JP2519209B2 - Variable damping force type hydraulic shock absorber - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber used for suspension of a vehicle, and more particularly to a variable damping force hydraulic shock absorber with adjustable damping force.

Conventional technology Since this type of conventional hydraulic shock absorber has a constant damping force regardless of running conditions such as road condition or vehicle speed, the running performance, riding comfort, or maneuverability of the vehicle can be adjusted according to the running conditions. I couldn't make it good.

Therefore, a piston that slides in a cylinder filled with hydraulic fluid is provided with a damping force variable mechanism that allows the damping force to be selected arbitrarily by switching the passage cross-sectional area, so that the damping force can be adjusted according to running conditions. Various types of the above are also provided by the present applicant (see, for example, Japanese Patent Application No. 58-206386).

An example of such a damping force variable hydraulic shock absorber will be schematically described with reference to FIG. 5 schematically showing, 1 is an outer cylinder fixed to the axle side, and 2 is provided in the outer cylinder 1. And a cylinder 3 filled with hydraulic fluid therein, 3 is a reservoir chamber in which the hydraulic fluid and gas coexist, and 4 is provided in a piston rod 5 fixed to the vehicle body side, and the cylinder 2 is provided with upper and lower fluid chambers.
A piston that slides up and down while being separated into 6 and 7, wherein the piston 4 moves the working fluid from the upper fluid chamber 6 to the lower fluid chamber 7 and from the lower fluid chamber 7 to the upper fluid chamber during the pressure stroke. Liquid chamber 6
Are provided with first and second through passages 8 and 9, respectively, which cause displacement flow, and at the outlets of the respective through passages 8 and 9, the expansion side valve 10 and the pressure side that give flow resistance to the working fluid during the above displacement flow. Valve 11
Is provided. Further, reference numeral 12 in the drawing denotes a base valve fixed to the inner lower end of the cylinder 2, and the base valve 12 is extended to the lower liquid chamber 7 and the reservoir chamber 3 at the time of the pressure stroke by extending like the piston 4. Replace each with a fluidized third,
Fourth through passages 13 and 14 are provided, and the respective through passages 13 and 14 are provided.
An expansion-side check valve 15 and a pressure-side valve 16 for providing flow resistance are provided at each outlet of the.

A communication passage 17 that communicates the upper and lower liquid chambers 6 and 7 and a variable mechanism 18 that adjusts the communication passage 17 from the fully closed state to the maximum opening area are provided in the center of the piston 4. The mechanism 18 can adjust the damping force according to the traveling conditions of the vehicle.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, in the conventional damping force variable type hydraulic shock absorber described above, the compression side damping force is the pressure side valve provided in the base valve 12.
16 and pressure side valve 11 and variable mechanism 18 provided on piston 4
Determined by When the variable mechanism 18 is operated to fully open the communication hole 17 during the pressure stroke, the flow resistance from the lower liquid chamber 7 to the upper liquid chamber 6 becomes the minimum, and the working fluid that has entered the piston rod 5 becomes lower. A minimum damping force corresponding to the flow resistance generated by the pressure side valve 16 when flowing into the reservoir chamber 3 from is obtained. Next, when the variable mechanism 18 is fully closed,
The hydraulic fluid in the lower liquid chamber 7 accompanying the entry of the piston 4 is discharged to the upper liquid chamber 6 by the pressure side valve 11 of the piston 4 and to the reservoir chamber 3 by the pressure side valve 16 of the base valve 12, respectively. It At this time, if the pressure side valve 11 is made rigid so that it will not be opened even with an extremely large pressure,
The entire amount of the hydraulic fluid to be discharged from the lower liquid chamber 7 passes through the pressure side valve 16 so that the flow resistance becomes maximum and the maximum damping force is obtained. However, at this time, the upper liquid chamber 6 is not compensated for the hydraulic fluid for the increase in volume, so that the negative pressure is reached. This negative pressure is generated until the pressure side valve 11 is set to have a predetermined rigidity or less. When negative pressure is generated, air race or cavitation is generated, which causes abnormal noise and destruction of components. Therefore, since the pressure side valve 11 can be set only to a predetermined rigidity or less such that negative pressure is not generated, there is a restriction on the magnitude of the flow resistance generated in the pressure side valve 11, and therefore the variable range of the damping force is small. There was a problem of becoming.

Means for Solving the Problems The present invention has been devised in view of the above-mentioned conventional problems, and is a cylinder provided in an outer cylinder fixed to the vehicle body side and filled with working fluid and gas inside. A piston rod having one end fixed to the axle side and the other end sealingly penetrating one end of the cylinder; and a piston rod of the piston rod for partitioning a lower portion of the cylinder into the liquid chamber and the lower liquid chamber. A piston fixed to the tip and slidably fitted in the cylinder, and a communication passage formed between the outer cylinder and the cylinder and having one end opened to the lower liquid chamber through a through hole, A fixed valve device fixed to the inside of the cylinder so as to separate the inside of the upper part of the cylinder into the upper liquid chamber and the reservoir chamber, and provided on the piston, and flows from the lower liquid chamber to the upper liquid chamber during the extension stroke. The first valve that gives flow resistance to the hydraulic fluid and And a check valve that allows a volume-compensating flow from the upper liquid chamber to the lower liquid chamber during the pressure stroke and the fixed valve device,
A second valve that gives flow resistance to the working fluid flowing from the upper liquid chamber to the reservoir chamber during the pressure stroke, a check valve that allows a volume-compensating flow from the reservoir chamber to the upper liquid chamber during the stroke, and the fixed valve device. A first bypass passage that is partially formed in the valve body and connects the upper liquid chamber and the reservoir chamber, and a portion is formed in the valve body of the fixed valve device to form an upper liquid chamber and a lower liquid chamber. And a variable mechanism provided in the fixed valve device for varying the passage cross-sectional areas of the first and second bypass passages via an orifice. It is characterized by that.

According to the present invention having the above-mentioned configuration, when the first and second bypass passages are opened by the variable mechanism, a part of the hydraulic fluid in the lower fluid chamber is formed in the piston during the extension stroke. It passes through another through passage and the first valve, and the remaining part flows into the upper liquid chamber through the second bypass passage having the variable mechanism. Therefore, the amount of hydraulic fluid flowing from the lower liquid chamber through the first valve into the upper liquid chamber is reduced by the flow rate through the second bypass passage, the flow resistance is reduced, and the damping force is also reduced. Further, the working fluid in the lower fluid pressure flows into the upper fluid chamber via the second bypass passage, and the working fluid flows from the reservoir chamber through another through passage formed in the fixed valve device. Then, the increase in volume due to the withdrawal of the piston rod is compensated.

On the other hand, during the pressure stroke, a part of the hydraulic fluid in the upper liquid chamber remains in one through passage provided with the second valve formed in the fixed valve device, and the rest remains in the first bypass passage provided with the variable mechanism. Through to the reservoir chamber. Therefore, the amount of hydraulic fluid flowing from the upper liquid chamber through the second valve into the reservoir chamber is reduced by the flow rate through the first bypass passage, the flow resistance is reduced, and the damping force is also reduced. At the same time, the working fluid from the upper liquid chamber flows into the lower liquid chamber through another through passage formed in the piston to compensate for the increase in volume accompanying the movement of the piston.

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

FIG. 1 shows an embodiment of a hydraulic shock absorber according to the present invention,
21 is an outer cylinder whose upper end is fixed to the vehicle body side, 22 is a cylinder 22 housed in this outer cylinder 21 whose upper and lower ends are sealed,
Gas is enclosed in the cylinder 22 together with the working fluid, and an annular communication passage 23 is formed between the cylinder 22 and the outer cylinder 21 to communicate the communication passage 23 with a lower liquid chamber described later. Through hole
24. 25, a lower end 25a is fixed to the axle side (not shown), and an upper end 25b cooperates with a seal member 26 provided on the lower end of the cylinder 22 to seally penetrate the lower end of the cylinder 22. Reference numeral 27 denotes a piston fixed to the upper end 25b of the piston rod 25 and slidably fitted in the cylinder 22. The piston 27 divides the lower portion of the cylinder 22 into upper and lower liquid chambers 28 and 29. are doing. The piston 27 is also provided with through passages 30 and 31 penetrating the upper and lower surfaces, a first valve 32 that opens and closes this one through passage 30, and a check valve 33 that opens and closes another through passage 31. The first valve 32 is an annular disc plate, which causes a flow resistance to the working fluid flowing from the lower liquid chamber 29 to the upper liquid chamber 28 through the through passage 30 to generate a damping force during the extension stroke. It is supposed to be generated. On the other hand, check valve 33
Is a check plate 35 and an annular spring seat.
And a conical spring 37 which is supported by 36 and biases the check plate 35 in the closing direction with a small elastic force, and allows only the working fluid to flow from the upper liquid chamber 28 to the lower liquid chamber 29. It is becoming like this. Further, on the lower surface of the spring seat 36, there is provided a stopper 38 that abuts against the guide member 26 and regulates the lowest moving position of the piston 27. Through hole
It is set not to block 24.

Reference numeral 39 in the figure is liquid-tightly fixed to the wall of the cylinder 22 above the piston 27 so as to separate the inside of the upper portion of the cylinder 22 into the upper liquid chamber 28 and the reservoir chamber 40 in which the working fluid and the gas are sealed. As shown in FIG. 2, the fixed valve device 39 includes through passages 41 and 42 formed through the upper and lower surfaces inside one side of the valve body 39a, and this one through passage 41.
And a check valve 44 for opening and closing another through hole 42. The second valve 43 is an annular disk plate, and the upper liquid chamber 28 passes through the through hole 41.
Flow resistance is generated in the working fluid flowing from the reservoir to the reservoir chamber 40. On the other hand, the check valve 44 has a check plate 46 and a conical spring 48 which is supported by an annular spring seat 47 and biases the check plate 46 in the closing direction with a small elastic force, and the reservoir chamber. Only the flow of hydraulic fluid from 40 to the upper liquid chamber 28 is allowed.

Further, the fixed valve device 39 includes two upper and lower communication holes 49 and 50 formed through the other side inside the valve body 39a in a direction perpendicular to the axis, and a cylindrical member 51 fixed through the central vertical direction.
The upper communication hole 49 has an outer opening 49a communicating with the reservoir chamber 40, while the lower communication hole 50 has an outer opening 50a provided in the communication passage 23. It communicates with the lower liquid chamber 29 via the passage 23 and the through hole 24. As shown in FIGS. 2 and 3A and 3B, the tubular member 51 has annular grooves 52 and 53 of a predetermined diameter formed on the outer periphery thereof facing the inner openings 49b and 50b of the communication holes 49 and 50. Each of the annular grooves 52, 53 is formed with two orifices 54, 55, 56, 57 having a large diameter and a small diameter, respectively, at positions separated by a predetermined angle of 120 °. The upper bypass 54 or 55-the upper annular groove 52-the upper communication hole 49 constitutes the first bypass passage B1, and the lower communication hole 50-the lower annular groove 53-the lower orifice 56 or 57. The second bypass passage B2 is configured.

In the figure, 61 is a damping force variable mechanism provided in the fixed valve device 39, which has an inner hollow rotating member 58 rotatably supported inside the cylindrical member 51 via a bearing 62,
The rotary member 58 mainly includes an output shaft 64 that transmits the driving force of the actuator 63. The rotating member
The inside of the 58 is formed in a hollow shape, and movable communication holes 59 and 60 that selectively oppose the respective orifices 54 to 57 are formed as the rotating member 58 rotates. Therefore, the orifices 54 to 57 are fully closed, and the movable communication holes 59 and 60 are selectively opposed to the orifices 54 to 57 so that the upper fluid chamber 28 to the reservoir chamber 40 are closed.
The damping force is adjusted by changing the flow resistance of the working fluid flowing from the lower liquid chamber 29 to the upper liquid chamber 28.

Further, the output shaft 64 is connected to an actuator 63 with its upper end projecting through a seal 65 at the center of the upper end of the cylinder 22 in a liquid-tight manner, and this actuator 63 is not shown in the drawing, for example, a damping force setting device or a motor control unit. It is driven by an output signal of a motor drive circuit that receives a signal from the motor, and its rotation is controlled according to the traveling condition and the road surface condition of the vehicle.

Next, the operation of this embodiment having the above configuration will be described.

First, the orifices 54 to 57 of the tubular member 51 are rotated by the rotary member 58.
If the piston rod 25 with the piston 27 descends in the cylinder 22, the piston 27
As a result, the lower liquid chamber 29 becomes a high pressure, so that the working liquid in the lower liquid chamber 29 passes through the through hole 30 of the piston 27 and receives the flow resistance at the first valve 32, and pushes the first valve 32 open. As a result, an orifice is formed, and when passing through the orifice at a high speed, the static pressure is changed into a dynamic pressure, the pressure drops, and the orifice flows into the upper liquid chamber 28. Thus, due to the pressure difference between the upper liquid chamber 28 and the lower liquid chamber 29, the piston 27 is urged upward, and an extension-side damping force that tends to prevent the extension stroke is generated. At this time, since the volume of the upper liquid chamber 28 increases with the movement of the piston 27, the hydraulic fluid in the reservoir chamber 40 flows from the through hole 42 through the check valve 44 to compensate the volume.

On the other hand, the piston rod 25 with the piston 27
When the inside of 22 is raised, the upper liquid chamber 28 becomes a high pressure by the piston 27, contrary to the case of the above-described extension stroke, so that the upper liquid chamber
Of the hydraulic fluid 28, the piston rod 25 entry volume is pushed open by the second valve 43 while receiving a strong flow resistance from the through hole 41 of the fixed valve device 39 by the second valve 43 to form an orifice. When passing at a high speed, the static pressure is changed to a dynamic pressure, the pressure drops, and the fluid flows into the reservoir chamber 40. Thus, due to the pressure difference between the upper liquid chamber 28 and the lower liquid chamber 29, the piston 27 is urged downward to generate a pressure side damping force that tries to prevent the pressure stroke. At this time, since the volume of the lower liquid chamber 29 increases with the movement of the piston 27, the remaining part of the hydraulic fluid in the upper liquid chamber 28 passes from the through hole 31 through the check valve 33 to the lower liquid chamber 29. And the volume is compensated.

Next, when the movable communication holes 59, 60 of the rotating member 58 match any one of the orifices 54 to 57 of the tubular member 51, first, during the extension stroke, the hydraulic fluid in the high pressure lower fluid chamber 29 is first As shown by the solid line arrow in FIG.
Through the lower communication hole 50, and the cylindrical member 51
Through the lower annular groove 53, the lower orifice 56 or 57 having a predetermined diameter selected through the lower movable communication hole 60 and the hollow portion 58a, and then flows into the upper liquid chamber 28. Therefore,
The flow resistance of the working fluid flowing from the lower liquid chamber 29 to the upper liquid chamber 28 decreases according to the size of the orifices 56, 57 of the variable mechanism 61, and the damping force also decreases.

On the other hand, during the pressure stroke, the upper liquid chamber 28
A part of the hydraulic fluid in the inside passes through the hollow portion 58a of the rotating member 58 as shown by the broken line arrow in FIG. 2 and flows through the upper movable communication hole 59 into the upper orifice 54 or 55 having a predetermined diameter selected in advance. It then flows into the upper annular groove 52, then enters the upper communication hole 49 as it is, and then flows into the reservoir chamber 40 through the gap between the edge of the opening 49a and the inner wall surface of the cylinder 22. Therefore, the upper liquid chamber
The flow resistance of the hydraulic fluid flowing from 28 to the reservoir chamber 40 decreases according to the size of the orifices 54, 55 of the variable mechanism 61, and the damping force also decreases. Further, the flow of the volume compensation accompanying the movement of the piston 27 during the extension stroke and the pressure stroke is performed by the check valves 44 and 33 without causing flow resistance. In particular, each bypass passage B1, B
The lower liquid chamber 29
Since a part of the hydraulic fluid therein flows into the upper liquid chamber 28 through the second bypass passage B2 as described above, the volume compensating action is performed more smoothly. Therefore, the upper liquid chamber 28 and the lower liquid chamber 29
No negative pressure is generated in the first and second valves 32, 43.
It is possible to increase the maximum damping force by increasing the rigidity of the and the upper and lower orifices 54, 55, 56 and 57 of the first and second bypass passages B1 and B2 by setting them arbitrarily. The variable width can be widened from 0 to the maximum damping force.

FIG. 4 shows another arrangement of the actuator used in the above embodiment. The actuator 63 is provided at the upper end of the output shaft 64 extended upward, and the actuator 63 is provided at a position separated from the outer cylinder 21. It is also possible to do so. This increases the degree of freedom in layout of the shock absorber fixed to the vehicle body side.

EFFECTS OF THE INVENTION As is clear from the above description, according to the damping force variable hydraulic shock absorber of the present invention, the lower liquid accompanying the movement of the piston is caused in both the extension stroke and the pressure stroke. Since the volume compensation for the chamber and the upper liquid chamber is performed by the first and second check valves, negative pressure is not generated even if the rigidity of the first and second valves is increased. Therefore, the first
The rigidity of the second valve can be increased to set an arbitrarily high damping force. Also, since the orifice of the first and second bypass passages can be set to an arbitrary size and the damping force can be set to 0,
The variable width of the damping force can be widened.

[Brief description of drawings]

FIG. 1 is a cutaway sectional view showing an embodiment of a variable damping force type hydraulic shock absorber according to the present invention, and FIG. 2 is an enlarged sectional view showing a fixed valve device used in this embodiment, and FIG. -A figure and 3-b figure are the sectional views on the AA line and BB line of FIG.
FIG. 4 is a partial sectional view showing another arrangement of the actuator, and FIG. 5 is a schematic view showing a conventional hydraulic shock absorber. 21 …… Outer cylinder, 22 …… Cylinder, 23 …… Communication passage, 24 …… Through hole, 25 …… Piston rod, 27 …… Piston, 28 …… Upper fluid chamber, 29 …… Lower fluid chamber, 32 …… 1st valve, 33 ... Check valve, 39 ... Fixed valve device, 39a ... Valve body, 40 ... Reservoir chamber, 43 ... Second valve, B1 ...
First bypass passage, B2 ... Second bypass passage, 54-57 ...
… Orifice, 61 …… Variable mechanism.

Claims (1)

(57) [Claims] 1. A cylinder provided in an outer cylinder fixed to a vehicle body and having a working fluid and a gas filled therein, one end of which is fixed to an axle side, and the other end of which is a sealing end of the cylinder. A piston rod penetrating through the piston, and a piston fixedly mounted on the tip of the piston rod so as to separate the inside of the lower part of the cylinder into the liquid chamber and the lower liquid chamber, and slidably fitted into the cylinder. A communication passage formed between the outer cylinder and the cylinder and having one end opened to the lower liquid chamber through a through hole; and an upper liquid chamber and a reservoir chamber to separate the upper portion of the cylinder from the upper liquid chamber and the reservoir chamber. A fixed valve device fixed to the first piston, and a first valve provided on the piston for imparting flow resistance to the working fluid flowing from the lower liquid chamber to the upper liquid chamber at the time of extension and the upper liquid chamber to the lower liquid chamber at the time of pressure stroke. To allow volume compensation flow to Lock valve and a second valve provided in the fixed valve device for providing flow resistance to the working fluid flowing from the upper liquid chamber to the reservoir chamber during the pressure stroke, and a volume compensating flow from the reservoir chamber to the upper liquid chamber during the stretching process. A permissible check valve, a first bypass passage that is partially formed in the valve body of the fixed valve device and connects the upper liquid chamber and the reservoir chamber, and a part of the first bypass passage in the valve body of the fixed valve device. A second bypass passage that is formed to communicate the upper liquid chamber and the lower liquid chamber through the communication passage, and the fixed valve device is provided with an inner diameter of the passage cross-sectional area of the first and second bypass passages. A variable damping force type hydraulic shock absorber, comprising a variable mechanism for changing the pressure through a plurality of different orifices.