JPH0658360A - Hydraulic buffer device for vehicle - Google Patents

Abstract

PURPOSE:To improve comfortableness and ensure maneuver stability by meeting all oscillating conditions and attenuating these effectively without increasing the basic length of a hydraulic buffer device itself and with a simple structure. CONSTITUTION:A base valve 5 is provided with only a check valve 6 for sucking hydraulic oil which opens only in the elongation process of a hydraulic buffer device, and the valve 6 is fixed on the lower bottom of the hydraulic cylinder 1. Moreover, a pressure side damping force generating valve 14 is separated from the base valve 5 and is elasticallysupported to the outer wall side of the hydraulic cylinder 1 so as to slide smoothly to form a floating type which has an accumulator effect and an automatic high/low switching function for pressure side damping force, thus meeting all vibration for effective damping.

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 for a vehicle which automatically controls the pressure side damping force generated during a compression stroke depending on the magnitude of the pressure side operation stroke of the piston or the piston speed.

[0002]

2. Description of the Related Art A hydraulic shock absorber used for a vehicle suspension system appropriately suppresses various large and small unsprung vibrations caused by a disturbance from the road surface, and also prevents resonance generated on the spring from riding. In addition to improving comfort, suppressing damping such as rolling and pitching by increasing the damping force generated on the compression side during steering, acceleration and deceleration, etc., as well as improving steering stability. Is desirable.

Particularly in recent years, as tires have become more radial and flatter as in recent years, there is a tendency to increase the pressure side operating speed of the hydraulic shock absorber, which causes the ride comfort to deteriorate further. Therefore, how to suppress these with a hydraulic shock absorber is an important and urgent issue.

However, in order to improve the riding comfort, generally, when high frequency vibration with a small piston stroke is generated, the damping force generated on the compression side of the hydraulic shock absorber is kept low and the disturbance from the road surface is transmitted to the vehicle body on the spring. It is necessary to prevent it as much as possible and to increase the damping force on the compression side so that the vibration damping effect can be sufficiently exerted when resonance occurs in which the piston stroke becomes large or when relatively slow large vibration occurs.

At the same time, even when the piston speed is relatively small but the stroke is large, and vibrations such as rolling and pitching occur during acceleration and deceleration, the damping force generated on the pressure side of the hydraulic shock absorber is increased to cause these phenomena. Must be controlled.

As described above, in order to exert a sufficient vibration damping effect on all the conditions, mutually contradictory conditions are required. Therefore, the ride comfort is improved and the steering stability is satisfied in accordance with all these conditions. It is very difficult to secure the sex, and it requires some special means.

From this point of view, as a hydraulic shock absorber for a vehicle provided with the above-mentioned means for solving the problems, for example, one disclosed in Japanese Patent Application Publication No. 535/1993 is disclosed. Already proposed.

That is, this is one in which two upper and lower stoppers are provided inwardly of the lower part of the working cylinder in the hydraulic shock absorber, and are located between these stoppers to generate a compression side damping force generating valve and a suction valve which operates during the extension stroke. A base valve equipped with and is slidably inserted.

Then, the bottom of the movable type base valve is supported by a support spring having a spring force weaker than that of the compression side damping force generating valve, thereby increasing the hydraulic pressure at the beginning of the piston stroke during the compression stroke and during the small stroke. It is designed to be absorbed by the movement of the base valve.

That is, the low damping force region before the generation of the prescribed compression side damping force is covered by the accumulator effect accompanying the movement of the base valve, and the damping side generated damping force is reduced when vibration such as high frequency vibration having a relatively small piston stroke is generated. It keeps these vibrations and absorbs and dampens them.

Further, when a large stroke vibration occurs, such as when resonance occurs where the piston speed is high and the stroke is large, or when rolling or pitching occurs during steering or acceleration / deceleration where the piston speed is small and the stroke is large. Similarly to the above, while preventing the impact from being generated during the initial operation by lowering the base valve, the pressure-side damping force is increased by operating the pressure-side damping force generation valve after the base valve hits the lower stopper and is locked. , These vibrations are also effectively dampened.

[0012]

However, in this structure, since the base valve is slidably supported in the lower portion of the working cylinder of the hydraulic shock absorber, the space is limited by the sliding space and the storage space of the support spring. There is a drawback that the operation stroke as a hydraulic shock absorber cannot be made large.

Further, in addition to the above, the entire base valve having a relatively large mass including the compression side damping force generating valve and the suction valve during the extension stroke is made movable, so that the responsiveness at the initial stage of operation is poor. As a result, the accumulator effect due to the movement of the base valve may be delayed, and not only the shock absorbing action at the initial operation may not be sufficiently performed but also the damping action particularly at the time of high frequency vibration may not be effectively performed. There were problems such as being there.

Further, even when vibrations such as rolling and pitching occur during steering and acceleration / deceleration, the accumulator effect associated with the movement of the base valve is performed.
There is also a problem that these vibrations cannot be immediately suppressed.

Therefore, an object of the present invention is to deal with all vibration conditions with a simple structure without effectively increasing the basic length of the hydraulic shock absorber itself, and effectively dampen these conditions to improve the ride comfort. An object of the present invention is to provide an improved hydraulic shock absorber for a vehicle of this type, which can exhibit excellent effects in improving and ensuring steering stability.

[0016]

As means for achieving the above object, the present invention is provided with a cylinder body composed of an inner and outer double cylinder for partitioning a reservoir chamber between the working cylinder and the outer shell. A vehicle hydraulic system in which a piston having an expansion side damping force generation valve is slidably inserted into the working cylinder, and a compression side damping force generation valve is interposed in the oil passage connecting the working cylinder and the reservoir chamber. In the shock absorber, the compression side damping force generating valve is elastically supported on the outer peripheral portion of the working cylinder so as to be displaceable in the flow direction of the hydraulic oil, and a restricting means for restricting displacement of the compression side damping force generating valve by a certain amount or more is provided. The configuration was adopted.

[0017]

As a result, according to the present invention, the piston speed is small for small input strokes, such as when passing through irregularities on the road surface, without increasing the basic length of the hydraulic shock absorber. On the other hand, the accumulator effect accompanying the movement of the compression side damping force generating valve absorbs and alleviates the shock due to the thrusting up, while keeping the compression side damping force low and improving the riding comfort.

On the other hand, for an input having a large piston stroke and speed, the shock immediately after the start of the compression operation is absorbed,
While mitigating, thereafter, the compression side damping force is increased to absorb and buffer the vibration.

For an input having a relatively small piston speed such as rolling during steering or pitching during acceleration / deceleration, but with a large stroke, the same high compression side damping force as when the compression side damping force generating valve is fixed. To occur immediately to ensure steering stability.

Further, in addition to the above, since the mass of the movable portion itself becomes small, it is possible to perform responsiveness to shock absorption and shock absorbing action and high / low automatic switching action of the compression side damping force at the initial stage of operation of the hydraulic shock absorber. it can.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows only a main part of a vehicle hydraulic shock absorber according to the present invention. The cylinder body of the hydraulic shock absorber is composed of an operating cylinder 1 and an outer shell 2 which are fitted inside and outside double, These working cylinder 1 and outer shell 2
The upper ends of are connected concentrically by a rod guide (not shown).

On the other hand, the lower end of the outer shell 2 has a mounting eye 3
It is closed by a bottom cap 4 having an inner wall, and thereby a reservoir chamber C is defined between the working cylinder 1 and the outer shell 2.

A piston (not shown) equipped with an expansion-side damping force generating valve and a suction valve that operates during a compression stroke is slidably inserted into the working cylinder 1. Is divided into an upper hydraulic oil chamber A and a lower hydraulic oil chamber B (A is not shown).

A piston rod (not shown), which serves as a piston, penetrates the upper end rod guide and extends outward, and its upper end is connected to the body side which is on a spring, and the bottom cap 4 side is provided with a mounting eye 3. It is connected to the wheel side, which is an unsprung part, via the.

The upper working oil chamber A and the lower working oil chamber B of the cylinder 1 are filled with working oil, and the reservoir chamber C is filled with working oil leaving a gas portion at the upper part.

A base valve 5 is arranged at the bottom of the working cylinder 1 so as to be sandwiched between the base valve 5 and the bottom cap 4. The base valve 5 is provided with only a suction valve 6 that opens during the extension stroke. .

A cylindrical spring guide 7 is erected from the base valve 5 in the reservoir chamber C, and a hydraulic oil suction passage 8 is provided between the spring guide 7 and the outer shell 2 during the extension stroke. Has become.

The upper end of the hydraulic oil suction passage 8 communicates directly with the hydraulic oil portion in the reservoir chamber C, and the lower end thereof communicates with the port 10 of the suction valve 6 through the notch 9 formed in the lower portion of the base valve 5. There is.

On the other hand, a valve chamber 11 is provided between the spring guide 7 and the working cylinder 1.
The upper part of 1 communicates with the hydraulic oil part of the reservoir chamber C through a slit 12 formed in the upper half part of the spring guide 7.
Moreover, the lower end communicates with the lower working oil chamber B in the working cylinder 1 through a notch 13 formed in the outer peripheral portion of the base valve 5.

In the valve chamber 11, the working cylinder 1
A compression-side damping force generating valve 14 is slidably provided along the outer wall of the pressure-side damping force generating valve 14 and the spring guide 7 between the compression-side damping force generating valve 14 and the spring guide 7.
5 is formed.

The compression side damping force generating valve 14 is normally pressed against the base valve 5 by the restoring force of a support spring 17 interposed between the upper end of the spring guide 7 and a washer 16. The spring 17 keeps the floating state.

As can be seen from the structural description of the embodiment described above, the present invention separates the floating type pressure side damping force generating valve 14 having the accumulator effect from the base valve 5 and slides it to the outer wall side of the working cylinder 1. It is characterized in that it is arranged freely.

Next, the operation of the hydraulic shock absorber will be described.

During the compression stroke of the hydraulic shock absorber, the lower working oil chamber B of the working cylinder 1 is accompanied by the downward movement of the piston.
The hydraulic oil inside pushes the suction valve of the piston open and flows into the upper hydraulic oil chamber A, and at the same time, the hydraulic oil in an amount corresponding to the piston rod intrusion volume into the working cylinder 1 is notched in the base valve 5. 13 to the reservoir chamber C through the throttle passage 15 and the slit 12 of the spring guide 7.

As a result, a hydraulic pressure corresponding to the piston speed is generated in the lower hydraulic oil chamber B by the flow resistance of the throttle passage 15, and this hydraulic pressure acts as a compression side damping force from the piston rod to the vehicle body side.

On the other hand, in the above case, when the piston speed exceeds a certain value, the flow resistance of the throttle passage 15 causes a pressure difference above and below the compression side damping force generating valve 14, which is a predetermined value or more. Then, the compression side damping force generating valve 14 rises while bending the support spring 17.

The rise of the compression side damping force generating valve 14 is
An accumulator effect is exerted on the hydraulic fluid flowing from the lower hydraulic fluid chamber B toward the reservoir chamber C, and as a result, the flow rate of the hydraulic fluid passing through the throttle passage 15 is reduced accordingly, and the compression side damping force is reduced. This is lower than in the case where the force generation valve 14 is fixed and does not operate.

The magnitude of the compression side damping force in the above case can be set in advance by appropriately selecting the set load and spring constant of the support spring 17 and the flow resistance of the throttle passage 15.

From this fact, when the high-speed vibration with a high piston speed and a small stroke is generated, the accumulator effect accompanying the movement of the compression-side damping force generating valve 14 keeps the compression-side damping force low, and the mass of the mass is relatively small. The small compression side damping force generation valve 14 suppresses the transmission of high frequency vibration to the vehicle body side with good responsiveness.

Contrary to the above case, if vibration occurs such that both the piston stroke and the piston speed exceed a certain value, the pressure difference between the upper and lower sides of the pressure side damping force generating valve 14 exceeds a predetermined value, and the pressure side damping force is exceeded. Generation valve 14
Is pushed up to the position where the support spring 17 is compressed most, and thereafter, the maximum raised position is restrained from further displacement.

As a result, the compression side damping force generating valve 14
Absorbs and buffers the shock generation in the initial stage of the stroke accompanying the movement to the highest position, and thereafter, as in the case where the compression side damping force generation valve 14 is fixed, the amount corresponding to the penetration volume of the piston rod is reduced. All the hydraulic oil flows through the throttle passage 15, so that the damping force generated on the compression side becomes high.

From this fact, when vibration occurs in which both the piston stroke and the piston speed are large, such as when resonance occurs or when a large protrusion is passed over at high speed, the compression side damping force generating valve 14 moves to generate an initial impact. While preventing the above, thereafter, when the compression side damping force generating valve 14 is locked at the most raised position, a predetermined high compression side damping force is generated to effectively absorb and buffer those vibrations.

The magnitude of the compression side damping force at this time is
It can be set not only by adjusting the flow resistance of the throttle passage 15 but also by adjusting the length of the slit 12 in the spring guide 7.

That is, if the length of the slit 12 is shortened so that the fitting length of the compression side damping force generating valve 14 to the spring guide 7 does not change even when the support spring 17 is compressed most, the highest compression side damping force is obtained. On the contrary, if the length of the slit 12 is increased so that the fitting length of the compression side damping force generating valve 14 is shortened when the support spring 17 is fully compressed, the partial pressure side damping force is reduced.

On the other hand, when vibration such as rolling or pitching that occurs during steering or acceleration / deceleration, where the piston speed is slow, the compression side damping force generating valve 14 does not move and the lowermost position is maintained. From the beginning, a predetermined high compression side damping force is generated to effectively absorb and dampen those vibrations. During the expansion stroke of the hydraulic shock absorber with respect to the above compression stroke, the compression side damping force generation valve 14 quickly returns to the original lowermost position by the restoring force of the support spring 17, and the inside of the upper hydraulic chamber A The hydraulic oil pushes the expansion side damping force generating valve of the piston open and flows into the lower hydraulic oil chamber B,
At this time, the extension side damping force is generated according to the piston speed by the flow resistance of the hydraulic oil that pushes the extension side damping force generation valve open.

Further, the shortage of the hydraulic oil caused by the withdrawal of the piston rod from the operating cylinder 1 pushes the intake valve 6 from the reservoir chamber C through the hydraulic oil suction passage 8, the notch 9 of the base valve 5 and the port 10. It is compensated by the hydraulic oil that is sucked into the lower hydraulic oil chamber B while opening.

The operation has been described above based on the structural example of FIG. 1. Here, the damping force characteristic will be described in order to further deepen the understanding of the present invention.

The displacement and speed of a hydraulic shock absorber (hereinafter referred to as a damper) when the vehicle passes through a protrusion on the road surface is schematically shown in FIG. 2, and an increase in the pressure-side damper speed deteriorates the riding comfort. Cause

In FIG. 2, the relation between the damper displacement and the generated damping force is shown in FIG. 3 by paying attention to the range of the code T which is the first cycle.

In FIG. 3, the broken line shows the damping force characteristic when the compression side damping force generating valve 14 is fixed, and the solid line shows the damping force characteristic according to the present invention.

Characteristic a in FIG. 3 is a damping force characteristic when the pressure side piston speed is low and the damping force does not increase until the pressure side damping force generating valve 14 moves.
The same damping force is generated when is fixed.

When the compression-side piston speed exceeds a certain value, the damping force has the b characteristic, and the accumulator effect due to the movement of the compression-side damping force generation valve 14 prevents a rapid increase in the damping force immediately after the start of the compression operation, resulting in a shock due to thrust. Is alleviated.

When the piston speed on the pressure side further increases, the damping force now exhibits the c characteristic, and immediately after the start of the compression operation, the shock due to the thrust is alleviated as in the case of the b characteristic, but thereafter the support spring 17 The compression-side damping force generation valve 14 rises to a position where is fully compressed to generate a high damping force.

In the case of the b and c characteristics, the support spring 17 compressed in the latter half of the compression side stroke is used.
Since there is a region where the compression side damping force generation valve 14 is pushed back by and the damping force rises, the total amount of absorbed energy is not so different from when the compression side damping force generation valve 14 is fixed, and therefore the compression side stroke increases. There is no.

As a result, when the damper stroke is short and the speed is high, such as when passing through unevenness on the road surface, the shock due to thrusting up is absorbed,
Improves riding comfort while mitigating.

On the other hand, for an input having a large damper stroke and a high speed, the shock immediately after the start of the compression operation is absorbed and alleviated, and thereafter the compression side damping force is increased to absorb and buffer the vibration.

Further, for an input having a small damper speed such as rolling during steering or pitching during acceleration / deceleration, the same damping force as when the compression side damping force generating valve 14 is fixed is generated, and steering stability is improved. Secure.

[0059]

As described above, according to the present invention, the floating type compression side damping force generating valve having the accumulator effect is separated from the base valve and slidably arranged on the outer wall side of the working cylinder. So, without increasing the basic length of the hydraulic shock absorber itself,
Moreover, it is possible to cope with all vibration conditions and effectively damp them with a simple configuration.

At the same time, since the mass of the compression side damping force generating valve is also reduced, the responsiveness in the initial stage of operation is improved,
As a result, it is possible to exert excellent effects in improving riding comfort and ensuring steering stability.

Further, with respect to vibrations such as rolling and pitching during steering or acceleration / deceleration with a low piston speed,
Without moving the compression-side damping force generating valve, that is, without generating the accumulator effect, it is possible to effectively suppress the generation of vibrations with a high compression-side damping force from the beginning.

[Brief description of drawings]

FIG. 1 is a front view showing a longitudinal section of a main part of a vehicle hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing displacement and speed of a hydraulic shock absorber when a vehicle passes through a road protrusion.

FIG. 3 is a graph showing the relationship between the displacement of the hydraulic shock absorber and the damping force.

[Explanation of symbols]

 B Lower hydraulic oil chamber C Reservoir chamber 1 Operating cylinder 2 Outer shell 5 Base valve 6 Suction valve 7 Spring guide 11 Valve chamber 12 Slit 13 Notch 14 Pressure side damping force generating valve 15 Throttle passage 17 Support spring

Claims (1)

[Claims] 1. A cylinder body comprising an inner and outer double cylinder that divides a reservoir chamber between an operating cylinder and an outer shell, and a piston having an extension side damping force generating valve is slidably inserted into the operating cylinder. In addition, in a vehicle hydraulic shock absorber in which a compression side damping force generating valve is interposed in the oil path connecting the inside of the operating cylinder and the reservoir chamber, the compression side damping force generating valve is used to flow the working oil to the outer peripheral portion of the working cylinder. A hydraulic shock absorber, which is elastically supported so as to be displaceable with respect to a direction, and provided with a restricting means for restricting displacement of the compression side damping force generation valve by a certain amount or more.