A high damping quasi-zero stiffness vibration isolator based on low-density metal rubber

Abstract

The present invention relates to a high damping quasi-zero stiffness vibration isolator based on low-density metal rubber, comprising a base and a shell covering the base, wherein a force transmission shaft extending into the shell is vertically penetrated through the top of the shell, a vertical spring is arranged on the periphery of the force transmission shaft, and a sphere is arranged at the lower end of the force transmission shaft; a plurality of negative stiffness components evenly distributed along the circumference are arranged inside the shell, and the negative stiffness components include a support, a cavity with an opening toward the center of the shell is arranged on the support, a connecting rod extending toward the center of the shell is arranged in the cavity, a roller located obliquely below the sphere and abutting against the sphere is connected to one end of the connecting rod toward the center of the shell, and a negative stiffness spring and low-density metal rubber are arranged in the cavity for pushing the connecting rod outward. The present invention can effectively isolate low-frequency vibrations, effectively curb vibrations in the low-frequency resonance zone, so that the vibration isolator can isolate low-frequency large-amplitude vibrations, and at the same time change the propagation direction of the damping force, eliminating the negative impact of the damping force vibration isolation effect.

Description

Technical Field

[0001] The invention belongs to the technical field of low-frequency and large-amplitude vibration reduction, in particular to a high-damping quasi-zero-rigidity vibration isolator based on low-density metal rubber. Background Art

[0002] Mechanical vibration refers to the reciprocating motion of a mechanical system at a certain equilibrium position under the excitation of a vibration source. Mechanical vibration is beneficial in some specific cases, but in most cases vibration is harmful. For example, vibration will generate dynamic loads and cause fatigue of parts. The low-frequency vibration generated by the ship's propulsion shaft system will not only affect its quietness but also cause resonance of the crew's body organs, thus affecting the crew's physical and mental health. The vibration of machine tools will affect the machining accuracy of workpieces, and the vibration of precision instruments will greatly reduce its accuracy... Therefore, it is very necessary to take effective vibration reduction measures for mechanical systems. According to the classical vibration isolation theory, the use of passive vibration isolation methods to isolate vibration can effectively reduce vibrations with a frequency greater than the natural frequency of the system. Under the condition of a certain mass of the vibration reference, the natural frequency of the system depends on the stiffness of the system. The greater the stiffness, the greater the natural frequency of the system. Therefore, there is an inherent contradiction in the linear vibration isolation system that the lower the isolation frequency, the smaller the static load it can carry. Therefore, how to effectively reduce the impact of low-frequency vibration on the system has always been a major engineering problem.

[0003] Low-density metal rubber is a high-damping vibration reduction material made of metal wire through a series of processes such as winding, stamping, and post-processing. The density refers to the proportion of internal pores to solid materials. When the density is about 50%, it is low density. The space network structure similar to rubber polymer is formed by the internal interlaced and intertwined fluffy metal wires. It has the advantages of not fearing corrosive environments, high and low temperature resistance, and long fatigue aging life. At the same time, due to its low density, it has a good elastic damping effect. In parallel with the quasi-zero stiffness structure, it can play a good attenuation role for low-frequency signals. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a high-damping quasi-zero stiffness vibration isolator based on low-density metal rubber, which can isolate low-frequency and large-amplitude vibrations, while changing the propagation direction of the damping force and eliminating the negative impact of the damping force vibration isolation effect.

[0005] The present invention is implemented by the following scheme: a high-damping quasi-zero stiffness vibration isolator based on low-density metal rubber, including a base and a shell covering the base, a force transmission shaft extending into the shell is vertically penetrated through the top of the shell, a vertical spring is arranged on the periphery of the force transmission shaft, and a sphere is arranged at the lower end of the force transmission shaft; a plurality of negative stiffness components evenly distributed along the circumference are arranged inside the shell, the negative stiffness component includes a support, a cavity with an opening toward the center of the shell is arranged on the support, a connecting rod extending toward the center of the shell is arranged in the cavity, the connecting rod one end of the connecting rod toward the center of the shell is connected to a roller located obliquely below the sphere and abutting against the sphere, and a negative stiffness spring and low-density metal rubber for pushing the connecting rod outward are arranged in the cavity.

[0006] Furthermore, an external threaded portion is provided at the upper end of the force transmission shaft and is connected to a spring cover via a locking nut, and the vertical spring is located between the spring cover and the top of the housing.

[0007] Furthermore, the metal rubber is an annular cylinder, the negative stiffness spring is sleeved on the outer periphery of the metal rubber, a horizontal guide hole is formed inside the metal rubber, one end of the connecting rod is located in the cavity and extends into the horizontal guide hole of the metal rubber, and a positioning protrusion is provided on the connecting rod that slides with the horizontal guide hole.

[0008] Furthermore, the inner bottom surface of the cavity is provided with a convex ring protruding outward, and the metal rubber sleeve is arranged on the convex ring.

[0009] Furthermore, a guide end cover is connected to the opening of the cavity by a first bolt, a guide hole slidingly matched with the connecting rod is opened in the center of the guide end cover, and a first sealing ring is provided on the inner wall of the guide hole; a baffle is provided at the part of the connecting rod located in the cavity, and the metal rubber and the negative stiffness spring are sandwiched between the baffle and the bottom surface of the cavity.

[0010] Furthermore, a second sealing ring is provided on the inner wall of the through hole at the top of the shell for passing the force transmission shaft; the support of the negative stiffness component is connected to the base through a second bolt, and a flange is provided on the outer periphery of the lower part of the shell, and the flange and the base are connected through a third bolt.

[0011] Furthermore, the number of the negative stiffness components is four, and the centers of the circles where the four negative stiffness components are located coincide with the axis center line of the force transmission shaft.

[0012] Compared with the prior art, the present invention has the following beneficial effects: the present invention cleverly adopts rollers and the shaft end balls of the force transmission shaft, and designs a mechanism that can form a geometric surface relationship with a negative stiffness function. The negative stiffness mechanism has a large displacement stroke, and the force transmission shaft is connected in parallel with the positive stiffness spring at the top of the vibration isolator, so that the vibration isolator has a quasi-zero stiffness characteristic under the rated load and can effectively isolate low-frequency vibrations. In addition, research on quasi-zero stiffness vibration isolators has shown that when the external excitation amplitude is large, the quasi-zero stiffness vibration isolator may experience amplitude jumps, thereby causing it to lose its ability to isolate low-frequency vibrations. Introducing appropriate damping in the vibration isolator can effectively avoid the occurrence of this phenomenon. Therefore, the present invention uses low-density metal rubber in parallel with the coil spring in the negative stiffness mechanism to provide a larger damping, so that the vibration isolator can effectively curb low-frequency and large-amplitude vibrations.

[0013] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments and related drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is an overall stereogram of an embodiment of the present invention;

[0015] Figure 2 is a cross-sectional view of an embodiment of the present invention;

[0016] Figure 3 is a cross-sectional view of a negative stiffness component in an embodiment of the present invention;

[0017] Figure 4 is a principle diagram of a vibration isolator in an initial state of an embodiment of the present invention;

[0018] Figure 5 is a principle diagram of a vibration isolator in a quasi-zero stiffness state according to an embodiment of the present invention;

[0019] Figure 6 is a principle diagram of a vibration isolator in a working state according to an embodiment of the present invention;

[0020] Figure 7 is a graph showing the restoring force and displacement of a vibration isolator according to an embodiment of the present invention;

[0021] Explanation of the numbers in the figure: 1-spring baffle, 2-vertical spring, 3-sphere, 4-negative stiffness component, 5-base, 6-locking nut, 4-force transmission shaft 7, 8-second sealing ring, 9-housing 9, 10-second bolt, 11-third bolt, 12-support, 13-negative stiffness spring, 14-low-density metal rubber, 15-horizontal guide hole, 16-positioning protrusion, 17-first bolt, 18-guide end cover, 19-first sealing ring, 20-connecting rod, 21-pin, 22-roller. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] like Figures 1 to 3 As shown, a high damping quasi-zero stiffness vibration isolator based on low-density metal rubber includes a base 5 and a shell 9 covering the base, a force transmission shaft 7 extending into the shell is vertically penetrated through the top of the shell 9, a vertical spring 2 is arranged on the periphery of the force transmission shaft 7, and the vertical spring 2 is used to provide a positive stiffness restoring force, and a sphere 3 is arranged at the lower end of the force transmission shaft 7; a plurality of negative stiffness components 4 uniformly distributed along the circumference are arranged inside the shell, and the circumference center of the circle where the plurality of negative stiffness components are located coincides with the axial center line of the force transmission shaft, and the negative stiffness component includes a support 12, and the support 12 is provided with a cavity with an opening toward the center of the shell. A connecting rod 20 extending toward the center of the shell is provided in the cavity. The connecting rod 20 is connected to a roller 22 located obliquely below the sphere and abutting against the sphere at one end thereof facing the center of the shell. The roller is rotatably mounted on the connecting rod through a pin 21. When the vibration isolator is working, the rolling of the roller 22 around the pin 21 can convert the sliding friction between the roller 22 and the sphere 3 into rolling friction, thereby reducing the influence of static friction on the vibration isolator and preventing the sphere 3 from being stuck between the two rollers 22. To ensure the movement of the roller 22, the roller 22 and the pin 21 are matched by clearance fit, and the pin 21 and the connecting rod 20 are matched by interference fit. The cavity is provided with a negative stiffness spring 13 and a low-density metal rubber 14 for pushing the connecting rod outward. The negative stiffness spring 13 is used to provide a negative stiffness restoring force for providing damping for the vibration isolator. The low-density metal rubber is made of a metal wire that is specially wound. The roller 22 and the ball 3 are used to change the direction of the elastic force generated by the negative stiffness spring 13. The low-density metal rubber and the negative stiffness spring 13 are connected in parallel. When the vibration isolator receives external excitation, the negative stiffness spring 13 provides a restoring force for the negative stiffness component, and the low-density metal rubber 14 provides a damping force. The damping element is arranged in the negative stiffness component of the vibration isolator so that the damping force is transmitted in the horizontal direction and will not generate a force on the base 5 in the vertical direction, thereby eliminating the influence of the damping force on the vibration isolation effect.

[0025] The present invention adopts a stiffness nonlinear method to design a passive vibration isolator so that the system reaches a so-called "quasi-zero stiffness state". In this working state, the system has high static stiffness and low dynamic stiffness, so it can effectively isolate low-frequency vibrations. When the vibration amplitude of the vibration source exceeds a certain critical value by adopting this nonlinear method, the amplitude-frequency response of the system will show an amplitude jump phenomenon. The occurrence of this phenomenon will not only significantly increase the response amplitude of the system in the low-frequency resonance zone, but also increase the starting vibration isolation frequency of the vibration isolator. Introducing appropriate damping in the system can effectively avoid the occurrence of this phenomenon. The present invention designs a negative stiffness structure based on the geometric surface relationship between the negative stiffness roller and the sphere at the end of the force transmission shaft. The negative stiffness structure is connected in parallel with the top positive stiffness coil spring to obtain a vibration isolator with a quasi-zero stiffness characteristic under rated load. At the same time, low-density metal rubber is connected in parallel with the coil spring in the negative stiffness mechanism to provide a larger damping, so that the vibration isolator can effectively curb low-frequency vibrations while avoiding the amplitude jump phenomenon caused by the large excitation amplitude.

[0026] In this embodiment, the upper end of the force transmission shaft 7 is provided with an external threaded portion and is connected to a spring cover 1 through a locking nut 6 , and the vertical spring is located between the spring cover 1 and the top of the housing 9 .

[0027] In this embodiment, the metal rubber 14 is an annular cylinder, the negative stiffness spring 13 is sleeved on the outer periphery of the metal rubber 14, a horizontal guide hole 15 is formed inside the metal rubber, one end of the connecting rod is located in the cavity and extends into the horizontal guide hole of the metal rubber, and a positioning protrusion 16 that slides with the horizontal guide hole is provided on the connecting rod.

[0028] In this embodiment, a convex ring protruding outward is provided on the inner bottom surface of the cavity, and the metal rubber sleeve is arranged on the convex ring.

[0029] In this embodiment, a guide end cover 18 is connected to the opening of the cavity by a first bolt 17, a guide hole for slidingly cooperating with the connecting rod is opened in the center of the guide end cover, and a first sealing ring 19 is provided on the inner wall of the guide hole; a baffle is provided at the part of the connecting rod located in the cavity, and the metal rubber and the negative stiffness spring are sandwiched between the baffle and the bottom surface of the cavity.

[0030] In this embodiment, a second sealing ring 8 is provided on the inner wall of the through hole at the top of the shell for passing the force transmission shaft. The force transmission shaft 7 and the through hole at the top of the shell are clearance-matched and sealed with the second sealing ring 8. The support of the negative stiffness component is connected to the base through a second bolt 10, and a flange is provided on the outer periphery of the lower part of the shell, and the flange and the base are connected through a third bolt 11.

[0031] In this embodiment, the number of the negative stiffness components is four, and the centers of the circles where the four negative stiffness components are located coincide with the axis center line of the force transmission shaft.

[0032] In order to clearly express the principle of the vibration isolator, Figure 4 , 5, 6, the circles on both sides represent the rollers 22 in the negative stiffness element, and the middle circle represents the shaft end ball 3. When the vibration isolator is not subjected to any force, it is in the state as shown in the attached Figure 4 The initial state shown, at this time, the horizontal spring 13, the vertical spring 2 are both in the initial state. The design parameters are: the radius of the roller 22 , the radius of the ball 3 at the end of the shaft , the distance between the center of the ball 3 at the end of the shaft and the line connecting the centers of the two rollers 22 , the distance between the center of roller 22 and the vertical center axis The design can be carried out according to the actual static load and vibration amplitude.

[0033] When the isolator is under the design rated load Under the action of the shaft 7, the shaft 7 moves downward, making the vertical spring 2 in a compressed state. The two rollers 22 produce a radial movement under the squeezing action of the small ball 3 at the shaft end, making the horizontal spring in a compressed state. When the center of the small ball 3 at the shaft end and the center of the two rollers 22 are in the same straight line, the vibration isolator is in the state as shown in the attached figure. Figure 4 The quasi-zero stiffness state shown in Fig. Figure 5 , the forces marked in 6 only reflect the direction of the force and do not truly reflect its point of action.

[0034] The vibration isolator in the quasi-zero stiffness state becomes as follows when subjected to external excitation. Figure 6 In the working state shown, the shaft end ball 3 performs reciprocating mechanical vibration, and its equilibrium position is the line connecting the centers of the two rollers. During the whole process, the force generated by the horizontal spring 13 is always in the horizontal direction. Due to the surface relationship between the two rollers 22 and the shaft end ball 3, the force generated by the horizontal spring 13 is transmitted to the shaft end ball 3 along the roller 22, and a vertical component is generated to offset the force generated by the vertical spring 2, thereby reducing the stiffness of the vibration isolator in the vertical direction. When the vertical component is exactly equal to the force generated by the vertical spring 2 through reasonable parameter selection, the vibration isolator is in a quasi-zero stiffness state at the equilibrium position.

[0035] The following analysis is based on two assumptions:

[0036] ① Each moving pair is lubricated and in good contact, and the effect of friction on the vibration isolator is ignored.

[0037] ② The roller and the small ball at the end of the shaft have greater rigidity and the influence of their tiny deformation on the analysis can be ignored.

[0038] When the isolator is in the Figure 4 In the initial state shown, it is assumed that the radius of the small ball at the end of the shaft is: , the radius of the two rollers is: , the distance between the center of the ball at the end of the shaft and the horizontal line is: , the distance between the center of the roller and the vertical center line is: , then there is a geometric constraint:

[0039] (1)

[0040] When the isolator is in the Figure 6 In the working state shown, it is assumed that the displacement of the small ball at the end of the isolator from the equilibrium position under the action of the excitation force is: , the angle between the center of the small ball at the shaft end and the center of the roller and the horizontal line is: , then there is a geometric constraint:

[0041] (2)

[0042] (3)

[0043] In the working state, the static force on the shaft can be expressed as:

[0044] (4)

[0045] in: It represents the effect of the positive stiffness device on the small ball at the end of the shaft, that is, the force generated by the vertical spring. It represents the force of the negative stiffness device on the small ball at the end of the shaft, that is, the force of the two rollers on the small ball at the end of the shaft.

[0046] Assume the vertical spring stiffness is: , the stiffness of the horizontal spring and metal rubber is: Then there is the following relationship:

[0047] For rated loads: (5)

[0048] The forces generated by a positive stiffness spring are: (6)

[0049] Displacement of horizontal spring motion: (7)

[0050] Force in the horizontal spring: (8)

[0051] From the force relationship in the figure, it can be obtained that the vertical force generated by the negative stiffness mechanism on the axis can be expressed as:

[0052] (9)

[0053] Substituting equations (3) and (8) into equation (9), we can obtain:

[0054] (10)

[0055] Substituting equations (5), (6), and (10) into equation (4), the expression of the suspension restoring force with respect to displacement can be expressed as: (11)

[0056] By differentiating the expression of suspension restoring force with respect to displacement, we can get the expression of suspension stiffness with respect to displacement: (12)

[0057] According to the characteristics of quasi-zero stiffness isolator, when When the suspension stiffness K=0, that is:

[0058] (13)

[0059] Substituting the above equation into equation (13) and equation (12) yields the following relationship:

[0060] (14)

[0061] Analysis of vibration isolator response travel:

[0062] When the response amplitude of the isolator under excitation satisfies the following relationship:

[0063] (15)

[0064] The vibration isolator is in a quasi-zero stiffness state and satisfies the above analysis. When the shaft end ball is separated from the roller constraint isolator, the stiffness becomes Linear vibration isolators.

[0065] In actual engineering applications, specific parameters can be designed according to the rated load and vibration magnitude that the vibration isolator needs to withstand. Assume that the rated mass of the vibration isolator is: , then the rated load , the response amplitude X of the vibration isolator is less than 5cm, that is , the radius of the roller and the radius of the small ball at the end of the shaft are both 5cm, that is .

[0066] Will Substituting into formula (4), we can get the distance between the center of the roller and the center axis in the initial state:

[0067]

[0068] Will and Substituting into formula (5) we can get the vertical spring stiffness:

[0069]

[0070] Will Substituting into formula (14) we can get the horizontal spring stiffness:

[0071]

[0072] Substituting the above parameters into formula (12) we can get Figure 7 The relationship between restoring force and displacement is shown.

[0073] The outstanding advantages of the present invention are as follows: ① A quasi-zero stiffness vibration isolator is designed by utilizing the surface relationship between the roller and the small ball at the end of the shaft so that it can effectively isolate low-frequency vibrations. ② Low-density and high-damping metal rubber is used as the damping element of the vibration absorber in the negative stiffness component, which effectively reduces the amplitude response of the vibration isolator in the low-frequency resonance zone, and at the same time changes the transmission direction of the damping force, eliminating the negative impact of the damping force on the vibration isolation effect. The present invention is mainly used in some fields that are more sensitive to low-frequency vibrations, such as: vibration reduction of various precision instruments, vibration reduction of ships and vessels, vibration reduction in the aerospace field, etc.

[0074] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

[0075] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by integrated molding using a casting process) (except when it is obviously impossible to use an integrated molding process).

[0076] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0077] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0078] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A high damping quasi-zero stiffness vibration isolator based on low-density metal rubber, characterized by: The invention comprises a base and a shell covering the base, wherein a force transmission shaft extending into the shell is vertically penetrated through the top of the shell, a vertical spring is arranged on the periphery of the force transmission shaft, and a sphere is arranged at the lower end of the force transmission shaft; a plurality of negative stiffness components evenly distributed along the circumference are arranged inside the shell, and the negative stiffness components comprise a support seat, a cavity with an opening toward the center of the shell is arranged on the support seat, a connecting rod extending toward the center of the shell is arranged in the cavity, a roller located obliquely below the sphere and abutting against the sphere is connected to the connecting rod at one end toward the center of the shell, a negative stiffness spring and a low-density metal rubber for pushing the connecting rod outward are arranged in the cavity; the metal rubber is an annular column The negative stiffness spring is sleeved on the outer periphery of the metal rubber, a horizontal guide hole is formed inside the metal rubber, one end of the connecting rod located in the cavity extends into the horizontal guide hole of the metal rubber, and a positioning protrusion that slides with the horizontal guide hole is provided on the connecting rod; a convex ring that protrudes outward is provided on the inner bottom surface of the cavity, and the metal rubber sleeve is arranged on the convex ring; a guide end cover is connected to the opening of the cavity through a first bolt, a guide hole that slides with the connecting rod is opened in the center of the guide end cover, and a first sealing ring is provided on the inner wall of the guide hole; a baffle is provided on the part of the connecting rod located in the cavity, and the metal rubber and the negative stiffness spring are sandwiched between the baffle and the inner bottom surface of the cavity.

2. The high damping quasi-zero stiffness vibration isolator based on low-density metal rubber according to claim 1, characterized in that: The upper end of the force transmission shaft is provided with an external threaded portion and is connected with a spring stop cover via a locking nut, and the vertical spring is located between the spring stop cover and the top of the housing.

3. The high damping quasi-zero stiffness vibration isolator based on low-density metal rubber according to claim 1, characterized in that: A second sealing ring is provided on the inner wall of the through hole at the top of the shell for passing the force transmission shaft; the support of the negative stiffness component is connected to the base through a second bolt, a flange is provided on the periphery of the lower part of the shell, and the flange and the base are connected through a third bolt.

4. The high damping quasi-zero stiffness vibration isolator based on low-density metal rubber according to claim 1, characterized in that: The number of the negative stiffness components is four, and the centers of the circles where the four negative stiffness components are located coincide with the axis center line of the force transmission shaft.

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