JPH02118226A - Dynamic vibration absorbing device - Google Patents

Abstract

PURPOSE:To reduce natural frequency without increasing the static deflecting quantity of springs and easily regulate the natural frequency, and improve the quality and performance of the title device by putting a vibrator in a liquid vessel and enabling a water contacting range to be adjusted. CONSTITUTION:A vibrator 4 is supported by a supporting base 7 with a liquid vessel which is fixed to a main system 1 via springs 5 and a part of the vibrator 4 is immersed in the liquid in the supporting base 7 with liquid vessel. The portion in the liquid of the vibrator is adjusted in the position of a water level 10. Hence, the regulation of natural frequency like reducing the natural frequency without increasing the static deflecting quantity of a spring can be easily carried out to improve the quality and performance of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dynamic vibration damping device that is applied to damping vertical vibrations and horizontal vibrations of a ship's accommodation structure or propulsion engine. The present invention is also applicable to damping vertical vibrations and horizontal vibrations of land structures such as bridges and observation platforms.

[Prior Art] The basic structure of a dynamic vibration absorber, which has been conventionally known as one of the means for suppressing structural vibration, is that a vibrator 4 is supported by a spring 5, as shown in FIG. Main system (vibration structure) 1
is combined with

[Problem to be solved by the invention] As shown in Fig. 3, the action of the dynamic vibration reducer is as follows: When the natural frequency ND of the dynamic vibration absorber is made to match the frequency NR of the excitation force, the vibration of the main system 1 is Although it decreases from the solid line 8 to the broken line 9, adjusting the natural frequency ND of the dynamic vibration absorber requires changing the weight of the vibrator 4 and the rigidity of the spring 5, which is not easy to do.

Furthermore, in order to lower the natural frequency ND of the dynamic vibration reducer, it is necessary to increase the amount of static deflection of the spring 5, which raises concerns about the strength of the spring 5.

[Means for Solving the Problem] A dynamic vibration absorber according to the present invention is a dynamic vibration absorber that absorbs vibrations using a vibrator supported by a spring, in which the vibrator is placed in a liquid tank and a part of the vibrator is Along with immersing it in liquid,
It is characterized by being able to adjust the water contact range of the vibrator.

[Function] In the dynamic vibration absorber of the present invention, by changing the water contact range of the vibrator, the additional water mass Δm related to the vibrator changes. The natural frequency ND of the dynamic vibration absorber is given by the following formula, so by changing the additional water mass Δm, the natural frequency N can be changed. can be adjusted. If the mass of the vibrator is mDs and the stiffness of the spring is kD, then ND-kD, mD+Δm/2yr...(1) Next, when lowering the natural frequency Np of the dynamic vibration reducer,
In conventional dynamic vibration absorbers, the mass mD of the vibrator is increased, or
Since the spring stiffness kD had to be reduced, the static deflection of the spring ink d ST was increasing.

However, in the case of the dynamic vibration absorber of the present invention, it is sufficient to increase the additional water mass Δm in equation (1), and therefore the water level is raised, so the buoyant force acting on the vibrator increases. Therefore, in the case of the dynamic vibration reducer of the present invention, the static deflection ff1dsT of the spring tends to decrease.

In addition, fluctuating water pressure generated by vibrations generated in the vibrator via the fluid acts on the main system. Here, if the vibration amplitude of the main system is expressed as X9 hours/minutes, then the fluctuating water pressure acting on the main system is proportional to one, so the damping force kD-X of the dynamic vibration absorber can be increased.

(Example〕 Embodiments of the present invention are shown in FIGS. 1 and 2.

FIG. 1 shows a dynamic vibration absorber for vertical vibrations as a first embodiment of the present invention, and FIG. 2 shows a dynamic vibration absorber for horizontal vibrations as a second embodiment of the present invention. The direction of vibration is indicated by an arrow in each figure. In the case of the vertical vibration shown in Figure 1, the additional water mass Δm is proportional to the square of the width of the vibrator at the water level 10 position, so if the shape of the vibrator 4 is made as shown in Figure 1, the water level By moving 10, the additional water mass Δm can be gradually changed. Furthermore, since the same buoyant force as the weight of the fluid removed by the submerged portion of the vibrator 4 acts on the vibrator 4, an increase in the amount of static deflection of the spring 5 can be suppressed.

Furthermore, as mentioned above, the same phase force as the force acting through the spring 5 acts on the main system 1 through the fluid 6, so the vibration damping force of the dynamic vibration absorber is increased compared to the conventional dynamic vibration absorber. There is a tendency to

In the case of the horizontal vibration in FIG. 2, the additional water mass Δm is proportional to the stuttering of the vibrator at the water level 10 position, so no special design is required for the shape of the vibrator as in the vertical vibration. Similarly to the vertical vibration, the natural frequency ND of the dynamic vibration absorber can be easily determined.
Since it is possible to adjust the damping force and increase the damping force, it is possible to improve the performance as a dynamic vibration absorber.

[Effects of the Invention] Since the present invention is configured as described above, it produces the following effects.

(1) By disposing fluid (water) between the main system of the dynamic vibration absorber of the present invention and the dynamic vibration absorber and changing the amount of water, the natural frequency of the dynamic vibration absorber can be easily adjusted.

(2) The natural frequency can be lowered without increasing the amount of static deflection of the spring.

(3) Furthermore, since the force acting on the main system can be increased, the quality and performance of the product can also be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram (cross-sectional view) of the first embodiment of the present invention, and
The figure is a block diagram (cross-sectional view) of a second embodiment of the present invention, FIG. 3 is an explanatory diagram of the operation of a dynamic vibration absorber, and FIG. 4 is a diagram showing the configuration of a conventional dynamic vibration absorber. DESCRIPTION OF SYMBOLS 1... Main system, 2... Dynamic vibration absorber for vertical vibration according to the present invention, 3... Dynamic vibration absorber for horizontal vibration according to the present invention, 4...
・Vibrator, 5... Spring, 6... Fluid, 7... Support with liquid tank, 8... Vibration response curve of main system without dynamic vibration absorber, 9... Dynamic vibration absorption Vibration response curve of the main system in the case of equipment, 10...Water level Applicant's representative Patent attorney Takehiko Suzue Figure Figure Figure Figure

Claims (1)

[Claims] In a dynamic vibration damping device that absorbs vibrations using a vibrator supported by a spring, the vibrator is placed in a liquid tank, part of the vibrator is immersed in the liquid, and the water contact range of the vibrator can be adjusted. A dynamic vibration absorption device characterized by: