JP2010249315A - Static pressure gas bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a static pressure gas bearing achieved high rigidity over a wide frequency region by variable autogenous throttling having high responsiveness. <P>SOLUTION: One part of a bearing surface includes a flexible bearing surface 1 formed from a flexible member 7 having flexibility, and the flexible member includes an air intake hole 3 forming autogenous throttling so as to perform variable autogenous throttling. A pressure change of a gas inside a bearing cavity Cr is directly transmitted to the flexible bearing surface 1. Since this static pressure gas bearing does not have a movable article, variable autogenous throttling having high responsiveness is achieved. With this structure, a static pressure gas bearing achieved high responsiveness over a wide frequency region is provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an increase in rigidity of a hydrostatic gas bearing that supports a movable body in a non-contact manner and is used in a positioning device such as a precision processing machine, a precision measuring machine, or a semiconductor manufacturing apparatus.

  In order to improve the performance of a positioning device used in a precision processing machine, a precision measuring machine, a semiconductor manufacturing apparatus, etc., it is necessary to upgrade a bearing that supports a positioning object. When the required level of positioning accuracy is on the nanometer level, static pressure gas bearings are generally used because of features such as frictionless, dust-free and low heat generation due to non-contact support. However, when aiming at higher positioning accuracy reaching the sub-nanometer level, a general static pressure gas bearing has a problem of insufficient rigidity.

  Conventionally, in order to increase the rigidity, there has been proposed a variable-throttle type static pressure gas bearing having an element that changes the flow rate according to a change in load acting on the bearing gap. The elements that change the flow rate are classified into two types, that is, an air supply position and an exhaust position, depending on the arrangement position, and two types, that is, an automatic adjustment throttle and a control throttle, depending on the method.

  The automatic adjustment throttle is a system that automatically adjusts the throttle using the pressure fluctuation in the bearing gap. The control diaphragm is a method of adjusting the diaphragm by sensing a change in the bearing gap and controlling an actuator such as a piezoelectric element. Thereafter, the automatic adjustment throttle provided at the supply position is provided with the automatic supply adjustment throttle, the control throttle provided at the supply position is provided with the supply control throttle, the automatic adjustment throttle provided at the exhaust position is provided with the exhaust automatic adjustment throttle, and the exhaust position. This control throttle is called an exhaust control throttle.

  As these specific prior arts, there is one disclosed in Patent Document 1 regarding an automatic air supply adjustment throttle. This is because a movable object to be a variable throttle is added to the fixed air supply throttle, and the pressure chamber (described as the lower pocket in the text of Patent Document 1) for operating the movable object, the flow connecting the bearing gap and the pressure chamber. It is the structure provided with the path. The pressure fluctuation in the bearing gap due to the change in the bearing gap is transmitted to the pressure chamber via the flow path connecting the bearing gap and the pressure chamber, and the movable object is operated to adjust the flow rate to the bearing gap. Stiffening is planned.

  Further, there is an air supply control throttle disclosed in Patent Document 2. This has a structure in which the slot interval of the slot-shaped air supply throttle is changed by an adjustment sleeve driven by a piezoelectric element. The amount of change in the bearing gap is sensed by a separately provided displacement sensor, feedback control is performed, and the piezoelectric element is driven so as to cancel the amount of change in the bearing gap, thereby achieving high rigidity.

  Further, there is an exhaust control throttle disclosed in Patent Document 3. This is a configuration in which an exhaust control throttle that can be driven by a piezoelectric element is incorporated in an exhaust passage provided in a region surrounded by an air supply passage in a radial static pressure gas bearing. A displacement sensor provided separately senses the amount of change in the bearing gap, performs feedback control, and drives the piezoelectric element to cancel the amount of change in the bearing gap, thereby changing the exhaust flow rate and increasing the rigidity. Yes.

Japanese Patent Publication No. 6-8651 JP 2001-107963 A Japanese Patent Laid-Open No. 4-131518

  However, what is disclosed in Patent Document 1 above is a configuration including a pressure chamber, a flow path connecting the bearing gap and the pressure chamber, and a movable object, and responsiveness of an element that changes the flow rate with respect to a load variation. However, there is a problem that it is difficult to obtain high rigidity at a high frequency. In addition, the load capacity in the portion where the bearing gap is large is maintained to some extent, and there is room for high rigidity by reducing the load capacity in the region where the bearing gap is large.

  Moreover, since what was disclosed by the said patent documents 2 and 3 is the high rigidity technique using control, actuators, such as a displacement sensor and a piezoelectric element, are essential. This complicates the device configuration and necessitates peripheral devices for driving the piezoelectric elements, which makes the device expensive.

  In addition, the response of the air supply control throttle or the exhaust control throttle is limited by the resonance frequency of the fixed portion of the piezoelectric element and the piezoelectric element itself, so that it is difficult to respond in a high frequency region, and high rigidity is obtained. I couldn't.

  An object of the present invention is to provide a hydrostatic gas bearing having high responsiveness and realizing high rigidity even in a high frequency region.

  In order to solve the above-mentioned problems, a static pressure gas bearing according to the present invention includes a bearing surface facing the guide surface with a bearing gap therebetween, and a static pressure gas bearing in which a gas is interposed in the bearing gap. An air supply path for supplying the gas and / or an exhaust path for exhausting the gas from the bearing gap, and a flexible member is disposed between the air supply path and / or the exhaust path and the bearing gap. The flexible member is deformed by the difference between the gas pressure on the air supply path side of the flexible member and / or the gas pressure on the exhaust path side of the flexible member and the gas pressure on the bearing gap side. Features.

  Realization of high rigidity over a wide frequency range by using a static pressure gas bearing with a highly responsive automatic adjustment throttle according to the present invention in a positioning device used in precision processing machines, precision measuring machines or semiconductor manufacturing equipment. It is possible to provide a hydrostatic gas bearing.

It is a figure explaining the static pressure gas bearing by 1st Embodiment. It is explanatory drawing of the load characteristic curve of a static pressure gas bearing. It is the schematic of the static pressure gas bearing by 1st Embodiment. It is a figure explaining the static pressure gas bearing by 2nd Embodiment. It is the schematic of the static pressure gas bearing by other embodiment. It is the schematic of the static pressure gas bearing by 5th Embodiment. It is the schematic of the static pressure gas bearing by 6th Embodiment. It is the schematic of the static pressure gas bearing by 7th Embodiment. It is explanatory drawing of the load characteristic curve of a static pressure gas bearing. It is the schematic of the static pressure gas bearing by a modification. It is the schematic of the static pressure gas bearing by 8th Embodiment. It is the schematic of the static pressure gas bearing by 9th Embodiment. It is the schematic of the static pressure gas bearing by 10th Embodiment. It is the schematic of the static pressure gas bearing by 11th Embodiment.

(First embodiment)
DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a static pressure gas bearing having a first automatic adjustment throttle according to a first embodiment. FIG. 1 shows a static pressure gas bearing 10. The guide surface 9a is supported by the bearing surface 2 facing the guide surface 9a of the guide portion 9 with a bearing gap Cr therebetween and the gas interposed in the bearing gap Cr. 5 is an air supply path for supplying the gas to the bearing gap Cr. Reference numeral 7 denotes a flexible member disposed between the air supply path and the bearing gap. In the present embodiment, the flexible member 7 is formed of a thin plate formed at one end of the air supply path 5 provided in the base 6 and formed integrally with the base 6, for example. The flexible member 7 is provided with an air supply hole 3 that allows the bearing gap Cr and the air supply path 5 to communicate with each other. Pressurized gas from a pressurized gas supply source (not shown) is supplied from the air supply hole 3 through the air supply path 5. Supply to bearing gap Cr. The surface of the flexible member 7 that faces the guide surface 9a is hereinafter referred to as a flexible bearing surface 1, and the other bearing surface 2 (the surface of the base 6 that faces the guide surface 9a) is non-flexible. This is called a neutral bearing surface.

  In general static pressure gas bearings, pressurized gas is supplied to the bearing gap Cr via a restriction, and the load is supported by the pressure of the gas film formed in the bearing gap Cr. Therefore, when the load increases, the bearing gap Cr decreases, the gas pressure on the bearing gap side of the throttle increases, and the gas pressure in the bearing gap Cr balances with the load. However, the static pressure gas bearing 10 of the present embodiment adjusts the amount of pressurized gas supplied to the bearing gap Cr by a variable self-contained throttle. Here, the self-contained throttle is when the diameter of the air supply hole 3 is d and the height indicating the distance between the air supply hole edge 4 and the guide surface 9a facing the air supply hole edge 4 is the self-contained throttle height h. The side surface of the virtual cylinder having a diameter d and a self-made throttle height h acts as a throttle.

  This embodiment is characterized in that an air supply hole 3 for forming a self-contained throttle is provided in a flexible member 7 having flexibility. The flexible member 7 is deformed in accordance with the load acting on the bearing, and the self-drawing throttle height h changes. That is, it becomes a variable aperture. Hereinafter, the conventional self-contained throttle is referred to as a fixed self-contained throttle, and is an automatic air supply adjusting throttle used for the static pressure gas bearing of the present invention, wherein the self-constrained diaphragm whose flexible bearing surface is deformed is a variable self-constrained throttle. I will call it.

  FIGS. 1B, 1C, and 1D are views for explaining the operating principle of a static pressure gas bearing having a variable self-contained throttle that is an air supply automatic adjustment throttle according to the first embodiment. FIG. 1B shows a state in which the load acting on the bearing and the gas pressure in the bearing gap are balanced. Here, the air gap is narrowed by a self-contained throttle composed of the air supply hole edge 4 of the air supply hole 3 and the guide surface 9a facing the air supply hole edge 4 formed in the flexible member 7 for communicating the bearing gap Cr and the air supply path 5. The gas pressure immediately after is referred to as the gas pressure on the bearing gap side. The gas pressure on the air supply path side of the air supply hole 3 opened in the flexible member 7 as the air supply pressure Ps is referred to as the gas pressure on the air supply path side. Since the gas pressure Ps on the air supply path side is larger than the gas pressure P0 on the bearing gap side, the flexible bearing surface 1 protrudes toward the opposing guide surface 9a due to the pressure difference between both sides sandwiching the flexible member 7. Will be bent.

  According to the static pressure gas bearing 10 provided with the variable self-contained throttle according to the present embodiment, in order to keep the balance when the load is reduced from the balanced state shown in FIG. As described above, the pressure of the gas on the bearing gap side decreases from P0 to P2 (P2 <P0). Therefore, the pressure difference between both sides of the flexible member 7 is increased, and the flexible bearing surface 1 is deformed in a direction approaching the opposing guide surface 9a. As a result, the self-generated throttle height h decreases from h0 to h2 (h2 <h0), the throttle effect increases, and the flow rate into the bearing gap Cr decreases, so that the load reduction amount is balanced. The pressure in the bearing gap decreases. At this time, the fluctuation amount of the bearing clearance Cr is smaller in the variable self-forming throttle of the present invention than in the case of the conventional fixed self-forming throttle. That is, high rigidity is achieved.

  When the load increases from the balanced state shown in FIG. 1B, the gas pressure on the bearing gap side is changed from P0 to P1 (P1> P0) as shown in FIG. ). When the pressure difference between the gas on the air supply path side and the bearing gap side sandwiching the flexible member 7 is reduced, the flexible bearing surface 1 is deformed in a direction away from the opposing guide surface 9a. Then, the self-generated throttle height h increases from h0 to h1 (h1> h0), the throttle effect decreases, and the flow rate into the bearing gap Cr increases. As a result, the pressure in the bearing gap increases so as to balance the amount of load increase. At this time, the fluctuation amount of the bearing clearance is smaller in the variable self-contained throttle of the present invention than in the case of the conventional fixed self-formed throttle. That is, high rigidity is achieved.

  FIG. 2 is a diagram illustrating the operating principle of a static pressure gas bearing having a variable self-contained throttle according to the present invention, using a load characteristic curve. In the variable self-contained throttle, the pressure difference between the gas on both sides sandwiching the flexible member 7 is the largest, that is, the deflection becomes large, and the gas pressure difference between the both sides sandwiching the flexible member 7 is the smallest, that is, the deflection. It is considered that the amount of bending of the flexible member 7 is fixed in a case where the value becomes smaller. And the load characteristic at the time of treating virtually as a fixed aperture is shown with the former by a two-dot chain line, and the latter by a dotted line. According to the variable self-contained diaphragm according to the present invention, the load characteristic indicated by the two-dot chain line in FIG. 2B and the load characteristic indicated by the dotted line in FIG. Can be realized. As shown in FIG. 2 (a), the rigidity is expressed as a ratio of the load capacity fluctuation amount and the bearing gap fluctuation amount, and as shown in FIG. 2 (b), the rigidity is indicated by the two-dot chain line and the dotted line. By realizing the load characteristics that change, the rigidity can be increased.

  Thus, according to the variable self-contained throttle according to the present invention, the load change is compensated not by the bearing clearance change but by the change of the flexible bearing surface as in the case of the fixed self-formed throttle. Can do. As a result, the bearing gap fluctuation amount with respect to the load fluctuation amount can be made smaller than in the case of the fixed self-contained throttle. That is, the rigidity can be increased.

  In addition, the pressure change of the gas in the bearing gap Cr can be directly transmitted to the flexible member 7 which is an element for adjusting the flow rate without going through the pressure chamber or the flow path connecting the pressure chamber and the bearing gap Cr. it can. Furthermore, since there is no movable object, an automatic adjustment diaphragm having high responsiveness can be realized. Thereby, the static pressure gas bearing which realized high rigidity over a wide frequency range can be provided.

  In order to obtain an automatic adjustment diaphragm in this method, it is a necessary condition that the diaphragm is a self-contained diaphragm. That is, the relationship between the diameter d of the air supply hole 3 and the self-contained throttle height h needs to satisfy d / 4> h. When the above expression is not satisfied, the throttle becomes an orifice throttle that exhibits a throttling effect depending on the area of the air supply hole 3, so that the throttle does not change due to the change of the flexible bearing surface 1, and does not become an automatic adjustment throttle. Further, the automatic adjustment diaphragm (variable self-contained diaphragm) of the present invention cannot be realized unless the flexible member 7 is bent by the pressure difference. The flexible member 7 is formed of, for example, a plate-like member having the air supply holes 3. When the air supply hole 3 is formed at the center of the plate-like member, the plate thickness t [m] of the plate-like member and the Young's modulus E [Pa], the relation of the thin disk a [m] corresponding to the radius of the air supply path 5

を満たす形状であることを特徴とする。

It is the shape which satisfy | fills.

  The relational expression is a condition of the flexible member 7 for obtaining the effect of the present invention. By designing each parameter so as to satisfy the relational expression, the deformation amount of the flexible member 7 becomes 0.1 μm or more per 1 atm of pressure difference between both sides of the flexible member 7. In the static pressure gas bearing 10, the supply pressure Ps is generally 5 atm as a gauge pressure, and the bearing gap Cr is 5 μm or more. At this time, when the deformation amount of the flexible member 7 is less than 0.1 μm per atm, the deformation amount of the flexible member 7 is 0.5 μm (= 5 atm × 0.1 μm / atm) at the maximum. Even when used with a bearing gap Cr of 5 μm, the amount of deformation is only 10% or less. Therefore, the effect of increasing the rigidity by the variable self-contained diaphragm is very small in practice. By determining the shape of the flexible member 7 so as to satisfy the above relational expression, the amount of deformation of the flexible portion per pressure difference 1 atm on both sides of the flexible member 7 becomes 0.1 μm or more, and the self-contained throttle is variable. Acting as a throttle, the rigidity of the static pressure gas bearing 10 can be increased.

  FIG. 3 shows a schematic configuration of the hydrostatic gas bearing according to the first embodiment, wherein (a) is a schematic sectional view thereof, and (b) is a schematic plan view viewed from the guide surface side. Portions common to those in FIG. The bearing surface opposed to the guide surface 9a with a bearing gap Cr has eight flexible bearing surfaces 1 formed by flexible members 7 having flexibility. In the first embodiment, the example in which the variable self-contained diaphragms are arranged at eight places is shown, but the place and the number of the arranged places are not limited. Note that the flexible bearing surface 1 and the air supply hole 3 may be provided on the movable body side or the fixed body side.

(Second Embodiment)
FIG. 4 is a schematic cross-sectional view showing a schematic configuration of the hydrostatic gas bearing according to the second embodiment. FIG. 4A shows a schematic configuration of the hydrostatic gas bearing according to the second embodiment, FIG. 4B is a schematic sectional view thereof, and FIG. 4C is a schematic plan view seen from the guide surface side. Portions common to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  The hydrostatic gas bearing 20 according to the present embodiment is provided with a recess 18 on the bearing surface facing the guide surface 9a with a bearing gap Cr therebetween. Eight flexible bearing surfaces 1 having air supply holes 3 acting as variable self-contained throttles are arranged on the bottom surface of a recess 18 provided in the bearing surface 2. In FIG. 7, there are eight variable self-contained diaphragms, but there are no restrictions on the location and number of arrangements.

  In the above-described configuration, the purpose of the recess 18 is to increase the self-drawing height h, which is the distance between the air supply hole edge and the guide surface 9a facing, by the depth of the recess 18. In this way, the amount of deformation per unit pressure difference between both sides of the flexible bearing surface 1 can be increased as compared with the case where there is no recess 18, and the effect of the variable self-contained throttle is enhanced and the rigidity is increased. The action of can be enhanced.

  The flexible bearing surface 1 is a thin disk and has an air supply hole 3 that forms a self-contained throttle in the center. When the thin disk has a radius a [m], a thickness t [m], and a Young's modulus E [Pa],

を満たす形状であり、薄肉円板である可撓部材７を挟む両側の気体の圧力差「Ｐｓ−Ｐ０」により、圧力差１ａｔｍあたりで、薄肉円板中心部は０．１μｍ以上変形する。給気孔３は相対する案内面９ａとの関係により自成絞りを形成している。すなわち、給気孔３の直径をｄとし、また、自成絞り高さ（給気孔縁４と、給気孔縁４と対向する案内面９ａとの高さ）をｈとしたとき、

The central part of the thin disk is deformed by 0.1 μm or more per pressure difference of 1 atm due to the pressure difference “Ps−P0” of the gas on both sides of the flexible member 7 which is a thin disk. The air supply hole 3 forms a self-contained throttle by the relationship with the opposing guide surface 9a. That is, when the diameter of the air supply hole 3 is d, and the self-contained throttle height (height of the air supply hole edge 4 and the guide surface 9a facing the air supply hole edge 4) is h,

の関係が成り立つような範囲で、給気孔直径と、軸受使用時の軸受隙間Ｃｒが決定されている。

The diameter of the air supply hole and the bearing clearance Cr when the bearing is used are determined in such a range that the above relationship holds.

  Thereby, the air supply hole 3 formed in the flexible bearing surface 1 acts as a variable self-contained throttle, and the load change to the bearing can be compensated by the operation of the variable self-constant throttle, not the bearing gap fluctuation. . The amount of change in the bearing clearance relative to the change in load capacity can be made smaller than in the case of the fixed self-contained throttle. That is, the rigidity can be increased.

(Third embodiment)
FIG. 5A is a schematic plan view of the static pressure gas bearing according to the third embodiment, as viewed from the guide surface side. Portions common to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. In the static pressure gas bearing according to the present embodiment, a groove-shaped groove 28 is provided on the bearing surface 2. Then, variable self-contained throttles comprising flexible bearing surfaces and air supply holes made of a flexible member having flexibility are provided at four locations of the mouth-shaped groove 28. In the present embodiment, there are four variable self-contained diaphragms, but there are no restrictions on the location and number of arrangements.

(Fourth embodiment)
FIG. 5B is a schematic plan view of the static pressure gas bearing according to the fourth embodiment, viewed from the guide surface side. Portions common to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. In the static pressure gas bearing according to the present embodiment, a flexible bearing surface having an air supply hole 3 acting as a variable self-contained throttle is included in a square-shaped groove 38 and is disposed at one location on the rectangular bearing surface 2. Has been. In the present embodiment, there is one variable self-contained diaphragm arrangement, but there are no restrictions on the location and number of arrangements.

  FIG. 5C is a schematic plan view showing a round bearing having a variable self-contained throttle included in a circular groove according to a modification, as viewed from the guide surface side. Portions common to those in FIG. In the hydrostatic gas bearing according to this modification, a flexible bearing surface having an air supply hole 3 acting as a variable self-contained throttle is included in a circular groove 48 provided on the bearing surface, and a round bearing surface 2 is formed. Are arranged in four places. In FIG. 5 (c), there are four variable self-contained diaphragms, but there are no restrictions on the location and number of arrangements.

  FIG. 5 (d) is a schematic plan view showing a round bearing having a variable self-contained diaphragm contained in a circle-and-cross compound groove according to another modification, as viewed from the guide surface side. Portions common to those in FIG. In the static pressure gas bearing according to this modification, a flexible bearing surface having an air supply hole 3 acting as a variable self-contained throttle is included in a circular and cross-shaped groove 58 provided on the bearing surface, and has a round shape. The bearing surface 2 is arranged at one location. In FIG. 5 (d), there is one variable self-contained diaphragm, but there is no limitation on the location and number of the arrangement.

  FIG. 5 (e) is a schematic plan view showing a ring-shaped bearing having a variable self-contained diaphragm included in a circular groove according to still another modification, as viewed from the guide surface side. Portions common to those in FIG. In the static pressure gas bearing according to this modification, a flexible bearing surface having an air supply hole 3 acting as a variable self-contained throttle is included in a circular groove 68 provided on the bearing surface, and the ring-shaped bearing surface has There are 4 locations. In FIG. 5 (e), there are four variable self-contained diaphragms, but there are no restrictions on the location and number of arrangements. Further, the groove may be a polygon, or a composite shape in which the polygon, the center of gravity of the polygon, and each vertex are combined, and a typical example of the polygon is the above-mentioned mouth shape, and the polygon and the polygon A typical example of the composite shape in which the center of gravity and each side or each vertex are combined is the above-mentioned rice field shape.

  In the configuration shown in FIG. 5, the groove has the effect of spreading the pressure at the outlet portion of the air supply hole in the bearing gap over the entire bearing surface. Compared to the case without grooves, the load capacity of the bearing can be increased and the rigidity can be increased. Further, when the bearing surface shape is a square shape, it is desirable to form a mouth-shaped or rice-shaped groove. When the bearing surface shape is a round shape, it is desirable to form a groove having a circular shape or a combined shape of a circle and a cross. Further, when the bearing surface shape is a ring shape, it is desirable to form a circular groove. Thus, by setting it as a desirable groove shape with respect to a bearing surface shape, the load capacity of a bearing can be raised efficiently and rigidity can be improved.

(Fifth embodiment)
6A and 6B show a static pressure gas bearing according to a fifth embodiment, in which FIG. 6A is a schematic sectional view thereof, and FIG. 6B is a schematic plan view viewed from a guide surface side. Portions common to those in FIG. In the static pressure gas bearing 80 according to the present embodiment, the flexible bearing surface 1 having the air supply hole 3 acting as a variable self-contained throttle is included in a groove 69 having a square shape provided on the bearing surface, One place is placed at the intersection. Further, eight air supply holes 3 acting as a fixed throttle are arranged in a square-shaped groove 78 provided on the bearing surface. Here, the fixed restriction is, for example, a self-contained restriction or an orifice restriction. Although not shown, for example, a slot stop or a surface stop may be used as the fixed stop. In this embodiment, the variable self-contained diaphragm is disposed at one place and the fixed diaphragm is disposed at eight places. However, the place and number of the places are not limited.

  In the above configuration, the fixed throttle formed on the non-flexible bearing surface may be any one of a self-contained throttle, an orifice throttle, or a slot throttle, or a combination of a plurality. Combining the variable self-made throttle provided on the flexible bearing surface with the fixed throttle is effective in improving the manufacturability of the bearing incorporating the variable throttle. When a plurality of variable self-formed apertures are formed on one bearing, it is necessary to manage the dimensional accuracy between the variable self-formed apertures. Therefore, by reducing the number of variable self-made apertures as much as possible and making up for the insufficient load capacity with a fixed aperture, it is not necessary to manage the dimensional accuracy between the variable self-made apertures, which is effective in improving manufacturability and reducing costs. is there.

(Sixth embodiment)
FIG. 7 is a sixth embodiment, showing an angular bearing having a variable self-formed aperture included in a mouth-shaped groove, in which a non-flexible bearing surface is formed of a lubricious material, a) is a schematic cross-sectional view thereof, and (b) is a schematic plan view viewed from the guide surface side. Portions common to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. As shown in FIG. 7, the hydrostatic gas bearing 90 according to the present embodiment has a mouth-shaped groove 88 provided on the bearing surface facing the guide surface 9a with a bearing gap Cr therebetween. The flexible bearing surface 1 by the flexible member 7 which has flexibility is provided in four places of the groove-shaped groove 88. A portion other than the flexible bearing surface 1 is provided with a non-flexible bearing surface 2 in which layers of a lubricating material are laminated.

  A flexible bearing surface 1 having an air supply hole 3 acting as a variable self-contained throttle is included in a mouth-shaped groove 88 provided on the bearing surface, and is arranged at four locations on the mouth-shaped bearing surface. . The lubricating material is, for example, a resin or graphite fixed by means such as adhesion, or a non-flexible bearing surface coated by means such as sputtering or plating. Typical coating materials include DLC, fluorine-based materials, materials containing molybdenum disulfide, materials containing graphite, and the like, but it is possible to select the most suitable material depending on the use state and use environment. . In the present embodiment, the variable self-contained diaphragms are arranged in four places, but the place and the number of the places are not limited. By forming the non-flexible bearing surface with a lubricious material, the galling resistance of the bearing can be enhanced. Thereby, it is possible to prevent galling of the bearing at the time of touchdown due to sudden trouble such as when the supply gas is stopped or a load larger than expected is applied.

(Seventh embodiment)
FIG. 8 is a seventh embodiment showing a static pressure gas bearing having an automatic exhaust adjustment throttle, wherein (a) is a schematic cross-sectional view thereof, and (b) is a schematic plan view viewed from the guide surface side. (C), (d) is a figure explaining operation | movement of a flexible thin board.

  In FIG. 8, Ps indicates the supply air pressure, Pa1 and Pa2 indicate the ambient pressure, 73 indicates the exhaust path for exhausting the gas to the ambient pressure environment Pa1, and Pe indicates the pressure at the point where the gas flows into the exhaust path 73 from the bearing gap. ing. In the hydrostatic gas bearing according to the present embodiment, the bearing surface facing the guide surface 72 with the bearing gap Cr interposed therebetween includes the gas ejection surface 71, and the bearing clearance from the gas ejection surface 71 communicated with the air supply path 77a. A high-pressure gas film is generated by compressed gas such as compressed air supplied to Cr. A flexible thin plate 74 that is an elastic body is provided in a region surrounded by the gas ejection surface 71 of the bearing surface.

  The exhaust path 73 is provided with an exhaust gap 73 b formed by a narrow gap between the surface of the flexible thin plate 74 on the side opposite to the bearing gap (exhaust path side) and the fixing portion 710. The fixing portion 710 may be a part of the base 78, or may be configured by another member provided integrally with the base 78. The exhaust gap 73 b and the bearing gap Cr of the exhaust path 73 are communicated with each other through an exhaust hole 73 a formed in the flexible thin plate 74.

  The flexible thin plate 74 operates in conjunction with a pressure change in the bearing gap Cr. When the load on the bearing increases and the pressure of the bearing gap Cr increases, the pressure on the bearing gap side of the flexible thin plate 74 becomes larger than the pressure on the exhaust path side, and FIG. 8 (c) to (d) As shown in the figure, it is deformed in a direction away from the guide surface 72. As a result, the exhaust gap 73b of the exhaust passage 73 is narrowed, and the exhaust flow rate is reduced, whereby the bearing gap internal pressure is further increased. In this way, the bearing gap pressure that increases as the load on the bearing increases is not compensated by the decrease in the bearing gap Cr, but is compensated by the deformation of the flexible thin plate 74 so that the inside of the bearing gap Cr is increased. Can be held constant. That is, high rigidity can be achieved.

  FIG. 9A is a general load characteristic curve of the bearing and is an explanatory diagram of rigidity. The ratio of the change in the load capacity W to the change in the bearing gap Cr is rigidity. High rigidity corresponds to increasing the rate of change in load capacity with respect to change in bearing clearance Cr.

  FIG. 9B is a diagram illustrating the operating principle of the exhaust automatic adjustment throttle based on load characteristics. In the exhaust automatic adjustment throttle, considering that the throttle amount of the exhaust automatic adjustment throttle is virtually fixed in the case where the throttle is the tightest and the throttle is the most loose, the former load characteristic is indicated by a dotted line and the latter The load characteristics are indicated by a two-dot chain line.

  According to the exhaust automatic adjustment throttle according to the present embodiment, when the load on the bearing changes, as shown by the solid line in FIG. 9B connecting the load characteristic indicated by the dotted line and the load characteristic indicated by the two-dot chain line. Load characteristics can be realized. For example, when the load on the bearing is increased from zero, the bearing clearance Cr changes from the curve indicated by the two-dot chain line in FIG. 9B to the curve indicated by the dotted line through the curve indicated by the solid line. Follow.

  The exhaust automatic adjustment throttle has an effect of reducing the load capacity in a portion where the bearing clearance Cr is large, which does not require the load capacity in practical use. On the other hand, the air supply automatic adjustment throttle has such an effect that it has an effect of increasing the load capacity of the portion where the bearing clearance Cr is small compared to the case of the fixed throttle. By combining both, high rigidity can be achieved in a wide region of the bearing gap Cr.

  In addition, the pressure fluctuation in the bearing gap Cr can be directly transmitted to the exhaust automatic adjustment throttle without passing through the pressure chamber or the flow path that connects the pressure chamber and the bearing gap Cr. An automatic adjustment aperture can be realized. Thereby, the static pressure gas bearing which realized high rigidity also in a high frequency field can be provided.

  FIGS. 10A and 10B show a modification of the seventh embodiment. Portions common to those in FIG. In the seventh embodiment, the gas ejection surface 1 is a porous throttle, but the gas ejection surface may be a surface including an air supply hole 77 that forms a self-contained throttle or an orifice throttle. An air supply automatic adjustment throttle may be used. Of course, the variable self-contained diaphragm described in the first to sixth embodiments may be used. When used in combination with the variable self-contained diaphragm described in the first to sixth embodiments, higher rigidity can be realized than when either one is used.

(Eighth embodiment)
11A and 11B show a static pressure gas bearing according to an eighth embodiment, wherein FIG. 11A is a schematic cross-sectional view thereof, and FIG. 11B is a schematic plan view viewed from the guide surface side. Portions common to those in FIG.

  In the seventh embodiment, the path from the bearing gap Cr to the exhaust gap 73b is one central point. In the present embodiment, instead of the exhaust hole 73a communicating the bearing gap Cr and the exhaust gap 73b, the exhaust gas is exhausted. A circular slit 713 having a diameter larger than that of the hole 73a is provided.

  In this way, by disposing the place from the bearing gap Cr to the exhaust gap 73b on the outer diameter side, the amount of change in the internal pressure of the bearing gap Cr due to the deformation of the flexible thin plate 74 is increased, and the rigidity is increased. Can be high.

(Ninth embodiment)
12A and 12B show a static pressure gas bearing according to a ninth embodiment, wherein FIG. 12A is a schematic sectional view thereof, and FIG. 12B is a schematic plan view viewed from the guide surface side. Portions common to those in FIG.

  In the present embodiment, the groove 76 communicating with the exhaust gap 73b serves to make the pressure Pe in the portion flowing into the exhaust gap 73b from the bearing gap Cr substantially equal to the pressure in the groove. The effect of the exhaust automatic adjustment throttle becomes greater as the load characteristics of the fixed exhaust throttle fixed with the throttle throttled the most relaxed and the fixed exhaust throttle fixed with the throttle throttled the farthest are different. By extending the groove 76 from the exhaust gap 73b to the vicinity of the gas ejection surface, the range of the pressure Pe can be expanded from one central point to the outer periphery. That is, by adding the groove 76, it is possible to reduce the load capacity of the fixed exhaust throttle, which is fixed with the throttle being the most loose, over the entire bearing gap. The load characteristics of the fixed exhaust throttle that is fixed with the throttle being tightened to the maximum do not change even if the groove 76 is present. As a result, the amount of change in pressure in the bearing gap due to the change in the automatic adjustment throttle can be increased, and the rigidity can be increased as compared with the case where there is no groove 76.

(Tenth embodiment)
FIG. 13 shows a static pressure gas bearing according to the tenth embodiment, wherein (a) is a schematic sectional view thereof, and (b) is a schematic plan view viewed from the guide surface side. (C), (d) is a figure explaining operation | movement. Portions common to those in FIG.

  The gas ejection surface 71 is made of a porous material hollowed out in a rectangular shape, and the elastic hinge 75 that is an elastic body is disposed along the inner side surface of the porous material. The exhaust gap 73b in the present embodiment is a narrow gap between the surface of the elastic hinge 75 on the side opposite to the porous material and the fixing portion 710. The fixing portion 710 may be a part of the base 78, or may be configured by another member provided integrally with the base 78. The pressure on the inner side surface of the porous material also changes in conjunction with the pressure fluctuation of the bearing gap Cr. The elastic hinge 75 is interlocked with the pressure change of the inner side surface of the porous material, the load on the bearing increases, the pressure of the bearing gap Cr increases, and the pressure on the inner side surface of the porous material increases. 13 (c) to FIG. 13 (d), the exhaust gap 73b is deformed in a narrowing direction. That is, it changes in the direction of decreasing the exhaust flow rate. By reducing the exhaust flow rate, the internal pressure of the bearing gap Cr further increases. As described above, the bearing clearance Cr is kept constant by compensating the pressure in the bearing clearance Cr, which increases with an increase in the load on the bearing, not by reducing the bearing clearance Cr but by compensating the operation of the elastic hinge 75. can do. That is, high rigidity can be achieved.

(Eleventh embodiment)
FIG. 14 is a schematic cross-sectional view showing a static pressure gas bearing according to the eleventh embodiment. Portions common to those in FIG.

  In this embodiment, an automatic exhaust adjustment throttle is applied to a radial bearing. An automatic exhaust adjustment throttle is formed by disposing a flexible thin plate 74 in a region sandwiched between the gas ejection surfaces 1 in the axial direction. Based on the same principle as in the case of the flat bearing shown in the seventh embodiment, the pressure in the bearing gap, which increases as the load on the bearing increases, is not compensated by the decrease in the bearing gap Cr, but is flexible. The bearing gap Cr can be kept constant by compensating by the operation of the thin thin plate 74. That is, high rigidity can be achieved.

  In FIG. 14, the flexible thin plates 74 are arranged every 90 degrees, and the flexible thin plates 74 facing each other by 180 degrees operate in the reverse direction. For example, when the shaft 79 moves upward in FIG. 18, the flexible thin plate 74 on the upper side of the paper throttles the flow rate, and the flexible thin plate 74 on the lower side of the paper increases the flow rate in the direction of increasing the pressure. , Moves in the direction of decreasing pressure, and as a result, pushes the shaft 79 back downward in the drawing. The arrangement of the flexible thin plate 74 need not be every 90 degrees, but may be arranged every 30 degrees, every 60 degrees, or at other intervals.

  In the present invention, the galling resistance of the bearing can be enhanced by imparting lubricity to the gas ejection surface. As a result, it is possible to prevent the occurrence of galling of the bearing at the time of touchdown due to sudden trouble such as when the supply gas is stopped or a load larger than expected is applied.

  Here, the gas ejection surface having lubricity is, for example, a surface made of a graphite material fixed by adhesion, or the gas ejection surface is coated with DLC (diamond-like carbon) or molybdenum disulfide by means such as sputtering or plating. Surface.

DESCRIPTION OF SYMBOLS 1 Flexible bearing surface 2 Inflexible bearing surface 3 Air supply hole 5 Air supply path 6 Base | substrate 7 Flexible member 9 Guide part 9a Guide surface 18 Recessed part 28 Groove

Claims (13)

A bearing surface facing the guide surface with a bearing gap therebetween,
In a static pressure gas bearing in which a gas is interposed in the bearing gap,
An air supply path for supplying the gas to the bearing gap and / or an exhaust path for exhausting the gas from the bearing gap;
A flexible member is disposed between the air supply path and / or the exhaust path, and the bearing gap,
The flexible member is deformed by a difference between a gas pressure on the air supply path side of the flexible member and / or a gas pressure on the exhaust path side of the flexible member and a gas pressure on the bearing gap side. Static pressure gas bearing.   2. The air supply hole according to claim 1, wherein the flexible member is a thin plate, and the thin plate is provided with an air supply hole that connects the air supply path and the bearing gap to form a self-contained throttle. The static pressure gas bearing described. The thin plate is a thin disc having the air supply hole as a center, and the relationship between the radius a [m], the thickness t [m], and the Young's modulus E [Pa] of the thin disc.

The static pressure gas bearing according to claim 2, wherein the static pressure gas bearing has a shape satisfying the above.   The hydrostatic gas bearing according to claim 2 or 3, wherein a concave portion is provided on the bearing surface, and the air supply hole is provided on a bottom surface of the concave portion.   The hydrostatic gas bearing according to claim 2 or 3, wherein a groove is provided on the bearing surface, and the air supply hole is provided on a bottom surface of the groove.   The groove is any one of a square shape, a square shape, a circular shape, a combined shape of a circle and a cross, a polygon, and a combined shape of a polygon and the center of the polygon and each side or each vertex. The hydrostatic gas bearing according to claim 5, wherein   The static pressure gas bearing according to any one of claims 1 to 6, wherein a fixed throttle is formed on the bearing surface.   The hydrostatic gas bearing according to any one of claims 1 to 7, wherein the bearing surface is made of a lubricious material.   9. The hydrostatic gas bearing according to claim 8, wherein the lubricating material is graphite or a material containing graphite.   The static pressure gas bearing according to claim 8, wherein the lubricating material is a resin.   The static pressure gas bearing according to claim 1, wherein the flexible member is a thin plate, and the thin plate is provided with an exhaust hole for communicating the exhaust passage with the bearing gap.   The static pressure gas bearing according to claim 1, wherein the flexible member is an elastic hinge disposed in the exhaust passage.   The hydrostatic gas bearing according to claim 11, wherein a groove communicating with the exhaust path is provided in a region surrounded by a gas ejection surface of the bearing surface.

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