JP2009197943A - Gas bearing spindle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas bearing spindle which stably operates even if a rotating shaft rotates at high speed. <P>SOLUTION: The gas bearing spindle 1 is equipped with a rotating shaft 10 and a bearing sleeve 30. The bearing sleeve 30 is arranged in a manner opposed to at least a part of a lateral side of the rotating shaft 10. Further, the bearing sleeve 30 includes a mixture of carbon and material different from carbon in linear expansion coefficient. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas bearing spindle, and more particularly to a gas bearing spindle that can be used stably even during high-speed rotation.

  Conventionally known is a gas bearing spindle in which a rotating shaft is supported with respect to a housing by supplying a gas such as compressed air to a minute gap between the rotating shaft and a member facing the rotating shaft inside the housing. ing. In such a gas bearing spindle, the rotating shaft is supported in a non-contact state with respect to the housing. For this reason, not only the friction loss in the bearing is small, but also the rotating shaft and the member facing the rotating shaft are not usually in direct contact, so that the member is not fatigued or worn as long as it is in a normal operating state. Taking advantage of such features, gas bearing spindles are widely used as high-speed spindles used in precision processing machines, hole processing machines, electrostatic coating machines and the like.

  Various proposals have been made to improve the performance of the gas bearing spindle. For example, in order to avoid seizure of the rotating shaft even if the rotating shaft and a member facing the rotating shaft come into contact, a bearing sleeve having an inner wall made of graphite is employed as the member facing the rotating shaft. Has been proposed. In addition, a configuration has been proposed in which a bearing sleeve as a member facing the rotating shaft is supported by an O-ring with respect to the housing to absorb the whirling vibration of the rotating shaft (for example, Japanese Patent Laid-Open No. 2002-2002). -295470 (referred to as Patent Document 1 hereinafter)).

  FIG. 4 is a schematic cross-sectional view showing a journal bearing portion of a conventional gas bearing spindle (hydrostatic air bearing spindle) disclosed in Patent Document 1. An example of a conventional gas bearing spindle will be described with reference to FIG.

  In the conventional gas bearing spindle shown in FIG. 4, a bearing sleeve 130 is disposed on the outer diameter surface of the rotating shaft 110 with a journal bearing gap 113 for the gas bearing spaced apart. Both end portions of the bearing sleeve 130 are supported by the housing 120 via four O-rings 141 to 144. The O-rings 141 and 142 hermetically seal the circumferential space 122 between the housing 120 and the bearing sleeve 130, and attenuate the swinging vibration of the rotating shaft 110 by its elasticity. The rotating shaft 110 is rotatably supported in a non-contact manner by high-pressure gas supplied to the bearing gap 113. Although not shown, the rotating shaft 110 is supported in a non-contact manner in the axial direction by high-pressure gas.

The high-pressure gas for the gas bearing is supplied to the circumferential space 122 between the inner diameter of the housing 120 and the outer diameter of the bearing sleeve 130 through an air supply passage 121 formed in the housing 120. Then, the high-pressure gas is jetted into the bearing gap 113 on the outer periphery of the rotary shaft 110 from a plurality of circumferentially formed bearing nozzles 151 near both ends of the bearing sleeve 130. In addition, a tool etc. can be attached to the right end of the rotating shaft 110 in FIG. The rotating shaft 110 is driven by a driving means (not shown).
JP 2002-295470 A

In the gas bearing spindle, in order to improve seizure resistance, the bearing sleeve 130 is often made of graphite having excellent lubricity, and the rotating shaft 110 is often made of a steel-based metal. However, such a conventional gas bearing spindle may cause the following problems. That is,
(1) When the rotating shaft 110 rotates at high speed, heat is generated by gas friction in the bearing gap 113. However, since the bearing sleeve 130 is usually elastically supported by the housing 120 by the O-rings 141 to 144, the heat transfer from the bearing sleeve 130 to the housing 120 is not good. As a result, heat radiation from the bearing gap 113 is poor, and the temperature of the rotating shaft 110 and the bearing sleeve 130 may rise. Then, the linear expansion coefficient of graphite, which is the material of the bearing sleeve 130, is smaller than that of the steel-based material, which is the material of the rotating shaft 110. For this reason, when the rotating shaft 110 rotates at a high speed, the bearing gap 113 gradually becomes narrow, and in some cases, the bearing gap 113 may become zero and the rotating shaft 110 and the bearing sleeve 130 may come into contact with each other. Such a problem is more serious for high-speed applications.

For example, the bearing sleeve 130 is made of graphite having a linear expansion coefficient α ₁ = 4 × 10 ⁻⁶ / ° C., and the rotating shaft 110 is made of stainless steel having a linear expansion coefficient α ₂ = 17 × 10 ⁻⁶ / ° C. Think. Here, it is assumed that the inner radius of the bearing sleeve 130 (journal bearing radius) r ₁ = 20 mm and the bearing gap 113 (bearing radius gap) Cr = 0.005 mm. In this case, assuming that the temperature rise of each member is uniform, Cr = 0 when the temperature rise is about 19 ° C. (= ΔT). This can be calculated from the following equation.

ΔCr ₁ = r ₁ (α ₂ −α ₁ ) ΔT (where ΔCr _{1 is the} amount of change in the bearing radius clearance)
As a method for preventing the phenomenon of Cr = 0 as described above (the phenomenon of zero bearing radius gap), it is conceivable to first set the bearing gap 113 large. However, if the bearing clearance 113 is increased, the bearing rigidity decreases, and therefore, this is not applicable when the gas bearing spindle requires high rigidity. Further, it is not preferable to increase the bearing gap 113 from the viewpoint of suppressing swinging.

  On the other hand, a method of forming the rotating shaft 110 with a material such as Invar alloy or ceramics having a linear expansion coefficient as small as that of graphite is also conceivable. However, such a material is generally expensive and can be said to be a practical solution. Absent.

  (2) In the gas bearing spindle shown in FIG. 4, the graphite bearing sleeve 130 is elastically supported by the housing 120 because of the relative damping between the rotating shaft 110 and the bearing sleeve 130 due to the damping performance associated with the elastic deformation of the O-ring. This is to attenuate the vibration. At this time, since the graphite bearing sleeve 130 has a light mass, the vibration of the bearing sleeve 130 tends to increase with respect to the housing 120. Since the vibration of the bearing sleeve 130 also has a tilt component, the rotating shaft 110 supported by the bearing sleeve 130 also generates a whirling vibration with a tilt. As a result, in the thrust bearing portion disposed on the side opposite to the side on which the tool is installed (tool side) of the rotary shaft 110, contact between the rotary shaft 110 and other members, or the tool side of the rotary shaft 110 with respect to the housing 120 There may be a problem with the amount of shaft runout.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a gas bearing spindle that operates stably even when the rotating shaft rotates at a high speed. is there.

  A gas bearing spindle according to the present invention includes a rotating shaft and a bearing sleeve. The bearing sleeve is disposed to face at least a part of the side surface of the rotating shaft. The bearing sleeve includes a mixture of carbon and a material having a coefficient of linear expansion different from that of carbon. The bearing sleeve may be formed with a gas supply hole for supplying gas to a gap between the bearing sleeve and a part of the side surface of the rotating shaft.

  In this manner, the lubricity of the bearing sleeve can be ensured by using carbon, and the linear expansion coefficient of the entire bearing sleeve can be adjusted. For this reason, it becomes possible to make the difference of the linear expansion coefficient of a rotating shaft and a bearing sleeve smaller than the case where a bearing sleeve is comprised only from carbon. In this case, when the rotating shaft and the bearing sleeve are thermally expanded by heat due to gas friction accompanying the rotation of the rotating shaft, the dimensional change due to the thermal expansion between the rotating shaft and the bearing sleeve is greater than when a bearing sleeve made of only carbon is used. The difference can be reduced. As a result, there is no gap between the rotating shaft and the bearing sleeve due to the dimensional change, and it is possible to suppress the occurrence of a defect that the rotating shaft and the bearing sleeve are in contact with each other. Here, the mixture of carbon and the above-mentioned material is a mixture of carbon and the above-mentioned material, or a mixture of carbon and the above-mentioned material subjected to a predetermined treatment such as firing, heat treatment or pressure treatment. The thing which at least one part of the said material reacted is included.

  The gas bearing spindle may further include a housing that holds a bearing sleeve via an elastic member. In this case, the relative vibration between the bearing sleeve and the rotating shaft can be attenuated by the elastic member. Further, when the bearing sleeve is held in the housing by such an elastic member, the heat transfer from the bearing sleeve to the housing is not so good, and the temperature between the rotating shaft and the bearing sleeve is likely to rise. Therefore, it is particularly effective to reduce the difference in linear expansion coefficient between the rotating shaft and the bearing sleeve according to the present invention.

  In the gas bearing spindle, the rotating shaft may be formed of a material having a larger linear expansion coefficient than carbon. The material constituting the mixture may have a linear expansion coefficient larger than that of carbon. In this case, the difference in the coefficient of linear expansion between the bearing sleeve and the rotating shaft can be made smaller than when the bearing sleeve is made of only carbon as in the prior art. For this reason, the possibility that the rotating shaft and the bearing sleeve thermally expand due to the heat accompanying the rotation of the rotating shaft and contact with each other can be reduced.

  In the gas bearing spindle, the material constituting the mixture may be a resin. The portion of the bearing sleeve that faces the rotating shaft may be formed of a molded body obtained by molding a mixture of carbon and resin. In this case, the degree of freedom for adjusting the linear expansion coefficient of the portion of the bearing sleeve that faces the rotating shaft can be increased by adjusting the resin composition.

  In the gas bearing spindle, the material constituting the mixture may be a metal. The portion of the bearing sleeve that faces the rotating shaft may be a sintered body of carbon and metal. In this case, the linear expansion coefficient of the portion of the bearing sleeve that faces the rotating shaft can be arbitrarily adjusted by selecting the type of metal.

  In the gas bearing spindle, the bearing sleeve may include a mass adjusting component for adjusting the mass of the bearing sleeve. In this case, the mass of the bearing sleeve and the position of the center of gravity can be arbitrarily adjusted by the mass and arrangement of the mass adjusting parts. For this reason, the position of the center of gravity and the mass of the bearing sleeve can be set so as to suppress the vibration of the bearing sleeve with respect to a member such as a housing that holds the bearing sleeve.

  In the gas bearing spindle, a plurality of mass adjusting parts may be installed on the bearing sleeve. The plurality of mass adjusting components may be arranged at positions that are axisymmetric with respect to the central axis of the bearing sleeve. In this case, when the bearing sleeve vibrates with the rotation of the rotating shaft, the abnormal vibration caused by the mass adjusting component being disposed at an asymmetrical position (biased position) with respect to the central axis of the bearing sleeve. Can be suppressed.

  In the gas bearing spindle, a plurality of mass adjusting parts may be installed on the bearing sleeve. The position of the center of gravity of the bearing sleeve in the direction along the central axis of the bearing sleeve may be located at the center in the direction along the central axis of the bearing sleeve. In this case, it is possible to suppress the occurrence of abnormal vibration in the bearing sleeve, which may occur when the position of the center of gravity is shifted from the center in the direction along the center axis of the bearing sleeve.

  In the gas bearing spindle, the material constituting the mass adjustment component may have a linear expansion coefficient value equal to or greater than the linear expansion coefficient value of the material constituting the bearing sleeve other than the mass adjustment component. The mass adjusting component may be fixed to the bearing sleeve by fitting at least a part of the mass adjusting component into the bearing sleeve. In this case, when the temperature of the bearing sleeve rises with the rotation of the rotary shaft, the dimensional change due to thermal expansion is greater in the mass adjusting component than in the portion other than the mass adjusting component in the bearing sleeve. Therefore, due to the thermal expansion, it is possible to prevent the mass adjusting component from being removed from a portion where a part of the mass adjusting component is fitted into the bearing sleeve.

  In the gas bearing spindle, the mass adjusting component may be detachably attached to the bearing sleeve. In this case, it is possible to easily adjust the mass of the bearing sleeve and the position of the center of gravity by installing and removing the mass adjusting component.

  In the gas bearing spindle, the bearing sleeve may be formed with a fixing hole that is internally threaded. A threaded portion may be formed on the surface of the mass adjusting component. The mass adjusting component may be fixed by being screwed into the fixing hole. In this case, the mass adjusting component can be easily fixed to the bearing sleeve.

  In the gas bearing spindle, a threaded portion may be formed along the outer periphery of the side surface at the side surface end of the bearing sleeve. The mass adjusting component may be a ring-shaped member having a threaded inner peripheral portion. The mass adjusting component may be fixed by fitting the inner peripheral portion subjected to the screw processing with the screw processing portion of the bearing sleeve. In this case, the mass adjusting component can be easily fixed to the bearing sleeve.

  According to the present invention, it is possible to obtain a gas bearing spindle that operates stably even during high-speed rotation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a gas bearing spindle according to Embodiment 1, which is an embodiment of the present invention. With reference to FIG. 1, the gas bearing spindle 1 in Embodiment 1 of this invention is demonstrated.

  As shown in FIG. 1, the gas bearing spindle 1 according to the first embodiment includes a rotating shaft 10, a bearing sleeve 30, and a housing 20. The bearing sleeve 30 is a cylindrical member in which a bearing sleeve through hole 33 that is a through hole surrounding a part of the outer peripheral surface 11 </ b> A of the rotating shaft 10 is formed. The housing 20 surrounds the bearing sleeve 30 and holds the bearing sleeve 30 via rubber O-rings 41 to 44 as elastic members. The rotating shaft 10 and the bearing sleeve 30 are arranged with a journal bearing gap 13 of about 10 μm or more and 40 μm or less separated.

  The rotating shaft 10 includes a cylindrical (rod-shaped) shaft portion 11 and a flange portion 12 formed at one end of the shaft portion 11 and having a disk shape having a diameter larger than that of the shaft portion 11. ing. A holding portion 19 for holding a tool or the like is formed at the other end of the shaft portion 11. The bearing sleeve 30 is formed with a plurality of journal nozzles 51. The journal nozzle 51 is formed on the peripheral wall of the bearing sleeve 30. The journal nozzle 51 supplies bearing gas to the journal bearing gap 13 provided between the inner peripheral surface of the bearing sleeve through-hole 33 and the outer peripheral surface 11A of the shaft portion 11 of the rotary shaft 10.

  The journal nozzles 51 are arranged to form two rows extending in the circumferential direction on the inner peripheral surface of the bearing sleeve through-hole 33. The journal nozzles 51 are formed in one row on each of both sides sandwiching the central portion of the bearing sleeve 30 in the direction in which the bearing sleeve through-hole 33 extends (the axial direction in the shaft portion 11 of the rotary shaft 10). The journal nozzle 51 is connected to a sleeve air supply path 52 formed on the peripheral wall of the bearing sleeve 30.

  With the above configuration, the bearing sleeve 30 functions as a gas journal bearing that supports the rotating shaft 10 in a radial direction (a direction perpendicular to the axial direction of the shaft portion 11) in a non-contact manner with respect to the housing 20. The journal nozzle 51 is preferably formed so that the distances from the central portion of the bearing sleeve 30 to the journal nozzles 51 on both sides in the axial direction of the shaft portion 11 are substantially equal. Thereby, the pressure distribution in the journal bearing gap 13 is symmetric with respect to the central portion of the bearing sleeve 30 in the axial direction. In this way, the rotary shaft 10 is supported in a balanced manner in the axial direction with respect to the bearing sleeve 30.

  The journal nozzle 51 is an annular space (a space surrounded by the O-rings 42 and 43 in the circumferential space 22) that is a space closed by the sleeve air supply path 52, the bearing sleeve 30, the housing 20, and the O-rings 42 and 43. And a bearing gas supply passage 21 formed in the housing 20 through a space.

  A gas thrust bearing member 60 having an annular shape is disposed inside the housing 20. The gas thrust bearing member 60 is disposed such that one end face thereof faces each of the end faces 12A on both sides of the flange portion 12 of the rotating shaft 10. The gas thrust bearing member 60 and the flange portion 12 of the rotary shaft 10 are arranged with a thrust bearing gap 14 of about 10 μm or more and 50 μm or less separated. A plurality of gas thrust bearing members 60 are provided to supply gas to the thrust bearing gap 14 provided between the one surface facing the flange portion 12 and the end surface 12A of the flange portion 12 facing the flange portion 12. The thrust nozzle 61 is formed. A plurality of thrust nozzles 61 are formed in a direction along the circumferential direction of the flange portion 12. The thrust nozzle 61 is connected to a thrust bearing supply passage 62 formed in the gas thrust bearing member 60. The thrust bearing air supply passage 62 is connected to a bearing gas supply passage 21 formed in the housing 20. That is, the thrust nozzle 61 is connected to the bearing gas supply path 21 via the thrust bearing supply path 62. The bearing gas supply path 21 has a function of supplying a high-pressure gas such as air, and is connected to a bearing gas supply source such as an air compressor (not shown) disposed outside the gas bearing spindle 1. .

  A part of the flange portion 12 (outer peripheral portion) includes a thin portion 12B having a smaller axial thickness than a portion adjacent to the outer peripheral portion in the flange portion 12 (for example, a portion of the flange portion 12 facing the thrust nozzle 61). Is formed. A plurality of turbine blades 15 arranged along the circumferential direction of the flange portion 12 are formed on one surface of the thin portion 12B. The turbine blade 15 has a plate shape and receives the blown gas to rotate the rotating shaft 10 in the circumferential direction of the flange portion 12.

  Further, the housing 20 is disposed on the outer peripheral side of the flange portion 12, has an opening at a position facing the turbine blade 15, and a driving gas such as compressed air from the inner wall of the housing 20 toward the turbine blade 15. A turbine nozzle 73 is formed so as to be able to eject the gas. The turbine nozzle 73 is connected to a circumferential groove 72 formed so as to extend in a direction along the outer periphery of the flange portion 12. The circumferential groove 72 is connected to the driving gas supply path 71. That is, the turbine nozzle 73 is connected to the driving gas supply path 71 via the circumferential groove 72. The driving gas supply path 71 has a function of supplying a gas such as high-pressure air, and is connected to a driving gas supply source such as an air compressor (not shown) disposed outside the gas bearing spindle 1.

  A driving gas discharge path 75 is formed in the housing 20. The driving gas discharge passage 75 is a surface on the side where the turbine blade 15 is formed in the thin portion 12B of the flange portion 12 and is located at a position facing the inner peripheral side region from the region where the turbine blade 15 is formed. One opening is provided, and the other opening is provided on the outer wall of the housing 20.

  In the above structure, the bearing sleeve 30 includes a base body 31 that is a bearing portion, and a mass adjusting component 32 described later. The base body 31 has a bearing sleeve through hole 33, and the inner peripheral surface of the bearing sleeve through hole 33 faces the outer peripheral surface 11 </ b> A of the rotary shaft 10. Rubber O-rings 41 to 44, which are elastic members, are fitted on both end faces of the bearing sleeve 30 and end faces of the outer diameter side face in the direction in which the bearing sleeve through-hole 33 extends (the axial direction of the rotary shaft 10). . The bearing sleeve 30 is held with respect to the housing 20 via the O-rings 41 to 44. The relative vibration between the bearing sleeve 30 and the rotary shaft 10 can be damped by the O-rings 41 to 44 as the elastic members.

  Here, the bearing sleeve 30 is disposed so as to face at least a part of the side surface of the rotating shaft 10. The base body 31 which is a portion facing the rotating shaft 10 in the bearing sleeve 30 includes a mixture of carbon and carbon and a material having a different linear expansion coefficient. More specifically, the base body 31 of the bearing sleeve 30 is formed of a molded body obtained by molding a mixture of carbon and a material having a different linear expansion coefficient from the carbon. For example, the base body 31 of the bearing sleeve 30 is formed of a molding material made of a mixture of carbon and resin, or a sintered material of carbon and metal. The cylindrical shaft portion 11 of the rotating shaft 10 is formed of a steel-based metal (for example, stainless steel) that is an example of a material having a larger linear expansion coefficient than carbon. In addition, phenol resin can be used for resin mixed with the said carbon, for example. Moreover, in the molding material which consists of the mixture of the said carbon and resin, the composition ratio of carbon uses the thing of 65% or more by volume ratio, for example. In this case, the degree of freedom for adjusting the linear expansion coefficient of the portion (base body 31) facing the rotating shaft 10 in the bearing sleeve 30 can be increased by adjusting the resin composition and the carbon composition ratio. The reason why the volume ratio is 65% as the lower limit of the composition ratio of carbon in the mixture of carbon and resin is that the seizure resistance performance at the time of contact between the bearing sleeve 30 and the rotating shaft 10 is lowered when the volume ratio is lower than that ratio. Because. The higher the carbon composition ratio, the better the seizure resistance performance, but the sleeve has a lower coefficient of linear expansion, and the improvement effect of the coefficient of linear expansion on the sleeve made of only carbon cannot be expected (that is, bearing Select the optimal composition ratio according to the operating conditions of

  As for the sintered material of carbon and metal, for example, iron (Fe) or copper (Cu) can be used as the metal mixed with carbon. In the sintered material, for example, the mixing ratio of carbon is 25% or less by volume ratio. In this case, the linear expansion coefficient of the base body 31 in the bearing sleeve 30 can be arbitrarily adjusted by selecting the composition ratio of carbon and the type of metal. In addition, the upper limit of the mixing ratio of carbon in the sintered body of carbon and metal is set to 25% by volume because normal carbon sintering becomes difficult if the carbon is further increased.

  As described above, in the gas bearing spindle 1 shown in FIG. 1, carbon is used to ensure lubricity on the surface of the bearing sleeve through-hole 33 in the bearing sleeve 30 and to increase the linear expansion coefficient of the bearing sleeve 30 as a whole. Can be adjusted. For this reason, it becomes possible to make the difference of the linear expansion coefficient of the rotating shaft 10 and the bearing sleeve 30 smaller than the case where the bearing sleeve 30 is comprised only from carbon. In this case, when the rotary shaft 10 and the bearing sleeve 30 are thermally expanded by heat due to gas friction accompanying the rotation of the rotary shaft 10, the rotation shaft 10 and the bearing sleeve 30 can be compared with the case where the bearing sleeve made of only carbon is used. The difference in dimensional change due to thermal expansion can be reduced. As a result, the journal bearing gap 13 between the rotating shaft 10 and the bearing sleeve 30 is eliminated due to the dimensional change, and the occurrence of a defect that the rotating shaft 10 and the bearing sleeve 30 come into contact can be suppressed.

  A plurality of tap holes 34 are formed, for example, circumferentially on both end faces of the bearing sleeve 30 so as to be axially symmetric with respect to the rotation axis. The inner peripheral surface of the tap hole 34 as a fixing hole is threaded. A mass adjusting component 32 is inserted and fixed in the tap hole 34. A threaded portion is formed on the outer peripheral portion of the mass adjusting component 32. That is, the mass adjustment component 32 is fixed by being screwed into the tap hole 34, and the mass adjustment component 32 is detachably installed on the bearing sleeve 30 from another viewpoint. From another viewpoint, the mass adjusting component 32 is fixed to the bearing sleeve 30 by fitting at least a part of the mass adjusting component 32 into the bearing sleeve 30 (specifically, the base body 31). . With such a configuration, the mass adjusting component 32 can be easily fixed to the bearing sleeve 30, and the mass and the position of the center of gravity of the bearing sleeve 30 can be easily adjusted by attaching and detaching the mass adjusting component 32. be able to. Note that the length of the mass adjusting component 32 is adjusted so that the weight and the center of gravity of the bearing sleeve 30 are optimized before being screwed into the tap hole 34.

  The linear expansion coefficient of the material constituting the mass adjusting component 32 is a line of the material constituting the base body 31 constituting the bearing sleeve 30 (the material constituting the portion other than the mass adjusting component 32 in the bearing sleeve 30). Preferably, it is equal to or larger than the expansion coefficient. In this case, when the temperature of the bearing sleeve 30 rises while the rotary shaft 10 is rotating, the mass is adjusted by a dimensional change (for example, an increase in the diameter of the tap hole 34) due to thermal expansion of the base body 31 in which the tap hole 34 is formed. Since the dimensional change due to the thermal expansion of the component 32 (for example, the increase in the diameter of the mass adjustment component 32) is larger, it is possible to suppress the mass adjustment component 32 from coming out of the tap hole 34.

  In the gas bearing spindle 1, a plurality of mass adjusting parts 32 may be installed on the bearing sleeve 30 as shown in FIG. 1. The position of the center of gravity of the bearing sleeve 30 in the direction along the central axis of the bearing sleeve 30 is located at the center in the direction along the central axis of the bearing sleeve 30. In this case, it is possible to suppress the occurrence of abnormal vibration in the bearing sleeve 30 that may occur when the position of the center of gravity deviates from the central portion in the direction along the central axis of the bearing sleeve 30.

  Further, the plurality of mass adjusting parts 32 are arranged at positions symmetrical with respect to the central axis of the bearing sleeve 30. Specifically, for example, the plurality of mass adjusting parts 32 are arranged so as to be arranged at equal intervals on the circumference around the central axis of the bearing sleeve 30. In this case, when the bearing sleeve 30 vibrates with the rotation of the rotating shaft 10, the mass adjusting component 32 is disposed at an asymmetrical position (biased position) with respect to the central axis of the bearing sleeve 30. It is possible to suppress the occurrence of abnormal vibration.

  Next, the operation of the gas bearing spindle 1 shown in FIG. 1 will be described. Bearing gas such as compressed air supplied from a bearing gas supply source (not shown) is supplied to the journal bearing gap 13 through the bearing gas supply path 21, the circumferential space 22, the sleeve air supply path 52, and the journal nozzle 51. . Further, the bearing gas supplied from a bearing gas supply source (not shown) is supplied to the thrust bearing gap 14 through the bearing gas supply path 21, the thrust bearing supply path 62 and the thrust nozzle 61. Thereby, in the journal bearing gap 13 and the thrust bearing gap 14, a gas film (gas layer) is formed by the supplied bearing gas. As a result, the rotating shaft 10 is supported in a non-contact and rotatable manner with respect to the housing 20 in a direction (radial direction) and an axial direction (axial direction) perpendicular to the axial direction of the rotating shaft 10.

  A driving gas supplied from a driving gas supply source such as an air compressor (not shown) is supplied from the driving gas supply passage 71 to the turbine nozzle 73 through the circumferential groove 72. The driving gas supplied to the turbine nozzle 73 is ejected toward the turbine blade 15. Then, the driving force (torque) that rotates around the axis of the rotary shaft 10 is applied to the flange portion 12 by receiving the jetted driving gas at the turbine blade 15. As a result, the rotating shaft 10 rotates around the axis. The driving gas that gives the driving force to the rotating shaft 10 is discharged from the driving gas discharge path 75 to the outside of the gas bearing spindle 1.

  As described above, the bearing sleeve 30 of the gas bearing spindle 1 shown in FIG. 1 has the base body 31 formed of a molding material of carbon and resin, or a sintered material of carbon and metal. By adjusting the type and blending ratio of the metal, the linear expansion coefficient of the bearing sleeve 30 can be made closer to the linear expansion coefficient of the steel-based metal than graphite compared to the case where the base body 31 is formed of graphite alone. it can. For this reason, even if a relatively inexpensive steel-based metal material is adopted for the rotary shaft 10, the amount of reduction in the bearing gap (journal bearing gap 13) due to heat generation of the bearing portion during rotation is small, and stable bearing performance can be obtained. .

For example, if the linear expansion coefficient of graphite is about 4 × 10 ⁻⁶ / ° C., the mixing ratio of carbon in the molding material of carbon and resin is appropriately selected within the above volume ratio conditions, The linear expansion coefficient can be set to about 15 × 10 ⁻⁶ / ° C. In the case of a sintered material of carbon and metal, the carbon mixing ratio can be appropriately selected within the above volume ratio conditions. For example, the linear expansion coefficient can be about 12 × 10 ⁻⁶ / ° C.

  Here, the resin-based molding material is produced, for example, by mixing powdered carbon and liquid phenolic resin in the above ratio and hot-press molding, and the metal-based sintered body is carbon powder. And metal powder are mixed in the above ratio, pressed and molded in a mold, and then heated and solidified in a furnace at a temperature lower than the melting point of the metal.

  The material of the base body 31 constituting the bearing sleeve 30 is a molding material or sintered material in which carbon and other materials are mixed, and since carbon is included, the base body made of a conventional graphite body alone. Similar to 31, seizure resistance at the time of a contact accident between the rotating shaft 10 and the bearing sleeve 30 is kept good. Further, in order to improve the corrosion resistance and wear resistance, a surface treatment layer such as a plating treatment such as hard chrome plating may be formed on the surface of the rotary shaft 10.

  The bearing sleeve 30 is supported on the housing 20 by O-rings 41 to 44. Further, a mass adjusting component 32 is added to the base body 31 of the bearing sleeve 30. By arbitrarily adjusting the length of the mass adjustment component 32 (that is, the weight of the mass adjustment component 32), the mass of the bearing sleeve 30 can be brought close to an optimum value. Further, by adjusting the weight and arrangement of the mass adjusting component 32, the position of the center of gravity in the axial direction of the bearing sleeve 30 can be adjusted. For this reason, the vibration of the bearing sleeve 30 during rotation can be effectively damped. Therefore, the swing amount of the rotating shaft 10 is small, the contact between the flange portion 12 of the thrust bearing portion and the gas thrust bearing member 60 can be prevented, and the swing amount of the shaft end of the rotating shaft 10 can also be suppressed.

  As described above, according to the gas bearing spindle 1 of the first embodiment, since the amount of change in the bearing gap (journal bearing gap 13) of the rotating shaft 10 is small, the bearing performance is stable and the whirling vibration of the rotating shaft 10 is achieved. Can be efficiently attenuated.

(Embodiment 2)
FIG. 2 is a schematic cross-sectional view of the gas bearing spindle according to the second embodiment which is an embodiment of the present invention. With reference to FIG. 2, the gas bearing spindle 1 in Embodiment 2 of this invention is demonstrated.

  The gas bearing spindle 1 shown in FIG. 2 basically has the same configuration as the gas bearing spindle 1 shown in FIG. However, in the gas bearing spindle 1 shown in FIG. 2, the mass adjusting component 32 is arranged on the side surface (circumferential outer peripheral side surface) with respect to the axial direction of the bearing sleeve 30 instead of the both end surface portions of the bearing sleeve 30. Is different from the gas bearing spindle 1 shown in FIG. That is, in the gas bearing spindle 1 shown in FIG. 2, the tap hole 34 is formed in the center portion in the axial direction of the bearing sleeve 30 on the outer peripheral side surface of the base body 31 constituting the bearing sleeve 30. The adjustment part 32 is screwed and fixed.

  Even with such a configuration, the same effect as the gas bearing spindle 1 shown in FIG. 1 can be obtained.

(Embodiment 3)
FIG. 3 is a schematic cross-sectional view of a gas bearing spindle according to Embodiment 3, which is an embodiment of the present invention. With reference to FIG. 3, the structure of the gas bearing spindle 1 in Embodiment 3 of this invention is demonstrated.

  The gas bearing spindle 1 shown in FIG. 3 basically has the same configuration as the gas bearing spindle 1 shown in FIG. However, in the gas bearing spindle 1 shown in FIG. 3, threaded portions 45 are formed at both ends of the outer peripheral side surface of the base body 31 constituting the bearing sleeve 30. The threaded portion 45 is formed in a recess formed in a circumferential shape at both ends of the outer peripheral side surface of the base body 31. More specifically, a threaded portion 45 is formed on the wall surface along the central axis of the bearing sleeve 30 of the circumferentially formed recess. A mass adjusting component 32 that is ring-shaped and screwed inward is fixed to the recess. The mass adjusting component 32 is made of metal, for example.

  In the gas bearing spindle 1 shown in FIG. 3, the same effect as the gas bearing spindle 1 shown in FIG. 1 can be obtained. Further, in the gas bearing spindle 1 shown in FIG. 3, since the ring-shaped mass adjusting parts 32 are installed at both ends of the bearing sleeve 30, when the process of inserting and removing the bearing sleeve 30 with respect to the housing 20 is performed. In addition, there is no fear of damaging the outer diameter side corners of the base body 31 against the housing 20 or the like, and the above process can be easily performed.

  In the first to third embodiments, the case where the journal nozzles 51 are formed in two rows as an example of the gas bearing spindle of the present invention has been described. However, the gas bearing spindle of the present invention is not limited to this, The journal nozzles 51 may be formed so as to form three or more rows. In the first to third embodiments, a total of four grooves are formed, one on each of the end face side and the outer diameter side face side of the bearing sleeve 30, and O-rings 41 to 44 as elastic members are fitted. Although the case has been described, for the purpose of improving airtightness, three or more grooves may be formed, and three or more elastic members (for example, O-rings) may be fitted in the grooves, respectively.

  Further, a plurality of grooves may be formed on the end surface side of the base body 31 of the bearing sleeve 30 or a plurality of grooves may be formed on the outer peripheral side surface (side surface facing the circumferential space 22) of the base body 31. In this case, the whirling vibration of the bearing sleeve 30 and the rotating shaft 10 can be more reliably absorbed by the O-ring as an elastic member. Conversely, for the purpose of reducing the rigidity of the elastic member, one elastic member may be fitted into the outer diameter side corners on both end faces of the bearing sleeve 30. Specifically, a groove is formed so as to cut off corners of the outer diameter side (outer peripheral side) of both end faces of the base body 31 constituting the bearing sleeve 30, and an elastic member is disposed in the groove. In this way, the function of the elastic member for journal bearing and the elastic member for thrust bearing can be shared by the one elastic member (for example, O-ring).

  The embodiment disclosed this time should 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 spindle device according to the present invention is advantageously applied to a spindle device using a static pressure gas bearing as a bearing and used for a work spindle device or a tool spindle device of a precision processing machine or a precision inspection device.

It is a cross-sectional schematic diagram of the gas bearing spindle of Embodiment 1 which is one embodiment of this invention. It is a cross-sectional schematic diagram of the gas bearing spindle of Embodiment 2 which is one embodiment of this invention. It is a cross-sectional schematic diagram of the gas bearing spindle of Embodiment 3 which is one embodiment of this invention. It is a cross-sectional schematic diagram which shows the journal bearing part of the conventional gas bearing spindle (hydrostatic air bearing spindle).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Gas bearing spindle, 10 Rotating shaft, 11 Shaft part, 11A Outer peripheral surface, 12 Flange part, 12A End surface, 12B Thin wall part, 13 Journal bearing gap, 14 Thrust bearing gap, 15 Turbine blade, 19 Holding part, 20 Housing, 21 Gas supply path for bearing, 22 circumferential space, 30 bearing sleeve, 31 base body, 32 parts for mass adjustment, 33 bearing sleeve through hole, 34 tap hole, 41-44 O-ring, 45 threaded portion, 51 journal nozzle, 52 sleeve air supply path, 60 gas thrust bearing member, 61 thrust nozzle, 62 thrust bearing air supply path, 71 driving gas supply path, 72 circumferential groove, 73 turbine nozzle, 75 driving gas discharge path.

Claims (11)

A rotation axis;
A bearing sleeve arranged to face at least a part of a side surface of the rotating shaft,
The bearing sleeve is a gas bearing spindle including a mixture of carbon and a material having a different linear expansion coefficient from the carbon. The rotating shaft is formed of a material having a larger linear expansion coefficient than the carbon,
The gas bearing spindle according to claim 1, wherein the material constituting the mixture has a linear expansion coefficient larger than a linear expansion coefficient of the carbon. The material constituting the mixture is a resin,
2. The gas bearing spindle according to claim 1, wherein a portion of the bearing sleeve that faces the rotating shaft is configured by a molded body obtained by molding a mixture of the carbon and the resin. The material constituting the mixture is a metal,
The gas bearing spindle according to claim 1, wherein a portion of the bearing sleeve that faces the rotating shaft is a sintered body of the carbon and the metal.   The gas bearing spindle according to claim 1, wherein the bearing sleeve includes a mass adjusting component for adjusting a mass of the bearing sleeve. A plurality of the mass adjusting parts are installed on the bearing sleeve,
The gas bearing spindle according to claim 5, wherein the plurality of mass adjusting parts are disposed at positions that are axisymmetric with respect to a central axis of the bearing sleeve. A plurality of the mass adjusting parts are installed on the bearing sleeve,
6. The gas bearing spindle according to claim 5, wherein a position of a center of gravity of the bearing sleeve in a direction along the central axis of the bearing sleeve is located at a central portion of the bearing sleeve in a direction along the central axis. The material constituting the mass adjustment component has a value of a linear expansion coefficient equal to or greater than the value of the linear expansion coefficient of the material constituting the portion other than the mass adjustment component in the bearing sleeve,
The gas bearing spindle according to claim 5, wherein the mass adjusting component is fixed to the bearing sleeve by fitting at least a part of the mass adjusting component into the bearing sleeve. .   The gas bearing spindle according to claim 5, wherein the mass adjusting component is detachably installed on the bearing sleeve. The bearing sleeve is formed with a fixing hole that is internally threaded,
A threaded portion is formed on the surface of the mass adjusting component,
The gas bearing spindle according to claim 9, wherein the mass adjusting component is fixed by being screwed into the fixing hole. A threaded portion is formed on the side surface end of the bearing sleeve along the outer periphery of the side surface,
The mass adjusting component is a ring-shaped member having a threaded inner peripheral portion,
The gas bearing spindle according to claim 9, wherein the mass adjusting component is fixed by fitting an inner peripheral portion on which the threading is performed with the threading portion of the bearing sleeve.

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