JP2007092974A - Thrust gas bearing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thrust gas bearing mechanism capable of suppressing vibration of an interval of a clearance of a bearing. <P>SOLUTION: This thrust gas bearing mechanism 10 is composed of an intermediate bearing body 20, a base 50, and the clearance 40 of the bearing in which they face each other. A gas supply port 24, a recessed part 26 for speed reduction having larger diameter than that of the gas supply port 24, and a plurality of gas flow passage shallow channels 28 are provided in a bottom face part of the intermediate bearing body 20. Speed of flow of the gas jetted from the gas supply port 24 is reduced in the recessed part 26 for speed reduction, then is led into each of the plurality of gas flow passage shallow channels 28, is guided into the thin and shallow channels, and flows along the radial direction. The gas stopped in a terminal part 30 leaks out while being restricted in the clearance 40 of the bearing to levitate the intermediate bearing body 20 for the base 50. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thrust bearing mechanism, and more particularly, a thrust for supplying gas to a bearing gap between a gas receiving wall of a base and a gas receiving surface of a bottom surface portion of a shaft to float and hold the shaft with respect to the base. The present invention relates to a gas bearing mechanism.

  As the thrust bearing mechanism, in addition to the one that supports the load in the thrust direction of the rotating shaft with the rolling bearing mechanism, etc., a support fluid such as oil is supplied to the gap between the shaft and the base that supports the shaft to support it. There are known ones that support a shaft in a floating manner with respect to a base by a static pressure or a dynamic pressure of a fluid. The latter is called a fluid thrust bearing mechanism, and oil, magnetic fluid, gas or the like is used as the fluid.

  An example of the structure of the fluid thrust bearing mechanism is a combination of a cylindrical shaft and a cylindrical support member having a bottom having an inner diameter corresponding to the outer shape of the shaft, and the center of the bottom surface of the shaft facing the bottom of the support member. The fluid is ejected from the fluid supply port provided in the section, and the bottom surface of the shaft is floated with respect to the bottom of the support member. In this case, the bottom portion of the support member serves as a fluid receiving wall, and the bottom portion of the shaft serves as a fluid receiving surface. Both the fluid receiving wall and the fluid receiving surface may be flat surfaces.

  In addition, a radial slit diaphragm should be provided in the bearing gap in order to suppress noise and improve control stability, etc., for the control of the gap spacing of the so-called bearing gap, which is the gap between the fluid receiving wall and the fluid receiving surface. Is also known. The radial slit diaphragm is a plurality of slits having a shallow groove depth extending in the radial direction from the fluid supply port at the center of the shaft, that is, extending in the radial direction toward the outer periphery and having a terminal portion. The fluid throttling effect when the fluid flowing in the groove flows out to the bearing gap between the fluid receiving wall and the fluid receiving surface is utilized to improve the controllability of the clearance gap of the bearing gap.

  Thus, utilization of the thrust fluid bearing which has a radial slit aperture | diaphragm in the part of the bearing clearance gap between a fluid receiving wall and a fluid receiving surface is achieved. The radial slit diaphragm is used for improving the controllability of the clearance gap of the bearing gap as described above, but may have different characteristics depending on the type of fluid. For example, when controlling the clearance gap of the bearing gap with high accuracy, comparing the use of oil as the fluid with the use of gas such as air, the fluid resistance increases when the fluid flows into the narrow gap from the fluid supply port. It is said that when the gas is used, the gap interval tends to vibrate slightly due to the difference in fluid viscosity as compared with the case where oil is used for the fluid due to sudden change and contraction flow.

  As described above, in the thrust gas bearing mechanism having the conventional radial slit diaphragm, there is a possibility that the clearance gap of the bearing gap vibrates, and there is a limit to the high accuracy of the axial positioning.

  The objective of this invention is providing the thrust gas bearing mechanism which can suppress the vibration of the clearance gap of a bearing clearance.

  A thrust gas bearing mechanism according to the present invention is a thrust gas bearing that supplies gas to a bearing gap between a gas receiving wall of a base and a gas receiving surface of a bottom surface portion of the shaft to float and hold the shaft with respect to the base. A gas supply port provided in the gas receiving wall or the gas receiving surface, a deceleration recess provided in the gas receiving wall or the gas receiving surface and surrounding the gas supply port, and an outer periphery of the bearing gap beyond the deceleration recess. And a gas flow path shallow groove having a terminal portion extending in the direction.

  Further, in the thrust gas bearing mechanism according to the present invention, the gas supply port is a circular opening, the deceleration depression is concentric with the circular opening of the gas supply port, has a diameter larger than the diameter of the circular opening, and has a shallow gas flow path. The grooves are a plurality of shallow grooves that radially extend from the gas supply port toward the outer peripheral direction, and the end portion of each gas flow path shallow groove has a shape that extends in the circumferential direction rather than the width of the shallow groove. Is preferred.

  Moreover, in the thrust gas bearing mechanism according to the present invention, it is preferable that the depth of the depression for deceleration and the depth of the gas channel shallow groove are the same.

  With the above configuration, a gas supply port is provided in the gas receiving wall or the gas receiving surface, and a deceleration depression is provided in the gas receiving wall or the gas receiving surface so as to surround the gas supply port, and the outer circumferential direction of the bearing gap extends beyond the deceleration depression. A gas flow path shallow groove is provided that extends toward the end and includes a terminal portion. A so-called radial slit diaphragm is formed by the gas flowing out from the shallow groove of the gas flow path into the bearing gap, but the gas flowing out from the gas supply port becomes a depression for spreading around the gas supply port before entering the shallow groove of the gas flow path. Flows in. In other words, the gas does not flow suddenly from the gas supply port into the narrow gas flow path shallow groove, but once spreads to the deceleration recess and decelerates, it flows into the gas flow path shallow groove. Therefore, the degree of contraction can be reduced by this deceleration, and vibrations when flowing into the gas flow path shallow groove can be suppressed.

  Both the gas supply port and the deceleration recess may be provided on the gas receiving wall, or both may be provided on the gas receiving surface, or one may be provided on the gas receiving wall and the other on the gas receiving surface. . The gas flow path shallow groove is provided on the side where the depression for deceleration is provided.

  Further, a decelerating recess is provided concentrically with the diameter larger than the gas supply port of the circular opening, and a plurality of gas flow channel shallow grooves extending radially outward from the gas supply port as a center are provided. The end portion of each has a shape extending in the circumferential direction rather than the width of the shallow groove. Therefore, the depression for decelerating can be easily obtained by performing a process of concentrating with a gas supply port and having a larger diameter than the gas supply port.

  In addition, since the depth of the deceleration recess and the depth of the gas flow path shallow groove are the same, the speed reduction recess and the gas flow path shallow groove can be obtained by the same processing method.

  As described above, according to the thrust gas bearing mechanism according to the present invention, it is possible to suppress the vibration of the gap interval of the bearing gap interval.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In the following, the thrust bearing mechanism will be described in the form of an intermediate bearing mechanism for transmitting the thrust output of the actuator to a base such as a moving table, but this is an embodiment that utilizes high accuracy of the gap interval, In addition to this, it can of course be applied to a thrust bearing mechanism of a general rotating shaft. In the following description, the gas supply port is provided on the bottom surface of the intermediate bearing body, but may be provided on the gas receiving wall of the base. Similarly, the decelerating recess and the gas flow path shallow groove are provided on the bottom surface of the intermediate bearing body, but may be provided on the gas receiving wall of the base. In addition, the shape, dimensions, arrangement of shallow grooves, the number thereof, and the like described below are merely examples, and can be appropriately changed according to the application.

  FIG. 1 is a diagram illustrating the configuration of the thrust gas bearing mechanism 10. The thrust gas bearing mechanism 10 is used in a thrust force transmission mechanism that transmits the output in the X-axis direction of the actuator 8 to the base 50 of the moving table via the intermediate bearing body 20. For example, in order to move the moving table in the X-axis direction with high accuracy, it is necessary to increase the accuracy of movement of the actuator 8 and to increase the accuracy of the clearance gap of the thrust gas bearing mechanism. Here, the thrust gas bearing mechanism 10 is configured by the intermediate bearing body 20, the base 50, and the bearing gap 40 where they face each other.

  FIG. 1A shows a bottom surface portion of the intermediate bearing body 20 when the base 50 is removed, and FIG. 1B shows a thrust force transmission mechanism including the thrust gas bearing mechanism 10 as shown in FIG. It is sectional drawing cut | disconnected along the AA line | wire.

  The thrust gas bearing mechanism 10 has a gas receiving wall 52 that is a surface that receives the thrust of the base 50 and a gas receiving surface 22 that is a bottom surface portion of the intermediate bearing body 20 facing each other. The bearing gap 40 is used between the two. The intermediate bearing body 20 is a columnar member provided with a through hole 23 along the central axis. The through hole 23 opens as a gas supply port 24 in the gas receiving surface 22. As shown in FIG. 1A, the gas receiving surface 22 of the intermediate bearing body 20 is provided with a speed reduction recess 26 and a plurality of gas flow path shallow grooves 28 in addition to the opening of the gas supply port 24.

  Each gas flow path shallow groove 28 extends radially toward the outer peripheral direction along the radial direction around the gas supply port 24, and has a terminal portion 30. In the case of FIG. 1, there are 16 gas flow path shallow grooves 28, that is, the gas supply ports 24 are provided radially at intervals of 22.5 degrees in the circumferential direction. It can be increased or decreased according to performance. 1A and 1B, a part of the flow of the gas 6 flowing from the gas supply port 24 to the bearing gap 40 is indicated by a flow line with an arrow.

  FIG. 2 is an enlarged view of the periphery of one gas flow path shallow groove 28. The gas flow path shallow groove 28 shown here is disposed along the line BB in FIG. 2A shows a bottom surface portion of the intermediate bearing body 20, and FIG. 2B is a cross-sectional view taken along the line BB, in which the base 50, the gas receiving wall 52, and the bearing gap 40 are shown. It is.

  The gas supply port 24 is a circular opening provided at the center of the bottom surface portion of the intermediate bearing body 20 as described above, and has a function of supplying bearing support gas from the through hole 23 to the bearing gap 40. As an example of the dimensions, the diameter of the intermediate bearing body can be about 30 mm, and the diameter of the gas supply port 24 can be about 5 mm.

  The deceleration recess 26 is a shallow recess having a diameter larger than the diameter of the gas supply port 24 and concentric with the gas supply port 24. In FIG. 2A, the height of the gas receiving surface 22 is (0) and the height of the deceleration recess 26 is (−), and the deceleration recess 26 is submerged from the gas receiving surface 22. Is shown. The decelerating recess 26 is a flow passage cross section of the gas supply port 24 before the gas 6 flowing out from the gas supply port 24, in fact, the gas 6 to be ejected is guided to the plurality of gas flow channel shallow grooves 28 to flow in the radial direction. It has a function of once spreading it over a wider channel cross section and decelerating the flow velocity. The degree of deceleration is determined by the size of the diameter of the decelerating recess 26 relative to the diameter of the gas supply port 24, the depth of the indentation of the decelerating recess 26, and the like. For example, the diameter of the gas supply port 24 may be about 5 mm, and the diameter of the deceleration recess 26 may be about 10 mm. Further, the recess depth of the deceleration recess 26 is about 10 μm to 20 μm, preferably about 12 μm to 15 μm.

  The gas flow path shallow groove 28 is a thin shallow groove extending from the deceleration depression 26 toward the outer peripheral direction of the intermediate bearing body 20 and having a terminal portion 30. In FIG. 2A, the height of the gas flow path shallow groove 28 is set to (−), and it is shown that the gas passage surface 22 is sinking. The end portion 30 has a shape in which the gas flow path shallow groove 28 extends in the outer peripheral direction along the radial direction, and then extends in the circumferential direction as shown in FIG. That is, after the gas flow path shallow groove 28 extends by a predetermined length along the radial direction, the extending direction of the gas flow path shallow groove 28 is changed to be along the circumferential direction, and ends a little. From another point of view, the end portion 30 has a shape extending in the circumferential direction while widening the width when extending along the radial direction of the gas flow path shallow groove 28.

  The functions of the gas flow path shallow groove 28 and its end portion 30 are functions of a so-called radial slit diaphragm. That is, the gas ejected from the gas supply port 24 is decelerated by the decelerating recess 26, then guided to each of the plurality of gas flow path shallow grooves 28, and guided along the narrow shallow grooves to flow along the radial direction. Since the gas flow path shallow groove 28 has the terminal portion 30, the flowing gas stops there. The gas that has reached the dead end leaks while being constricted between the gas receiving surface 22 and the gas receiving wall 52 facing each other, and widens the gap between the gas receiving surface 22 and the gas receiving wall 52 to form the bearing gap 40. Then, the intermediate bearing body 20 is levitated with respect to the base 50.

  The bearing gap 40 is formed by the relationship between the pressing force of the intermediate bearing body against the base 50, that is, the thrust force applied to the base 50 via the intermediate bearing body 20 by the actuator 8 and the supply pressure of the gas supplied to the bearing gap 40. Can be determined by That is, the bearing gap can be controlled by controlling the gas supply pressure, and the gap gap of the bearing gap can be controlled to be constant by controlling the gas supply pressure according to the thrust force. Alternatively, the gap interval can be freely controlled so as to be a predetermined one.

  As an example of the dimensions of the gas flow path shallow groove 28, the diameter of the intermediate bearing body 20 is about 30 mm and the diameter of the deceleration recess 26 is about 10 mm, and the outer periphery along the radial direction of the gas flow path shallow groove 28. The width of the portion extending in the direction can be about 0.6 mm, and the distance along the radial direction from the center of the gas supply port 24 to the outermost peripheral side of the terminal portion 30 can be 12 mm. In this case, the length along the radial direction from the outermost peripheral side of the deceleration recess 26 to the outermost peripheral side of the terminal portion 30 of the gas flow path shallow groove 28 is (12 mm−10 mm / 2) = 7 mm. In the case where the end portion 30 extends in the circumferential direction, the 16 gas flow path shallow grooves 28 are provided at intervals of 22.5 degrees with respect to the circumferential angle around the gas supply port 24. It is possible to make the spread about 16 degrees at an angle in the circumferential direction centering on. The groove depth of the gas flow path shallow groove 28 can be the same as the depression depth of the deceleration depression 26. Of course, from the standpoint of use and performance, the aperture effect may be changed by making it shallower or deeper than the recess depth of the deceleration recess 26.

  The operation of the thrust gas bearing mechanism 10 having the above configuration will be described. In the thrust gas bearing mechanism 10 in the thrust force transmission mechanism, the actuator 8 moves the intermediate bearing body 20 in the X-axis direction toward the base 50 of the moving table. A gas 6 having a controlled supply gas pressure is supplied from a gas supply unit (not shown) to a through hole 23 provided at the center in the axial direction of the intermediate bearing body 20. Since the through-hole 23 opens as a gas supply port 24 in the gas receiving surface 22 which is the bottom surface portion of the intermediate bearing body 20, the gas 6 flows between the gas receiving wall 52 of the base 50 and the gas receiving surface 22 of the intermediate bearing body 20. It flows out into the bearing gap 40 between the two. The magnitude of the supply gas pressure is preferably controlled in accordance with the thrust force of the actuator 8 so as to keep the clearance gap of the bearing gap 40 constant. When the change in thrust force is small, the supply gas pressure may be kept constant.

  The gas 6 ejected from the gas supply port 24 spreads in a circular reduction depression 26 having a diameter larger than the diameter of the gas supply port 24 and is decelerated here. Thereafter, the decelerated gas is guided from the decelerating recess 26 to the gas flow path shallow groove 28 extending in the outer peripheral direction along the radial direction. Since the gas flow path shallow groove 28 becomes a dead end at the end portion 30, the gas flowing through the gas flow path shallow groove 28 leaks toward the bearing gap 40 there. When leaking out, the gas is throttled by the gap between the gas receiving wall 52 and the gas receiving surface 22. By this restriction, the flow is rectified, the turbulence of the flow is suppressed, and the stability of maintaining the gap interval of the bearing gap 40 is improved.

  The cross-sectional area of the flow path surface of the gas flow path shallow groove 28 is 0.6 mm × (10 μm to 20 μm) in the above example, and is markedly greater than the flow path cross-sectional area of the gas supply port 24 even when 16 lines are combined. small. For this reason, when a high-pressure and high-speed gas is supplied here, a contracted flow is generated on the input side thereof, and as a result, a vibration in which the gap interval varies may occur. The decelerating recess 26 provided between the gas supply port 24 and the gas flow path shallow groove 28 has a diameter larger than the diameter of the gas supply port 24 and alleviates a sudden change in the cross-sectional area of the flow path, thereby reducing the gas supply port 24. Since the flow velocity of the gas 6 from the engine is decelerated, the vibration of the gap interval of the bearing gap 40 is suppressed. Therefore, the clearance gap of the bearing gap 40 can be maintained with high accuracy, and the movement drive in the X-axis direction of the base 50 of the moving table via the intermediate bearing body 20 by the actuator 8 can be made with high accuracy. .

  In the above description, it has been described that the deceleration depression 26 and the gas flow path shallow groove 28 having the terminal portion 30 are formed in the bottom surface portion of the intermediate bearing body 20. Such a structure can be realized by using a precise etching process, coining process, shot peening process, or the like at the bottom surface of the intermediate bearing body 20. Further, the portion including the deceleration recess 26 and the gas flow path shallow groove 28 having the terminal portion 30 is formed in a separate member using the above-described processing method, and is fixed to the intermediate bearing body 20 having a flat bottom surface portion. It can also be attached.

  The structure of another thrust gas bearing mechanism 60 that suppresses the vibration of the bearing gap 40 is shown in FIGS. Here, the same reference numerals are given to the same elements as those in FIGS. 1 and 2, and the detailed description will be omitted below. FIGS. 3A and 3B are diagrams illustrating the configuration of the thrust gas bearing mechanism 60 corresponding to FIGS. 1A and 1B. Here, a thrust gas bearing mechanism 60 is constituted by the intermediate bearing body 70, the base 50, and the bearing gap 40 where they face each other. As described above, the thrust gas bearing mechanism 60 here is different in the structure of the intermediate bearing body 70 from the thrust gas bearing mechanism 10 described in FIGS. 1 and 2.

  As shown in FIG. 3A, the gas receiving surface 22 of the intermediate bearing body 70 has a plurality of fan-shaped recesses 72 and an R portion 74 around the gas supply port 24 in addition to the gas supply port 24 opening. Provided. In FIG. 3A, the height of the surface of the gas receiving surface 22 is (0), and the height of the fan-shaped recess 74 is (−), which indicates that the fan-shaped recess 72 is sinking from the gas receiving surface 22. It is.

  The fan-shaped recess 72 is a recess that expands in a fan shape while extending radially in the outer peripheral direction around the gas supply port 24. In the case of FIG. 3, four fan-shaped indentations 72 are provided, but the number can be increased or decreased according to the application and required performance. The recess depth of the fan-shaped recess 72 is about 10 μm to 20 μm, preferably about 12 μm to 15 μm, similarly to the deceleration recess 26 described with reference to FIGS. 1 and 2.

  A portion of the gas receiving surface 22 is left in the form of a thin band between adjacent fan-shaped depressions 72. The width W of the thin strip-shaped portion can be about W = 1 mm to 2 mm in the example in which the diameter of the intermediate bearing body described in FIG. 1 is about 30 mm and the diameter of the gas supply port is about 5 mm.

  The R portion 74 is an R portion that smoothens the circumferential edge of the circular opening of the gas supply port 24. The size of R may be an appropriate size that does not disturb the gas flow. Further, instead of the R portion, a recess (-) groove portion lower than the fan-shaped recess (-) may be formed around the circular opening of the gas supply port 24, and the flow may be reduced there.

  FIG. 4 is an enlarged view of the peripheral portion of the gas receiving surface 22 in the band-shaped portion between the two fan-shaped depressions 72. The gas receiving surface 22 of the belt-like portion shown here is arranged along the line BB in FIG.

  Here, in FIG.3 (b) and FIG. 4, a part of flow of the gas 6 which flows into the bearing clearance 40 from the gas supply port 24 is shown by the flow line with an arrow. In this way, the gas 6 flowing out from the gas supply port 24 is guided by the fan-shaped recess 72 and flows while spreading toward the outer peripheral direction. And since it becomes a dead end at the edge of the planar shape of the fan-shaped depression 72, the gas that has reached the dead end leaks while being constricted between the gas receiving surface 52 and the gas receiving wall 52 facing the gas receiving surface 22, and the gas receiving surface 22 and the gas. The gap between the receiving wall 52 and the bearing wall 52 is widened to form the bearing gap 40, and the intermediate bearing body 70 is floated with respect to the base 50.

  Here, the fan-shaped depression 72 is guided to the fan-shaped depression 72 having a large area although it is a shallow depression. Therefore, compared with the narrow gas flow path shallow groove 28 described with reference to FIG. Therefore, the vibration of the gap interval of the bearing gap 40 due to the sudden change of the flow path cross-sectional area can be suppressed, and the gap interval of the bearing gap 40 can be maintained with high accuracy.

  In these bearing mechanisms, when the supply pressure is controlled to control the gap interval between the gas receiving wall and the gas receiving surface to act as an actuator, the bearing interval can be made highly accurate by adopting the above configuration. Is particularly useful. Moreover, the stroke as an actuator can also be taken large by arrange | positioning the bearing mechanism which takes said structure in series.

It is a figure explaining the structure of the thrust gas bearing mechanism of embodiment which concerns on this invention. In embodiment which concerns on this invention, it is an enlarged view of the peripheral part of a gas flow path shallow groove | channel. It is a figure explaining the structure of the thrust gas bearing mechanism of other embodiment. FIG. 4 is a partially enlarged view of FIG. 3.

Explanation of symbols

  6 Gas, 8 Actuator, 10, 60 Thrust gas bearing mechanism, 20, 70 Intermediate bearing body, 22 Gas receiving surface, 23 Through hole, 24 Gas supply port, 26 Deceleration recess, 28 Gas flow path shallow groove, 30 End , 40 Bearing gap, 50 base, 52 gas receiving wall, 72 fan-shaped depression, 74 R part.

Claims (3)

A thrust gas bearing mechanism that supplies gas to a bearing gap between the gas receiving wall of the base and the gas receiving surface of the bottom surface portion of the shaft to float and hold the shaft with respect to the base,
A gas supply port provided in the gas receiving wall or the gas receiving surface;
A recess for deceleration provided on the gas receiving wall or the gas receiving surface and surrounding the gas supply port;
A gas flow path shallow groove having a terminal end extending toward the outer peripheral direction of the bearing gap over the depression for deceleration;
A thrust gas bearing mechanism comprising: The thrust gas bearing mechanism according to claim 1,
The gas supply port is a circular opening,
The deceleration recess is concentric with the circular opening of the gas supply port and has a diameter larger than the diameter of the circular opening,
The gas flow path shallow grooves are a plurality of shallow grooves extending radially outward from the gas supply port.
A thrust gas bearing mechanism, wherein the end portion of each gas flow path shallow groove has a shape that extends in the circumferential direction rather than the width of the shallow groove. The thrust gas bearing mechanism according to claim 1,
A thrust gas bearing mechanism characterized in that the depth of the recess for deceleration is the same as the depth of the gas channel shallow groove.

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