JP2010159863A - Aerostatic bearing spindle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an static pressure gas bearing spindle capable of keeping sufficiently high self-excited vibration generating pressure compared with service air supply pressure even when housings having joining faces of poor surface accuracy are assembled to each other. <P>SOLUTION: The aerostatic bearing spindle comprises a rotary shaft 1, and a fixed part 20 for surrounding an outer circumferential surface of the rotary shaft 1 across a bearing space 5 to which the gas for bearing for rotatably supporting the rotary shaft 1. The fixed part 20 includes a housing 2 and sheets 41, 42. The housing 2 consists of a plurality of members 21, 22, 23, and the plurality of members 21, 22, 23 are coupled with at least one joining part between the plurality of members 21, 22, 23 via the sheets 41, 42 having the characteristic more deformable than the housing 2. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a hydrostatic gas bearing spindle, and more particularly, to a hydrostatic gas bearing spindle that rotatably supports a rotating shaft with respect to a fixed portion with a bearing gap interposed therebetween.

  The hydrostatic gas bearing spindle is used in precision measuring instruments and precision inspection devices because its rotational axis is supported in a non-contact state with respect to the bearing surface, and therefore has high rotational accuracy.

  For example, Japanese Unexamined Patent Application Publication No. 2003-301841 (Patent Document 1) discloses a static pressure gas bearing spindle used for precision measuring machines, precision inspection devices, and the like. In this hydrostatic gas bearing spindle, the main shaft is supported in the radial direction through a minute bearing gap in a non-contact state with the bearing surfaces facing the main shafts of the two bearing sleeves. A journal bearing portion is formed by the outer diameter surface of the main shaft, the bearing surface facing the main shaft of the two bearing sleeves, and the compressed gas supplied to the minute bearing gap.

  The main shaft is integrally formed by screwing with the thrust plate. Both surfaces of the thrust plate in the axial direction are supported in the axial direction through a minute bearing gap in a non-contact state with the bearing surfaces facing the thrust plates of the two bearing sleeves. A thrust bearing portion is formed by both axial surfaces of the thrust plate provided integrally with the main shaft, bearing surfaces facing the thrust plates of the two bearing sleeves, and compressed gas supplied to a minute bearing gap. . The bearing sleeve is fixed to the housing by appropriate means.

  A motor rotor is attached to the main shaft, and a motor stator is attached to the housing. The main shaft is rotated by a driving force generated by an electromagnetic force acting between the motor rotor and the motor stator.

  Each bearing sleeve of the two bearing sleeves constituting the journal bearing portion is formed with a plurality of fine air supply holes that open to the bearing surface facing the main shaft. The plurality of air supply holes are arranged at equal intervals in the circumferential direction. In each bearing sleeve, a plurality of air supply holes are provided in two rows in the axial direction to form an air supply row.

  Each of the two bearing sleeves constituting the thrust bearing portion is formed with a plurality of fine air supply holes that open to the bearing surface facing the thrust plate. The plurality of air supply holes are arranged at equal intervals in the circumferential direction. In each bearing sleeve, a plurality of air supply holes are provided in a line on the circumference, and form an air supply line.

  In this hydrostatic gas bearing spindle, when compressed gas is supplied from the bearing air supply port, the compressed gas passes through the air supply passage provided in the housing from the air supply hole of the air supply row to the journal bearing portion and the thrust bearing. It flows into the bearing clearance of the part. The pressure of the compressed gas in the bearing gap generates a bearing reaction force that balances the weight of the spindle and the external load.

JP 2003-301841 A

  In the static pressure gas bearing spindle used in the precision measuring machine and precision inspection apparatus described above, the housing includes a plurality of bearing housings and a motor housing. Since these housing members are used for measurement, the outer dimensions are relatively small and the mass is light. The joint surfaces between the plurality of bearing unit housings and the joint surfaces between the bearing unit housing and the motor unit housing are formed by planes that intersect the axial direction. Since each housing member is small and light and the joining surface is a simple flat surface, it is possible to finish the joining surface of each housing member with high accuracy.

  In addition, since each housing member is small and light, the outer diameter part of each housing member can be aligned and centering can be performed at the time of an assembly | attachment. Therefore, it is not necessary to provide a fitting portion (inlay portion) that serves as a reference for centering. After centering, the housing members are screwed together by bolts.

  However, in a static pressure gas bearing spindle for processing such as wafer surface processing, the load applied during use is larger than that of the static pressure gas bearing spindle for the precision measuring apparatus and precision inspection apparatus described above. Therefore, in order to realize a load capacity corresponding to this load, it is necessary to increase the outer diameter of the hydrostatic gas bearing spindle. Moreover, since the torque required for processing by rotating a grindstone or a workpiece attached to the tip is large, a motor as a drive source also requires a large motor.

  Therefore, in a hydrostatic gas bearing spindle for processing such as wafer surface processing, the size of each housing member is large and the mass is heavy, so it is difficult to finish the joint surface of each housing member with high accuracy. is there. Also, it is not easy to align the outer shape when assembling. For this reason, it is necessary to form a fitting portion (inlay portion) serving as a reference for centering in addition to a joining surface formed by planes intersecting in the axial direction at the joining portion between the housing members. This complicates the shape of the joint including the joint surface. Moreover, since each housing member is large and heavy, the processing accuracy of the manufactured joint portion tends to deteriorate.

  By the way, in the static pressure gas (air) bearing spindle, when the pressure for supplying the air supplied to the bearing portion is increased, self-excited vibration is generated in the bearing portion because the air has compressibility. For this reason, in a static pressure gas bearing spindle, the self-excited vibration generation pressure (supply pressure at which self-excited vibration is generated) is used as the supply air pressure (used to prevent self-excited vibration from being generated in the bearing portion during use. It is necessary to design and manufacture a high pressure with a sufficient margin against the bearing gas supply pressure).

  Especially in the static pressure gas bearing spindle for processing, the environment used is poor compared to the static pressure gas bearing spindle used for precision measuring equipment and precision inspection equipment mainly used for disc inspection equipment. There are large changes in factors that affect bearing performance, such as bearing clearance. Therefore, it is necessary to increase the margin of the self-excited vibration generation pressure with respect to the used supply air pressure.

  However, when the housing members are assembled to each other with bolts in a state where the surface accuracy of the joint surface is poor, a large force is locally applied to the housing, thereby deforming the bearing surface shape of the bearing member (for example, micro deformation on the order of microns). Or tilt). As the bearing surface is deformed in this way, the self-excited vibration generating pressure is reduced. As a result, the margin of the self-excited vibration generating pressure with respect to the used supply air pressure is lost, and the housing may not be practical.

  In addition, if the joint surface is tightened with poor surface accuracy, the joint surface is fixed in a partially contacted state, so that the rigidity of the housing joint surface is reduced, and the housing is joined compared to the case of full contact. The natural frequency of the part is greatly reduced. As a result, the natural frequency of the joint portion of the housing approaches the self-excited frequency or a frequency several times the self-excited frequency, and resonance easily occurs when the self-excited vibration is generated in the bearing portion.

  The present invention has been made in view of the above problems, and the object thereof is to keep the self-excited vibration generation pressure sufficiently high with respect to the supply air pressure even when the housings having the joint surfaces with poor surface accuracy are assembled to each other. It is to provide a hydrostatic gas bearing spindle that can be used.

  Another object of the present invention is to provide a hydrostatic gas bearing spindle that can suppress resonating with the self-excited frequency of the bearing portion by reducing the natural frequency of the joint surface of the housing. It is.

  The hydrostatic gas bearing spindle of the present invention includes a rotating shaft and a fixing portion that surrounds the outer peripheral surface of the rotating shaft with a bearing gap supplied with a bearing gas for rotatably supporting the rotating shaft. ing. The fixed part includes a housing and a seat. The housing is composed of a plurality of members, and the plurality of members are coupled to at least one joint portion between the plurality of members via a sheet having characteristics that are more easily deformed than the housing.

  According to the static pressure gas bearing spindle of the present invention, a plurality of members are coupled to a joint portion between a plurality of members of the housing via a sheet having characteristics that are more easily deformed than the housing. Thereby, when the housing is tightened with the bolt, the sheet is deformed in the thickness direction corresponding to the joint surface of the housing that is in contact with the sheet. Therefore, since the contact area on the joint surface is increased, deformation of the bearing surfaces of the plurality of members of the housing can be reduced even when the housing is tightened. Thereby, the self-excited vibration generating pressure can be kept sufficiently high with respect to the used supply air pressure. Therefore, it is possible to suppress the occurrence of self-excited vibration.

  Moreover, since the contact area in a joint surface becomes large, it can suppress that the rigidity of the joint surface of a housing falls. Thereby, it can suppress that it resonates with the self-excited frequency of a bearing part by the natural frequency of the joint surface of a housing falling.

Further, the vibration can be reduced by the deformation of the sheet.
In the above hydrostatic gas bearing spindle, the seat is preferably made of rubber.

  In the above hydrostatic gas bearing spindle, the seat is preferably made of plastic.

  In the above hydrostatic gas bearing spindle, the seat is preferably made of a damping material.

  As described above, according to the hydrostatic gas bearing spindle of the present invention, the self-excited vibration generating pressure can be kept sufficiently high with respect to the used air supply pressure.

It is a schematic sectional drawing of the static pressure gas bearing spindle in one embodiment of this invention. It is a schematic sectional drawing of the junction part of the sheet | seat and housing of a static pressure gas bearing spindle in one embodiment of this invention. It is a schematic sectional drawing of the junction part of the sheet | seat and housing of a static pressure gas bearing spindle in one embodiment of this invention. It is a schematic plan view of the sheet | seat of the static pressure gas bearing spindle in one embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the configuration of a static pressure gas bearing spindle according to an embodiment of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view of a static pressure gas bearing spindle according to an embodiment of the present invention. Referring to FIG. 1, the static pressure gas bearing spindle in one embodiment of the present invention mainly includes a rotating shaft 1, a fixed portion 20, and sheets 41 and 42.

  Referring to FIG. 1, the rotating shaft 1 is supported on the fixed portion 20 by the pressure of the bearing gas supplied through the bearing gap 5. The fixed portion 20 includes a housing 2, a bearing sleeve 3, and sheets 41 and 42. The sheets 41 and 42 constitute the sheet 4. The housing 2 includes a plurality of members 21, 22, and 23, and sheets 41 and 42 are interposed between the members 21, 22, and 23.

  The rotating shaft 1 includes a front main shaft 11, a rear main shaft 12, a front thrust plate 13, and a rear thrust plate 14. The rotating shaft 1 is configured to be rotatable about a virtual axis A. The rotary shaft 1 is formed with a hole 15 penetrating in the axial direction about the virtual axis A.

  The front main shaft 11 has a convex shape in which the outer diameter is smaller than that of the central portion 113 at the front end portion 111 and the rear end portion 112 in the axial direction. The rear main shaft 12 has a convex shape formed at the front end 121 with an outer diameter similar to the outer diameter of the rear end 112 of the front main shaft 11. The rear end 112 of the front main shaft 11 and the front end 121 of the rear main shaft 12 are disposed so as to contact each other. A flange portion 122 is formed rearward from the front end portion 121. The rear main shaft 12 extends rearward from the flange portion 122 to form a central portion 123. Further, a rear portion 124 having a small outer diameter formed rearward from the central portion 123 is formed.

  The front thrust plate 13 has a cylindrical shape. The front thrust plate 13 has a concave shape at the rear end 131. The front thrust plate 13 is screwed to the front main shaft 11 in a state where the concave shape and the convex shape of the front end portion of the front main shaft 11 are fitted. The rear thrust plate 14 has a cylindrical shape. The rear thrust plate 14 is screwed to the front main shaft 11 and the rear main shaft 12 in a state where the rear thrust plate 14 is fitted into the convex shape of the rear end portion 112 of the front main shaft 11 and the convex shape of the front end portion 121 of the rear main shaft 12. Yes.

  The fixed portion 20 includes the housing 2 and the bearing sleeve 3. The bearing sleeve 3 is disposed so that its inner peripheral surface faces the outer peripheral surface of the front main shaft 11. The housing 2 is disposed such that the inner peripheral surface thereof is in contact with the outer peripheral surface of the bearing sleeve 3.

  The housing 2 includes a bearing housing 21, a spindle base housing 22, and a motor housing 23. A seat 41 is interposed between the bearing housing 21 and the spindle base housing 22. A seat 42 is interposed between the spindle base housing 22 and the motor housing 23.

  The bearing sleeve 3 has a front bearing sleeve 31 and a rear bearing sleeve 32. The front bearing sleeve 31 and the rear bearing sleeve 32 have a cylindrical shape. The front part of the front bearing sleeve 31 and the rear part of the rear bearing sleeve 32 constitute a flange part.

  The bearing housing 21 has a hollow shape. A front bearing sleeve 31 and a rear bearing sleeve 32 are fitted and fixed to the bearing housing 21.

  FIG. 2 is an enlarged schematic cross-sectional view of a P1 portion in FIG. Referring to FIG. 2, the hollow bearing housing 21 has an inlay portion 71 and a joint surface 7 in the vicinity of the rear outer periphery thereof.

  The joint surface 7 of the bearing housing 21 is screwed to the joint surface 8 of the spindle base housing 22 inserted using the spigot portion 71 as a guide via the seat 41. The spindle base housing 22 screwed through the seat 41 has a hollow shape.

  The sheet 41 is formed of a thin hollow disk-like rubber sheet having a thickness of about 0.5 mm, for example. As the rubber, for example, natural rubber, butadiene rubber, chloroprene rubber, nitrile rubber, urethane rubber, silicon rubber, or the like having a relatively strong resilience can be used. For this reason, the sheet | seat 41 has the characteristic which is easier to deform | transform than a housing.

  FIG. 4 is a schematic plan view of the sheet 41. In the seat 41, a sheet air supply path 81 that constitutes a part of the air supply path 74 is formed. In addition, a seat exhaust path 82 is formed that constitutes a part of the exhaust path for exhausting the supplied bearing gas (not shown in FIG. 1). Moreover, the sheet | seat cooling water channel 83 which comprises a part of cooling water channel for cooling the fixing | fixed part 20 which is not illustrated in FIG. 1 is formed. Also, a bolt hole 84 for screwing the bearing housing 21 and the spindle base housing 22 is formed.

  Referring to FIG. 1, the front main shaft 11 is inserted through the bearing gap 51 on the inner diameter side of the front bearing sleeve 31 and the rear bearing sleeve 32. Further, the front thrust plate 13 is disposed at the front end 111 of the front main shaft 11 so as to face the front end surface of the front bearing sleeve 31 with a bearing gap 52 therebetween. The rear thrust plate 14 is disposed at the rear end portion 112 of the front main shaft 11 so as to face the rear end surface of the rear bearing sleeve 32 with a bearing gap 53 therebetween.

  In the front bearing sleeve 31 and the rear bearing sleeve 32, a plurality of fine air supply holes 76 are arranged at equal intervals in the circumferential direction toward the front main shaft 11 arranged on the inner diameter side to form an air supply row. Has been. The front bearing sleeve 31 has a plurality of fine air supply holes 75 arranged at equal intervals in the circumferential direction toward the front thrust plate 13. The rear bearing sleeve 32 has a plurality of fine air supply holes 75 arranged at equal intervals in the circumferential direction toward the rear thrust plate 14. The air supply holes 75 and 76 are connected to the air supply port 73 via the air supply path 74.

  Thus, the thrust bearing in which the front end face of the front bearing sleeve 31, the rear end face of the front thrust plate 13, and the bearing gas supplied to the bearing gap 52 therebetween support the rotary shaft 1 in the axis A direction. It is comprised so that it may function as a part. A journal bearing portion in which the inner peripheral surface of the front bearing sleeve 31, the outer peripheral surface of the front main shaft 11, and the bearing gas supplied to the bearing gap 51 therebetween support the rotary shaft 1 in the axis A direction. Is configured to function as The thrust bearing portion and the journal bearing portion constitute a bearing portion of the static pressure gas bearing spindle.

  FIG. 3 is an enlarged schematic cross-sectional view of a P2 portion in FIG. Referring to FIG. 3, the spindle base housing 22 has an inlay portion 72 and a joint surface 9 in the vicinity of the rear outer periphery thereof. The joint surface 9 of the spindle base housing 22 is screwed to the joint surface 10 of the motor housing 23 inserted using the spigot portion 72 as a guide via a seat 42. The sheet 42 is formed of a thin hollow disk-like rubber sheet having a thickness of about 0.5 mm, for example.

  The planar shape of the seat 42 is substantially the same as the schematic plan view of the seat 41 shown in FIG. 4, but the diameter of the seat air supply path 81 is set in accordance with the diameter of the air supply path 74 of the motor housing 23. It is formed larger.

  With reference to FIG. 1, a motor rotor 77 fixed to the rear end surface of the central portion 123 of the rear main shaft 12 and the outer peripheral surface of the rear portion 124 is disposed inside the motor housing 23. Corresponding to the position of the motor rotor 77 in the axial direction, a motor stator 78 is installed so as to face the outer peripheral surface of the motor rotor 77 with a predetermined gap. A driving force in the rotational direction is generated by the electromagnetic force between the motor rotor 77 and the motor stator 78, and the rotary shaft 1 rotates.

  With the above configuration, when compressed air, which is a bearing gas, is supplied from the air supply port 73, the bearing gas passes through the air supply path 74 to form journal supply portions 75, 76 that form a supply line. And flows into the thrust bearing. A bearing reaction force that balances the weight of the main shaft and the external load is generated by the supply pressure of the compressed air. For this reason, the rotating shaft 1 is rotationally driven while being supported in a non-contact state, and a highly accurate rotational motion is realized.

  In addition, in the above, although the sheet | seat 4 demonstrated the rubber sheet, you may be comprised with the plastics. Moreover, the sheet | seat 4 may be comprised with the damping material.

Next, the effect of the static pressure gas bearing spindle of this Embodiment is demonstrated.
According to the static pressure gas bearing spindle of the present embodiment, the bearing housing 21, the spindle base housing 22 and the motor housing 23 are screwed together via the seats 41 and 42, respectively.

  Since the sheets 41 and 42 are more easily deformed than the housing 2, even when the surface accuracy of the joining surfaces 7, 8, 9, and 10 is poor, It is elastically deformed partially in the thickness direction in accordance with the shape error of the joint surfaces 7, 8, 9, and 10. Thereby, the contact area of the joint surfaces 7, 8, 9, and 10 can be increased.

  Therefore, it can be relieved that a large contact stress is locally generated on the joint surfaces 7, 8, 9, and 10. Therefore, nonuniform stress is less likely to act on the housing 2.

  For this reason, deformation (for example, minute deformation or inclination) of the bearing surface 6 formed of the journal bearing surface 61 and the thrust bearing surface 62 is suppressed.

  In addition, the self-excited vibration generation pressure is lower than the self-excited vibration generation pressure when the shape of the bearing surface 6 is not deformed due to the deformation of the shape of the bearing surface 6, but according to the hydrostatic gas bearing spindle of the present embodiment. For example, deformation of the bearing surface 6 shape is suppressed. For this reason, it is possible to suppress the self-excited vibration generation pressure designed with a sufficient margin with respect to the used supply air pressure from being reduced to be equal to or lower than the used supply air pressure. Thereby, the self-excited vibration generating pressure can be kept sufficiently high with respect to the used supply air pressure. Therefore, it is possible to suppress the occurrence of self-excited vibration.

  Further, since the contact areas are large, the joint surfaces 7, 8, and 9 of the housing 2 are firmly fixed, so that the rigidity of the joint surfaces 7, 8, and 9 of the housing 2 is suppressed from being lowered. Thereby, it can suppress that it resonates with the self-excited frequency of a bearing part by the natural frequency of the junction part of the housing 2 falling.

  Further, since the seat 4 has a damping performance, the seat 4 can be damped by absorbing minute vibrations generated in the bearing portion. Moreover, it can suppress that it develops into a big self-excited vibration. Furthermore, vibration caused by electromagnetic force generated between the motor rotor 77 and the motor stator 78 can be attenuated. Further, it is possible to prevent the vibration of the motor portion 79 from being transmitted to the spindle base housing 22.

  Moreover, in the above, although the case where the sheet | seat 4 was comprised with rubber was demonstrated, the sheet | seat 4 may be comprised with the plastics. As the plastic, for example, a plastic having a high elongation rate and a relatively high compressive strength, such as polypropylene, polycarbonate, nylon 66, polyacetal, and fluororesin, can be used.

  Moreover, the sheet | seat 4 may be comprised with the damping material. As the damping material, for example, a restraint type damping material composed of a single layer plate of a polymer viscoelastic body, a restraint type damping material and a damping alloy in which a polymer viscoelastic body and a thin plate of a high rigidity body are laminated. is there. Of these damping materials, a material with a loss factor of 0.1 or more, which is one of the indexes representing vibration damping performance, and having stable characteristics with respect to temperature change, usage period, etc. is used. obtain.

  In addition, in the above, although the structure where the sheet | seat 4 was interposed in between between each housing was demonstrated, the location where the sheet | seat 4 is interposed may be one place.

  In addition to air, gases such as nitrogen, argon, helium, hydrogen, and oxygen can be employed as the bearing gas.

  Each embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be particularly advantageously applied to a hydrostatic gas bearing spindle that rotatably supports a rotating shaft with respect to a fixed part across a bearing gap.

  DESCRIPTION OF SYMBOLS 1 Rotating shaft, 2 Housing, 3 Bearing sleeve, 4, 41, 42 Seat, 5 Bearing clearance, 6 Bearing surface, 7, 8, 9, 10 Joint surface, 11 Front main shaft, 12 Rear main shaft, 13 Front thrust plate , 14 Rear thrust plate, 21 Bearing housing, 22 Spindle base housing, 23 Motor housing, 31 Front bearing sleeve, 32 Rear bearing sleeve, 51, 52, 53 Bearing clearance, 61 Journal bearing surface, 62 Thrust bearing surface.

Claims (4)

A rotation axis;
A fixing portion that surrounds an outer peripheral surface of the rotating shaft across a bearing gap to which a bearing gas for rotatably supporting the rotating shaft is provided;
The fixing portion includes a housing and a seat,
The housing is composed of a plurality of members, and the plurality of members are coupled to the at least one joint portion between the plurality of members via the sheet having characteristics that are more easily deformable than the housing. Hydrostatic gas bearing spindle.   The hydrostatic gas bearing spindle according to claim 1, wherein the sheet is made of rubber.   The hydrostatic gas bearing spindle according to claim 1, wherein the sheet is made of plastic.   The hydrostatic gas bearing spindle according to claim 1, wherein the seat is made of a damping material.

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