JPH045788Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a hydraulic shock absorber, and particularly to a variable damping force hydraulic shock absorber suitable as a shock absorber for an automobile suspension system.

(Prior art) As a variable damping force hydraulic shock absorber equipped with a tube, a piston, and a piston rod, in addition to the valve mechanism for generating the original damping force provided in the piston, there are two liquid chambers partitioned on both sides of the piston. There is a piston rod with a bypass that communicates with the piston rod, and a cylindrical valve body with multiple orifices of different diameters that can be operated from the outside to open and close the bypass, making the damping force variable (for example,
-191448 Publication, Utility Model Application Publication No. 1987-102536).

(Problems to be Solved by the Invention) In the above-mentioned type of variable damping force hydraulic shock absorber, flow noise may be generated when liquid passes through the valve body. The reason for this is that the liquid that has passed through the orifice is guided inside the valve body, where a severe pressure drop occurs due to a sudden increase in the flow path area, and when multiple orifices are provided,
One example of this is that liquids collide with each other inside the valve body. This tendency is particularly significant since a large amount of liquid passes through the orifice during extension of the piston rod.

In the hydraulic shock absorber described in Japanese Utility Model Application No. 60-177346, a housing is provided near the piston of the piston rod, and a control valve is placed within the housing, and the end of the control valve is used to increase the hydraulic pressure in the housing. It is supported by a collar which is shaped so that it can move freely, forming a so-called intermediate chamber.

Although it is possible to reduce flow noise by providing an intermediate chamber, since the area of the intermediate chamber is larger than the area of the orifice, the pressure drop due to the rapid expansion of the flow path area still appears large. To solve this problem, countless intermediate chambers must be provided.

An object of the present invention is to provide a hydraulic shock absorber that can reduce flow noise by suppressing a severe pressure drop caused by rapid expansion of liquid that has passed through a valve body.

(Means for Solving the Problems) The present invention divides the inside of the tube into two liquid chambers using a piston, and forms a bypass communicating the two liquid chambers in a piston rod coupled to the piston. A hydraulic shock absorber having a cylindrical valve body disposed on the piston rod to vary the amount of liquid flowing through the bypass, the valve body being disposed inside the valve body and gradually reducing the velocity of the liquid flowing when the piston rod is extended. It includes an area changing member formed as follows.

(Function) When the piston rod extends, the liquid guided from the orifice to the inside of the valve body moves along the area changing member. Since the area changing member is formed to gradually reduce the velocity of the liquid, that is, to gradually increase the flow path area, a drop in liquid pressure due to a sudden change in the flow path area does not substantially occur, and the viscosity of the liquid increases. Only the pressure drop due to Thus, the noise generated when liquid flows through the orifice is significantly reduced.

Conventionally, a soundproof cap or soundproof sheet was attached to the attachment point of the hydraulic shock absorber to the vehicle body in order to prevent the sound of flowing liquid from entering the vehicle interior, but according to the present invention, the effect of reducing the sound of flowing liquid is Since these parts are large, these parts are no longer necessary, and costs can be reduced.

The area changing member is a small part, and only one piece needs to be attached to the valve body, so there is little increase in cost.

(Embodiment) As shown in FIG. 1, the hydraulic shock absorber 10 has a tube 12 partitioned into two liquid chambers A and B by a piston 14, and a piston rod 16 connected to the piston 14 divided into two liquid chambers. While forming a bypass 18 that communicates A and B, a valve body 20 is disposed on the piston rod 16 in order to change the amount of liquid flowing through the bypass 18.

In the illustrated embodiment, the hydraulic shock absorber 10 is of the so-called twin-tube type, having an outer tube 22 arranged coaxially with the tube 12 outside the tube 12 .

Piston 14 is slidably disposed within tube 12 . A piston band 24 and an O-ring 26 are attached to the outer peripheral surface of the piston 14 to partition the inside of the tube 12 into a liquid chamber A and a liquid chamber B.
The liquid chamber A is a chamber in which liquid pressure is generated when the piston rod 16 is extended, and the liquid chamber B is a chamber in which a liquid pressure is generated when the piston rod 16 is extended.
This is a chamber in which hydraulic pressure is generated when 6 is contracted.

The end of the piston rod 16 passes through the piston 14, and the piston 14 and the piston rod 16 are connected as described below. The piston 14 is
A plurality of ports 28 (one shown) to allow liquid to flow when the piston rod 16 is extended, and a plurality (one shown) to allow liquid to flow when the piston rod 16 is retracted.
ports 30 at intervals in the circumferential direction,
Liquid chambers A and B communicate through these ports 28 and 30.

The piston rod 16 enters the tube 12 through a rod guide and seal member (not shown) located at the open end of the tube 12. The bypass 18 in the illustrated embodiment has a passage 19a extending diametrically through the piston rod 16 and communicating with the liquid chamber A, and a passage 19a extending from the end face of the piston rod 16 in its axial direction beyond the piston 14, while communicating with the liquid chamber B. , on the other hand, a passage 19b communicating with the passage 19a, and a passage 19c opened in the diametrical direction from the passage 19b. The passage 19c is a passage 33 of the auxiliary member 32 fitted to the piston rod 16.
It communicates with liquid chamber A through.

The valve body 20 is formed in a cylindrical shape and has a plurality of orifices 21a with different diameters spaced apart in the circumferential direction, and further has a plurality of orifices 21a with different diameters spaced apart from the orifices 21a in the axial direction. orifices 21b are spaced apart in the circumferential direction. The orifice 21a can communicate with the passage 19a of the bypass 18, and the orifice 21b can communicate with the passage 19c. The plurality of orifices 21a and the plurality of orifices 21b have the same size arrangement of apertures in a planar state, and are also in the same phase.

An area changing member 34 is arranged inside the valve body 20. As shown in FIGS. 1 and 2, the area changing member 34 integrally includes a tapered changing portion 35a and a mounting portion 35b, and the changing portion 35a has a positioning notch 35c for mounting. A through hole 35d is provided in the portion 35b. The changing portion 35a is the valve body 20
In cooperation with the inner circumferential surface of the piston rod 16, it forms a passageway 38 through which liquid flows when the piston rod 16 is extended.

The passage 38 is formed so as to gradually reduce the velocity of the flowing liquid when the piston rod 16 is extended, that is, so that the passage area constituted by its radial cross-sectional area gradually increases. In the illustrated embodiment, the changing portion 35a is tapered and the inner circumferential surface of the valve body 20 is a straight surface, so the taper angle of the changing portion 35a is made small to gradually increase the flow area of the passage 38. let And orifice 2 of passage 38
The area of the portion facing 1a is the orifice 21a.
Make it as small as the area of This prevents the liquid flowing from the orifice 21a from expanding rapidly.

The area changing member 36 shown in FIG. 3 is formed in a cylindrical shape and has restraining parts 37a and 37b on its outer peripheral surface, and these restraining parts are fitted into the valve body 20. In this fitted state, the orifice 21a of the valve body is connected to the passage 37.
The passage 37c opens to the hole 37c through the hole 37d.
e, communicates with unwidened hole 37f. Here, passage 37
The flow passage area of c is slightly larger than the area of the orifice 21a, and the hole 37d is smaller than the passage 37c.
The flow path area of the hole 37f is slightly larger than that of the hole 37d, and the flow path area of the hole 37f is slightly larger than that of the hole 37e. Thus, the flow path area is gradually increasing. The area changing member 36 has a through hole 37g for pin insertion and a notch 37 for positioning.
h is provided in the same way as the area changing member 34.

The area changing member 34 is arranged inside the valve body 20, and the pin 39 is inserted into the hole of the valve body 20 and the hole 35d of the area changing member. After that, the valve body 20
It is rotatably inserted into the piston rod 16 and rotatably supported in a structure known per se.

An annular leaf spring 40 is arranged above the auxiliary member 32. The leaf spring 40 covers the passage 33 and prevents the flow of liquid from the liquid chamber A to the liquid chamber B when the piston rod 16 is extended.
6, the flow of liquid from liquid chamber B to liquid chamber A is allowed. The spring constant of the leaf spring 40 is small, and when a slight hydraulic pressure is generated in the liquid chamber B, the leaf spring 40
leaves the auxiliary member 32.

The piston rod 16 has a leaf spring 40, an auxiliary member 32, a coil spring 42, a leaf spring 44, and the piston 1.
4. Insert the leaf spring 46, washer 48, and coil spring 50 in this order, screw the nut 52 into the piston rod 16, and attach these parts to the nut 52.
and the shoulder of the piston rod 16, and then assembled to the piston rod 16.

(Operation of the Embodiment) The hydraulic shock absorber 10 is used by sealing oil or other liquid in the tube 12 and in the lower part of the gap between the tubes 12 and 22.

When the piston rod 16 extends: When the speed of the piston 14 is small, the liquid in the liquid chamber A flows from the bypass 18 to the orifice 21 of the valve body 20.
It flows through a. At this time, orifice 21a
Damping force is generated depending on the diameter of the Orifice chair 2
Since the flow area of the passage 38 is small, the liquid flowing into the passage 38 from 1a flows through the passage 38 without causing a pressure drop due to a change in area, and the velocity gradually decreases. Further, even if liquid flows into the passage 38 from the plurality of orifices 21a, the liquid flows smoothly without colliding with each other due to the effect of the changing portion 35a of the area changing member 34.

When the speed of the piston 14 increases, the liquid in the liquid chamber A flows outside the orifice 21a and through the port 28 of the piston 14, pushing down the leaf spring 46 and generating a large damping force.

When the piston rod 16 contracts: When the speed of the piston 14 is small, the liquid in the liquid chamber B flows from the passage 19b to the orifice 21b to the passage 33.
In addition to pushing up the leaf spring 40 and flowing into the liquid chamber A, the liquid flows from the orifice 21a to the passage 19a, flows toward the liquid A, and generates a damping force.

As the speed of the piston 14 increases, the liquid flows through a foot valve (not shown), where a damping force is generated.

[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 of the area changing member shown in Fig. 1, and Fig. 3 is a sectional view of another area changing member. be. 10...Hydraulic shock absorber, 12...Tube, 14
...Piston, 16...Piston rod, 18...
... bypass, 20 ... valve body, 34, 36 ... area changing member, 38 ... passage.

Claims (1)

[Scope of utility model registration request] The inside of the tube is divided into two liquid chambers by a piston,
forming a bypass communicating the two liquid chambers in a piston rod coupled to the piston;
A hydraulic shock absorber includes a cylindrical valve body arranged on the piston rod to change the amount of liquid flowing through the bypass, the hydraulic shock absorber being arranged inside the valve body and gradually reducing the velocity of the liquid flowing when the piston rod is extended. A hydraulic shock absorber comprising an area changing member configured to.