JP2007192737A - Method for evaluating performance of dynamic pressure bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of evaluating the performance of a dynamic pressure bearing that can accurately and simply evaluate the performance of the dynamic pressure bearing. <P>SOLUTION: An input shaft 3 is rocked about an x-axis in a direction indicated by β in figure 1, in a state in which the rotation part of a spindle motor 1 is rotated about a z-axis, in the direction indicated by α in Figure 1. Thus, a radial gap between the rotation shaft part of the spindle motor 1 and a sleeve part of the spindle motor 1 is changed, by making gyro load act on the rotation part and making the rotation part rock about a y-axis, in the direction indicated by γ in the Figure 1. The value of the gyro load is calculated, and the rigidity of the dynamic pressure bearing, having the spindle motor 1, and the radial load capacity are measured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a performance evaluation method for a hydrodynamic bearing.

  Conventionally, as a method for evaluating the performance of a slide bearing, there is a method for evaluating the performance of a hydrostatic bearing described in Japanese Patent Application Laid-Open No. 2000-202737 (Patent Document 1).

  This performance evaluation method of a hydrostatic bearing is performed using a determination device including a main shaft to which a cutter or the like is attached, an air hydrostatic spindle, a hydrostatic bearing, a load applying device, and a displacement measuring device.

  The static air pressure spindle has an inner peripheral cylindrical surface. The aerostatic spindle is disposed radially outward of a part of the main shaft so as to cover one end of the main shaft. The hydrostatic bearing is disposed between one end of the main shaft and the aerostatic spindle. The load applying device applies a load acting in the radial direction to the main shaft by bringing a load applying member into contact with the other end portion of the main shaft opposite to the hydrostatic bearing side. . Further, the displacement measuring device measures a radial displacement of the other end of the main shaft.

  The hydrostatic bearing performance determining method applies a load to the main shaft by bringing the load applying member into contact with the other end of the rotating main shaft when the hydrostatic bearing is driven. . Then, the displacement measuring device measures the displacement of the other end of the main shaft during driving of the hydrostatic bearing, and measures the rigidity of the main shaft, the load capacity of the hydrostatic bearing, and the like. .

  However, in the conventional method for determining the performance of a hydrostatic bearing, the rigidity of the main shaft, the load capacity of the hydrostatic bearing, and the like are measured by bringing the load application member into contact with the rotating main shaft. Therefore, when the output of the motor for rotating the main shaft is small, the rotation of the main shaft is stopped by the frictional force between the main shaft and the load applying member, and the rigidity of the main shaft and the load capacity of the hydrostatic bearing are reduced. There is a problem that it cannot be measured. Further, since the load applying member is in contact with the main shaft, there is a problem that the main shaft is easily damaged.

In the conventional method for determining the performance of a hydrostatic bearing, the load application member is brought into contact with the other end portion of the main shaft, so that a large moment of force acts on the main shaft. For this reason, the slide bearing whose performance is evaluated needs to satisfy the condition that the load capacity is large, and this method has a problem that it cannot be applied to a bearing having a small load capacity such as a hydrodynamic bearing.
JP 2000-202737 A

  Then, the subject of this invention is providing the performance evaluation method of the dynamic pressure bearing which can evaluate the performance of a dynamic pressure bearing correctly and simply.

In order to solve the above problems, the performance evaluation method of the hydrodynamic bearing of the present invention is:
A method for evaluating the performance of a dynamic pressure bearing having a dynamic pressure generating groove on at least one of an outer peripheral surface of a shaft and an inner peripheral surface of a sleeve accommodating the shaft,
A gyro load acting on the rotating shaft or sleeve by rotating or swinging the hydrodynamic bearing around a direction orthogonal to the shaft in a state where the shaft or the sleeve is rotated. And a gap measuring step for measuring a gap between the shaft and the sleeve that changes based on the above.

  Note that the rocking around the direction perpendicular to the shaft means that the rocking is made around the direction perpendicular to the central axis of the shaft, and of course, the rocking is oblique with respect to the central axis of the shaft. Even if it is around the direction, as long as it swings around the component in the right-angle direction, it is included in the swing around the direction orthogonal to the shaft.

  When the hydrodynamic bearing is rotated or oscillated around a direction orthogonal to the shaft in a state where the shaft or the sleeve is rotated, a gyro load acts on the rotating shaft or the sleeve. . The rotating shaft or sleeve rotates or swings around a direction orthogonal to both the direction of the shaft and the direction orthogonal to the shaft. As a result, the rotating or oscillating shaft or sleeve is displaced in a direction orthogonal to both of the above, depending on the performance of the hydrodynamic bearing (support rigidity, load capacity, etc.).

  According to the present invention, the performance of the hydrodynamic bearing is evaluated using a gyro load applied to the shaft or the sleeve by rotating or swinging the shaft or the sleeve. Therefore, unlike the conventional method, there is no need to bring the load applying member into contact with the rotating shaft. Therefore, the measurement can be performed even if the rotational power for rotating the shaft or sleeve is small. Even with a hydrodynamic bearing having a small capacity, the performance can be evaluated easily and accurately.

  Further, according to the present invention, unlike the conventional method, there is no need to bring the load applying member into contact with the rotating shaft, so that the shaft is not damaged.

  In one embodiment of the method for evaluating the performance of a hydrodynamic bearing, a fluid having conductivity is filled between the shaft and the sleeve, and the gap measuring step is performed between the shaft and the sleeve. The size of the gap with respect to the gyro load is measured by measuring the voltage or electric resistance between them.

  According to the embodiment, a fluid having conductivity is filled between the shaft and the sleeve, and the gyro load is measured by measuring a voltage or an electric resistance between the shaft and the sleeve. Since the size of the gap with respect to is measured, the fluctuation of the gap with respect to the applied load can be accurately measured.

  In one embodiment, the hydrodynamic bearing performance evaluation method continuously measures the voltage or electrical resistance between the shaft and the sleeve while continuously changing the gyro load. The size of the gap with respect to is continuously measured.

  According to the above embodiment, since the size of the gap with respect to the gyro load is continuously measured, the fluctuation of the gap with respect to the additional load can be measured more precisely.

  In one embodiment, the method for evaluating the performance of a dynamic pressure bearing calculates at least one of rigidity and load capacity of the dynamic pressure bearing based on the gyro load and a gap between the shaft and the sleeve.

  According to the embodiment, at least one of the rigidity and the load capacity of the hydrodynamic bearing can be measured easily and accurately.

  According to the performance evaluation method of a hydrodynamic bearing of the present invention, the performance of the hydrodynamic bearing is evaluated by using the gyro load added to the shaft or the sleeve by rotating or swinging the shaft or the sleeve. There is no need to contact the shaft with a load application member, and measurement can be performed even if the rotational power for rotating the shaft or sleeve is small. Even if it is a hydrodynamic bearing with a smaller load capacity than a hydrostatic bearing, Performance can be evaluated easily and accurately.

  In addition, according to the performance evaluation method of the hydrodynamic bearing of the present invention, it is not necessary to bring the load applying member into contact with the shaft, so that the shaft is not damaged.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view of a performance evaluation apparatus for performing a performance evaluation method for a hydrodynamic bearing according to an embodiment of the present invention.

  The performance evaluation apparatus includes a pedestal 1, a spindle motor 2 fixed on the pedestal 1, and an input shaft 3.

  The pedestal 1 is a plate member whose mounting surface has a rectangular shape. Further, the spindle motor 2 is fixed substantially at the center of the mounting surface of the base 1. Further, as shown in FIG. 1, the input shaft 3 is in a direction parallel to a plane perpendicular to the central axis of the spindle motor 2 and from the approximate center of the width direction portion around the pedestal 1. It extends in a direction parallel to the longitudinal direction. The input shaft 3 is fixed to the pedestal 1, and the input shaft 3 is in a state incapable of relative movement with the pedestal 1. The input shaft 3 is rotated or oscillated by power from a motor or the like (not shown).

  In this performance evaluation apparatus, the pedestal 1 and the spindle motor 2 on the pedestal 1 are rotated or oscillated around the input shaft 3 by rotating or oscillating the input shaft 3.

  FIG. 2 is a cross-sectional view of the spindle motor 2.

  As shown in FIG. 2, the spindle motor 1 includes a rotating part 11, a fixed part 12, a voltmeter 13, and a displacement sensor 14.

  The rotating part 11 includes a cylindrical part 20, an end face part 21, and a rotating shaft part 22. A rotor 23 is disposed on the inner peripheral cylindrical surface of the cylindrical portion 20. The end surface portion 21 extends radially inward from the inner peripheral surface of one end of the cylindrical portion 20 and completely seals one end of the cylindrical portion 20. The rotating shaft portion 22 extends inward in the axial direction from the approximate center of the end surface portion 21. The rotating shaft portion 22 includes a main body 25 and a flange 26 connected to one end of the main body 25. On the outer peripheral surface of the main body 25, herringbone type dynamic pressure generating grooves 27 are formed over the entire circumference at two axial positions separated in the axial direction. The flange 26 is formed at the end of the rotating shaft 22 opposite to the end surface 21 side.

  The fixing portion 12 includes a sleeve portion 28, a flange portion 29, and a lid portion 30. A stator 32 is disposed on the outer peripheral cylindrical surface of the sleeve portion 28. The outer peripheral surface of the stator 32 and the inner peripheral surface of the rotor 23 are opposed to each other in the radial direction. The flange portion 29 is connected to one end of the sleeve portion 28. The flange portion 29 extends in a direction perpendicular to the central axis of the sleeve portion 28. The sleeve portion 28 and the flange portion 29 define a flange accommodating space 34 that accommodates the flange 26, and a main body accommodating space 35 that accommodates the flange accommodating space 34 and accommodates the main body 25 of the rotary shaft portion 22. . The lid portion 30 is fitted into the inner peripheral cylindrical surface of the flange portion 29 in a state where the flange 26 is accommodated in the flange accommodating space 34 and the main body 25 is accommodated in the main body accommodating space 35. The opening of the flange portion 29 is closed without a gap. After the lid portion 30 is fitted and fixed to the inner peripheral cylindrical surface of the flange portion 29, the conductive dynamic pressure fluid is filled between the fixing portion 12 and the rotary shaft portion 22. It has become.

  The voltmeter 13 measures the voltage between the rotating part 11 and the fixed part 12. The voltmeter 13 and the rotating part 11 are connected by a first electric wiring 37, and the voltmeter 13 and the fixing part 12 are connected by a second electric wiring 38. . A slip ring 40 is attached to one end of the first electric wiring 37 on the rotating part 11 side. The slip ring 40 is slidably contacted on the outer surface of the rotating part 11, and reliably connects the voltmeter 13 and the rotating rotating part 11.

  The displacement sensor 14 measures the displacement of the cylindrical portion 20. Specifically, as shown in FIGS. 1 and 2, when the spindle motor is stopped, the central axis of the rotary shaft portion 22 is disposed on the z axis, and the flange portion 29 is perpendicular to the z axis and x When the input sensor 3 is arranged on the x-axis so as to be parallel to the plane including the axis, the displacement sensor 14 is arranged on the x-axis. The displacement sensor 14 measures the distance a from the displacement sensor 14 to the outer peripheral surface of the cylindrical portion 20.

  The spindle motor 2 rotates the rotor 23 with respect to the stator 32 to rotate, for example, a disk or the like placed on the end surface portion 21 of the rotating portion 11.

  Hereinafter, a performance evaluation method for a hydrodynamic bearing according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  In FIG. 1, for simplicity, the voltmeter 13 and the displacement sensor 14 are not shown. For ease of explanation, as shown in FIGS. 1 and 2, when the performance evaluation device is stopped, the center axis of the spindle motor 2 is disposed on the z axis, and the pedestal 1 is It is assumed that the input shaft 3 is disposed on the x-axis and is disposed parallel to a plane including the x-axis and the y-axis perpendicular to the axis.

  First, a gap measuring step is performed. In this gap measuring step, the spindle motor 2 is turned on, the rotor 23 is rotated with respect to the stator 32, and the rotating portion 11 is rotated with respect to the fixed portion 12 by α in FIG. Rotate at an angular velocity ω [rad / s] in the direction shown. Then, with the rotating shaft portion 22 rotating, the input shaft 3 is swung at a swing angular velocity Θ [rad / s] in the direction indicated by β in FIG. Thus, the rotating unit 11 is swung in a direction indicated by γ in FIG. 1 around a direction perpendicular to both the direction of the central axis of the rotating unit 11 and the direction of the input shaft 3.

  In other words, by rotating the rotating part 11 around the z-axis at an angular velocity ω and swinging the spindle motor 2 around the x-axis at a swinging angular speed Θ, a gyro load is applied to the rotating part 11, The rotating part 11 is swung around the y-axis shown in FIG.

  Then, by measuring the voltage between the rotating part 11 and the fixed part 12 using the voltmeter 3, the radial gap between the rotating shaft part 25 and the sleeve part 28 corresponding to the voltage one-to-one is calculated. To do. Specifically, the voltage is continuously measured by continuously changing the oscillation angular velocity Θ, and the radial gap is continuously measured.

  The conductive hydrodynamic fluid (oil) filled between the rotary shaft portion 22 and the sleeve portion 28 has a high insulation resistance, and thus usually exhibits a low potential (high resistance value). However, a radial gap is caused by a gyro load. As the voltage decreases, the voltage increases (the resistance value decreases). Here, since there is a one-to-one correspondence between the voltage and the gap for each type of conductive dynamic pressure fluid (oil), the radial gap can be accurately determined by measuring the voltage (or resistance value). It can be measured.

Subsequently, a gyro load calculation step is performed. In this gyro load calculation step, the inertia moment I [kgm ² ] around the central axis of the rotating shaft portion 22 of the rotating portion 11, the angular velocity ω [rad / s], the swing angular velocity Θ [rad / s], two From the span r [m] of the hydrodynamic bearing 27, the gyro load J [N] is calculated from the following equation (1).
J = I × ω × Θ / r (1)

  Finally, a performance evaluation process is performed. In this performance evaluation step, the oscillation frequency Θ is continuously changed, the gyro load is continuously changed, and the radial gap with respect to each gyro load is measured. Then, the rigidity of the hydrodynamic bearing, which is the change in the position of the rotary shaft portion 22 with respect to the gyro load, is obtained, and the radial load capacity is calculated by calculating the gyro load when the rotary shaft portion 22 and the sleeve portion 28 are in contact with each other. Ask.

  FIG. 3 is a diagram illustrating an example of the radial load capacity calculated using the performance evaluation method for the hydrodynamic bearing of the embodiment.

  In FIG. 3, the horizontal axis indicates the oscillation frequency, and the vertical axis indicates the gyro load and the radial load capacity. Also, the straight line indicated by a in FIG. 3 indicates the radial load capacity, and the straight line indicated by b in FIG. 3 indicates the gyro load. In FIG. 3, P, Q, R, and S are graphs showing the relationship between time and voltage when the oscillation frequency is 0.42, 0.62, 0.74, and 0.9.

  As shown in FIG. 3, when the oscillation frequency is increased, that is, the gyro load is increased, the voltage is increased and the radial clearance is increased as shown in P, Q, R, and S. . In this measurement, the radial load capacity calculated based on the gyro load and the radial gap at that point is calculated to be 13.8 [N].

  According to the performance evaluation method for a hydrodynamic bearing of the above embodiment, the spindle motor 2 is swung while the rotary unit 11 is rotated, thereby using the gyro load added to the rotary unit 11. Evaluate performance. Therefore, unlike the conventional method, there is no need to bring the load applying member into contact with the rotating rotating part 11, so that the measurement can be performed even if the rotational power for rotating the rotating part 11 is small, compared with a hydrostatic bearing. Even with a hydrodynamic bearing with a small load capacity, the performance can be evaluated easily and accurately.

  Further, according to the performance evaluation method of the hydrodynamic bearing of the above embodiment, unlike the conventional method, there is no need to bring the load applying member into contact with the rotating rotating part 11, so that the rotating part 11 may be damaged. Absent.

  Moreover, according to the performance evaluation method of the dynamic pressure bearing of the above embodiment, the conductive dynamic pressure fluid is filled between the rotary shaft portion 25 and the sleeve portion 28, and the rotary shaft portion 25 (the rotary portion 11). ) And the sleeve portion 28 (fixed portion 12), the size of the radial gap with respect to the gyro load is measured, so that the variation of the radial gap with respect to the additional load can be measured accurately.

  In addition, according to the performance evaluation method of the hydrodynamic bearing of the above embodiment, since the size of the radial gap with respect to the gyro load is continuously measured, the fluctuation of the radial gap with respect to the additional load can be measured more precisely.

  Further, according to the performance evaluation method for a hydrodynamic bearing of the above embodiment, at least one of the rigidity and the load capacity of the hydrodynamic bearing can be measured easily and precisely.

  In the hydrodynamic bearing performance evaluation method of the above embodiment, the radial gap was measured by measuring the voltage between the rotating portion and the fixed portion. However, the displacement sensor shown in FIG. The radial gap may be directly measured by measuring the gap a in the x-axis direction with the rotating unit 11.

  Moreover, in the performance evaluation method of the hydrodynamic bearing of the above embodiment, the radial gap is measured by measuring the voltage between the rotating part and the fixed part. However, in the present invention, the resistance between the rotating part and the fixed part is measured. By doing so, the radial gap may be measured.

  Moreover, in the performance evaluation method of the hydrodynamic bearing of the above embodiment, the gyro load is applied to the rotating portion 11 by swinging the base 1 (dynamic pressure bearing). ) May be rotated to apply a gyro load to the rotating portion.

  In the method for evaluating the performance of the hydrodynamic bearing of the above embodiment, the rotating portion 11 that is the shaft member is rotated and the fixed portion that is the sleeve member is stationary. However, in the present invention, the sleeve member is rotated. The shaft member may be stationary.

  Further, in the performance evaluation method of the hydrodynamic bearing of the above embodiment, the fluctuation of the radial gap is continuously measured by continuously changing the oscillation frequency, but in the present invention, a plurality of discrete oscillation frequencies are used. Measurement may be performed to measure a plurality of discrete radial gaps.

  Moreover, in the performance evaluation method of the hydrodynamic bearing of the above embodiment, the change in the radial gap was measured by changing the oscillation frequency, changing the gyro load, but in the present invention, the rotating shaft member or The change in the radial gap may be measured by changing the angular velocity ω of the sleeve member and changing the gyro load.

  Further, in the above embodiment, the performance evaluation method of the dynamic pressure bearing of the present invention is applied to the dynamic pressure bearing in which the dynamic pressure generating grooves 27 are formed at two locations in the axial direction of the rotating shaft portion. The dynamic pressure bearing performance evaluation method is based on the generation of dynamic pressure at two locations in the axial direction of the rotating shaft, such as a dynamic pressure bearing with a dynamic pressure generating groove formed on the inner peripheral surface of the sleeve member facing the shaft member. You may apply to dynamic pressure bearings other than the dynamic pressure bearing in which the groove | channel is formed.

  Further, the performance evaluation method of the hydrodynamic bearing according to the present invention is applied to the end surface of the flange of the shaft member (corresponding to the end surface of the flange 26 in FIG. 2) and the receiving surface of the flange in the sleeve member (in FIG. May be applied to a thrust dynamic pressure bearing in which a dynamic pressure generating groove is formed in at least one of them.

  Of course, the idea of the present invention to determine the performance of the bearing using the gyro load is not limited to the determination of the performance of the hydrodynamic bearing, and of course, the determination of the performance of the slide bearing such as a hydrostatic bearing. Of course, it is applicable to.

It is a perspective view of the performance evaluation apparatus which performs the performance evaluation method of the dynamic pressure bearing of one Embodiment of this invention. It is sectional drawing of the spindle motor which the said performance evaluation apparatus has. It is a figure showing an example of the radial load capacity | capacitance calculated using the performance evaluation method of the dynamic pressure bearing of the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 2 Spindle motor 3 Input shaft 11 Rotating part 12 Fixed part 13 Voltmeter 14 Displacement sensor 23 Rotor 32 Stator 27 Dynamic pressure generating groove

Claims (4)

A method for evaluating the performance of a dynamic pressure bearing having a dynamic pressure generating groove on at least one of an outer peripheral surface of a shaft and an inner peripheral surface of a sleeve accommodating the shaft,
A gyro load acting on the rotating shaft or sleeve by rotating or swinging the hydrodynamic bearing around a direction orthogonal to the shaft in a state where the shaft or the sleeve is rotated. A method for evaluating the performance of a hydrodynamic bearing, comprising: a gap measuring step for measuring a gap between the shaft and the sleeve that changes based on the above. In the performance evaluation method of the hydrodynamic bearing according to claim 1,
Between the shaft and the sleeve is filled with a fluid having conductivity,
The method for evaluating the performance of a hydrodynamic bearing, wherein the gap measuring step measures the size of the gap with respect to the gyro load by measuring a voltage or an electric resistance between the shaft and the sleeve. In the method for evaluating the performance of the hydrodynamic bearing according to claim 2,
By continuously measuring the voltage or electrical resistance between the shaft and the sleeve while continuously changing the gyro load, the size of the gap with respect to the gyro load is continuously measured. For evaluating the performance of hydrodynamic bearings. In the method for evaluating performance of a hydrodynamic bearing according to any one of claims 1 to 3,
A method for evaluating the performance of a hydrodynamic bearing, wherein at least one of rigidity and load capacity of the hydrodynamic bearing is calculated based on the gyro load and a gap between the shaft and the sleeve.

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