JP2009068542A - Spindle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely restrain the generation of an air hammer caused by the compressibility of air. <P>SOLUTION: A spindle 14 is rotatably supported to a housing 12 via porous air bearings 26 and 28. The spindle 14 is connected to a motor rotary shaft 44 of an electric motor 38 via a flange 18. The housing 12 has air passages 30 and 32 exhausting air introduced from an air supply port 34 from an exhaust port 36 via the porous air bearings 26 and 28. The porous air bearings 26 and 28 are constituted by integrating a radial bearing and a thrust bearing. The porous air bearings 26 and 28 have pockets 50 and 52 introducing and storing air flowing on thrust receiving surfaces 26b and 28b of the porous air bearings 26 and 28, air exhaust passages 54 and 56 introducing air stored in the pockets 50 and 52 to the air passage 32, and orifices 58 and 60 adjusting flow rates of air passing through the air exhaust passages 54 and 56. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a spindle device suitable for rotating a spindle rotatably supported by a static pressure gas bearing by an electric motor and transmitting the rotational force of the spindle to a precision measuring instrument or processing machine.

  The spindle device is used as an element of a machine tool that rotationally drives a tool such as cutting and grinding, or as an element of an inspection machine that rotationally drives a magnetic disk or the like. In this type of spindle device, a spindle (spindle shaft), which is a rotating shaft, is supported by a cylindrical housing via a static pressure gas bearing, and a motor rotating shaft of an electric motor is connected to the spindle to drive the electric motor. Thus, the spindle is driven to rotate. At this time, the static pressure gas bearing is supplied with air to form a gap with the spindle, and supports the spindle in a non-contact manner so that the spindle can rotate at high speed.

  On the other hand, high rigidity is required for a spindle device used for precision processing machines, precision measuring instruments, and the like. Therefore, the most rigid porous air bearing among the air bearings is adopted as the static pressure gas bearing of the spindle device.

  However, when an air bearing is used as the static pressure gas bearing, self-excited vibration called an air hammer may occur due to air compressibility. In particular, when a porous air bearing is used as the air bearing, the porous itself becomes an air reservoir, and an air hammer is more easily generated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a spindle device that can reliably suppress the generation of an air hammer due to air compressibility.

  In order to achieve the above object, according to the present invention, a spindle is rotatably supported by a cylindrical housing via a static pressure gas bearing, and an electric motor is provided in parallel in the housing, and one end side in the longitudinal direction of the spindle. In addition, in the spindle device, the motor rotating shaft of the electric motor is connected, and the housing is formed with an air passage for discharging the air introduced from the air supply port from the exhaust port through the static pressure gas bearing. The static pressure gas bearing is configured by integrating a radial bearing that receives a radial load from the spindle and a thrust bearing that receives a thrust load from a flange of the spindle. A pocket for storing air generated in a gap between the hydrostatic gas bearing and the spindle, and the air stored in the pocket is guided to the air passage. And A discharge passage, is characterized in that the aperture to adjust the flow rate of air is formed passing through the air discharge channel.

  According to such a configuration, when air flowing through the bearing gap or air passing through the static pressure gas bearing is introduced into the pocket, the pocket stores the introduced air and serves as a buffer for discharging the stored air to the air discharge path. It can function and can increase the pressure of air in the bearing gap, and as a result, the rigidity can be increased. Further, the flow rate is controlled by the throttle in the process in which the air introduced into the pocket flows through the air discharge path. At that time, the air attenuation action by the throttle is enhanced, and the occurrence of an air hammer (self-excited vibration) due to the compressibility of the air can be reliably suppressed.

  In configuring the spindle device, the following elements can be added. Preferably, the pocket is formed on a thrust receiving surface of the hydrostatic gas bearing.

  According to such a configuration, since the pocket is formed opposite to the thrust receiving surface of the static pressure gas bearing, the thrust of the static pressure gas bearing out of the air flowing through the bearing gap and the air passing through the static pressure gas bearing. Air flowing on the receiving surface can be smoothly guided to the pocket.

  Preferably, flanges are formed on both ends of the spindle in the longitudinal direction, and static pressure gas bearings are disposed on the outer periphery of the spindle adjacent to the flanges.

  According to such a configuration, the static pressure gas bearing is disposed adjacent to each flange, so that the spindle can be smoothly supported by each static pressure gas bearing.

  Preferably, each of the static pressure gas bearings is formed with the pocket, an air discharge path and a throttle, and the pocket of each of the static pressure gas bearings is formed on a thrust receiving surface of each of the static pressure gas bearings. .

  According to such a configuration, the pocket, the air discharge path, and the throttle are formed in each static pressure gas bearing as a fixing member, and the air discharge path communicates with the air passage, so that air can be discharged smoothly. it can. Moreover, since the pocket of each static pressure gas bearing is formed opposite to the thrust receiving surface of each static pressure gas bearing, the static pressure of the air flowing through the bearing gap and the air passing through each static pressure gas bearing Air flowing on the thrust receiving surface of the gas bearing can be smoothly guided to the pocket.

  Suitably, the said static pressure gas bearing is comprised with the porous air bearing. Thereby, air permeability can be improved.

  According to the present invention, generation of an air hammer can be reliably suppressed, and a highly rigid spindle device can be realized.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a spindle apparatus showing an embodiment of the present invention. In FIG. 1, a spindle device 10 includes a metal (stainless steel) housing 12 formed in a substantially cylindrical shape, and a cylindrical spindle (spindle shaft) 14 is rotatable in the housing 12 as a rotation axis. It is stored.

  Cylindrical flanges 16 and 18 are disposed at both ends in the longitudinal direction of the spindle 14, and the flanges 16 and 18 are respectively connected to both ends in the longitudinal direction of the spindle 14 via bolts (not shown). . The flanges 16 and 18 are respectively formed with through holes 22 and 24 connected to the through hole 20 of the spindle 14. The through hole 20 or the through hole 22 functions as, for example, a chuck mechanism, and the through hole 20 or the through hole 22 is connected to a tool such as cutting and polishing, or a magnetic disk. Note that the flanges 16 and 18 can be integrally formed at both ends in the longitudinal direction of the spindle 14.

  A pair of porous air bearings 26 and 28 are disposed between the housing 12 and the spindle 14 along the longitudinal direction (axial direction) of the spindle 14 as a static pressure gas bearing. The porous air bearings 26 and 28 are configured by integrating a radial bearing that receives a radial load (a load in the radial direction) from the spindle 14 and a thrust bearing (a load in the thrust direction) that receives a thrust load from the spindle 14. Yes. The opposed surfaces of the porous air bearings 26, 28 to the outer periphery of the spindle 14 are configured as radial receiving surfaces 26a, 28a for receiving a radial load, and the opposed surfaces of the porous bearings 26, 28 to the flanges 16, 18 are The thrust receiving surfaces 26b and 28b are configured to receive a thrust load.

  The housing 12 is formed with an air passage 30 for supplying air to the porous air bearings 26 and 28 and an air passage 32 for exhausting the supplied air. 34 is supplied with air from an air supply source. The air introduced into the air supply port 34 is supplied to the porous air bearings 26, 28 through the air passage 30, and the air that has passed through the porous air bearings 26, 28 passes through the air passage 32 to the exhaust port 36. It comes to be discharged from. In the process in which the air from the air supply source is exhausted from the exhaust port 36 through the air passage 30, the porous air bearings 26, 28 and the air passage 32, a part of the air is outside the spindle 14 and each porous air bearing 26. , 28 and the bearing gap between the porous air bearing 26 and the flange 16 and the bearing gap between the porous air bearing 28 and the flange 18.

  At this time, the porous air bearings 26, 28 are supported by the housing 12, and the surfaces facing the spindle 14 function as radial receiving surfaces 26 a, 28 a for receiving a radial load, and facing the flanges 16, 18. The surfaces function as thrust receiving surfaces 26b and 28b for receiving a thrust load, and the spindle 14 and the flanges 16 and 18 can be rotatably supported in a non-contact state.

  On the other hand, an electric motor 38 is juxtaposed to the housing 12 adjacent to the housing 12, and the electric motor 38 is housed and fixed in a cylindrical motor bracket 40. One end of the motor bracket 40 in the longitudinal direction is connected to the housing 12, and the other end in the longitudinal direction is closed by a cover 42.

  The electric motor 38 includes a motor rotating shaft 44, a rotor 46, and a stator 48, and one end side in the longitudinal direction (axial direction) of the motor rotating shaft 44 is connected to the flange 18 via a bolt (not shown). A rotor 46 is press-fitted and fixed to the outer periphery. A stator 48 that generates a rotating magnetic field is disposed outside the rotor 46, and the stator 48 is fixed to the inner wall surface of the motor bracket 40. The electric motor 38 transmits the rotational force accompanying the rotation of the rotor 46 to the flange 18 via the motor rotation shaft 44, and rotationally drives the spindle 14.

  In the spindle device 10 having the above-described configuration, air from an air supply source is supplied to the porous air bearings 26 and 28, and the spindle 14 and the flanges 16 and 18 are rotatably supported by the porous air bearings 26 and 28 in a non-contact state. In addition, when the spindle 14 is rotationally driven by the electric motor 38, the air from the air supply source is exhausted from the exhaust port 36 through the air passage 30, the porous air bearings 26 and 28, and the air passage 32. If micro pockets associated with chamfering of the porous air bearings 16 and 18 are formed at the intersection between the flange 16 and the porous air bearing 26 or at the intersection between the flange 18 and the porous air bearing 18, An air hammer (self-excited vibration) may occur due to compressibility. If an air hammer is generated, it cannot be used at a high supply pressure and high rigidity cannot be obtained.

  Therefore, in the present embodiment, in order to quickly discharge the air that has passed through the porous air bearings 26 and 28 to the outside, among the fixing members of the spindle device 10 such as the housing 12 and the porous air bearings 26 and 28. As shown in FIG. 2, the porous air bearings 26 and 28 introduce pockets 50 and 52 for storing air discharged into the bearing gap and air that has passed through the porous air bearings 26 and 28, and pockets 50, Air discharge paths 54 and 56 for guiding the air stored in 52 to the air passage 32 and throttles 58 and 60 for adjusting the flow rate of the air passing through the air discharge paths 54 and 56 are provided.

  At this time, the pockets 50 and 52 are formed on the thrust receiving surfaces 26b and 28b of the porous air bearings 26 and 28, respectively. That is, the pockets 50 and 52 of the porous air bearings 26 and 28 are thrust receiving surfaces 26b of the porous air bearings 26 and 28 among the air discharged into the bearing gap and the air passing through the porous air bearings 26 and 28, respectively. , 28b is introduced and stored, functions as a buffer for discharging the stored air to the air discharge passages 54 and 56, and in the process in which the air passes through the bearing gap and the porous air bearings 26 and 28, the bearing gap The air pressure can be increased, and as a result, the rigidity can be increased.

  On the other hand, when the air flowing through the bearing clearance and the air passing through the porous air bearings 26 and 28 and flowing through the thrust receiving surfaces 26b and 28b are introduced into the pockets 50 and 52, the air passes through the pockets 50 and 52. In the process of flowing through the air discharge paths 54 and 56, the flow rate is controlled by the throttles 58 and 60. At this time, the air attenuation action by the throttles 58 and 60 is enhanced, and the occurrence of an air hammer (self-excited vibration) due to the compressibility of the air can be reliably suppressed.

  According to the present embodiment, the air flowing through the thrust receiving surfaces 26b and 28b out of the air flowing through the bearing gap and the air passing through the porous air bearings 26 and 28 is introduced and stored in the pockets 50 and 52. Since the air is discharged to the air discharge passages 54 and 56, the air pressure in the bearing gap can be increased, and as a result, the rigidity can be increased.

In addition, according to the present embodiment, the flow rate is controlled by the throttles 58 and 60 in the process in which the air introduced into the pockets 50 and 52 flows through the air discharge passages 54 and 56, so Therefore, the occurrence of an air hammer (self-excited vibration) due to air compressibility can be reliably suppressed.

  Further, according to this embodiment, the pockets 50 and 52, the air discharge paths 54 and 56, and the throttles 58 and 60 are formed in the porous air bearings 26 and 28 as the fixing members, and the air discharge paths 54 and 56 are formed in the air. Since the passage 32 is communicated, air can be discharged smoothly.

It is sectional drawing of the spindle apparatus which shows one Example of this invention. It is sectional drawing of an air discharge path.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Spindle apparatus, 12 Housing, 14 Spindle, 16, 18 Flange, 26, 28 Porous air bearing, 30, 32 Air passage, 38 Electric motor, 44 Motor rotating shaft, 46 Rotor, 48 Stator, 50, 52 Pocket, 54 , 56 Air discharge path, 58, 60 Aperture

Claims (5)

A spindle is rotatably supported by a cylindrical housing via a static pressure gas bearing, an electric motor is arranged in parallel with the housing, and a motor rotation shaft of the electric motor is connected to one end side in the longitudinal direction of the spindle. In the spindle device in which the housing is formed with an air passage for discharging air introduced from the air supply port from the exhaust port through the static pressure gas bearing,
The static pressure gas bearing is configured by integrating a radial bearing that receives a radial load from the spindle and a thrust bearing that receives a thrust load from a flange of the spindle. A pocket for storing air generated in a gap between the static pressure gas bearing and the spindle, an air discharge path for guiding the air stored in the pocket to the air passage, and a throttle for adjusting a flow rate of air passing through the air discharge path A spindle device characterized in that is formed.   The spindle device according to claim 1, wherein the pocket is formed on a thrust receiving surface of the hydrostatic gas bearing.   2. The spindle according to claim 1, wherein flanges are formed at both ends in the longitudinal direction of the spindle, and static pressure gas bearings are respectively disposed on the outer periphery of the spindle adjacent to the flanges. Spindle device.   Each of the static pressure gas bearings is formed with the pocket, an air discharge path, and a throttle, and the pocket of each of the static pressure gas bearings is formed on a thrust receiving surface of each of the static pressure gas bearings. The spindle device according to claim 3.   5. The spindle device according to claim 1, wherein the static pressure gas bearing is formed of a porous air bearing. 6.

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