WO1988000684A2

WO1988000684A2 - Encapsulated motion transducer

Info

Publication number: WO1988000684A2
Application number: PCT/US1987/001670
Authority: WO
Inventors: Gerald John Philips
Original assignee: Gerald John Philips
Priority date: 1986-07-18
Filing date: 1987-07-20
Publication date: 1988-01-28
Also published as: EP0288489A1; WO1988000684A3; JPH01500776A

Abstract

A method and apparatus for determining the length of bearing defects along the direction of rolling, including also a transducer system with high frequency (10,000 Hz) capability for detecting and measuring the displacement and/or vibration of objects placed in contact therewith. Fiber optics guide light from a light source to the target via a light coupling medium, and back to a signal generating means. The system includes a reflective target for reflecting incident light and vibrating in unison with a contacted object. In one version, a truncated spherical member, providing the target and the object contacting surface, is biased by Belleville springs. The light guiding fiber optics, springs and light coupling medium are sealed from the hostile environment of the transducer. In another version, a crowned cylindrical ruby tip provides the object contacting surface and is biased by the cantilever spring. The light guiding fiber optics and cantilever are sealed from the hostile environment of the transducer.

Description

ENCAPSULATED MOTION TRANSDUCER
BACKGROUND OF THE INVENTION 1. Technical Field of the Invention
The invention relates to an encapsulated motion transducer, and more particularly to a transducer for measuring displacement and very small amplitude vibrations in hostile environmental conditions such as grease, oil, metallic sludge, corrosion, high ambient vibration, high temperature, electrical, and electromagnetic interference.

2. Background Related Art
Fiber optic devices for the detection and measurement of displacement and vibration have been disclosed by U.S. Patent No. 3,273,447 to Frank and by U.S. Patent No. 3,327,584.to Kissinger. Those devices have the capability to provide displacement measurements over a wide frequency range, including the range 0-10,000 Hz. However, the output of those devices attributable to Kissinger, which have been commercially marketed, are proportional to target surface motion as well as target surface reflectivity. To sense and measure motion precisely with these devices it is necessary to ensure that the target surface reflectivity is constant while measurements are being taken.

It has been found that accurate dynamic measurements can not be made with unencapsulated fiber optic devices in environments where there is contamination of the target surface or of the optical path to the target surface. Other non-contact motion transducers, such as eddy current or capacitive types also suffer a degradation of performance when used in an environment that causes metallic based contamination to collect at the sensing tip. For example when using these unencapsulated devices to monitor bearing vibration in the manner disclosed in
U.S.

Patent No. 4,196,629 (which is hereby incorporated by reference), it was found that bearings corrode in their housings and that bearing lubricant migrates towards the sensing area mixing with the corrosion products as it migrates
The mixing of corrosion products and lubricant creates a metallic sludge that degrades the performance of any transducer that is sensitive to metallic substances or is dependent upon a clear optical path to the target.

Contact probes generally overcome fouling problems. However, these devices have a very limited frequency capability. Dial indicators and linear variable differential transformers are two examples of contact sensors that provide accurate position measurements but can not be used to measure vibrations in the displacement domain up to 10,000 hertz.

A surface-contacting fiber optic displacement transducer has been disclosed by Philips in U.S.

application serial No. 748,084, filed September 24, 1985, and is designed to overcome work surface reflectivity problems by encapsulating the fiber optic sensor tip. The elastomeric biasing means of those devices have been found to create distortions in the frequency response of light that is reflected from the sensing means reflective surface. A typical frequency response of the device using elastomeric biasing is shown in Figure 1. The desired frequency response is a straight line as indicated on the figure. Distortions of the type shown in Figure 1 significantly degrade the capacity of these devices to provide precise motion measurements at all frequencies of vibration. Furthermore, to minimize the amount of distortion, the force generated by the elastomeric biasing means must be kept very small.

Thus, intimate contact between sensor means and target surface can not be maintained with these devices when vibrations are present which generate acceleration forces on the sensor tip which exceed the small elastomeric spring force. A loss of intimate contact can occur when the target vibrates excessively or when the device is installed in a moving vehicle that is subject to large accelerations.

The elastomeric biasing means disclosed in the above application has a restricted amount of motion that is .003 inch or only slightly more. This restriction prohibits the setting of an operational gap at what is known as the optical peak in the response curve of the devices attributable to Kissinger. The optical peak, a typical example of which is indicated in Figure 2, is the region at the peak of the output curve where changes in the amplitude of reflected light are proportional only to target surface reflectivity changes and not to gap changes. The optical peak is thus the only point at which reflec tivity of a target surface can be accurately and reliably checked for its absolute value. This is important because reflective surfaces can oxidize or otherwise degrade over a period of timer especially when subjected to elevated temperatures.

The restricted range of motion of the device in the application also markedly increases the sensitivity of the device to installation errors thereby rendering the device much less practical to employ.

Many bearings are subject to extremes of operating temperatures. An example of this application would be small high speed turbomachinery with bearings located close to hot turbines. Normal bearing operating temperatures run up to 400 F.

Mildly elevated temperatures are considered to be in the range 400-600 F. A limited number of special bearing applications extend to 1000 F and even higher. The above application does not provide considerations for operation at elevated temperatures.

Electrical noise and electromagnetic interference are problems frequently encountered with electrical sensing devices. These interferences are particularly troublesome when very low amplitude vibrations are to be measured. In the device disclosed by U.S.Patent No. 4,196,629 to Philips low amplitude bearing vibrations are sensed and converted to bearing noise levels. That noise level reading is degraded when the sensing instrument self-noise and/or ambient noise interfere with the motion sensing device.

Miserentino et al., U.S. Patent 4171,645, disclosed displacement probes that combined noncontact fiber optic transducers with self-contained contact targets. Miserentino does not provide for high frequency measurement capability in any of his several embodiments. In fact, it is obvious from his embodiments that only low frequency vibration or simple position measurements are possible from his teachings. The prior displacement probe, illustrated in U.S. Patent No. 4,171,645 to Miserentino, et al, includes a target in the form of a ball or planar member. The target is held in contact with a vibrating surface by gravity, a set of springs, a balloon device or a jet spray of gas.

However, the
Miserentino, et al probe lacks means for sealing the transducer elements from hostile environmental interferences, lacks material means for achieving successful operation at elevated temperatures, lacks coupling means to maximize the amount of light throughput, lacks means for overcoming ambient and self-generated noise, and it lacks a method for maintaining sensor contact with test objects in hostile vibration environments.

Sichling et al., U.S. Patent 4,379,26, disclosed an optical sensing device which contains a vibrating spring whose frequency of vibration is determined by the parameter p to be measured.

Sichling does not specify how fast the parameter p may vary and it is obvious from the embodiments given that high frequency measurements are not possible with his teachings.

Thalman in U.S. Patent 4,591,712 disclosed a sensing apparatus wherein a reciprocal plunger is utilized to after the amount of light reflected back into an enclosed bundle of fiber optic elements.

Thalman does not provide for high frequency capability in his device and it is obvious that his device could not be used for high frequency vibration measurements.

An encapsulated motion transducer has been disclosed in copending application Serial No.

886,827, filed July 18, 1986, and is designed to operate in hostile environments with a high frequency capability.

The embodiments submitted in U.S. applications 748,084 and 886,827 can be used to measure displacement of vibrating objects but - there are problems and limitations with those embodiments. The high frequency response of any spring-mass system is limited by the first resonant mode of vibration of the system. A typical response curve for a springmass system is shown in Figure 1A successful sensor design 1A one that operates in the flat region below the resonant peak and where the resonant peak is above 10,000 Hz.

The resonant frequency is proportional to the stiffness of the spring and inversely proportional to the mass of the moving elements. Therefore, in the design of a spring-mass system to obtain the highest possible resonant frequency, the designer should strive to achieve the largest spring stiffness and the smallest mass. In the copending application, the mass of the sapphire tip can not be optimized to extremely small values because the design requires a ball diameter larger than the diameter of the springs. The spring elements are likewise forced to larger than optimum values because the fiber optic elements must pass through the springs in the embodiments shown. The stiffness of the spring elements can not be set at values that are high enough to compensate for the large masses of the embodiments given.

High spring stiffnesses cause high contact pressures between the tip and the object surface which can result in contact deformations, permanent denting and other problems. In fabricating and testing embodiments shown ln the copending application, the highest resonant frequency that was practically obtainable was approximately 700 Hz.

Other problems such as friction among the spring elements and between the tip and casing were found to degrade the performance of devices of the copending application by reducing the actual resonant frequency below the value calculated where frictional effects are not considered.

In the device disclosed by U.S. Patent No.

4,1,629 to Philips vibration measurements are made up to 10,000 Hz. Thus, there is a continuing need in the state-of-the-art for a contact displacement transducer with high frequency capability to 10,000
Hz.

In U.S. patent No. 4,196,629 the outer race of a ball bearing is deflected outward radially in the vicinity surrounding each of the balls, and a fiber optic proximity probe can be used to detect those deflections. Three types of waveforms are disclosed which result from defects on the outer ring, inner ring, or ball. Also explained is the peak to RMS ratio of the waveforms which could be used as an indicator of impending bearing failures.

Experience with bearing failures in rotating machines indicates that defects on bearing component parts often grow to be of quite significant size prior to the initiation of catastrophic failure. For example, cracks or spills initiated on bearing inner or outer rings have been found to have grown to the point where they cover the entire circumference of the ring. There is therefore, a continuing need in the state of the art of bearing vibration monitoring to be able to determine the size of bearing defects.

Other types of non-contact motion transducers that do not use light sensing means are also available commercially. Of those, eddy-current and
v capacitance sensing devices are very common. These devices are not sensitive to target surface reflectivity variations but their usefulness in hostile environmental conditions is significantly degraded by metallic contamination, by elevated temperatures, and by electrical and electromagnetic interferences.

DISCLOSURE OF THE INVENTION
The invention provides a method for determining the length of bearing defects along the direction of rolling and a contact transducer for making vibration measurements in the displacement domain with a high frequency capability to 10,000 Hz.

The transducer sensing means is a non-contact fiber optic bundle whose light throughput is modulated by motion of a cantilever beam. A ruby contact tip is bonded to the beam. In operation, the ruby tip is biased against a vibrating object by forces from the cantilever beam which has been initially deflected a predetermined amount. Sealing means are provided to protect the sensing means from contamination and fouling.

The invention overcomes hostile environmental interference problems, optical path fouling, and metallic debris contamination problems by encapsulat ing the motion transducer sensing means and sealing it from outside sources of contamination. Furtherr this invention is operable at elevated temperatures with- proper selection of suitable materials.

Furthermore, this invention resolves very small amplitude nigh frequency vibrations by providing a highly reflective target surface and by providing coupling means to maximize the transfer of light through the internal elements of the sensor.

Additionally, this invention markedly improves the signal to noise ratio of optical sensing devices of the Kissinger type by using pulsed light sources.

It is a primary objective of this invention to provide an encapsulated fiber optic motion transducer which eliminates hostile environmental interference and optical path fouling problems.

Another purpose of this invention is to provide an encapsulated fiber optic motion transducer which maintains intimate contact with a vibrating target at all times.

Another important purpose of this invention is to provide an encapsulated motion transducer that is not affected by physical environment or atmospheric problems such as contamination of the sensing path by gaseous, liquid or solid substances.

Yet another purpose of this invention is to provide an encapsulated motion transducer having a flat frequency response from DC to any higher frequency desired which response can be calculated and controlled by design.

It is another objective of this invention to provide a contact displacement transducer with a flat frequency response from zero to 10,000 Hz.

Another purpose of this invention is to provide an encapsulated fiber optic contact transducer with a flat frequency response capability from zero to 10,000 Hz. Still another feature of this invention is the provision of an encapsulated fiber optic motion transducer using pulsed light sources to improve sensor signal to noise ratio.

Still yet another feature of this invention is the provision of an encapsulated motion transducer with means for checking sensor light path degradation without requiring sensor disassembly.

A further feature of this invention is the provision of an encapsulated fiber optic motion transducer using single fibers instead of bundled fibers.

Yet another feature of this invention is to maximize the intensity of light throughput of the sensor.

Still another feature of this invention is the provision of an encapsulated motion transducer for operation at elevated temperatures.

A transducer system detects and measures the displacement and/or vibration of objects placed in contact therewith. The system includes a reflective target for reflecting incident light and vibrating in unison with a contacted object. Fiber optics guide light from a light source to the target, via a Light coupling medium, and back to a light generating means. In one version, a truncated spherical member, providing the target and the object contacting surface, is biased by Belleville springs. In another version, tailored for flat frequency response to 10,100 hertz, a cylindrical ruby tip is adhesively bonded to a cantilever spring. The ruby tip is crowned to accommodate misalignment and to minimize contact stresses. The ruby tip is biased against an object surface by the cantilever spring. The cantilever spring also provides a reflective target for the fiber optic elements.

The light guiding fiber optics and cantilever spring are sealed from the hostile environment of the transducer.

BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the attendant features thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered ln connection with the accompanying drawings wherein:
Figure 1 is a typical frequency response curve using elastomeric biasing.

Figure 2 is a curve comparing output voltage to gap size. Figure 3 shows a first embodiment of the invention.

Figure 3a shows the encapsulated end of the invention isolated and in cross-section.

Figure 4 shows another embodiment of the invention in cross-section wherein the light source is pulsed.

Figure 5 shows another embodiment of the invention wherein the target means are not mounted to the sensing means.

Figure 5a shows the encapsulator isolated and in cross-section.

Figure 6 is a typical response curve of a spring-mass system;
Figure 7 is a schematic of a first embodiment of the invention
Figure 8 shows the target end of the invention in cross-section
Figure 9 shows another embodiment of the invention wherein the fiberoptic elements are passed through a connector Joint;
Figure 10 shows another embodiment of the invention wherein the tip and spring elements are mounted in a bearing housing and the fiber optic light guiding elements are removable therefrom;
Figure 11 is a schematic view of a contact transducer ln contact with an undamaged rolling element bearing;
Figure lia is a graphic illustration of an undamaged bearing;
Figure 12 is a block diagram of the circuitry used to display bearing damage;
Figures 13-18 are views similar to figure 6 illustrating various amounts of bearing damage:

and
Figures 13a-18a illustrate the display of the damaged bearing of figures 13-18.

MODES FOR CARRYING OUT THE INVENTION
Referring now to the drawings, like reference characters designate identical or corresponding parts throughout the several views.

Referring to Figure 3, numeral 1 designates a plurality of fiber optic light guides which are mounted inside of an encapsulator 2 at one end and which are bifurcated at the opposite end into two groups a and b where light source means 3 and light detector means 4 are provided. The light source means 3 provides continuous illumination of either visible or invisible light to the fiber optic light guides ia. The detector means 4 is sensitive to the intensity of light that is returned through the fiber optic light guides b.

Referring to Figure 3a which shows the sensing end of the encapsulator in cross-section, the fiber optic light guides i are shown bounded by a rigid sheathing which is so configured to provide support fora plurality of spring elements in the form of stainless steel Belleville springs 5. The fiber optic light guides i are divided into a plurality of conventional groups, at least one group ia constituting light transmitting fiber optics and at least another group b constituting light receiving fiber optics. The fiber optics of both groups merge to form a substantially unitary peripheral surface which :s truncated to form a substantially planar surface 6.

A media 7 surrounding the fiber optic probe i can be air or it can be fitted with a liquid, gas, vacuum or elastomeric solid material so as to improve the transmission of light and to retard oxidation or other degradation of a reflective target surface 8.

The liquid medium and the elastomeric solid medium have an index of refraction equal to or substantially equal to the index of refraction of the light guide means. The reflective target surface 8 is a highly polished surface on a sapphire transducer tip 9 or other material having a density and wear resistance similar thereto. A highly reflective coating 10 is applied to the polished target surface 8. The transducer tip 9 provides contact with a test object ii, the motion of which is to be determined.

In the present configuration the fiber optic light guides i, spring elements 5, and tip 9 are housed ln a stainless steel casing 12 and sealed at both ends from outside contamination. At the sensing end, a shoulder 13 is provided to retain the transducer tip 9 within the transducer casing 12 in the absence of physical contact with the test object ii. During assembly of the transducer the spring elements 5 are forced into compression. A flexible seal 14 of silicone rubber or other similar material designed to tolerate high temperatures is shown which is fixedly attached to the tip 9 and also to the casing 12. The seal provides for the retention of the light conducting media 7 within the transducer and prevention from migration of outside contaminants to the inside of the transducer. A protective cover 15 is provided which is fixedly attached to the casing 12.

At the other end of the casing 12, rigid sealing means 16 are provided between the fiber optic probe 1 and the casing 12.

In the design of the transducer, to ensure intimate contact of the tip 9 with the test object 11, the mass of the tip 9 and the springs 5 and the force provided by the springs are determined by calculation so that the spring force always exceeds the forces due to acceleration of the tip mass 9 and the spring mass 5 under any encountered operating condition.

In assembly of the transducer, the gap between the sensing surface 6 and the reflective target surface 8 is set at the optical peak of the response curve which is shown in Figure 2. This gap set allows for verification of the optical path effectiveness without disassembly of the sensor when the sensor is free of any contact with the test object ii.

In operation, the tip 9 is brought into contact with the test obJect ii such that the gap between the sensing surface 6 and the reflective target surface 8 is reduced to the region of greatest sensitivity, which is shown in Figure 2. Where larger gaps between the sensing surface 6 and the target surface 8 are desired, the assembly can be arranged to set the pre-operational gap at any desired value provided the sealing means 14 can accommodate the additional movement and provided that the spring 5 and tip 9 masses are properly set to maintain intimate contact between the tip 9 and the test object ii at all dynamic operating conditions.

Figure 4 illustrates an alternative method of using light to detect motion of the reflective target surface 8 within the encapsulator 2. The light source means 19 are pulsed to provide a train of light pulses with regular spacing 21. As the reflective target surface 8 vibrates with test object 11 movement, the incident light pulses are modulated such that the pulse train of reflected light 23 has irregular spacings, the pattern of which is precisely related to the motion of the target surface 8. The detector means 25 convert the spatial irregularities of the pulse train 23 into a signal representative of target motion. In this manner, the dependence upon the intensity of returned light to generate a signal related to motion is eliminated and the signal to noise ratio of the sensor is substantially improved.

Figure 5 illustrates an alternative way of encapsulating the sensing elements with the encapsulator 30. The encapsulator is not mounted on the fiber optic light guides as was the case in
Figure 3. The encapsulator is mounted in a holding device 31 near a test object 32 such that the internal spring elements are sufficiently compressed.

A plug cap 33 provides sealing means. As illustrated in Figure 5a, the encapsulator 30 comprises a tip 34, - a reflective target surface 35, spring elements 36, a casing 38, a flexible seal 40 which is fixedly attached 10 the tip 34 and to the casing 38, a protective cover 42 which is fixedly attached to the casing 38, and a spring compressor 43. In this embodiment of the invention the plug cap 33 is removed and the fiber optic probe i inserted into the encapsulator 30 when measurements are to be taken.

The fiber optic probe 1 is withdrawn from the encapsulator 30 when measurements are not being taken. The plug cap 33 is placed on the encapsulator 30 when the probe i is withdrawn.

Thus, the invention overcomes hostile environmental interference problems of non-contact proximity detectors by encapsulating the sensing end of these devices thereby protecting them from outside sources of contamination. In so doing, means are also provided to maximize the transfer of light through the sensor. The tip 9 and the spring elements 5 should be selected so that intimate contact between the tip 9 and the test object ii is maintained at all times. The proper design can be achieved by considering the accelerations of the environment in which the transducer will be placed. The materials disclosed in this invention should provide for successful operation of the transducer up to 600 F. A pulsed light source can be used to obtain increased signal to noise ratio with bundled fibers or with single fibers.

Figure 6 illustrates a typical response curve for a spring-mass system.

Referring to Figure 7, numeral 1 designates a plurality of fiber optic light guides which pass into a housing 2 at one end and which are bifurcated at the opposite end into two groups ia and b where a light source 3 and a light detector 4 are provided.

The Light source 3 provides continuous illumination of either visible or invisible Light to the fiber optic light guides ia. The detector 4 is sensitive to the intensity of light that is returned through the fiber optic light guides b.

Referring to Figure 8 which shows the sensing end of the invention ln cross-section, the fiber optic light guides i are shown encased in a rigid housing 2. A stainless steel cantilever spring 5 protrudes over the fiber optic elements at a slight angle which is set so that light reflected into the light guides 1 is at its maximum value. The underside of the cantilever provides a reflective target for the fiber optic elements and therefore should be large enough to cover the spot of light subtended by the fiber optic bundle. The cantilever is electropolished to maximize reflectivity.

In operation, the sensor is brought into contact with the object such that the cantilever 5 is deflected toward the fiber bundle i. The amount of initial deflection should be greater than any operational deflection expected to be encountered. A ruby tip 6 is bonded to the cantilever using adhesives 7 suitable for the temperature operating range expected. The adhesives should also be unaffected by any oils or greases or other substances which may come into contact with the sensor. The preferred embodiment uses an activator cured adhesive which has a urethane methacrylate ester base.

Structural epoxy adhesives are also available which will work quite well. The ruby tip 6 has a crown radius which should be as large as possible to minimize contact stresses between the ruby tip 6 and a vibrating object 9. The radius should not be so large however that misalignment between tip and object surfaces would cause edge loading of the ruby tip. In the preferred embodiment, the diameter of the ruby tip is one millimeter and the crown radius is 2.5 mm. In the preferred embodiment, misalignments up to 5 degrees can be tolerated. A flexible seal 10 is made of silicone rubber and is adhesively bonded to the cantilever 5, the fiber bundle housing 2, and the ruby tip 6 using an adhesive ii that is suitable for the operating temperature range to be encountered.

This adhesive should also be unaffected by any oils or greases or other substances that may come into contact with the sealing means. A silicone RTV adhesive is used In the preferred embodiment. An outer ring 12 is provided to enclose the sealing means and to provide support to the cantilever element. The outer ring 12 is bonded in place with adhesives 13 that are suitable for the temperature range to be encountered. Structural epoxy adhesives are adequate for this purpose.

In the design of the transducer, the masses of all the moving elements; the ruby tip 6, the spring 5, the adhesives 7 and 11. and the flexible seal 10 should be considered and kept as small as possible.

In the preferred embodiment, the total of the masses of the moving elements should not exceed 0.00004 lbs.

The spring rate of the cantilever spring 5 should be selected to be large enough to result in a resonant frequency above 10,000 Hz. In the preferred embodiment, the spring rate should be at least 200 lb/In. The maximum deflection of the cantilever spring 5 and the resultant contact force between the tip 6 and object 9 should be limited to values that give safe contact pressures at the tip/object interface. In the preferred embodiment, maximum cantilever deflection is 0.008 inch and the maximum contact pressure is 250,000 psi.

Figure 9 illustrates an alternative embodiment of the invention wherein the fiber bundle i is terminated in a connector 15 which contains a pair of fiber optic bundles 16a and 16b. A mating connector 17 contains a pair of light guiding fiber optics 18a and 18b. A light source means 20 transmits light to the fiber optic guide 18a which couples to the light guide l6a. Light is reflected back into the fiber optic light guide 16b from the cantilever beam 5, coupled to the light guide 18b and transmitted to a light detector means 21.

Figure 10 illustrates another alternative embodiment of the invention wherein the tip 6, cantilever 5 and sealing elements 10 are mounted and affixed to a bearing housing 25 and wherein a fiber optic light guide means 26 can be manually adjusted to set the gap between the fiber bundle 26 and the cantilever beam 5. In this configuration, the fiber optic light guide could be inserted temporarily into position for recording of measurements. When measurements are not being taken, the fiber optic light guides can be removed. In that case, a plug cap is inserted in place of the fiber optic bundle 26 to protect the reflective surface of the cantilever 5 from contamination.

Figure 11 shows a contact transducer 30 with high frequency capability which is in contact with the stationary outer ring of a rolling element bearing; The rolling element 32 may be a ball or a roller of any type. A low frequency waveform is shown figure ll(a) which is developed by the action of rolling elements passing by the transducer. The time u is the time between successive passages of rolling elements. A high frequency waveform is shown for a typical bearing that is free of defects. A damage display is shown which is a bar graph having u units along the horizontal axis. When a bearing has no defect damage, the damage display shows all bars at approximately the same height.

The damage display operates in accordance with the block diagram shown in Figure 12. A machine such as an electric motor 40 is monitored with a tachometer probe 42, to generate a signal at the shaft rotational frequency, and with a bearing motion transducer 44. The waveform from the bearing transducer is passed through a band pass filter 46 to separate out the load dependent deflection component of the bearing signal. That signal and the shaft tachometer signal are sent to a frequency ratio counter 48 to compute the bearing speed ratio (BSR) as described in Patent No. 4,196,629. The bearing motion signal is also sent through a high pass filter 50 which eliminates the load dependent deflection data. The signal is then sent to a peak detector 52 which will detect spikes in the bearing signal that are caused by damage on the component parts of the bearing.

The output of the peak detector 52 is sent to the damage display 54 which is a bar graph display in the preferred embodiment. The load dependent component of the bearing signal is sent to a period counter 56 which measures the time between successive roller passages. The BSR, which is the output from the frequency ratio counter 48, is sent to a processor 58 which puts the BSR value into component damage equations for computation of proper trigger signals. The multiplier/divider 60 modifies the period of the bearing load dependent deflection in accordance with values determined by the damage equations. The trigger signal 62 for the damage display will thereby be perfectly synchronized to the frequency of operation of the bearing component parts.

The processor 58 can also be a human interface whereby the BSR is read and then used to calculate the bearing damage frequencies 0 for outer ring damage, I for inner ring damages R for roller damage, and C for cage damage in accordance with the formulas
O=RPMxBSR, I=RPMx (n-BSR), R=RPMxBSR ( (OD+ID) /d +2)/n, and C=RPMxBSR/n where RPM is the inner ring rotational speed, n is the number of rolling elements, OD is the outer diameter of the bearing, ID is the inner diameter of the bearing, and d is the diameter of the rolling element.

A small amount of damage 60 on a bearing outer ring 62 will result in the waveforms and display shown in Figure 13 (a) where the display time is set to be u which is equal to i/O. The value of v in
Figure 13 (a) will depend upon the location of the transducer 64 with respect to the defect 60. A large damage 66 on a bearing outer ring 68 in Figure 14 results in the waveform and display shown in Figure 14(a). The greater length of damage along the outer ring in the direction of rolling causes impacts to occur over a longer time duration w. The size of the damage is determined from the ratio w/u where the quantity u is proportional to the length between two rolling elements along the circumference of the outer raceway.

A small amount of damage 80 on a bearing inner ring 82 in Figure 15 results ln the waveform and damage display shown in Figure 15(a) where the display time x is set to be i/I. The time i/I is proportional to the length between two adjacent rollers along the length of the inner ring.

A large amount of damage 90 on the inner ring 92 in Figure 16 results in the waveform and damage display shown in Figure 16(a). A measure of the length of the damage is found by computing the ratio y/x. When this ratio equals i.O, the length of the defect is equal to the length between rolling elements. It is seen from Figures 15 (a) and 16 (a) that the amplitude of the spikes in the high frequency waveform modulates with an interval of time z. That interval z is equal to the per:od of one shaft revolution. When the ratio y/x approaches i.O, the damage display should be changed to be synchronized with z. In this manner, the display will indicate the size of the damage as a fraction of the circumference of the inner ring.

A small amount of damage 100 on a rolling element 102 in Figure 17 will result in the waveforms shown in Figure 17 (a) where the display time is set to be a which is equal to i/R. As the damage on a roller grows, the width of the bar graph will grow proportionately and the size of the damage can be read as a fraction of the roller semidiameter.

Figure 18 shows more than one rolling element 112 with a defect 110. The high frequency waveform and damage display will appear as shown in Figure 18 (a) where the display time is set to be b which is is equal to 1/C. In this mode, a bar will appear for each rolling element that is damaged.

In summary, the invention achieves a high frequency capability to make displacement measurements with a contacting device by properly focusing non-contacting fiber optic sensing means at a reflective cantilever spring that biases a ruby tip against an object whose motion is to be measured. By proper design, the masses of the moving elements are minimized and the spring stiffness of the cantilever adjusted for maximum frequency response at safe contact stress levels. In so doing, the advantages of fiber optic displacement sensors namely high frequency response, small size and immunity from electrical and electromagnetic noises are combined with the non-fouling properties of contacting sensors.

It will be understood that variations and modifications may be effected without department from the spirit and scope of the novel concepts of this invention. Namely, the material of the cantilever which is stainless steel in the preferred embodiment could likely be beryllium copper for its good endurance strength, or titanium for its high Young's
Modulus, or some composite material to which a reflective coating may or may not be applied. It is also suggested that contact tips of various shapes, materials, or configurations can be designed to enhance the reliability, performance, or ease of manufacture of the invention. For example, the tip may be mechanically affixed to the spring beam or the beam itself may be curved or dimpled to form its own contact tip.

It is further suggested that dynamic motion of the cantilever beam may be sensed by means other than light sensing means; for example, eddy current or capacitance sensing means may be used.

Claims

WHAT IS CLAIMED IS: "

1. A transducer system for detecting and measuring displacement and vibration of objects placed into contact with the transducer system, comprising: (a) light reflecting means for reflecting incident light and for vibrating in unison with a contacted object having a dynamic motion; (b) light guiding means for guiding transmitted and reflected light to and from the reflecting means: (c) contacting means for contacting the test object and for supporting the light reflecting means; (d) biasing means for biasing the contacting means to precisely follow dynamic motion of a test object; (e) a light source associated with the light transmitting means for transmitting light to the light reflecting means and; (f) means for generating a signal from light received from the light guiding means.

2. A system according to claim 1, further comprising sealing means for sealing the light reflecting means from outside sources of contamination.

3. A system according to claim 2, further comprising light coupling means for coupling and optimizing transfer of light between the light guiding means and the light reflecting means.

4. A system according to claim 3, wherein the light coupling means is a gas, a liquid or a vacuum.

5. A system according to claim 3, wherein the light coupling means is an elastomeric solid having an index of refraction substantially equal to the index of refraction of the light guiding means.

6. A system according to claim 2, further comprising means for calibrating an optical peak in a response curve in the absence of contact with any object.

7. A system according to claim 2, wherein the light source is continuous.

8. A system according to claim 2, wherein the light source is pulsed.

9. A system according to claim 2, wherein the signal generating means converts light reflection intensity into motion signals.

10. A system according to claim 8, wherein the signal generating means converts spatial irregularities of light pulses into motion signals.

11. A system according to claim 1, wherein the light guiding means comprises a plurality of light conducting fiber optics divided into a plurality of fiber optic groups, at least one group having light transmitting fibers and at least one group having light receiving fibers, the fiber optics of both groups merged to form a substantially unitary peripheral surface which surface is truncated to form a substantially planar surface parallel to the light reflecting means.

12. A system according to claim 1, wherein the light guiding means comprises a single fiber.

13. A system according to claim 2, wherein the light guiding means comprises a plurality of fiber optics, having at least one light transmitting fiber and at least one light receiving fiber.

14. A system according to claim 1, wherein the reflecting means comprises a substantially flat surface of a substantially reflective material.

15. A system as claimed in claim 1, wherein the reflecting means comprises an undersurface of a cantilever spring.

16. A system as claimed in claim 1, wherein the contacting means comprises an outer peripheral surface substantially arcuate in shape and wherein the contacting means further comprises a substantially cylindrical member of ruby material having one flat and one crowned end.

17. A system as claimed in claim 13, wherein the contacting means has a diameter of about lmm and a crown end radius of about 2.5mm.

18. A system as claimed in claim 2, wherein the contacting means comprises an outer peripheral surface substantially arcuate in shape and wherein the contacting means further comprises a material with the physical properties of sapphire.

v 19. A system as claimed in claim 16, wherein the contacting means is of ceramic material.

20. A system according to claim 1, wherein the biasing means are comprised of metallic springs.

21. A system according to claim 1, wherein the biasing means comprises a cantilever spring having a spring rate of 2OOlb./in.

22. A system as according to claim 1, wherein the biasing means comprises a cantilever spring having a maximum deflection of 0.008 in. and a maximum contact pressure of 250,000 psi.

23. A system according to claim 1, having a means for determining damage from impact activity of a defect in a rolling element bearing, comprising: (a) means for generating a signal at a shaft rotational frequency; (b) means for computing a bearing speed ratio from the generated signals; (c) means for displaying the impact activity, the display means showing a low frequency wavefbrm and a high frequency waveform developed by the action of rolling elements passing by the contacting means and a time equal to the rate of bearing operation.

24. A method of determining impact activity of a rolling element bearing comprising: (a) contacting a bearing housing with a transducer system and generating signals showing relative motion between a bearing and a bearing housing; (b) displaying the impact activity of the bearing from the generated signals with a high and low frequency waveform developed by the action of the rolling elements and a time equal to the rate of bearing operation.

25. The method of claim 22, further comprising measuring the time between successive passes of rolling elements on a stationary ring of a rolling element bearing to determine damage to the stationary ring.

26. The method of claim 22, further comprising measuring the rotation period of a rotating ring in a rolling element bearing to determine damage to the rotating ring.

27. The method of claim 22, further comprising measuring the rotation period of a rolling element in a rolling element bearing to determine damage to the rolling element.

28. The method of claim 22, further comprising measuring time between successive passes of rolling elements passing a point on a rotating ring to determine damage to the rotating ring.

29. The method of claim 22, further comprising measuring a rotation period of a cage, in a rotating element bearing having a cage, to determine damage to a rolling element.

30. The method of claim 27, further comprising determining damage to the cage.

31. The method of claim 22, further comprising generating a signal at a shaft rotational frequency and computing bearing speed ratio.

32. A transducer comprising: (a) means for contacting an object; (b) a cantilever spring for biasing the contacting means to follow the dynamic motion of the object; (c) means responsive to the movement of the spring for generating a signal commensurate therewith.

33. A transducer according to claim 32, where the responsive means includes means for reflecting incident light off of said spring.

34. A transducer according to claim 32, including sealing means, the sealing means being fixedly attached to the cantilever spring whereby movement of the light reflecting means is unaffected by contact with said sealing means.