JPH04307142A - Earthquake-proof system - Google Patents

Abstract

PURPOSE:To enable it perform a quake-free operation even in an exorbitant vibration, in an earthquake-proof system. CONSTITUTION:In this earthquake-proof system 1, an upper plate 4 is supported by spherical bearings 6a-6d free of slide motion with a lower plate 5, and a wire 15 being installed so as to come into slidingly contact with lower blocks 9a-9i set up in the lower plate 4 and upper blocks 8a-8h on the upper plate 4 is drawn by a relative displacement between the upper plate 4 and the lower plate 5. The wire 15 is connected to a rod 17b of a gas spring 17 via a chain 16, wrapped on a sprocket 14 of a rotator 10, and a wire 20, thus the relative displacement between both upper and lower plates 4 and 5 is absorbed by dint of resilient force of the gas spring 17. The rotator 10 is rotated by displacement of the wire 1 5, static inertia moment in this rotator 10 acts on the wire 15, and the extent of frequency in the upper plate 4 is reduced, thereby checking a long periodic vibration. With this constitution, even if a vibration large in acceleration is inputted into the lower plate 5, it can be effectively damped by the gas spring 17.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seismic isolation device, and more particularly to a seismic isolation device configured to perform seismic isolation even when excessive vibration occurs.

0002

2. Description of the Related Art Conventionally, seismic isolation devices have been developed to prevent earthquake damage to valuable, precision, and dangerous objects.

[0003] As such a seismic isolation device, for example, as shown in Japanese Utility Model Application No. 62-170848 previously proposed by the present applicant, the above-mentioned object is placed on an upper plate, and then The plate is slidably provided on the lower plate fixed to the installation surface,
There is a device that uses spring means to absorb the sliding displacement of the lower plate relative to the upper plate when an earthquake occurs.

In this device, a plurality of pulleys are provided on the upper surface of the lower plate, and a plurality of pulleys are also provided on the lower surface of the upper plate, and a wire with one end fixed to the lower plate is looped around these pulleys. It is mounted so that Furthermore, in this seismic isolation device, the other end of the wire is connected to the spring means, so that when the upper plate and the lower plate are displaced relative to each other due to an earthquake, the wire is pulled, and the displacement of the wire is absorbed by the spring means. There is.

[0005]

[Problem to be Solved by the Invention] In the seismic isolation device configured as described above, in the case of a relatively small earthquake, the upper plate and the lower plate will be displaced relative to each other depending on the frequency of the earthquake, and the objects placed on it will be damaged by the earthquake. Seismic isolation works to prevent vibration. However, if an excessive earthquake with large amplitude occurs, the lower plate will slide with a large acceleration relative to the upper plate, which may exceed the stroke limit that the lower plate can slide against the upper plate. be.

That is, the lower plate vibrates with a large amplitude due to an excessive earthquake, and as a result, the spring means becomes fully extended.
There was a problem in that the vibrations could no longer be absorbed, and the earthquake would be transmitted directly to the objects on which they were placed, causing them to collapse. Therefore, an object of the present invention is to provide a seismic isolation device that solves the above problems.

[0007]

[Means for Solving the Problems] The present invention comprises a lower plate fixed to an installation surface, an upper plate on which an object is placed and slidable with respect to the lower plate, and the lower plate. a plurality of lower pulleys arranged at intervals on the upper surface of the upper plate; a plurality of upper pulleys arranged at intervals so as to be alternately arranged with the plurality of lower pulleys on the lower surface of the upper plate; The plurality of lower pulleys and upper pulleys are mounted so as to approximately form a loop around the outer periphery, and one end of the loop forms a loop due to displacement of the upper pulley with respect to the lower pulley due to relative displacement between the upper plate and the lower plate. A cable-like body is stretched so as to be displaced to the side and has its other end fixed; and a spring means for displacing and applying a load to the cable-like body, wherein the seismic isolation device comprises a spring means for displacing and applying a load to the cable-like body, wherein the base isolation device is adapted to a displacement of one end of the cable-like body that is displaced by a relative displacement between the upper plate and the lower plate. An inertial mass that moves accordingly is provided between the loop of the cable and the spring means, and is configured to provide resistance to displacement of the cable.

[0008]

[Operation] As the upper plate and the lower plate are displaced relative to each other, the cable body is pulled against the spring means, and the displacement of the cable body moves the inertial mass, applying a static inertial force to the cable body. It is applied to make the upper plate vibrate over a long period. Therefore, even if an excessive earthquake occurs, the upper plate will not be displaced to the stroke limit with respect to the lower plate, and the spring means will be prevented from becoming fully extended.

[0009]

Embodiment FIGS. 1 to 3 show an embodiment of the seismic isolation device according to the present invention.

In each figure, an object 2 such as a computer, a work of art, etc. is placed on a seismic isolation device 1.

The seismic isolation device 1 is installed on a floor (installation surface) 3, and the object 2 is placed on an upper plate 4 of the seismic isolation device 1. This upper plate 4 is slidably provided on a lower plate 5 fixed to the floor 3. That is, as will be described later, in the seismic isolation device 1, when an earthquake occurs, the lower plate 5 slides relative to the upper plate 4, and the sliding displacement between the lower plate 5 and the upper plate 4 at that time will be described later. The gas spring 17 expands and contracts to prevent the placed object 2 from collapsing.

Spherical bearings 6a to 6d are fixed on the lower plate 4 of the seismic isolation device 1 at four corners. In Figures 1 and 3, 1
As shown by dotted lines, sliding plates 7a to 7d having high hardness are provided at four corners of the lower surface of the upper plate 4. The upper plate 4 is a sliding plate 7a
~7d are brought into contact with the spherical bearings 6a~6d, and the lower plate 5 is
are placed opposite each other on top.

On the lower surface of the upper plate 4, a plurality of rotatably supported upper pulleys 8a to 8h are arranged at intervals in the form of a generally rectangular loop. ~
A plurality of lower pulleys 9a to 9i are rotatably provided at intervals so as to form the same loop as 8h.

That is, the upper pulleys 8a to 8i and the lower pulley 9a
.about.9h are arranged alternately at intervals, arranged in a generally square loop shape, and arranged in substantially the same manner on each side. The wire 15 is connected to the upper pulley 8a~
8i and lower pulleys 9a to 9h in a loop shape, and one end extends into the loop.

10 is a rotating body serving as an inertial mass, and as shown in FIG. 4, a rotating shaft 10a is rotatably supported by a bearing 13 inserted into a cylindrical bearing portion 12 protruding from the lower plate 5. . Further, a sprocket 14 is provided in the middle of the rotating shaft 10a, and a chain 16 connected to a wire (rope-shaped body) 15 meshes with this sprocket 14. Therefore, the rotating body 10 moves in the rotational direction as one end of the wire 15 is displaced.

The rotating body 10 is about to stand still due to static inertia, and a ring 10b shaped like a donut when viewed from above is connected to the rotating shaft 10a by four arms 10c. That is, the structure is such that the inertial force accompanying the rotation of the rotating body 10 becomes a moment of inertia corresponding to the length of the arm 10c and is expanded. Therefore, a larger inertial force can be obtained with a compact configuration, and the installation space is also small. Further, since the rotating body 10 has the shape of a hollowed out disk, it can be installed in a narrow space between the upper plate 4 and the lower plate 5.

Reference numeral 17 denotes a gas spring, which includes a cylinder 17a filled with gas, and a rod 17b that is pressed by the pressure inside the cylinder 17a and protrudes from the cylinder 17a.
and has. The base end 17c of the cylinder 17a is locked to the lower plate 5, and the tip of the rod 17b fits into the guide groove of a pair of guide rails 18a, 18b extending on the lower plate 5. A slider 19 is connected.

The other end of the wire 15 as a cable-like body is locked to a lower pulley 9a, and upper pulleys 8a to 8i and lower pulleys 9b to 9h.
It is mounted in a loop shape so that it alternately slides into contact with the outer periphery of the Further, one end of the wire 15 is drawn in so as to extend inside the loop from the lower pulley 9h, and is connected to the chain 16 described above. The chain 16 is wound around the sprocket 14 of the rotating body 10 and extends toward the gas spring 17, and its end is connected to a wire 20 that is locked to the protruding pin 19a of the slider 19.

Therefore, the upper pulleys 8a to 8i and the lower pulley 9a
The pressing force of the gas spring 17 acts as a tension on the wire 15 mounted at ~9h through the wire 20 and chain 16, and each wire 15, chain 16, and wire 20 are tensioned without loosening. be done.

Further, the upper plate 4 of the seismic isolation device 1 is normally locked by the action of a locking member 21 provided on the lower plate 5.

Therefore, even if an external force is applied to the object 2 by, for example, touching the object 2, the upper plate 4 will not touch the lower plate 5.
The placed object 2 is stably supported by the seismic isolation device 1 without sliding against it.

The locking member 21 is held at the locking position by, for example, a solenoid (not shown), and when a seismic sensor (not shown) detects an earthquake, the holding by the solenoid is released and the upper plate 4 and lower plate The plates 5 can now slide relative to each other.

Here, when an earthquake or vibration occurs, the locking member 21 is released from the top plate 4, and the top plate 4 is released.
slides against the lower plate 5 and starts seismic isolation operation.

Here, when the lower plate 5 is displaced, for example, in the X1 direction, the upper plate 4 tends to stand still due to static inertia, and the lower pulley 9c is displaced relative to the upper pulleys 8b and 8c in a direction in which the wire 15 is stretched.

Therefore, the chain 16 connected to the wire 15 is pulled in the A direction, and the wire 20 connected to the chain 16 is pulled in the C direction. The slider 19 to which the wire 20 is connected is connected to the guide rail 1.
8a, 18b in the C direction to displace the rod 17b in the compression direction. In this way, this wire 1
5 is absorbed by the rod 17b of the gas spring 17 being pressed in the compression direction.

[0026] Also, as mentioned above, the wire 15 and the chain 16
, the wire 20 is displaced in accordance with the relative displacement of the upper plate 4, and the sprocket 14 with which the chain 16 meshes is driven to rotate.

The rotating body 10, which is integral with the sprocket 14, rotates around the rotating shaft 10a. At that time, rotating body 1
The moment of inertia due to the inertial force that attempts to keep the chain 1 still is acts on the chain 16 as a load, and the speed at which the wire 15 is pulled out is reduced, thereby reducing the acceleration of the upper plate 4.

Therefore, the upper plate 4 will move relatively with an acceleration smaller than the acceleration of the earthquake. That is, the upper plate 4 performs a seismic isolation operation at a lower frequency, that is, a longer period, and at a slower speed than when the inertial force of the rotating body 10 is not applied.

Further, when the lower plate 5 is displaced in the direction of arrow X2, the lower pulley 9g on the opposite side moves to the wire 15.
This force is absorbed by the gas spring 17.

As the wire 15 is displaced, the rotating body 10 is rotated as described above, and the acceleration of the upper plate 4 is reduced by its inertial force.

Further, when the lower plate 5 is displaced in the direction of arrow Y1, the wire 15 is pulled by the lower pulley 9e and receives a force extending against the upper pulleys 8d and 8e. This force is absorbed by the gas spring 17 and reduced by the inertial force of the rotating body 10.

Similarly, when the lower plate 5 is displaced in the direction of the arrow Y2, the wire 15 is pulled by the lower pulleys 9a, 9i and receives a force extending against the upper pulleys 8a, 8b. This force is absorbed by the gas spring 17 and reduced by the inertial force of the rotating body 10.

[0033] In this way, the seismic isolation operation of the seismic isolation device 1 prevents the placed object 2 on the upper plate 4 from collapsing.

In the vibration system having the rotating body 10 and the gas spring 17 as described above, the natural frequency f can be conceptually expressed by the following equation.

[0035]

[Math 1]

[0036] However, Keq: equivalent spring constant M of the seismic isolation device
: Mass of upper plate 4 Meq: Inertial mass According to the above equation, by increasing the inertial mass Meq, the natural vibration signal number f becomes smaller.

[0037] Furthermore, the relationship between the response magnification τ' when an inertial mass is added and the response magnification τ when no inertial mass is added, excluding various conditions such as attenuation, is τ' = τ・d
...It is represented by (2).

Further, d in equation (2) is an input reduction coefficient,

[0039]

[Math 2]

It is expressed as follows.

From equations (2) and (3), as Meq increases, d decreases and τ' decreases, so adding an inertial mass as in the present invention can reduce the response magnification.

Therefore, when the static inertial force of the rotating body 10 is applied to the wire 15, the relative displacement of the upper plate 4 due to an earthquake becomes a long period, as shown in FIG. 5, and the response magnification can be reduced.

Therefore, even if a relatively large earthquake occurs, the inertial mass of the rotating body 10 prevents the upper plate 4 from sliding against the lower plate 5 to the stroke end, and the seismic energy is transferred to the gas spring 17. It can be absorbed effectively by compression action. Moreover, since the moment of inertia due to the rotation of the rotating body 10 is utilized, a larger inertial force can be obtained by simply increasing the weight of the rotating body 10.
Even if a larger object 2 is placed, collapse can be prevented by a long-period seismic isolation operation with a compact configuration. FIG. 6 shows main parts of a modification of the present invention.

In the figure, a pair of linear bearings 22 and 23 are provided in parallel on the upper surface of the lower plate 5, and a sliding body 2 as an inertial mass is mounted on the linear bearings 22 and 23.
4 is slidably mounted. An end of the wire 15 is connected to one end of the sliding body 24.

Therefore, the sliding body 24 moves in the direction A due to the displacement of the upper plate 4 with respect to the lower plate 5 described above, and the wire 15
gives an inertial force that tries to keep it stationary. Moreover, the sliding body 24
A wire 25 is connected to the other end, and this wire 2
5 slides on pulleys 26 and 27 provided on the upper surface of the lower plate 5 and is connected to the slider 19 of the gas spring 17 described above. Therefore, as the slider 24 moves in the A direction, the slider 19 moves in the C direction, applying the compressive force of the gas spring 17 to the wire 25.

In the above-described embodiment, the inertial mass is constituted by the rotating body 10, but instead of this, the sliding body 24 may be configured to move linearly in accordance with the displacement of the wire 15. As in the previous embodiment, the vibration frequency of the upper plate 5 can be reduced to achieve long-period displacement.

In the above embodiment, a gas spring was used as the spring means, but other means such as a coil spring may also be used.

Further, the shape of the rotating body 10 is not limited to the above-mentioned shape, but may be any shape as long as it can be accommodated within the space between the upper plate 4 and the lower plate 5.

Further, it is of course possible to use other low-friction members instead of the spherical bearings that slidably support the upper plate 4.

[0050]

[Effects of the Invention] As mentioned above, the seismic isolation device according to the present invention has
For example, when vibrations due to an earthquake are transmitted to the lower plate and the lower plate is displaced relative to the upper plate, the cable-shaped body is pulled against the spring means and the displacement of the upper plate is absorbed by the spring means, thereby damping the vibration. At the same time, the inertial mass is operated by the displacement of the cable, and inertial force is applied to the cable to reduce the acceleration of the cable. Therefore, the vibration of the upper plate becomes a long-period vibration with a low frequency, and it is possible to suppress the upper plate to a slow acceleration vibration, and furthermore, it is possible to reduce the response magnification and suppress the amplitude between the upper plate and the lower plate. This eliminates the inconvenience that even if an excessive earthquake occurs, the upper and lower plates slide to the stroke end of the spring means and cannot absorb the vibration, and even if a large acceleration is input to the lower plate, the upper plate and the lower plate cannot absorb the vibration. Since the plate slides with long-period vibration, the acceleration can be reduced and absorbed by the spring means, and has features such as being able to prevent the placed object from collapsing without increasing the stroke of the spring means.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of a seismic isolation device according to the present invention.

FIG. 2 is a side view of the seismic isolation device.

FIG. 3 is a plan view of the seismic isolation device.

FIG. 4 is an enlarged side sectional view for explaining the bearing structure of the rotating body.

FIG. 5 is a diagram showing the relationship between frequency and response magnification.

FIG. 6 is a perspective view of a modification of the invention.

[Explanation of symbols]

1 Seismic isolation device 2 Placed objects 4 Top plate 5 Lower plate 6a-6d Spherical bearing 7a-7d Sliding board 8a-8h Upper pulley 9a-9i Lower pulley 10 Rotating body 14 Sprocket 15,20 wire 16 Chain 17 Gas spring

Claims (1)

[Claims] Claim 1: A lower plate fixed to an installation surface, an upper plate on which an object is placed and slidable with respect to the lower plate, and a spaced apart upper plate on the upper surface of the lower plate. A plurality of lower pulleys arranged at intervals, a plurality of upper pulleys arranged at intervals so as to be arranged alternately with the plurality of lower pulleys on the lower surface of the upper plate, and the plurality of lower pulleys and upper pulleys. is mounted so as to approximately form a loop around the outer periphery of the plate, and is tensioned so that one end forming the loop is displaced toward the loop side by displacement of the upper pulley relative to the lower pulley due to relative displacement between the upper plate and the lower plate. A cord-shaped body is provided, the other end of which is fixed, and a cord is connected to one end of the cord-shaped body, and is elastically displaced in accordance with relative displacement between the upper plate and the lower plate, and is attached to the cord-shaped body. and a spring means for applying a load. between the loop of the cord and the spring means;
A seismic isolation device characterized in that it is configured to provide resistance to displacement of the cable-like body.