Measuring and testing – Dynamometers – Responsive to force
Reexamination Certificate
1999-11-09
2001-09-11
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to force
C073S581000
Reexamination Certificate
active
06286374
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a preload measuring apparatus of a rolling bearing which is assembled into each type of precision rotational portions such as a spindle motor, rotary actuator, rotary encoder, or the like, of a video tape recorder (VTR), hard disk drive (HDD), laser beam printer (LBP), or similar device.
A rolling bearing which is assembled into a precision rotational portion such as a spindle motor, rotary actuator, rotary encoder, or the like, used in a VTR, HDD, LBP, or similar device, is required to be very accurately produced to prevent a whirling motion and a deflection in the axial direction. Accordingly, a rolling bearing to support the spindle is used under the condition that a preload in the axial direction is applied. By applying the preload, the rigidity of the bearing is kept high, the deflection accuracy of the shaft is increased, and the slippage of a ball at the high speed rotation is prevented.
As such the rolling bearing to support the spindle of the VTR, HDD, LBP, or the like, there are following rolling bearings: for example, as shown in FIG.
11
(
a
), a pair of respectively independent rolling bearings assembled onto a rotation shaft by press fitting or adhesion; as shown in
FIG. 11
(
b
), a rolling bearing which has double-row raceways in the outer ring, and to which the preload is applied by press fitting or adhering the divided inner ring to be moveable in the axial direction; or as shown in
FIG. 11
(
c
), a rolling bearing which has double-row raceways in the inner ring and the outer ring respectively, and to which the preload is applied at assembling by changing the dimension of the pitch of the raceway.
In the other words, in the rolling bearing shown in
FIG. 11
(
a
), an inner race member thereof comprises a shaft and two inner rings attached to the shaft, and an outer race member thereof comprises two outer rings which are respectively mated with the inner rings. In the rolling bearing shown in FIG.
11
(
b
), an inner race member comprises a shaft and two inner rings attached to the shaft, and an outer race member thereof comprises a common outer ring having two raceways which are respectively mated with the two inner rings. In the rolling bearing shown in FIG.
11
(
c
), an inner race member thereof comprises a shaft having two raceways, and an outer race member thereof comprises an outer ring having two raceways which are respectively mated with the two raceways of the shaft.
However, in any method of the above description, it is difficult to measure the preload after the assembling of the rolling bearing, because the preload is different according to the positional dimension of each member.
Accordingly, for example, Japanese Patent Examined Publication No. Hei. 2-61100 disclose a preload measuring method wherein the resonance frequency of the bearing apparatus itself is obtained by applying a minute vibration onto the rolling bearing, and this resonance frequency is converted into the preload by using a constant relationship between the resonance frequency of the rolling bearing and the preload.
However, in such the preload measuring method, there is still a problem which will be described below. That is, noise vibration is generated due to a disturbance of the mechanical system when a minute vibration is applied onto the rolling bearing, and therefore the preload can not be accurately measured due to this noise vibration.
Further, as the rolling bearing becomes small and then the mass of the outer ring becomes small, the resonance frequency of the rolling bearing appears on the high frequency side. As shown in
FIG. 7
, the vibration peak appears, for example, near 20 kHz at which the noise is relatively strong. At that time the resonance frequency is covered with the noise, so that it becomes difficult to detect the resonance frequency. Accordingly, the accuracy of the measurement is lowered, and the rigidity or the preload of the rolling bearing which are calculated, becomes incorrect.
SUMMARY OF THE INVENTION
The present invention is made to solve such the conventional problems, and an object of the present invention is to provide a preload measuring apparatus of a rolling bearing which can accurately measure the preload working on the rolling bearing by preventing the influence due to vibration of the disturbance.
The above-mentioned object can be achieved by a preload measuring apparatus for measuring a preload of a rolling bearing which includes an inner race member, an outer race member, and a plurality of rolling elements rotatably interposed between the inner race member and the outer race member, the preload measuring apparatus , according to the present invention comprising a bearing support member, a pressurization member, an excitation member, a vibration sensor and a controller. The bearing support member supports both ends of the inner race member in the axial direction of the rolling bearing. The pressurization member loads a predetermined weight to one of the both ends of the inner race member in the axial direction through the bearing support member. The excitation member applies vibration to the inner race member in the axial direction while the predetermined weight is loaded on the inner race member the pressurization member. The vibration sensor detects a vibration which is generated on the outer race member and is caused by the vibration of the inner race member. The controller is capable of calculating a resonance frequency of the rolling bearing through an output signal of the vibration sensor and also calculating a true preload of the rolling bearing in accordance with the thus calculated resonance frequency, the true preload defining a preload of the rolling bearing before the predetermined weight is loaded on the inner race member.
In the above-mentioned preload measuring apparatus according to the present invention, it is preferable that the inner race member comprises an inner ring and a shaft rigidly secured to the inner ring, and the bearing support supports both ends of the shaft in the axial direction.
In the above-mentioned preload measuring apparatus according to the present invention, it is preferable that the inner race member comprises an inner ring and a shaft rigidly secured to the inner ring, and the bearing support member supports one end of the shaft in the axial direction and one end surface of the inner ring in the axial direction.
In the above-mentioned preload measuring apparatus according to the present invention, it is preferable that the inner race member comprises a shaft having a raceway on its peripheral surface.
In the above-mentioned preload measuring apparatus according to the present invention, it is preferable to further comprises a pressurization detect member detecting a pressure of the inner race member which is loaded by the pressurization means, wherein when an output of the pressurization detect member reaches a predetermined value, the excitation means begins to apply the vibration to the inner race member.
In the above-mentioned preload measuring apparatus according to the present invention, it is preferable that the excitation member comprises at least two piezoelectric elements applying vibration to the inner race member while loading the predetermined weight on the inner race member in the axial direction, the piezoelectric elements having reverse phases and the same amplitudes each other.
In the above-mentioned preload measuring apparatus according to the present invention, it is preferable to further comprises a weight member attached to the outer race member, wherein the vibration sensor detects the vibration of outer race member through the weight member.
In the above-mentioned preload measuring apparatus according to the present invention, it is preferable that the loading operation of the pressurization member is stopped when a resonance frequency output from the vibration sensor coincides with a predetermined frequency.
In addition, the above object can be attained by a preload measuring apparatus, according to the pr
Iwatani Nobuo
Kudo Hiroyuki
Maeda Takashi
Shibazaki Hiroshi
Noori Max
NSK Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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