Rotary machinery low-frequency circumferential vibration isolation device based on high static and low dynamic stiffness

Abstract

The invention provides a rotating machine low-frequency annular vibration isolation device based on high static and low dynamic stiffness. The rotating machine low-frequency annular vibration isolation device comprises a flange inner ring and a flange outer ring which are concentrically arranged; two linear connecting rods; a plurality of quasi-zero stiffness thrust connecting rods and quasi-zero stiffness tension connecting rods; wherein the linear connecting rods, the quasi-zero stiffness thrust connecting rods and the tension connecting rods are symmetrically distributed between the inner ring and the outer ring of the flange, and the two linear connecting rods are distributed at an angle of 180 degrees; the quasi-zero-stiffness thrust connecting rod and the pull connecting rod are arranged on the two sides of the straight line where the two linear connecting rods are located respectively. The annular multi-direction vibration isolation structure is established through the annularly-distributed elastic components, multi-direction vibration energy is dispersed and attenuated while the bearing stability of the device is guaranteed, a structural strength checking mechanism is matched, the engineering problem of complex vibration mode suppression and system safety cooperative control is effectively solved, the operation reliability of power equipment is remarkably improved, and the reliability of the power equipment is improved. And therefore, the vibration isolation requirement of the power device in actual engineering application can be better met.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration isolation, and particularly to a low-frequency circumferential vibration isolation device for rotating machinery based on high static and low dynamic stiffness. Background Technique

[0002] In practical engineering applications, the impact and vibration of mechanical equipment are inevitable during operation, and often result in undesirable vibration and fatigue phenomena. Therefore, in the early design stage, vibration isolation measures are introduced to effectively avoid the deterioration of vibration, thereby improving the operational reliability of the device. With the continuous development of modern industrial technology, the requirements for vibration reduction and noise reduction in fields such as precision instruments, medical equipment, and aerospace have been continuously increasing, and the design of traditional linear vibration isolation devices can no longer meet their vibration isolation requirements. The quasi-zero stiffness isolator has the characteristics of "high static and low dynamic" (high static stiffness to support the load and low dynamic stiffness to achieve low-frequency vibration isolation). In recent years, it has received much attention in the field of vibration reduction and noise reduction. The emergence of the quasi-zero stiffness vibration isolation method provides a new idea for solving this problem. The quasi-zero stiffness structure has the advantages of high load-bearing mass, small dynamic stiffness, no obvious resonance phenomenon, and significantly better vibration isolation performance in the low-frequency region. With the development of the quasi-zero stiffness theory, the design of quasi-zero stiffness structures has emerged continuously. Currently, according to the vibration direction of the vibration isolation object, these structures can be divided into single-direction quasi-zero stiffness isolators and multi-direction quasi-zero stiffness isolators. For example: The invention patent with the publication number CN 118881689 A, titled "A Compact Low-Frequency Vibration Isolation Device with a Parallel Magnetic Negative Stiffness Structure", proposes a low-frequency vibration isolator using a parallel arrangement of three linear magnetic negative stiffness vibration isolation mechanisms. This device has the advantages of a compact structure and strong load-bearing capacity. The invention patent with the publication number CN 118757537 A, titled "A Quasi-Zero Stiffness Low-Frequency Vibration Isolator with Three-Degree-of-Freedom Decoupling", proposes a quasi-zero stiffness low-frequency vibration isolator combining a slide rail group and a flexible double circular arc beam. This device has the advantages of high space utilization rate and multi-directional vibration isolation. The invention patent with the publication number CN 118757537 A, titled "A Six-Degree-of-Freedom Quasi-Zero Stiffness Vibration Isolation Platform", proposes a multi-degree-of-freedom quasi-zero stiffness vibration isolation platform based on an air spring. This device has the ability to adjust the bearing capacity and stiffness.

[0003] Although the unidirectional quasi-zero stiffness vibration isolator has achieved good application effects, the structural design of such vibration isolation devices only has the characteristics of high static stiffness and low dynamic stiffness in one degree of freedom, and the movement in other directions is completely restricted. In practical engineering applications, due to reasons such as imbalance and misalignment, rotating machinery may cause vibration transmission in any circumferential direction. Since the vibration of the vibration source does not exist only in a single degree of freedom, the effect of the unidirectional quasi-zero stiffness vibration isolator is quite limited at this time. Due to the existence of non-diagonal terms in the stiffness matrices in different directions of the multi-directional vibration isolator, a single-direction excitation causes vibration responses in multiple directions, resulting in a vibration coupling problem and reducing the low-frequency vibration isolation effect. Especially in the face of problems such as large self-weight, low vibration frequency, and small installation space of precision equipment, it is difficult to meet the low-frequency vibration reduction requirements by using the traditional quasi-zero stiffness structure.

[0004] Aiming at the challenges that power devices such as motors and shaft systems of underwater vehicles often face circumferential low-frequency vibrations during actual operation, facing the problems of concentrated low-frequency vibration energy, easy to cause structural resonance, and insufficient means of acoustic stealth performance, traditional linear vibration isolation systems are difficult to balance large load-bearing and low starting vibration isolation frequencies. Summary of the Invention

[0005] Aiming at the problems that traditional linear systems are difficult to simultaneously achieve low dynamic stiffness and high static stiffness and suppress multi-directional complex vibration modes, the present invention provides a low-frequency circumferential vibration isolation device for rotating machinery based on high static and low dynamic stiffness, aiming to innovate and optimize the vibration isolation system. Through annularly distributed elastic components, a circumferential multi-directional vibration isolation structure is established to disperse and attenuate multi-directional vibration energy while ensuring the load-bearing stability of the device. Cooperating with the structural strength checking mechanism, it effectively solves the engineering problems of coordinated control of complex vibration mode suppression and system safety, significantly improves the operation reliability of power equipment, and thus better serves the vibration isolation requirements of power devices in practical engineering applications.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A low-frequency circumferential vibration isolation device for rotating machinery based on high static and low dynamic stiffness, the device includes: A flange inner ring and a flange outer ring arranged concentrically; two linear connecting rods; a plurality of quasi-zero stiffness thrust connecting rods and quasi-zero stiffness tension connecting rods; Among them, the linear connecting rods, quasi-zero stiffness thrust connecting rods, and tension connecting rods are all symmetrically distributed between the flange inner ring and the outer ring, and the two linear connecting rods are distributed at 180 degrees; The quasi-zero stiffness thrust connecting rods and tension connecting rods are respectively arranged on both sides of the straight line where the two linear connecting rods are located.

[0007] Furthermore, the quasi-zero stiffness thrust connecting rod includes: a helical spring, a negative stiffness mechanism, a thrust connecting rod sleeve, a sliding bearing, a bushing, and a thrust sliding rod; Inside the thrust connecting rod sleeve, there are successively arranged a sliding bearing installation cavity, a middle installation cavity, and a bushing installation cavity from the end close to the inner ring of the flange to the end close to the outer ring of the flange. The sliding bearing installation cavity and the bushing installation cavity are respectively installed with a sliding bearing and a bushing. The thrust sliding rod successively penetrates through the sliding bearing, the middle installation cavity, and the bushing from the end of the thrust connecting rod sleeve close to the inner ring of the flange to the end of the thrust connecting rod sleeve close to the outer ring of the flange; The helical spring is assembled on the thrust sliding rod in a pre-compressed state, and is located between the negative stiffness mechanism and the end of the tension connecting rod sleeve close to the outer ring of the flange.

[0008] Further, the quasi-zero stiffness tension connecting rod includes: a helical spring, a negative stiffness mechanism, a sliding bearing, a bushing, a tension connecting rod sleeve, and a tension sliding rod; Inside the tension connecting rod sleeve, there are successively arranged a bushing installation cavity, a middle installation cavity, and a sliding bearing installation cavity from the end close to the inner ring of the flange to the end close to the outer ring of the flange. The sliding bearing installation cavity and the bushing installation cavity are respectively installed with a sliding bearing and a bushing. The tension sliding rod successively penetrates through the bushing, the middle installation cavity, and the sliding bearing from the end of the tension connecting rod sleeve close to the inner ring of the flange to the end of the tension connecting rod sleeve close to the outer ring of the flange; The helical spring is assembled on the tension sliding rod in a pre-compressed state, and is located between the negative stiffness mechanism and the end of the thrust connecting rod sleeve close to the inner ring of the flange.

[0009] Further, the linear connecting rod includes: a helical spring, a bushing, a linear connecting rod sleeve, a linear sliding rod, a linear shaft retaining ring, and a linear spring base; Inside the linear connecting rod sleeve, there are successively arranged a first bushing installation cavity, a middle installation cavity, and a second bushing installation cavity from the end close to the inner ring of the flange to the end close to the outer ring of the flange. The two bushings are respectively installed in the first bushing installation cavity and the second bushing installation cavity. The linear sliding rod successively penetrates through the bushing, the middle installation cavity, and the bushing from the end of the linear connecting rod sleeve close to the inner ring of the flange to the end of the linear connecting rod sleeve close to the outer ring of the flange; The linear spring base is fixedly connected to the linear sliding rod, and the linear shaft retaining ring is fixedly connected to the bushing installed in the first bushing installation cavity; The helical spring is assembled in a pre-compressed state between the linear shaft retaining ring and the linear spring base.

[0010] Further, the negative stiffness mechanism is installed in the middle installation cavity and includes an inner magnetic ring and an outer magnetic ring. The inner magnetic ring is fixed to the tension sliding rod or the thrust sliding rod, and the outer magnetic ring is fixed to the inner wall of the tension connecting rod sleeve or the thrust connecting rod sleeve. And the inner magnetic ring and the outer magnetic ring are magnetized in the same direction to generate a repulsive force.

[0011] Furthermore, the thrust slide bar, the tension slide bar, and the linear slide bar are all stepped shafts.

[0012] Furthermore, one end of the thrust slide bar, the tension slide bar, and the linear slide bar close to the inner ring of the flange is provided with a connecting ring, and the end close to the outer ring of the flange is a free end. Nuts are connected to both ends. One end of the thrust slide bar, the tension slide bar, and the linear slide bar close to the inner ring of the flange is connected to the inner ring of the flange through a rivet rod.

[0013] Furthermore, one end of the thrust connecting rod sleeve, the tension connecting rod sleeve, and the linear connecting rod sleeve close to the outer ring of the flange are all connected to the outer ring of the flange through an axial displacement limiting member.

[0014] Furthermore, the thrust connecting rod sleeve, the tension connecting rod sleeve, and the linear connecting rod sleeve are all formed by splicing two half sleeves and are fastened by screws and nuts.

[0015] Furthermore, the inner walls of the sleeves of the thrust connecting rod sleeve and the tension connecting rod sleeve are provided with grooves for fixing the outer magnetic ring.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention solves the problem that traditional quasi-zero stiffness vibration isolators are mostly single-degree-of-freedom vibration isolators or multi-degree-of-freedom vibration isolation platforms and cannot solve the problem of circumferential vibration isolation. Traditional quasi-zero stiffness vibration isolators mostly adopt linear or planar layouts, while the circumferential design achieves the consistency of multi-directional mechanical properties through a circular symmetric structure (such as a circular spring, a circular negative stiffness unit, or a magnetic ring). This design can evenly distribute the load, enhance the stability and load-bearing capacity of the system. The circular symmetric design reduces the influence of external disturbances (such as eccentric loads, etc.) on the system performance and improves the vibration isolation stability.

[0017] (2) The present invention solves the contradiction between low dynamic stiffness and high static stiffness that traditional linear vibration isolators cannot solve.

[0018] Through the parallel combination of positive stiffness elements (such as springs) and negative stiffness elements (such as magnetic repulsion or preloading structures) arranged in a ring, the stiffness approaches zero near the equilibrium position while maintaining a high static load-bearing capacity. The circumferential layout can avoid the instability problem of negative stiffness units in traditional designs. The symmetry of the circular structure enables it to have good isolation effects on multi-directional vibrations (such as axial, radial, and even torsional vibrations), breaking through the limitations of the single-direction performance of traditional vibration isolators.

[0019] (3) The present invention solves the problem that large-load vibration isolators are large in volume and not compact in structure.

[0020] (4) The present invention meets the requirements of complex working conditions. By combining structural innovation (ring layout) and mechanical property innovation (quasi-zero stiffness), the circumferential quasi-zero stiffness vibration isolator solves the bottleneck problems of traditional vibration isolators in low-frequency and multi-directional vibration isolation, and has high load-bearing capacity, wide frequency band and strong adaptability, providing a reference for the development direction of the future high-end equipment vibration control field. Description of the Drawings

[0021] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0022] Figure 1 It is a schematic diagram of the overall structure of a compact low-frequency vibration isolation device for a circumferential high-static-low-dynamic stiffness rotating machine; Figure 2 It is a schematic diagram of the quasi-zero stiffness thrust connecting rod with (a) the outer magnetic ring and spring assembled and (b) not assembled, and (c) the position of the shaft retaining ring on the thrust slide rod; Figure 3 It is a schematic diagram of the quasi-zero stiffness tension connecting rod with (a) the outer magnetic ring and spring assembled and (b) not assembled, and (c) a schematic diagram of the position of the shaft retaining ring on the tension slide rod; Figure 4 It is a schematic diagram of the linear connecting rod with (a) the spring assembled and (b) not assembled, and (c) a schematic diagram of the position of the shaft retaining ring on the linear slide rod; Figure 5 It is a structural model of a pair of coaxial ring permanent magnets, (a) is a schematic diagram; (b) is an equivalent model; Figure 6 It is the magnetic force-displacement curve obtained by the finite element method and the theoretical model; Figure 7 It is a schematic diagram of the inner magnetic ring retaining ring, the magnetic ring retaining ring and the shaft retaining ring, where (a) is the inner magnetic ring retaining ring, (b) is the magnetic ring retaining ring, and (c) is the schematic diagram of the shaft retaining ring; Figure 8 It is a schematic diagram of the quasi-zero stiffness thrust connecting rod sleeve (linear connecting rod sleeve) and the quasi-zero stiffness tension connecting rod sleeve, where (a) is a schematic diagram of the quasi-zero stiffness thrust connecting rod sleeve and the linear connecting rod sleeve, and (b) is a schematic diagram of the quasi-zero stiffness tension connecting rod sleeve; Figure 9 It is a schematic diagram of the inner and outer rings of the flange; Figure 10 It is a schematic diagram of the overall installation of the vibration isolator, (a) the inner ring of the support frame is connected to the internal motor, and (b) the outer ring of the support frame is connected to the housing; Figure 11For the circumferential static stiffness distribution of the vibration isolator, (a) relationship between the displacement of the inner ring of the support frame and the magnitude of the restoring force, (b) relationship between the displacement of the inner ring of the support frame and the stiffness; Figure 12 It is a length locator for the elastic connecting rod.

[0023] Wherein, 1. Inner flange ring; 2. Outer flange ring; 3. Quasi-zero stiffness thrust connecting rod; 4. Quasi-zero stiffness tension connecting rod; 5. Linear connecting rod; 6. Rivet rod; 7. Axial displacement limiting member; 8. Helical spring; 9. Outer magnetic ring; 10. Thrust connecting rod sleeve; 11. Sliding bearing; 12. Bush; 13. Inner magnetic ring; 14. Thrust sliding rod; 15. Inner magnetic ring retaining ring; 16. Magnetic ring retaining ring; 17. Shaft retaining ring; 18. Tension connecting rod sleeve; 19. Tension sliding rod; 20. Linear connecting rod sleeve; 21. Linear shaft retaining ring; 22. Linear sliding rod; 23. Linear spring base. Specific embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0025] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0026] Embodiment 1 As Figure 1As shown in the figure, this embodiment provides a low-frequency circumferential vibration isolation device for rotating machinery based on high static and low dynamic stiffness, which realizes the quasi-zero stiffness characteristic based on the principle of parallel connection of positive and negative stiffness, and uses a permanent magnet ring as the negative stiffness mechanism in the thrust and tension connecting rods. This rotating machinery low-frequency vibration isolation device mainly consists of three parts: a rigid component, a connecting rod, and a hinged component. Among them, the rigid component includes an inner flange ring and an outer flange ring; the connecting rods are divided into three categories: a quasi-zero stiffness thrust connecting rod, a quasi-zero stiffness tension connecting rod, and a linear connecting rod. The quasi-zero stiffness connecting rod includes an inner magnetic ring, an outer magnetic ring, a sleeve, a sliding rod, and a helical spring, etc. The linear connecting rod does not contain negative stiffness components such as magnetic rings; the hinged component includes a rivet rod and an inner ring axial displacement limiting component, etc. This vibration isolation device uses a pair of coaxial annular permanent magnets to achieve negative stiffness, and the helical spring provides positive stiffness. The vibration isolation flange of the precision equipment is composed of three quasi-zero stiffness tension connecting rods, three quasi-zero stiffness thrust connecting rods, and two linear spring connecting rods. One vibration isolation flange is installed at each of the front and rear ends of the power device. The design of the quasi-zero stiffness connecting rod enables the system to exhibit the quasi-zero stiffness characteristic at a specific vibration frequency, that is, near the static equilibrium position, the response of the system to small vibrations is almost zero, thus achieving efficient low-frequency vibration reduction. Each vibration isolation flange can provide vibration isolation effects in multiple degrees of freedom, thereby comprehensively reducing the impact of vibration on the power device and improving the stability and reliability of the equipment.

[0027] Specifically, the device includes: An inner flange and an outer flange arranged concentrically; two linear connecting rods; multiple quasi-zero stiffness thrust connecting rods and quasi-zero stiffness tension connecting rods; Among them, the linear connecting rods, the quasi-zero stiffness thrust connecting rods, and the tension connecting rods are all symmetrically distributed between the inner and outer flange rings, and the two linear connecting rods are distributed at 180 degrees; The quasi-zero stiffness thrust connecting rods and the tension connecting rods are respectively arranged on both sides of the straight line where the two linear connecting rods are located.

[0028] As Figure 2 shown, the quasi-zero stiffness thrust connecting rod 3 includes: a helical spring 8, a negative stiffness mechanism, a thrust connecting rod sleeve 10, a sliding bearing 11, a bushing 12, and a thrust sliding rod 14.

[0029] A sliding bearing installation cavity, a middle installation cavity, and a bushing installation cavity are sequentially arranged in the thrust connecting rod sleeve 10 from the end close to the inner flange ring to the end close to the outer flange ring. The sliding bearing installation cavity and the bushing installation cavity are respectively installed with a sliding bearing and a bushing. The thrust sliding rod sequentially passes through the sliding bearing, the middle installation cavity, and the bushing from the end of the thrust connecting rod sleeve close to the inner flange ring to the end of the thrust connecting rod sleeve close to the outer flange ring; The negative stiffness mechanism is installed in the middle installation cavity, including an inner magnetic ring and an outer magnetic ring. The inner magnetic ring is fixed to the thrust slide rod, and the outer magnetic ring is fixed to the inner wall of the thrust connecting rod sleeve. The inner magnetic ring and the outer magnetic ring are magnetized in the same direction to generate a repulsive force.

[0030] In a further embodiment, two shaft retaining rings 17 of the quasi-zero stiffness thrust connecting rod 3 are respectively assembled in the grooves reserved for them on the thrust slide rod 14. An inner magnetic ring retaining ring 15 and a magnetic ring retaining ring 16 are installed between these two retaining rings, and an inner magnetic ring 13 is placed between them. The outer magnetic ring 9 is assembled in the inner groove of the thrust connecting rod sleeve 10. The helical spring 8 is assembled in a pre-compressed state on the other side of the shaft retaining ring, and a sliding bearing 11 is sleeved on the thrust slide rod. Finally, the two half sleeves of the thrust connecting rod are connected with screws and nuts, and the two ends of the slide rod are fastened with nuts to complete the assembly of the quasi-zero stiffness component.

[0031] Figure 2 Figures (a) and (b) are respectively schematic structural diagrams of the quasi-zero stiffness thrust connecting rod without the outer magnetic ring and the spring assembled. Figure 2 Figure (c) shows the position of the shaft retaining ring on the thrust slide rod. A linear bearing is sleeved on a section of the thrust slide rod to ensure that the slide rod always moves in a straight line during the movement process, preventing it from tilting and causing the vibration isolator to lose its vibration isolation effect. The other end with a circular ring-like hole is hinged to the inner ring of the flange through an axial displacement limiting member.

[0032] There are multiple grooves at the middle position of the thrust slide rod for installing baffles and retaining rings to achieve the conduction of the spring elastic force and the magnetic force of the magnetic ring. The grooves at the thrust slide rod will clamp the shaft retaining ring, and the shaft retaining ring will fix the spring baffle, the inner magnetic ring and the inner magnetic ring retaining ring on the thrust slide rod on both sides. The main function of the shaft retaining ring is to fix the inner magnetic ring and support the helical spring, and cooperate with the grooves on the thrust slide rod to transfer the spring elastic force and the magnetic force of the magnetic ring to the thrust slide rod.

[0033] As Figure 3 shown, the quasi-zero stiffness tension connecting rod includes: a helical spring, a negative stiffness mechanism, a sliding bearing, a bushing, a tension connecting rod sleeve, and a tension slide rod; Among them, an inner bushing installation cavity, a middle installation cavity, and a sliding bearing installation cavity are sequentially arranged in the tension connecting rod sleeve from the end close to the inner ring of the flange to the end close to the outer ring of the flange. The sliding bearing installation cavity and the bushing installation cavity respectively install a sliding bearing and a bushing. The tension slide rod sequentially passes through the bushing, the middle installation cavity, and the sliding bearing from the end of the tension connecting rod sleeve close to the inner ring of the flange to the end of the tension connecting rod sleeve close to the outer ring of the flange; The negative stiffness mechanism is installed in the middle installation cavity, including an inner magnetic ring and an outer magnetic ring. The inner magnetic ring is fixed to the tension slide rod, and the outer magnetic ring is fixed to the inner wall of the tension connecting rod sleeve. The inner magnetic ring and the outer magnetic ring are magnetized in the same direction to generate a repulsive force.

[0034] In a further embodiment, two shaft retaining rings 17 of the quasi-zero stiffness tension connecting rod 4 are respectively assembled in the grooves reserved for them on the tension slide rod 19. An inner magnetic ring retaining ring 15 and a magnetic ring retaining ring 16 are installed between these two retaining rings, and an inner magnetic ring 13 is placed between them. The outer magnetic ring 9 is assembled in the inner groove of the tension connecting rod sleeve 18. The spring 8 is assembled in a pre-compressed state on the other side of the shaft retaining ring, and a sliding bearing 11 is sleeved on the tension slide rod. Finally, the two half sleeves of the tension connecting rod are connected with screws and nuts, and the two ends of the slide rod are fastened with nuts to complete the assembly of the quasi-zero stiffness component.

[0035] Figure 3 Figures (a) and (b) are respectively schematic diagrams of the quasi-zero stiffness thrust connecting rod with and without the outer magnetic ring and spring assembled. Figure 3 Figure (c) shows the position of the shaft retaining ring on the thrust connecting rod. Here, the assembly process of the quasi-zero stiffness tension connecting rod is the same as that of the quasi-zero stiffness thrust connecting rod. The difference between the two lies in the slightly different sleeve structures at their connections with the inner flange and whether the force provided by their slide rods is tension or thrust. Here, both the quasi-zero stiffness thrust connecting rod and the tension connecting rod use the same pair of coaxial annular permanent magnets as the negative stiffness mechanism, and the two annular permanent magnets used have the same magnetization direction to ensure that they repel each other during movement, thereby realizing the negative stiffness characteristic. When the vibration isolation flange is affected by vibration and moves vertically upward or downward, the inner magnetic ring also generates a vertical displacement, thus creating a height difference with the outer magnetic ring, thereby generating magnetic force and negative stiffness to offset the positive stiffness. Therefore, the designed quasi-zero stiffness vibration isolation flange can achieve low stiffness characteristics while ensuring the load-bearing capacity, thereby realizing excellent low-frequency vibration isolation performance. A helical spring is used as the positive stiffness mechanism in the quasi-zero stiffness mechanism to support the load and provide positive stiffness. To ensure the compactness of the vibration isolation device, the height of the helical spring is minimized as much as possible while ensuring its stiffness and compression stroke.

[0036] As Figure 4 shown, the linear connecting rod includes: a helical spring, a shaft sleeve, a linear connecting rod sleeve, a linear slide rod, a linear shaft retaining ring, and a linear spring base; Wherein, a first shaft sleeve installation cavity, a middle installation cavity, and a second shaft sleeve installation cavity are successively arranged in the linear connecting rod sleeve from the end close to the inner circle of the flange to the end close to the outer circle of the flange. The two shaft sleeves are respectively installed in the first shaft sleeve installation cavity and the second shaft sleeve installation cavity. The linear slide rod successively penetrates through the shaft sleeve, the middle installation cavity, and the shaft sleeve from the end of the linear connecting rod sleeve close to the inner circle of the flange to the end of the linear connecting rod sleeve close to the outer circle of the flange; The linear spring base is fixedly connected to the linear slide rod, and the linear shaft retaining ring is fixedly connected to the shaft sleeve installed in the first shaft sleeve installation cavity; In a further embodiment, two shaft retaining rings 17 of the linear connecting rod 5 are respectively assembled in the grooves reserved for them on the linear slide rod 22. A linear shaft retaining ring 21 is installed between these two retaining rings and assembled in the linear connecting rod sleeve 20. The helical spring 8 is assembled in a pre-compressed state on the other side of the shaft retaining ring, and a linear spring base 23 is sleeved on the tension slide rod. Finally, the two half sleeves of the connecting rod are connected with screws and nuts, and the two ends of the slide rod are fastened with nuts to complete the assembly of this component.

[0037] Figure 4 Figures (a) and (b) are respectively the structural schematic diagrams of the linear connecting rod with and without the spring assembled. Figure 4 Figure (c) shows the position of the shaft retaining ring on the linear slide rod. The sleeve structure of the linear connecting rod is the same as that of the quasi-zero stiffness thrust connecting rod, but its internal slide rod structure is different. Only a spring is installed inside the linear connecting rod as a positive stiffness mechanism, and there is no magnetic ring to provide negative stiffness. Therefore, this structure is not a quasi-zero stiffness component.

[0038] In addition, the sliding bearing components in the three types of connecting rods work under sliding friction, which has the advantages of smooth operation, reliability, and no noise. Under the condition of liquid lubrication, the sliding surfaces are separated by lubricating oil and do not come into direct contact, greatly reducing friction losses and surface wear. Moreover, the oil film has a certain vibration absorption capacity, which can enhance the vibration damping effect. The main function of the sliding bearing is to reduce the frictional force generated by the guiding shaft during vertical movement, ensure the guiding function of the guiding shaft, and prevent the quasi-zero stiffness vibration isolator from tilting during movement.

[0039] A limiting structure is designed in the sleeve. On the one hand, it prevents the quasi-zero stiffness vibration isolator from having too large a movement stroke, and on the other hand, it realizes the pre-compression of the positive stiffness mechanism. A groove for installing the outer magnetic ring is left in the sleeve to fix it. Therefore, the design of the width dimension of the groove needs to have an interference fit with the width of the outer magnetic ring. And there is also a round hole at the lower end of the bearing platform for installing the sliding bearing and connecting it to the guiding shaft. In this way, it is possible to ensure that the quasi-zero stiffness vibration isolator only generates displacement in the vertical direction during movement, avoiding movement and deflection in other planar directions, thereby ensuring the stability of the movement of the quasi-zero stiffness vibration isolator and its low-frequency vibration isolation performance.

[0040] In this embodiment, the quasi-zero stiffness component includes a negative stiffness mechanism and a positive stiffness mechanism: A pair of coaxial annular permanent magnets are used as the negative stiffness mechanism, which can not only minimize the space size of the quasi-zero stiffness thrust (pressure) connecting rod to the greatest extent, but also reduce the mutual frictional force between the mechanisms, improve the low-frequency vibration isolation performance of the vibration isolation device, and meet the compactness condition. The permanent magnets used are magnetic rings, and their geometric parameters are shown in Table 1.

[0041] Table 1 Geometric parameters of the permanent magnet

[0042] Based on Coulomb's law, an axially magnetized toroidal permanent magnet is equivalent to two thin coils with opposite current directions and equal magnitudes located on the inner and outer toroidal surfaces. Therefore, first, the two toroidal permanent magnets are respectively equivalent to two thin coils, with their inner and outer radii being 、 and 、 , as shown in Figure 5 . Secondly, the turn arrangement of the thin coil is related to the equivalent current density. Specifically, the equivalent current in each filament is , is the magnetic permeability of vacuum, and the number of turns is ensured to be large enough; finally, the total force between a pair of coaxial toroidal permanent magnets is equal to the superposition of the forces between each pair of filaments.

[0043] Therefore, according to the equivalent theoretical model of a pair of coaxial toroidal permanent magnets, the magnetic force between them can be expressed as:

[0044] where 、 、 and are:

[0045] In the above formula, 、 、 and are all axial force equations between two coaxial filaments and can be given by the following formula:

[0046] In the formula, and are the currents in the equivalent filaments of the inner and outer toroidal permanent magnets, respectively, in A; and are the first and second complete elliptic integrals with respect to the modulus .

[0047]

[0048] In the formula, is the axial distance between the inner and outer toroidal permanent magnets, in m; is the axial distance between the centers of the two filaments, in m; and are the inner and outer radii of the inner toroidal permanent magnet, respectively, in m; and are the inner and outer radii of the outer toroidal permanent magnet, respectively, in m; and are the axial heights of the internal annular permanent magnet and the external annular coil, respectively, in m; and are the axial turns of the internal and external annular permanent magnets equivalent to thin coils, respectively, in turns. Using the above theoretical model and the finite element software COMSOL Multiphysics, the magnetic force between a pair of coaxial annular coils and permanent magnets given in Table 1 is calculated, and the results are as Figure 6 shown, where the red solid line represents the analytical result and the cyan square represents the finite element simulation result. It can be found from the figure that the magnetic force results obtained by the theoretical model and the finite element method are basically the same, verifying the accuracy of the magnetic force theoretical model.

[0049] The positive stiffness mechanism in this embodiment is a helical spring: A helical spring is an elastic element widely used in various types of machinery and can produce large deformations under load. Helical springs are often selected as the positive stiffness mechanism in the quasi-zero stiffness mechanism. The positive stiffness mechanism used here is a 30 mm - 3 mm helical spring (where 30 mm is the length and 3 mm is the wire diameter), and its dimensional parameters are shown in Table 2. The material selected for it is 1023 carbon steel plate (SS) and its material parameters. The designed quasi-zero stiffness vibration isolator pre-compresses the positive stiffness element to avoid plastic deformation of the helical spring.

[0050] Table 2 Spring dimensional parameters

[0051] In a further embodiment, the model of the sliding bearing 11 is LM10UU, that is, 10×19×29 mm, and the material is high-carbon chromium bearing steel. Its rated dynamic load is 370 N and its rated static load is 540 N. It is fixed in the round hole of the bearing platform and contacts the guide shaft.

[0052] As Figure 7 shown, (a) is the structure of the inner magnetic ring retaining ring, (b) is the structure of the magnetic ring retaining ring, and (c) is the structure of the shaft retaining ring.

[0053] As Figure 8 shown, the sleeve of the quasi-zero stiffness connecting rod is composed of two half-sleeves and is fastened by screws and nuts during installation, Figure 8 which are the structural schematic diagrams of the thrust connecting rod sleeve (linear connecting rod sleeve) and the tension connecting rod sleeve respectively. Here, the structures of the thrust connecting rod sleeve and the linear connecting rod sleeve are the same.

[0054] Among them, (a) is the structure of the thrust connecting rod sleeve and the linear connecting rod sleeve, and (b) is the structure of the tension connecting rod sleeve.

[0055] As Figure 9As shown in the figure, it is a schematic structural diagram of the inner flange ring and the outer flange ring. The materials of the inner and outer rings of the vibration isolation flange are both 2014-T4. The outer side of the outer flange ring is connected to the load-bearing platform through threaded holes, and the reserved holes on the inner side of the outer flange ring are connected to the end of the quasi-zero stiffness connecting rod through rivet rods. As Figure 9 shown, the outer side of the inner flange ring is hinged to the inner ring axial displacement limiting member through a reserved hole, and threaded holes are provided on the inner flange ring for connecting to the vibration-isolated power device.

[0056] In a further embodiment, the thrust slide rod, the tension slide rod, and the linear slide rod are all stepped shafts. Further, a connecting ring is provided at one end of the thrust slide rod, the tension slide rod, and the linear slide rod close to the inner flange ring, and the end close to the outer flange ring is a free end, and nuts are connected at both ends. One end of the thrust slide rod, the tension slide rod, and the linear slide rod close to the inner flange ring is connected to the inner flange ring through a rivet rod.

[0057] In a further embodiment, one end of the thrust connecting rod sleeve, the tension connecting rod sleeve, and the linear connecting rod sleeve close to the outer flange ring are all connected to the outer flange ring through an axial displacement limiting member.

[0058] Introduction to the vibration isolation function of the device in this embodiment: The invented vibration isolation device realizes the quasi-zero stiffness characteristic by setting a parallel mechanism of a positive stiffness element and a negative stiffness element in each tension connecting rod and thrust connecting rod. Among them, the positive stiffness element is a helical spring, and the negative stiffness element is a pair of annular permanent magnets with the same magnetization direction. The front and rear two identical vibration isolation devices are fixedly connected to the vibration-isolated engine through the threaded holes on the inner flange ring to achieve the performance of low-frequency vibration isolation. The complete installation schematic diagram is as Figure 10 shown, where (a) is a schematic diagram of the connection between the inner ring of the support frame and the internal motor, and (b) is a schematic diagram of the connection between the outer ring of the support frame and the housing.

[0059] Three quasi-zero stiffness tensile connecting rods are installed above each vibration isolation flange, and three quasi-zero stiffness thrust connecting rods are installed below. Two linear connecting rods are installed on the left and right sides. Under the initial conditions, the springs in each quasi-zero stiffness tensile connecting rod are assembled in a pre-compressed state. Since the springs are compressed, they will squeeze the spring baffle fixed to the guide rod upward. The provided tensile force is transmitted to the engine through the inner magnetic ring - shaft retaining ring - guide rod - hinge point. At the same time, the springs in each thrust connecting rod are also assembled in a pre-compressed state. Since the springs are compressed, they will squeeze the spring baffle upward, providing an upward thrust for the engine. The resultant force direction of the tensile force and thrust provided by the tensile connecting rod and the thrust connecting rod is vertically upward, and its magnitude is equal to the self-weight of the engine, thereby realizing the bearing of the vibration isolation flange on the engine in the static state. In the horizontal direction, stable bearing and anti-torsion are achieved through two spring linear connecting rods. When the isolator undergoes vertical vibration, the springs in the tensile connecting rod and the thrust connecting rod are stretched or compressed, and the relative positions of the inner and outer magnetic rings change, thereby realizing the vertical quasi-zero stiffness and achieving the vibration isolation effect.

[0060] Starting from the rightmost connecting rod and increasing counterclockwise, let the stiffnesses of the 8 circumferential connecting rods be . Let the pre-compression amount of all springs be , with tension being positive and compression being negative. Then the compression amounts of the 8 connecting rods are , where the horizontal connecting rods are all in tension. Taking = 8mm and the stiffness are all as an example, the circumferential static stiffness distribution of the isolator can be obtained as shown in Figure 11 . Through comparative analysis, it can be seen that the present design can achieve circumferential stiffness matching, and by introducing a magnetic negative stiffness mechanism, the circumferential dynamic stiffness can be further reduced. As shown in Figure 11 is a schematic diagram of the circumferential static stiffness distribution of the isolator, where (a) is a schematic diagram of the relationship between the displacement of the inner ring of the support frame and the magnitude of the restoring force, and (b) is a schematic diagram of the relationship between the displacement of the inner ring of the support frame and the stiffness.

[0061] The biggest difficulty in assembling the vibration isolation support frame lies in how to keep the circumferential connecting rod lengths consistent without pre-compression. Therefore, the present design adopts a threaded nut rotary adjustment mechanism to ensure that the installation lengths of the connecting rods are kept consistent and play a role in positioning the connecting rods during the installation process, and the positioning is cancelled by pre-compression after the installation is completed. First, the springs inside the elastic connecting rods are pre-compressed by adjusting the nuts at both ends. Using a standard locator, as shown in Figure 12 , the fastening positions of the nuts can be determined. When installing a single support frame, it can be directly assembled due to the addition of the positioning mechanism. When applying the support frame to an underwater vehicle, since the resultant force of the internal static load and the spring pre-compression of the isolator is equal in magnitude and opposite in direction. Therefore, at this time, the positioning nuts can be gradually loosened, and the nuts then become the vibration limiting mechanism of the vibration isolation support frame, avoiding serious vibration deterioration of the equipment.

[0062] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A low-frequency circumferential vibration isolation device for rotating machinery based on high static and low dynamic stiffness, characterized in that, The device includes: A flange inner ring and a flange outer ring arranged concentrically; two linear connecting rods; a plurality of quasi-zero stiffness thrust connecting rods and quasi-zero stiffness tension connecting rods; Wherein, the linear connecting rods, the quasi-zero stiffness thrust connecting rods and the tension connecting rods are all symmetrically distributed between the flange inner ring and the outer ring, and the two linear connecting rods are distributed at 180 degrees; The quasi-zero stiffness thrust connecting rods and the tension connecting rods are respectively arranged on both sides of the straight line where the two linear connecting rods are located.

2. The low-frequency circumferential vibration isolation device for a rotating machine based on high static and low dynamic stiffness according to claim 1, characterized in that, The quasi-zero stiffness thrust connecting rod includes: a helical spring, a negative stiffness mechanism, a thrust connecting rod sleeve, a sliding bearing, a bushing, and a thrust sliding rod; Wherein, a sliding bearing installation cavity, a middle installation cavity and a bushing installation cavity are sequentially arranged in the thrust connecting rod sleeve from the end close to the flange inner ring to the end close to the flange outer ring. The sliding bearing installation cavity and the bushing installation cavity are respectively installed with a sliding bearing and a bushing. The thrust sliding rod sequentially penetrates through the sliding bearing, the middle installation cavity and the bushing from the end of the thrust connecting rod sleeve close to the flange inner ring to the end of the thrust connecting rod sleeve close to the flange outer ring; The helical spring is assembled on the thrust sliding rod in a pre-compressed state, and is located between the negative stiffness mechanism and the end of the tension connecting rod sleeve close to the flange outer ring.

3. A low-frequency circumferential vibration isolation device for a rotating machine based on high static and low dynamic stiffness according to claim 2, characterized in that, The quasi-zero stiffness tension connecting rod includes: a helical spring, a negative stiffness mechanism, a sliding bearing, a bushing, a tension connecting rod sleeve, and a tension sliding rod; Wherein, a bushing installation cavity, a middle installation cavity and a sliding bearing installation cavity are sequentially arranged in the tension connecting rod sleeve from the end close to the flange inner ring to the end close to the flange outer ring. The sliding bearing installation cavity and the bushing installation cavity are respectively installed with a sliding bearing and a bushing. The tension sliding rod sequentially penetrates through the bushing, the middle installation cavity and the sliding bearing from the end of the tension connecting rod sleeve close to the flange inner ring to the end of the tension connecting rod sleeve close to the flange outer ring; The helical spring is assembled on the tension sliding rod in a pre-compressed state, and is located between the negative stiffness mechanism and the end of the thrust connecting rod sleeve close to the flange inner ring.

4. A low-frequency circumferential vibration isolation device for a rotating machine based on high static and low dynamic stiffness according to claim 3, characterized in that, The linear connecting rod includes: a helical spring, a bushing, a linear connecting rod sleeve, a linear sliding rod, a linear shaft retaining ring, and a linear spring base; Wherein, a first bushing installation cavity, a middle installation cavity and a second bushing installation cavity are sequentially arranged in the linear connecting rod sleeve from the end close to the flange inner ring to the end close to the flange outer ring. The two bushings are respectively installed in the first bushing installation cavity and the second bushing installation cavity. The linear sliding rod sequentially penetrates through the bushing, the middle installation cavity and the bushing from the end of the linear connecting rod sleeve close to the flange inner ring to the end of the linear connecting rod sleeve close to the flange outer ring; The linear spring base is fixedly connected to the linear sliding rod, and the linear shaft retaining ring is fixedly connected to the bushing installed in the first bushing installation cavity; The helical spring is assembled between the linear shaft retaining ring and the linear spring base in a pre-compressed state.

5. A low-frequency circumferential vibration isolation device for rotating machinery based on high static and low dynamic stiffness according to claim 3, characterized in that, The negative stiffness mechanism is installed in the middle installation cavity and includes an inner magnetic ring and an outer magnetic ring. The inner magnetic ring is fixed to the tension sliding rod or the thrust sliding rod, and the outer magnetic ring is fixed to the inner wall of the tension connecting rod sleeve or the thrust connecting rod sleeve, and the inner magnetic ring and the outer magnetic ring are magnetized in the same direction to generate a repulsive force.

6. The circumferential vibration isolation device for rotating machinery with high static and low dynamic stiffness according to claim 4, characterized in that The thrust sliding rod, the tension sliding rod and the linear sliding rod are all stepped shafts.

7. A low-frequency circumferential vibration isolation device for a rotating machine based on high static and low dynamic stiffness according to claim 4, characterized in that One end of the thrust slide bar, the tension slide bar and the linear slide bar close to the inner ring of the flange is provided with a connecting ring, and the end close to the outer ring of the flange is a free end. Nuts are connected to both ends. One end of the thrust slide bar, the tension slide bar and the linear slide bar close to the inner ring of the flange is connected to the inner ring of the flange through a rivet rod.

8. A low-frequency circumferential vibration isolation device for rotating machinery based on high static and low dynamic stiffness according to claim 4, characterized in that, One end of the thrust connecting rod sleeve, the tension connecting rod sleeve and the linear connecting rod sleeve close to the outer ring of the flange are all connected to the outer ring of the flange through an axial displacement limiting member.

9. The low-frequency circumferential vibration isolation device for a rotating machine based on high static and low dynamic stiffness according to claim 4, characterized in that The thrust connecting rod sleeve, the tension connecting rod sleeve and the linear connecting rod sleeve are all formed by splicing two half sleeves and are fastened by a screw and a nut.

10. A low-frequency circumferential vibration isolation device for rotating machinery based on high static and low dynamic stiffness according to claim 5, characterized in that The inner wall of the sleeve of the thrust connecting rod sleeve and the tension connecting rod sleeve is provided with a groove for fixing the outer magnetic ring.

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