JP4041925B2 - Method for evaluating swing characteristics of rolling bearing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in an evaluation method for a rolling bearing device used in a portion that swings slightly at high speed, such as a swing arm bearing for a magnetic disk device.
[0002]
[Prior art]
For example, torque evaluation of a conventional swing arm bearing device is performed by using a torque measuring device as shown in FIGS. 11 and 12 to evaluate the rotational torque of the bearing at a low speed.
Further, the fretting resistance of the bearing is evaluated by measuring fretting wear using a bearing outer ring swing tester as shown in FIG.
[0003]
[Problems to be solved by the invention]
Recently, magnetic disk devices are increasingly required to have higher density. For this reason, the width of the track for recording signals on the disk is becoming narrower, and the swing arm equipped with a head for recording and reproducing signals has a higher access speed to the target track and higher accuracy in positioning performance. Is required. Therefore, the ball bearing that supports the swing arm is required to have no torque fluctuation like a torque spike, low torque, and the like in order to satisfy high speed control and high accuracy.
[0004]
Conventionally, in a bearing for a swing arm, a torque measuring device as shown in FIGS. 11 and 12 is used. In this device, the inner ring of the ball bearing 40 is driven to rotate at low speed, the force transmitted from the outer ring to the housing 41 and the bar 42 is measured and converted by the load cell (strain gauge) 43, and the torque and torque fluctuation of the two ball bearings are evaluated. is doing. However, since the load cell 43 used here can measure strain in only one direction, it was not possible to evaluate the difference between the going and returning torque during swinging, so-called torque hysteresis. Also, torque fluctuations that occur in actual machines, such as the phenomenon of large torque changes that occur when reversing from going to returning, cannot be accurately reproduced.
[0005]
Further, in the bearing outer ring swing tester as shown in FIG. 13, the outer ring of the test ball bearing 46 is driven to swing by the AC servo motor 44 through the housing 45 to swing several million to several hundred million times. The fretting wear after the dynamic test is measured to evaluate the anti-fretting performance. Here, the housing 45 is supported by the apparatus by a preload spring 46 and a support bearing 47. In this apparatus, when the test machine is disassembled, the ball moves and the fretting wear state changes, so that it cannot be disassembled until the end of the test. Therefore, the torque cannot be measured during the fretting performance evaluation test, and before and after this test, the torque measurement using the apparatus shown in FIGS. 11 and 12 can only be evaluated. That is, it was not possible to directly measure the torque fluctuation according to the progress of fretting wear.
[0006]
Accordingly, the present invention provides a ball bearing and a ball bearing unit driven by a motor, and measures the bearing current such as torque and torque fluctuation of the ball bearing and ball bearing unit by measuring the drive current of the motor. A characterization method is provided.
[0007]
[Means for Solving the Problems]
The swing characteristic evaluation method of the present invention drives the ball bearing and the ball bearing unit by a motor, and measures the drive current of the motor to measure the bearing characteristics such as torque and torque fluctuation of the ball bearing and the ball bearing unit. It is characterized by evaluating.
[0008]
[Action]
According to the present invention, the ball bearing unit is driven by the same motor as the actual machine, and the drive current of the motor is measured to evaluate the bearing characteristics such as torque and torque fluctuation of the ball bearing and the ball bearing unit. Such torque phenomena, for example, torque fluctuations such as torque hysteresis and torque spikes can be evaluated. Moreover, in the fretting test, torque in the test process can be measured, so that torque fluctuations according to the progress of fretting wear can be evaluated.
[0009]
Embodiment
In the first embodiment, in the swing characteristic evaluation method for a rolling bearing device including a rolling bearing, a swing arm fixed to the outer ring of the rolling bearing, and a voice coil motor, a step of fixing the inner ring of the rolling bearing to a fixed shaft. And a step of seeking the non-contact displacement meter, a step of controlling the voice coil motor so as to keep the distance between the non-contact displacement meter and the swing arm at a predetermined distance, and a drive current of the voice coil motor is measured. A step and a step of evaluating the swing characteristics of the rolling bearing device based on the drive current.
[0010]
In the second embodiment, in the swing characteristic evaluation method of a rolling bearing device comprising a rolling bearing, a swing arm fixed to the outer ring of the rolling bearing, and a voice coil motor, a step of fixing a non-contact displacement meter, a rolling A step of seeking the inner ring of the bearing, a step of controlling the voice coil motor so as to keep a distance between the non-contact displacement meter and the swing arm at a predetermined distance, a step of measuring a drive current of the voice coil motor, And a step of evaluating the swing characteristics of the rolling bearing device based on the drive current.
A drive current for causing the swing arm to perform a tracking operation may be applied to the voice coil motor.
[0011]
In the third embodiment, in a swing characteristic evaluation method for a rolling bearing device including a rolling bearing and a voice coil motor, a step of swinging an outer ring of the rolling bearing by a voice coil motor within a predetermined angle range, and a voice coil A step of measuring the drive current of the motor and a step of evaluating the swing characteristics of the rolling bearing device based on the drive current are provided.
[0012]
【Example】
FIG. 1 is an explanatory view of a first embodiment of a torque measuring device using a drive motor of the present invention, for example, a voice coil motor. The same motor 3 and swing arm 4 as the actual machine are attached to a housing 2 in which two ball bearings 1 for testing are incorporated. The tip of the swing arm 4 is a target 6 of a non-contact displacement meter 5 (in the actual machine, a magnetic head is attached at this position). The non-contact displacement meter 5 mounted on the rotary stage 7 can perform an operation 9 corresponding to a seek operation of an HDD (hard disk drive) by driving and controlling the rotary stage 7 with a rotary stage driver 8. When the non-contact displacement meter 5 performs a seek equivalent operation 9 (for example, a step feed of several μm at the head position), the gap between the target 6 attached to the tip of the swing arm 4 and the non-contact displacement meter 5 is kept constant. In addition, the motor 3 is driven while being controlled by the driver 10, and the swing arm 4 also performs a seek equivalent operation 9. The data of the drive current 11 of the motor 3 is taken into the personal computer 12 and converted into torque, so that the relationship between the head equivalent position of the HDD and the torque can be obtained. Next, when the operation 13 corresponding to the tracking of the HDD is performed, the drive current 11 is generated so that the target 6 slightly vibrates at a constant frequency of a sine wave (for example, several tens of Hz) with an amplitude that is a fraction of the track width. To control. The driving current of the tracking equivalent operation 13 is a state in which a minute current fluctuation is added to the current in the seek equivalent operation 9, and is taken into the personal computer as described above, converted into torque, and the head equivalent position of the HDD. The relationship with torque can be obtained (FIG. 2). That is, it is possible to measure and evaluate the drive current, that is, the bearing torque, in which the movements of both tracking and seek are simulated as in the actual machine. The tracking equivalent operation may be driven with various waveforms instead of the sine wave. The driving frequency may be several Hz to several hundred Hz.
[0013]
Further, although the test bearing is preferably in the form of the same ball bearing unit as the actual machine, it is possible to simply evaluate the form in which two ball bearings are preloaded with a jig.
In addition, it is preferable to use a personal computer for drive control of the rotary stage, but an oscillator may be used. The drive current data is preferably taken into a personal computer, but may be output directly to an XY plotter or the like.
[0014]
Note that a voice coil motor is preferable as the drive motor for swinging. The rotary stage is preferably a motor capable of high-resolution rotational positioning (micron order) at the head position, such as a megatorque motor (trade name).
[0015]
FIG. 3 shows an explanatory diagram of a second embodiment of the torque measuring device using the same motor as the actual machine of the present invention. In this embodiment, the non-contact displacement meter 5 is fixed by being attached to a fixed support bar 20. The difference from the first embodiment is a seek equivalent operation 21, in which the inner ring of the test ball bearing 1 is rotated by the rotational drive of the shaft attached to the rotary positioning motor 22, and the seek is relatively performed with respect to the swing arm 4. The equivalent operation 21 is performed. The rotational positioning motor 22 is driven and controlled by a motor driver 23. The tracking equivalent operation 13 and the data acquisition of the motor drive current 11 are the same as in the first embodiment.
[0016]
As in the first embodiment, a voice coil motor is preferable as the swing drive motor, and a DC servo motor is preferable as the rotational positioning motor.
[0017]
4 to 6 show the structure of the third embodiment. 4 is a front view, FIG. 5 is a sectional view, and FIG. 6 is a plan view. Unlike the first and second embodiments, this embodiment corresponds to an improvement of a conventional bearing outer ring swing tester and can evaluate the anti-fretting performance. The same motor 32 as the actual machine is attached to a housing 31 in which several test ball bearings 30 (four in the drawing) are incorporated. The motor 32 is driven and controlled by a driver 33. The ball bearing 30 is preloaded by a preload spring 34, and the bearing outer ring is oscillated through the housing 31 by the same motor 32 as the actual machine. The test bearing 30 is preferably evaluated in the form of a ball bearing unit, but may not be a unit. In the fretting durability test, the bearing outer ring is swung several million to several hundred million times (constant area seek) with a swing angle of several degrees and a vibration of several tens of Hz. The swing angle of the fretting test is desirably set to an angle within a range in which the ball of the ball bearing does not move. Further, instead of the rotary stage and the DC servo motor as in the first and second embodiments, the swing angle is measured by counting the pulses output from the encoder 35 attached to the upper part of the housing, and the motor To seek operation. Before and after fretting and in the middle of the test, seek is performed at the swing angle corresponding to the maximum stroke without disassembling the test machine. The drive current of the voice coil motor at that time is taken into the personal computer and converted to torque, equivalent to the head of the HDD. The relationship between position and torque can be determined.
[0018]
The condition of the fretting test may be not only a constant area seek but also a so-called random seek that swings randomly between the maximum strokes.
[0019]
As in the first embodiment, a voice coil motor is preferable as the swing drive motor.
[0020]
7 and 8 show examples of torque measurement using the torque measuring device according to the first embodiment of the present invention. The horizontal axis indicates the angle of the head position (target), and the vertical axis indicates the torque. In the measurement, data is plotted when the maximum stroke is reciprocated three times (seek) while tracking. FIG. 7 shows a case of grease lubrication. FIG. 8 shows a lubrication method in which oil is used as a lubricant and oil is applied to the raceway surface in advance, and so-called oil plating is applied. Show. From this measurement result, it can be seen that, in the case of grease lubrication, the torque fluctuation at the turn-back increases rapidly. In addition, in the case of oil lubrication, it can be seen that torque fluctuation and torque hysteresis are smaller than that of grease lubrication, and that there is no sudden torque fluctuation of turning. As described above, according to this evaluation method, torque fluctuation and torque hysteresis due to a difference in lubrication can be evaluated in the same state as the actual machine.
[0021]
9 and 10 show examples of torque measurement using the fretting tester according to the third embodiment of the present invention. The horizontal axis indicates the angle of the head position (target), and the vertical axis indicates the torque. The measurement plots data when the seek operation is performed at the maximum stroke after rocking 2 million times and 10 million times before the test. FIG. 9 shows the case of grease lubrication, and FIG. 10 shows the case of oil lubrication (oil plating). From the measurement results, it can be seen that fretting wear occurs at both ends of the swing range and is progressing. The torque change before and after the test is almost the same between grease lubrication and oil lubrication. As described above, according to this evaluation method, it is possible to know the progress of fretting wear without disassembling the testing machine.
[0022]
【The invention's effect】
According to the present invention, the ball bearing unit is driven by the same motor as the actual machine, and the drive characteristics of the ball bearing and the ball bearing unit are evaluated by measuring the drive current of the motor. Such torque phenomena, for example, torque fluctuations such as torque hysteresis and torque spikes can be evaluated. Moreover, in the fretting test, torque in the test process can be measured, so that torque fluctuations according to the progress of fretting wear can be evaluated.
[Brief description of the drawings]
FIG. 1 is a diagram showing a torque measuring apparatus according to a first embodiment.
FIG. 2 is a diagram illustrating a relationship between a head equivalent position and torque in the first embodiment.
FIG. 3 is a diagram showing a torque measuring device according to a second embodiment.
FIG. 4 is a front view showing the structure of a third embodiment.
FIG. 5 is a cross-sectional view showing the structure of a third embodiment.
FIG. 6 is a plan view showing the structure of a third embodiment.
FIG. 7 is a diagram showing a torque hysteresis measurement example of the first embodiment.
FIG. 8 is a diagram illustrating an example of torque hysteresis measurement according to the first embodiment.
FIG. 9 is an example of torque measurement during the fretting test of the third embodiment.
FIG. 10 is an example of torque measurement during the fretting test of the third embodiment.
FIG. 11 is a diagram showing a conventional torque measuring device.
FIG. 12 shows a conventional torque measuring device.
FIG. 13 is a view showing a conventional bearing outer ring rocking tester.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ball bearing 2 Housing 3 Motor 4 Swing arm 5 Non-contact displacement meter 6 Target 7 Rotation stage 8 Rotation stage driver 9 Seek equivalent operation 10 Driver 11 Drive current 12 Personal computer 13 Tracking equivalent operation

Claims (2)

In a rolling characteristic evaluation method for a rolling bearing in which a rolling bearing having an inner ring fixed to a fixed shaft and an outer ring fixed to a housing is driven to swing by a voice coil motor to evaluate torque and torque fluctuation of the rolling bearing. ,
Oscillating by driving the voice coil motor and limiting the rotation of the outer ring within a predetermined angle range;
A step of measuring a driving current of Oite the voice coil motor step of the swing,
A step of evaluating the torque of the rolling bearing, torque fluctuation based on the drive current obtained in the step of measuring , and
In the step of swinging, the rotation angle of the outer ring is detected by counting pulses output from the encoder using an encoder provided in the housing and connected to the voice coil motor. Evaluation method of bearing swing characteristics.   The rolling bearing evaluation method according to claim 1, wherein the rolling bearing is a ball bearing.

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