Static 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

Technical Field

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

Background Art

[0002] Conventionally, in semiconductor manufacturing devices such as mask exposure devices, an air slide has been used as a device for scanning and positioning a stage with high precision. Examples of such an air slide include those employing an orifice throttle and a surface throttle. When foreign matter enters the gas supply hole of such an air slide, the gas supply amount changes, the rigidity decreases, and the dynamic posture of the moving body cannot be stabilized.

[0003] Therefore, as described in Patent Document 1, a hydrostatic bearing device provided with a porous member in a bearing portion and provided with an air supply hole and an exhaust groove for exhausting pressurized fluid in the porous member has been used. The hydrostatic bearing device described in Patent Document 1 can increase the ejection area of compressed gas. Therefore, although the bearing rigidity can be increased, there is a problem that vibration occurs due to the gas compression effect in the porous body. In particular, in the semiconductor manufacturing process, with the high integration and high performance of semiconductor elements, etc., reduction of micro-vibration with respect to the stage is required.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Means for Solving the Problems

[0005] The hydrostatic gas bearing device according to this disclosure comprises a movable member and a fixed member. A recess is located on the bearing surface of the base body of the movable member or the fixed member, and an opening for a gas supply hole is located at the bottom of the recess. A porous body, which serves as a gas ejection part, is located in the recess so as not to protrude from the bearing surface. A first groove is located on the surface of the porous body, extending from the central region of the surface to the outer circumference of the porous body. A second groove communicating with the first groove is located on the bearing surface of the base body. The cross-sectional area of ​​the first groove is larger than the cross-sectional area of ​​the second groove. [Brief explanation of the drawing]

[0006] [Figure 1] This is an explanatory diagram showing an example in which a hydrostatic gas bearing device according to one embodiment of the present disclosure is installed in a linear guide device. [Figure 2A] This is a plan view showing the main parts of a hydrostatic gas bearing device according to one embodiment of the present disclosure. [Figure 2B] This is a plan view showing a modified example of a key part of a hydrostatic gas bearing device according to one embodiment of the present disclosure. [Figure 2C] This is a plan view showing another modified example of a key part of a hydrostatic gas bearing device according to one embodiment of the present disclosure. [Figure 3] This is an explanatory diagram showing a cross-section cut along the line XX shown in Figure 2A. [Figure 4] This is a plan view showing the bottom surface of the recess. [Figure 5] This is a plan view showing the main parts of a hydrostatic gas bearing device according to another embodiment of the present disclosure. [Figure 6] This is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. [Figure 7] This is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. [Figure 8] This is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. [Figure 9A] This is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. [Figure 9B] This is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. [Figure 10] This is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. [Figure 11A] This is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. [Figure 11B] This is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. [Modes for carrying out the invention]

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

[0008] The hydrostatic gas bearing device according to this disclosure, having the above-described configuration, can reduce micro-vibrations and the decrease in rigidity due to clogging of the gas supply holes.

[0009] A hydrostatic gas bearing device according to one 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 a hydrostatic gas bearing device according to one embodiment of the present disclosure is installed in a linear guide device. The hydrostatic gas bearing device according to one embodiment comprises a movable member 1 and a fixed member 2.

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

[0011] The movable member 1 and the fixed member 2 are formed of, for example, ceramics or metal. Examples of the ceramics forming the movable member 1 and the fixed member 2 include ceramics mainly composed of, for example, alumina, zirconia, silicon carbide, silicon nitride, or aluminum nitride. Examples of the metal include, for example, aluminum and stainless steel. The movable member 1 and the fixed member 2 may be formed of the same material or different materials.

[0012] In this specification, "main component" means a component that occupies 80% by mass or more in a total of 100% by mass of the components constituting the ceramics. The identification of each component contained in the ceramics is performed by an X-ray diffractometer using CuKα rays, and the content of each component may be determined by, for example, an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer or a fluorescent X-ray analyzer.

[0013] Hereinafter, an embodiment in which gas is ejected from the bearing surface 1a of the base body of the movable member 1 will be described based on FIGS. 2A to 4. FIG. 2A is a plan view showing a main part of a hydrostatic gas bearing device according to an embodiment of the present disclosure. FIG. 3 is an explanatory view showing a cross section cut along the X-X line described in FIG. 2A. FIG. 4 is a plan view showing the bottom surface 11a of the recess 11. As shown in FIGS. 2A to 4, a recess 11 and a gas supply hole 12 having an opening 12a in a part of the bottom surface 11a of the recess 11 are located on the bearing surface 1a of the base body of the movable member 1.

[0014] A 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 part. The porous body 3 is fixed to the recess 11 so as not to protrude from the bearing surface 1a of the base body of the movable member 1.

[0015] As shown in FIGS. 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 concave portion 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 concave portion 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 an ejection portion. The gas supply hole 12 may be, for example, a lateral hole formed from the side surface of the base body, a vertical hole formed from the bottom surface of the base body, or a combination of a lateral hole formed from the side surface of the base body and a vertical hole connecting the lateral hole and 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, aluminum nitride, or the like. The porous body 3 may be formed of the same material as the member (in one embodiment, the movable member 1) in which the concave portion 11 is located. When the porous body 3 is formed of the same material as the member in which the concave portion 11 is located, a difference in thermal expansion coefficient is less likely to occur, and stress is less likely to occur even during temperature changes. Therefore, it is less likely that turbulent flow is generated due to deformation or the like, and micro-vibration due to turbulent flow is further reduced. The porosity of the porous body 3 is not limited, and may be, for example, 20% or more and 50% or less. The average particle diameter of the porous body 3 is not limited, and may be, for example, 10 μm or more and 100 μm or less.

[0017] The porosity of the porous body 3 is obtained, for example, by the mercury intrusion method. The mercury intrusion method is a method of obtaining the porosity by pressing mercury into the pores of the porous body 3 (sample) using a mercury intrusion porosimeter (mercury intrusion method), and may be obtained 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 concave portion 11. For example, the upper surface of the porous body 3 and the bearing surface of the base body (in one embodiment, the bearing surface 1a of the base body of the movable member 1) may be flush. When the upper surface of the porous body 3 and the bearing surface of the base body are flush, turbulent flow due to the step between the upper surface of the porous body 3 and the bearing surface of the base body is less likely to occur. As a result, micro-vibration due to turbulent flow is 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, epoxy adhesives such as Araldite (registered trademark, manufactured by Huntsman Japan) and Tollseal (manufactured by Agilent) can be used for bonding. Furthermore, the porous body 3 may be bonded to the entire surface of the recess 11 other than the opening 12a of the gas supply hole 12. When the porous body 3 is bonded to the entire surface of the recess 11 other than 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 later. As a result, the gas is more easily dispersed throughout the porous body 3, and micro-vibrations are further reduced.

[0020] The surface of the porous body 3 is provided with a plurality of radially oriented first grooves 41. When viewed from above, the first grooves 41 are formed extending outward from the central region of the porous body 3, as shown in Figure 2A. The number of first grooves 41 is not limited to at least one groove extending from the central region of the surface of the porous body 3 to the outer circumference of the porous body 3. From the viewpoint of homogenizing the pressure distribution in the plane, there may be 3 to 8 first grooves 41. 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 length of the first groove 41 is not particularly limited. This cross-sectional shape may be, for example, a U-shape where the opening and bottom of the groove are the same width, a V-shape where the width of the opening is greater than the width of the bottom, or a U-shape (a shape with a curve at the bottom). In particular, from the viewpoint of reducing gas turbulence, a V-shape or U-shape where the width of the opening is greater than the width of the bottom is also acceptable. 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 elongated (width is smaller than depth). Therefore, losses due to resistance tend to be larger, so it is better for the groove width to be greater than the depth. However, if the depth is too large relative to the width, micro-vibrations tend to increase. Therefore, it is good for the width to be 100 times the depth or less.

[0022] In multiple first grooves 41, the angle formed by two adjacent first grooves 41 may be the same. This configuration allows the gas flowing through the first grooves 41 to be more uniform. As a result, variations in gas flow are reduced. In Figure 2A, four first grooves 41 are formed at 90° intervals.

[0023] The bearing surface of the base body (in one embodiment, the bearing surface 1a of the base body of the movable member 1) is provided with a plurality of second grooves 42 that communicate with the first groove 41.

[0024] Since the second groove 42 is in communication with the first groove 41, it is positioned in a straight line with the first groove 41, as shown in Figure 2A. 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] A hydrostatic gas bearing device according to one embodiment has a first groove 41 and a second groove 42. Therefore, the gas ejected from the porous body 3 can be moved to the second groove 42 by the first groove 41. As a result, the gas can be moved to the base of the movable member 1. Thus, a buoyant force can be generated at the base of the movable member 1, and the buoyant force stabilizes, reducing micro-vibrations.

[0026] The bearing surface 1a of the base body may be provided with a first intersecting groove 51 that intersects with the second groove 42. With this configuration, the gas flowing through the second groove 42 can also be dispersed in the direction intersecting with the second groove 42, further reducing micro-vibrations. Examples of "intersections" include two-way, three-way, and four-way intersections. A two-way intersection means a structure that extends in two directions from the intersection point, for example, an L-shape. A three-way intersection means a structure that extends in three directions from the intersection point, for example, a T-shape and a Y-shape. A four-way intersection means a structure that extends in four directions from the intersection point, for example, a cross shape, an X-shape and a swastika shape.

[0027] The first intersecting groove 51 may be connected at the end of the second groove 42, or it may be connected in the middle of the second groove 42. The end of the first intersecting groove 51 may be connected to the second groove 42, or the middle of the first intersecting groove 51 may be connected to the second groove 42. 42 It may be connected.

[0028] The first intersecting groove 51 is adjacent to the second groove 42 They may be connected to each other. This makes it easier to supply gas uniformly to the bearing surface 1a. In Figure 2A, the first intersecting groove 51 is positioned to connect the ends of the second grooves 42. In Figure 2A, the first intersecting groove 51 is formed in a rectangular shape to match the rectangular bearing surface 1a when viewed from above. Thus, it is preferable that the first intersecting groove 51 be formed parallel to the outer shape of the bearing surface 1a. However, the shape of the first intersecting groove 51 is not limited as long as it is formed to connect the second grooves 42 to each other.

[0029] For example, the first intersecting groove 51 may be formed in an annular shape to connect the second grooves 42, as shown in Figure 2A. The first intersecting groove 51 may be similar in shape to the bearing surface 1a of the base body (if the bearing surface 1a is rectangular as in Figure 2A, then the first intersecting groove 51 will 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 Figure 2A, the first intersecting groove 51 is formed in an annular shape to connect the ends of the second groove 42. However, as shown in Figure 2B, the first intersecting groove 51 may be formed in an annular shape to connect portions of the second groove 42 other than the ends. Figure 2B is a plan view showing a modified example of the main part of a hydrostatic gas bearing device according to one embodiment of the present disclosure.

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

[0032] As shown in Figure 5, the porous body 3 may further be provided with at least one second intersecting groove 52 that intersects with the first groove 41. Figure 5 is a plan view showing the main part of a hydrostatic gas bearing device according to another embodiment of the present disclosure. The provision of the second intersecting groove 52 reduces variations in 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 groove 52 may be similar in shape to the porous body 3 when viewed from above. In Figure 5, when viewed from above, the porous body 3 has a circular shape, and the second intersecting groove 52 also has a circular shape (annular). In Figure 5, the second intersecting groove 52 has a circular shape (annular). However, the second intersecting groove 52 is not limited to annular shapes as long as it can connect the first grooves 41.

[0034] The arithmetic mean roughness Ra of the bearing surface of the base (bearing surface 1a of the base 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 base 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 base 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 is relatively rough, which can slow down the velocity of the flowing gas. As a result, vibrations are absorbed and micro-vibrations are reduced. On the other hand, the bearing surface of the base is relatively smooth. Therefore, the gas can spread uniformly on the bearing surface (bearing surface 1a), and the movable member 1 can 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, which can slow down the velocity of the flowing gas. 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 spread uniformly across 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 substrate 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). The measurement conditions are a magnification of 240x, no cutoff value λs, a cutoff value λc of 0.08 mm, and no cutoff value fs. The measurement range of one surface to be measured is 1420 μm × 1070 μm, and four measurement ranges should be set from the surface to be measured. Four lines to be measured should be drawn at approximately equal intervals within each measurement range, and the surface roughness should be measured. The length of each line to be measured is 1320 μm.

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

[0039] The cross-sectional area of ​​the first groove 41 refers to the area of ​​the region enclosed by a virtual plane passing through the surface of the porous body 3 and the inner wall of the first groove 41 in a cross-section obtained by cutting the first groove 41 perpendicular to its extension direction. The cross-sectional area of ​​the second groove 42 refers to the area of ​​the region enclosed by a virtual plane passing through the bearing surface of the base and the inner wall of the second groove 42 in a cross-section obtained by cutting the second groove 42 perpendicular to its extension direction.

[0040] As shown in Figure 6, a plurality of recesses 11 may be located on the bearing surface of the base (the 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. Figure 6 is a plan view showing the main part of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. By fixing the plurality of porous bodies 3 to each of the plurality of recesses 11, the gas ejection within the bearing surface becomes uniform. As a result, this type of fixing structure can be applied, for example, to a larger bearing surface area.

[0041] In an embodiment in which multiple porous bodies 3 are fixed to each of the 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 as one unit, then multiple units are located on the bearing surface 1a, and each unit may be positioned independently so that the units do not come into contact with each other.

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

[0043] Furthermore, as shown in Figure 8, adjacent units may be connected by a shared groove 54, where a portion of the first intersecting groove 51 of one unit and a portion of the first intersecting groove 51 of the other unit are shared. In other words, among adjacent units, a portion of the first intersecting groove 51 of one unit may include the shared groove 54, and a portion of the first intersecting groove 51 of 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 spreads more 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 connecting groove 53 on the bearing surface of the base (the bearing surface 1a of the base of the movable member 1), is not limited to any method of forming grooves.

[0045] For example, the grooves may be formed by grinding or polishing after the porous body 3 and the base of the movable member 1 (or the base of the fixed member 2) have been manufactured, or the grooves may be formed in advance when the porous body 3 and the base are manufactured. As a method for forming the grooves in advance, if the porous body 3 and the base are made of ceramics, a precursor (molded body) in which the parts that will become the grooves are formed can be obtained, and this precursor can be fired. Alternatively, the grooves may be formed after the porous body 3 has been 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 formed integrally. As a result, the positional accuracy of the first groove 41 and the second groove 42 is improved.

[0046] The hydrostatic gas bearing device according to this 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 to connect the ends of the second groove 42. However, in the hydrostatic gas bearing device according to this disclosure, in addition to the first intersecting groove, a further intersecting groove may be provided between the first intersecting groove and the porous body. This further intersecting groove only needs to be provided for at least one circumference, 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 a 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 connecting the ends of the second groove 42. However, there may be three or more such units. These units may be arranged in a linear fashion, in a grid pattern vertically and horizontally, or randomly.

[0048] Figure 9A is a plan view showing the main part of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. In the hydrostatic gas bearing device of Figure 2A, other porous bodies 3a and other first grooves 41a located on the other porous bodies 3a may be located in the middle of the first intersecting groove 51. Even in such a case, it can be said that adjacent second grooves 42 are connected by the first intersecting groove 51.

[0049] Figure 9B is a plan view showing the main part of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. In the hydrostatic gas bearing device of Figure 2A, other porous bodies 3a and other first grooves 41a located on the other porous bodies 3a may be located at the connection between the second groove 42 and the first intersecting groove 51. Even in such a case, the first intersecting groove 51 can be said to intersect the second groove 42.

[0050] The configurations shown in Figures 9A and 9B allow for an increase in the number of porous bodies to which the gas is supplied. As a result, the gas can be distributed uniformly across the bearing surface, further reducing micro-vibrations.

[0051] Figure 10 is a plan view showing the main part of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. The hydrostatic gas bearing device of Figure 10 can be said to have 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. In Figure 10, it can be said that another porous body 3a and another first groove 41a located on the porous body 3a are located at the connection point between the second groove 42 and the first intersecting groove 51. Even with such a configuration, the buoyancy force of the movable member 1 is stable and micro-vibrations are reduced.

[0052] Figure 11A is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. The hydrostatic gas bearing device of Figure 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 Figure 11A, the first intersecting groove 51 does not have to have an annular structure.

[0053] Figure 11B is a plan view showing the main parts of a hydrostatic gas bearing device according to yet another embodiment of the present disclosure. In Figure 11B, in the hydrostatic gas bearing device of Figure 11A, 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. Even in this case, the first intersecting groove 51 can be said to intersect with the second groove 42. Even with configurations like those in Figures 11A and 11B, the buoyancy force of the movable member 1 is stable and micro-vibrations are reduced. [Examples]

[0054] The hydrostatic gas bearing apparatus according to this disclosure will be described in detail below with reference to examples and comparative examples, but the hydrostatic gas bearing apparatus according to this disclosure is not limited to the following examples.

[0055] (Example 1) First, a hydrostatic gas bearing device as shown in Figure 1 was fabricated. The movable member 1 included in the hydrostatic gas bearing device of Example 1 is made of alumina, and was fabricated using alumina with a purity of 99.5% by mass. The dimensions of the four bearing surfaces 1a are 100 mm in width and 100 mm in length in the direction of movement.

[0056] Each of the four bearing surfaces 1a contains one unit, as shown in Figure 2A, which includes a porous body 3, a first groove 41, a second groove 42, and a first intersecting groove 51. Both the second groove 42 and the first intersecting groove 51 have a width of 1 mm and a depth of 0.02 mm. The first intersecting groove 51 has a square-shaped annular structure when viewed from above. In the first intersecting groove 51, the length in the direction perpendicular to the direction of movement of the movable member 1 is 50 mm, and the length in the direction of movement of the movable member 1 is 50 mm.

[0057] The porous body 3 is made of alumina, fabricated using alumina with a purity of 99.5% by mass, has an average particle size of 80 μm, and a porosity of 40%. The porous body 3 has a diameter of 10 mm. The first groove 41 located in the porous body 3 has 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 is made of alumina, and was manufactured using alumina with a purity of 99.5% by mass. The length and width of the fixed member 2 are 80 mm, and the length in the longitudinal direction (length in the direction in which the movable member 1 moves) is 300 mm.

[0059] (Comparative Example 1) A hydrostatic gas bearing device was fabricated in the same manner as in Example 1, except that an orifice diaphragm with 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, 4 kgf / cm³ of gas is supplied to the gas supply hole 12 of the movable member 1. 2 Compressed gases were supplied to each of the structures, and their stiffness and micro-vibrations were measured. Stiffness was measured by the change in levitation when a load was applied. Micro-vibrations were 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 a rigidity comparable to that of 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 those of the hydrostatic gas bearing device of Comparative Example 1.

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

[0063] (1) The hydrostatic gas bearing device according to this disclosure comprises a movable member and a fixed member. A recess is located on the bearing surface of the base body of the movable member or the fixed member, and an opening for a gas supply hole is located on the bottom surface of the recess. A porous body, which serves as a gas ejection part, is located in the recess so as not to protrude from the bearing surface. A first groove is located on the surface of the porous body, extending from the central region of the surface to the outer circumference of the porous body. A second groove is located on the bearing surface of the base body, communicating with the first groove.

[0064] With regard to embodiments of the present disclosure, embodiments shown in (2) to (16) below are further disclosed.

[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, there are at least two second grooves, and the first intersecting grooves connect 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 substrate are flush. (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 recesses other than the openings of the gas supply holes. (9) In the hydrostatic gas bearing device described in any of (1) to (8) above, there are at least two first grooves, and the angle formed by two adjacent first grooves is the same. (10) In the hydrostatic gas bearing device described in any of (1) to (9) above, the porous body further has a second intersecting groove that intersects with the first groove. (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, if a 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 as one unit, then multiple units are located on the bearing surface, and adjacent units are connected by sharing at least a part of the second groove or at least a part of the first intersecting groove. (13) In the hydrostatic gas bearing device described in (11) above, if a 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 as one unit, then multiple units are located on the bearing surface, and each unit is independent so that the units do not 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 to each other via a communication groove. (15) In the hydrostatic gas bearing device described in any of (1) to (14) above, the arithmetic mean roughness Ra of the bearing surface of the base body 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 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. [Explanation of Symbols]

[0066] 1. Movable member 1a Bearing surface of the base of the movable member 11 recess 11a Bottom surface of the recess 12 Gas supply port 12a Opening of the gas supply port 2 Fixing members 2a Bearing surface of the base of the fixing member 3. Porous material 3a Other porous materials 41 First groove 41a Other first grooves 42 2nd groove 51 First intersecting groove 52 Second intersecting groove 53 Communication groove 54 Common groove

Claims

1. It comprises a movable member and a fixed member, A recess is located on the bearing surface of the base of the movable member or the fixed member, and an opening for a gas supply hole is located on the bottom surface of the recess. In the recess, a porous body that serves as a gas ejection point is positioned so as not to protrude from the bearing surface. A first groove is located on the surface of the porous body, extending from the central region of the surface to the outer circumference of the porous body. A second groove communicating with the first groove is located on the bearing surface of the base body. The cross-sectional area of ​​the first groove is greater than the cross-sectional area of ​​the second groove. Static gas bearing device.

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

3. The hydrostatic gas bearing device according to claim 2, wherein at least two of the second grooves are located, and the first intersecting grooves connect adjacent second grooves.

4. The hydrostatic gas bearing device according to claim 2 or 3, wherein the first intersecting groove is annular.

5. The hydrostatic 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 substrate are flush.

6. The hydrostatic 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 recess is located.

7. The hydrostatic gas bearing device according to any one of claims 1 to 3, wherein at least the bottom surface of the porous body is bonded to the recess.

8. The hydrostatic gas bearing device according to claim 7, wherein the porous body is bonded to the entire surface of the recess other than the opening of the gas supply hole.

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

10. The hydrostatic gas bearing device according to any one of claims 1 to 3, wherein the porous body further has a second intersecting groove that intersects with the first groove.

11. A hydrostatic gas bearing device according to any one of claims 1 to 3, wherein 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. The hydrostatic gas bearing device according to claim 2 or 3, wherein 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 as one unit, a plurality of such units are located on the bearing surface, and adjacent units are connected by sharing at least a portion of each unit.

13. The hydrostatic gas bearing device according to claim 2 or 3, wherein 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 as one unit, a plurality of such units are located on the bearing surface, and each unit is independent so as not to come into contact with one another.

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

15. The hydrostatic gas bearing device according to any one of claims 1 to 3, wherein 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. The hydrostatic gas bearing device according to any one of claims 1 to 3, wherein 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.

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