CN112762123A - Two-degree-of-freedom quasi-zero-rigidity low-frequency vibration isolation device - Google Patents

Abstract

The invention relates to the technical field of low-frequency vibration isolation, in particular to a two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device, wherein a support flat plate is used for placing a body to be isolated, the upper end and the lower end of an upper vertical plane spring in an upper quasi-zero stiffness vibration isolator are respectively and vertically fixed on the support flat plate and a middle mass block, one end of an upper nonlinear spring is connected with the side surface of the support flat plate, the other end of the upper nonlinear spring is connected with an upper horizontal moving mechanism to realize horizontal movable adjustment, a vertical moving mechanism drives the support flat plate to realize up-and-down movement adjustment, the upper end and the lower end of a lower vertical plane spring in a lower quasi-zero stiffness vibration isolator are respectively and vertically fixed on a middle mass block and a base, one end of a lower nonlinear spring is connected with the middle mass block, the other end of the lower nonlinear spring is connected with the, in a specific frequency region, the vibration isolation performance is superior to that of a single-degree-of-freedom quasi-zero-stiffness vibration isolation system.

Description

A two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device

technical field

The invention relates to the technical field of low-frequency vibration isolation, in particular to a low-frequency vibration isolation device with two degrees of freedom quasi-zero stiffness.

Background technique

Vibration is a ubiquitous physical phenomenon in nature, especially in daily life and industrial production. In some cases, vibration will bring certain harm to our scientific research and production activities. The traditional linear vibration isolator is faced with the contradiction between the bearing capacity and the vibration isolation effect, while the quasi-zero stiffness vibration isolation system, as an emerging nonlinear low-frequency vibration isolation technology, has changed the traditional concept of vibration isolation of the linear system. The quasi-zero stiffness vibration isolation system is composed of positive and negative stiffness structures in parallel. It not only has sufficient static stiffness to support the vibration-isolated equipment, and has good stability, but also has small dynamic stiffness near the equilibrium position, which reduces the natural frequency of the system and reduces low-frequency vibration isolation. Good performance. Therefore, the quasi-zero stiffness vibration isolation system takes into account the contradiction between stability and vibration isolation performance.

The single-degree-of-freedom quasi-zero stiffness vibration isolation system can achieve good vibration isolation in the low frequency stage, and its vibration isolation performance is comparable to that of the linear vibration isolation system in the medium and high frequency stages. With the rapid development of science and technology, the performance requirements of precision machinery, shipborne equipment and high-speed vehicles are getting higher and higher. Traditional linear vibration isolation systems and single-degree-of-freedom quasi-zero stiffness vibration isolation systems have been difficult to meet all walks of life. growing demand.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of the above-mentioned existing production technology, the applicant provides a low-frequency vibration isolation device with two degrees of freedom quasi-zero stiffness, which can not only reduce the initial vibration isolation frequency of the system, widen the vibration isolation frequency bandwidth, but also provide a low-frequency vibration isolation device with two degrees of freedom. In the frequency region, the vibration isolation performance is better than that of the single-degree-of-freedom quasi-zero stiffness vibration isolation system.

The technical scheme adopted by the present invention is as follows: a two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolator, comprising a base, an upper-layer quasi-zero stiffness vibration isolator, a lower-layer quasi-zero stiffness vibration isolator, a support plate, a middle mass block, two An upper horizontal moving mechanism, two lower horizontal moving mechanisms and a vertical moving mechanism, the support plate is horizontally arranged above the middle mass block, and the support plate is used to place the vibration isolator;

The upper-layer quasi-zero stiffness vibration isolator includes the upper-layer nonlinear spring, the upper-layer nonlinear spring outer guide sleeve and the upper-layer vertical plane spring. The linear spring is limited in the outer guide sleeve of the upper nonlinear spring and can be extended and retracted along the sleeve length direction of the upper nonlinear spring outer guide sleeve. There are two upper nonlinear springs and are symmetrically distributed on both sides of the supporting plate. One end of the upper layer nonlinear spring is connected to the side of the supporting plate, and the other end of the upper layer nonlinear spring is connected to the upper layer horizontal moving mechanism to realize horizontal movable adjustment. The upper horizontal moving mechanism is installed on the base, and the vertical moving mechanism is installed on the base. up, the vertical movement mechanism drives the support plate to achieve up and down movement adjustment;

The lower layer quasi-zero stiffness vibration isolator includes the lower layer nonlinear spring, the lower layer nonlinear spring outer guide bush and the lower layer vertical plane spring. The upper and lower ends of the lower layer vertical plane spring are vertically fixed on the middle mass block and the base, respectively. The linear spring is limited in the outer guide sleeve of the lower nonlinear spring and can be moved along the sleeve length direction of the lower nonlinear spring outer guide sleeve. There are two lower nonlinear springs and are symmetrically distributed on both sides of the middle mass block. , one end of the lower nonlinear spring is connected with the middle mass block, and the other end of the lower nonlinear spring is connected with the lower horizontal moving mechanism to realize horizontal movable adjustment, and the lower horizontal moving mechanism is installed on the base.

As a further improvement of the above technical solution:

The upper-layer quasi-zero stiffness vibration isolator includes an upper-layer vertical damper, and the upper and lower ends of the upper-layer vertical damper are respectively vertically fixed on the support plate and the intermediate mass block.

The upper-layer quasi-zero stiffness vibration isolator includes upper-layer transverse damping, two upper-layer transverse dampers are symmetrically distributed on both sides of the supporting plate, one end of the upper-layer transverse damping is connected to the side of the supporting plate, and the other end of the upper-layer transverse damping is connected to the upper layer. The horizontal movement mechanism is connected.

The lower-layer quasi-zero stiffness vibration isolator includes a lower-layer vertical damper, and the upper and lower ends of the lower-layer vertical damper are respectively vertically fixed on the middle mass block and the base.

The lower-layer quasi-zero stiffness vibration isolator includes a lower-layer transverse damper, two lower-layer transverse dampers are symmetrically distributed on both sides of the supporting plate, one end of the lower-layer transverse damper is connected to the side of the intermediate mass block, and the other end of the lower-layer transverse damper is connected to the side of the intermediate mass block. The lower level horizontal moving mechanism is connected.

The base includes a base and two parallel opposite side plates vertically fixed on the base. The upper ends of the two side plates are respectively suspended with horizontally arranged fixing plates, and the lower vertical plane spring and the lower vertical damping The lower ends are respectively fixed on the base, the vertical moving mechanism is one screw, the vertical moving mechanism is two and are respectively installed on two fixed plates, the vertical moving mechanism is arranged vertically, and the lower ends of the two vertical moving mechanisms are symmetrically abutted. against the two edges of the upper surface of the support plate.

The upper-layer horizontal moving mechanism includes two screws, an upper-layer vertical slide plate and an upper-layer lateral guide rail. The upper-layer lateral guide rail is installed on the lower plate surface of the fixed plate. , The other end of the upper non-linear spring is respectively fixed on one side of the upper vertical slide plate, the second screw is installed on the side plate of the base, and the end of the second screw is against the other side of the upper vertical slide plate. .

The lower horizontal moving mechanism includes screws 3, a lower vertical sliding plate and a lower lateral guide rail. The lower horizontal guide rail is installed on the base of the base. The other end of the lower non-linear spring is respectively fixed on one side plate of the lower vertical sliding plate, the third screw is installed on the side plate of the base, and the end of the third screw abuts on the other side plate of the lower vertical sliding plate.

The upper non-linear spring outer guide sleeve is in the shape of a circular tube, and both ends of the circular tube are provided with end caps, and the two ends of the upper non-linear spring respectively freely pass through the end caps at both ends of the circular tube.

The structure of the lower layer nonlinear spring outer guide sleeve is the same as that of the upper layer nonlinear spring outer guide sleeve.

The beneficial effects of the present invention are as follows: when the vibration isolator is placed on the upper surface of the supporting plate, both the upper vertical plane spring and the lower vertical plane spring will be compressed, and the upper layer can be made nonlinear by screwing the second and third screws. The spring and the underlying nonlinear spring are in a horizontal position. If the mass of the vibration isolator changes, by adjusting the vertical movement mechanism, the entire vibration isolation system can return to the equilibrium state. By selecting the appropriate structural parameters and mechanical parameters of the system, and using the horizontal moving mechanism and the vertical moving mechanism in combination, the stiffness of the system is zero. When the vibration isolator vibrates near the equilibrium position, the natural frequency of the system is low and the bearing capacity is large. Therefore, the vibration isolation system can achieve the goal of low-frequency vibration reduction, not only can reduce the initial vibration isolation frequency of the system, broaden the vibration isolation frequency bandwidth, but also in a specific frequency region, the vibration isolation performance is better than that of a single degree of freedom. Zero stiffness vibration isolation system.

Description of drawings

FIG. 1 is a schematic structural diagram of the present invention when no vibration isolator is added.

Fig. 2 is the structural representation when the present invention is used;

Fig. 3 is the sectional view of the upper vertical plane spring of the present invention;

Figure 4 is a comparison diagram of the force transmissibility curves of the two-degree-of-freedom system and the single-degree-of-freedom system under different vertical damping ratios of the upper-layer quasi-zero stiffness vibration isolator;

Figure 5 is a comparison diagram of the force transmissibility curves of the two-degree-of-freedom system and the single-degree-of-freedom system under the working conditions where the ratio of the stiffness of the lower vertical plane spring to the upper vertical plane spring is different;

Fig. 6 is a comparison diagram of the force transmissibility curves of the two-DOF system and the single-DOF system under different working conditions with the mass ratio of the intermediate mass block to the vibration-isolated body.

Among them: 1. Base; 2. Lower vertical plane spring; 3. Lower vertical damping; 4. Lower lateral guide; 5. Lower nonlinear spring; 6. Lower vertical sliding plate; 7. Screw three; 8. Lower non-linear spring Linear spring outer guide sleeve; 9. Intermediate mass block; 10. Lower lateral damping; 11. Upper vertical plane spring; 12. Upper vertical damping; 13. Screw two; 14. Upper nonlinear spring outer guide sleeve; 15. Upper layer non-linear spring; 16. Upper layer vertical sliding plate; 17, Upper layer lateral damping; 18, Upper layer lateral guide rail; 19, Fixed plate; 20, Support plate; 21, Vertical moving mechanism;

Detailed ways

The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in Figures 1-6, the two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device of this embodiment includes a base 1, an upper-layer quasi-zero stiffness vibration isolator, a lower-layer quasi-zero stiffness vibration isolator, a supporting plate 20, and an intermediate mass Block 9, two upper horizontal moving mechanisms, two lower horizontal moving mechanisms and vertical moving mechanism 21, a support plate 20 is horizontally arranged above the middle mass block 9, and the support plate 20 is used to place the vibration isolator 22;

The upper layer quasi-zero stiffness vibration isolator includes the upper layer nonlinear spring 15, the upper layer nonlinear spring outer guide sleeve 14 and the upper layer vertical plane spring 11. The upper and lower ends of the upper layer vertical plane spring 11 are respectively vertically fixed on the supporting plate 20 and the intermediate mass. On block 9, the upper non-linear spring 15 is limited in the outer guide sleeve 14 of the upper non-linear spring and can be limited and telescopic along the sleeve length direction of the upper non-linear spring outer guide sleeve 14. The upper non-linear spring 15 is two. And symmetrically distributed on both sides of the support plate 20, one end of the upper layer nonlinear spring 15 is connected to the side of the support plate 20, and the other end of the upper layer nonlinear spring 15 is connected to the upper layer horizontal movement mechanism to realize horizontal movable adjustment, and the upper layer horizontal movement mechanism Installed on the base 1, the vertical moving mechanism 21 is installed on the base 1, and the vertical moving mechanism 21 drives the support plate 20 to achieve up and down adjustment;

The lower layer quasi-zero stiffness vibration isolator includes the lower layer nonlinear spring 5, the lower layer nonlinear spring outer guide sleeve 8 and the lower layer vertical plane spring 2. The upper and lower ends of the lower layer vertical plane spring 2 are respectively vertically fixed on the middle mass block 9 and the base. On the seat 1, the lower non-linear spring 5 is limited in the lower non-linear spring outer guide sleeve 8 and can be extended and retracted along the sleeve length direction of the lower non-linear spring outer guide sleeve 8. The lower non-linear spring 5 is two. And symmetrically distributed on both sides of the middle mass block 9, one end of the lower nonlinear spring 5 is connected with the middle mass block 9, and the other end of the lower nonlinear spring 5 is connected with the lower horizontal moving mechanism to realize horizontal movable adjustment, and the lower horizontal moving mechanism Mounted on base 1.

The upper-layer quasi-zero stiffness vibration isolator includes an upper-layer vertical damper 12 , and the upper and lower ends of the upper-layer vertical damper 12 are vertically fixed on the support plate 20 and the intermediate mass block 9 respectively.

The upper-layer quasi-zero stiffness vibration isolator includes an upper-layer transverse damper 17, two upper-layer transverse dampers 17 are symmetrically distributed on both sides of the support plate 20, one end of the upper-layer transverse damper 17 is connected to the side of the support plate 20, and the upper-layer transverse damper 17 is The other end is connected with the upper horizontal moving mechanism.

The lower-layer quasi-zero stiffness vibration isolator includes a lower-layer vertical damper 3 , and the upper and lower ends of the lower-layer vertical damper 3 are vertically fixed on the intermediate mass block 9 and the base 1 respectively.

The lower-layer quasi-zero stiffness vibration isolator includes a lower-layer transverse damper 10, two lower-layer transverse dampers 10 are symmetrically distributed on both sides of the support plate 20, one end of the lower-layer transverse damper 10 is connected to the side of the middle mass block 9, and the lower-layer transverse damper 10 The other end is connected with the lower horizontal moving mechanism.

The base 1 includes a base and two parallel opposite side plates vertically fixed on the base. The upper ends of the two side plates are respectively suspended with horizontally arranged fixing plates 19. The lower vertical plane spring 2 and the lower vertical damping The lower ends of 3 are respectively fixed on the base, the vertical moving mechanism 21 is one screw, the vertical moving mechanism 21 is two and is respectively installed on the two fixing plates 19, the vertical moving mechanism 21 is arranged vertically, and the two vertical moving mechanisms 21 are arranged vertically. The lower end of the moving mechanism 21 abuts against both edges of the upper surface of the supporting plate 20 symmetrically.

The upper horizontal moving mechanism includes two screws 13, an upper vertical sliding plate 16 and an upper horizontal guide rail 18. The upper horizontal guide rail 18 is installed on the lower surface of the fixed plate 19. The other end of the lateral damping 17 and the other end of the upper non-linear spring 15 are respectively fixed on one side surface of the upper vertical sliding plate 16, the second screw 13 is installed on the side plate of the base 1, and the end of the second screw 13 abuts against On the other side board surface of the upper vertical sliding plate 16 .

The lower horizontal moving mechanism includes screws 3 7, a lower vertical sliding plate 6 and a lower lateral guide rail 4. The lower lateral guide rail 4 is installed on the base of the base 1, and the lower end of the lower vertical sliding plate 6 and the lower lateral guide rail 4 form a lateral sliding fit, and the lower lateral guide rail 4 constitutes a lateral sliding fit. The other end of the damper 10 and the other end of the lower non-linear spring 5 are respectively fixed on one side surface of the lower vertical sliding plate 6, the third screw 7 is installed on the side plate of the base 1, and the end of the third screw 7 abuts against the On the other side of the lower vertical slide plate 6 .

The upper non-linear spring outer guide sleeve 14 is in the shape of a circular tube with end caps provided at both ends of the circular tube, and the two ends of the upper non-linear spring 15 respectively freely pass through the end caps at both ends of the circular tube.

The structure of the lower layer nonlinear spring outer guide sleeve 8 is the same as that of the upper layer nonlinear spring outer guide sleeve 14 .

The main working principle of the present application is: as shown in FIG. 1 , when the vibration-isolated body 22 is not placed, both the upper nonlinear spring 15 and the lower nonlinear spring 5 are in an inclined state. When the vibration isolator 22 is placed on the upper surface of the supporting plate 20, the upper vertical plane spring 11 and the lower vertical plane spring 2 will be compressed. By screwing the second screw 13 and the screw third 7, the upper nonlinear spring 15 and the lower nonlinear spring 5 are in a horizontal position. The cross-sectional view of the upper vertical plane spring 11 is shown in Figure 3, where b ₁ is the thickness of the outer plane, and b ₂ is the thickness of the inner plane. As long as the thickness of the outer plane and the thickness of the inner plane are reasonably designed, the required upper vertical plane can be obtained. stiffness of spring 11. If the mass of the vibration isolator 22 changes, by adjusting the vertical movement mechanism 21, the entire vibration isolation system can be brought back to a balanced state. By selecting appropriate structural parameters and mechanical parameters of the system, and using the horizontal moving mechanism and the vertical moving mechanism 21 in combination, the stiffness of the system is zero. When the vibration-isolated body 22 vibrates near the equilibrium position, the natural frequency of the system is relatively low, and the bearing capacity is relatively large. Therefore, the vibration isolation system can achieve the goal of low frequency vibration reduction.

上层准零刚度隔振器的竖直阻尼比为

下层垂向平面弹簧2与上层垂向平面弹簧11的刚度之比为

中间质量块9与被隔振体22的质量之比为

其中，

c_h1为上层隔振器的横向阻尼系数，c₁为上层隔振器的竖直阻尼系数。Let the lateral damping ratio of the upper quasi-zero stiffness isolator be

The vertical damping ratio of the upper quasi-zero stiffness isolator is:

The ratio of the stiffness of the lower vertical plane spring 2 to the upper vertical plane spring 11 is

The mass ratio of the intermediate mass 9 to the vibration isolator 22 is

in,

c _h1 is the lateral damping coefficient of the upper vibration isolator, and c ₁ is the vertical damping coefficient of the upper vibration isolator.

The force transmissibility is an important index to evaluate the vibration isolation performance of the vibration isolation system, which is defined as the ratio of the amplitude of the force transmitted to the foundation by the vibration isolation system under the action of the excitation force to the amplitude of the excitation force. The smaller the force transmissibility of the system, the better the vibration isolation effect of the system. When there is a harmonic excitation force acting on the isolated body 22 in the vibration isolation system, reasonable lateral damping ratio, vertical damping ratio, stiffness ratio and mass ratio are selected, and numerical analysis method is used to compare and study the quasi-zero of two degrees of freedom. Vibration isolation performance of rigid vibration isolation systems and single degree of freedom systems.

Under the different working conditions of the vertical damping ratio of the upper quasi-zero stiffness vibration isolator, the force transfer rate curves of the two-DOF system and the single-DOF system are compared in Figure 4. The vertical damping ratio of the upper-layer quasi-zero stiffness vibration isolator is shown in Figure 4. The change of , has little effect on the first peak value of the force transmissibility, the larger the damping ratio, the peak-to-valley increase of the force transmissibility, and the decrease of the second peak value; when the damping ratio increases to a larger value (ζ ₁ =0.5), Both the valley and the second peak will gradually disappear.

Figure 5 is a comparison diagram of the force transfer rate curves of the two-DOF system and the single-DOF system under the working conditions where the ratio of the stiffness of the lower vertical plane spring 2 to the upper vertical plane spring 11 is different. The first peak of the vibration frequency decreases with the decrease of the stiffness ratio, and shifts to the low frequency region, the initial vibration isolation frequency decreases, and the vibration isolation frequency bandwidth increases; while the peak-valley and the second peak value decrease with the decrease of the stiffness ratio And increase, the peak-to-valley increase is relatively large.

As shown in Fig. 6, under the condition that the mass ratio of the intermediate mass 9 and the vibration isolator 22 is different, observing the force transmissibility curves of the two-degree-of-freedom system and the single-degree-of-freedom system, it is found that the greater the mass ratio, the greater the force The first peak of the transmissibility slightly increased, and appeared to shift to the low frequency region; both the peak-valley and the second peak increased significantly with the increase of the mass ratio.

Comparing and analyzing Fig. 4, Fig. 5 and Fig. 6, it can be seen that compared with the single-degree-of-freedom quasi-zero stiffness vibration isolation system, the force transmissibility curve of the two-degree-of-freedom quasi-zero stiffness vibration isolation system will have two peaks and one peak and valley; Although the local area vibration isolation effect of the second peak is relatively weak, the vibration isolation performance in the frequency domain near the peak and valley is significantly enhanced; by selecting reasonable parameters, the peak force transmissibility and initial vibration isolation frequency of the system can be reduced, and the isolation can be expanded. vibration interval. When the frequency ratio Ω>1.96, the attenuation rate of the force transmissibility of the system increases significantly, the vibration isolation performance in this frequency band is obviously better than that of the single-degree-of-freedom quasi-zero stiffness vibration isolation system, and the low-frequency vibration isolation performance is further improved.

The above description is an explanation of the present invention, not a limitation of the present invention. For the limited scope of the present invention, refer to the claims, and any form of modification can be made within the protection scope of the present invention.

Claims (10)

1. The utility model provides a two degree of freedom quasi-zero rigidity low frequency vibration isolation devices which characterized in that: the vibration isolator comprises a base (1), an upper-layer quasi-zero stiffness vibration isolator, a lower-layer quasi-zero stiffness vibration isolator, a supporting flat plate (20), a middle mass block (9), two upper-layer horizontal moving mechanisms, two lower-layer horizontal moving mechanisms and a vertical moving mechanism (21), wherein the supporting flat plate (20) is horizontally arranged above the middle mass block (9), and the supporting flat plate (20) is used for placing a vibration isolator (22);

the upper-layer quasi-zero stiffness vibration isolator comprises an upper-layer nonlinear spring (15), an upper-layer nonlinear spring outer guide sleeve (14) and an upper-layer vertical plane spring (11), wherein the upper end and the lower end of the upper-layer vertical plane spring (11) are respectively and vertically fixed on a support flat plate (20) and a middle gauge block (9), the upper-layer nonlinear spring (15) is limited in the upper-layer nonlinear spring outer guide sleeve (14) and can do limited telescopic movement along the sleeve length direction of the upper-layer nonlinear spring outer guide sleeve (14), the upper-layer nonlinear springs (15) are two and are symmetrically distributed on two sides of the support flat plate (20), one end of the upper-layer nonlinear spring (15) is connected with the side surface of the support flat plate (20), the other end of the upper-layer nonlinear spring (15) is connected with an upper-layer horizontal moving mechanism to achieve horizontal movable adjustment, the upper-layer horizontal moving mechanism is installed on a base (1), and the vertical moving mechanism (21) is installed on the base (1), the vertical moving mechanism (21) drives the supporting flat plate (20) to realize up-and-down movement adjustment;

the lower-layer quasi-zero stiffness vibration isolator comprises a lower-layer nonlinear spring (5), a lower-layer nonlinear spring outer guide sleeve (8) and a lower-layer vertical plane spring (2), the upper end and the lower end of the lower-layer vertical plane spring (2) are respectively and vertically fixed on a middle mass block (9) and a base (1), the lower-layer nonlinear spring (5) is limited in the lower-layer nonlinear spring outer guide sleeve (8) and can move in a limiting and telescopic mode along the sleeve length direction of the lower-layer nonlinear spring outer guide sleeve (8), the lower-layer nonlinear spring (5) is two and symmetrically distributed on two sides of the middle mass block (9), one end of the lower-layer nonlinear spring (5) is connected with the middle mass block (9), the other end of the lower-layer nonlinear spring (5) is connected with a lower-layer horizontal movement mechanism to achieve horizontal movable adjustment, and the lower-layer horizontal movement mechanism is.

2. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 1, wherein: the upper-layer quasi-zero stiffness vibration isolator comprises an upper-layer vertical damper (12), and the upper end and the lower end of the upper-layer vertical damper (12) are respectively and vertically fixed on a support flat plate (20) and a middle mass block (9).

3. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 2, wherein: the upper-layer quasi-zero stiffness vibration isolator comprises upper-layer transverse damping (17), the upper-layer transverse damping (17) is two and is symmetrically distributed on two sides of a supporting flat plate (20), one end of the upper-layer transverse damping (17) is connected with the side face of the supporting flat plate (20), and the other end of the upper-layer transverse damping (17) is connected with an upper-layer horizontal moving mechanism.

4. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 3, wherein: the lower-layer quasi-zero stiffness vibration isolator comprises a lower-layer vertical damper (3), and the upper end and the lower end of the lower-layer vertical damper (3) are respectively and vertically fixed on a middle mass block (9) and a base (1).

5. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 4, wherein: the quasi-zero stiffness vibration isolator comprises lower-layer transverse damping (10), the lower-layer transverse damping (10) is two and symmetrically distributed on two sides of a supporting flat plate (20), one end of the lower-layer transverse damping (10) is connected with the side face of a medium mass block (9), and the other end of the lower-layer transverse damping (10) is connected with a lower-layer horizontal moving mechanism.

6. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 5, wherein: base (1) includes that base and vertical two parallel relative curb plates of fixing on the base, the upper end of two curb plates inwards overhang respectively has fixed plate (19) that the level was arranged, the lower extreme of vertical planar spring (2) of lower floor and vertical damping (3) of lower floor is fixed respectively on the base, vertical moving mechanism (21) are screw one, vertical moving mechanism (21) are two and install respectively on two fixed plates (19), vertical moving mechanism (21) vertical the arranging, the lower extreme symmetry of two vertical moving mechanism (21) supports the both edges that lean on at the last face that supports dull and stereotyped (20).

7. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 6, wherein: the upper horizontal moving mechanism comprises a second screw (13), an upper vertical sliding plate (16) and an upper horizontal guide rail (18), the upper horizontal guide rail (18) is installed on the lower plate surface of the fixing plate (19), the upper end of the upper vertical sliding plate (16) and the upper horizontal guide rail (18) form a transverse sliding fit, the other end of the upper transverse damper (17) and the other end of the upper nonlinear spring (15) are respectively fixed on one side plate surface of the upper vertical sliding plate (16), the second screw (13) is installed on a side plate of the base (1), and the end part of the second screw (13) abuts against the other side plate surface of the upper vertical sliding plate (16).

8. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 7, wherein: lower floor's horizontal migration mechanism includes three (7) of screw, perpendicular slide (6) of lower floor and lower floor transverse guide (4), install on the base of base (1) lower floor transverse guide (4), the lower extreme and lower floor transverse guide (4) of the perpendicular slide (6) of lower floor constitute horizontal sliding fit, the other end of lower floor's horizontal damping (10), the other end of lower floor's nonlinear spring (5) is fixed respectively on one side face of the perpendicular slide (6) of lower floor, install on the curb plate of base (1) three (7) of screw, the tip of three (7) of screw supports and leans on the opposite side face of the perpendicular slide (6) of lower floor.

9. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 1, wherein: the upper nonlinear spring outer guide sleeve (14) is in a circular tube shape, end covers are arranged at two ends of the circular tube, and two ends of the upper nonlinear spring (15) freely penetrate through the end covers at two ends of the circular tube respectively.

10. The two-degree-of-freedom quasi-zero stiffness low-frequency vibration isolation device according to claim 9, wherein: the structure of the lower nonlinear spring outer guide sleeve (8) is the same as that of the upper nonlinear spring outer guide sleeve (14).

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