CN111120557B - Design method of ultralow frequency vibration isolator - Google Patents

Design method of ultralow frequency vibration isolator Download PDF

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CN111120557B
CN111120557B CN202010015099.8A CN202010015099A CN111120557B CN 111120557 B CN111120557 B CN 111120557B CN 202010015099 A CN202010015099 A CN 202010015099A CN 111120557 B CN111120557 B CN 111120557B
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permanent magnet
annular permanent
negative stiffness
radius
bearing
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CN111120557A (en
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周振华
杜荣华
傅逸轩
戴志辉
周民瑞
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Changsha University of Science and Technology
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Changsha University of Science and Technology
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F6/00—Magnetic springs; Fluid magnetic springs, i.e. magnetic spring combined with a fluid
    • F16F6/005—Magnetic springs; Fluid magnetic springs, i.e. magnetic spring combined with a fluid using permanent magnets only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F1/00—Springs
    • F16F1/02—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant
    • F16F1/04—Wound springs
    • F16F1/12—Attachments or mountings
    • F16F1/121—Attachments or mountings adjustable, e.g. to modify spring characteristics
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F2228/00—Functional characteristics, e.g. variability, frequency-dependence
    • F16F2228/04—Frequency effects
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F2228/00—Functional characteristics, e.g. variability, frequency-dependence
    • F16F2228/06—Stiffness
    • F16F2228/066—Variable stiffness
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F2230/00—Purpose; Design features
    • F16F2230/0005—Attachment, e.g. to facilitate mounting onto confer adjustability

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Vibration Prevention Devices (AREA)

Abstract

The invention relates to the field of ultralow frequency vibration reduction and isolation, and discloses a design method of an ultralow frequency vibration isolator.A vibration isolator to be designed comprises a vibration isolation bearing bedplate, wherein the vibration isolation bearing bedplate is connected with a bearing rod, the bearing rod is coaxially installed with an upper shell, a lower shell and a base, an upper external annular permanent magnet is arranged on the inner wall of the upper shell, a lower external annular permanent magnet is arranged on the inner wall of the lower shell, an upper internal annular permanent magnet is arranged in the upper external permanent magnet, and a lower internal annular permanent magnet is arranged in the lower external annular permanent magnet; then determining the inner radius and the outer radius of the upper inner annular permanent magnet; changing the width of the air gap and changing the height of the upper inner and outer annular magnets; forming a new negative stiffness characteristic curve; obtaining a larger negative stiffness characteristic; and calculating the negative stiffness characteristic of the combined negative stiffness magnetic spring, and designing the parameters of the load-bearing spiral spring. The invention realizes the excellent performance of the vibration isolator on the isolation of ultralow frequency vibration.

Description

Design method of ultralow frequency vibration isolator
Technical Field
The invention relates to the field of ultralow frequency vibration reduction and isolation, in particular to a design method of an ultralow frequency vibration isolator.
Background
Along with the improvement of the intensity of a vibration source in the environment, the vibration frequency and the vibration amplitude are diversified, and the vibration isolator becomes a vibration control technology which is most researched and most widely applied in vibration control. In aerospace engineering, high-precision navigation instruments and precision measurement instruments in aerospace vehicles have very strict requirements on vibration environments and working conditions. The ultra-precision processing technology is the main component in the advanced technologies such as nuclear energy, large-scale integrated circuit, laser and the like, and the requirement on the vibration isolation performance of processing equipment is stricter. In the field of micro-electro-mechanical systems, the actions and operations performed by the micro-electro-mechanical systems become finer and finer, the size of an operation object has been increased to a nanometer level or even a sub-nanometer level, and the vibration isolation stability of the system structure has become a main factor influencing the performance of the micro-electro-mechanical systems. The low-frequency and ultra-low-frequency vibration means vibration having a vibration frequency of 5Hz or less. The vibration of large mechanical equipment, bridges, earthquakes, large dams, high-rise buildings and the like belongs to low-frequency vibration. The manufacturing precision of modern precision machining and manufacturing is also developed to the micron or even nanometer level, the vibration isolation technical requirement for the precision machining machine tool is also increased day by day, and the vibration isolation stability is a main factor influencing the performance of the precision machining machine tool. Therefore, great attention has been paid to the isolation of low-frequency and ultra-low-frequency vibrations. Conventional vibration isolators typically employ a vibration isolation system formed by a combination of a resilient member, a damping member and an inertial member. However, with the development of technology, the requirements for vibration environment and vibration isolation technology are continuously increased, the conventional vibration isolation cannot adapt to the characteristic change of the external vibration environment in real time, and particularly, the passive vibration isolation has poor vibration isolation effect under the low frequency and ultralow frequency vibration of less than 1Hz, so that the passive vibration isolation is limited in many occasions. The low-frequency vibration isolation of the vibration isolator can be realized by reducing the natural frequency, the reduction of the natural frequency is mainly realized by reducing the rigidity of a system and increasing the mass of a load, the reduction of the rigidity can cause larger static deformation, the stability of the vibration isolator is reduced, and the system characteristic cannot be changed by changing the mass of an object in real time in actual work.
The vibration isolator formed by connecting the positive stiffness unit and the negative stiffness unit in parallel is proved to be a good method for broadening the bandwidth to inhibit low-frequency vibration. These vibration isolators typically have high static and low dynamic stiffness characteristics, with the load-bearing coil springs providing high static support stiffness for supporting the payload, and the parallel connection of the positive and negative stiffness springs providing low dynamic stiffness for improved low frequency vibration isolation performance.
An invention patent named 'quasi-zero stiffness vibration isolator' (application number: CN109737168) proposes a negative stiffness mechanism based on a transverse combination mechanical spring, which can be adjusted to lower the natural frequency of the vibration damping system. The invention patent named as 'a two-degree-of-freedom ultralow frequency vibration isolator' (CN106321707) provides a vibration isolation mechanism with an adjustable negative stiffness magnetic spring connected in parallel with an air spring and a spiral spring, which realizes the characteristics of high static stiffness and low dynamic stiffness and the characteristics of lower inherent frequency and high load of a system. An invention patent named 'an ultralow frequency vibration isolator based on parallel connection of positive and negative stiffness springs' (application number: CN 102619916B) provides a negative stiffness structure of a cam and a transverse spring.
Although the invention patent and the negative stiffness mechanism proposed at the present stage can reduce the natural frequency of the vibration isolator to a certain extent, the isolation and the suppression of low-frequency vibration are realized. However, for a negative stiffness system, because the negative stiffness structure has a nonlinear stiffness characteristic, an ultra-low negative stiffness brings a strong nonlinear stiffness characteristic at a balance position, and when a larger negative stiffness is obtained, the stability of the vibration isolation system at a working point is poor. A certain contradiction exists between the ultralow rigidity and the position stability of the vibration isolation system; however, in the ultralow frequency vibration isolator studied at the present stage, due to the strong nonlinear stiffness characteristic brought by the negative stiffness structure, the isolation performance of the vibration isolator is greatly influenced under different amplitudes, and under the excitation of large amplitude, the phenomena of sub-harmonic, super-harmonic resonance and frequency jump of the vibration isolation system can be caused, so that the performance of the vibration isolation system is influenced, and even the system is damaged. Therefore, how to enhance the strength of the negative stiffness and solve the problem of unstable system caused by the excessive nonlinearity of the negative stiffness structure, the natural frequency of the vibration isolation system is reduced, the stability of the system is improved, the low-frequency vibration signal isolation is expanded, the overall structure is simplified and the cost is optimized, which is of great importance for the design of the ultra-low frequency vibration isolator.
Disclosure of Invention
The invention provides a design method of an ultralow frequency vibration isolator to solve a series of problems. The vibration isolator does not need external energy supply, has a simple structure, is easy to realize, has excellent economy and high reliability, adopts the principle of parallel connection of positive stiffness and negative stiffness, and combines the nonlinear stiffness characteristics of the upper negative stiffness magnetic spring and the lower negative stiffness magnetic spring through the parallel connection of the upper negative stiffness magnetic spring and the lower negative stiffness magnetic spring, thereby obviously reducing the inherent frequency of a system, simultaneously reducing the influence near a working point due to the nonlinear stiffness characteristics, expanding the vibration attenuation bandwidth, improving the vibration isolation performance, and particularly having good inhibition effect on low-frequency and ultralow-frequency vibration. Meanwhile, the adjustable load component is provided for the vibration isolator, the vibration isolator can perform work balance adjustment under different loads, and the influence of load change on the performance of the vibration isolator is prevented.
The problems to be solved by the invention are realized by the following technical scheme:
a design method of an ultralow frequency vibration isolator specifically comprises the following steps:
1) the ultra-low frequency vibration isolator comprises a vibration isolation bearing bedplate, wherein the vibration isolation bearing bedplate is connected with a bearing rod, the bearing rod is fixed at the top of the bearing rod, the bearing rod is coaxially installed with an upper sliding bearing, a lower sliding bearing, an upper shell, a lower shell and a base, the lower surface of the lower sliding bearing is fixedly connected with the base, the upper surface of the lower sliding bearing is fixedly connected with the lower shell, the upper surface of the lower shell is fixedly connected with the upper shell, and the upper surface of the upper shell is fixedly connected with the upper sliding bearing. The upper sliding bearing and the lower sliding bearing are fixedly installed with the shell and are installed in coaxial contact with the bearing rod, so that the bearing rod is guaranteed to move along the axial direction with small friction single degree of freedom, and the movement of other degrees of freedom is limited.
2) Preliminarily determining the inner radius r of the upper inner annular permanent magnet according to the structural size of the shell, the structural size of the bearing rod, the assembly requirement and the maximum negative stiffness strength value11Outer radius r12Inner radius r of upper outer annular permanent magnet13And an outer radius r14A value range;
3) changing the width omega of the air gap between the upper inner annular permanent magnet and the upper outer annular permanent magnet1According to the confirmed inner radius r of the upper inner annular permanent magnet11Outer radius r12Inner radius r of upper outer annular permanent magnet13And an outer radius r14Value range, determine omega1A value range within which omega is varied1Taking omega when the negative stiffness value is maximum1According to the confirmed omega1Housing structural dimensions, carrier bar structural dimensions and assembly requirements to identify the inner radius r of the upper inner annular permanent magnet11Outer radius r12Inner radius r of upper outer annular permanent magnet13And an outer radius r14And (4) specific values are taken.
4) Varying the height h of the upper inner annular permanent magnet1And height h of the upper outer annular permanent magnet2. The difference between the heights of the two is kept and the heights are changed simultaneously, the negative stiffness strength value of the stiffness characteristic curve of the negative stiffness magnetic spring is changed along with the change of the negative stiffness strength value, and the nonlinear stiffness characteristic is not changed along with the change of the negative stiffness strength value; keeping the heights of the two equal and changing simultaneously, the negative stiffness strength value of the stiffness characteristic curve of the negative stiffness magnetic spring changes along with the height of the two, and the nonlinear stiffness characteristicDoes not change with it; keeping one of the heights unchanged and the other height changed, and changing the negative stiffness strength and the nonlinear stiffness characteristic of the stiffness characteristic curve of the negative stiffness magnetic ring; to observe the concave-convex characteristic change existing in the rigidity characteristic curve at the central balance position;
5) combining the concave-convex characteristic curve and the convex-concave characteristic curve to form a new negative stiffness characteristic curve, analyzing the concave-convex characteristic curve matching rule to determine that the secondary nonlinear component of the negative stiffness characteristic of the combined parallel negative stiffness magnetic spring becomes zero after combination, and further determining the height h of the upper inner annular permanent magnet of the upper negative stiffness magnetic spring1And height h of the upper outer annular permanent magnet2And the height h of the lower inner annular permanent magnet of the lower negative-stiffness magnetic spring3And the height h of the lower outer annular permanent magnet4The values of the radius and the air gap width of the magnetic ring which is taken by the concave-convex characteristic curve matched with the double magnetic rings are unchanged, and the air gap width omega between the lower inner annular permanent magnet and the lower outer annular permanent magnet of the lower negative-stiffness magnetic spring is determined according to the structural assembly requirement2Inner radius r of lower inner annular permanent magnet21Outer radius r22Inner radius r of lower outer annular permanent magnet23And an outer radius r24，r21＝r11,r22＝r12,r23＝r13,r24＝r14；
6) The structural parameters of an upper inner annular permanent magnet and an upper outer annular permanent magnet of an upper negative stiffness magnetic spring and the structural parameters of a lower inner annular permanent magnet and a lower outer annular permanent magnet of a lower negative stiffness magnetic spring are confirmed by the design method, so that a larger negative stiffness characteristic is obtained in a working area of the combined negative stiffness magnetic spring, meanwhile, the interference of strong nonlinear characteristics caused by strong negative stiffness values is reduced, and the vibration isolation stability of the system is optimized;
7) according to the positive and negative stiffness parallel principle, the negative stiffness magnetic spring needs to be used in parallel with the load-bearing spiral spring, the negative stiffness characteristic of the combined negative stiffness magnetic spring is calculated according to the structural parameters and the numerical values of the magnetic ring parameters, the required stiffness characteristic of the load-bearing spiral spring is designed, the stiffness value of the load-bearing spiral spring is confirmed, and therefore the parameters of the load-bearing spiral spring are designed.
Furthermore, an upper outer annular permanent magnet is arranged on the inner wall of the upper shell, a lower outer annular permanent magnet is arranged on the inner wall of the lower shell, an upper inner annular permanent magnet is arranged in the upper outer annular permanent magnet, a lower inner annular permanent magnet is arranged in the lower outer annular permanent magnet, the magnetization directions of the upper inner annular permanent magnet and the lower outer annular permanent magnet are the same along the axial direction. The upper inner annular permanent magnet and the lower inner annular permanent magnet are coaxially mounted with the bearing rod and fixed on the bearing rod, the upper inner annular permanent magnet and the upper outer annular permanent magnet are coaxially mounted, the lower inner annular permanent magnet and the lower outer annular permanent magnet are coaxially mounted, the upper inner annular permanent magnet and the upper outer annular permanent magnet form an upper negative stiffness magnetic spring, the lower inner annular permanent magnet and the lower outer annular permanent magnet form a lower negative stiffness magnetic spring, the nonlinear stiffness characteristic of the upper negative stiffness magnetic spring is matched with the nonlinear stiffness characteristic of the lower negative stiffness magnetic spring, the linear stiffness characteristic of the vibration isolator is formed, the bearing rod extends into the base and is connected with the upper end of the spiral spring, and the lower end of the spiral spring is mounted on the central shaft body of the base.
Further, in the work process, the radial central planes of the upper inner annular permanent magnet and the upper outer annular permanent magnet are overlapped, the radial central planes of the lower inner annular permanent magnet and the lower outer annular permanent magnet are overlapped, and the overlapped surface is the work central plane of the vibration isolator.
Furthermore, the lower end of the bearing rod is coaxially installed with the adjustable component, the lower end of the adjustable component is connected with the spiral spring, and the adjustable component can vertically move up and down along the bearing rod so as to realize the vertical movement of the spiral spring.
Furthermore, the upper sliding bearing and the upper shell are fixed through an upper outer magnetic ring fixing cover, the upper sliding bearing is fixed on the inner wall of the upper outer magnetic ring fixing cover, the upper shell is fixed on the outer wall of the upper outer magnetic ring fixing cover, and the upper outer magnetic ring fixing cover fixes the upper outer annular permanent magnet on the inner wall of the upper shell.
Furthermore, the lower sliding bearing, the lower shell and the base are fixed through a lower outer magnetic ring fixing cover, the lower sliding bearing is fixed on the inner wall of the lower outer magnetic ring fixing cover, the lower shell is fixed on the upper surface of the lower outer magnetic ring fixing cover, the base is fixed on the outer wall of the lower outer magnetic ring fixing cover, and the lower outer magnetic ring fixing cover fixes the lower external annular permanent magnet on the inner wall of the lower shell.
Furthermore, the upper sliding bearing and the upper outer magnetic ring fixing cover, the upper outer magnetic ring fixing cover and the upper shell, the lower outer magnetic ring fixing cover and the base, the lower sliding bearing and the lower outer magnetic ring fixing cover, the lower shell and the lower outer magnetic ring fixing cover, and the upper shell and the lower shell are fixedly connected by bolts. The upper and lower outer annular permanent magnets of the upper negative stiffness spring and the lower negative stiffness spring are arranged on the inner sides of the upper shell and the lower shell and are fixedly connected with the upper shell and the lower shell through upper and lower outer magnetic ring fixing covers and upper and lower shell bolts.
The invention has the beneficial effects that:
(1) the inherent frequency of the system is reduced by adopting the negative stiffness structure, and the ultralow frequency vibration isolation performance of the vibration isolator is obtained.
(2) The parallel structure of the upper negative stiffness magnetic spring and the lower negative stiffness magnetic spring is provided, so that the inherent frequency of the system is further reduced, the problem of strong nonlinearity brought by the super-strong negative stiffness structure is optimized, and the stability of the vibration isolator is optimized compared with the common permanent magnet negative stiffness structure.
(3) The adjustable device is added, so that the working position of the vibration isolator can be adjusted according to different load changes, and the working performance of the vibration isolator is optimized.
(4) The sliding bearing is adopted to limit the bearing rod to move in the direction required by work, the whole structure is compact to mount, the bearing rod is mounted through the bolts and the screws, the bearing rod is convenient to manufacture, assemble and maintain, and the influence of external interference on the vibration isolation performance of the system is reduced.
Drawings
Fig. 1 is a schematic external view of the ultra-low frequency vibration isolator provided by the invention.
Fig. 2 is a schematic front view of the ultra-low frequency vibration isolator provided by the invention.
Fig. 3 is a schematic top view of the ultralow frequency vibration isolator according to the present invention.
Fig. 4 is a schematic cross-sectional view of a-a and a B-B of the ultra low frequency vibration isolator according to the present invention.
Fig. 5 is a schematic diagram of the vibration isolator for realizing ultralow-frequency natural frequency by matching the double negative-stiffness magnetic springs provided by the invention.
Fig. 6 is a schematic structural parameter diagram of the combined negative-stiffness magnetic spring provided by the present invention.
Fig. 7 is a stiffness characteristic curve of a negative stiffness magnetic spring in a design process of the ultra-low frequency vibration isolator provided by the invention.
Fig. 8 is a stiffness characteristic curve of the double-magnetic-spring negative stiffness matching in the design process of the ultra-low frequency vibration isolator provided by the invention.
Fig. 9 is a flow chart of the design of the ultra-low frequency vibration isolator provided by the invention.
Reference numerals: 1. a vibration isolation bearing platen; 2. a carrier bar; 3. an upper outer magnetic ring fixing cover; 4. an upper housing; 5. a lower housing; 6. a lower outer magnetic ring fixing cover; 7. a base; 8. an upper slide bearing; 9. a lower slide bearing; 10. an upper inner annular permanent magnet; 11. an upper outer annular permanent magnet; 12. a lower inner annular permanent magnet; 13. a lower outer annular permanent magnet; 14. an adjustable component; 15. a coil spring.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 4, the ultra-low frequency vibration isolator according to the present invention includes a vibration isolation bearing platen 1 and a bearing rod 2, wherein the bearing rod 2 is coaxially installed with an upper sliding bearing 8, a lower sliding bearing 9, an upper outer magnetic ring fixing cover 3, a lower outer magnetic ring fixing cover 6, an upper housing 4, a lower housing 5, and a base 7. The lower outer magnetic ring fixing cover 6 is fixedly connected with the base 7 through bolts, the lower sliding bearing 9 and the lower shell 5 are fixedly connected to the lower outer magnetic ring fixing cover 6 through bolts, and the upper shell 4 is fixedly connected with the lower shell 5 through bolts. The upper slide bearing 8, the upper outer magnetic ring fixing cover 3 and the upper housing 4 are fixedly connected with each other. The carrier bar 2 is restricted from moving in the vertical direction by the upper slide bearing 8 and the lower slide bearing 9. The upper outer annular permanent magnet 11 is fixed on the inner wall of the upper shell 4 by the upper shell 4 and the upper outer magnetic ring fixing cover 3, and the lower inner annular permanent magnet 12 is fixed on the inner wall of the upper shell 5 by the lower shell 5 and the lower outer magnetic ring fixing cover 9. The upper inner annular permanent magnet 10 and the lower inner annular permanent magnet 12 are coaxially arranged with the carrier bar 2 and fixed on the upper middle part of the carrier bar 2. The upper inner annular permanent magnet 10 and the upper outer annular permanent magnet 11 are coaxially mounted to form an upper negative stiffness magnetic spring, and the lower inner annular permanent magnet 12 and the lower outer annular permanent magnet 13 are coaxially mounted to form a lower negative stiffness magnetic spring. The adjustable assembly 14 and the carrier bar 2 are coaxially mounted and the adjustable assembly 14 is vertically movable, enabling vertical movement of the helical spring 15 and thus load adjustability. When the system is in a working state, the radial central planes of the upper inner annular permanent magnet 10 and the upper outer annular permanent magnet 11 are overlapped, the radial central planes of the lower inner annular permanent magnet 12 and the lower outer annular permanent magnet 13 are overlapped, and the upper inner annular permanent magnet and the lower outer annular permanent magnet are matched to form a combined negative-stiffness magnetic spring structure.
FIG. 5 is a schematic diagram of the combined negative stiffness magnetic spring and positive stiffness of the vibration isolator of the present invention in parallel connection to achieve ultra low frequency: in the present invention, the coil spring 15 constitutes a load-bearing coil spring for providing a load-bearing force to the vibration isolator, and has a stiffness kIs just(ii) a The upper inner annular permanent magnet 10 and the upper outer annular permanent magnet 11 constitute an upper negative stiffness magnetic spring, and the lower inner annular permanent magnet 12 and the lower outer annular permanent magnet 13 constitute a lower negative stiffness magnetic spring. The upper negative stiffness magnetic spring and the lower negative stiffness magnetic spring are connected in parallel to form a combined negative stiffness magnetic spring of the vibration isolator, and the stiffness of the combined negative stiffness magnetic spring is kNegative pole(ii) a Through the parallel connection, the equivalent rigidity of the vibration isolator system is k ═ kIs just+kNegative pole(ii) a By negative stiffness value kNegative poleIs negative and corresponds to a positive stiffness kIs justAnd subtracting a stiffness value to reduce the integral equivalent stiffness k of the system, thereby achieving the purpose of reducing the natural frequency of the system. The magnetic ring permanent magnet is adopted, so that the magnetic ring permanent magnet is simple in structure, low in cost, compact and simple and convenient to install. The invention adopts the adjustable component 14, and the whole load of the vibration isolator can be adjusted by adjusting the compression of the spiral spring 15And the working central point of the vibration isolator is kept unchanged.
In order to eliminate the strong nonlinearity of the vibration isolator near the working point caused by the strong negative stiffness of the negative stiffness magnetic spring, the stable work of the vibration isolator is influenced, the nonlinearity influence is eliminated by combining the negative stiffness magnetic springs, the linearization is realized, the stable negative stiffness characteristic of the combined negative stiffness magnetic spring near the working point is kept, and the performance influence of harmonic resonance and frequency hopping on the vibration isolator is eliminated.
In order to realize the combination of the upper inner annular permanent magnet 10 and the upper outer annular permanent magnet 11 of the negative stiffness magnetic spring to form the upper negative stiffness magnetic spring, the lower inner annular permanent magnet 12 and the lower outer annular permanent magnet 13 form the lower negative stiffness magnetic spring. The upper negative stiffness magnetic spring and the lower negative stiffness magnetic spring are connected in parallel to form a combined negative stiffness magnetic spring of the vibration isolator. The present invention proposes the following design method. The structural parameters of the combined negative-stiffness magnetic spring are shown in FIG. 6: the upper inner annular permanent magnet 10 has a height h1Inner radius of r11Outer radius r12Upper outer annular permanent magnet 11 of height h2Inner radius of r13Outer radius r14The lower inner annular permanent magnet 10 has a height h3Inner radius of r21Outer radius r22The lower outer annular permanent magnet 11 has a height h4Inner radius of r23Outer radius r24The width of the air gap of the upper negative stiffness magnetic spring is omega1，ω1＝r13-r12The width of the air gap of the lower negative stiffness magnetic spring is omega2，ω1＝r23-r22. The upper inner annular permanent magnet 10 and the upper outer annular permanent magnet 11 of the upper negative stiffness magnetic spring, and the lower inner annular permanent magnet 12 and the lower outer annular permanent magnet 13 of the lower negative stiffness magnetic spring in this embodiment are magnetized in the axial direction, and the directions are all kept the same.
The design method of the combined negative-stiffness magnetic spring is illustrated by fig. 7, 8 and 9, and the inner radius r of the upper inner annular permanent magnet 10 is preliminarily determined according to the structural size of the shell, the structural size of the carrier bar, the assembly requirement and the maximum negative stiffness strength value11Outer radius r12Inner radius r of upper outer annular permanent magnet 1113And an outer radius r14And (4) value range. Confirming the inner radius r of the upper inner annular permanent magnet 10 according to the above step11Outer radius r12Inner radius r of upper outer annular permanent magnet 1113And an outer radius r14Value range, determining air gap width omega1And (4) value range. Within a range of values, the air gap width omega is changed1The negative stiffness value and the non-linear characteristic of the negative stiffness characteristic curve of the magnetic spring are changed along with the change of the negative stiffness value and the non-linear characteristic curve. According to the width omega of the air gap1Within the value range, the air gap width omega when the negative rigidity value is maximum is taken1. Depending on the housing construction size, the carrier bar construction size, the assembly requirements and the air gap width ω1Confirming the inner radius r of the upper inner annular permanent magnet 1011Outer radius r12Inner radius r of upper outer annular permanent magnet 1113And an outer radius r14And (4) specific values are taken. FIG. 7 is a view showing the change of the height h of the upper inner annular permanent magnet 101And maintaining the height h of the upper outer annular permanent magnet 112The stiffness characteristic curve at the center equilibrium position has a variation in the concave-convex characteristic without change. Fig. 8 shows a new combined negative stiffness characteristic curve formed by combining an upper negative stiffness curve and a lower negative stiffness curve through a concave-convex characteristic curve. And analyzing the concave-convex characteristic curve matching rule to determine that the secondary nonlinear component of the negative stiffness characteristic of the combined parallel negative stiffness magnetic spring becomes zero after combination. Thereby determining the height h of the upper inner annular permanent magnet 10 of the upper negative rate magnetic spring1And the height h of the upper outer annular permanent magnet 112And the height h of the lower inner annular permanent magnet 12 of the lower negative-stiffness magnetic spring3And the height h of the lower outer annular permanent magnet 134. Magnetic ring radius and air gap width omega for concave-convex characteristic curve matching double magnetic rings1The inner radius r of the lower inner annular permanent magnet 12 of the lower negative-stiffness magnetic spring is determined according to the structural assembly requirements without change21Outer radius r22Inner radius r of lower outer annular permanent magnet 1323And an outer radius r24。
ω1＝ω2r21＝r11,r22＝r12,r23＝r13,r24＝r14. According to the positive and negative stiffness parallel principle, the negative stiffness magnetic spring needs to be used in parallel with the load-bearing spiral spring, the negative stiffness characteristic of the combined negative stiffness magnetic spring is calculated according to the numerical values of the structural parameters and the magnetic ring parameters, the stiffness characteristic needed by the load-bearing spiral spring 15 is designed, the stiffness value of the load-bearing spiral spring 15 is confirmed, and therefore the parameters of the load-bearing spiral spring 15 are designed.
By the design method, the working area of the combined negative-stiffness magnetic spring can obtain larger negative-stiffness characteristic, simultaneously reduce the interference of strong nonlinear characteristic caused by strong negative-stiffness value, thereby optimizing the vibration isolation stability of the system, matching the nonlinear stiffness characteristic of the upper negative stiffness magnetic spring with the nonlinear stiffness characteristic of the lower negative stiffness magnetic spring to form the linear stiffness characteristic of the vibration isolator, not only keeping the vibration isolator isolated against ultralow frequency vibration, but also meeting the requirements of different bearing capacities, meanwhile, by combining the nonlinear stiffness characteristic matching of the negative stiffness magnetic spring, the nonlinear stiffness characteristic of the vibration isolator near the working point is optimized, the linear stiffness characteristic range of the vibration isolator is further expanded, the influence of the amplitude on the performance of the vibration isolator is eliminated to a great extent, the natural frequency of a system is reduced, and the excellent performance of the vibration isolator on the isolation of ultralow-frequency vibration is realized.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (6)

1. A design method of an ultralow frequency vibration isolator specifically comprises the following steps:
1) the ultra-low frequency vibration isolator to be designed comprises a vibration isolation bearing bedplate (1), wherein the vibration isolation bearing bedplate (1) is connected with a bearing rod (2), the bearing rod (2) is coaxially installed with an upper sliding bearing (8), a lower sliding bearing (9), an upper shell (4), a lower shell (5) and a base (7), the lower surface of the lower sliding bearing (9) is fixedly connected with the base (7), the upper surface of the lower sliding bearing (9) is fixedly connected with the lower shell (5), the upper surface of the lower shell (5) is fixedly connected with the upper shell (4), the upper surface of the upper shell (4) is fixedly connected with the upper sliding bearing (8), the ultra-low frequency vibration isolator is characterized in that an upper external annular permanent magnet (11) is arranged on the inner wall of the upper shell (4), a lower external annular permanent magnet (13) is arranged on the inner wall of the lower shell (5), and an upper internal annular permanent magnet, a lower inner annular permanent magnet (12) is arranged in the lower outer annular permanent magnet (13), the upper inner annular permanent magnet (10) and the lower inner annular permanent magnet (12) are coaxially mounted with the bearing rod (2) and fixed on the bearing rod (2), the upper inner annular permanent magnet (10) and the upper outer annular permanent magnet (11) are coaxially mounted, the lower inner annular permanent magnet (12) and the lower outer annular permanent magnet (13) are coaxially mounted, the bearing rod (2) extends into the base (7) and is connected with the upper end of a spiral spring (15), and the lower end of the spiral spring (15) is mounted on a central shaft body of the base (7);
2) preliminarily determining the inner radius r of the upper inner annular permanent magnet according to the structural size of the shell, the structural size of the bearing rod, the assembly requirement and the maximum negative stiffness strength value11Outer radius r12Inner radius r of upper outer annular permanent magnet13And an outer radius r14A value range;
3) changing the width omega of the air gap between the upper inner annular permanent magnet and the upper outer annular permanent magnet1According to the confirmed inner radius r of the upper inner annular permanent magnet11Outer radius r12Inner radius r of upper outer annular permanent magnet13And an outer radius r14Value range, determine omega1A value range within which omega is varied1Taking omega when the negative stiffness value is maximum1According to the confirmed omega1Housing structural dimensions, carrier bar structural dimensions and assembly requirements to identify the inner radius r of the upper inner annular permanent magnet11Outer radius r12Inner radius r of upper outer annular permanent magnet13And an outer radius r14Specifically taking values;
4) changing the upper inner annular permanent magnetHeight h of1And height h of the upper outer annular permanent magnet2Or keeping the heights equal and simultaneously changing or keeping the difference between the heights and simultaneously changing or keeping one of the heights constant and the other height changing; to observe the concave-convex characteristic change existing in the rigidity characteristic curve at the central balance position;
5) combining the concave-convex characteristic curve and the convex-concave characteristic curve to form a new negative stiffness characteristic curve, analyzing the concave-convex characteristic curve matching rule to determine that the secondary nonlinear component of the negative stiffness characteristic of the combined parallel negative stiffness magnetic spring becomes zero after combination, and further determining the height h of the upper inner annular permanent magnet of the upper negative stiffness magnetic spring1And height h of the upper outer annular permanent magnet2And the height h of the lower inner annular permanent magnet of the lower negative-stiffness magnetic spring3And the height h of the lower outer annular permanent magnet4The values of the radius and the air gap width of the magnetic ring which is taken by the concave-convex characteristic curve matched with the double magnetic rings are unchanged, and the air gap width omega between the lower inner annular permanent magnet and the lower outer annular permanent magnet of the lower negative-stiffness magnetic spring is determined according to the structural assembly requirement2Inner radius r of lower inner annular permanent magnet21Outer radius r22Inner radius r of lower outer annular permanent magnet23And an outer radius r24，r21＝r11,r22＝r12,r23＝r13,r24＝r14；
6) Confirming the structural parameters of an upper inner annular permanent magnet and an upper outer annular permanent magnet of an upper negative stiffness magnetic spring and the structural parameters of a lower inner annular permanent magnet and a lower outer annular permanent magnet of a lower negative stiffness magnetic spring, obtaining a larger negative stiffness characteristic in a working area of the combined negative stiffness magnetic spring, reducing the interference of strong nonlinear characteristics caused by strong negative stiffness values, and optimizing the vibration isolation stability of the system;
7) according to the positive and negative stiffness parallel principle, the negative stiffness magnetic spring needs to be used in parallel with the load-bearing spiral spring, the negative stiffness characteristic of the combined negative stiffness magnetic spring is calculated according to the structural parameters and the numerical values of the magnetic ring parameters, the required stiffness characteristic of the load-bearing spiral spring is designed, the stiffness value of the load-bearing spiral spring is confirmed, and therefore the parameters of the load-bearing spiral spring are designed.
2. The design method of an ultra low frequency vibration isolator according to claim 1, characterized in that the radial central planes of the upper inner annular permanent magnet (10) and the upper outer annular permanent magnet (11) are coincident, and the radial central planes of the lower inner annular permanent magnet (12) and the lower outer annular permanent magnet (13) are coincident.
3. The design method of an ultra low frequency vibration isolator according to claim 2, characterized in that the lower end of the carrier rod (2) is coaxially installed with an adjustable component (14), the lower end of the adjustable component (14) is connected with the helical spring (15), and the adjustable component (14) can realize the vertical movement of the helical spring (15).
4. A design method of an ultra low frequency vibration isolator according to any one of claims 1 to 3, characterized in that the upper sliding bearing (8) is fixed with the upper housing (4) by an upper outer magnetic ring fixing cover (3), the upper sliding bearing (8) is fixed on the inner wall of the upper outer magnetic ring fixing cover (3), the upper housing (4) is fixed on the outer wall of the upper outer magnetic ring fixing cover (3), and the upper outer magnetic ring fixing cover (3) fixes the upper outer annular permanent magnet (11) on the inner wall of the upper housing (4).
5. The design method of an ultra low frequency vibration isolator according to claim 4, wherein the lower sliding bearing (9), the lower housing (5) and the base (7) are fixed by a lower outer magnetic ring fixing cover (6), the lower sliding bearing (9) is fixed on the inner wall of the lower outer magnetic ring fixing cover (6), the lower housing (5) is fixed on the lower outer magnetic ring fixing cover (6), the base (7) is fixed on the outer wall of the lower outer magnetic ring fixing cover (6), and the lower outer magnetic ring fixing cover (6) fixes the lower outer annular permanent magnet (13) on the inner wall of the lower housing (5).
6. The design method of an ultra-low frequency vibration isolator according to claim 5, wherein the upper sliding bearing (8) and the upper outer magnetic ring fixing cover (3), the upper outer magnetic ring fixing cover (3) and the upper housing (4), the lower outer magnetic ring fixing cover (6) and the base (7), the lower sliding bearing (9) and the lower outer magnetic ring fixing cover (6), the lower housing (5) and the lower outer magnetic ring fixing cover (6), and the upper housing (4) and the lower housing (5) are fixedly connected by bolts.
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