JP3906142B2 - Bearing NRRO measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for measuring NRRO (Non-Repeatable Run-Out).
[0002]
[Prior art]
There is NRRO as an index indicating the performance of the bearing. NRRO is vibration that is asynchronous with the rotational speed. For example, in the case of a ball bearing for an HDD spindle motor, if the NRRO is large, it causes a data read / write failure and hinders the improvement of the HDD track density.
Here, since NRRO is measured separately into an axial component and a radial component, in a conventional NRRO measurement device, in order to measure NRRO in the axial direction, a sensor disposed in the axial direction; In order to measure the NRRO in the radial direction, sensors arranged in the radial direction were separately provided (for example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-145552
[Problems to be solved by the invention]
In the conventional measuring apparatus, it is necessary to install the sensor in the axial direction and in the radial direction, respectively, which is expensive.
Accordingly, the present invention is not necessarily measured by separate sensors, and an object thereof is to provide a NRRO measurement equipment of a bearing can be obtained respectively the NRRO axial component and a radial component of the bearing.
[0005]
[Means for Solving the Problems]
The present invention is an apparatus for measuring the NRRO of a bearing from vibrations generated by rotation of the bearing , comprising a measuring surface inclined at a predetermined angle with respect to the rotation axis direction and the radial direction of the bearing, and A measurement jig that vibrates with vibration due to rotation, a sensor that measures displacement due to vibration of the measurement surface, and a process that obtains a frequency component corresponding to the vibration frequency of NRRO that the displacement measured by the sensor is to be obtained by frequency analysis And means for calculating vibrations in the direction of appearance of the desired NRRO, and the measurement jig is driven to rotate and can swing in the rotational axis direction and the radial direction of the bearing. The bearing is rotatably supported by the air bearing, one of the inner ring and the outer ring of the bearing is fixed, and the other is supported by the measuring jig, and the measurement is performed. Characterized in that it is rotated driven through the ingredients.
[0006]
The measurement surface of the measuring jig inclined at a predetermined angle with respect to the rotation axis direction and the radial direction of the bearing exhibits vibration due to both vibrations in the rotation axis direction and vibrations in the radial direction. Therefore, as in the present invention, the vibration caused by the rotation of the bearing, by measuring the measurement surface inclined at a predetermined angle with respect to the rotation axis direction and the radial direction of the bearing, based on the vibration of the rotating shaft direction vibration And vibrations based on radial vibrations. Here, although there are several components in NRRO, the vibration frequency of NRRO in a certain bearing can be theoretically determined. By utilizing this and analyzing the frequency of the measured vibration, the frequency component of NRRO desired to be obtained from the vibration measured by the sensor can be obtained.
[0007]
Further, since the appearance direction (rotation axis direction / radial direction) of NRRO is known for each component, the necessary NRRO is calculated by calculating the vibration in the appearance direction of the desired NRRO based on the measured tilt angle of the surface. Can be requested.
As described above, in the present invention, since both the axial NRRO and the radial NRRO can be obtained from the vibration measured by the sensor, the rotational axis sensor and the radial sensor are prepared separately. There is no need to do.
[0008]
In addition, the measurement jig is provided that vibrates with vibration caused by the rotation of the bearing, the measurement jig includes a measurement surface inclined at a predetermined angle with respect to the rotation axis direction and the radial direction of the bearing , and the sensor includes the measurement surface. Since the displacement due to the vibration is measured , the bearing itself does not have to have a measurement surface inclined at a predetermined angle, so that various bearings can be measured.
[0009]
The sensor is preferably arranged in a direction perpendicular to the measurement surface.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The NRRO measuring device 1 of the present invention includes a sensor device 2 and a processing device (computer) 3 for automatically calculating the NRRO by calculating the output of the sensor device 2.
The sensor device 2 includes a device main body 6 that supports and rotates a bearing (ball bearing) 5 that is a measured object, and a sensor 7 that measures vibration of the bearing 5. The apparatus main body 6 is for rotating the bearing 5 to the outer ring, and is configured to fix the inner ring 5a and to rotatably support the outer ring 5b. More specifically, the apparatus main body 6 includes a shaft body 61 that is fitted inside the inner ring 5 a, and the inner ring 5 a is fixed by the shaft body 61. Further, the apparatus main body 6 is configured to support the outer ring 5 b via the measuring jig 62.
[0011]
The measuring jig 62 is connected to the rotating device 64 via the rotating shaft 63 and is driven to rotate by the rotating device 64. The measuring jig 62 is rotatably supported by an air bearing 65, and is given an air preload so as to pressurize in the direction A in the figure. Since the measurement jig 62 is supported by the air bearing 65, the measurement jig 62 can swing in the rotational axis direction and the radial direction, and the vibration generated by the rotation of the bearing 5 similarly occurs in the measurement jig 62. It is like that.
The
[0012]
The measurement jig 62 is formed with a measurement surface 62 a that is a measurement target of the sensor 7. The measurement surface 62 a has a tapered chamfered shape formed over the entire circumferential direction at the top of the measurement jig 62. The measurement surface 62a is inclined at a predetermined angle θ1 (= 45 °) with respect to the rotation axis direction, and is also inclined at a predetermined angle with respect to the radial direction.
[0013]
The sensor 7 is a non-contact displacement sensor, and for example, a capacitance type sensor is used. Since the NRRO shake is very small, a displacement sensor having a minimum resolution of 0.1 nm or less is used.
The sensor 7 is disposed in a direction orthogonal to the measurement surface 62a. The inclination angle θ2 of the sensor 7 with respect to the radial direction is 45 °. That is, (inclination angle θ1 of the measurement surface) = (inclination angle θ2 of the sensor) = θ.
[0014]
The sensor 7 measures vibration on the measurement surface 62a. Since the measurement surface 62a is inclined with respect to the rotation axis direction and the radial direction, the measurement surface 62a can be subjected to axial vibrations or radial vibrations in the bearing 5. Vibration occurs. The sensor 7 measures such vibration as vibration in a direction inclined by an angle θ with respect to the rotation axis direction and the radial direction.
In addition, by measuring vibration through the measuring jig 62, measurement is possible even if a surface inclined by a predetermined angle does not exist in the measurement object.
[0015]
The output signal of the sensor 7 is given to the processing device 3. The processing device 3 is configured, for example, by adding an A / D conversion device to a personal computer and mounting a calculation program necessary for obtaining NRRO.
FIG. 2 shows functional blocks in the processing device 3. In the processing device 3, the analog output signal of the displacement sensor 7 is converted into a digital signal by the A / D conversion device 31. Further, the frequency analysis of the signal is performed by the FFT unit 32.
[0016]
Further, the processing device 3 includes a vibration frequency calculation unit 33 that calculates a vibration frequency corresponding to each component generated as NRRO in the bearing 5 that is a measured object. The vibration frequency generated as NRRO can be obtained by calculation based on bearing specifications (number of balls, ball diameter, pitch circle diameter, contact angle) and measurement conditions (rotational speed of the outer ring). The bearing specifications and measurement conditions may be input to the processing device 3 by the user, or may be selected from the bearing specifications or measurement conditions stored in the processing device 3 in advance.
[0017]
The generated vibration frequency (Hz) varies depending on the number of undulation peaks in the NRRO due to the undulation of the outer ring raceway. These generated vibration frequencies can be obtained by calculation. Further, the vibration direction (radial direction, axial direction) of NRRO varies depending on the component. The vibration direction differs depending on whether the number of undulation peaks is N or (N ± 1). In the case of N, the vibration occurs in the axial direction, and in the case of N + 1 or N-1, the vibration occurs in the radial direction.
[0018]
The processing device 3 performs an operation for obtaining NRRO based on the above points. First, the vibration frequency for each component of NRRO to be obtained is calculated, and the peak value at this vibration frequency is read from the vibration frequency analysis result. This reading is performed for each NRRO component (33a, 33b, 33c). For example, if the vibration frequency of a component of NRRO to be obtained is 200 Hz, the peak value (frequency component) at the vibration frequency (200 Hz) is read from the result of frequency analysis. Since the read peak value is originally the voltage value (V) of the sensor output, data d1, d2, d3 converted into displacement (nm) are obtained (34a, 34b, 34c).
[0019]
When the axial direction and the radial direction are measured by separate sensors, the NRRO value in each component is obtained by the above processing. In this embodiment, the values d1, d2, d3 obtained by the processing of 34a, 34b, 34c are obtained. Since the vibration in the axial direction and the vibration in the radial direction are measured from the direction of θ, they are different from the original vibration amount. Therefore, an operation for returning to the original vibration amount is performed.
That is, as shown in FIG. 3, the vibration d in the measurement direction (d is one of d1, d2, d3, for example) causes the NRRO component vibrating in the axial direction or the radial direction to be the measurement direction θ of the sensor. Since it is equal to the one that has been disassembled, it may be returned to the original axial vibration or radial vibration. For example, d / sin θ may be calculated to obtain axial vibration, and d / cos θ may be calculated to obtain radial vibration (35a, 35b, 35c). Specifically, in the case of the N-1 peak component, since the vibration is in the radial direction, the NRRO value of the component can be obtained by calculating d1 / cos θ. The obtained NRRO value is displayed on the screen (36a, 36b, 36c).
[0020]
The processing device 3 may further determine the quality of the bearing 5 from the obtained NRRO value. In this determination, the NRRO value is compared with a standard value, and if the NRRO value is within the standard value, it is determined as a non-defective product, and if it is outside the standard value, it is determined as a defective product. The standard value is preferably stored in the processing device 3 in advance.
[0021]
The present invention is not limited to the above embodiment. For example, in the above embodiment, the case of outer ring rotation is illustrated, but even in the case of inner ring rotation, the same measurement can be performed. In the case of inner ring rotation, the device 1 changes the “outer ring” in the above description to “inner ring”. It will be replaced. In addition, when the measured object (bearing) has an inclined surface inclined by a predetermined angle, the inclined surface may be used as a measurement surface for measuring the sensor 7.
[0022]
【The invention's effect】
In the present invention, since both the axial NRRO and the radial NRRO can be obtained from the vibration measured by the sensor, it is not necessary to separately prepare the rotational axis sensor and the radial sensor.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an NRRO measurement apparatus.
FIG. 2 is a functional block diagram of a processing apparatus.
FIG. 3 is an explanatory diagram of processing in the processing apparatus.
[Explanation of symbols]
1 NRRO Measuring Device 2 Sensor Device 5 Bearing (Measurement Object)
62 Measuring jig 62a Measuring surface 7 Sensor

Claims (2)

An apparatus for measuring the NRRO of the bearing from vibration generated by the rotation of the bearing,
A measurement jig that includes a measurement surface that is inclined at a predetermined angle with respect to the rotation axis direction and the radial direction of the bearing, and that vibrates with vibration due to rotation of the bearing;
A sensor for measuring displacement due to vibration of the measurement surface;
Means for performing a process for obtaining a frequency component corresponding to the vibration frequency of the NRRO desired to be obtained by frequency analysis of the displacement measured by the sensor, and a process for calculating a vibration in the direction of appearance of the desired NRRO ;
The measurement jig is rotatably driven, and is rotatably supported by an air bearing so as to be able to swing in the rotation axis direction and the radial direction of the bearing,
An NRRO measuring apparatus for a bearing, wherein one of an inner ring and an outer ring of the bearing is fixed, and the other is supported by the measuring jig and is driven to rotate through the measuring jig . The bearing NRRO measurement apparatus according to claim 1, wherein the sensor is arranged in a direction orthogonal to the measurement surface .

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