JP2009055777A - Spindle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely restrict generation of air hammer regardless of usage conditions. <P>SOLUTION: A spindle 14 is supported in a freely rotating state through air bearings 16, 18 in a housing 12. The spindle 14 is jointed with a motor rotating shaft 44 of an electric motor 38 through a flange 22. A vibration deadening ring 52 is mounted at an edge portion in an axial direction of the motor rotating shaft 44 through a rubber ring 54 so that air hammer accompanying vibration of the spindle 14 is absorbed with the vibration deadening ring 52. <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, a processing machine, or the like.

  The spindle device is used as one element of a machine tool that rotationally drives tools such as cutting and grinding, or as one element of an inspection machine that rotationally drives a magnetic head, a magnetic disk, and 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.

  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. This vibration is likely to occur when a pocket serving as an air reservoir is provided in the bearing portion, such as an orifice throttle bearing as an air bearing. Further, when a porous bearing is used as the air bearing, the porous itself becomes an air reservoir, and if the aperture on the bearing surface is small, an air hammer is more likely to occur.

  For this reason, when an air bearing is used, there is a case where an air hammer is prevented from being generated by using a self-formed throttle instead of the orifice throttle. Further, when using a porous bearing as an air bearing, there has been proposed one in which the surface of the bearing is crushed with a sealing agent to increase the restriction so as to suppress the generation of an air hammer (see Patent Document 1). There has been proposed a structure in which another porous plate is attached to the surface of a porous member to form a two-layered bearing throttle so as to suppress the occurrence of an air hammer (see Patent Document 2).

  That is, in the prior art, a device has been devised to suppress the generation of the air hammer by weakening the influence of the compressibility of the air that is the cause of the air hammer.

JP-A-2-256915

JP 2001-56027 A

  In the prior art, a porous bearing is used as an air bearing to suppress the occurrence of an air hammer. However, in the case of a porous bearing, parameters relating to the occurrence of an air hammer include the air permeability of the bearing, the air supply Since there are many factors such as pressure, bearing clearance, and natural frequency of the rotating body, the occurrence of an air hammer cannot be reliably suppressed unless these factors are taken into consideration.

  For example, when the throttle on the bearing surface is strengthened, there is an effect to suppress the generation of the air hammer, but depending on the conditions, the air hammer may be generated, and the generation of the air hammer may not be reliably suppressed.

  Specifically, in order to increase the rigidity of the air bearing, if the air supply pressure is increased or a long and thin member with a low natural frequency is attached to the spindle, the generation of the air hammer cannot be reliably suppressed depending on the use conditions. Sometimes. In particular, when an elongated motor rotation shaft of an electric motor having a low natural frequency is used, an air hammer is more likely to be generated, and the generation of the air hammer may not be reliably suppressed.

  The fact that an air hammer is generated depending on the usage conditions means that in the manufacture of a spindle device, if all parts are finally assembled and testing is not performed for the occurrence of an air hammer under various usage conditions, the generation of an air hammer will occur. It means that the presence or absence of can not be confirmed. In addition, when an air hammer occurs in the final process, it is necessary to disassemble the spindle device, repair the air bearing portion and reassemble it, and then test whether the air hammer is generated. When the air hammer is generated in the test for the occurrence of the air hammer, it is necessary to repeat the disassembly and assembly of the spindle device. If the generation of the air hammer cannot be suppressed even after repeated disassembly and assembly of the spindle device, the air bearing must be manufactured again.

  That is, if an air hammer is generated depending on the use conditions, productivity is poor and cost reduction is difficult. Moreover, even when a highly rigid spindle device is manufactured, the generation of an air hammer cannot be reliably suppressed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a spindle device that can reliably suppress the occurrence of an air hammer regardless of use conditions.

  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 in which the motor rotation shaft of the electric motor is connected, the motor rotation shaft is mounted with a vibration absorber that absorbs vibration caused by the generation of an air hammer. .

  According to the present invention, since the motor rotating shaft is equipped with a vibration absorber that absorbs vibration caused by the generation of the air hammer, a highly rigid orifice bearing or porous bearing is used as the static pressure gas bearing. Even if the bearing is used at a high air supply pressure, the generation of an air hammer can be reliably suppressed, and a highly rigid and inexpensive spindle device can be realized.

  In configuring the spindle device, the following elements can be added. Preferably, the vibration absorber is attached to the outer periphery of the motor rotation shaft via an elastic body.

  According to this configuration, the vibration associated with the generation of the air hammer can be further absorbed by mounting the vibration absorber on the outer periphery of the motor rotation shaft via the elastic body.

  Preferably, the vibration absorber is attached to an end portion of the motor rotation shaft that is a part away from the spindle among both end portions of the motor rotation shaft.

  According to such a configuration, by attaching the vibration absorber to the end of the motor rotation shaft which is a part away from the spindle among the both ends of the motor rotation shaft, the motor rotation shaft has a small diameter and a low natural frequency. Even if it uses, generation | occurrence | production of an air hammer can be suppressed reliably.

  In the present invention, a spindle is rotatably supported by a cylindrical housing via a hydrostatic gas bearing, an electric motor is provided in parallel with the housing, and one end of the electric motor in the longitudinal direction of the spindle is provided. In the spindle device in which the motor rotation shaft is connected, the motor rotation shaft is mounted with a damper having a damper adjusting function for absorbing vibration caused by the generation of the air hammer.

  According to the present invention, the motor rotating shaft is equipped with a damper with a damper adjusting function that absorbs vibration caused by the generation of the air hammer. Therefore, a highly rigid orifice bearing or porous bearing is used as the static pressure gas bearing. Even when the static pressure gas bearing is used at a high supply pressure, the generation of an air hammer accompanying the rotation of the spindle can be reliably suppressed, and a highly rigid and inexpensive spindle device can be provided.

  In configuring the spindle device, the following elements can be added. Preferably, the vibration absorber is attached to the outer periphery of the motor rotation shaft via an elastic body.

  According to this configuration, the vibration associated with the generation of the air hammer can be further absorbed by mounting the vibration absorber on the outer periphery of the motor rotation shaft via the elastic body.

  Preferably, the vibration absorber is provided with a vibration damping ring that is formed in a substantially annular shape and has a slit in a part of its circumferential direction, and the vibration damping ring has an adjustable width in the circumferential direction. The screw to be attached is installed.

  According to such a configuration, the vibration isolating ring is equipped with a screw that adjusts the width of the slit in the circumferential direction, so it is optimal to adjust the width of the slit in the circumferential direction of the vibration isolating ring with the screw. It can be assembled to have a large spring constant.

  Preferably, the screw is formed by adjusting the width of the slit in the circumferential direction of the damping ring, changing the tightening margin of the elastic body, and adjusting the spring constant.

  According to such a configuration, the screw is adjusted by adjusting the width of the slit in the circumferential direction of the vibration isolation ring, and the spring constant is adjusted by changing the tightening margin of the elastic body, thereby assembling the spring constant to be optimum. And generation of an air hammer can be more reliably suppressed.

  Preferably, the vibration absorber is attached to an end portion of the motor rotation shaft that is a part away from the spindle among both end portions of the motor rotation shaft.

  According to such a configuration, by attaching the vibration absorber to the end of the motor rotation shaft which is a part away from the spindle among the both ends of the motor rotation shaft, the motor rotation shaft has a small diameter and a low natural frequency. Even if it uses, generation | occurrence | production of an air hammer can be suppressed reliably.

  Preferably, the vibration absorber is attached to an outer periphery of the motor rotation shaft via a first elastic body, and a cover that covers the vibration absorber is attached to the vibration absorber via a second elastic body, The cover is connected to a ring fixed to the outer periphery of the motor rotation shaft.

  According to such a configuration, since the cover is attached to the vibration absorber via the second elastic body, and the cover is connected to the ring fixed to the outer periphery of the motor rotation shaft, even when the electric motor is accelerated or decelerated. It is possible to prevent the vibration absorber from moving.

  Preferably, the vibration absorber is connected to the ring via a pin.

  According to such a configuration, since the vibration absorber is connected to the ring and the pin, it is possible to prevent the vibration absorber from slipping during sudden acceleration / deceleration of the electric motor.

  Preferably, the vibration absorber is disposed between a pressing plate fixed to a longitudinal end of the motor rotation shaft and a flange of the motor rotation shaft, and a first elastic body is provided on an outer periphery of the motor rotation shaft. The second elastic body is mounted between the pressing plate and the vibration absorber, and the third elastic body is mounted between the flange and the vibration absorber.

  According to such a configuration, the vibration absorber is disposed between the pressing plate and the flange of the motor rotating shaft, and is mounted on the outer periphery of the motor rotating shaft via the first elastic body, and between the pressing plate and the vibration absorber. Since the second elastic body is attached to the flange, and the third elastic body is attached between the flange and the vibration absorber, it is possible to prevent the vibration absorber from moving during sudden acceleration / deceleration of the electric motor.

  Preferably, the vibration absorber is connected to the flange via a pin.

  According to such a configuration, since the vibration absorber is connected to the flange via the pin, it is possible to prevent the vibration absorber from slipping during sudden acceleration / deceleration of the electric motor.

  Preferably, the first elastic body is configured by a number of O-rings selected from a single or a plurality of O-rings.

  According to such a configuration, when the first elastic body is used, the damper effect (damping property) of the vibration absorber is adjusted by using the number of O-rings selected from a single or a plurality of O-rings. Can do.

  Preferably, the static gas bearing is composed of a porous air bearing, and a resin-impregnated layer is formed on the surface thereof. The flow rate before impregnation with the resin is Q1, and the flow rate after impregnation with the resin is Q2. Q2 / Q1 is adjusted to 0.4 or less.

  According to such a configuration, the resin impregnated layer is formed on the surface of the porous air bearing, the flow rate before impregnation with the resin is Q1, and the flow rate after impregnation with the resin is Q2, Q2 / Q1 is 0.4. By adjusting to the following, the volume acting as a pocket inside the resin-impregnated layer is reduced and the volume of air compression / expansion is also reduced, so that the occurrence of an air hammer can be suppressed.

  In the present invention, a spindle is rotatably supported by a cylindrical housing via a hydrostatic gas bearing, an electric motor is provided in parallel with the housing, and one end of the electric motor in the longitudinal direction of the spindle is provided. In a method for adjusting a spindle device in which a motor rotating shaft is connected, and a vibration absorber that absorbs vibration caused by the generation of an air hammer is attached to the motor rotating shaft, the displacement of the main vibration system including the motor rotating shaft An equation of motion of the main vibration system including displacement of the vibration absorber, a movement equation of the vibration absorber including displacement of the main vibration system and displacement of the vibration absorber, respectively, and the main vibration system in each of the movement equations The spring constant of the elastic body of the vibration absorber is adjusted by using the mass ratio of the mass of the vibration absorber and the mass of the main vibration system as a variable so that the displacement of the vibration absorber is minimized.

  According to the present invention, the equation of motion of the main vibration system including the displacement of the main vibration system including the motor rotating shaft and the vibration absorber, and the equation of motion of the vibration absorber including the displacement of the main vibration system and the vibration absorber are respectively represented. By adjusting the spring constant of the elastic body of the vibration absorber with the mass ratio of the mass of the vibration absorber and the mass of the main vibration system as a variable so that the displacement of the main vibration system in each equation of motion is minimized ,

  According to the present invention, a highly rigid orifice bearing or a porous bearing is used as a static pressure gas bearing, and even if the static pressure gas bearing is used at a high supply pressure, the generation of an air hammer can be reliably suppressed. A highly rigid and inexpensive spindle device can be provided.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a sectional view of a spindle apparatus showing an embodiment of the present invention. In FIG. 1, a spindle device 10 includes a metal housing 12 formed in a substantially cylindrical shape, and a cylindrical spindle (spindle shaft) is rotatably accommodated in the housing 12 as a rotation shaft. Between the housing 12 and the spindle 14, a pair of air bearings 16 and 18 are arranged along the longitudinal direction (axial direction) of the spindle 14 as a static pressure gas bearing.

  Cylindrical flanges 20 and 22 are disposed at both ends in the longitudinal direction of the housing 12, and the flanges 20 and 22 are respectively connected to both ends in the longitudinal direction of the spindle 14 via bolts (not shown). . The flanges 20 and 22 are respectively formed with through holes 26 and 28 connected to the through hole 24 of the spindle 14. The through hole 26 or the through hole 24 functions as a chuck mechanism, for example, and the through hole 26 or the through hole 24 is connected to a tool such as cutting and polishing, or a magnetic disk or a magnetic head.

  Air passages 30 and 32 are formed in the housing 12, and air from an air supply source is supplied to the air supply port 34 of the air passage 30. The air introduced into the air supply port 34 is discharged from the exhaust port 36 via the air passages 30 and 32. In the process in which air from the air supply source is exhausted from the exhaust port 36 via the air passages 30 and 32, a part of the air is exhausted from the bearing gap between the outer periphery of the spindle 14 and the air bearings 16 and 18. At the same time, the air is discharged from the bearing gap between the air bearing 16 and the flange 20 and the bearing gap between the air bearing 18 and the flange 22. At this time, a surface of the air bearings 16 and 18 facing the spindle 14 functions as a radial receiving surface 16a and 18a that receives a radial load, and a surface of the bearings 16 and 18 that faces the flanges 20 and 22 is an axial load. The air bearings 16 and 18 are configured to rotatably support the spindle 14 and the flanges 20 and 22 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 rotation shaft 44, a rotor 46, and a stator 48, and one end side in the longitudinal direction (axial direction) of the motor rotation shaft 44 is connected to the flange 22 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 22 via the motor rotation shaft 44 to drive the spindle 14 to rotate.

  Here, since the spindle device 10 is used in a high-precision processing machine, the air bearings 16 and 18 are required to have high rigidity. In order to increase the rigidity of the air bearings 16 and 18, the air supply pressure of the air supplied to the air supply port 34 is used twice as high as normal (1 Mpa). Further, since the spindle 14 is directly rotated by the electric motor 38, the motor rotating shaft 44 has a small diameter and an elongated shape (having a low natural frequency).

  In the spindle device 10 configured as described above, when the electric motor 38 is not connected to the spindle 14, an air hammer is not generated even if the supply pressure of the air supplied to the supply port 34 is increased, but the spindle 14 has a flange. When the electric motor 38 is connected via the air inlet 22, an air hammer is generated when the intake pressure of the air supplied to the air inlet 34 is increased.

  Therefore, in this embodiment, when a highly rigid orifice bearing or a porous bearing is used as the air bearings 16 and 18, the vibration absorbing member that absorbs the vibration caused by the generation of the air hammer at the axial end portion of the motor rotating shaft 44. A configuration in which the container 50 is mounted is adopted.

  The vibration absorber 50 includes a vibration suppression ring 52 formed in a substantially cylindrical shape, and the vibration suppression ring 52 is fixed to the outer peripheral surface of the motor rotation shaft 44 via a rubber ring 54 that is an elastic body. . When using the damping ring 52 or the rubber ring 54, an optimum value is set as the mass of the damping ring 52 or the spring constant of the rubber ring 54 based on the vibration frequency of the air hammer and the mass of the rotating portion of the electric motor 38. To do. The vibration damping effect can be further enhanced by fixing the vibration damping ring 52 to a portion of the motor rotating shaft 44 that is further away from the spindle 14.

  On the other hand, as the rubber ring 54, an easily available O-ring can be used. When an O-ring is used as the rubber ring 54, the O-ring is fixed to the outer peripheral surface of the motor rotating shaft 44 with a tightening margin and is supported by the damping ring 52, so that it does not shift or move. .

  According to the present embodiment, high-rigidity orifice bearings and porous bearings are used as the air bearings 16 and 18, and even when used at a high air supply pressure, generation of an air hammer can be reliably suppressed. A rigid and inexpensive spindle device can be realized.

  Further, according to the present embodiment, since the damping ring 52 is attached to the outer periphery of the motor rotation shaft 44 via the rubber ring 54, vibration associated with the generation of the air hammer can be absorbed more.

  Furthermore, according to the present embodiment, the vibration absorber 50 is attached to the end of the motor rotation shaft 54 that is a part away from the spindle 14 at both ends of the motor rotation shaft 54. Even if a thin one having a low natural frequency is used, generation of an air hammer can be reliably suppressed.

(Second embodiment)
On the other hand, as the rubber ring 54, an easily available O-ring can be used. When an O-ring is used as the rubber ring 54, the O-ring is fixed to the outer peripheral surface of the motor rotating shaft 44. However, the spring constant of the O-ring is an important parameter, and the spring constant changes depending on the tightening margin of the O-ring. It becomes difficult to assemble with the optimal constant.

  Therefore, in the second embodiment, as shown in FIG. 2, as the damping ring 52, a ring having a slit 56 in a part of its circumferential direction is used, and a screw hole 58 is formed at a position substantially orthogonal to the slot 56. The screw 60 is mounted in the screw hole 58, the width of the slit 56 is adjusted by the screw 60, and the spring constant can be adjusted by changing the tightening margin of the O-ring. That is, the vibration absorber 50 functions as a vibration absorber that can be adjusted by a damper. For this reason, by adjusting the width of the slot 56 with the screw 60 and adjusting the spring constant by changing the tightening allowance of the O-ring, it can be assembled so as to obtain an optimal spring constant, and the generation of an air hammer can be prevented. It can suppress more reliably.

  Further, by forming O-ring grooves 62 and 64 on the inner peripheral side of the damping ring 52 and mounting the O-rings in the O-ring grooves 62 and 64, the O-ring is used as a motor rotation shaft by using the damping ring 52. When fixed to the outer peripheral surface of 44, the O-ring does not move out of position, and the O-ring can be reliably fixed to the outer peripheral surface of the motor rotating shaft 44.

  According to the present embodiment, high-rigidity orifice bearings and porous bearings are used as the air bearings 16 and 18, and even when used at a high air supply pressure, generation of an air hammer can be reliably suppressed. A rigid and inexpensive spindle device can be realized.

  Further, according to the present embodiment, it is possible to assemble the spring constant by adjusting the width of the slit 56 with the screw 60 and adjusting the spring constant by changing the tightening margin of the O-ring. The occurrence of an air hammer can be more reliably suppressed.

  Further, according to the present embodiment, the vibration absorber 50 is attached to the end of the motor rotation shaft 54 that is a part away from the spindle 14 at both ends of the motor rotation shaft 54. Even if a thin one having a low natural frequency is used, generation of an air hammer can be reliably suppressed.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a small-diameter portion 44b is formed adjacent to the large-diameter portion 44a of the motor rotating shaft 44 at the axial end portion of the motor rotating shaft 44, and an iron balance ring 80 is attached to the small-diameter portion 44b. A vibration damping ring 52 is disposed adjacent to the ring 80, and the vibration damping ring 52 is attached to the small diameter portion 44b via O-rings 82 and 84 as first elastic bodies. The cover 86 is covered with a substantially hook-shaped cover 86, and the balance ring 80 and the cover 86 are connected via bolts 88. The configurations of the spindle 14 and the electric motor 38 are the same as those in the first embodiment.

  At this time, the damping ring 52 is formed with O-ring grooves 62 and 64 for mounting the O-rings 82 and 84, and O-ring grooves 66, 68, and 70 are formed at portions contacting the cover 86. In addition, an O-ring groove 72 is formed at a portion in contact with the balance ring 80. O-rings 90, 92, and 94 as second elastic bodies are attached to the O-rings 66, 68, and 70, and an O-ring 96 as a third elastic body is attached to the O-ring groove 72. A through hole 98 for inserting the motor rotating shaft 44 is formed at the center of the cover 86.

  According to the present embodiment, high-rigidity orifice bearings and porous bearings are used as the air bearings 16 and 18, and even when used at a high air supply pressure, generation of an air hammer can be reliably suppressed. A rigid and inexpensive spindle device can be realized.

  Further, according to this embodiment, the damping ring 52 is attached to the small diameter portion 44b of the motor rotating shaft 44 via the O-rings 82 and 84, and the cover 86 is attached to the damping ring via the O-rings 90, 92 and 94. 52, and the cover 86 is connected to the balance ring 80 via the bolts 88, so that the vibration absorber 50 can be prevented from moving during sudden acceleration / deceleration of the electric motor 38. Note that it is not necessary to use all of the O-rings 90, 92, 94, and 96, and any combination can be used in consideration of a damper effect by the O-ring.

  Next, an adjustment method for minimizing the displacement of the vibration absorber 50 will be described for the vibration absorber (dynamic damper) 50 of the third embodiment. First, the cover 86 shown in FIG. 3 is hit with an impact hammer from the direction of arrow A, the vibration state of the vibration absorber 50 is detected with the acceleration pickup from the direction of arrow B, and the vibration absorber 50 is monitored while monitoring the detection output of the acceleration pickup. Adjust the stiffness.

At this time, a vibration system model when the vibration absorber 50 is attached to the motor rotating shaft 44 is shown in FIG. In FIG. 4, m ₁ is the mass of the main vibration system including the motor rotating shaft 44, k ₁ is the rigidity of the main vibration system, m ₂ is the mass of the vibration absorber 50, k ₂ is the rigidity of the vibration absorber, c Is a damping coefficient of the vibration absorber 50, and P is an external force generated by an impact hammer, the equation of motion of the main vibration system is expressed by the following equation (1).

  On the other hand, the equation of motion of the vibration absorber 50 is expressed by the following equation (2).

If the conditions for minimizing x ₁ are given by the simultaneous differential equations of Equations 1 and 2, the vibration of the vibration absorber 50 by the air hammer is also minimized. The values of m ₁ and k ₁ were obtained from the transfer function (displacement / force) of impact excitation as the equivalent mass and equivalent rigidity when the model was replaced with a one-degree-of-freedom system.

The condition for minimizing the displacement x ₁ of the main vibration system is k ₂ = μ · k ₁ / (1 + μ) ² when the mass ratio is μ = m ₂ / m ₁ .

  That is, the spring constant of the elastic body of the vibration absorber 50, that is, k2 is adjusted so that the displacement x1 of the main vibration system in each equation of motion is minimized.

  FIG. 5 shows a characteristic diagram of a vibration test result using an impact hammer when the vibration absorber 50 is not attached to the motor rotating shaft 44. FIG. 6 shows a characteristic diagram of a vibration test result using an impact hammer when the vibration absorber 50 is mounted on the motor rotating shaft 44.

  5 and 6, it can be seen that the damping effect can be improved by about 24 dB by attaching the vibration absorber 50 to the motor rotating shaft 44 via the O-rings 82 and 84 than when the vibration absorber 50 is not attached.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG. In the present embodiment, a through hole 100 is formed in a part of the vibration damping ring 52, a hole 102 is formed in the balance ring 80 so as to face the through hole 100, and rotation is prevented in the through hole 100 and the hole 102. For example, the vibration suppression ring 52 and the balance ring 80 are connected via the pin 104, and the other configuration is the same as that of the third embodiment.

  According to the present embodiment, high-rigidity orifice bearings and porous bearings are used as the air bearings 16 and 18, and even when used at a high air supply pressure, generation of an air hammer can be reliably suppressed. A rigid and inexpensive spindle device can be realized.

  Further, according to the present embodiment, since the damping ring 52 is connected to the balance ring 80 via the pin 104, it is possible to prevent the vibration absorber 50 from slipping during sudden acceleration / deceleration of the electric motor 38. it can.

(5th Example)
Next, a fifth embodiment of the present invention will be described with reference to FIG. In this embodiment, a ring 110 as an auxiliary motor rotating shaft is connected to a longitudinal end portion of the motor rotating shaft 44 via a connecting plate 108, and a bolt 114 is connected to a flange 112 of the ring 110 and an axial end portion of the ring 110. The damping ring 52 is disposed between the holding plate 116 and the holding plate 116 fixed in place, and the damping ring 52 is attached to the outer periphery of the ring 110 via O-rings 118, 120, and 122 as first elastic bodies. An O-ring 124 as a second elastic body is mounted between the vibration ring 52 and the pressing plate 116, and an O-ring 126 as a third elastic body is mounted between the flange 112 and the damping ring 52. The other configuration is the same as that of the first embodiment.

  At this time, in the damping ring 52, O-ring grooves 128, 130, and 132 are formed at portions that come into contact with the ring 110, and O-ring grooves 134 are formed at portions that come into contact with the pressing plate 116, and come into contact with the flange 112. O-ring grooves 136 are formed in the portions to be operated, and O-rings 118 to 126 are mounted in the O-ring grooves 128 to 136, respectively.

  According to the present embodiment, high-rigidity orifice bearings and porous bearings are used as the air bearings 16 and 18, and even when used at a high air supply pressure, generation of an air hammer can be reliably suppressed. A rigid and inexpensive spindle device can be realized.

  Further, according to the present embodiment, the damping ring 52 is attached to the outer periphery of the ring 110 via the O-rings 118, 120, and 122, and the damping ring 52 is supported by the pressing plate 116 via the O-ring 124. Therefore, the vibration absorber 50 can be prevented from moving during sudden acceleration / deceleration of the electric motor 38.

  In the present embodiment, it is not always necessary to use three O-rings 128, 130, and 132 as elastic bodies, and the number of O-rings 128, 130, and 132 can be adjusted while confirming a damper effect (attenuation) as an elastic body. That is, one, two, or three O-rings can be used.

(Sixth embodiment)
The air bearings 16 and 18 used in the spindle device 10 can obtain a load capacity by supplying high-pressure air to the bearing gap through a throttle as a static pressure air bearing. Therefore, since the spindle 14 rotates without contact with the air bearings 16 and 18, the spindle 14 exhibits excellent characteristics such as extremely low friction, low vibration, low heat generation, low dust generation, and high rotation accuracy. Used in the machine. A throttle (not shown) provided in the air passage 30 is attached to give rigidity to the air film and obtain a load capacity. The air bearings 16 and 18 are classified according to the throttle system.

  As this type of restriction, for example, a self-contained restriction or an orifice restriction that provides a narrowing action by providing a plurality of narrow holes is most often used. In addition, the porous diaphragm that gives a squeezing action with a breathable material itself such as a sintered material has numerous fine holes formed on the bearing surface, making it ideal as a diaphragm and having the best bearing performance. In each of the above embodiments, this type of air bearing is used.

  On the other hand, when the air bearings 16 and 18 are used, an air hammer may be generated. The air hammer is a vibration phenomenon peculiar to an air bearing, and the cause thereof is air compressibility.

  Specifically, in air bearings, if there is a pocket that collects air in the flow path from the throttle to the bearing gap, there will be a difference between the amount of air flowing into the pocket and the amount of outflow from the pocket depending on the conditions. As a result, air tends to expand and contract in the pocket due to its compressibility. This is a phenomenon called an air hammer, which causes large vibrations accompanied by abnormal noise. That is, when an orifice restrictor is provided in the air passage 30, if the ratio of the pocket volume after the restrictor to the volume of the bearing gap increases, the air repeatedly expands and contracts with the pressure density, and an air hammer is generated. .

  On the other hand, parameters relating to the air hammer include an air supply pressure, a bearing gap, a pocket volume, a size of a throttle resistance, and a small vibration for a rotating part. In consideration of these parameters, in this embodiment, as shown in FIG. 9, when the air bearings 16 and 18 are configured as porous bearings, resin impregnated layers 17 and 19 are formed on the bearing surfaces to reduce the drawing resistance. Try to make it bigger.

  That is, if the porous bearing is not impregnated with resin, the aperture and the pocket are mixed in the porous, and a hammer is generated. On the other hand, if the porous bearing is impregnated with resin, the resin-impregnated portion becomes an aperture, and there is no pocket after the aperture, and it is considered that no air hammer occurs.

  In addition, one of the factors that cause an air hammer when the air bearings 16 and 18 are porous bearings is that the path from the portion of the resin impregnated layers 17 and 19 where the throttling is strongest to the bearing surface. It is a pocket.

  Therefore, in this embodiment, when the resin impregnated layers 17 and 19 are formed on the air bearings 16 and 18, the flow rate before the resin impregnation (material flow rate) is Q1, and the flow rate after the air bearings 16 and 18 are impregnated with the resin. When Q2 is Q2, Q2 / Q1 is small and the amount of resin impregnation is large. Thereby, the volume which acts as a pocket inside resin impregnation layers 17 and 19 became small, and the volume which compresses and expands air could be made small. It is assumed that the air hammer could be avoided by this.

  Next, as the air bearings 16 and 18, the length in the radial direction is 90 mm, the inner diameter is 200 mm, the outer diameter is 320 mm, and the resin impregnated layers 17 and 19 are formed on the surface. In order to confirm the correlation between the presence and absence, the characteristics relating to the flow rates Q1 and Q2 were measured. As a result, results as shown in FIG. 10 were obtained for Q2 / Q1.

  On the other hand, from FIG. 10, it was confirmed that when Q2 / Q1 is small, for example, 0.4 or less, and the mass increase rate is high (the resin impregnation amount is large), there is an air hammer suppressing effect.

  According to the present embodiment, when the air bearings 16 and 18 are used as porous bearings, the resin impregnated layers 17 and 19 are formed on the shaft surfaces of the air bearings 16 and 18 so that Q2 / Q1 is 0.4 or less. Thus, the air hammer can be suppressed.

It is sectional drawing of the spindle apparatus which shows 1st Example of this invention. It is a figure which shows 2nd Example of this invention, Comprising: (a) is a front view of a damping ring, (b) is principal part sectional drawing of a damping ring. It is principal part sectional drawing of the spindle apparatus which shows 3rd Example of this invention. It is a schematic diagram of the vibration system model in 3rd Example. It is a characteristic view which shows the test result of the vibration test by an impact hammer when not attaching a vibration absorber to a motor rotating shaft. It is a characteristic view which shows the test result of the vibration test by an impact hammer when mounting a vibration absorber on a motor rotating shaft. It is principal part sectional drawing of the spindle apparatus which shows 4th Example of this invention. It is principal part sectional drawing of the spindle apparatus which shows 5th Example of this invention. It is principal part sectional drawing of the spindle apparatus which shows 6th Example of this invention. It is a correlation diagram of the presence or absence of the occurrence of an air hammer due to a bearing flow rate Q2 / Q1 and a mass increase (resin impregnation amount).

Explanation of symbols

  10 Spindle device, 12 Housing, 14 Spindle, 16, 18 Bearing, 20, 22 Flange, 30, 32 Air passage, 38 Electric motor, 44 Motor rotating shaft, 46 Rotor, 48 Stator, 50 Vibration absorber, 52 Damping ring, 54 Rubber ring, 56 Slot, 60 Screw, 62, 64, 68, 70, 72 O-ring groove, 80 Balance ring, 82, 84 O-ring, 86 Cover, 90, 92, 94, 96 O-ring, 104 pin, 116 Presser plate, 118, 120, 122 O-ring

Claims (15)

  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, the motor rotating shaft is mounted with a vibration absorber that absorbs vibration caused by the generation of an air hammer.   The spindle device according to claim 1, wherein the vibration absorber is attached to an outer periphery of the motor rotation shaft via an elastic body.   3. The spindle device according to claim 1, wherein the vibration absorber is attached to a motor rotating shaft end portion which is a part away from the spindle among both end portions of the motor rotating shaft. 4.   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, the motor rotating shaft is mounted with a damper having a damper adjusting function for absorbing vibration caused by the generation of an air hammer.   The spindle apparatus according to claim 4, wherein the vibration absorber is attached to an outer periphery of the motor rotation shaft via an elastic body.   The vibration absorber is provided with a vibration-damping ring that is formed in a substantially annular shape and has a slit in a part of its circumferential direction, and a screw that adjusts the width of the slit in the circumferential direction is attached to the vibration-damping ring. The spindle device according to claim 4 or 5, wherein the spindle device is formed.   The spindle according to claim 6, wherein the screw is formed by adjusting a width of a slit in a circumferential direction of the damping ring, changing a tightening margin of the elastic body, and adjusting a spring constant. apparatus.   The vibration absorber is attached to a motor rotary shaft end portion which is a part away from the spindle among both end portions of the motor rotary shaft. The spindle device according to the item.   The vibration absorber is attached to the outer periphery of the motor rotation shaft via a first elastic body, and a cover that covers the vibration absorber is attached to the vibration absorber via a second elastic body. The spindle device according to claim 1, wherein the spindle device is connected to a ring fixed to an outer periphery of the motor rotation shaft.   The spindle device according to claim 9, wherein the vibration absorber is connected to the ring via a pin.   The vibration absorber is disposed between a pressing plate fixed to a longitudinal end portion of the motor rotation shaft and a flange of the motor rotation shaft, and is mounted on the outer periphery of the motor rotation shaft via a first elastic body. The second elastic body is mounted between the pressing plate and the vibration absorber, and the third elastic body is mounted between the flange and the vibration absorber. The spindle device described in 1.   The spindle device according to claim 9, wherein the vibration absorber is connected to the flange via a pin.   The spindle device according to claim 9 or 11, wherein the first elastic body includes a number of O-rings selected from a single or a plurality of O-rings.   The static gas bearing is composed of a porous air bearing, and a resin-impregnated layer is formed on the surface thereof. The flow rate before impregnation with the resin is Q1, and the flow rate after impregnation with the resin is Q2. The spindle apparatus according to claim 1, wherein Q2 / Q1 is adjusted to 0.4 or less. 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 adjusting method of the spindle device in which the motor rotating shaft is equipped with a vibration absorber that absorbs vibration caused by the generation of the air hammer,
Equations of motion of the main vibration system including displacement of the main vibration system including the motor rotation shaft and displacement of the vibration absorber, and equations of motion of the vibration absorber including displacement of the main vibration system and displacement of the vibration absorber, respectively And the spring constant of the elastic body of the vibration absorber with the mass ratio of the mass of the vibration absorber and the mass of the main vibration system as a variable so that the displacement of the main vibration system in each equation of motion is minimized. A method for adjusting a spindle device, comprising adjusting

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