A longitudinal and torsional coupling low-frequency vibration isolator based on electromagnetic negative stiffness

Abstract

This invention discloses a longitudinally and torsionally coupled low-frequency vibration isolator based on electromagnetic negative stiffness. It consists of a magnetic spring and a helical torsion spring connected in parallel on a central shaft. The magnetic spring is a negative stiffness spring with longitudinal and torsional negative stiffness, composed of an outer magnetic ring and an inner magnetic ring coaxially arranged and rotatable relative to each other on the central shaft. The inner magnetic ring is fixedly connected to the central shaft, and the outer magnetic ring is located on the outer circumference of the inner magnetic ring. The helical torsion spring is a positive stiffness spring with longitudinal and torsional positive stiffness, composed of a first helical torsion spring and a second helical torsion spring located at both ends of the central shaft. Both the first and second helical torsion springs are fixedly sleeved on the central shaft with central holes and connected to the outer magnetic ring via peripheral through holes. This invention enables the vibration isolator to achieve high static stiffness and low dynamic stiffness characteristics in both the longitudinal and torsional directions, effectively reducing the longitudinal and torsional stiffness at the static equilibrium position, and achieving longitudinally and torsionally coupled low-frequency vibration isolation.

Description

Technical Field

[0001] This invention relates to vibration isolators, and more specifically to a vibration isolator for suppressing low-frequency torsional vibration, low-frequency longitudinal vibration and their coupled vibration response in shaft systems. Background Technology

[0002] Mechanical vibration is ubiquitous in production activities. Although vibration is frequently used in industry for screening, conveying, and pile driving, providing numerous conveniences for actual production, it can harm mechanical systems, affect production practices, and even endanger the lives of workers under most operating conditions. Shaft systems are prevalent in automobiles, ships, aerospace, and other fields. During the transmission of force and torque, shaft systems experience longitudinal and torsional vibrations, which are often coupled. Suppressing either longitudinal or torsional vibration alone is not ideal. Low-frequency vibration responses below 10Hz are often present in the shaft systems of various precision equipment. If these low-frequency vibration responses cannot be effectively suppressed, they can cause mechanical fractures, fatigue damage, reduced machining accuracy, and excessive operating noise in precision components. Therefore, effective control of these vibration responses is necessary.

[0003] In practical engineering, the sources of vibration response in shaft systems are very complex and difficult to suppress at the source. Vibration isolation technology is the preferred control method. Recent studies have shown that, compared with traditional vibration isolation devices, nonlinear vibration isolation devices can solve low-frequency and even ultra-low-frequency vibration control problems. Common nonlinear vibration isolation devices for shaft systems include torsion spring isolators, high-pressure airbag isolators, and inclined coil spring isolators. However, these nonlinear shaft isolators have limited load-bearing capacity and unstable performance. Therefore, passive quasi-zero stiffness isolators, designed by parallel connection of negative stiffness structures and positive stiffness elements, have attracted widespread attention. These isolators have high static stiffness, which can reduce static displacement, and can provide small dynamic stiffness near the vibration equilibrium position to reduce the system's resonant frequency, thereby improving the system's vibration isolation performance. Passive quasi-zero stiffness isolators have a good isolation effect on small displacement vibration responses. However, due to the strong nonlinearity of magnetic spring stiffness, they cannot effectively isolate low-frequency large displacement vibration responses.

[0004] Patent document CN212220526U discloses a "semi-active control vibration isolation system for longitudinal vibration of a propulsion shaft system", patent document CN114877019A discloses a "hysteresis capacitive metamaterial vibration isolator for torsional vibration suppression of a rotor system", and patent document CN114412963A discloses a "radial vibration isolation device for a high-temperature superconducting magnetic levitation flywheel". All of these are vibration isolators used to suppress the longitudinal vibration response, torsional vibration response and radial vibration response of a shaft or rotor system. However, these vibration isolators can only suppress single-degree-of-freedom vibration response, and there is no effective vibration isolation device to deal with the low-frequency vibration response coupled with longitudinal and torsional vibration. Summary of the Invention

[0005] To avoid the problems existing in the prior art, the present invention provides a longitudinal and torsional coupled low-frequency vibration isolator based on electromagnetic negative stiffness, which aims to effectively isolate the low-frequency longitudinal vibration, low-frequency torsional vibration and their coupled vibration response of the shaft system along the longitudinal and torsional directions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The features of this invention, a low-frequency vibration isolator based on electromagnetic negative stiffness with longitudinal and torsional coupling, are as follows:

[0008] The vibration isolator is used to transmit power between the outer end cover and the central shaft, and to isolate the interfering torque and the interfering longitudinal force; a magnetic spring and a helical arm torsion spring are connected in parallel on the central shaft;

[0009] The magnetic spring is a negative stiffness spring with longitudinal negative stiffness and torsional negative stiffness, consisting of an outer magnetic ring and an inner magnetic ring coaxially arranged on a central shaft and rotatable relative to each other; the inner magnetic ring is fixedly connected to the central shaft, and the outer magnetic ring is located on the outer periphery of the inner magnetic ring;

[0010] The spiral arm torsion spring is a positive stiffness spring with longitudinal positive stiffness and torsional positive stiffness, which is composed of a first spiral arm torsion spring and a second spiral arm torsion spring set at both ends of the central shaft; the first spiral arm torsion spring and the second spiral arm torsion spring are both fixedly sleeved on the central shaft with a central hole and fixedly connected to the outer magnetic ring by the outer peripheral through hole.

[0011] By using parallel negative stiffness springs and positive stiffness springs, the vibration isolator can obtain high static stiffness and low dynamic stiffness characteristics in the longitudinal and torsional directions, thereby reducing the longitudinal stiffness and torsional stiffness at the static equilibrium position and realizing low-frequency vibration isolation with longitudinal and torsional coupling.

[0012] The present invention, based on the longitudinal and torsional coupling low-frequency vibration isolator with electromagnetic negative stiffness, is also characterized by:

[0013] The outer magnetic ring in the magnetic spring is composed of several circumferentially magnetized neodymium iron boron outer ring magnetic tiles. Each outer ring magnetic tile is locked to the outer magnetic ring teeth on the inner wall of the outer magnetic ring slot. The two ends of the outer magnetic ring are respectively secured by the left end cap and the right end cap of the outer magnetic ring.

[0014] The inner magnetic ring in the magnetic spring is composed of several circumferentially magnetized neodymium iron boron inner ring magnetic tiles. Each inner ring magnetic tile is locked to the inner magnetic ring teeth on the inner wall of the inner magnetic ring slot. The two ends of the inner magnetic ring are respectively secured by the left baffle and the right baffle of the inner magnetic ring.

[0015] The number of outer and inner ring magnetic tiles is equal. In the magnetic spring at the equilibrium position, the outer and inner ring magnetic tiles at the corresponding radial positions are magnetized in the same direction and their sector angle and longitudinal height are aligned.

[0016] The present invention, based on the longitudinal and torsional coupling low-frequency vibration isolator with electromagnetic negative stiffness, is also characterized by:

[0017] The magnetization direction of adjacent outer ring magnetic tiles is set to be the same;

[0018] Alternatively, the magnetization directions of adjacent outer ring magnetic tiles can be set to opposite, and the number of outer ring magnetic tiles can be 2N, where N is an integer;

[0019] The present invention, based on the longitudinal and torsional coupling low-frequency vibration isolator with electromagnetic negative stiffness, is also characterized by:

[0020] The first helical arm torsion spring is fitted onto the left end of the central shaft with its first central hole, and is fixed to the first shoulder of the central shaft by the first nut using the first threaded section on the central shaft.

[0021] The second helical arm torsion spring is fitted onto the right end of the central shaft with its second central hole, and is fixed to the second shoulder of the central shaft by the second nut through the third threaded section of the central shaft;

[0022] The outer magnetic ring slot is fixedly connected at the left end to the left end cap of the outer magnetic ring, the first helical arm torsion spring, and the outer end cap by a first screw passing through the first countersunk hole of the outer end cap, the first outer peripheral through hole of the first helical arm torsion spring, and the second outer peripheral through hole of the left end cap of the outer magnetic ring and the first threaded hole of the outer magnetic ring slot in sequence. The outer magnetic ring slot is fixedly connected at the right end to the right end cap of the outer magnetic ring, the second helical arm torsion spring, and the torsion spring fixing ring fitted on the right end of the central shaft by a second screw passing through the second countersunk hole of the torsion spring fixing ring, the third outer peripheral through hole of the second helical arm torsion spring, and the fourth outer peripheral through hole of the right end cap of the outer magnetic ring and the second threaded hole of the outer magnetic ring slot in sequence.

[0023] The left baffle of the inner magnetic ring is fixed to the first shoulder of the central shaft, and is fixed to the third threaded hole of the inner magnetic ring slot by a third screw passing through the third countersunk hole of the left baffle of the inner magnetic ring.

[0024] The right baffle of the inner magnetic ring is fastened by a third nut, which is threadedly engaged with the second threaded section at the right end of the central shaft.

[0025] The present invention also features a longitudinal and torsional coupling low-frequency vibration isolator based on electromagnetic negative stiffness, wherein the first and second spiral arm torsion springs are elastic thin sheets of the same material and size parameters, having multiple spiral arms with the same direction of rotation, an Archimedean spiral shape, a rectangular cross section, and the ability to be torsional and longitudinally deformable. The first and second spiral arm torsion springs are installed at both ends of the central shaft with opposite directions of rotation, so that the vibration isolator can obtain linear torsional positive stiffness when torsion in two different directions.

[0026] The present invention, based on the longitudinal and torsional coupling low-frequency vibration isolator with electromagnetic negative stiffness, is also characterized by:

[0027] By selecting the size parameters of the outer magnetic ring, inner magnetic ring, first spiral arm torsion spring and second spiral arm torsion spring, the vibration isolator satisfies Equation (1) and Equation (2), thereby making the vibration isolator have quasi-zero stiffness characteristics in both the longitudinal and torsional directions.

[0028] K r_m = K r_s1 +K r_s2 (1)

[0029] K z_m =2K z_s (2)

[0030] In the formula:

[0031] With K r_m This indicates the torsional negative stiffness of the magnetic spring;

[0032] With K r_s1 This indicates the torsional stiffness of the helical arm torsion spring when it twists clockwise.

[0033] With K r_s2 This indicates the torsional stiffness of the helical arm torsion spring when it twists counterclockwise;

[0034] With K z_m This indicates the longitudinal negative stiffness of the magnetic spring;

[0035] With K z_s This indicates the longitudinal stiffness of the helical arm torsion spring.

[0036] The present invention, based on the longitudinal and torsional coupling low-frequency vibration isolator of electromagnetic negative stiffness, is characterized by the following: An electromagnetic coil is installed, in which a coil frame is fixedly installed in each spaced outer magnetic ring tooth. A coil is wound around the outer circumference of the coil frame, and the outer ring magnetic tiles in the corresponding outer magnetic ring teeth are embedded in the coil frame. The electromagnetic coil, outer magnetic ring, and inner magnetic ring together constitute an electromagnetic negative stiffness spring. The magnitude and direction of the current in the coil are adjusted in real time according to the torsional and longitudinal displacements of the vibration isolator, so that the magnetic field generated by the coil along the circumferential direction is superimposed with the magnetic field generated by the outer magnetic ring, thereby adjusting the longitudinal and torsional negative stiffness values ​​of the negative stiffness spring to achieve active vibration isolation.

[0037] The present invention is characterized by a longitudinal and torsional coupling low-frequency vibration isolator based on electromagnetic negative stiffness, wherein, except for the outer magnetic ring, inner magnetic ring and coil, the rest of the structure uses non-magnetic or weakly magnetic materials.

[0038] Compared with existing technologies, the positive effects of this invention are reflected in:

[0039] 1. The present invention connects an electromagnetic negative stiffness spring and a helical arm torsion spring in parallel to form a quasi-zero stiffness mechanism. Under longitudinal-torsional coupled low-frequency vibration excitation, the quasi-zero stiffness mechanism can simultaneously isolate low-frequency longitudinal vibration, low-frequency torsional vibration and their coupled vibration response.

[0040] 2. When the coil is not energized, the inner and outer magnetic rings provide permanent magnet longitudinal negative stiffness and permanent magnet torsional negative stiffness. When the coil is energized, the electromagnetic longitudinal negative stiffness and electromagnetic torsional negative stiffness can be adjusted by changing the magnitude and direction of the current in the coil, thereby obtaining ideal vibration isolation performance and realizing integrated active and passive vibration isolation.

[0041] 3. The vibration isolator of the present invention can significantly suppress the torsional vibration, longitudinal vibration and their coupled vibration response of the shaft system, and has a wide vibration isolation frequency band.

[0042] 4. The vibration isolator of this invention has a compact structure and can be applied to precision micro-instruments. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the longitudinal and torsional coupling low-frequency vibration isolator structure based on electromagnetic negative stiffness according to the present invention.

[0044] Figure 2a , Figure 2b and Figure 2c for Figure 1 View along AA; where, Figure 2a This is a schematic diagram showing that the magnetization direction of both the outer and inner ring magnetic tiles is counterclockwise along the circumference. Figure 2b This is a schematic diagram showing that the magnetization direction of both the outer and inner ring magnetic tiles is clockwise along the circumference. Figure 2cThis is a schematic diagram showing that the magnetization direction of the outer and inner magnetic rings alternates between clockwise and counterclockwise along the ring direction.

[0045] Figure 3a and Figure 3b This is a schematic diagram of the coil being energized in this invention; wherein, Figure 3a The direction of the magnetic field generated when the coil is energized is counterclockwise along the circumference. Figure 3b The direction of the magnetic field generated by the coil after it is energized is clockwise along the circumference. The dashed arrow represents the direction of the magnetic field generated by the coil, and the solid arrow represents the direction of the magnetic field generated by the magnet.

[0046] Figure 4 This is a schematic diagram of the outer end cover of the vibration isolator of the present invention;

[0047] Figure 5a This is a schematic diagram of the first helical arm torsion spring in the vibration isolator of the present invention;

[0048] Figure 5b This is a schematic diagram of the second helical arm torsion spring of the present invention;

[0049] Figure 6a This is a schematic diagram of the left end cover of the outer magnetic ring in the vibration isolator of the present invention;

[0050] Figure 6b This is a schematic diagram of the right end cover of the outer magnetic ring in the vibration isolator of the present invention;

[0051] Figure 7 This is a schematic diagram of the outer magnetic ring slot in the vibration isolator of the present invention;

[0052] Figure 8 This is a schematic diagram of the torsion spring retaining ring in the vibration isolator of the present invention;

[0053] Figure 9 This is a schematic diagram of the central shaft in the vibration isolator of the present invention;

[0054] Figure 10 This is a schematic diagram of the inner magnetic ring slot in the vibration isolator of the present invention;

[0055] Figure 11 This is a schematic diagram of the left baffle of the magnetic ring inside the vibration isolator of the present invention;

[0056] Figure 12 This is a diagram showing the torque-rotational displacement relationship of the helical arm torsion spring in the vibration isolator of this invention;

[0057] Figure 13 This is a diagram showing the relationship between the total rotational stiffness and rotational displacement of the vibration isolator.

[0058] Figure 14 This is a diagram showing the relationship between the total longitudinal stiffness and longitudinal displacement of the vibration isolator.

[0059] Figure 15aThis is a diagram for evaluating the torsional vibration isolation performance of the vibration isolator.

[0060] Figure 15b This is a diagram for evaluating the longitudinal vibration isolation performance of the vibration isolator.

[0061] The diagram labels are as follows: 1. Outer end cap; 1.1 Fifth threaded section; 1.2 First countersunk hole; 2. First screw; 3. First helical arm torsion spring; 3.1 First outer peripheral through hole; 3.2 First center hole; 4. Left end cap of outer magnetic ring; 4.1 Second outer peripheral through hole; 5. Outer magnetic ring slot; 5.1 Outer magnetic ring retaining tooth; 5.2 First threaded hole; 5.3 Second threaded hole; 6. Outer magnetic ring; 7. Inner magnetic ring; 8. Right end cap of outer magnetic ring; 8.1 Fourth outer peripheral through hole; 9. Second screw; 10. Second helical arm torsion spring; 10.1 Third outer peripheral through hole; 10.2 Second center hole. 11 Torsion spring fixing collar, 11.1 Second countersunk hole, 12 Central shaft, 12.1 First threaded section, 12.2 First shoulder, 12.3 Second threaded section, 12.4 Second shoulder, 12.5 Third threaded section, 12.6 Fourth threaded section, 13 Third nut, 14 Second nut, 15 Right baffle of inner magnetic ring, 16 Inner magnetic ring slot, 16.1 Third threaded hole, 16.2 Inner magnetic ring retaining tooth, 17 Third screw, 18 Right baffle of inner magnetic ring, 18.1 Third countersunk hole, 19 First nut, 20 Coil, 21 Coil frame. Detailed Implementation

[0062] like Figure 1 As shown, in this embodiment, a longitudinally and torsionally coupled low-frequency vibration isolator based on electromagnetic negative stiffness is used to transmit power between the outer end cover 1 and the central shaft 12, and to isolate interference torque and interference longitudinal force. A magnetic spring and a helical arm torsion spring are connected in parallel on the central shaft 12. The magnetic spring is a negative stiffness spring with longitudinal negative stiffness and torsional negative stiffness, consisting of an outer magnetic ring 6 and an inner magnetic ring 7 coaxially arranged on the central shaft 12 and rotatable relative to each other. The inner magnetic ring 7 is fixedly connected to the central shaft 12, and the outer magnetic ring 6 is located on the outer periphery of the inner magnetic ring 7. The helical arm torsion spring is a positive stiffness spring with longitudinal positive stiffness and torsional positive stiffness, consisting of a first helical arm torsion spring 3 and a second helical arm torsion spring 10 arranged at both ends of the central shaft 12. The first helical arm torsion spring 3 and the second helical arm torsion spring 10 are both fixedly sleeved on the central shaft 12 with a central hole, and fixedly connected to the outer magnetic ring 6 with a peripheral through hole. By using parallel negative stiffness springs and positive stiffness springs, the vibration isolator can obtain high static stiffness and low dynamic stiffness characteristics in the longitudinal and torsional directions, thereby reducing the longitudinal stiffness and torsional stiffness at the static equilibrium position and realizing low-frequency vibration isolation with longitudinal and torsional coupling.

[0063] In practice, the corresponding technical measures also include:

[0064] like Figure 2a , Figure 2b and Figure 2cAs shown, the outer magnetic ring 6 in the magnetic spring is composed of several circumferentially magnetized neodymium iron boron outer ring magnetic tiles. Each outer ring magnetic tile is secured to the outer magnetic ring teeth 5.1 on the inner wall of the outer magnetic ring slot 5. The two ends of the outer magnetic ring 6 are respectively secured by the outer magnetic ring left end cap 4 and the outer magnetic ring right end cap 8. The inner magnetic ring 7 in the magnetic spring is composed of several circumferentially magnetized neodymium iron boron inner ring magnetic tiles. Each inner ring magnetic tile is secured to the inner magnetic ring teeth 16.2 on the inner wall of the inner magnetic ring slot 16. The two ends of the inner magnetic ring 7 are respectively secured by the inner magnetic ring left baffle 18 and the inner magnetic ring right baffle 15. The number of outer and inner ring magnetic tiles is equal. In the magnetic spring at the equilibrium position, the outer and inner ring magnetic tiles at corresponding radial positions have the same magnetization direction and the sector angle and longitudinal height are aligned.

[0065] The magnetization direction of adjacent outer ring magnetic tiles is set to be the same;

[0066] Alternatively, the magnetization directions of adjacent outer ring magnetic tiles can be set to opposite, and the number of outer ring magnetic tiles can be 2N, where N is an integer;

[0067] According to the magnetic charge model, when the magnetization directions of the outer and inner magnetic tiles in the outer magnetic ring 6 and the inner magnetic ring 7 are the same, the magnetic charge on the circumferential section of each outer magnetic tile in the outer magnetic ring 6 is opposite to the magnetic charge on the circumferential section of the adjacent outer magnetic tile. This leads to a decrease in the magnetic charge density between adjacent outer magnetic tiles, a weakening of the magnetic field generated by the outer magnetic tiles, and a significant decrease in the magnetic force and magnetic torque experienced by the inner magnetic ring 7. When the magnetization directions of adjacent outer (inner) magnetic tiles in the outer magnetic ring 6 and the inner magnetic ring 7 are opposite, the magnetic charge on the circumferential section of each outer magnetic tile in the outer magnetic ring 6 is opposite to the magnetic charge on the adjacent outer magnetic tile. The magnetic charge on the circumferential cross section of the ring magnetic tile is the same, which leads to an increase in the magnetic charge density between adjacent outer ring magnetic tiles. This enhances the superposition of the magnetic field generated by the outer ring magnetic tiles, and significantly increases the magnetic force and magnetic torque on the inner magnetic ring 7. The opposite magnetization direction of adjacent outer (inner) magnetic tiles in the outer magnetic ring 6 and inner magnetic ring 7 results in greater magnetic negative stiffness and a larger range of magnetic negative stiffness. The same magnetization direction of the outer and inner ring magnetic tiles in the outer magnetic ring 6 and inner magnetic ring 7 makes it easier to install the magnetic tiles due to the mutual attraction between adjacent inner (outer) ring magnetic tiles.

[0068] like Figure 1 , Figure 4 , Figure 5a , Figure 5b , Figure 6a , Figure 6b , Figure 7 , Figure 8 and Figure 9 As shown, the first helical arm torsion spring 3 is fitted onto the left end of the central shaft 12 with its first central hole 3.2, and is fixed to the first shoulder 12.2 of the central shaft 12 by the first nut 19 using the first threaded section 12.1 on the central shaft 12;

[0069] The second spiral arm torsion spring 10 is fitted onto the right end of the central shaft 12 through its second central hole 10.2, and is fixed to the second shoulder 12.4 of the central shaft 12 by the second nut 13 through the third threaded section 12.5 of the central shaft 12.

[0070] The outer magnetic ring slot 5 is fixedly connected to the left end cap 4 of the outer magnetic ring, the first spiral arm torsion spring 3, and the outer end cap 1 at the left end. It is fixed by the first screw 2 passing through the first countersunk hole 1.2 of the outer end cap 1, the first outer peripheral through hole 3.1 of the first spiral arm torsion spring 3, and the second outer peripheral through hole 4.1 of the left end cap 4 of the outer magnetic ring to the first threaded hole 5.2 of the outer magnetic ring slot 5. The outer magnetic ring slot 5 is fixedly connected to the right end cap 8 of the outer magnetic ring, the second spiral arm torsion spring 10, and the torsion spring fixing ring 11 fitted on the right end of the central shaft 12 at the right end. It is fixed by the second screw 9 passing through the second countersunk hole 11.1 of the torsion spring fixing ring 11, the third outer peripheral through hole 10.1 of the second spiral arm torsion spring 10, and the fourth outer peripheral through hole 8.1 of the right end cap 8 of the outer magnetic ring to the second threaded hole 5.3 of the outer magnetic ring slot 5.

[0071] like Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown, the left baffle 18 of the inner magnetic ring is fixed to the first shoulder 12.2 of the central shaft 12, and is fixed to the third threaded hole 16.1 of the inner magnetic ring slot 16 by the third screw 17 passing through the third countersunk hole 18.1 of the left baffle 18 of the inner magnetic ring;

[0072] The right baffle 15 of the inner magnetic ring is fastened by the third nut 14, which is threaded into the second threaded section 12.3 at the right end of the central shaft 12.

[0073] like Figure 5a , Figure 5b As shown, in the helical arm torsion spring, the first helical arm torsion spring 3 and the second helical arm torsion spring 10 are elastic sheets of the same material and size parameters, with multiple helical arms that have the same direction of rotation, are in the shape of an Archimedean spiral, have a rectangular cross section, and can be twisted and deformed longitudinally.

[0074] like Figure 12 As shown, when the torsion spring is twisted and deformed clockwise, the spiral arm is compressed and the torsional stiffness gradually increases; when the torsion spring is twisted and deformed counterclockwise, the spiral arm is stretched and the torsional stiffness gradually decreases; therefore, the first spiral arm torsion spring 3 and the second spiral arm torsion spring 10 are installed at both ends of the central shaft 12 with opposite directions of rotation so that the vibration isolator can obtain linear torsional stiffness when twisted in two different directions.

[0075] By selecting the size parameters of the outer magnetic ring 6, the inner magnetic ring 7, the first helical arm torsion spring 3, and the second helical arm torsion spring 10, the vibration isolator satisfies Equations 1 and 2, thereby giving the vibration isolator quasi-zero stiffness characteristics in both the longitudinal and torsional directions.

[0076] K r_m = K r_s1 +K r_s2 (1)

[0077] K z_m =2K z_s (2)

[0078] In the formula:

[0079] With K r_m This indicates the torsional negative stiffness of the magnetic spring;

[0080] With K r_s1 This indicates the torsional stiffness of the helical arm torsion spring when it twists clockwise.

[0081] With K r_s2 This indicates the torsional stiffness of the helical arm torsion spring when it twists counterclockwise;

[0082] With K z_m This indicates the longitudinal negative stiffness of the magnetic spring;

[0083] With K z_s This indicates the longitudinal stiffness of the helical arm torsion spring;

[0084] like Figure 2a , Figure 2b , Figure 2c , Figure 3a and Figure 3b As shown, to achieve active vibration isolation, an electromagnetic coil is set up: a coil frame 21 is fixedly set in each of the spaced outer magnetic ring teeth 5.1, and a coil 20 is wound around the outer circumference of the coil frame 21. The outer ring magnetic tiles in the corresponding positions of the outer magnetic ring teeth 5.1 are embedded in the coil frame 21. The electromagnetic coil, outer magnetic ring 6 and inner magnetic ring 7 together constitute an electromagnetic negative stiffness spring. The magnitude and direction of the current in the coil 20 are adjusted in real time according to the torsional displacement and longitudinal displacement of the vibration isolator, so that the magnetic field generated by the coil 20 along the circumferential direction is superimposed with the magnetic field generated by the outer magnetic ring 6, thereby adjusting the longitudinal negative stiffness value and torsional negative stiffness value of the negative stiffness spring, thereby achieving active vibration isolation.

[0085] like Figure 4 and Figure 9 As shown, the fifth threaded section 1.1 of the outer end cover 1 and the fourth threaded section 12.6 of the central shaft 12 are used to connect the driving shaft and the driven shaft.

[0086] Except for the outer magnetic ring 6, inner magnetic ring 7 and coil 20, the rest of the structure uses non-magnetic or weakly magnetic materials.

[0087] The working principle of this invention is as follows: During the longitudinal and torsional movements of the central shaft 12 relative to the outer end cover 1, the outer magnetic ring 6, inner magnetic ring 7, and coil 20, together with the first helical arm torsion spring 3 and the second helical arm torsion spring 10, form a high static stiffness and low dynamic stiffness structure. When the coil 20 is not energized, within the small rotational and longitudinal displacement range near the equilibrium position, the magnetic torque and longitudinal magnetic force of the magnetic spring are very small, and the overall dynamic stiffness is as follows: Figure 13 and Figure 14 As shown, the value is essentially zero. At this point, the transmitted torque and longitudinal force are provided solely by the first helical arm torsion spring 3 and the second helical arm torsion spring 10. When the coil 20 is energized, the magnitude and direction of the magnetic field generated by the coil 20 can be controlled by adjusting the current magnitude and direction of the coil 20. This allows for a longer stroke and a larger amplitude negative stiffness characteristic. Within the range of large rotational and longitudinal displacements near the equilibrium position, the aforementioned high static stiffness and low dynamic stiffness characteristics are present. Figure 15a and Figure 15b As shown, the longitudinal and torsional vibration isolation transmissibility of the vibration isolator has the following advantages over its corresponding linear vibration isolator (i.e., removing the outer magnetic ring 6, inner magnetic ring 7, and coil 20): 1. The isolation frequencies for torsional and longitudinal motions are reduced by more than 50%; 2. The torsional and longitudinal vibration isolation efficiencies in the low-frequency region are far superior to those of the linear vibration isolator. Therefore, the present invention has the ability to isolate low-frequency longitudinal vibrations and low-frequency torsional vibrations.

Claims

1. A low-frequency vibration isolator based on electromagnetic negative stiffness with longitudinal and torsional coupling, characterized in that: The vibration isolator is used to transmit power between the outer end cover (1) and the central shaft (12) and to isolate interference torque and interference longitudinal force; a magnetic spring and a helical arm torsion spring are connected in parallel on the central shaft (12); the magnetic spring is a negative stiffness spring with longitudinal negative stiffness and torsional negative stiffness, which is composed of an outer magnetic ring (6) and an inner magnetic ring (7) coaxially arranged on the central shaft (12 and rotatable relative to each other; the inner magnetic ring (7) is fixedly connected to the central shaft (12), and the outer magnetic ring (6) is located on the outer periphery of the inner magnetic ring (7); The spiral arm torsion spring is a positive stiffness spring with longitudinal positive stiffness and torsional positive stiffness, consisting of a first spiral arm torsion spring (3) and a second spiral arm torsion spring (10) set at both ends of the central shaft (12). The first spiral arm torsion spring (3) and the second spiral arm torsion spring (10) are both fixedly sleeved on the central shaft (12) with a central hole and fixedly connected to the outer magnetic ring (6) by the outer peripheral through hole. The parallel arrangement of negative stiffness spring and positive stiffness spring enables the vibration isolator to obtain high static stiffness and low dynamic stiffness characteristics in the longitudinal and torsional directions, so as to reduce static balance. The longitudinal stiffness and torsional stiffness of the position realize low-frequency vibration isolation through longitudinal and torsional coupling; the outer magnetic ring (6) in the magnetic spring is composed of several circumferentially magnetized neodymium iron boron outer ring magnetic tiles, each outer ring magnetic tile is fastened to the outer magnetic ring teeth (5.1) on the inner wall of the outer magnetic ring slot (5), and the two ends of the outer magnetic ring (6) are fastened by the left end cap (4) and the right end cap (8) of the outer magnetic ring respectively; the inner magnetic ring (7) in the magnetic spring is composed of several circumferentially magnetized neodymium iron boron inner ring magnetic tiles, each inner ring magnetic tile is fastened to the inner magnetic ring. The inner magnetic ring teeth (16.2) on the inner wall of the groove (16) are locked together. The two ends of the inner magnetic ring (7) are fastened by the left baffle (18) and the right baffle (15) of the inner magnetic ring respectively. The number of outer ring magnetic tiles and inner ring magnetic tiles are equal. In the magnetic spring at the equilibrium position, the outer ring magnetic tiles and inner ring magnetic tiles at the corresponding radial positions have the same magnetization direction and the sector angle and longitudinal height are aligned. The magnetization direction of adjacent outer ring magnetic tiles is set to be the same, or the magnetization direction of adjacent outer ring magnetic tiles is set to be opposite. The number of outer ring magnetic tiles is 2N, where N is an integer.

2. The longitudinally and torsionally coupled low-frequency vibration isolator based on electromagnetic negative stiffness according to claim 1, characterized in that: The first helical arm torsion spring (3) is fitted onto the left end of the central shaft (12) through its first central hole (3.2), and is fixed to the first shoulder (12.2) of the central shaft (12) by the first nut (19) via the first threaded section (12.1) on the central shaft (12); the second helical arm torsion spring (10) is fitted onto the right end of the central shaft (12) through its second central hole (10.2), and is fixed to the right end of the central shaft (12) by the second nut (13) via the third threaded section (12.5) on the central shaft (12). The second shoulder (12.4) of the central shaft (12); the outer magnetic ring slot (5) is fixedly connected at the left end to the left end cover (4) of the outer magnetic ring, the first helical arm torsion spring (3) and the outer end cover (1), by the first screw (2) passing through the first countersunk hole (1.2) of the outer end cover (1), the first outer peripheral through hole (3.1) of the first helical arm torsion spring (3), the second outer peripheral through hole (4.1) of the left end cover (4) of the outer magnetic ring and the first threaded hole (5.2) of the outer magnetic ring slot (5). Fixed; the outer magnetic ring slot (5) is fixedly connected at the right end to the outer magnetic ring right end cap (8), the second spiral arm torsion spring (10), and the torsion spring fixing ring (11) fitted on the right end of the central shaft (12). This is achieved by the second screw (9) passing sequentially through the second countersunk hole (11.1) of the torsion spring fixing ring (11), the third outer peripheral through hole (10.1) of the second spiral arm torsion spring (10), and the fourth outer peripheral through hole (8.1) of the outer magnetic ring right end cap (8) and the second screw of the outer magnetic ring slot (5). The inner magnetic ring left baffle (18) is fixed to the first shoulder (12.2) of the central shaft (12), and is fixed to the third threaded hole (16.1) of the inner magnetic ring slot (16) by the third screw (17) passing through the third countersunk hole (18.1) of the inner magnetic ring left baffle (18); the inner magnetic ring right baffle (15) is fastened by the third nut (14), and the third nut (14) is threadedly engaged with the second threaded section (12.3) at the right end of the central shaft (12).

3. The longitudinally and torsionally coupled low-frequency vibration isolator based on electromagnetic negative stiffness according to claim 1, characterized in that: In the spiral arm torsion spring, the first spiral arm torsion spring (3) and the second spiral arm torsion spring (10) are elastic thin sheets of the same material and size parameters, with multiple spiral arms that have the same direction of rotation, are in the shape of an Archimedean spiral, have a rectangular cross section, and can be twisted and deformed longitudinally. The first spiral arm torsion spring (3) and the second spiral arm torsion spring (10) are installed at both ends of the central shaft (12) with opposite directions of rotation, so that the vibration isolator can obtain linear torsional stiffness when twisted in two different directions.

4. The longitudinally and torsionally coupled low-frequency vibration isolator based on electromagnetic negative stiffness according to claim 1, characterized in that: By selecting the size parameters of the outer magnetic ring (6), inner magnetic ring (7), first helical arm torsion spring (3), and second helical arm torsion spring (10), the vibration isolator satisfies equations (1) and (2), thereby making the vibration isolator have quasi-zero stiffness characteristics in both the longitudinal and torsional directions; K r_m = K r_s1 +K r_s2 (1); K z_m =2K z_s (2); In the formula: K r_m This represents the torsional negative stiffness of a magnetic spring; expressed in K. r_s1 This indicates the torsional stiffness of the helical arm torsion spring when it twists clockwise; expressed in K. r_s2 This indicates the torsional stiffness of the helical arm torsion spring when it twists counterclockwise; expressed in K. z_m This represents the longitudinal negative stiffness of the magnetic spring; expressed in K. z_s This indicates the longitudinal stiffness of the helical arm torsion spring.

5. The longitudinally and torsionally coupled low-frequency vibration isolator based on electromagnetic negative stiffness according to claim 1, characterized in that: The electromagnetic coil is set up by fixing a coil frame (21) in each of the spaced outer magnetic ring teeth (5.1). The coil (20) is wound around the outer circumference of the coil frame (21). The outer ring magnetic tile in the corresponding position of the outer magnetic ring teeth (5.1) is embedded in the coil frame (21). The electromagnetic coil, the outer magnetic ring (6) and the inner magnetic ring (7) together constitute the electromagnetic negative stiffness spring. The magnitude and direction of the current in the coil (20) are adjusted in real time according to the torsional displacement and longitudinal displacement of the vibration isolator, so that the magnetic field generated by the coil (20) along the circumferential direction is superimposed with the magnetic field generated by the outer magnetic ring (6), thereby adjusting the longitudinal negative stiffness value and the torsional negative stiffness value of the negative stiffness spring to achieve active vibration isolation.

6. The longitudinally and torsionally coupled low-frequency vibration isolator based on electromagnetic negative stiffness according to claim 1, characterized in that: Except for the outer magnetic ring (6), inner magnetic ring (7) and coil (20), the rest of the structure uses non-magnetic or weakly magnetic materials.

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