JPS6040840A - Single cylinder oil damper - Google Patents

Abstract

PURPOSE:To absorb high-frequency low amplitude vibration in a simple structure by storing an elastic body absorbing high-frequency low-amplitude vibration in a free piston separating a liquid chamber from a gas chamber. CONSTITUTION:A free piston 16 is of a hollow structure and provided with an opening 19 connected to a liquid chamber 14. An elastic body 20 comprising a plurality of hollow spherical or cylindrical rubber or rubber elastic bodies is stored in the free piston. The elastic body 20 is adapted to decrease its volume substantially rectilinearly at the contraction stroke of a rod 15 until the pressure in the liquid chamber and in its turn the pressure in the free piston 16 amounts to a fixed pressure P and to keep its volume substantially constant for the pressure more than a fixed value. Thus, high-frequency low amplitude vibration can be absorded effectively by deformation of the elastic body 20.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a monocylindrical oil damper, and particularly to an oil damper that has a simple structure and can effectively absorb high frequency and small amplitude vibrations.

An example of a conventional oil damper that isolates high-frequency, small-amplitude vibrations is shown in FIG. This involves surrounding the tube 1 with a base shell/I/2, dividing the inside of the tube 1 into two liquid chambers 41 and 5 by means of a piston 3, and connecting a rod 6 to the piston 3. In a double-tube oil damper in which one liquid chamber 5 in the tube 1 is communicated with the inside of the base shell 2 by a compression valve 7 provided at the end opposite to the rod 6, the compression valve 7 and the base shell 2 are connected to each other. A chamber 8 communicating with the one liquid chamber 5 via a compression valve 7 is provided between the end wall 2a, and a metal bellows 9 filled with nitrogen gas and oil is provided within this chamber 8. .

In this double-tube oil damper, when the piston 3 makes a pushing stroke in response to high-frequency, small-amplitude vibration, oil in the liquid chamber 5 flows into the chamber 8 through the orifice 10 and applies hydraulic pressure to the bellows 9. As a result, the bellows 9 is compressed and its volume is reduced, so the piston 3
Of the oil that is forced to flow, the amount of oil that passes through the combination valve 7 and flows out between the tube 1 and the base shell 2 is calculated by subtracting the amount of oil that flows into the chamber 8 from the total flowing oil. The damping force generated by the compression valve 7 is also reduced by this amount, and the transmission of vibration is suppressed.

This is almost the same in the pulling stroke of the piston 3, and since the pressure drop in the liquid chamber 5 is compensated for by the oil in the chamber 8, the damping force is reduced by the compensation amount.

However, in this conventional technology, since it is a double-tube oil damper, the structure is slender, and there are problems in that aeration and cavitation occur. Is there a layer of structure? There was a problem of increasing the MQa and increasing the basic length of the damper.

This invention advantageously solves the problems of the prior art, and enables high-frequency, small-amplitude vibration without increasing the basic length, with an extremely simple structure, and without causing aeration, cavitation, etc. The purpose is to provide a so-called gas-filled monocylindrical oil damper that can absorb gas.

The monocylindrical oil damper of the present invention is a gas-filled monocylindrical throat oil damper in which the free piston has a hollow structure and opens into one of the liquid chambers to allow oil to flow in and out of the inside thereof. In addition, an elastic material is housed inside the free piston, and the volume decreases almost linearly until a certain pressure is reached, but the volume does not substantially decrease when the pressure exceeds that pressure. In particular, for high-frequency, small-amplitude vibrations, the pressure rise and fall within the liquid chamber is
By compensating mainly by decreasing and increasing the volume of the elastic material in the free piston, effective absorption is achieved, and in the contraction side stroke of the rod due to large-amplitude vibration, the internal pressure of the free piston is reduced by the decrease in the volume of the elastic material. When the pressure reaches a pressure range that does not normally occur, the vibration is damped by an orifice provided in the piston, similar to conventional oil dampers of this type.

The present invention will be explained below based on illustrated examples.

FIG. 2 is a sectional view showing an embodiment of the present invention, in which reference numeral 11 indicates a tube, and reference numeral 12 indicates a piston slidably fitted into the tube 11.

This piston 12 has valves, orifices, etc. (not shown), and defines two liquid chambers 18, 14 within the tube 11. A rod 15 is connected to the piston 12 and extends through the liquid chamber 18 in the axial direction and projects out of the tube 11. A connecting portion to the sprung side of the automobile body, for example, is provided at the 1° end of the rod.

Further, 16 in the figure defines a gas chamber 17 on the opposite side of the rod 15 and adjacent thereto. The free piston 16 here has a hollow structure formed by pressing or rolling, for example, and has an opening 19 communicating with the liquid chamber 14.

Furthermore, in this example, an elastic body 20 made of a plurality of hollow spherical or cylindrical rubber or rubber-like elastic bodies is housed in the free piston 16.

Here, as is clear from the graph shown in FIG. 8, the elastic body 20 causes the pressure in the liquid chamber 14 and the pressure in the free piston 16 to reach a constant pressure P during the contraction side stroke of the rod 15. The volume decreases almost linearly until the pressure is reached, while the volume remains constant for pressures beyond that point.

Such deformation behavior of the elastic body 20 is brought about by selecting the hollow volume of each elastic body so that when the free piston internal pressure reaches the pressure P, the hollow part of each elastic body is almost completely crushed. The elastic body that has been crushed into a lump will not reduce its volume even if the internal pressure of the free piston exceeds the pressure P(i-.Here, the hollow part of each bullet (1≦L) is Note that the value of the constant pressure P described above can of course be appropriately selected depending on the increased pressure within the liquid chamber 14 due to high-frequency, small-amplitude vibration.

In the monocylindrical oil damper described above, when it is subjected to high frequency and small amplitude vibration, when the rod 15 is in the contraction side stroke, the liquid chamber 14 and the free piston 16
When the internal pressure increases, the volume of the elastic material 2o decreases in accordance with the pressure increase, so the oil flow rate passing through the oriice of the piston 12 is reduced by an amount equivalent to the amount of oil flowing from the liquid chamber 14 into the free piston 16. This results in a decrease in the damping force generated by the damper.

As a result, for example, a high jN wave small vibration 1Illi! is transmitted from the connection part 21 to the unsprung side of the vehicle body to the tube 11! The vibrations are hardly transmitted to the rod 15 and are effectively absorbed by the elastic deformation of the elastic member 2o. In addition, in such vibration absorption, when the volume of the elastic body 2o decreases linearly from the body 6VA to the volume B as shown by the solid line in FIG. Since the volume also decreases linearly from volume a to volume a as shown by the broken line in the figure, this nitrogen gas also provides more effective vibration absorption due to the change in volume.

On the other hand, during the extension stroke of the rod 15, the internal pressure of the liquid chamber 13 increases and the internal pressure of the liquid chamber 14 decreases. Elastic material 2o-.

This is advantageously compensated by the expansion of the piston 12, so that the flow of oil flowing from the liquid chamber 13 into the liquid chamber 14 through the piston 12, for example, through the pulp, is correspondingly reduced, so that the high-frequency, small-amplitude vibrations are absorption takes place.

In addition, the range of large-amplitude vibration damping caused by this oil damper is
During the contraction side stroke of the rod 15, the elastic member 20
The conventional oil damper and I'1 are lit by the oil flow after the volume decreases, and by the oil flow after the elastic member 20 expands during the extension stroke of the rod 15, respectively.

FIG. 4 is a cross-sectional view showing a modification of the present invention, in which a rubber film 22 is airtightly fixed within the free piston 16 adjacent to the free piston 15A D 19, and the rubber film 22 is used to secure the free piston. The elastic body 20 is constructed by sealing air within the elastic body 16.

Due to the action of the constant pressure P described above, this elastic material 20 has a volume as shown in FIG. Since it decreases linearly, high-frequency, small-amplitude vibrations can be effectively absorbed as in the example described above.

FIG. 5 is a sectional view showing another modification of the present invention, in which the elastic member 2° is made of closed-cell urethane foam 28 fitted inside the free piston 16. Since the urethane foam 23 linearly decreases in volume until each of its bubbles is almost completely crushed, this also provides sufficient absorption of high-frequency, small-amplitude vibrations.

This invention has been explained above based on the illustrated examples, but the elastic material 2
The volume change at 0 does not necessarily have to be exactly linear;
Further, the elastic material 2o may be made to undergo some volume change due to a pressure of 2 or more.

Therefore, according to the present invention, in a monocylindrical oil damper, in particular, the free piston is made into a hollow structure, and the free piston is opened to one of the liquid chambers. By simply storing an elastic material whose volume decreases almost linearly but whose volume does not substantially decrease in response to higher pressures, high-frequency, small-amplitude vibrations can be effectively generated by the deformation of the elastic material. In addition to the unique effects of a gas-filled monocylindrical oil damper, the structure can be made even more hii Q' than conventional technology.
Furthermore, a great practical effect is brought about in that the basic length of the damper can be made sufficiently short.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional example, Fig. 2 is a sectional view showing an embodiment of the present invention, Fig. 3 is a graph showing changes in volume of elastic material and nitrogen gas with respect to free piston internal pressure, and Fig. 4 is a graph showing changes in volume of elastic material and nitrogen gas with respect to free piston internal pressure. A cross-sectional view showing a modification of this invention, Figure @5 is a cross-section IA showing another modification of this invention. 11...Tube 12...Piston 13.14.
...Liquid chamber 15...Rod 16...Free piston 17...Gas chamber 19...Opening 20...Elastic material 22...Rubber membrane 28...Urethane foam patent applicant Brideston Tire Co., Ltd. Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A tube, a piston forming two liquid chambers in the tube, a rod connected to the piston, and one liquid chamber in the tube on the opposite side of the rod. and a free piston forming an adjacent gas chamber. 1. A monocylindrical oil damper, characterized in that it houses an elastic material whose volume decreases almost linearly, but whose volume does not substantially decrease in response to higher pressures.