JP4973520B2 - Gas spring vibration isolator - Google Patents

Description

  The present invention relates to a gas spring type vibration isolator for installing a precision instrument such as an electron microscope in a state of being substantially insulated from floor vibration.

  Conventionally, as a vibration isolator of this type, as described in Patent Documents 1 and 2, for example, a gimbal mechanism is incorporated into a piston of a vibration isolator using a diaphragm-type air spring (hereinafter referred to as a gimbal piston). It is known that a spring characteristic that is soft also in the horizontal direction can be obtained by converting the horizontal displacement between the supported body and the floor into a swinging motion of the piston.

  In such a vibration isolator, as shown schematically in FIG. 8, the piston a of the air spring is divided into a disk-shaped load disk b and a cylindrical piston main body c positioned therebelow. The outer periphery of the main body c is held by a rubber diaphragm d (flexible member). Further, a bottomed cylindrical extending portion c1 extending downward from the piston main body c is provided, and a rod e (supporting column portion) hanging downward from the load disk b is provided, and a lower end of the rod e is provided. The portion is pivotally supported at the bottom of the downwardly extending portion c1.

  With this structure, in the conventional vibration isolator, the spring characteristic in the vertical direction is soft as a natural property of the air spring, and excellent vibration isolation performance is obtained over a wide frequency range, and the gimbal piston swings. Thus, the spring characteristics in the horizontal direction can be made soft. That is, when the floor is displaced in the horizontal direction with respect to the load disc b, the diaphragm d bends in the opposite phase with the piston body c sandwiched therebetween, so that the piston body c is tilted and shaken as shown by the arrows in FIG. This causes vibration to be absorbed.

Then, when the piston main body c swings, the support point of the rod e rises geometrically and the center of gravity of the supported body increases, so that a restoring force is generated to return to the original position, which is horizontal. It becomes the spring force of the direction. This horizontal spring force can be made very small, for example, by setting the length of the rod e, etc. Therefore, according to the gimbal piston, the horizontal spring characteristics can be as soft as the vertical direction. Therefore, it is possible to obtain excellent vibration isolation performance over a wide frequency range.
Japanese Examined Patent Publication No. 62-7409 Japanese Patent No. 3611356

  By the way, in recent years, for example, as the analysis capability of an electron microscope has increased, its weight has increased. There is a demand for a small (footprint). In this respect, in the vibration isolator using the air spring as in the conventional example, it is inevitable that the whole is increased in size as the supporting load is increased, and the above-described requirements cannot be sufficiently satisfied.

  On the other hand, the inventor of the present application conceived that a part of the load is supported by using a coil spring or the like together with other mechanical spring elements, and the coil spring is arranged below the gimbal piston mainly in terms of space efficiency. A vibration isolator having a structure in which the piston main body portion c is supported from below by arranging concentrically around the extending portion c1 was manufactured. However, as a result of experiments using the vibration isolator, it was found that the vibration isolation performance in the horizontal direction is greatly reduced as a result of the coil spring preventing the swing of the gimbal piston.

  That is, the gimbal piston as shown in FIG. 8 has a swing center at the support height of the piston main body c by the diaphragm d, and when a horizontal vibration is input, a downwardly extending portion from the lower end of the rod e. When the piston main body c swings due to the horizontal force acting on the bottom of c1, when the piston main body c is supported by a coil spring from below, the center of swinging is apparently displaced downward. As a result, the swinging moment is reduced, and in some cases, it does not swing.

  The present invention has been made on the basis of such novel knowledge, and the object thereof is to provide a gas spring type vibration isolator equipped with a gimbal piston, while increasing the load support capability by using a coil spring together, while providing a gimbal piston. Is to ensure the required vibration isolation performance in the horizontal direction.

  In order to achieve the above object, in the present invention, the arrangement of the coil spring used for supporting the load as described above has been devised so that the piston main body always oscillates by horizontal vibration input. It is.

  Specifically, in the first aspect of the present invention, a piston for supporting the load of the supported body is disposed in the vicinity of the opening on the upper surface of the case, and the space between the piston and the opening is closed by an annular flexible member. An anti-vibration device comprising a gas spring that defines a gas chamber inside the case and holds the piston at least vertically movable by the flexible member to elastically support the supported body. It is a target.

  The piston has a piston main body portion having a through hole in the vertical direction and a hollow portion communicating with the lower portion of the through hole, and extends downward from the piston main body portion. And the lower extension portion are arranged to extend vertically in the hollow portion of the downward extension portion, and the lower end is pivotally supported by the bottom portion of the downward extension portion, while the upper end is located above the piston body portion. A support column that receives the load of the supported body, i.e., a gimbal piston, and a coil spring is provided so as to surround and surround the outer periphery of the downwardly extending portion of the gimbal piston. Is supported by the case while the piston main body is supported at the upper end, and the height position of the center between the support height of the piston main body by the flexible member and the lower end of the coil spring than It is obtained by setting lower the height position of the lower end of the support portion.

  In the gas spring type vibration isolator having the above-described configuration, first, since the supported body is supported in the vertical direction by the gas spring as in the conventional example described above, a wide frequency range with respect to the vibration input in the vertical direction. Excellent vibration isolation performance can be obtained. Moreover, since the load is supported by the coil spring used together, the load supporting performance can be sufficiently increased without increasing the size of the entire apparatus.

  In addition, if the coil spring is changed as necessary, the load support performance and spring characteristics can be changed without changing the other parts, so that a wide range of required specifications can be used while sharing many of the parts. It becomes possible, and the apparatus cost can be greatly reduced. Of course, it is also possible to adjust the height using a leveling valve, etc., and to automatically respond to the movement of the center of gravity accompanying the operation of the mounted equipment, and it is easy to make a structure that obtains attenuation by gas flow resistance is there.

  On the other hand, in the vibration isolator configured as described above, the horizontal vibration is absorbed by the swing of the gimbal piston. As described above, the piston main body is supported by the coil spring from below. Since the swing center is displaced downward, the gimbal piston is difficult to swing, and in some cases, it may not swing.

  In this regard, the inventor of the present application conducted an experiment using the vibration isolator fabricated as described above. As a result, when the piston main body is supported by the coil spring from below, the center of oscillation apparently appears. The present invention has been completed by finding that it is displaced approximately in the center with the lower end of the coil spring. That is, in the above configuration, by setting the height position of the lower end of the support column portion of the gimbal piston to be lower than the apparent swing center of the piston main body portion displaced downward as described above, The piston main body can be reliably swung by the horizontal force acting on the bottom of the downwardly extending portion from the lower end.

  In addition, since the support height of the piston main body by a flexible member such as a diaphragm or a bellows varies depending on dimensional variations of parts and assembly tolerances, it also varies depending on the amount of gas filled in the gas chamber. For convenience, the height of the lower end of the support column portion of the gimbal piston is preferably set lower than the central portion of the coil spring in the vertical direction (Claim 2).

  Thus, according to the present invention, by using the coil spring together with the gas spring, a sufficiently large load supporting performance can be obtained by the compact vibration isolator, and the gimbal piston can be swung in the horizontal direction as well. Soft spring characteristics can be realized and the required vibration isolation performance can be ensured.

  Here, in order to facilitate the swinging of the gimbal piston as described above, it is better that the lower end of the support column portion on which the horizontal force acts is farther away from the apparent swing center of the piston body portion. The longer the support pillar part is, the better the higher the lower end of the coil spring is.

  However, the longer the support column, the larger the entire device is inevitably enlarged. On the other hand, the shorter the length of the coil spring is, the higher the spring constant is. Therefore, the vibration isolation performance may be lowered in both the vertical and horizontal directions.

  Therefore, it is more preferable to provide a configuration in which a spherical load receiving surface is provided at the upper end of the support column portion of the piston so as to support the load of the supported body in a rollable manner (Claim 3). For example, when a horizontal vibration is input, the support column tilts and the supported body rolls on the load receiving surface at the upper end thereof. Can absorb horizontal vibration. Therefore, extremely soft spring characteristics can be realized in the horizontal direction, and the vibration isolation performance can be further enhanced.

  In addition, if the supported body is supported by the spherical load receiving surface, both of them are in a point contact state, so that unnecessary rotational force does not act on the supported body from the coil spring as the support height changes. Thus, there is no possibility that vibrations in the rotational direction are added to the support by such rotational force.

  Further, the damping material may be wound so as to be in sliding contact with the outer periphery of the coil spring (Claim 4), and in this way, the spring constant of the gas spring is increased due to the addition of the coil spring, A damping force having an appropriate magnitude can be easily obtained.

  As described above, according to the gas spring type vibration isolator according to the present invention, a gimbal mechanism is incorporated in the piston of the gas spring so that high vibration isolation performance can be obtained not only in the vertical direction but also in the horizontal direction. Further, by using a coil spring together, it is possible to obtain a high load supporting performance while being compact.

  Further, in order to prevent the coil spring used together so as to prevent the swing of the gimbal piston as much as possible, the gimbal piston should be lower than the apparent swing center of the piston main body that is displaced downward by the influence of the coil spring. Since the height position of the lower end of the support column portion is set, even if there is a coil spring, the swing of the gimbal piston can be ensured and the required vibration isolation performance can be ensured in the horizontal direction.

  Furthermore, if a spherical load receiving surface is provided at the upper end of the piston support column portion so as to support the supported body in a freely rolling manner, the vibration in the horizontal direction can be more smoothly performed together with the swinging of the gimbal piston. Can be absorbed, and extremely high vibration isolation performance can be obtained in the horizontal direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows how the gas spring vibration isolator according to the present invention is used, and details are not shown. For example, a precision instrument 1 such as an electron microscope is mounted on a surface plate 2 and mounted on a floor. It is supported by a plurality of isolators 3,... (Gas spring type vibration isolator) so as to be almost insulated from vibration. In each isolator 3,..., The surface plate 2 and the device 1 (mounted device) mounted thereon are supported, but the shared load to each isolator 3 is slightly different even in a stationary state. Furthermore, it may change with the operation of the support.

  The surface plate 2 is made of a thick plate material having a rectangular shape in plan view as an example, and has a width on one end side (left side) of the longitudinal direction X (the left-right direction in the figure, also simply referred to as the left-right direction hereinafter). One isolator 3 is disposed at a substantially central portion in the direction Y (the vertical direction in FIG. 5A, also referred to as the front-rear direction hereinafter), and the other end side (right side) opposite to the longitudinal direction. Are provided with one isolator 3, 3 at each end in the front-rear direction Y.

  The surface plate 2 supported in such a manner is capable of swinging around each axis in addition to translational motion along the three axes of the left-right direction X, the front-rear direction Y, and the up-down direction Z. The translational motion and the rocking motion are superposed on each isolator 3 that supports the surface plate 2. However, since the motion of each isolator 3 is very small, it can be regarded as substantially only translational motion along the three axes of X, Y, and Z.

  As shown in FIG. 2, the isolator 3 includes a gimbal piston having the same basic structure as that of the conventional example (Patent Document 1) as an air spring in the vertical direction Z, as shown in the cross-section in FIG. It has basically soft spring characteristics in both the horizontal direction (Y direction and X direction). In the example of the figure, the case of the isolator 3 has a substantially quadrangular prism shape, and a side wall 11 is erected on a bottom plate 10 made of a metal plate material. A circular opening 12a substantially orthogonal to the direction axis Z is formed.

  A donut-shaped piston body 13 is inserted into the opening 12a. A central hole 13a having a circular cross section passes through the piston body 13 in the vertical direction along the axis Z, while a tapered surface 13b (see FIG. 3) is slightly reduced in diameter toward the lower part of at least the lower half of the outer periphery. Is formed. An annular diaphragm 14 is disposed so as to reach the periphery of the opening 12a after covering the outer peripheral side from the lower surface of the piston body 13. That is, the diaphragm 14 and the piston main body 13 close the opening 12a on the upper surface of the case to define the air chamber 15, and an air spring that mainly supports the load in the vertical direction is configured.

  The diaphragm 14 is made of, for example, a rubber elastic film in which a woven fabric is embedded as a reinforcing material. As shown by a phantom line in FIG. 3, the diaphragm 14 is once formed into a hat shape with a round hole in the center portion, and then the peripheral wall of the hat The portion is bent in the middle and folded downward to form a deep dish shape shown by a solid line in FIG. An outer peripheral portion 14a corresponding to the hat collar portion is bonded to the upper surface of the top plate 12 of the case and is sandwiched between the fastening ring 16 and an inner peripheral portion 14b surrounding the round hole. Are bonded to the lower surface of the piston body 13, and an annular roll portion 14c that is curved upward is formed between them.

  The diaphragm 14 has a large flexibility with respect to the displacement in the vertical direction of the piston body 13 by bending the annular roll portion 14c so as to wave up and down between the piston body 13 and the fastening ring 16. In addition, the left and right roll portions 14c sandwiching the piston body 13 bend in opposite directions in the vertical direction, so that the piston body 13 swings around the horizontal axis (swing center). (See FIG. 4). That is, in the gimbal piston, the swing center of the piston body 13 is originally located at the support height h1 by the diaphragm 14 (see FIG. 5).

  A cylindrical piston well 18 is attached to the piston body 13 so as to extend substantially vertically downward from the inner peripheral side of the lower surface thereof. A disk-shaped flange 18a having a large diameter is formed at the upper end of the piston well 18. This is overlapped with the lower surface of the piston main body 13 and fastened by a fastening member (not shown) to connect the inner peripheral side portion 14b of the diaphragm 14. It is pinched. In this state, the hollow portion 18b of the piston well 18 communicates with the central hole 13a of the piston body 13, while the lower end of the hollow portion 18b is closed by a disc-shaped cap 19.

  That is, the piston well 18 and the cap 19 constitute a bottomed cylindrical downward extending portion extending downward from the piston main body 13, and the upper surface of the cap 19, that is, the bottom portion of the downward extending portion. The lower end part of the support rod 20 (support column part) for supporting the load of a to-be-supported body is pivotally supported. The support rod 20 extends in the vertical direction along the axis Z in the hollow portion 18a of the piston well 18, and, for example, a steel ball 20a is embedded in the lower end portion thereof. In the example shown in the figure, a rubber elastic ring 21 for positioning the support rod 20 on the axis Z is extrapolated on the lower end side of the support rod 20.

  On the other hand, the upper end of the support rod 20 protrudes upward from the upper surface of the piston body 13 and abuts against the lower surface of the disk-shaped load disk 22. The load disk 22 is joined to the lower surface of the surface plate 2 and receives the load of the supported body, while being supported by the support rod 20 from below and spaced above the piston body 13. The diameter of the load disk 22 is larger than the outer diameter of the piston body 13 and is substantially the same as the tightening ring 16 in the illustrated example.

  In this embodiment, the upper end of the support rod 20 is in contact with the lower surface of the load disk 22 so as to be able to roll and in a point contact state, and is projected upward so as to receive the load of the supported body via the load disk 22. The spherical load receiving surface 20b is provided. That is, the load disk 22 can roll with respect to the load receiving surface 20b at the upper end of the support rod 20 and is pivotally supported by the bottom of the piston well 18 via the support rod 20. The horizontal vibration between the floor 18 and the floor is absorbed by both the swing 18 and the tilt of the support rod 20.

  More specifically, as shown in FIG. 4, for example, when the case is displaced to the left side of the drawing with respect to the load disk 22 due to floor vibration, the piston body 13 and the piston well 18 are integrated and the lower end thereof is displaced to the right side. And the upper side of the support rod 20 is tilted to the right side of the figure, and the load disk 22 rolls on the load receiving surface 20b at the upper end of the support rod 20 with the horizontal displacement (vibration). ) Is absorbed.

  Thus, when horizontal vibrations are absorbed by the swinging of the piston body 13 and the piston well 18 and the tilting of the support rod 20, the contribution ratios of both are omitted, although detailed explanations are omitted. It changes in accordance with the ratio of the curvature radius R of 20b and the length L of the support rod 20, and the contribution ratio of the oscillation of the piston main body 13 and the like increases when R ≧ 2 × L. When <2 × L, the contribution ratio of the tilt of the support rod 20 increases.

  Further, when the piston main body 13 and the like swing and the support rod 20 tilts as described above, the supported body slightly rises accordingly, so that a restoring force due to gravity is generated and the piston main body 13 and The piston well 18 and the support rod 20 try to return to the original upright state, and this becomes the horizontal spring force of the isolator 3. However, if R <L, no restoring force is generated and the state becomes unstable. Therefore, R ≧ L must be set as shown in FIG.

  By incorporating the gimbal mechanism into the piston as described above, in the isolator 3 of this embodiment, the horizontal displacement between the supported body and the floor is converted into the swinging motion of the gimbal piston. A spring characteristic that is soft in the horizontal direction can be obtained. Of course, in the vertical direction, the spring characteristics inherent to the air spring are obtained.

  In this embodiment, as a characteristic part of the present invention, the piston body 13 is supported from below, and the coil spring 23 is disposed so as to receive a part of the load of the supported body. In the illustrated example, the coil spring 23 is disposed so as to surround and surround the outer periphery of the piston well 18, and the lower end thereof is fitted to the boss portion 10 a that bulges from the upper surface of the case bottom plate 10, The upper end of the coil spring 23 is in contact with a seat portion formed on the lower surface of the flange 18 a at the upper end of the piston well 18.

  Thus, by using the coil spring 23 together and supporting the piston body 13 together with the air spring from the lower side, the maximum support load of the isolator 3 can be sufficiently increased without making the air chamber 15 large, that is, with a compact configuration. Can be bigger. Further, unlike the case where the load is supported only by the coil spring 23, the height of the supported body can be easily adjusted by supplying and discharging air from the air chamber 15. That is, as shown in FIG. 2, the isolator 3 is provided with a well-known leveling valve 24. By supplying and discharging air to and from the air chamber 15 through a passage (not shown), the support height is made substantially constant. To maintain.

  On the other hand, when supported by the coil spring 23 from below, the swinging of the piston body 13 is thereby restricted. That is, as described above, the original oscillation center of the piston body 13 is at the support height h1 by the diaphragm 14 (see FIG. 5), and the coil spring 23 that supports it from below is centered on its lower end. Since the piston body 13 is to be swung, the apparent rocking center of the piston body 13 is displaced downward. As a result, the rocking moment of the piston body 13 and the piston well 18 is reduced. Or it may stop swinging.

  In detail, generally, as described above, the horizontal spring constant Kj of the gimbal piston due to the swinging of the piston main body 13 and the piston well 18 is P, the internal pressure of the air spring is P, the effective pressure receiving area is A, and the piston The distance from the swing center of the main body 13 to the horizontal input point, that is, the pivot point at the lower end of the support rod 20, is represented by the following (Equation 1). Kj = (PA × 100 / d) + Kr (Equation 1) where Kr is a spring constant of the rubber elastic ring 21 extrapolated to the support rod 20.

  Further, in the case where a spherical load receiving surface 20b is provided at the upper end of the support rod 20 as in this embodiment and the load disk 22 is supported so as to be able to roll, the rolling of the load disk 22 and the support rod The horizontal spring constant Kd obtained by tilting 20 is expressed as follows, where the radius of curvature of the load receiving surface 20b is R and the length L of the support rod 20 is: Kd = {PA × 100 × ( R−L) / L} + Kr (Expression 2), and the total horizontal spring constant Kt obtained by combining these Kj and Kd is expressed by the following (Expression 3): Kt = Kj × Kd / (Kj + Kd) (Formula 3).

  The inventor of the present application prototyped the isolator 3 using the coil spring 23 as described above, measured the spring constant Kt in the horizontal direction, and assumed that the coil spring 23 had no influence (Formula 3). The value of the interval d in the above (Expression 1) was corrected so that the calculated value by () matched the measured value. Then, when the height of the swing center of the piston body 13 is obtained based on the corrected distance d, it appears that the support height h1 of the piston body 13 by the diaphragm 14 and the height of the lower end of the coil spring 23 are increased. It was found that the height h3 is approximately the center of the height h2.

  Based on such knowledge, in this embodiment, as shown in FIG. 5, the horizontal input points with respect to the piston main body 13 and the piston well 18, that is, the height h4 of the lower end of the support rod 20 are set to the apparent fluctuation. The height is set lower than the height h3 of the moving center, and by doing so, a swinging moment is reliably generated by the horizontal force acting on the bottom (cap 19) of the piston well 18 from the lower end of the support rod 20. be able to.

  Strictly speaking, the support height h1 of the piston body 13 by the diaphragm 14 changes depending on the dimensional variation of parts and assembly tolerances, and also changes depending on the amount of air filled in the air chamber 15. The height h4 of the lower end of the support rod 20 may be set lower than the vertical central portion of the coil spring 23.

  With such a setting, even when the horizontal vibration is input, a rocking moment is surely generated around the rocking center of the piston body 13 and the coil spring 23 supports the piston body 13 from below. Since the gimbal piston oscillates in response to the vibration input, the support rod 20 tilts as described above, and the load disk 22 rolls on the load receiving surface 20b at the upper end thereof. The vibration in the direction can be absorbed smoothly, and the spring characteristics in the horizontal direction can be made very soft.

  In FIG. 6, the surface plate 2 and the mounted device 1 (supported body) are supported by three isolators 3,... As in this embodiment, and the horizontal vibration transmissibility of any one isolator 3 is measured. Results are shown. The solid line graph of the same figure is that of the isolator 3 of this embodiment, while the broken line graph shows the height h4 of the lower end of the support rod 20 so that the swing of the gimbal piston is inhibited by the coil spring. 13 is set higher than the apparent rocking center.

  From the figure, in the isolator 3 according to the present invention, a resonance peak appears at a low frequency of about 2 Hz as shown by a solid line graph, and in a wide frequency range due to the soft spring characteristic as in the case where no coil spring is added. It can be seen that excellent vibration isolation performance can be obtained. On the other hand, in the broken line graph, the resonance peak is about 6 Hz. As a result, the vibration of the gimbal piston is hindered by the coil spring, and the vibration isolation performance is deteriorated.

  Therefore, according to the isolator 3, ... (gas spring type vibration isolator) according to this embodiment, first, the supported body is supported by the air spring as in the conventional general air spring type vibration isolator. Therefore, the spring characteristics in the vertical direction can be made soft, and excellent vibration isolation performance over a wide frequency range can be obtained with respect to vibration input. In addition, since the part of the load is supported by the coil spring 23 provided therewith, the load supporting performance can be sufficiently enhanced while having a compact outer dimension.

  In addition, by using the coil spring 23 in combination, the load support performance and spring characteristics of the isolator 3 can be changed by changing the specifications of the coil spring 23 as necessary, without changing other parts. Since it is possible to meet a wide range of required specifications while sharing many of the parts, the cost of the apparatus can be greatly reduced due to the mass production effect.

  Of course, since the original function of the air spring type vibration isolator can be obtained, by adjusting the support height using the leveling valve 24, it is possible to automatically cope with the movement of the center of gravity associated with the operation of the mounted device 1. In addition, it is possible to have a structure in which attenuation is obtained by air flow resistance at that time.

  On the other hand, the swing center of the piston body 13 is displaced downward due to the influence of the coil spring 23 used in combination, and there is a possibility that the spring characteristics in the horizontal direction may be lowered, but it is further lower than the swing center. Thus, by setting the height h4 of the lower end of the support rod 20 that is the pivot point of the gimbal piston, the swing of the gimbal piston is ensured, and the tilt of the support rod 20 and the rolling of the load disk 22 are combined. Excellent horizontal vibration isolation performance can be obtained as a very soft spring characteristic that smoothly absorbs horizontal vibration.

  Further, in the structure in which the load disk 22 is supported in a point contact state by the spherical load receiving surface 20b, unnecessary rotation of the supported body from the coil spring 23 via the piston main body 13 with a change in the support height. No force acts, and there is no worry that extra rotational vibration is added to the supported body by such rotational force.

  In the above-described embodiment, the air spring may be a gas spring filled with, for example, nitrogen gas. Further, the arrangement of the surface plate 2 and the isolators 3, 3,... Shown in FIG. 1 is merely an example of the usage mode, and the shape of the surface plate 2 and the arrangement of the isolators 3, 3,. Of course, the number of isolators 3, 3,... May be four or more.

  FIG. 7 shows an example. A cylindrical damping material made of high damping rubber such as fluoro rubber, butyl rubber, epoxidized natural rubber or the like so as to be in sliding contact with the outer periphery of the coil spring 23 in the isolator 3 of the embodiment. 24 may be wound. In this way, even if the spring constant in the vertical direction of the isolator 3 is increased due to the addition of the coil spring 23, a damping force having an appropriate magnitude can be easily obtained.

  Further, the piston of the isolator 3 does not have to have the load receiving surface 20b at the upper end of the support rod 20 as in the above-described embodiment, and includes, for example, a conventionally known gimbal piston as schematically shown in FIG. It may be. However, in such a case, in order to soften the spring in the horizontal direction, it is preferable to make the coil spring 23 as short as possible and the support rod 20 as long as possible. Therefore, the outer shape of the isolator 3 tends to increase in the vertical direction.

  Furthermore, the isolator 3 of the above embodiment is of a so-called passive type, but the present invention is a so-called active type vibration isolator in which vibration of the supported body is reduced by applying an antiphase force by an actuator. It is also applicable to.

  As described above, the gas spring type vibration isolator according to the present invention can obtain a large load supporting performance while being compact in combination with a coil spring and has sufficient vibration removal not only in the vertical direction but also in the horizontal direction. Vibration performance can be secured, and industrial applicability is high.

It is a schematic diagram which shows the usage condition of the isolator (gas spring type vibration isolator) which concerns on embodiment of this invention, (a) is a top view, (b) is a front view. It is a longitudinal cross-sectional view which shows the structure of an isolator. It is a disassembled perspective view which assembles a diaphragm, a piston, and a coil spring to a case. FIG. 3 is a view corresponding to FIG. 2 exaggeratingly showing a state in which the supported body is displaced in the horizontal direction. FIG. 3 is a view corresponding to FIG. 2 and showing the relationship between the height of the swing center of the piston body and the height of the lower end of the support rod. It is a graph which shows an example of the horizontal vibration isolation performance by the isolator of embodiment compared with the case where rocking | fluctuation of a gimbal piston is inhibited. FIG. 3 is a view corresponding to FIG. 2 according to another embodiment in which a damping material is wound around a coil spring. It is a schematic diagram of the conventional isolator which has a gimbal piston.

Explanation of symbols

1 On-board equipment (supported body)
2 Surface plate (supported body)
3 Isolator (vibration isolation device)
10 Bottom plate (case)
11 Side wall (case)
12 Top plate (case)
12a Upper surface opening 13 Piston body (piston)
13a Through hole 14 Diaphragm (flexible member)
15 Air chamber (gas chamber)
18 Piston well (lower extension)
18b Hollow part 19 Cap (lower extension part)
20 Support rod (support column)
22 Load disk 23 Coil spring h1 Diaphragm support height of piston body h2 Coil spring lower end height h3 Center height of piston body support height and coil spring lower end height h4 Support rod lower end height Z Vertical direction Axis

Claims (4)

A piston for supporting the load of the supported body is disposed in the vicinity of the opening on the upper surface of the case, and the space between the piston and the opening is closed by an annular flexible member to define a gas chamber inside the case. A vibration isolator comprising a gas spring that elastically supports the supported body by holding the piston at least vertically movable by the flexible member,
The piston is
A piston body having a through hole in the vertical direction;
A bottomed cylindrical downward extending portion extending downward from the piston main body portion, having a hollow portion communicating with the lower portion of the through hole;
It is arranged so as to extend vertically in the hollow part of the lower extension part, and the lower end is pivotally supported by the bottom part of the lower extension part, while the upper end is located above the piston body part and is supported. A support column that receives the load of the body,
A coil spring is provided so as to surround and surround the outer periphery of the downward extension part, and the lower end is supported by the case, while the upper end supports the piston body part,
The height position of the lower end of the support column is set lower than the central height position of the support height of the piston main body by the flexible member and the height of the lower end of the coil spring. Gas spring vibration isolator.   The gas spring type vibration isolator according to claim 1, wherein a height of the lower end of the support pillar portion of the piston is set lower than a central portion of the coil spring in the vertical direction.   The gas spring type vibration isolator according to claim 1 or 2, wherein a spherical load receiving surface is provided at an upper end of the support column portion of the piston so as to support the load of the supported body in a rollable manner. .   The gas spring type vibration isolator according to any one of claims 1 to 3, wherein a damping material is wound so as to be in sliding contact with the outer periphery of the coil spring.

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