JP2004177166A - Nrro measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy in measuring NRRO by reducing locational deviations of a bearing to be measured. <P>SOLUTION: In this NRRO measuring apparatus, with one bearing ring of the bearing positioned by a holder, NRRO of the bearing is measured by rotating the other bearing ring of the bearing and detecting oscillations generated on the side of the other bearing ring by a distrion sensor. The holder is provided with an air jet hole for jetting air from a face opposed to the one bearing ring held by the holder. By the effects of hydrostatic pressure by the air jetted from the air jet hole regardless of the gap between the holder and the one bearing ring, the NRRO is measured with the axis of the bearing centripetal to the axis of the holder. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an NRRO measuring device.
[0002]
[Prior art]
An index indicating the performance of a bearing is NRRO (Non-Repeatable Run-Out). NRRO is a vibration that is asynchronous to the rotation speed. For example, in the case of a ball bearing for an HDD spindle motor, if the NRRO is large, it causes a trouble in data reading and writing and hinders an improvement in the track density of the HDD.
A general device for measuring NRRO is disclosed as a conventional technique in, for example, Patent Document 1.
FIG. 3 shows an example of a conventional general NRRO measuring apparatus 100. The device 100 includes an arbor 102 fitted on the inner peripheral surface of a bearing inner ring 101, the bearing is positioned by the arbor 102, and the inner ring 101 becomes a stationary wheel. The outer ring 103 is driven to rotate by an air spindle shaft 104. The radial deflection of the air spindle shaft 104 is measured by a displacement measuring sensor 105. Then, a desired NRRO can be measured by Fourier transforming the output of the sensor 105.
[0003]
[Patent Document 1]
Patent No. 2820697 (FIG. 8)
[0004]
[Problems to be solved by the invention]
However, since a small gap may exist between the arbor 102 and the inner circumference of the inner ring 101, the gap causes a displacement of a bearing as an object to be measured. Therefore, the run-out measured by the sensor 105 includes a displacement due to a bearing position shift, and the position shift reduces the measurement accuracy of the NRRO.
The present invention has been made in view of such a problem, and has as its object to reduce the positional deviation of a bearing as an object to be measured and improve NRRO measurement accuracy.
[0005]
[Means for Solving the Problems]
The present invention relates to a bearing in which one bearing of a bearing is positioned by a holder, and the other bearing of the bearing is rotated to detect a run-out generated on the other bearing ring by a displacement sensor. In the apparatus for measuring the NRRO, the holder is provided with an air ejection hole for ejecting air from a surface facing the one orbital ring held by the holder, and the holder and the one orbital ring Irrespective of the gap therebetween, the NRRO is measured in a state where the axis of the bearing is centered on the axis of the holder by the static pressure effect of the air ejected from the air ejection hole.
[0006]
According to the present invention, the bearing is centered on the holder axis by the static pressure effect of the air jetted from the air ejection holes of the holder. Therefore, even if there is a gap between the holder and the bearing ring held by the holder, the occurrence of positional deviation is suppressed, and the measurement accuracy of NRRO is improved.
[0007]
Further, in the present invention, it is preferable that the holding tool is an arbor fitted to an inner periphery of an inner ring of a bearing, and the air ejection hole is formed on an outer peripheral surface of the arbor. In this case, a static pressure effect by air is obtained between the outer peripheral surface of the arbor and the inner periphery of the inner ring, and the bearing is centered on the arbor by the static pressure effect.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 and 2 show an NRRO measuring device 1 according to the embodiment. The rolling bearing 2 as an object to be measured of the NRRO measuring device 1 is configured by arranging a rolling element (ball) 5 between an inner ring (track ring) 3 and an outer ring (track ring) 4.
[0009]
The NRRO measuring apparatus 1 uses an inner ring (one raceway ring) 3 as a stationary wheel, rotates an outer race (other raceway ring) 4, and detects a radial run-out generated on the outer race 4 by a non-contact type displacement sensor 6. The output signal of the displacement sensor 6 is detected and subjected to Fourier transform (FFT) to measure the NRRO value.
[0010]
The NRRO measuring device 1 includes an air spindle 8 for rotating the outer ring 4 and a drive system 9 for rotating the air spindle 8. The air spindle 8 is configured such that a vertically extending spindle shaft 10 is supported by a spindle body 11, and a lower end 10 a of the spindle shaft 10 is interlocked with a drive system 9 via a coupling unit 12.
The drive system 9 includes a drive spindle 14 and a drive motor 15 that drives the drive spindle 14 to rotate. The drive motor 15 rotationally drives a spindle shaft 17 of the drive spindle 14 via a belt 16. The upper end 17a of the spindle shaft 17 is connected to the coupling part 12.
[0011]
The coupling unit 12 uses a magnet coupling, the spindle shafts 10 and 17 are not directly connected, and the vibration generated in the drive system 9 is not transmitted to the air spindle 8 side. 9 to the air spindle 8 side. When a rubber coupling or the like is used as the coupling unit 12, the vibration generated in the drive system 9 is transmitted to the air spindle 8 side. However, by using the magnet coupling, the vibration generated in the drive system 9 is air-driven. There is no transmission to the spindle and bearing 2. Therefore, the displacement sensor 6 can measure the shake without being affected by the vibration generated in the drive system 9.
[0012]
The NRRO measuring device 1 includes an arbor (holding tool) 19 for positioning and holding the inner ring 3. The outer diameter of the arbor 19 is substantially the same as the inner peripheral diameter of the inner race 3, is fitted inside the inner peripheral surface 3 a from above the inner race 3, positions the bearing 2, and holds the inner race 3 as a stationary wheel. . An air supply passage 20 extending in the axial direction is formed inside the arbor 19, and compressed air is supplied toward the tip of the arbor 19 through the air supply passage 30. The arbor 19 is provided with air ejection holes 21 so that the compressed air is ejected from the arbor outer peripheral surface 19a which is a surface facing the inner ring inner peripheral surface 3a toward the inner ring inner peripheral surface 3a when fitted to the inner ring 3. Are formed in communication with the air supply passage 20. The plurality of air ejection holes 21 are arranged at equal intervals in the circumferential direction of the arbor 19, and specifically, are arranged in four equal intervals in the circumferential direction.
[0013]
The compressed air jetted from each air jet hole 21 of the arbor outer peripheral surface 19a causes a static pressure effect between the arbor outer peripheral surface 19a and the inner race inner peripheral surface 3a, and the bearing 2 as an object to be measured is centered. In the case of the NRRO measuring device 1 for a miniature bearing, a small gap is easily generated particularly between the outer peripheral surface 19a of the arbor and the inner peripheral surface 3a of the inner ring. The axial center of the outer ring 5 and the spindle shaft 10 do not shift in the axial direction due to the clearance when the outer ring 5 rotates. Therefore, the displacement sensor 6 can detect the axial deflection of the spindle shaft 10 with high accuracy, and can perform NRRO measurement with high accuracy.
[0014]
Note that the present invention is not limited to the above embodiment. For example, the displacement sensor 6 may detect a runout on the outer peripheral surface of the outer race 4.
Further, the NRRO measuring device may be configured to measure the NRRO by rotating the inner wheel 3 with the outer wheel 4 as a stationary wheel, and detecting the shake on the inner wheel 3 side. In this case, the holder for positioning the outer ring 4 can be configured to fit on the outer peripheral surface of the outer ring 4, and the air ejection holes 31 eject air toward the outer peripheral surface of the outer ring 4 to center the outer ring 4. Can be configured as
[0015]
【The invention's effect】
According to the present invention, the bearing is centered on the holder axis by the static pressure effect of the air ejected from the air ejection holes of the holder, so that the bearing is held between the holder and the bearing ring held by the holder. Even if there is a gap, occurrence of positional deviation is suppressed, and the measurement accuracy of NRRO is improved.
[Brief description of the drawings]
FIG. 1 is an enlarged view of a main part of an NRRO measuring device.
FIG. 2 is an overall view including a drive system of the NRRO apparatus.
FIG. 3 is an enlarged view of a main part of a conventional NRRO measuring device.
[Explanation of symbols]
Reference Signs List 1 NRRO measuring device 2 Rolling bearing 3 Inner ring (one raceway ring)
4 Outer ring (the other race)
6 Displacement sensor 19 Arbor (holding tool)
21 Air outlet

Claims (2)

With one race of the bearing positioned by the holder, the other race of the bearing is rotated, and the run-out generated on the other race is detected by a displacement sensor to measure the NRRO of the bearing. Device
The holding tool includes an air ejection hole that jets air from a surface facing the one orbit ring held by the holding tool,
Irrespective of the gap between the holding tool and the one orbital ring, in a state where the axis of the bearing is centered on the axis of the holding tool due to the static pressure effect of the air jetted from the air ejection holes. An NRRO measuring device for measuring NRRO. The retainer is an arbor fitted to the inner periphery of the inner ring of the bearing,
The NRRO measuring apparatus according to claim 1, wherein the air ejection hole is formed on an outer peripheral surface of the arbor.

Images