Fiber optic machinery performance monitor

• US 4,196,629 A
• Filed: 10/23/1978
• Issued: 04/08/1980
• Est. Priority Date: 10/23/1978
• Status: Expired due to Term

• Current Assignee: Gerald J. Philips
• Original Assignee: Gerald J. Philips
• Inventors: Philips, Gerald J.
• Primary Examiner(s): Yasich, Daniel M.
• Application Number:
  US05/953,826
• Time in Patent Office: 533 Days
• Field of Search: 73/593, 73/655, 73/505, 73/507, 73/510, 73/657, 73/660, 73/661, 73/462, 324/175
• US Class Current: 73/593
• CPC Class Codes: F16C 19/52 with devices affected by abnormal or undesired conditions
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G01M 1/16 by oscillating or rotating the body to be tested
• CPC Class Codes: G01M 1/32 by adding material to the body to be tested, e.g. by correcting-weights
• CPC Class Codes: G01M 13/04 Bearings
• CPC Class Codes: G01P 3/443 mounted in bearings bearings F16C
• CPC Class Codes: G01P 3/486 delivered by photo-electric detectors

Abstract

This system monitors the operation of ball bearings in rotating machinery by continuously measuring the radial deflections of the outer race of these bearings using a fiber optic proximity probe. A second sensor is used to measure the rate of rotation of the machine'"'"'s shaft. One of the frequency components in the signal produced by the proximity probe will be equal to the rate at which the balls in the bearing pass by the probe. The ratio of this ball pass frequency to the rotation frequency from the second probe is computed. The ratio of the peak value to the RMS value of the higher frequency noise components from the proximity probe signal is also computed. These two ratios are used to predict oncoming bearing failures and to determine if bearings have been properly installed. The component of the proximity probe output which is at the frequency of rotation of the rotor may be filtered and its phase angle may be measured to determine the angular placement of any unbalanced weight on the rotor.

Claims

1. A system for monitoring operating conditions of and indicating defects and surface roughness in an antifriction bearing having an inner race mounted on a shaft for rotation, a fixedly mounted outer race, and rotatable elements disposed between the races comprising in combination:

an elongate bundle of fiber optics having one extremity in communication with a light source and its other extremity terminating in a sensing end mounted in close proximity to the outward radial surface of the outer race for illuminating a portion thereof and for receiving reflected light signals therefrom which varies in magnitude with the distance between the outer race and the sensing end whereby each of the rotatable elements in moving along the outer race cause outward elastic deformations thereof which are sensed by the sensing end;

means for converting the light signals received by the sensing end into electric signals;

tachometer probe and circuit means for producing an electric signal whose frequency is equal to the rate of rotation of the shaft;

means computing the frequency at which rotatable elements pass the sensing end divided by the frequency of shaft rotation thereby monitoring operating conditions of the antifriction bearing;

filter means passing components of the electric signals whose frequencies are equal to the rate of shaft rotation and the rate at which rotatable elements pass the sensing end; and

additional circuit means computing root mean square value and peak value and the ratio of the peak value to root mean square value of the passed electric signals whereby said values provide a measure of surface roughness and defects.

2. A system for monitoring operating conditions of and indicating defects and surface roughness in an antifriction bearing having an inner race mounted on a shaft for rotation, a fixedly mounted outer race, and rotatable elements disposed between the races comprising in combination:

light transmitting sensing means mounted in close proximity to the outward radial surface of the outer race for detecting variations in the distance between the outer race and sensing means as rotatable elements passing along the outer race cause outward elastic deformations in the outer race;

means associated with the sensing means for converting said detected variations into electric signals;

tachometer probe and circuit means for producing electric signals whose frequency is equal to the rate of rotation of the shaft;

means computing the frequency at which rotatable elements pass the sensing means divided by the frequency of shaft rotation thereby monitoring operating conditions of the antifriction bearing;

filter means passing the components of the electric signals whose frequencies are equal to the rate of shaft rotation and the rate at which rotatable elements pass the sensing means; and

additional circuit means computing root mean square value and peak value and the ratio of the peak value to root means square value of the passed electric signals whereby said values provide a measure of surface roughness and defects.

3. A method of determining the angular position of unbalanced weight on a shaft comprising the steps of:

mounting the shaft on a rotatable inner race of an antifriction bearing wherein the outer race is fixedly mounted in a housing and rotatable load transmitting elements are disposed between the races;

rotating the shaft whereby loads transmitted by the rotatable elements to the outer races cause radially outward elastic deformations in proportion to the unbalanced weight;

generating a first electrical signal whose frequency corresponds to the shaft rotation and whose phase angle is synchronized with the angular position of a fixed timing point on the shaft;

producing a second electrical signal whose amplitude is proportional to the size of the deformations on the outer race;

filtering the second signal to remove all frequency components except those which are equal to the frequency of rotation of the shaft;

measuring the phase angle difference between the filtered second signal and the first signal whereby the phase angle difference is proportional to the difference in angular position between the fixed timing point on the shaft and the location of the maximum deformation on the outer race thus identifying the unbalanced weight position.

4. The method according to claim 3 involving an additional step of measuring the amplitude of the filtered second signal for determining the relative size of the unbalanced weight.

5. The method according to claim 3 wherein the step of producing the second signal is accomplished by using an optical fiber probe for transmitting a light signal onto the periphery of the outer race, receiving light reflected therefrom, and converting the received light signal into electrical signals.