Adjustable magnetic preloading static pressure air floating cushion

Abstract

The invention discloses an adjustable magnetic force preloading static pressure air floating cushion, and relates to the technical field of air floating transmission, the adjustable magnetic force preloading static pressure air floating cushion comprises a floating cushion frame, a ferromagnetic material iron plate and a permanent magnet, the ferromagnetic material iron plate is installed on a base load plane, the air floating cushion frame is arranged above the ferromagnetic material iron plate, the bottom surface of the air floating cushion frame is an air floating surface, and the permanent magnet is installed on the ferromagnetic material iron plate. The ferromagnetic material iron plate and the permanent magnet are arranged in the air floating surface and the air floating cushion frame, an air flow channel is arranged in the air floating surface and the air floating cushion frame, and when air is supplied into the air flow channel, an air film gap is formed between the air floating surface and the ferromagnetic material iron plate, the ferromagnetic material iron plate and the permanent magnet with the adjustable position are arranged in the air floating cushion, and the position of the permanent magnet is adjusted through the differential thread mechanism; according to the air floating cushion, the magnetic force is used for changing the distance between the magnetic force and the motion surface, fine adjustment of the preloading force is achieved, an air film rigidity curve obtained through CFD simulation is referred, compared with a traditional preloading mode, the air floating cushion can achieve the optimal rigidity under different working conditions, and adjustment is convenient and accurate.

Description

Technical Field

[0001] The invention relates to the technical field of air floating transmission, and in particular to an adjustable magnetic preload static pressure air floating cushion. Background Art

[0002] At present, the application of precision and ultra-precision machining technology in my country is no longer limited to a few departments such as national defense and aerospace, but has expanded to many fields of the national economy. At present, there are increasingly higher requirements for the productivity and stability of machine tools. The precision micro-displacement worktable system with high precision and good equipment stability occupies an extremely important position in the field of modern cutting-edge industrial production and scientific research. It directly affects the level of precision and ultra-precision cutting and machining, the level of precision measurement and the level of ultra-large-scale integrated circuit production. At the same time, its various technical indicators are important symbols of the high-tech development level of various countries. The repeatability and straightness of the precision micro-displacement worktable system directly affect the accuracy of production and processing.

[0003] Hydrostatic air flotation technology is a new technology that uses high-pressure gas as a lubricating and bearing medium to replace the traditional mechanical ball and screw displacement mechanism to achieve zero-friction, zero-pollution submicron or even nanometer-level positioning / displacement motion. It is mostly based on guide rails, turntables or air flotation pads. Among them, air flotation pads are regarded as ideal supporting components in the ultra-precision field because of their open structure, wider application range, more predictable performance and high reconfigurability. According to the characteristics of hydrostatic air flotation technology, air flotation pads have low stiffness at low loads and need to be preloaded to achieve higher stiffness. Existing preloads are generally closed bilateral air flotation preloads (limited by usage), gravity preloads, and vacuum preloads.

[0004] Among the many preloading methods, gravity preloading cannot achieve fine-tuning of the preloading force and the load-bearing method will take up a certain amount of space; vacuum preloading technology is relatively more popular, but the fine-tuning of the vacuum force is often achieved by changing the air pressure, which requires an external vacuum pump to provide negative pressure and is difficult to provide a stable preloading force. In addition, the vacuum chamber required for vacuum preloading will occupy the air flotation surface area, resulting in a larger design requirement for the air flotation surface area. Because absolute vacuum cannot be achieved in the air flotation structure, the thickness of the air film changes greatly with the working conditions, and the vacuum preloading is very likely to fail when subjected to impact loads; due to the particularity of air flotation technology, the stiffness change of the gas support part (air film) is nonlinear, so it is particularly important to accurately control the air film of the air flotation cushion in the working condition near the maximum stiffness through the preloading force to improve the performance of the air flotation cushion. Based on the above reasons, it is difficult for existing preloading technologies to accurately achieve this preloading purpose. Therefore, an adjustable magnetic preload static pressure air flotation cushion is needed to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide an adjustable magnetic preload static pressure air floating cushion to solve the problems existing in the prior art mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] An adjustable magnetic preload static pressure air floating cushion, comprising an air floating cushion frame, a ferromagnetic iron plate and a permanent magnet, wherein the ferromagnetic iron plate is installed on a base plane, an air floating cushion frame is arranged above the ferromagnetic iron plate, the bottom surface of the air floating cushion frame is an air floating surface, an air flow channel is arranged in the air floating surface and the air floating cushion frame, and when air is supplied into the air flow channel, an air film gap is formed between the air floating surface and the ferromagnetic iron plate;

[0008] A groove is arranged in the middle of the air-floating surface, a permanent magnet is arranged in the groove, and an adjusting mechanism for adjusting the distance between the permanent magnet and the ferromagnetic material iron plate is installed on the air-floating cushion frame.

[0009] Preferably, the air flow channel includes a throttle hole, an annular air channel and an air supply port. A plurality of throttle holes are equidistantly arranged on the circumference of the air flotation surface. The throttle holes are connected to the annular air channel in the air flotation cushion frame. An air supply port is provided on the side of the air flotation cushion frame, and the air supply port is connected to the annular air channel.

[0010] Preferably, the adjustment mechanism is a differential thread mechanism, and the permanent magnet is installed on the output end of the differential thread mechanism.

[0011] Preferably, the leads of the two screws on the screw of the differential thread mechanism are 2 mm and 1 mm respectively.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The present invention arranges a ferromagnetic iron plate and a permanent magnet with an adjustable position in an air flotation cushion, and uses a differential thread mechanism to adjust the position of the permanent magnet, so as to change the distance between the magnetic force and the moving surface to achieve fine adjustment of the preload force. With reference to the air film stiffness curve obtained by CFD simulation, compared with the traditional preload method, the air flotation cushion of the present invention can achieve the optimal stiffness of the air flotation cushion under different working conditions, and the adjustment is convenient and accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0015] Figure 2 This is a diagram showing the influence of the thickness of the ferromagnetic material iron plate on the preload force of the present invention.

[0016] Figure 3 This is a relationship diagram of the magnetic force changing with the gap in the present invention.

[0017] Figure 4 Graph showing the relationship between the air film thickness and the bearing capacity of the air floating cushion of the present invention.

[0018] Figure 5 Graph showing the relationship between the air film thickness and the stiffness of the air floating cushion of the present invention.

[0019] In the figure: 1. air floating surface; 2. air floating cushion frame; 3. annular airway; 4. throttle hole; 5. ferromagnetic material iron plate; 6. air film gap; 7. permanent magnet; 8. differential thread mechanism; 9. base load plane. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0021] See also Figure 1-5 , the present invention provides the following technical solutions:

[0022] An adjustable magnetic preload static pressure air floating cushion comprises an air floating cushion frame 2, a ferromagnetic material iron plate 5 and a permanent magnet 7. The ferromagnetic material iron plate 5 is installed on a base plane 9. The air floating cushion frame 2 is arranged above the ferromagnetic material iron plate 5. The bottom surface of the air floating cushion frame 2 is an air floating surface 1. Air flow channels are arranged in the air floating surface 1 and the air floating cushion frame 2. When air is supplied to the air flow channel, an air film gap 6 is formed between the air floating surface 1 and the ferromagnetic material iron plate 5. In this state, the working load gravity and the magnetic preload force are balanced with the upward air floating force.

[0023] The air flow channel includes a throttle hole 4, an annular air channel 3 and an air supply port. A plurality of throttle holes 4 are equidistantly arranged on the circumference of the air flotation surface 1. The throttle holes 4 are connected to the annular air channel 3 in the air flotation cushion frame 2. An air supply port is provided on the side of the air flotation cushion frame 2, and the air supply port is connected to the annular air channel 3.

[0024] A groove is provided in the middle of the air floating surface 1, and a permanent magnet 7 is provided in the groove. An adjusting mechanism for adjusting the distance between the permanent magnet 7 and the ferromagnetic material iron plate 5 is installed on the air floating cushion frame 2. The adjusting mechanism is a differential thread mechanism 8, and the permanent magnet 7 is installed on the output end of the differential thread mechanism 8; the leads of the two screws on the screw of the differential thread mechanism 8 are 2mm and 1mm respectively; the permanent magnet 7 is pushed up and down by manually adjusting the differential thread mechanism 8, and the magnetic force is controlled by controlling the distance between the permanent magnet 7 and the ferromagnetic material iron plate 5 to adjust the air film thickness, thereby adjusting the air floating cushion to the optimal stiffness.

[0025] By controlling the distance between the ferromagnetic iron plate 5 and the permanent magnet 7, according to the vacuum force calculation formula Where: r is the relative magnetic permeability of the material, μ0 is the vacuum magnetic permeability, S is the surface area of ​​the magnetic field and the material, and B is the magnetic flux density at the surface of the magnetic field and the material.r , the effective area S and the magnetic flux density B at the effective surface are jointly determined. When the cross-sectional area of ​​the permanent magnet 7 and the magnetic permeability of the ferromagnetic characteristic layer are fixed, the magnetic force is mainly determined by the magnetic flux density on the surface of the ferromagnetic material, and the magnetic flux density is determined by the magnetic field distribution of the magnet. The smaller the spacing, the greater the magnetic flux density. The differential thread structure is used to realize the micro-displacement generated during rotation. According to the differential thread displacement calculation formula L = N (Ph1 ± Ph2), where: L is the actual displacement distance of the movable nut, N is the number of revolutions of the screw, Ph1 is the lead of screw 1, and Ph2 is the lead of screw 2. As long as the lead difference between the two screws is 1mm, a micro-displacement with a resolution of 1μm can be achieved through rotation.

[0026] Through simulation and experimental analysis, the feasibility of the magnetic preload air flotation block to control the air film at the micron level is verified. Figure 2 As shown, the experiment shows that the force between the permanent magnet 7 and the ferromagnetic material iron plate 5 is affected by the material thickness and the action gap. The curve shows the trend of the magnetic force between the magnet and the material with the material thickness under different action gaps. When the spacing is constant, as the thickness of the ferromagnetic material increases, the interactive magnetic force also increases. This is because the magnetic flux density passes through the material more as the material thickness increases, making the magnetic force more prominent. However, when the thickness increases to a certain level, the magnetic flux density approaches saturation with the ferromagnetic material, causing the magnetic force change to slow down.

[0027] like Figure 3 As shown, the experimental data of the change of magnetic force with the action gap are fitted through the experimental results. The theoretical curves and the experimental curves in the two groups of experiments are highly consistent. There is a certain difference between the theoretical magnetic force and the experimental value, but the error does not exceed 10%. By comparing the range of magnetic preload required by the bearing, the action gap is adjusted through the differential thread mechanism 8. The error can achieve micron-level control of the air film thickness. Figure 4-5 As shown, the stiffness and static stability of the air floating cushion are improved by adjusting the magnitude of the magnetic force.

[0028] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An adjustable magnetic preload static pressure air flotation cushion, characterized in that: The invention comprises an air-floating cushion frame (2), a ferromagnetic iron plate (5) and a permanent magnet (7); the ferromagnetic iron plate (5) is mounted on a base plane (9); an air-floating cushion frame (2) is arranged above the ferromagnetic iron plate (5); the bottom surface of the air-floating cushion frame (2) is an air-floating surface (1); an air flow channel is arranged inside the air-floating surface (1) and the air-floating cushion frame (2); when air is supplied into the air flow channel, an air film gap (6) is formed between the air-floating surface (1) and the ferromagnetic iron plate (5); A groove is provided in the middle of the air-floating surface (1), a permanent magnet (7) is provided in the groove, and an adjustment mechanism for adjusting the distance between the permanent magnet (7) and the ferromagnetic material iron plate (5) is installed on the air-floating cushion frame (2).

2. The adjustable magnetic preload static pressure air flotation cushion according to claim 1, characterized in that: The air flow channel comprises a throttle hole (4), an annular air passage (3) and an air supply port. A plurality of throttle holes (4) are equidistantly arranged on the circumference of the air flotation surface (1). The throttle holes (4) are connected to the annular air passage (3) in the air flotation cushion frame (2). An air supply port is arranged on the side of the air flotation cushion frame (2), and the air supply port is connected to the annular air passage (3).

3. The adjustable magnetic preload static pressure air flotation cushion according to claim 1, characterized in that: The adjustment mechanism is a differential thread mechanism (8), and the permanent magnet (7) is mounted on the output end of the differential thread mechanism (8).

4. The adjustable magnetic preload static pressure air flotation cushion according to claim 3, characterized in that: The leads of the two screws on the screw of the differential screw mechanism (8) are 2 mm and 1 mm respectively.

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