JPH0366944A - Damping device - Google Patents

Abstract

PURPOSE:To select the most suitable constant of springs at a real time by providing a cylindrical spring element formed enclosing a magnetic fluid in a cylinder and a coil to control the constant of the springs of the afore- mentioned spring element. CONSTITUTION:A vibration body 1 is arranged through a floor 8 and a spring 7, and the floor 8 furthermore forms a vibrating system to be arranged through a base 20 and a spring 9. There are a great number of fine bubbles 17 of less than the number mu scattered in a magnetic fluid 5 inside a piston cylinder 3. An angular velocity omega of an external force or a vibromotive force working upon a vibrating body 1 is detected by a vibration sensor 11 and a vibration analyser 12. The amount io of an electric current to give a spring constant of the magnetic fluid 5 is computed by a computer 13. A mass 6 and a piston 2 and the magnetic fluid 5 oscillate by way of flowing an electric current to a coil 4 by an electric current controller 14. Consequently, it is possible to absorb the vibration of the vibrating body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vibration damping device I applied to a dynamic vibration absorbing device such as a vibration table, a vibration excitation device, a vibration absorption table, and a rotating machine.

[Conventional technology]

Conventional vibration damping technology supports the vibrating body with mechanical springs (or dampers) and selects the ratio of the natural frequency of this system to the frequency of the external force to damp the vibration of the vibrating body or suppress the vibration. Techniques for preventing transmission are well known. In addition, technologies such as dynamic vibration absorbers and dynamic dampers that absorb vibration energy and dampen vibrations by attaching vibration absorbers with a natural frequency that matches the frequency of external force to vibrating bodies are in practical use.

[Problem to be solved by the invention]

The characteristics of vibration systems such as vibration absorbers that prevent the transmission of vibration from the machine to the foundation and absorb the vibrations of the machine itself are determined by elements such as mass, spring constant, damping constant, and the frequency of the external force, and the purpose of vibration suppression is Techniques for determining the values of these elements according to the conditions have been in practice for a long time. Furthermore, since these elements can only take fixed values in the vibration system, vibration damping is effective only for a specific frequency of external force, and vibration damping may become insufficient if the frequency of external force changes. In some cases, the vibration may even increase.

The reason for this is that the values of the elements that determine the vibration characteristics, such as mass, spring constant, and damping constant, cannot be easily controlled as described above. For example, it is not possible to change the spring constant of a vibration system without changing the number of springs installed on a machine stand or increasing or decreasing the number of springs.

In particular, if the most important spring that determines the vibration characteristics can be easily and quickly changed using an external signal, it is easy to infer that an excellent vibration suppressor that can cope with any frequency change Iζ of external force can be provided. An object of the present invention is to solve the above-mentioned conventional problems and provide a vibration damping device that can easily change the spring constant in real time.

[Means to solve the problem]

The vibration damping device according to the present invention includes: (1) a cylindrical spring element formed by enclosing a magnetic fluid in which microbubbles are dispersed in a fluid;
0(2) A damping spring Iζ has a fixed mass; means for calculating the natural frequency from the spring constant of the element; means for measuring the frequency of the external force acting on the damped body; It is characterized by comprising means for calculating a target value.

That is, in the present invention, for example, a liquid in which fine magnetic powder is dispersed in a non-Nineton fluid such as pseudoplastic fluid or Bingham fluid in which fine air bubbles are dispersed is sealed inside a cylinder, and the cylinder is strengthened from the outside. A magnetic field that can be made variable is applied, a current is controlled to select the strength of this magnetic field, a mass is fixed on the piston, the natural vibration of the system is calculated using the current as a parameter, and the frequency of the external force is measured. , the appropriate natural frequency is adjusted to the current value Iζ from the values of these frequencies.

[Effect]

Generally, a fluid has incompressible properties, but according to the present invention, by sealing fine air bubbles into a cylinder, it becomes compressible and can be used as a spring element.

By using Bingham fluid or plastic fluid as the fluid, separation from the liquid due to rising of bubbles can be prevented. In addition, by enclosing a fine magnetic powder and making this fluid a magnetic fluid, the spring constant can be determined by the strength of the magnetic field applied to it, and the spring constant can be easily and quickly changed depending on the strength of the magnetic field. become. The strength of the magnetic field can be easily changed by providing a 1ζ coil outside the cylinder and controlling the value of the current flowing through it. If an appropriate mass is fixedly installed on the piston, the natural frequency of the mass-piston spring system is determined by the mass and the spring constant, so the natural frequency can be controlled extremely easily by external current using such a spring element. It is obvious that it can be done. Therefore, when the frequency of the external force is known using a vibration meter and an analyzer, the natural frequency along the nine points of IffJ vibration can be determined by selecting an appropriate current value from Iζ. That is, according to the present invention, an appropriate vibration damping system according to the frequency of external force can be automatically realized in real time, and the function of the vibration damping device can be dramatically improved0. This is a diagram showing one embodiment, in which a vibrating body 1 is arranged via a floor 8 and a spring 7, and the floor 8 is further arranged via a foundation 10 and a spring 9, forming a vibration system. Vibrating body here! Above is the cylinder 3 and the coil 4 wound around it.
A dynamic vibration absorber is placed, consisting of a piston 2, a mass W6 connected to the piston 2, and a magnetic fluid 5. The vibration sensor 11 and the vibration analyzer 12 detect the angular velocity ω of the external force or excitation force acting on the vibrating body l, and the calculator 13 adjusts the magnetic field so that the natural frequency of the spring-mass system of the mass 6 matches ω. The strength of the magnetic field that gives the spring constant k of the fluid 5, that is, the magnitude of the current 1. Calculate. This is =−ω”, k=k
It can be uniquely selected from the relationship (i,). Thus, when the current controller I4 causes a current of i=1° to flow through the coil 4, the mass 6, the piston 2, and the magnetic fluid 5 resonate, and the vibrations of the vibrating body 1 can be absorbed.

FIG. 2 is a diagram showing details of the magnetic fluid 5 inside the piston 2 and the cylinder 3. In the magnetic fluid 6, a large number of microbubbles I7 of several micrometers or less are dispersed. It is obtained by blowing air into the interior through a fine nozzle. Furthermore, fine magnetic substances are also mixed into the fluid. The fluid used is a Bingham fluid or a plastic fluid (such as a melt of delicate ester or polymer material) having characteristics such as the shear rate r and shear force τ as shown in FIG. A microfluid with a buoyancy of T6- or less is dispersed in the liquid without floating up. The spring constant can be selected to some extent depending on the proportion of air bubbles mixed in. In other words, a liquid with a high rate of air bubbles has a weak initial spring constant.

Figure 4 shows the relationship between the current strength i (or magnetomotive force ni: ni mini n microcoil or magnetic field H) and the spring constant. The effect restricts the movement of the bubbles contained therein, resulting in a large spring constant.The present invention has the advantage that the spring constant of the magnetic fluid sealed in the cylinder can be freely selected depending on the strength of the magnetic field, that is, the current. Because of this, the natural frequency of the mass-spring system can be automatically changed in real time, so even if the angular velocity ω on the excitation side changes, efficient damping can always be performed.

In the above embodiments, a dynamic vibration absorber has been described, but the present invention is not limited to this. For example, the dynamic vibration absorber can be installed between a rotating machine and a floor to reduce the transmission of vibration force and avoid dangerous rotation. Needless to say, the present invention can also be applied to a traversal vibrator such as the above, or, on the contrary, a device that vibrates an object.

〔Effect of the invention〕

Conventionally, the spring constant of a vibration system could only take a fixed value, but according to the present invention, the optimal spring constant can be automatically selected in real time, making it possible to always provide an optimal vibration damping system. effective.

As a result of such technical effects 1, effects such as improved safety such as improved reliability and reduced vibration and noise can be obtained.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a system configuration according to an embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of the magnetic fluid in FIG. 1.
FIG. 3 is a diagram showing the relationship between fluid shear velocity t and shear force 1, and FIG. 4 is a diagram showing the relationship between magnetomotive force n1 and spring constant. ! ... Vibrating body, 2... Piston, 3... Cylinder, 4... Coil, 5... Magnetic fluid, 6... Mass,
11... Vibration sensor, I2... Vibration analyzer, I3.
...Arithmetic unit, 14...Current controller. 18. Fine powder magnetic material

Claims (2)

[Claims] (1) A cylindrical spring element in which a magnetic fluid made by dispersing microbubbles in a fluid is sealed in a cylinder; A vibration damping device characterized by comprising a controlling coil. (2) a mass fixed to a vibration damping spring, a means for calculating a natural frequency from a spring constant of the spring element, a means for measuring the frequency of an external force applied to the damped body, and a means for calculating the frequency of each of the vibrations. 2. The vibration damping device according to claim 1, further comprising means for comparing the numbers and calculating a target value of the current for instructing a change in the natural frequency.