CN114135631A - Quasi-zero stiffness vibration isolator capable of adjusting negative stiffness in non-contact mode - Google Patents
Quasi-zero stiffness vibration isolator capable of adjusting negative stiffness in non-contact mode Download PDFInfo
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- CN114135631A CN114135631A CN202111505435.8A CN202111505435A CN114135631A CN 114135631 A CN114135631 A CN 114135631A CN 202111505435 A CN202111505435 A CN 202111505435A CN 114135631 A CN114135631 A CN 114135631A
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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
- F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
- F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
- F16F15/03—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using magnetic or electromagnetic means
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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
- F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
- F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
- F16F15/04—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using elastic means
- F16F15/046—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using elastic means using combinations of springs of different kinds
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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
- F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
- F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
- F16F15/04—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using elastic means
- F16F15/06—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using elastic means with metal springs
- F16F15/067—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using elastic means with metal springs using only wound springs
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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
- F16F2222/00—Special physical effects, e.g. nature of damping effects
- F16F2222/06—Magnetic or electromagnetic
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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
- F16F2228/00—Functional characteristics, e.g. variability, frequency-dependence
- F16F2228/06—Stiffness
- F16F2228/063—Negative stiffness
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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
- F16F2230/00—Purpose; Design features
- F16F2230/18—Control arrangements
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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
- F16F2238/00—Type of springs or dampers
- F16F2238/02—Springs
- F16F2238/026—Springs wound- or coil-like
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Abstract
The invention discloses a quasi-zero stiffness vibration isolator capable of adjusting negative stiffness without contact, which comprises a vibration isolation box body, and an anti-overturning device, a negative stiffness electromagnetic adjusting device and a positive stiffness spring adjusting device which are arranged in the vibration isolation box body; the vibration isolation box body comprises a lower supporting platform, an upper supporting platform and four side plates enclosed between the upper and lower supporting platforms; the anti-overturning device comprises four anti-overturning mechanisms which are sequentially arranged end to end, the four anti-overturning mechanisms are symmetrically arranged along a diagonal line, and the middle parts of the four anti-overturning mechanisms are enclosed to form a central area; the negative stiffness electromagnetic adjusting device comprises two negative stiffness generating modules which are oppositely arranged, and the negative stiffness generating modules face the central area; the positive rate spring adjustment device is mounted within the central region. The invention has the beneficial effects that: the invention has the characteristics of low natural frequency and high static bearing capacity, and can ensure that the resonance frequency is very low on the premise of ensuring the bearing capacity, thereby widening the vibration isolation frequency band and improving the vibration isolation effect; and the positive stiffness and the negative stiffness can be adjusted according to actual requirements.
Description
Technical Field
The invention relates to the technical field of vibration isolation, in particular to a quasi-zero stiffness vibration isolator capable of adjusting negative stiffness in a non-contact mode.
Background
The passive vibration isolator is a load-bearing energy-consuming element, has the advantages of simple structure, low energy consumption, easy realization, good economy and the like, and is a main means for isolating the transmission of the dynamic mechanical vibration of the ship to the ship body. However, most passive vibration isolators designed based on the classical vibration isolation theory have input and output frequency retentivity, and have no effect on the change of the frequency spectrum structure of the radiation noise of ships; and the linear vibration isolation system has less excitation frequency to the outside
The isolation capability of low-frequency line spectrum which is multiplied by the natural frequency of the system is limited; meanwhile, the contradiction between large bearing capacity, ultralow frequency vibration isolation, ultralow rigidity, position stability, low resonance point transmission rate and high attenuation rate in a wide frequency range always restricts the engineering application of the passive vibration isolator.
The bearing capacity of the quasi-zero stiffness vibration isolator with the positive stiffness element and the negative stiffness element connected in parallel depends on the positive stiffness element, the negative stiffness element can reduce the dynamic stiffness of the system, the characteristics of high static stiffness for supporting isolated equipment and low dynamic stiffness for reducing the vibration transfer rate can be obtained, the low-frequency vibration isolation performance near a working point can be ensured, the stability of the system can be improved, and the quasi-zero stiffness vibration isolator has a wide application prospect. However, the installation space on the ship is limited, the engineering vibration isolator must be designed compactly, and the existing negative stiffness mechanism is often an inclined spiral spring, an inclined connecting rod or a buckling beam and occupies a large space. In addition, the quasi-zero stiffness vibration isolator is a combined type vibration isolator which has smaller combined stiffness within a certain interval of a static balance position. If the weight of the object to be subjected to vibration isolation is not the designed ideal weight, namely the object to be subjected to vibration isolation is placed on the quasi-zero stiffness vibration isolator and cannot be stabilized at the ideal static balance position, the performance of the quasi-zero stiffness vibration isolator is seriously influenced.
Disclosure of Invention
The invention aims to provide a quasi-zero stiffness vibration isolator which is small in non-linear degree and easy to adjust and can adjust negative stiffness in a non-contact mode, aiming at the defects of the prior art.
The technical scheme adopted by the invention is as follows: a quasi-zero stiffness vibration isolator capable of adjusting negative stiffness without contact comprises a vibration isolation box body, and an overturn prevention device, a negative stiffness electromagnetic adjusting device and a positive stiffness spring adjusting device which are arranged in the vibration isolation box body; the vibration isolation box body comprises a lower supporting platform, an upper supporting platform and four side plates enclosed between the upper and lower supporting platforms; the anti-overturning device comprises four anti-overturning mechanisms which are sequentially arranged end to end, and the top and the bottom of each anti-overturning mechanism are respectively connected and fixed with the upper supporting platform and the lower supporting platform; the four anti-overturning mechanisms are symmetrically arranged along a diagonal line, and the middle parts of the four anti-overturning mechanisms surround to form a central area; the negative stiffness electromagnetic adjusting device comprises two negative stiffness generating modules which are oppositely arranged, and the negative stiffness generating modules face the central area; the positive stiffness spring adjusting device is installed in the central area and comprises a worm and gear mechanism and a spiral spring, the worm and gear mechanism is installed on the lower supporting platform, the input end of the worm and gear mechanism penetrates through the side plate to extend out of the vibration isolation box body, the output end of the worm and gear mechanism is connected with the spiral spring, the spiral spring is vertically arranged, and the worm and gear mechanism can drive the spiral spring to move in the vertical direction.
According to the scheme, each anti-overturning mechanism is provided with a supporting structure, and the supporting structure comprises a first fixed block, a second fixed block, a third fixed block, a fourth fixed block, a plurality of transverse reeds and a plurality of vertical reeds, wherein the first fixed block, the second fixed block and the third fixed block are connected with a lower supporting platform; the second fixed block is arranged at the upper part of the first fixed block and is connected with the third fixed block through at least one transverse reed; the third fixed block is connected with the fourth fixed block through at least one vertical reed.
According to the scheme, each negative stiffness generating module comprises a C-shaped yoke and a permanent magnet, and the bottom and the top of the C-shaped yoke are respectively connected with the upper supporting platform and the lower supporting platform; the open sides of the C-shaped yokes of the two negative stiffness generating modules are opposite; an upper middle yoke and a lower middle yoke are arranged in the opening of the C-shaped yoke, and coils are wound outside the two middle yokes to form an electromagnet; the permanent magnet and the two electromagnets are vertically arranged in the opening of the C-shaped yoke in the same polar direction, the permanent magnet is positioned between the two electromagnets, and the three electromagnets form a closed magnetic loop in the C-shaped yoke; the permanent magnet is connected with the upper supporting platform through the supporting plate.
According to the scheme, the supporting plates of the two negative stiffness generating modules are connected through a connecting plate, a height indicating needle is arranged on the connecting plate, and the height indicating needle and the permanent magnet are located at the same height; one end of the height indicating needle extends out of the side plate.
According to the scheme, the supporting plate is an L-shaped supporting plate, the top of the vertical section of the supporting plate is connected with the upper supporting platform, and the horizontal section of the supporting plate is provided with the permanent magnet; the connecting plate is connected with the vertical section of the supporting plate.
According to the scheme, the negative stiffness generation module is also provided with limiting rubbers which are arranged at the upper end and the lower end of the support structure of the anti-overturning mechanism.
According to the scheme, the coil is a water-cooling coil.
According to the scheme, the worm and gear mechanism comprises a plurality of supports, a worm and a worm gear, wherein the supports are arranged on the lower supporting platform at intervals; the worm sequentially penetrates through the supports and then extends out of the operation hole in the side plate; the worm is matched with the worm wheel, the middle part of the worm wheel is in threaded fit with the vertical bolt, and the bottom of the vertical bolt is connected with the lower supporting platform; the spiral spring is coaxially matched with the turbine, the upper end of the spiral spring is in contact with the inner top of the upper supporting platform, the lower end of the spiral spring is fixed on the turbine, and when the worm is rotated, the turbine rotates along with the spiral spring and drives the spiral spring to lift along the axis direction of the vertical bolt.
According to the scheme, the positive stiffness spring adjusting device is further provided with two groups of limiting mechanisms which are symmetrically distributed on the outer sides of the spiral springs, each limiting mechanism comprises a limiting rod and a limiting block, the limiting rods are vertically arranged, and the lower ends of the limiting rods are connected with the lower supporting platform; the limiting block is fixed on the limiting rod.
According to the scheme, the C-shaped yoke and the middle yoke are made of DT4C materials, and the permanent magnet is made of rare earth permanent magnet materials.
The invention has the beneficial effects that:
(1) the quasi-zero stiffness vibration isolator has the characteristics of low inherent frequency and high static bearing capacity, and can ensure that the resonance frequency is very low on the premise of ensuring the bearing capacity, thereby widening the vibration isolation frequency band and improving the vibration isolation effect; and the positive stiffness and the negative stiffness can be adjusted according to actual requirements.
(2) The negative stiffness electromagnetic adjusting device adopts three magnets arranged in the vertical homopolar direction, has no mechanical friction, does not need lubrication, has long service life and small nonlinear degree, and can be well matched with positive stiffness.
(3) The electromagnet in the negative stiffness electromagnetic adjusting device is wound with the coil, the negative stiffness can be controlled through current, adjustment is easy, and self-adaptive control of the negative stiffness of the quasi-zero stiffness vibration isolator is facilitated.
(4) Except the electromagnet and the permanent magnet, other devices in the vibration isolator are made of metal materials which are not magnetic conductive or weak magnetic conductive, and the interference on the magnetic field generated by the permanent magnet is avoided.
(5) And the position of the spring is controlled to be unchanged, the coil current of the electromagnet is regulated, and the negative stiffness is controlled to be matched with the positive stiffness, so that the device can adapt to loads with different weights.
(6) The vibration isolator has the advantages of compact structure, large bearing capacity, simplicity and convenience in control and the like, has a good vibration isolation effect on equipment with large amplitude excitation and different weights, and is wide in vibration isolation frequency band and high in amplitude attenuation rate.
Drawings
Fig. 1 is a schematic overall structure diagram of an embodiment of the present invention.
Fig. 2 is a top view of the present embodiment without the upper support platform.
Fig. 3 is a schematic connection diagram of the anti-overturning device, the negative stiffness electromagnetic adjusting device and the positive stiffness spring adjusting device in the embodiment.
Fig. 4 is an assembly view of the overturn preventing device in this embodiment.
Fig. 5 is an assembly diagram of the negative stiffness electromagnetic adjustment device in the present embodiment.
Fig. 6 is an assembly diagram of the positive rate spring adjusting device in the present embodiment.
Fig. 7 is a graph of static stiffness versus displacement calculation in this example.
Wherein: 1. a lower support platform; 2. a machine leg; 3. a bolt A; 4. a side plate; 5. an upper support platform; 6. a bolt B; 7. an operation hole; 8. a wire hole; 9. a display aperture; 10. a negative stiffness electromagnetic adjustment device; 11. a positive stiffness spring adjustment device; 12. an anti-toppling device; 13. a bolt C; 14. a bolt D; 15. a transverse spring leaf; 16. a vertical reed; 17. a bolt E; 18. a support structure; 18.1, a first fixed block; 18.2, a second fixed block; 18.3, a third fixed block; 18.4, a fourth fixed block; 19. a C-shaped yoke; 20. a permanent magnet; 21. a coil; 22. limiting rubber; 23. a height indicating needle; 24. a vertical bolt; 25. a worm and gear mechanism; 26. a worm; 27. a coil spring; 28. a support; 29. a limiting rod; 30. a limiting block; 31. a support plate; 31.1, a vertical section; 31.2, a horizontal section; 32. a connecting plate; 33. an intermediate yoke.
Detailed Description
For a better understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
The quasi-zero stiffness vibration isolator capable of adjusting negative stiffness without contact as shown in fig. 1 to 3 comprises a vibration isolation box body, and an anti-overturning device 12, a negative stiffness electromagnetic adjusting device 10 and a positive stiffness spring adjusting device 11 which are arranged in the vibration isolation box body; the vibration isolation box body comprises a lower supporting platform 1, an upper supporting platform 5 and four side plates 4 enclosed between the upper and lower supporting platforms 1; the overturn preventing device 12 comprises four overturn preventing mechanisms which are sequentially arranged end to end, and the top and the bottom of each overturn preventing mechanism are respectively connected and fixed with the upper supporting platform 1 and the lower supporting platform 1; the four anti-overturning mechanisms are symmetrically arranged along a diagonal line, and the middle parts of the four anti-overturning mechanisms surround to form a central area; the negative stiffness electromagnetic adjusting device 10 comprises two negative stiffness generating modules which are oppositely arranged, and the negative stiffness generating modules face to the central area; the positive stiffness spring adjusting device 11 is installed in the central area, the positive stiffness spring adjusting device 11 comprises a worm gear mechanism 25 and a spiral spring 27, the worm gear mechanism 25 is installed on the lower supporting platform 1, the input end of the worm gear mechanism 25 penetrates through the side plate 4 to extend out of the vibration isolation box body, the output end of the worm gear mechanism 25 is connected with the spiral spring 27, the spiral spring 27 is vertically arranged, and the worm gear mechanism 25 can drive the spiral spring 27 to move in the vertical direction.
In the invention, as shown in the vibration isolation box body shown in fig. 1, the lower support platform 1 is connected with the side plate 4 through a plurality of bolts B6, and the bottom of the lower support platform 1 is connected with the machine leg 2 through a bolt A3; the upper supporting platform 5 is connected with the side plate 4 in an embedded mode. The side plate 4 is provided with an operation hole 7 for operating the worm 26, a wire hole 8 for accessing a power wire and a display hole 9 for displaying a balance position.
The anti-overturning device 12 provides torsional rigidity for the whole device, and can effectively prevent the vibration isolator from generating larger torsional amplitude. In the overturn preventing device 12 shown in fig. 4, each overturn preventing mechanism is provided with a supporting structure 18, and the supporting structure 18 comprises a first fixed block 18.1 (which can be connected by bolts) connected with the lower supporting platform 1, a second fixed block 18.2, a third fixed block 18.3, a fourth fixed block 18.4 (which is connected by bolts D14) connected with the upper supporting platform 5, and a plurality of transverse reeds 15 and a plurality of vertical reeds 16; the second fixed block 18.2 is arranged at the upper part of the first fixed block 18.1, and the second fixed block 18.2 is connected with the third fixed block 18.3 through at least one transverse spring 15; the third holding block 18.3 is connected to the fourth holding block 18.4 by at least one vertical spring 16.
In this embodiment, the second fixing block 18.2 is connected to the third fixing block 18.3 through two parallel transverse reeds 15, and the third fixing block 18.3 is connected to the fourth fixing block 18.4 through one vertical reed 16; each reed is respectively connected with the corresponding fixed block through a bolt E17.
The negative stiffness electromagnetic adjusting device 10 adopts a vertical homopolar arrangement form of three magnets as a negative stiffness generating module, and is used for realizing self-adaptive control of the negative stiffness of the quasi-zero stiffness vibration isolator. As shown in fig. 5, the negative stiffness electromagnetic adjusting device 10 includes two negative stiffness generating modules arranged oppositely, each negative stiffness generating module includes a C-shaped yoke 19, a permanent magnet 20, and two middle yokes 33 wound with coils 21, the C-shaped yoke 19 is respectively connected (bolted) to the lower support platform 1; the open sides of the C-shaped yokes 19 of the two negative rigidity generation modules are opposite and are positioned below the transverse reeds 16; an upper middle yoke 33 and a lower middle yoke 33 are arranged in an opening of the C-shaped yoke 19, and a coil 21 is wound outside the two middle yokes 33 to form an electromagnet; the permanent magnet 20 and the electromagnets are vertically arranged in the opening of the C-shaped yoke in the same polar direction, the permanent magnet 20 is positioned between the two electromagnets, the permanent magnet 20 and the electromagnets form a closed magnetic loop in the C-shaped yoke 19, and a repulsive force is generated between the permanent magnet 20 and the electromagnets; the permanent magnet 20 is connected to the upper support platform 5 by a support plate 31. In this embodiment, the coil 21 is wound around the middle of the intermediate yoke 33, and the upper end of the intermediate yoke 33 is connected to the upper support platform 5 by a bolt.
In the invention, the support plate 31 is positioned in the central area, the permanent magnet 20 is connected with the upper support platform 5 through the support plate 31 and moves together with the upper support platform 5, and in the moving process, the permanent magnet induces a magnetic field with electromagnets at the upper end and the lower end and generates magnetic force in the same direction as the displacement direction, thereby realizing negative rigidity. The coil 21 is connected with the electric wire led in from the wire hole 8, and the negative stiffness of the vibration isolator is controlled by changing the current input into the coil 21. In the closed magnetic loop of the C-shaped yoke 19, the coil 21 of the electromagnet is not electrified, the middle yoke 33 can induce a magnetic field by the permanent magnet 20 to generate corresponding negative rigidity, and the excitation current in the same direction as the original magnetic field can be input to the coil 21 to enhance the negative rigidity.
Preferably, the support plates 31 of the two negative stiffness generating modules are connected through a connecting plate 32, the connecting plate 32 is provided with a height indicating pin 23, and the height indicating pin 23 and the permanent magnet 20 are located at the same height; one end of the height indicating needle 23 extends out of the side plate 4 from the display hole 9 and is used for displaying the real-time position of the permanent magnet 20, so that the position of the balance point of the quasi-zero stiffness vibration isolator can be conveniently adjusted.
In this embodiment, the support plate 31 is an L-shaped support plate, the top of the vertical section 31.1 of the support plate 31 is connected with the upper support platform 5 (which can be connected by a bolt C13), and the horizontal section of the support plate 31 is provided with the permanent magnet 20; the connecting plate 32 is connected to the vertical section of the support plate 31.
Preferably, the negative stiffness generating module is further provided with limiting rubbers 25, and the limiting rubbers 25 are arranged at the upper and lower ends of the support structure 18 of the anti-overturning mechanism (particularly, at the upper and lower portions of the first fixing block 18.1) to prevent the permanent magnet 20 from colliding with the C-shaped yoke 19 during the movement. In this embodiment, the connecting plate 32, the support plate 31 and the height indicating needle 23 are all reciprocated up and down along with the permanent magnet 20, and the connecting plate 32 is moved between the upper and lower portions of the first fixing block 18.1.
Preferably, the coil 21 is a water-cooling coil 21, which can effectively solve the problem of heat generation of the coil 21.
And the positive stiffness spring adjusting device 11 is used for realizing the control of the positive stiffness of the zero-stiffness vibration isolator. As shown in fig. 6, the worm gear and worm mechanism 25 includes a plurality of supports 28, a worm 26 and a worm wheel, wherein the plurality of supports 28 are arranged on the lower supporting platform 1 at intervals (can be connected by bolts); the worm 26 sequentially passes through each support 28 and then extends out of an operation hole on the side plate 4; the worm 26 is matched with the worm wheel, the middle part of the worm wheel is in threaded fit with the vertical bolt 24, and the bottom of the vertical bolt 24 is connected with the lower supporting platform 1; coil spring 27 and the coaxial cooperation of turbine, and the upper end of coil spring 27 and the interior top contact of last supporting platform 5, the lower extreme of coil spring 27 is fixed on the turbine, and when rotating worm 26, the turbine rotates thereupon to drive coil spring 27 and go up and down along the axis direction of vertical bolt 24, change coil spring 27's positive rigidity value, thereby be convenient for adjust the balance point position of accurate zero rigidity isolator. In this embodiment, there are 3 supports 28, which can fix the position of the worm 2626, so as to effectively control the vertical movement of the coil spring 27.
Preferably, the positive stiffness spring adjusting device 11 is further provided with two sets of limiting mechanisms symmetrically distributed on the outer side of the coil spring 27 to limit the coil spring 27 to shift left and right and move only in the vertical direction; the limiting mechanism comprises a limiting rod 29 and a limiting block 30, the limiting rod 29 is vertically arranged, and the lower end of the limiting rod is connected with the lower supporting platform 1; the limiting block 30 is fixed on the limiting rod 29.
In the invention, the C-shaped yoke 19 and the middle yoke 33 are both made of DT4C material with low coercive force and high magnetic permeability, and the permanent magnet 20 is made of rare earth permanent magnet material; other parts and structures are made of non-magnetic or weak magnetic materials, such as 304 stainless steel.
The working principle of the negative stiffness electromagnetic adjusting device 10 is as follows: the middle permanent magnet 20 magnetizes the upper and lower intermediate yokes 33, thereby generating an attractive force. The magnitude and the direction of the current of the coil 21 are changed, so that the magnitude and the direction of the magnetic field inside the intermediate yoke 33 are changed, and the magnitude of the electromagnetic negative stiffness is changed. The force applied to the intermediate yoke 33 can be divided into the acting force between the permanent magnet 20 and the permanent magnet 33 (permanent magnetic acting force) and the acting force between the magnetic field caused by the current of the coil 21 and the permanent magnet 20 (electromagnetic acting force), wherein the permanent magnetic acting force is:
in the formula, FpcRepresents the permanent magnet force, N; a is1Denotes constant coefficient, Nm4；q1Representing a displacement parameter (q)1＝zc+a2)，m；zcRepresents the distance, mm, of the permanent magnet 20 from the intermediate yoke 33 when the permanent magnet 20 is in the intermediate equilibrium position; a is2Represents the constant coefficient of displacement, m; z represents the vertical displacement, mm, of the permanent magnet 20 from the equilibrium position.
The electromagnetic force is:
in the formula, FpeRepresents the electromagnetic force, N; a is3Denotes the current parameter, A-1(ii) a sign represents a sign function; i represents the coil 21 current, a; b3Denotes the current parameter, A-1；b1Denotes constant coefficient, Nm4；q2Representing a displacement parameter (q)2＝zc+b2)，m；b2Representing the constant coefficient of displacement, m.
The permanent magnet 20 and the electromagnet have the same magnetization direction, and the structure is similar to a three-magnet negative-stiffness structure. When no current is applied to the coil 21, the magnetic flux density is small, and the magnetic flux density is mainly generated by the permanent magnet 20. As the magnitude of the current increases, the magnetic flux density also increases. When no current is applied to the coil 21, a three-magnet negative stiffness structure can be formed due to a magnetic field induced by the permanent magnet 20 in the electromagnet, so that a negative stiffness phenomenon exists, and the negative stiffness phenomenon is more obvious along with the increase of the current.
The working principle of the invention is as follows: the invention provides negative rigidity by utilizing a vertical homopolar arrangement structure of three magnets, wherein a permanent magnet 20 is arranged in the middle, electromagnets are arranged at the upper part and the lower part, and a C-shaped yoke 19 is used for closing a magnetic loop; the total stiffness of the system at the equilibrium position is small after the coil springs 27 are connected in parallel (the static stiffness-displacement calculation curve of the vibration isolator is shown in figure 6). When the vibration isolator is used, a vibration-isolated object is fixed at the center of the upper part of the upper supporting platform 5, and when the mass of the vibration-isolated object changes, the current of the coil 21 and the worm 26 are adjusted to enable the negative stiffness to be matched with the positive stiffness, so that the vibration isolator can be in a balance position. Therefore, the whole device has small dynamic stiffness and low natural frequency during vibration. When the whole device is in a static state, the permanent magnet 20 is positioned between the two middle yokes 33, and due to symmetry, the axial force generated by the electromagnet on the permanent magnet 20 is zero, so that the static bearing capacity of the vibration isolator cannot be influenced.
Details not described in this specification are within the skill of the art that are well known to those skilled in the art. The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. A quasi-zero stiffness vibration isolator capable of adjusting negative stiffness without contact is characterized by comprising a vibration isolation box body, and an anti-overturning device, a negative stiffness electromagnetic adjusting device and a positive stiffness spring adjusting device which are arranged in the vibration isolation box body; the vibration isolation box body comprises a lower supporting platform, an upper supporting platform and four side plates enclosed between the upper and lower supporting platforms; the anti-overturning device comprises four anti-overturning mechanisms which are sequentially arranged end to end, and the top and the bottom of each anti-overturning mechanism are respectively connected and fixed with the upper supporting platform and the lower supporting platform; the four anti-overturning mechanisms are symmetrically arranged along a diagonal line, and the middle parts of the four anti-overturning mechanisms surround to form a central area; the negative stiffness electromagnetic adjusting device comprises two negative stiffness generating modules which are oppositely arranged, and the negative stiffness generating modules face the central area; the positive stiffness spring adjusting device is installed in the central area and comprises a worm and gear mechanism and a spiral spring, the worm and gear mechanism is installed on the lower supporting platform, the input end of the worm and gear mechanism penetrates through the side plate to extend out of the vibration isolation box body, the output end of the worm and gear mechanism is connected with the spiral spring, the spiral spring is vertically arranged, and the worm and gear mechanism can drive the spiral spring to move in the vertical direction.
2. The quasi-zero stiffness vibration isolator of claim 1 wherein each anti-overturning mechanism is provided with a support structure comprising a first fixed block, a second fixed block, a third fixed block connected with a lower support platform, a fourth fixed block connected with an upper support platform, and a plurality of transverse springs and a plurality of vertical springs; the second fixed block is arranged at the upper part of the first fixed block and is connected with the third fixed block through at least one transverse reed; the third fixed block is connected with the fourth fixed block through at least one vertical reed.
3. The quasi-zero stiffness vibration isolator of claim 1 wherein each negative stiffness generating module comprises a C-yoke and a permanent magnet, the bottom and top of the C-yoke being connected to the upper and lower support platforms, respectively; the open sides of the C-shaped yokes of the two negative stiffness generating modules are opposite; an upper middle yoke and a lower middle yoke are arranged in the opening of the C-shaped yoke, and coils are wound outside the two middle yokes to form an electromagnet; the permanent magnet and the two electromagnets are vertically arranged in the opening of the C-shaped yoke in the same polar direction, the permanent magnet is positioned between the two electromagnets, and the three electromagnets form a closed magnetic loop in the C-shaped yoke; the permanent magnet is connected with the upper supporting platform through the supporting plate.
4. The quasi-zero stiffness vibration isolator according to claim 3, wherein the support plates of the two negative stiffness generating modules are connected through a connecting plate, and a height indicator pin is arranged on the connecting plate and is positioned at the same height as the permanent magnet; one end of the height indicating needle extends out of the side plate.
5. The quasi-zero stiffness vibration isolator of claim 4 wherein the support plate is an L-shaped support plate, the top of the vertical section of the support plate is connected with the upper support platform, and the horizontal section of the support plate is provided with the permanent magnet; the connecting plate is connected with the vertical section of the supporting plate.
6. The quasi-zero stiffness vibration isolator according to claim 3, wherein the negative stiffness generating module is further provided with limiting rubbers disposed at upper and lower ends of the support structure of the anti-overturning mechanism.
7. The quasi-zero stiffness vibration isolator of claim 3 wherein the coil is a water cooled coil.
8. The quasi-zero stiffness vibration isolator of claim 1 wherein the worm gear and worm mechanism includes a plurality of standoffs, a worm, and a worm gear, the plurality of standoffs being spaced apart on the lower support platform; the worm sequentially penetrates through the supports and then extends out of the operation hole in the side plate; the worm is matched with the worm wheel, the middle part of the worm wheel is in threaded fit with the vertical bolt, and the bottom of the vertical bolt is connected with the lower supporting platform; the spiral spring is coaxially matched with the turbine, the upper end of the spiral spring is in contact with the inner top of the upper supporting platform, the lower end of the spiral spring is fixed on the turbine, and when the worm is rotated, the turbine rotates along with the spiral spring and drives the spiral spring to lift along the axis direction of the vertical bolt.
9. The quasi-zero stiffness vibration isolator according to claim 8, wherein the positive stiffness spring adjusting device is further provided with two sets of limiting mechanisms symmetrically distributed on the outer sides of the spiral springs, each limiting mechanism comprises a limiting rod and a limiting block, the limiting rods are vertically arranged, and the lower ends of the limiting rods are connected with the lower supporting platform; the limiting block is fixed on the limiting rod.
10. The quasi-zero stiffness vibration isolator of claim 3 wherein the C-shaped yoke and the intermediate yoke are made of DT4C material and the permanent magnets are made of rare earth permanent magnet material.
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