JP3460499B2 - Prolonged period of vibration isolation system using canceling spring - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration isolation system which can easily extend a natural vibration in a small amplitude range by using a canceling spring having a linear characteristic having a constant spring constant. The present invention relates to a method for prolonging the period of an anti-vibration system using a canceling spring, which can be made periodical and thus can improve micro vibration absorption performance as much as possible. 2. Description of the Related Art Generally, as a vibration isolation system applied to a vibration-isolated building, a vibration isolation table, or the like, an object such as a building or a vibration isolation table is mounted on a base such as a base or a base via a buffer spring. The vibration body is provided so as to be relatively displaceable in the horizontal direction, and a buffer spring absorbs the horizontal vibration on the base side so that the horizontal vibration is not transmitted to the vibration receiving body side. As the cushioning spring, a laminated rubber elastic body or a coil spring formed by alternately laminating and integrating a rubber plate and a steel plate is often used. When it is necessary to provide good vibration absorption performance from a small amplitude to a large amplitude, the buffer spring has a non-linear characteristic having a smaller spring constant at a small displacement and a larger spring constant at a large displacement. We adopt what we present. [0004] However, it is difficult to design and manufacture the above-mentioned shock-absorbing spring to have a desired non-linear characteristic, and it takes time and effort to develop and manufacture the shock-absorbing spring. There is a problem that the manufacturing cost becomes very high. When the cushioning spring bears the load of the object to be removed, it is necessary to have a rigidity capable of withstanding the load. The spring constant in the displacement region cannot be made too small, and there is a limit to prolonging the natural oscillation in the small amplitude range, and vibration-free buildings such as research facilities and LSI factories that dislike minute vibrations and precision There is a problem that vibration absorption performance of a vibration isolation table or the like cannot be effectively improved. The present invention has been made in view of the above problems, and has as its object to reduce the amplitude of horizontal vibration transmitted to an object to be vibration-isolated provided horizontally on a base via a buffer spring. Spring that can increase the natural frequency of the region with a simple configuration at low cost using a canceling spring having a linear characteristic and thereby improve the vibration absorption performance in the small amplitude range as much as possible. An object of the present invention is to provide a method for extending the period of a vibration isolation system using a computer. [0007] In order to achieve the above object, in a method for extending a vibration isolation system using a canceling spring according to the present invention, a relative displacement in a horizontal direction on a substrate is provided. For a vibration isolation system having a flexible vibration-isolated body and a buffer spring having a horizontal elastic restoring force characteristic expressed by Q = q (x) between the base and the vibration-isolated body, In extending the natural oscillation in the small amplitude range using a canceling spring having a linear characteristic with a constant spring constant ks, the canceling spring has no relative displacement between the vibration-receiving body and the base. In this state, an initial amount of compressive strain δ ₀ is given between them, and they are mounted at right angles with a mounting width H, and the horizontal component P _x of the elastic restoring force P acts as a canceling force of the elastic restoring force Q of the buffer spring. So that the offset spring and the cushioning spring are combined. Horizontal elastic restoring force characteristic R = q
(X) The initial compression strain amount δ ₀ , the mounting width H, and the spring constant Ks of the canceling spring are set under the condition that the spring constant of + P _x becomes 0 when the relative displacement does not occur. And [0008] According to the method of extending the vibration removing system using the canceling spring according to the present invention having the above-described configuration, the canceling spring is perpendicular to the base and the vibration-free body in a state where no relative displacement occurs between them. Even when the initial compressive strain amount δ ₀ is given, the horizontal component force that offsets the horizontal elastic restoring force of the shock-absorbing spring is in a state where the base and the vibration-free body are not relatively displaced even if the initial compressive strain amount δ ₀ is given. Does not occur and does not function as a canceling spring. On the other hand, when a relative displacement x occurs between the base and the vibration-isolated body, a horizontal component force P _x = −ks · δ ₀ · sin θ according to the relative displacement angle θ.
This horizontal component Px acts as a canceling force of the elastic restoring force Q of the buffer spring. That is, cancellation springs horizontal component force P _x of the elastic restoring force P is present a non-linear characteristic is based on the sin curve, reduce the elastic restoring force of the buffer spring. Here, the amount of distortion δ of the canceling spring due to the relative displacement x is δ ₀ − {(x ² + H ² ) ^1/2 −H},
Since sin θ is x / (x ² + H ² ) ^1/2 , the above-described canceling force can be expressed as a function of the horizontal displacement x, and the known horizontal elastic restoring force characteristic Q = q (x) of the shock-absorbing spring. Horizontal elastic restoring force characteristics R =
Q + P _x can also be expressed as a function expression of the displacement x. In order to increase the period of the natural vibration in the small amplitude range of the vibration isolation system and improve the performance of absorbing the minute vibration, the elastic restoring force characteristic R = Q + P of the composite spring is required.
_{What is} necessary is just to make the spring constant of x as close to 0 as possible in a desired range near the vibration origin of the displacement x = 0. That is, the elastic restoring force characteristic R of the composite spring that can be expressed as a function expression of the displacement x
What is necessary is to make the inclination at the displacement x = 0 of = Q + P _x horizontal. Therefore, the elastic restoring force characteristic R = Q of the composite spring
By substituting x = 0 into a partial differential equation obtained by partially differentiating + P _x with a displacement x, a solution of a spring constant ks, an initial compressive strain amount δ ₀ , and a mounting width H at which this is zero is calculated, thereby obtaining various types of offset springs. The setting can be determined, the natural vibration in the small-amplitude region of the vibration isolation system can be lengthened with a simple configuration and at a low cost by using a canceling spring having linear spring characteristics, and the performance of absorbing minute vibrations can be improved. Can be improved. FIG. 1 shows a schematic configuration of an embodiment of a precision vibration isolation table adjusted by a method of extending a vibration isolation system using a canceling spring according to the present invention. , FIG. 2
FIG. 2 is an explanatory diagram showing an enlarged state of an essential part in FIG. 1 and exaggerating its operation state. As shown in FIGS. 1 and 2, a precision vibration isolation table 4 which is an object to be vibration-isolated is provided on a top surface of a base 6 as a base via a buffer spring device 2 so as to be relatively displaceable in a horizontal direction. Vibration at a small amplitude is suppressed by a damper 5 attached between the reaction force receiving member 3 fixed to the upper surface of the side base 6. The buffer spring device 2 is interposed between the precision vibration isolation table 4 and the base 6 which move relatively in parallel to each other, and is composed of a main buffer spring 8 and a canceling spring 10 combined. The main shock absorbing spring 8 is an elastic body formed by sequentially laminating a rubber plate 8a and a steel plate 8b and uniformly forming the rubber plate 8a over the entire length thereof. Therefore, the vertical subsidence caused by the horizontal displacement hardly occurs and is negligible. Here, assuming that the elastic restoring force of the main buffer spring 8 is Q and its spring characteristic can be expressed by Q = q (x), the main spring 8 has a rubber plate 8a over its entire length as described above.
3 and the steel plate 8b are laminated and uniformly formed.
As shown in FIG. 7, the horizontal spring characteristic Q = q (x) exhibits a linear characteristic in which the spring constant k is substantially constant irrespective of the horizontal displacement x, and can be expressed as Q = k · x. On the other hand, a coil spring having a linear characteristic is used as the canceling spring 10, and a vertical displacement between the precision vibration isolator 4 and the base 6, that is, a relative displacement, It is arranged at right angles to the direction. More specifically, as shown in FIG. 2, the offset spring 10 is provided with an initial compressive strain amount (length) δ ₀ , and has a mounting width H between the base 6 and the lower part of the precision vibration isolation table 4. When the precision anti-vibration table 4 is displaced horizontally relative to the base 6,
Horizontal component force P _x of the elastic restoring force P of the offset spring 10 is adapted to act on precise vibration isolation table 4. That is, if the angle (relative displacement angle) from the vertical direction of the canceling spring 10 inclined according to the horizontal displacement x of the precision vibration isolation table 4 is θ, the precision vibration isolation table 4 has the following formula (1). ), The horizontal component force P _{x of the} canceling spring 10 acts as a canceling force of the elastic restoring force Q of the main buffer spring 8.
The spring characteristic of the canceling force exhibits a non-linear characteristic based on a sin curve. P _x = −P · sin θ = -Ks ・ Δ ₀・ sin θ ... (1) Also, the distortion amount δ is δ = δ ₀ + H − (X ² + H ² ) ^1/2 (2) Therefore, the elastic restoring force P of the canceling spring 10 is P = ks · δ.
Is P = −ks · ｛δ ₀ + H − (X ² + H ² ) ^1/2 ｝ (3), and sin θ is sin θ = x / (x ² + H ² ) ^1/2 ... (4) horizontal component force P _x cancellation spring 10 which acts, P _x = -ks · ｛Δ ₀ + H- (x ² + H ² ) ^1/2 ｝ · ｛x / (x ² + H ² ) ^1/2 ｝ こ と が (5) it can. Therefore, assuming that the horizontal spring characteristic of the buffer spring device 2 in which the main buffer spring 8 and the offset spring 10 are combined is R, R = Q + P _x = k × x−ks ｛Δ ₀ + H- (x ² + H ² ) ^1/2 ｝ · ｛x / (x ² + H ² ) ^1/2 ｝ = x [k−ks · ｛δ ₀ + H- (x ² + H ² ) ^{1 / 2} · {1 / (x} 2 + H 2) 1/2} may represent a ......... (6). Here, in order to improve the vibration absorbing performance of the precision vibration isolation table 4 in the small amplitude range, particularly, the performance of absorbing minute vibrations, the natural vibration near the vibration origin at the displacement x = 0 should be as long as possible. The vibration origin x = 0
It is necessary to make the spring constant in the vicinity as close to zero as possible.
Therefore, the condition that at least the spring constant at the vibration origin x = 0 becomes 0 is a condition for setting the spring constant ks of the canceling spring 10, the initial amount of compressive strain δ _0, and the mounting width H. That is, in the elastic restoring force characteristic of the buffer spring device 2 represented by the above equation (6), the inclination at the displacement x = 0, which is the origin of the vibration, may be set to zero. That is, the displacement x in the horizontal elastic restoring force Px of the canceling spring 10
= 0 (spring constant) and displacement x = 0 of the main buffer spring 8
It is sufficient that the sum with the inclination (spring constant k) becomes zero. Here, the inclination of the elastic restoring force Px in the horizontal direction of the canceling spring 10 is obtained by partially differentiating the above equation (5) with the displacement x.
It can be expressed by a differential equation . Then, when x = 0 is substituted into this partial differential equation,
Thus, the inclination at the vibration origin can be obtained. On the other hand, since the inclination of the main buffer spring 8 is k, the inclination is obtained by substituting x = 0 into the k and the partial differential equation.
Is the condition that the sum with the inclination at the vibration origin is 0?
Thus, the spring constant ks, the initial compressive strain amount δ ₀ , and the mounting width H may be obtained. [0028] Further, ks satisfying the above conditions, H, [delta] ₀
Is a solution for setting the inclination (spring constant) at the vibration origin of the composite spring to zero. Here, a plurality of combinations of solutions are obtained for ks, H, and δ ₀ , and a desired vibration isolation region can be obtained from among them, depending on the application of the vibration isolation system. What is necessary is just to select the solution of the combination from which the most suitable nonlinear characteristic is obtained. Further, various settings of the canceling spring 10 can be determined as described above. The canceling spring 10 is specifically configured as shown in FIG. 4 , for example. That is, the upper spring seat 16 and the lower spring seat 18 are integrally formed on the extensible upper rod 12 and the lower rod 14 which are fitted to each other so as to be slidable with their axes aligned. Upper and lower ends are engaged with these spring seats 16 and 18 to provide a coil spring 20 having excellent linear characteristics. At the ends of the upper and lower rods 12, 14, mounting holes 22 for pin connection are provided.
24, and the dimensions of each member are designed so that the span L of the upper and lower mounting holes 22, 24 becomes H + δ ₀ calculated and determined as described above with the coil spring 20 having a natural length.
The spring constant of the coil spring 20 used is naturally set to ks. The canceling spring 10 is mounted vertically on the precision vibration isolation table 4 and the base 6 in a state where they are not displaced in the horizontal direction. At this time, the precision anti-vibration table 4
The span of the engagement pin for attaching the offset spring provided on the side and the base 6 side is set to H, and the initial compression strain is applied to the coil spring 20 of the offset spring 10 with the offset spring 10 attached. Yields the quantity (length) δ ₀ . Therefore, as described above, in the precision anti-vibration table 4 buffered by the buffer spring device 2, the main buffer spring 8
Since the spring constant at the vibration origin of the buffer spring device 2 exhibiting the non-linear characteristics of the combination of the spring spring and the canceling spring 10 is 0, and the spring constant in the vicinity thereof is as close to 0 as possible, The natural vibration of the precision anti-vibration table 4 in the amplitude range is made as long as possible, and the minute vibration input from the base 6 to the precision anti-vibration table 4 can be effectively absorbed. In addition, a canceling spring 10 having a constant linear spring characteristic ks regardless of the displacement x is used, and no horizontal displacement is generated between the precise anti-vibration table 4 and the anti-vibration table 6. A simple configuration of vertically arranging and attaching in a state is sufficient. Further, if the canceling spring 10 is manufactured by using a coil spring which can be easily designed and manufactured with a predetermined spring constant ks and has excellent linear characteristics, the characteristics of the buffer spring device 2 can be adjusted at low cost and with high accuracy. be able to. The initial strain δ is applied to the coil spring 20 of the canceling spring 10 formed to have the desired spring constant ks.
_In some cases, the length in the state where ₀ is given does not fit well within the mounting width H. In such a case, as shown in FIG.
As shown in FIG. 5, it may be attached via the elastic restoring force transmitting means 28. That is, the first and second cylinder mechanisms 30,
32 is adopted as the elastic restoring force transmission means 28, and a first cylinder mechanism 30 using oil, which is an incompressible fluid, as a working fluid is vertically disposed between the base 6 and the precision vibration isolation table 4. The first cylinder mechanism 30 attaches the cylinder 30a side and the piston 30b side to the precision anti-vibration table 4 and the base 6 by means of a pin joint by a universal joint, respectively, with the calculated mounting width H, while the second cylinder mechanism Reference numeral 32 denotes a communication pipe 34 which is laid on the base 6 and whose cylinder 32a side is fixed, and the pressure chamber 31 of the first cylinder mechanism 30 and the pressure chamber 33 of the second cylinder mechanism 32 are formed of a flexible pipe. To communicate. And the second cylinder mechanism 3
2 has one end 2 of the coil spring 20 on the side of the piston 32b.
0a, and the other end 20b is connected to the bracket 36 for receiving the reaction force. The bracket 36 is fixed to the base 6. At this time, in the first cylinder mechanism 30 and the second cylinder mechanism 32, the pressure receiving areas of both the pistons 30b and 32b are set to be equal, and the piston operation stroke of the first cylinder mechanism 30 is directly changed to the second cylinder mechanism 32. The piston operating stroke may be set to be equal to the piston operating stroke, but the pressure receiving area may be changed to make the piston operating stroke proportional to the area ratio as in the illustrated example. In this case, of course, it is necessary to change the setting of the spring constant of the coil spring 20 in accordance with the ratio of the operation stroke. It is possible to freely set the size such as the length.
The degree of freedom such as the space for disposing the cylinder mechanism 32 is increased. The second cylinder mechanism 32 does not necessarily need to be disposed on the base 6, but can be disposed on a separate fixed system, and the degree of freedom of the installation location is high. The working fluid may be any other than oil as long as it is incompressible. In the above-described embodiment, the main cushion spring 8 having a linear characteristic is employed. However, a main cushion spring having a non-linear characteristic may be employed. The present invention can also be applied to a vibration isolation system for a vibration-isolated building in a research facility or an LSI factory that dislikes minute vibrations. As described above in detail in the embodiments,
According to the method for lengthening the period of the vibration isolating system using the canceling spring according to the present invention, the canceling spring having a linear characteristic in which the spring constant ks is constant is relatively displaced between the base and the object to be damped. The initial compression strain δ ₀
, And attached with the mounting width H to be combined with the buffer spring,
At this time, the spring constant ks, the initial compressive strain amount δ _0, and the mounting width H are set by satisfying the condition that the spring constant at the origin of vibration in the horizontal elastic restoring force characteristic of the composite spring is 0. With such a simple configuration, the natural vibration in the small amplitude range of the vibration isolation system can be made as long as possible, and a vibration isolation system excellent in the performance of absorbing minute vibrations can be provided at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a schematic configuration of a vibration isolation table provided with a buffer spring device adjusted by a spring characteristic adjustment method according to the present invention. FIG. 2 is an explanatory diagram showing an enlarged state of a main part in FIG. 1 and exaggerating an operation state thereof. FIG. 3 conceptually illustrates a relationship between a characteristic Q of an elastic restoring force of a buffer spring, a characteristic P _x of a horizontal component force of an elastic restoring force of a canceling spring, and a spring characteristic R of a composite spring in a state where they are combined. It is a graph shown typically. FIG. 4 is a diagram showing a specific configuration example of a canceling spring used in the present invention. FIG. 5 is a schematic configuration diagram showing another installation example of the canceling spring according to the present invention. [Description of Signs] 2 Buffer spring device 4 Precision anti-vibration table 6 Base 8 Main buffer spring 10 Cancellation spring 12 Upper rod 14 Lower rod 16 Upper spring seat 18 Lower spring seat 20 Coil spring 22, 24 Mounting hole 26 Casing 28 Insertion Hole 30 First cylinder mechanism 32 Second cylinder mechanism 34 Communication pipe

Claims (1)

(57) [Claims 1] A vibration-removing body that is relatively displaceable in a horizontal direction is provided on a base, and a horizontal elastic restoring force characteristic is provided between the base and the vibration-receiving body. A method of extending the natural vibration in a small amplitude range using a canceling spring having a linear characteristic with a constant spring constant ks for a vibration isolation system including a buffer spring expressed by Q = q (x). Wherein the offset spring gives an initial amount of compressive strain δ ₀ between the anti-vibration body and the base in a state where no relative displacement occurs between them, and is attached at a right angle with an installation width H; provided to the horizontal component P _x of the elastic restoring force P acts as a canceling force of the elastic restoring force Q of the buffer spring, the horizontal direction of the elastic restoring of the phase killing spring and the buffer spring and a composite spring complexed with state the spring constant force characteristic R = q (x) + P x does not occur in the relative displacement And setting the initial compression strain amount δ ₀ , the mounting width H, and the spring constant Ks of the canceling spring under the condition of ₀ .