JP2003314611A - Floating body base isolating construction and floating body base isolation structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a floating body base isolating construction and a floating body base isolation structure equipped with an air chamber capable of enhancing the base isolation effect while the height of the air chamber in the floating body is suppressed. <P>SOLUTION: Base isolation is established by floating the floating body 3 in a liquid chamber 1 filled with a liquid 2, wherein the floating body 3 is furnished below with an opening bounded by an air chamber ceiling 4b and an inner wall 4a, and when the floating body 3 is put afloat in the liquid chamber 1, the air chamber 4 is formed surrounded by them and an air chamber liquid surface 2b. The ceiling 4b is furnished with air holes 4c, and over them capacity varying mechanisms 5 are provided with the capacities variable in compliance with the change of the internal pressure. In association with the change of the internal pressure generated when the air chamber liquid surface 2b rises and falls owing to an external vibration, the capacity varying mechanisms 5 are expanded and contracted to form a weak air spring. Thereby an up-and-down base isolation in good performance can be obtained with the air chamber 4 smaller than according to the conventional technique. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a floating body vibration isolation structure and a floating body vibration isolation structure.

[0002]

2. Description of the Related Art Conventionally, it is known that a structure is elastically supported to isolate a short-period vibration. 2. Description of the Related Art In recent years, a floating body vibration isolation structure, which can obtain a vibration isolation effect by a relatively simple mechanism of floating a structure in a liquid, has been attracting attention. The floating structure floating in the liquid
Generally, an almost ideal vibration isolation effect is obtained for horizontal vibration. However, if the floating structure is supported by buoyancy, no vibration isolation effect can be obtained for vertical vibration. Therefore, as shown in FIG.
As shown in (a), the floating body 3 floated in the liquid tank 1.
There is proposed a floating body vibration isolation structure in which an air chamber 4 is provided inside and the air in the air chamber 4 acts on the floating body 3 as a weak spring. FIG. 10B shows a modified example thereof, in which the stability of the floating body 3 is improved by providing the air gaps 8 ... And the plurality of air chambers 4 ... In the air chamber.

[0003]

However, the conventional floating body vibration isolation structure as described above has a problem that the structure becomes unstable when the vibration isolation performance is improved. Hereinafter, this will be briefly described with reference to FIGS.

The conventional floating body vibration isolation structure can be modeled by the sectional structure shown in FIG. The floating body 3 is a tubular member whose upper end is closed and whose lower end is open.
It is floated on the liquid 2 with the density ρ filled in the. In the equilibrium state at rest, the floating body 3 sinks from the liquid surface 2a by the depth D, and the inner wall 4a of the floating body 3 and the liquid surface 2b in the air chamber form an air chamber 4 having a width B and a height H. At this time, the pressure inside the air chamber 4 becomes higher than the outside atmospheric pressure by (ρ · g · Δh) due to the height Δh from the liquid surface 2a to the liquid surface 2b in the air chamber. However, g is gravitational acceleration.

In the conventional floating body vibration isolation structure in which the floating body 3 does not have the air chamber 4, the vertical movement of the liquid tank 1 due to external vibration such as an earthquake is directly transmitted to the floating body 3, so that vibration isolation performance in the vertical direction can be obtained. Absent. On the other hand, by providing the air chamber 4 at the bottom of the floating body, the air inside the air chamber 4 acts as a spring against vertical movement, and thus vertical vibration isolation performance can be exhibited.

The frequency response characteristic of such a model is 1
The frequency response characteristic of the vibration system with degrees of freedom is obtained, and a graph as shown in FIG. 12 is obtained. The horizontal axis of the graph is the excitation frequency f
(Hz), and the vertical axis represents the response magnification M which is the ratio of the vertical motion amplitude of the floating body 3 to the vibration amplitude. The response magnification becomes a peak at the response peak frequency f _p (response curve 25a),
The response ratio sharply decreases at higher excitation frequencies, and the response ratio becomes 1 or less at f ₀ or higher in the figure (response curve 25).
b). Therefore, it has a vibration isolation effect that the response is lower than the vibration input. Therefore, to obtain a high-performance isolation effect over a wide frequency band, weaken the air spring,
It is necessary to lower f _p . Achieving such a weak spring has hitherto been dealt with by increasing the height H of the air chamber.

However, increasing the height H of the air chamber corresponds to increasing the center of gravity of the floating body 3, and as a result, the stability of the floating body 3 may be significantly impaired. There was a problem that a large dead space occurs.

The present invention has been made in view of the above problems, and a floating body vibration isolation structure capable of improving the vibration isolation effect while suppressing the height of the air chamber of the floating body to be low, and such a structure. It is an object of the present invention to provide a floating body vibration-isolating structure provided with.

[0009]

In order to solve the above-mentioned problems, in the invention described in claim 1, the floating structure floating in the liquid receives pressure from a part of the liquid surface of the liquid. A floating body vibration isolation structure including an air chamber is used, in which the volume of the air chamber is variable in accordance with the fluctuation of the internal pressure. By doing so, a weaker air spring can be configured as compared with the case where the volume of the air chamber is constant.

According to a second aspect of the present invention, in the floating body vibration isolation structure according to the first aspect, a structure is used in which the volume of the air chamber is made variable by elastically expanding and contracting a part of the air chamber.
Therefore, the strength of the air spring can be adjusted by adjusting the strength of elasticity when a part of the air chamber expands and contracts.

According to a third aspect of the invention, there is used a floating body vibration isolation structure comprising the floating body vibration isolation structure according to the first or second aspect. Therefore, it is possible to provide a floating body vibration isolation structure having the action of the floating body vibration isolation structure according to the first or second aspect.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. Throughout all the drawings, the same or corresponding members are designated by the same reference numerals. FIG. 1 is an explanatory view showing a schematic configuration of a vertical cross section of an embodiment of a floating body vibration isolation structure according to the present invention.

The floating body vibration isolation structure according to the present invention has an opening surrounded by an inner wall 4a at the lower end, and the upper portion thereof is provided with the air chamber ceiling portion 4
The floating body 3 blocked with b is floated on a liquid tank 1 filled with a liquid 2 such as fresh water, seawater, groundwater, muddy water, oil, and the like, and the air chamber ceiling 4b, the inner wall 4a ... Air chamber 4 enclosed by surface 2b and containing air
And a volume variable mechanism 5 is provided in a part of the air chamber 4.

The floating body 3 may have any shape and material as long as it can form the air chamber 4 when floated on the liquid 2. For example, wood, synthetic resin, steel, concrete or a combination thereof. It may be made of things.

The variable volume mechanism 5, as shown in FIG.
Covering the upper portion of the air hole 4c provided in the air chamber ceiling portion 4b,
For example, a balloon-shaped stretchable body made of an elastically stretchable material such as a rubber film is provided, and is expanded when the internal pressure of the air chamber 4 rises and contracts when the internal pressure falls, and the volume of the air chamber 4 is variable. It is a mechanism.

The above description is for explaining the structure of the characteristic part of the present invention for improving the vibration isolation effect in the vertical direction, and it does not mean that it is not moored in the horizontal direction at all. It goes without saying that a weak spring mechanism or the like for mooring the floating body 3 may be provided in the liquid tank 1 in order to maintain the horizontal position when stationary.

Next, the operation of the floating body vibration isolation structure according to the present invention will be described. In order to simplify the description, the variable volume mechanism 5 and the air chamber 4 according to the present invention are modeled as a tubular body having a cross-sectional area B. FIG. 2 is a conceptual diagram showing the model.

The variable volume mechanism 5 includes a distal end portion 50a whose distal end is covered with a distal end lid 50d and an elastic portion 5 which vertically expands and contracts.
0b, and the other portion of the air chamber 4 is represented as the liquid level 2b of the air chamber fluctuates in the rear end portion 50c which is a cylindrical body having the same cross-sectional area B.

The relationship between the liquid level in the air chamber 2b and the volume change of the variable volume mechanism 5 is as follows: When the liquid level in the air chamber 2b rises by Δx, the pressure in the air chamber 4 rises by Δp. Then, it is assumed that the tip lid 50d rises by (ε · Δx). Here, ε is a volume change rate obtained by converting the elasticity of the expansion / contraction part 50b and the actual size of the variable volume mechanism 5 into a ratio to a volume change (b · Δx) due to the liquid level 2b in the air chamber, and 0 ≦ That is, ε ≦ 1. ε = 0 is
This is a case where the variable volume mechanism 5 has no elasticity at all, which corresponds to the case of the related art.

Now, assuming that such a change in the state of the air in the air chamber 4 is an adiabatic change, and Δx is small,
The amount of pressure increase Δp is expressed as Δp = (γ · P ₀ / V ₀ ) · (1-ε) · B · Δx (1). Here, P ₀ and V ₀ respectively represent the pressure and volume in the air chamber 4 in the initial state, and γ represents the specific heat ratio (γ = 1.4 for air). According to the equation (1), Δp becomes smaller as ε is closer to 1, so that the reaction force (elastic restoring force) due to the increase in internal pressure with respect to Δx becomes smaller. Therefore,
When the air chamber 4 is regarded as an air spring, it can be seen that a so-called weak air spring is realized, just as the spring constant is reduced.

Next, in order to consider the difference from the prior art,
The condition for obtaining the same strength of the air spring is obtained by the conventional technique. When the volume of the air chamber 4 is not variable and the volume in the initial state is V ₀ ^* , the pressure increase amount is Δp ^*, and adiabatic change is assumed in the same manner as above, Δp ^* = (γ · P ₀ / V ₀ ^* )・ B · Δx (2)

The condition that the strengths of the air springs are the same is Δp
Since it is equivalent to = Δp ^* , V ₀ = (1−ε) · V ₀ ^* (3) is obtained from the equations (1) and (2). Therefore, it is understood that V ₀ <V ₀ ^* , and the larger ε is, the smaller the initial volume of the air chamber 4 can be. For example, if the variable volume mechanism 5 is configured so that ε = 0.9, the volume of the air chamber 4 that does not change is only 10%.

The above will be verified with specific numerical examples. As an example, the size of the air chamber 4 can be set to B =
When 3.8 m and D = 0.8 m and H = 1 m, Δh =
It was set to 0.64 m. The cross-sectional shape of the liquid tank 1 is B ₀ =
5 m and H ₀ = 1 m. In FIG. 3A, assuming that ε = 0 (corresponding to the related art), the height H of the air chamber 4 is H = 1.
The frequency response characteristics when changed to 0, 2.0, 10.0 (m) are calculated, and the results are shown in a graph. The horizontal axis of the graph is the vibration frequency, the unit is (Hz), and the vertical axis is the response magnification M which is the ratio of the vertical motion amplitude of the floating body 3 to the vertical vibration amplitude. In this calculation, the attenuation due to the viscosity of the air in the air chamber 4 and the liquid 2 was ignored.

Response curves 10a and 10b, 11a and 11
b, 12a, 12b are H = 1.0, 2.0,
It is a response characteristic at 10.0 (m). Each is
Similar to FIG. 12, the response of the vibration system with one degree of freedom is shown. That is, as the vibration frequency f increases, the response magnification M gradually increases, the response magnification M becomes infinite at one response peak frequency, and when the vibration frequency f further increases, the response magnification M sharply decreases. At the vibration frequency and above, M <1.
In each of the above response curves, the values of the response peak frequencies are f ₁ , f ₂ and f ₃ , respectively. Specifically, f ₁ = 2.55 Hz, f ₂ = 1.80 Hz, f ₃ =
It was 0.88 Hz.

FIG. 3 (b) is a graph showing the results of calculating the frequency response characteristics when the volume expansion coefficient ε is changed to ε = 0, 0.5, 0.9 with H = 1.0 m. It is a representation. The vertical axis, horizontal axis, and unit of the graph are the same as those in FIG.

Response curves 10a, 10b, 13a, 13
b, 14a and 14b are ε = 0, 0.5, 0.
It is a frequency response characteristic at the time of 9. Also in this case, FIG.
2 shows the response of a vibration system with one degree of freedom similar to FIG.
In each of the above response curves, the values of the response peak frequency are f ₁ , f ₄ , and f ₅ , respectively. here,
It was f ₅ = 0.88Hz. This is equal to f ₃ when H = 10.0 m in the prior art. Therefore, when ε = 0.9, it was verified that the same air spring strength can be obtained by setting the height H of the air chamber 4 to 10% of the height of the air chamber 4 which is not variable.

The result of calculating the change in the response peak frequency f _p when ε is changed in this way is shown in FIG.
It shows in (c). The horizontal axis of the graph is the volume change rate ε, the left vertical axis is the response peak frequency f _p , and the unit is (Hz).
The vertical axis on the right side is the response peak frequency f _p0 = 2.55 Hz when ε = 0, and each f _p is made dimensionless (f _p / f
_p0 ) Indicates the scale.

The response peak curve 16 has a maximum value of f _p0 and gradually decreases with an increase of ε in a substantially linear curve. The degree of decrease gradually increases, and when ε = 1, f _p = It is 0.14 Hz. Therefore, ε
It can be seen that for a very weak air spring having a ratio of about 1, the response peak frequency is about 1/19 when there is no change in the volume of the air chamber. When ε = 0.76, the response peak frequency becomes 1/2. By performing the calculation shown in FIG. 3C in this manner, the ε of the air spring for obtaining the desired response peak frequency can be obtained.

Next, regarding a modified example of the variable volume mechanism 5,
This will be described with reference to FIGS. 4 (a), 4 (b) and 4 (c). Figure 4
(A) shows that the tubular portion 5b connected to the air hole 4c is provided, and the upper end portion thereof is made of rubber, vinyl, cloth or the like, and the volume of the air chamber 4 can be varied by expanding or contracting or moving up and down. This is an example including a film structure 5a for

FIG. 4B shows an example in which the air hole 4c is provided with a bellows structure 5c which is elastically expanded and contracted in the vertical direction such as used in a foot pump or bellows. The bellows structure 5c has a bellows shape formed of rubber or the like, or an elastic member such as a coil spring is provided inside or outside the bellows in the circumferential direction, and is fixed to the air chamber ceiling 4b and the upper part of the bellows structure 5c. It is possible to adopt a device in which the vertical expansion and contraction of the bellows is elastically restricted. It is conceivable to realize such an expansion / contraction mechanism by diverting the air spring 6 as shown in FIG. 4 (c), for example.

Needless to say, the above may be combined appropriately. For example, it is possible to use the film structure 5a and the bellows structure 5c together for the same floating body 3.

Next, a description will be given of an embodiment of a floating body vibration isolation structure in which the floating body vibration isolation structure according to the present invention is partially provided.
5 to 9 are schematic explanatory views of vertical cross sections for explaining the floating body vibration isolation structure according to the present invention. In addition,
The same parts as those described above are designated by the same reference numerals, and the description thereof will be omitted. In addition, although the bellows structure is shown as the variable volume mechanism 5, this is for convenience of illustration, and the variable volume mechanism 5 can adopt various configurations as described above.

FIG. 5 shows an example in which the floating body 3 is constructed by horizontally connecting a plurality of independent floating body vibration isolation portions 30 having the floating body vibration isolation structure according to the present invention. Each of the floating body vibration isolation parts 30 is divided by a wall body such as an inner wall 4a, a partition 8 and the like, and has an opening below, and the opening is closed by the liquid level 2b in the air chamber. An air chamber ceiling portion 4b facing the liquid surface 2a is provided at an intermediate position in each vertical direction, and a volume varying mechanism 5 is attached with a hole provided in a part thereof. The variable volume mechanism 5 is configured to be housed in the expansion mechanism chamber 9 above the air chamber ceiling portion 4b, in which a space is secured so as not to protrude above the height of the receiving surface 3a above the floating body 3 at the maximum volume. There is. The receiving surface 3a is a surface on which the structure to be isolated can be mounted, and is covered with, for example, a plate member. However, the upper surface of the expansion mechanism chambers 9 ... May be provided with ventilation holes for venting air.

According to this structure, the floating body 3 is supported by the plurality of floating body vibration isolating portions 30 ... And each has the variable volume mechanism 5. Therefore, for example, an eccentric load is generated due to its own weight or the load of the load. However, there is an advantage that the floating body 3 can be held horizontal by adjusting the pressure of each air chamber 4 by the variable volume mechanism 5.

The floating body isolation structure according to the present invention is shown in FIG.
As shown in FIG. 3, the floating body vibration isolation portion 30 described above is provided, and for example, the floating body vibration isolation portion 3 is provided in the independent liquid tanks 1a and 1b.
It may consist of a floating body 3 in which 0s are arranged and coupled. With this configuration, there is an advantage that the total area of the liquid tank in which the floating body 3 is floated can be reduced.

A more specific example of the floating body vibration isolation structure will be shown below. First, FIG. 7 shows that the entire building 18 is arranged on the receiving surface 3 a of the floating body 3 described with reference to FIG. 5, and the horizontal direction vibration isolation mechanism 17 is provided between the floating body 3 and the liquid tank 1. It is an example of a floating body vibration isolation structure configured by providing.

FIG. 8 shows a floating body 3 in which the liquid tank 1 is constructed inside a building 18 and a part or all of the floor surface inside the building 18 is provided with a floating body vibration isolator 30 ... In this example, the horizontal mooring mechanism 17 is provided between the floating body 3 and the building 18 or the liquid tank 1. The receiving surface 3a is
For example, a person 21 works or arranges equipment 22a, equipment 22b, etc. to use as a vibration-isolated floor.

Further, FIG. 9 shows that the liquid tank 24 provided in a portable manner is filled with the liquid 2 and the floating body 3 provided with the floating body vibration isolator 30 is floated between the liquid tank 24 and the floating body 3. The horizontal mooring mechanism 17 is disposed on the receiving surface 3a, and the structure / equipment such as the precision instrument 23 requiring vibration isolation is disposed on the receiving surface 3a.

In any of the above, it goes without saying that the floating body 3 shown in FIG. 5 may be replaced with the type of the floating body 3 shown in FIG.

As described above, according to the present invention, various floating body vibration isolation structures can be constructed regardless of the size and use of the structure, and the height of the four air chambers is higher than that of the conventional structure. Since it can be made epoch-making, it is possible to provide a floating body vibration isolating structure that requires a small arrangement space and has a very wide range of applications.

In the above description, the variable volume mechanism 5 is provided in the air chamber ceiling 4b above the air chamber 4, but the pressure of the air is equal in the air chamber 4, so for example the inner wall It may be provided on a side portion such as 4a or the end cut 8.

Although the variable volume mechanism 5 is provided in a part of the air chamber 4, it may not be provided so as to cover the air hole 4c as described above. As long as it is connected to the air chamber 4, for example, an air flow path is provided between the air hole 4c by an appropriate pipe line or tube, and the volume variable mechanism 5 is provided at a position apart from the air chamber ceiling portion 4b. Good.

[0043]

As described above, according to the first aspect of the invention, an air spring that is weaker than that of the floating body vibration isolation structure in which the volume of the air chamber is constant can be formed. There is an effect that it can be lowered and excellent vibration isolation characteristics can be exhibited over a wider frequency range. Further, even with the same vibration isolation characteristic, there is an effect that it is possible to make a compact structure in which the height is suppressed lower than in the conventional case.

According to the second aspect of the invention, since the strength of the air spring can be adjusted by adjusting the amount of elasticity when a part of the air chamber expands and contracts, it is easy to change the vibration isolation characteristic. Produce an effect.

In the invention described in claim 3, since the floating body vibration isolation structure having the function of the floating body vibration isolation structure according to claim 1 or 2 can be obtained, the invention described in claim 1 or 2 Has the same effect as the invention.

[Brief description of drawings]

FIG. 1 shows an embodiment of a floating body vibration isolation structure according to the present invention,
It is explanatory drawing which shows schematic structure of a vertical cross section.

FIG. 2 is a conceptual diagram showing a volume variable mechanism and an air chamber model according to the present invention.

FIG. 3 is a graph showing calculation results of frequency response characteristics of the floating body vibration isolation structure according to the related art and the present invention.

FIG. 4 is an explanatory view of a vertical cross section showing a schematic configuration of a modified example of the volume variable mechanism according to the present invention.

FIG. 5 is an explanatory view of a vertical cross section showing a first example of the floating body vibration isolation structure according to the present invention.

FIG. 6 is an explanatory view of a vertical cross section showing a second example of the floating body vibration isolation structure according to the present invention.

FIG. 7 is an explanatory view of a vertical cross section showing a third example of the floating body vibration isolation structure according to the present invention.

FIG. 8 is an explanatory view of a vertical cross section showing a fourth example of the floating body vibration isolation structure according to the present invention.

FIG. 9 is an explanatory view of a vertical cross section showing a fifth example of the floating body vibration isolation structure according to the present invention.

FIG. 10 is an explanatory view of a vertical cross section showing an example of a conventional floating body isolation structure and a modified example thereof.

FIG. 11 is a model diagram of a conventional floating body vibration isolation structure.

FIG. 12 is a graph showing frequency response characteristics of a conventional floating body vibration isolation structure.

[Explanation of symbols]

1, 1a, 1b, 24 Liquid tank 2 liquid 2a Liquid level 2b Liquid level in air chamber 3 floating body 4 air chambers 4a inner wall 4b Air chamber ceiling 5 Volume variable mechanism 5a Membrane structure 5b tube 5c bellows structure 5d movable cylinder member 6 air spring 17 Horizontal mooring mechanism 18 buildings 20 Floating body isolation stand 21 people 22a equipment 22b equipment 23 Precision equipment 30 Floating body isolation section

Continued front page    (72) Inventor Tsuyoshi Nozu             Shimizu Construction 1-3-2 Shibaura, Minato-ku, Tokyo             Within the corporation F-term (reference) 2D046 DA07                 3J048 AA02 BE02 DA01 EA38

Claims (3)

[Claims] 1. A floating body isolation structure comprising a floating structure floating in a liquid and an air chamber for receiving pressure from a part of the liquid surface of the liquid, wherein the volume of the air chamber is equal to the internal pressure of the floating structure. Floating body isolation structure characterized by being variable according to fluctuations. 2. The floating body vibration isolation structure according to claim 1, wherein the volume is variable by elastically expanding and contracting a part of the air chamber. 3. A floating body vibration isolating structure comprising the floating body vibration isolating structure according to claim 1.