JPH0620913Y2 - Variable damping force type hydraulic shock absorber - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a damping force variable hydraulic shock absorber used for a vehicle suspension.

2. Description of the Related Art As is well known in the prior art, various hydraulic shock absorbers used in suspensions for automobiles are provided with damping force varying means so that the damping force can be adjusted according to the running conditions of the vehicle. (For example, see Japanese Patent Laid-Open No. 58-81243).

As shown in FIG. 4, a conventional damping force variable type hydraulic shock absorber of this type has a piston rod 2 that penetrates into the inside from one end side of a cylinder 1 filled with hydraulic fluid, and a piston rod 2 A piston 3 is provided which is fixed to one end of a rod 2 and is slidable while separating the inside of the cylinder 1 into an upper liquid chamber 4 and a lower liquid chamber 5, and the piston 3 includes an upper liquid chamber 4 and a lower liquid chamber. Pressure side port 6 and expansion side port 7 that communicate with chamber 5 respectively
And a plate-shaped pressure-side damping valve 8 for assisting flow resistance to generate a damping force to the hydraulic fluid that is displacing and flowing between the upper and lower liquid chambers 4 and 5 through the pressure-side port 6 and the extension-side port 7 and the assist. The extension side damping valve 9 assisted by the spring 9a is arranged vertically. On the other hand, a central hole 10 is formed through the piston rod 2 in the direction of the inner central axis thereof, and side holes 11 and 12 are arranged in two stages to connect the central hole 10 and the upper liquid chamber 4 to each other. Are formed in a substantially radial direction, and damping force varying means 13 is mounted in the central hole 10. The damping force varying means 13 includes a plurality of orifices 15, 1 formed in a cylindrical rotary valve 14 and having different opening areas.
6 is selectively switched depending on the relative relationship with the side holes 11 and 12, thereby changing the flow passage area of the side holes 11 and 12, bypassing the damping valves 8 and 9, and the upper liquid chamber 4 and the lower part. By controlling the bypass flow rate of the working fluid flowing between the fluid chamber 5 and
Damping force is 3 for hard H, medium M, and soft S
It is designed to be variably controlled in stages. A check valve 17 having a constant orifice 18 is provided at the lower end of the piston rod 2.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the conventional damping force variable type hydraulic shock absorber described above, the damping force is adjusted mainly by selectively switching the orifices 15 and 16 of the rotary valve 14 and adjusting the damping valves. The characteristics of the damping force on the extension side, which depend on the spring characteristics of Nos. 8 and 9 and have a great influence on the quality of the steering performance, have a fixed orifice 15 at a low piston speed range such as when the vehicle is at a high speed.
It is determined only by the diameter of 16, and is determined by the spring characteristics of the extension side damping valve 9 and the assist spring 9a in the medium and high speed regions of the piston speed. Therefore, the damping force characteristic has a low degree of freedom, and in particular, in the low speed region of the piston speed in the soft S and medium M, the rapid rising characteristic of the damping force cannot be obtained as shown in FIG. 5B. As a result,
There is a problem that good steering performance of the vehicle cannot be obtained.

Means for Solving the Problems The present invention has been devised in view of the above-mentioned conventional problems, and in particular, the piston rod is formed with an introduction passage that communicates the upper liquid chamber and the central hole, and the central hole is formed. It is characterized in that a control means for variably controlling the opening area of the introduction passage according to the hydraulic pressure passing through the damping force varying means is provided therein.

According to the present invention, when the piston rod moves to the extension side, when the high pressure hydraulic fluid in the upper liquid chamber flows into the lower liquid chamber, the damping force is generated by the damping force generating means, while the piston rod is introduced from the introduction passage. When the damping force varying means is set to soft S or medium M, the hydraulic fluid flowing into the central hole through the damping force varying means is used as a signal hydraulic pressure for the control means. This control means controls the opening degree of the introduction passage by this control means, and the working fluid that has passed through the introduction passage flows into the lower liquid chamber through the central hole.
Then, in the low speed region of the piston speed, the signal hydraulic pressure becomes relatively weak, so that the opening amount of the introduction passage is controlled to be small by the control means, so that a quick rising characteristic of the damping force is obtained.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, 21 is a cylinder filled with hydraulic fluid, 22 is a piston rod which is arranged so as to be able to penetrate through one end of the cylinder 21 in a removable manner, and 23 is fixed to the lower portion of the piston rod 22. Is a piston that slides while separating the inside of the cylinder 21 into an upper liquid chamber 24 and a lower liquid chamber 25, and this piston 23 has an upper liquid chamber 24 and a lower liquid chamber 24 as shown in FIGS. An expansion-side port 26 and a compression-side port 27 that communicate with the liquid chamber 25, and a disk-shaped expansion-side damping valve 28 that selectively opens and closes the upper and lower openings of the ports 26, 27.
And the compression side damping valve 29. The extension side damping valve 28 is an assist spring mounted between an annular spring seat 30 arranged at the lower end of the expansion side damping valve 28 and a retainer 53 screwed to the lower end of the piston rod. The valve 31 is urged in the valve closing direction. The damping valves 28 and 29 are respectively provided in the upper liquid chamber 24 and the lower liquid chamber 25.
In response to the pressure of the working fluid inside, the outer circumference of the washers 32a and 32b is used as a fulcrum to bend according to the pressure, thereby giving a flow resistance to the working fluid passing through the damping valves 28 and 29 to generate a damping force. Has become.

On the other hand, as shown in FIGS. 3A to 3C, the piston rod 22 has a central hole 33 along the inner central axis direction, and two upper and lower stages facing each other that connect the central hole 33 and the upper liquid chamber 24. And side holes 34 and 35 are provided. Further, damping force varying means 36 is provided in the center hole 33. The damping force varying means 36 has one end connected to a drive rod 37 driven by an actuator (not shown),
A cylindrical rotary valve 38 rotatably housed in the center hole 33 is configured as a main element, and two types of orifices 39 and 40 having different opening areas are formed in the body of the rotary valve 38. (Fig. 3 AC)
reference). Then, the orifices 39 and 40 are selectively switched depending on the relative relationship with the respective side holes 34 and 35, whereby the flow passage areas of the side holes 34 and 35 are changed, and the upper liquid chamber 24 and the lower liquid chamber 25. By controlling the bypass flow rate between and, the damping force is variably controlled. That is, when the damping force is set to the soft S according to the vehicle traveling condition,
The rotary valve 38 is rotated via the drive rod 37 to select the orifice 39 having a large opening area (see FIG. 3A). When the damping force is to be medium M, the orifice 40 having a small opening area is selected ( 3B), when it is desired to set the hard H, the side holes 34, 35 and the orifices 39, 40 are not communicated with each other, that is, the rotary valve 38 prevents the hydraulic oil from flowing into the center hole 33. Blocks 34 and 35 (see FIG. 3C)
It is like this.

The inner peripheral surface of the piston 23 near the compression-side damping valve 29 is in constant communication with the upper liquid chamber 24 via a fan-shaped groove 41 on the upper surface of the piston as shown in FIGS. 1 and 2A and 2B. The oil introduction hole 42 is formed along the axial direction.
On the other hand, on the peripheral wall of the lower end portion of the piston rod 22, auxiliary side holes 43 that communicate the oil introducing hole 42 and the central hole 33 are formed so as to penetrate in the diametrical direction.
3 and 3 form an introduction passage. Further, below the rotary valve 38 in the center hole 33 of the piston rod 22,
Control means 4 for variably controlling the opening area of the auxiliary side hole 43.
4 and a check valve 45 that shuts off the inflow of the working fluid from the rotary valve 38 into the lower fluid chamber 25, mainly when the piston rod 22 moves toward the extension side. More specifically, the control means 44 is provided in a substantially cylindrical spool valve 46 that is slidable in the center hole 33 in the axial direction, and a lower end edge of the spool valve 46 and a tip side of the center hole 33. And a return spring 48 mounted between the tubular spring retainer 47 and the tubular spring retainer 47. The spool valve 4
6 is an auxiliary side hole 43 and its own axial hole 4 in the center of the peripheral wall.
A communication hole 46b communicating with 6a is formed in the diameter direction, and the auxiliary hole 43 is closed at a position where the communication hole 46b and the auxiliary hole 43 do not coincide with each other by the spring force of the return spring 48, that is, the outer peripheral surface 46c. Is biased to the upper position.

On the other hand, the check valve 45 is slidably provided in the center hole 33 and has a stepped cylindrical spring retainer 49 having a through hole 49a in the upper wall, and is slidably arranged in the spring retainer 49. A small-diameter disk-shaped check plate 50 that opens and closes the opening end of the axial hole 46a of the spool valve 46, and a check spring 51 that is installed in the spring retainer 49 and biases the check plate 50 in the closing direction of the opening end. I have it.

Further, the spool valve 46 is configured such that a step portion 46d provided on the outer periphery of the upper portion abuts on the lower end edge of the spring retainer 49 to restrict the maximum upward movement. still,
Reference numeral 52 in the drawing denotes a cylindrical stopper press-fitted into the center hole 33.

The operation of the above configuration will be described below. First, when the piston rod 22 moves in the pressure side direction, the lower liquid chamber 2
Since the pressure of the hydraulic fluid in 5 becomes high, when the hydraulic fluid passes through the pressure side damping valve 29 through the pressure side port 27, and when the damping force varying means 36 is set to the soft S or medium M, As shown by the arrow A, the central hole 33
Check plate 5 from the lower end side through axial hole 46a
0 is pushed open against the spring force of the check spring 51, and the predetermined flow resistance is passed when passing through the damping force varying means 36 through the notch 49b of the check retainer 49 and the through hole 49a. In response to this, effective damping action is performed.

On the other hand, when the piston rod 22 moves in the extension direction and the piston 23 moves to the upper liquid chamber 24 side, and when the damping force is selected to be soft S, the pressure in the upper liquid chamber 24 increases and the operation is performed. As shown by the arrow B in FIG.
The expansion side damping valve 28 is opened and flows into the lower liquid chamber 25 while acting on the expansion side damping valve 28 through the expansion side port 26. The generated damping force is applied here. On the other hand, a part of the hydraulic fluid flows into the central hole 33 from the side holes 34 and 35 through the large diameter orifice 39, and then passes through the through hole 49a to the check plate 5.
0 Press the upper surface (arrow C). That is, since the hydraulic pressure acts as a signal hydraulic pressure for the control means 44 and presses the spool valve 46 downward against the spring force of the return spring 48, the communication hole 46b is moved along with the downward movement of the spool valve 46.
The auxiliary side hole 43 is matched with the spring force of the return spring 48 and the signal hydraulic pressure by a predetermined amount. Therefore, the hydraulic fluid flowing from the fan-shaped groove 41 into the oil introduction hole 42 flows into the axial hole 46a from the relatively large controlled opening of the auxiliary side hole 43 and the communication hole 46b as shown by the arrow D, and as it is. It flows into the lower liquid chamber 25 from the central hole 33.

Further, when the orifice 40 having a small opening area of the rotary valve 38 is selected to obtain the damping force of the medium M, the flow rate of the hydraulic fluid flowing into the central hole 33 becomes small, but the signal hydraulic pressure is sufficiently secured. Therefore, through hole 49
The upper surface of the check plate 50 is pressed through "a", and the spool valve 46 is pressed downward in the same manner as described above. Therefore, the hydraulic fluid that has flowed into the oil introduction hole 42 when the communication hole 46b and the auxiliary hole 43 are aligned by a predetermined amount passes from the relatively small controlled opening of the auxiliary hole 43 and the communication hole 46b to the axial hole 4
6a and flows into the lower liquid chamber 25.

Further, by closing all of the orifices 39 and 40, the hard H
When the damping force is selected, the hydraulic fluid is prevented from flowing into the central hole 33, so that the check plate 50 simply closes the opening end of the axial hole 46a by the spring force of the check spring 51. The spool valve 46 is not pressed. Therefore, the hydraulic fluid in the upper liquid chamber 24 passes through the extension side port 26 of the damping force generating means and becomes only the damping force by the extension side damping valve 28.

Thus, when the damping force is soft S and medium M, the opening amount of the auxiliary side hole 43 is adjusted according to the hydraulic pressure passing through the center hole 33, and the flow rate of the hydraulic fluid passing through the auxiliary side hole 43 is adjusted with high accuracy. Since it can be controlled, it is possible to set a large adjustment range of the damping force when the piston rod 22 moves in the extension side. Then, in the soft S and the piston 23 speed low speed range at the time of medium M, the signal hydraulic pressures become relatively weak, and therefore the spool valve 46 causes the communication hole 46.
The matching amount between b and the auxiliary side hole 43, that is, the opening amount is controlled to be small. Therefore, as shown in FIG. 5A, the characteristic that the rising speed of the damping force rapidly increases can be obtained.

Further, in this embodiment, since the check valve 45 is housed in the center hole 33 of the piston rod 22 and the conventional check nut and thick check sheet are omitted, the degree of freedom of the damping force is ensured. The number of parts can be drastically reduced, and the assembling work becomes extremely easy.

The specific configuration of the present invention is not limited to this embodiment, and an example in which the damping force is changed in three steps has been described above, but it may be changed in two steps or four steps. It is also possible to appropriately change the spring force of the return spring 48 to change the movement characteristic of the spool valve 46 that moves in relation to the signal hydraulic pressure.

Effect of the Invention As is clear from the above description, according to the present invention, the damping force adjustment on the extension side of the piston rod does not depend on the fixed orifice diameter of the damping force varying means, but rather on the damping force varying means. Since it is performed by variably controlling the opening area of the introduction passage by the control means that operates according to the signal hydraulic pressure that has passed, the damping force can be adjusted with high precision, and
The degree of freedom is improved. Therefore, a quick rising characteristic of the damping force in the low piston speed region can be obtained. As a result, both maneuverability of the vehicle and good riding comfort can be satisfied.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an embodiment of a variable damping force type hydraulic shock absorber according to the present invention, FIG. 2A is a longitudinal sectional view of a piston used in this embodiment, and FIG. The piston is a plan view, FIG. C is a bottom view of the piston, and FIG. 3 is II of FIG.
In the sectional view taken along the line I-III, A is an explanatory view showing a state in which soft damping force is selected, B is medium, and C is hard, respectively.
FIG. 5 is a longitudinal sectional view showing a conventional damping force variable hydraulic shock absorber, FIG. 5A is a damping force characteristic diagram of this embodiment, and FIG. 5B is a damping force characteristic diagram of a conventional example. 21 ... Cylinder, 22 ... Piston rod, 23 ...
Piston, 24 ... upper liquid chamber, 25 ... lower liquid chamber, 33
...... Central hole, 36 ...... Damping force varying means, 42 ...... Oil introduction hole (introduction passage), 43 ...... Auxiliary side hole (introduction passage), 44
...... Control means.

Claims (1)

[Scope of utility model registration request] 1. A piston rod sealingly penetrating from one end side of a cylinder to the inside, and a piston rod fixed to one end of the piston rod and separated in the cylinder into an upper liquid chamber and a lower liquid chamber. And a damping force generating means for generating a damping force by imparting flow resistance to the hydraulic fluid that is displaced and displaced between the upper liquid chamber and the lower liquid chamber, and the piston rod. In the central hole that is formed to penetrate through in the inner axial direction of and that connects the upper liquid chamber and the lower liquid chamber,
In a hydraulic shock absorber provided with damping force varying means for variably controlling the generated damping force by changing the opening area of the central hole, an introduction passage for communicating the upper liquid chamber and the central hole with the piston rod. And a damping force variable hydraulic pressure, characterized in that control means for variably controlling the opening area of the introduction passage in accordance with the signal hydraulic pressure passing through the damping force varying means is formed in the central hole. Shock absorber.