JPH109325A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the attitude variation of a car body at the initial period of steering and the like effectively, by generating a suffieient axial force even in a minute stroke speed scope of a piston. SOLUTION: A cylinder 10, and a piston 30 having an inner cylinder chamber 40 where a control piston 42 is arranged movable to reciprocate, are provided, and the control piston divides the inner cylinder chamber 40 into an inner upper chamber 44 and an inner lower chamber 46 communicated with a cylinder upper chamber 32 and a cylinder lower chamber 34 respectively. To the control piston 42, a check valve 66 to permit only the flow of an operating oil from the inner upper chamber to the inner lower chamber, and a check valve 78 to permit only the flow of the operating oil from the inner lower chamber to the inner upper chamber, are provided, the control piston is energized to a standard position by compression coil springs 76 and 88, and when the control piston is displaced by a specific distance from the standard position, it is abutted to the end wall of the inner cylinder chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber incorporated in a suspension of a vehicle such as an automobile, and more particularly to a shock absorber improved to generate a required axial force even in a small stroke speed range of a piston. Related.

[0002]

2. Description of the Related Art A shock absorber incorporated in a suspension of a vehicle such as an automobile is disclosed in, for example, Japanese Patent Laid-Open No. 2-195.
As described in Japanese Patent Application Laid-Open No. 039,039, in a region where the piston speed is relatively low, the damping force is generated by the oil passing through the orifice of the damping force generating valve in the closed state (orifice region), and the piston In the region where the speed is relatively high, the opening amount of the damping force generating valve gradually increases as the piston speed increases (valve region), so that the ratio of the increase in damping force to the increase in piston speed is higher than that in the orifice region. It is configured to be smaller.

According to such a shock absorber having two regions of an orifice region and a valve region, the damping force in a region where the piston speed is high is excessively large as compared with a shock absorber having only the orifice region or the valve region. Thus, the damping force in a region where the piston speed is low can be increased while preventing the vehicle from becoming unstable, whereby good steering stability of the vehicle can be secured without deteriorating the riding comfort of the vehicle.

[0004]

However, in the small stroke speed range of the piston, such as in the initial stage of steering or the initial stage of acceleration / deceleration, the differential pressure between the two cylinder chambers is small. A sufficient damping force cannot be generated even by the shock absorber having the two regions, and therefore, the change in the posture of the vehicle body cannot be effectively suppressed.

In order to solve such a problem, in order to generate a sufficient damping force even in the small stroke speed range of the piston, the effective passage cross-sectional area of the orifice must be reduced. The damping force in an area where the stroke speed of the piston is medium to high is excessive and the ride comfort of the vehicle deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional shock absorber, and a main problem of the present invention is that oil flows through an orifice in a small stroke speed range of a piston. Generates a sufficient axial force even in the small stroke speed range of the piston, thereby reducing the riding comfort of the vehicle without deteriorating the ride comfort. Is to effectively suppress the change in the posture of the vehicle body.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the main object as described above is the structure of claim 1, that is, the cylinder and the cylinder are reciprocally fitted and cooperated with the cylinder. A piston that defines first and second cylinder chambers, a cylinder chamber device that connects and connects the first and second cylinder chambers to each other, and the cylinder chamber that is reciprocally disposed within the cylinder chamber device. A control piston that divides the inside of the device into third and fourth cylinder chambers that communicate with the first and second cylinder chambers, respectively, and that communicates with the third and fourth cylinder chambers provided in the control piston; First and second communication paths to be connected, and a first check valve that allows only the flow of hydraulic oil from the third cylinder chamber to the fourth cylinder chamber via the first communication path, Before the fourth cylinder chamber A second check valve that allows only the flow of hydraulic oil toward the third cylinder chamber through the second communication passage, and the control valves are disposed in the third and fourth cylinder chambers and cooperate with each other to perform the control. First and second elastic biasing means for biasing the piston to a standard position, wherein the control piston is configured to abut on an end wall of the cylinder chamber device when displaced by a predetermined distance from the standard position. This is achieved by a shock absorber characterized in that:

According to the first aspect of the present invention, in the extension stroke of the shock absorber, the volume of the first cylinder chamber decreases and its pressure increases, and the volume of the second cylinder chamber increases. When the pressure decreases, at the beginning of the extension stroke, the pressure in the third cylinder chamber increases and the pressure in the fourth cylinder chamber decreases, so that the control piston increases the volume of the third cylinder chamber. Then, the fourth cylinder chamber is relatively displaced with respect to the cylinder chamber apparatus in a direction in which the volume of the cylinder chamber apparatus decreases, the first elastic urging means expands, and the second elastic urging means is compressed. A force is applied to the piston in a direction that suppresses displacement of the piston in the extension direction with a magnitude proportional to the relative displacement of the control piston.

Further, when the extension stroke further continues and the control piston is displaced by a predetermined distance from the standard position, the control piston comes into contact with the end wall of the cylinder chamber device and cannot be further displaced relative to the cylinder chamber device. Hydraulic oil in one cylinder chamber flows to the fourth cylinder chamber and the second cylinder chamber via the third cylinder chamber, the first communication passage, and the first check valve, and the hydraulic oil flows through the first check chamber. Damping force is generated by the flow resistance when passing through the valve.

Similarly, at the beginning of the contraction stroke, the pressure in the fourth cylinder chamber increases and the pressure in the third cylinder chamber decreases. The third cylinder is relatively displaced with respect to the cylinder chamber device in a direction in which the volume of the cylinder chamber is reduced, the second elastic urging means expands, and the first elastic urging means is compressed. Is applied to the piston in a direction that suppresses the displacement of the piston in the contraction direction with a magnitude proportional to the relative displacement of the piston.

When the contraction stroke is further continued and the control piston is displaced by a predetermined distance from the standard position, the control piston comes into contact with the end wall of the cylinder chamber device and cannot be further displaced relative to the cylinder chamber device. Hydraulic oil in the second cylinder chamber flows to the third cylinder chamber and the first cylinder chamber via the fourth cylinder chamber, the second communication passage, and the second check valve, and the hydraulic oil flows through the second check chamber. Damping force is generated by the flow resistance when passing through the valve.

Therefore, according to the configuration of the first aspect, the elastic stroke of the elastic urging means accompanying the relative displacement of the control piston causes the minute stroke speed of the piston to be increased in both the extension stroke and the contraction stroke of the shock absorber. Since a force independent of the passage of the hydraulic oil through the check valve is generated in the region, a sufficient axial force is generated even in the small stroke speed region of the piston.

[0013]

According to a preferred aspect of the present invention, in the configuration of the first aspect, the cylinder chamber device is provided inside the piston (preferred aspect 1).

According to a preferred embodiment of the present invention, in the configuration of the above-mentioned claim 1 or the preferred embodiment 1, the first and second elastic biasing means cooperate with each other to move the control piston to the standard position. It is configured to urge the valve elements of the first and second check valves to the valve closing position while being urged (preferred embodiment 2).

According to a preferred embodiment of the present invention, in the configuration of the preferred embodiment 1, the piston includes a main body having a cylinder chamber device therein, and a first cylinder chamber integrally connected to the main body. , And a rod portion extending to the outside of the cylinder, and the main body portion is configured to carry a rebound stopper in the first cylinder chamber (preferred embodiment 3).

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a partial longitudinal sectional view showing one embodiment of a shock absorber according to the present invention constituted as a double-cylinder type shock absorber. FIG. 2 is an enlarged view showing a main part of the shock absorber shown in FIG. It is a partial longitudinal section.

In these figures, reference numeral 10 denotes a cylinder. The cylinder 10 includes an inner cylinder 14 and an outer cylinder 16 which extend concentrically along an axis 12.
Contains. Although not shown, the upper ends of the inner cylinder 14 and the outer cylinder 16 are closed by an upper cap, and the lower end of the outer cylinder 16 is closed by a lower cap 18 fixed thereto.
The lower end of the inner cylinder 14 is fixed to the lower end of the outer cylinder 16 and is a base valve assembly 20 known per se.
Supported by The inner cylinder 14 and the outer cylinder 16 cooperate with the upper cap to define an annular reservoir chamber 22. The reservoir chamber 22 is filled with a high-pressure gas 24 and an oil 26 as a working fluid. The base valve assembly 20 cooperates with the lower cap 18 to freely communicate with the reservoir chamber 22.
8 is defined.

A piston 30 is arranged in the inner cylinder 14 so as to be able to reciprocate along the axis 12. The piston 30 includes a rod portion 30A extending along the axis 12,
Piston body 3 integrally formed at the lower end of the rod
0B. The piston body 30B cooperates with the inner cylinder 14 and the like to define a cylinder upper chamber 32 as a first cylinder chamber above the cylinder upper chamber 32 and a cylinder lower chamber 34 as a second cylinder chamber below the piston cylinder 30B. doing.

The piston body 30B has a substantially cylindrical shape, and a seal band 31 is fixed to the outer peripheral surface of the lower end thereof, and the seal band slidably contacts the inner surface of the inner cylinder 14 with the seal band. . A flange 35 is formed integrally with the upper end of the piston body 30B, and an annular rebound stopper 36 is fixed to the upper surface of the flange. The piston body 30B is formed as a separate part from the rod 30A. For example, the piston body 3 is screwed or welded to the lower end of the piston body 30B.
OB may be fixed to the lower end.

A cap 38 is fixed to the lower end of the piston body 30B.
In cooperation with the internal cylinder chamber 40 as a cylinder chamber device
Has been demarcated. A control piston 42 is disposed in the inner cylinder chamber 40 so as to be able to reciprocate along the axis 12. The control piston 42 divides the internal cylinder chamber 40 into an internal upper chamber 44 as a third cylinder chamber and an internal lower chamber 46 as a fourth cylinder chamber. The inner upper chamber 44 is connected to the cylinder upper chamber 32 through a plurality of communication holes 48 provided at the upper end of the piston body 30B, and the inner lower chamber 46 is connected to a plurality of communication holes 50 provided in the cap 38. Is connected to the lower cylinder chamber 34 in communication.

The control piston 42 includes a shaft 52 extending substantially along the axis 12 and a control piston body 58 fitted to the shaft and secured to the shaft 52 by lock nuts 54 and 56 and the like. I have. The control piston body 58 is provided with a plurality of first communication passages 60 and a plurality of second communication passages 62 for mutually connecting and connecting the inner upper chamber 44 and the inner lower chamber 46 to each other. Further, a seal band 64 is fixed to the outer peripheral surface of the control piston main body 58, and the seal band 64 is slidably contacted tightly with the inner surface of the piston main body 30B with the seal band.

The inner lower chamber 46 is provided with a first check valve 66 that permits only the flow of oil from the inner upper chamber 44 to the inner lower chamber 46 through the communication passage 60. The check valve 66 has a substantially annular plate-shaped valve element 72 fitted to the shaft 52 and fixed to the control piston main body 58 by the lock nut 54 via the sleeve 68 and the shim 70. A compression coil spring 76 as an elastic urging means is elastically mounted between a spring seat 74 which fits reciprocally and abuts on the valve element 72 and the inner wall surface 38A of the cap 38.

Similarly, the inner upper chamber 44 is provided with a second check valve 78 which permits only the flow of oil from the inner lower chamber 46 to the inner upper chamber 44 through the communication passage 62. The check valve 78 is fitted on the shaft 52 and the sleeve 80 and the shim 82
The control piston body 5 by the lock nut 56 through the
8 having a substantially annular plate-shaped valve element 84 fixed to
A compression coil spring 88 as an elastic biasing means is elastically mounted between a spring seat 86 which reciprocates with the sleeve 80 and abuts on the valve element 84 and the inner end wall 40A of the inner cylinder chamber 40. .

In the illustrated embodiment, the elastic biasing means is a compression coil spring. However, the elastic biasing means may be a tension coil spring, or may be rubber or another rubber-like elastic body. Or a spring having a non-linear characteristic such as a gas bag.

Thus, the check valves 66 and 78 are connected to the compression coil springs 76 and 88 via the spring seats 74 and 86, respectively.
2 to abut the control piston body 58 to the valve closing position shown in FIG. The control piston 42 is urged to the standard position shown in FIG. 2 by the compression coil springs 76 and 88. When the control piston 42 is at the standard position, the upper end and the lower end of the shaft 52 are located at the inner end wall 40A and the inner end wall 40A, respectively. It is arranged at a predetermined distance from the wall surface 38A.

In the initial stage of the extension stroke of the shock absorber constructed as described above, the volume of the cylinder upper chamber 32 decreases and its pressure increases, and the volume of the cylinder lower chamber 34 increases and its pressure increases. By decreasing, the inner upper chamber 4
4, the pressure in the inner lower chamber 46 decreases, and as a result, as shown in FIG. 3, the control piston 42 is displaced downward from the standard position relative to the piston body 30B in the figure.

Accordingly, the compression coil spring 88 expands, but the compression coil spring 76 is compressed, and a force for urging the piston 30 downward in the figure is generated by these compression coil springs, and the force is applied to the piston body 30B. It is proportional to the relative displacement of the control piston 42 from the standard position.

When the cylinder 10 and the piston 30 are further displaced relative to each other in the extending direction, the lower end of the shaft 52 comes into contact with the inner wall surface 38A of the cap 38, as shown in FIG. 30B
, The check valve 66 opens against the spring force of the compression coil spring 76, and the oil in the inner upper chamber 44 is released from the communication passage 60 and the check valve. The oil flows through the internal lower chamber 46 via the communication port 66, further flows through the communication hole 50 to the cylinder lower chamber 34, and a damping force is generated by the flow resistance when the oil passes through the check valve 66.

Similarly, at the beginning of the contraction stroke of the shock absorber, the volume of the cylinder lower chamber 34 decreases and its pressure increases, and the volume of the cylinder upper chamber 32 increases and its pressure decreases. Then, the pressure in the internal lower chamber 46 increases and the pressure in the internal upper chamber 44 decreases, whereby the control piston 42 is displaced upward in the figure relative to the piston main body 30B.

Therefore, the compression coil spring 76 expands but the compression coil spring 88 is compressed, and a force for urging the piston 30 upward in the drawing is generated by these compression coil springs, and the force is also controlled for the piston body 30B. It is proportional to the relative displacement of the piston 42 from the standard position.

When the cylinder 10 and the piston 30 are further displaced relative to each other in the contraction direction, the upper end of the shaft 52 abuts on the inner end wall 40A of the internal cylinder chamber 40, and the control piston 42 is further moved relative to the piston body 30B. The check valve 78 opens against the spring force of the compression coil spring 88, and the internal lower chamber 4
6 flows through the communication passage 62 and the check valve 78 to the internal upper chamber 44, and further through the communication hole 48, the cylinder upper chamber 3.
2, damping force is generated by the flow resistance when the oil passes through the check valve 78.

FIG. 5 is a graph showing the operation of the illustrated embodiment at the time of steering, acceleration / deceleration, etc. in comparison with the operation of a conventional shock absorber, and FIG. 6 shows the case where the vehicle body vibrates up and down. 4 is a graph showing the operation of the illustrated embodiment in comparison with the operation of a conventional shock absorber.

In these figures, the upper stage shows the cylinder 1
The relative displacement of the piston 30 with respect to 0 is shown, and the lower part shows the change in the axial force of the shock absorber with a solid line for the embodiment and a broken line for the conventional technology. In these figures, + and-indicate the direction of extension and contraction of the shock absorber, respectively.

As can be seen from FIG. 5, according to the illustrated embodiment, even when the relative speed of the piston 30 with respect to the cylinder 10 is small, the internal upper chamber 44 and the internal lower chamber 46 generated by the relative displacement of the piston with respect to the cylinder. The control piston 42 is driven relatively to the piston main body 30B by the pressure difference between the piston body 30B and the compression coil spring 76 or 88 is compressed to generate a force opposing the relative displacement of the piston with respect to the cylinder. In addition, it is possible to effectively suppress a change in the posture of the vehicle body at the initial stage of steering or the initial stage of acceleration / deceleration.

On the other hand, in the conventional shock absorber, when the relative speed of the piston with respect to the cylinder is small, the oil passes through the orifice of the damping force generating valve relatively easily, so that a sufficient damping force is obtained. Does not occur, it is not possible to sufficiently oppose the relative displacement of the piston with respect to the cylinder, and therefore, it is not possible to effectively suppress a change in the attitude of the vehicle body at the initial stage of steering or acceleration / deceleration.

As can be seen from FIG. 6, the axial force of the illustrated embodiment when the vehicle body vibrates up and down, especially in the region where the direction of the relative displacement of the piston with respect to the cylinder is reversed, the shaft of the conventional shock absorber. Although a slight phase lag occurs with respect to the force, the overall structure is the same as the axial force of the conventional shock absorber, so that the structure of the illustrated embodiment does not significantly deteriorate the ride comfort of the vehicle.

In particular, according to the illustrated embodiment, since the internal cylinder chamber 40 as the cylinder chamber device is provided in the piston main body 30B of the piston 30, the cylinder chamber device is provided outside the cylinder 10 and the piston 30. As compared with the case where the shock absorber is attached to the vehicle, a better assemblability can be ensured, and the passage between the cylinder upper chamber 32 and the inner upper chamber 44 and the cylinder lower chamber 3
The response between the shock absorber and the shock absorber can be increased by shortening the passage between the inner chamber 4 and the inner lower chamber 46.

If necessary, a control piston (4
A cylinder chamber device for reciprocatingly accommodating 2) is provided outside the cylinder and the piston as a unit integrally with the cylinder 10 or as a separate device, and has an inner upper chamber and an inner lower chamber as third and fourth cylinder chambers. May be connected to the cylinder upper chamber 32 and the cylinder lower chamber 34 as first and second cylinder chambers by conduits or the like. In this case, the diameter of the shock absorber can be reduced as compared with the case of the illustrated embodiment.

According to the illustrated embodiment, the compression coil springs 76 and 88 as the first and second elastic urging means are used.
Cooperate with each other to bias control piston 42 to its normal position, and to provide a valve element 72 of first check valve 66, respectively.
And the function of urging the valve element 84 of the second check valve 78 to the valve closing position, so that two kinds of elastic urging means which individually perform these functions are used. The number of parts and the number of assembling steps of the shock absorber can be reduced as compared with the case where the shock absorber is performed.

If necessary, the elastic urging means is elastically mounted between the control piston main body 58 and the inner wall surface 38A of the cap 38 and the inner end wall 40A of the inner cylinder chamber 40, and connects the valve element of the check valve. Other elastic biasing means for biasing to the valve closing position may be elastically provided between the spring seat 74 and the lock nut 54 and between the spring seat 86 and the lock nut 56. In this case, a spring characteristic for urging the control piston to the standard position and a spring characteristic for urging the valve element of the check valve to the valve closing position can be individually set.

According to the illustrated embodiment, a flange 35 is formed integrally with the upper end of the piston main body 30B.
Since the rebound stopper 36 is fixed on the upper surface of the flange, a stay for supporting the rebound stopper fixed to the rod portion of the piston by welding or the like at a position away from the piston body in the conventional shock absorber. Can be omitted.

Since the axial length of the piston body 30B may be slightly longer than the reciprocating distance of the control piston 42, the rebound stopper 36 is fixed to the flange 35 in the illustrated embodiment. Also in the structure, the distance between the lower end of the piston body and the upper end of the rebound stopper can be made substantially the same as in the case of the conventional shock absorber.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments may be included within the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in the illustrated embodiment, the control piston 42 reciprocates along the axis 12 of the shock absorber.
By setting the 0 axis in a direction different from the axis 12, the control piston may be configured to reciprocate in a direction different from the reciprocating direction of the piston 30, for example, in a direction crossing the axis 12.

Although the illustrated embodiment is configured as a double-cylinder type shock absorber, the shock absorber according to the present invention is a single-cylinder type shock absorber in which an increase or decrease in the volume of a piston in a cylinder is absorbed by a free piston or a gas bag. It may be configured as a shock absorber.

[0047]

As is apparent from the above description, according to the present invention, in both the extension stroke and the contraction stroke of the shock absorber, the elastic deformation of the elastic urging means accompanying the relative displacement of the control piston causes the elastic deformation. In the micro stroke speed range of the piston, a force is generated that does not depend on the hydraulic oil passing through the check valve, so that sufficient axial force can be generated even in the micro stroke speed range of the piston. ,
As a result, it is possible to effectively suppress a change in the posture of the vehicle body at an early stage of steering or an initial stage of acceleration / deceleration without deteriorating the riding comfort of the vehicle.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view showing one embodiment of a shock absorber according to the present invention configured as a double-cylinder type shock absorber.

FIG. 2 is an enlarged partial longitudinal sectional view showing a main part of the shock absorber shown in FIG. 1 in a neutral position.

FIG. 3 is an enlarged partial longitudinal sectional view showing a main part of the shock absorber shown in FIG. 1 in an initial position of an extension stroke.

FIG. 4 is an enlarged partial longitudinal sectional view showing a main part of the shock absorber shown in FIG. 1 in a position after an initial stage of an extension stroke.

FIG. 5 is a graph showing the operation of the illustrated embodiment at the time of steering, acceleration / deceleration, etc., in comparison with the operation of a conventional shock absorber.

FIG. 6 is a graph showing the operation of the illustrated embodiment when the vehicle body vibrates up and down in comparison with the operation of a conventional shock absorber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Cylinder 14 ... Inner cylinder 16 ... Outer cylinder 32 ... Cylinder upper chamber 34 ... Cylinder lower chamber 40 ... Inner cylinder chamber 42 ... Control piston 44 ... Inner upper chamber 46 ... Inner lower chamber 60, 62 ... Communication passage 66 ... First Check valve 76: Compression coil spring 78: Second check valve 88: Compression coil spring

Claims (1)

[Claims] A cylinder, a piston reciprocally fitted to the cylinder and cooperating with the cylinder to define first and second cylinder chambers, and a first and second cylinder chamber. Cylinder chamber devices that are connected to each other, and third and fourth cylinder chambers that are arranged reciprocally in the cylinder chamber devices and communicate with the first and second cylinder chambers in the cylinder chamber devices, respectively. A control piston to split,
First and second communication passages provided in the control piston and connecting the third and fourth cylinder chambers to each other,
A first check valve that allows only a flow of hydraulic oil from the third cylinder chamber to the fourth cylinder chamber via the first communication passage; and a second communication port from the fourth cylinder chamber. A second check valve that allows only the flow of hydraulic oil toward the third cylinder chamber via a passage, and is disposed in the third and fourth cylinder chambers and cooperates with each other to move the control piston to a standard position. And first and second elastic biasing means for biasing the control piston so as to abut against an end wall of the cylinder chamber device when the control piston is displaced by a predetermined distance from the standard position. And shock absorber.