JP2002242990A - Floating type vertical vibration isolation method - Google Patents

Abstract

(57) [Problem] To provide a sealed air chamber on the liquid tank side of a floating body for reducing vibration in the vertical direction by a spring effect due to compressibility of air, thereby sacrificing the stability and stability of the floating body. And reduce vibration in the vertical direction. SOLUTION: A floating body 12 such as a structure or a precision instrument or device.
A sealed air chamber 14 is provided on the side of the liquid tank 11 on which the air is floated.
The closed air chamber 14 and the liquid tank 11 communicate with each other at the lower part,
The liquid 13a flowing into and out of the closed air chamber 14 is constantly pressurized by air pressure. Vibration in the vertical direction with respect to the floating body 12 is reduced by a spring effect due to the compressibility of air on the side of the liquid tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a floating type vertical vibration isolating method for reducing vertical vibration of a structure or a precision instrument or device by a liquid tank and a floating body inside the liquid tank.

[0002]

As a means for seismic isolation of a structure from an earthquake, there is a method of using a floating body floating in a liquid tank. This seismic isolation method has ideal seismic isolation performance for horizontal short-period vibration components, but has no effect on vertical components represented by earthquakes, mechanical vibrations, etc. It is already known.

As one means for solving the problem of the vertical vibration, as shown in FIG. 10A, the bottom of the liquid 3 in the liquid tank 2 fixed to the ground 1 is recessed in an airtight air chamber 5. It has been proposed to float the floating body 4 and reduce the vibration by utilizing the compressibility of the air in the floating body 4 by a spring effect against the vertical vibration. However, such a structure has the following new problems in realizing it.

A large dead space is generated in the floating body 4. In order for the air chamber 5 in the floating body 4 to exhibit a sufficient vibration isolation effect, the air chamber 5 having a relatively large volume is required. For this reason, an unusable space (dead space) is generated inside the floating body 4.

The stability of the floating body 4 decreases. By providing the air chamber 5 at the bottom, the center of gravity of the floating body 4 becomes very high.
In addition, a liquid level exists inside the floating body 4. It is widely known that these factors significantly reduce the ability to recover from roll motion. That is, there is a serious problem in stability, such as the floating body 4 tilting greatly against an eccentric load or a moving load.

[0006] Regarding this decrease in stability, FIG.
As shown in FIG. 5, the interior of the air chamber 5 is partitioned into several airtight air chambers 5a, 5b, and 5c by a partition 6, so that the air chamber 5 can be suppressed to some extent.
In order to obtain the same resilience performance as that of a floating body without a space, many sections are required.

There is a high danger when the airtightness of the air chamber 5 is lost. If the airtightness of the air chamber 5 is lost for some reason, the floating body 4 will be placed in a very dangerous situation.
For example, in the case of the floating body 4 shown in FIG. 10 (B), if air in any of the air chambers 5a, 5b, 5c leaks, the function of the air chamber in that part is lost, and the entire area tends to sink, and In a part, the part is inclined by sinking, and in the worst case, there is a risk that an accident such as overturning may occur.

[0008] Maintenance becomes complicated. Air chamber 5
Since the is provided airtightly at the bottom of the floating body 4, the maintenance work is not easy, and in some cases, the floating body 4 may need to be pulled out of the liquid tank 2.

The present invention has been conceived in order to solve the problem of vertical vibration isolation by the above-mentioned floating body. The object of the present invention is to reduce vibration in the vertical direction by utilizing a spring effect due to the compressibility of air. While maintaining the same floating performance as a floating structure without air chambers, the stability and stability of the floating body can be ensured, and the seismic isolation of the floating body, which tends to be limited to seismic isolation of the structure, after transportation or installation of various equipment It is an object of the present invention to provide a new floating type vertical vibration isolation method which can be widely applied to vertical vibration isolation.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a closed air chamber provided at a side of a liquid tank on which a floating body such as a structure or a precision instrument or apparatus is floated, and the sealed air chamber and the liquid tank are connected to each other. Are communicated with each other at the lower part, and the liquid flowing into and out of the sealed air chamber is constantly pressurized by air pressure, and the vertical vibration with respect to the floating body is reduced by the spring effect due to the compressibility of the air on the side of the liquid tank. It is.

With the above-described structure, in addition to the horizontal vibration-isolation / vibration-proof performance of the conventional floating-type vibration-isolation means, it is possible to exhibit performance in vertical vibration. Especially effective for vertical high-frequency micro-vibration, it is used not only for seismic isolation of structures, but also as a vibration-isolation means after transport or installation of precision equipment and devices that dislike high-frequency vibration. I can do it.

Also, since there is no air chamber at the bottom of the floating body, the stability of the floating body is relatively high, and even if air in the sealed air chamber on the side of the liquid tank may leak to the outside. Since the liquid level supporting the floating body is kept horizontal and descends, the floating body does not tilt. That is, the stability when the airtightness is lost is much higher than when the air chamber is provided in the floating body.

Furthermore, maintenance work such as air pressure adjustment is much easier than in the case where an air chamber is provided in a floating body, and the closed air chamber on the side of the liquid tank may become dead space. Even if there is, the outside is separated from the floating body, so that it is possible to design the shape and arrangement flexibly.

In addition to the liquid tank being fixed to the ground or the like, the liquid tank can be configured to have a size that can be moved together with the sealed air chamber in accordance with the scale of the equipment or apparatus to be transported or installed. It only needs to be disassembled after draining the liquid, it can be done easily at low cost, so it requires considerable cost to remove it. Absent.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the figure, reference numeral 11 denotes a liquid tank of a required scale;
A floating body having a rectangular cross section floating in a liquid (for example, water) 13 injected into the liquid tank 11. Although not shown in the figure, an arbitrary structure or various devices and devices are installed on the upper surface or inside the floating body 12.

Numeral 14 denotes a sealed air chamber having a required height provided on both sides of the liquid tank 11, and an opening provided at a lower portion thereof.
The liquid 13a, which is in communication with the inside of the liquid tank so that a part of the liquid 13 flows in and out, flows into the closed air chamber 14 from the liquid tank 11 by the pressure of the air in the closed air chamber. When pressurized, the balance is maintained at a position where the liquid level is lower than that of the floating body installation portion at rest.

For example, as shown in FIG. 2, two points P and Q at the same height in the liquid tank and the closed air chamber have the same pressure, and in such a state, an external force is applied upward from the outside. When the arrow (arrow) is applied, the pressure of the liquid 13 in the liquid tank 11 increases due to the influence of inertia. This pressure increase occurs instantaneously in the AA ′ portion where the floating body 12 exists, but the pressure increase in the closed air chamber 14 having a certain volume
In the part B ', since air has sufficient compressibility,
Air pressure hardly increases momentarily.

The point P on the liquid tank side is located deeper from the liquid surface than the point Q on the closed air chamber side, and as a result, as shown in FIG. growing. Thereby, the liquid 13 in the liquid tank 11 flows out to the closed air chamber 14,
The liquid level of the floating body installation portion is lowered by an amount corresponding to the movement of the liquid (trying to return to the original liquid level position).

On the other hand, when the direction of the external force (arrow) is downward, as shown in FIG. 4, the flow of the liquid is changed to the liquid tank side, and the above-described series of actions are all performed in the opposite directions, and the vertical movement is further increased. Floating body installation part A for continuous vibration external force
-A 'and the closed air chamber part BB' move up and down in opposite directions.

In this case, the volume of the sealed air chamber 14 corresponds to the softness of the air spring, and the larger the sealed air chamber 14 is, the lower the response peak frequency of the vertical movement becomes. The pressure (= difference in liquid level) applied to the closed air chamber 14 is a factor that determines the magnitude of the inertial force accompanying the vibration, and changes the amplitude of the vertical movement of the liquid level. In other words, the higher the pressure of the air to be added (= the greater the difference in liquid level), the better the vibration isolation function.

FIG. 5 shows that each part has the size (mm) shown, water is used as the liquid, the air pressure in the closed air chamber 14 is set to 0.028 kgf / cm ² , and 1 Hz to 1 Hz.
This figure shows a model for a vertical vibration experiment used for measuring a displacement in a state where the vertical vibration of the floating body 12 is sufficiently periodic after a sine wave vibration of 3 Hz is input and the vibration is started. .

FIG. 6 shows an experimental value and a calculated value of the response magnification at each frequency according to the above experimental model. In the experiment, the response peaks at an excitation frequency of 4.5 Hz, and the response peaks.
The upper and lower vibration isolating effects were confirmed at Hz or higher. In both the experiment and the calculation, the response magnification was minimum at around 6 Hz, and tended to gradually approach 0.6 as the frequency was increased, and the agreement between the two values was good.

In the comparison between the experimental value and the calculated value, the calculated value shows an infinite response magnification at a peak frequency of about 4.5 Hz, but this does not take into account the viscosity of the liquid in the calculation in this study. In fact, the viscosity of the liquid (including the damping factor such as friction) acts, and the liquid crystal shows a finite response magnification even at the peak frequency such as the experimental value. It is presumed that this acts as an effect, and that the response magnification at the peak frequency decreases as the viscosity of the liquid used therein increases.

In the case of a liquid having a high density, the peak frequency shifts to a lower frequency side, and there is no change in the response characteristics in a high frequency band. However, it was speculated that there was no effect on vibration isolation performance in the high frequency band. Therefore, according to the model experiment, the vibration isolating means of the present invention may obtain a more efficient vibration isolating effect depending on the viscosity and density of the liquid used therein.

FIG. 7 shows the results of calculations on the assumption of an actual machine. Type A in the figure assumes a scale 10 times that of the experimental model in FIG. 6, and Type B shows the volume of the closed air chamber 14 of Type A. In half. That is, the height of the closed air chamber 14 is 4.45 m in Type A,
In eB, it is 2.23 m, and other scales such as the depth and the size of the floating body 12 are assumed to be ten times as large as those of the experimental model.

The response peak frequency of the actual device is represented by Type
A is about 0.6 Hz, Type B is about 0.8 Hz,
Although Type B having a small volume of the sealed air chamber 14 has a slightly higher peak frequency, the vibration spectrum of the seismic motion is lower than the predominant frequency band of 1 Hz or more.

In a high frequency band of 1 Hz or more, Type
Since the response magnification of both A and TypeB is less than 1, it is clear that a sufficient vertical vibration isolation effect can be expected with at least this scale.
While securing the restoration performance and stability of the floating body, the vibration isolation (seismic isolation) performance of the floating body type has been further improved in combination with the original horizontal vibration isolation.

FIG. 8 shows a case in which the method of the present invention is applied to a vibration isolator for precision equipment. The liquid tank 11 is housed together with the closed air chambers 14 on both sides to accommodate precision equipment 15. And a floating body 1
2 is formed in a box shape, in which a precision instrument 15 is placed, and the precision instrument 15 is floated on a liquid 13 by a floating body 12.

Even in such a vibration isolator, the liquid 13a flowing into the closed air chambers 14 from the liquid tank is always pressurized by the pressure of the air. Vibration is reduced by the spring effect due to the compressibility of the air on the side of the liquid tank.
Demonstrate a sufficient vibration isolation function.

FIG. 9 shows a case in which the present invention is applied to a base-isolated floor of a building 16. A required floor is formed as a liquid tank 11, and both sides thereof are partitioned into the closed air chambers 14, 14, and the liquid tank is formed. The floating body 12 is floated on the liquid 13 injected into the liquid crystal 11 and the floating body 12 has a seismic isolation floor. Even with such a base-isolated floor structure,
In the closed air chambers 14, 14, the liquid 13a is constantly pressurized by the pressure of the air, whereby the vertical vibration of the floating body 12 is reduced by the spring effect of the compressibility of the air on the side of the liquid tank. The 16 required floors can be used as seismic isolation structures more than the other floors.

FIG. 10 shows a case where the present invention is applied to the seismic isolation of the whole building. The liquid tank 11 is fixedly mounted on the ground 17 together with the closed air chambers 14 on both sides, and the building 16 is placed in the liquid tank 11. The floating body 12 has a structure floating on a liquid 13. Even in such a case, the liquid 1
3a is constantly pressurized by the pressure of the air, whereby the vertical vibration of the building 16 is reduced by the spring effect due to the compressibility of the air on the side of the liquid tank.
Numeral 6 is seismically isolated from vertical vibrations in combination with the horizontal seismic isolation by the floating body 12, and the seismic isolation effect is further improved.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an apparatus showing an outline of a floating type vertical vibration isolating method according to the present invention.

FIG. 2 is an explanatory diagram showing a flow direction of a liquid with respect to an upward external force same as above.

FIG. 3 AA ′ site (A) and BB ′ in FIG.
It is pressure state explanatory drawing of a part (B).

FIG. 4 is an explanatory diagram showing a flow direction of a liquid with respect to a downward external force.

FIG. 5 is a longitudinal sectional view of an experimental model showing each part together with a real number.

FIG. 6 is a diagram showing an experimental value and a calculated value of a response magnification to vertical excitation in an experimental model.

FIG. 7 is a diagram showing experimental values and calculated values of two types of response magnification in an actual machine assuming a scale 10 times that of an experimental model.

FIG. 8 is a schematic explanatory view when applied to a vibration isolation device such as a precision instrument.

FIG. 9 is a schematic explanatory view when applied to a base-isolated floor structure in a building.

FIG. 10 is a schematic explanatory view when applied to the seismic isolation structure of the whole building.

FIG. 11 is a schematic longitudinal sectional view of two types (A) and (B) of a conventional floating body seismic isolation structure using a floating body having a closed air chamber.

[Explanation of symbols]

 Reference Signs List 11 liquid tank 12 floating body 13 liquid in liquid tank 13a liquid in closed air chamber 14 closed air chamber 15 precision equipment 16 building 17 ground

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsuyoshi Nozu 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation F-term (reference) 3J048 AA07 BE02 BE03 DA01 EA38 3J069 AA69 BB10 DD50 EE19 EE80

Claims (1)

[Claims] 1. A closed air chamber is provided on a side of a liquid tank on which a floating body such as a structure or a precision instrument or device floats, and the closed air chamber and the liquid tank are communicated with each other at a lower portion. 1. A floating body type vertical vibration isolating method, wherein a liquid flowing into and out of a floating body is constantly pressurized by air pressure, and vertical vibration with respect to the floating body is reduced by a spring effect due to compressibility of air on a side of the liquid tank.