Multi-spring combined quasi-zero stiffness vibration isolator

Abstract

The invention discloses a multi-spring combined quasi-zero stiffness vibration isolator. A positive stiffness mechanism and a plurality of negative stiffness mechanisms are ingeniously arranged between a base and a bearing platform, wherein the positive stiffness mechanism is composed of linear bearings, vertical springs and guide rods, and the negative stiffness mechanisms form a quasi-zero stiffness system. The low-frequency vibration isolator not only can bear a vibration isolation object with larger mass, but also can effectively reduce the dynamic stiffness of a vibration isolation system, so that the inherent frequency of the whole system is close to zero, and the vibration isolator has good low-frequency vibration isolation performance during low-frequency vibration; compared with other vibration isolators, the telescopic arm structure and the baffle can effectively guarantee that the spring stretches out and draws back on the same horizontal line, it is guaranteed that a negative stiffness mechanism can effectively work, the spring can be prevented from being unstable, better vibration isolation performance is achieved in low-frequency vibration isolation, and the resonance peak value of the vibration isolator is remarkably reduced. Meanwhile, the limiting mechanism can prevent the negative stiffness mechanism from being excessively compressed or stretched, the situation that the negative stiffness mechanism is damaged is avoided, and the vibration isolator can be widely applied to the fields of vibration isolation of automobiles, precise instruments and equipment, ship equipment and the like.

Description

Technical Field

[0001] The invention relates to a multi-spring combined quasi-zero stiffness vibration isolator, belonging to the field of vibration control. Background Art

[0002] With the continuous development of industry and science and technology, vibration isolation technology has been widely used in precision instruments, mechanical equipment, aerospace, transportation and other fields. Most traditional vibration isolators use linear spring structures to protect equipment and its precision components by absorbing and reducing vibration. However, the vibration isolation effect of linear vibration isolators in low-frequency vibration environments is limited, and it is difficult to meet certain application scenarios with high precision requirements. In order to solve this problem, quasi-zero stiffness vibration isolators (QZS) came into being. Quasi-zero stiffness vibration isolators can achieve extremely low equivalent stiffness within a small deformation range through nonlinear elastic elements or combined structures, thereby providing excellent vibration isolation performance in the low frequency band. This type of vibration isolator can not only effectively reduce the vibration transmissibility, but also adapt to a wider frequency range. Especially in fields that require high precision and high stability, such as precision instruments, optical platforms, and micro-electromechanical systems, quasi-zero stiffness vibration isolators show great advantages. Therefore, quasi-zero stiffness vibration isolators have gradually become an important direction for the research and application of vibration isolation technology.

[0003] Most of the existing vibration isolation technologies are still positive stiffness spring vibration isolation. The traditional positive stiffness spring vibration isolation has a high force transmission rate and poor vibration isolation performance. With the rapid development of quasi-zero stiffness vibration isolators, there are some quasi-zero stiffness vibration isolators. For example, CN 202520846 U designed a low-frequency vibration isolator for basic excitation, which uses a combination of positive and negative stiffness to achieve low-frequency vibration isolation. However, the force transmission rate curve shows that its resonance peak is high, and the energy of external vibration will be transmitted to the inside of the system, resulting in significant vibration amplification, which will have a series of adverse effects, such as vibration amplification, system fatigue damage, and noise generation. Summary of the invention

[0004] The present invention provides a multi-spring combined quasi-zero stiffness vibration isolator, which cleverly arranges a positive stiffness mechanism consisting of a linear bearing, a vertical spring, and a guide rod and a plurality of negative stiffness mechanisms between a base and a load-bearing platform to form a quasi-zero stiffness system, so that the stiffness of the system at a balanced position is close to zero, thereby greatly reducing the natural frequency of the system, thereby improving its vibration isolation capability and achieving better vibration isolation effect within a low-frequency vibration isolation range.

[0005] The technical solution of the present invention is:

[0006] The present invention provides a multi-spring combined quasi-zero stiffness vibration isolator, comprising a base 1, a linear bearing 2, a limit mechanism 3, a first spring 5, a guide rod 6, a connector 7, a load-bearing platform 8, and a negative stiffness structure;

[0007] The base 1 is provided with a first through hole penetrating along a first direction; the linear bearing 2 is fixedly mounted on the base 1, and the inner ring hole of the linear bearing 2 is communicated with the first through hole to form a guide hole;

[0008] The load-bearing platform 8 includes a load-bearing part and a connecting part, one side of the load-bearing part is used to place the vibration-isolated object, and the other side of the load-bearing part is connected to one end of the connecting part; the other end of the connecting part is connected to one end of a guide rod 6, and at least part of the other end of the guide rod 6 is inserted into the inner ring hole of the linear bearing 2, so as to guide the movement of the guide rod 6 along the first direction through the guide hole; a first spring 5 is sleeved on the guide rod 6, and one end face of the first spring 5 is in contact with the other end face of the connecting part, and the other end face of the first spring 5 is in contact with the end face of the linear bearing 2 away from the base 1; a plurality of connectors 7 are arranged at intervals along the circumferential direction at the other end of the connecting part;

[0009] Multiple limiting mechanisms 3 are installed on the base 1 and are arranged at intervals along the circumference of the linear bearing 2. There is a gap between the end face of the limiting mechanism 3 away from the base 1 and the end face of the other side of the load-bearing part, so as to limit the travel of the load-bearing platform 8 after the vibration-isolated object is placed; each of the limiting mechanisms 3 is connected between the end away from the base 1 and the corresponding connector 7 through a negative stiffness structure.

[0010] Furthermore, the negative stiffness structure includes a second spring 9, a telescopic arm 10, a first rotating connection with a limit position, and a second rotating connection with a limit position; the second spring 9 is sleeved on the outer periphery of the telescopic arm 10, and one end of the second spring 9 and the telescopic arm 10 is fixed to one end of the first rotating connection with a limit position, and the other end of the second spring 9 and the telescopic arm 10 is fixed to one end of the second rotating connection with a limit position; the other end of the first rotating connection with a limit position is rotationally matched with the connector 7, and the other end of the second rotating connection with a limit position is rotationally matched with the limiting mechanism 3.

[0011] Furthermore, the first rotating connector with a limit position and the second rotating connector with a limit position have the same structure, both including a baffle 11, a rotating shaft 12 and a connecting block 13; the limiting mechanism 3 and the connector 7 are provided with a mounting hole 14 for mounting the rotating shaft 12 of the negative stiffness mechanism; the rotating shaft 12 is installed in the mounting hole 14 to realize the rotational connection between the connector 7 and the connecting block 13 in the first rotating connector with a limit position, and to realize the rotational connection between the limiting mechanism 3 and the connecting block 13 in the second rotating connector with a limit position; the connecting block 13 is fixedly connected to one side of the baffle 11 at one end away from the rotating shaft 12, and the other side of the baffle 11 is fixedly connected to the ends of the second spring 9 and the telescopic arm 10, and the end surface of the other side of the baffle 11 is parallel to the two end surfaces of the second spring 9 and the telescopic arm 10.

[0012] The beneficial effects of the present invention are as follows: the multi-spring combined quasi-zero stiffness vibration isolator provided by the present invention can not only withstand vibration isolation objects of greater mass, but also effectively reduce the dynamic stiffness of the vibration isolation system, making the natural frequency of the entire system close to zero, so that the vibration isolator has good low-frequency vibration isolation performance during low-frequency vibration; compared with other vibration isolators, the telescopic arm structure and baffle can effectively ensure that the spring is extended and retracted on a horizontal line, ensuring that the negative stiffness mechanism can work effectively, and can also prevent the spring from becoming unstable, and has better vibration isolation performance at low frequency, and the resonance peak value of the vibration isolator is also significantly reduced. At the same time, its limit mechanism can prevent the negative stiffness mechanism from being over-compressed or stretched, avoiding damage to the negative stiffness mechanism, and can be widely used in the fields of automobile, precision instruments and equipment, and ship equipment vibration isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the present invention

[0014] Figure 2 It is a structural front view of the present invention

[0015] Figure 3 This is a comparison chart of the force transmission rate between the present invention and traditional linear vibration isolation.

[0016] Figure 4 This is a comparison of the force transmission rate of the present invention and other quasi-zero stiffness isolators under the same parameters.

[0017] Figure 5 This is a comparison diagram of displacement excitation and response curves of the present invention at different frequencies

[0018] The numbers in the figure are: 1-base, 2-linear bearing, 3-limiting mechanism, 4-bolt, 5-first spring, 6-guide rod, 7-connector, 8-load-bearing platform, 9-second spring, 10-telescopic arm, 11-baffle, 12-rotating shaft, 13-connecting block, 14-mounting hole. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0020] Example 1: Figure 1-5As shown, a multi-spring combination quasi-zero stiffness vibration isolator includes a base 1, a linear bearing 2, a limit mechanism 3, a first spring 5, a guide rod 6, a connector 7, a load-bearing platform 8, and a negative stiffness structure; the base 1 is provided with a first through hole penetrating along a first direction; the linear bearing 2 is fixedly mounted on the base 1, and the inner ring hole of the linear bearing 2 is communicated with the first through hole to form a guide hole; the load-bearing platform 8 includes a load-bearing part and a connecting part, one side of the load-bearing part is used to place an object to be isolated, and the other side of the load-bearing part is connected to one end of the connecting part; the other end of the connecting part is connected to one end of the guide rod 6, and at least part of the other end of the guide rod 6 is inserted into the inner ring hole of the linear bearing 2 (when the multi-spring combination quasi-zero stiffness vibration isolator is in the initial state, that is, when the load-bearing platform 8 does not place an object to be isolated, the guide rod 6 is inserted into the inner ring hole of the linear bearing 2). At least part of one end of the rod 6 is inserted into the inner ring hole of the linear bearing 2) to guide the movement of the guide rod 6 along the first direction through the guide hole; a first spring 5 is sleeved on the guide rod 6 and one end face of the first spring 5 is in contact with the other end face of the connecting part, and the other end face of the first spring 5 is in contact with the end face of the linear bearing 2 away from the base 1; a plurality of connectors 7 are arranged at intervals along the circumferential direction at the other end of the connecting part; a plurality of limiting mechanisms 3 are installed on the base 1 and are arranged at intervals along the circumference of the linear bearing 2, and there is a gap between the end face of the limiting mechanism 3 away from the base 1 and the end face of the other side of the load-bearing part, so as to limit the travel of the load-bearing platform 8 after the vibration-isolated object is placed; the end of each limiting mechanism 3 away from the base 1 is connected to the corresponding connector 7 through a negative stiffness structure.

[0021] In the embodiment of the present invention, the first direction is the axial direction of the guide rod 6, that is, Figure 1 , 2 Vertical orientation shown.

[0022] Specifically, refer to Figure 1 , 2 , the base 1 is provided with a linear bearing 2 and a limiting mechanism 3 arranged vertically, that is, the axial direction of the two is the first direction; further, the base 1 and the linear bearing 2 can be fixedly connected by a bolt 4; one end of the limiting mechanism 3 is fixed to the base 1 (the two are of an integrated design or a split design. If a split design is adopted, the limiting mechanism 3 and the base 1 can be connected and fixed by means of threads, etc.); by setting the limiting mechanism 3, on the one hand, it can be used to install a negative stiffness structure, and on the other hand, it can be used to limit the travel of the load-bearing platform 8 after the vibration-isolated object is placed; Figure 1 The orientation shown is used for explanation. When no vibration-isolated object is loaded, the vertical distance between the upper surface of the limiting mechanism 3 and the lower surface of the load-bearing platform 8 is set to 10 cm, thereby preventing the vibration isolator from being damaged due to excessive stroke.

[0023] Furthermore, the negative stiffness structure includes a second spring 9, a telescopic arm 10, a first rotating connection with a limit position, and a second rotating connection with a limit position; the second spring 9 is sleeved on the outer periphery of the telescopic arm 10, and one end of the second spring 9 and the telescopic arm 10 is welded and fixed to one end of the first rotating connection with a limit position, and the other end of the second spring 9 and the telescopic arm 10 is welded and fixed to one end of the second rotating connection with a limit position; the other end of the first rotating connection with a limit position is rotationally matched with the connector 7, and the other end of the second rotating connection with a limit position is rotationally matched with the limiting mechanism 3.

[0024] The second spring 9 and the telescopic arm 10 are coaxially arranged, and when the multi-spring combination quasi-zero stiffness vibration isolator is in the initial state, that is, when the load-bearing platform 8 does not place the vibration-isolated object, the second spring 9 and the telescopic arm 10 are in an inclined state. Figure 1 As shown in the installation diagram, the connection position of the second spring 9, one end of the telescopic arm 10 and the first limited rotation connection member is higher than the connection position of the second spring 9, the other end of the telescopic arm 10 and the second limited rotation connection member. In the technical solution of the present invention, the second spring 9 cooperates with the telescopic arm 10 to avoid irregular deformation of the tilt spring of the vibration isolator to prevent affecting the vibration isolation performance of the vibration isolator.

[0025] In the present invention, the negative stiffness structure is evenly distributed on the outer circle of the load-bearing platform 8, and the parameters of the second spring 9, telescopic arm 10, baffle 11, rotating shaft 12 and connecting block 13 of the negative stiffness mechanism are all the same. It should be noted that the negative stiffness structure is generally selected in an even number, such as two, four, six, or eight. Figure 1 , 2 In the figure, eight are shown, that is, the outer circle of the load-bearing platform 8 is divided into eight equal parts.

[0026] Furthermore, the first rotating connector with a limit position and the second rotating connector with a limit position have the same structure, both including a baffle 11, a rotating shaft 12 and a connecting block 13; the limiting mechanism 3 and the connector 7 are provided with a mounting hole 14 for mounting the rotating shaft 12 of the negative stiffness mechanism; the rotating shaft 12 is installed in the mounting hole 14 to realize the rotational connection between the connector 7 and the connecting block 13 in the first rotating connector with a limit position, and to realize the rotational connection between the limiting mechanism 3 and the connecting block 13 in the second rotating connector with a limit position; the connecting block 13 is fixedly connected to one side of the baffle 11 at one end away from the rotating shaft 12, and the other side of the baffle 11 is fixedly connected to the ends of the second spring 9 and the telescopic arm 10, and the end surface of the other side of the baffle 11 is parallel to the two end surfaces of the second spring 9 and the telescopic arm 10.

[0027] The working principle of the present invention is as follows:

[0028] by Figure 1 The perspective shown is used as an example for explanation: the object to be isolated is placed on the load-bearing platform 8, and the load-bearing platform 8 moves downward; the downward movement of the load-bearing platform 8 drives the guide rod 6 to move downward, thereby compressing the first spring 5 mounted on the guide rod 6; at the same time, the telescopic arm 10 is compressed, and as the telescopic arm 10 compresses, the second spring 9 is compressed.

[0029] When the quasi-zero stiffness isolator reaches the equilibrium position, the mass of the isolated object is fully supported by the first spring 5, the telescopic arm 10 and the second spring 9 are compressed and moved to the horizontal, and at this time the second spring 9 only has horizontal force and no vertical force is generated; when the load-bearing platform 8 jumps up and down at the equilibrium position, the second spring 9 will generate a component force in the vertical direction, and has a negative stiffness characteristic in the vertical direction, which can offset the positive stiffness generated by the first spring 5, so that the dynamic stiffness of the system approaches zero. At this time, the system is a quasi-zero stiffness system.

[0030] By applying the above technical solution, it can be known that when the object to be isolated is placed on the stage and reaches near the equilibrium position, the first spring generates positive stiffness in the vertical direction, and the negative stiffness mechanism generates negative stiffness in the vertical direction. According to the principle of cancellation of positive and negative stiffness, the stiffness of the system at this time is zero, that is, when the object to be isolated vibrates up and down at the equilibrium position, the dynamic stiffness is extremely low and can be considered to be equal to zero. The natural frequency of the entire system is naturally very low, thereby achieving the purpose of low-frequency vibration isolation.

[0031] In order to verify the superiority of the vibration isolation performance of this quasi-zero stiffness isolator, it is explained from multiple aspects as follows:

[0032] 1. Force Transmission Rate Analysis

[0033] The system's equation of motion (1) is established using Newton's second law, and the harmonic balance method is further used to solve the system's amplitude-frequency response function (2), and the force transfer rate formula (3) of the system is obtained. The traditional linear vibration isolation force transfer rate formula is as shown in formula (4). The force transfer rate is used to evaluate the vibration isolation performance of the quasi-zero stiffness isolator. The force transfer rate refers to the proportional relationship between the input force and the output force. According to the force transfer rate expression, the force transfer rate mainly depends on factors such as the damping ratio ζ of the vibration isolation system, the restoring force coefficient ε of the vibration isolation system, and the excitation amplitude. The present invention uses a numerical analysis method to study the force transfer rate curve of the system under the same excitation amplitude and damping ratio conditions under the action of a simple harmonic excitation force, and compares it with a linear vibration isolation system. During the study, the system's damping ratio ζ is set to 0.01, the restoring force coefficient ε=4, and the excitation amplitude is 0.1, and the force transfer rate curve of the linear system is added for comparison. The force transfer rate curve is as follows Figure 3 shown.

[0034]

[0035] Where: U represents dimensionless displacement, ζ represents the damping ratio of the vibration isolation system, T represents the transmissibility, Ω represents the frequency, represents the excitation amplitude of the force, A represents the response amplitude of the system, ε represents the restoring coefficient of the system, T f Denotes the force transmission rate of the quasi-zero stiffness system of the present invention, T l Represents the force transmission rate of a conventional linear system.

[0036] Low frequency vibration usually refers to vibration with a frequency range of 1Hz to 20Hz, and ultra-low frequency usually refers to vibration with a frequency below 1Hz, also known as the sub-Hertz range. Figure 3 It can be seen that the quasi-zero stiffness vibration isolator of the present invention has better vibration isolation performance than the traditional linear system in the low frequency range, and also has a lower peak value when resonance occurs.

[0037] In order to further verify the superiority of the vibration isolation performance of the quasi-zero stiffness vibration isolator of the present invention, by consulting other related studies on vibration isolators, the force transmission rate of the vibration isolator of the present invention and that of the vibration isolator disclosed in CN 202520846 U is compared and analyzed while keeping the parameters the same. The comparison curve is shown in FIG. Figure 4 As shown. Figure 4 It can be seen that the quasi-zero stiffness isolator of the present invention has a lower force transmission rate than the CN202520846U isolator during low-frequency vibration, and also has a lower resonance peak value. Therefore, it can be seen that the quasi-zero stiffness isolator has better vibration isolation performance.

[0038] 2. Analysis of displacement transmissibility

[0039] The displacement transmissibility is used to evaluate the vibration isolation performance of the quasi-zero stiffness isolator. The displacement transmissibility refers to the ratio of the input displacement to the output displacement after the vibration isolation system is subjected to simple harmonic displacement excitation. z The formula is as follows, A is the response amplitude of the system, Z is the system displacement excitation, and φ is the angle between the tilt spring and the horizontal plane.

[0040]

[0041] Table 1 Simulation parameters

[0042] parameter Numeric M 5kg n 6 <![CDATA[K0]]> 2.688N / mm

[0043] The vibration isolation system of the present invention is numerically simulated by the fourth-order Runge-Kutta method. Table 1 shows the system parameters during the simulation (in Table 1, M is the mass of the object to be isolated, n is the number of spring coils, and K0 is the spring stiffness). When a sinusoidal excitation is applied to the vibration isolation system, the displacement excitation amplitude is 2 mm, and the excitation frequencies are 0.6 Hz, 0.9 Hz, 1 Hz, and 2 Hz, respectively. Based on the simulation parameters, the curves of the vibration isolator at the above four excitation frequencies are obtained, and the curves include an excitation curve and a response curve, as shown in FIG. Figure 5 As shown. Figure 5 It can be seen that in a relatively short period of time, the response curve of the system reaches a stable state from the slight fluctuation at the beginning. At the same time, it can be seen that the displacement excitation amplitude applied to the system is much larger than the displacement response amplitude. Under given different excitation frequencies, the vibration isolator always maintains good vibration isolation performance. At the same time, with the increase of the excitation frequency, the displacement response amplitude of the vibration isolation system gradually decreases, and the vibration isolation performance of the vibration isolator gradually increases. It should be noted that with the structure shown in Example 1 of the present invention, a spring with a stiffness of 2.688N / mm and a number of turns of 6 can achieve a bearing capacity of 50N.

[0044] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A multi-spring combined quasi-zero stiffness vibration isolator, It is characterized in that It comprises a base (1), a linear bearing (2), a limiting mechanism (3), a first spring (5), a guide rod (6), a connector (7), a load-bearing platform (8), and a negative stiffness structure; The base (1) is provided with a first through hole penetrating along a first direction; the linear bearing (2) is fixedly mounted on the base (1), and the inner ring hole of the linear bearing (2) is arranged in communication with the first through hole to form a guide hole; The load-bearing platform (8) comprises a load-bearing part and a connecting part, one side of the load-bearing part is used to place an object to be isolated from vibration, and the other side of the load-bearing part is connected to one end of the connecting part; the other end of the connecting part is connected to one end of a guide rod (6), and at least a part of the other end of the guide rod (6) is inserted into the inner ring hole of the linear bearing (2) so as to guide the movement of the guide rod (6) along a first direction through the guide hole; a first spring (5) is sleeved on the guide rod (6), and one end face of the first spring (5) is in contact with the other end face of the connecting part, and the other end face of the first spring (5) is in contact with the end face of the linear bearing (2) away from the base (1); a plurality of connectors (7) are arranged at intervals along the circumferential direction at the other end of the connecting part; A plurality of the limiting mechanisms (3) are mounted on the base (1) and are spaced apart along the circumference of the linear bearing (2); an end face of the limiting mechanism (3) away from the base (1) and an end face of the other side of the load-bearing part are spaced apart to limit the travel of the load-bearing platform (8) after the vibration-isolated object is placed thereon; an end of each limiting mechanism (3) away from the base (1) is connected to the corresponding connector (7) via a negative stiffness structure.

2. The multi-spring combined quasi-zero stiffness vibration isolator according to claim 1, It is characterized in that The negative stiffness structure comprises a second spring (9), a telescopic arm (10), a first rotation connection member with a limit position, and a second rotation connection member with a limit position; the second spring (9) is sleeved on the outer periphery of the telescopic arm (10), and one end of the second spring (9) and the telescopic arm (10) is fixed to one end of the first rotation connection member with a limit position, and the other end of the second spring (9) and the telescopic arm (10) is fixed to one end of the second rotation connection member with a limit position; the other end of the first rotation connection member with a limit position is rotationally matched with the connector (7), and the other end of the second rotation connection member structure with a limit position is rotationally matched with the limiting mechanism (3).

3. The multi-spring combined quasi-zero stiffness vibration isolator according to claim 2, It is characterized in that The first limited rotation connecting member and the second limited rotation connecting member have the same structure, and both include a baffle (11), a rotating shaft (12) and a connecting block (13); the limiting mechanism (3) and the connector (7) are provided with a mounting hole (14) for mounting the rotating shaft (12) of the negative stiffness mechanism; the rotating shaft (12) is installed in the mounting hole (14) to realize the rotation connection between the connector (7) and the connecting block (13) in the first limited rotation connecting member, and to realize the rotation connection between the limiting mechanism (3) and the connecting block (13) in the second limited rotation connecting member; the end of the connecting block (13) away from the rotating shaft (12) is fixedly connected to one side of the baffle (11), and the other side of the baffle (11) is fixedly connected to the ends of the second spring (9) and the telescopic arm (10), and the end surface of the other side of the baffle (11) is parallel to the two end surfaces of the second spring (9) and the telescopic arm (10).

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