Rigidity-adjustable horizontal vibration isolator

Abstract

A rigidity-adjustable horizontal vibration isolator can solve the problems that the horizontal rigidity of an existing passive vibration isolator is not easy to adjust, the bearing range is limited, and the low-frequency vibration isolation effect is poor, and is characterized in that the rigidity-adjustable horizontal vibration isolator comprises a lower platform arranged for a bearing structure below a supporting base, and a load platform covers the upper portion of an upper platform of the bearing structure; four spherical hinges forming four vertexes of a square and vertically supporting the load platform are arranged on the lower platform at the two ends of the supporting seat in the x-axis direction, and a first horizontal spring for balancing displacement in the x-axis direction and a second horizontal spring for balancing displacement in the y-axis direction are arranged on the periphery of the upper end of each spherical hinge; one end of the first horizontal spring and one end of the second horizontal spring are hung on the load platform, and the other end of the first horizontal spring and the other end of the second horizontal spring are hung on the upper platform.

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 to 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, The vibration isolation effect is achieved only when the vibration is multiple times greater than that of the original vibration. Therefore, to achieve the isolation of low-frequency vibration, it is necessary to reduce the natural frequency of the system. An effective method is to achieve quasi-zero stiffness by connecting positive stiffness and negative stiffness structures in parallel. Some related studies are as follows:

[0003] The invention patent with publication number CN 111677799 A, entitled "Three-degree-of-freedom electromagnetic vibration isolator based on horizontal pre-compression spring", realizes three-degree-of-freedom electromagnetic vibration isolation by connecting a magnetic spring in parallel with four horizontal pre-compression springs evenly distributed along the circumference, and at the same time realizes a high utilization rate of magnetic materials and a structural design without a guide mechanism. However, the vibration isolation system is easily disturbed by the external magnetic field, and it is not convenient to adjust the stiffness to achieve quasi-zero according to different load masses.

[0004] The invention patent with publication number CN 115388117 A, entitled "quasi-zero vibration isolator in horizontal direction", uses the inverted pendulum to provide negative stiffness, the beam group to provide positive stiffness, and adjusts the ratio of the first and second sections of the inverted pendulum to achieve zero-frequency vibration isolation in the full circumference direction of the load horizontally. The additional damping is small, and high-precision horizontal vibration isolation can be achieved. However, the use of a single inverted pendulum structure reduces the stability of the system and limits the load-bearing range.

[0005] The existing quasi-zero stiffness isolators are not easy to adjust in terms of stiffness and have a limited load range, making it difficult to meet the ultra-low frequency vibration isolation requirements of different loads. The present invention proposes a horizontal vibration isolator with adjustable stiffness, which aims to adjust the horizontal stiffness to quasi-zero, thereby reducing the natural frequency of the vibration 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, an object of the present invention is to provide a horizontal vibration isolator with adjustable stiffness, which can solve the problems of difficult adjustment of horizontal stiffness, limited load range and poor low-frequency vibration isolation effect of existing passive vibration isolators.

[0007] The technical solution of the present invention is as follows:

[0008] A horizontal vibration isolator with adjustable stiffness, characterized in that it includes a lower platform arranged for a bearing structure below a support seat, a load platform covering an upper platform of the bearing structure, four ball hinges forming four vertices of a square and uprightly supporting 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, and one end of the first horizontal spring and the second horizontal spring are both hung on the load platform and the other end is hung on the upper platform.

[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 limit rod (9) is fixed to the side of the load platform (1); a limit hole (721) is arranged at a corresponding position of the support side plate (72); the limit rod (9) moves only within the limit hole (721), thereby improving the stability of the system.

[0018] 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. The two ends of the connecting rod (4) are respectively fixedly connected to the upper platform (5) and the lower platform (3). 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).

[0019] The ball hinge (2) comprises a rotating rod (22), the upper end of the rotating rod (22) is an upper ball joint connecting part (21), the lower end of the rotating rod (22) is a lower ball joint connecting part (23), the ball joint connecting part comprises a rotating rod ring (231), a support (232), a joint shaft (233) and a pin shaft (234) which are coaxially matched, and the rotating rod (231) is used to realize full-circle 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 the 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 present invention is a schematic structural diagram of a horizontal vibration isolator with adjustable stiffness.

[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 of the medium load platform, upper platform, horizontal spring and ball hinge.

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

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

[0032] Figure 8 It is the dimensionless stiffness-displacement characteristic curve realized by simulation of 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 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; 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 ( Figure 1-Figure 8 ) and Examples illustrate the present invention.

[0035] Figure 1 The present invention is a schematic structural diagram of a horizontal vibration isolator with adjustable stiffness. 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 of the medium load platform, upper platform, horizontal spring and ball hinge. Figure 6 for Figure 1 Schematic diagram of the support base structure. Figure 7 It 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 arranged for a bearing structure below a support seat 7, a load platform 1 covering an upper platform 5 of the bearing structure, four ball hinges 2 forming four vertices of a square and uprightly supporting the load platform 1 are arranged on the lower platform 3 at both ends of the support seat in the x-axis direction, and 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 respectively arranged around the upper end of each ball hinge 2, and one end of the first horizontal spring and the second horizontal spring are both hung on the load platform 1 and the other end is hung on the upper platform 5.

[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 limit rod (9) is fixed to the side of the load platform (1); a limit hole (721) is arranged at a corresponding position of the support side plate (72); the limit rod (9) moves only within the limit hole (721), thereby improving the stability of the system.

[0045] 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. The two ends of the connecting rod (4) are respectively fixedly connected to the upper platform (5) and the lower platform (3). 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).

[0046] The ball hinge (2) comprises a rotating rod (22), the upper end of the rotating rod (22) is an upper ball joint connecting part (21), the lower end of the rotating rod (22) is a lower ball joint connecting part (23), the ball joint connecting part comprises a rotating rod ring (231), a support (232), a joint shaft (233) and a pin shaft (234) which are coaxially matched, and the rotating rod (231) is used to realize full-circle 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, and the horizontal spring stiffness is adjusted to achieve low-frequency horizontal vibration isolation for different mass loads.

[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), a supporting side plate (72) and a supporting foot (73). The horizontal vibration isolator can achieve low-frequency vibration isolation by selecting a suitable horizontal spring (8) so that the horizontal stiffness is adjustable.

[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 respectively fixedly connected to the upper platform (5) and the lower platform (3) of the load-bearing structure; 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 arranged 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 arranged on the side of the load platform (1) in the x and y directions and are symmetrically distributed. Two first transverse pull plates (11) on the same side are far apart to reduce the influence of angular vibration. A second transverse pull plate (51) is fixed at a corresponding position on the side of the upper platform (5). A horizontal spring (8) is hung between the first transverse pull plate (11) and the second transverse pull plate (51).

[0052] At least four first horizontal springs (81) are arranged in the x direction, and the total stiffness is k x At least four second horizontal springs (82) are arranged in the y direction, and the total stiffness is 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 bottom plate (71), a support side plate (72) and a support foot (73); a vertical limit rod (9) is fixed to the side of the load platform (1); a limit hole (721) is arranged at a corresponding position of the support side plate (72); the limit rod (9) moves only in the limit 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 in y direction f 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 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 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), a supporting side plate (72) and a supporting foot (73). The horizontal vibration isolator can achieve low-frequency vibration isolation by selecting a suitable horizontal spring (8) so that the horizontal stiffness is adjustable. 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 respectively fixedly connected to the upper platform (5) and the lower platform (3) of the load-bearing structure; 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 arranged 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.

[0057] like Figure 5 As shown, four first transverse pull plates (11) are arranged in the x and y directions on the side of the load platform (1), which are symmetrically distributed. The two first transverse pull plates (11) on the same side are far apart to reduce the influence of angular vibration. A second transverse pull plate (51) is fixed at a corresponding position on the side of the upper platform (5). A horizontal spring (8) is hung between the first transverse pull plate (11) and the second transverse pull plate (51). At least four first horizontal springs (81) are arranged in the x direction, and the total stiffness is k x At least four second horizontal springs (82) are arranged in the y direction, and the total stiffness is 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 comprises a support base plate (71), a support side plate (72) and a support foot (73); a vertical limit rod (9) is fixed to the side of the load platform (1); a limit hole (721) is provided at a corresponding position of the support side plate (72); the limit rod (9) moves only in the limit 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 deflection angle of the ball hinge, represents the second derivative of θ, and x is the horizontal spring deformation.

[0060] Apply small angle approximation to θ: sinθ≈θ, cosθ≈1, and we get:

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

[0062] When 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] Non-dimensionalize the above formula and let Then there is right The equivalent stiffness K of the isolator is obtained by taking the derivative: Therefore, the stiffness of the vibration isolator can be adjusted by designing 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.

[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, let the vibration isolator stiffness K = 0, and we get That is, when the system satisfies At the equilibrium position Zero stiffness is achieved.

[0066] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

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

2. The horizontal vibration isolator with adjustable stiffness according to claim 1, characterized in that: Include the following expressions: 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.

3. The horizontal vibration isolator with adjustable stiffness according to claim 1, characterized in that: Include the following expressions: 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; 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.

4. 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.

5. 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 limit rod (9) is fixed to the side of the load platform (1); a limit hole (721) is arranged at a corresponding position of the support side plate (72); the limit rod (9) moves only within the limit hole (721), thereby improving the stability of the system.

6. The horizontal vibration isolator with adjustable stiffness according to claim 5, characterized in that: 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. The two ends of the connecting rod (4) are respectively fixedly connected to the upper platform (5) and the lower platform (3). 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).

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

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