JP5436333B2 - Seismic isolation device - Google Patents

Description

  The present invention relates to a seismic isolation device that reduces ground motion and effectively protects a floor structure.

  The seismic isolation device is a device that reduces vibrations (earthquake motion) during an earthquake with a flexibly displaceable isolator and transmits the vibrations to a floor structure loaded with computers and precision equipment as much as possible. There are seismic isolation devices that function in the vertical direction and those that function in the horizontal direction. As the vertical seismic isolation device, for example, an air spring is used, and as the spring constant of the air spring is smaller, the vibration of the ground (floor slab) is not transmitted to the floor structure.

  However, simply reducing the spring constant and extending the natural period causes the floor structure to sway in response to load fluctuations due to movement or walking of residents and workers on the floor structure of the building. Can occur. In particular, if the spring constant of the seismic isolation device is further reduced in order to effectively isolate a large earthquake with large vibrations, the spring element becomes softer, so that the vibration on the floor structure is not affected by load fluctuations. It gets bigger.

  Therefore, an auxiliary tank is provided in parallel with the air spring, and an electromagnetic valve, which is an electrically driven valve, is provided in a piping section connecting the air spring and the auxiliary tank, and the occurrence of an earthquake is detected by an earthquake wave detection sensor. And a technique for switching the spring constant of the air spring is disclosed (for example, Patent Document 1). Furthermore, a technique is also known in which a valve is disposed between the air spring and the auxiliary tank, and the opening degree of the valve is controlled by vibration detection means (for example, Patent Document 2).

JP-A-6-185193 JP 7-173955 A

  By using the technology described above, the spring constant of the air spring is increased during normal times to increase rigidity, and the shaking of the floor structure in response to load changes due to human movement or walking is suppressed. By reducing the spring constant of the spring and extending the natural period, the influence on the floor structure due to the vibration of the floor slab can be reduced. However, any technology requires an expensive sensor for detecting an earthquake, an electromagnetic valve driven through electricity, and an electric circuit for linking both, and the configuration becomes complicated. The reliability has been lowered, and the number of parts, occupied volume and manufacturing cost have been increased.

  The present invention has been made in view of such a problem, and an object thereof is to provide a highly reliable and low cost seismic isolation device without using an expensive sensor or electromagnetic valve.

In order to solve the above-described problems, a seismic isolation device according to the present invention includes a floor slab of a building and an air spring narrowly mounted on the floor structure, an auxiliary tank connected to the air spring through an air flow path, an air flow disposed in the road, and a relief valve pressure difference between the air spring and the auxiliary tank communicates the air spring and the auxiliary tank open the valve becomes equal to or larger than a predetermined threshold value, the relief valve is from the pressure of the auxiliary tank a valve that opens when pressure of the air spring is increased above a predetermined threshold, a valve that opens when pressure from the auxiliary tank pressure of the air spring is increased above a predetermined threshold is characterized that you have provided in parallel.

The - relief valve, the predetermined threshold is a plurality of different valves may be provided.

  According to the present invention, it is possible to switch the seismic isolation capability with a simple configuration using the air pressure of an air spring without using an expensive sensor or solenoid valve, thereby improving reliability, as well as the number of parts, occupied volume In addition, the manufacturing cost can be reduced.

It is explanatory drawing for demonstrating the schematic structure of a seismic isolation system. It is explanatory drawing for demonstrating operation | movement of a relief valve. It is explanatory drawing which showed the example which utilizes a relief valve bidirectionally. It is a timing chart for demonstrating operation | movement of a relief valve. It is explanatory drawing which showed the control block diagram for demonstrating level control. It is explanatory drawing which showed the structure of the relief valve. It is a timing chart for demonstrating operation | movement of a relief valve. It is explanatory drawing which showed the change of the frequency characteristic with respect to the damping effect of a relief valve.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Seismic isolation system 100)
FIG. 1 is an explanatory diagram for explaining a schematic configuration of the seismic isolation system 100. The seismic isolation system 100 includes a floor slab 110, a seismic isolation device 120, and a floor structure 130, and can effectively protect the floor structure 130 by reducing seismic motion.

  The floor slab 110 is a floor structure at the top of a structure foundation in a building or a floor structure between upper and lower floors, and indicates a plank such as stone or concrete that supports a load perpendicular to the surface. In the present embodiment, the floor slab 110 vibrates integrally with the ground during an earthquake. The seismic isolation device 120 is a device that reduces vibration applied to the floor slab 110 during an earthquake and transmits the vibration to the floor structure 130 as much as possible. In the present embodiment, an air spring is used as a vertical isolator that does not transmit vibration. The floor structure 130 corresponds to a floor portion of an area where a resident or worker can move within a building.

  When an earthquake or the like occurs, the floor slab 110 vibrates integrally with the ground. However, since the seismic isolation device 120 reduces vibration transmitted from the floor slab 110 to the floor structure 130, the floor slab 110 is on the floor structure 130. The impact of the earthquake on residents and workers is reduced. However, simply to soften the spring element (air spring) of the seismic isolation device 120 in order to enhance the seismic isolation capability, the load fluctuations caused by movement or walking of residents or workers on the floor structure 130 can be prevented. However, the floor structure 130 is shaken, and the resident and the worker feel uncomfortable. Further, when a computer or a precision device is loaded on the floor structure 130, the influence of such vibration must be avoided as much as possible.

  Therefore, in the present embodiment, an auxiliary tank is provided in parallel with the air spring constituting the seismic isolation device 120, and the spring constant of the air spring is switched using the change in the air pressure in the air spring. Thus, in normal times, the spring constant of the air spring is increased, the rigidity of the floor structure 130 and the floor slab 110 is increased, and the swing of the floor structure 130 in response to a load change due to movement or walking of a person is prevented. In the event of an earthquake, the spring constant is reduced to reduce the vibration transmitted from the floor slab 110 to the floor structure 130. Furthermore, since the switching of the spring constant can be realized with a simple configuration using the air pressure of the air spring without using an expensive sensor or solenoid valve, the reliability is improved, and the number of parts, occupied volume and The manufacturing cost can be reduced. Hereinafter, the detailed structure of the seismic isolation apparatus 120 which can implement | achieve such an objective is demonstrated.

(Seismic isolation device 120)
As shown in FIG. 1, the seismic isolation device 120 includes an air spring 150, an auxiliary tank 152, a relief valve 154, a relative displacement detector 156, an air pressure controller 158, an air source 160, a servo valve 162, It is comprised including.

  The air spring 150 is an elastic body formed by enclosing air (gas) of a predetermined pressure in an exterior formed of a bellows type or diaphragm type flexible container. The air spring 150 is confined to the floor slab 110 and the floor structure 130 of the building. Further, the air spring 150 can arbitrarily set a spring constant by changing the volume of air contained therein, and can realize extremely soft elasticity. Therefore, it is possible to reduce micro-earthquakes that cannot be absorbed by the metal springs, and it is difficult to resonate depending on the earthquake motion. Here, the air spring 150 using air is employed, but not limited to air, a fluid spring or the like enclosing a fluid according to the application such as a liquid can also be used. Here, for convenience of explanation, the gas in the air spring 150 is expressed as air, but the component is not limited and various gases can be applied.

  If a metal spring is used as the elastic body of the seismic isolation device, if the weight of the load on the floor structure 130 changes due to downsizing such as a computer and the natural frequency of the floor structure 130 increases (the natural period is shortened). Accordingly, the metal spring itself must be replaced with a new metal spring having a large spring constant. Moreover, the problem that a seismic isolation capability will fall by hardening of such a metal spring will also arise. The air spring 150 used in the present embodiment is advantageous in maintaining maintenance and seismic isolation capability because the natural frequency hardly changes even when the loaded load changes.

  In addition, since the air spring 150 is an elastic body formed of a flexible container, it has not only the vertical direction but also the horizontal isolation capability. Separately, a laminated rubber or the like is generally used. However, in this embodiment, for convenience of explanation, attention is paid only to the action of the air spring 150 that performs vertical isolation, and description of the horizontal isolation is omitted.

  The auxiliary tank (auxiliary air chamber) 152 is formed of a pressure resistant container formed with an internal volume three times that of the air spring 150, for example, and is connected to the air spring 150 through the air flow path 170.

  The relief valve 154 is disposed in the air flow path 170, and the air pressure in the air spring 150 greatly fluctuates due to an earthquake. When the pressure difference between the air spring 150 and the auxiliary tank 152 exceeds a predetermined threshold, the valve itself is automatically turned on. The air spring 150 and the auxiliary tank 152 are communicated with each other. When the pressure difference between the air spring 150 and the auxiliary tank 152 becomes less than the predetermined threshold again, the relief valve 154 is closed.

  The relief valve 154 communicates the air spring 150 and the auxiliary tank 152 to increase the apparent volume of the air spring 150 and to switch the spring constant of the air spring 150 to a smaller value. For example, in the case where the air spring 150 has a bellows shape, if the rate of change of the cross-sectional area of the air spring 150 is ignored, the spring constant of the air spring 150 is roughly proportional to the reciprocal of the internal volume, and the natural frequency is It is proportional to the square root of the spring constant. Therefore, when the internal volume of the auxiliary tank 152 is three times that of the air spring 150 and the air spring 150 and the auxiliary tank 152 are communicated, the spring constant of the air spring 150 is 1 / (1 + 3) = Since the natural frequency becomes 1 / √4 = ½ times, if the natural frequency when the auxiliary tank 152 is not connected is 1 Hz, the natural frequency becomes 0.5 Hz. .

  FIG. 2 is an explanatory diagram for explaining the operation of the relief valve 154. In normal times, a load change occurs when a person moves or walks on the floor structure 130, but the pressure fluctuation is small, so that the valve of the relief valve 154 does not open as shown in FIG. Therefore, the internal volume of the air spring 150 that determines the natural period of the seismic isolation device 120 (the spring constant of the air spring 150) is generally enclosed in the air spring 150 as shown by hatching in FIG. Since it is limited only to the air which exists, the rigidity of the floor structure 130 and the floor slab 110 is maintained comparatively high. In this way, it is possible to prevent the floor structure 130 from shaking due to a load change caused by a person's movement or walking.

  However, in normal times, it is not necessary to completely limit the air communication between the air spring 150 and the auxiliary tank 152, and a minute hole (orifice) may be provided between the two. Thus, although the time constant is long, the air pressure of the air spring 150 and the auxiliary tank 152 can be kept equal from a long-term viewpoint.

  On the other hand, when an earthquake (a large earthquake) with a vibration of a predetermined magnitude or more occurs, the pressure fluctuation transmitted from the floor slab 110 to the air spring 150 increases, and the pressure in the air spring 150 is increased by the pressure from the floor slab 110. Suddenly rises or falls. Then, according to the pressure fluctuation, the pressure difference between the air spring 150 and the auxiliary tank 152 becomes a predetermined threshold value or more, the relief valve 154 is opened as shown in FIG. 2B, and the air spring 150 and the auxiliary tank 152 are connected. Communicate.

  In this case, the apparent internal volume of the air spring 150 that determines the natural period of the seismic isolation device 120 (the spring constant of the air spring 150) is a volume including the auxiliary tank 152 as shown by hatching in FIG. In addition, it is possible to reduce the vibration transmitted from the floor slab 110 to the floor structure 130 by extending the natural period, in other words, to improve the seismic isolation performance. Here, the magnitude of vibration applied to the floor slab 110 is detected by the relief valve 154 using the air pressure itself in the air spring 150.

  By the way, when an earthquake occurs, the floor slab 110 vibrates and the vertical relative displacement between the floor slab 110 and the floor structure 130 increases or decreases. That is, since both the compressive force and the tensile force are applied to the air spring 150 from the floor slab 110, the relief valve 154 has not only a positive value not less than a predetermined threshold value in the air spring 150 but also an absolute value not less than the predetermined threshold value. Even a negative value should open the valve. Therefore, in this embodiment, a relief valve 154 that can handle both positive and negative atmospheric pressure is used.

  FIG. 3 is an explanatory view showing an example in which the relief valve 154 is used bidirectionally. In the relief valve 154, a valve that opens when the pressure of the air spring 150 becomes higher than a predetermined threshold value above the pressure of the auxiliary tank 152 and a valve that opens when the pressure of the auxiliary tank 152 becomes higher than the pressure value of the air spring 150 by a predetermined threshold value are in parallel. Is provided. Such valves having different functions may be provided in parallel in one relief valve 154, or may be provided in each of the plurality of relief valves 154, and the relief valves 154 may be connected in parallel. Here, the operation will be described using two relief valves 154a and 154b each having a valve having a different function.

  At normal times, the air pressures of the air spring 150 and the auxiliary tank 152 are set to be equal, and as shown in FIG. 3A, each of the relief valves 154a and 154b is in a closed state. ing. Therefore, the spring constant of the air spring 150 is determined only by the air enclosed in the air spring 150.

  Here, when the floor slab 110 rises due to an earthquake, the air spring 150 is compressed as shown in FIG. 3B, and the air pressure of the air spring 150 becomes higher than a predetermined threshold value by the air pressure of the auxiliary tank 152, and one relief valve. 154a is opened, and air is discharged from the air spring 150 toward the auxiliary tank 152. When the floor slab 110 is lowered, as shown in FIG. 3C, the air pressure of the air spring 150 becomes lower than the air pressure of the auxiliary tank 152 by a predetermined threshold or more, and the other relief valve 154b is opened. Air is discharged toward The operation of the relief valves 154a and 154b will be described in more detail.

  FIG. 4 is a timing chart for explaining the operation of the relief valves 154a and 154b. In FIG. 4, the horizontal axis indicates time, and the vertical axis of each timing chart indicates displacement and atmospheric pressure. 4, the vertical position 172 of the floor slab 110, the vertical position 174 of the floor structure 130, the air pressure 176 in the air spring 150, the air pressure 178 in the auxiliary tank 152, and the open / close state of the relief valve 154a 180, the open / close state 182 of the relief valve 154b changes on the same time axis.

  In normal times, the vertical position 172 of the floor slab 110 does not substantially change, but the vertical position 174 of the floor structure 130 slightly varies according to a load change caused by the movement of a person. However, since the fluctuation amount of the air pressure 176 in the air spring 150 due to the fluctuation is equal to or less than the predetermined threshold value, the open / close states 180 and 182 of the relief valves 154a and 154b do not shift from the closed state to the open state. Therefore, the spring constant of the air spring 150 is maintained at a relatively large value, and the floor structure 130 can be prevented from shaking.

At this time, the floor slab 110 vibrates in the vertical direction due to the earthquake, and at an arbitrary time t ₁ , the air pressure 176 in the air spring 150 is greater than the air pressure 178 in the auxiliary tank 152 by a predetermined threshold value as indicated by an arrow in FIG. If it becomes higher above, the open / close state 180 of the relief valve 154a shifts from the closed state to the open state.

When the relief valve 154a is opened, air is discharged from the air spring 150 to the auxiliary tank 152, and the air pressure 178 of the auxiliary tank 152 follows the transition while keeping the difference from the air pressure 176 of the air spring 150 at a predetermined threshold. At time t ₂ when the atmospheric pressure 176 in the air spring 150 returns to the extreme value and the atmospheric pressure difference from the auxiliary tank 152 becomes less than a predetermined threshold, the open / close state 180 of the relief valve 154a is closed, and the auxiliary tank 152 The atmospheric pressure 178 at that time is maintained.

Subsequently, the pressure 176 of the air spring 150 is reduced, at time _{t 3,} a pressure difference between the air spring 150 and the auxiliary tank 152 is again above a predetermined threshold, this time open closed state 182 of the relief valve 154b is from the closed state Transition to the state. When the relief valve 154b is opened, air is discharged from the auxiliary tank 152 to the air spring 150, and the air pressure in the auxiliary tank 152 also follows the change while maintaining the difference from the air pressure 176 of the air spring 150 at a predetermined threshold. To do. The open or closed state 182 of the valve of the relief valve 154b at t ₄ when pressure 176 in the air spring 150 is a pressure difference between the auxiliary tank 152 folded extrema is less than the predetermined threshold value is closed and the auxiliary tank 152 The atmospheric pressure 178 at that time is maintained.

  Thus, even if the vibration of the floor slab 110 is applied to the air spring 150 in either the vertical direction or the vertical direction, the relief valves 154a and 154b are opened, so the seismic isolation device 120 reduces the spring constant of the air spring 150. The natural period can be extended.

  Thereafter, when the vibration to the floor slab 110 is eliminated, the air pressures of the air spring 150 and the auxiliary tank 152 may differ depending on the timing. However, the atmospheric pressure 178 of the auxiliary tank 152 becomes equal to the atmospheric pressure 176 of the air spring 150 with a long time constant by the above-described minute hole and level control described later.

  As described above, in the seismic isolation device 120 of this embodiment, the seismic isolation capability can be switched with a simple configuration using the air pressure of the air spring 150 itself without using an expensive sensor or solenoid valve. It is possible to improve the number of parts, reduce the number of parts, the occupied volume and the manufacturing cost.

  Further, the relief valve 154 attenuates relative vibration between the floor slab 110 and the floor structure 130 not only by switching the spring constant of the air spring 150 but also by friction of air in its own opening and the air flow path 170. Also serves as a damping mechanism. In the seismic isolation device 120 of the present embodiment, a damping effect is generated by the relief valve 154 and the air flow path 170. Therefore, in order to attenuate relative vibration between the floor slab 110 and the floor structure 130, a hydraulic damper is separately provided. Etc., which is advantageous in terms of cost.

  By the way, in the air spring 150, the internal volume in the air spring 150 changes and the vertical position of the floor structure 130 changes according to the load fluctuation on the floor structure 130 in order to obtain the internal pressure corresponding to the load fluctuation. There is a case. Therefore, in this embodiment, the level control of the floor structure 130 is performed as follows using the relative displacement detector 156, the air pressure controller 158, the air source 160, and the servo valve 162 shown in FIG.

  The relative displacement detector 156 is installed on the floor slab 110 to detect a laser reflection time with respect to the floor structure 130, a speedometer or an accelerometer installed on the floor slab 110 and the floor structure 130, respectively. The relative displacement (relative distance in the vertical direction) between the floor slab 110 and the floor structure 130 is detected. Here, when using a speedometer or an accelerometer, the relative displacement detection unit 156 individually acquires the respective speeds and accelerations from the floor slab 110 and the floor structure 130 and integrates them once or twice, thereby integrating each other. The displacement is obtained, and the relative displacement is derived from the difference.

  The air pressure control unit 158 generates a control command that cancels the displacement according to the displacement of the floor structure 130 itself due to the load variation on the floor structure 130, and transmits the control command to a servo valve 162 described later.

  The air source 160 is composed of a compressor, and can supply air pressure to the air spring 150 and the auxiliary tank 152 to arbitrarily add atmospheric pressure higher than atmospheric pressure.

  The servo valve 162 controls the air pressure of the air source 160 according to a control command from the air pressure control unit 158, and increases or decreases the air pressure of the air spring 150 and the auxiliary tank 152. Further, at the time of initial setting, air is supplied from the air source 160 so that the air pressure of both the air spring 150 and the auxiliary tank 152 becomes a predetermined air pressure set in advance.

  FIG. 5 is an explanatory diagram showing a control block diagram for explaining the level control. Here, level control is performed to stabilize the relative displacement of the floor structure 130 with respect to the floor slab 110 by using the air spring 150 as an actuator by controlling the air pressure in the air spring 150.

  In the control system shown in FIG. 5, when the relative displacement detected by the relative displacement detector 156 increases, that is, when the floor structure 130 rises with respect to the floor slab 110, the servo valve 162 reduces the air pressure of the air spring 150. The air spring 150 is compressed and the floor structure 130 is lowered. When the relative displacement detected by the relative displacement detector 156 is reduced, that is, when the floor structure 130 is lowered with respect to the floor slab 110, the servo valve 162 increases the air pressure of the air spring 150 to expand the air spring 150. The floor structure 130 is raised.

  As described above, when the earthquake does not occur or when the magnitude of the earthquake is extremely small, the closed loop shown in FIG. 5 is functioned to further increase the rigidity, and the floor structure 130 is not vibrated depending on the load change caused by the movement of the person. Can be. When the vibration of the floor slab 110 increases, the seismic isolation device 120 can cut the closed loop of FIG. 5 and reduce the spring constant of the air spring 150 through the relief valve 154 to reduce the vibration applied to the floor slab 110. It becomes.

  With the above-described seismic isolation device 120, the seismic isolation capability can be maintained with only a simple configuration using the air pressure of the air spring 150. However, if the relief valve 154 is opened only with a threshold value of 1, the spring element of the air spring 150 becomes sharply soft at the time of an earthquake, and the seismic isolation capability increases at a time and the rigidity of the seismic isolation device 120 that supports the floor structure 130 is increased. However, the floor structure 130 will drop rapidly. Therefore, the relief valve 154 of the present embodiment is set so as to open stepwise with a plurality of different predetermined threshold values.

  FIG. 6 is an explanatory view showing another configuration example of the relief valve 154. A plurality of valves having different predetermined threshold values may be provided in parallel in one relief valve 154, or may be provided in each of the plurality of relief valves 154, and the relief valves 154 may be connected in parallel. Here, three relief valves 154c, 154d, and 154e having predetermined threshold values Pc, Pd, and Pe are provided. It is assumed that the predetermined threshold values of the relief valves 154c, 154d, and 154e satisfy the relationship Pc <Pd <Pe. Here, when all of the three relief valves 154c, 154d, and 154e are opened, the optimum apertures of the air spring 150 and the auxiliary tank 152 are set.

  For ease of understanding, only the valve that opens when the pressure of the air spring 150 becomes higher than the pressure of the auxiliary tank 152 will be described here, and the valve that opens when the pressure of the auxiliary tank 152 becomes higher than the pressure of the air spring 150. Since description is duplicated, explanation is omitted.

  FIG. 7 is a timing chart for explaining the operation of the relief valves 154c, 154d, and 154e. In FIG. 7, the horizontal axis indicates time, and the vertical axis of each timing chart indicates displacement and atmospheric pressure. The vertical position 172 of the floor slab 110, the vertical position 174 of the floor structure 130, the air pressure 176 in the air spring 150, the air pressure 178 in the auxiliary tank 152, and the open / close state of the relief valve 154c shown in FIG. The open / close state 186 of the relief valve 154d and the open / close state 188 of the relief valve 154e change on the same time axis.

  As in FIG. 4, the vertical position 172 of the floor slab 110 does not substantially change in the normal state, but the vertical position 174 of the floor structure 130 slightly varies according to the load change caused by the movement of the person. However, the fluctuation amount of the air pressure 176 in the air spring 150 due to the fluctuation is equal to or less than the predetermined threshold value Pc of the relief valve 154c (the predetermined threshold value Pc is set sufficiently high so as not to be reached by human movement or the like). The open / close states 184, 186, and 188 of the relief valves 154c, 154d, and 154e do not shift from the closed state to the open state.

In this case, seismic floor slab 110 is vibrated vertically upwardly by, at any time _{t 5,} when the air pressure 176 in the air spring 150 is higher than a predetermined threshold value Pc from pressure 178 in the auxiliary tank 152, the relief valve 154c Only the open / close state 184 transitions from the closed state to the open state. At this time, only the relief valve 154c is opened and the opening area is small, so that the flow resistance of the air flow path 170 including the relief valve 154c is increased, and a strong damping effect is obtained. Therefore, although the internal volume is the sum of the air spring 150 and the auxiliary tank 152, the spring constant of the air spring 150 is not rapidly reduced, and the lowering speed of the floor structure 130 is also suppressed.

When the vibration of the floor slab 110 continues to increase, the pressure of the air spring 150 increases, and the pressure difference becomes greater than or equal to the predetermined threshold values Pd and Pe at time points t ₆ and t ₇ , respectively. As shown in the open / close state 188 of the valve 154e, the relief valves 154d and 154e are sequentially opened. Then, since the opening area gradually increases, the flow resistance of the air flow path 170 also decreases, and the seismic isolation force increases with a decrease in damping force.

  In this way, in the relief valve 154, a plurality of predetermined threshold values are set, and the valve is sequentially opened according to the pressure applied to the air spring 150, so that the damping force decreases stepwise and the seismic isolation force is reduced. It will go up step by step. Therefore, the descent of the floor structure 130 also becomes gentle. Here, the relief valve 154 is provided in three stages, for example, but the number is not limited to three, and may be two stages or four or more stages. Further, the opening degree of the valve may be continuously changed according to the pressure applied to the air spring 150.

  In addition, when the earthquake is not a large earthquake as shown in FIG. 7 and the air pressure of the air spring 150 does not exceed the predetermined threshold value Pe, for example, rises only to a value not less than the predetermined threshold value Pc and less than the predetermined threshold value Pd, Since only the valve 154c is opened, a certain amount of damping effect can be expected. Therefore, not only a rapid change in pressure but also the displacement itself of the floor structure 130 descending according to the magnitude of the earthquake can be suppressed.

  Hereinafter, the relationship between the change in the damping effect by the relief valve 154 and the natural frequency will be described in detail. FIG. 8 is an explanatory diagram showing changes in frequency characteristics with respect to the damping effect of the relief valve 154. In FIG. 8, the horizontal axis represents frequency, and the vertical axis represents response rate (output amplitude / input amplitude). Further, each curve in FIG. 8 shows frequency characteristics when the attenuation effect is changed from 0 to ∞.

  As can be understood with reference to FIG. 8, when the opening area of the relief valve 154 is small, for example, when the damping effect is ∞, the natural frequency is relatively high. Subsequently, when the damping effect is reduced, the response rate when resonating at the natural frequency is lowered and the natural frequency itself is lowered. When the damping effect is 0.5, the response rate is minimized. If the damping effect is further reduced, the response rate also starts to increase as the natural frequency decreases.

  The damping effect in FIG. 8 corresponds to the open / closed state of the plurality of stages of relief valves 154. Therefore, the state in which the air pressure in the air spring 150 is still low and any of the multiple-stage relief valves 154 is closed corresponds to the damping effect ∞, and the damping effect decreases as the relief valves 154 open sequentially. The natural frequency is lowered. Thus, it is understood that the natural frequency can be lowered and the natural period can be prolonged stepwise by opening the valves of the relief valve 154 sequentially.

  As described above, the seismic isolation device 120 described above can switch the seismic isolation capability with a simple configuration using the air pressure of the air spring 150, thereby improving the reliability and reducing the number of parts, occupied volume and manufacturing cost. It becomes possible to plan. Further, by making the relief valve 154 multi-stage, it is possible to suppress a rapid drop in the vertical direction of the floor structure 130.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  INDUSTRIAL APPLICATION This invention can be utilized for the seismic isolation apparatus which reduces a ground motion and protects a floor structure effectively.

110 ... Floor slab 120 ... Seismic isolation device 130 ... Floor structure 150 ... Air spring 152 ... Auxiliary tank 154 ... Relief valve 156 ... Relative displacement detector 158 ... Air pressure controller 160 ... Air source 162 ... Servo valve

Claims (2)

An air spring confined to the floor slab of the building and the floor structure;
An auxiliary tank connected to the air spring through an air flow path;
A relief valve that is disposed in the air flow path and opens when the pressure difference between the air spring and the auxiliary tank exceeds a predetermined threshold value, and communicates the air spring and the auxiliary tank;
Equipped with a,
In the relief valve, a valve that opens when the pressure of the air spring becomes higher than a predetermined threshold by a pressure higher than the pressure of the auxiliary tank and a valve that opens when the pressure of the auxiliary tank becomes higher than a predetermined threshold by a pressure of the air spring are arranged in parallel. It provided seismic isolation device according to claim Rukoto. The seismic isolation device according to claim 1 , wherein the relief valve is provided with a plurality of valves having different predetermined threshold values.

Images