JPS5947175B2 - Vibration isolator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration isolator for vibration-isolating and supporting precision equipment, and more particularly to a vibration isolator that can adjust spring stiffness in the horizontal direction.

When equipment is supported by a vibration isolator, the vibration transmission rate (Tr) between the equipment and the floor is expressed by the following equation.

1 → 7 lower Tr = fn However, f: Frequency of floor vibration fn: Natural frequency of vibration isolator As shown in the above formula, it is necessary to reduce the value of fn to lower the vibration transmissibility. .

In general, fn = 2 to 10 (Hz), but if the equipment to be vibration-isolated is, for example, precision equipment such as IC, LSI manufacturing equipment, electron microscopes, or bolography equipment, fn may be adjusted upward, downward, or horizontally. It is required that fn is 2 Hz or less in both directions.

Conventionally, in order to meet such requirements, as shown in Fig. 1, an air spring 1 was used and a plurality of anti-vibration rubbers 2 were attached to the bottom of the additional tank 1a of this air spring. .

Adding an air spring A vibration-proof rubber is attached to the bottom of the tank.
This is especially to reduce the natural frequency in the horizontal direction.
With this structure, it is difficult to set its natural frequency to 2 Hz or less.

This is because in order to set the natural frequency low, the spring constant of the vibration isolator must be set small, but in the above structure, the height of the additional tank of the air spring must be increased, or the vibration isolator must be The installation position must be close to the axis of the additional tank, which impairs the stability of the equipment on the air spring and creates a risk of it falling over.

The present invention has been made in consideration of this point, and an object of the present invention is to provide a vibration isolating device that can set a particularly low natural frequency in the horizontal direction.

The invention will be explained below with reference to embodiments shown in the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention. In the figure, an air spring 10 is formed by connecting an air spring main body 10a and an additional tank 10b forming an air chamber thereof.

The additional tank 10b of the air spring 10 is fitted into a container 11 with an open top, and its bottom is lifted up by a hanging shaft 13 swingably suspended from an inner protrusion 12 at the top of the container 11.

The hanging shaft 13 is secured to the inner protruding edge 12 of the upper part of the container with a nut 14, and is suspended such that its lower end can freely rotate.

The natural frequency fn in the above configuration is expressed by the following equation.

Further, the damping liquid 15 is poured into the container 11 to the extent that the bottom of the additional tank 10b is immersed therein.

This damping liquid 15 is used to damp the shaking of the additional tank 10b as quickly as possible, and is preferably silicone oil, for example.

The vibration isolator having the above configuration was tested under the following conditions.

Length l of zero-hanging shaft: 37.8cm Moment of inertia I of zero-hanging shaft: 6.36X04M 〇Young's modulus E: 2. I x 106F'=Q/c
rrtO tower mass m: 0.82Kg・s e c2/c
In the m theoretical formula, when substituted into the above formula, fn'': 1.004 (Hz) The actual measurement result is almost the same value as the theoretical value, fn' = 1.1 (Hz).

When the vibration isolating device of the above embodiment is used, 3 to 4 units are arranged at appropriate intervals for the precision equipment to be supported with vibration isolation, and a surface plate support ( (not shown) are arranged.

As described above, according to the vibration isolating device of the present invention, since the air spring is suspended with the bottom raised, the installation state of the air spring is stable and there is no risk of it falling over, and moreover, the required natural frequency is can get.

Moreover, since the structure is simple, it can be constructed at low cost.

In addition, when damping liquid is placed in the container, the resonance magnification of the resonance frequency becomes smaller, and the shaking time of the air spring can be shortened, making it easier to operate precision equipment that is supported with vibration isolation. make it easier.

Furthermore, by appropriately adjusting the amount of damping fluid injected, the natural frequency and swing time can be adjusted.

Although ordinary water may be used as the damping liquid, for example, when silicone oil having a viscosity of 10,000 to 100,000 centistokes is used, the following advantages can be obtained.

■ Viscosity is stable due to very little change in viscosity due to temperature.

■It has low vapor pressure, low volatility, and is odorless, so there is no environmental pollution in the cream room for IC and LSI manufacturing.

[Brief explanation of drawings]

FIG. 1 is a front view showing a conventional vibration isolator, and FIG. 2 is a partially longitudinal front view showing an embodiment of the vibration isolator according to the present invention. 10...Air spring, 10a...Air spring body, 10b...Additional tank, 11...
...Container, 13... Hanging shaft, 15...
...damping fluid.

Claims (1)

[Claims] 1. An additional tank equipped with an air spring is fitted into a container with an open top, and the bottom of the additional tank is lifted by a hanging shaft swingably suspended from the top of the container. Anti-vibration device. 2. The vibration isolating device according to claim 1, wherein the damping liquid is injected into the container to a height such that the bottom of the additional tank is immersed therein. 3. The vibration isolating device according to claim 2, which uses silicone oil as the damping fluid.