Hydrostatic gas bearing device

Abstract

A hydrostatic gas bearing device according to the present disclosure comprises: a movable member; and a fixed member. A recess is located on a bearing surface of a base of the movable member or the fixed member, and an opening of a gas supply hole is located on the bottom surface of the recess. A porous body serving as a gas jetting-out part is positioned in the recess so as not to protrude from the bearing surface. In the surface of the porous body, a first groove reaching the outer circumference of the porous body from the center region of the surface is located. In the bearing surface of the base, a second groove in communication with the first groove is located.

Description

Hydrostatic Gas Bearing Device

[0001] The present disclosure relates to an aerostatic bearing device.

[0002] Conventionally, in semiconductor manufacturing equipment such as mask exposure equipment, air slides have been used as devices for scanning and positioning stages with high precision. Examples of such air slides include those that employ orifice diaphragms and surface diaphragms. When foreign matter gets into the gas supply holes of such air slides, the amount of gas supplied changes, reducing rigidity and making the dynamic posture of the moving body unstable.

[0003] Therefore, as described in Patent Document 1, a hydrostatic bearing device is used in which a porous member is provided in the bearing portion, and the porous member is provided with an air supply hole and an exhaust groove for exhausting the pressurized fluid. The hydrostatic bearing device described in Patent Document 1 can enlarge the area from which compressed gas is ejected. Therefore, although the bearing rigidity can be increased, there is a problem in that vibrations are generated due to the compression effect of the gas within the porous body. In particular, in semiconductor manufacturing processes, with the increasing integration and performance of semiconductor elements, there is a demand for reducing micro-vibrations on the stage.

[0004] Japanese Patent Application Publication No. 5-10330

[0005] The hydrostatic gas bearing device according to the present disclosure comprises a movable member and a fixed member. A recess is located in the bearing surface of the base of the movable member or the fixed member, and the opening of a gas supply hole is located at the bottom of the recess. A porous body that serves as a gas ejection port is located in the recess so as not to protrude from the bearing surface. A first groove is located in the surface of the porous body, extending from the central region of the surface to the outer periphery of the porous body. A second groove that communicates with the first groove is located in the bearing surface of the base.

[0006] 2B is an explanatory diagram showing an example in which an externally pressurized gas bearing device according to an embodiment of the present disclosure is provided in a linear guide device. FIG. 2C is a plan view showing a main portion of an externally pressurized gas bearing device according to an embodiment of the present disclosure. FIG. 2D is a plan view showing a modified example of the main portion of an externally pressurized gas bearing device according to an embodiment of the present disclosure. FIG. 2E is a plan view showing a modified example of the main portion of an externally pressurized gas bearing device according to an embodiment of the present disclosure. FIG. 2F is an explanatory diagram showing a cross section taken along line X-X shown in FIG. 2A. FIG. 2G is a plan view showing a bottom surface of a recess. FIG. 2H is a plan view showing a main portion of an externally pressurized gas bearing device according to another embodiment of the present disclosure. FIG. 2H is a plan view showing a main portion of an externally pressurized gas bearing device according to yet another embodiment of the present disclosure. FIG. 2I is a plan view showing a main portion of an externally pressurized gas bearing device according to yet another embodiment of the present disclosure. FIG. 2J is a plan view showing a main portion of an externally pressurized gas bearing device according to yet another embodiment of the present disclosure. FIG. 10 is a plan view showing a main portion of an externally pressurized gas bearing device according to still another embodiment of the present disclosure.

[0007] As described above, conventional hydrostatic bearing devices have the problem of vibrations occurring due to the compression effect of gas within the porous medium. Therefore, there is a need for a hydrostatic gas bearing device that can reduce the loss of rigidity caused by micro-vibrations and clogging of the gas supply holes.

[0008] By virtue of having the above-described configuration, the hydrostatic gas bearing device according to the present disclosure can reduce the reduction in rigidity caused by micro-vibrations and clogging of the gas supply holes.

[0009] An externally pressurized gas bearing device according to an embodiment of the present disclosure will be described with reference to Figures 1 to 4. Figure 1 is an explanatory diagram showing an example in which an externally pressurized gas bearing device according to an embodiment of the present disclosure is provided in a linear guide device. The externally pressurized gas bearing device according to the embodiment includes a movable member 1 and a fixed member 2.

[0010] The movable member 1 is arranged to surround the fixed member 2, which has a substantially rectangular prism shape. The movable member 1 and the fixed member 2 are positioned with a gap between them and are not in contact with each other. A hydrostatic gas layer is formed by ejecting compressed gas from the bearing surface 1 a of the base of the movable member 1 or the bearing surface 2 a of the base of the fixed member 2. Therefore, the movable member 1 can be moved along the fixed member 2 using a separate driving means (not shown) while the movable member 1 and the fixed member 2 are not in contact with each other.

[0011] The movable member 1 and the fixed member 2 are made of, for example, ceramics or metal. Examples of ceramics that make up the movable member 1 and the fixed member 2 include ceramics whose main component is alumina, zirconia, silicon carbide, silicon nitride, or aluminum nitride. Examples of metals include aluminum and stainless steel. The movable member 1 and the fixed member 2 may be made of the same material or different materials.

[0012] In this specification, the term "main component" refers to a component that accounts for 80% by mass or more of the total 100% by mass of the components constituting the ceramic. Each component contained in the ceramic is identified using an X-ray diffractometer using CuKα radiation, and the content of each component can be determined using, for example, an ICP (Inductively Coupled Plasma) emission spectrometer or an X-ray fluorescence analyzer.

[0013] An embodiment in which gas is ejected from the bearing surface 1a of the base body of the movable member 1 will be described below with reference to Figures 2A to 4. Figure 2A is a plan view showing a main portion of an hydrostatic gas bearing device according to an embodiment of the present disclosure. Figure 3 is an explanatory diagram showing a cross section taken along line X-X shown in Figure 2A. Figure 4 is a plan view showing the bottom surface 11a of the recess 11. As shown in Figures 2A to 4, the bearing surface 1a of the base body of the movable member 1 is provided with a recess 11 and a gas supply hole 12 having an opening 12a in part of the bottom surface 11a of the recess 11.

[0014] The porous body 3 is located in the recess 11. The depth of the recess 11 is not limited and is, for example, 1 mm or more and 10 mm or less. The porous body 3 is a member that serves as a gas ejection portion. The porous body 3 is fixed to the recess 11 so as not to protrude from the bearing surface 1 a of the base body of the movable member 1.

[0015] 3 and 4, a gas supply hole 12 communicating with the outside of the movable member 1 is connected to the bottom surface 11a of the recess 11. As shown in Fig. 4, the gas supply hole 12 has an opening 12a in a part of the bottom surface 11a of the recess 11. Gas is supplied from the outside of the movable member 1 through the gas supply hole 12 to the porous body 3 serving as the jetting portion. The gas supply hole 12 may be, for example, a horizontal hole formed in the side surface of the base, a vertical hole formed in the bottom surface of the base, or a combination of a horizontal hole formed in the side surface of the base and a vertical hole connecting the horizontal hole to the bottom surface 11a.

[0016] The porous body 3 is formed of, for example, ceramics. Examples of such ceramics include ceramics mainly composed of alumina, zirconia, silicon carbide, silicon nitride, or aluminum nitride. The porous body 3 may be formed of the same material as the member in which the recess 11 is located (in one embodiment, the movable member 1). If the porous body 3 is formed of the same material as the member in which the recess 11 is located, differences in thermal expansion coefficients are unlikely to occur and stress is unlikely to occur even when the temperature changes. Therefore, turbulence is unlikely to occur due to deformation, etc., and micro-vibrations caused by turbulence are further reduced. The porosity of the porous body 3 is not limited and may be, for example, 20% to 50%. The average particle diameter of the porous body 3 is not limited and may be, for example, 10 μm to 100 μm.

[0017] The porosity of the porous body 3 can be determined, for example, by mercury intrusion porosimetry. Mercury intrusion porosimetry is a method in which mercury is injected (mercury intrusion porosimetry) into the pores of the porous body 3 (sample) using a mercury intrusion porosimeter to determine the porosity, and may be determined in accordance with JIS R 1655-2003.

[0018] The thickness of the porous body 3 is not limited as long as it does not protrude from the recess 11. For example, the upper surface of the porous body 3 and the bearing surface of the base (in one embodiment, the bearing surface 1a of the base of the movable member 1) may be flush. When the upper surface of the porous body 3 and the bearing surface of the base are flush, turbulence due to a step between the upper surface of the porous body 3 and the bearing surface of the base is less likely to occur. As a result, micro-vibrations caused by turbulence are further reduced.

[0019] At least the bottom surface of the porous body 3 may be bonded to the bottom surface 11a of the recess 11. Bonding at least the bottom surface of the porous body 3 to the bottom surface 11a of the recess 11 can increase the fixing strength of the porous body 3. The bonding method is not limited, and for example, an epoxy adhesive such as Araldite (registered trademark, manufactured by Huntsman Japan) or ThorSeal (manufactured by Agilent Technologies) may be used for bonding. Furthermore, the porous body 3 may be bonded to the entire surface of the recess 11 except for the opening 12a of the gas supply hole 12. When the porous body 3 is bonded to the entire surface of the recess 11 except for the opening 12a of the gas supply hole 12, gas flows more easily from the gas supply hole 12 to the first groove 41 described below. As a result, the gas is more easily dispersed throughout the porous body 3, and micro-vibrations are further reduced.

[0020] A plurality of radial first grooves 41 are provided on the surface of the porous body 3. In plan view, the first grooves 41 are formed from the central region of the porous body 3 outward, as shown in FIG. 2A . The number of first grooves 41 is not limited as long as at least one first groove 41 is formed extending from the central region of the surface of the porous body 3 to the outer periphery of the porous body 3. From the viewpoint of uniform pressure distribution within the surface, the number of first grooves 41 may be three to eight. The width and depth of the first grooves 41 are not limited. The width may be, for example, 0.5 mm to 2 mm. The depth may be, for example, 0.005 mm to 0.05 mm.

[0021] The cross-sectional shape perpendicular to the longitudinal direction of the first groove 41 is not particularly limited. This cross-sectional shape may be, for example, a U-shape, in which the opening and bottom of the groove are the same width, a V-shape, or a U-shape (a shape with a curved bottom), in which the opening width of the groove is larger than the bottom width. From the perspective of reducing gas turbulence, a V-shape or U-shape, in which the opening width of the groove is larger than the bottom width, may be used. When comparing grooves with the same cross-sectional area but different widths and depths, the surface area of ​​the groove is larger when the groove is vertically elongated (the width is smaller than the depth). Therefore, since losses due to resistance tend to increase, it is preferable that the groove width be larger than the depth. However, if the depth is too large relative to the width, micro-vibrations tend to increase. Therefore, the width should be no more than 100 times the depth.

[0022] The angles formed by two adjacent first grooves 41 among the plurality of first grooves 41 may be the same. With such a configuration, the gas flowing through the first grooves 41 becomes more uniform. As a result, variations in the gas flow are reduced. In Fig. 2A, four first grooves 41 are formed at 90° intervals.

[0023] A plurality of second grooves 42 communicating with the first grooves 41 are provided in the bearing surface of the base (in one embodiment, the bearing surface 1 a of the base of the movable member 1 ).

[0024] 2A , the second groove 42 is in communication with the first groove 41 and is therefore positioned in a straight line with the first groove 41. The width and depth of the second groove 42 are, for example, the same as the width and depth of the first groove 41.

[0025] The hydrostatic gas bearing device according to one embodiment has first grooves 41 and second grooves 42. Therefore, the gas ejected from the porous body 3 can be moved to the second grooves 42 by the first grooves 41. As a result, the gas can be moved to the base of the movable member 1. Therefore, a buoyancy force can be generated in the base of the movable member 1, and the buoyancy force is stabilized, reducing micro-vibrations.

[0026] The bearing surface 1a of the base body may be provided with first intersecting grooves 51 that intersect with the second grooves 42. With this configuration, the gas flowing through the second grooves 42 can be dispersed in a direction intersecting with the second grooves 42, further reducing micro-vibrations. Examples of "intersecting" include two-crossing, three-crossing, and four-crossing. Two-crossing refers to a structure in which two directions extend from an intersection, such as an L-shape. Three-crossing refers to a structure in which three directions extend from an intersection, such as a T-shape and a Y-shape. Four-crossing refers to a structure in which four directions extend from an intersection, such as a cross-shape, an X-shape, and a swastika-shape.

[0027] The first intersecting groove 51 may be connected to the second groove 42 at an end thereof or in the middle of the second groove 42. The first intersecting groove 51 may be connected to the second groove 42 at an end thereof or in the middle of the first intersecting groove 51 to the second groove 45.

[0028] The first intersecting grooves 51 may connect adjacent second grooves 45. This facilitates uniform gas supply to the bearing surface 1a. In FIG. 2A, the first intersecting grooves 51 are positioned so as to connect the ends of the second grooves 42. In FIG. 2A, the first intersecting grooves 51 are formed in a rectangular shape in plan view to match the rectangular bearing surface 1a. In this way, it is preferable that the first intersecting grooves 51 be formed parallel to the outer shape of the bearing surface 1a. However, the shape of the first intersecting grooves 51 is not limited as long as they are formed so as to connect the second grooves 42.

[0029] For example, as shown in FIG. 2A , the first intersecting groove 51 may be formed in a ring shape so as to connect the second grooves 42 to each other. The first intersecting groove 51 may have a shape similar to the bearing surface 1a of the base (for example, if the bearing surface 1a is rectangular as shown in FIG. 2A , the first intersecting groove 51 may be rectangular). This makes it easier to supply gas uniformly to the bearing surface 1a. The width and depth of the first intersecting groove 51 are, for example, the same as the width and depth of the first groove 41.

[0030] In Fig. 2A, the first intersecting groove 51 is formed in an annular shape so as to connect the ends of the second grooves 42. However, as shown in Fig. 2B, the first intersecting groove 51 may be formed in an annular shape so as to connect portions other than the ends of the second grooves 42. Fig. 2B is a plan view showing a modified example of a main part of an externally pressurized gas bearing device according to an embodiment of the present disclosure.

[0031] Furthermore, the first intersecting groove 51 may have a partially annular structure as shown in Figure 2C (in the present disclosure, such a partially annular structure is also considered to be annular). Figure 2C is a plan view showing another modified example of the main part of the hydrostatic gas bearing device according to an embodiment of the present disclosure.

[0032] As shown in Fig. 5, the porous body 3 may further be provided with at least one second intersecting groove 52 that intersects and connects with the first groove 41. Fig. 5 is a plan view showing a main portion of an hydrostatic gas bearing device according to another embodiment of the present disclosure. The provision of the second intersecting groove 52 reduces variations in the gas flow. The second intersecting groove 52 may connect multiple first grooves 41. This makes it easier to supply gas uniformly to the surface of the porous body 3.

[0033] The second intersecting grooves 52 may have a shape similar to that of the porous body 3 when viewed in a plane. In Fig. 5, the porous body 3 has a circular shape when viewed in a plane, and the second intersecting grooves 52 also have a circular shape (annular). In Fig. 5, the second intersecting grooves 52 have a circular shape (annular). However, the second intersecting grooves 52 are not limited to annular shapes as long as they can connect the first grooves 41.

[0034] The arithmetic mean roughness Ra of the bearing surface of the substrate (bearing surface 1a of the substrate of the movable member 1), the surface of the porous body 3, and the inner wall surface of each groove is not limited. For example, the arithmetic mean roughness Ra of the bearing surface of the substrate may be smaller than the arithmetic mean roughness Ra of the inner wall surface of the second groove 42. If the arithmetic mean roughness Ra of the bearing surface of the substrate is smaller than the arithmetic mean roughness Ra of the inner wall surface of the second groove 42, the inner wall surface of the second groove 42 will be relatively rough, and the speed of the flowing gas can be slowed. As a result, vibrations are absorbed and micro-vibrations are reduced. On the other hand, the bearing surface of the substrate is relatively smooth. Therefore, the gas can easily spread uniformly over the bearing surface (bearing surface 1a), allowing the movable member 1 to move smoothly.

[0035] Furthermore, the arithmetic mean roughness Ra of the surface of the porous body 3 may be smaller than the arithmetic mean roughness Ra of the inner wall surface of the first groove 41. When the arithmetic mean roughness Ra of the surface of the porous body 3 is smaller than the arithmetic mean roughness Ra of the inner wall surface of the first groove 41, the inner wall surface of the first groove 41 is relatively rough, and the speed of the flowing gas can be slowed down. As a result, vibrations are absorbed and micro-vibrations are reduced. On the other hand, the surface of the porous body 3 is relatively smooth. Therefore, the gas can easily spread uniformly over the surface of the porous body 3, allowing the movable member 1 to move smoothly.

[0036] The arithmetic mean roughness Ra of the bearing surface of the base may be, for example, 0.1 μm or more and 1.0 μm or less. The arithmetic mean roughness Ra of the surface of the porous body 3 may be, for example, 0.1 μm or more and 2.0 μm or less. The arithmetic mean roughness Ra of the inner wall surface of the first groove 41 may be, for example, 0.5 μm or more and 3.0 μm or less. The arithmetic mean roughness Ra of the inner wall surface of the second groove 42 may be, for example, 1.0 μm or more and 4.0 μm or less.

[0037] The arithmetic mean roughness Ra of the bearing surface of the substrate, the surface of the porous body 3, and the inner wall surface of each groove can be measured in accordance with JIS B 0601:2001 using a shape analysis laser microscope (Keyence Corporation, VK-X1100 or its successor model). Measurement conditions include a measurement magnification of 240x, no cutoff value λs, a cutoff value λc of 0.08 mm, and no cutoff value fs. The measurement range on one surface to be measured is 1420 μm × 1070 μm, and four measurement ranges are set on each surface to be measured. Surface roughness measurements are performed by drawing four lines at approximately equal intervals within each measurement range. The length of each line to be measured is 1320 μm.

[0038] The cross-sectional area of ​​the first grooves 41 may be the same as or larger than the cross-sectional area of ​​the second grooves 42. The porous body 3 tends to have a high pressure and a high airflow resistance due to the throttling effect of the micropores (molecules are compressed when a fluid passes through the small holes). Therefore, by providing grooves on the surface of the porous body 3 as described above, the airflow resistance of the first grooves 41 can be reduced, allowing gas to be smoothly supplied to the second grooves 42. The cross-sectional areas of the first grooves 41 and the second grooves 42 can be adjusted to desired cross-sectional areas by changing at least one of the depth and width of each groove.

[0039] The cross-sectional area of ​​the first grooves 41 means the area of ​​a region surrounded by an imaginary plane passing through the surface of the porous body 3 and the inner wall of the first groove 41 in a cross section of the first groove 41 cut perpendicular to the extension direction. The cross-sectional area of ​​the second grooves 42 means the area of ​​a region surrounded by an imaginary plane passing through the bearing surface of the base and the inner wall of the second groove 42 in a cross section of the second grooves 42 cut perpendicular to the extension direction.

[0040] As shown in Fig. 6, a plurality of recesses 11 may be located on the bearing surface of the base (bearing surface 1a of the base of the movable member 1), and a plurality of porous bodies 3 may be fixed to each of the plurality of recesses 11. Fig. 6 is a plan view showing a main part of an hydrostatic gas bearing device according to yet another embodiment of the present disclosure. By fixing a plurality of porous bodies 3 to each of the plurality of recesses 11, gas ejection within the bearing surface becomes uniform. As a result, a structure in which the porous bodies are fixed in this manner can be applied to bearing surfaces with a larger area, for example.

[0041] In an embodiment in which multiple porous bodies 3 are fixed to multiple recesses 11, as shown in Figure 6, if one porous body 3, a first groove 41 provided in the porous body 3, a second groove 42 communicating with the first groove 41, and a first intersecting groove 51 intersecting with the second groove 42 are considered to be one unit, multiple units are located on the bearing surface 1a, and each unit may be located independently so that they do not come into contact with each other.

[0042] When each unit is positioned independently, adjacent units may be connected via a communication groove 53, as shown in Fig. 7. Fig. 7 is a plan view showing the main parts of an hydrostatic gas bearing device according to yet another embodiment of the present disclosure. When adjacent units are connected via a communication groove 53, variations in the gas flow in each unit are reduced. As a result, the gas tends to spread evenly across the bearing surface (bearing surface 1a).

[0043] Furthermore, as shown in Fig. 8, adjacent units may be connected by a shared groove 54 between a portion of the first intersecting groove 51 in one unit and a portion of the first intersecting groove 51 in the other unit. In other words, a portion of the first intersecting groove 51 in one of the adjacent units may include a shared groove 54, and a portion of the first intersecting groove 51 in the other unit may also include this shared groove 54. This reduces variations in the gas flow between adjacent porous bodies 3. As a result, the gas is more likely to spread uniformly across the bearing surface (bearing surface 1a).

[0044] The method for forming the first groove 41 and the second intersecting groove 52 on the surface of the porous body 3, and the method for forming the second groove 42, the first intersecting groove 51 and the communicating groove 53 on the bearing surface of the base (the bearing surface 1a of the base of the movable member 1), are not limited as long as they are methods for forming grooves.

[0045] For example, after the porous body 3 and the base of the movable member 1 (or the base of the fixed member 2) are fabricated, the grooves may be formed by grinding or polishing, or the grooves may be formed in advance when the porous body 3 and the base are fabricated. When the porous body 3 and the base are made of ceramics, a method for forming the grooves in advance involves obtaining a precursor (molded body) in which the portions that will become the grooves are formed, and then firing this precursor. Alternatively, the grooves may be formed after the porous body 3 is fixed to the recess 11 of the base. In this case, the first groove 41 and the second groove 42 communicating with the first groove 41 are integrally formed. This improves the positional accuracy of the first groove 41 and the second groove 42.

[0046] The hydrostatic gas bearing device according to the present disclosure is not limited to the hydrostatic gas bearing device according to the above-described embodiment. In the hydrostatic gas bearing device according to the above-described embodiment, a first intersecting groove 51 is provided connecting the ends of the second grooves 42. However, in the hydrostatic gas bearing device according to the present disclosure, in addition to the first intersecting groove, an additional intersecting groove may be provided between the first intersecting groove and the porous body. This additional intersecting groove only needs to be provided around at least one periphery, and may be provided concentrically with the first intersecting groove.

[0047] In the hydrostatic gas bearing device according to the other embodiment described above, two units are shown, each including one porous body 3, first grooves 41 provided in the porous body 3, second grooves 42 communicating with the first grooves 41, and first intersecting grooves 51 connecting the ends of the second grooves 42. However, three or more such units may be present. The units may be arranged in a straight line, in a vertical and horizontal grid pattern, or randomly.

[0048] 9A is a plan view showing a main portion of an externally pressurized gas bearing device according to yet another embodiment of the present disclosure. In the externally pressurized gas bearing device of FIG. 2A, another porous body 3 a and another first groove 41 a located on the other porous body 3 a may be located midway along the first intersecting groove 51. Even in such a case, it can be said that the first intersecting groove 51 connects adjacent second grooves 42.

[0049] 9B is a plan view showing a main portion of an externally pressurized gas bearing device according to yet another embodiment of the present disclosure. In the externally pressurized gas bearing device of FIG. 2A, another porous body 3 a and another first groove 41 a located on the other porous body 3 a may be located at the connection portion between the second groove 42 and the first intersecting groove 51. Even in such a case, it can be said that the first intersecting groove 51 intersects with the second groove 42.

[0050] 9A and 9B, the number of porous bodies to which gas is supplied can be increased, allowing the gas to flow uniformly over the bearing surface, further reducing micro-vibrations.

[0051] Figure 10 is a plan view showing the main parts of an externally pressurized gas bearing device according to yet another embodiment of the present disclosure. The externally pressurized gas bearing device of Figure 10 can be said to have a porous body 3, a first groove 41 located on this porous body 3, a second groove 42 communicating with the first groove 41, and a first intersecting groove 51 intersecting the second groove 42. In Figure 10, another porous body 3a and another first groove 41a located on the porous body 3a can be said to be located at the connection between the second groove 42 and the first intersecting groove 51. Even with this configuration, the levitation force of the movable member 1 is stabilized and micro-vibrations are reduced.

[0052] Fig. 11A is a plan view showing a main portion of an externally pressurized gas bearing device according to yet another embodiment of the present disclosure. The externally pressurized gas bearing device of Fig. 11A has a porous body 3, a first groove 41 located on the porous body 3, a second groove 42 communicating with the first groove 41, and a first intersecting groove 51 intersecting the second groove 42. As shown in Fig. 11A, the first intersecting groove 51 does not have to have an annular structure.

[0053] Figure 11B is a plan view showing a main portion of an externally pressurized gas bearing device according to yet another embodiment of the present disclosure. In Figure 11B, another porous body 3a and another first groove 41a located on the other porous body 3a are located at the end of the first intersecting groove 51 in the externally pressurized gas bearing device of Figure 11A. Even in this case, it can be said that the first intersecting groove 51 intersects with the second groove 42. Even with the configurations shown in Figures 11A and 11B, the levitation force of the movable member 1 is stabilized and micro-vibrations are reduced.

[0054] The hydrostatic gas bearing device according to the present disclosure will be specifically described below using examples and comparative examples, but the hydrostatic gas bearing device according to the present disclosure is not limited to the following examples.

[0055] Example 1 First, an aerostatic bearing device as shown in Figure 1 was fabricated. The movable member 1 included in the aerostatic bearing device of Example 1 was made of alumina with a purity of 99.5% by mass. The dimensions of each of the four bearing surfaces 1a were 100 mm wide and 100 mm long in the direction of movement.

[0056] Each of the four bearing surfaces 1a includes one unit including a porous body 3, a first groove 41, a second groove 42, and a first intersecting groove 51 as shown in FIG. 2A. The second groove 42 and the first intersecting groove 51 each have a width of 1 mm and a depth of 0.02 mm. The first intersecting groove 51 has a square annular structure in a plan view. The length of the first intersecting groove 51 in the direction perpendicular to the moving direction of the movable member 1 is 50 mm, and the length in the moving direction of the movable member 1 is 50 mm.

[0057] The porous body 3 is made of alumina, and is fabricated using alumina with a purity of 99.5% by mass, with an average particle size of 80 μm and a porosity of 40%. The porous body 3 has a diameter of 10 mm. The first grooves 41 located in the porous body 3 have a width of 1 mm and a depth of 0.02 mm.

[0058] The fixed member 2 included in the hydrostatic gas bearing device of Example 1 was made of alumina with a purity of 99.5% by mass. The vertical and horizontal lengths of the fixed member 2 were 80 mm, and the length in the longitudinal direction (the length in the direction in which the movable member 1 moves) was 300 mm.

[0059] Comparative Example 1 An aerostatic bearing device was produced in the same manner as in Example 1, except that an orifice restrictor having an opening diameter of 0.2 mm was used instead of the porous body 3 used in Example 1.

[0060] In the hydrostatic gas bearing device of Example 1 and the hydrostatic gas bearing device of Comparative Example 1, a gas supply hole 12 of the movable member 1 was supplied with 4 kgf / cm ２ Compressed gas was supplied to each of the sensors, and the stiffness and micro-vibration were measured. The stiffness was measured by measuring the amount of change in the floating height when a load was applied. The micro-vibration was measured by measuring the minute displacement of the moving body using a capacitance displacement meter.

[0061] The hydrostatic gas bearing device of Example 1 had the same level of rigidity as the hydrostatic gas bearing device of Comparative Example 1. On the other hand, the hydrostatic gas bearing device of Example 1 was able to reduce micro-vibrations to about 1 / 10 of that of the hydrostatic gas bearing device of Comparative Example 1.

[0062] The embodiments of the present disclosure have been described above. However, the invention according to the present disclosure is not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of the present disclosure as shown in (1) below.

[0063] (1) The hydrostatic gas bearing device according to the present disclosure comprises a movable member and a fixed member. A recess is located in the bearing surface of the base of the movable member or the fixed member, and the opening of a gas supply hole is located at the bottom of the recess. A porous body that serves as a gas ejection port is located in the recess so as not to protrude from the bearing surface. A first groove is located in the surface of the porous body, extending from the central region of the surface to the outer periphery of the porous body. A second groove that communicates with the first groove is located in the bearing surface of the base.

[0064] The present disclosure further discloses the following embodiments (2) to (16).

[0065] (2) In the hydrostatic gas bearing device described in (1) above, a first intersecting groove that intersects with the second groove is located on the bearing surface. (3) In the hydrostatic gas bearing device described in (1) or (2) above, at least two second grooves are located, and the first intersecting groove connects adjacent second grooves. (4) In the hydrostatic gas bearing device described in any of (1) to (3) above, the first intersecting groove is annular. (5) In the hydrostatic gas bearing device described in any of (1) to (4) above, the surface of the porous body and the bearing surface of the base are flush with each other. (6) In the hydrostatic gas bearing device described in any of (1) to (5) above, the porous body is made of the same material as the member in which the recess is located. (7) In the hydrostatic gas bearing device described in any of (1) to (6) above, at least the bottom surface of the porous body is bonded to the recess. (8) In the hydrostatic gas bearing device described in (7) above, the porous body is bonded to the entire surface of the recess except for the opening of the gas supply hole. (9) In the hydrostatic gas bearing device described in any of (1) to (8) above, at least two first grooves are located, and the angles formed by two adjacent first grooves are the same. (10) In the hydrostatic gas bearing device described in any of (1) to (9) above, the porous body further includes second intersecting grooves that intersect with the first grooves. (11) In the hydrostatic gas bearing device described in any of (1) to (10) above, a plurality of recesses are located on the bearing surface, and a plurality of porous bodies are located in each of the plurality of recesses. (12) In the hydrostatic gas bearing device described in (11) above, when one porous body, a first groove located in the porous body, a second groove communicating with the first groove, and a first intersecting groove intersecting the second groove are considered to be one unit, a plurality of units are located on the bearing surface, and adjacent units are connected by sharing at least a portion of the second groove or at least a portion of the first intersecting groove. (13) In the hydrostatic gas bearing device described in (11) above, when one porous body, a first groove located in the porous body, a second groove communicating with the first groove, and a first intersecting groove intersecting the second groove are considered to be one unit, a plurality of units are located on the bearing surface, and each unit is independent so as not to come into contact with each other.(14) In the hydrostatic gas bearing device described in (13) above, in at least two units, adjacent units are connected via a communicating groove. (15) In the hydrostatic gas bearing device described in any one of (1) to (14) above, the arithmetic mean roughness Ra of the bearing surface of the base is smaller than the arithmetic mean roughness Ra of the inner wall surface of the second groove. (16) In the hydrostatic gas bearing device described in any one of (1) to (15) above, the arithmetic mean roughness Ra of the surface of the porous body is smaller than the arithmetic mean roughness Ra of the inner wall surface of the first groove.

[0066] REFERENCE SIGNS LIST 1 Movable member 1a Bearing surface of base of movable member 11 Recess 11a Bottom surface of recess 12 Gas supply hole 12a Opening of gas supply hole 2 Fixed member 2a Bearing surface of base of fixed member 3 Porous body 3a Other porous body 41 First groove 41a Other first groove 42 Second groove 51 First intersecting groove 52 Second intersecting groove 53 Communication groove 54 Shared groove

Claims

1. Comprising a movable member and a fixed member, a concave portion is located on a bearing surface of a base body of the movable member or the fixed member, and an opening of a gas supply hole is located on a bottom surface of the concave portion, a porous body serving as a gas ejection portion is positioned in the concave portion so as not to protrude from the bearing surface, a first groove extending from a central region of the surface to an outer periphery of the porous body is located on the surface of the porous body, a second groove communicating with the first groove is located on the bearing surface of the base body A static pressure gas bearing device.

2. The static pressure gas bearing device according to claim 1, wherein a first intersecting groove intersecting with the second groove is located on the bearing surface.

3. The static pressure gas bearing device according to claim 2, wherein at least two second grooves are located, and the first intersecting groove connects adjacent second grooves.

4. The static pressure gas bearing device according to any one of claims 1 to 3, wherein the first intersecting groove is annular.

5. The static pressure gas bearing device according to any one of claims 1 to 3, wherein the surface of the porous body and the bearing surface of the base body are flush.

6. The static pressure gas bearing device according to any one of claims 1 to 3, wherein the porous body is made of the same material as the member in which the concave portion is located.

7. The static pressure gas bearing device according to any one of claims 1 to 3, wherein at least a bottom surface of the porous body is adhered to the concave portion.

8. The static pressure gas bearing device according to claim 7, wherein the porous body is adhered to the entire surface of the concave portion except for the opening of the gas supply hole.

9. The static pressure gas bearing device according to any one of claims 1 to 3, wherein at least two first grooves are located, and an angle formed by two adjacent first grooves has the same angle.

10. The static pressure gas bearing device according to any one of claims 1 to 3, wherein a second intersecting groove intersecting with the first groove is further located in the porous body.

11. The static pressure gas bearing device according to any one of claims 1 to 3, wherein a plurality of the concave portions are located on the bearing surface, and a plurality of the porous bodies are located in the plurality of the concave portions respectively.

12. When one porous body, the first groove located in the porous body, the second groove communicating with the first groove, and the first intersecting groove intersecting with the second groove are taken as one unit, a plurality of the units are located on the bearing surface, and adjacent units are connected by sharing at least a part of each unit. The static pressure gas bearing device according to claim 11.

13. When taking one of the porous bodies, the first groove positioned in the porous body, the second groove communicating with the first groove, and the first intersecting groove intersecting with the second groove as one unit, the units are located at a plurality of positions on the bearing surface, and each unit is independent so that the units do not contact each other. The static pressure gas bearing device according to claim 11.

14. In at least two of the units, adjacent units are connected to each other via a communication groove. The static pressure gas bearing device according to claim 13.

15. The arithmetic mean roughness Ra of the bearing surface of the base is smaller than the arithmetic mean roughness Ra of the inner wall surface of the second groove. The static pressure gas bearing device according to any one of claims 1 to 3.

16. The arithmetic mean roughness Ra of the surface of the porous body is smaller than the arithmetic mean roughness Ra of the inner wall surface of the first groove. The static pressure gas bearing device according to any one of claims 1 to 3.