JP2002317848A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the vehicle traveling stability by increasing the spring force repelling the inclination when the vehicle is inclined, and to improve the workability in assembling, replacement and the like. SOLUTION: A gas chamber C is defined by a free piston 7 in a cylinder 1 wherein a rod-side chamber A and a bottom-side chamber B are defined by a piston 5. An accumulator 12 having an oil chamber A and a gas chamber D is connected by a first oil passage 8 provided with a damping force generating part 9. A communication passage 14 communicates the oil chamber B and the first oil passage 8, and is provided with a spring constant selector valve 13 for communicating and blocking the communication passage 14. Accordingly, when the spring constant selector valve 13 communicates the communication passage 14, two gas chambers C, D are compressed, whereby a spring constant is decreased, and the ride quality can be improved. On the other hand, when the spring constant selector valve 13 blocks the communication passage 14, only the gas chamber C is compressed, whereby the spring constant is increased and the rolling of the vehicle 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 hydraulic shock absorber which is provided, for example, in a vehicle and is suitable for use in damping vibration.

[0002]

2. Description of the Related Art Generally, a vehicle or the like is provided with a suspension device for suspending a vehicle body on wheels. The suspension device includes a hydraulic shock absorber for damping vibrations, and a suspension spring for elastically supporting the vehicle body on wheels. And is constituted by.

Here, a hydraulic shock absorber constituting a suspension device is slidably inserted into a cylinder having one end closed by a bottom cap and a rod guide provided on the other end, and slidably inserted into the cylinder. The piston is roughly constituted by a piston that defines a rod-side oil chamber and a bottom-side oil chamber inside the cylinder, and a piston rod one end of which is fixed to the piston and the other end of which extends and retracts from the cylinder via the rod guide. ing. In addition, the hydraulic shock absorber includes a damping force generating unit that generates a damping force by giving resistance to the oil fluid flowing when the piston rod is expanded and contracted from the cylinder.

[0004] Some hydraulic shock absorbers include an accumulator for accommodating oil discharged from the cylinder in accordance with the volume of the piston rod when the piston rod enters the cylinder. This type of hydraulic shock absorber is known, for example, from Japanese Patent Application Laid-Open No. 2-113140. Further, JP-A-2-113140
In the hydraulic shock absorber according to the above publication, a damping force adjusting type damping force generator is provided in the middle of an oil liquid passage connecting a cylinder (oil chamber) and an accumulator.

In the hydraulic shock absorber configured as described above, for example, the bottom side of the cylinder is mounted on the wheel side of the vehicle, and the protruding end side of the piston rod is mounted on the vehicle body side of the vehicle. Then, during normal traveling, the damping force of the damping force generating section is adjusted to be small, and the riding comfort is improved. On the other hand, when the vehicle turns a corner (when cornering), the damping force of the damping force generating unit is increased to suppress the vehicle from rolling.

On the other hand, the hydraulic shock absorber includes, for example, the left side of the vehicle,
The hydraulic chamber of the hydraulic shock absorber arranged on the right is connected by a pipe.
No. 29914.

In the hydraulic shock absorber disclosed in Japanese Utility Model Publication No. 47-29914, a rod-side oil chamber of a left-side hydraulic shock absorber and a bottom-side oil chamber of a right-side hydraulic shock absorber are connected by piping, and a right-side hydraulic shock absorber is provided. And the bottom oil chamber of the left hydraulic shock absorber is connected by piping.

As a result, when the vehicle corners, the suspension located on the outer side contracts and the suspension located on the inner side tends to expand. But,
When the piston rod of the outer hydraulic shock absorber contracts, the pressure in the lower oil chamber increases, and this pressure acts on the upper oil chamber of the inner hydraulic shock absorber via piping. As a result,
Since the elongating operation of the piston rod of the inner hydraulic shock absorber is suppressed, rolling during cornering is suppressed.

[0009]

In the above-described hydraulic shock absorber disclosed in Japanese Patent Application Laid-Open No. 2-113140, an adjusting function is provided in a damping force generating section to adjust the magnitude of the damping force according to the running state of the vehicle. are doing. However, since the damping force only gives resistance to the flowing oil liquid, the time required for the vehicle body to lean when cornering is only slowed down.For example, when traveling on a large corner, the vehicle body is moved by the radius of the corner and the traveling speed In this case, there is a problem that the roll cannot be suppressed due to tilting to a tilt angle (stationary roll) corresponding to the angle.

In the hydraulic shock absorber disclosed in Japanese Utility Model Publication No. 47-29914, two hydraulic shock absorbers are connected via a pipe.
There is a problem that it takes time and effort to arrange the piping, and the workability is reduced. Furthermore, in this hydraulic shock absorber,
Since the resistance is generated when the oil liquid flows through the pipe, there is a problem that the response speed is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a hydraulic shock absorber which can change a spring force and has good mounting properties.

When the hydraulic shock absorber of the present invention is used in an automobile, when the vehicle is inclined in the left-right direction and the front-rear direction (when the posture is changed), the spring force repelling the inclination is increased to increase the vehicle force. Running stability can be improved.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a hydraulic shock absorber according to the present invention is slidably inserted in a cylinder, and is provided with a first chamber in the cylinder. A piston defined in the second chamber, a piston rod one end of which is fixed to the piston, and the other end of which protrudes outside; a first spring element connected to the first chamber and comprising an accumulator; A second spring element connected to the second chamber and comprising an accumulator, between the first chamber and the first spring element, or between the second chamber and the second spring element; A damping element provided at least in between the first chamber and a first hydraulic circuit comprising the first chamber and a first spring element; and a second hydraulic circuit comprising the second chamber and a second spring element. A communication passage connecting the hydraulic circuit, and a first hydraulic circuit provided in the communication passage. When communication with permitting the flow of hydraulic fluid cross direction between the second hydraulic circuit, constituted by a switching valve for switching between cut-off state in which the flow from at least one to the other.

With this configuration, when the piston rod is displaced with the switching valve communicating with the communication passage, the oil liquid in one chamber is supplied to the first spring element and the second spring element. Since the power is supplied to both, the spring force at this time is reduced. Thereby, the piston rod can be easily displaced.

On the other hand, when the piston rod is displaced with the switching valve blocking the communication path, only one of the first spring element and the second spring element is greatly compressed, and the spring force at this time is reduced. growing.

According to the second aspect of the present invention, by connecting the communication passage between the chamber in the cylinder and the damping element, the amount of the oil liquid flowing to the damping element when the switching valve is shut off. Can be made larger than the amount of oil liquid at the time of communication, so that the damping force when the switching valve is shut off can be made larger than the damping force at the time of communication.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example in which a hydraulic shock absorber according to a first embodiment of the present invention is provided in a vehicle such as a four-wheeled vehicle will be described in detail with reference to FIGS. In addition,
FIG. 4 illustrates a pattern of the configuration of the hydraulic shock absorber according to the present invention. The first embodiment corresponds to the pattern (A).

Reference numeral 1 denotes a cylindrical cylinder which forms an outer shell of the hydraulic shock absorber.
, And the lower side is closed by the bottom cap 3. A rod guide 4 is provided inside the upper cap 2 to guide a piston rod 6 described later slidably in the axial direction. And cylinder 1
In the bottom cap 3 side, a mounting portion (not shown) adapted to the vehicle is welded, and the wheel side of the vehicle (not shown)
Attached to

Reference numeral 5 denotes a piston slidably inserted into the cylinder 1. The piston 5 is connected to the upper rod-side oil chamber A corresponding to the first chamber of the present invention and the upper chamber of the present invention. A lower bottom oil chamber B corresponding to the second chamber is defined.

Reference numeral 6 denotes a piston rod inserted into the cylinder 1. The lower end of the piston rod 6 is attached to the piston 5. Further, the upper end side of the piston rod 6 protrudes out of the cylinder 1 via the rod guide 4 and the like so as to be extendable and contractable. Have been.

A free piston 7 is located below the piston 5 and slidably inserted into the cylinder 1. The free piston 7 is a gas in which pressurized gas is sealed between the free piston 7 and the bottom cap 3. Room C is defined. Here, the bottom oil chamber B, the free piston 7, and the gas chamber C constitute a gas spring as a second spring element, and further constitute a second hydraulic circuit.

When the piston rod 6 is contracted and the piston 5 is displaced downward, the free piston 7 is displaced downward to compress the gas chamber C. At this time, the gas chamber C is compressed to increase the spring force and the spring constant.

On the other hand, when the piston rod 6 is extended and the piston 5 is displaced upward, the free piston 7
The gas chamber C is displaced upward to expand the gas chamber C. At this time, the gas chamber C expands to reduce the spring force and the spring constant. As described above, the spring constant of the gas chamber C increases as the gas chamber C is compressed via the free piston 7.

8 has one end connected to the rod-side oil chamber A,
The other end is a first oil passage connected to the accumulator 12,
A damping force generating section 9 as a damping element is provided in the middle of the first oil passage 8.

The damping force generating section 9 has a damping valve 10 on the extension side and a damping valve 11 on the contraction side.
The accumulator 12, the first oil passage 8, the damping force generator 9, and the rod-side oil chamber A constitute a first hydraulic circuit of the present invention.

Here, when the piston rod 6 is extended, the extension-side damping valve 10 resists the oil liquid flowing through the first oil passage 8 from the rod-side oil chamber A to the bottom-side oil chamber B. It gives a damping force. Also, when the piston rod 6 is contracted, the damping valve 11 on the contraction side is an oil liquid flowing through the first oil passage out of the oil liquid flowing from the bottom oil chamber B to the accumulator 12 and the rod oil chamber A. To generate damping force.

Reference numeral 12 denotes an accumulator as a first spring element connected to the first oil passage 8, and in the accumulator 12, a gas chamber D filled with pressurized gas is provided. D functions as a gas spring. The accumulator 12 supplies and discharges the oil liquid between the rod-side oil chamber A and the bottom-side oil chamber B according to the expansion and contraction displacement of the piston rod 6.

Reference numeral 13 denotes a spring constant switching valve as a switching valve provided in a communication passage 14 connecting the bottom side oil chamber B and the first oil passage 8. This spring constant switching valve 13
Communicates and shuts off the bottom side oil chamber B as the second hydraulic circuit and the rod side oil chamber A and the accumulator 12 as the first hydraulic circuit.

The spring constant switching valve 13 is formed as an electromagnetic on-off valve. The spring-constant switching valve 13 is normally in the valve-open position (a) as shown in FIG.
It is in. On the other hand, when a signal is received from a control unit (neither is shown) which detects a lateral acceleration (lateral G) acting on the vehicle, a steering operation amount, a sinking amount of the vehicle, and the like, a signal shown in FIG. To the valve closing position (b).

The hydraulic shock absorber according to the present embodiment has the above-described configuration, and the operation thereof will be described next.

When the spring constant switching valve 13 is in the valve open position (a)
When the piston rod 6 is contracted and the piston 5 is displaced downward in a state where the communication path 14 is communicated,
As shown by the solid arrows in FIG. 1, the oil liquid in the bottom oil chamber B compresses the gas chamber C via the free piston 7, and also communicates via the communication passage 14 and the first oil passage 8. The gas flows into the accumulator 12 and compresses the gas chamber D. Further, a part of the oil liquid in the bottom oil chamber B flows into the expanding rod oil chamber A via the first oil passage 8 and the damping force generation unit 9.

When the piston rod 6 is extended and the piston 5 is displaced upward, the gas chamber C expands and the free piston 7 is displaced upward, as shown by the dotted arrow in FIG. The oil liquid in the accumulator 12 is the first
The oil liquid in the rod-side oil chamber A that flows into the bottom-side oil chamber B via the oil passage 8 and the communication path 14
Flows through the oil passage 8, the damping force generating section 9, and the communication passage 14 into the bottom side oil chamber B.

On the other hand, when the piston rod 6 is contracted and the piston 5 is displaced downward with the spring constant switching valve 13 at the valve closing position (b) and the communication path 14 is shut off, the solid line in FIG. As indicated by the arrow, the bottom oil chamber B
The oil liquid inside greatly compresses only the gas chamber C via the free piston 7. At this time, the rod-side oil chamber A, which expands, is supplied from the accumulator 12 to the main passage 8 and the damping force generator 9.
The oil liquid is supplied via.

When the piston rod 6 is extended and the piston 5 is displaced upward, the gas chamber C expands and the free piston 7 is displaced upward, as shown by the dotted arrow in FIG. At this time, the oil liquid in the rod-side oil chamber A, which contracts, flows into the accumulator 12 via the first oil passage 8 and the damping force generation unit 9.

Next, the operation when the hydraulic shock absorber according to the present embodiment is applied to an automobile will be described.

First, when the vehicle is running straight, the spring constant switching valve 13 communicates with the communication passage 14 by a signal from the control unit. The oil liquid in the side oil chamber A and the bottom oil chamber B compresses or expands both the gas chamber C in the cylinder 1 and the gas chamber D of the accumulator 12. The amount of oil at this time is equal to the cross-sectional area of the piston rod x the amount of movement of the piston rod 6, and the gas chambers C and D are simply compressed and expanded, respectively (for example, by half), and the spring force at this time is small Become. Therefore, the piston rod 6 can be easily (softly) expanded and contracted,
The ride comfort of the vehicle can be improved.

Further, at this time, the damping force generating section 9 acts to reduce the resistance to the oil flowing through the first oil passage 8 and the communication passage 14 between the rod-side oil chamber A, the bottom-side oil chamber B, and the accumulator 12. To attenuate vibration.

On the other hand, when the vehicle runs on a corner (corner), the spring constant switching valve 13 of the hydraulic shock absorber located outside the corner shuts off the communication passage 14 according to a signal from the control unit. The oil liquid in the bottom oil chamber B compresses and expands only the gas chamber C in the cylinder 1 according to the expansion and contraction displacement of the rod 6. Further, the amount of oil at this time is equal to the cross-sectional area of the piston × the amount of movement of the piston rod 6, the gas chamber C is largely compressed, and its spring force is increased. Therefore, the pressure (spring force) of the gas chamber C acts in the direction of extending the piston rod 6 and suppresses the contraction and displacement of the piston rod 6 (hard), so that the rolling of the vehicle during cornering can be suppressed. Can be. In particular, in the present embodiment, since the bottom oil chamber B is completely shut off from the rod oil chamber A, a larger force can be generated.

At this time, the damping force generating part 9 is connected between the rod side oil chamber A and the accumulator 12 by the second oil passage 8.
A resistance is given to the oil liquid flowing through to attenuate the vibration.

Thus, according to the present embodiment, when the vehicle is running straight, the spring constant switching valve 1
By communicating between the bottom side oil chamber B and the accumulator 12 by 3 and compressing the two gas chambers C and D, the spring force and the constant of each gas chamber C and D can be reduced. The rod 6 can be easily expanded and contracted, and the riding comfort can be improved.

On the other hand, when the vehicle runs on a corner,
The spring constant switching valve 13 of the hydraulic shock absorber located outside the corner cuts off the communication between the bottom oil chamber B and the accumulator 12 or the rod side chamber A, and compresses only the gas chamber C. Spring force and spring constant can be increased. As a result, it is possible to suppress the piston rod 6 from contracting and displacing due to the spring force (gas pressure) of the gas chamber C. Therefore, even when traveling on a large corner, it is possible to suppress the vehicle from rolling during cornering. In addition, running stability can be improved.

Further, the hydraulic shock absorber of the present embodiment does not use a pipe connecting the hydraulic shock absorbers as in the prior art Japanese Utility Model Publication No. 47-29914, so that the hydraulic shock absorber is mounted on the vehicle. The work efficiency of the piping can be improved by omitting the piping work, etc., and the response speed can be increased because the piping connecting the hydraulic shock absorbers is not used. Can be improved.

In the first embodiment, the valve in which the spring constant switching valve 13 is in the open state and the closed state is shown. However, the present invention is not limited to this. Only the flow to the rod-side oil chamber A and the accumulator 12, which is the first hydraulic circuit, may be shut off, and may act as a check valve that allows reverse flow. Thus, only the spring force at the time of contraction can be made variable. Further, if the check valve is provided in the opposite direction, the spring force can be increased only when the check valve is extended.

Further, in the first embodiment, the first oil passage 8 and the communication passage 14 are shown to be connected to the rod-side oil chamber A and the bottom-side oil chamber B from the outer peripheral side of the cylinder 1. However, this is schematically shown, for example, the piston rod 6 is hollow, and the passage is formed so as to extend in the axial direction from the tip and open only to either the rod-side oil chamber A or the bottom-side oil chamber B. A first oil passage and a second oil passage may be provided.

In the first embodiment, the free piston 7 is provided in the cylinder 1, and the free piston 7
However, the present invention is not limited to this. For example, as in the second embodiment shown in FIG. An accumulator 21 as another second spring element having a gas chamber E forming a second spring element so as to communicate with the chamber B ′ may be connected via a second oil passage 22.

Further, as another embodiment of the present invention,
The configurations of the patterns (A) to (H) shown in FIG. 4 are conceivable. In FIG. 4, the same components as those in the first embodiment are denoted by the same reference numerals, and the description of the configuration and operation is omitted.

(A) is a schematic view of the first and second embodiments, wherein 33 is a first accumulator as a first spring element, and 34 is a first accumulator as a second spring element. This is a second accumulator. The first accumulator 33 and the second accumulator 34 are connected to a first chamber A and a second chamber A via a first oil passage 31 and a second oil passage 32, respectively.
Is connected to the room B.

The first oil passage 31 is provided with a first damping element 35. The first damping element 35 includes an orifice that generates a damping force in each process of expansion and contraction, and a damping valve.

The first oil passage 31 and the second oil passage 32 are
4, a switching valve 13 is provided in the middle of the communication passage 14 to disconnect the communication passage 14.

The operation of the pattern (A) is the same as that of the first embodiment.

(B) is different from (A) in that the second oil passage 3
2, with the addition of a second damping element 36,
The same is true. Thereby, in the above (A), only a part of the oil liquid flowing out from the bottom side oil chamber B at the time of contraction flows to the damping element 35, and it is difficult to set a large damping force on the contraction side. Since the entire amount of the oil liquid flowing out of the bottom oil chamber B at the time of contraction generates a damping force by the resistance of the second damping element 36, a large damping force can be set.

(C) differs from (B) in that the first oil passage 3
1 in which the first damping element 35 in FIG. With such a configuration, the damping force on the contraction side can be set large, contrary to (A), but it is difficult to set the damping force on the extension side large.

(D) shows the first state of the communication path 14 of (A).
The connection position with the oil passage 31 is changed to the cylinder side of the first damping element 35. In this case, the switching valve 13
Communication, the amount of oil flowing through the first damping element 35 is reduced during communication and increased during interruption, and as a result, the damping force at the time of communication becomes smaller than the damping force at the time of interruption.
Therefore, in (D), the communication force and the cutoff of the switching valve 13 can increase the spring force and also increase the damping force.

As a result, in general, when the spring force is increased, the convergence of the vibration is deteriorated. However, in (D), since the damping force is also increased, the convergence of the vibration is also improved.

(E) shows the first state of the communication path 14 of (B).
The connection position between the oil passage 31 and the second oil passage 32 is changed to the cylinder side of the first damping element 35 and the second damping element 36. Also in this case, the damping force is variable together with the spring force as in (D).

(F) differs from (E) in that the first oil passage 3
1 in which the first damping element 35 in FIG. Also in this case, the damping force is variable together with the spring force as in (D).

(G) shows the first state of the communication path 14 of (B).
The connection position with the oil passage 31 is changed to the cylinder side of the first damping element 35. Also in this case, the damping force is variable together with the spring force as in (D).

(H) shows the second state of the communication path 14 of (B).
The connection position with the oil passage 32 is changed to the second damping element 36 cylinder side. Also in this case, the damping force is variable together with the spring force as in (D).

In the above-mentioned respective patterns, the switching valve 13 is a communicating and shut-off valve. However, instead of the shut-off state, a valve which allows a flow in only one direction may be used.

In each pattern, the piston 5 is not provided with a flow path. However, the present invention is not limited to this, and the flow of the oil liquid between the chambers A and B is limited only when the pressure in the cylinder becomes high in the piston portion. May be provided.

Further, when it is desired to make only the contraction-side spring force variable, a damping valve allowing the flow from the rod-side oil chamber A to the bottom-side oil chamber B may be provided in the piston portion. If only the piston is desired to be variable, a damping valve allowing flow from the bottom oil chamber B to the rod oil chamber A may be provided in the piston portion.

Next, a third embodiment will be described with reference to FIG.

In the third embodiment, FIG. 4F is embodied. 1 and 4 (F) are given the same reference numerals, and description thereof is omitted.

The hydraulic shock absorber 50 forms a cylinder main body from an inner cylinder 51 and an outer cylinder 52.
A first oil chamber A as a first chamber by the piston 53;
The second chamber is defined as a bottom side oil chamber B. A hollow piston rod 54 is attached to the piston 53, and a rotary type actuator 55 composed of a stepping motor is attached to a protruding end of the piston rod 54. The actuator 55 is connected to a control unit (not shown), and is energized and controlled according to a change in the posture of the vehicle body.

An operation rod 57 to which a shutter 56 is attached is connected to the actuator 55. The shutter 56 is provided with a notch 56A and a wall 56B. The shutter 56 opens and closes a communication hole 58 provided in the piston rod 54 by a rotation operation to cut off communication between the rod-side oil chamber A and the bottom-side oil chamber B. Perform The shutter 56 constitutes the switching valve of the present invention, and the communication hole 58 constitutes a communication passage.

At the upper part of the cylinder 51, there is provided a cylinder communication hole 60 for communicating the first reservoir chamber 59 provided between the cylinder 51 and the outer cylinder 51 with the rod-side oil chamber A. The first reservoir chamber 59 is separated from the outer compressed gas chamber F by a rubber partition 61, and the first reservoir chamber 59 of the present invention is formed by the compressed gas chamber F, the partition 61, and the first reservoir chamber 59. It constitutes a spring element. The first spring element, the rod-side oil chamber A and the cylinder communication hole 60 constitute a first hydraulic circuit of the present invention.

When the opening area of the cylinder communication hole 60 is reduced, the cylinder communication hole 60 acts as a damping element, and the third embodiment has the same configuration as that of FIG.

A bottom valve member 63 is fixed to the cylinder 51 at the lower end of the bottom oil chamber B, and a free piston 64 is slidably provided below the bottom valve member 63. The free piston 64 defines an oil chamber 65 and a gas chamber G in which compressed gas is sealed. The free piston 64 oil chamber 65 and the gas chamber G constitute a second spring element of the present invention. In addition, the second spring element and the bottom valve member 6
3. The second hydraulic circuit of the present invention is constituted by the bottom oil chamber B.

The bottom valve member 63 has an expansion-side damping valve 7 that generates a damping force by generating a resistance against the flow of the oil liquid between the bottom-side oil chamber B and the oil chamber 65.
0 and a contraction-side damping valve 71 are provided, and constitute the damping element of the present invention.

The damping valves 70 and 71 are constituted by disk valves used in a normal hydraulic shock absorber.

The piston 53 has an extension-side damping valve 72 that generates a damping force by generating a resistance against the flow of the oil liquid between the rod-side oil chamber A and the bottom-side oil chamber B.
And a contraction-side damping valve 73 is provided. The extension-side damping valve 72 is a normal damping valve through which oil fluid flows from a low piston speed. 0.6m / piston speed
The valve does not open below s and opens at higher speeds, and acts as a relief valve when the pressure in the bottom oil chamber B becomes excessively high.

The operation of the hydraulic shock absorber according to the third embodiment configured as described above will be described.

First, when the vehicle is traveling linearly, the notch 56A of the shutter 56 opens the communication hole 58 by the actuator 55, and according to the displacement of the piston rod 54, The oil liquid in the rod-side oil chamber A and the bottom-side oil chamber B compresses or expands both the gas chamber F and the gas chamber G. The oil amount at this time is the cross-sectional area of the piston rod x the amount of movement of the piston rod 54,
The gas chambers F and G are each compressed and expanded only slightly (for example, half), and the spring force at this time is reduced. Therefore, the piston rod 54 can be easily (softly) expanded and contracted and displaced, and the riding comfort of the vehicle can be improved.

At this time, the oil liquid for compressing and expanding the gas chamber G (for example, the oil liquid that is half the cross-sectional area of the piston rod × the movement amount of the piston rod 54) is attenuated on the extension side of the bottom valve member 63. The oil flows through the valve 70 and the damping valve 71 on the compression side, and a resistance is given to the flowing oil liquid to attenuate the vibration.

On the other hand, when the vehicle travels (corners) at a corner, the shutter 56 of the hydraulic shock absorber located outside the corner is driven by the energizing operation of the actuator 55, and the communication hole 58 is formed in the wall 56B of the shutter 56. Is shut off, the oil liquid in the bottom oil chamber B compresses only the gas chamber G according to the contraction displacement of the piston rod 54. Further, the amount of oil at this time is a large amount of the cross-sectional area of the piston multiplied by the amount of movement of the piston rod 54, the gas chamber G is largely compressed, and its spring force is increased. Also, all of this large amount of oil liquid passes through the damping valve 71 on the contraction side,
A large damping force will be generated. Therefore, the gas chamber G
The pressure (spring force) acts in a direction to extend the piston rod 54 and suppresses the contraction and displacement of the piston rod 54 (hard), so that rolling of the vehicle during cornering can be suppressed. Since the damping force also increases, vibration can be effectively suppressed.

In the case where the piston is greatly pushed up by a projection on the road surface or the like during the cornering, the damping valve 73 on the compression side of the piston 53 is opened to prevent the pressure in the bottom oil chamber B and the gas chamber G from rising sharply. I do.

Further, with respect to the extension displacement of the piston rod 54, the damping valve 72 on the extension side of the piston 53 opens, so that the spring force is relatively small.

If the damping valve 72 on the extension side of the piston 53 is eliminated, a large spring force can be obtained in both expansion and contraction.

In each of the above embodiments, the gas chamber and the oil chamber of the accumulator are defined by a free piston, but may be formed by a metal bellows or rubber. Furthermore, in each of the above embodiments, an example is shown in which a pressurized gas is used as the spring element.
D, G, etc. may be opened to the atmosphere, and a coil spring may be arranged inside the gas chamber to press the free piston.

In each of the above-described embodiments, the lateral acceleration (lateral G) acting on the switching valve on the vehicle, the steering operation amount, the sinking amount of the vehicle, and the like are larger than the set values. Although it has been described that the switching is performed automatically at times, the present invention is not limited to this. For example, a configuration in which the driver manually switches the spring switching valve may be employed. further,
A configuration may be employed in which the torsional force generated during cornering of the stabilizer provided between the left and right unsprung portions is mechanically transmitted to the spring switching valve for switching.

Further, in each of the above-described embodiments, the case where the rolling that occurs when the vehicle corners is described as an example, but instead, the rear side of the vehicle is prevented from sinking when the vehicle accelerates. (Anti-squat)
The present invention may be applied to a case or a case where the rear side of the vehicle is prevented from sinking when decelerating (anti-dive).

In the embodiment, the case where the hydraulic shock absorber is applied to a four-wheeled vehicle has been described as an example. However, the present invention is not limited to this, and the hydraulic shock absorber provided in another vehicle such as a two-wheeled vehicle is exemplified. It is good also as a structure applied to a vessel.

[0083]

As described above in detail, according to the present invention, the hydraulic shock absorber is slidably inserted into the cylinder and the first chamber and the second chamber inside the cylinder. A defined piston, a piston rod fixed at one end to the piston, and a piston rod protruding at the other end to the outside; a first spring element connected to the first chamber and formed of an accumulator; And a second spring element comprising an accumulator and at least one of between the first chamber and the first spring element or between the second chamber and the second spring element. Connecting the provided damping element, a first hydraulic circuit composed of the first chamber and the first spring element, and a second hydraulic circuit composed of the second chamber and the second spring element; Communication passage, and a first hydraulic circuit and a second hydraulic circuit provided in the communication passage.
And a switching valve that switches between a communication state that permits the flow of oil liquid in the mutual direction between the hydraulic circuit and the cutoff state that blocks the flow from at least one to the other.
With a simple configuration, the spring constant can be changed by operating the switching valve.

Therefore, when the hydraulic shock absorber of the present invention is used in an automobile, it is possible to switch between a state of good riding comfort and a state of high steering stability by suppressing a change in posture by operating the switching valve. It becomes possible.

According to the second aspect of the present invention, by connecting the communication path between the chamber in the cylinder and the damping element, the amount of oil flowing through the damping element when the switching valve is shut off. Can be made larger than the amount of oil liquid at the time of communication, so that the damping force when the switching valve is shut off can be made larger than the damping force at the time of communication.

Thus, the damping force can be increased at the same time as the spring force, so that even when the spring force is large, the vibration can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a hydraulic shock absorber according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing the hydraulic shock absorber in a state where a main passage is shut off by a spring constant switching valve in the first embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a hydraulic shock absorber according to a second embodiment of the present invention.

FIG. 4 is eight types of circuit diagrams showing a hydraulic shock absorber according to a modification of the present invention.

FIG. 5 is a longitudinal sectional view showing a hydraulic shock absorber according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 5 Piston 6 Piston rod 7 Free piston (2nd spring element) 8 1st oilway 9 Damping force generation part (damping element) 10, 11 Damping valve 12 Accumulator (1st spring element) 13 Spring constant switching Valve (switching valve) 14 Communication passage A Rod-side oil chamber (first chamber) B Bottom-side oil chamber (second chamber) C Gas chamber (second spring element) D Gas chamber (first spring element)

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Nakamura 1-6-3 Fujimi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Tokiko Corporation F-term (reference) 3D001 AA02 DA03 EB32 3J069 AA53 EE63 EE68

Claims (2)

[Claims] 1. A cylinder, a piston slidably inserted in the cylinder, and a first chamber and a second chamber defined in the cylinder, one end of which is fixed to the piston, and the other end of which is fixed to the piston. A piston rod having a side projecting to the outside, a first spring element connected to the first chamber and comprising an accumulator, a second spring element connected to the second chamber and comprising an accumulator, A damping element provided between at least one of the first chamber and the first spring element, or at least one of between the second chamber and the second spring element; A first hydraulic circuit including a spring element; a communication path connecting the second chamber and a second hydraulic circuit including the second spring element; a first hydraulic circuit provided in the communication path; Communication between the circuit and the second hydraulic circuit to allow fluid flow in opposite directions; Hydraulic shock absorber comprising constituted by a switching valve for switching between cut-off state in which the flow to the other one from Kutomo. 2. The hydraulic shock absorber according to claim 1, wherein the communication passage is connected between a chamber in the cylinder and the damping element.