JPH0519626Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention relates to a damping force adjustment device for a hydraulic shock absorber used in suspension systems of automobiles, motorcycles, etc. The present invention relates to a damping force adjustment device for a hydraulic shock absorber that has a large damping force difference over a high speed range and exhibits relatively linear characteristics.

[Prior Art] As a hydraulic shock absorber equipped with this type of damping force adjustment device, for example, the one shown in Japanese Patent Application Publication No. 84241 of 1984 has been generally known.

That is, in this device, a piston is slidably inserted into a cylinder to divide the inside of the cylinder into an upper oil chamber and a lower oil chamber, and from the piston,
A piston rod extends out of the cylinder through the upper oil chamber.

The piston has a first extension damping valve and a first compression damping valve arranged in parallel, which communicate between the upper and lower oil chambers. A compression stroke in which a damping force on the expansion side is generated by applying flow resistance to the hydraulic oil flowing from the upper oil chamber whose volume is reduced through the side damping valve to the lower oil chamber which is expanding, and conversely, the piston rod moves into the cylinder. Sometimes, the first pressure-side damping valve applies flow resistance to the hydraulic oil flowing from the lower oil chamber to the upper oil chamber, thereby generating a pressure-side damping force.

On the other hand, in parallel with the above, inside the piston rod,
A main bypass oil passage that communicates between the upper and lower oil chambers, and a sub-bypass oil passage that branches from the main bypass oil passage and leads to the lower oil chamber, respectively, and an end of the main bypass oil passage on the lower oil chamber side. A second expansion-side damping valve and a compression-side damping valve are arranged in two layers in the piston nut, and a sub-damping valve is installed in the main bypass oil passage to open and close the main bypass oil passage. A switching valve forming a variable orifice is provided between the bypass oil passage and the switching valve, which is operated from the outside to control opening and closing of both bypass oil passages.

As a result, when both bypass ports are closed together with the switching valve, hydraulic oil flows only through the first expansion and compression side damping valves as the hydraulic shock absorber expands and contracts. generates high damping force.

On the other hand, if only the main bypass oil passage is opened using the switching valve, the hydraulic oil will flow through the second expansion and compression damping valves in addition to the first expansion and compression damping valves. Flow resistance decreases and damping force decreases.

Furthermore, when both bypass oil passages are opened with the switching valve, the flow of hydraulic oil passing through the variable orifice is also added, and the damping force is further reduced, thus causing the variable orifice and the second expansion and compression side damping valves to work together. In this way, a relatively linear damping force characteristic with a large damping force difference is obtained from a low speed range to a high speed range of the expansion/contraction speed of the hydraulic shock absorber.

[Problems to be solved by the invention] However, in the above-mentioned conventional device, the second expansion-side and compression-side damping valves are stacked in two stages inside the piston nut, which has a relatively small diameter among the piston assembly. Because it is necessary to arrange the damping valves at the same time, these second expansion-side and compression-side damping valves must be constructed with extremely small diameters, which makes it difficult in terms of design to provide a predetermined damping force characteristic. Moreover, the problem arises that the piston nut becomes longer in the axial direction, and its effective stroke as a hydraulic shock absorber becomes shorter accordingly.

Of course, a type of hydraulic shock absorber in which sub-valves are housed in a disk placed on the piston has been known for some time, so we moved the variable orifice of the switching valve to the main bypass oil path side and placed the disk on the piston. It is also conceivable to connect the sub-bypass oil passage to the sub-bypass oil passage, arrange the second expansion-side and compression-side damping valves in two stages in this disk, and control the opening and closing of the sub-bypass oil passage and the variable orifice with the switching valve. However, even if this alone solves the design problem in that the second rebound and compression side damping valves can be made larger than before,
On the other hand, since the axial length of the disk becomes long, it is still impossible to solve the problem that the effective stroke as a hydraulic shock absorber becomes short.

Therefore, the object of this invention is to provide an improved damping force adjustment device for this type of hydraulic shock absorber, which can prevent a decrease in its effective stroke as much as possible without impairing its original damping force characteristics. It is to be.

[Means for Solving the Problems] According to this invention, the above object is to divide the inside of the cylinder into an upper oil chamber and a lower oil chamber by slidably inserting a piston that carries a piston rod into the cylinder. The first oil chamber communicates with the piston between the upper and lower oil chambers.
In addition, the piston rod has a main bypass oil passage that extends between the upper and lower oil chambers, and a middle part of this main bypass oil passage is passed through an oil passage through a disk placed on the piston. Sub-bypass oil passages leading from the openings to the upper oil chambers are formed, and second cracking pressures are set lower than those of the first expansion-side and compression-side damping valves at the upper and lower openings of the oil passage through the disc. Equipped with expansion and compression damping valves, and
This is achieved by arranging a switching valve located within the main bypass oil passage to control the opening areas of the main bypass oil passage and the sub-bypass oil passage.

[Function] That is, second expansion side and compression side damping valves are provided at the upper and lower openings of the through-oil passage of the disk that communicates with the sub-bypass oil passage, and this through-oil passage is opened and closed by a switching valve. As a result, there is no need to surround the second expansion/contraction and compression side damping valves with the disk, and the disk itself constitutes the sub-bypass oil passage and also serves as the valve seat for the second expansion and compression side damping valves. The effective stroke as a hydraulic shock absorber can be ensured by shortening the axial length without impairing the performance as the second expansion-side and compression-side damping valve.

[Example] Hereinafter, an example of this invention will be described based on FIGS. 1 to 5.

A piston 18 is slidably inserted into the cylinder 17, and the piston 18 divides the inside of the cylinder 17 into an upper oil chamber 21 and a lower oil chamber 22. A piston rod 19 extends outward through a bearing (not shown) of the cylinder 17.

An outer shell 20 is provided on the outer periphery of the cylinder 17 and is arranged concentrically with the outer shell 20 to define a reservoir chamber 23 between the two. The lower oil chamber 22 communicates with the cylinder 17 through a check seal (not shown) provided.
It communicates with the reservoir chamber 23 through a base valve (not shown) provided at the bottom of the tank.

The upper ends of the cylinder and outer shell are sealed by bearings, and the lower ends are sealed by a lower cap 26 having a bracket 24, and a cover 25 hangs down from the piston rod 19 to cover the outer periphery of the outer shell 20.

Thus, the hydraulic shock absorber is connected to the piston rod 19.
The upper end of the lower cap 26 is connected to the vehicle body side and the bracket 24 of the lower cap 26 is connected to the axle side, so that it is installed between the sprung mass and the unsprung mass of an automobile or motorcycle.

As shown in detail in FIG.
A first rebound damping valve 31 and a first compression damping valve 53 are arranged on the lower surface of the 8 and the upper surface of the 8, respectively.
The expansion side and compression side damping valves 31 and 53 are both configured as flexible leaf valves, and open and close the expansion side port 36a and the compression side port 36b bored in the piston 18.

Note that the lower end opening of the expansion side port 36a and the upper end opening of the pressure side port 36b are raised in an annular manner around each opening, and regardless of the presence of the other damping valve 53, 31, the expansion side port 36a is Room 21
The pressure side port 36b is kept in communication with the lower oil chamber 22, respectively.

The first extension damping valve 31 is connected to a piston nut 35 screwed to the lower end of the piston rod 19.
The valve spring 55 is disposed between the piston 18 and the main valve 54, and the valve spring 55 presses the piston 18 against the expansion-side port 36a of the piston 18 by the restoring force of the valve spring 55.

A disk 50 is fitted into the outer periphery of the lower part of the piston rod 19 located above the piston 18 via a valve stopper 51.
0 includes an annular groove 10 formed on the inner circumferential surface and an axial through-oil passage 12 that communicates with the annular groove 10 via a through hole 11.

In this case, in order to conveniently form the annular groove 10, the through hole 11, and the through oil passage 12 in the disk 50, in this embodiment, the disk 50 is divided into two parts.

Similar to the piston 18, this disk 50
On the upper surface of the second expansion side damping valve 29,
Second compression side damping valves 52 are respectively disposed on the lower surface. In this embodiment, these second expansion side and compression side damping valves 29 and 52 are both configured as flexible leaf valves, and the disk 50 The upper and lower openings of the through-oil passage 12 are opened and closed.

These pistons 18 and disks 50, which have respective valves on their upper and lower surfaces, are connected to the valve stopper 2.
7, spacer 28, second rebound damping valve 29, disk 50, second compression damping valve 52, valve stopper 51 with shims interposed on the upper and lower surfaces, first compression damping valve 53, piston 18, first The expansion side damping valves 31 are sequentially inserted into the lower outer circumferential surface of the piston rod 19, and the piston nuts 3
5 and the shoulder 33 of the piston rod 19.

On the other hand, the piston rod 19 has a lower oil chamber 22.
an axial oil passage 44 that opens to the oil passage 4; a through hole 46 that extends from the oil passage 44 to the upper end;
Oil holes 40 and 56 are formed in the radial direction from 4, respectively.

The oil hole 56 opens to the upper oil chamber 21 , and the oil hole 56 and the oil passage 44 connect the upper and lower oil chambers 21 and 21 in parallel with the first expansion side and compression side damping valves 31 and 53 of the piston 18 . It constitutes a main bypass oil passage 30 connecting between 22 and another oil hole 4.
0 communicates from the annular groove 10 of the disk 50 through the through hole 11 to the through oil passage 12, and these oil holes 40, the annular groove 10, the through hole 11, and the through oil passage 12 form the second expansion side and compression side damping valves. 29, 52 and the oil passage 44 to form a sub-bypass oil passage 32 that connects the upper and lower oil chambers 21, 22.

A hollow cylindrical stopper 47 is press-fitted into the oil passage 44 of the piston rod 19, and a switching valve 39 is rotatably inserted above the cylindrical stopper 47.

The switching valve 39 has a variable orifice 37 facing the oil hole 56 on the piston rod 19 side, and a variable orifice 37 that faces the oil hole 56 on the piston rod 19 side.
It has a variable port 38 facing 0 and is connected to a control rod 34 rotatably inserted from the outside through a through hole 46 of the piston rod 19, and the switching valve 39 is connected from the outside via this control rod 34. By rotating the
These variable orifices 37 and variable ports 38 are connected to the main bypass oil passage 30 and the sub-bypass oil passage 3.
2 can be controlled to open and close.

The hydraulic system in the piston section is shown in an equivalent circuit as shown in FIG. 3 during the extension stroke, and as shown in FIG. 4 during the compression stroke.

As can be seen from the above equivalent circuit diagram, in this embodiment, the second expansion-side damping valve 29 has an inner peripheral edge bent downward during the extension stroke of the hydraulic shock absorber, and an outer peripheral edge bent upward during the compression stroke. Although it is configured as a joint valve for extension and compression, it is not necessary to do so, and in order to make it easier to understand, in the following explanation of the operation, it will be explained as a valve exclusively for the expansion side. do.

Next, we will discuss the operation.

Both the variable orifice 37 and the variable port 38 of the switching valve 39 are connected to the oil hole 5 on the piston rod 19 side.
Fully open for 6,40, main bypass oil line 3
During the extension stroke when both the 0 and sub-bypass oil passages 32 are in the open state, the hydraulic oil in the upper oil chamber 21 first flows from the oil hole 56 to the variable orifice 3.
7 and flows into the lower oil chamber 22 through 7. Then, when the extension speed increases, the second extension-side damping valve 29 is also pushed open in parallel with the above, and the flow begins to flow into the lower oil chamber 22. When the extension speed increases further, the first The rebound damping valve 29 is also pushed open, allowing the flow to flow into the lower oil chamber 22. Thus, due to the action of the variable orifice 37 and the second rebound damping valve 29, relatively soft and linear rebound damping force characteristics are achieved. is obtained (fifth
Figure Fr2).

In the above case, the hydraulic oil in an amount corresponding to the volume of the piston rod 19 leaving the cylinder 17 is transferred from the reservoir chamber 23 to the lower oil chamber 22 without resistance through the check valve of the base valve.
will be replenished to.

Also, during the compression stroke, an amount of hydraulic oil corresponding to the volume of the piston rod 19 entering the cylinder 17 is pushed out from the lower oil chamber 22 through the base valve to the reservoir chamber 23, and at that time, the hydraulic oil is forced out through the base valve. The hydraulic pressure in the lower oil chamber 22 increases due to the flow resistance of the hydraulic oil.

The hydraulic oil in the lower oil chamber 22 that has caused this oil pressure increase flows into the upper oil chamber 21 through the variable orifice 37, the second pressure damping valve 52, and the first pressure damping valve 53, as in the case of the extension stroke. Thus, by the action of the variable orifice 37 and the second compression damping valve 52, a relatively soft and linear compression damping force characteristic is obtained (FIG. 5 Fc2).

Next, when the control rod 34 is operated to close both the variable orifice 37 and the variable port 38, both the main bypass oil passage 30 and the sub-bypass oil passage 32 are shut off, so during the extension stroke, the first Only the first compression damping valve 31 is pushed open during the compression stroke, and only the first compression damping valve 53 is pushed open to allow hydraulic oil to flow, resulting in high damping force on both the rebound and compression sides. This shows the characteristics (Fr1, Fc1 in Figure 5).

On the other hand, when the control rod 34 is operated to throttle both the variable orifice 37 and the variable port 38, the flow of hydraulic oil itself is directed to the variable orifice 37 during both the extension stroke and the compression stroke.
is the same as when the variable port 38 is fully opened, but these variable orifice 37 and variable port 38
The smaller the opening area of the first expansion side,
The damping force characteristics are shown in which the expansion and contraction speeds of the compression side damping valves 31 and 53 and the second expansion and compression side damping valves 29 and 52 that reach the cracking pressure have shifted to the lower speed side (Fr3, Fc3 in Fig. 5).

That is, compared to the damping force characteristics a and b without the variable orifice 37, there will be a large difference in the low damping force portion in the low speed range.

[Effects of the invention] As described above, according to this invention, the oil passage through the disk disposed on the piston is made into a sub-bypass oil passage, and the upper and lower openings of this oil passage are provided with second expansion side and compression side damping. By arranging the valves, compared to the case where the second expansion side and compression side damping valves, which were conventionally stacked in two stages and housed inside the piston rod, were simply placed inside the disk placed on the piston.
Since the disk itself constitutes the sub-bypass oil passage and also serves as the valve seat for the second expansion-side and compression-side damping valves, there is no need to surround these second expansion-side and compression-side damping valves with a disk. Since the axial length of the minute disk can be shortened, it is possible to maintain the effective stroke as a hydraulic shock absorber without impairing the original damping force characteristics.

[Brief explanation of the drawing]

Fig. 1 is a partially longitudinal front view of a hydraulic shock absorber according to an embodiment of the invention, Fig. 2 is a detailed longitudinal sectional view showing an enlarged view of the piston section in Fig. 1, and Fig. 3 is an extension stroke. FIG. 4 is an equivalent circuit diagram showing the hydraulic system of the piston section during the compression stroke. FIG. 5 is a graph showing the damping force characteristics. 10...Annular groove, 11...Through hole, 12...Through oil passage, 17...Cylinder, 18...Piston, 1
9... Piston rod, 21... Upper oil chamber, 22
...Lower oil chamber, 23...Reservoir chamber, 29...Second growth side damping valve, 30...Main bypass oil passage, 31...First growth side damping valve, 32...Sub-bypass oil passage, 34...control rod,
35...Piston nut, 37...Variable orifice, 38...Variable port, 39...Switching valve,
40... Oil hole, 44... Oil passage, 50... Disc, 52... Second pressure side damping valve, 53... First pressure side damping valve, 56... Oil hole.

Claims (1)

[Claims for Utility Model Registration] 1. A piston serving as a piston rod is slidably inserted into a cylinder, the inside of the cylinder is divided into an upper oil chamber and a lower oil chamber, and the upper and lower oil chambers are communicated with the piston. In addition to installing the first expansion side and compression side damping valves in parallel, the piston rod has a main bypass oil passage extending between the upper and lower oil chambers, and an oil passage passing through the disk disposed on the piston in the middle of this main bypass oil passage. Sub-bypass oil passages are formed from the upper and lower openings leading to the upper oil chamber, and the upper and lower openings of the oil passage through the disk are provided with a first expansion-side damping valve and a first compression-side damping valve with a lower cracking pressure than the first compression-side damping valve. 2 expansion side and compression side damping valves are respectively disposed, and a switching valve is further disposed within the main bypass oil passage to control the opening area of the main bypass oil passage and the sub-bypass oil passage. Damping force adjustment device for hydraulic shock absorbers. 2. The damping force adjustment device for a hydraulic shock absorber according to claim 1, wherein the switching valve for controlling the opening area of the main bypass oil passage and the sub-bypass oil passage is a rotary valve provided with a variable orifice and a variable port. .