 is a detailed view of part D of FIG. The figure is a graph showing the damping force characteristic on the piston side of the first embodiment, wherein (a) is the characteristic of the first-stage disk valve, (b) is the characteristic of the second-stage disk valve, and (c) is the second. FIG. 7 is a graph showing the damping force characteristics of the hydraulic shock absorber of the first embodiment, and FIG. 8 is a graph showing the pressure difference of the first stage disc valve on the piston side and the valve of the first embodiment. 9 is a graph showing a rising portion of the damping force of the first embodiment, FIG. 10 is a cross-sectional view showing a piston of the second embodiment, and FIG. 11 is a cross-sectional view of the second embodiment. FIG. 12 is a cross-sectional view showing a guide member, and FIG. 12 is a graph showing a conventional damping force characteristic, wherein (a) shows a valve characteristic, (b) shows an orifice hole characteristic, FIG. 3 is a graph showing damping force characteristics of a conventional hydraulic shock absorber. 1 ... Cylinder tube 1a ... Upper liquid chamber 1b ... Lower liquid chamber 2 ... Guide member 4 ... Base 4e ... First stage disc valve 403 ... Second communication passage 5 ... Piston 5d ... 1 stage Eye disc valve 503 Second communication passage 7 Reservoir chamber 8 Piston rod 11 Piston ring 12 Seal ring

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-116134 (JP, A) JP-A-57-119035 (JP, U) JP-A-57-23448 (JP, U) JP-A-61-23448 87242 (JP, U) Japanese Utility Model Showa 59-15852 (JP, U) U.S. Pat.

Claims (2)

(57) [Claims] 1. A cylinder tube having one end sealed by a guide member and the other end sealed to a reservoir chamber by a base, and a cylinder tube provided at the tip of a piston rod guided by the guide member. A piston that partitions the upper liquid chamber and the lower liquid chamber, a communication passage formed in the piston so as to communicate the upper liquid chamber and the lower liquid chamber, and a base that communicates the lower liquid chamber with the reservoir chamber. Provided in at least one of the communication passages formed in, the disk valve structure portion that opens to generate a damping force when the hydraulic fluid flows through the communication passage with the stroke of the piston, In the disc valve structure, a first-stage disc valve and a second-stage disc valve are arranged in series from an upstream side in a communication direction of the hydraulic fluid in the communication path, and the first-stage disc valve is arranged in series. The valve is formed to have a relatively low rigidity relative to the second-stage disk valve, and the first-stage disk valve is formed to have a structure having no constant orifice that covers the communication path over the entire circumference. On the other hand, the second-stage disc valve is provided with a constant orifice that secures a flow path having a constant cross-sectional area in a closed state, and a seam that seals between the two liquid chambers between the piston and the cylinder tube around the piston. A hydraulic shock absorber comprising: a piston ring having no seal; and a seamless seal ring for sealing the upper liquid chamber and the outside of the cylinder tube on the guide member. 2. The seal ring is in close contact with the piston rod, has an interval with respect to the guide member that can follow the eccentricity of the piston rod, and has a position regulating member provided on the guide member. 2. The hydraulic shock absorber according to claim 1, wherein the movement of the piston rod in the axial direction is restricted by the member.