An air-floating large-load low-rigidity vibration isolation structure and design method

Abstract

An air-floating, large-load, low-rigidity vibration isolation structure and design method. The present invention aims to solve the problem of how to effectively control and isolate tiny vibrations in ultra-precision machining, aerospace technology, and microelectronics manufacturing. The present invention includes an upper isolator plate, a lower isolator plate, and an inner cavity of the isolator. The inner cavity of the isolator is located between the upper isolator plate and the lower isolator plate, and the upper end of the inner cavity of the isolator is connected to the middle of the lower surface of the upper isolator plate through a rotating member. The present invention comprehensively utilizes the advantages of air-floating supports and air springs, taking into account the characteristics of large loads and low stiffness in the vertical direction, achieving zero stiffness in the radial direction, and having extremely high passive vibration isolation value; taking into account the advantages of large load capacity, extremely low stiffness, and high vibration isolation efficiency, it can meet the vibration isolation needs of large-load systems. The present invention belongs to the field of precision instrument vibration isolation control technology.

Description

Technical Field

[0001] The invention relates to an air-floating large-load low-rigidity vibration isolation structure and a design method thereof, and belongs to the technical field of precision instrument vibration isolation control. Background Art

[0002] With the development of precision machining, precision measurement, and aerospace technology, more stringent requirements are being placed on the dynamic stability and vibration resistance of mechanical structures, the accuracy of ultra-fine testing and machining, and the scientific experimental environment. In particular, some ultra-precision machining equipment and microelectronics equipment have increasingly stringent requirements for micro-vibration prevention. The control and isolation of micro-vibrations has become a bottleneck for many cutting-edge scientific applications.

[0003] Since the 1970s, microelectronics technology has been developing towards large-scale and ultra-large-scale integrated circuits, and its circuit integration has been continuously improved [1]. In particular, from 2001 to 2010, the wafer size in advanced semiconductor processes increased from 150mm to 300mm, while the line feature size decreased from 130nm to 45nm, and the relative measurement uncertainty of the workpiece position measurement link increased from 10-7 to 10 -8 The semiconductor manufacturing industry is projected to reach 28nm in line width by 2012. Achieving these precision requirements invariably relies on micro-vibration isolation technology and devices. In the aerospace industry, the requirements for dimensions and precision in the processing, assembly, and testing of related equipment and equipment are becoming increasingly stringent. These precision requirements have moved from microns to hundreds of nanometers, significantly increasing the uncertainty requirements for measurement, sometimes even requiring nanometer and sub-nanometer precision. For example, the machining of parabolic mirrors for large astronomical telescopes requires maximum dimensions of several meters, while surface accuracy must exceed λ / 10 and geometric shape error must be less than 0.05μm. In 1984, the LOD™ large optical diamond turning lathe, recognized as the world's most accurate, was launched. Jointly developed by the Lawrence Livemore Laboratory and the Air Force's III Wright Aeronautical Research Institute in the United States, it is primarily used for machining large optical lenses used in laser fusion. Its machining accuracy for a 1.625m large astronomical telescope can reach 0.025μm. The vibration reduction technology of the LODTM lathe uses a granite base, air vibration pads, a separate foundation and other technologies to ensure the high precision requirements of machining.

[0004] As an essential core component for precision machining, precision measurement, precision experiments, etc., vibration isolation equipment with significant vibration isolation effect will become one of the core technologies for improving the information equipment industry. According to linear vibration theory, when the excitation frequency exceeds the natural frequency of the system, times, the linear vibration isolation system can effectively isolate low-frequency vibrations from the foundation. Therefore, reducing the system's natural frequency can improve vibration isolation performance. This can be achieved by reducing system stiffness or increasing the system's effective load mass, but this will weaken the load capacity and stability of the vibration isolation system. There is a mutually restrictive relationship between the two, so a design trade-off between the two is inevitable. Summary of the Invention

[0005] The present invention aims to solve the problem of how to effectively control and isolate tiny vibrations in ultra-precision machining, aerospace technology and microelectronics manufacturing, and further proposes an air-floating large-load low-rigidity vibration isolation structure and a design method.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] The present invention comprises an isolator upper plate, a isolator lower plate and an isolator inner cavity. The isolator inner cavity is located between the isolator upper plate and the isolator lower plate, and the upper end of the isolator inner cavity is connected to the middle of the lower surface of the isolator upper plate through a rotating member.

[0008] Furthermore, the inner cavity of the vibration isolator includes an inner cylinder and an outer cylinder, which are arranged from inside to outside, and the upper end of the inner cylinder is connected to the upper plate of the vibration isolator through a rotating member.

[0009] Furthermore, the rotating part includes a rubber hinge, an upper ejector pin and a lower ejector pin, the upper end of the rubber hinge is connected to the lower surface of the isolator upper plate through the upper ejector pin, and the lower end of the rubber hinge is connected to the upper end of the isolator inner cylinder through the lower ejector pin.

[0010] Furthermore, the rotating member is a bowl bearing.

[0011] Furthermore, an outer cylinder air hole is provided at the lower portion of the outer cylinder of the vibration isolator.

[0012] Furthermore, an inner cylinder ring belt is provided at the lower portion of the inner cylinder of the vibration isolator.

[0013] Furthermore, radial air flotation holes are provided on the side wall of the inner cylinder of the vibration isolator; and vertical air flotation holes are provided on the bottom of the outer cylinder of the vibration isolator.

[0014] Furthermore, an air inlet hole is provided on the lower plate of the vibration isolator.

[0015] A design method for an air-floating large-load low-rigidity vibration isolation structure comprises the following steps:

[0016] Step 1: Determine the load mass m and vertical natural frequency w of the vibration isolation system;

[0017] Step 2: Calculate the vertical stiffness of the isolator cavity based on the natural frequency and load mass. The relationship between the three is as follows:

[0018] (1.1)

[0019] Where m is the load mass, w is the vertical natural frequency, and K is the vertical stiffness;

[0020] Step 3: Determine the specific parameters of the inner cavity of the vibration isolator based on the stiffness of the inner cavity of the vibration isolator. The stiffness formula of the inner cavity of the vibration isolator is expressed as follows:

[0021] (1.2)

[0022] Where A is the effective area of ​​the isolator cavity, V0 is the volume of the air chamber in the isolator cavity, K is the gas constant, P atm is atmospheric pressure;

[0023] Step 4: Design the shape and size of the outer wall of the inner cavity of the vibration isolator and the shape and size of the inner wall of the outer cavity of the vibration isolator according to the determined inner cavity area of ​​the vibration isolator, and reasonably design the internal shape of the inner cavity of the vibration isolator and the external shape of the outer cavity of the vibration isolator;

[0024] Step 5: Calculate the stiffness range of the isolator's inner cavity under different expansion chamber volumes based on the specific dimensions of the design, and then calculate the system's natural frequency to see if it meets the usage requirements. If not, further reduce the effective area A of the isolator's inner cavity and redesign Step 3.

[0025] Step 6: Design the external structure.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention adopts a structure in which a non-contact air-floating support is combined with an inner cavity of a vibration isolator in series;

[0028] 2. The axial stiffness of the inner cavity of the vibration isolator of the present invention is extremely low, which can ensure the load capacity and low stiffness of the vibration isolator;

[0029] 3. This passive air-floating shock absorber comprehensively utilizes the advantages of air-floating support and air spring, taking into account the characteristics of large load and low stiffness in the vertical direction, and achieving zero stiffness in the radial direction, with extremely high passive vibration isolation value;

[0030] 4. The present invention combines the advantages of large load capacity, extremely low stiffness and high vibration isolation efficiency, and can meet the vibration isolation requirements of large load systems. At the same time, its radial theoretical stiffness is close to zero. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural diagram of the first embodiment of the present invention;

[0032] Figure 2 It is a structural diagram of the second embodiment of the present invention. DETAILED DESCRIPTION

[0033] Specific implementation method 1: Combination Figure 1 This embodiment is described. This embodiment includes a vibration isolator upper plate 1, a vibration isolator lower plate 2, a vibration isolator inner cylinder 3, a vibration isolator outer cylinder 4, a rubber hinge 5, an upper ejector pin 6, and a lower ejector pin 7. The vibration isolator inner cylinder 3 and the vibration isolator outer cylinder 4 are arranged from the inside to the outside and are located between the vibration isolator upper plate 1 and the vibration isolator lower plate 2. The middle part of the lower surface of the vibration isolator upper plate 1 is connected to the upper end of the vibration isolator inner cylinder 3 through the rubber hinge 5.

[0034] Preferably, the upper end of the rubber hinge 5 is connected to the lower surface of the isolator upper plate 1 through an upper ejector pin 6 , and the lower end of the rubber hinge 5 is connected to the upper end of the isolator inner cylinder 3 through a lower ejector pin 7 .

[0035] Preferably, the lower portion of the vibration isolator outer cylinder 4 is provided with an outer cylinder air hole 4-1, the lower portion of the vibration isolator inner cylinder 3 is provided with an inner cylinder ring belt 3-1, and the vibration isolator lower plate 2 is provided with an air inlet hole 2-1.

[0036] The inner cylinder annular band 3-1 is used to collect the gas released from the annular air film and release it to the external environment through the outer cylinder air hole to prevent the released gas from interfering with the movement of the vibration isolator inner cylinder 3. Its cross section is not limited to a rectangle.

[0037] The shapes of the outer wall of the vibration isolator inner cylinder 3, the inner wall of the vibration isolator outer cylinder 4 and the main air chamber structure in the vibration isolator inner cylinder 3 are not limited to the following Figure 1 The cylindrical shape shown may also be other symmetrical shapes, in particular an equilateral polygonal cylinder, provided that the center of gravity and the vertical principal axis of inertia of the inner cylinder 3 and the outer cylinder 4 of the vibration isolator are collinear.

[0038] This device forms static air flotation surfaces between the inner wall of the isolator's outer cylinder 4 and the outer wall of the isolator's inner cylinder 3, and between the upper surface of the isolator's lower plate 2 and the lower surface of the isolator's outer cylinder 4 base. The air films typically have a thickness of approximately 7 μm. Both of these static air flotation structures are inflated by gas from the main air chamber through flotation holes in the side walls of the isolator's inner cylinder 3 and the base of the isolator's outer cylinder 4, respectively. Gas entering the annular air film between the inner wall of the isolator's outer cylinder 4 and the outer wall of the isolator's inner cylinder 3 is discharged to the outside through the gap between the outer wall of the isolator's outer cylinder 4 and the upper structure, as well as through the outer cylinder air holes in the isolator's outer cylinder 4. Gas entering the bottom air film 10 between the upper surface of the isolator's lower plate 2 and the lower surface of the isolator's outer cylinder 4 base directly overflows through the flotation gap, forming a complete gas flow cycle.

[0039] Specific implementation method 2: Combination Figure 2To illustrate this embodiment, this embodiment includes a vibration isolator upper plate 1, a vibration isolator lower plate 2, a vibration isolator inner cylinder 3, a vibration isolator outer cylinder 4, and a ball bowl bearing 8. The vibration isolator inner cylinder 3 and the vibration isolator outer cylinder 4 are arranged from the inside to the outside and are located between the vibration isolator upper plate 1 and the vibration isolator lower plate 2. The middle part of the lower surface of the vibration isolator upper plate 1 is connected to the upper end of the vibration isolator inner cylinder 3 through the ball bowl bearing 8.

[0040] The function of the ball bowl bearing is to ensure the vertical load and horizontal freedom between the inner cylinder 3 of the vibration isolator and the upper top plate. It is not limited to the ball bowl bearing, and other hinges can also be used to achieve the same purpose.

[0041] Preferably, radial air flotation holes 3-1 are provided on the sidewall of the inner cylinder 3 of the vibration isolator; vertical air flotation holes 4-2 are provided on the bottom of the outer cylinder 4 of the vibration isolator; and an air inlet hole 2-1 is provided on the lower plate 2 of the vibration isolator.

[0042] The vibration isolation structure can be roughly divided into three parts: the air chamber structure, the thrust bearing-like structure, and the radial air bearing structure. Ideally, the air chamber pressure remains stable, and these structures work together to make the system extremely stiff in the vertical direction and zero stiffness in the horizontal direction.

[0043] In the vibration isolation system, the upper plate 1 of the vibration isolator is connected to the isolated platform via screws, while the lower plate 2 of the vibration isolator is fixed to the foundation. The enclosed space formed by the inner and outer cylinders 3 and 4 of the vibration isolator constitutes the main air chamber of the device's air spring structure. During operation, clean air continuously enters the main air chamber and the external expansion chamber through the air inlet holes of the lower plate 2, maintaining the inner cylinder 3 suspended at the specified operating height and replenishing the air lost in the main air chamber due to static pressure flotation.

[0044] Specific implementation method three: Combination Figure 1 and Figure 2 This embodiment describes a design method for an air-floating, high-load, low-rigidity vibration isolation structure, which is characterized by comprising the following steps:

[0045] Step 1: Determine the load mass m and vertical natural frequency w of the vibration isolation system (based on the frequency band of the ambient vibration signal to be isolated);

[0046] Step 2: Calculate the vertical stiffness of the isolator cavity based on the natural frequency and load mass. The relationship between the three is as follows:

[0047] (1.1)

[0048] Where m is the load mass, w is the vertical natural frequency, and K is the vertical stiffness;

[0049] Step 3: Determine the specific parameters of the inner cavity of the vibration isolator based on the stiffness of the inner cavity of the vibration isolator. The stiffness formula of the inner cavity of the vibration isolator is expressed as follows:

[0050] (1.2)

[0051] Where A is the effective area of ​​the inner cavity of the vibration isolator. Figure 1 Where is the outer circle area of ​​the inner cylinder of the vibration isolator (or the inner wall cross-sectional area of ​​the outer cavity of the vibration isolator), V0 is the volume of the air chamber in the inner cavity of the vibration isolator, which can be calculated according to the size of the auxiliary air chamber during the initial design. The volume of the auxiliary air chamber is generally between 5-30L, K is the gas constant, P atm is atmospheric pressure;

[0052] Step 4: Design the shape and size of the outer wall of the inner cavity of the vibration isolator and the shape and size of the inner wall of the outer cavity of the vibration isolator according to the determined inner cavity area of ​​the vibration isolator, and reasonably design the internal shape of the inner cavity of the vibration isolator and the external shape of the outer cavity of the vibration isolator;

[0053] Step 5: Calculate the stiffness range of the isolator's inner cavity under different expansion chamber volumes based on the specific dimensions of the design, and then calculate the system's natural frequency to see if it meets the usage requirements. If not, further reduce the effective area A of the isolator's inner cavity and redesign Step 3.

[0054] Step 6: Design the external structure, which includes the upper plate of the vibration isolator, the lower plate of the vibration isolator, the rubber bearing, the ball bowl bearing (or flexible hinge) and other matching structures.

[0055] Working principle:

[0056] The designed vibration isolation structure's vertical stiffness is equal to the series stiffness of the isolator's inner cavity and the bottom air membrane 10. Similarly, the horizontal stiffness is equal to the series stiffness of the annular air membrane 9 and the bottom air membrane 10. The advantage of this structure is that the vertical stiffness of the isolator's inner cavity is much smaller than that of the bottom air membrane 10, resulting in a vertical stiffness approximately equal to that of an air spring. The theoretical horizontal stiffness of the bottom air membrane 10 is zero, far smaller than the horizontal stiffness of the annular air membrane 9, resulting in a theoretical zero horizontal stiffness.

[0057] Specifically, the annular air membrane 9 only applies radial force to the isolator's inner cylinder 3, constraining its horizontal movement. Vertically, the annular air membrane 9 prevents mechanical contact between the isolator's inner cylinder 3 and the outer cylinder 4, allowing the isolator's inner cylinder 3 to float within the outer cylinder 4 and move freely up and down. Without friction between the inner and outer walls of the isolator's inner cylinder 3 and outer cylinder 4, the system's vertical stiffness and damping characteristics are entirely determined by the main air chamber within the isolator's inner cylinder 3. Ideally, assuming extremely high system air replenishment efficiency, the pressure changes within the main air chamber caused by the movement of the isolator's inner cylinder 3 are negligible, meaning the pressure in the main air chamber remains constant. In this scenario, the buoyancy force exerted by the gas within the main air chamber on the isolator's inner cylinder 3 is balanced by the weight of the load, resulting in the system's vertical stiffness approaching zero, and ground vibration interference is completely isolated and filtered out of the system.

[0058] In actual applications, the air pressure in the main air chamber cannot remain absolutely stable. When the isolator's inner cylinder 3 moves vertically due to vibration, the volume of the main air chamber within it continuously changes. Assuming this change occurs instantaneously, before the system's air circuit has time to replenish gas from the outside, and with the gas temperature unchanged, the ideal gas state equation shows that as the air chamber volume changes, the internal gas pressure also changes inversely. Consequently, the vertical load and support forces in the system are no longer balanced. The resulting force acts on the platform to generate a restoring force, and the system's vertical stiffness is no longer zero. Its effect can be approximated by the stiffness of the isolator's inner cavity. Since air chamber stiffness is inversely proportional to its volume, increasing its volume can reduce the system's stiffness and enhance its vibration damping performance. This approach not only reduces system stiffness but also stabilizes the effects of pressure fluctuations caused by the refill process. The main and auxiliary air chambers are connected by an air pipe. This pipe acts as a roughly throttle orifice in the system, determining the system's damping characteristics. During operation, the air flow system continuously replenishes the main and auxiliary air chambers to compensate for the loss of air due to the static pressure flotation structure. As the air flows between the two chambers, it generates heat and loses a certain amount of mechanical energy as it passes through the orifice due to resistance. The greater the flow rate, the faster the energy loss and the greater the damping of the structure.

[0059] On the other hand, the system forms a bottom static pressure air film between the upper surface of the isolator lower plate 2 and the lower surface of the base plate of the isolator outer cylinder 4. This air film suspends the isolator outer cylinder 4 above the isolator lower plate 2, and the radial stiffness of the air film is negligible, resulting in very low radial stiffness of the system. In practice, the system's radial stiffness is primarily caused by the horizontal tilting force component generated by the rubber hinge on the isolator inner cylinder 3. Therefore, when the isolator outer cylinder 4 and the isolator inner cylinder 3 are near their operating positions, the system's horizontal stiffness is approximately zero. The vertical stiffness of the bottom air film 10, however, is relatively large. Since it is connected in series with the main air chamber in the system, and the main air chamber's stiffness is much smaller than that of the bottom air film 10, the system's vertical stiffness can be approximately equal to that of the main air chamber.

[0060] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement of the above embodiments made according to the technical essence of the present invention, within the spirit and principles of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A design method for an air-floating, high-load, low-rigidity vibration isolation structure, characterized in that: It includes the following steps: Step 1: Determine the load mass m and vertical natural frequency w of the vibration isolation system; Step 2: Calculate the vertical stiffness of the isolator cavity based on the natural frequency and load mass. The relationship between the three is as follows: (1.1) Where m is the load mass, w is the vertical natural frequency, and K is the vertical stiffness; Step 3: Determine the specific parameters of the inner cavity of the vibration isolator based on the stiffness of the inner cavity of the vibration isolator. The stiffness formula of the inner cavity of the vibration isolator is expressed as follows: (1.2) Where A is the effective area of ​​the isolator cavity, V0 is the volume of the air chamber in the isolator cavity, which can be calculated according to the size of the auxiliary air chamber during the initial design. The volume of the auxiliary air chamber is between 5-30L, K is the gas constant, and P atm is atmospheric pressure; Step 4: Design the shape and size of the outer wall of the inner cavity of the vibration isolator and the shape and size of the inner wall of the outer cavity of the vibration isolator according to the determined inner cavity area of ​​the vibration isolator, and reasonably design the internal shape of the inner cavity of the vibration isolator and the external shape of the outer cavity of the vibration isolator; Step 5: Calculate the stiffness range of the isolator's inner cavity under different expansion chamber volumes based on the specific dimensions of the design, and then calculate the system's natural frequency to see if it meets the usage requirements. If not, further reduce the effective area A of the isolator's inner cavity and redesign step 3. Step 6: Designing an external structure, wherein the external structure includes an upper vibration isolator plate (1), a lower vibration isolator plate (2), and an inner vibration isolator cavity, wherein the inner vibration isolator cavity is located between the upper vibration isolator plate (1) and the lower vibration isolator plate (2), and the upper end of the inner vibration isolator cavity is connected to the middle portion of the lower surface of the upper vibration isolator plate (1) through a rotating member; The inner cavity of the vibration isolator includes an inner cylinder (3) and an outer cylinder (4) of the vibration isolator, the inner cylinder (3) and the outer cylinder (4) of the vibration isolator are arranged from the inside to the outside, and the upper end of the inner cylinder (3) of the vibration isolator is connected to the upper plate (1) of the vibration isolator through a rotating member; The rotating part comprises a rubber hinge (5), an upper ejector pin (6) and a lower ejector pin (7); the upper end of the rubber hinge (5) is connected to the lower surface of the upper plate (1) of the vibration isolator via the upper ejector pin (6); the lower end of the rubber hinge (5) is connected to the upper end of the inner cylinder (3) of the vibration isolator via the lower ejector pin (7); the side wall of the inner cylinder (3) of the vibration isolator is provided with radial flotation holes (3-1); and the bottom of the outer cylinder (4) of the vibration isolator is provided with vertical flotation holes (4-2).

2. The design method of an air-floating high-load low-rigidity vibration isolation structure according to claim 1 is characterized by: The rotating part is a ball bowl bearing (8).

3. The design method of an air-floating high-load low-rigidity vibration isolation structure according to claim 2 is characterized by: An outer cylinder air hole (4-1) is provided at the lower portion of the vibration isolator outer cylinder (4).

4. The design method of an air-floating high-load low-rigidity vibration isolation structure according to claim 2 is characterized by: An inner cylinder ring belt (3-1) is provided at the lower portion of the vibration isolator inner cylinder (3).

5. The design method of an air-floating high-load low-rigidity vibration isolation structure according to claim 1 is characterized in that: An air inlet hole (2-1) is provided on the lower plate (2) of the vibration isolator.

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