JPS6353330A - Vertical pendulum type dynamic vibration reducer - Google Patents

Abstract

PURPOSE:To enable a long-period vibration to be damped by providing, on the tip of an arm, which makes a swinging movement by the aid of a supporting shaft on a supporting base, a dead weight, between the arm and the point making a relative motion, a viscoelastic body, and between the other strut and the arm, an elastic body respectively. CONSTITUTION:A dead weight 8 is provided on the tip of an arm 6 which makes a swinging movement by the aid of a supporting shaft 4 on a supporting base 2 which is extended at a structure 1, and an elastic body 12 is provided between a strut 10 and the arm 6, and then, a viscoelastic body 22 is provided between the arm 6 and the neighborhood of the base of the supporting base 2. In addition, a coil spring 14 is placed between a projection 3 which is extended at the structure 1. Thereby, the kinetic energy is converted to the thermal energy so as to be absorbed, and then, the characteristic frequency is adjusted by means of the angle alpha0 between the elastic body 12 and the arm 6, and the period is adjusted by means of the arm length and the spring constant. And therefore, while this device has a miniature and simple structure, it is enabled to damp a long-period vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for suppressing vertical vibrations of a structure such as a fishing bridge.

[Conventional technology]

FIG. 4 is an explanatory diagram showing an example of a conventional cantilever type dynamic vibration absorber. In the figure, 1 is a structure to be damped, 2 is a support provided on this structure 1, 4 is a support shaft interposed between this support 2 and arm 6, and 8 is provided on arm B. A dead weight,
12a is a balance spring spirally provided between the support base 2 and the arm 6.

Next, this operation will be explained. f, M If the relic 1 is considered to be part of a fishing bridge, and is subjected to wind pressure in the lateral direction of the fishing bridge, that is, in the direction perpendicular to the plane of the paper, then the fishing bridge is subjected to strong vertical vibrations due to the Karman vortex. If the period of the natural vibration of the bridge girder matches the period of the Karman vortex generated by the wind, it will resonate and eventually break.

As a preventive measure, the cantilever type dynamic vibration absorber shown in Fig. 4 above is fixed to the bridge girder with its arm A aligned in the same direction, so that the natural frequency of the bridge girder and the natural frequency of the cantilever type dynamic vibration absorber are matched. If this is done, the vibration of the bridge girder will be converted into kinetic energy of the weight 8 of the dynamic vibration absorber, thereby preventing the bridge girder from being destroyed.

Now, if the vibrating portion of this dynamic vibration absorber, such as the arm 6, is to suppress extremely long-period vibration, the period of the dynamic vibration absorber described above will be too short. Therefore, there is a limit to the lengthening of the position of the M weight 8.

The present invention aims to solve the above problems.

[Means for solving problems]

(1) In the vertical pendulum type four-force vibration absorber according to the present invention, a weight provided at the tip of an arm that can rotate in a fan shape via a support shaft on a support stand protruding from the structure, and An elastic body is interposed between a column protruding from the support and the arm, and a viscoelastic body is interposed between the arm and a portion that moves relative to the arm.

(2) In another vertical pendulum type hill shaker according to the present invention, a weight provided at the tip of an arm that can rotate in a nine-shape shape via a support shaft on a support stand protruding from a structure, and an upper Ri [In a vertical pendulum type dynamic vibration absorber in which an elastic body is interposed between a pillar protruding from the relic and the above-mentioned arm, and a viscoelastic body is provided between the above-mentioned arm and a place that moves relative to the above-mentioned structure, An elastic body is interposed between the arm and another support stand protruding from the arm.

[Effect]

(1) In this invention, when the structure vibrates up and down due to wind pressure, etc., the weight provided at the end of the arm attached to the support base via the spindle tries to maintain its current position. Angle α between the arm and the elastic body interposed between the protruding support and the arm.

changes with vibration. A viscoelastic body interposed between the arm and a portion that moves relative to the arm acts to absorb vibrations of the arm. Also, if the angle α0 is made smaller, the natural frequency of this dynamic vibration absorber becomes smaller, and if the position of the weight is changed,
If you change the spring constant of the elastic body, the natural frequency will change.

(2) In another aspect of the present invention, in addition to the effect described in item (1) above, by increasing the tension of the elastic body (tension spring), the natural frequency of this vibration system is further reduced.

[Actual trip 1j] FIGS. 1(a), (b), and (c) are explanatory diagrams of an embodiment of the present invention. In the figure, 1 is the structure to be damped, 2 is a support stand protruding from this structure 1, 4 is a support shaft interposed between the arm 6 and the support stand 2, and 8 is the support of this arm. A weight provided at the end that can be moved from side to side; 10 is a gate-shaped column protruding from the structure 1; 12 is an elastic body (coil spring) engaged between the arms from the top of the column;
1, 11a are engagement points that can adjust the position of this elastic body, 2
2 is a viscoelastic body interposed between the arm 6 and the vicinity of the base of the support base 20, and 20 is a half-moon-shaped circle whose diameter is the engagement point 11 of the elastic body with the support shaft 4, which is the fulcrum of the arm B. arc, 24
is an arrow indicating the vibration direction of the structure 1, and t is an arrow indicating the vibration direction of the structure 1.

is the length of the elastic body 12, α0 is the length of the elastic body 12 and the arm 6
11 is the arm length.

Next, this operation will be explained. The dynamic vibration reducer configured as described above is installed on an F4 structure 1 such as a bridge girder to which vibration is to be allocated.

Assuming that this bridge girder is long from side to side, when the wind is perpendicular to the plane of the paper, a periodic Nakalman vortex is generated on the downstream side. Due to the action of this Karman vortex, the structure 1 undergoes strong vibration in the direction of arrow 24. At this time, if the period of the Karman vortex matches the natural period of structure 1, then I
fi: l-o increases more and more and eventually destroys it.

In order to prevent the structure 1 from vibrating as described above, the vertical pendulum type dynamic vibration absorber according to the present invention is equipped with a device having the same natural frequency as the structure 1, and absorbs the kinetic energy of the structure 1. While converting the energy of weight 8 into 13-force energy, arm 6
and a fixed part of the pond, for example, a part of the support base 2 ((If the interposed viscoelastic body 22 converts kinetic energy into thermal energy and absorbs it, the natural frequency changes. , the period T changes as the spring constant of the elastic body 12 changes.This relationship is shown in the first equation.

However, ■: Rate of inertia of the pendulum g: Acceleration of gravity: When the pendulum is in the rest position, let kto be the length that the spring is actually stretched.

As a result, we were able to invent a vertical pendulum type dynamic vibration absorber that is small and simple in structure, yet is capable of suppressing long-period vibrations.

FIGS. 2(a) and 2(b) are explanatory diagrams showing another embodiment of the present invention. In the figure, 1 to 24. α0 is the first
Same as that in the figure, 3 is a protrusion provided on structure 1, 4 a
r4b is a support shaft provided on the protrusion 3, and 14.14m is an end 7a of the arm 6a provided in the middle of arm B.

This is an elastic body interposed between the support shaft 7b and the support shafts 4a and 4b.

Next, this operation will be explained. This dynamic vibration absorber has a period T which is even longer than that of the dynamic vibration absorber shown in the embodiment of FIG.
This is a device that absorbs vibrations. The equation for the period T of this device is shown in the second equation.

However, β is the spring constant of the main spring, β' is the spring constant of the auxiliary spring, and ' is the actual length of the auxiliary spring when the pendulum is at rest.

Also, a is the length between the support shaft 4 and the support point 11 of the arm 6, a' is the length between the support shaft 4 and the ends 7a and 7b, X' is the distance between the support base 2 and the protrusion 3, Z, / are the ends 7a, 7b and the support shaft 4a
, 4b, and X is the distance between the support base 2 and the gate-shaped column 10.

As can be understood from equation (2) above, it can be seen that the period is longer than that of the embodiment shown in FIG.

3(a) and 3(b) are actual design drawings of the groove bottom of the embodiment shown in FIGS. 2(a) and 2(b).

Since the symbol numbers and operations in the figures are the same as or equivalent to those shown in FIGS. 2(a) and 2(b), their explanations will be omitted. Although the viscous damper is not shown in this figure, it is effective if it is interposed between members that move relative to each other due to vibration.

What is common to all of the embodiments shown in FIGS. 1 to 5 is that when the natural period of the structure 1 whose vibration is to be damped is known, to is shown in the figure.

α6 r H+ a, &', It is a good idea to set the value indicated by the symbol at the bottom so that it can be adjusted at any time on site. ◎ At that point, it is extremely easy to move the weight 8 to the left or right, but when the M pulls, etc. An adjustment device may be provided.

〔Effect of the invention〕

(1) As explained above, in this invention, it is common knowledge that a weight is provided at the tip of an arm provided in X parallel to the structure whose vibration is to be damped, and a weight is provided between the arm and the support provided protruding from the structure. An elastic body (0-il spring) that can adjust the mounting angle is provided on the arm, and a viscoelastic body is also provided between the arm and the member that moves relative to it, resulting in a small and simple structure, but a relatively long-period vertical pendulum type. We were able to obtain a dynamic vibration absorber.

(2) According to another aspect of the present invention, an elastic body 14.
14a, it was possible to obtain a dynamic vibration absorber with a longer period than the dynamic vibration absorber of the embodiment shown in FIG.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are explanatory views of one embodiment of the present invention, and FIGS. 2(a) and (b) show another embodiment of the present invention. (a) is a plane view. Figure, (b) is a front view,
FIGS. 3(a) and (b) show (a) l-! of the dynamic vibration absorber according to the invention shown in FIGS. 2(a) and (b). ,Plan view,
(b) is a front view, and FIG. 4 is an explanatory diagram of a conventional vertical pendulum type dynamic vibration absorber. In the figure, 1 is a structure, 2 is a support base, 4 is a support shaft, 6 is an arm, 8 is a weight, 10 is a column, 12 is an elastic body, 20 is an arc, 22 is a viscoelastic body, 6 is a protrusion, α. is the angle and H is the arm length. In addition, in each case, the giant 1 symbol indicates the same or equivalent part. Agent Patent Attorney Masaru Sato Figure 1 (a) (b) 1: Lid cutter 2: Support a 4: Support shaft 6 ：Arm 2nd figure 7a, 7b gong evil 4th figure 6・Ryo-to 3rd figure 6.6a: Arm 7a, 7b: Shimu

Claims (2)

[Claims] (1) An elastic force is provided between a weight provided at the tip of an arm that can rotate in a fan shape via a spindle on a support stand protruding from the structure, a column protruding from the structure, and the arm. interpose the body,
A vertical pendulum type dynamic vibration absorber, characterized in that a viscoelastic body is interposed between the arm and a portion that moves relative to each other. (2) An elastic force is provided between a weight provided at the tip of an arm that can rotate in a fan shape via a spindle on a support stand protruding from the structure, a column protruding from the structure, and the arm. interpose the body,
In a vertical pendulum type dynamic vibration absorber in which a viscoelastic body is provided between the arm and a point that moves relative to the arm, an elastic body is interposed between the arm and another support stand protruding from the structure. A vertical pendulum type dynamic vibration absorber featuring: