JP2011007323A - Base isolation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in walking performance on a floor surface in a base isolation device improving a quake-absorbing effect.SOLUTION: The base isolation device 100 reduces vertical vibrations transmitted to a quake-absorbing subject 1 while supporting the quake-absorbing subject 1. It includes a disc 21 rotatably configured in a horizontal plane, and a motion converting mechanism 22 converting a vertical motion that acts on the subject 1 into the rotational motion of the disc 21. The rotation inertial mass of the disc 21 is set 0.05-0.3 times of the mass of the subject 1.

Description

  The present invention relates to a seismic isolation device that protects a building or the like from vertical shaking of an earthquake.

  Conventionally, a seismic isolation device is known in which the natural period of a structure is made longer than the vibration period of a seismic wave, that is, by making the period longer, so that the vibration of the structure does not follow the vibration of the earthquake (for example, , See Patent Document 1).

  In the seismic isolation device disclosed in Patent Document 1, between the seismic isolation object (floor or the like) and the support structure, a vertical seismic isolation portion that exhibits elastic restoring force and inertia related to vertical vibration. A mass addition mechanism for increasing the mass is provided. The mass addition mechanism includes a disk having a predetermined mass and a motion conversion mechanism that rotates the disk in conjunction with the vertical movement of the seismic isolation target structure.

JP 2004-44748 A

  By the way, in such a seismic isolation device, when the disk rotates in conjunction with the vertical motion of the seismic isolation object by the motion conversion mechanism, a rotational inertia moment is generated, and the inertia involved in the vertical motion of the seismic isolation object. Although the mass increases and the vertical period of the seismic isolation object can be lengthened, an inertial force proportional to the relative acceleration between the seismic isolation object and the support structure acts at the same time by the mass addition mechanism. To do. This relative acceleration becomes prominent on the short period side where the seismic isolation object vibrates in the opposite phase with respect to the support structure, so that the inertial force of the short period component is easily transmitted to the seismic isolation object, and the seismic isolation performance is improved. There was the inconvenience of getting worse. Even if the mass addition mechanism described above is applied, it is necessary to support the seismic isolation object with a soft spring as a prerequisite for seismic isolation performance. In this case, there is a disadvantage that the walking ability of the floor surface is deteriorated.

This invention is made | formed in view of said situation, and it aims at providing the seismic isolation apparatus which can improve a seismic isolation effect.
Moreover, an object of this invention is to suppress the deterioration of the walkability of a floor surface in such a seismic isolation apparatus.

In order to solve the above problems, the present invention employs the following means.
The present invention provides a seismic isolation device that supports a seismic isolation object and reduces vertical vibration transmitted to the seismic isolation object, the mass body being rotatable in a horizontal plane, A motion conversion mechanism that converts a vertical motion acting on the seismic object into a rotational motion of the mass body, and the rotational inertial mass of the mass body is not less than 0.05 times the mass of the seismic isolation object 0 • Use seismic isolation devices that are less than 3 times.

  According to the present invention, the rotational inertial mass of the mass body is limited to not more than 0.3 times the mass of the seismic isolation object, so that the inertia of the short period component transmitted from the motion conversion mechanism to the seismic isolation object Force (= rotational inertial body mass × relative acceleration) can be suppressed. In addition, since the rotational inertial mass of the mass body is 0.05 times or more that of the seismic isolation object, it is possible to lengthen the vertical vibration of the seismic isolation object. The vibration in the vertical direction transmitted to can be reduced.

  In this case, more preferably, the acceleration of the seismic isolation object can be reduced by setting the rotational inertial mass of the mass body to 0.2 times the mass of the seismic isolation object. Can be seismically isolated.

  In the above invention, the motion conversion mechanism is a combination of a ball screw shaft and a ball screw nut, and one of the ball screw shaft and the ball screw nut is provided on the seismic isolation object, and the other is provided on the mass body. It is good to be.

  By combining the motion conversion mechanism with a ball screw shaft and a ball screw nut, for example, when the ball screw nut is provided on the seismic isolation object and the ball screw shaft is provided on the mass body, the vertical motion of the seismic isolation object (ball screw nut) is reduced. It is converted into the rotational motion of the ball screw shaft. Thereby, the mass body rotates, and the inertial mass involved in the vertical motion of the seismic isolation object is efficiently increased by the rotation inertia moment. Further, by using the ball screw, the vertical motion of the seismic isolation object can be smoothly converted into the rotational motion of the mass body, and the seismic isolation effect can be improved.

In the above invention, the lead angle of the ball screw shaft may be 10 degrees or more and 30 degrees or less.
When the lead angle of the ball screw shaft is increased, that is, the lead length of the ball screw shaft is increased, the vertical motion of the ball screw nut can be efficiently converted into the rotational motion of the ball screw shaft. On the other hand, if the lead angle of the ball screw shaft is reduced, that is, the lead length of the ball screw shaft is shortened, the rotation angle of the mass body accompanying the vertical motion of the seismic isolation object can be increased, so that the rotational inertial mass is increased. be able to.

  Here, generally, the conversion efficiency into the rotational motion needs to be 95% or more. Therefore, by setting the lead angle of the ball screw shaft to 10 degrees or more and 30 degrees or less, more preferably about 17 degrees where the lead length of the ball screw shaft is substantially equal to the diameter, the vertical motion of the ball screw nut is changed to the rotational motion of the ball screw shaft. It is possible to perform effective seismic isolation while efficiently converting and suppressing a decrease in rotational inertial mass of the mass body.

The said invention WHEREIN: It is good also as providing the braking mechanism which brakes rotation of the said mass body.
By damping the rotation of the mass body by the braking mechanism, the vibration damping effect of the seismic isolation object can be obtained. Thereby, also when the rotational inertia mass of a mass body is small, the vibration of the vertical direction of a seismic isolation object can be reduced effectively.
In addition, by braking the rotation of the mass body by the braking mechanism, the vertical motion of the seismic isolation object can be suppressed, and when the seismic isolation object is the floor, the walking ability of the floor surface can be improved. .

In the above invention, an anti-vibration rubber or a viscoelastic body having a vertical frequency of 1.5 to 3.5 Hz between the seismic isolation object and the motion conversion mechanism is provided. It is good also as providing.
High-frequency vibrations that are difficult to convert into a rotational motion of a mass body by a motion conversion mechanism (for example, by providing a vibration-proof rubber or a viscoelastic body such that the vertical frequency of the seismic isolation object is 3.5 Hz or less) Even when vibration of 10 Hz or higher) occurs, the vibration can be absorbed and the seismic isolation object can be isolated. In addition, by using anti-vibration rubber or viscoelastic body so that the vertical frequency of the seismic isolation object is 1.5 Hz or more, the walking ability of the floor surface is ensured when the seismic isolation object is the floor. can do.

In the above invention, the seismic isolation object may be held movably in the vertical direction, and may include a vertical movement guide that restrains movement in the horizontal direction.
By holding the seismic isolation object movably in the vertical direction by the vertical movement guide, it is possible to prevent a horizontal load from being applied to the motion conversion mechanism by restraining the horizontal movement.

  According to the present invention, it is possible to improve the seismic isolation effect. Moreover, there exists an effect that the deterioration of the walkability of a floor surface can be suppressed.

It is a side view which shows schematic structure of one Embodiment of this invention. It is a sectional side view explaining the effect | action of the brake mechanism of FIG. It is the side view which modeled the seismic isolation apparatus of FIG. 1 in examination of rotational inertial mass. It is a graph which shows the relationship between rotational inertia mass ratio and acceleration in case a damping constant is 0.3. It is a graph which shows the relationship between a rotation inertia mass ratio and a displacement in case a damping constant is 0.3. It is a graph which shows the relationship between a rotation inertia mass ratio and acceleration in case a damping constant is 0.1. It is a graph which shows the relationship between a rotation inertia mass ratio and a displacement in case a damping constant is 0.1. It is a graph which shows the relationship between the lead angle of a ball screw, and conversion efficiency. It is the frequency analysis result of the acceleration wave of a vibration stand in a vibration test. It is the frequency analysis result of the acceleration wave of a base isolation frame in a vibration test. It is the side view which modeled the seismic isolation apparatus of FIG. 1 in examination of vibration-proof rubber. It is a figure explaining the item of the model of FIG. It is a graph which shows the relationship between the spring constant of vibration-proof rubber in a steady state, and an acceleration response magnification. It is a graph which shows the relationship between the spring constant of vibration-proof rubber in a transient state, and an acceleration response magnification. It is the side view which modeled the seismic isolation apparatus of FIG. 1 in examination of a viscoelastic body. It is a figure explaining the item of the model of FIG. It is a graph which shows the relationship between the spring constant of a viscoelastic body in a steady state, and an acceleration response magnification. It is a graph which shows the relationship between the spring constant of a viscoelastic body in a transient state, and an acceleration response magnification.

Hereinafter, an embodiment of the seismic isolation device of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of a seismic isolation device 100 according to an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a seismic isolation object (for example, a floor and a load on the floor), and reference numeral 2 denotes a support structure (for example, a building beam) that supports the seismic isolation object 1. The seismic isolation object 1 is supported by the support structure 2 via the air spring 13. The air spring 13 can adjust the level of the seismic isolation object 1 by changing the internal air pressure.

  The seismic isolation device 100 is disposed between the seismic isolation object 1 and the support structure 2, supports the seismic isolation object 1, and is transmitted in the vertical direction transmitted from the support structure 2 to the seismic isolation object 1. It is a device that reduces vibration. The seismic isolation device 100 includes a mass addition mechanism 20, a spline mechanism (vertical movement guide) 30, an anti-vibration rubber 31, and a brake mechanism (braking mechanism) 40 as main components.

  The mass addition mechanism 20 is a mechanism that increases the inertial mass of the seismic isolation object 1 in conjunction with the vertical movement of the seismic isolation object 1. The mass addition mechanism 20 includes a disk (mass body) 21 that is rotatable in a horizontal plane, and a motion conversion mechanism 22 that converts the vertical motion acting on the seismic isolation object 1 into the rotational motion of the disk 21. I have.

The disk 21 has a predetermined mass and is rotated by the motion conversion mechanism 22 to generate a rotational moment of inertia. The rotational inertia mass at this time will be described later.
The motion conversion mechanism 22 is configured by a combination of a ball screw nut 23 supported by a support metal 25 fixed to the lower surface of the seismic isolation object 1 and a ball screw shaft 24 screwed into the ball screw nut 23.

  The ball screw shaft 24 is disposed with its axis line oriented in the vertical direction, is screwed into the ball screw nut 23, and is rotatably held by a bearing 28 fixed to the support structure 2. A disk 21 is fixed to the ball screw shaft 24 between the ball screw nut 23 and the bearing 28 in the axial direction. The lead angle (lead length) of the ball screw shaft 24 will be described later.

  By having the above-described configuration, the motion conversion mechanism 22 converts the vertical motion of the seismic isolation object 1 (ball screw nut 23) into the rotational motion of the ball screw shaft 24 and is fixed to the ball screw shaft 24. Is supposed to rotate.

  The spline mechanism 30 includes a cylindrical member 33 fixed to the support structure 2, a bearing 34 provided inside the cylindrical member 33, and a shaft body 35 fixed to the seismic isolation object 1. The shaft body 35 is inserted into the cylindrical member 33 and is supported by the bearing 34 so as to be movable in the vertical direction. By having such a configuration, the spline mechanism 30 holds the seismic isolation object 1 so as to be movable in the vertical direction and restrains the horizontal movement of the seismic isolation object 1.

  The anti-vibration rubber 31 is provided between the seismic isolation object 1 and the mass addition mechanism 20. The anti-vibration rubber 31 absorbs micro vibrations of a short period due to an earthquake, but may be a viscoelastic body instead of the anti-vibration rubber. The detailed specifications of the vibration-proof rubber 31 and the viscoelastic body will be described later.

ここで、Ｌはボールネジ軸２４のリード長、Ｒはボールネジ軸２４の軸心と押付け力Ｐの作用点との間の距離、μは円盤２１の摩擦係数を表している。なお、ここでは、運動変換機構２２による回転運動と上下運動との変換効率は１．０と仮定している。 The brake mechanism 40 is a mechanism that brakes the rotation of the disk 21 by sandwiching the eccentric position of the disk 21 from both sides perpendicular to the radial direction, and brakes the vertical movement of the seismic isolation object 1. Here, the detailed structure of the brake mechanism 40 is shown in FIG. As shown in FIG. 2, in the brake mechanism 40, the relationship between the braking force F acting on the seismic isolation object 1 and the pressing force P applied to the disk 21 is expressed as follows.

Here, L represents the lead length of the ball screw shaft 24, R represents the distance between the axis of the ball screw shaft 24 and the point of action of the pressing force P, and μ represents the friction coefficient of the disk 21. Here, it is assumed that the conversion efficiency between the rotary motion and the vertical motion by the motion conversion mechanism 22 is 1.0.

The operation of the seismic isolation device 100 having the above configuration will be described below.
According to the seismic isolation device 100 of this embodiment, when the seismic isolation object 1 moves up and down, the motion is converted into the rotational motion of the disk 21 via the ball screw nut 23 and the ball screw shaft 24. A rotation inertia moment is generated by the rotation of the disk 21, and the inertial mass involved in the vertical vibration of the seismic isolation object 1 is increased by the rotation inertia moment. Here, the inertial force of the short period component transmitted to the seismic isolation object 1 is suppressed by making the increasing inertial mass 0.3 times or less that of the seismic isolation object 1. Further, by making the increasing inertial mass 0.05 times or more that of the seismic isolation object 1, the natural period T of the vertical vibration of the seismic isolation object 1 is lengthened and transmitted to the seismic isolation object 1. It is possible to reduce vertical vibrations.

[Examination of rotational inertial mass]
Here, the rotational inertial mass of the disk 21 will be described with reference to FIGS.
Here, in the seismic isolation device 100 having the above configuration, the influence of the rotational inertial mass of the disk 21 on the seismic isolation performance was examined as follows.

(1) Seismic isolation object As a specific example of the seismic isolation object 1, consider a seismic isolation frame and the load loaded on it.
The total weight W1 (the weight of the seismic isolation object 1) of the base isolation frame and the load loaded thereon was set to 3000 kg, and the vibration characteristics (frequency and damping constant) were set as follows.
・ Damping constant: 2 types of h = 0.3, h = 0.1 ・ Frequency: 3 types of f = 1.2 Hz, 1.0 Hz, and 0.8 Hz Here, h = 0.3 is an oil damper and This is a case in which attenuation by the air spring is considered, and h = 0.1 assumes a case in which only the attenuation of the air spring is considered.
A frequency of 1.2 Hz corresponds to a normal seismic isolation frequency, and 0.8 Hz assumes a case where a sleeve type air spring is applied.

(2) Study Model FIG. 3 is a diagram in which the seismic isolation device 100 is modeled in performing this study.
In FIG. 3, ΔM3 is a rotational inertia mass of the disk 21, F3 is a braking force (braking force), K1 is a spring constant of the air spring 13, C1 and C′1 are damping coefficients of the oil damper and the air spring 13, and F1 is a spline. The frictional force of the mechanism 30, W3 represents the weight of the connection hardware connecting the seismic isolation object 1 and the ball screw nut 23, K3 represents the spring constant of the vibration isolating rubber 31, and C 3 represents the damping coefficient of the vibration isolating rubber 31.

(3) Model specifications The model specifications for this study are as follows.
K1: Spring constant at which the frequency is 1.2 Hz, 1.0 Hz, 0.8 Hz when W1 = 3000 kg C′1: When W1 = 3000 kg, the damping constant h = 0.1 at the above frequency When the damping coefficient C1: W1 = 3000 kg, the damping coefficient at which the damping constant h = 0.2 at the above frequency (the damping constant h = 0.3 is considered as C′1 + C1).
F1: Frictional force of spline mechanism = 14kg
F3: Braking force = 200kg
K3: Anti-vibration rubber spring constant = 350 kg / cm
C3: Damping coefficient of anti-vibration rubber = 2 kgs / cm
W3: Connection hardware weight = 20kg

(4) Study Method Here, ΔM3 (rotational inertial mass) was changed, and the response of the base isolation frame to the JMA Kobe UD earthquake (maximum acceleration = 332 Gal) was obtained.
Since the JMA Kobe UD earthquake includes a periodic component of about 0.5 seconds to 1 second, seismic isolation performance (response acceleration) compared to standard earthquakes (for example, El Centro UD earthquake, Taft UD earthquake, Hachinohe UD earthquake) It is an earthquake that is difficult to obtain.

(5) Examination results Regarding the relationship between the maximum response value (acceleration, displacement) of the base isolation frame and the rotational inertial mass ratio (rotational inertial mass / base isolation object mass), the damping constant of the base isolation frame is set to h = 0.3 FIGS. 4 and 5 show the cases where the above-mentioned cases are performed, and FIGS. 6 and 7 show the cases where the damping constant of the base isolation frame is set to h = 0.1, respectively.

  As shown in FIGS. 4 to 7, the maximum acceleration of the base isolation floor (mounting base) is centered on the rotational inertial mass ratio of 0.2 when the frequency of the base isolation base is 1.0 Hz or 1.2 Hz. However, when the frequency of the base isolation frame is 0.8 Hz, it is understood that a large base isolation performance can be obtained even when the rotational inertia mass ratio is 0.05. This tendency is almost the same even when the damping constant of the base isolation frame changes. Considering that the frequency and damping constant of the base isolation frame vary depending on the load, the rotational inertial mass ratio should be set in the range of 0.05 to 0.3, more preferably 0.2. It can be seen that effective seismic isolation can be performed.

  As the rotational inertial mass ratio becomes larger than 0.3, the response acceleration of the base isolation frame gradually increases. This is because the inertial force represented by the product of the rotational inertial mass and the relative acceleration of the base isolation frame is It is thought that the response acceleration increased gradually as a result of an increase in the rotational inertial mass ratio and an increase in the relative acceleration of the short-period component that caused the base isolation frame to swing in antiphase with respect to the shaking of the earthquake. Further, when the seismic isolation frequency is 1.2 Hz and 1.0 Hz, the seismic isolation performance is remarkably lowered when the rotational inertial mass ratio is smaller than 0.1, but this is because the rotational inertial mass ratio becomes too small. This is thought to be because the effect on the lengthening of the base isolation cycle (decreasing the base isolation frequency) is reduced. However, when the base isolation frequency is 0.8 Hz, that is, when the base isolation cycle is originally long, a large base isolation performance is maintained even if the rotational inertial mass ratio is as small as 0.05.

[Examination of lead length]
Next, the lead length of the ball screw shaft 24 will be described with reference to FIG.
Here, in the seismic isolation device 100 having the above configuration, the influence of the lead length of the ball screw shaft 24 on the seismic isolation performance was examined as follows.
(1) Study Model In the mechanism that converts the vertical motion of the ball nut 23 into the rotational motion of the ball screw shaft 24, the reverse efficiency (conversion efficiency) η at that time is shown in FIG.
As shown in FIG. 8, the reverse efficiency η varies depending on the lead angle β and the friction coefficient μ. However, as the lead angle β increases, the influence of the friction coefficient μ decreases, and the reverse efficiency η approaches 100%. Recognize.

The relationship between the thrust F of the ball nut 23 and the torque T of the ball screw shaft 24 is expressed by the following equation (2). From this equation, it can be seen that when the conversion efficiency η is small, the ball screw shaft 24 does not rotate unless a large thrust F acts. It can also be seen that the same is true when the lead length L of the ball screw shaft 24 is small.

  Although the motion conversion mechanism 22 is provided between the seismic isolation object 1 and the support structure 2, when a large F is generated in the vertical direction, the force is transmitted to the seismic isolation object 1 and inhibits the seismic isolation performance. Therefore, it is better that the lead angle β and the lead length L are larger.

On the other hand, a disk 21 is fixed to the ball screw shaft 24 and used as a rotary inertia mass body.
The rotational inertia mass ΔM added to the seismic isolation object 1 by the rotation of the disk 21 is expressed by the following equation (3). From this equation, it can be seen that the mass effect decreases in inverse proportion to the square of the lead length L of the ball screw shaft 24.

(2) Examination Results As shown in the equation (2), when the lead angle β of the ball screw shaft 24 is increased, that is, when the lead length L of the ball screw shaft 24 is increased, the vertical movement of the ball screw nut 23 is caused to rotate the ball screw shaft 24. It can be efficiently converted into motion.
On the other hand, as shown in the expression (3), when the lead angle β of the ball screw shaft 24 is made small, that is, when the lead length L of the ball screw shaft 24 is made short, the rotation angle of the disk 21 accompanying the vertical motion of the seismic isolation object 1. Can be increased, and its rotational inertial mass can be increased.

  Here, generally, the conversion efficiency into the rotational motion needs to be 95% or more. Therefore, the vertical movement of the ball screw nut 23 is achieved by setting the lead angle β of the ball screw shaft 24 to 10 degrees or more and 30 degrees or less, more preferably about 17 degrees where the lead length L of the ball screw shaft 24 is substantially equal to the outer diameter of the shaft. Can be efficiently converted into a rotational motion of the ball screw shaft 24, and a reduction in the rotational inertial mass of the disk 21 can be suppressed to achieve effective seismic isolation.

(3) Case study As a case study based on the above examination results, the conversion efficiency of the ball screw shaft 24a with the shaft outer diameter and the lead length approximately equal to each other, and the ball screw shaft 24b with the lead length twice the shaft outer diameter, respectively. consider.
In the case of the ball screw shaft 24a whose shaft outer diameter and lead length are substantially equal, the lead angle β is 17 degrees, and referring to FIG. 8, a conversion efficiency close to 100% can be obtained regardless of the friction coefficient μ.

  In the case of the ball screw shaft 24b whose lead length is twice the outer diameter of the shaft, the lead angle β is 31 degrees. Here, as shown in FIG. 8, since the conversion efficiency has a characteristic of gradually approaching 100% when the lead angle β exceeds a certain level, the conversion efficiency of the ball screw shaft 24 b is not much different from the conversion efficiency of the ball screw shaft 24 a. I can guess.

  On the other hand, if the mounted disk 21 is the same, in the case of the ball screw shaft 24b in which the lead length is twice the outer diameter of the shaft, the mass effect ΔM is the same as the outer diameter of the shaft as shown in the equation (3). The lead length is ¼ of the ball screw shaft 24a which is substantially equal.

Therefore, it is the ball screw shaft 24a that has a shaft outer diameter and a lead length substantially equal to each other that can achieve conversion efficiency close to 100% while suppressing a reduction in mass effect.
The outer diameter of the shaft (more precisely, the cross-sectional area of the shaft) is determined by the axial force acting on the ball screw shaft (= ΔM × relative acceleration). The longer the load of the larger axial force is required, the longer the lead length is. Therefore, the conversion efficiency can be improved.

[Examination of anti-vibration rubber specifications]
Next, the specifications of the anti-vibration rubber 31 will be described with reference to FIGS.
Here, in the seismic isolation device 100 having the above configuration, the influence of the vibration absorption region of the vibration isolating rubber 31 on the seismic isolation performance was examined as follows.

(1) Shaking table test FIGS. 9 and 10 show the results of the shaking table test when the seismic isolation device 100 according to the present embodiment is directly attached to the base isolation frame. FIG. 9 shows the frequency analysis result of the shaking table acceleration wave, and FIG. 10 shows the frequency analysis result of the seismic isolation frame acceleration wave.

  As shown in FIG. 9, the vibration table acceleration has an excellent vibration component of about 5 Hz. On the other hand, regarding the base isolation frame acceleration, as shown in FIG. 10, although the 5 Hz component is reduced to about half, it can be seen that the vibration component of 10 Hz or more is amplified. This is because even if the lead length of the ball screw shaft 24 is substantially equal to the outer diameter of the shaft and the conversion efficiency from linear motion to rotational motion is close to 100%, the conversion is not performed for high vibration components exceeding 10 Hz. Indicates that it cannot be done instantly.

(2) Study model From the results of the shaking table test, it was confirmed that high-frequency components of 10 Hz or more were transmitted to the seismic isolation frame by installing the seismic isolation device 100 of this embodiment. Anti-vibration rubber was selected to remove high-frequency components using an analytical model.

(3) Study Method Response analysis is performed when a sine wave (maximum acceleration = 100 Gal) of 5 Hz, 7.5 Hz, 10 Hz, and 15 Hz is input by changing the spring constant of the anti-vibration rubber 31 in the model shown in FIG. Then, the relationship between the spring constant of the anti-vibration rubber 31 and the response acceleration was obtained. In addition, model specifications at that time are shown in FIG.

(4) Analysis Results FIG. 13 and FIG. 14 show the relationship between the spring constant of the vibration-proof rubber 31 and the acceleration response magnification. Here, FIG. 13 shows the result when the response becomes a steady state after the sine wave input, and FIG. 14 shows the result of the maximum value including the result of the transient state.
As shown in FIG. 13 and FIG. 14, the vibration reduction effect by the vibration isolating rubber 31 can be confirmed. If the vibration isolating rubber 31 reduces the component of 10 Hz or more to half or less, the spring constant K of the vibration isolating rubber 31 is as follows. Is required to be 1500 kg / cm or less. Further, in order to secure walking ability, if the deformation by a person having a weight of 70 kg is suppressed to 0.2 cm or less, the spring constant K of the vibration-proof rubber 31 needs to be 350 kg / cm or more.

The frequency f determined from the spring constant K and the mass M of the seismic isolation object 1 is calculated from the following equation.

Here, since M = 3000/980 = 3.06 kgs ² / cm, the frequency is calculated as follows.
When K = 350kg / cm, f ≒ 1.5Hz
In the case of K = 1500 kg / cm, f≈3.5 Hz
Therefore, it can be seen that if the vibration-isolating rubber 31 having a spring constant such that the seismic isolation object 1 vibrates in the range of 1.5 Hz to 3.5 Hz is selected, a vibration component of 10 Hz or more can be removed. That is, the vertical motion of the seismic isolation object 1 is converted into the rotational motion of the disk 21 by the motion conversion mechanism 22 by the vibration isolating rubber 31 while ensuring the walking ability of the floor surface when the seismic isolation object 1 is a floor. It can be seen that short-period microvibrations that are difficult to do can be absorbed.

[Examination of viscoelastic body specifications]
Next, the specification of the viscoelastic body used in place of the vibration-proof rubber 31 will be described with reference to FIGS.

(1) Study model The viscoelastic body selection for removing the high frequency component of 10 Hz or more was performed using the analysis model of FIG. FIG. 16 shows model specifications. The model specifications shown in FIG. 12 are obtained by replacing the vibration-proof rubber with a viscoelastic body. The viscoelastic body was used at a temperature of 20 ° C., and a material having a loss coefficient ηd defined by the following formula of approximately 1.0 was used.

  Here, C represents a damping coefficient of the viscoelastic body, K represents a spring constant of the viscoelastic body, and ω represents an excitation circular frequency.

(2) Examination method In the model shown in FIG. 15, the spring constant of the viscoelastic body is changed, and a response analysis is performed when a sine wave of 5 Hz, 7.5 Hz, 10 Hz, 15 Hz (maximum acceleration = 100 Gal) is input, The relationship between the spring constant of the viscoelastic body and the response acceleration was obtained.

(3) Analysis Results FIGS. 17 and 18 show the relationship between the spring constant of the viscoelastic body and the acceleration response magnification. Here, FIG. 17 shows the result when the response is in a steady state after the sine wave is input, and FIG. 18 shows the result of the maximum value including the result of the transient state.
As shown in FIG. 17 and FIG. 18, the vibration reduction effect by the viscoelastic body can be confirmed, but if the viscoelastic body halves the component of 10 Hz or more, as the spring constant K of the viscoelastic body, As in the case of the anti-vibration rubber, 1500 kg / cm or less is required. Further, in order to secure walking ability, if the deformation by a person with a weight of 70 kg is suppressed to 0.2 cm or less, the spring constant K of the viscoelastic body needs to be 350 kg / cm or more.

  Since the frequency determined from the spring constant K and the mass M of the seismic isolation object 1 is the same as that of the anti-vibration rubber, it is 1.5 Hz to 3.5 Hz with respect to the seismic isolation object 1. It can be seen that vibration components of 10 Hz or more can be removed if a viscoelastic body having a vibrating spring constant is selected.

  As described above, according to the seismic isolation device 100 according to the present embodiment, the motion conversion mechanism 22 is limited by limiting the rotational inertial mass of the disk 21 to 0.3 times or less the mass of the seismic isolation object 1. Thus, it is possible to suppress the inertial force of the short period component transmitted to the seismic isolation object 1 from Further, by making the rotational inertial mass of the mass body 0.05 times or more that of the seismic isolation object 1, the vertical vibration of the seismic isolation object 1 can be lengthened, and the seismic isolation object 1 is supported. By following the vibration of the structure 2, it is possible to reduce the vertical vibration transmitted to the seismic isolation object 1.

  In this case, more preferably, the acceleration of the seismic isolation object 1 can be reduced by setting the rotational inertial mass of the disk 21 to 0.2 times the mass of the seismic isolation object 1. 1 can be effectively isolated.

  Further, the motion converting mechanism 22 is a combination of a ball screw shaft 24 and a ball screw nut 23, and the lead angle of the ball screw shaft 24 is 10 degrees or more and 30 degrees or less, more preferably, the lead length of the ball screw shaft 24 is substantially equal to the diameter. By setting the degree to about 50 degrees, the vertical motion of the ball screw nut 23 can be efficiently converted into the rotational motion of the ball screw shaft 24, and the reduction of the rotational inertial mass of the disk 21 can be suppressed and effective seismic isolation can be performed. .

Moreover, the vibration damping effect of the seismic isolation object 1 can be obtained by braking the rotation of the disk 21 by the brake mechanism 40. Thereby, even when the rotational inertial mass of the disk 21 is small, the vibration in the vertical direction of the seismic isolation object 1 can be effectively reduced.
In addition, by braking the rotation of the disk 21 by the brake mechanism 40, the vertical motion of the seismic isolation object 1 can be suppressed, and when the seismic isolation object 1 is a floor, the walking performance of the floor surface is improved. be able to.

  Further, a vibration isolating rubber or a viscoelastic body having a vertical frequency of 1.5 to 3.5 Hz is provided between the seismic isolation object 1 and the mass addition mechanism 20. Thus, when high-frequency vibration (for example, vibration of 10 Hz or more) that is difficult to be converted into the rotational motion of the disk 21 by the motion conversion mechanism 22 is generated, the vibration is absorbed and the base isolation object 1 is isolated. In addition, the walking ability of the floor surface when the seismic isolation object 1 is a floor can be ensured.

  In addition, the spline mechanism 30 holds the seismic isolation object 1 so as to be movable in the vertical direction, and restrains the movement in the horizontal direction, so that the anti-vibration rubber 31 that is weak against the load in the horizontal direction, the motion conversion mechanism 22, and It is possible to prevent a horizontal load from being applied to the air spring 13.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.
For example, in this embodiment, although the example which provided one seismic isolation apparatus with respect to the seismic isolation object 1 was demonstrated, it is good also as providing multiple seismic isolation apparatuses with respect to the seismic isolation object 1. In that case, what is necessary is just to make the total rotational inertia mass of the disk 21 in each seismic isolation device 0.05 times or more and 0.3 times or less of the mass of the seismic isolation object 1.

  In the present embodiment, the mass body rotated by the motion conversion mechanism 22 is described as the disk 21. However, the inertial mass involved in the vertical motion of the seismic isolation object 1 is increased by generating a rotational inertia moment. The mass body to be rotated may be rod-shaped or plate-shaped.

  In the present embodiment, the seismic isolation object 1 has been described as being supported by the air spring 13. However, any object having a restoring force and capable of supporting the seismic isolation object 1 may be used. For example, rubber Alternatively, a coil spring may be used.

DESCRIPTION OF SYMBOLS 1 Seismic isolation object 2 Support structure 13 Air spring 20 Mass addition mechanism 21 Disk 22 Motion conversion mechanism 23 Ball screw nut 24 Ball screw shaft 30 Spline mechanism 31 Anti-vibration rubber 40 Brake mechanism 100 Seismic isolation device

Claims (6)

A seismic isolation device that supports a seismic isolation object and reduces vertical vibration transmitted to the seismic isolation object,
A mass body that is rotatable in a horizontal plane;
A motion conversion mechanism for converting a vertical motion acting on the seismic isolation object into a rotational motion of the mass body;
A seismic isolation device in which the rotational inertial mass of the mass body is 0.05 to 0.3 times the mass of the seismic isolation object.   The motion conversion mechanism is a combination of a ball screw shaft and a ball screw nut, and one of the ball screw shaft and the ball screw nut is provided in the seismic isolation object, and the other is provided in the mass body. 1. The seismic isolation device according to 1.   The seismic isolation device according to claim 2, wherein a lead angle of the ball screw shaft is 10 degrees or more and 30 degrees or less.   The seismic isolation device according to any one of claims 1 to 3, further comprising a braking mechanism that brakes rotation of the mass body.   The anti-vibration rubber | gum and viscoelastic body in which the frequency of the vertical direction of the said seismic isolation object becomes 1.5 Hz or more and 3.5 Hz or less are provided between the said seismic isolation object and the said motion conversion mechanism. The seismic isolation device according to claim 4. The seismic isolation device according to any one of claims 1 to 5, further comprising a vertical movement guide that holds the seismic isolation object movably in a vertical direction and restrains a movement in a horizontal direction.

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