JPH0552235A - Viscous damper - Google Patents

Abstract

PURPOSE:To provide a viscous damper with which the sufficient vibration suppressing effect can be obtained in the ordinary use and the damping effect can be obtained surely even in case of the large vibration in the resonance point passing or in an earthquake. CONSTITUTION:A viscous damper is equipped with a cylinder 11 in which the working fluid 15 having viscosity is accommodated and a piston 12 which slidingly moves in the axial direction in the cylinder 11. The relative vibration along the axial direction of the cylinder 11 and the piston 12 is attenuated by the transfer resistance of the working fluid 15. The fluid 15 is a magnetic fluid. A magnet 17 for magnetizing the magnetic fluid 15 is installed on the peripheral wall side of the cylinder 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a viscous damper applied to various plant equipment and other equipment for vibration isolation.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
As an anti-vibration support device for the on-board device 2, there is known a device in which an elastic support member 3 such as rubber or a spring and a viscous damper 4 are installed in parallel.

In this case, the viscous damper 4 is generally constituted by a cylinder containing a working fluid having a viscosity and a piston sliding in the cylinder in the axial direction. A fluid having a high viscosity such as oil is used as the fluid, and the cylinder or the piston is
A flow path is provided that connects the cylinder chambers at both ends in the axial direction to each other.

When, for example, an earthquake or other vibration occurs, the relative vibration along the movement of the cylinder and the piston in the axial direction is damped by the accompanying movement resistance of the working fluid.

[0005]

In the above-mentioned conventional viscous damper, since the viscous resistance due to the fluid in the cylinder is uniform, the damping coefficient of the viscous damper is substantially constant regardless of the vibration amplitude. Is becoming Therefore, for example, there is a problem that excessive vibration occurs when passing through the resonance point, or conversely, if the setting of the resonance point is changed to avoid this, a situation in which sufficient vibration damping effect cannot be obtained during normal use, etc. It was

The present invention has been made in consideration of such circumstances, and it is of course possible to obtain a sufficient vibration-proof effect during normal use, and also a reliable damping effect even when passing through a resonance point or during a large vibration such as an earthquake. An object of the present invention is to provide a viscous damper that can obtain

[0007]

In order to achieve the above object, the present invention comprises a cylinder containing a viscous working fluid, and a piston that slides in the cylinder in the axial direction. In a viscous damper that attenuates relative vibration along the movement along the axial direction with a piston by the movement resistance of the working fluid accompanying it, the fluid is a magnetic fluid, and the magnetic fluid is magnetized on the peripheral wall side of the cylinder. A feature is that a magnet is provided.

Preferably, the magnet is arranged so as to be separated from the neutral position of the piston in the axial direction, and the position can be adjusted in the axial direction. More preferably, the magnet is a permanent magnet and has a split structure.

[0009]

The inventor has investigated the above-mentioned conventional problems. As a result, the following was revealed. That is, the damping force R of the viscous damper is given by v, where v is the relative movement speed between the piston and the cylinder.

[0010]

## EQU1 ## R = cv is represented by (1). Here, c is a viscous damping coefficient determined by the dimensions of the piston and the cylinder and the viscosity coefficient μ of the fluid. From this equation (1), it can be seen that the damping force R when the viscous damper vibrates increases in proportion to the relative moving speed v between the piston and the cylinder.

In the vibration-damping support device shown in FIG. 2, the mass of the device 2 is M, the spring constant of the elastic support member 3 is K, the viscous damping coefficient of the viscous damper is c, and the external force F = Psin ωt is applied to the device 2. Consider the case where the periodic force of is applied in the x direction. At this time, the maximum value Ps of the force transmitted to the support base 1 is

[0012]

[Equation 2]

Ps / obtained by the above equation (2)
P is called the force transmissibility, and is the natural frequency ω _{0 of the} system.
When the ratio of the vibration force to the frequency ω of the exciting force is plotted on the horizontal axis, the curve shown in FIG. 3 is obtained using the damping coefficient ratio ζ as a parameter. Therefore, as the vibration isolation direction, ω / ω ₀ is Design the anti-vibration system so that it is as above. As you can see from Figure 3,

[0014]

[Equation 3] Then, the larger the damping coefficient ratio ζ, the smaller the transmissivity,

[0015]

[Equation 4] Then, the smaller the damping coefficient ratio ζ, the smaller the transmissivity, The damping coefficient ratio ζ has an inverse effect on the transmissibility with the boundary being. When considering vibration isolation with the device 2 as a rotating machine, the unbalanced force remaining in the rotor is the excitation force, and its frequency is

[0016]

[Equation 5] However, when the rotation speed increases or decreases,

[0017]

[Equation 6] Therefore, large vibration will occur depending on the selection of the damping coefficient ratio ζ. Therefore, if the required damping coefficient ratio ζ is selected, there is a drawback that the vibration isolation performance in rated operation is deteriorated. In some cases, the vibration control system ω ₀ must be selected in the seismic frequency region, and in such a case, there is a drawback that large vibration occurs during an earthquake. Therefore, the inventor solves the irrational fact that, if the viscosity of the fluid in the piston-type viscous damper is partially changed, the conventional vibration damping effect, which is generated due to the constant damping coefficient of the fluid, cannot be obtained. The idea was that it would be possible to do so, and the focus was on the use of magnetic fluids and magnets as means.

That is, it is known that the viscosity coefficient of a magnetic fluid generally increases in a magnetic field. Based on this, as described above, the present invention uses a magnetic fluid as the fluid contained in the cylinder, arranges a magnet on the side wall of the cylinder, and changes the damping coefficient depending on the location by setting the magnet position. Is.

According to this structure, even with the viscous damper using the same fluid, the viscosity of the necessary portion can be increased by the magnet, so that sufficient vibration isolation performance can be set in the rated operation range. At the same time, a sufficient vibration damping effect can be obtained even during a large vibration.

In particular, when the magnet is arranged at a position away from the neutral position of the piston, when a small vibration occurs in the normal operating range during rated operation in which the piston operates only at a position close to the neutral position, Since the viscosity coefficient is small, the damping coefficient ratio ζ becomes small, and a sufficient damping effect can be obtained under a good vibration transmissibility. Further, when the vibration becomes large, the position of the magnet is located away from the neutral position of the piston, so that the viscosity coefficient becomes large and the amplification of the vibration can be surely suppressed. In other words, the characteristic of the viscous damper used for the anti-vibration support can be set so that a large damping force is generated when the vibration is large, and excessive vibration can be prevented.
Further, if the position of the magnet can be adjusted in the axial direction, it is possible to set an appropriate damping coefficient ratio ζ according to the type of device, the occurrence state of vibration, and the like.

Further, if the magnets are permanent magnets, the structure is simple and the above-mentioned movable structure can be easily realized. Further, if the magnets are divided structures, the viscous parts can be changed at different places. Can be performed more finely and easily.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the viscous damper according to the present embodiment has a hermetically sealed cylinder 11 whose axial center is arranged in the vertical direction, and a piston which is slidably inserted in the cylinder 11 in the vertical direction. 12 is included. A piston rod 13 integrally projecting downward from the piston 12 is coupled and fixed to a not-shown base stand or the like in an upright state, and a coupling member 14 integrally projecting upward from the upper end of the cylinder 11 is shown in the figure. Not connected and fixed to the upper device (see FIG. 2).

A viscous magnetic fluid 15 is accommodated in the cylinder 11, and the magnetic fluid 15 passes through a groove-shaped magnetic fluid passage 16 formed on the outer peripheral surface of the piston 14 and extending in the vertical direction. The cylinders 11 are allowed to flow into the cylinder chambers 11a and 11b on the upper and lower ends thereof.

On the outer peripheral surface side of the cylinder 11, a pair of upper and lower ring-shaped magnets, for example, permanent magnets 17 are arranged axially separated from the neutral position of the piston 12, that is, located at the upper and lower ends. Are arranged coaxially with the cylinder 11. As a result, the magnetic fluid 15 is magnetized near the upper and lower ends of the cylinder 11. Each of the permanent magnets 17 is configured to be separable, and can be assembled and installed by arbitrarily changing the axial installation position of the cylinder 11.

However, when relative vibration occurs between the equipment to which the connecting member 14 and the piston rod 12 are connected, the base, and the like, the piston rod 13 moves the cylinder 11
Relative vibration occurs in the interior, and vibration damping is performed by the movement resistance of the magnetic fluid 15 accompanying the relative vibration.

In this case, the initial position of the piston 12 is shown in FIG.
As shown in FIG. 2, when the cylinder 11 is located at the substantially central position in the axial direction, while the piston head 12a slides within a range where it does not reach the permanent magnet 17, that is, within a certain range a in the upper part of FIG. Magnetic fluid 1 flowing in fluid passage 16
No. 5 is outside the range of the magnetic field generated by the permanent magnet 17, so that the viscosity does not become particularly large, so the damping force is 5
Is relatively small, which is determined by the shape of the passage 16 and the viscosity coefficient of the magnetic fluid 15 in the normal state.

On the other hand, the vibration is large and the above range a
When the piston 12 enters the position of the permanent magnet 17 beyond the range and vibrates, the magnetic fluid 15 comes to pass through the passage 16 in the region of the magnetic field by the permanent magnet 17.
The viscosity coefficient of 5 becomes large, and the damping force becomes large.

Therefore, in the past, the damping coefficient of the viscous damper was always the same regardless of the amplitude of vibration, so excessive vibration occurs when passing through the resonance point, and conversely, in order to avoid this, sufficient vibration isolation during normal use. In contrast to this, according to the present embodiment, a sufficient damping effect can be obtained with a small damping coefficient during normal use, while in the case of a large vibration such as a resonance point passage or an earthquake, the magnetic fluid 15 The magnetic field increases the viscosity to obtain a reliable damping force, and in any case, the vibration increase can be surely suppressed.

Therefore, according to the configuration of the present embodiment described above, even in the case of the viscous damper using the same fluid, the viscosity of the necessary portion is increased by the permanent magnet 17, so that the rated operation and the large vibration are performed. In any case, there is an excellent effect that a sufficient vibration damping effect can be obtained.

The permanent magnets 17 are used as the magnets because the structure is simple and the movements described above can be performed easily, and it goes without saying that they can be electromagnets. If an electromagnet is applied, the viscosity of the magnetic fluid can be changed variously by adjusting the magnetic force. Further, the magnet is of a divided structure so that it can be moved in the axial direction of the cylinder 11, and it is easy to change the damping coefficient ratio ζ at an appropriate position according to the type of equipment, the state of occurrence of vibration, and the like. However, it is also possible to apply other means of transportation.

[0032]

As described above, according to the present invention, in the piston type viscous damper, the viscous fluid is a magnetic fluid, and a magnetic field is formed on the peripheral wall side of the cylinder to change the fluid viscosity in a certain region. Therefore, it is possible to obtain a sufficient and reliable anti-vibration effect with a small damping coefficient at the normal use position and a large damping coefficient at the time of large vibration.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a vibration isolation system.

FIG. 3 is a graph showing a vibration damping effect.

[Explanation of symbols]

 11 Cylinder 12 Piston 15 Magnetic Fluid 17 Magnet

Claims (1)

[Claims] 1. A cylinder containing a viscous working fluid, and a piston that slides in the cylinder in the axial direction. Relative vibrations of the cylinder and the piston in the axial direction cause movement of the working fluid. In a viscous damper that is attenuated by resistance, the fluid is a magnetic fluid, and a magnet that magnetizes the magnetic fluid is provided on a peripheral wall side of the cylinder.