Static gas bearing

Abstract

To provide a hydrostatic gas bearing that can suppress deformation of porous plate material. [Solution] A hydrostatic gas bearing comprising a porous plate material and a housing on which the porous plate material is stacked and fixed, wherein the porous plate material has a bearing surface and a porous plate material side mating surface which is the opposite surface of the bearing surface, the housing has a housing side mating surface which abuts the porous plate material side mating surface and a crimping portion which protrudes in the stacking direction from the outer peripheral edge of the housing side mating surface over the entire circumference and crimps and fixes the porous plate material, an air supply cavity is provided between the porous plate material and the housing, formed by recessing one or both of the porous plate material side mating surface and the housing side mating surface in the stacking direction and forming an annular shape when viewed from the stacking direction, and the housing is provided with an air supply port which penetrates in the stacking direction and communicates with the air supply cavity.

Description

Technical Field

[0001] The present invention relates to a hydrostatic gas bearing.

Background Art

[0002] In machine tools, semiconductor manufacturing equipment, etc. that require high guiding accuracy, hydrostatic gas bearings may be used. A hydrostatic gas bearing is a device that generates a thin film of gas between a bearing surface and an object to be supported. Since the object to be supported is supported in a non-contact state with the bearing surface, the positioning of the object to be supported can be achieved with high accuracy. As an example of such a hydrostatic gas bearing, there is one that uses a porous plate material (hereinafter referred to as a porous plate).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In addition to the porous plate, the hydrostatic gas bearing includes a base material that supports the porous plate, and the porous plate is stacked on the base material. A supply air cavity into which compressed air flows is provided between the porous plate and the base material. The supply air cavity described in Patent Document 1 is located at the central portion of the porous plate and has a circular shape. In such a supply air cavity, when the hydrostatic gas bearing is driven, the central portion of the porous plate may be deformed so as to protrude toward the bearing surface side by the pressure of the compressed air in the supply air cavity (also referred to as the bearing supply air pressure). Such deformation may impair the performance of the bearing by causing the amount of gas ejected from the bearing surface to be non-uniform or the protruding portion to come into contact with the object to be supported.

[0005] The present invention has been made in view of the above problems, and its objective is to provide a hydrostatic gas bearing that suppresses deformation of porous plate material, improves surface accuracy on the bearing surface, and enables uniform air ejection. [Means for solving the problem]

[0006] The above objective of the present invention is achieved by the following configuration. (1) Porous plate material and A housing on which the porous plate material is stacked and which secures the porous plate material, A hydrostatic gas bearing comprising, The porous plate material has a bearing surface and a porous plate material side mating surface which is the opposite side of the bearing surface. The housing has a housing-side mating surface that abuts against the porous plate material-side mating surface, and a crimping portion that protrudes from the outer peripheral edge of the housing-side mating surface in the loading direction over its entire circumference and crimps and fixes the porous plate material. Between the porous plate material and the housing, an air supply cavity is provided, which is formed by recessing one or both of the mating surfaces on the porous plate material side and the mating surface on the housing side in the loading direction, and is annular in shape when viewed from the loading direction. The housing is provided with an air intake port that penetrates in the loading direction and communicates with the air intake cavity. A hydrostatic gas bearing characterized by the following features. [Effects of the Invention]

[0007] According to the present invention, the force applied to the porous plate material in the loading direction by the bearing air supply pressure can be dispersed and reduced, thereby suppressing deformation of the porous plate material. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a front view of a hydrostatic gas bearing according to an embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view taken along the line II-II in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing an enlarged view of the outer surface of the porous plate material shown in Figure 2. [Figure 4] Figure 4 is a side view of a hydrostatic gas bearing according to an embodiment of the present invention, viewed from the radial direction. [Figure 5] Figure 5 is a cross-sectional view showing a magnified view of the area around the air intake cavity. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a front view of a hydrostatic gas bearing according to an embodiment of the present invention. Figure 2 is a cross-sectional view taken along the line II-II in Figure 1.

[0010] As shown in Figures 1 and 2, the hydrostatic gas bearing 100 comprises a porous plate material 1 and a housing 2 on which the porous plate material 1 is loaded and which secures the porous plate material. In the following description, the direction in which the porous plate material 1 and the housing 2 overlap is referred to as the loading direction. Of the loading directions, the direction in which the porous plate material 1 is arranged as viewed from the housing 2 (upper side in Figure 2) is referred to as one side of the loading direction. The side opposite to the one side of the loading direction (lower side in Figure 2) is referred to as the other side of the loading direction. In this embodiment, the porous plate material 1 and the housing 2 are circular as viewed from the loading direction. The central axis passing through the center of the circular porous plate material 1 and housing 2 and extending in the loading direction as viewed from the loading direction is denoted as O, and the direction away from the central axis O is referred to as the radially outward direction. The direction approaching the central axis O (opposite side of the radially outward direction) is referred to as the radially inward direction.

[0011] The porous plate material 1 is made of a porous material such as graphite, carbon, ceramics, or a sintered metal powder, and is formed into a plate shape. The porous plate material 1 has a bearing surface 11 and a porous plate material side mating surface 12 which is the opposite surface of the bearing surface 11. The bearing surface 11 is a plane facing the object to be supported (not shown), and supports the object to be supported (not shown) by ejecting compressed air supplied through the air intake port 23 and air intake cavity 3, which will be described later.

[0012] In particular, as shown in Figure 2, the housing 2 has a housing-side mating surface 21 on which the porous plate material 1 is stacked and which abuts against the porous plate material side mating surface 12 of the porous plate material 1, and a bottom surface 22 which is the opposite side of the housing-side mating surface 21.

[0013] As shown in Figures 1 and 2, the housing 2 is provided with an air intake port 23 that penetrates the housing 2 in the loading direction and communicates with the air intake cavity 3, which will be described later. The air intake port 23 is a hole with a cylindrical inner surface that extends from the bottom surface 22 of the housing 2 to the air intake cavity 3. In particular, as shown in Figure 1, when viewed from the loading direction, the diameter of the air intake port 23 is larger than the width W of the air intake cavity 3, and the center of the air intake port 23 is formed to overlap with the air intake cavity 3. Compressed air for operating the hydrostatic gas bearing 100 is supplied to the air intake cavity 3 through the air intake port 23.

[0014] Figure 3 is a cross-sectional view showing an enlarged view of the outer circumferential surface of the porous plate material shown in Figure 2. As shown in Figures 2 and 3, the outer circumferential surface of the porous plate material 1, which connects the outer circumferential edge of the bearing surface 11 and the outer circumferential edge of the porous plate material side mating surface 12, has a chamfered surface 13, a stepped surface 14, a crimped conical surface 15, and a crimped cylindrical surface 16. The diameter of the porous plate material side mating surface 12 is larger than the diameter of the bearing surface 11. The chamfered surface 13 is formed to chamfer the outer circumferential edge of the bearing surface 11. The chamfered surface 13 is connected to the outer circumferential edge of the bearing surface 11 and is a conical surface that is inclined radially outward as it approaches the other side in the loading direction. A stepped surface 14, which is formed as a cylindrical surface extending to the other side in the loading direction, is connected to the other end of the chamfered surface 13 in the loading direction. A crimped conical surface 15, which is a conical surface that slopes radially outward as it extends toward the other side in the loading direction, is connected to the other end of the stepped surface 14 in the loading direction. A crimped cylindrical surface 16, which is formed in a cylindrical shape and extends toward the other side in the loading direction, is connected to the other end of the crimped conical surface 15 in the loading direction. The crimped conical surface 15 and the crimped cylindrical surface 16 come into contact with the crimped portion 31 of the housing 2, which will be described later. By forming the chamfered surface 13 and the stepped surface 14, chipping and other damage to the outer edge of the porous plate material 1 can be prevented.

[0015] The housing 2 has a clamping portion 31 that protrudes in the loading direction over the entire circumference from the outer peripheral edge of the housing mating surface 21 and clamps and fixes the porous plate material 1. The clamping portion 31 includes a cylindrical portion 32 that is connected to the housing mating surface 21 and formed in a cylindrical shape, and a bending portion 33 that is connected to one end of the cylindrical portion 32 in the loading direction and bends inward in the radial direction. The bending portion 33 is formed by clamping the clamping portion 31 inward in the radial direction, and is formed to extend in a direction toward the inside in the radial direction as it goes from one end of the cylindrical portion 32 in the loading direction toward one side in the loading direction. The inner peripheral surface of the cylindrical portion 32 abuts against the clamped cylindrical surface 16 of the porous plate material 1, and the inner peripheral surface of the bending portion 33 abuts against the clamped conical surface 15 of the porous plate material 1.

[0016] As described above, the porous plate material 1 is clamped and fixed by the clamping portion 31 over the entire circumference of the outer peripheral surface. As a result, the porous plate material 1 is fixed with a uniform force in the circumferential direction, and when compressed air is supplied to the air supply cavity 3, the force applied to the porous plate material 1 is likely to be dispersed in the circumferential direction, and deformation of the porous plate material 1 is suppressed.

[0017] FIG. 4 is a side view of the hydrostatic gas bearing according to the embodiment of the present invention viewed from the radial direction. As shown in FIGS. 1 to 4, the bending portion 33 of the clamping portion 31 is provided with a plurality of slits 34 that are arranged at equal intervals in the circumferential direction and are formed so as to notch the bending portion 33 in the radial direction. The slit 34 is formed to extend from the tip of the bending portion 33 to the boundary between the bending portion 33 and the cylindrical portion 32, and has a U-shape or a C-shape when viewed from the radial direction. By providing the slit 34, the bending portion 33 is likely to bend inward in the radial direction when the clamping portion 31 is clamped.

[0018] FIG. 5 is a cross-sectional view showing an enlarged periphery of the air supply cavity. As shown in FIGS. 1, 2, and 5, between the porous plate material 1 and the housing 2, one or both of the porous plate material side mating surface 12 and the housing side mating surface 21 are recessed in the stacking direction, and an air supply cavity 3 formed in an annular shape when viewed from the stacking direction is provided. In the present embodiment, in the housing 2, a recess 4 in which the housing side mating surface 21 is recessed on the other side in the stacking direction is formed. By overlapping the porous plate material 1 on the housing side mating surface 21, an air supply cavity 3 is formed in the space surrounded by the recess 4 and the porous plate material side mating surface 12. Further, the air supply cavity 3 according to the present embodiment is formed in an annular shape when viewed from the stacking direction, and the cross section perpendicular to the circumferential direction is rectangular. That is, as particularly shown in FIG. 5, the air supply cavity 3 includes a cavity inner peripheral surface 5 located on the inner side in the radial direction of the air supply cavity 3, a cavity outer peripheral surface 6 located on the outer side in the radial direction of the air supply cavity 3, a cavity bottom surface 7 located on the other side in the stacking direction of the air supply cavity 3, and a cavity ceiling surface 8 located on one side in the stacking direction of the air supply cavity 3, and is defined by these.

[0019] As shown in FIGS. 2 and 5, the ratio W / D of the radial width W of the air supply cavity 3 when viewed from the stacking direction to the depth D of the air supply cavity 3 in the stacking direction is preferably 1.0 or less. The width W of the air supply cavity 3 is the size of the gap in the radial direction between the cavity inner peripheral surface 5 and the cavity outer peripheral surface 6. Further, the depth D of the air supply cavity 3 is the size of the gap in the stacking direction between the cavity bottom surface 7 and the cavity ceiling surface 8. Here, a force that pushes the cavity ceiling surface 8 in one direction in the stacking direction is applied to the porous plate material 1 by the pressure of the compressed air supplied to the air supply cavity 3. Therefore, by reducing the area of the cavity ceiling surface 8, the force applied to the porous plate material 1 in one direction in the stacking direction is reduced, and deformation of the porous plate material is suppressed.

[0020] Furthermore, it is preferable that the pressure distribution inside the air supply cavity 3 is uniform regardless of the circumferential position when compressed air is supplied. The hydrostatic gas bearing 100 can stably support the object to be supported (not shown) by uniformly injecting compressed air from the bearing surface 11 after it passes through the porous plate material 1. In addition, deformation of the porous plate material 1 is suppressed because the force of the compressed air pressure pushing the porous plate material 1 to one side in the loading direction is uniform in the circumferential direction. Therefore, it is preferable to increase the cross-sectional area of ​​the air supply cavity 3 perpendicular to the circumferential direction, thereby making it easier for compressed air to flow circumferentially inside the air supply cavity 3, and thus equalizing the pressure inside the air supply cavity 3.

[0021] For the reasons stated above, it is preferable that the width W of the air supply cavity 3 be set small enough so that the porous plate material 1 does not deform due to the pressure of compressed air. Furthermore, it is preferable that the cross-sectional area perpendicular to the circumferential direction of the air supply cavity 3 (i.e., width W and depth D) be set large enough so that the pressure distribution inside the air supply cavity 3 is uniform in the circumferential direction. Therefore, it is preferable that the width W is set to be at least less than or equal to the depth D, that is, the ratio of width W to depth D W / D is set to 1.0 or less. The specific sizes of width W and depth D are set appropriately depending on the pressure of the compressed air, the Young's modulus of the porous plate material, etc., but for example, width W and depth D are set in the range of 1 mm to 4 mm each.

[0022] As shown in Figure 2, in this embodiment, the air supply cavity 3, which is formed in an annular shape when viewed from the loading direction, is formed concentrically with the porous plate material 1. In this case, the diameter R1 of the inner circumferential surface 5 of the cavity that defines the radial inner end of the air supply cavity 3 is preferably 40% to 60% of the diameter R2 of the crimped cylindrical surface 16 of the porous plate material 1. Furthermore, it is even more preferable that the diameter R1 is 50% to 60% of the diameter R2.

[0023] By increasing the diameter R1 of the inner circumferential surface 5 of the annular air supply cavity 3, the point of application of the pressure from compressed air that pushes the porous plate material 1 to one side in the loading direction can be brought closer to the outer circumferential surface to which the porous plate material 1 is crimped and fixed. This suppresses deformation near the center of the porous plate material 1. On the other hand, increasing the diameter R1 of the inner circumferential surface 5 of the cavity causes the air supply cavity 3 to be formed closer to the outer edge of the porous plate material 1, resulting in a larger area of ​​the cavity ceiling surface 8. A larger area of ​​the cavity ceiling surface 8 increases the force with which the porous plate material 1 is pushed to one side in the loading direction by the pressure from compressed air, which is undesirable from the viewpoint of suppressing deformation of the porous plate material 1. Due to the above conflicting circumstances, the diameter R1 of the inner circumferential surface 5 of the cavity is preferably 40% to 60% of the diameter R2 of the crimped cylindrical surface 16 of the porous plate material 1, and more preferably 50% to 60%.

[0024] Furthermore, if the diameter R1 is less than 40% of the diameter R2, it becomes more difficult to suppress deformation near the center of the porous plate material 1, and the compressed air does not flow easily to the outer edge of the porous plate material 1, making it difficult for the compressed air to be uniformly sprayed from the bearing surface 11.

[0025] According to the first embodiment of the hydrostatic gas bearing 100, compressed air is supplied from the air inlet 23 to the air intake cavity 3, and then passed through the porous plate material 1 and injected from the bearing surface 11. As a result, a thin film of gas is formed on the bearing surface 11, and the object to be supported (not shown) can be supported in a non-contact manner.

[0026] When compressed air is supplied to the air supply cavity 3, the porous plate material 1 is subjected to a pushing force in one direction in the loading direction due to the pressure of the compressed air. In this embodiment, the air supply cavity 3 is formed in a concentric ring shape with respect to the porous plate material 1, and the outer surface of the porous plate material 1 is crimped and fixed. Furthermore, the air supply cavity 3 is positioned towards the radially outer side of the porous plate material 1, and the ratio of the width W of the air supply cavity 3 to its depth D, W / D, is set to 1.0 or less. These measures prevent the porous plate material 1 from deforming due to the pressure of the compressed air.

[0027] It should be noted that the present invention is not limited to the embodiments illustrated above, and can be modified as appropriate without departing from the spirit of the invention. In other words, the static gas bearing 100 is provided with an annularly formed air supply cavity 3, and the outer surface of the porous plate material 1 is crimped and fixed by the housing 2, so that the porous plate material 1 is not easily deformed by the pressure of compressed air.

[0028] For example, in this embodiment, a recess 4 is provided on the housing-side mating surface 21 to form an annular air supply cavity 3, but the air supply cavity 3 may also be formed by providing a recess 4 on the porous plate material-side mating surface 12. Alternatively, the air supply cavity 3 may be formed by providing recesses 4 on both the porous plate material-side mating surface 12 and the housing-side mating surface 21. Furthermore, the cross-section of the air supply cavity 3 perpendicular to the circumferential direction does not have to be rectangular.

[0029] Furthermore, the shape of the porous plate material 1 and the housing 2 as viewed from the loading direction is not limited to a circle, but may be rectangular or the like. The shape of the air supply cavity 3 is also not limited to a ring shape as long as it can uniformly supply compressed air to the porous plate material 1, and the shape of the air supply cavity 3 as viewed from the loading direction is not limited to a ring shape, but may be formed as a rectangular ring or the like. Moreover, the shape of the outer circumferential surface of the porous plate material 1 can be appropriately modified, for example, by not forming a stepped surface 14, and by making the chamfered surface 13 and the crimped conical surface 15 a continuous shape. The crimped portion 31 of the housing 2 is also not limited to the example shape, for example, by forming a slit 34 that extends from the tip of the bent portion 33 to the cylindrical portion 32.

[0030] As described above, the following matters are disclosed in this specification: (1) Porous plate material and A housing on which the porous plate material is stacked and which secures the porous plate material, A hydrostatic gas bearing comprising, The porous plate material has a bearing surface and a porous plate material side mating surface which is the opposite side of the bearing surface. The housing has a housing-side mating surface that abuts against the porous plate material-side mating surface, and a crimping portion that protrudes from the outer peripheral edge of the housing-side mating surface in the loading direction over its entire circumference and crimps and fixes the porous plate material. Between the porous plate material and the housing, an air supply cavity is provided, which is formed by recessing one or both of the mating surfaces on the porous plate material side and the mating surface on the housing side in the loading direction, and is annular in shape when viewed from the loading direction. The housing is provided with an air intake port that penetrates in the loading direction and communicates with the air intake cavity. A hydrostatic gas bearing characterized by the following features. This configuration allows for the dispersion and reduction of the load-direction force applied to the porous plate material by the bearing air supply pressure, thereby suppressing deformation of the porous plate material, improving surface accuracy on the bearing surface, and providing a hydrostatic gas bearing that can uniformly eject air.

[0031] (2) The crimping portion is provided with a plurality of slits arranged at equal intervals in the circumferential direction. The static gas bearing according to (1), characterized in that it is a static gas bearing. With this configuration, the slit makes the crimping section easier to bend, thus facilitating the crimping process.

[0032] (3) The ratio W / D of the width W of the air supply cavity as viewed from the loading direction to the depth D of the air supply cavity in the loading direction is 1.0 or less. A static gas bearing as described in (1) or (2), characterized in that... This configuration allows for a uniform pressure distribution within the air intake cavity, and by narrowing the width of the air intake cavity, the force applied to the porous plate material can be reduced.

[0033] (4) The porous plate material is circular when viewed from the loading direction. A hydrostatic gas bearing as described in any one of (1) to (3), characterized by the above. With this configuration, the force distribution applied to the porous plate material tends to be more uniform in the circumferential direction, making the porous plate material less prone to deformation.

[0034] (5) The air supply cavity is formed concentrically with the porous plate material when viewed from the loading direction, The diameter of the inner surface of the air supply cavity is 40% to 60% of the diameter of the porous plate material. The static gas bearing according to (4), characterized in that This configuration allows the point of application of compressed air pressure, which pushes the porous plate material in the loading direction, to be brought closer to the outer edge where the porous plate material is crimped and fixed, thereby suppressing deformation near the center of the porous plate material. In addition, the area over which the porous plate material is pushed in the loading direction by compressed air pressure can be reduced. [Explanation of symbols]

[0035] 1 Porous plate material 2 Housing 3. Intake Cavity 4 recesses 5. Inner surface of the cavity 6. Outer surface of the cavity 7 Cavity bottom 8 Cavity ceiling surface 11 Bearing surface 12. Joint surface on the porous plate side 13 Chamfered surface 14 Step surface 15 Crimped conical surface 16 Cylindrical surface to be crimped 21 Housing side mating surface 22 Bottom 23 Air supply port 31 Crimping section 32 Cylindrical section 33. Bending section 34 slits 100 Static gas bearing

Claims

1. Porous board material, A housing on which the porous plate material is stacked and which secures the porous plate material, A hydrostatic gas bearing comprising, The porous plate material has a bearing surface and a porous plate material side mating surface which is the opposite side of the bearing surface. The housing has a housing-side mating surface that abuts against the porous plate material-side mating surface, and a crimping portion that protrudes from the outer peripheral edge of the housing-side mating surface in the loading direction over its entire circumference and crimps and fixes the porous plate material. Between the porous plate material and the housing, an air supply cavity is provided, which is formed by recessing one or both of the mating surfaces on the porous plate material side and the mating surface on the housing side in the loading direction, and is annular in shape when viewed from the loading direction. The housing is provided with an air intake port that penetrates in the loading direction and communicates with the air intake cavity. A hydrostatic gas bearing characterized by the following features.

2. The crimping portion is provided with a plurality of slits arranged at equal intervals in the circumferential direction. A hydrostatic gas bearing according to claim 1, characterized in that...

3. The ratio W / D of the width W of the air intake cavity as viewed from the loading direction to the depth D of the air intake cavity in the loading direction is 1.0 or less. A hydrostatic gas bearing according to claim 1 or 2, characterized in that...

4. The porous plate material is circular when viewed from the loading direction. A hydrostatic gas bearing according to claim 1 or 2, characterized in that...

5. The aforementioned air intake cavity is formed concentrically with the porous plate material when viewed from the loading direction. The diameter of the inner surface of the air supply cavity is 40% to 60% of the diameter of the porous plate material. The static gas bearing according to claim 4, characterized in that

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