CN115789164A - Rubber and electromagnetism parallel connection adjustable rigidity low-frequency vibration isolation device - Google Patents
Rubber and electromagnetism parallel connection adjustable rigidity low-frequency vibration isolation device Download PDFInfo
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Abstract
The invention discloses a rubber and electromagnetism parallel connection adjustable rigidity low-frequency vibration isolation device which comprises an upper supporting platform, a rubber supporting structure, a base, a central shaft and a vibration isolator, wherein the upper supporting platform is positioned at the top of the rubber supporting structure, the inside of the rubber supporting structure is communicated up and down, the bottom of the rubber supporting structure is connected with the base, and the bottom surface of the upper supporting platform, the inner wall surface of the rubber supporting structure and the upper surface of the base are enclosed to form a cavity; center pin and isolator are installed in the cavity, and the upper end of center pin is passed through lock nut 7 and is linked to each other with the bottom of going up supporting platform, and the lower extreme of center pin links to each other with the bottom of isolator. The beneficial effects of the invention are as follows: based on the principle of parallel connection of positive stiffness and negative stiffness, the vibration isolation device with rubber and electromagnetism connected in parallel is provided, so that the vibration isolation device is high in bearing capacity, compact and simple in structure; when the load mass or external excitation changes, the rigidity of the vibration isolation system can be easily adjusted in real time by using the electromagnetic adjusting mechanism, so that the system is ensured to have high bearing capacity and low-frequency vibration isolation performance, and the low-frequency or ultra-low-frequency vibration isolation effect of the vibration isolation system is enhanced.
Description
Technical Field
The invention relates to the technical field of vibration isolation, in particular to a rigidity-adjustable low-frequency vibration isolation device with rubber and electromagnetism connected in parallel.
Background
In the engineering field, vibration is a main cause of instability of the device, and improving the vibration condition in the operation process of the device is an important measure for improving the operation reliability of the device. The traditional linear stiffness vibration isolator has good isolation effect on medium and high frequency vibration, but has unsatisfactory isolation effect on low frequency vibration. In recent years, researchers have proposed negative stiffness mechanisms in order to break through the performance bottleneck of linear vibration isolation systems. The negative stiffness mechanism and the positive stiffness system are connected in parallel at the balance position, so that the positive stiffness near the balance position of the system can be counteracted, lower dynamic stiffness is achieved, and the bearing static stiffness and the static displacement of a load when the system is in zero compression are not influenced, so that the inherent frequency of the system is reduced while the bearing capacity of the system is not reduced, and the vibration isolation frequency band is expanded. Since twenty-first century, with the development of engineering practice, the demand for low-frequency vibration isolation is becoming stronger, and various vibration isolators with quasi-zero stiffness characteristics have been developed. The quasi-zero stiffness system can be divided into the following according to the difference of the negative stiffness elastic elements: inclined spring type, euler buckling rod type, horizontal spring type, ball type and magnetic system.
Although the quasi-zero stiffness vibration isolator has an excellent low-frequency vibration isolation effect, the vibration isolation performance of the quasi-zero stiffness vibration isolator is very sensitive to the load mass, when the load mass changes, the load balance position changes, the vibration isolator is not in a quasi-zero state, and the vibration isolation performance is greatly reduced. However, the superior low-frequency performance of the quasi-zero stiffness vibration isolator is seriously limited by the bearing quality, and when the system is in an underload condition, an overload condition and other unstable conditions, the system is difficult to move near the static balance position of the system, so that the vibration isolation effect is poor.
In order to reduce the sensitivity of the quasi-zero stiffness to the load bearing mass, so that the quasi-zero stiffness has a good low-frequency vibration isolation effect even when the load balance position changes, researchers have proposed novel vibration isolation devices in succession. The invention discloses CN 112696454A, which is an invention patent of a magnetic suspension type quasi-zero stiffness electromagnetic vibration isolator with active negative stiffness, the bearing capacity of the vibration isolator is further enhanced by adopting an amplifying mechanism and a DIESOLE type electromagnet, the displacement state of a negative stiffness mechanism is measured in real time according to a sensor, the active negative stiffness is realized under the matching of a controller and a driver, the real-time linear negative stiffness is realized, the multistable phenomenon is avoided, and the complex dynamics phenomena such as jumping and the like of the vibration isolator in the working process are prevented. The invention discloses a quasi-zero stiffness vibration isolator with the publication number of CN112460177A and the invention patent of a quasi-zero stiffness vibration isolator with the self-adaptive negative stiffness adjustment, and provides a quasi-zero stiffness vibration isolator with the self-adaptive negative stiffness adjustment. However, most of the existing vibration isolation devices adopt a mechanical spring as a positive stiffness adjusting device, and the bearing capacity of the existing vibration isolation devices is limited, so that the existing vibration isolation devices cannot be well applied to engineering practice. Secondly, the existing vibration isolation device generally adopts a mechanical structure to adjust negative stiffness, and the problems of complex structure, poor adjustment sensitivity, poor stability and the like of the negative stiffness adjusting device exist, so that the load bearing range is small and the adaptability is poor.
Disclosure of Invention
The invention aims to provide a rigidity-adjustable low-frequency vibration isolation device with rubber and electromagnetism connected in parallel, aiming at the defects of the prior art.
The technical scheme adopted by the invention is as follows: a low-frequency vibration isolator with adjustable rigidity and connected in parallel by rubber and electromagnetism comprises an upper supporting platform, a rubber supporting structure, a base, a central shaft and a vibration isolator,
the upper supporting platform is positioned at the top of the rubber supporting structure, the interior of the rubber supporting structure is communicated up and down, the bottom of the rubber supporting structure is connected with the base, and a cavity is formed by the bottom surface of the upper supporting platform, the inner wall surface of the rubber supporting structure and the upper surface of the base in a surrounding manner; center pin and isolator are installed in the cavity, and the upper end of center pin links to each other with the bottom of last supporting platform, and the lower extreme of center pin links to each other with the bottom of isolator.
According to the scheme, the upper part of the outer wall surface of the rubber supporting structure extends outwards to form a skirt-shaped structure.
According to the scheme, the vibration isolator is a linear magnetic type negative stiffness low-frequency vibration isolator and comprises a vibration isolation box body, and two spring positive stiffness modules and two electromagnetic negative stiffness modules which are arranged in the vibration isolation box body;
the top of the vibration isolation box body is connected with the middle connecting platform, and the base of the vibration isolation box body is fixed on the base; the two spring positive stiffness modules are symmetrically arranged at the upper part and the lower part of the electromagnetic negative stiffness module;
the upper end of the central shaft is connected with the upper supporting platform through a locking nut, and the lower end of the central shaft sequentially penetrates through the spring positive stiffness module, the electromagnetic negative stiffness module and the spring positive stiffness module which are located on the upper portion in the vibration isolation box body and are located on the lower portion in the vibration isolation box body, and is connected with the base of the vibration isolation box body.
According to the scheme, the electromagnetic negative stiffness module comprises an upper annular permanent magnet, a middle annular permanent magnet and a lower annular permanent magnet which are sequentially arranged along the axial direction of a central shaft, wherein the upper annular permanent magnet and the lower annular permanent magnet are symmetrically arranged at the upper part and the lower part of the middle annular permanent magnet; coaxial annular coils are correspondingly arranged outside each permanent magnet, and the annular coils are fixed with the corresponding annular coil boxes; the three annular permanent magnets can move along the axial direction in the cavity inside the corresponding annular coil along with the central shaft;
the axial displacement of the central shaft can be adjusted through the two spring positive stiffness modules, so that the relative positions of the annular permanent magnet and the corresponding coil are changed, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
According to the scheme, the spring positive stiffness module comprises a spiral spring, a limiting piece and an adjusting piece; the spiral spring is sleeved on the central shaft, one end of the spiral spring is connected with the adjusting piece, and the adjusting piece is matched with the central shaft; the other end of the spiral spring is connected with the upper end face of the limiting piece; the central shaft penetrates through the center of the limiting piece; the electromagnetic negative stiffness module is arranged between the limiting parts of the two spiral spring positive stiffness modules; when the adjusting pieces of the two spring positive stiffness modules are adjusted, the compression amounts of the two spiral springs can be changed, and further the axial position of the central shaft is changed, so that the relative positions of the annular permanent magnet and the corresponding annular coil are adjusted, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
According to the scheme, the limiting piece is a linear bearing, and the linear bearings of the two spring positive stiffness modules are symmetrically arranged on the central shaft along the balance position of the vibration isolation device; one end of the spiral spring is connected with the end face of the linear bearing, and the linear bearing is connected with the annular coil box body.
According to the scheme, the three annular lines are vertically and coaxially and symmetrically arranged to form the attraction type electromagnetic negative stiffness mechanism; the upper and lower two annular coils are respectively and symmetrically arranged at two ends of the middle annular coil, and are introduced with currents with the same direction and magnitude.
According to the scheme, the annular coils are water-cooling coils.
According to the scheme, the three annular permanent magnets and the three annular coils are vertically, coaxially and symmetrically arranged to form the repelling electromagnetic negative stiffness mechanism; the annular permanent magnets are fixedly connected with the central shaft through fixing rings, and the three annular coils are coaxial with the corresponding annular permanent magnets in equal height.
According to the scheme, the vertical distance between the annular coils is 14-15 mm, the vertical distance between the annular permanent magnets is 14-15 mm, and the transverse distance between the annular coils and the corresponding permanent magnets is 4-5 mm.
The beneficial effects of the invention are as follows: the invention provides a rigidity-adjustable low-frequency vibration isolation device with rubber and electromagnetism connected in parallel based on the principle that positive rigidity and negative rigidity are connected in parallel, and aims to ensure that a system has high bearing capacity and low-frequency vibration isolation performance, adjust the negative rigidity of a vibration isolator in real time according to the change of load mass, ensure that the vibration isolation frequency of the vibration isolation system at a balance position is in a quasi-zero state, and enhance the low-frequency or ultralow-frequency vibration isolation effect of the vibration isolation system. The vibration isolation device is mainly suitable for occasions with large load mass, change and limited installation space, and adopts a combination form of positive stiffness and negative stiffness of rubber and linear springs, so that the vibration isolation device has strong bearing capacity and a compact and simple structure; when the load mass or the external excitation changes, the rigidity of the vibration isolation system can be adjusted in real time more easily by using the electromagnetic adjusting mechanism. In addition, the linearity of the negative stiffness in the low-frequency vibration isolation device is improved by adopting a coupling mode of the attraction type electromagnetic negative stiffness mechanism and the repulsion type electromagnetic negative stiffness mechanism. In addition, the invention can utilize the rough adjusting nut and the fine adjusting nut to adjust the negative stiffness in advance according to the load mass change, and further ensure that the vibration isolation frequency of the vibration isolation system at the balance position is in a quasi-zero state, thereby improving the performance stability of the vibration isolation system.
Drawings
Fig. 1 is a schematic overall structure diagram of an embodiment of the present invention.
Fig. 2 is a sectional view of the entire structure of the present embodiment.
Fig. 3 is a schematic view of the overall structure of the internal case of the resonator in this embodiment.
Fig. 4 is a front sectional view showing the internal case structure of the resonator in this embodiment.
Fig. 5 is a side sectional view of the internal case structure of the resonator in this embodiment.
Fig. 6 is a schematic connection diagram of the linear bearing device, the attraction type electromagnetic negative stiffness adjusting device, the repulsion type electromagnetic negative stiffness adjusting device, and the positive stiffness spring adjusting device in the internal box body of the isolator in this embodiment.
Wherein: 1. an upper support platform; 2. a linear coil spring; 3. an upper end annular coil; 4. a middle loop coil; 5. a lower end annular coil; 6. a vibration isolation inner box base; 7. locking the nut; 8. fine adjustment of the nut; 9. an upper end linear bearing; 10. a fixing ring; 11. a box body inside the vibration isolator; 12. a lower end linear bearing; 13. coarse adjustment of the nut; 14. a central shaft; 15. a long through bolt; 16. an upper end annular permanent magnet; 17. a lower annular permanent magnet; 18. a middle annular permanent magnet; 19. a middle annular coil box body; 20. an upper linear spring housing; 21. a lower annular coil box body; 22. a base box body; 23. an upper annular coil box body; 24. a rubber support structure; 25. a bottom base; 26. a skirt structure.
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 low-frequency vibration isolation device with adjustable rigidity and connected with rubber and electromagnetism in parallel as shown in figures 1-2 comprises an upper supporting platform 1, a rubber supporting structure 24, a base 15, a central shaft 14 and a vibration isolator,
the upper supporting platform 1 is positioned at the top of the rubber supporting structure 24, the interior of the rubber supporting structure 24 is communicated up and down, the bottom of the rubber supporting structure 24 is connected with the base 25, and the bottom surface of the upper supporting platform 4, the inner wall surface of the rubber supporting structure 24 and the upper surface of the base 25 are enclosed to form a cavity; the center shaft 14 and the vibration isolator are arranged in the cavity (the vibration isolator is not contacted with the inner wall of the cavity), the upper end of the center shaft 14 is connected with the bottom of the upper supporting platform 1 through a locking nut 7, and the lower end of the center shaft 14 is connected with the bottom of the vibration isolator.
Preferably, the upper portion of the outer wall surface of the rubber supporting structure 24 protrudes outwards to form a skirt structure 26, and this structure design can provide greater supporting rigidity and better supporting effect.
In the present invention, as shown in fig. 1 to 3, the upper support platform 1 is fixedly connected to the central shaft 14 and the rubber support structure 24 by a plurality of bolts and locking nuts 7, and carries a vibration isolation object, specifically, the vibration isolation object is provided on the upper support platform 1.
Preferably, as shown in fig. 3 to 6, the vibration isolator 25 is a linear magnetic type negative stiffness low-frequency vibration isolator, and includes a vibration isolation box 11, two spring positive stiffness modules and two electromagnetic negative stiffness modules installed in the vibration isolation box 11;
the base 6 of the vibration isolation box body 11 is fixed on the base 25; the two spring positive stiffness modules are symmetrically arranged at the upper part and the lower part of the electromagnetic negative stiffness module;
the upper end of the central shaft 14 is connected with the upper supporting platform 1 through a locking nut 7, and the lower end of the central shaft 14 sequentially penetrates through a spring positive stiffness module, an electromagnetic negative stiffness module and a spring positive stiffness module which are positioned at the upper part in the vibration isolation box body 11 and the lower part in the vibration isolation box body 11 and is connected with the base 6 of the vibration isolation box body;
the electromagnetic negative stiffness module comprises an upper annular permanent magnet 16, a middle annular permanent magnet 18 and a lower annular permanent magnet 17 which are sequentially arranged along the axial direction of a central shaft 14, wherein the upper annular permanent magnet and the lower annular permanent magnet are symmetrically arranged at the upper part and the lower part of the middle annular permanent magnet 18; coaxial annular coils (an upper annular coil 3, a middle annular coil 4 and a lower annular coil 5 are respectively and correspondingly arranged outside each annular permanent magnet), and the annular coils are fixed with corresponding annular coil boxes (each annular coil respectively corresponds to an upper annular coil box 23, a middle annular coil box 19 and a lower annular coil box 21); the three annular permanent magnets can move along the axial direction in the cavity inside the corresponding annular coil along with the central shaft 14; the axial displacement of the central shaft can be adjusted through the two spring positive stiffness modules, so that the relative positions of the annular permanent magnet and the corresponding coil are changed, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
Preferably, the positive spring stiffness module comprises a coil spring 2, a limiting member and an adjusting member; the spiral spring 2 is sleeved on the central shaft 14, one end of the spiral spring 2 is connected with the adjusting piece, and the adjusting piece is matched with the central shaft 14; the other end of the spiral spring 2 is connected with the upper end face of the limiting piece; the central shaft 14 passes through the center of the limiting piece; the electromagnetic negative stiffness module is arranged between the limiting parts of the two spring positive stiffness modules; when the adjusting parts of the two spring positive stiffness modules are adjusted, the compression amount of the two spiral springs 2 can be changed, and further the axial position of the central shaft 14 is changed (the upper supporting platform 1 moves along with the central shaft 14 synchronously), so that the relative positions of the annular permanent magnet and the corresponding annular coil are adjusted, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
In the invention, an upper supporting platform 1 is arranged on a locking nut 7, the upper end of a central shaft 14 penetrates through the locking nut 7 and extends into a reserved notch of the upper supporting platform 1, and the upper supporting platform 1 can axially move along with the central shaft 14; the lower end of the central shaft 14 is connected with the base through a locking nut 7, and a notch for axial movement of the central shaft 14 is reserved in the base 26.
Preferably, the adjusting member is an adjusting nut, and the outer peripheral surface of the central shaft 14 is provided with an external thread adapted to the adjusting nut. . The coil spring 2 is a linear coil spring. Specifically, the adjusting nut of the upper spring positive stiffness module is a fine adjusting nut 8, the adjusting nut of the lower spring positive stiffness module is a coarse adjusting nut 13, the thread pitches of the two nuts are different, the thread pitch of the coarse adjusting nut 13 is larger than that of the fine adjusting nut 8, the coarse adjusting nut 13 can be used for large position adjustment, the fine adjusting nut 8 can be used for fine adjustment, the structural design is simple, but both coarse adjustment and fine adjustment are taken into consideration, and the operation is convenient.
Preferably, the limiting member is a linear bearing, and the linear bearings (the upper portion is an upper linear bearing 9, and the lower portion is a lower linear bearing 12) of the two spring positive stiffness modules are symmetrically arranged on the central shaft 14 along the balance position of the vibration isolation device (the central shaft 14 is matched with the inner ring of the linear bearing); one end of the spiral spring 2 is connected with the end face of the linear bearing, and the linear bearing is respectively connected with the annular coil box body through a plurality of through bolts 15 which are axially arranged at intervals. Specifically, an upper linear bearing 9 of the upper spring positive stiffness module is in bolted connection with an upper annular coil box body 23, and a lower linear bearing 11 of the lower spring positive stiffness module is in bolted connection with a lower annular coil box body 21; two linear bearings are arranged on the outer sides of the upper annular coil and the lower annular coil, so that the coaxiality of the box body and the central shaft 14 can be ensured, and the friction during movement is reduced. The upper surfaces of the two linear bearings are provided with spring notches, so that the position of the spiral spring 2 can be effectively limited.
In the present invention, three ring-shaped permanent magnets are mounted on a central shaft 14 through a fixing ring 10. The upper annular permanent magnet 16 is correspondingly provided with an upper annular coil 3 and an upper annular coil box body 23, the middle annular permanent magnet 18 is correspondingly provided with a middle annular coil 4 and a middle annular coil box body 19, and the lower annular permanent magnet 17 is correspondingly provided with a lower annular coil 5 and a lower annular coil box body 21; baffle rings are arranged in the three annular coil boxes 19, 20 and 21 and used for fixing the corresponding annular coils. The vibration isolation box body 11 comprises a spring box body at the top (such as a top spring box body 20 in fig. 1-4), three ring-shaped coil box bodies at the middle (such as an upper ring-shaped coil box body 23, a middle ring-shaped coil box body 19 and a lower ring-shaped coil box body 21 in the drawings) and a spring box body at the bottom (reference numeral 22), and all the box bodies are fixedly connected through external bolts. The spring box 22 at the bottom is also the base box of the whole vibration isolation device, and the base 6 is provided with bolt holes which can be used for being fixedly connected with the base 25; the coarse adjustment nut 13 of the lower spring positive stiffness module is mounted on the base 6.
In the invention, the linear bearing adopts a sliding bearing with an aluminum shell and a tetrafluoroethylene resin lining so as to avoid the influence of a common steel ball linear bearing on a magnetic field; the annular permanent magnets are all made of rare earth permanent magnet materials; the central shaft 14, the fixing ring 10, the bolt and the nut and other parts and structures are made of non-magnetic conductive or weak magnetic conductive materials, such as 304 stainless steel; each box body is made of aluminum alloy materials.
In the invention, the components of the electromagnetic negative stiffness module can respectively form an attraction type electromagnetic negative stiffness mechanism and a repulsion type electromagnetic negative stiffness mechanism.
The three annular coils 3, 4 and 5 are vertically and coaxially symmetrically arranged to form the attraction type electromagnetic negative stiffness mechanism. As shown in fig. 3 and 4, the attraction type electromagnetic negative stiffness mechanism includes two upper and lower annular coils 3 and 5 arranged symmetrically and a middle annular coil 4, and each annular coil is formed by winding an enameled wire. The two upper and lower identical toroidal coils 3 and 5 are respectively positioned at two ends of the middle toroidal coil 4 along the central axis 14, are symmetrically arranged, and are supplied with currents with the same direction and the same magnitude. The three annular coils are fixed with each other; the annular coils are water-cooling coils, so that the heating problem of the coils can be effectively solved.
The three annular permanent magnets 16, 17 and 18 and the three annular coils 3, 4 and 5 are vertically, coaxially and symmetrically arranged to form the repelling electromagnetic negative stiffness mechanism. As shown in fig. 3 and 4, the repulsive electromagnetic negative stiffness mechanism includes three pairs of paired structures (an upper annular coil 3 and an upper end annular permanent magnet 16, a middle annular coil 4 and a middle annular permanent magnet 18, a lower annular coil 5 and a lower end annular permanent magnet 17) composed of annular coils and permanent magnets, and the paired structures of the three pairs of annular coils and the permanent magnets are symmetrically arranged along a central axis 14. Preferably, the annular permanent magnets in the three pairs of paired structures are all fixedly connected with the central shaft 14 through the fixing ring 10, and the three annular coils 3, 4 and 5 are mutually fixed and are all coaxial with the corresponding annular permanent magnets 16, 17 and 18 in equal height. The vertical distance of the paired structures formed by the three pairs of annular coils and the corresponding permanent magnets is 14-15 mm (namely the vertical distance between the annular coils is 14-15 mm, the vertical distance between the annular permanent magnets is 14-15 mm), and the transverse distance between the annular coils and the corresponding annular permanent magnets is 4-5 mm. The annular permanent magnets in the three pairs of paired structures are axially magnetized, and only axial force acts on the annular permanent magnets, namely, only axial negative stiffness is generated, which is known from two-dimensional axial symmetry of the annular permanent magnets and the annular coils.
The positive-rate rubber spring adjusting device employs two linear coil springs 2 and a rubber support structure 24. As shown in fig. 4 to 6, the linear coil spring 2 is sleeved on the central shaft 14 and is located outside the two linear bearings 9 and 12; the rubber supporting structure 24 is arranged on the outer side of the vibration isolator internal box body 11 and is connected with the upper supporting platform 1 and the vibration isolator internal box body 11 through a plurality of bolts and locking nuts 7; one end of the linear spring 2 is pressed on the notches of the linear bearings 9 and 12, and the other end is respectively pressed on the rough adjusting nut 13 and the fine adjusting nut 8 of the central shaft. The design of the two spiral springs in the middle of compression can ensure that the load cannot be separated from the springs when the vibration isolation system generates large displacement due to resonance.
In the invention, the linear bearing adopts a sliding bearing with an aluminum shell and a tetrafluoroethylene resin lining to avoid the influence of a common steel ball linear bearing on a magnetic field; the annular permanent magnets 16, 17 and 18 are all made of rare earth permanent magnet materials; the rubber supporting structure 24 is made of rubber materials and weak magnetic materials; the components and structures of the central shaft, the fixed ring, the bolt, the nut and the like are all made of non-magnetic or weak-magnetic materials, such as 304 stainless steel; the box body is made of aluminum alloy.
The equilibrium position refers to a position in which the system is at rest. The balance position in the invention is the position of the middle annular permanent magnet at the vertical center of the middle annular coil. According to the electromagnetic negative stiffness generation mechanism of the magnetic element configuration, the attractive electromagnetic negative stiffness mechanism generates softening negative stiffness, because the attractive force between the magnets is inversely proportional to the square of the distance, and the farther away from the equilibrium position, the closer to one end of the magnet, the larger the generated force difference. The repulsive electromagnetic negative stiffness mechanism produces a stiff negative stiffness because the more out of balance the repulsive force between the magnetic elements is smaller. Therefore, the repelling type electromagnetic negative stiffness mechanism and the attracting type electromagnetic negative stiffness mechanism are coupled, the nonlinear parts of the softening stiffness characteristic and the hardening stiffness characteristic are mutually offset, the linear parts are mutually superposed, and the negative stiffness value is improved while the negative stiffness linearity is improved. The use of permanent magnets or toroidal coils can produce negative stiffness of either softening or hardening characteristics, with the negative stiffness produced between the permanent magnets being greater but not adjustable; the size of the magnetic field can be controlled by controlling the exciting current of the annular coil, but the current carrying capacity is limited, and the negative rigidity generated by the electromagnetic force between the annular coils is too weak; therefore, the electromagnetic negative stiffness module is designed by selecting the combination configuration of the annular coil and the annular permanent magnet, so that the adjustable negative stiffness is realized, and a larger adjustable range is obtained.
In the invention, the repelling electromagnetic negative stiffness mechanism comprises three annular permanent magnets 16, 17 and 18 and three annular coils 3, 4 and 5. When current is introduced into the annular coil, the current-carrying ring excites a constant magnetic field due to the magnetic effect of the current and generates interaction force with the annular permanent magnet. The distribution of magnetic fields generated by magnetic elements such as permanent magnets and coils in vacuum is relatively regular, and the electromagnetic field generated by the magnetic elements can be calculated so as to calculate the electromagnetic force.
According to the superposition theorem, the axially magnetized annular permanent magnet can be equivalent to a reversely magnetized cylindrical permanent magnet superposed in a cylindrical permanent magnet. The axially magnetized ring magnet can be equivalent to two thin solenoids positioned on the inner and outer annular surfaces, the current in the two solenoids is equal in magnitude and opposite in direction, and the currents are respectively as follows:
in the formula, mu 0 Is magnetic permeability (H/m) in vacuum, inner I in Is the internal equivalent solenoid current value (A), I out Is the external equivalent solenoid current value (A), h is the equivalent solenoid axial height (m), N eq Is the equivalent number of turns (turns) of the equivalent solenoid, and J is the equivalent polarization (C/m) 2 )。
In the invention, the attraction type electromagnetic negative stiffness mechanism adopts three annular coils 3, 4 and 5, wherein two identical annular coils are introduced with currents with the same direction and the same magnitude. When current is introduced into the toroidal coil, the two current-carrying rings 1 and 2 respectively excite a constant magnetic field due to the magnetic effect of the current, and generate an interaction force.
The biot-savart law describes the magnetic field excited by the current element at any point in space:
wherein I is a source current (A), dl is a minute line element (m) of the source current, r is a distance (m) from a current element to an excitation magnetic field point, and e r Is a unit vector (A.m) of current element pointing to the excitation magnetic field point, B is magnetic induction intensity (T), mu 0 Is the magnetic permeability (H/m) in vacuum.
The acting force of the current element Idl on the current carrying ring from the other current carrying ring is as follows:
dF＝Idl×B (4)，
the interaction force F between the two current-carrying rings can be obtained by integrating the formula:
F＝∫ l dF (5)，
since the two current-carrying rings are concentric, the electromagnetic force is known to be axial based on symmetry. Because the integral is complex, the analytic solution is difficult to solve, and the elliptic integral is also used for expression, so that:
in the formula I 1 Is the current value (A), I of the current-carrying ring 1 2 Is the current value (A), r of the current-carrying ring 2 1 Is the radius (m), r of the current-carrying ring 1 2 Radius (m) of the current-carrying ring 2, z is the vertical distance (m) between two current-carrying rings, and k is
K (K) and E (K) are full elliptic integrals of the first and second classes, respectively, with K as the modulus. The direction of the interaction force between the two current-carrying rings is determined by the direction of the excitation currentAccording to the ampere rule, when the current directions in the two current carrying rings are the same, the electromagnetic forces are mutually attracted, and otherwise, the electromagnetic forces are mutually exclusive. To this end, the electromagnetic force between the two current carrying rings has been determined, and the superposition of the forces between the current carrying rings, i.e. the electromagnetic force between the energized coils or solenoids, can be solved. And the electromagnetic force between the annular coil and the annular permanent magnet can be obtained by combining the equivalent relation between the axial magnetizing permanent magnet and the solenoid.
The working principle of the invention is as follows: the rubber supporting structure 24 and the linear spiral spring 2 are adopted to provide positive stiffness and have high bearing capacity, and the attraction type electromagnetic negative stiffness mechanism and the repulsion type electromagnetic negative stiffness mechanism are coupled to provide linear negative stiffness, so that the nonlinear parts of the softening stiffness characteristic and the hardening stiffness characteristic are mutually offset, and the linearity of the negative stiffness in the quasi-zero stiffness vibration isolator is improved. When the system is in a static equilibrium position, the acting forces between the three ring-shaped permanent magnets 16, 17, 18 and the three ring-shaped coils 3, 4, 5 are mutually counteracted, and the system is in a stable state. The vibration isolation system has the advantages that the dynamic stiffness is very low near the static balance position, the electromagnetic negative stiffness can be combined with the positive stiffness of the rubber and the spring, the vibration isolation performance of the control system can be better adjusted, and the attraction type electromagnetic negative stiffness mechanism is coupled with the repulsion type electromagnetic negative stiffness mechanism, so that the stability of the vibration isolation system is improved. When the system is subjected to external excitation force, the central shaft vertically moves, so that the annular permanent magnet deviates from a balance position, repulsive electromagnetic force is generated between the annular permanent magnet and the annular coils, and attractive electromagnetic force is also generated between the other three annular coils, so that negative rigidity is provided, and a nonlinear part can be effectively offset. The negative stiffness in the movement process is offset with the positive stiffness provided by the rubber and the spring, so that the dynamic frequency of the system is reduced, and the vibration caused by the exciting force can be effectively isolated. When the load mass changes, the current in the electromagnet can be adjusted in real time according to the change of the load mass by utilizing the coarse adjusting nut, the fine adjusting nut and the electromagnetic negative rigidity structure, and the negative rigidity is adjusted in real time in advance; in addition, the current in the electromagnet can be controlled in real time according to the load mass change through the electromagnetic negative stiffness adjusting module, and the negative stiffness is adjusted in real time, so that the vibration isolation frequency of the vibration isolation device at a balance position is guaranteed to be in a quasi-zero state.
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 in the protection scope of the present invention.
Claims (10)
1. A low-frequency vibration isolation device with adjustable rigidity and parallelly connected rubber and electromagnetism is characterized by comprising an upper supporting platform, a rubber supporting structure, a base, a central shaft and a vibration isolator,
the upper supporting platform is positioned at the top of the rubber supporting structure, the interior of the rubber supporting structure is communicated up and down, the bottom of the rubber supporting structure is connected with the base, and a cavity is formed by the bottom surface of the upper supporting platform, the inner wall surface of the rubber supporting structure and the upper surface of the base in a surrounding manner; center pin and isolator are installed in the cavity, and the upper end of center pin is passed through lock nut 7 and is linked to each other with the bottom of going up supporting platform, and the lower extreme of center pin links to each other with the bottom of isolator.
2. The adjustable stiffness low frequency vibration isolator as claimed in claim 1, wherein an upper portion of an outer wall surface of the rubber support structure is outwardly protruded to form a skirt structure.
3. The adjustable stiffness low frequency vibration isolator according to claim 2, wherein the vibration isolator is a linear magnetic type negative stiffness low frequency vibration isolator, which comprises a vibration isolation box body, two spring positive stiffness modules and two electromagnetic negative stiffness modules, wherein the two spring positive stiffness modules and the two electromagnetic negative stiffness modules are arranged in the vibration isolation box body;
the top of the vibration isolation box body is connected with the middle connecting platform, and the base of the vibration isolation box body is fixed on the base; the two spring positive stiffness modules are symmetrically arranged at the upper part and the lower part of the electromagnetic negative stiffness module;
the upper end of the central shaft is connected with the upper supporting platform through a locking nut, and the lower end of the central shaft sequentially penetrates through the spring positive stiffness module, the electromagnetic negative stiffness module and the spring positive stiffness module which are located on the upper portion in the vibration isolation box body and are located on the lower portion in the vibration isolation box body, and is connected with the base of the vibration isolation box body.
4. The adjustable stiffness low frequency vibration isolator according to claim 3, wherein the electromagnetic negative stiffness module comprises an upper annular permanent magnet, a middle annular permanent magnet and a lower annular permanent magnet which are sequentially arranged along the axial direction of the central shaft, and the upper and lower annular permanent magnets are symmetrically arranged on the upper part and the lower part of the middle annular permanent magnet; coaxial annular coils are correspondingly arranged outside each permanent magnet, and the annular coils are fixed with the corresponding annular coil boxes; the three annular permanent magnets can move along the axial direction in the cavity inside the corresponding annular coil along with the central shaft;
the axial displacement of the central shaft can be adjusted through the two spring positive stiffness modules, so that the relative positions of the annular permanent magnet and the corresponding coil are changed, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
5. The adjustable stiffness low frequency vibration isolation device according to claim 4, wherein the spring positive stiffness module comprises a coil spring, a limiting member and an adjusting member; the spiral spring is sleeved on the central shaft, one end of the spiral spring is connected with the adjusting piece, and the adjusting piece is matched with the central shaft; the other end of the spiral spring is connected with the upper end face of the limiting piece; the central shaft penetrates through the center of the limiting piece; the electromagnetic negative stiffness module is arranged between the limiting parts of the two spiral spring positive stiffness modules; when the adjusting pieces of the two spring positive stiffness modules are adjusted, the compression amounts of the two spiral springs can be changed, and further the axial position of the central shaft is changed, so that the relative positions of the annular permanent magnet and the corresponding annular coil are adjusted, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
6. The adjustable stiffness low frequency vibration isolation device according to claim 5, wherein the limiting member is a linear bearing, and the linear bearings of the two spring positive stiffness modules are symmetrically arranged on the central shaft along the balance position of the vibration isolation device; one end of the spiral spring is connected with the end face of the linear bearing, and the linear bearing is connected with the annular coil box body.
7. The adjustable rigidity low-frequency vibration isolation device according to claim 4, wherein three circular lines are vertically coaxially and symmetrically arranged to form an attraction type electromagnetic negative rigidity mechanism; the upper and lower two annular coils are respectively and symmetrically arranged at two ends of the middle annular coil, and are introduced with currents with the same direction and magnitude.
8. The adjustable stiffness low frequency vibration isolation device according to claim 7 wherein said toroidal coils are water cooled coils.
9. The adjustable rigidity low-frequency vibration isolation device according to claim 4, wherein three annular permanent magnets and three annular coils are vertically, coaxially and symmetrically arranged to form a repulsive electromagnetic negative rigidity mechanism; the annular permanent magnets are fixedly connected with the central shaft through fixing rings, and the three annular coils are coaxial with the corresponding annular permanent magnets in equal height.
10. The adjustable stiffness low frequency vibration isolation mounting according to claim 7, wherein the vertical spacing of the toroidal coil is 14 to 15mm, the vertical spacing of the toroidal permanent magnet is 14 to 15mm, and the lateral spacing of the toroidal coil and the corresponding permanent magnet is 4 to 5mm.
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