An adjustable quasi-zero stiffness vibration isolator with optimal equilibrium position indication

Abstract

This invention relates to the field of low-frequency vibration control technology, and particularly to an adjustable quasi-zero stiffness vibration isolator with an optimal equilibrium position indicator. The isolator includes an upper pressure plate, a lower pressure plate, an upper connecting plate, a lower connecting plate, and an intermediate connecting plate. A positive stiffness mechanism is provided between the upper and lower connecting plates, and a negative stiffness mechanism is provided between the upper and intermediate connecting plates. The negative stiffness mechanism includes a vertical rod, a connecting rod, a horizontal rod, and a disc spring. An optimal equilibrium indicator is provided between the horizontal rod and the support guide frame. A height adjustment mechanism is provided between the intermediate and lower connecting plates. When the load deviates from the design value, the distance between the intermediate and lower connecting plates is changed by the height adjustment mechanism, and the isolator is adjusted to the optimal static equilibrium position by relying on the positioning block's insertion into the positioning hole. This prevents the negative stiffness mechanism from transmitting vertical force, achieving quasi-zero stiffness characteristics. This invention has a compact structure, intuitive and reliable adjustment, and can stably maintain excellent low-frequency vibration isolation performance under variable load conditions.

Description

Technical Field

[0001] This invention relates to the field of low-frequency vibration control technology, and in particular to an adjustable zero-stiffness vibration isolator with an optimal equilibrium position indicator. Background Technology

[0002] In the field of vibration control technology, traditional linear vibration isolators (such as spring isolators and rubber isolators) generally face severe challenges in low-frequency vibration isolation. These devices rely on the inherent stiffness of the material to provide support, resulting in a relatively high natural frequency of the system. When the external excitation frequency is close to or lower than this natural frequency, the isolator will lose its effective isolation function and may even enter the resonance range, causing a significant amplification of the vibration amplitude. Therefore, traditional linear vibration isolators have inherent limitations in suppressing low-frequency vibrations and cannot meet the stringent requirements for low-frequency vibration control in fields such as aerospace, precision instruments, and high-end equipment.

[0003] To overcome the aforementioned bottlenecks, researchers have proposed a quasi-zero stiffness vibration isolation technology based on nonlinear mechanical properties. The core principle of this technology lies in connecting positive and negative stiffness elements in parallel, utilizing nonlinear interactions to achieve near-zero stiffness within a specific displacement range, thereby significantly reducing the system's natural frequency and broadening the low-frequency isolation bandwidth. Currently, various structural forms for achieving quasi-zero stiffness have been extensively studied, such as elastic laminates based on bistable structures, negative stiffness mechanisms using diagonal bar springs based on geometric nonlinearity principles, cam-roller nonlinear transmission mechanisms, and flexible coupling systems utilizing magnetic levitation or airbag media. However, existing quasi-zero stiffness vibration isolators generally face the problem of "load mismatch," which is extremely sensitive to external loads. When the load in actual operating conditions deviates from the design preset value, the system's equilibrium position changes, causing the quasi-zero stiffness working zone to be disrupted or shifted. The isolator then struggles to maintain its optimal quasi-zero stiffness state, significantly weakening the vibration isolation effect.

[0004] To address the aforementioned load mismatch problem, existing research attempts to combine adjustable mechanisms with quasi-zero stiffness structures, dynamically compensating for load changes by introducing adaptive adjustment devices or external control methods. However, such methods often suffer from drawbacks such as high structural complexity, inconvenient adjustment operations, slow response speed, or lack of clear adjustment benchmarks.

[0005] Therefore, there is an urgent need for an adjustable quasi-zero stiffness vibration isolator that can guarantee quasi-zero stiffness performance, provide a clear indication of the optimal equilibrium position, and enable quick and easy load adaptation adjustment. Summary of the Invention

[0006] The purpose of this invention is to provide an adjustable zero-stiffness vibration isolator with an optimal balance position indicator, thereby solving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides an adjustable zero-stiffness vibration isolator with an optimal equilibrium position indicator, comprising an upper pressure plate, a lower pressure plate, an upper connecting plate fixed below the upper pressure plate, and a lower connecting plate fixed above the lower pressure plate. A positive stiffness mechanism is provided between the upper connecting plate and the lower connecting plate to provide a force to resist deformation in the vertical direction. An intermediate connecting plate is also provided between the upper connecting plate and the lower connecting plate, and a negative stiffness mechanism is provided between the upper connecting plate and the intermediate connecting plate. The upper part of the negative stiffness mechanism is connected to the upper connecting plate, and the lower part is connected to the intermediate connecting plate. A height adjustment mechanism is provided between the intermediate connecting plate and the lower connecting plate. By adjusting the height adjustment mechanism, the distance between the intermediate connecting plate and the lower connecting plate can be changed to ensure that the optimal vibration isolation characteristics of the quasi-zero stiffness vibration isolator are maintained under different load conditions.

[0008] Preferably, the upper pressure plate and the upper connecting plate, and the lower pressure plate and the lower connecting plate are all connected by bolts.

[0009] Preferably, the positive stiffness mechanism includes multiple sets of spring damping modules evenly distributed around the vertical central axis of the vibration isolator. The upper end of the spring damping module is connected to the upper connecting plate, and its lower end is connected to the lower connecting plate. Each spring damping module includes a helical spring and a damper disposed inside the helical spring.

[0010] Preferably, the negative stiffness mechanism includes an optimal balance indicator and a disc spring. The optimal balance indicator includes a vertical rod, a connecting rod, and a horizontal rod symmetrically arranged between the upper connecting plate and the middle connecting plate. One end of the vertical rod is fixedly connected to the lower surface of the upper connecting plate by a bolt, and the other end is hinged to one end of the connecting rod. The other end of the connecting rod is hinged to one end of the horizontal rod, and the other end of the horizontal rod is threadedly connected to a disc spring.

[0011] Preferably, a support guide frame is also fitted on the horizontal bar, and the support guide frame is fixedly connected to the intermediate connecting plate by bolts; The horizontal bar has receiving grooves on both sides of its body. Small springs and positioning blocks are installed in the receiving grooves. One end of the small spring is connected to the inner wall of the receiving groove, and the other end is fixedly connected to the positioning block. The outer tube wall of the support guide frame has positioning holes that are adapted to the outer diameter of the positioning block. When the vibration isolator reaches the optimal static balance position, the positioning block is embedded in the positioning hole of the support guide frame under the action of the small spring force to generate a positioning indication.

[0012] Preferably, the height adjustment mechanism includes a top block, an upper support frame, a lower support frame, a spiral rod, and a bottom block. The top block is fixedly connected to the lower surface of the intermediate connecting plate, and the bottom block is fixedly connected to the upper surface of the lower connecting plate. The two upper support frames are symmetrically arranged on both sides of the top block. The top of the upper support frame is hinged to the bottom of the top block, and the bottom of the lower support frame is hinged to the bottom block. The bottom of the upper support frame and the top of the lower support frame are hinged to each other through a connecting rod. The two connecting rods are connected to each other through a helical rod. One end of the helical rod is threaded, and the threaded end is threaded with the connecting rod on one side, while the connecting rod on the other side is slidably engaged with the helical rod. When turning the screw rod, the upper support and the lower support move closer to each other or further apart to adjust the distance between the intermediate connecting plate and the lower connecting plate.

[0013] Preferably, at the optimal static equilibrium position, the vertical rod and the connecting rod are perpendicular to each other, the disc spring is under compression, and the negative stiffness mechanism does not transmit the vertical component of force to the upward connecting plate.

[0014] Preferably, the positive stiffness mechanism is arranged radially outside the negative stiffness mechanism and the height adjustment mechanism, forming a radially nested structure.

[0015] Therefore, this invention provides an adjustable quasi-zero stiffness vibration isolator with an optimal equilibrium position indicator, which has the following beneficial effects: This invention adopts a quasi-zero stiffness design with a parallel positive stiffness mechanism and a negative stiffness mechanism, and utilizes disc springs, connecting rod guiding mechanisms, and helical spring damping modules to construct a compact nonlinear mechanical system, which can achieve vibration isolation characteristics of "high static stiffness support and low dynamic stiffness response". Compared with traditional linear vibration isolators, it can significantly reduce the system's initial vibration isolation frequency, effectively suppress low-frequency vibrations over a wide frequency range, and solve the technical problem of low-frequency vibration isolation.

[0016] This invention incorporates an optimal balance indicator in a negative stiffness mechanism. The device employs a structure where a horizontal rod is integrated into a support guide frame. Through the mechanical interaction of a small spring and a positioning block, the positioning block automatically engages with the positioning hole in the support guide frame when the vibration isolator reaches its optimal static balance position, providing a clear indication of positioning. This mechanical indicator structure requires no external sensors or electrical control, offering advantages such as low cost, high reliability, and intuitive feedback. It effectively solves the problem of difficulty in determining and adjusting the optimal balance position of existing quasi-zero stiffness vibration isolators.

[0017] This invention incorporates a height adjustment mechanism between the intermediate connecting plate and the lower connecting plate. When the actual load deviates from the design load, the upper and lower supports are moved closer or further apart by rotating a helical rod, precisely adjusting the distance between the intermediate and lower connecting plates. Combined with an optimal balance indicator, this allows the vibration isolator to be quickly restored to its optimal static balance position. This design enables the vibration isolator to operate stably at its optimal near-zero stiffness under various load conditions, significantly improving its adaptability to variable load conditions in practical applications. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the overall structure of an adjustable zero-stiffness vibration isolator with an optimal balance position indicator in an embodiment of the present invention. Figure 2 This is a schematic diagram of the overall structure of an adjustable zero-stiffness vibration isolator with optimal balance position indication from a second perspective in an embodiment of the present invention. Figure 3 This is a cross-sectional view of an adjustable zero-stiffness vibration isolator with an optimal equilibrium position indicator according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the negative stiffness mechanism in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the horizontal bar in an embodiment of the present invention; Figure 6 This is a schematic diagram of the supporting guide frame in an embodiment of the present invention; Figure 7 This is a simplified structural motion diagram of an adjustable zero-stiffness vibration isolator with an optimal equilibrium position indicator, according to an embodiment of the present invention. Figure Labels 1. Upper pressure plate; 2. Upper connecting plate; 3. Optimal balance indicator; 301. Vertical rod; 302. Connecting rod; 303. Horizontal rod; 304. Support guide frame; 305. Positioning block; 306. Small spring; 307. Rotating pin; 4. Disc spring; 5. Spring damping module; 501. Helical spring; 502. Damping; 6. Intermediate connecting plate; 7. Height adjustment mechanism; 701. Top block; 702. Upper support frame; 703. Lower support frame; 704. Helical rod; 705. Bottom block; 709. Connecting rod; 8. Lower connecting plate; 9. Lower pressure plate. Detailed Implementation

[0019] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0020] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0022] Example like Figure 1-7 As shown, this invention discloses an adjustable zero-stiffness vibration isolator with an optimal balance position indicator. The isolator in this embodiment generally includes an upper pressure plate 1, a lower pressure plate 9, an upper connecting plate 2 bolted to the lower part of the upper pressure plate 1, and a lower connecting plate 8 bolted to the upper part of the lower pressure plate 9. A positive stiffness mechanism is provided between the upper connecting plate 2 and the lower connecting plate 8, and an intermediate connecting plate 6 is also provided between them.

[0023] The positive stiffness mechanism includes multiple sets of spring-damping modules 5 evenly distributed around the vertical central axis of the vibration isolator. Each spring-damping module 5 consists of a helical spring 501 and a damper 502 disposed inside the helical spring 501. The upper end of the spring-damping module 5 is connected to the upper connecting plate 2, and the lower end is connected to the lower connecting plate 8. The helical spring 501 generates an elastic force proportional to the deformation in the vertical direction, forming a positive stiffness characteristic, used to bear static loads and provide restoring force against deformation; the damper 502 plays the role of suppressing resonance peaks and accelerating vibration attenuation. The circumferential distribution of multiple sets of spring-damping modules 5 ensures that the vibration isolator is subjected to uniform force when bearing vertical loads, avoiding eccentric loading.

[0024] A negative stiffness mechanism is provided between the upper connecting plate 2 and the intermediate connecting plate 6. This negative stiffness mechanism includes an optimal balance indicator 3 and a disc spring 4. The optimal balance indicator 3 includes a vertical rod 301, a connecting rod 302, and a horizontal rod 303 arranged symmetrically on both sides. The upper end of the vertical rod 301 is fixed to the lower surface of the upper connecting plate 2 by bolts, and its lower end is hinged to the outer end of the connecting rod 302 by a rotating pin 307. The inner end of the connecting rod 302 is hinged to one end of the horizontal rod 303 by a rotating pin 307. The other end of the horizontal rod 303 is connected to the disc spring 4 by threads.

[0025] To ensure that the horizontal rod 303 can only move horizontally without tilting, a support guide frame 304 is bolted to the intermediate connecting plate 6. The horizontal rod 303 passes through the channel of the support guide frame 304 and can slide axially along the channel. The support guide frame 304 and the interior of the horizontal rod 303 together constitute the specific execution part of the optimal balance indicator device: receiving grooves are opened on both sides of the horizontal rod 303, and small springs 306 and positioning blocks 305 are installed in the receiving grooves. One end of the small spring 306 is connected to the inner wall of the receiving groove, and the other end is fixedly connected to the positioning block 305. Correspondingly, a positioning hole adapted to the outer diameter of the positioning block 305 is opened on the outer tube wall of the support guide frame 304.

[0026] When the upper connecting plate 2 undergoes vertical displacement relative to the intermediate connecting plate 6, the vertical rod 301 drives the connecting rod 302 to swing, which in turn pushes the horizontal rod 303 to move horizontally, thereby compressing or releasing the disc spring 4. The reaction force of the disc spring 4 is transmitted back to the upper connecting plate 2 through the horizontal rod 303, the connecting rod 302, and the vertical rod 301. In the optimal static equilibrium position, the vertical rod 301 and the connecting rod 302 are perpendicular to each other, and the connecting rod 302 and the horizontal rod 303 are horizontally collinear. At this time, the compression of the disc spring 4 is the largest, but the component of the restoring thrust it generates, transmitted through the connecting rod 302 to the vertical rod 301, is exactly in the horizontal direction. Therefore, the negative stiffness mechanism does not transmit the vertical component of the force to the upper connecting plate 2, and the static load is entirely borne by the positive stiffness mechanism. When the upper connecting plate 2 undergoes a slight upward displacement, the vertical rod 301 drives the connecting rod 302 to swing, causing the horizontal rod 303 to move backward, reducing the pressure on the disc spring 4. However, it should be noted that the disc spring 4 is always under compression; the disc springs 4 do not separate. The reaction force of the disc spring 4 generates an upward component force through the connecting rod 302. This component force is opposite to the downward restoring force of the positive stiffness mechanism, thus reducing the overall stiffness of the system. Conversely, when the upper connecting plate 2 displaces downward, the negative stiffness mechanism generates a downward component force, similarly weakening the positive stiffness. By rationally designing the disc spring stiffness, connecting rod length, and initial angle, quasi-zero stiffness characteristics can be achieved near the equilibrium position, significantly reducing the system's natural frequency and effectively isolating low-frequency vibrations. The damper 502 continuously absorbs vibration energy during this process, further optimizing the dynamic response.

[0027] When adjusting the vibration isolator's balance position, the horizontal rod 303 slides horizontally within the support guide frame 304. Before the vibration isolator reaches its optimal static balance position, the positioning block 305 is pressed against the inner wall of the support guide frame 304 by the elastic force of the small spring 306 and moves with the horizontal rod 303. Once the vibration isolator reaches its optimal static balance position (i.e., the position where the vertical rod 301 is perpendicular to the connecting rod 302), the positioning block 305 automatically engages in the positioning hole of the support guide frame 304 under the push of the small spring 306, thus obtaining a clear indication of the position reached.

[0028] When the actual load differs from the design load, the static balance position of the vibration isolator will shift, causing the vertical rod 301 and connecting rod 302 to no longer be perpendicular, thus disrupting the quasi-zero stiffness working area. To address this issue, this embodiment includes a height adjustment mechanism 7 between the intermediate connecting plate 6 and the lower connecting plate 8. This height adjustment mechanism 7 comprises a top block 701, upper support frames 702, lower support frames 703, a helical rod 704, and a bottom block 705. The top block 701 is fixedly connected to the lower surface of the intermediate connecting plate 6, and the bottom block 705 is fixedly connected to the upper surface of the lower connecting plate 8. Two upper support frames 702 are symmetrically arranged on both sides of the top block 701, with their top ends hinged to the bottom of the top block 701; two lower support frames 703 are symmetrically arranged on both sides of the bottom block 705, with their bottom ends hinged to the bottom block 705. The bottom ends of the upper support frames 702 and the top ends of the lower support frames 703 are hinged together by connecting rods 709, and the connecting rods 709 on the left and right sides are connected together by helical rods 704. One end of the screw rod 704 is threaded, and the threaded end is threadedly engaged with the connecting rod 709 on one side, while the connecting rod 709 on the other side is slidably engaged with the screw rod.

[0029] When the operator rotates the screw rod 704, the connecting rods 709 on both sides move closer or further apart, which in turn causes the upper support 702 and the lower support 703 to move closer or further apart, thereby changing the vertical distance between the intermediate connecting plate 6 and the lower connecting plate 8. This adjustment can compensate for static balance drift caused by load changes: while rotating the screw rod 704, observe or feel the positioning signal of the optimal balance indicator 3. Once the positioning block 305 is engaged in the positioning hole, it indicates that the vibration isolator has returned to the new optimal static balance position. At this time, the negative stiffness mechanism is once again in a state of not transmitting vertical force, and the quasi-zero stiffness characteristics are re-established.

[0030] To fully utilize the internal space and reduce the overall axial height, this embodiment adopts a radially nested layout. The positive stiffness mechanism (multiple sets of spring damping modules 5) is arranged radially outside the negative stiffness mechanism and the height adjustment mechanism 7, meaning the positive stiffness mechanism circumferentially surrounds the internal negative stiffness and adjustment parts. This structure makes the vibration isolator more compact radially, facilitating installation and use in space-constrained engineering equipment. After the entire device is connected to the external structure via the upper pressure plate 1 and the lower pressure plate 9, it can stably operate at the optimal quasi-zero stiffness state under variable load conditions, achieving efficient low-frequency vibration isolation.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A tunable quasi-zero stiffness vibration isolator with optimal equilibrium position indication, characterized by: It includes an upper pressure plate, a lower pressure plate, an upper connecting plate fixed below the upper pressure plate, and a lower connecting plate fixed above the lower pressure plate. A positive stiffness mechanism is provided between the upper connecting plate and the lower connecting plate to provide a force to resist deformation in the vertical direction. An intermediate connecting plate is also provided between the upper connecting plate and the lower connecting plate, and a negative stiffness mechanism is provided between the upper connecting plate and the intermediate connecting plate. The upper part of the negative stiffness mechanism is connected to the upper connecting plate, and the lower part is connected to the intermediate connecting plate. A height adjustment mechanism is provided between the intermediate connecting plate and the lower connecting plate. By adjusting the height adjustment mechanism, the distance between the intermediate connecting plate and the lower connecting plate can be changed to ensure that the optimal vibration isolation characteristics of the quasi-zero stiffness vibration isolator are maintained under different load conditions. The negative stiffness mechanism includes an optimal balance indicator and a disc spring. The optimal balance indicator includes a vertical rod, a connecting rod, and a horizontal rod symmetrically arranged between the upper connecting plate and the middle connecting plate. One end of the vertical rod is fixedly connected to the lower surface of the upper connecting plate by a bolt, and the other end is hinged to one end of the connecting rod. The other end of the connecting rod is hinged to one end of the horizontal rod, and the other end of the horizontal rod is threadedly connected to a disc spring.

2. A tunable quasi-zero stiffness vibration isolator with optimal balance position indication according to claim 1, characterized in that: The upper pressure plate and the upper connecting plate, as well as the lower pressure plate and the lower connecting plate, are all connected by bolts.

3. A tunable quasi-zero stiffness vibration isolator with optimal balance position indication according to claim 2, characterized in that: The positive stiffness mechanism includes multiple sets of spring damping modules evenly distributed around the vertical central axis of the vibration isolator. The upper end of the spring damping module is connected to the upper connecting plate, and its lower end is connected to the lower connecting plate. Each spring damping module includes a helical spring and a damper disposed inside the helical spring.

4. An adjustable zero-stiffness vibration isolator with optimal equilibrium position indication according to claim 1, characterized in that: A support guide frame is also fitted onto the horizontal bar, and the support guide frame is fixedly connected to the intermediate connecting plate by bolts. The horizontal bar has receiving grooves on both sides of its body. Small springs and positioning blocks are installed in the receiving grooves. One end of the small spring is connected to the inner wall of the receiving groove, and the other end is fixedly connected to the positioning block. The outer tube wall of the support guide frame has positioning holes that are adapted to the outer diameter of the positioning block. When the vibration isolator reaches the optimal static balance position, the positioning block is embedded in the positioning hole of the support guide frame under the action of the small spring force to generate a positioning indication.

5. An adjustable zero-stiffness vibration isolator with optimal equilibrium position indication according to claim 4, characterized in that: The height adjustment mechanism includes a top block, an upper support frame, a lower support frame, a spiral rod, and a bottom block. The top block is fixedly connected to the lower surface of the intermediate connecting plate, and the bottom block is fixedly connected to the upper surface of the lower connecting plate. The two upper support frames are symmetrically arranged on both sides of the top block. The top of the upper support frame is hinged to the bottom of the top block, and the bottom of the lower support frame is hinged to the bottom block. The bottom of the upper support frame and the top of the lower support frame are hinged to each other through a connecting rod. The two connecting rods are connected to each other through a helical rod. One end of the helical rod is threaded, and the threaded end is threaded with the connecting rod on one side, while the connecting rod on the other side is slidably engaged with the helical rod. When turning the screw rod, the upper support and the lower support move closer to each other or further apart to adjust the distance between the intermediate connecting plate and the lower connecting plate.

6. An adjustable zero-stiffness vibration isolator with optimal equilibrium position indication according to claim 5, characterized in that: At the optimal static equilibrium position, the vertical rod and the connecting rod are perpendicular to each other, the disc spring is under compression, and the negative stiffness mechanism does not transmit the vertical component of force to the upward connecting plate.

7. An adjustable zero-stiffness vibration isolator with optimal equilibrium position indication according to claim 6, characterized in that: The positive stiffness mechanism is arranged radially outside the negative stiffness mechanism and the height adjustment mechanism, forming a radially nested structure.

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