A horizontal vibration isolator with adjustable stiffness

Abstract

A horizontal vibration isolator with adjustable stiffness can solve the problems of difficult adjustment of horizontal stiffness, limited load-bearing range and poor low-frequency vibration isolation effect of existing passive vibration isolators. It is characterized in that it includes a lower platform provided for the load-bearing structure below the support seat, a load platform covered above the upper platform of the load-bearing structure, and four ball hinges with four vertices forming a square that uprightly supports the load platform on the lower platform at both ends of the support seat in the x-axis direction. A first horizontal spring that balances the displacement in the x-axis direction and a second horizontal spring that balances the displacement in the y-axis direction are respectively provided around the upper end of each ball hinge. The first horizontal spring and the second horizontal spring are both hung on the load platform at one end and on the upper platform at the other end.

Description

Technical Field

[0001] The invention belongs to the technical field of precision vibration isolation, and in particular relates to a horizontal vibration isolator with adjustable stiffness. Background Art

[0002] In the field of precision measurement, it is often necessary to isolate low-frequency micro-vibrations from the external environment to reduce interference with the measurement system. According to different vibration suppression methods, vibration isolators can be divided into passive vibration isolation and active vibration isolation. Passive vibration isolation reduces the vibration amplitude by designing a reasonable mechanical structure. It has a simple structure and a wide range of applications. For linear stiffness vibration isolation systems, when the excitation frequency is greater than the natural frequency of the system, Therefore, to achieve low-frequency vibration isolation, it is necessary to reduce the natural frequency of the system. An effective method is to achieve quasi-zero stiffness by connecting positive and negative stiffness structures in parallel. Some related research is as follows:

[0003] Patent publication number CN 111677799 A, titled "Three-degree-of-freedom electromagnetic vibration isolator based on horizontal pre-compression springs," utilizes a magnetic spring in parallel with four circumferentially distributed horizontal pre-compression springs to achieve three-degree-of-freedom electromagnetic vibration isolation. This achieves high magnetic material utilization and a structural design without a guide mechanism. However, this vibration isolation system is susceptible to interference from external magnetic fields and is difficult to adjust for quasi-zero stiffness based on varying load masses.

[0004] The invention patent, publication number CN 115388117 A, titled "Horizontal Quasi-Zero Vibration Isolator," utilizes an inverted pendulum to provide negative stiffness and a beam assembly to provide positive stiffness. By adjusting the ratio of the first and second sections of the inverted pendulum, zero-frequency vibration isolation is achieved along the entire horizontal circumference of the load. This minimizes additional damping and enables high-precision horizontal vibration isolation. However, the use of a single inverted pendulum structure reduces system stability and limits the load-bearing range.

[0005] Existing quasi-zero stiffness isolators are difficult to adjust, have a limited load range, and are unable to meet the ultra-low-frequency vibration isolation requirements of varying loads. This paper proposes a horizontal vibration isolator with adjustable stiffness, designed to adjust the horizontal stiffness to quasi-zero, thereby reducing the natural frequency of the isolation system and achieving a low-frequency vibration isolation effect. Summary of the Invention

[0006] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a horizontal vibration isolator with adjustable stiffness, which can solve the problems of the existing passive vibration isolators that the horizontal stiffness is difficult to adjust, the load range is limited, and the low-frequency vibration isolation effect is poor.

[0007] The technical solutions of the present invention are as follows:

[0008] A horizontal vibration isolator with adjustable stiffness is characterized in that it includes a lower platform arranged for a bearing structure below a support seat, a load platform covering the upper platform of the bearing structure, and four ball hinges forming four vertices of a square that uprightly support the load platform are arranged on the lower platform at both ends of the support seat in the x-axis direction. A first horizontal spring for balancing the displacement in the x-axis direction and a second horizontal spring for balancing the displacement in the y-axis direction are respectively arranged around the upper end of each ball hinge. The first horizontal spring and the second horizontal spring are both hung on the load platform at one end and on the upper platform at the other end.

[0009] Include the following expressions:

[0010]

[0011] where f x is the x-direction natural frequency of the horizontal isolator, k x is the total stiffness of the horizontal spring in the x direction, h is the height of the horizontal spring from the bottom of the ball hinge, m is the load mass, g is the acceleration due to gravity, H is the height of the ball hinge, and f y is the natural frequency of the horizontal isolator in the y direction, k y is the total horizontal spring stiffness in the y direction.

[0012] Include the following expressions:

[0013]

[0014] Where K is the dimensionless total stiffness of the horizontal isolator, is the approximate angular displacement, is the intermediate quantity, k is the horizontal spring stiffness, x is the horizontal spring deformation, and θ is the deflection angle of the ball hinge;

[0015] make and The horizontal vibration isolator achieves zero stiffness in the horizontal direction, that is, the horizontal vibration isolator is in the equilibrium position. At K=0.

[0016] The load platform and the upper platform are both provided with transverse pull plates connected with horizontal springs.

[0017] The support seat comprises a support base plate (71), a support side plate (72) and a support foot (73); a vertical limiting rod (9) is fixed to the side of the load platform (1); a limiting hole (721) is provided at a corresponding position of the support side plate (72); the limiting rod (9) moves only within the limiting hole (721), thereby improving the stability of the system.

[0018] The supporting base plate (71) is provided with a plurality of through holes, and the connecting rod (4) passes through the supporting base plate (71) through the through holes. The two ends of the connecting rod (4) are fixedly connected to the upper platform (5) and the lower platform (3) respectively. The upper platform (5) is connected to the upper end of the vertical spring (6), and the lower end of the vertical spring (6) is fixedly connected to the supporting base plate (71).

[0019] The ball hinge (2) includes a rotating rod (22), the upper end of the rotating rod (22) is an upper ball joint connector (21), the lower end of the rotating rod (22) is a lower ball joint connector (23), the ball joint connector includes a rotating rod ring (231), a support (232), a joint shaft (233) and a pin (234) that are coaxially matched, and the rotating rod (231) is used to achieve full-circumferential swing within a certain range.

[0020] The technical effects of the present invention are as follows:

[0021] 1. The present invention forms an inverted pendulum through a ball hinge to provide horizontal negative stiffness, which is combined with a horizontal positive stiffness spring to achieve quasi-zero stiffness in the horizontal direction, and has a low-frequency vibration isolation effect.

[0022] 2. The present invention makes it easy to adjust the horizontal stiffness by hanging a horizontal spring with appropriate stiffness, and is suitable for quasi-zero stiffness adjustment of different mass loads.

[0023] 3. The present invention utilizes four ball hinges that can swing within a certain range to form an inverted pendulum, and the support seat is provided with a limiting hole, which effectively improves the stability of the system compared with the traditional single inverted pendulum structure.

[0024] 4. The present invention utilizes a bearing structure to transfer the load gravity to the vertical spring, thereby improving the bearing capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure is a structural schematic diagram of a horizontal vibration isolator with adjustable stiffness according to the present invention.

[0026] Figure 2 yes Figure 1 Schematic diagram of the side structure.

[0027] Figure 3 for Figure 1 Schematic diagram of the structure of the ball hinge.

[0028] Figure 4 for Figure 3 Schematic diagram of the exploded structure of the ball joint connection.

[0029] Figure 5 for Figure 1 Bottom-view diagram of the medium-load platform, upper platform, horizontal spring, and ball hinge.

[0030] Figure 6 for Figure 1 Schematic diagram of the support seat structure.

[0031] Figure 7 This is the equivalent kinetic model of the present invention.

[0032] Figure 8 This is the dimensionless stiffness-displacement characteristic curve simulated by the present invention. Figure 8 The vertical axis is the dimensionless system stiffness K (the scale value is 0, 0.2, ···, 0.8, 1), and the horizontal axis is the displacement (Scale values ​​-1, -0.5, 0, 0.5, 1). Figure 8 The middle curve shows that when in equilibrium When , the system stiffness K = 0, that is, zero stiffness is achieved at the equilibrium position.

[0033] The accompanying reference numerals are as follows: 1-load platform; 2-ball hinge; 3-lower platform; 4-connecting rod; 5-upper platform; 6-vertical spring; 7-support seat; 8-horizontal spring; 9-limiting rod; 11-first transverse pull plate; 21-upper ball joint connector; 22-rotation axis; 23-lower ball joint connector; 231-rotation rod ring; 232-support seat; 233-joint axis; 234-pin shaft; 51-second transverse pull plate; 71-support bottom plate; 72-support side plate; 721-limiting hole; 73-support foot; 81-first horizontal spring; 82-second horizontal spring; m-load mass; h-height from horizontal spring to bottom end of ball hinge; H-ball hinge length; θ-ball hinge deflection angle; K-system stiffness; That is, the dimensionless displacement in the x-axis direction approximates the deflection angle θ of the ball hinge. DETAILED DESCRIPTION

[0034] Below is the attached figure ( Figures 1-8 ) and Examples illustrate the present invention.

[0035] Figure 1 The figure is a structural schematic diagram of a horizontal vibration isolator with adjustable stiffness according to the present invention. Figure 2 yes Figure 1 Schematic diagram of the side structure. Figure 3 for Figure 1 Schematic diagram of the structure of the ball hinge. Figure 4 for Figure 3 Schematic diagram of the exploded structure of the ball joint connection. Figure 5 for Figure 1 Bottom-view diagram of the medium-load platform, upper platform, horizontal spring, and ball hinge. Figure 6 for Figure 1 Schematic diagram of the support seat structure. Figure 7 This is the equivalent kinetic model of the present invention. Figure 8This is the dimensionless stiffness-displacement characteristic curve simulated by the present invention. Figures 1 to 8 As shown, a horizontal vibration isolator with adjustable stiffness includes a lower platform 3 provided for a bearing structure below a support seat 7, a load platform 1 covered above an upper platform 5 of the bearing structure, and four ball hinges 2 forming four vertices of a square that uprightly support the load platform 1 are provided on the lower platform 3 at both ends of the support seat in the x-axis direction. A first horizontal spring 81 for balancing the displacement in the x-axis direction and a second horizontal spring for balancing the displacement in the y-axis direction are provided around the upper end of each ball hinge 2. The first horizontal spring and the second horizontal spring are both hung on the load platform 1 at one end and on the upper platform 5 at the other end.

[0036] Include the following expressions:

[0037]

[0038] where f x is the x-direction natural frequency of the horizontal isolator, k x is the total stiffness of the horizontal spring in the x direction, h is the height of the horizontal spring from the bottom of the ball hinge, m is the load mass, g is the acceleration due to gravity, H is the height of the ball hinge, and f y is the natural frequency of the horizontal isolator in the y direction, k y is the total horizontal spring stiffness in the y direction.

[0039] Include the following expressions:

[0040]

[0041] Where K is the dimensionless total stiffness of the horizontal isolator, is the approximate angular displacement, is the intermediate quantity, k is the horizontal spring stiffness, x is the horizontal spring deformation, and θ is the deflection angle of the ball hinge;

[0042] make and The horizontal vibration isolator achieves zero stiffness in the horizontal direction, that is, the horizontal vibration isolator is in the equilibrium position. At K=0.

[0043] Both the load platform 1 and the upper platform 5 are provided with transverse pull plates (11, 51) for hanging horizontal springs.

[0044] The support seat comprises a support base plate (71), a support side plate (72) and a support foot (73); a vertical limiting rod (9) is fixed to the side of the load platform (1); a limiting hole (721) is provided at a corresponding position of the support side plate (72); the limiting rod (9) moves only within the limiting hole (721), thereby improving the stability of the system.

[0045] The supporting base plate (71) is provided with a plurality of through holes, and the connecting rod (4) passes through the supporting base plate (71) through the through holes. The two ends of the connecting rod (4) are fixedly connected to the upper platform (5) and the lower platform (3) respectively. The upper platform (5) is connected to the upper end of the vertical spring (6), and the lower end of the vertical spring (6) is fixedly connected to the supporting base plate (71).

[0046] The ball hinge (2) includes a rotating rod (22), the upper end of the rotating rod (22) is an upper ball joint connector (21), the lower end of the rotating rod (22) is a lower ball joint connector (23), the ball joint connector includes a rotating rod ring (231), a support (232), a joint shaft (233) and a pin (234) that are coaxially matched, and the rotating rod (231) is used to achieve full-circumferential swing within a certain range.

[0047] The present invention discloses a horizontal vibration isolator with adjustable stiffness, comprising: a load platform, a ball hinge, a horizontal spring, a bearing structure, and a support seat. The bearing structure comprises an upper platform, a connecting rod, a vertical spring, and a lower platform. The upper platform and the lower platform are fixedly connected by a connecting rod, and the two ends of the vertical spring are connected to the upper platform and the support seat. The load platform and the bearing mechanism are connected by a ball hinge to form an inverted pendulum structure, which provides negative stiffness. Combined with the positive stiffness horizontal spring, the system has a quasi-zero stiffness characteristic. By adjusting the stiffness of the horizontal spring, low-frequency horizontal vibration isolation can be achieved for loads of different masses.

[0048] A horizontal vibration isolator with adjustable stiffness comprises a load platform (1), a ball hinge (2), a horizontal spring (8), a bearing structure and a support seat, wherein the bearing structure comprises an upper platform (5), a vertical spring (6), a connecting rod (4) and a lower platform (3), and the support seat comprises a supporting bottom plate (71), supporting side plates (72) and supporting feet (73). The horizontal vibration isolator is adjustable in horizontal stiffness by selecting a suitable horizontal spring (8), thereby achieving low-frequency vibration isolation.

[0049] The load platform (1) is connected to the upper end of the ball hinge (2), and the lower end of the ball hinge (2) is connected to the lower platform (3) of the load-bearing structure. The plurality of ball hinges (2) are symmetrically distributed about the central axis of the load platform (1); the support base plate (71) is provided with a plurality of through holes, and the connecting rod (4) passes through the support base plate (71) through the through holes, and the two ends are fixedly connected to the upper platform (5) and the lower platform (3) of the load-bearing structure respectively; the upper platform (5) is connected to the upper end of the vertical spring (6), and the lower end of the vertical spring (6) is fixedly connected to the support base plate (71); the upper platform (5), the vertical spring (6), the connecting rod (4) and the support base plate (71) are all located above the lower platform (3).

[0050] The ball hinge (2) has a height of H, a rotating rod (22) is installed in the middle, and ball joint connectors (21, 23) are provided at both ends; the rotating rod ring (231), the support (232), the joint shaft (233) and the pin shaft (234) of the ball joint connectors (21, 23) are coaxially matched, and the rotating rod (231) can swing in all directions within a certain range.

[0051] Four first transverse pull plates (11) are provided on the side of the load platform (1) in both the x and y directions and are symmetrically distributed. Two first transverse pull plates (11) on the same side are spaced far apart to reduce the influence of angular vibration. Second transverse pull plates (51) are fixed at corresponding positions on the side of the upper platform (5). A horizontal spring (8) is connected between the first transverse pull plates (11) and the second transverse pull plates (51).

[0052] At least four first horizontal springs (81) are provided in the x direction, and the total stiffness is k x At least four second horizontal springs (82) are provided in the y direction, with a total stiffness of k y The height of the horizontal spring from the bottom end of the ball hinge is h. By flexibly increasing, decreasing or replacing the horizontal spring, the low-frequency vibration isolation requirements of different mass loads can be met.

[0053] The support seat comprises a support base plate (71), a support side plate (72) and a support foot (73); a vertical limiting rod (9) is fixed to the side of the load platform (1); a limiting hole (721) is provided at a corresponding position of the support side plate (72); the limiting rod (9) moves only within the limiting hole (721), thereby improving the stability of the system.

[0054] The x-direction natural frequency f of the horizontal vibration isolator with adjustable stiffness is x for Natural frequency f in the y direction y for Where m is the load mass, k x is the total stiffness of the first horizontal spring (81) in the x direction, k y is the total stiffness of the second horizontal spring (82) in the y direction, g is the acceleration of gravity, h is the height of the horizontal spring (8) from the bottom end of the ball hinge (2), and H is the height of the ball hinge (2). When the system satisfies and When , zero stiffness is achieved in the horizontal direction.

[0055] like Figure 1 and Figure 2As shown, the present invention provides a horizontal vibration isolator with adjustable stiffness, comprising: a load platform (1), a ball hinge (2), a horizontal spring (8), a bearing structure and a support base, wherein the bearing structure comprises an upper platform (5), a vertical spring (6), a connecting rod (4) and a lower platform (3), and the support base comprises a supporting bottom plate (71), supporting side plates (72) and supporting feet (73). The horizontal vibration isolator can achieve adjustable horizontal stiffness and low-frequency vibration isolation by selecting a suitable horizontal spring (8). The load platform (1) is connected to the upper end of the ball hinge (2), and the lower end of the ball hinge (2) is connected to the lower platform (3) of the load-bearing structure. The plurality of ball hinges (2) are symmetrically distributed about the central axis of the load platform (1); the support base plate (71) is provided with a plurality of through holes, and the connecting rod (4) passes through the support base plate (71) through the through holes, and the two ends are fixedly connected to the upper platform (5) and the lower platform (3) of the load-bearing structure respectively; the upper platform (5) is connected to the upper end of the vertical spring (6), and the lower end of the vertical spring (6) is fixedly connected to the support base plate (71); the upper platform (5), the vertical spring (6), the connecting rod (4) and the support base plate (71) are all located above the lower platform (3).

[0056] like Figure 3 and Figure 4 As shown, the ball hinge (2) has a height of H, a rotating rod (22) is installed in the middle, and ball joint connectors (21, 23) are provided at both ends; the rotating rod ring (231), the support (232), the joint shaft (233) and the pin (234) of the ball joint connectors (21, 23) are coaxially matched, and the rotating rod (231) can swing in all directions within a certain range.

[0057] like Figure 5 As shown, four first transverse pull plates (11) are provided on the side of the load platform (1) in both the x and y directions, and are symmetrically distributed. The two first transverse pull plates (11) on the same side are relatively far apart to reduce the influence of angular vibration. A second transverse pull plate (51) is fixed at the corresponding position on the side of the upper platform (5). A horizontal spring (8) is connected between the first transverse pull plate (11) and the second transverse pull plate (51). At least four first horizontal springs (81) are provided in the x direction, and the total stiffness is k x At least four second horizontal springs (82) are provided in the y direction, with a total stiffness of k y The height of the horizontal spring from the bottom end of the ball hinge is h. By flexibly increasing, decreasing or replacing the horizontal spring, the low-frequency vibration isolation requirements of different mass loads can be met.

[0058] like Figure 6 As shown, the support seat includes a support base plate (71), a support side plate (72) and a support foot (73); a vertical limiting rod (9) is fixed to the side of the load platform (1); a limiting hole (721) is provided at a corresponding position of the support side plate (72); the limiting rod (9) moves only in the limiting hole (721), thereby improving the stability of the system.

[0059] Due to symmetry, the dynamic model of a horizontal isolator with adjustable stiffness in the x or y direction can be simplified as follows: Figure 7 As shown, the dynamic equation of the horizontal vibration isolator with adjustable stiffness is: Where m is the load mass, k is the total stiffness of the horizontal spring, and in the x direction k = k x , in the y direction k = k y , h is the height from the horizontal spring to the bottom of the ball hinge, H is the length of the ball hinge, θ is the angle of deflection of the ball hinge, represents the second derivative of θ, and x is the horizontal spring deformation.

[0060] Perform a small angle approximation on θ using sinθ≈θ, cosθ≈1, and we can get:

[0061] The root r of the corresponding differential equation is:

[0062] When kh 2 When -mgH>0, the isolator vibrates stably and its natural frequency f is: For different mass loads m, the natural frequency of the system can be reduced by adjusting the stiffness k of the horizontal spring.

[0063] Further solving the stiffness-displacement characteristics of the vibration isolator, the moment M is:

[0064] Make the above formula dimensionless and let Then there is right The equivalent stiffness K of the isolator is obtained by differentiation: Therefore, the stiffness of the isolator can be adjusted by designing the height h from the horizontal spring to the bottom end of the ball hinge, the ball hinge length H and the horizontal spring stiffness k.

[0065] Draw the dimensionless stiffness-displacement characteristic curve of the system as Figure 8 As shown in the simulation results, the vibration isolator can achieve quasi-zero stiffness and is suitable for isolating low-frequency vibrations. At this point, let the isolator stiffness K = 0, and we get That is, when the system satisfies At the equilibrium position Zero stiffness is achieved.

[0066] Any content not described in detail in this specification is prior art known to those skilled in the art. It should be noted that the above description is intended to help those skilled in the art understand the present invention, but does not limit the scope of protection of the present invention. Any equivalent substitution, modification, improvement, and / or simplification of the above description that does not depart from the essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A horizontal vibration isolator with adjustable stiffness, characterized in that: The invention comprises a lower platform provided for the bearing structure below the support base, a load platform covering the upper platform of the bearing structure, four ball hinges forming four vertices of a square and supporting the load platform at both ends of the lower platform in the x-axis direction of the support base, a first horizontal spring balancing displacement in the x-axis direction and a second horizontal spring balancing displacement in the y-axis direction are provided around the upper end of each ball hinge, one end of each of the first and second horizontal springs being hung on the load platform and the other end being hung on the upper platform; The following expression is used to determine the When the x-direction is zero stiffness, Zero stiffness is achieved in the y direction when: , where f x is the x-direction natural frequency of the horizontal isolator, k x is the total stiffness of the horizontal spring in the x direction, h is the height of the horizontal spring from the bottom end of the ball hinge, m is the load mass, g is the acceleration due to gravity, H is the height of the ball hinge, and f y is the natural frequency of the horizontal isolator in the y direction, k y is the total horizontal spring stiffness in the y direction; The following expression is used to determine the height h from the horizontal spring to the bottom of the ball hinge, the ball hinge length H and the horizontal spring stiffness k, which can be used to adjust the stiffness of the vibration isolator. Time At K=0, the horizontal vibration isolator is in the equilibrium position Zero stiffness at: , Where K is the dimensionless total stiffness of the horizontal isolator, is the approximate angular displacement, is the intermediate quantity, k is the horizontal spring stiffness, x is the horizontal spring deformation, and θ is the deflection angle of the ball hinge.

2. The horizontal vibration isolator with adjustable stiffness according to claim 1, characterized in that: The load platform and the upper platform are both provided with transverse pull plates connected with horizontal springs.

3. The horizontal vibration isolator with adjustable stiffness according to claim 1, characterized in that: The support seat comprises a support base plate (71), a support side plate (72) and a support foot (73); a vertical limiting rod (9) is fixed to the side of the load platform (1); a limiting hole (721) is provided at a corresponding position of the support side plate (72); the limiting rod (9) moves only within the limiting hole (721), thereby improving the stability of the system.

4. The horizontal vibration isolator with adjustable stiffness according to claim 3, characterized in that: The supporting base plate (71) is provided with a plurality of through holes, and the connecting rod (4) passes through the supporting base plate (71) through the through holes. The two ends of the connecting rod (4) are fixedly connected to the upper platform (5) and the lower platform (3), respectively. The upper platform (5) is connected to the upper end of the vertical spring (6), and the lower end of the vertical spring (6) is fixedly connected to the supporting base plate (71).

5. The horizontal vibration isolator with adjustable stiffness according to claim 1, characterized in that: The ball hinge (2) includes a rotating rod (22), the upper end of the rotating rod (22) is an upper ball joint connecting part (21), and the lower end of the rotating rod (22) is a lower ball joint connecting part (23). The ball joint connecting part includes a rotating rod ring (231), a support (232), a joint shaft (233) and a pin (234) that are coaxially matched. The rotating rod (231) is used to achieve full-circumferential swing within a certain range.

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