JP2001027274A - Damping force varying device in shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the high frequency noise by comprising a second damping force generating means capable of adjusting an opening of a communication path between hydraulic fluid chambers, and a by-pass the relieving the sudden change of liquid pressure in the flowing-out of the hydraulic fluid from the second damping force generating means to the hydraulic fluid chambers. SOLUTION: A spool calve 230 fixed to a shaft 231 is axially displaced, and acted as a damping force varying mechanism for changing an effective flow path cross section of a by-pass passage 212. Though bubbles are generated in some cases when the hydraulic oil is passed through a gap between the spool valve 230 and the by-pass passage 212 in an expanding stroke with a high operating speed of a shock absorber, the liquid pressure in a sub-valve case 260 communicated with a piston upper chamber 202 side through an opening 263 of a lower surface, is high near an opening 261 of its inlet gradually lowered toward the opening 263 side, and approximately equalized to the pressure of an upper chamber 202 near the opening 263. Whereby a path between the opening 261 and 263 functions as a by-pass for relieving the sudden change of pressure, the deforming is dispersed, and the generation of high frequency noise can be inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force varying device for a shock absorber capable of changing a damping force of a shock absorber.

[0002]

2. Description of the Related Art A shock absorber capable of variably controlling a damping force to be generated is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-4667, and an example of the structure is shown in FIG. In a cylinder 1, a piston 3 fixed to a piston rod 2
Is housed, and the upper cylinder 1 is moved by the piston 3.
A and a lower chamber 1B. The piston 3 reciprocates in the cylinder 1 with the expansion and contraction of the shock absorber. At this time, the working fluid in the cylinder 1 moves via the circulation port 3A or the circulation port 3B formed in the piston 3, and at this time, A damping force is generated by the flow resistance of the fluid.

Further, the piston rod 2 has a hollow cylindrical shape, and has a structure in which the upper cylinder chamber 1A and the lower cylinder chamber 1B communicate with each other by an opening 2B formed in the side wall of the piston rod 2. The hollow portion of the piston rod 2 forms a bypass passage 2A that communicates between the upper cylinder chamber 1A and the lower cylinder chamber 1B. In the bypass passage 2A, a spool valve 4 that is driven to be displaced along the axial direction of the cylinder 1 is provided. When the spool valve 4 is displaced, a position between the bypass passage 2A and the spool valve 4 is increased. The clearance, that is, the effective flow path cross-sectional area changes, and the damping force is changed by this action.

[0004]

In the state where the bypass passage 2A is shut off by the action of the spool valve 4, the working fluid does not flow through the bypass passage 2A during both the extension stroke and the contraction stroke of the shock absorber. 3 through the distribution ports 3A and 3B. In contrast,
When the spool valve 4 is displaced and the bypass passage 2A is in a communicating state, the working fluid flows through the opening 2 of the bypass passage 2A.
Via B, it becomes possible to circulate between the cylinder upper chamber 1A and the cylinder lower chamber 1B. In the contraction stroke of the shock absorber, the working fluid flows along the path shown by the arrow in FIG. 6, but when the operating speed of the shock absorber is high and the flow of the working fluid is fast, the working fluid is bypassed to the spool valve 4. Gap between passage 2A (variable orifice)
When passing through, air bubbles may be generated. The air bubbles pass through the opening 2B together with the working fluid and enter the sub-valve case 5, where the cylinder upper chamber 1
Since the hydraulic pressures are substantially equal to each other in A, the hydraulic pressure sharply drops at the opening 2B. By this action, the air bubbles that have reached the inside of the sub-valve case 5 disappear instantaneously, and at that time, high-frequency noise is generated.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a damping force variable device in a shock absorber capable of reducing high-frequency sound generated by the disappearance of bubbles as described above. It is in.

[0006]

According to a first aspect of the present invention, there is provided a shock absorber having a damping force varying device provided for a rod housed in a cylinder to separate a hydraulic fluid chamber in the cylinder. A first damping force generating means for generating a damping force by the movement of a working fluid accompanying the expansion and contraction of the shock absorber, and a hydraulic fluid chamber disposed in a rod provided with the first damping force generating means and separated from each other. A second damping force generating means having a communication path for communication and having an adjustable opening degree of the communication path; and a sudden change in hydraulic pressure when the working fluid flows out of the second damping force generating means into the working fluid chamber. And a hydraulic pressure change alleviating means having a bypass path for alleviating the pressure.

By interposing the hydraulic pressure change alleviating means between the second damping force generating means and the hydraulic fluid chamber, the hydraulic fluid chamber is arranged from the second damping force generating means side in the bypass passage of the hydraulic pressure change alleviating means. The fluid pressure tends to gradually decrease toward the side, and a sudden change in the fluid pressure generated between the second damping force generating means and the working fluid chamber is reduced. By this operation, the disappearance of bubbles is caused to be dispersed in the process of the working fluid traveling in the bypass passage, and the generated high-frequency sound is suppressed as compared with the case where the bubbles disappear instantaneously.

According to a second aspect of the present invention, there is provided a damping force variable device in a shock absorber, wherein the hydraulic pressure change reducing means according to the first aspect uses a flexible member as a part of a member defining a bypass path.

The high-frequency sound generated when the bubbles disappear can be effectively attenuated by the flexure of the flexible member.

According to a third aspect of the present invention, in the shock absorber variable damping device, the bypass path in the first aspect is a bent flow path.

By forming the bypass passage by bending the flow passage, a bypass passage for alleviating a sudden change in hydraulic pressure can be effectively formed in a limited space, and the flow resistance in the bent portion is large. As a result, the change in the liquid pressure is suppressed, so that rapid disappearance of bubbles is suppressed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the accompanying drawings.

FIG. 1 shows a damping force variable system of a shock absorber. In this damping force variable system, a shock absorber 100 is disposed between a vehicle body and a suspension member, and a damping force variable device 200 for controlling a damping force generated by the shock absorber 100 is formed separately from the shock absorber 100. The high pressure hose 110 is connected between them. Further, a gas chamber 120 is connected to the variable damping device 200, and the internal pressure is changed by supplying and discharging oil into and from the gas chamber 120, and this pressure change causes the variable damping device 200 and the high-pressure hose 110 to be connected. The power is transmitted to the shock absorber 100 via the power supply. As a result, the pressure balance in the shock absorber 100 changes, and the shock absorber 100 expands and contracts to a position where the balance is again achieved. With this operation, the vehicle height is controlled to be raised or lowered.

FIG. 2 shows a damping force variable device 200.

In the cylinder 201, a piston rod 2
A piston 220 fixed to the end of the cylinder 10 is accommodated therein, and the cylinder upper chamber 2 is partitioned by the piston 220.
02 and the cylinder lower chamber 203 are each filled with a working oil as a working fluid.

The piston 220 has a first flow port 2 whose upper opening is covered by an extension side leaf valve 223.
21 and a second communication port 222 whose lower opening is covered by a contraction-side leaf valve 224. In the extension stroke of the shock absorber 100, the operating oil flows through the first communication port 221 to the cylinder lower chamber. From 203, it moves to the cylinder upper chamber 202, and a damping force is generated by the flow resistance at this time. In the contraction stroke, the working oil flows through the second circulation port 222 through the cylinder upper chamber 202.
To the cylinder lower chamber 203, and a damping force is generated by the flow resistance at this time.

The piston rod 210 has a hollow cylindrical shape, and has a structure in which the cylinder upper chamber 202 and the cylinder lower chamber 203 communicate with each other through an opening 211 formed in a side wall. Therefore, the piston rod 2
The hollow portion 10 functions as a bypass passage 212 that allows the working fluid to flow between the upper cylinder chamber 202 and the lower cylinder chamber 203 without passing through the inside of the piston 220.

In the bypass passage 212, there is disposed a spool bubble 230 which is displaced and driven along the axial direction of the cylinder 201. When the spool valve 230 is displaced, the effective flow passage of the bypass passage 212 is cut off. The area changes. Therefore, the spool valve 230 functions as a variable orifice that changes the flow resistance.

The spool valve 230 has a cylindrical shape with irregularities formed on the outer peripheral surface, and is fixed to a shaft 231 penetrating the center thereof. This shaft 23
A worm 232 is integrally formed on the upper part of the worm gear 1. The worm 232 is fitted into the female screw 233, and the worm 232 and the female screw 233 are in an engaged state. Further, a permanent magnet 241 is fixed to the outer peripheral portion of the female screw 233,
A coil 242 is disposed at a position facing the permanent magnet 241 to constitute a step motor 240 in which the permanent magnet 241 is on the rotor side and the coil 242 is on the stator side.

The coil 242 is held by a bobbin 234, and the bobbin 234 is
In a state positioned by 36, it is fixed to the inner housing 204 side in the cylinder 201.

The worm 232, the female screw 233, and the permanent magnet 241 are covered by a cap cover 237 having a base end fixed to a support 235.
A stationary support 235 and a cap cover 237,
Bearing 250 is interposed between rotatable female screw 233 and female screw 233 is rotatably supported by support 235 and cap cover 237.

Accordingly, by rotating the step motor 240, the female screw 233 on the rotor side rotates,
Worm 232 and shaft 2 meshed with female screw 233
31 is displaced along the axial direction. By this action, the spool valve 230 fixed to the shaft 231 is displaced along the axial direction to change the effective flow path cross-sectional area of the bypass passage 212. The shaft 23
1 is provided with a detent (not shown).
The worm 232 and the shaft 23
1 can be displaced along the axial direction without rotating.

On the other hand, the opening 21 of the piston rod 210
1, a sub-valve case 260 is provided.
The sub-valve case 260 is hollow and has an opening 261 at a position corresponding to the opening 211 of the piston rod 210.
Having. A flexible thin plate 262 is fixed to the upper surface of the sub-valve case 260 and is closed, and an opening 263 is formed on the lower surface to form the upper piston chamber 202.
Is in communication with

When the bypass passage 212 is in a communicating state,
The flow of the working oil flowing through the bypass passage 212 is
This is indicated by an arrow in FIG. For convenience of explanation, only the flow of the working oil flowing through the bypass passage 212 is illustrated, and the flow of the working oil flowing in the piston 220 is not illustrated.

During the contraction stroke of the shock absorber 100, the operating oil flows from the opening 263 through the sub-valve case 2.
The piston rod 210 enters the bypass passage 212 via the opening 261 and the opening 211, and flows out from the lower end of the piston rod 210 into the lower piston chamber 203. In the extension stroke of the shock absorber 100, the operating oil flows from the lower end of the piston rod 210, and the opening 211,
Piston upper chamber 2 via opening 261 and opening 263
Outflow to 02.

Although the operating oil moves along such a path, when the operating speed of the shock absorber is high and the flow of the operating oil is high, the operating oil flows through the spool valve 230 and the bypass passage 212, particularly during the extension stroke. When passing through the gap (variable orifice) between the holes, bubbles may be generated due to cavitation. The generated air bubbles pass through the openings 211 and 261 together with the working oil and enter the sub-valve case 260, where the air bubbles disappear and the high-frequency sound is generated.

However, as described above, the sub-valve case 260 communicates with the upper piston chamber 202 through the opening 263 on the lower surface, and the liquid near the opening 211 serving as an inlet of the sub-valve case 260 is provided. High pressure, opening 2
The fluid pressure gradually decreases toward the 63 side, and the fluid pressure near the opening 263 becomes substantially the same as that of the upper piston chamber 202. As described above, the passage between the opening 261 and the opening 263 in the sub-valve case 260 is
It functions as a detour path for alleviating sudden pressure changes, and when the working oil travels through this detour path, defoaming is dispersed and generated, and the generated bubbles are instantaneously defoamed. The generated high-frequency sound can be suppressed as compared with the case of (1). At the same time, since the thin plate 262 serving as a member constituting the bypass passage has flexibility, the thin plate 262 is bent by receiving the vibration wave generated at the time of defoaming. Sound can be attenuated effectively.

In place of the flexible thin plate 262,
The opening 26 after the thin plate 262 is removed as shown in FIG.
4, a leaf valve 265 may be provided to cover the opening 264 in an openable and closable state. The leaf valve 265 also has flexibility,
The same effect as in the case where 62 is provided can be obtained. When the leaf valve 265 is pushed open by the hydraulic pressure of the operating oil, the operating oil flows through the opening 263 and the opening 264.
Through the piston upper chamber 202.

Further, such a sub-valve case 260
In another embodiment, as shown in FIG.
The bypass passage formed between the opening 61 and the opening 263 may be configured as a flow passage bent so as to be folded back.
By forming the bypass passage in a bent shape as described above, the bypass passage for mitigating a sudden change in hydraulic pressure can be effectively formed in a limited space. At the same time, in the bent portion 266, the flow resistance of the working oil becomes large and the hydraulic pressure change is suppressed. Therefore, the intervening bent portion in the detour passage further disperses the defoaming, and the high-frequency noise generated at the time of defoaming. Can be reduced.

[0030]

As described above, according to the damping force variable device in the shock absorber according to each claim, when flowing out of the second damping force generating means to the working fluid chamber, the bypass passage through which the working fluid flows is provided. In the detour passage, the hydraulic pressure tends to gradually decrease from the second damping force generating means side to the working fluid chamber side, so that the second damping force generating means, the working fluid chamber, A sudden change in hydraulic pressure occurring during the period can be reduced. By this action, even when air bubbles due to cavitation are included in the working fluid, the defoaming is dispersed and generated in the process of the working fluid traveling in the bypass passage, and the generated air bubbles are instantly defoamed. It is possible to reduce the generated high frequency sound as compared with the case where

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a damping force variable system of a shock absorber according to an embodiment.

FIG. 2 is a longitudinal sectional view showing a main part of the variable damping device.

FIG. 3 is an enlarged longitudinal sectional view showing the vicinity of a sub-valve case in FIG. 2;

FIG. 4 is an enlarged longitudinal sectional view showing the vicinity of a sub-valve case according to another embodiment.

FIG. 5 is a longitudinal sectional view showing another embodiment of the sub-valve case.

FIG. 6 is an enlarged longitudinal sectional view showing constituent parts of a conventional damping force variable device.

[Explanation of symbols]

100: shock absorber, 200: damping force variable device 210: piston rod, 220: piston (first damping force generating means) 230: spool valve (second damping force generating means), 24
0: Step motor 260: Sub-valve case (fluid pressure change reducing means)

Claims (3)

[Claims] A first damping force is provided for a rod housed in a cylinder, separates a working fluid chamber in the cylinder, and generates a damping force by movement of a working fluid accompanying expansion and contraction of a shock absorber. Generating means, and a communication path disposed in a rod provided with the first damping force generating means and communicating between the separated hydraulic fluid chambers, and an opening degree of the communication path is adjustable. A second damping force generating means; and a hydraulic pressure change reducing means having a bypass passage for mitigating a sudden hydraulic pressure change when the working fluid flows out of the second damping force generating means into the working fluid chamber. A variable damping force device for the shock absorber provided. 2. The damping force variable device in a shock absorber according to claim 1, wherein said hydraulic pressure change reducing means uses a flexible member as a part of a member that partitions said bypass passage. 3. The damping force varying device in a shock absorber according to claim 1, wherein the bypass passage is a bent flow passage.