JPH04312223A - Hydraulic shock absorber - Google Patents

Abstract

PURPOSE:To check rapid increase in damping force by altering the initial load of a main valve through hydraulic pressure in a back pressure chamber whose hydraulic pressure is established through an upstream valve to alter an initial load on pressing force due to an electrostriction member and a downstream valve formed as a relief valve for fixed throttling. CONSTITUTION:The initial load of an upstream valve 23 provided on the upstream side of a back pressure chamber R is altered into a lowering tendency by applying voltage to an electrostriction member 12. The flow rate of a working oil passing through an upstream valve 23 therefore decreases, and the hydraulic pressure in the back pressure chamber R thereby loweres. Thus the back pressure in a main valve 22 loweres, and the damping force caused by the main valve 22 is altered into the lowering tendency.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a hydraulic shock absorber configured so that the damping force generated can be changed by the pressing force from an electrostrictive member.

0002

BACKGROUND OF THE INVENTION Various hydraulic shock absorbers have been proposed in the past in which the damping force generated is changed by the pressing force from an electrostrictive member.

For example, if the damping force generating section in a hydraulic shock absorber has a structure as shown in FIG. When the pressing force from the electrostrictive member 2 (not shown) is applied as shown in the figure, the outer circumferential end of the main valve 1, which is the left end in the figure, is pressed against the opposing seat part 3. The initial load at the outer peripheral end of the main valve 1 will tend to increase, and from then on, the flow of hydraulic oil through the outer peripheral end of the main valve 1 (
(indicated by a solid line arrow in the figure) increases, and the damping force generated by the main valve 1 increases.

As a result, according to a hydraulic shock absorber having a damping force generating section having the above structure, compared to a conventional hydraulic shock absorber that uses a rotary valve to change the generated damping force, the actuator and control valve can be changed. Since it is not necessary to use it, it is possible to reduce the number of parts, which has the advantage of reducing costs.

However, in the proposed structure shown in FIG. 2, the pressing force from the electrostrictive member 2 that determines the amount of deflection of the outer peripheral end of the main valve 1, that is, the amount of distortion of the electrostrictive member 2, is minute. Therefore, there is an inconvenience that the outer circumferential end of the main valve 1 cannot be deflected to a large extent, and therefore the damping force cannot be changed to a large extent.

[0006] Therefore, a damping force generating section having a structure as shown in FIG. It is said that the initial load of the main valve 1 can be changed by changing.

That is, the hydraulic pressure in the back pressure chamber R is caused by a so-called pilot flow (indicated by a solid arrow in the diagram) that is branched from the upstream side of the so-called main flow (indicated by a solid arrow in the diagram) that deflects the outer peripheral end of the main valve 1. (indicated by a broken line arrow), and the initial load is changed by applying a voltage to the electrostrictive member 2 (not shown), which is located upstream of the back pressure chamber R during the pilot flow. a variable valve 4 on the upstream side, and an orifice 5, which is a fixed throttle, arranged on the downstream side of the back pressure chamber R.
It is said that it is set by .

When the pressing force (indicated by an arrow in the figure) from the electrostrictive member 2 acts on the inner peripheral end of the upstream variable valve 4, which is the right end in the figure, the variable valve 4 moves to the left end in the figure. The outer peripheral side end is separated from the opposing seat part 3, that is,
The initial load is set to be small.

As a result, when a predetermined voltage is applied to the electrostrictive member 2, the amount of oil flowing through the variable valve 4 increases, and the oil pressure developed between the variable valve 4 and the orifice 5, that is, the back pressure chamber It becomes possible to increase the oil pressure at R,
Therefore, according to the hydraulic shock absorber having the damping force generating section having the structure shown in FIG. This allows for a wide range of changes, making it possible to adjust the damping force over a wide range.

0010

[Problems to be Solved by the Invention] However, in the hydraulic shock absorber having the damping force generating section having the structure shown in FIG. There is a disadvantage that the initial load on the valve 1 becomes extremely large and the generated damping force becomes extremely high.

That is, in the damping force generating section having the structure shown in FIG. Therefore, even if the initial load in the variable valve 4 is slightly changed, the orifice 5 can exert a predetermined throttling effect and a predetermined oil pressure can be established in the back pressure chamber R. Therefore, the orifice 5 must be formed to have as small a diameter as possible.

As a result, the orifice 5 acts like a plug that cannot compensate for the large flow of hydraulic oil. Therefore, in order to gradually increase the oil pressure in the back pressure chamber R, the initial load on the variable valve 4 is reduced. Even if the flow rate of hydraulic oil through the variable valve 4 is gradually increased by gradually decreasing the flow rate of the hydraulic oil, the oil pressure in the back pressure chamber R will suddenly increase, and the damping force generated by the main valve 1 will increase. There is an inconvenience that the amount increases rapidly.

The present invention was devised in view of the above-mentioned circumstances, and its purpose is, of course, to be able to vary the damping force to a greater extent than the amount of strain in the electrostrictive member. In particular, it is possible to prevent a sudden increase in the oil pressure in the back pressure chamber, thereby preventing a sudden increase in the damping force generated by the main valve, and also to generate a stable damping force during the expansion and contraction operation of the main valve. An object of the present invention is to provide a hydraulic shock absorber having a damping force generating section.

[0014]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the structure of the present invention is such that the hydraulic oil from the upper oil chamber in the cylinder is disposed outside of the shock absorber body when the shock absorber body is expanded and contracted. In a hydraulic shock absorber configured to flow into a lower oil chamber in a cylinder through a main valve in a damping force generating part of a damping force generator, changing the oil pressure in a back pressure chamber formed on the back side of the main valve causes the main valve to The initial load of is changed, and the oil pressure in the back pressure chamber is set by an upstream valve disposed on the upstream side of the back pressure chamber and a downstream valve disposed on the downstream side of the back pressure chamber. In addition, the upstream valve can change its initial load by the pressing force from the electrostrictive member, and the downstream valve is a leaf valve for fixed throttle.

[0015]

[Operation] Therefore, when the shock absorber main body expands and contracts, the hydraulic oil from the upper oil chamber inside the cylinder always flows into the damping force generating section disposed outside the shock absorber main body, and is also collected within the damping force generating section. The hydraulic oil flows into the lower oil chamber in the cylinder through the main valve of the system, and when the hydraulic oil passes through the main valve, a predetermined damping force is generated at the main valve.

[0016] When the hydraulic oil passes through the main valve in a one-way state, the initial load at the upstream valve disposed upstream of the back pressure chamber is changed to a decreasing tendency by applying a voltage to the electrostrictive member. Then, the flow rate of the hydraulic oil through the upstream valve is reduced, and the oil pressure in the back pressure chamber formed on the back side of the main valve is reduced.

As a result, the back pressure at the main valve is reduced, and the damping force generated by the main valve is changed to a lower tendency.

[0018] Furthermore, since the downstream valve in the so-called pilot flow that establishes a predetermined oil pressure in the back pressure chamber is a leaf valve for fixed restriction, the orifice effect is not caused in the pilot flow.

As a result, a sudden increase in oil pressure is not caused in the back pressure chamber to which oil pressure is introduced from the pilot flow, and the damping force adjustment set by the main valve can be stably performed as set.

[0020]

[Embodiment] The hydraulic shock absorber according to an embodiment of the present invention will be described below based on the drawings. 20.

The shock absorber main body 10 is formed by defining an upper oil chamber A and a lower oil chamber B in the cylinder 11 by a piston 13 connected to the tip of a piston rod 12 that extends and retracts from the cylinder 11. On the other hand, the cylinder 11 and the cylinder 1
A reservoir chamber C is formed between the outer cylinder 14 and the outer cylinder 14 disposed outside of the outer cylinder 1.

The lower oil chamber B communicates with the upper oil chamber A via the expansion side check valve 13a provided in the piston 13, and the upper oil chamber A communicates with the shock absorber body 10, that is, the outer cylinder 1.
It is assumed that the oil passage 15a is connected to the outside of the oil passage 15a.

In addition, the reservoir room C communicates with the distributed oil path 15b on the outside of the applicable shock body 10 along with the oil path 15a, and the base valve portion 16 via the pressure side check valve 16a. It communicates with oil chamber B.

As a result, in the shock absorber main body 10, the hydraulic oil always flows in a one-way manner.

On the other hand, each of the oil passages 15a and 15b has its end connected to the damping force generating section 20,
The damping force generating section 20 includes a main valve 22 housed in a casing member 21, a back pressure chamber R formed on the back side of the main valve 22, and an upstream side of the back pressure chamber R. a downstream valve 24 disposed on the downstream side of the back pressure chamber R, and an electrostrictive member 2 for changing the initial load in the upstream valve 23. .

To explain briefly, the casing member 21 is formed into a cylindrical shape with a bottom so as to have a chamber 21a of an appropriate size inside, and has walls on its wall so as to communicate with the chambers 21a. Opened inflow port 21b
and a discharge port 21c, and an inflow port 2
1b is connected to an oil passage 15a, and the discharge port 21c is connected to an oil passage 15b.

Furthermore, the upper end opening of the casing member 21 is
It is sealed by the lower end side of a cap member 25 screwed thereon, and the lower end portion of the cap member 25 extends to the center of the chamber 21a.

An annular partition member 26 is interposed on the outer periphery of the lower end of the cap member 25, and the partition member 26 vertically divides the chamber 21a into a lower chamber D and an upper chamber. It is assumed that room E will be formed.

Note that the partition member 26 is similar to the cap member 2.
5 is fixed with a nut 27 screwed onto the inner periphery of the lower end.

The lower chamber D and the upper chamber E are provided with a port 26a which is opened so as to penetrate through the wall thickness of the partition member 26.
However, the port 26a is said to be closed from the upper chamber E side by the main valve 22.

That is, the main valve 22 is composed of an annular leaf valve, and its inner peripheral end is a fixed end held between the cap member 25 and the partition member 26, and its outer peripheral end connects the partition member 26 to the seat member. The main valves 22 have free ends adjacent to each other so that the hydraulic oil from the lower chamber D side bends the outer peripheral end of the main valve 22 and flows out to the upper chamber E side.

The back pressure chamber R formed on the back side of the main valve 22 is connected to the outer periphery of the lower end of the cap member 25, and
The cap member 25 is partitioned into an annular housing member 28 interposed on the outer periphery of the lower end, and an annular urging member 29 fitted on the inner periphery of the lower end of the housing member 28. It is assumed that the hydraulic pressure in the flow of hydraulic oil branched from the lower chamber D is guided to the pressure chamber R.

That is, the nut 27 has a hollow portion 27a communicating with the lower chamber D at its lower end axial portion, and a port 27b communicating with the hollow portion 27a at its upper end axial portion. Assume that the upstream valve 23 is arranged to close off the downstream end of the port 27b, which is the upper end in the figure, from the back pressure chamber R side.

In this embodiment, the upstream valve 23 is an annular leaf valve, and its outer peripheral end is a free end adjacent to the upper outer peripheral end of the lower nut 27 serving as a seat. , its inner circumferential end is fixedly fixed to the inner circumferential upper end of the lower nut 27.

Further, the upstream valve 23 has the lower end of the push member 30 in contact with the upper surface of the inner circumferential end of the upstream valve 23, which is slightly closer to the outer circumferential end than the inner circumferential end.
When a downward pressing force from 0 is applied, the outer circumferential end thereof is pressed against the outer circumferential upper end of the lower nut 27, and the initial load is changed to an upward tendency.

Therefore, according to the upstream valve 23,
As the initial load is changed to a rising tendency, the flow rate of the hydraulic oil from the lower oil chamber D to the back pressure chamber R via the upstream valve 23 tends to decrease.

As a result, the oil pressure in the back pressure chamber R is adjusted to decrease, the back pressure to the main valve 22 is reduced, and the damping force generated by the main valve 22 is adjusted to decrease. That will happen.

[0038] The push member 30 is attached to the cap member 2.
The push member 30 is housed in the shaft core of the lower end thereof in a so-called liquid-tight state so as to be able to slide vertically in the figure, and the lower end of the electrostrictive member 2 is adjacent to the upper end of the push member 30. There is.

In this embodiment, the electrostrictive member 2 is made of a piezoelectric element, and is housed so that its rear end, which is the upper end in the figure, is fixed to the upper end side axis of the cap member 25. The elongation force caused by the strain and deformation caused when a predetermined voltage is applied is used as the pressing force on the push member 30.

Incidentally, at the rear end of the electrostrictive member 2, there is an end of a lead wire 32 that is inserted through a through hole 31a formed in the axial center of a stopper member 31 screwed onto the inner periphery of the upper end of the cap member 25. parts are electrically connected.

By the way, the back pressure chamber R communicates with the upper chamber E via a downstream valve 24, and the downstream valve 24 is used for a fixed throttle in a so-called pilot flow.

That is, the downstream valve 24 is arranged to close the downstream end, which is the upper end in the drawing, of the port 28a opened at the upper end side of the housing member 28 from the upper chamber E side. .

The outer peripheral end of the downstream valve 24 is a free end adjacent to the upper outer peripheral end of the lower housing member 28 serving as a seat, and the inner peripheral end is connected to the lower housing member 28 and the upper cap. It is said that it is held between the member 25 and the member 25.

Therefore, the so-called orifice effect is not caused by the downstream valve 24, and therefore,
When the oil pressure in the back pressure chamber R is adjusted to have an increasing tendency, problems such as a sudden increase in oil pressure will not occur.

In the hydraulic shock absorber according to this embodiment formed as described above, when the shock absorber main body 10 is extended or contracted, the hydraulic oil from the upper oil chamber A is always supplied to the shock absorber through the oil passage 15a. The oil flows into the damping force generating section 20 disposed outside the main body 10, and the oil disposed outside the damping force generating section 20 flows through the main valve 22 housed inside the damping force generating section 20. 15b into the reservoir chamber C or the lower oil chamber B, and when the hydraulic oil passes through the main valve 22, a predetermined damping force is generated in the main valve 22.

When the hydraulic oil passes through the main valve 22 in a one-way manner, the back pressure in the back pressure chamber R formed on the back side of the main valve 22 is changed. When the initial load at the upstream valve 23 disposed on the upstream side of the back pressure chamber R is changed to a decreasing tendency by the voltage application operation, the flow rate of the hydraulic oil through the upstream valve 23 is reduced. As a result, the oil pressure in the back pressure chamber R decreases.

As a result, the back pressure in the main valve 22 is reduced, and the damping force generated by the main valve 22 is changed to a decreasing tendency.

That is, the previously high damping force generated by the damping force generating section 20 is changed to a low damping force, and therefore, when the hydraulic shock absorber is mounted on a vehicle, the damping force is changed to a low damping force. To ensure a soft ride in the vehicle,
It becomes possible to improve the steering stability of the vehicle.

In order to return the damping force generated by the damping force generating section 20 to its original high state, it is sufficient to release the voltage applied to the electrostrictive member 2. At this time, the initial load on the upstream valve 23 is reduced. The value is returned to the initial low value, and the upstream valve 2
3 increases, the oil pressure at the back pressure element R increases, and the back pressure at the main valve 22 increases.

In this case, the downstream valve 24 for controlling the oil pressure in the back pressure chamber R is assumed to be a leaf valve in the present invention, so it is different from the conventional example in which this type of downstream valve is an orifice (see FIG. 3). ) etc., the so-called pressure accumulation phenomenon due to the orifice effect is not caused, and therefore, the hydraulic pressure in the back pressure chamber R can be controlled as set, and stable damping force can be expected to be generated.

In the illustrated embodiment, the oil passage 15
a, 15b are formed in the shape of a so-called pipe to form a damping force generating section 20.
is separated from the shock absorber main body 10, but instead of this, the pipe-like oil passages 15a and 15b are omitted and the damping force generating section 20 is separated from the shock absorber main body 10. It goes without saying that the shock absorber may be integrally connected to the outer circumferential surface of the outer cylinder 14 constituting the shock absorber main body 10.

Furthermore, in the illustrated embodiment, when a voltage is applied to the electrostrictive member 2 and the initial load of the upstream valve 23 is changed, the oil pressure in the back pressure chamber R tends to decrease. However, it goes without saying that instead of this, the oil pressure in the back pressure chamber R may be set so that it tends to increase when the initial load of the upstream valve 23 is changed.

[0053]

As described above, according to the present invention, when the shock absorber main body expands and contracts, the hydraulic fluid always passes through the main valve in the damping force generating section in a one-way state, so that the predetermined damping is achieved. Not only will the action be performed in a stable manner, but also the back pressure, which is the hydraulic pressure in the back pressure chamber formed on the back side of the main valve, will be generated in a stable manner, so the pilot supply circuit will Since it is independent from the shock absorber body, the pilot pressure supplied to the main valve is not affected by the level of oil pressure in the shock absorber body, especially in the upper oil chamber in the cylinder. This has the advantage that stable damping force can be expected to be generated according to the setting.

[Brief explanation of drawings]

FIG. 1 is a partially schematic longitudinal sectional view of a hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a partially enlarged vertical cross-sectional view showing only the main parts of a damping force generating section in a conventional hydraulic shock absorber.

FIG. 3 is a partially enlarged vertical cross-sectional view showing only the main parts of a damping force generating section in a hydraulic shock absorber as another conventional example.

[Explanation of symbols]

2 Electrostrictive member 10 Buffer body 11 Cylinder 20 Damping force generation part 22 Main valve 23 Upstream valve 24 Downstream valve A Upper oil chamber B Lower oil chamber R　Back pressure chamber

Claims (1)

[Claims] [Claim 1] When the shock absorber main body is expanded or retracted, hydraulic oil from the upper oil chamber inside the cylinder flows into the lower oil chamber inside the cylinder through a main valve in a damping force generating section disposed outside the shock absorber main body. In the hydraulic shock absorber formed as above, the initial load of the main valve is changed by changing the oil pressure in the back pressure chamber formed on the back side of the main valve, and the oil pressure in the back pressure chamber is It is set by an upstream valve disposed on the upstream side of the chamber and a downstream valve disposed on the downstream side of the back pressure chamber, and the upstream valve absorbs its initial load by the pressing force from the electrostrictive member. 1. A hydraulic shock absorber characterized in that the downstream valve is a fixed throttle leaf valve.