JPH0442595Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a hydraulic shock absorber, and more particularly to a hydraulic shock absorber suitable for installation in a suspension system of an automobile.

(Prior Art) Hydraulic shock absorbers installed in automobile suspension systems are usually set to have as low a damping force as possible in order to improve riding comfort. However, when driving on a place with large changes in the road surface with low damping force, the vehicle body shakes significantly, which can cause motion sickness and worsen ride comfort. To avoid this, it is necessary to set the damping force of the hydraulic shock absorber so that the damping force is low for high-frequency vibrations on the unsprung part, and high for low-frequency vibrations on the sprung part. be.

Using a hydraulic shock absorber, the damping force can be adjusted externally by opening and closing the passage provided in the piston rod using an actuator-operated valve body.
Appropriate control can prevent the deterioration of riding comfort as described above. Among these hydraulic shock absorbers with adjustable damping force, in those in which the valve body is mechanically operated (for example, Japanese Patent Application Laid-Open No. 59-217027), the operating rod is disposed to penetrate the piston rod,
An actuator is coupled to a portion of the operating rod that projects outward from the piston rod. Also, those that operate the valve body electrically (for example,
No. 27257), a solenoid is placed within the piston rod.

(Problems to be solved by the invention) In both of the above hydraulic shock absorbers, the structure of the piston rod is complicated, and in the former, a considerably large space for the actuator is required at the attachment point of the hydraulic shock absorber to the vehicle body. is necessary. In addition, in order to perform appropriate control according to driving conditions, various sensors and control equipment such as a CPU are required, which increases costs.

The purpose of this invention is to suppress high costs, to have a simpler structure than conventional ones, to have a lower damping force against high frequency vibrations under the sprung portion, and to reduce high frequency vibrations under the sprung portion. The damping force increases against frequency vibration. The purpose of the present invention is to provide a hydraulic shock absorber.

(Means for Solving the Problem) A hydraulic shock absorber according to the present invention includes a cylinder, the cylinder is movably disposed within the cylinder, and the interior of the cylinder is divided into a first liquid chamber and a second liquid chamber. A partitioning piston having two sets of ports communicating the first and second liquid chambers, and a piston rod coupled to the piston and extending to the outside of the cylinder through the second liquid chamber. include. The piston rod includes a hole of substantially the same diameter that opens into the first fluid chamber and extends in the axial direction, a first passage that extends from the hole to the outer peripheral surface and communicates with the second fluid chamber, and the piston. The fluid chamber has a throttle passage having a diameter smaller than the diameter of the first passage, which extends from the hole at a position farther from the first passage to the outer circumferential surface and communicates with the second liquid chamber. A spool having a second passage allowing communication of the bore with the first passage is disposed axially movably within the bore of the piston rod and defines a pressure chamber with which the throttle passage is always in communication. A cylindrical stop is secured within the bore and a spring is disposed between the stop and the spool to bias the spool toward the throttle passage. When the spool is in a biased position, the second passageway is connected to the first passageway.
It is formed so as to communicate with the passage.

(Function) Since the piston rod extends outward through the second fluid chamber, when the piston rod contracts, fluid pressure is generated in the first fluid chamber, and when the piston rod extends, fluid pressure is generated in the second fluid chamber. Hydraulic pressure is generated.

When the piston rod retracts, the liquid in the first liquid chamber flows toward the second liquid chamber through one of the two sets of peats provided in the piston and a valve associated with one of the ports. through the hole, stopper, and from the second passage of the spool through the first passage, creating a small damping force.

When the piston rod expands in a short period of time, that is, in the region of high-frequency vibration, the amount of liquid entering the pressure chamber from the throttle passage is small due to the throttling action of the throttle passage, and the movement of the spool is small, so that the second passage of the spool becomes smaller than the first passage. It is in communication with the passageway. As a result, the liquid in the second liquid chamber flows toward the first liquid chamber through the other of the two sets of ports provided in the piston and the valve associated with this other port, and the liquid flows through the first passage. From there, it flows through a second passage in the spool, through a stopper, and through a hole in the piston rod, creating a small damping force.

When the piston rod is extended for a long period of time, ie in the region of low frequency vibrations, the amount of liquid entering the pressure chamber from the throttle passage is large and the movement of the spool is large, so that the second passage is separated from the first passage.
As a result, the liquid in the second liquid chamber flows only through the other of the two sets of ports provided on the piston and the valve associated with this other port, generating a large damping force.

(Effect) When the piston rod contracts, the spool is biased by the spring, and the stopper is cylindrical, so that the inner diameter of the stopper can be adjusted to prevent the liquid in the first liquid chamber from flowing even with the slightest movement of the piston rod. Since it can be enlarged to reach the spool through the stopper, the spool can always be held in a biased position.
As a result, the second passageway of the spool is in communication with the first passageway, and liquid flows through the hole in the piston rod as well as through one of the two sets of ports on the piston. As a result, the damping force generated can be kept small.

When the piston rod is extended, the damping force of the hydraulic shock absorber can be maintained in a small state because the second passage of the spool communicates with the first passage during high frequency vibrations corresponding to unsprung vibrations. Moreover, since the second passage is separated from the first passage during low-frequency vibration corresponding to vibration on a spring, the damping force of the hydraulic shock absorber can be maintained in a large state. In this way, even if the damping force of the hydraulic shock absorber is set low, it is possible to prevent the occurrence of large vibrations during driving and improve ride comfort.

Since the spool is not operated from the outside, actuators and control electronic equipment are not required, and as a result of suppressing high costs, it can be applied to various types of popular cars, trucks, etc.

Since it is not necessary to arrange a rod for operating the spool on the piston rod, the structure of the piston rod is not complicated, and since the diameter of the hole in the piston rod is substantially the same, processing is easy. .

(Embodiment) The hydraulic shock absorber 10 includes a cylinder 12, a piston 14, and a piston rod 16, as shown in FIGS. 1 and 2.

The cylinder 12 is filled with oil or other liquid.
A wheel support (not shown) is coupled to the lower end of the cylinder 12.

Piston 14 is movably arranged inside cylinder 12 . A piston band 18 and a piston ring 20 are attached to the outer peripheral surface of the piston 14, and the inside of the cylinder 12 is partitioned into a first liquid chamber 22 and a second liquid chamber 24.

The piston 14 passes through one end 17 of the piston rod 16, and a nut 26 is attached to the end 17.
Screw in the piston 14 and piston rod 16.
are combined. The other end of the piston rod 16 passes through the second fluid chamber 24, extends outward through a seal member (not shown) disposed at the open end of the cylinder 12, and a rod guide, and is coupled to the vehicle body.

The piston 14 has two sets of ports communicating with the first liquid chamber 22 and the second liquid chamber 24, namely, a plurality of ports 28 through which liquid flows when the piston rod 16 is extended, and a plurality of ports 3 through which liquid flows when the piston rod 16 contracts.
0 (each shows one) at intervals in the circumferential direction, and a leaf spring valve body 32 that opens and closes the port 28 is located below the port 28, and a valve body 32 that is a leaf spring that opens and closes the port 28 is located above the port 30. A leaf spring valve body 34 is arranged to open and close the valve body.

The inner peripheral edge of the valve body 32 is held between the nut 26 and the piston 14, and the outer peripheral edge of the valve body 32 receives the spring force of the coil spring 38 via the spring receiver 36, and is directed toward the open end of the port 28. It is biased. The spring force of the coil spring 36 is large, and a large damping force is generated here when the piston rod 16 is extended. On the other hand, the inner peripheral edge of the valve body 34 is connected to the stopper 4.
0 and the piston 14, the outer peripheral edge of the valve body 34 receives the spring force of the coil spring 42, and the port 3
0 toward the open end. The spring force of the coil spring 42 is small, and the piston rod 1
6, a small damping force is generated during the contraction.

The piston rod 16 opens into the first liquid chamber 22 at its end face, has a hole 44 of substantially the same diameter extending from the end face in the axial direction beyond the piston 14, and a hole 44 extending from the hole 44 to the outer peripheral surface and containing the second liquid chamber. A first passage 46 communicating with the chamber 24 extends from the hole 44 to the outer circumferential surface at a position farther from the piston 14 than the distance between the first passage 46 and the piston 14,
It has a throttle passage 48 that communicates with the second liquid chamber 24. The throttle passage 48 has a diameter equal to that of the first passage 46.
It is formed to be smaller than the diameter of the A shoulder 45 is provided in the hole 44 , and the hole 4 above the shoulder 45 is provided with a shoulder 45 .
The diameter of part 4 has been reduced.

The spool 5 is inserted into the hole 44 of the piston rod 16.
0 is arranged so as to be movable in the axial direction. Upper land 51a and lower land 51b of spool 50
The diameter of the spool 50 is sized for a loose fit in the bore 44 of the piston rod, and the spool 50 is sized for a loose fit in the bore 44 of the piston rod.
It is possible to move upward until it hits . and,
A pressure chamber 52 is defined above the spool 50, with which the throttle passage 48 always communicates.

The spool 50 has a second passage 54 that allows the hole 44 to communicate with the first passage 46 . In the illustrated embodiment, the second passage 54 is an annular groove 55a formed between the upper land 51a and the lower land 51b.
and a plurality (four shown in the figure) of vertical grooves 55b extending from the lower end of the outer peripheral surface in the axial direction.
When the spool 50 abuts the shoulder 45 of the hole 44, the annular groove 55a faces the first passage 46.
As a result, the hole 44 includes the vertical groove 55b and the annular groove 5.
It communicates with the first passage 46 via 5a.

The spool 50 is connected to the throttle passage 48 by the spring 56.
It is biased toward the shoulder 45 and is pressed against the shoulder 45. The cylindrical stopper 58 is connected to the piston rod 1.
Press fit the spring 56 into the hole 44 of the stopper 5.
8 and the spool 50.

The spring force of the spring 56 is such that when the piston rod 16 makes a long extension stroke, the spool 50 is pushed back by the hydraulic pressure introduced into the pressure chamber 52, and the second spool 50 is pushed back.
passage 54 is blocked from first passage 46, but during a short extension stroke, due to the delay in liquid flow through throttle passage 48, before spool 50 is moved by hydraulic pressure. It is determined in relation to the effective area of the throttle passage 48 so that the extension stroke is completed. In this case, a long extension stroke means that the vibration frequency is, for example, 1, which is the natural frequency of the spring.
Set it to ~1.5Hz.

(Operation of the embodiment) When the piston rod 16 contracts: The liquid in the liquid chamber 22 passes through the port 30 and the valve body 3
4 and flows toward the liquid chamber 24. At the same time, since the spool 50 is in the position shown in FIG.
from the second passage 54 of the spool 50 to the first passage 46 to the liquid chamber 2.
It flows towards 4. As a result, the amount of liquid passing through the port 30 of the piston 14 decreases, and the generated damping force characteristic becomes A in FIG. 4.

When the piston rod 16 extends: The hydraulic pressure in the liquid chamber 24 becomes greater than that in the liquid chamber 22, so the differential pressure acts on the pressure chamber 52, but when the piston rod 16 makes a short extension stroke. That is, at the time of high frequency vibration, the liquid flow through the restriction passage 48 is delayed due to its restriction action, so that the force based on the liquid pressure is applied to the spool 5.
The extension of the piston rod 16 is completed before the piston rod reaches zero. As a result, the second passage 54 of the spool 50 is connected to the first passage 46 of the piston rod 16.
Since the liquid in the liquid chamber 24 passes through the port 28 and flows by pressing down the valve body 32, the liquid flows from the first passage 46 to the second passage 54,
The liquid flows through the hole 44 toward the liquid chamber 22, and the flow becomes B in FIG.
Low damping force characteristics can be obtained.

When the piston rod 16 undergoes a long extension stroke, that is, when there is a low frequency vibration, the extension stroke takes longer than the delay of the liquid flow through the throttle passage 48, so that the high liquid pressure generated in the liquid chamber 24 eventually decreases. is guided to the pressure chamber 52, and the spool 50
It is pushed downward as shown. As a result, the second passage 54 of the spool 50 is disengaged from the first passage 46 of the piston rod 16.
The liquid in the liquid chamber 24 passes through the port 28 and reaches the valve body 3.
2 and flows toward the liquid chamber 22, resulting in a high damping force characteristic C.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the main parts of the hydraulic shock absorber according to the present invention, Fig. 2 is a sectional view taken along line 2-2 in Fig. 1, and Fig. 3 is a sectional view showing the spool being pushed down. FIG. 4 is a sectional view of the main part showing the state, and is a characteristic diagram of the damping force. 10... Hydraulic shock absorber, 12... Cylinder, 14
... Piston, 16 ... Piston rod, 22,
24...liquid chamber, 44...hole, 46...first passage, 48...throttle passage, 50...spool, 52
...pressure chamber, 54 ... second passage, 56 ... spring, 58 ... stopper.

Claims (1)

[Scope of utility model registration request] a cylinder; and two sets of pistons that are movably disposed within the cylinder and partition the inside of the cylinder into a first liquid chamber and a second liquid chamber, the pistons communicating with the first and second liquid chambers. a piston rod coupled to the piston and extending out of the cylinder through the second fluid chamber, the piston rod opening into the first fluid chamber and extending axially; a hole of a diameter, a first passage extending from the hole to the outer peripheral surface and communicating with the second liquid chamber, and a distance from the hole to the outer peripheral surface at a position farther from the piston than the first passage; a piston rod having a throttle passage having a diameter smaller than the diameter of the first passage, the piston rod extending and communicating with the second fluid chamber; a spool that defines a pressure chamber that is always in communication with the spool and has a second passage that allows the hole to communicate with the first passage; a cylindrical stopper fixed in the hole; a spring disposed between the spool and the spool biasing the spool toward the throttle passage, the second passage communicating with the first passage when the spool is in the biased position; A hydraulic shock absorber designed to