JPS584219B2 - Boushin Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration isolator, and more particularly to a vibration isolator that has an extremely small natural frequency and can exhibit a sufficient vibration isolating effect even against low frequency disturbances.

The vibration model of a vibration isolator using a normal linear spring is the first one.
As shown in the figure, the sum of the mass of the vibration isolating table of the vibration isolating device and the mass of the machine to be vibration-proofed, such as a precision measuring instrument placed on it, is M, and the weight of the support spring of the vibration isolating table is The spring constant is k, the fluid friction is λ, and the disturbance from the foundation is x in the direction of the arrow in Figure 1.
0 and the movement of the shaking table is x, the following equation (1) holds true.

Mx+λ(x-x0)+k(x-x0)=0(1)(1
), as usual, x0=x0sinωt, x=Xs
Find the vibration transmissibility of the displacement of the vibration isolation table (hereinafter simply referred to as vibration transmissibility) X/X0 as in(ωt-ψ) (X0, where X is the total amplitude, ω is the disturbance frequency, and ω is the phase lag angle). And so.

The relationship between the vibration transmissibility X/X0 expressed by the above equation (2) and the disturbance frequency ω is shown in a graph as shown in FIG.

As is clear from Figure 2, the vibration transmissibility is almost 1 when the frequency ω of the disturbance is smaller than the natural frequency ωn, and conventional vibration isolators are It has no anti-vibration effect against external disturbances.

In order to reduce the natural frequency ωn, it is clear from equation (3) that the spring constant k should be reduced, but the initial deflection (sinking amount) of the vibration isolation table must be kept below a certain limit. , the spring constant k cannot be made very small.

An object of the present invention is to provide a vibration isolating device in which the initial deflection of a vibration isolating table is not excessive and the natural frequency is extremely low, thereby achieving a vibration isolating effect even against extremely low frequency disturbances. With the goal.

In order to achieve the above object, the present invention elastically supports a vibration isolating table on which a machine to be vibration-isolated is placed on a foundation surface via a support elastic body, and also supports the vibration isolating table and the foundation surface. A compressed first auxiliary elastic body separate from the support elastic body is placed between the fixed one support member and the vibration isolator and another support member fixed to the foundation surface. , a second compressed auxiliary elastic body, which is separate from the elastic body and which is paired with the first auxiliary elastic body and is arranged in a relational position so as to sandwich the vibration isolating table together with the first auxiliary elastic body, is sheared during expansion and contraction, respectively. The first and second auxiliary elastic bodies are provided in such a way that they are not affected by vibration or bending, and when the vibration isolating table is in a static equilibrium state, the expansion and contraction directions of both the first and second auxiliary elastic bodies coincide with the expansion and contraction direction of the supporting elastic body. It is characterized in that the vertical component of the elasticity of the auxiliary elastic body and the restoring force of the supporting elastic body cancel each other out when the vibration isolating table is displaced from the above-mentioned balanced state. .

Embodiments of the present invention will be described below with reference to FIGS. 3 to 10.

In FIG. 3, the reference numeral 1 indicates a vibration isolating table, and this vibration isolating table 1 has a machine to be vibration-proofed, such as a precision measuring instrument P, etc., mounted on the upper surface, and a long and narrow protrusion with a rectangular cross section on the lower surface. It is a plate-like member with a T-shaped cross section, which is integrally formed with two parts.

This anti-vibration table 1 is installed on the foundation surface B via a plurality of telescopic guide posts 3, 3 provided at the corners of the lower surface, and each guide post 3 receives the load of the anti-vibration table 1. A support elastic body 4 (the illustrated one is a coil spring; hereinafter referred to as a support coil spring) is wound.

Therefore, the vibration isolating table 1 is elastically supported on the base surface B via the support coil springs 4, 4.

Note that in order to elastically support the vibration isolating table, it is needless to say that other elastic bodies such as vibration isolating rubber may be used instead of the coil springs 4, 4 as shown.

On the other hand, as shown in FIG. 3, FIG. 4, and FIG. It is provided parallel to the protrusion 2 so that the inner surface of the receiving member 5 and the side surface of the protrusion 2 face each other.

A pair of inner brackets 6, 6 are provided on both sides of the protruding part 2 along the length direction of the protruding part 2, and a support shaft 7 supported by each inner bracket 6 in parallel with the base surface B has a , one end of a sliding rod 9 having a truncated conical spring receiving collar 8 is rotatably supported.

Also, the inner bracket 6 on the inner side of the receiving member 5
Outer brackets 11, 11 similar to the inner bracket 6 are provided at positions facing the inner bracket 6, and the support shaft 7 carried by each outer bracket 11 is provided with a male threaded portion 12 at one end and a guide hole 13 at the other end. The one end of the guide rod 14 is rotatably supported, and the sliding rod 9 and the guide hole are slidably fitted.

Therefore, when the vibration isolating table 1 moves up and down, the sliding rod 9 slides in the guide rod 14, and these shaft support ends rotate around the support shaft 7.

An adjustment nut 15 having a conical surface symmetrical to the conical surface of the spring receiving collar portion 8 is screwed into the male threaded portion 12 .

Furthermore, a compressed auxiliary elastic body 16 (the one shown is a coil spring; hereinafter referred to as auxiliary coil spring) is wound between the spring receiving collar 8 of the sliding rod and the adjustment nut 15.

Since both ends of the auxiliary coil spring 16 are in contact with a conical surface, it is easy to align its axis with the axes of the sliding rod 9 and the guide rod 14, but the conical surfaces are mutually parallel planes. There is no problem.

Each auxiliary coil spring 16 exerts elasticity in a direction to enlarge the gap between the receiving member 5 and the protrusion 2 of the vibration isolating table,
As a result, the protruding portion 2 of the vibration isolating table receives elasticity so as to be held from both sides by a pair (two pairs in the illustrated embodiment) of auxiliary coil springs 16, 16.

The dimensions and specifications of each member described above are based on the gravity of the vibration isolation table 1 on which the machine M to be vibration-isolated is mounted and the support coil springs 4, 4.
When the elastic forces of the supporting coil springs 4 and 4 are balanced and in a stationary state, the axes (or expansion/contraction directions) of the pair of auxiliary coil springs 16, 16 coincide with each other, and the axis (
or expansion/contraction direction) shall be set at right angles.

A vibration model of the vibration isolator according to the present invention configured as described above can be schematically illustrated as shown in FIG.

However, in FIG. 6, parts given the same reference numerals as those in FIGS. 3 to 5 correspond to parts equivalent to those in FIGS. 3 to 5.

Note that both ends of the auxiliary coil springs 16, 16 can be considered to be rotatably supported.

In FIG. 6, the vibration isolation table 1 on which the machine to be isolated is mounted is in a static equilibrium state, and a pair of auxiliary coil springs 16,
16 (with a spring constant of ks) exert an elasticity F0 on the vibration isolation table 1 perpendicularly (horizontally in the case shown) to the axis of the support coil spring 4, but these elasticities F0,
Since F0 acts to cancel each other out, it has no effect on the vibration system in a static equilibrium state.

Next, the vibration isolation table 1 is moved a minute distance x in the direction of the arrow in Figure 7 (upward).
When calculating the magnitude of the restoring force when the displacement is, the elongation δ and elasticity F of each auxiliary coil spring 16 are as follows (5)
, as shown in equation (6).

However, l is the length of the auxiliary coil spring 16 in the static equilibrium state.

Therefore, as shown in FIG. 8, a component force Fs in the direction of expansion and contraction of the support spring 4 (the one shown is directed upward) is generated.

This component force Fs is expressed by the following equation (7). On the other hand, the downward restoring force Fx by the support spring 4 is Fx=kx (8).

Therefore, overall, considering that there are two pairs of auxiliary coil springs 16 on the left and right sides (we are considering the vibration model shown in FIG. 6, not the embodiment shown in FIGS. 3 to 5), Restoring force F1 acting on the vibration isolation table 1 as a whole
Considering that x is minute, the spring constant ke and natural frequency ωe of an equivalent support coil spring that exhibits the restoring force F1 in the absence of the auxiliary coil springs 16 and 16 are ( 9) From formula, it becomes.

As is clear from equations (10) and (11) above, k=(
2F0)/l, and if ke is set to a value close to 0, ωe
The value of can be made extremely small.

In this way, it is possible to obtain a vibration isolating device that has a large vibration isolating effect even against disturbances of extremely small frequencies (see FIG. 2).

Note that the adjustment of ke is performed by rotating the adjustment nut 15 (see FIGS. 4 and 5) and changing the value of F0.

FIG. 9 shows a modified embodiment of the present invention, in which spring fixing plugs are provided in place of the inner and outer brackets 6 and 11 provided on the protruding portion 2 and the receiving member 5 of the vibration isolating table. 17 is provided in a protruding manner, and the end of the compressed auxiliary coil spring 16 is fitted into this spring fixing stopper 17 and fixed.

In this way, unlike the case using the rotating pair shown in FIGS. 3, 4, and 5, the elasticity generated in the auxiliary coil spring 16 due to the displacement of the vibration isolating table from the static equilibrium state is simply the auxiliary coil spring 16. In addition to the elongation of the coil spring, elasticity caused by the shear and bending moment of the auxiliary coil spring is added, but if the initial compressive force F0 is determined taking these restoring forces into consideration, then the equivalent support described above can be obtained. The spring constant of the spring can be made extremely small.

Generally, in a coil spring, the elasticity caused by the shearing and bending described above is smaller than that caused by the spring's elongation, so the one shown in FIG. be equivalent.

By fixing both ends of the auxiliary coil spring 16 as shown in FIG. 9, an advantage arises in that the structure is extremely simple.

Further, FIG. 10 shows another modified embodiment of the present invention, and this modified embodiment includes a supporting elastic body 4 and an auxiliary elastic body 1 of the vibration isolating table 1.
6 is made of anti-vibration rubber instead of a coil spring.

In this case, a bracket 6 as shown in FIGS. 3 to 5, for example, is installed between the vibration isolating rubber serving as the auxiliary elastic body and the vibration isolating table 1, and between the vibration isolating rubber serving as the auxiliary elastic body and the receiving member 5. ，
11 and a rotating pair of shafts 7 are interposed, respectively, to prevent the vibration isolating rubber 16 from being sheared or bent.

When both ends of the vibration isolating rubber 16 as an auxiliary elastic body are fixed, the displacement of the vibration isolating table 1 generates stress in response to shearing and bending moments in the vibration isolating rubber 16, and the elasticity exerted by these external forces is applied to the supporting elastic body. The restoring force of the vibration isolating rubber 4 is almost the same as that of the anti-vibration rubber 4, and its influence cannot be ignored, so the restoring force of the supporting elastic body 4 and the vertical component of the elasticity due to the extension of the auxiliary elastic body 16 are canceled out. This is because the principle of the present invention, which is to do so, no longer holds true.

If the dimension in the length direction (direction perpendicular to the plane of the paper) of the protrusion 2 of the anti-vibration rubber as an auxiliary elastic body is made sufficiently large, and a pair of rotating pairs are provided at each edge in the expansion/contraction direction, As shown in FIG. 5, there is an advantage that rotation around an axis perpendicular to the base surface B can be prevented even without providing two pairs of auxiliary elastic bodies 16.

As is clear from the above description, in the present invention, the vertical component of the elasticity of the auxiliary elastic body 16 and the restoring force of the supporting elastic body 4 act to cancel each other out, and the supporting elastic body 4 Since the apparent spring constant can be made extremely small, the natural frequency of the vibration isolator can be made extremely small, and therefore the vibration isolating effect is extremely good.

In addition, the structure is simple, small and lightweight, and even a small vibration isolator can be easily installed without taking up much space.

[Brief explanation of drawings]

Figure 1 is a diagram showing the vibration model of a conventional vibration isolator, Figure 2
The figure is a graph showing the relationship between disturbance frequency and vibration transmissibility in a vibration isolator using the damping ratio as a parameter. Figure 3 is an enlarged front view of the auxiliary elastic body part, Figure 5 is Figure 3 V
- A partial cross-sectional enlarged plan view of the auxiliary elastic body section viewed from line V, FIG. 6 is a line diagram showing the static balance state of the vibration model of the vibration isolator according to the present invention, and FIG. 7 is a line diagram showing its displacement state. Figure, 8th
The figure is a vector diagram showing the restoring force of the vibration model shown in FIGS. 6 and 7, FIG. 9 is a front view showing a modified embodiment of the present invention, and FIG. 10 is a vector diagram showing the restoring force of the vibration model shown in FIGS. FIG. 3 is a front view of the vibration isolator. 1... Anti-vibration table, 2... Protrusion, 4...
...Supporting elastic body, 5...Receiving material, 16...
...Auxiliary elastic body, B...Foundation surface, P...
...Machines that should be vibration-proofed.

Claims (1)

[Claims] 1. A vibration isolation table on which the machine to be vibration-isolated is mounted is elastically supported on the foundation surface via an elastic supporting body, and a support member fixed to the foundation surface is provided between the vibration isolation table and the , a compressed first auxiliary elastic body separate from the support elastic body; and a compressed first auxiliary elastic body separate from the support elastic body; forming a pair, and arranged in a relationship position so as to sandwich the vibration isolating table together with the first auxiliary elastic body.
A second compressed auxiliary elastic body separate from the supporting elastic body is provided so as not to be affected by shearing or bending during expansion and contraction, and when the vibration isolating table is in a static equilibrium state, the first and second compressed auxiliary elastic bodies are The expansion and contraction directions of both auxiliary elastic bodies in step 2 are made to match and are perpendicular to the expansion and contraction direction of the support elastic body, so that when the vibration isolating table is displaced, the restoring force of the support elastic body and the elasticity of the auxiliary elastic body are in the vertical direction. A vibration isolating device characterized in that component forces cancel each other out.